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Internal - Combustion engine |
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Fuel combustion takes place in a confined space, and
produces expanding gases that are used to provide mechanical power. The
four-stroke reciprocating engine that is used in automobiles is the most common
internal-combustion engine. In this mechanism, mechanical power is supplied by
a piston that is fitted inside a cylinder. On a downstroke of the piston, the
first stroke, fuel that has been mixed with air (by fuel injection or using a
carburetor) enters the cylinder through an intake valve; the piston moves up to
compress the mixture at the second stroke. At ignition, the third stroke, a
spark from a spark plug ignites the mixture, forcing the piston down; in the
exhaust stroke, an exhaust valve opens to vent the burned gas as the piston
moves up. The piston is connected to a crankshaft by means of a rod. The
reciprocating (up and down) movements of the piston rotate the crankshaft,
which is connected by gearing to the drive wheels of the automobile. The
ignition spark is provided by an electrical system whose power comes from a
battery. This also supplies power to the starting system, which is a small
electric motor that turns the crankshaft until the engine takes over. Water
circulating around the cylinders cool the engine, and lubrication occurs motor
oil that is driven around the moving engine parts by an oil pump. Small
vehicles like lawn mowers and motorcycles use the two-stroke engine, which
combines intake and compression in the first stroke and power and exhaust in
the second. |
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Diesel engine |
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This type of internal combustion engine was patented in 1892 by the German
engineer Rudolph Diesel. It burns fuel oil instead of gasoline and is heavier
and more powerful than the gasoline engine. It differs from the gasoline engine
in that the ignition of fuel is caused by compression of air in its cylinders
instead of by a spark. By varying the amount of fuel injected in the cylinder,
the speed and power of the diesel are controlled. Industrial and municipal
electric generators, continuously operating pumps such as those used in oil
pipelines, and ships, trucks, locomotives, and other such automobiles widely
use diesel to power. |
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