Page 191 - The Jet Engine

17: Water injection

Contents Page

Introduction 181
Compressor inlet injection 183

Combustion chamber

injection 184

water/methanol mixture (coolant). When methanol is
added to the water it gives anti-freezing properties
and also provides an additional source of fuel. A
typical turbo-jet engine thrust restoration curve is
shown in fig. 17-1 and a turbo-propeller engine
power restoration and boost curve is shown in fig.
17-2.
INTRODUCTION 2. There are two basic methods of injecting the
coolant into the airflow. Some engines have the
1. The maximum power output of a gas turbine coolant sprayed directly into the compressor inlet,
engine depends to a large extent upon the density or but the injection of coolant into the combustion
weight of the airflow passing through the engine. chamber inlet is usually more suitable for axial flow
There is, therefore, a reduction in thrust or shaft compressor engines. This is because a more even
horsepower as the atmospheric pressure decreases distribution can be obtained and a greater quantity of
with altitude, and/or the ambient air temperature coolant can be satisfactorily injected.
increases. Under these conditions, the power output
can be restored or, in some instances, boosted for 3. When water/methanol mixture is sprayed into the
take-off by cooling the airflow with water or compressor inlet, the temperature of the compressor

181