Piston engine induction icing
In a random moment last night (ok, it wasn't totally random, I was reading up on carb icing) I started wondering why fuel-injected piston engines don't suffer from induction icing.
Air, as I understand it, enters an intake. It passes across a throttle butterfly, just as it would in a carburetted engine. With a low throttle setting, the butterfly will create a considerable venturi effect and cause a depression, and an associated drop in the temperature of the air. Why does the water vapour in the air not then come out of suspension and freeze, as it does in a carburettor?
I can think of two differences. First of all, the fuel is not mixed with the air until a considerable way after the butterfly in the case of the fuel injected system. The latent heat used in fuel vapourisation helps reduce the temperature of the air, and this temperature reduction wouldn't be present with fuel injection. The second difference is the absense of the carburettor venturi in the fuel injected system, the sole venturi effect being provided by the throttle butterfly. But I thought that both of these were relatively minor effects?
I must be missing something somewhere. Can anyone fill in the gaps and tell me what's wrong with my argument?
Thanks,
FFF
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