Page 95 - The Jet Engine

9: Internal air system

Contents Page

Introduction 85
Cooling 86

Turbine cooling
Bearing chamber cooling
Accessory cooling
Sealing 89

Labyrinth seals
Ring seals
Hydraulic seals
Carbon seals
Brush seals
Hot gas ingestion
Control of bearing loads 91
Aircraft services 93

internal engine and accessory unit cooling, bearing
chamber sealing prevention of hot gas ingestion into
the turbine disc cavities, control of bearing axial
loads, control of turbine blade tip clearances (Part 5)
INTRODUCTION and engine anti-icing (Part 13). The system also
supplies air for the aircraft services. Up to one fifth of
1. The engine internal air system is defined as the total engine core mass airflow may be used for
those airflows which do not directly contribute to the these various functions.
engine thrust. The system has several important
functions to perform for the safe and efficient 2. An increasing amount of work is done on the air,
operation of the engine. These functions include as it progresses through the compressor, to raise its

85