Pulsejet calculators

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Al Belli
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Pulsejet calculators

Post by Al Belli » Sun Jul 18, 2004 7:53 pm

I have noticed quite a difference in the dimensions between Bruce's calculator results, and those of Eric's V1.4 .
Has anyone used either of these calculators to produce a running pulsejet ? And which one would You recommend using ?

Al Belli

Hank
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Calculationous

Post by Hank » Sun Jul 18, 2004 8:35 pm

Hello, Al- I've used several of the calculators that are available from one souce or another on the internet. Outside of spreadsheets I do not use the Excel program that Erics calculator is encrypted in, I do not know its parameters.
The calculator I used in constructing a 35 lb. static thrust unit was provided by Forrest Eckstein on the "old" Home-Made Pulsejets site.
While not providing a print-out capability of data it was the closest in agreeing with what pencil, paper and hand-held calculator congered.
Send me you eMail addy if you do not have this little gem and want it.

Hank Gulfrose@Juno.com

Eric
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Post by Eric » Fri Jul 23, 2004 3:55 am

Well I may be a little partial on the matter, but i reccomend using my calculator. Bruces calculator does not tend to produce engine dimensions that are even close to what real world engines should be. Plus my excel program has a bit more to offer.

What matters most in designing a pulsejet is the tailpipe section. Recently a student in england made a beautiful pulsejet, I believe it is what is listed as the Pulso 1 engine on the download page. He could not get it to run and he increased the tailpipe lenght to what my calculator predicted as the propper size for the diameter tailpipe and it ran. There have been quite a few people who emailed me telling me that they built an engine with a tailpipe from my calculator. The largest engine I have made using my calculator is a 100 pound thrust engine, which reminds me I should really update my website sometime. I also built a 20 pound thrust "high efficiency petal valve" type engine from the calculator.

The reason as to why it is "encrypted" is because i dont really want anyone easily copying and pasting the formulas and making a similar copy and calling it their own.

When I present my thesis, I will also make avaliable the book I wrote back a year ago to go along with it . It sums up a good portion of the research I did, and how to improve the design of modern pulsejets significantly.

Eric

Al Belli
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Calculators

Post by Al Belli » Fri Jul 23, 2004 11:41 am

Hi Eric,

The data and results yielded by Your calculator agree with My survey of successful pulsejet designs. My calculations also agree With those yielded by Your calculator. We are fortunate to have Your Excel spreadsheet available to Us. Thanks for Your efforts.

Al Belli

skyfrog
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5kg thrust pulse-jet

Post by skyfrog » Sat Jul 24, 2004 3:36 pm

Hi,

I'm building a 5kg thrust pulse-jet, here's the design obtained by eric's calculator (I believe there's drawing attached in the program, but I can't see it, so I made an assumption as below) :

Thrust = 5 Kg
Exhaust Pipe Diameter B = 4.75cm
Tailpipe Length C = 68.10cm
Combustion Chamber Length D = 13.62cm (assuming this equals CC diameter too)
Exhaust Cone Length E = 13.62cm
Exhaust Pipe Length F = 40.86cm

I found that for most working design, they tends to have D/B ratio around 2.0, doesn't have such high value as this one D/B = 2.87, what should I do ? make a bigger tail pipe ? Any help would be much appreciated.
Long live jet engine !
Horace
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Rescyou
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I remembered

Post by Rescyou » Sat Jul 24, 2004 4:57 pm

I just remembered I started on a set of pulse jet equations quite some time ago and never got it finished. I posted what I have here for you guys:

http://www.rescyou.com/pulsemath/

Most of it is based around the accurate estimation of intake hole areas. I think you can see from the example that the eliptical hole is pretty much 10% greater in area as compared to the area of a circle.

This stuff is not confirmed nor proven correct in any way, shape or form and I'm posting it as I don't think I'll ever finish the thing.

I had started on some ratio formulas as well which can be seen at the bottom of that page, but I'd have to take a close look to see exactly what the they were for.

Lemme know if the formulas show up for you or not, it was a direct html export from word.

s.
The mind of a man is the man himself.

Eric
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Post by Eric » Sun Jul 25, 2004 3:55 am

Well I tried to reply earlier but my computer crashed after writing up a nice big post... So here it is in the shortest possible way.

The diamter of the combustion chamber is not equal to its lenght. It is goverened by the dimensions of the valve system you make. Three recomended dimensions are given as the variable G. 1 each for the different types of valve systems (petal valve, high efficiency petal valve, and valve grid)

The most important part of the pulsejet is the lenght of the tailpipe, you can vary the lenghts of the C.C. and cone / exhaust pipe and it will still run as long as the overall lenght is right. The ratios that are built into the calculator are good for all around performance.

Good luck,
Eric

Mike Everman
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Post by Mike Everman » Sun Jul 25, 2004 4:37 am

Eric, your calculator is a nice piece of work. If memory serves, you have the three categories of valve type, but no actual numerical ratios for the valve area with respect to some dimension. It would be a nice addition.
Mike
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skyfrog
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Post by skyfrog » Sun Jul 25, 2004 6:02 am

Eric wrote:The diamter of the combustion chamber is not equal to its lenght. It is goverened by the dimensions of the valve system you make. Three recomended dimensions are given as the variable G. 1 each for the different types of valve systems (petal valve, high efficiency petal valve, and valve grid)
Gee thanks, that's really short and clear.
Long live jet engine !
Horace
Jetbeetle

evildrome
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Post by evildrome » Wed Jul 28, 2004 12:02 pm

Hi Eric,

Thanks for the calculator. Its a fine piece fo work. I shall be using it to make my first pulse jet.

I want to try the Argus valve grid but I don't know whether to go with one big row of valves or many rows of smaller valves. This is where an indication of how valve area relates to the overall design would be very helpfull.

Thanks,

Wilson.

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