Page 55 - The Jet Engine

5: Turbines

Contents Page

Introduction 45
Energy transfer from gas flow

to turbine 49

Construction 51
Nozzle guide vanes
Turbine discs
Turbine blades
Contra-rotating turbines
Dual alloy discs
Compressor-turbine matching 53

Materials 53

Nozzle guide vanes
Turbine discs
Turbine blades
Balancing 57

temperature. High stresses are involved in this
process, and for efficient operation, the turbine blade
tips may rotate at speeds over 1,500 feet per second,
The continuous flow of gas to which the turbine is
INTRODUCTION exposed may have an entry temperature between
850 and 1,700 deg. C. and may reach a velocity of
1. The turbine has the task of providing the power to over 2,500 feet per second in parts of the turbine.
drive the compressor and accessories and, in the
case of engines which do not make use solely of a jet 2. To produce the driving torque, the turbine may
for propulsion, of providing shaft power for a consist of several stages each employing one row of
propeller or rotor. It does this by extracting energy stationary nozzle guide vanes and one row of moving
from the hot gases released from the combustion blades (fig. 5-1). The number of stages depends
system and expanding them to a lower pressure and upon the relationship between the power required

45