Subject : Power Plant Engineering

Topic: Chap 4- Combined Cycles

Difficulty: Medium

Some of the important properties to be considered while selecting the fuel for gas turbine are as follows:

Volatility

This property has a major effect on starting and combustion efficiency of the engine particularly at low temperature and other adverse conditions. The volatility of the fuel should be such that it is conducive to a quick and successful restart blowout of flame.

Highly volatile fuels are also not desirable as they have the following disadvantages:

i) They are more susceptible to fire (although they have less tendency to explode).

ii) They are conducive to vapour lock to excessive loss of fuel during flight because of evaporation of certain lighter

hydrocarbons.

Therefore, in case of aircraft gas turbines in which the quantity of fuel used is sufficiently high, the fuel wastage will also be more if the fuel is highly volatile.

Combustion products

The products of combustion should not be in the form of solids because they tend to deposit on the combustion chambers, turbine blades and vanes and cause a loss in efficiency.

Energy contents

Fuel should have greater heating value so that fuel consumption may be less.

Lubricating properties

The fuel should provide a certain amount of lubrication of friction surfaces of fuel pumps.

Availability

The fuel selected should be available in large quantities so that it is cheaper.