GasSavers_maximilian |
06-04-2009 01:54 PM |
Why do pulse jets lose power at high speed?
Not about cars, but it is an engine at least! I have always been interested in valved pulse jets and was curious if anyone knew the theoretical reasons they lose power at higher speeds. I once saw an old book that showed a design that got around this by enclosing the engine in a shroud that had a diffuser to slow the incoming air down. They didn't discuss why it was a problem though, which was very frustrating.
I have my own theory, but would love to be sanity checked. I think it's because the valves rely on the pressure of the explosion to close them. They cannot move instantly, so a small amount of combustion pressure leaks out before they close. At higher speeds the ram air pressure is greater, causing the valves to take longer and longer to act, thus losing progressively more power.
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