How come heavy rain doesn't seem to have any effect on combustion of prop and jet engines?

Question

I mean, it would seem that there would be the need for some kind of compensation for the literal damping effect all that water would have. (Liquid or gas.)

Answer 1

It can. Before engine management systems became

sophisitcated, there were incidents where turbines

flamed out due to water injestion.

Answer 2

Well the pilots just fly above it and no more rain.

In addition, engines have compressor wash where they spray water directly to the engine intake so it is just a good bath for the compressor and it is free from nature.

Answer 3

Brant -

It can. Water ingestion tests are part of the engine certification process for turbine engines. The critical point generally occurs while the engine is running at flight idle through really nasty weather at relatively low altitude. Most of the water ingested by turbofan engines is centrifuged outward by the fan, so it does not get ingested by the core (where the combustion occurs), but the tests are still done carefully to make sure that the minimum flight idle is capable of maintaining  thrust and operability at the worst case combination of water droplet size, inlet velocity, and rotor speed. Turbine engines are capable of ingesting prodigious amounts of water, and they are designed and tested with a safety margin.

ADDED: Water injection is a method of adding thrust by adding mass flow, but it is designed to be done at max throttle, not idle, and the water is added at a reduced rate compared to, say, flying through a thunderstorm. Water injection is not used much any more; it was a feature on KC-135 and B52-G military aircraft.

Answer 4

A piston engined aircraft works just like a car's engine.  It has an air intake system that filters the air and keeps most of the rain water out of the intake.  In a jet engine, some rain water does enter into the engine's air intake, and may cool the fires a bit, but it would take a really heavy flow of water to put the fires out.  Some early jet engines actually injected additional water into the engines to create more thrust and improve take-off performance

Answer 5

You need some serious rain to degrade thrust in a modern jet engine...40 inches an hour will degrade thrust.

Answer 6

It does.

Water vapor is less dense than air and it doesn't support combustion.   There is a power loss in both piston and turbine engines due to elevated humidity.  Piston engines generally have a filtered air source but turbine engines do not; so the rain will go right in.  Usually a continuous ignition system is activated to prevent a flameout in a turbine engine in rainy conditions.

Water injection is used on turbine engines to increase power.  The reason why it increases power is because it is injected under pressure (it doesn't displace the air already in the engine) so it adds to the mass gas flow instead of taking away from it.  It also has a cooling effect that allows more fuel to be burned without exceeding the maximum temperatures.

Answer 7

Larry got it perfect (and I learned a few new things here too).