Please put your "I am new and need help" question here.

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PyroJoe
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Re: Please put your "I am new and need help" question here.

Post by PyroJoe » Wed Apr 18, 2012 6:39 pm

5 Liters should support a tailpipe diameter near 2.98 inches or 75.80mm. Intake would be near 2.62 inches or 66.70mm diameter. That would be a large engine and require alot of fuel.

There is some issues with aerodynamic valving that need to be covered to facilitate the ease of starting.

This was a neat one:
viewtopic.php?p=35963&highlight=#35963

There is also one with multiple intakes and exhaust pipes, will see if I can find it and post it here.
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Storm
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Re: Please put your "I am new and need help" question here.

Post by Storm » Thu Apr 19, 2012 12:07 pm

Yes that is a neat one. I wonder how it compares to other shapes, the thread doesn't expand on performance, I like how the tail flairs from the start.

I had seen the small one on youtube
http://www.youtube.com/watch?v=1QD7U0ogXWM

How did you come up with the figures for the 5 Liter CC?

Any insight into wave mechanics of the pulsejet?
Last edited by Storm on Thu Apr 19, 2012 1:29 pm, edited 1 time in total.
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PyroJoe
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Re: Please put your "I am new and need help" question here.

Post by PyroJoe » Thu Apr 19, 2012 1:28 pm

First I converted liters to cubic inches.
5 liters=305.12 cubic inches

Then I scaled the recipe CC (the one with the cone section) to have a mass property volume of 305.12, this gave the diameter of the tail.
Just for kicks I seperated the cone and the cylinder to see how their volumes compare. The cylinder would be about 167ci and the cone portion about 138.12ci.

Also I scaled a 305.12ci sphere. It is interesting how much volume is packed into a sphere. Also there wouldn't be very many weak seams to fail.

Wave mechanisms, maybe on a mass flow basis. Deflagration generates a positive pressure source, that pressure source drives mass flow out of whatever ports are available. All mass flows obtain a velocity away from the deflagration volume. The deflag pressure reaches ambient, then since all the velocities are away from the source, the source will drop below ambient.

This will reverse the mass flows towards the deflagration volume for refill and possible pre compression. Pressure doesn't have to reach zero as its driving mass flow, it can exit the tail or intake with overpressure, releasing that pressure into the environment. hence some engines release pressure waves.

The closer to the source pressure the mass flow/(remaining pressure) is released, the stronger the over pressure wave will be. Thus it is important for noise reduction to try to convert as much pressure to high velocity mass flow before the pressure is dumped into the environment (by tail or intake).
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Storm
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Re: Please put your "I am new and need help" question here.

Post by Storm » Thu Apr 19, 2012 1:55 pm

This is what I had in mind for the CC, I got excited early (weeks ago) and drilled a TLAR 2.5" (60mm) hole in it for the exhaust before considering the requirements, hense my queries. I havn't drilled or decided upon intake(s), as this was an experimental ie: not intended for any practical use I was thinking of setting intakes radialy like a Logan but at an angle so as to create a vortex. any opinions?
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PyroJoe
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Re: Please put your "I am new and need help" question here.

Post by PyroJoe » Thu Apr 19, 2012 2:21 pm

Thats very close for TLAR method, you must have a good calibration of your eye. :D

There are some details of aerodynamic valving that will help in ease of starting and fill ratio. A sphere may be a little tough to sweep the entire volume of residual exhaust gas.
I will post some basic illustrations to explain aerodynamic valving under the recipe topic. May take a day or more to produce them.

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Re: Please put your "I am new and need help" question here.

Post by Storm » Thu Apr 19, 2012 2:30 pm

Thankyou for taking the time to help me PyroJoe.
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Re: Please put your "I am new and need help" question here.

Post by nalexandrov » Wed Sep 19, 2012 8:24 pm

Can you guys tell me what you think of my thermojet measurements?

1.5" ID tailpipe/28" long
3" ID chamber/6" long
2x inputs, ID .92"/4" long

Someone mentioned i could signifigantly shorten my tailpipe, but it does not match with pyrojoes calibar method. Any advice?

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Re: Please put your "I am new and need help" question here.

Post by Mike Everman » Wed Sep 19, 2012 8:44 pm

My advice is to start with the recipe and get good at spark and fuel, and have fun with your motor several times. Then cut and try different things. As you shorten the tail, it will become progressively hard to start and at some point, will not sustain itself at all. It takes practice to get a marginal engine started.
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Start a thread in the valveless section with your build log and we'll follow along.
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nalexandrov
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Re: Please put your "I am new and need help" question here.

Post by nalexandrov » Thu Sep 20, 2012 12:01 am

Interesting. So you think it would be safe to go from 28" to 20" so I could use a standard peice of tubing? How steadfast is the odd multiple rule for the intake?

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Re: Please put your "I am new and need help" question here.

Post by tubajock » Thu Nov 08, 2012 6:16 pm

I am new and just finished building 2 12lbs Beck Chinese pulse jet engines with some success. I am looking for how to make augmenters for both the intake and exhaust, as far as dimintions (Diameter, total length, size of each cone etc.)

Choppers
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Re: Please put your "I am new and need help" question here.

Post by Choppers » Fri Dec 21, 2012 4:35 am

Hello everybody, my name is Scot and I'm new to pulsejet engines. I've already built an electra-1 engine, and it started and ran great. I'm going to try to post a picture of it running but I'm new to these type of groups. I'm a good builder and have access to a large machine shop with lots of stainless and mild steel, welders, rollers, plasma cutters and lathes. It's at my work and I know how to use all the equipment, it's a regular builders Wonderland. I had fun building the Electra, but I wish I would have built it out of un-galvanize steel because the zinc was a pain! I have a question about my tailpipe, the zinc burnt on all but the last inch at the very end, there it left a perfect ring of untouched galvanization. Is this trying to tell me something? Shorten an inch? Flair? Will be looking for plans, more advanced, something loud with power!

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Re: Please put your "I am new and need help" question here.

Post by Mark » Mon Dec 24, 2012 3:46 am

Note the tail stays cooler. The pulsejet "breathes" some cool air from the tailpipe, that is there is an inflow phase when the air is rarified after the explosion. I have a Project Squid paper where they used high speed photography and quartz window the length of a Dyna-jet to capture the slug of air going back up the tailpipe to some degree, not all the way to the combustion chamber however. This one is said to run at 220 to 240 cycles per second. It's funny how fast air can move when it senses a partial vacuum.
http://www.youtube.com/watch?v=68MRkGxhvRE
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Re: Please put your "I am new and need help" question here.

Post by Mark » Mon Dec 24, 2012 10:46 pm

I had a pulsejet made of galvanized plumbing pipe, the tail 1.5 inches in diameter. It formed a fragile ring of zinc at the very end which I broke free from the inside edge of the pipe. It was kind of neat to see. I suppose the zinc coating melted and got pushed towards the exhaust end. You want to avoid breathing the exhaust of course so galvanized jets should always be run outside of a garage or other enclosed areas.
http://www.anvilfire.com/iForge/tutor.p ... fety3/demo
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gettylee
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Re: Please put your "I am new and need help" question here.

Post by gettylee » Fri Feb 15, 2013 4:12 am

hello,i recently built a fwe as my 1st project&than built a hpx as my 2nd,both have 7.5 inch conical chambers,i got them running fairly quickly on 14oz propane can,although,thay flamed out at about half a tank,prolem solved when submerging can in warm water,the HPX STYLE seems to be way more powerful than the fwe,my qwestion is,how can I make a liquid fuel system? this hpx just might have what it takes to fly a rc plane?

senthil19
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Re: Please put your "I am new and need help" question here.

Post by senthil19 » Sun Feb 24, 2013 7:09 am

Hi Everyone,

I Doing my engineering project on pulse jet, and i have decided to do a FWE engine "LADY ANNE BOLEYN Rev.06" from Larry Cottrill. I'm lacking detail plans of tat, i tried to draw something from the File Below, It will be better if some one provides me some detail plans. I Have also added the drawings which i have drawn.
NX Graphics Window Image.pdf
My designs, if there is anything wrong please inform.
(77.69 KiB) Downloaded 238 times
FWE_evolution_(rev02)[1].GIF
LADY ANNE BOLEYN Rev.06, is from this image

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