The Physics of a Diesel Engine

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The Physics of a Diesel Engine

The world we live in is surrounded by diesel engines. They are on the freeways, railways, airways, and are one of the leading electricity producers in the world. They are also becoming more popular in automobiles. These engines are efficient and reliable and they are getting very sophisticated. However, the physics behind these engines has not changed.

By way of definition, courtesy of Diesel Engine

Engineering: [a] diesel engine is an internal combustion engine in which the chemical energy of fuel is transformed into thermal energy of the cylinder charge, in consequence of the self-ignition and combustion of fuel in the engine cylinder after compression of the air charge in the cylinder (p1 Makartchouk).

There are basically two types of diesel engines, two-stroke and four-stroke. In a two-stroke engine the piston is forced from the top of the cylinder by the expanding air fuel mixture. Before the piston reaches the bottom of the cylinder the used mixture, (called exhaust), is forced out of the cylinder by the incoming fresh air. The fresh air relies upon a blower, air induction system, to propel it into the combustion chamber. During this time period the piston begins to travel to the top of the cylinder and compress the fresh air sufficient to raise the temperature in the combustion chamber, (area between the top of the cylinder and the cylinder head at top dead center), to 1000-1200 degrees Fahrenheit (p12 Dagel). The fuel is then injected under pressure into the combustion chamber, the air ignites the fuel and the gases begin to expand finishing one cycle.

A four-stroke engine begins the same way as the two-stroke with the expanding gases pushing the piston downward, called the ...

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...n chamber rises dramatically. The combined fuel and air molecules bounce off one another and since the path of least resistance is the piston, the piston moves downward creating mechanical work.

Applying physics to something in everyday use creates a new appreciation for what actually happens when you step on the accelerator pedal or see a truck pulling 40,000 plus pounds up a steep incline. With even a basic study of physics my worldview has changed. I now look at that cold piece of cast iron sitting in an engine compartment on a molecular level.

Works Cited

Dagel, John F., and Robert N. Brady. Diesel Engine and Fuel System Repair. Ohio: Prentice Hall, 2002.

Kirkpatrick, Larry D., and Gerald F. Wheeler. Physics A World

View. Florida: Harcourt College Publishers, 2001. Makartchouk, Andrei. Diesel Engine Engineering. New York: Marcel Dekker, Inc., 2002.

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