Page 156 - Aeronautical Engineer Data Book

Principles of propulsion 129
Table 8.3 Continued
Nozzle
The rear portion of a jet engine in which the gases
produced in the combustor are accelerated to high
velocities.
Pressure ratio
The ratio of pressure across the compression stage (or
turbine stages) of an engine.
A surge
A disturbance of the airflow through the engine’s
compressor, often causing ‘stall’ of the compressor blades
Thrust
A measurement of engine power.
Thrust reverser
A mechanical device that redirects the engine exhaust
and air stream forward to act as a brake when an aircraft
lands. The rotating parts of the engine do not change
direction; only the direction of the exhaust gases.
Thrust specific fuel consumption
The mass (weight) of fuel used per hour for each unit of
thrust an engine produces.
Turbine
The turbine consists of one or more rows of blades
mounted on a disc or drum immediately behind the
combustor. Like the compressor, the turbine is divided
into a low pressure and a high pressure section. The high
pressure turbine is closest to the combustor and drives
the high pressure compressor through a shaft connecting
the two. The low pressure turbine is next to the exhaust
nozzle and drives the low pressure compressor and fan
through a separate shaft.

8.5 Power ratings
Figure 8.7 shows comparative power ratings for
various generic types of civil and military
aircraft.