BCDSVP idea...

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mk
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BCDSVP idea...

Post by mk » Sun Aug 08, 2004 11:51 am

Hello all!

After about one week of internet connection problems I can post something potentially new to the forum. I got this idea while building the thrust rectifier for the K-PT 05a.

It works by using the intake blast of one of the two engine assembly as a compression stage for the other one (note: two engines should work 180° of phase, regarding to the formula 360°/n, where 'n' is the number of engines having a distance lower than one wave length to each other). So compression should begin its work just after one engine has nearly finished/ has began stopping air draw-back through the partial vacuum in the CC. Than compression works completely when the returning flame front ignits the new air/ fuel mixture at the back of the CC, if you will, the CC gets an over pressure from the exhaust AND an the intake side. You would get a higher pressure at the beginning of each cycle, what would increase the degree of effectiveness.

This 'compression plus' shouldn't have a lot or any disadvantages through charging losses (regarding to reaction products like CO, CO2, NOx, H2O,... in the burned gases of the other, 'charging engine'), because of the 'cold air plug' remaining in the 'U'-bend and the intake nozzle of the - at this moment so called - 'charging engine'. So when overpressure works, an extra charge of air enters the - at this moment so called - 'charged engine'.

If it works without any regulation parts, simply with the 'U'-bend, then the difficulty is in timing detail (a lot of trial and error work with 'U'-bend lengths and 'U'-bend distances), using compression advantages and the extra air of the 'cold air plug' but not getting any disadvantages trough reaction products of the charging cycle, current AND (with more attention) following one(s)! Maybe the 'cold air plug' shouldn't be used completely, just up to a half for getting an extra at the following cycle at the other engine, too.

I think you can understand how it works - still in my mind and on paper. Look at the drawing of the arrangement to get an idea.

Any comments, suggestions, etc.?
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mk

Stuart
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it would work

Post by Stuart » Sun Aug 08, 2004 4:19 pm

Great idea, it would work. The -out of phase- will likely set up on it's own.
I'm writing an automated airplane designer in java, useful later when you guys get ready to bolt a p-jet onto some wings

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Post by jmhdx » Wed Aug 11, 2004 6:26 pm

Hi mk, glad to see your mind is busy. I hope I have a shortcut for you.
Build two identical engines of your proven KPT design and point the intakes at each other(a long length of angle iron would be useful), start them both three feet apart then slowly bring them closer together. I'm imagining if they are brought slowly enough together they will move into phase with eachover. If it works and an improvement is percieved then why not design with this function in mind ie shorter narrower intakes?
There might be great merrit in having two straight lockwoods with a u-bend as there would be more power per square inch of surface area than a bent type.

Offering no evidence as usual,
Mike.

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Re: BCDSVP idea...

Post by tufty » Wed Aug 11, 2004 7:01 pm

mk wrote:Hello all!
It works by using the intake blast of one of the two engine assembly as a compression stage for the other one (note: two engines should work 180° of phase, regarding to the formula 360°/n, where 'n' is the number of engines having a distance lower than one wave length to each other). So compression should begin its work just after one engine has nearly finished/ has began stopping air draw-back through the partial vacuum in the CC. Than compression works completely when the returning flame front ignits the new air/ fuel mixture at the back of the CC, if you will, the CC gets an over pressure from the exhaust AND an the intake side. You would get a higher pressure at the beginning of each cycle, what would increase the degree of effectiveness.
<random thought>

Rather than having the 'u' away from the inlets, could you not make the inlets radically shorter and much bigger, and have the 'u' protrude _into_ them? This might help 'draw' mixture into motor 2 when motor one fires. I guess this would work better on a 'chinese' configuration, as there will still be losses from the inlets.

Simon

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Re: BCDSVP idea...

Post by Nick » Thu Aug 12, 2004 9:39 am

I think Troy Legner did this a couple of years ago, but that might have been valved PJ's exhaust to exhaust. ?
I know Bruno was in close contact with Troy, maybe he can shed some light on that?

Nick

Graham C. Williams
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Re: BCDSVP idea...

Post by Graham C. Williams » Thu Aug 12, 2004 4:25 pm

Dear Mk.
How about using the pulse to increase the plugging effect? Using it this way (late in the induction cycle) it may be possible to reduce the length of the induction pipe and increase the fill or at least get the filling starting earlier.

Have you considered how long the path length will have to be?
What are you going to do to stop the compression wave taking the shortest possible path length to the other induction pipe? Perhaps a large plate between the two motors with the U bend mounted in this plate.
Finally, have you considered the wave structure within this bent pipe? I don't think it will simply conduct the pressure wave around the bend.

Graham.

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Re: BCDSVP idea...

Post by mk » Thu Aug 12, 2004 8:17 pm

Really great and helpful replies!! Thank you all!! I alway like getting to know other opinions.

I have two K-PT 05b engines at the moment, one nice and new build (another injector as well) and the so called "ugly" testing one. I could also modify/ change the K-PT 04d for getting a second K-PT 04a...I may try something when I have got a compressor or a new hot-air gun.
But first I should finish my thrust stand...just looking for a suitable balance at the moment.


Especially to Graham:

1. No. I'd do it per "trial and error" work, if it works like I've thoght.
2. I didn't take it into observance. In my way of thinking a wall or something like that needed might not be needed, but it could be added easily. The engines are synchronizing itself just being placed next to each other, "U" gives yust an "extra" this way.
3. "Not completely", I'd say. The "U"-bend acts like a damper for special (high) frequencies. There could be problems, of cours, but the airflow/ massflow can't disappear (friction not considered) only because of the "U"-bend. There should be at least some "extra" in the end.
mk

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Re: BCDSVP idea...

Post by Graham C. Williams » Thu Aug 12, 2004 11:12 pm

Dear Martin.
Try not to confuse the Compression wave with the blast of hot air from the combustion. They move at different velocities. This is one of the major realisations that led to the Phoenix motor. The compression wave travels ahead of the Combustion gas. Yes, the compression wave will cause the air in it's wake to flow in the same direction as the Compression wave. It would help you a lot with your understanding to draw a simple Wave against Time diagram of the events as you would like them to occur, you can then superimpose the combustion gas flow (I’d call this the blast gas), it's velocity can be 0.2 to 0.35 of the Compression waves velocity.
Viv has posted some good pictures showing this effect in another posting.

Graham.

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Re: BCDSVP idea...

Post by mk » Sat Aug 14, 2004 8:50 am

To Graham:

OK, I know what you mean now. I really mixed something up.
Therefore:

3. No, I havent considered the wave structure.
Perhaps the bend mutilates the wave front, but at least it gets changed in some ways. Mainly through the difference of inner and outer path/ arc lengths in the bend and rarely through reflection effects.
I cannot tell or predict something, because I'm in no ways an expert. Testing is the only option for me.
mk

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Re: BCDSVP idea...

Post by Bruno Ogorelec » Sun Aug 15, 2004 5:07 pm

Graham C. Williams wrote:Dear Martin.
Try not to confuse the Compression wave with the blast of hot air from the combustion. They move at different velocities. This is one of the major realisations that led to the Phoenix motor. The compression wave travels ahead of the Combustion gas. Yes, the compression wave will cause the air in it's wake to flow in the same direction as the Compression wave. It would help you a lot with your understanding to draw a simple Wave against Time diagram of the events as you would like them to occur, you can then superimpose the combustion gas flow (I’d call this the blast gas), it's velocity can be 0.2 to 0.35 of the Compression waves velocity.
Viv has posted some good pictures showing this effect in another posting.

Graham.
A very important point. You have to decide whether you want to utilize the wave, the flow or both. All three may be possible, but utilizing even one is damned difficult, as the Albion guys can tell you. Since breaking away from the Albion group, I have concentrated on utilizing the flow, while trying to prevent the waves from skewing my scenario. The Albion team has apparently pursued the waves instead. It may well be a more fruitful approach, but we'll see. The jury is still out.

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Re: BCDSVP idea...

Post by mk » Mon Aug 16, 2004 6:56 pm

Bruno wrote:A very important point. You have to decide whether you want to utilize the wave, the flow or both. All three may be possible, but utilizing even one is damned difficult, as the Albion guys can tell you. Since breaking away from the Albion group, I have concentrated on utilizing the flow, while trying to prevent the waves from skewing my scenario. The Albion team has apparently pursued the waves instead. It may well be a more fruitful approach, but we'll see. The jury is still out.
Seems like you'll always have to consider both, waves and flow, I mean in their affects. Even if you just want to support one...
mk

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Re: BCDSVP idea...

Post by Bruno Ogorelec » Mon Aug 16, 2004 7:13 pm

Yes, yes, certainly. Waves and flows must both be considered very carefully no matter what you intend to do. From what Milisavljevic is saying the heat release rate seems to be the governing factor in setting off both. What I was saying was a gross oversimplification, which is something most of us use when we describe the events in a pulsejet.

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Re: BCDSVP idea...

Post by mk » Mon Aug 16, 2004 7:23 pm

Bruno wrote:Yes, yes, certainly. Waves and flows must both be considered very carefully no matter what you intend to do.
Then I learned something new right now...I haven't considered waves till today.

Seems like the BCDSVP might mostly benefit from compression wave effects than from flow effects...hmmm...just as I wrote: Testing is the only option.
mk

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Re: BCDSVP idea...

Post by Graham C. Williams » Thu Aug 19, 2004 11:06 am

--From what Milisavljevic is saying the heat release rate seems to be the governing factor in setting off both.--

Absolutely. The rate of heat release is what really drives these motors.

Graham.

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