Diesel

The diesel engine is a type of internal combustion engine; more specifically, it is a compression ignition engine, in which the fuel is ignited by being suddenly exposed to the high temperature and pressure of a compressed gas, rather than by a separate source of ignition, such as a spark plug, as is the case in of the gasoline engine.

This is known as the diesel cycle, after German engineer Rudolf Diesel, who invented it in 1892 and received the patent on February 23, 1893 (1893-02-23). Diesel intended the engine to use a variety of fuels including coal dust. He demonstrated it in the 1900 Exposition Universelle (World's Fair) using peanut oil (see biodiesel).

How diesel engines work

When a gas is compressed, its temperature rises (see the combined gas law); a diesel engine uses this property to ignite the fuel. Air is drawn into the cylinder of a diesel engine and compressed by the rising piston at a much higher compression ratio than for a spark-ignition engine, up to 25:1. The air temperature reaches 700–900 °C, or 1300–1650 °F. At the top of the piston stroke, diesel fuel is injected into the combustion chamber at high pressure, through an atomising nozzle, mixing with the hot, high-pressure air. The resulting mixture ignites and burns very rapidly. This contained explosion causes the gas in the chamber to heat up rapidly, which increases its pressure, which in turn forces the piston downwards. The connecting rod transmits this motion to the crankshaft, which is forced to turn, delivering rotary power at the output end of the crankshaft. Scavenging (pushing the exhausted gas-charge out of the cylinder, and drawing in a fresh draught of air) of the engine is done either by ports or valves. To fully realize the capabilities of a diesel engine, use of a turbocharger to compress the intake air is necessary; use of an aftercooler/intercooler to cool the intake air after compression by the turbocharger further increases efficiency.

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