(3) Cycle Characteristics and Variations. The fourstroke/cycle
pistontype engine is designed to perform four events: intake, compression,
power, and exhaust. One cycle (four events) is completed as the crankshaft
rotates twice for a total of 720 degrees. Each event is completed within 180
degrees of crankshaft rotation and is called a stroke. Gas turbine engine
operation consists of four events that are essentially the same as the
reciprocating engine. Air is first drawn through the air inlet section that
relates to the intake event. It then passes through the compressor section,
relating to the compression event. The air then enters the combustor, mixes
with fuel, and is ignited. As the airfuel mixture burns, the pressure
increase is directed through the turbines that extract work from the flowing
gases which relates to the power event. Passing through the turbines, the used
gases are exhausted to the atmosphere, relating to the exhaust event. Figure
118 illustrates the comparison of events between the fourstroke/cycle piston
type engine and the gas turbine.
Figure 118. Comparison of Piston Engine to Turbine Engine.
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