Power Plant Engineering

(d) Hydraulic Starting Motor. It consists of a hydraulic starter motor for main engine, an accu-
mulator, a hydraulic pump motor for auxiliary power unit (A.P.U.).
Discharging the hydraulic accumulator to power a hydraulic pump motor starts APU. The hy-
draulic pump motor is driven with APU (Fig. 9.16) to start main engine and recharge accumulator. It is
suitable for aircraft engine better.
Hydraulic starter
motor
Accumulator
Hydraulic
pump motor
Main
engine
A.P.U.
Spark
rate
resistor
Discharge
gap
H.T. connection
to ignitor plug
Safety registor
Reservior
capacity
Secondary
Primary
Supressor
Spare rate
resistor
L.T. connection
A.C. supply
Transformer
Fig. 9.16. Hydraulic Starter Motor.
Fig. 9.17. Ignition System.
9.6.2 IGNITION SYSTEMS
Ignition system is utilized to initiate spark during the starting. Once it starts, the combustion is
continuous and the working of ignition system is cut-off automatically. The following are the types of
ignition system.
1. Capacitor discharge system.
(a) High tension system and (b) Low tension system.
2. Induction system.
3. A. C. power circuits.
Here, A.C. power circuit ignition system is discussed. Fig. 9.17 shows the arrangement of A.C.
power circuit. It receives an alternating current that is passed through a transformer and rectifier to
charge a capacitor. When the voltage in the capacitor is equal to the breakdown value of a sealed dis-
charge gap, the capacitor discharges the energy across the face of the ignition plug. Safety and discharge
resistors are fitted in the circuit.
9.6.3 LUBRICATION SYSTEM
9.6.3.1 Elements of Lubrication System
The following are the elements of lubrication system of a gas turbine
1. Oil tank,
2. Oil pump,

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POWER PLANT ENGINEERING
3. Filter and strainer,
4. Relief valve,
5. Oil cooler,
6. Oil and pipe line,
7. Magnetic drain plug,
8. By-pass, valve, and
9. Warning devices.