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Engine Efficiency
Engine efficiency of thermal engines is the relationship between the total energy contained in the fuel, and the amount of energy used to perform useful work. There are two classifications of thermal engines- #Internal combustion (gasoline, diesel and gas turbine-Brayton cycle engines) and # External combustion engines ( steam piston, steam turbine, and the Stirling cycle engine). Each of these engines has thermal efficiency characteristics that are unique to it. Engine efficiency, transmission design, and tire design all contribute to a vehicle's fuel efficiency. Mathematical definition The efficiency of an engine is defined as ratio of the useful work done to the heat provided. : \eta = \frac = \frac where, Q_1 is the heat absorbed and Q_1-Q_2 is the work done. Please note that the term work done relates to the power delivered at the clutch or at the driveshaft. This means the friction and other losses are subtracted from the work done by thermodynamic expansion. Thus an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Engine
An engine or motor is a machine designed to convert one or more forms of energy into mechanical energy. Available energy sources include potential energy (e.g. energy of the Earth's gravitational field as exploited in hydroelectric power generation), heat energy (e.g. geothermal), chemical energy, electric potential and nuclear energy (from nuclear fission or nuclear fusion). Many of these processes generate heat as an intermediate energy form, so heat engines have special importance. Some natural processes, such as atmospheric convection cells convert environmental heat into motion (e.g. in the form of rising air currents). Mechanical energy is of particular importance in transportation, but also plays a role in many industrial processes such as cutting, grinding, crushing, and mixing. Mechanical heat engines convert heat into work via various thermodynamic processes. The internal combustion engine is perhaps the most common example of a mechanical heat engine, in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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. Octane rating does not relate directly to the power output or the energy content of the fuel per unit mass or volume, but simply indicates gasoline's capability against compression. Whether or not a higher octane fuel improves or impairs an engine's performance depends on the design of the engine. In broad terms, fuels with a higher octane rating are used in higher-compression gasoline engines, which may yield higher power for these engines. Such higher power comes from the fuel's higher compression by the engine design, and not directly from the gasoline. In contrast, fuels with lower octane (but higher cetane numbers) are ideal for diesel engines because diesel engines (also called compression-ignition engines) do not compress the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Inertia
Inertia is the idea that an object will continue its current motion until some force causes its speed or direction to change. The term is properly understood as shorthand for "the principle of inertia" as described by Newton in his first law of motion. After some other definitions, Newton states in his first law of motion: The word "perseveres" is a direct translation from Newton's Latin. Other, less forceful terms such as "to continue" or "to remain" are commonly found in modern textbooks. The modern use follows from some changes in Newton's original mechanics (as stated in the ''Principia'') made by Euler, d'Alembert, and other Cartesians. The term inertia comes from the Latin word ''iners'', meaning idle, sluggish. The term inertia may also refer to the resistance of any physical object to a change in its velocity. This includes changes to the object's speed or direction of motion. An aspect of this property is the tendency of objects to keep moving in a straight lin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Four-stroke Cycle Engine Valves
A poppet valve (also called mushroom valve) is a valve typically used to control the timing and quantity of gas or vapor flow into an engine. It consists of a hole or open-ended chamber, usually round or oval in cross-section, and a plug, usually a disk shape on the end of a shaft known as a valve stem. The working end of this plug, the valve face, is typically ground at a 45° bevel to seal against a corresponding valve seat ground into the rim of the chamber being sealed. The shaft travels through a valve guide to maintain its alignment. A pressure differential on either side of the valve can assist or impair its performance. In exhaust applications higher pressure against the valve helps to seal it, and in intake applications lower pressure helps open it. The poppet valve was invented in 1833 by American E.A.G. Young of the Newcastle and Frenchtown Railroad. Young had patented his idea, but the Patent Office fire of 1836 destroyed all records of it. Etymology The word p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 and early electric motor speed controllers. Camshafts in piston engines are usually made from steel or cast iron, and the shape of the cams greatly affects the engine's characteristics. History Trip hammers are one of the early uses of a form of cam to convert rotating motion, e.g. from a waterwheel, into the reciprocating motion of a hammer used in forging or to pound grain. Evidence for these exists back to the Han Dynasty in China, and they were widespread by the medieval period. The camshaft was described in 1206 by engineer Al-Jazari. He employed it as part of his automata, water-raising machines, and water clocks such as the castle clock. Once the rotative version of the steam engine was developed in the late 18th century, the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 two solid surfaces in contact. Dry friction is subdivided into ''static friction'' ("stiction") between non-moving surfaces, and ''kinetic friction'' between moving surfaces. With the exception of atomic or molecular friction, dry friction generally arises from the interaction of surface features, known as asperities (see Figure 1). *Fluid friction describes the friction between layers of a viscous fluid that are moving relative to each other. *Lubricated friction is a case of fluid friction where a lubricant fluid separates two solid surfaces. *Skin friction is a component of drag, the force resisting the motion of a fluid across the surface of a body. *Internal friction is the force resisting motion between the elements making up a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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-called compression-ignition engine (CI engine). This contrasts with engines using spark plug-ignition of the air-fuel mixture, such as a petrol engine ( gasoline engine) or a gas engine (using a gaseous fuel like natural gas or liquefied petroleum gas). Diesel engines work by compressing only air, or air plus residual combustion gases from the exhaust (known as exhaust gas recirculation (EGR)). Air is inducted into the chamber during the intake stroke, and compressed during the compression stroke. This increases the air temperature inside the cylinder to such a high degree that atomised diesel fuel injected into the combustion chamber ignites. With the fuel being injected into the air just before combustion, the dispersion of the fuel i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 run on diesel fuel, gases, or dual fuel. This type of engine was first used in ships and stationary power-generating plants, and is now used for some railway locomotives such as the GE PowerHaul. It was adapted by Mazda for their KJ-ZEM V6, used in the Millenia sedan, and in their Eunos 800 sedan (Australia) luxury cars. More recently, Subaru has combined a Miller-cycle flat-4 with a hybrid driveline for their concept "Turbo Parallel Hybrid" car, known as the Subaru B5-TPH, and Nissan has introduced a small three-cylinder engine with variable intake valve timing that claims to operate an Atkinson cycle at low load (thus the lower power density is not a handicap), or a Miller cycle when under light boost in the low-pressure, supercharg ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 automobile engines. While originally seen exclusively in hybrid electric applications such as the earlier-generation Toyota Prius, later hybrids and some non-hybrid vehicles now feature engines with variable valve timing, which can run in the Atkinson cycle as a part-time operating regimen, giving good economy while running in Atkinson cycle, and conventional power density when running as a conventional, Otto cycle engine. Design Atkinson produced three different designs that had a short compression stroke and a longer expansion stroke. The first Atkinson-cycle engine, the ''differential engine'', used opposed pistons. The second and best-known design was the ''cycle engine'', which used an over-center arm to create four piston strokes in one ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 static compression ratio, calculated based on the relative volumes of the combustion chamber and the cylinder when the piston is at the bottom of its stroke, and the volume of the combustion chamber when the piston is at the top of its stroke. The dynamic compression ratio is a more advanced calculation which also takes into account gasses entering and exiting the cylinder during the compression phase. Effect and typical ratios A high compression ratio is desirable because it allows an engine to extract more mechanical energy from a given mass of air–fuel mixture due to its higher thermal efficiency. This occurs because internal combustion engines are heat engines, and higher compression ratios permit the same combustion temperature t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Variable Displacement
Variable displacement is an automobile engine technology that allows the engine displacement to change, usually by deactivating cylinders, for improved fuel economy. The technology is primarily used in large, multi-cylinder engines. Many automobile manufacturers have adopted this technology as of 2005, although the concept has existed for some time prior to this. Theory of operation Cylinder deactivation is used to reduce the fuel consumption and emissions of an internal combustion engine during light-load operation. In typical light-load driving the driver uses only around 30 percent of an engine’s maximum power. In these conditions, the throttle valve is nearly closed, and the engine needs to work to draw air. This causes an inefficiency known as pumping loss. Some large capacity engines need to be throttled so much at light load that the cylinder pressure at top dead centre is approximately half that of a small 4-cylinder engine. Low cylinder pressure results in lower fuel ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cetane Number
Cetane number (cetane rating) is an indicator of the combustion speed of diesel fuel and compression needed for ignition. It plays a similar role for diesel as octane rating does for gasoline. The CN is an important factor in determining the quality of diesel fuel, but not the only one; other measurements of diesel fuel's quality include (but are not limited to) energy content, density, lubricity, cold-flow properties and sulphur content.Werner Dabelstein, Arno Reglitzky, Andrea Schütze and Klaus Reders "Automotive Fuels" in ''Ullmann's Encyclopedia of Industrial Chemistry'', 2007, Wiley-VCH, Weinheim. Definition The cetane number (or CN) of a fuel is defined by finding a blend of cetane and isocetane with the same ignition delay. Cetane has a cetane number defined to be 100, while isocetane's measured cetane number is 15, replacing the former reference fuel alpha-methylnaphthalene, which was assigned a cetane number of 0. Once the blend is known, the cetane number is calcula ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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