fuel applied to the atomizer assembly. A serious
acceleration stabilizer solenoid. If at any time the
engine speed reaches 110 percent, the 110-percent
overspeed could damage the engine. Therefore, it is the
switch opens, opening the ground circuit to the coil of
function of the 110-percent switch to open--which, in
the fuel-holding relay, causing it to open. This action
turn, will close the fuel solenoid valve and cut the
de-energizes the fuel solenoid valve and the bleed-load
supply of fuel off. This will stop the engine when
valve circuit. Fuel flow to the engine is stopped, the
overspeed occurs.
load valve closes, and the engine is shut down.
Q12-3. Which of the following sections of a turbine is
SYSTEM FUEL CONTROL
designed to increase the pressure of the air
and discharge it to the combustion chamber?
Fuel flow to the engine determines engine rpm and
1.
The turbine section
turbine temperature, and must be accurately
2.
The accessory section
controlled. During starting and acceleration, fuel is
3.
The combustion section
controlled by the fuel pump and control unit,
4.
The compressor section
acceleration overtemp thermostat, and fuel atomizer
assembly. The pneumatic portion of the fuel pump and
Q12-4. Which of the following sections of a gas
control unit functions during the starting cycle to
turbine engine contains the starter, oil pump,
increase fuel pressure in relation to the increase of
centrifugal switch, the fuel pump, and the
compressor pressure by reducing the amount of fuel
allowed to bypass, thus increasing the pressure applied
1.
The accessory section
t o t h e f u e l a t o m i z e r a s s e m b l y. I f t h e t u r b i n e
2.
The compressor section
temperature exceeds the specified value during the
3.
The turbine section
start cycle, the acceleration overtemp thermostat opens
4.
The enclosure section
and allows more fuel to bypass, thereby reducing the
pressure of the fuel applied to the fuel atomizer
Q12-5. Which of the following components of the fuel
assembly.
control unit is designed to control fuel to the
atomizer and deliver a portion of the fuel
The fuel atomizer assembly is constructed with a
received from the fuel pump back to the pump
dual discharge orifice; this arrangement includes a
inlet?
valve called a flow-divider valve, which remains
closed at low pressure (starting pressures) and opens as
1.
The discharge valve
acceleration increases, allowing an increase of fuel to
2.
The bypass valve
flow at higher rpm. The correct amount of fuel is
3.
The metering valve
supplied to the engine and is properly atomized at all
4.
The check valve
speeds.
Q12-6. How does the acceleration stabilizer control
and stabilize the rate of acceleration?
GOVERNED OPERATION
1. By limiting the output of the fuel pump
After the engine has reached a steady state, this
2. By limiting the amount of air taken into
condition is maintained from no-load to full-load
the engine
(except when the engine is overloaded) by the fuel
3. By bleeding control air pressure off the
pump and control unit. The mechanical governor of the
diaphragm and bypassing fuel away from
fuel pump and control unit automatically regulates the
the engine
fuel flow to match the power demands placed upon the
4. By increasing fuel pressure to the
turbine wheel, maintaining a substantially constant
atomizer during low-speed conditions by
turbine wheel speed. This is done by sensing the speed
using an accumulator
of the turbine through the flyweights of the control
Q12-7. What type of fuel atomizer is used on the gas
unit. During underspeed condition, the governor
turbine engines found in support equipment?
restricts fuel bypass, which increases the pressure
applied to the fuel atomizer assembly; this, in turn,
1.
A full flow
increases turbine speed. To compensate for an
2.
A dual orifice
overspeed condition, fuel flow is decreases by
3.
A variable output
bypassing more fuel and reducing the pressure of the
4.
A adjustable nozzle
12-12
