Page 69 - The Jet Engine

6: Exhaust system

Contents Page

Introduction 59
Exhaust gas flow 61

Construction and materials 63

INTRODUCTION

1. Aero gas turbine engines have an exhaust 2. The temperature of the gas entering the exhaust
system which passes the turbine discharge gases to system is between 550 and 850 deg. C. according to
atmosphere at a velocity, and in the required the type of engine and with the use of afterburning
direction, to provide the resultant thrust. The velocity (Part 16) can be 1,500 deg. C. or higher. Therefore,
and pressure of the exhaust gases create the thrust it is necessary to use materials and a form of con-
in the turbo-jet engine (para. 5) but in the turbo- struction that will resist distortion and cracking, and
propeller engine only a small amount of thrust is prevent heat conduction to the aircraft structure.
contributed by the exhaust gases, because most of
the energy has been absorbed by the turbine for 3. A basic exhaust system is shown in fig. 6-1. The
driving the propeller. The design of the exhaust use of a thrust reverser (Part 15), noise suppressor
system therefore, exerts a considerable influence on (Part 19) and a two position propelling nozzle entails
the performance of the engine. The areas of the jet a more complicated system as shown in fig. 6-2. The
pipe and propelling or outlet nozzle affect the turbine low by-pass engine may also include a mixer unit
entry temperature, the mass airflow and the velocity (fig. 6-4) to encourage a thorough mixing of the hot
and pressure of the exhaust jet. and cold gas streams.

59