Cutting noise

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PyroJoe
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Re: Cutting noise

Post by PyroJoe » Wed May 09, 2012 7:57 pm

My concern on that one is it may re ingest a significant quantity of spent gas.

Some of the stuff I haven't tested looks like this. With a partial cone or just a portion of pipe placed over some holes between the intake and the augmentor pipe.
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Last edited by PyroJoe on Thu May 10, 2012 2:40 pm, edited 1 time in total.

Bruno Ogorelec
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Re: Cutting noise

Post by Bruno Ogorelec » Wed May 09, 2012 8:21 pm

PyroJoe wrote:My concern on that one is it may re ingest a significant quantity of spent gas.
I don't think so. The chamber will not fill with spent gas. It is already full of air, which will be slightly compressed. It will function like an air spring.

PyroJoe
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Re: Cutting noise

Post by PyroJoe » Wed May 09, 2012 8:58 pm

I may have missed something. If thats supposed to be a spring, I see it as subordinate to the CC pressure, which makes the spring loaded from the CC gas as thats the most significant pressure source. If it is to work as a fresh air spring, that would require the spring to be loaded with fresh air to a point greater or equal to the CC pressure.

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Re: Cutting noise

Post by Bruno Ogorelec » Thu May 10, 2012 4:38 am

PyroJoe wrote:I may have missed something. If thats supposed to be a spring, I see it as subordinate to the CC pressure, which makes the spring loaded from the CC gas as thats the most significant pressure source. If it is to work as a fresh air spring, that would require the spring to be loaded with fresh air to a point greater or equal to the CC pressure.
Why? It works as a spring at any pressure by the virtue of the fact that it is a closed vessel filled with an elastic medium. The exhaust gas exerts pressure on the medium inside and compresses it. (The medium inside, whatever it may be, absorbs overpressure.) When the exhaust gas pressure abates, it springs back.

The whole thing works as a tube with elastic walls and rigid ends. The elasticity probably needs to be tuned. Probably by varying the number and size of the holes.

In continuous operation the medium will probably be a mixture of air and spent gas and the engine will certainly rebreathe some, but probably not enough to worry about.

PyroJoe
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Re: Cutting noise

Post by PyroJoe » Thu May 10, 2012 1:28 pm

The more I look at it, it appears it could benefit from the head pressure from motion, that could give the fresh air load a couple extra pounds. Also a long CC would allow a higher fill ratio of fresh air up front in that area. The flame travel would shift deeper in the engine, and some drift velocity could have the vessel filling mostly with fresh air.

Run statically, with the CC pressure near double of ambient, I see it could possibly fill 50% with spent gas. I guess some stuff is just built for speed.

My recent goal is to contain the pressure as much as possible, and run it through the L/D to transfer as much pressure possible to velocity to cut down the noise. The fraction engines appear to do it best. The blended bodies need it the most as they have short L/D ratios especially in the intakes and tend to have the most violent of natures.

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Re: Cutting noise

Post by PyroJoe » Thu May 10, 2012 3:44 pm

A question presents itself, if 0 psi overpressure is achieved, is anything reflected at the tailpipe opening?

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Re: Cutting noise

Post by Mike Everman » Thu May 10, 2012 5:46 pm

PyroJoe wrote:A question presents itself, if 0 psi overpressure is achieved, is anything reflected at the tailpipe opening?
Ed Zachary. The answer has to be no, but you'd never get to that level of cancelling, so the motor can't be dependent on a full reflection or it will not resonate.
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PyroJoe
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Re: Cutting noise

Post by PyroJoe » Thu May 10, 2012 6:17 pm

Ed Zachary? Is that really where you want to go with this?
Good god we're at cancelling again? I give thanks to Viv for leading me to water. And to M, I get it now.

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