The diesel engine (also recognized as a compression-ignition or CI engine) is an internal combustion engine in which ignition of the fuel that has been injected into the combustion chamber is caused by the high temperature which a gas achieves (i.e. the air) when greatly compressed ( adiabatic compression ). Diesel engines operate by compressing only the air. Then in that case the initial stress ought to be sixty-four atmospheres, or for 800° centigrade the pressure ought to be ninety atmospheres, and so on. Into the air thus compressed is then progressively introduced from the exterior finely divided fuel, which ignites on introduction, since the air is at a temperature far above the igniting-point of the fuel.
Having said that the original cycle proposed by Rudolf Diesel in 1892 was a continual temperature cycle (a cycle based on the Carnot theory) which would demand much greater compression than what is required for compression ignition. To make this a lot more clear, let it be assumed that the subsequent combustion shall take place at a temperature of 700°.
Low-speed diesel engines (as made use of in ships and other applications exactly where overall engine weight is somewhat unimportant) can have a thermal efficiency that exceeds 50%. Notice that there is no longer a mention of compression temperatures exceeding the temperature of combustion.
Use in locomotives, trucks, heavy equipment and electrical energy generation plants followed later. Now all that is pointed out is the compression should be high adequate for ignition. This increases the air temperature inside the cylinder to such a higher degree that it ignites atomised diesel fuel that is injected into the combustion chamber.
This contrasts with spark-ignition engines such as a petrol engine ( gasoline engine) or gas engine (utilizing a gaseous fuel as opposed to petrol ), which use a spark plug to ignite an air-fuel mixture. A tiny efficiency loss is also avoided compared to two-stroke non-direct-injection gasoline engines since unburned fuel is not present at valve overlap and for that reason no fuel goes directly from the intake/injection to the exhaust.