FM 1-506 Fundamentals of Aircraft Power Plants ... - Survival Books

WWW.SURVIVALEBOOKS.COMFM 1-506exhaust). The difference is that in a turbine engine all ofthese events happen simultaneously, whereas in thereciprocating engine each event must follow the precedingevent. Another difference is that in a turbine engineeach operation in the cycle is performed by a separatecomponent designed for its particular function; in thereciprocating engine all of the functions are performedin one component.Note that the reciprocating engine obtains its workoutput by employing very high pressures (as much as 1000pounds per square inch [psi]) in the cylinder duringcombustion. With these high pressures a greater amountof work can be obtained from a given quantity of fuel,thereby raising the thermal efficiency of this type engine.On the other hand, a turbine engine’s thermal efficiencyis limited by the ability of its compressor to build up highpressures without excesive temperature rises. Ideally, aturbine engine should burn as much fuel as possible inorder to raise the gas temperature and increase the usefuloutput.Energy added in the form of fuel is more thanenough to drive the compressor. The remaining energyproduces the thrust or power for useful work.NOTE: Thermal efficiency is defined asthe relationship between the potential heatenergy in the fuel and the actual energy outputof the engine.2-6