Power Plant Engineering

9.6.4 FUEL SYSTEM AND CONTROLS
9.6.4.1 Fuel System
Fig. 9.19 shows a fuel system used in gas turbine. Basically there are two sub-system-low pres-
sure and high pressure. The low-pressure system consists of a fuel tank, boost pump, strainer, dual fine
oil filters, 
∆
p indicator and ordinary valves. There is a two stages filter process on the low-pressure side
of the system. The purpose of 7.5 micron strainer is to collect the large particles impurities. The boost
pump (centrifugal pump) is used to boost the pressure so that it may overcome the pressure drop in the
two stage of filtration. In the fine filter, all small solid particles are collected as well as the water that
may have passed through water separator located in the users fuel supply system. The dual filter ar-
rangement allows for switching to an alternate element without having shutting down for the change. It
is the 
∆
p indicator, which warns the operator of the filter condition by indicating the red light for switch
over. The red light glows as soon as the oil pressure drop through the working fine filter crosses over a
pre-determined value.
∆
P
Indicator
Low pressure
strainer
Here fuelled cooled
oil cooler and fuel
heater may be provided
especially for aviation 
turbine
Fuel
tank
Booster
pump
Duplex
low
Pressure
filter
Relief valve
Main
fuel pump
Fuel
control
Solenoid
valve
Flow divider
Fuel
Fuel
C
T
Strainer
(Shut-off
valve)
CC
Fig. 9.19. Fuel System for Gas Turbine.

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POWER PLANT ENGINEERING
The high-pressure system consists of main fuel pump, relief valve, strainer, fuel control, shut-off
valve, flow distributor and nozzles. The main fuel pump generates the oil pressure sufficient to be
injected in the combustion chamber. The relief valve installed around the main fuel pump is to protect
the fuel system from excessively high pressure created by the shut-off valve or clogging of the passage
in the fuel system by transferring the excess fuel to the pump inlet. The function of shut-off valve is very
simply to interrupt the supply of the fuel to the combustion chamber and affect a shut down of the
turbine automatically or manually. It is also used for interrupting the flow of other fluids such as the gas
supply pressure to the pneumatic starter, the flow to the pneumatically driven pumps and the supply to
auxiliary fuel lines such as the starting fuel injector. Generally, the shut-off valve is of solenoid type. The
gas turbine requires that the fuel should be well distributed in the various fuel injectors. Flow divider
accomplishes the work. 1t is a pressure sensitive valve which positions the valve opening determined by
the pressure at inlet to the flow divider.
Fuel
Air
Air
Fuel spray
Splash
plate and
heat shield
Air
Main fuel
Primary
Fuel