Pressure gain combustor (for real!)

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Bona
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Pressure gain combustor (for real!)

Post by Bona » Mon Oct 05, 2015 1:25 am

Hello fellow pulsejetters,

My name is Paulo Bonagura. I'm an electrical engineer living in southern Brazil. It's been 13 years or so since I last posted on this forum. Now I'm back with some good news.

Back then, after bouncing some ideas with Bruno Ogorelec, Larry Cotrill, Viv, and other forum members (sorry, I can't remember all the names), I proposed a new theory to better understand the operation of pulsejets, so called "acoustic theory". Later I learned about a relatively new branch of physics called thermoacoustics which addresses the problem in the same way I was proposing.

I worked for some time on this theory and created an electrical equivalent model. Although simple, the model offered enough insight of the phenomena happening inside the pulsejet to allow a better understanding the well-know problems connected to pulsejets, like noise, vibration, and low fuel efficiency. Both the theory of operation and computer model enabled me to develop a different and innovative arrangement to address all these problems, but working on the very same principles of the conventional design, i.e. self-sustained combustion and no moving parts, except for the valve. The new arrangement provided a gain of pressure and, most importantly, a STEADY EXHAUST FLOW, which could reduce the noise by several orders of magnitude and virtually eliminate the vibration.

However, for personal reasons, even in face of such exciting results, I had to slow down my work on the project for several years, but I never had abandoned it.

Recently I partnered with a friend who was kind enough to fund me, so I could resume my work. By resume my work I mean building a proof of concept to implement the new arrangement physically, beyond the computer model.

The good news is that the proof of concept is now working, as you can see in the video below.

https://youtu.be/8jpxHVTk2zM

And it is working as expected! It achieved 5%+ of pressure gain and the exhaust flow is almost steady (within 10% of the exhaust velocity).

In the video, the moment I take my hand off the fuel valve is also the moment I remove the compressed air supply, so the combustor works autonomously for the rest of the video.

I'm posting this because we want to share our excitement with all of you and we hope you will understand that we cannot disclose much more by now.

In summary, it is a pressure gain combustor that could be readily applied to a properly designed gas turbine, which would bring a significant improvement on thermodynamic efficiency, reducing fuel consumption and NOx emissions.

We hope you enjoy.

Regards,

Paulo

tufty
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Re: Pressure gain combustor (for real!)

Post by tufty » Mon Oct 05, 2015 5:21 am

That's extremely cool, Paulo.

I'm sure we'd all be interested in more details. Have you instrumented your combustor?

metiz
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Re: Pressure gain combustor (for real!)

Post by metiz » Mon Oct 05, 2015 1:22 pm

tufty wrote:I'm sure we'd all be interested in more details.
All three of us!

Very nice work Bona! Good to see some progress going on still. Can you share any more data, like the workings, without going into too much detail?
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Bona
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Re: Pressure gain combustor (for real!)

Post by Bona » Tue Oct 06, 2015 4:59 pm

Hello guys,

Thank you for the feedback. I'm sorry but I'm really not allowed to disclose much. I hope I'll be able to do so in the near future.

I'll just say that it is based on the same principles as the pulsejet. The novelty is the approach from the thermoacoustic point of view, which enabled creating several internal structures to do the trick of having pulsed combustion and steady exhaust flow in the same machine. Something like a rectifier and filter used in electronics.

Now me and my partner are negotiating more funding to develop it further and hoping that some turbine manufacturer will show interest in this new technology.

Cheers,
Paulo

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Re: Pressure gain combustor (for real!)

Post by metiz » Tue Oct 06, 2015 9:27 pm

How could your engine be used in, or with turbines?
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Bona
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Re: Pressure gain combustor (for real!)

Post by Bona » Wed Oct 07, 2015 12:57 am

metiz wrote:How could your engine be used in, or with turbines?
It can be used in a turbine as a combustor (or combustion chamber) to replace of the so called constant pressure combustor. The constant pressure combustor has an inherent pressure drop (a few percent). By eliminating the pressure loss, or better, by providing some pressure gain, you could remove one or more compressor stages, which would clearly increase the overall efficiency of the turbine engine. There are many research projects on this matter.

Best regards,
Paulo

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Re: Pressure gain combustor (for real!)

Post by Mike Everman » Mon Oct 19, 2015 5:59 pm

Very cool, Paulo. I'll also be very interested in hearing about the instrumentation used when you can talk about it. When comparing to the so called constant pressure combustor, what is the volumetric difference? Can this be done in the same volume with the same massflow?
Mike
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Bona
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Re: Pressure gain combustor (for real!)

Post by Bona » Tue Oct 27, 2015 8:37 pm

Hi Mike,

I'm sorry to say that my partner and I have been reprimanded by the interested party for disclosing the video and the information we have disclosed so far. They are assessing this project and putting a high value on it, and now we're bound by an NDA, so we can't disclose anything more as of now. Nevertheless I can say that the figures I mentioned are confirmed by measurements and you know it doesn't take a physics lab to make those simple measurements ;)

I'm really sorry for being so secretive. Please don't take me wrong, I never meant to post this just to tease you guys. I wanted to share my excitement for having achieved this after so many years of research work.

Unfortunately the old threads on this matter are not available anymore. I've searched the forum but it looks like the oldest posts are from 2003, and the threads on the acoustic theory date back to 2001 or so.

I'm still working on this project and I hope I'll be allowed to post another video showing some more of the operation.

Cheers,
Paulo

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