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Internal combustion Engines
A cycle is a series of events that happen over and over again, e.g. Winter, Spring, Summer, Fall.
The four parts to the cycle of an internal combustion engine are intake, compression, power, and exhaust.
A stroke is the motion of a piston up or down. A piston that move up then down has move through two stokes.
Carburetion is the process of creating a fuel-air mixture.
A four-stroke cycle engine accomplishes the four parts of the cycle in four strokes.
A two-stroke cycle engine accomplishes the four parts of the cycle in two strokes.
Four-Stroke Cycle Otto (Gasoline) Engine
- Intake. The inlet valve opens and a fuel-air mixture is brought into the cylinder as the piston moves down.
- Compression. The valves shut and the piston moves up compressing the fuel-air mixture. The volume is reduced to about 1/8th of its original volume. The pressure and temperature go up.
- Power. Just after top dead center the spark plug ignites the
fuel which burns to rapidly increase the pressure, which drives the
- Exhaust. As the piston moves up the exhaust valve opens to permit the products of combustion to leave the cylinder.
Gas Turbine Engines
In a gas turbine engine the four parts to the cycle happen on a continuous basis.
- Intake. Air is taken into the engine.
- Compression. An axial compressor raises the pressure to several thousand pounds per square inch.
- Combustion. Fuel is sprayed into the combusion chamber and ignited.
- Power (exhaust). The hot air first goes through a turbine
that drives the compressor. Then the thrust is developed as the air
leaves the exhause nozzle.
There are four types of gas turbine engines:
- Turbo Jet. The jet engine develops its thrust in the exhaust nozzle.
- Turbofan. The turbofan increases engine efficiency by using a ducted fan that brings cold air around the engine.
- Turboprop. In a turboprop engine, the hot gas drives a
turbine that drives a propeller, taking advantage of the higher
efficiency of propeller driven aircraft at lower speeds and altitude.
- Turboshaft. The turboshaft engine drive boat, ships,
and helicopters. The exhaust of the gas generator section drives a power
turbine which drives a shaft to propel a boat propeller or helicopter
Last updated on 10 July 2010 by P.A. Wiedorn