normal operation. It distributes the fuel to the
control of the engine. Flyweights, opposed by
pilot connection on each of the nozzles. After fuel
spring force, position the pilot valve plunger as
pressure to the flow divider reaches about 150
a function of engine speed. The pilot valve plunger
psig, fuel is supplied to the main connection of
directs servo oil pressure to position the output
each fuel nozzle. The six nozzles are positioned
shaft. The centrifugal governor is set to regulate
to extend into their respective combustion liners.
engine speed at 480 to 580 engine rpm above the
Fuel from the pilot manifold flows through the
normal EG operating speed. It has been factory
center hole in the tip of each nozzle. This forms
adjusted between 14,300 to 14,400 rpm. This
a spray pattern in the combustion liner. Main
equals between 62 and 62.5 Hz generator output.
manifold fuel is supplied to the holes in the
Compressor Inlet Temperature/
periphery of the nozzle tip. From there it is
Compressor Discharge Pressure Sensor
sprayed into the combustion liner and mixed with
compressor air for combustion.
The CIT/CDP sensor (fig. 3-18, item 11)
senses both CIT and CDP. It regulates servo oil
Fuel Manifold Drain Valve
from the EG to the acceleration limiter in the LFV
The fuel manifold drain valves are spring-
in relation to CIT and CDP. The acceleration
loaded, normally closed, solenoid-operated valves
limiter, in turn, schedules fuel flow as a function
located at the bottom of the manifold (figs. 3-18
of servo oil pressure. During the start cycle (above
and 3-19). They drain fuel from the manifolds to
2200 rpm) and during rapid accelerations, the
the waste oil drain tank during coastdown. The
acceleration limiter overrides the input from the
valves are open (energized) only during the
EG. This limits the maximum fuel flow and
2-minute period determined by the coastdown
prevents compressor stall and/or excessive TIT.
timer. On the model 139 these valves are
Below 2200 rpm, the regulated oil pressure from
also open any time the engine is below 2200
the CIT/CDP sensor is blocked by the start
rpm.
temperature limit control valve. This assures the
turbine starts on the minimum fuel flow at
Start Limit Control Valve
lightoff. The CIT/CDP sensor is mounted on the
The start limit control valve is a normally
inlet air plenum. The temperature sensing element
open, three-way, solenoid-operated valve. It is
protrudes into the inlet airstream.
located in the regulated servo oil supply line
Fuel Shutoff Valve
between the CIT/CDP sensor and the LFV (fig.
3-18, item 12). Below 2200 rpm in the start cycle,
The fuel shutoff valve is a normally closed,
the valve is energized. This blocks the regulated
solenoid-operated valve. It is located in the line
oil supply and ports the oil from the acceleration
between the LFV and the fuel manifold. All fuel
limiter (part of the liquid fuel valve) to drain. This
to the fuel nozzles must pass through this valve.
causes the fuel valve to remain against the mini-
During the start cycle, the valve is opened
mum fuel flow stop until the engine reaches 2200
(energized) by the electronic speed switch circuit
rpm. Between 2,200 and 12,780 rpm, the valve is
at 2200 rpm. The valve is closed (de-energized)
normally de-energized (open). However, if TIT
by the control circuits to shut down the engine.
exceeds 1500F, the valve is intermittently energized/
Models 104 and 139 Flow Divider,
de-energized until temperature drops below 1500F.
Fuel Manifold, and Fuel Nozzles
Above 12,780 rpm, the valve is electrically locked
out of the system (de-energized).
Fuel flow from the fuel shutoff valve is
directed to the manifolds by a flow divider. The
LUBE OIL SYSTEM
divider has an internal pressure-actuated valve.
The lube oil systems on the model 104 and
During start-up, the flow divider allows fuel to
model 139 are almost identical. The engine
be supplied to only the pilot manifold. When fuel
receives synthetic lube oil (MIL-L-23699) from the
pressure reaches about 150 psig, the valve opens.
GTGS reduction gear lube oil system.
This allows fuel to be supplied to the main
The engine and reduction gear lube systems
manifold.
share a common supply tank, filter, and cooler.
Two fuel manifolds, pilot and main, supply
The supply tank is the reduction gear sump,
fuel to the six fuel nozzles. Both manifolds are
while the filter is base mounted inside the
Teflon-lined hoses with braided steel armor. Each
reduction gear section of the enclosure. The
manifold is fitted with a solenoid-operated drain
oil cooler is mounted remotely under the module.
valve at its low point. The pilot manifold receives
Please follow figure 3-21 to help you understand
fuel from the flow divider during start-up and
3-26
