Gas Trubine Starting Machanisam

 How Gas Turbine Start and Working

Starting, Lubrication and Fuel Systems

Starting Systems

Gas turbine engines are started by turning the compressor at sufficient speed to initiate and sustain combustion. After the engine has reached its self-sustaining or self-accelerating speed, the starter can be deactivated.

If the starter is cut off below the self-sustaining speed, the engine may decelerate because it doesn't have enough energy to overcome its own friction and operating losses. It may also suffer a "hung start" in which it idles at a speed so low that it is unable to accelerate enough to obtain proper operating parameters.

A hung-start engine will overheat because of a lack of cooling air. The starter must therefore continue to boost engine speed well above self sustaining speed to avoid hot or hung (false) start or a combination of both. In a hot start, the engine lights off, but, because of a lack of adequate cooling and combustion air, the exhaust gas temperature exceeds the allowable limit for the engine.

At the proper points in the starting sequence, the starter and, usually, the ignition system will cut off. The higher the rpm before the starter cuts out, the shorter will be the total time required for the engine to attain idle rpm, because the engine and the starter are working together.

All gas turbine starters must be able to produce sufficient torque to start the engine properly. Gas turbines must get to a certain minimum idle rate for a start to be satisfactory. Hence, the torque characteristics of an acceptable starter.