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What causes "hot-start" and "wet-start" when starting jet engine i.e. CFM-56B?
I understand that letting the fuel in too early (before sufficient spooling or rpm has been attained) can result in fuel flooding the combustion chamber thus preventing a good start of igniton. But what about hot starts?
2 Answers
- PhilipthepaleLv 71 month ago
Jet/turbine engines rely on generous airflow to prevent overheating.
If the TOT [temp] gets too high while starting, when the airflow is still low and fuel is being burned, engine components can be compromised and the engine should be fully inspected and [usually] overhauled.
- ?Lv 71 month ago
A hot start occurs when the engine isn't spinning fast enough to push sufficient air. If the fuel is ignited before there is enough air flowing around the chamber to cool it, its temperature will increase dramatically and exceed the design limits of the combustion chamber and turbine blades, thus causing a failure. This condition is known as a hot start. A low or flat battery can cause this, since it doesn't spin the engine fast enough.
That's why turbine and jet pilots watch the temperature very closely and if it rockets they cut the fuel off immediately. You shut the fuel off to stop the fire and continue to motor the engine on the starter to draw in cooling air.
