![Four stroke engine diagram](https://upload.wikimedia.org/wikipedia/commons/4/47/Four_stroke_engine_diagram.jpg)
An internal combustion engine (ICE or IC engine) is a
heat engine
In thermodynamics and engineering, a heat engine is a system that converts heat to mechanical energy, which can then be used to do mechanical work. It does this by bringing a working substance from a higher state temperature to a lower state ...
in which the
combustion
Combustion, or burning, is a high-temperature exothermic redox chemical reaction between a fuel (the reductant) and an oxidant, usually atmospheric oxygen, that produces oxidized, often gaseous products, in a mixture termed as smoke. Combusti ...
of a
fuel
A fuel is any material that can be made to react with other substances so that it releases energy as thermal energy or to be used for work. The concept was originally applied solely to those materials capable of releasing chemical energy but ...
occurs with an
oxidizer
An oxidizing agent (also known as an oxidant, oxidizer, electron recipient, or electron acceptor) is a substance in a redox chemical reaction that gains or " accepts"/"receives" an electron from a (called the , , or ). In other words, an oxid ...
(usually air) in a
combustion chamber
A combustion chamber is part of an internal combustion engine in which the fuel/air mix is burned. For steam engines, the term has also been used for an extension of the firebox which is used to allow a more complete combustion process.
Interna ...
that is an integral part of the
working fluid
For fluid power, a working fluid is a gas or liquid that primarily transfers force, motion, or mechanical energy. In hydraulics, water or hydraulic fluid transfers force between hydraulic components such as hydraulic pumps, hydraulic cylinders, a ...
flow circuit. In an internal combustion engine, the expansion of the high-
temperature
Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measured with a thermometer.
Thermometers are calibrated in various temperature scales that historically have relied o ...
and high-
pressure
Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country and e ...
gases produced by combustion applies direct
force
In physics, a force is an influence that can change the motion of an object. A force can cause an object with mass to change its velocity (e.g. moving from a state of rest), i.e., to accelerate. Force can also be described intuitively as a p ...
to some component of the engine. The force is typically applied to
piston
A piston is a component of reciprocating engines, reciprocating pumps, gas compressors, hydraulic cylinders and pneumatic cylinders, among other similar mechanisms. It is the moving component that is contained by a cylinder and is made gas-tig ...
s (
piston engine
A reciprocating engine, also often known as a piston engine, is typically a heat engine that uses one or more reciprocating pistons to convert high temperature and high pressure into a rotating motion. This article describes the common featu ...
),
s (
gas turbine
A gas turbine, also called a combustion turbine, is a type of continuous flow internal combustion engine. The main parts common to all gas turbine engines form the power-producing part (known as the gas generator or core) and are, in the directi ...
), a
rotor (Wankel engine), or a
nozzle
A nozzle is a device designed to control the direction or characteristics of a fluid flow (specially to increase velocity) as it exits (or enters) an enclosed chamber or pipe.
A nozzle is often a pipe or tube of varying cross sectional area, a ...
(
jet engine
A jet engine is a type of reaction engine discharging a fast-moving jet of heated gas (usually air) that generates thrust by jet propulsion. While this broad definition can include rocket, Pump-jet, water jet, and hybrid propulsion, the term ...
). This force moves the component over a distance, transforming
chemical energy
Chemical energy is the energy of chemical substances that is released when they undergo a chemical reaction and transform into other substances. Some examples of storage media of chemical energy include batteries, Schmidt-Rohr, K. (2018). "How ...
into
kinetic energy
In physics, the kinetic energy of an object is the energy that it possesses due to its motion.
It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its accele ...
which is used to propel, move or power whatever the engine is attached to. This replaced the
external combustion engine
An external combustion engine (EC engine) is a reciprocating heat engine where a working fluid, contained internally, is heated by combustion in an external source, through the engine wall or a heat exchanger. The fluid then, by expanding and ...
for applications where the weight or size of an engine was more important.
The first commercially successful internal combustion engine was created by
Ătienne Lenoir
Jean Joseph Ătienne Lenoir, also known as Jean J. Lenoir (12 January 1822 â 4 August 1900), was a Belgian- French engineer who developed the internal combustion engine in 1858. Prior designs for such engines were patented as early as 1807 (D ...
around 1860,
and the first modern internal combustion engine, known as the
Otto engine
The Otto engine was a large stationary single-cylinder internal combustion four-stroke engine designed by the German Nicolaus Otto. It was a low-RPM machine, and only fired every other stroke due to the Otto cycle, also designed by Otto.
Types ...
, was created in 1876 by
Nicolaus Otto
Nicolaus August Otto (10 June 1832, Holzhausen an der Haide, Nassau â 26 January 1891, Cologne) was a German engineer who successfully developed the compressed charge internal combustion engine which ran on petroleum gas and led to the mode ...
. The term ''
internal combustion engine
An internal combustion engine (ICE or IC engine) is a heat engine in which the combustion of a fuel occurs with an oxidizer (usually air) in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal combus ...
'' usually refers to an engine in which combustion is
intermittent
Intermittency is a behavior of dynamical systems: regular alternation of phases of apparently periodic and chaotic dynamics.
Intermittent or intermittency may also refer to:
*Intermittent river or stream, the one that ceases to flow every year or ...
, such as the more familiar
two-stroke
A two-stroke (or two-stroke cycle) engine is a type of internal combustion engine that completes a Thermodynamic power cycle, power cycle with two strokes (up and down movements) of the piston during one power cycle, this power cycle being comple ...
and
four-stroke
A four-stroke (also four-cycle) engine is an internal combustion (IC) engine in which the piston completes four separate strokes while turning the crankshaft. A stroke refers to the full travel of the piston along the cylinder, in either directio ...
piston engines, along with variants, such as the
six-stroke piston engine and the
Wankel rotary engine
The Wankel engine (, ) is a type of internal combustion engine using an eccentric rotary design to convert pressure into rotating motion. It was invented by German engineer Felix Wankel, and designed by German engineer Hanns-Dieter Paschke. T ...
. A second class of internal combustion engines use continuous combustion:
gas turbine
A gas turbine, also called a combustion turbine, is a type of continuous flow internal combustion engine. The main parts common to all gas turbine engines form the power-producing part (known as the gas generator or core) and are, in the directi ...
s,
jet engine
A jet engine is a type of reaction engine discharging a fast-moving jet of heated gas (usually air) that generates thrust by jet propulsion. While this broad definition can include rocket, Pump-jet, water jet, and hybrid propulsion, the term ...
s and most
rocket engine
A rocket engine uses stored rocket propellants as the reaction mass for forming a high-speed propulsive jet of fluid, usually high-temperature gas. Rocket engines are reaction engines, producing thrust by ejecting mass rearward, in accordanc ...
s, each of which are internal combustion engines on the same principle as previously described.
Firearm
A firearm is any type of gun designed to be readily carried and used by an individual. The term is legally defined further in different countries (see Legal definitions).
The first firearms originated in 10th-century China, when bamboo tubes ...
s are also a form of internal combustion engine,
though of a type so specialized that they are commonly treated as a separate category, along with weaponry such as mortars and anti-aircraft cannons. In contrast, in
external combustion engine
An external combustion engine (EC engine) is a reciprocating heat engine where a working fluid, contained internally, is heated by combustion in an external source, through the engine wall or a heat exchanger. The fluid then, by expanding and ...
s, such as
steam
Steam is a substance containing water in the gas phase, and sometimes also an aerosol of liquid water droplets, or air. This may occur due to evaporation or due to boiling, where heat is applied until water reaches the enthalpy of vaporization ...
or
Stirling engine
A Stirling engine is a heat engine that is operated by the cyclic compression and expansion of air or other gas (the ''working fluid'') between different temperatures, resulting in a net conversion of heat energy to mechanical work.
More specif ...
s, energy is delivered to a working fluid not consisting of, mixed with, or contaminated by combustion products. Working fluids for external combustion engines include air, hot water,
pressurized water or even
boiler
A boiler is a closed vessel in which fluid (generally water) is heated. The fluid does not necessarily boil. The heated or vaporized fluid exits the boiler for use in various processes or heating applications, including water heating, central h ...
-heated
liquid sodium
Sodium is a chemical element with the symbol Na (from Latin ''natrium'') and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table. Its only stable isot ...
.
While there are many stationary applications, most ICEs are used in mobile applications and are the primary power supply for
vehicle
A vehicle (from la, vehiculum) is a machine that transports people or cargo. Vehicles include wagons, bicycles, motor vehicles (motorcycles, cars, trucks, buses, mobility scooters for disabled people), railed vehicles (trains, trams), wa ...
s such as
cars
A car or automobile is a motor vehicle with wheels. Most definitions of ''cars'' say that they run primarily on roads, seat one to eight people, have four wheels, and mainly transport people instead of goods.
The year 1886 is regarded as t ...
,
aircraft
An aircraft is a vehicle that is able to fly by gaining support from the air. It counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines ...
and
boats
A boat is a watercraft of a large range of types and sizes, but generally smaller than a ship, which is distinguished by its larger size, shape, cargo or passenger capacity, or its ability to carry boats.
Small boats are typically found on inl ...
. ICEs are typically powered by
hydrocarbon
In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and hydrophobic, and their odors are usually weak or ex ...
-based fuels like
natural gas
Natural gas (also called fossil gas or simply gas) is a naturally occurring mixture of gaseous hydrocarbons consisting primarily of methane in addition to various smaller amounts of other higher alkanes. Low levels of trace gases like carbo ...
,
gasoline
Gasoline (; ) or petrol (; ) (see ) is a transparent, petroleum-derived flammable liquid that is used primarily as a fuel in most spark-ignited internal combustion engines (also known as petrol engines). It consists mostly of organic co ...
,
diesel fuel
Diesel fuel , also called diesel oil, is any liquid fuel specifically designed for use in a diesel engine, a type of internal combustion engine in which fuel ignition takes place without a spark as a result of compression of the inlet air and t ...
, or
ethanol
Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an Alcohol (chemistry), alcohol with the chemical formula . Its formula can be also written as or (an ethyl ...
.
Renewable fuels
Renewable Fuels are fuels produced from renewable resources. Examples include: biofuels (e.g. Vegetable oil used as fuel, ethanol, methanol from clean energy and carbon dioxide or biomass, and biodiesel) and Hydrogen fuel (when produced with ren ...
like
biodiesel
Biodiesel is a form of diesel fuel derived from plants or animals and consisting of long-chain fatty acid esters. It is typically made by chemically reacting lipids such as animal fat (tallow), soybean oil, or some other vegetable oil with ...
are used in compression ignition (CI) engines and
bioethanol
Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an Alcohol (chemistry), alcohol with the chemical formula . Its formula can be also written as or (an ethyl ...
or
ETBE
Ethyl ''tertiary''-butyl ether (ETBE), also known as ethyl ''tert''-butyl ether, is commonly used as an oxygenate gasoline additive in the production of gasoline from crude oil. ETBE offers equal or greater air quality benefits than ethanol ...
(ethyl tert-butyl ether) produced from bioethanol in spark ignition (SI) engines. As early as 1900 the inventor of the diesel engine,
Rudolf Diesel
Rudolf Christian Karl Diesel (, ; 18 March 1858 â 29 September 1913) was a German inventor and Mechanical engineering, mechanical engineer who is famous for having invented the diesel engine, which burns diesel fuel; both are named after him.
...
, was using peanut oil to run his engines. Renewable fuels are commonly blended with fossil fuels.
Hydrogen
Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic, an ...
, which is rarely used, can be obtained from either fossil fuels or renewable energy.
History
Various
scientist
A scientist is a person who conducts Scientific method, scientific research to advance knowledge in an Branches of science, area of the natural sciences.
In classical antiquity, there was no real ancient analog of a modern scientist. Instead, ...
s and
engineer
Engineers, as practitioners of engineering, are professionals who invent, design, analyze, build and test machines, complex systems, structures, gadgets and materials to fulfill functional objectives and requirements while considering the l ...
s contributed to the development of internal combustion engines. In 1791,
John Barber developed the
gas turbine
A gas turbine, also called a combustion turbine, is a type of continuous flow internal combustion engine. The main parts common to all gas turbine engines form the power-producing part (known as the gas generator or core) and are, in the directi ...
. In 1794 Thomas Mead patented a
gas engine
A gas engine is an internal combustion engine that runs on a gaseous fuel, such as coal gas, producer gas, biogas, landfill gas or natural gas. In the United Kingdom, the term is unambiguous. In the United States, due to the widespread use of ...
. Also in 1794, Robert Street patented an internal combustion engine, which was also the first to use
liquid fuel
Liquid fuels are combustible or energy-generating molecules that can be harnessed to create mechanical energy, usually producing kinetic energy; they also must take the shape of their container. It is the fumes of liquid fuels that are flammable ...
, and built an engine around that time. In 1798,
John Stevens built the first American internal combustion engine. In 1807,
French
French (french: français(e), link=no) may refer to:
* Something of, from, or related to France
** French language, which originated in France, and its various dialects and accents
** French people, a nation and ethnic group identified with Franc ...
engineers
Nicéphore Niépce
Joseph NicĂ©phore NiĂ©pce (; 7 March 1765 â 5 July 1833), commonly known or referred to simply as NicĂ©phore NiĂ©pce, was a French inventor, usually credited with the invention of photography. NiĂ©pce developed heliography, a technique he use ...
(who went on to invent
photography
Photography is the art, application, and practice of creating durable images by recording light, either electronically by means of an image sensor, or chemically by means of a light-sensitive material such as photographic film. It is employed ...
) and
Claude Niépce
Claude FĂ©lix Abel NiĂ©pce (1764â1828) was a French inventor and the older brother of the more celebrated NicĂ©phore NiĂ©pce. Claude traveled to England to try to find a sponsor for their internal combustion engine and died there. His brother's ...
ran a prototype internal combustion engine, using controlled dust explosions, the
Pyréolophore
The Pyréolophore () was probably the world's first internal combustion engine. It was invented in the early 19th century in Chalon-sur-SaÎne, France, by the Niépce brothers: Nicéphore (who went on to invent photography) and Claude. In 1807 ...
, which was granted a patent by
Napoleon Bonaparte
Napoleon Bonaparte ; it, Napoleone Bonaparte, ; co, Napulione Buonaparte. (born Napoleone Buonaparte; 15 August 1769 â 5 May 1821), later known by his regnal name Napoleon I, was a French military commander and political leader who ...
. This engine powered a boat on the
SaĂŽne
The SaÎne ( , ; frp, Sona; lat, Arar) is a river in eastern France. It is a right tributary of the RhÎne, rising at Vioménil in the Vosges department and joining the RhÎne in Lyon, at the southern end of the Presqu'ßle.
The name deri ...
river in France.
In the same year,
Swiss
Swiss may refer to:
* the adjectival form of Switzerland
* Swiss people
Places
* Swiss, Missouri
* Swiss, North Carolina
*Swiss, West Virginia
* Swiss, Wisconsin
Other uses
*Swiss-system tournament, in various games and sports
*Swiss Internation ...
engineer
François Isaac de Rivaz
François Isaac de Rivaz (Paris, December 19, 1752 – Sion, July 30, 1828) was a French-born Swiss inventor and a politician. He invented a hydrogen-powered internal combustion engine with electric ignition and described it in a French patent ...
invented a hydrogen-based internal combustion engine and powered the engine by electric spark. In 1808, De Rivaz fitted his invention to a primitive working vehicle â "the world's first internal combustion powered automobile". In 1823,
Samuel Brown Samuel Brown may refer to:
* Samuel Brown (Royal Navy officer) (1776â1852), English pioneer suspension bridge engineer and inventor
* Samuel Brown (engineer) (died 1849), English inventor of early internal combustion engine
* Samuel Brown (Wisco ...
patented the first internal combustion engine to be applied industrially.
In 1854 in the
UK, the Italian inventors
Eugenio Barsanti
Father Eugenio Barsanti (12 October 1821 â 19 April 1864), also named NicolĂČ, was an Italian engineer, who together with Felice Matteucci of Lucca invented the first version of the internal combustion engine in 1853. Their patent request was gr ...
and
Felice Matteucci
Felice Matteucci (February 12, 1808 – September 13, 1887) was an Italian hydraulic engineer who co-invented an internal combustion engine with Eugenio Barsanti. Their patent request was granted in London on June 12, 1854, and published in Lo ...
obtained the certification: "Obtaining Motive Power by the Explosion of Gases". In 1857 the Great Seal Patent Office conceded them patent No.1655 for the invention of an "Improved Apparatus for Obtaining Motive Power from Gases". Barsanti and Matteucci obtained other patents for the same invention in France, Belgium and Piedmont between 1857 and 1859. In 1860,
Belgian
Belgian may refer to:
* Something of, or related to, Belgium
* Belgians, people from Belgium or of Belgian descent
* Languages of Belgium, languages spoken in Belgium, such as Dutch, French, and German
*Ancient Belgian language, an extinct language ...
engineer
Jean Joseph Etienne Lenoir
Jean may refer to:
People
* Jean (female given name)
* Jean (male given name)
* Jean (surname)
Fictional characters
* Jean Grey, a Marvel Comics character
* Jean Valjean, fictional character in novel ''Les Misérables'' and its adaptations
* Jean ...
produced a gas-fired internal combustion engine.
In 1864,
Nicolaus Otto
Nicolaus August Otto (10 June 1832, Holzhausen an der Haide, Nassau â 26 January 1891, Cologne) was a German engineer who successfully developed the compressed charge internal combustion engine which ran on petroleum gas and led to the mode ...
patented the first atmospheric gas engine. In 1872, American
George Brayton
George Bailey Brayton was an American mechanical engineer and inventor. He was noted for introducing the constant pressure engine that is the basis for the gas turbine, and which is now referred to as the Brayton cycle.
Brayton's Ready Motor
...
invented the first commercial liquid-fueled internal combustion engine. In 1876,
Nicolaus Otto
Nicolaus August Otto (10 June 1832, Holzhausen an der Haide, Nassau â 26 January 1891, Cologne) was a German engineer who successfully developed the compressed charge internal combustion engine which ran on petroleum gas and led to the mode ...
began working with
Gottlieb Daimler
Gottlieb Wilhelm Daimler (; 17 March 1834 â 6 March 1900) was a German engineer, industrial designer and industrialist born in Schorndorf (Kingdom of WĂŒrttemberg, a federal state of the German Confederation), in what is now Germany. He was a ...
and
Wilhelm Maybach
Wilhelm Maybach (; 9 February 1846 â 29 December 1929) was an early German engine designer and industrialist. During the 1890s he was hailed in France, then the world centre for car production, as the "King of Designers".
From the late 19th ce ...
, patented the compressed charge, four-cycle engine. In 1879,
Karl Benz
Carl Friedrich Benz (; 25 November 1844 â 4 April 1929), sometimes also Karl Friedrich Benz, was a German engine designer and automotive engineer. His Benz Patent Motorcar from 1885 is considered the first practical modern automobile and fir ...
patented a reliable
two-stroke
A two-stroke (or two-stroke cycle) engine is a type of internal combustion engine that completes a Thermodynamic power cycle, power cycle with two strokes (up and down movements) of the piston during one power cycle, this power cycle being comple ...
gasoline engine. Later, in 1886, Benz began the first commercial production of motor vehicles with an internal combustion engine, in which a three-wheeled, four-cycle engine and chassis formed a single unit.
In 1892,
Rudolf Diesel
Rudolf Christian Karl Diesel (, ; 18 March 1858 â 29 September 1913) was a German inventor and Mechanical engineering, mechanical engineer who is famous for having invented the diesel engine, which burns diesel fuel; both are named after him.
...
developed the first compressed charge, compression ignition engine. In 1926,
Robert Goddard
Robert Hutchings Goddard (October 5, 1882 â August 10, 1945) was an American engineer, professor, physicist, and inventor who is credited with creating and building the world's first Liquid-propellant rocket, liquid-fueled rocket. ...
launched the first liquid-fueled rocket. In 1939, the
Heinkel He 178
The Heinkel He 178 was an experimental aircraft designed and produced by the German aircraft manufacturer Heinkel. It was the world's first aircraft to fly using the thrust from a turbojet engine.
The He 178 was developed to test the jet propul ...
became the world's first
jet aircraft
A jet aircraft (or simply jet) is an aircraft (nearly always a fixed-wing aircraft) propelled by jet engines.
Whereas the engines in propeller-powered aircraft generally achieve their maximum efficiency at much lower speeds and altitudes, je ...
.
Etymology
At one time, the word ''engine'' (via
Old French
Old French (, , ; Modern French: ) was the language spoken in most of the northern half of France from approximately the 8th to the 14th centuries. Rather than a unified language, Old French was a linkage of Romance dialects, mutually intelligib ...
, from
Latin
Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...
''ingenium'', "ability") meant any piece of
machinery
A machine is a physical system using power to apply forces and control movement to perform an action. The term is commonly applied to artificial devices, such as those employing engines or motors, but also to natural biological macromolecule ...
âa sense that persists in expressions such as ''
siege engine
A siege engine is a device that is designed to break or circumvent heavy castle doors, thick city walls and other fortifications in siege warfare. Some are immobile, constructed in place to attack enemy fortifications from a distance, while other ...
''. A "motor" (from Latin ''motor'', "mover") is any machine that produces mechanical
power
Power most often refers to:
* Power (physics), meaning "rate of doing work"
** Engine power, the power put out by an engine
** Electric power
* Power (social and political), the ability to influence people or events
** Abusive power
Power may a ...
. Traditionally,
electric motor
An electric motor is an Electric machine, electrical machine that converts electrical energy into mechanical energy. Most electric motors operate through the interaction between the motor's magnetic field and electric current in a Electromagneti ...
s are not referred to as "engines"; however, combustion engines are often referred to as "motors". (An ''
electric engine
An electric motor is an electrical machine that converts electrical energy into mechanical energy. Most electric motors operate through the interaction between the motor's magnetic field and electric current in a wire winding to generate force ...
'' refers to a
locomotive
A locomotive or engine is a rail transport vehicle that provides the Power (physics), motive power for a train. If a locomotive is capable of carrying a payload, it is usually rather referred to as a multiple unit, Motor coach (rail), motor ...
operated by electricity.)
In boating, an internal combustion engine that is installed in the hull is referred to as an engine, but the engines that sit on the transom are referred to as motors.
Applications
![Montreal power backup](https://upload.wikimedia.org/wikipedia/commons/b/bf/Montreal_power_backup.jpg)
Reciprocating piston engines are by far the most common power source for land and water
vehicle
A vehicle (from la, vehiculum) is a machine that transports people or cargo. Vehicles include wagons, bicycles, motor vehicles (motorcycles, cars, trucks, buses, mobility scooters for disabled people), railed vehicles (trains, trams), wa ...
s, including
automobile
A car or automobile is a motor vehicle with Wheel, wheels. Most definitions of ''cars'' say that they run primarily on roads, Car seat, seat one to eight people, have four wheels, and mainly transport private transport#Personal transport, pe ...
s,
motorcycle
A motorcycle (motorbike, bike, or trike (if three-wheeled)) is a two or three-wheeled motor vehicle steered by a handlebar. Motorcycle design varies greatly to suit a range of different purposes: long-distance travel, commuting, cruising ...
s,
ship
A ship is a large watercraft that travels the world's oceans and other sufficiently deep waterways, carrying cargo or passengers, or in support of specialized missions, such as defense, research, and fishing. Ships are generally distinguished ...
s and to a lesser extent,
locomotive
A locomotive or engine is a rail transport vehicle that provides the Power (physics), motive power for a train. If a locomotive is capable of carrying a payload, it is usually rather referred to as a multiple unit, Motor coach (rail), motor ...
s (some are electrical but most use Diesel engines). Rotary engines of the Wankel design are used in some automobiles, aircraft and motorcycles. These are collectively known as internal-combustion-engine vehicles (ICEV).
Where high power-to-weight ratios are required, internal combustion engines appear in the form of
combustion turbine
A gas turbine, also called a combustion turbine, is a type of continuous flow internal combustion engine. The main parts common to all gas turbine engines form the power-producing part (known as the gas generator or core) and are, in the directio ...
s, or sometimes Wankel engines.
Powered aircraft
A powered aircraft is an aircraft that uses onboard propulsion with mechanical power generated by an aircraft engine of some kind.
Aircraft propulsion nearly always uses either a type of propeller, or a form of jet propulsion. Other potential ...
typically use an ICE which may be a reciprocating engine. Airplanes can instead use
jet engine
A jet engine is a type of reaction engine discharging a fast-moving jet of heated gas (usually air) that generates thrust by jet propulsion. While this broad definition can include rocket, Pump-jet, water jet, and hybrid propulsion, the term ...
s and
helicopter
A helicopter is a type of rotorcraft in which lift and thrust are supplied by horizontally spinning rotors. This allows the helicopter to take off and land vertically, to hover, and to fly forward, backward and laterally. These attributes ...
s can instead employ
turboshaft
A turboshaft engine is a form of gas turbine that is optimized to produce shaftpower rather than jet thrust. In concept, turboshaft engines are very similar to turbojets, with additional turbine expansion to extract heat energy from the exhaust ...
s; both of which are types of turbines. In addition to providing propulsion,
airliner
An airliner is a type of aircraft for transporting passengers and air cargo. Such aircraft are most often operated by airlines. Although the definition of an airliner can vary from country to country, an airliner is typically defined as an ...
s may employ a separate ICE as an
auxiliary power unit
An auxiliary power unit (APU) is a device on a vehicle that provides energy for functions other than propulsion. They are commonly found on large aircraft and naval ships as well as some large land vehicles. Aircraft APUs generally produce 115&n ...
. Wankel engines are fitted to many
unmanned aerial vehicle
An unmanned aerial vehicle (UAV), commonly known as a drone, is an aircraft without any human pilot, crew, or passengers on board. UAVs are a component of an unmanned aircraft system (UAS), which includes adding a ground-based controller ...
s.
ICEs drive large electric generators that power electrical grids. They are found in the form of
combustion turbine
A gas turbine, also called a combustion turbine, is a type of continuous flow internal combustion engine. The main parts common to all gas turbine engines form the power-producing part (known as the gas generator or core) and are, in the directio ...
s with a typical electrical output in the range of some 100 MW.
Combined cycle power plant
A combined cycle power plant is an assembly of heat engines that work in tandem from the same source of heat, converting it into mechanical energy. On land, when used to make electricity the most common type is called a combined cycle gas turb ...
s use the high temperature exhaust to boil and superheat water steam to run a
steam turbine
A steam turbine is a machine that extracts thermal energy from pressurized steam and uses it to do mechanical work on a rotating output shaft. Its modern manifestation was invented by Charles Parsons in 1884. Fabrication of a modern steam turbin ...
. Thus, the efficiency is higher because more energy is extracted from the fuel than what could be extracted by the combustion engine alone.
Combined cycle power plants achieve efficiencies in the range of 50% to 60%. In a smaller scale,
stationary engine
A stationary engine is an engine whose framework does not move. They are used to drive immobile equipment, such as pumps, generators, mills or factory machinery, or cable cars. The term usually refers to large immobile reciprocating engines, pr ...
s like
gas engine
A gas engine is an internal combustion engine that runs on a gaseous fuel, such as coal gas, producer gas, biogas, landfill gas or natural gas. In the United Kingdom, the term is unambiguous. In the United States, due to the widespread use of ...
s or
diesel generator
A diesel generator (DG) (also known as a diesel Genset) is the combination of a diesel engine with an electric generator (often an alternator) to generate electrical energy. This is a specific case of engine generator. A diesel compression- ...
s are used for backup or for providing electrical power to areas not connected to an
electric grid
An electrical grid is an interconnected network for electricity delivery from producers to consumers. Electrical grids vary in size and can cover whole countries or continents. It consists of:Kaplan, S. M. (2009). Smart Grid. Electrical Power ...
.
Small engine
A small engine is the general term for a wide range of small-displacement, low-powered internal combustion engines used to power lawn mowers, generators, concrete mixers and many other machines that require independent power sources. These engin ...
s (usually 2âstroke gasoline/petrol engines) are a common power source for
lawnmower
A lawn mower (also known as a mower, grass cutter or lawnmower) is a device utilizing one or more revolving blades (or a reel) to cut a lawn, grass surface to an even height. The height of the cut grass may be fixed by the design of the mower, ...
s,
string trimmer
A string trimmer, also known by the portmanteau strimmer and the trademarks Weedwacker, Weed eater and Whipper Snipper. is a garden tool for cutting grass, small weeds, and groundcover. It uses a whirling monofilament line instead of a blade, ...
s,
chain saw
A chainsaw (or chain saw) is a portable gasoline-, electric-, or battery-powered saw that cuts with a set of teeth attached to a rotating chain driven along a guide bar. It is used in activities such as tree felling, limbing, bucking, pruning, ...
s,
leafblower
A leaf blower, commonly known as a blower, is a device that propels air out of a nozzle to move debris such as leaves and grass cuttings. Leaf blowers are powered by electric or gasoline motors. Gasoline models have traditionally been two-stro ...
s,
pressure washer
Pressure washing or power washing is the use of high-pressure water spray to remove loose paint, mold, grime, dust, mud, and dirt from surfaces and objects such as buildings, vehicles and concrete surfaces. The volume of a mechanical pressure w ...
s,
snowmobile
A snowmobile, also known as a Ski-Doo, snowmachine, sled, motor sled, motor sledge, skimobile, or snow scooter, is a motorized vehicle designed for winter travel and recreation on snow. It is designed to be operated on snow and ice and does not ...
s,
jet ski
Jet Ski is the brand name of a personal watercraft (PWC) manufactured by Kawasaki, a Japanese company. The term is often used generically to refer to any type of personal watercraft used mainly for recreation, and it is also used as a verb to ...
s,
outboard motor
An outboard motor is a propulsion system for boats, consisting of a self-contained unit that includes engine, gearbox and propeller or jet drive, designed to be affixed to the outside of the transom. They are the most common motorised method ...
s,
moped
A moped ( ) is a type of small motorcycle, generally having a less stringent licensing requirement than full motorcycles or automobiles. The term used to mean a similar vehicle except with both bicycle pedals and a motorcycle engine. Mopeds typic ...
s, and
motorcycle
A motorcycle (motorbike, bike, or trike (if three-wheeled)) is a two or three-wheeled motor vehicle steered by a handlebar. Motorcycle design varies greatly to suit a range of different purposes: long-distance travel, commuting, cruising ...
s.
Classification
There are several possible ways to classify internal combustion engines.
Reciprocating
By number of strokes:
*
Two-stroke engine
A two-stroke (or two-stroke cycle) engine is a type of internal combustion engine that completes a power cycle with two strokes (up and down movements) of the piston during one power cycle, this power cycle being completed in one revolution of t ...
** Clerk cycle
** Day cycle
*
Four-stroke engine
A four-stroke (also four-cycle) engine is an internal combustion (IC) engine in which the piston completes four separate strokes while turning the crankshaft. A stroke refers to the full travel of the piston along the cylinder, in either directio ...
(
Otto cycle
An Otto cycle is an idealized thermodynamic cycle that describes the functioning of a typical spark ignition piston engine. It is the thermodynamic cycle most commonly found in automobile engines.
The Otto cycle is a description of what happ ...
)
*
Six-stroke engine The term six-stroke engine has been applied to a number of alternative internal combustion engine designs that attempt to improve on traditional two-stroke and four-stroke engines. Claimed advantages may include increased fuel efficiency, reduced m ...
By type of ignition:
*
Compression-ignition engine
The diesel engine, named after Rudolf Diesel, is an internal combustion engine in which ignition of the fuel is caused by the elevated temperature of the air in the cylinder due to mechanical compression; thus, the diesel engine is a so-cal ...
*
Spark-ignition engine
A spark-ignition engine (SI engine) is an internal combustion engine, generally a petrol engine, where the combustion process of the air-fuel mixture is ignited by a spark from a spark plug. This is in contrast to compression-ignition engines, ty ...
(commonly found as
gasoline engine
A petrol engine (gasoline engine in American English) is an internal combustion engine designed to run on petrol (gasoline). Petrol engines can often be adapted to also run on fuels such as liquefied petroleum gas and ethanol blends (such as ''E ...
s)
By mechanical/thermodynamic cycle (these cycles are infrequently used but are commonly found in
hybrid vehicles
A hybrid vehicle is one that uses two or more distinct types of power, such as submarines that use diesel when surfaced and batteries when submerged. Other means to store energy include pressurized fluid in hydraulic hybrids.
The basic princip ...
, along with other vehicles manufactured for
fuel efficiency
Fuel efficiency is a form of thermal efficiency, meaning the ratio of effort to result of a process that converts chemical potential energy contained in a carrier (fuel) into kinetic energy or work. Overall fuel efficiency may vary per device, wh ...
):
*
Atkinson cycle
The Atkinson-cycle engine is a type of internal combustion engine invented by James Atkinson in 1882. The Atkinson cycle is designed to provide efficiency at the expense of power density.
A variation of this approach is used in some modern aut ...
*
Miller cycle
In engineering, the Miller cycle is a thermodynamic cycle used in a type of internal combustion engine. The Miller cycle was patented by Ralph Miller, an American engineer, dated Dec 24, 1957. The engine may be two- or four-stroke and may be r ...
Rotary
*
Wankel engine
The Wankel engine (, ) is a type of internal combustion engine using an Eccentric (mechanism), eccentric rotary combustion engine, rotary design to convert pressure into rotating motion. It was invented by German engineer Felix Wankel, and desi ...
Continuous combustion
*
Gas turbine
A gas turbine, also called a combustion turbine, is a type of continuous flow internal combustion engine. The main parts common to all gas turbine engines form the power-producing part (known as the gas generator or core) and are, in the directi ...
engine
**
Turbojet
The turbojet is an airbreathing jet engine which is typically used in aircraft. It consists of a gas turbine with a propelling nozzle. The gas turbine has an air inlet which includes inlet guide vanes, a compressor, a combustion chamber, and ...
, through a propelling nozzle
**
Turbofan
The turbofan or fanjet is a type of airbreathing jet engine that is widely used in aircraft engine, aircraft propulsion. The word "turbofan" is a portmanteau of "turbine" and "fan": the ''turbo'' portion refers to a gas turbine engine which ac ...
, through a duct-fan
**
Turboprop
A turboprop is a turbine engine that drives an aircraft propeller.
A turboprop consists of an intake, reduction gearbox, compressor, combustor, turbine, and a propelling nozzle. Air enters the intake and is compressed by the compressor. Fuel ...
, through an unducted propeller, usually with variable pitch
**
Turboshaft
A turboshaft engine is a form of gas turbine that is optimized to produce shaftpower rather than jet thrust. In concept, turboshaft engines are very similar to turbojets, with additional turbine expansion to extract heat energy from the exhaust ...
, a gas turbine optimized for producing mechanical torque instead of thrust
*
Ramjet
A ramjet, or athodyd (aero thermodynamic duct), is a form of airbreathing jet engine that uses the forward motion of the engine to produce thrust. Since it produces no thrust when stationary (no ram air) ramjet-powered vehicles require an ass ...
, similar to a turbojet but uses vehicle speed to compress (ram) the air instead of a compressor.
*
Scramjet
A scramjet (supersonic combustion ramjet) is a variant of a ramjet airbreathing jet engine in which combustion takes place in supersonic airflow. As in ramjets, a scramjet relies on high vehicle speed to compress the incoming air forcefully ...
, a variant of the ramjet that uses supersonic combustion.
*
Rocket engine
A rocket engine uses stored rocket propellants as the reaction mass for forming a high-speed propulsive jet of fluid, usually high-temperature gas. Rocket engines are reaction engines, producing thrust by ejecting mass rearward, in accordanc ...
Reciprocating engines
Structure
![Piston and connecting rod](https://upload.wikimedia.org/wikipedia/commons/c/c8/Piston_and_connecting_rod.jpg)
The base of a reciprocating internal combustion engine is the
engine block
In an internal combustion engine, the engine block is the structure which contains the cylinders and other components. In an early automotive engine, the engine block consisted of just the cylinder block, to which a separate crankcase was atta ...
, which is typically made of
cast iron
Cast iron is a class of ironâcarbon alloys with a carbon content more than 2%. Its usefulness derives from its relatively low melting temperature. The alloy constituents affect its color when fractured: white cast iron has carbide impuriti ...
(due to its good wear resistance and low cost)
or
aluminum
Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. It has ...
. In the latter case, the cylinder liners are made of cast iron or steel,
or a coating such as
nikasil
Nikasil is a trademarked electrodeposited lipophilic nickel matrix silicon carbide coating for engine components, mainly piston engine cylinder liners.
Development
Nikasil was introduced by Mahle in 1967, and initially developed to allow Wankel ...
or
alusil
Alusil as a hypereutectic aluminium-silicon alloy (EN AC-AlSi17Cu4Mg / EN AC-48100 or A390) contains approximately 78% aluminium and 17% silicon. This alloy was theoretically conceived in 1927 by Schweizer & Fehrenbach, of the Badener Metall-Ware ...
. The engine block contains the
cylinders
A cylinder (from ) has traditionally been a three-dimensional solid, one of the most basic of curvilinear geometric shapes. In elementary geometry, it is considered a prism with a circle as its base.
A cylinder may also be defined as an infini ...
. In engines with more than one cylinder they are usually arranged either in 1 row (
straight engine
The straight or inline engine is an internal combustion engine with all cylinders aligned in one row and having no offset. Usually found in four, six and eight cylinder configurations, they have been used in automobiles, locomotives and aircraft ...
) or 2 rows (
boxer engine
A flat engine is a piston engine where the cylinders are located on either side of a central crankshaft. Flat engines are also known as horizontally opposed engines, however this is distinct from the less common opposed-piston engine design, ...
or
V engine
A V engine, sometimes called a Vee engine, is a common configuration for internal combustion engines. It consists of two cylinder banksâusually with the same number of cylinders in each bankâconnected to a common crankshaft. These cylinder b ...
); 3 rows are occasionally used (
W engine
A W engine is a type of piston engine where three or four cylinder banks use the same crankshaft, resembling the letter W when viewed from the front.
W engines with three banks of cylinders are also called "broad arrow" engines, due to their shap ...
) in contemporary engines, and other
engine configuration
The engine configuration describes the fundamental operating principles by which internal combustion engines are categorized.
Piston engines are often categorized by their cylinder layout, valves and camshafts. Wankel engines are often categorize ...
s are possible and have been used.
Single cylinder engine
A single-cylinder engine, sometimes called a thumper, is a piston engine with one cylinder. This engine is often used for motorcycles, motor scooters, go-karts, all-terrain vehicles, radio-controlled vehicles, portable tools and garden machinery ( ...
s (or ''thumpers'') are common for motorcycles and other small engines found in light machinery. On the outer side of the cylinder, passages that contain cooling fluid are cast into the engine block whereas, in some heavy duty engines, the passages are the types of removable cylinder sleeves which can be replaceable.
Water-cooled engines contain passages in the engine block where cooling fluid circulates (the
water jacket
A water jacket is a water-filled casing surrounding a device, typically a metal sheath having intake and outlet vents to allow water to be pumped through and circulated. The flow of water to an external heating or cooling device allows precise t ...
). Some small engines are air-cooled, and instead of having a water jacket the cylinder block has fins protruding away from it to cool the engine by directly transferring heat to the air. The cylinder walls are usually finished by
honing to obtain a cross hatch, which is able to retain more oil. A too rough surface would quickly harm the engine by excessive wear on the piston.
The
piston
A piston is a component of reciprocating engines, reciprocating pumps, gas compressors, hydraulic cylinders and pneumatic cylinders, among other similar mechanisms. It is the moving component that is contained by a cylinder and is made gas-tig ...
s are short cylindrical parts which seal one end of the cylinder from the high pressure of the compressed air and combustion products and slide continuously within it while the engine is in operation. In smaller engines, the pistons are made of aluminum; while in larger applications, they are typically made of cast iron.
The top wall of the piston is termed its ''crown'' and is typically flat or concave. Some two-stroke engines use pistons with a
deflector head. Pistons are open at the bottom and hollow except for an integral reinforcement structure (the piston web). When an engine is working, the gas pressure in the combustion chamber exerts a force on the piston crown which is transferred through its web to a
gudgeon pin
In internal combustion engines, the gudgeon pin (UK, wrist pin or piston pin US) connects the piston to the connecting rod, and provides a bearing for the connecting rod to pivot upon as the piston moves.Nunney, Malcolm James (2007) "The Reciproc ...
. Each piston has
rings
Ring may refer to:
* Ring (jewellery), a round band, usually made of metal, worn as ornamental jewelry
* To make a sound with a bell, and the sound made by a bell
:(hence) to initiate a telephone connection
Arts, entertainment and media Film and ...
fitted around its circumference that mostly prevent the gases from leaking into the crankcase or the oil into the combustion chamber.
A
ventilation system drives the small amount of gas that escapes past the pistons during normal operation (the blow-by gases) out of the crankcase so that it does not accumulate contaminating the oil and creating corrosion.
In two-stroke gasoline engines the crankcase is part of the airâfuel path and due to the continuous flow of it, two-stroke engines do not need a separate crankcase ventilation system.
![Diesel engine valve train](https://upload.wikimedia.org/wikipedia/commons/4/4e/Diesel_engine_valve_train.JPG)
The
cylinder head
In an internal combustion engine, the cylinder head (often abbreviated to simply "head") sits above the cylinders and forms the roof of the combustion chamber.
In sidevalve engines, the head is a simple sheet of metal; whereas in more modern ov ...
is attached to the engine block by numerous
bolts or
studs. It has several functions. The cylinder head seals the cylinders on the side opposite to the pistons; it contains short ducts (the ''ports'') for intake and exhaust and the associated intake
valves
A valve is a device or natural object that regulates, directs or controls the flow of a fluid (gases, liquids, fluidized solids, or slurries) by opening, closing, or partially obstructing various passageways. Valves are technically fittings ...
that open to let the cylinder be filled with fresh air and exhaust valves that open to allow the combustion gases to escape. However, 2-stroke crankcase scavenged engines connect the gas ports directly to the cylinder wall without poppet valves; the piston controls their opening and occlusion instead. The cylinder head also holds the
spark plug
A spark plug (sometimes, in British English, a sparking plug, and, colloquially, a plug) is a device for delivering electric current from an ignition system to the combustion chamber of a spark-ignition engine to ignite the compressed fuel/air ...
in the case of spark ignition engines and the
injector
An injector is a system of ducting and nozzles used to direct the flow of a high-pressure fluid in such a way that a lower pressure fluid is entrained in the jet and carried through a duct to a region of higher pressure. It is a fluid-dynamic ...
for engines that use direct injection. All CI (compression ignition) engines use fuel injection, usually direct injection but some engines instead use
indirect injection
Indirect injection in an internal combustion engine is fuel injection where fuel is not directly injected into the combustion chamber.
Gasoline engines equipped with indirect injection systems, wherein a fuel injector delivers the fuel at some po ...
. SI (spark ignition) engines can use a
carburetor
A carburetor (also spelled carburettor) is a device used by an internal combustion engine to control and mix air and fuel entering the engine. The primary method of adding fuel to the intake air is through the venturi tube in the main meteri ...
or fuel injection as port injection or
direct injection. Most SI engines have a single spark plug per cylinder but
some have 2. A
head gasket
In an internal combustion engine, a head gasket provides the seal between the engine block and cylinder head(s).
Its purpose is to seal the combustion gases within the cylinders and to avoid coolant or engine oil leaking into the cylinders. Leak ...
prevents the gas from leaking between the cylinder head and the engine block. The opening and closing of the valves is controlled by one or several
camshaft
A camshaft is a shaft that contains a row of pointed cams, in order to convert rotational motion to reciprocating motion. Camshafts are used in piston engines (to operate the intake and exhaust valves), mechanically controlled ignition systems ...
s and springsâor in some enginesâa
desmodromic mechanism that uses no springs. The camshaft may press directly the stem of the valve or may act upon a
rocker arm
In the context of an internal combustion engine, a rocker arm is a valvetrain component that typically transfers the motion of a pushrod to the corresponding intake/exhaust valve.
Rocker arms in automobiles are typically made from stamped steel ...
, again, either directly or through a
pushrod
A valvetrain or valve train is a mechanical system that controls the operation of the intake and exhaust valves in an internal combustion engine. The intake valves control the flow of air/fuel mixture (or air alone for direct-injected engines) ...
.
![18XER engine block](https://upload.wikimedia.org/wikipedia/commons/3/30/18XER_engine_block.jpg)
The crankcase is sealed at the bottom with a
sump
A sump is a low space that collects often undesirable liquids such as water or chemicals. A sump can also be an infiltration basin used to manage surface runoff water and recharge underground aquifers. Sump can also refer to an area in a cave ...
that collects the falling oil during normal operation to be cycled again. The cavity created between the cylinder block and the sump houses a
crankshaft
A crankshaft is a mechanical component used in a piston engine to convert the reciprocating motion into rotational motion. The crankshaft is a rotating shaft containing one or more crankpins, that are driven by the pistons via the connecting ...
that converts the reciprocating motion of the pistons to rotational motion. The crankshaft is held in place relative to the engine block by
main bearing
Main may refer to:
Geography
* Main River (disambiguation)
**Most commonly the Main (river) in Germany
* Main, Iran, a village in Fars Province
*"Spanish Main", the Caribbean coasts of mainland Spanish territories in the 16th and 17th centuries
...
s, which allow it to rotate. Bulkheads in the crankcase form a half of every main bearing; the other half is a detachable cap. In some cases a single ''main bearing deck'' is used rather than several smaller caps. A
connecting rod
A connecting rod, also called a 'con rod', is the part of a piston engine which connects the piston to the crankshaft. Together with the crank, the connecting rod converts the reciprocating motion of the piston into the rotation of the cranksh ...
is connected to offset sections of the crankshaft (the
crankpin
A crankpin or crank pin, also known as a rod bearing journal, is a mechanical device in an engine which connects the crankshaft to the connecting rod for each cylinder. It has a cylindrical surface, to allow the crankpin to rotate relative to the ...
s) in one end and to the piston in the other end through the gudgeon pin and thus transfers the force and translates the reciprocating motion of the pistons to the circular motion of the crankshaft. The end of the connecting rod attached to the gudgeon pin is called its small end, and the other end, where it is connected to the crankshaft, the big end. The big end has a detachable half to allow assembly around the crankshaft. It is kept together to the connecting rod by removable bolts.
The cylinder head has an
intake manifold
In automotive engineering, an inlet manifold or intake manifold (in American English) is the part of an engine that supplies the fuel/air mixture to the cylinders. The word ''manifold'' comes from the Old English word ''manigfeald'' (from the ...
and an
exhaust manifold
In automotive engineering, an exhaust manifold collects the exhaust gases from multiple cylinders into one pipe. The word ''manifold'' comes from the Old English word ''manigfeald'' (from the Anglo-Saxon ''manig'' anyand ''feald'' old and refe ...
attached to the corresponding ports. The intake manifold connects to the
air filter
A particulate air filter is a device composed of fibrous, or porous materials which removes solid particulates such as dust, pollen, mold, and bacteria from the air. Filters containing an adsorbent or catalyst such as charcoal (carbon) may als ...
directly, or to a carburetor when one is present, which is then connected to the
air filter
A particulate air filter is a device composed of fibrous, or porous materials which removes solid particulates such as dust, pollen, mold, and bacteria from the air. Filters containing an adsorbent or catalyst such as charcoal (carbon) may als ...
. It distributes the air incoming from these devices to the individual cylinders. The exhaust manifold is the first component in the
exhaust system
An exhaust system is used to guide reaction exhaust gases away from a controlled combustion inside an engine or stove. The entire system conveys burnt gases from the engine and includes one or more exhaust pipes. Depending on the overall system ...
. It collects the exhaust gases from the cylinders and drives it to the following component in the path. The
exhaust system
An exhaust system is used to guide reaction exhaust gases away from a controlled combustion inside an engine or stove. The entire system conveys burnt gases from the engine and includes one or more exhaust pipes. Depending on the overall system ...
of an ICE may also include a
catalytic converter
A catalytic converter is an exhaust emission control device that converts toxic gases and pollutants in exhaust gas from an internal combustion engine into less-toxic pollutants by catalyzing a redox reaction. Catalytic converters are usually ...
and
muffler
A muffler (North American and Australian English) or silencer (British English) is a device for reducing the noise emitted by the exhaust of an internal combustion engineâespecially a noise-deadening device forming part of the exhaust sys ...
. The final section in the path of the exhaust gases is the
tailpipe
An exhaust system is used to guide reaction exhaust gases away from a controlled combustion inside an engine or stove. The entire system conveys burnt gases from the engine and includes one or more exhaust pipes. Depending on the overall system ...
.
4-stroke engines
![4StrokeEngine Ortho 3D Small](https://upload.wikimedia.org/wikipedia/commons/d/dc/4StrokeEngine_Ortho_3D_Small.gif)
The ''top dead center'' (TDC) of a piston is the position where it is nearest to the valves; ''bottom dead center'' (BDC) is the opposite position where it is furthest from them. A ''stroke'' is the movement of a piston from TDC to BDC or vice versa, together with the associated process. While an engine is in operation, the crankshaft rotates continuously at a nearly constant
speed
In everyday use and in kinematics, the speed (commonly referred to as ''v'') of an object is the magnitude of the change of its position over time or the magnitude of the change of its position per unit of time; it is thus a scalar quanti ...
. In a 4-stroke ICE, each piston experiences 2 strokes per crankshaft revolution in the following order. Starting the description at TDC, these are:
# Intake, induction or suction: The intake valves are open as a result of the cam lobe pressing down on the valve stem. The piston moves downward increasing the volume of the combustion chamber and allowing air to enter in the case of a CI engine or an air-fuel mix in the case of SI engines that do not use
direct injection. The air or air-fuel mixture is called the ''charge'' in any case.
# Compression: In this stroke, both valves are closed and the piston moves upward reducing the combustion chamber volume which reaches its minimum when the piston is at TDC. The piston performs
work
Work may refer to:
* Work (human activity), intentional activity people perform to support themselves, others, or the community
** Manual labour, physical work done by humans
** House work, housework, or homemaking
** Working animal, an animal tr ...
on the charge as it is being compressed; as a result, its pressure, temperature and density increase; an approximation to this behavior is provided by the
ideal gas law
The ideal gas law, also called the general gas equation, is the equation of state of a hypothetical ideal gas. It is a good approximation of the behavior of many gases under many conditions, although it has several limitations. It was first stat ...
. Just before the piston reaches TDC, ignition begins. In the case of a SI engine, the spark plug receives a high voltage pulse that generates the spark which gives it its name and ignites the charge. In the case of a CI engine, the fuel injector quickly injects fuel into the combustion chamber as a spray; the fuel ignites due to the high temperature.
# Power or working stroke: The pressure of the combustion gases pushes the piston downward, generating more
kinetic energy
In physics, the kinetic energy of an object is the energy that it possesses due to its motion.
It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its accele ...
than is required to compress the charge. Complementary to the compression stroke, the combustion gases expand and as a result their temperature, pressure and density decreases. When the piston is near to BDC the exhaust valve opens. The combustion gases expand
irreversibly due to the leftover pressureâin excess of
back pressure
Back pressure (or backpressure) is a resistance or force opposing the desired flow of fluid through pipes, leading to friction loss and pressure drop. The term ''back pressure'' is a misnomer, as pressure is a scalar quantity, so it has a magnitu ...
, the gauge pressure on the exhaust portâ; this is called the ''blowdown''.
# Exhaust: The exhaust valve remains open while the piston moves upward expelling the combustion gases. For naturally aspirated engines a small part of the combustion gases may remain in the cylinder during normal operation because the piston does not close the combustion chamber completely; these gases dissolve in the next charge. At the end of this stroke, the exhaust valve closes, the intake valve opens, and the sequence repeats in the next cycle. The intake valve may open before the exhaust valve closes to allow better scavenging.
2-stroke engines
The defining characteristic of this kind of engine is that each piston completes a cycle every crankshaft revolution. The 4 processes of intake, compression, power and exhaust take place in only 2 strokes so that it is not possible to dedicate a stroke exclusively for each of them. Starting at TDC the cycle consists of:
# Power: While the piston is descending the combustion gases perform work on it, as in a 4-stroke engine. The same
thermodynamic
Thermodynamics is a branch of physics that deals with heat, work, and temperature, and their relation to energy, entropy, and the physical properties of matter and radiation. The behavior of these quantities is governed by the four laws of ther ...
considerations about the expansion apply.
# Scavenging: Around 75° of crankshaft rotation before BDC the exhaust valve or port opens, and blowdown occurs. Shortly thereafter the intake valve or transfer port opens. The incoming charge displaces the remaining combustion gases to the exhaust system and a part of the charge may enter the exhaust system as well. The piston reaches BDC and reverses direction. After the piston has traveled a short distance upwards into the cylinder the exhaust valve or port closes; shortly the intake valve or transfer port closes as well.
# Compression: With both intake and exhaust closed the piston continues moving upwards compressing the charge and performing work on it. As in the case of a 4-stroke engine, ignition starts just before the piston reaches TDC and the same consideration on the thermodynamics of the compression on the charge apply.
While a 4-stroke engine uses the piston as a
positive displacement pump
A pump is a device that moves fluids (liquids or gases), or sometimes slurries, by mechanical action, typically converted from electrical energy into hydraulic energy. Pumps can be classified into three major groups according to the method they u ...
to accomplish scavenging taking 2 of the 4 strokes, a 2-stroke engine uses the last part of the power stroke and the first part of the compression stroke for combined intake and exhaust. The work required to displace the charge and exhaust gases comes from either the crankcase or a separate blower. For scavenging, expulsion of burned gas and entry of fresh mix, two main approaches are described: Loop scavenging, and Uniflow scavenging. SAE news published in the 2010s that 'Loop Scavenging' is better under any circumstance than Uniflow Scavenging.
Crankcase scavenged
![Two-Stroke Engine](https://upload.wikimedia.org/wikipedia/commons/3/33/Two-Stroke_Engine.gif)
Some SI engines are crankcase scavenged and do not use poppet valves. Instead, the crankcase and the part of the cylinder below the piston is used as a pump. The intake port is connected to the crankcase through a
reed valve
Reed valves are a type of check valve which restrict the flow of fluids to a single direction, opening and closing under changing pressure on each face. Modern versions often consist of flexible metal or composite materials (fiberglass or carbon f ...
or a rotary disk valve driven by the engine. For each cylinder, a transfer port connects in one end to the crankcase and in the other end to the cylinder wall. The exhaust port is connected directly to the cylinder wall. The transfer and exhaust port are opened and closed by the piston. The reed valve opens when the crankcase pressure is slightly below intake pressure, to let it be filled with a new charge; this happens when the piston is moving upwards. When the piston is moving downwards the pressure in the crankcase increases and the reed valve closes promptly, then the charge in the crankcase is compressed. When the piston is moving downwards, it also uncovers the exhaust port and the transfer port and the higher pressure of the charge in the crankcase makes it enter the cylinder through the transfer port, blowing the exhaust gases. Lubrication is accomplished by adding ''
2-stroke oil
Two-stroke oil (also referred to as two-cycle oil, 2-cycle oil, 2T oil, or 2-stroke oil) is a special type of motor oil intended for use in crankcase compression two-stroke engines, typical of small gasoline-powered engines.
Use
Unlike a four- ...
'' to the fuel in small ratios. ''
Petroil'' refers to the mix of gasoline with the aforesaid oil. This kind of 2-stroke engine has a lower efficiency than comparable 4-strokes engines and releases more polluting
exhaust gases
Exhaust gas or flue gas is emitted as a result of the combustion of fuels such as natural gas, gasoline, gasoline (petrol), diesel fuel, fuel oil, biodiesel blends, or coal. According to the type of engine, it is discharged into the atmosphere th ...
for the following conditions:
* They use a ''
total-loss lubrication system'': all the lubricating oil is eventually burned along with the fuel.
* There are conflicting requirements for scavenging: On one side, enough fresh charge needs to be introduced in each cycle to displace almost all the combustion gases but introducing too much of it means that a part of it gets in the exhaust.
* They must use the transfer port(s) as a carefully designed and placed nozzle so that a gas current is created in a way that it sweeps the whole cylinder before reaching the exhaust port so as to expel the combustion gases, but minimize the amount of charge exhausted. 4-stroke engines have the benefit of forcibly expelling almost all of the combustion gases because during exhaust the combustion chamber is reduced to its minimum volume. In crankcase scavenged 2-stroke engines, exhaust and intake are performed mostly simultaneously and with the combustion chamber at its maximum volume.
The main advantage of 2-stroke engines of this type is mechanical simplicity and a higher
power-to-weight ratio
Power-to-weight ratio (PWR, also called specific power, or power-to-mass ratio) is a calculation commonly applied to engines and mobile power sources to enable the comparison of one unit or design to another. Power-to-weight ratio is a measuremen ...
than their 4-stroke counterparts. Despite having twice as many power strokes per cycle, less than twice the power of a comparable 4-stroke engine is attainable in practice.
In the US, 2-stroke engines were banned for road vehicles due to the pollution. Off-road only motorcycles are still often 2-stroke but are rarely road legal. However, many thousands of 2-stroke lawn maintenance engines are in use.
Blower scavenged
![Diesel engine uniflow](https://upload.wikimedia.org/wikipedia/commons/f/f7/Diesel_engine_uniflow.svg)
Using a separate blower avoids many of the shortcomings of crankcase scavenging, at the expense of increased complexity which means a higher cost and an increase in maintenance requirement. An engine of this type uses ports or valves for intake and valves for exhaust, except
opposed piston engine
An opposed-piston engine is a piston engine in which each cylinder has a piston at both ends, and no cylinder head. Petrol and diesel opposed-piston engines have been used mostly in large-scale applications such as ships, military tanks, and f ...
s, which may also use ports for exhaust. The blower is usually of the
Roots-type but other types have been used too. This design is commonplace in CI engines, and has been occasionally used in SI engines.
CI engines that use a blower typically use ''
uniflow scavenging
A two-stroke (or two-stroke cycle) engine is a type of internal combustion engine that completes a power cycle with two strokes (up and down movements) of the piston during one power cycle, this power cycle being completed in one revolution of ...
''. In this design the cylinder wall contains several intake ports placed uniformly spaced along the circumference just above the position that the piston crown reaches when at BDC. An exhaust valve or several like that of 4-stroke engines is used. The final part of the intake manifold is an air sleeve that feeds the intake ports. The intake ports are placed at a horizontal angle to the cylinder wall (I.e: they are in plane of the piston crown) to give a swirl to the incoming charge to improve combustion. The largest reciprocating IC are low speed CI engines of this type; they are used for marine propulsion (see
marine diesel engine
Marine propulsion is the mechanism or system used to generate thrust to move a watercraft through water. While paddles and sails are still used on some smaller boats, most modern ships are propelled by mechanical systems consisting of an electr ...
) or
electric power generation
Electricity generation is the process of generating electric power from sources of primary energy. For utilities in the electric power industry, it is the stage prior to its delivery (transmission, distribution, etc.) to end users or its storag ...
and achieve the highest thermal efficiencies among internal combustion engines of any kind. Some Diesel-electric
locomotive engine
A locomotive or engine is a rail transport vehicle that provides the motive power for a train. If a locomotive is capable of carrying a payload, it is usually rather referred to as a multiple unit, motor coach, railcar or power car; the us ...
s operate on the 2-stroke cycle. The most powerful of them have a brake power of around 4.5
MW or 6,000
HP. The
EMD SD90MAC
The EMD SD90MAC is a model of C-C diesel-electric locomotive produced by General Motors Electro-Motive Division. It is, with the SD80MAC, one of the largest single-engined locomotives produced by EMD, surpassed only by the dual-engined DDA4 ...
class of locomotives are an example of such. The comparable class
GE AC6000CW
The AC6000CW is a diesel electric locomotive built between 1995 and 2001 by GE Transportation. It is among the world's most powerful single-engined diesel locomotives. The locomotive was designed for extremely high horsepower needs, such as pull ...
whose prime mover has almost the same brake power uses a 4-stroke engine.
An example of this type of engine is the
WÀrtsilÀ-Sulzer RT-flex96-C turbocharged 2-stroke Diesel, used in large container ships. It is the most efficient and powerful reciprocating internal combustion engine in the world with a
thermal efficiency
In thermodynamics, the thermal efficiency (\eta_) is a dimensionless performance measure of a device that uses thermal energy, such as an internal combustion engine, steam turbine, steam engine, boiler, furnace, refrigerator, ACs etc.
For a he ...
over 50%. For comparison, the most efficient small four-stroke engines are around 43% thermally-efficient (SAE 900648); size is an advantage for efficiency due to the increase in the ratio of volume to surface area.
See the
external links
An internal link is a type of hyperlink on a web page to another page or resource, such as an image or document, on the same website or domain.
Hyperlinks are considered either "external" or "internal" depending on their target or destination ...
for an in-cylinder combustion video in a 2-stroke, optically accessible motorcycle engine.
Historical design
Dugald Clerk
Sir Dugald Clerk (sometimes written as Dugald Clark) KBE, LLD FRS (1854, Glasgow â 1932, Ewhurst, Surrey) was a Scottish engineer who designed the world's first successful two-stroke engine
in 1878 and patented it in England in 1881. He wa ...
developed the first two-cycle engine in 1879. It used a separate cylinder which functioned as a pump in order to transfer the fuel mixture to the cylinder.
In 1899
John Day simplified Clerk's design into the type of 2 cycle engine that is very widely used today.
Day cycle engines are crankcase scavenged and port timed. The crankcase and the part of the cylinder below the exhaust port is used as a pump. The operation of the Day cycle engine begins when the crankshaft is turned so that the piston moves from BDC upward (toward the head) creating a vacuum in the crankcase/cylinder area. The carburetor then feeds the fuel mixture into the crankcase through a
reed valve
Reed valves are a type of check valve which restrict the flow of fluids to a single direction, opening and closing under changing pressure on each face. Modern versions often consist of flexible metal or composite materials (fiberglass or carbon f ...
or a rotary disk valve (driven by the engine). There are cast in ducts from the crankcase to the port in the cylinder to provide for intake and another from the exhaust port to the exhaust pipe. The height of the port in relationship to the length of the cylinder is called the "port timing".
On the first upstroke of the engine there would be no fuel inducted into the cylinder as the crankcase was empty. On the downstroke, the piston now compresses the fuel mix, which has lubricated the piston in the cylinder and the bearings due to the fuel mix having oil added to it. As the piston moves downward it first uncovers the exhaust, but on the first stroke there is no burnt fuel to exhaust. As the piston moves downward further, it uncovers the intake port which has a duct that runs to the crankcase. Since the fuel mix in the crankcase is under pressure, the mix moves through the duct and into the cylinder.
Because there is no obstruction in the cylinder of the fuel to move directly out of the exhaust port prior to the piston rising far enough to close the port, early engines used a high domed piston to slow down the flow of fuel. Later the fuel was "resonated" back into the cylinder using an expansion chamber design. When the piston rose close to TDC, a spark ignited the fuel. As the piston is driven downward with power, it first uncovers the exhaust port where the burned fuel is expelled under high pressure and then the intake port where the process has been completed and will keep repeating.
Later engines used a type of porting devised by the Deutz company to improve performance. It was called the
Schnurle Reverse Flow system. DKW licensed this design for all their motorcycles. Their
DKW RT 125
The RT 125 was a German two-stroke motorcycle made by DKW in Zschopau in the 1930s, IFA and MZ in the 1950s and early 1960s, and DKW in Ingolstadt in the 1950s and 1960s. "RT" stands for "Reichstyp" or "National Model".
In the 1930s DKW pio ...
was one of the first motor vehicles to achieve over 100 mpg as a result.
Ignition
Internal combustion engines require ignition of the mixture, either by
spark ignition (SI) or
compression ignition (CI). Before the invention of reliable electrical methods, hot tube and flame methods were used. Experimental engines with
laser ignition Laser ignition is an alternative method for igniting mixtures of fuel and oxidiser. The phase of the mixture can be gaseous or liquid. The method is based on laser ignition devices that produce short but powerful flashes regardless of the pressure i ...
have been built.
Spark ignition process
![Point Ignition](https://upload.wikimedia.org/wikipedia/commons/6/67/Point_Ignition.JPG)
The spark-ignition engine was a refinement of the early engines which used Hot Tube ignition. When Bosch developed the
magneto
A magneto is an electrical generator that uses permanent magnets to produce periodic pulses of alternating current. Unlike a dynamo, a magneto does not contain a commutator to produce direct current. It is categorized as a form of alternator, ...
it became the primary system for producing electricity to energize a spark plug. Many small engines still use magneto ignition. Small engines are started by hand cranking using a
recoil start
Rope start (also called pull start or ''rewind start'') is a method of starting an internal combustion engine, usually on small machines, such as lawn mowers, chainsaws, ultralight aircraft, small outboard motors and portable engine-generators. Al ...
er or hand crank. Prior to
Charles F. Kettering
Charles Franklin Kettering (August 29, 1876 â November 25, 1958) sometimes known as Charles Fredrick Kettering was an American inventor, engineer, businessman, and the holder of 186 patents.
For the list of patents issued to Kettering, see, Le ...
of Delco's development of the automotive starter all gasoline engined automobiles used a hand crank.
Larger engines typically power their
starting motors and
ignition system
An ignition system generates a spark or heats an electrode to a high temperature to ignite a fuel-air mixture in spark ignition internal combustion engines, oil-fired and gas-fired boilers, rocket engines, etc. The widest application for spark ig ...
s using the electrical energy stored in a
leadâacid battery
The leadâacid battery is a type of rechargeable battery first invented in 1859 by French physicist Gaston PlantĂ©. It is the first type of rechargeable battery ever created. Compared to modern rechargeable batteries, leadâacid batteries have ...
. The battery's charged state is maintained by an
automotive alternator
An alternator is a type of electric generator used in modern automobiles to charge the battery and to power the electrical system when its engine is running.
Until the 1960s, automobiles used DC dynamo generators with commutators. As silicon-d ...
or (previously) a generator which uses engine power to create electrical energy storage.
The battery supplies electrical power for starting when the engine has a
starting motor system, and supplies electrical power when the engine is off. The battery also supplies electrical power during rare run conditions where the alternator cannot maintain more than 13.8 volts (for a common 12V automotive electrical system). As alternator voltage falls below 13.8 volts, the lead-acid storage battery increasingly picks up electrical load. During virtually all running conditions, including normal idle conditions, the alternator supplies primary electrical power.
Some systems disable alternator field (rotor) power during wide-open throttle conditions. Disabling the field reduces alternator pulley mechanical loading to nearly zero, maximizing crankshaft power. In this case, the battery supplies all primary electrical power.
Gasoline engines take in a mixture of air and gasoline and compress it by the movement of the piston from bottom dead center to top dead center when the fuel is at maximum compression. The reduction in the size of the swept area of the cylinder and taking into account the volume of the combustion chamber is described by a ratio. Early engines had
compression ratio
The compression ratio is the ratio between the volume of the cylinder and combustion chamber in an internal combustion engine at their maximum and minimum values.
A fundamental specification for such engines, it is measured two ways: the stati ...
s of 6 to 1. As compression ratios were increased, the efficiency of the engine increased as well.
With early induction and ignition systems the compression ratios had to be kept low. With advances in fuel technology and combustion management, high-performance engines can run reliably at 12:1 ratio. With low octane fuel, a problem would occur as the compression ratio increased as the fuel was igniting due to the rise in temperature that resulted.
Charles Kettering
Charles Franklin Kettering (August 29, 1876 â November 25, 1958) sometimes known as Charles Fredrick Kettering was an American inventor, engineer, businessman, and the holder of 186 patents.
For the list of patents issued to Kettering, see, Le ...
developed a
lead additive which allowed higher compression ratios, which was progressively
abandoned for automotive use from the 1970s onward, partly due to
lead poisoning
Lead poisoning, also known as plumbism and saturnism, is a type of metal poisoning caused by lead in the body. The brain is the most sensitive. Symptoms may include abdominal pain, constipation, headaches, irritability, memory problems, inferti ...
concerns.
The fuel mixture is ignited at different progressions of the piston in the cylinder. At low rpm, the spark is timed to occur close to the piston achieving top dead center. In order to produce more power, as rpm rises the spark is advanced sooner during piston movement. The spark occurs while the fuel is still being compressed progressively more as rpm rises.
The necessary high voltage, typically 10,000 volts, is supplied by an
induction coil
An induction coil or "spark coil" (archaically known as an inductorium or Ruhmkorff coil after Heinrich RĂŒhmkorff) is a type of electrical transformer used to produce high-voltage pulses from a low-voltage direct current (DC) supply. p.98 To ...
or transformer. The induction coil is a fly-back system, using interruption of electrical primary system current through some type of synchronized interrupter. The interrupter can be either contact points or a power transistor. The problem with this type of ignition is that as RPM increases the availability of electrical energy decreases. This is especially a problem, since the amount of energy needed to ignite a more dense fuel mixture is higher. The result was often a high RPM misfire.
Capacitor discharge ignition
Capacitor discharge ignition (CDI) or thyristor ignition is a type of automotive electronic ignition system which is widely used in outboard motors, motorcycles, lawn mowers, chainsaws, small engines, turbine-powered aircraft, and some cars. It w ...
was developed. It produces a rising voltage that is sent to the spark plug. CD system voltages can reach 60,000 volts. CD ignitions use step-up
transformer
A transformer is a passive component that transfers electrical energy from one electrical circuit to another circuit, or multiple circuits. A varying current in any coil of the transformer produces a varying magnetic flux in the transformer' ...
s. The step-up transformer uses energy stored in a capacitance to generate
electric spark
An electric spark is an abrupt electrical discharge that occurs when a sufficiently high electric field creates an ionized, electrically conductive channel through a normally-insulating medium, often air or other gases or gas mixtures. Michael F ...
. With either system, a mechanical or electrical control system provides a carefully timed high-voltage to the proper cylinder. This spark, via the spark plug, ignites the air-fuel mixture in the engine's cylinders.
While gasoline internal combustion engines are much easier to start in cold weather than diesel engines, they can still have cold weather starting problems under extreme conditions. For years, the solution was to park the car in heated areas. In some parts of the world, the oil was actually drained and heated overnight and returned to the engine for cold starts. In the early 1950s, the gasoline Gasifier unit was developed, where, on cold weather starts, raw gasoline was diverted to the unit where part of the fuel was burned causing the other part to become a hot vapor sent directly to the intake valve manifold. This unit was quite popular until electric
engine block heater
A block heater is used in cold climates to warm an engine prior to starting. They are mostly used for car engines; however they have also been used in aircraft engines.
The most common design of block heater is an electrical heating element embed ...
s became standard on gasoline engines sold in cold climates.
Compression ignition process
For ignition, diesel,
PPC
PPC may refer to:
Computing
* Personal programmable calculator, programmable calculators for personal use
* Pay-per-click, an internet advertising model
* PearPC, a PowerPC platform emulator
* Peercoin, a peer-to-peer cryptocurrency
* Periphera ...
and
HCCI Homogeneous Charge Compression Ignition (HCCI) is a form of internal combustion in which well-mixed fuel and oxidizer (typically air) are compressed to the point of auto-ignition. As in other forms of combustion, this exothermic reaction releases ...
engines rely solely on the high temperature and pressure created by the engine in its compression process. The compression level that occurs is usually twice or more than a gasoline engine. Diesel engines take in air only, and shortly before peak compression, spray a small quantity of diesel fuel into the cylinder via a fuel injector that allows the fuel to instantly ignite. HCCI type engines take in both air and fuel, but continue to rely on an unaided auto-combustion process, due to higher pressures and temperature. This is also why diesel and HCCI engines are more susceptible to cold-starting issues, although they run just as well in cold weather once started. Light duty diesel engines with
indirect injection
Indirect injection in an internal combustion engine is fuel injection where fuel is not directly injected into the combustion chamber.
Gasoline engines equipped with indirect injection systems, wherein a fuel injector delivers the fuel at some po ...
in automobiles and light trucks employ
glowplug
A glowplug (alternatively spelled as glow plug or glow-plug) is a heating device used to aid in starting diesel engines. In cold weather, high-speed diesel engines can be difficult to start because the mass of the cylinder block and cylinder he ...
s (or other pre-heating: see
Cummins ISB#6BT) that pre-heat the
combustion chamber
A combustion chamber is part of an internal combustion engine in which the fuel/air mix is burned. For steam engines, the term has also been used for an extension of the firebox which is used to allow a more complete combustion process.
Interna ...
just before starting to reduce no-start conditions in cold weather. Most diesels also have a battery and charging system; nevertheless, this system is secondary and is added by manufacturers as a luxury for the ease of starting, turning fuel on and off (which can also be done via a switch or mechanical apparatus), and for running auxiliary electrical components and accessories. Most new engines rely on electrical and electronic
engine control unit
An engine control unit (ECU), also commonly called an engine control module (ECM), is a type of electronic control unit that controls a series of actuators on an internal combustion engine to ensure optimal engine performance. It does this by re ...
s (ECU) that also adjust the combustion process to increase efficiency and reduce emissions.
Lubrication
![Overhead cam engine with forced oil lubrication (Autocar Handbook, 13th ed, 1935)](https://upload.wikimedia.org/wikipedia/commons/0/07/Overhead_cam_engine_with_forced_oil_lubrication_%28Autocar_Handbook%2C_13th_ed%2C_1935%29.jpg)
Surfaces in contact and relative motion to other surfaces require
lubrication
Lubrication is the process or technique of using a lubricant to reduce friction and wear and tear in a contact between two surfaces. The study of lubrication is a discipline in the field of tribology.
Lubrication mechanisms such as fluid-lubric ...
to reduce wear, noise and increase efficiency by reducing the power wasting in overcoming
friction
Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. There are several types of friction:
*Dry friction is a force that opposes the relative lateral motion of t ...
, or to make the mechanism work at all. Also, the lubricant used can reduce excess heat and provide additional cooling to components. At the very least, an engine requires lubrication in the following parts:
* Between pistons and cylinders
* Small bearings
* Big end bearings
* Main bearings
* Valve gear (The following elements may not be present):
** Tappets
** Rocker arms
** Pushrods
** Timing chain or gears. Toothed belts do not require lubrication.
In 2-stroke crankcase scavenged engines, the interior of the crankcase, and therefore the crankshaft, connecting rod and bottom of the pistons are sprayed by the
2-stroke oil
Two-stroke oil (also referred to as two-cycle oil, 2-cycle oil, 2T oil, or 2-stroke oil) is a special type of motor oil intended for use in crankcase compression two-stroke engines, typical of small gasoline-powered engines.
Use
Unlike a four- ...
in the air-fuel-oil mixture which is then burned along with the fuel. The valve train may be contained in a compartment flooded with lubricant so that no
oil pump is required.
In a ''splash lubrication system'' no oil pump is used. Instead the crankshaft dips into the oil in the sump and due to its high speed, it splashes the crankshaft, connecting rods and bottom of the pistons. The connecting rod big end caps may have an attached scoop to enhance this effect. The valve train may also be sealed in a flooded compartment, or open to the crankshaft in a way that it receives splashed oil and allows it to drain back to the sump. Splash lubrication is common for small 4-stroke engines.
In a ''forced'' (also called ''pressurized'') ''lubrication system'', lubrication is accomplished in a closed-loop which carries
motor oil
Motor oil, engine oil, or engine lubricant is any one of various substances used for the lubrication of internal combustion engines. They typically consist of base oils enhanced with various additives, particularly antiwear additives, deterg ...
to the surfaces serviced by the system and then returns the oil to a reservoir. The auxiliary equipment of an engine is typically not serviced by this loop; for instance, an
alternator
An alternator is an electrical generator that converts mechanical energy to electrical energy in the form of alternating current. For reasons of cost and simplicity, most alternators use a rotating magnetic field with a stationary armature.Go ...
may use
ball bearings
A ball bearing is a type of rolling-element bearing that uses balls to maintain the separation between the bearing races.
The purpose of a ball bearing is to reduce rotational friction and support radial and axial loads. It achieves this ...
sealed with their own lubricant. The reservoir for the oil is usually the sump, and when this is the case, it is called a ''
wet sump
Within piston engines, a wet sump is part of a lubrication system whereby the crankcase sump is used as an integral oil reservoir. An alternative system is the dry sump, whereby oil is pumped from a shallow sump into an external reservoir.Wet sum ...
'' system. When there is a different oil reservoir the crankcase still catches it, but it is continuously drained by a dedicated pump; this is called a ''
dry sump
A dry-sump system is a method to manage the lubricating motor oil in four-stroke and large two-stroke piston driven internal combustion engines. The dry-sump system uses two or more oil pumps and a separate oil reservoir, as opposed to a conve ...
'' system.
On its bottom, the sump contains an oil intake covered by a mesh filter which is connected to an oil pump then to an
oil filter
An oil filter is a filter designed to remove contaminants from engine oil, transmission oil, lubricating oil, or hydraulic oil. Their chief use is in internal-combustion engines for motor vehicles (both on- and off-road ), powered aircraft, r ...
outside the crankcase. From there it is diverted to the crankshaft main bearings and valve train. The crankcase contains at least one ''oil gallery'' (a conduit inside a crankcase wall) to which oil is introduced from the oil filter. The main bearings contain a groove through all or half its circumference; the oil enters these grooves from channels connected to the oil gallery. The crankshaft has drillings that take oil from these grooves and deliver it to the big end bearings. All big end bearings are lubricated this way. A single main bearing may provide oil for 0, 1 or 2 big end bearings. A similar system may be used to lubricate the piston, its gudgeon pin and the small end of its connecting rod; in this system, the connecting rod big end has a groove around the crankshaft and a drilling connected to the groove which distributes oil from there to the bottom of the piston and from then to the cylinder.
Other systems are also used to lubricate the cylinder and piston. The connecting rod may have a nozzle to throw an oil jet to the cylinder and bottom of the piston. That nozzle is in movement relative to the cylinder it lubricates, but always pointed towards it or the corresponding piston.
Typically forced lubrication systems have a lubricant flow higher than what is required to lubricate satisfactorily, in order to assist with cooling. Specifically, the lubricant system helps to move heat from the hot engine parts to the cooling liquid (in water-cooled engines) or fins (in air-cooled engines) which then transfer it to the environment. The lubricant must be designed to be chemically stable and maintain suitable viscosities within the temperature range it encounters in the engine.
Cylinder configuration
Common cylinder configurations include the
straight or inline configuration, the more compact
V configuration, and the wider but smoother
flat or boxer configuration.
Aircraft engine
An aircraft engine, often referred to as an aero engine, is the power component of an aircraft propulsion system. Most aircraft engines are either piston engines or gas turbines, although a few have been rocket powered and in recent years many ...
s can also adopt a
radial configuration, which allows more effective cooling. More unusual configurations such as the
H,
U,
X, and
W have also been used.
![Schemes](https://upload.wikimedia.org/wikipedia/commons/3/3c/Schemes.png)
Multiple cylinder engines have their valve train and crankshaft configured so that pistons are at different parts of their cycle. It is desirable to have the pistons' cycles uniformly spaced (this is called ''even firing'') especially in forced induction engines; this reduces torque pulsations and makes
inline engines with more than 3 cylinders statically
balanced
In telecommunications and professional audio, a balanced line or balanced signal pair is a circuit consisting of two conductors of the same type, both of which have equal impedances along their lengths and equal impedances to ground and to other ...
in its primary forces. However, some
engine configuration
The engine configuration describes the fundamental operating principles by which internal combustion engines are categorized.
Piston engines are often categorized by their cylinder layout, valves and camshafts. Wankel engines are often categorize ...
s require odd firing to achieve better balance than what is possible with even firing. For instance, a 4-stroke
I2 engine has better balance when the angle between the crankpins is 180° because the pistons move in opposite directions and inertial forces partially cancel, but this gives an odd firing pattern where one cylinder fires 180° of crankshaft rotation after the other, then no cylinder fires for 540°. With an even firing pattern, the pistons would move in unison and the associated forces would add.
Multiple crankshaft configurations do not necessarily need a
cylinder head
In an internal combustion engine, the cylinder head (often abbreviated to simply "head") sits above the cylinders and forms the roof of the combustion chamber.
In sidevalve engines, the head is a simple sheet of metal; whereas in more modern ov ...
at all because they can instead have a piston at each end of the cylinder called an
opposed piston
An opposed-piston engine is a piston engine in which each cylinder has a piston at both ends, and no cylinder head. Petrol and diesel opposed-piston engines have been used mostly in large-scale applications such as ships, military tanks, and ...
design. Because fuel inlets and outlets are positioned at opposed ends of the cylinder, one can achieve uniflow scavenging, which, as in the four-stroke engine is efficient over a wide range of engine speeds. Thermal efficiency is improved because of a lack of cylinder heads. This design was used in the
Junkers Jumo 205
The Jumo 205 aircraft engine was the most famous of a series of aircraft diesel engines produced by Junkers. The Jumo 204 first entered service in 1932. Later engines of this type comprised the experimental Jumo 206 and Jumo 208, with the Jumo ...
diesel aircraft engine, using two crankshafts at either end of a single bank of cylinders, and most remarkably in the
Napier Deltic
The Napier Deltic engine is a British opposed-piston valveless, supercharged uniflow scavenged, two-stroke diesel engine used in marine and locomotive applications, designed and produced by D. Napier & Son. Unusually, the cylinders were disp ...
diesel engines. These used three crankshafts to serve three banks of
double-ended cylinders arranged in an equilateral triangle with the crankshafts at the corners. It was also used in single-bank
locomotive engine
A locomotive or engine is a rail transport vehicle that provides the motive power for a train. If a locomotive is capable of carrying a payload, it is usually rather referred to as a multiple unit, motor coach, railcar or power car; the us ...
s, and is still used in
marine propulsion
Marine propulsion is the mechanism or system used to generate thrust to move a watercraft through water. While paddles and sails are still used on some smaller boats, most modern ships are propelled by mechanical systems consisting of an electr ...
engines and marine auxiliary generators.
Diesel cycle
![DieselCycle PV](https://upload.wikimedia.org/wikipedia/commons/6/65/DieselCycle_PV.svg)
Most truck and automotive diesel engines use a cycle reminiscent of a four-stroke cycle, but with temperature increase by compression causing ignition, rather than needing a separate ignition system. This variation is called the diesel cycle. In the diesel cycle, diesel fuel is injected directly into the cylinder so that combustion occurs at constant pressure, as the piston moves.
Otto cycle
The
Otto cycle
An Otto cycle is an idealized thermodynamic cycle that describes the functioning of a typical spark ignition piston engine. It is the thermodynamic cycle most commonly found in automobile engines.
The Otto cycle is a description of what happ ...
is the most common cycle for most cars' internal combustion engines that use gasoline as a fuel. It consists of the same major steps as described for the four-stroke engine: Intake, compression, ignition, expansion and exhaust.
Five-stroke engine
In 1879,
Nicolaus Otto
Nicolaus August Otto (10 June 1832, Holzhausen an der Haide, Nassau â 26 January 1891, Cologne) was a German engineer who successfully developed the compressed charge internal combustion engine which ran on petroleum gas and led to the mode ...
manufactured and sold a double expansion engine (the double and triple expansion principles had ample usage in steam engines), with two small cylinders at both sides of a low-pressure larger cylinder, where a second expansion of exhaust stroke gas took place; the owner returned it, alleging poor performance. In 1906, the concept was incorporated in a car built by EHV (
Eisenhuth Horseless Vehicle Company); and in the 21st century
Ilmor
Ilmor is a British independent high-performance motor racing engineering company. It was founded by Mario Illien and Paul Morgan in November 1983. With manufacturing based in Brixworth, Northamptonshire, and maintenance offices in Plymouth, Mic ...
designed and successfully tested a 5-stroke double expansion internal combustion engine, with high power output and low SFC (Specific Fuel Consumption).
Six-stroke engine
The
six-stroke engine The term six-stroke engine has been applied to a number of alternative internal combustion engine designs that attempt to improve on traditional two-stroke and four-stroke engines. Claimed advantages may include increased fuel efficiency, reduced m ...
was invented in 1883. Four kinds of six-stroke engines use a regular piston in a regular cylinder (Griffin six-stroke, Bajulaz six-stroke, Velozeta six-stroke and Crower six-stroke), firing every three crankshaft revolutions. These systems capture the waste heat of the
four-stroke
A four-stroke (also four-cycle) engine is an internal combustion (IC) engine in which the piston completes four separate strokes while turning the crankshaft. A stroke refers to the full travel of the piston along the cylinder, in either directio ...
Otto cycle with an injection of air or water.
The
Beare Head The Beare-head engine internal combustion engine technology combines a four-stroke engine bottom end and piston, with a ported cylinder head closely resembling that of a two-stroke engine. The head piston is smaller and moves at half cycling of the ...
and "piston charger" engines operate as
opposed-piston engine
An opposed-piston engine is a piston engine in which each cylinder has a piston at both ends, and no cylinder head. Petrol and diesel opposed-piston engines have been used mostly in large-scale applications such as ships, military tanks, and ...
s, two pistons in a single cylinder, firing every two revolutions rather than every four like a four-stroke engine.
Other cycles
The very first internal combustion engines did not compress the mixture. The first part of the piston downstroke drew in a fuel-air mixture, then the inlet valve closed and, in the remainder of the down-stroke, the fuel-air mixture fired. The exhaust valve opened for the piston upstroke. These attempts at imitating the principle of a
steam engine
A steam engine is a heat engine that performs mechanical work using steam as its working fluid. The steam engine uses the force produced by steam pressure to push a piston back and forth inside a cylinder. This pushing force can be trans ...
were very inefficient.
There are a number of variations of these cycles, most notably the
Atkinson Atkinson may refer to:
Places
*Atkinson, Nova Scotia, Canada
* Atkinson, Dominica, a village in Dominica
*Atkinson, Illinois, U.S.
* Atkinson, Indiana, U.S.
*Atkinson, Maine, U.S.
*Atkinson Lake, a lake in Minnesota, U.S.
*Atkinson, Nebraska, U. ...
and
Miller cycle
In engineering, the Miller cycle is a thermodynamic cycle used in a type of internal combustion engine. The Miller cycle was patented by Ralph Miller, an American engineer, dated Dec 24, 1957. The engine may be two- or four-stroke and may be r ...
s.
Split-cycle engines separate the four strokes of intake, compression, combustion and exhaust into two separate but paired cylinders. The first cylinder is used for intake and compression. The compressed air is then transferred through a crossover passage from the compression cylinder into the second cylinder, where combustion and exhaust occur. A split-cycle engine is really an
air compressor
An air compressor is a pneumatic device that converts power (using an electric motor, diesel or gasoline engine, etc.) into potential energy stored in pressurized air (i.e., compressed air). By one of several methods, an air compressor forces ...
on one side with a combustion chamber on the other.
Previous split-cycle engines have had two major problemsâpoor breathing (volumetric efficiency) and low thermal efficiency. However, new designs are being introduced that seek to address these problems.
The
Scuderi Engine
The Scuderi engine, formally called the Scuderi Split Cycle Engine, is a split cycle, internal combustion engine invented by Carmelo J. Scuderi (April 13, 1925 â October 16, 2002). Scuderi Group, an engineering and licensing company based ...
addresses the breathing problem by reducing the clearance between the piston and the cylinder head through various turbocharging techniques. The Scuderi design requires the use of outwardly opening valves that enable the piston to move very close to the cylinder head without the interference of the valves. Scuderi addresses the low thermal efficiency via firing after top dead center (ATDC).
Firing ATDC can be accomplished by using high-pressure air in the transfer passage to create sonic flow and high turbulence in the power cylinder.
The four-stroke crank-rocker engine with a curve cylinder was also invented to study its efficiency.
Combustion turbines
Jet engine
![Turbofan operation](https://upload.wikimedia.org/wikipedia/commons/7/75/Turbofan_operation.svg)
Jet engines use a number of rows of fan blades to compress air which then enters a
combustor
A combustor is a component or area of a gas turbine, ramjet, or scramjet engine where combustion takes place. It is also known as a burner, combustion chamber or flame holder. In a gas turbine engine, the ''combustor'' or combustion chamber is fed ...
where it is mixed with fuel (typically JP fuel) and then ignited. The burning of the fuel raises the temperature of the air which is then exhausted out of the engine creating thrust. A modern
turbofan
The turbofan or fanjet is a type of airbreathing jet engine that is widely used in aircraft engine, aircraft propulsion. The word "turbofan" is a portmanteau of "turbine" and "fan": the ''turbo'' portion refers to a gas turbine engine which ac ...
engine can operate at as high as 48% efficiency.
There are six sections to a turbofan engine:
* Fan
* Compressor
* Combustor
* Turbine
* Mixer
* Nozzle
Gas turbines
![Gas Turbine Power Plant](https://upload.wikimedia.org/wikipedia/commons/8/8a/Gas_Turbine_Power_Plant.JPG)
A gas turbine compresses air and uses it to turn a
turbine
A turbine ( or ) (from the Greek , ''tyrbÄ'', or Latin ''turbo'', meaning vortex) is a rotary mechanical device that extracts energy from a fluid flow and converts it into useful work. The work produced by a turbine can be used for generating e ...
. It is essentially a jet engine which directs its output to a shaft. There are three stages to a turbine: 1) air is drawn through a compressor where the temperature rises due to compression, 2) fuel is added in the
combuster
A combustor is a component or area of a gas turbine, ramjet, or scramjet engine where combustion takes place. It is also known as a burner, combustion chamber or flame holder. In a gas turbine engine, the ''combustor'' or combustion chamber is fed ...
, and 3) hot air is exhausted through turbine blades which rotate a shaft connected to the compressor.
A gas turbine is a rotary machine similar in principle to a
steam turbine
A steam turbine is a machine that extracts thermal energy from pressurized steam and uses it to do mechanical work on a rotating output shaft. Its modern manifestation was invented by Charles Parsons in 1884. Fabrication of a modern steam turbin ...
and it consists of three main components: a compressor, a combustion chamber, and a turbine. The temperature of the air, after being compressed in the compressor, is increased by burning fuel in it. The heated air and the products of combustion expand in a turbine, producing work output. About of the work drives the compressor: the rest (about ) is available as useful work output.
Gas turbines are among the most efficient internal combustion engines. The General Electric 7HA and 9HA turbine
combined cycle
A combined cycle power plant is an assembly of heat engines that work in tandem from the same source of heat, converting it into mechanical energy. On land, when used to make electricity the most common type is called a combined cycle gas turb ...
electrical plants are rated at over 61% efficiency.
Brayton cycle
![Brayton cycle](https://upload.wikimedia.org/wikipedia/commons/3/3c/Brayton_cycle.svg)
A gas turbine is a rotary machine somewhat similar in principle to a steam turbine. It consists of three main components: compressor, combustion chamber, and turbine. The air is compressed by the compressor where a temperature rise occurs. The temperature of the compressed air is further increased by combustion of injected fuel in the combustion chamber which expands the air. This energy rotates the turbine which powers the compressor via a mechanical coupling. The hot gases are then exhausted to provide thrust.
Gas turbine cycle engines employ a continuous combustion system where compression, combustion, and expansion occur simultaneously at different places in the engineâgiving continuous power. Notably, the combustion takes place at constant pressure, rather than with the Otto cycle, constant volume.
Wankel engines
![Wankel Cycle anim en](https://upload.wikimedia.org/wikipedia/commons/f/fc/Wankel_Cycle_anim_en.gif)
The Wankel engine (rotary engine) does not have piston strokes. It operates with the same separation of phases as the four-stroke engine with the phases taking place in separate locations in the engine. In
thermodynamic
Thermodynamics is a branch of physics that deals with heat, work, and temperature, and their relation to energy, entropy, and the physical properties of matter and radiation. The behavior of these quantities is governed by the four laws of ther ...
terms it follows the
Otto engine
The Otto engine was a large stationary single-cylinder internal combustion four-stroke engine designed by the German Nicolaus Otto. It was a low-RPM machine, and only fired every other stroke due to the Otto cycle, also designed by Otto.
Types ...
cycle, so may be thought of as a "four-phase" engine. While it is true that three power strokes typically occur per rotor revolution, due to the 3:1 revolution ratio of the rotor to the eccentric shaft, only one power stroke per shaft revolution actually occurs. The drive (eccentric) shaft rotates once during every power stroke instead of twice (crankshaft), as in the Otto cycle, giving it a greater power-to-weight ratio than piston engines. This type of engine was most notably used in the
Mazda RX-8
The Mazda RX-8 is a sports car manufactured by Japanese automobile manufacturer Mazda between 2002 and 2012. It was first shown in 2001 at the North American International Auto Show. It is the successor to the RX-7 and, like its predecessors in ...
, the earlier
RX-7
The Mazda RX-7 is a front-engine, rear-wheel-drive, rotary engine-powered sports car that was manufactured and marketed by Mazda from 1978 until 2002 across three generations, all of which made use of a compact, lightweight Wankel rotary engine. ...
, and other vehicle models. The engine is also used in unmanned aerial vehicles, where the small size and weight and the high power-to-weight ratio are advantageous.
Forced induction
Forced induction is the process of delivering compressed air to the intake of an internal combustion engine. A forced induction engine uses a
gas compressor
A compressor is a mechanical device that increases the pressure of a gas by reducing its volume. An air compressor is a specific type of gas compressor.
Compressors are similar to pumps: both increase the pressure on a fluid and both can transp ...
to increase the pressure, temperature and
density of the air. An engine without forced induction is considered a
naturally aspirated engine
Naturally may refer to:
;Albums
* ''Naturally!'', an album by Nat Adderley
* ''Naturally'' (Houston Person album)
* ''Naturally'' (J. J. Cale album)
* ''Naturally'' (John Pizzarelli album)
* ''Naturally'' (Sharon Jones album)
* ''Naturally'' ...
.
Forced induction is used in the automotive and aviation industry to increase engine power and efficiency. It particularly helps aviation engines, as they need to operate at high altitude.
Forced induction is achieved by a
supercharger
In an internal combustion engine, a supercharger compresses the intake gas, forcing more air into the engine in order to produce more power for a given displacement.
The current categorisation is that a supercharger is a form of forced induct ...
, where the compressor is directly powered from the engine shaft or, in the
turbocharger
In an internal combustion engine, a turbocharger (often called a turbo) is a forced induction device that is powered by the flow of exhaust gases. It uses this energy to compress the intake gas, forcing more air into the engine in order to pro ...
, from a turbine powered by the engine exhaust.
Fuels and oxidizers
All internal combustion engines depend on
combustion
Combustion, or burning, is a high-temperature exothermic redox chemical reaction between a fuel (the reductant) and an oxidant, usually atmospheric oxygen, that produces oxidized, often gaseous products, in a mixture termed as smoke. Combusti ...
of a
chemical fuel
A fuel is any material that can be made to react with other substances so that it releases energy as thermal energy or to be used for work. The concept was originally applied solely to those materials capable of releasing chemical energy but ...
, typically with oxygen from the air (though it is possible to inject
nitrous oxide
Nitrous oxide (dinitrogen oxide or dinitrogen monoxide), commonly known as laughing gas, nitrous, or nos, is a chemical compound, an oxide of nitrogen with the formula . At room temperature, it is a colourless non-flammable gas, and has a ...
to do more of the same thing and gain a power boost). The combustion process typically results in the production of a great quantity of thermal energy, as well as the production of steam and carbon dioxide and other chemicals at very high temperature; the
temperature reached is determined by the chemical make up of the fuel and oxidizers (see
stoichiometry
Stoichiometry refers to the relationship between the quantities of reactants and products before, during, and following chemical reactions.
Stoichiometry is founded on the law of conservation of mass where the total mass of the reactants equal ...
), as well as by the compression and other factors.
Fuels
The most common modern fuels are made up of
hydrocarbon
In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and hydrophobic, and their odors are usually weak or ex ...
s and are derived mostly from
fossil fuel
A fossil fuel is a hydrocarbon-containing material formed naturally in the Earth's crust from the remains of dead plants and animals that is extracted and burned as a fuel. The main fossil fuels are coal, oil, and natural gas. Fossil fuels m ...
s (
petroleum
Petroleum, also known as crude oil, or simply oil, is a naturally occurring yellowish-black liquid mixture of mainly hydrocarbons, and is found in geological formations. The name ''petroleum'' covers both naturally occurring unprocessed crud ...
). Fossil fuels include
diesel fuel
Diesel fuel , also called diesel oil, is any liquid fuel specifically designed for use in a diesel engine, a type of internal combustion engine in which fuel ignition takes place without a spark as a result of compression of the inlet air and t ...
,
gasoline
Gasoline (; ) or petrol (; ) (see ) is a transparent, petroleum-derived flammable liquid that is used primarily as a fuel in most spark-ignited internal combustion engines (also known as petrol engines). It consists mostly of organic co ...
and
petroleum gas
Liquefied petroleum gas (LPG or LP gas) is a fuel gas which contains a flammable mixture of hydrocarbon gases, specifically propane, propylene, butylene, isobutane and n-butane.
LPG is used as a fuel gas in HVAC, heating appliances, cookin ...
, and the rarer use of
propane
Propane () is a three-carbon alkane with the molecular formula . It is a gas at standard temperature and pressure, but compressible to a transportable liquid. A by-product of natural gas processing and petroleum refining, it is commonly used a ...
. Except for the fuel delivery components, most internal combustion engines that are designed for gasoline use can run on
natural gas
Natural gas (also called fossil gas or simply gas) is a naturally occurring mixture of gaseous hydrocarbons consisting primarily of methane in addition to various smaller amounts of other higher alkanes. Low levels of trace gases like carbo ...
or liquefied petroleum gases without major modifications. Large diesels can run with air mixed with gases and a pilot diesel fuel ignition injection. Liquid and gaseous
biofuel
Biofuel is a fuel that is produced over a short time span from biomass, rather than by the very slow natural processes involved in the formation of fossil fuels, such as oil. According to the United States Energy Information Administration (E ...
s, such as
ethanol
Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an Alcohol (chemistry), alcohol with the chemical formula . Its formula can be also written as or (an ethyl ...
and
biodiesel
Biodiesel is a form of diesel fuel derived from plants or animals and consisting of long-chain fatty acid esters. It is typically made by chemically reacting lipids such as animal fat (tallow), soybean oil, or some other vegetable oil with ...
(a form of diesel fuel that is produced from crops that yield
triglyceride
A triglyceride (TG, triacylglycerol, TAG, or triacylglyceride) is an ester derived from glycerol and three fatty acids (from ''tri-'' and ''glyceride'').
Triglycerides are the main constituents of body fat in humans and other vertebrates, as w ...
s such as
soybean
The soybean, soy bean, or soya bean (''Glycine max'') is a species of legume native to East Asia, widely grown for its edible bean, which has numerous uses.
Traditional unfermented food uses of soybeans include soy milk, from which tofu an ...
oil), can also be used. Engines with appropriate modifications can also run on
hydrogen
Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic, an ...
gas,
wood gas
Wood gas is a fuel gas that can be used for furnaces, stoves, and vehicles. During the production process, biomass or related carbon-containing materials are gasified within the oxygen-limited environment of a wood gas generator to produce a comb ...
, or
charcoal gas, as well as from so-called
producer gas
Producer gas is fuel gas that is manufactured by blowing a coke or coal with air and steam simultaneously. It mainly consists of carbon monoxide (CO), hydrogen (H2), as well as substantial amounts of nitrogen (N2). The caloric value of the produce ...
made from other convenient biomass. Experiments have also been conducted using powdered solid fuels, such as the
magnesium injection cycle The magnesium injection cycle (MAGIC) is an engine design under development by Mitsubishi Corporation and the Tokyo Institute of Technology that uses magnesium and water to generate power. .
Presently, fuels used include:
*
Petroleum
Petroleum, also known as crude oil, or simply oil, is a naturally occurring yellowish-black liquid mixture of mainly hydrocarbons, and is found in geological formations. The name ''petroleum'' covers both naturally occurring unprocessed crud ...
:
** Petroleum spirit (
North American
North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Ca ...
term:
gasoline
Gasoline (; ) or petrol (; ) (see ) is a transparent, petroleum-derived flammable liquid that is used primarily as a fuel in most spark-ignited internal combustion engines (also known as petrol engines). It consists mostly of organic co ...
,
British
British may refer to:
Peoples, culture, and language
* British people, nationals or natives of the United Kingdom, British Overseas Territories, and Crown Dependencies.
** Britishness, the British identity and common culture
* British English, ...
term: petrol)
**
Petroleum diesel
Diesel fuel , also called diesel oil, is any liquid fuel specifically designed for use in a diesel engine, a type of internal combustion engine in which fuel ignition takes place without a spark as a result of compression of the inlet air and t ...
.
**
Autogas
Autogas or LPG is liquefied petroleum gas (LPG) used as a fuel in internal combustion engines in vehicles as well as in stationary applications such as generators. It is a mixture of propane and butane.
Autogas is widely used as a "green" ...
(
liquified petroleum gas
Liquefied petroleum gas (LPG or LP gas) is a fuel gas which contains a flammable mixture of hydrocarbon gases, specifically propane, propylene, butylene, isobutane and n-butane.
LPG is used as a fuel gas in heating appliances, cooking equ ...
).
**
Compressed natural gas
Compressed natural gas (CNG) is a fuel gas mainly composed of methane (CH4), compressed to less than 1% of the volume it occupies at standard atmospheric pressure. It is stored and distributed in hard containers at a pressure of , usually in cy ...
.
**
Jet fuel
Jet fuel or aviation turbine fuel (ATF, also abbreviated avtur) is a type of aviation fuel designed for use in aircraft powered by gas-turbine engines. It is colorless to straw-colored in appearance. The most commonly used fuels for commercial a ...
(
aviation fuel
Aviation fuels are petroleum-based fuels, or petroleum and synthetic fuel blends, used to power aircraft. They have more stringent requirements than fuels used for ground use, such as heating and road transport, and contain additives to enhanc ...
)
**
Residual fuel
Fuel oil is any of various fractions obtained from the distillation of petroleum (crude oil). Such oils include distillates (the lighter fractions) and residues (the heavier fractions). Fuel oils include heavy fuel oil, marine fuel oil (MFO), bun ...
*
Coal
Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata called coal seams. Coal is mostly carbon with variable amounts of other elements, chiefly hydrogen, sulfur, oxygen, and nitrogen.
Coal is formed when dea ...
:
** Gasoline can be made from carbon (coal) using the
FischerâTropsch process
The FischerâTropsch process is a collection of chemical reactions that converts a mixture of carbon monoxide and hydrogen, known as syngas, into liquid hydrocarbons. These reactions occur in the presence of metal catalysts, typically at temperat ...
** Diesel fuel can be made from carbon using the
FischerâTropsch process
The FischerâTropsch process is a collection of chemical reactions that converts a mixture of carbon monoxide and hydrogen, known as syngas, into liquid hydrocarbons. These reactions occur in the presence of metal catalysts, typically at temperat ...
* Biofuels and vegetable oils:
**
Peanut oil
Peanut oil, also known as groundnut oil or arachis oil, is a vegetable oil derived from peanuts. The oil usually has a mild or neutral flavor but, if made with roasted peanuts, has a stronger peanut flavor and aroma. It is often used in American ...
and other
vegetable oils
Vegetable oils, or vegetable fats, are oils extracted from seeds or from other parts of fruits. Like animal fats, vegetable fats are ''mixtures'' of triglycerides. Soybean oil, grape seed oil, and cocoa butter are examples of seed oils, or fat ...
.
**
Woodgas
Wood gas is a fuel gas that can be used for furnaces, stoves, and vehicles. During the production process, biomass or related carbon-containing materials are gasified within the oxygen-limited environment of a wood gas generator to produce a comb ...
, from an onboard
wood gasifier
A wood gas generator is a gasification unit which converts timber or charcoal into wood gas, a producer gas consisting of atmospheric nitrogen, carbon monoxide, hydrogen, traces of methane, and other gases, which â after cooling and filtering ...
using solid wood as a fuel
** Biofuels:
***
Biobutanol
220px, Butanol, a C-4 hydrocarbon is a promising bio-derived fuel, which shares many properties with gasoline.
Butanol may be used as a fuel in an internal combustion engine. It is more similar to gasoline than it is to ethanol. A C4-hydrocarbon ...
(replaces gasoline).
***
Biodiesel
Biodiesel is a form of diesel fuel derived from plants or animals and consisting of long-chain fatty acid esters. It is typically made by chemically reacting lipids such as animal fat (tallow), soybean oil, or some other vegetable oil with ...
(replaces petrodiesel).
***
Dimethyl Ether
Dimethyl ether (DME; also known as methoxymethane) is the organic compound with the formula CH3OCH3,
(sometimes ambiguously simplified to C2H6O as it is an isomer of ethanol). The simplest ether, it is a colorless gas that is a useful precursor ...
(replaces petrodiesel).
***
Bioethanol
Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an Alcohol (chemistry), alcohol with the chemical formula . Its formula can be also written as or (an ethyl ...
and
Biomethanol
Methanol fuel is an alternative biofuel for internal combustion and other engines, either in combination with gasoline or independently. Methanol ( C H3 O H) is less expensive to produce sustainably than ethanol fuel, although it produces more ...
(
wood alcohol
Methanol (also called methyl alcohol and wood spirit, amongst other names) is an organic chemical and the simplest aliphatic alcohol, with the formula C H3 O H (a methyl group linked to a hydroxyl group, often abbreviated as MeOH). It is a lig ...
) and other
biofuel
Biofuel is a fuel that is produced over a short time span from biomass, rather than by the very slow natural processes involved in the formation of fossil fuels, such as oil. According to the United States Energy Information Administration (E ...
s (see
Flexible-fuel vehicle
A flexible-fuel vehicle (FFV) or dual-fuel vehicle (colloquially called a flex-fuel vehicle) is an alternative fuel vehicle with an internal combustion engine designed to run on more than one fuel, usually gasoline blended with either ethanol o ...
).
***
Biogas
Biogas is a mixture of gases, primarily consisting of methane, carbon dioxide and hydrogen sulphide, produced from raw materials such as agricultural waste, manure, municipal waste, plant material, sewage, green waste and food waste. It is a ...
*
Hydrogen
Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic, an ...
(mainly
spacecraft
A spacecraft is a vehicle or machine designed to fly in outer space. A type of artificial satellite, spacecraft are used for a variety of purposes, including communications, Earth observation, meteorology, navigation, space colonization, p ...
rocket engine
A rocket engine uses stored rocket propellants as the reaction mass for forming a high-speed propulsive jet of fluid, usually high-temperature gas. Rocket engines are reaction engines, producing thrust by ejecting mass rearward, in accordanc ...
s)
Even fluidized metal powders and explosives have seen some use. Engines that use gases for fuel are called gas engines and those that use liquid hydrocarbons are called oil engines; however, gasoline engines are also often colloquially referred to as "gas engines" ("
petrol engine
A petrol engine (gasoline engine in American English) is an internal combustion engine designed to run on petrol (gasoline). Petrol engines can often be adapted to also run on fuels such as liquefied petroleum gas and ethanol blends (such as ''E ...
s" outside North America).
The main limitations on fuels are that it must be easily transportable through the
fuel system to the
combustion chamber
A combustion chamber is part of an internal combustion engine in which the fuel/air mix is burned. For steam engines, the term has also been used for an extension of the firebox which is used to allow a more complete combustion process.
Interna ...
, and that the fuel releases sufficient
energy
In physics, energy (from Ancient Greek: áŒÎœÎÏγΔÎčα, ''enĂ©rgeia'', âactivityâ) is the quantitative property that is transferred to a body or to a physical system, recognizable in the performance of work and in the form of heat a ...
in the form of
heat
In thermodynamics, heat is defined as the form of energy crossing the boundary of a thermodynamic system by virtue of a temperature difference across the boundary. A thermodynamic system does not ''contain'' heat. Nevertheless, the term is al ...
upon
combustion
Combustion, or burning, is a high-temperature exothermic redox chemical reaction between a fuel (the reductant) and an oxidant, usually atmospheric oxygen, that produces oxidized, often gaseous products, in a mixture termed as smoke. Combusti ...
to make practical use of the engine.
Diesel engine
The diesel engine, named after Rudolf Diesel, is an internal combustion engine in which ignition of the fuel is caused by the elevated temperature of the air in the cylinder due to mechanical compression; thus, the diesel engine is a so-call ...
s are generally heavier, noisier, and more powerful at lower speeds than
gasoline engine
A petrol engine (gasoline engine in American English) is an internal combustion engine designed to run on petrol (gasoline). Petrol engines can often be adapted to also run on fuels such as liquefied petroleum gas and ethanol blends (such as ''E ...
s. They are also more fuel-efficient in most circumstances and are used in heavy road vehicles, some automobiles (increasingly so for their increased
fuel efficiency
Fuel efficiency is a form of thermal efficiency, meaning the ratio of effort to result of a process that converts chemical potential energy contained in a carrier (fuel) into kinetic energy or work. Overall fuel efficiency may vary per device, wh ...
over gasoline engines), ships,
railway
Rail transport (also known as train transport) is a means of transport that transfers passengers and goods on wheeled vehicles running on rails, which are incorporated in tracks. In contrast to road transport, where the vehicles run on a pre ...
locomotive
A locomotive or engine is a rail transport vehicle that provides the Power (physics), motive power for a train. If a locomotive is capable of carrying a payload, it is usually rather referred to as a multiple unit, Motor coach (rail), motor ...
s, and light
aircraft
An aircraft is a vehicle that is able to fly by gaining support from the air. It counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines ...
. Gasoline engines are used in most other road vehicles including most cars,
motorcycle
A motorcycle (motorbike, bike, or trike (if three-wheeled)) is a two or three-wheeled motor vehicle steered by a handlebar. Motorcycle design varies greatly to suit a range of different purposes: long-distance travel, commuting, cruising ...
s, and
moped
A moped ( ) is a type of small motorcycle, generally having a less stringent licensing requirement than full motorcycles or automobiles. The term used to mean a similar vehicle except with both bicycle pedals and a motorcycle engine. Mopeds typic ...
s. Note that in
Europe
Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...
, sophisticated diesel-engined cars have taken over about 45% of the market since the 1990s. There are also engines that run on
hydrogen
Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic, an ...
,
methanol
Methanol (also called methyl alcohol and wood spirit, amongst other names) is an organic chemical and the simplest aliphatic alcohol, with the formula C H3 O H (a methyl group linked to a hydroxyl group, often abbreviated as MeOH). It is a ...
,
ethanol
Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an Alcohol (chemistry), alcohol with the chemical formula . Its formula can be also written as or (an ethyl ...
,
liquefied petroleum gas
Liquefied petroleum gas (LPG or LP gas) is a fuel gas which contains a flammable mixture of hydrocarbon gases, specifically propane, propylene, butylene, isobutane and n-butane.
LPG is used as a fuel gas in heating appliances, cooking e ...
(LPG),
biodiesel
Biodiesel is a form of diesel fuel derived from plants or animals and consisting of long-chain fatty acid esters. It is typically made by chemically reacting lipids such as animal fat (tallow), soybean oil, or some other vegetable oil with ...
,
paraffin Paraffin may refer to:
Substances
* Paraffin wax, a white or colorless soft solid that is used as a lubricant and for other applications
* Liquid paraffin (drug), a very highly refined mineral oil used in cosmetics and for medical purposes
* Alkane ...
and
tractor vaporizing oil
Tractor vaporising oil (TVO) is a fuel for petrol-paraffin engines. It is seldom made or used today. In the United Kingdom and Australia, after the Second World War, it was commonly used for tractors until diesel engines became commonplace, es ...
(TVO).
Hydrogen
Hydrogen could eventually
replace conventional fossil fuels in traditional internal combustion engines. Alternatively
fuel cell
A fuel cell is an electrochemical cell that converts the chemical energy of a fuel (often hydrogen) and an oxidizing agent (often oxygen) into electricity through a pair of redox reactions. Fuel cells are different from most batteries in requ ...
technology may come to deliver its promise and the use of the internal combustion engines could even be phased out.
Although there are multiple ways of producing free hydrogen, those methods require converting combustible molecules into hydrogen or consuming electric energy. Unless that electricity is produced from a renewable sourceâand is not required for other purposesâhydrogen does not solve any
energy crisis
An energy crisis or energy shortage is any significant bottleneck in the supply of energy resources to an economy. In literature, it often refers to one of the energy sources used at a certain time and place, in particular, those that supply n ...
. In many situations the disadvantage of hydrogen, relative to carbon fuels, is
its storage.
Liquid hydrogen
Liquid hydrogen (LH2 or LH2) is the liquid state of the element hydrogen. Hydrogen is found naturally in the molecular H2 form.
To exist as a liquid, H2 must be cooled below its critical point of 33 K. However, for it to be in a fully li ...
has extremely low density (14 times lower than water) and requires extensive insulationâwhilst gaseous hydrogen requires heavy tankage. Even when liquefied, hydrogen has a higher specific energy but the volumetric energetic storage is still roughly five times lower than gasoline. However, the energy density of hydrogen is considerably higher than that of electric batteries, making it a serious contender as an energy carrier to replace fossil fuels. The 'Hydrogen on Demand' process (see
direct borohydride fuel cell Direct borohydride fuel cells (DBFCs) are a subcategory of alkaline fuel cells which are directly fed by sodium borohydride or potassium borohydride as a fuel and either air/oxygen or hydrogen peroxide as the oxidant. DBFCs are relatively new types ...
) creates hydrogen as needed, but has other issues, such as the high price of the
sodium borohydride
Sodium borohydride, also known as sodium tetrahydridoborate and sodium tetrahydroborate, is an inorganic compound with the formula Na BH4. This white solid, usually encountered as an aqueous basic solution, is a reducing agent that finds appli ...
that is the raw material.
Oxidizers
![Moore-single-cylinder-gasoline-engine](https://upload.wikimedia.org/wikipedia/commons/0/0c/Moore-single-cylinder-gasoline-engine.jpg)
Since air is plentiful at the surface of the earth, the oxidizer is typically atmospheric oxygen, which has the advantage of not being stored within the vehicle. This increases the power-to-weight and power-to-volume ratios. Other materials are used for special purposes, often to increase power output or to allow operation under water or in space.
* Compressed air has been commonly used in
torpedo
A modern torpedo is an underwater ranged weapon launched above or below the water surface, self-propelled towards a target, and with an explosive warhead designed to detonate either on contact with or in proximity to the target. Historically, su ...
es.
* Compressed
oxygen
Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as wel ...
, as well as some compressed air, was used in the Japanese
Type 93 torpedo
The was a -diameter torpedo of the Imperial Japanese Navy (IJN), launched from surface ships. It is commonly referred to as the Long Lance by most modern English-language naval historians, a nickname given to it after the war by Samuel Eliot Mori ...
. Some
submarines
A submarine (or sub) is a watercraft capable of independent operation underwater. It differs from a submersible, which has more limited underwater capability. The term is also sometimes used historically or colloquially to refer to remotely o ...
carry pure oxygen. Rockets very often use
liquid oxygen
Liquid oxygenâabbreviated LOx, LOX or Lox in the aerospace, submarine and gas industriesâis the liquid form of molecular oxygen. It was used as the oxidizer in the first liquid-fueled rocket invented in 1926 by Robert H. Goddard, an applica ...
.
*
Nitromethane
Nitromethane, sometimes shortened to simply "nitro", is an organic compound with the chemical formula . It is the simplest organic nitro compound. It is a polar liquid commonly used as a solvent in a variety of industrial applications such as in ...
is added to some racing and
model
A model is an informative representation of an object, person or system. The term originally denoted the Plan_(drawing), plans of a building in late 16th-century English, and derived via French and Italian ultimately from Latin ''modulus'', a mea ...
fuels to increase power and control combustion.
*
Nitrous oxide
Nitrous oxide (dinitrogen oxide or dinitrogen monoxide), commonly known as laughing gas, nitrous, or nos, is a chemical compound, an oxide of nitrogen with the formula . At room temperature, it is a colourless non-flammable gas, and has a ...
has been usedâwith extra gasolineâin tactical aircraft, and in specially equipped cars to allow short bursts of added power from engines that otherwise run on gasoline and air. It is also used in the Burt Rutan rocket spacecraft.
*
Hydrogen peroxide
Hydrogen peroxide is a chemical compound with the formula . In its pure form, it is a very pale blue liquid that is slightly more viscous than water. It is used as an oxidizer, bleaching agent, and antiseptic, usually as a dilute solution (3%â ...
power was under development for German World War II submarines. It may have been used in some non-nuclear submarines, and was used on some rocket engines (notably the
Black Arrow
Black Arrow, officially capitalised BLACK ARROW, was a British satellite carrier rocket. Developed during the 1960s, it was used for four launches between 1969 and 1971, all launched from the Woomera Prohibited Area in Australia. Its final flig ...
and the
Messerschmitt Me 163
The Messerschmitt Me 163 Komet is a rocket-powered interceptor aircraft primarily designed and produced by the German aircraft manufacturer Messerschmitt. It is the only operational rocket-powered fighter aircraft in history as well as th ...
rocket fighter).
* Other chemicals such as chlorine or fluorine have been used experimentally, but have not been found practical.
Cooling
Cooling is required to remove excessive heatâhigh temperature can cause engine failure, usually from wear (due to high-temperature-induced failure of lubrication), cracking or warping. Two most common forms of engine cooling are
air-cooled
Air-cooled engines rely on the circulation of air directly over heat dissipation fins or hot areas of the engine to cool them in order to keep the engine within operating temperatures. In all combustion engines, a great percentage of the heat ge ...
and
water-cooled
Cooling tower and water discharge of a nuclear power plant
Water cooling is a method of heat removal from components and industrial equipment. Evaporative cooling using water is often more efficient than air cooling. Water is inexpensive and non ...
. Most modern automotive engines are both water and air-cooled, as the water/liquid-coolant is carried to air-cooled fins and/or fans, whereas larger engines may be singularly water-cooled as they are stationary and have a constant supply of water through water-mains or fresh-water, while most power tool engines and other small engines are air-cooled. Some engines (air or water-cooled) also have an
oil cooler
Oil cooling is the use of engine oil as a coolant, typically to remove surplus heat from an internal combustion engine. The hot engine transfers heat to the oil which then usually passes through a heat-exchanger, typically a type of radiator know ...
. In some engines, especially for
turbine engine blade cooling and
liquid rocket engine cooling, fuel is used as a coolant, as it is simultaneously preheated before injecting it into a combustion chamber.
Starting
Internal combustion engines must have their cycles started. In reciprocating engines this is accomplished by turning the crankshaft (Wankel Rotor Shaft) which induces the cycles of intake, compression, combustion, and exhaust. The first engines were started with a turn of their
flywheel
A flywheel is a mechanical device which uses the conservation of angular momentum to store rotational energy; a form of kinetic energy proportional to the product of its moment of inertia and the square of its rotational speed. In particular, ass ...
s, while the first vehicle (the Daimler Reitwagen) was started with a hand crank. All ICE engined automobiles were started with hand cranks until
Charles Kettering
Charles Franklin Kettering (August 29, 1876 â November 25, 1958) sometimes known as Charles Fredrick Kettering was an American inventor, engineer, businessman, and the holder of 186 patents.
For the list of patents issued to Kettering, see, Le ...
developed the electric starter for automobiles. This method is now the most widely used, even among non-automobiles.
As diesel engines have become larger and their mechanisms heavier,
air starters have come into use. This is due to the lack of torque in electric starters. Air starters work by pumping compressed air into the cylinders of an engine to start it turning.
Two-wheeled vehicles may have their engines started in one of four ways:
* By pedaling, as on a bicycle
* By pushing the vehicle and then engaging the clutch, known as "run-and-bump starting"
* By kicking downward on a single pedal, known as "kick starting"
* By an electric starter, as in cars
There are also starters where a spring is compressed by a crank motion and then used to start an engine.
Some small engines use a pull-rope mechanism called "recoil starting", as the rope rewinds itself after it has been pulled out to start the engine. This method is commonly used in pushed lawn mowers and other settings where only a small amount of torque is needed to turn an engine over.
Turbine engines are frequently started by an electric motor or by compressed air.
Measures of engine performance
Engine types vary greatly in a number of different ways:
*
energy efficiency
Energy efficiency may refer to:
* Energy efficiency (physics), the ratio between the useful output and input of an energy conversion process
** Electrical efficiency, useful power output per electrical power consumed
** Mechanical efficiency, a ra ...
* fuel/propellant consumption (
brake specific fuel consumption
Brake-specific fuel consumption (BSFC) is a measure of the fuel efficiency of any prime mover that burns fuel and produces rotational, or shaft power. It is typically used for comparing the efficiency of internal combustion engines with a shaft out ...
for shaft engines,
thrust specific fuel consumption
Thrust-specific fuel consumption (TSFC) is the fuel efficiency of an engine design with respect to thrust output. TSFC may also be thought of as fuel consumption (grams/second) per unit of thrust (newtons, or N), hence ''thrust-specific''. This fig ...
for jet engines)
*
power-to-weight ratio
Power-to-weight ratio (PWR, also called specific power, or power-to-mass ratio) is a calculation commonly applied to engines and mobile power sources to enable the comparison of one unit or design to another. Power-to-weight ratio is a measuremen ...
*
thrust to weight ratio
Thrust-to-weight ratio is a dimensionless ratio of thrust to weight of a rocket, jet engine, propeller engine, or a vehicle propelled by such an engine that is an indicator of the performance of the engine or vehicle.
The instantaneous thrust-to-w ...
*
torque curves (for shaft engines),
thrust lapse
The behavior of a jet engine and its effect both on the aircraft and the environment is categorized into different engineering areas or disciplines. The understanding of how a particular fuel flow produces a definite amount of thrust at a partic ...
(jet engines)
*
compression ratio
The compression ratio is the ratio between the volume of the cylinder and combustion chamber in an internal combustion engine at their maximum and minimum values.
A fundamental specification for such engines, it is measured two ways: the stati ...
for piston engines,
overall pressure ratio
In aeronautical engineering, overall pressure ratio, or overall compression ratio, is the ratio of the stagnation pressure as measured at the front and rear of the compressor of a gas turbine engine. The terms ''compression ratio'' and ''pressure ...
for jet engines and gas turbines
Energy efficiency
Once ignited and burnt, the
combustion
Combustion, or burning, is a high-temperature exothermic redox chemical reaction between a fuel (the reductant) and an oxidant, usually atmospheric oxygen, that produces oxidized, often gaseous products, in a mixture termed as smoke. Combusti ...
productsâhot gasesâhave more available
thermal energy
The term "thermal energy" is used loosely in various contexts in physics and engineering. It can refer to several different well-defined physical concepts. These include the internal energy or enthalpy of a body of matter and radiation; heat, d ...
than the original compressed fuel-air mixture (which had higher
chemical energy
Chemical energy is the energy of chemical substances that is released when they undergo a chemical reaction and transform into other substances. Some examples of storage media of chemical energy include batteries, Schmidt-Rohr, K. (2018). "How ...
). This available energy is manifested as a higher
temperature
Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measured with a thermometer.
Thermometers are calibrated in various temperature scales that historically have relied o ...
and
pressure
Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country and e ...
that can be converted into
kinetic energy
In physics, the kinetic energy of an object is the energy that it possesses due to its motion.
It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its accele ...
by the engine. In a reciprocating engine, the high-pressure gases inside the cylinders drive the engine's pistons.
Once the available energy has been removed, the remaining hot gases are
vented (often by opening a
valve
A valve is a device or natural object that regulates, directs or controls the flow of a fluid (gases, liquids, fluidized solids, or slurries) by opening, closing, or partially obstructing various passageways. Valves are technically fittings ...
or exposing the exhaust outlet) and this allows the piston to return to its previous position (top dead center, or TDC). The piston can then proceed to the next phase of its cycle, which varies between engines. Any thermal energy that is not translated into work is normally considered a waste product and is removed from the engine either by an air or liquid cooling system.
Internal combustion engines are considered
heat engine
In thermodynamics and engineering, a heat engine is a system that converts heat to mechanical energy, which can then be used to do mechanical work. It does this by bringing a working substance from a higher state temperature to a lower state ...
s (since the release of chemical energy in combustion has the same effect as
heat
In thermodynamics, heat is defined as the form of energy crossing the boundary of a thermodynamic system by virtue of a temperature difference across the boundary. A thermodynamic system does not ''contain'' heat. Nevertheless, the term is al ...
transfer into the engine) and as such their theoretical efficiency can be approximated by idealized
thermodynamic cycle
A thermodynamic cycle consists of a linked sequence of thermodynamic processes that involve transfer of heat and work into and out of the system, while varying pressure, temperature, and other state variables within the system, and that eventuall ...
s. The thermal efficiency of a theoretical cycle cannot exceed that of the
Carnot cycle
A Carnot cycle is an ideal thermodynamic cycle proposed by French physicist Sadi Carnot in 1824 and expanded upon by others in the 1830s and 1840s. By Carnot's theorem, it provides an upper limit on the efficiency of any classical thermodynam ...
, whose efficiency is determined by the difference between the lower and upper
operating temperature
An operating temperature is the allowable temperature range of the local ambient environment at which an electrical or mechanical device operates. The device will operate effectively within a specified temperature range which varies based on the de ...
s of the engine. The upper operating temperature of an engine is limited by two main factors; the thermal operating limits of the materials, and the auto-ignition resistance of the fuel. All
metal
A metal (from Greek ÎŒÎÏÎ±Î»Î»ÎżÎœ ''mĂ©tallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts electricity and heat relatively well. Metals are typicall ...
s and
alloy
An alloy is a mixture of chemical elements of which at least one is a metal. Unlike chemical compounds with metallic bases, an alloy will retain all the properties of a metal in the resulting material, such as electrical conductivity, ductility, ...
s have a thermal operating limit, and there is significant research into
ceramic
A ceramic is any of the various hard, brittle, heat-resistant and corrosion-resistant materials made by shaping and then firing an inorganic, nonmetallic material, such as clay, at a high temperature. Common examples are earthenware, porcelain ...
materials that can be made with greater thermal stability and desirable structural properties. Higher thermal stability allows for a greater temperature difference between the lower (ambient) and upper operating temperatures, hence greater thermodynamic efficiency. Also, as the cylinder temperature rises, the fuel becomes more prone to auto-ignition. This is caused when the cylinder temperature nears the flash point of the charge. At this point, ignition can spontaneously occur before the spark plug fires, causing excessive cylinder pressures. Auto-ignition can be mitigated by using fuels with high auto-ignition resistance (
octane rating
An octane rating, or octane number, is a standard measure of a fuel's ability to withstand compression in an internal combustion engine without detonating. The higher the octane number, the more compression the fuel can withstand before detonating ...
), however it still puts an upper bound on the allowable peak cylinder temperature.
The
thermodynamic limit
In statistical mechanics, the thermodynamic limit or macroscopic limit, of a system is the limit for a large number of particles (e.g., atoms or molecules) where the volume is taken to grow in proportion with the number of particles.S.J. Blundel ...
s assume that the engine is operating under ideal conditions: a frictionless world, ideal gases, perfect insulators, and operation for infinite time. Real world applications introduce complexities that reduce efficiency. For example, a real engine runs best at a specific load, termed its
power band
The power band of an internal combustion engine or electric motor is the range of operating speeds under which the engine or motor is able to output the most power, that is, the maximum energy per unit of time. This usually means that maximum a ...
. The engine in a car cruising on a highway is usually operating significantly below its ideal load, because it is designed for the higher loads required for rapid acceleration. In addition, factors such as
wind resistance
In fluid dynamics, drag (sometimes called air resistance, a type of friction, or fluid resistance, another type of friction or fluid friction) is a force acting opposite to the relative motion of any object moving with respect to a surrounding flu ...
reduce overall system efficiency. Vehicle
fuel economy is measured in
miles per gallon
The fuel economy of an Car, automobile relates distance traveled by a vehicle and the amount of fuel consumption, fuel consumed. Consumption can be expressed in terms of volume of fuel to travel a distance, or the distance traveled per unit volu ...
or in liters per 100 kilometers. The volume of hydrocarbon assumes a standard energy content.
Even when aided with turbochargers and stock efficiency aids, most engines retain an ''average'' efficiency of about 18â20%. However, the latest technologies in
Formula One engines
Since its inception in 1947, Formula One has used a variety of engine regulations. "Formulae" limiting engine capacity had been used in Grand Prix racing on a regular basis since after World War I. The engine formulae are divided according t ...
have seen a boost in thermal efficiency past 50%.
There are many inventions aimed at increasing the efficiency of IC engines. In general, practical engines are always compromised by trade-offs between different properties such as efficiency, weight, power, heat, response, exhaust emissions, or noise. Sometimes economy also plays a role in not only the cost of manufacturing the engine itself, but also manufacturing and distributing the fuel. Increasing the engine's efficiency brings better fuel economy but only if the fuel cost per energy content is the same.
Measures of fuel efficiency and propellant efficiency
For stationary and shaft engines including propeller engines, fuel consumption is measured by calculating the
brake specific fuel consumption
Brake-specific fuel consumption (BSFC) is a measure of the fuel efficiency of any prime mover that burns fuel and produces rotational, or shaft power. It is typically used for comparing the efficiency of internal combustion engines with a shaft out ...
, which measures the mass flow rate of fuel consumption divided by the power produced.
For internal combustion engines in the form of jet engines, the power output varies drastically with airspeed and a less variable measure is used:
thrust specific fuel consumption
Thrust-specific fuel consumption (TSFC) is the fuel efficiency of an engine design with respect to thrust output. TSFC may also be thought of as fuel consumption (grams/second) per unit of thrust (newtons, or N), hence ''thrust-specific''. This fig ...
(TSFC), which is the mass of propellant needed to generate
impulses that is measured in either pound force-hour or the grams of propellant needed to generate an impulse that measures one kilonewton-second.
For rockets, TSFC can be used, but typically other equivalent measures are traditionally used, such as
specific impulse
Specific impulse (usually abbreviated ) is a measure of how efficiently a reaction mass engine (a rocket using propellant or a jet engine using fuel) creates thrust. For engines whose reaction mass is only the fuel they carry, specific impulse i ...
and
effective exhaust velocity
Specific impulse (usually abbreviated ) is a measure of how efficiently a reaction mass engine (a rocket using propellant or a jet engine using fuel) creates thrust. For engines whose reaction mass is only the fuel they carry, specific impulse is ...
.
Air and noise pollution
Air pollution
Internal combustion engines such as reciprocating internal combustion engines produce
air pollution
Air pollution is the contamination of air due to the presence of substances in the atmosphere that are harmful to the health of humans and other living beings, or cause damage to the climate or to materials. There are many different types ...
emissions, due to incomplete combustion of
carbon
Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent
In chemistry, the valence (US spelling) or valency (British spelling) of an element is the measure of its combining capacity with o ...
aceous fuel. The main derivatives of the process are
carbon dioxide
Carbon dioxide (chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is transpar ...
, water and some
soot
Soot ( ) is a mass of impure carbon particles resulting from the incomplete combustion of hydrocarbons. It is more properly restricted to the product of the gas-phase combustion process but is commonly extended to include the residual pyrolysed ...
âalso called
particulate matter
Particulates â also known as atmospheric aerosol particles, atmospheric particulate matter, particulate matter (PM) or suspended particulate matter (SPM) â are microscopic particles of solid or liquid matter suspended in the air. The ter ...
(PM). The effects of inhaling particulate matter have been studied in humans and animals and include asthma, lung cancer, cardiovascular issues, and premature death. There are, however, some additional products of the combustion process that include
nitrogen oxide Nitrogen oxide may refer to a binary compound of oxygen and nitrogen, or a mixture of such compounds:
Charge-neutral
*Nitric oxide (NO), nitrogen(II) oxide, or nitrogen monoxide
*Nitrogen dioxide (), nitrogen(IV) oxide
* Nitrogen trioxide (), or n ...
s and
sulfur
Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formula ...
and some uncombusted hydrocarbons, depending on the operating conditions and the fuel-air ratio.
Carbon dioxide emissions from internal combustion engines contribute to human-induced
climate change
In common usage, climate change describes global warmingâthe ongoing increase in global average temperatureâand its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to E ...
. Increasing the engine's
fuel efficiency
Fuel efficiency is a form of thermal efficiency, meaning the ratio of effort to result of a process that converts chemical potential energy contained in a carrier (fuel) into kinetic energy or work. Overall fuel efficiency may vary per device, wh ...
can reduce, but not eliminate, the amount of emissions as carbon-based fuel combustion produces . Since removing from engine exhaust is impractical, there is increasing interest in alternatives. Sustainable fuels such as
biofuel
Biofuel is a fuel that is produced over a short time span from biomass, rather than by the very slow natural processes involved in the formation of fossil fuels, such as oil. According to the United States Energy Information Administration (E ...
s,
synfuels, and
electric motor
An electric motor is an Electric machine, electrical machine that converts electrical energy into mechanical energy. Most electric motors operate through the interaction between the motor's magnetic field and electric current in a Electromagneti ...
s powered by batteries are examples.
Not all of the fuel is completely consumed by the combustion process. A small amount of fuel is present after combustion, and some of it reacts to form oxygenates, such as
formaldehyde
Formaldehyde ( , ) (systematic name methanal) is a naturally occurring organic compound with the formula and structure . The pure compound is a pungent, colourless gas that polymerises spontaneously into paraformaldehyde (refer to section F ...
or
acetaldehyde
Acetaldehyde (IUPAC systematic name ethanal) is an organic chemical compound with the formula CH3 CHO, sometimes abbreviated by chemists as MeCHO (Me = methyl). It is a colorless liquid or gas, boiling near room temperature. It is one of the mos ...
, or hydrocarbons not originally present in the input fuel mixture. Incomplete combustion usually results from insufficient
oxygen
Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as wel ...
to achieve the perfect
stoichiometric
Stoichiometry refers to the relationship between the quantities of reactants and products before, during, and following chemical reactions.
Stoichiometry is founded on the law of conservation of mass where the total mass of the reactants equal ...
ratio. The flame is "quenched" by the relatively cool cylinder walls, leaving behind unreacted fuel that is expelled with the exhaust. When running at lower speeds, quenching is commonly observed in diesel (compression ignition) engines that run on natural gas. Quenching reduces efficiency and increases knocking, sometimes causing the engine to stall. Incomplete combustion also leads to the production of
carbon monoxide
Carbon monoxide (chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the simple ...
(CO). Further chemicals released are
benzene
Benzene is an organic chemical compound with the molecular formula C6H6. The benzene molecule is composed of six carbon atoms joined in a planar ring with one hydrogen atom attached to each. Because it contains only carbon and hydrogen atoms, ...
and
1,3-butadiene
1,3-Butadiene () is the organic compound with the formula (CH2=CH)2. It is a colorless gas that is easily condensed to a liquid. It is important industrially as a precursor to synthetic rubber. The molecule can be viewed as the union of two viny ...
that are also
hazardous air pollutant
The National Emission Standards for Hazardous Air Pollutants (NESHAP) are air pollution standards issued by the United States Environmental Protection Agency (EPA). The standards, authorized by the Clean Air Act, are for pollutants not covered by ...
s.
Increasing the amount of air in the engine reduces emissions of incomplete combustion products, but also promotes reaction between oxygen and
nitrogen
Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...
in the air to produce
nitrogen oxide Nitrogen oxide may refer to a binary compound of oxygen and nitrogen, or a mixture of such compounds:
Charge-neutral
*Nitric oxide (NO), nitrogen(II) oxide, or nitrogen monoxide
*Nitrogen dioxide (), nitrogen(IV) oxide
* Nitrogen trioxide (), or n ...
s (). is hazardous to both plant and animal health, and leads to the production of
ozone
Ozone (), or trioxygen, is an inorganic molecule with the chemical formula . It is a pale blue gas with a distinctively pungent smell. It is an allotrope of oxygen that is much less stable than the diatomic allotrope , breaking down in the lo ...
(). Ozone is not emitted directly; rather, it is a secondary air pollutant, produced in the atmosphere by the reaction of and
volatile organic compound
Volatile organic compounds (VOCs) are organic compounds that have a high vapour pressure at room temperature. High vapor pressure correlates with a low boiling point, which relates to the number of the sample's molecules in the surrounding air, a ...
s in the presence of sunlight. Ground-level ozone is harmful to human health and the environment. Though the same chemical substance, ground-level ozone should not be confused with
stratospheric ozone
The ozone layer or ozone shield is a region of Earth's stratosphere that absorbs most of the Sun's ultraviolet radiation. It contains a high concentration of ozone (O3) in relation to other parts of the atmosphere, although still small in relat ...
, or the
ozone layer
The ozone layer or ozone shield is a region of Earth's stratosphere that absorbs most of the Sun's ultraviolet radiation. It contains a high concentration of ozone (O3) in relation to other parts of the atmosphere, although still small in rela ...
, which protects the earth from harmful ultraviolet rays.
Carbon fuels containing sulfur produce
sulfur monoxide
Sulfur monoxide is an inorganic compound with formula . It is only found as a dilute gas phase. When concentrated or condensed, it converts to S2O2 (disulfur dioxide). It has been detected in space but is rarely encountered intact otherwise.
Str ...
s (SO) and
sulfur dioxide
Sulfur dioxide (IUPAC-recommended spelling) or sulphur dioxide (traditional Commonwealth English) is the chemical compound with the formula . It is a toxic gas responsible for the odor of burnt matches. It is released naturally by volcanic activ ...
() contributing to
acid rain
Acid rain is rain or any other form of precipitation that is unusually acidic, meaning that it has elevated levels of hydrogen ions (low pH). Most water, including drinking water, has a neutral pH that exists between 6.5 and 8.5, but acid ...
.
In the United States, nitrogen oxides,
PM, carbon monoxide, sulfur dioxide, and ozone, are regulated as
criteria air pollutant
The U.S. National Ambient Air Quality Standards (NAAQS, pronounced ) are limits on atmospheric concentration of six pollutants that cause smog, acid rain, and other health hazards. Established by the United States Environmental Protection Agenc ...
s under the
Clean Air Act to levels where human health and welfare are protected. Other pollutants, such as benzene and 1,3-butadiene, are regulated as
hazardous air pollutant
The National Emission Standards for Hazardous Air Pollutants (NESHAP) are air pollution standards issued by the United States Environmental Protection Agency (EPA). The standards, authorized by the Clean Air Act, are for pollutants not covered by ...
s whose emissions must be lowered as much as possible depending on technological and practical considerations.
, carbon monoxide and other pollutants are frequently controlled via
exhaust gas recirculation
In internal combustion engines, exhaust gas recirculation (EGR) is a nitrogen oxide () emissions reduction technique used in petrol/gasoline, diesel engines and some hydrogen engines. EGR works by recirculating a portion of an engine's exhaust ...
which returns some of the exhaust back into the engine intake.
Catalytic converter
A catalytic converter is an exhaust emission control device that converts toxic gases and pollutants in exhaust gas from an internal combustion engine into less-toxic pollutants by catalyzing a redox reaction. Catalytic converters are usually ...
s are used to convert exhaust chemicals to (a
greenhouse gas
A greenhouse gas (GHG or GhG) is a gas that Absorption (electromagnetic radiation), absorbs and Emission (electromagnetic radiation), emits radiant energy within the thermal infrared range, causing the greenhouse effect. The primary greenhouse ...
), (water vapour, also a greenhouse gas) and (nitrogen).
Non-road engines
The emission standards used by many countries have special requirements for non-road engines which are used by equipment and vehicles that are not operated on the public roadways. The standards are separated from the road vehicles.
Noise pollution
Significant contributions to noise pollution are made by internal combustion engines. Automobile and truck traffic operating on highways and street systems produce noise, as do aircraft flights due to jet noise, particularly supersonic-capable aircraft. Rocket engines create the most intense noise.
Idling
Internal combustion engines continue to consume fuel and emit pollutants while idling. Idling is reduced by Start-stop system, stop-start systems.
Carbon dioxide formation
A good way to estimate the mass of carbon dioxide that is released when one litre of diesel fuel (or gasoline) is combusted can be found as follows:
As a good approximation the chemical formula of diesel is . Note that in reality diesel is a mixture of different molecules. As carbon has a molar mass of 12 g/mol and hydrogen (atomic) has a molar mass of about 1 g/mol, the fraction by weight of carbon in diesel is roughly .
The reaction of diesel combustion is given by:
2 + 3n 2n + 2n
Carbon dioxide has a molar mass of 44 g/mol as it consists of 2 atoms of oxygen (16 g/mol) and 1 atom of carbon (12 g/mol). So 12 g of carbon yields 44 g of carbon dioxide.
Diesel has a density of 0.838 kg per litre.
Putting everything together the mass of carbon dioxide that is produced by burning 1 litre of diesel can be calculated as:
The figure obtained with this estimation is close to the values found in the literature.
For gasoline, with a density of 0.75 kg/L and a ratio of carbon to hydrogen atoms of about 6 to 14, the estimated value of carbon emission from burning 1 litre of gasoline is:
See also
References
Bibliography
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*
* Patents:
**
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Further reading
*
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External links
Combustion videoâ in-cylinder combustion in an optically accessible, 2-stroke engine
Animated Enginesâ explains a variety of types
â Cut-away images and a good overview of the internal combustion engine
â Research at The University of Michigan
YouTubeâ Animation of the components and built-up of a 4-cylinder engine
YouTubeâ Animation of the internal moving parts of a 4-cylinder engine
retrieved May 9, 2009
* A file on unusual engine
* Aircraft Engine Historical Society (AEHS) â
{{DEFAULTSORT:Internal Combustion Engine
Internal combustion engine,
Engines, Internal combustion
Piston engines
Pollution
Air pollution