combustion chamber
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A combustion chamber is part of an
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 ...
in which the fuel/air mix is burned. For steam engines, the term has also been used for an extension of the
firebox Firebox may refer to: *Firebox (steam engine), the area where the fuel is burned in a steam engine *Firebox (architecture), the part of a fireplace where fuel is combusted *Firebox Records Firebox Records was a Finnish record label based in S ...
which is used to allow a more complete combustion process.


Internal combustion engines

In an
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 ...
, the pressure caused by the burning air/fuel mixture applies direct force to part of the engine (e.g. for a piston engine, the force is applied to the top of the piston), which converts the gas pressure into
mechanical energy In physical sciences, mechanical energy is the sum of potential energy and kinetic energy. The principle of conservation of mechanical energy states that if an isolated system is subject only to conservative forces, then the mechanical energy is ...
(often in the form of a rotating output shaft). This contrasts an external combustion engine, where the combustion takes place in a separate part of the engine to where the gas pressure is converted into mechanical energy.


Spark-ignition engines

In spark ignition engines, such as petrol (gasoline) engines, the combustion chamber is usually located in 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 ...
. The engines are often designed such that the bottom of combustion chamber is roughly in line with the top of 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 ...
. Modern engines with
overhead valves An overhead valve (OHV) engine, sometimes called a ''pushrod engine'', is a piston engine whose valves are located in the cylinder head above the combustion chamber. This contrasts with earlier flathead engines, where the valves were located bel ...
or overhead camshaft(s) use the top of the piston (when it is near
top dead centre In a reciprocating engine, the dead centre is the position of a piston in which it is either farthest from, or nearest to, the crankshaft. The former is known as Top Dead Centre (TDC) while the latter is known as Bottom Dead Centre (BDC). ...
) as the bottom of the combustion chamber. Above this, the sides and roof of the combustion chamber include the intake valves, exhaust valves and spark plug. This forms a relatively compact combustion chamber without any protrusions to the side (i.e. all of the chamber is located directly above the piston). Common shapes for the combustion chamber are typically similar to one or more half-spheres (such as the
hemi Hemi may refer to: People Surname * Jack Hemi (1914–1996), New Zealand freezing worker, rugby union and league player, shearer * Ronald Hemi (1933–2000), New Zealand rugby union player Given name * Hemi Bawa, Indian painter and sculptor * H ...
, pent-roof, wedge or kidney-shaped chambers). The older
flathead engine A flathead engine, also known as a sidevalve engine''American Rodder'', 6/94, pp.45 & 93. or valve-in-block engine is an internal combustion engine with its poppet valves contained within the engine block, instead of in the cylinder head, as ...
design uses a "bathtub"-shaped combustion chamber, with an elongated shape that sits above both the piston and the valves (which are located beside the piston).
IOE engine The intake/inlet over exhaust, or "IOE" engine, known in the US as F-head, is a four-stroke internal combustion engine whose valvetrain comprises OHV inlet valves within the cylinder head and exhaust side-valves within the engine block.V.A.W Hi ...
s combine elements of overhead valve and flathead engines; the intake valve is located above the combustion chamber, while the exhaust valve is located below it. The shape of the combustion chamber, intake ports and exhaust ports are key to achieving efficient combustion and maximising power output. Cylinder heads are often designed to achieve a certain "swirl" pattern (rotational component to the gas flow) and
turbulence In fluid dynamics, turbulence or turbulent flow is fluid motion characterized by chaotic changes in pressure and flow velocity. It is in contrast to a laminar flow, which occurs when a fluid flows in parallel layers, with no disruption between ...
, which improves the mixing and increases the flow rate of gasses. The shape of the piston top also affects the amount of swirl. Another design feature to promote turbulence for good fuel/air mixing is squish, where the fuel/air mix is "squished" at high pressure by the rising piston. The location of the spark plug is also an important factor, since this is the starting point of the ''flame front'' (the leading edge of the burning gasses) which then travels downwards towards the piston. Good design should avoid narrow crevices where stagnant "end gas" can become trapped, reducing the power output of the engine and potentially leading to engine knocking. Most engines use a single spark plug per cylinder, however some (such as the 1986-2009
Alfa Romeo Twin Spark engine Alfa Romeo Twin Spark (TS) technology was used for the first time in the Alfa Romeo Grand Prix car in 1914. In the early 1960s it was used in their race cars ( GTA, TZ) to enable it to achieve a higher power output from its engines. And in the ea ...
) use two spark plugs per cylinder.


Compression-ignition engines

Compression-ignition engines, such as
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 typically classified as either: * Direct injection, where the fuel is injected into the combustion chamber. Common varieties include unit direct injection and common rail injection. *
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 p ...
, where the fuel is injected into a swirl chamber or pre-combustion chamber. The fuel ignites as it is injected into this chamber and the burning air/fuel mixture spreads into the main combustion chamber. Direct injection engines usually give better fuel economy but indirect injection engines can use a lower grade of fuel.
Harry Ricardo Sir Harry Ralph Ricardo (26 January 1885 – 18 May 1974) was an English engineer who was one of the foremost engine designers and researchers in the early years of the development of the internal combustion engine. Among his many other works, ...
was prominent in developing combustion chambers for diesel engines, the best known being the ''Ricardo Comet''.


Gas turbine

In a continuous flow system, for example a jet engine combustor, the pressure is controlled and the combustion creates an increase in volume. The combustion chamber in
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 and
jet engines 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, water jet, and hybrid propulsion, the term typicall ...
(including
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 ...
s and
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 ...
s) is called the
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 ...
. The combustor is fed with high pressure air by the compression system, adds fuel and burns the mix and feeds the hot, high pressure exhaust into the turbine components of the engine or out the exhaust nozzle. Different types of combustors exist, mainly: * Can type: Can combustors are self-contained cylindrical combustion chambers. Each "can" has its own fuel injector, liner, interconnectors, casing. Each "can" get an air source from individual opening. * Cannular type: Like the can type combustor, can annular combustors have discrete combustion zones contained in separate liners with their own fuel injectors. Unlike the can combustor, all the combustion zones share a common air casing. * Annular type: Annular combustors do away with the separate combustion zones and simply have a continuous liner and casing in a ring (the annulus).


Rocket engine

If the gas velocity changes,
thrust Thrust is a reaction force described quantitatively by Newton's third law. When a system expels or accelerates mass in one direction, the accelerated mass will cause a force of equal magnitude but opposite direction to be applied to that syst ...
is produced, such as in the
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 ...
of a
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 ...
.


Steam engines

Considering the definition of combustion chamber used for internal combustion engines, the equivalent part 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 ...
would be the
firebox Firebox may refer to: *Firebox (steam engine), the area where the fuel is burned in a steam engine *Firebox (architecture), the part of a fireplace where fuel is combusted *Firebox Records Firebox Records was a Finnish record label based in S ...
, since this is where the fuel is burned. However, in the context of a steam engine, the term "combustion chamber" has also been used for a specific area between the firebox and the
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, centr ...
. This extension of the firebox is designed to allow a more complete combustion of the fuel, improving fuel efficiency and reducing build-up of soot and scale. The use of this type of combustion chamber is large steam locomotive engines, allows the use of shorter firetubes.


Micro combustion chambers

Micro combustion Micro-combustion is the sequence of exothermic chemical reaction between a fuel and an oxidant accompanied by the production of heat and conversion of chemical species at microscopic scale, micro level. The release of heat can result in the producti ...
chambers are the devices in which combustion happens at a very small volume, due to which surface to volume ratio increases which plays a vital role in stabilizing the flame.


See also

*
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 ...
*
Engine displacement Engine displacement is the measure of the cylinder volume swept by all of the pistons of a piston engine, excluding the combustion chambers. It is commonly used as an expression of an engine's size, and by extension as a loose indicator of the ...
*
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 ...
*
Variable compression ratio Variable compression ratio (VCR) is a technology to adjust the compression ratio of an internal combustion engine while the engine is in operation. This is done to increase fuel efficiency while under varying loads. Variable compression engines al ...


References

{{DEFAULTSORT:Combustion Chamber Engine technology Locomotive parts Gas turbine technology