internal combustion engine

(redirected from internal combustion)
Also found in: Dictionary, Thesaurus, Medical, Legal, Acronyms, Wikipedia.

internal combustion engine

[in′tərn·əl kəm′bəs·chən ‚en·jən]
(mechanical engineering)
A prime mover in which the fuel is burned within the engine and the products of combustion serve as the thermodynamic fluid, as with gasoline and diesel engines.

Internal combustion engine

A prime mover, the fuel for which is burned within the engine, as contrasted to a steam engine, for example, in which fuel is burned in a separate furnace. See Engine

The most numerous of internal combustion engines are the gasoline piston engines used in passenger automobiles, outboard engines for motor boats, small units for lawn mowers, and other such equipment, as well as diesel engines used in trucks, tractors, earth-moving, and similar equipment. For other types of internal combustion engines See Gas turbine, Rocket propulsion, Rotary engine, Turbine propulsion

The aircraft piston engine is fundamentally the same as that used in automobiles but is engineered for light weight and is usually air cooled. See Reciprocating aircraft engine

Characteristic features common to all commercially successful internal combustion engines include (1) the compression of air, (2) the raising of air temperature by the combustion of fuel in this air at its elevated pressure, (3) the extraction of work from the heated air by expansion to the initial pressure, and (4) exhaust. In 1862 Beau de Rochas proposed the four-stroke engine cycle as a means of accomplishing these conditions in a piston engine (see illustration). The engine requires two revolutions of the crankshaft to complete one combustion cycle. The first engine to use this cycle successfully was built in 1876 by N. A. Otto. See Otto cycle

Two years later Sir Dougald Clerk developed the two-stroke engine cycle by which a similar combustion cycle required only one revolution of the crankshaft. In 1891 Joseph Day simplified the two-stroke engine cycle by using the crankcase to pump the required air. Engines using this two-stroke cycle today have been further simplified by use of a third cylinder port which dispenses with the crankcase check valve used by Day. Such engines are in wide use for small units where fuel economy is not as important as mechanical simplicity and light weight. They do not need mechanically operated valves and develop one combustion cycle per crankshaft revolution. Nevertheless they do not develop twice the power of four-stroke cycle engines with the same size working cylinders at the same number of revolutions per minute (rpm). The principal reasons for this are (1) the reduction in effective cylinder volume due to the piston movement required to cover the exhaust ports, (2) the appreciable mixing of burned (exhaust) gases with the combustible mixture, and (3) the loss of some combustible mixture with the exhaust gases.

About 20 years after Otto first ran his engine, Rudolf Diesel successfully demonstrated an entirely different method of igniting fuel. Air is compressed to a pressure high enough for the adiabatic temperature to reach or exceed the ignition temperature of the fuel. Because this temperature is 1000°F (538°C) or higher, compression ratios of 12:1 to 23:1 are used commercially with compression pressures from about 440 to 800 psi (3 to 5.5 megapascals). The fuel is injected into the cylinders shortly before the end of the compression stroke, at a time and rate suitable to control the rate of combustion. See Diesel engine, Fuel injection

There are many characteristics of the diesel engine which are in direct contrast to those of the Otto engine. The higher the compression ratio of a diesel engine, the less the difficulties with ignition time lag. Too great an ignition lag results in a sudden and undesired pressure rise which causes an audible knock. In contrast to an Otto engine, knock in a diesel engine can be reduced by use of a fuel of higher cetane number, which is equivalent to a lower octane number.

The larger the cylinder diameter of a diesel engine, the simpler the development of good combustion. In contrast, the smaller the cylinder diameter of the Otto engine, the less the limitation from detonation of the fuel.

High intake-air temperature and density materially aid combustion in a diesel engine, especially of fuels having low volatility and high viscosity. Some engines have not performed properly on heavy fuel until provided with a supercharger. The added compression of the supercharger raised the temperature and, what is more important, the density of the combustion air. For an Otto engine, an increase in either the air temperature or density increases the tendency of the engine to knock and therefore reduces the allowable compression ratio.

Diesel engines develop increasingly higher indicated thermal efficiency at reduced loads because of leaner fuel-air ratios and earlier cutoff. Such mixture ratios may be leaner than will ignite in an Otto engine. Furthermore, the reduction of load in an Otto engine requires throttling, which develops increasing pumping losses in the intake system.

References in periodicals archive ?
is an Intellectual Property based company that has introduced patented Internal Combustion Engine technology that will take engine efficiency to the next level, a level beyond today's technological limitations.
Because it can use wet ethanol, the reconstituter makes it possible to save much of the energy that is otherwise wasted purifying the ethanol for use in internal combustion engines.
Rather than abandoning the internal combustion engine and the decades of progress made in its improvement, the Genesis technology will enable automobile makers to design power systems that run off hydrogen gas rather than fossil fuels -- thus eliminating a major source of pollution.
This guide introduces the use of basic thermodynamic engine cycle simulations in engine development and results for spark-ignition, internal combustion engines.
IMechE Internal Combustion Engines; Improving Fuel Economy and Emissions (2011: IMechE, London, UK)
Another key obstacle will be getting automakers to divest of their current long-range internal combustion engine investment plans and switch to the split-cycle design, which could be a monumental task given the fact that most of the world's automaker's are not flush with cash and willing to take a serious gamble on something as crucial as engine configurations.
Papers from an April 2005 conference cover a range of topics related to all areas of the internal combustion engine, from innovative designs and redesigns to emissions production mechanisms.
He predicts fuel cell vehicles will never have less than a $10,000 price premium over internal combustion vehicles.
Although similar questions can be raised about fuel cell cars, nearly everyone agrees that hydrogen-powered vehicles, producing only drinkable water out of their tailpipes, are an unambiguous improvement over internal combustion.
of the internal combustion poludizelny, a power of 330 hp, but not more than 360 horsepower, 8 cylinder, V-layout shaped cylinders; of the internal combustion engine, carburetor, cylinder capacity more than 11000 cm3, power over 250 hp, 6, 8 or 12 cylinders, arrangement of cylinders V-shaped

Full browser ?