# Fuel that doesnt need compression?

## Main Question or Discussion Point

Excuse the language. English is not my first language and in physics terms I might be lacking.

I was just brainstorming. Is there a fuel that could be used with efficiancy in a compression free engine?

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Borek
Mentor
Coal in a steam engine doesn't require compression, but somehow I don't think that's the answer you are looking for.

You may have to explain more precisely what you mean.

Coal good idea =)

I'm working on a design which I don't know if it will ever work.

The idea is an engine with minimal moving parts. And therefore cannot make compression. Or have to use FORCED compression from ? Ex a Jet compressor. I haven't figured that part out yet.

Borek
Mentor
Well. I had the idea of creating a rotating ball with slots. With a shaft in the center. A spinning ball. Without the wenkel compression principle that (wobbles). Therefore needing a compression free fuel. Or using some sort of forced induction to create compression in the slot before ignition.

Well. I had the idea of creating a rotating ball with slots. With a shaft in the center. A spinning ball. Without the wenkel compression principle that (wobbles). Therefore needing a compression free fuel. Or using some sort of forced induction to create compression in the slot before ignition.
Forced induction is not the same as compression.

Compression works becuase it puts a fixed quantitiy of fuel into a physically smaller space, allowing combusion at higher temperatures.

russ_watters
Mentor
If you are intending an engine where the air/fuel/exhaust is also the working fluid, then not using compression will severely limit the efficiency.

Out of interest, does this design incorporate some form of expansion of the gases once ignited?

Yes. Expansion of gases

russ_watters
Mentor
Note that pulse detonation still utilizes compression, it just does it in a novel way that uses the explosion's own shock wave to compress the mixture before combustion. Again, you don't want to eliminate compression: compression increases efficiency, it doesn't decrease it.

But if you still truly want compression-free combustion, you're describing a pulse-jet engine. But as far as fuels go, not compressing doesn't provide any limitations on fuel I'm aware of. Any conventional fuel should function in such an engine.

No. That was not really what I meant. I meant my design did not have a compressing cycle. The compression that becomes when combustion occurs i didn't put into account as compression when I said compression free. =) sorry about that.