The Diesel Engine
Diesel engines are very similar to the gasoline engine you may find in a car. They both are internal combustion engines, have a four stroke cycle, and convert chemical energy from fuel into mechanical energy. However, the manner in which the combustion stroke is attained sets these two engines apart, and although a seemingly meaningless change, a large change in efficiency results. (Diesel Engines vs. Gasoline Engines)
The diesel engine was invented by Rudolf Diesel in 1892. He learned about the extreme inefficiency of the gasoline engine and worked to produce something more practical. (Introduction to How Diesel Engines Work) The majority of diesel engines use a four stroke process. The strokes are intake, compression, combustion, and exhaust. The engine starts by driving the piston down to suck air into the cylinder through the intake valve. When the piston reaches the bottom, it reverses and drives up to compress the air. At maximum compression of the air, fuel is injected directly into the cylinder by a port in the engine head. The hot compressed air provides the energy for the gasoline to combust. The piston is driven downwards as the fuel burns. Lastly, the piston reverses direction a final time to expel the exhaust out of the chamber via the outlet valve. (Diesel Engines vs. Gasoline Engines)
If you didn’t pick up on the main difference, the diesel engine lacks a spark plug. The air is compressed to a much higher ratio than in a regular gasoline engine, in fact a 14:1 to 25:1 compression ratio range rather than an 8:1 to 12:1 range. This increase in pressure results in a high enough temperature for the fuel to ignite. This increased pressure serves another purpose as well, which actually is the main reason for the birth of the engine. Higher compressed air delivers more energy when combusted. The same size cylinder can deliver twice the power in a diesel engine because the volume of the more compressed air...
References: 1. Marshall B. 2010. How Diesel Engines Work: Diesel Engines vs. Gasoline Engines. Available from: http://auto.howstuffworks.com/diesel1.htm. Accessed 2010 Feb 7.
2. Marshall B. 2010. How Diesel Engines Work: Introduction to How Diesel Engines Work. Available from: http://auto.howstuffworks.com/diesel.htm. Accessed 2010 Feb 7.
3. Marshall B. 2010. How Diesel Engines Work: Diesel Fuel Injection. Available from: http://auto.howstuffworks.com/diesel2.htm. Accessed 2010 Feb 7.
4. Marshall B. 2010. How Diesel Engines Work: Diesel Fuel. Available from: http://auto.howstuffworks.com/diesel3.htm. Accessed 2010 Feb 7.
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