Page 23 - The Jet Engine

Working cycle and airflow

the turbine; the remainder, on its discharge to THE RELATIONS BETWEEN PRESSURE,
atmosphere, provides a propulsive jet. VOLUME AND TEMPERATURE

5. Because the turbo-jet engine is a heat engine, 7. During the working cycle of the turbine engine,
the higher the temperature of combustion the greater the airflow or 'working fluid' receives and gives up
is the expansion of the gases. The combustion heat, so producing changes in its pressure, volume
temperature, however, must not exceed a value that and temperature. These changes as they occur are
gives a turbine gas entry temperature suitable for the closely related, for they follow a common principle
design and materials of the turbine assembly. that is embodied in a combination of the laws of
Boyle and Charles. Briefly, this means that the
6. The use of air-cooled blades in the turbine product of the pressure and the volume of the air at
assembly permits a higher gas temperature and a the various stages in the working cycle is proportion-
consequently higher thermal efficiency. al to the absolute temperature of the air at those

Fig. 2-3 An airflow through divergent and convergent ducts.

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