Internal
-Combustion engine
 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.
Diesel
engine
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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