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

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

Post by ace_fedde » Fri Jul 17, 2009 4:51 pm

Mike,
Is it an idea to make this one sticky? Maybe you can some older newbee questions relocate here as well. I remember that is wasn't that easy for me, as a newbee, to find newbee-information.
We can also direct newbees here as they ask their questions "outside the box" to keep this topic functional.
I think their questions will still be answered while the topic is still inside the valveless forum, thus the questions will be noticed.
Fedde
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Re: Please put your "I am new and need help" question here.

Post by Joauml » Sat Aug 01, 2009 8:36 pm

I built a valveless pulse jet with some steel pipes(trash :) ),

Image


the combustion chambler have a stell pipe with several holes in it

obviously, it dont start, I blow air in the pipe, it make some bangs and it's only that, can you help me or it's a hopeless case? :lol:

* Im using propane as fuel

sorry for my bad english

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

Post by Mike Everman » Mon Aug 03, 2009 2:23 pm

many different geometries can work. You may never know if this one will work before you have successfully started and run a known design.
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Re: Please put your "I am new and need help" question here.

Post by firehawk010 » Wed Aug 26, 2009 7:26 am

Well, this seems as good of place as any to put this...

I had another of my many crazy ideas today, build a small valveless pulsejet out of an old CO2 cartridge i had lying by my keyboard, and not knowing anything about making valveless pulsejet engines, i found this place.

What i have gathered so far about a valveless pulsejet, is the air intake must be smaller than the exhaust, and that it needs a steady flow of fuel. I'll draw up a diagram when i get the time, but my idea was to drill a small hole in the bottom of the co2 cartridge, lay it on it's side, put a little lighter fluid in and try getting it to work. Unfortunately the only fuels i have are lighter fluid, white gas, and normal gas so does anyone think this would work, or am i just crazy?

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

Post by m1tch » Wed Aug 26, 2009 12:24 pm

Hi there, thought I would ask my question in here lol I am in the UK and need to try and find the plumbing parts needed for the 'ugly stick' pulse jet, I can't seem to be able to find those HUGE pipe reducers, can anyone help me out? I don't really wanna buy them in the states and ship them over lol

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

Post by ace_fedde » Wed Aug 26, 2009 2:10 pm

Firehawk,
You won't know till you try, see also Mike's post above yours. What you describe sounds like a jam jar, search for them on the forum and you will get some ideas.
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Re: Please put your "I am new and need help" question here.

Post by Mike Everman » Wed Aug 26, 2009 4:32 pm

firehawk010 wrote:
What i have gathered so far about a valveless pulsejet, is the air intake must be smaller than the exhaust, and that it needs a steady flow of fuel. I'll draw up a diagram when i get the time, but my idea was to drill a small hole in the bottom of the co2 cartridge, lay it on it's side, put a little lighter fluid in and try getting it to work. Unfortunately the only fuels i have are lighter fluid, white gas, and normal gas so does anyone think this would work, or am i just crazy?
Welcome, Firehawk. The intake and exhaust can be the same diameter, and at that size should be an exit area (total) vs. combustion chamber diameter of something less than .4 (at a guess). Small ones like that need a very fast fuel, like acetylene or hydrogen. Those other fuels will not work at this size; the flame speed is too low to get going. The fastest fuel you're likely to find short of these is methanol (sold as fuel dryer in car parts stores, here is marketed as "Heet"). Still, not easy, and not likely fast enough for this size. Go a bit bigger if you can. 2" cc's are quite manageable.
Mike
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Re: Please put your "I am new and need help" question here.

Post by Mike Everman » Wed Aug 26, 2009 4:35 pm

m1tch wrote:Hi there, thought I would ask my question in here lol I am in the UK and need to try and find the plumbing parts needed for the 'ugly stick' pulse jet, I can't seem to be able to find those HUGE pipe reducers, can anyone help me out? I don't really wanna buy them in the states and ship them over lol
If you can drill and tap a pipe thread, you can start with simple caps for the combustion chamber pipe. A good high temp sealant to use is "anti-seize" grease,( with a high molybdenum disulfide content.)
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Re: Please put your "I am new and need help" question here.

Post by firehawk010 » Wed Aug 26, 2009 5:20 pm

Thanks for the tips, i'm sure i got an old sharpie magnum hanging around here that i can try using the casing of.

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

Post by m1tch » Wed Aug 26, 2009 5:21 pm

Mike Everman wrote:
m1tch wrote:Hi there, thought I would ask my question in here lol I am in the UK and need to try and find the plumbing parts needed for the 'ugly stick' pulse jet, I can't seem to be able to find those HUGE pipe reducers, can anyone help me out? I don't really wanna buy them in the states and ship them over lol
If you can drill and tap a pipe thread, you can start with simple caps for the combustion chamber pipe. A good high temp sealant to use is "anti-seize" grease,( with a high molybdenum disulfide content.)
I have found some steel ducting that I might try and use, the combustion chamber will be 100mms in diameter, im not sure how big it should be though :( I have found reducers going from 100mm to 80mm, could I use that as a combustion chamber if I put some 100mm pipe in between? would 80mms each side for the intake and exhaust be ok, or would I need a smaller intake compared to the exhaust (diameter wise) ie get a reducer to reduce it down more on the intake side compared to the exhaust side?

Seems I can get reducers from 125mm to 80 and 125mm to 100mms, would that be ok?

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

Post by firehawk010 » Wed Aug 26, 2009 7:19 pm

Well, being the stubborn little @%$#@ i am i decided to try the co2 cartridge idea anyhow, and i would get three or four good pulses before it would cut. I'm gonna try widening the intake a little later on to see if that helps. i think the chamber on this one is around 2 inches long, but i dunno how thick the metal is so it's just a guess.

Also, is there a ratio for the length of the exhaust tube because i'm just winging it with a little tin foil untill i can get some pipe

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

Post by m1tch » Wed Aug 26, 2009 7:20 pm

Just had another look though some of the papers I have downloaded and found this:

Image

Would this be about right? I have created an Excel spreadsheet to caluclate all the values if you just plug in the diameter of the combustion chamber :) would make it easier for newbies like me to work things out with what we have lol can someone confirm that these numbers are about right/correct for a basic jet - Im sure that I will be adding a U bend onto it but I need to make a basic one first! lol

...Whoh, I just posted this up a minute after Firehawk asked about it lol

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

Post by vturbine » Thu Aug 27, 2009 5:20 am

I don't know enough about pulsejet design to say anything about performance.

But I can ask what is dimension "D" in your drawing? And what is the ID of the CC?

As a wild guess -- one and the same?
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Re: Please put your "I am new and need help" question here.

Post by Mike Everman » Thu Aug 27, 2009 5:57 am

Yes, D is the CC dia. This is cleaned up from the one in Kentfield's paper UAV 1998_3879.pdf which is in the essential reading.
Scaling down may or may not work, start with these lengths for sure. A couple of things:
You need a hot fuel, hydrogen or acetylene for this co2 size, so be ultra careful if you get to trying that. Don't confuse the whop-purdle-lurdle for running like a pulse-jet, which in this size will be a very loud squeal.
It will not work if you put the expansive tail on there, or at least your chances go way, way down that it will run. Just a straight tube for tail.
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Re: Please put your "I am new and need help" question here.

Post by m1tch » Thu Aug 27, 2009 9:08 am

Mike Everman wrote:Yes, D is the CC dia. This is cleaned up from the one in Kentfield's paper UAV 1998_3879.pdf which is in the essential reading.
Scaling down may or may not work, start with these lengths for sure. A couple of things:
You need a hot fuel, hydrogen or acetylene for this co2 size, so be ultra careful if you get to trying that. Don't confuse the whop-purdle-lurdle for running like a pulse-jet, which in this size will be a very loud squeal.
It will not work if you put the expansive tail on there, or at least your chances go way, way down that it will run. Just a straight tube for tail.
Do you suggest I use the intake D as a straight pipe to the comustion chamber and exit diameter as a straight pipe? Also I am guessing that the lenght of the comustion chamber needs to be worked out from the overal size (16.77D) minus all the other parts?

Not having a expansive tail sounds like a lot less work lol

P.S. Im loving your discription for a non-running pulse jet :)

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