Power Plant Engineering

GAS TURBINE POWER PLANT 283

(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

capacitySecondary

Primary

Supressor

Spare rateresistor

L.T. connectionA.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,