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# Thermoacoustic hovercraft silencer/engine

Solve the fuel efficiency and noise problems of hovercraft together
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The big problems with hovercraft are poor fuel efficiency, noise and poor cornering. The last problem isn't dealt with here, but the other two might be.

This is very sketchy.

Hovercraft engines are generally hotter than their surroundings. They are also noisy. Why not use both of these together to silence the hovercraft and increase efficiency by using thermoacoustic engines?

Surround the skirt with a series of drums with tubes leading up to the engine to channel the sound waves upwards. The air compression of the waves increases temperature and allows heat to flow inwards, which can be taken advantage of by one Stirling engine. The rarefaction lowers the temperature and can be used by another. The temperature difference is greater than with the sound alone because the engine is hot and the outside is relatively cold.

The output from each Stirling engine is then fed into the fan to increase the efficiency of the conventional engine already powering it.

OK, i know it's really vague but i do feel i'm onto something.

 — nineteenthly, May 02 2010

 You might want to do some numbers on the weight of a stirling engine (and all the drums and tubes) relative to the power it might scavenge and the lifting capacity that might provide.

 Most of the noise from a hovercraft comes not from the engines themselves, but from the vast volumes of air being moved around by fans.

Also look at the actual energy which can be recovered from sound. It's very small.
 — Twizz, May 04 2010

 So i feared. I'm sure there's a better way of doing it than this. My main difficulty is understanding properly how a thermoacoustic engine works. The Stirling engine may not be the best approach. I wonder if there's a scale issue - do smaller craft waste proportionately more energy through sound?

I'm trying to avoid the standing wave, though i suppose there could be some kind of resonance built up.
 — nineteenthly, May 04 2010

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