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Pulse Jet Questions

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Pulse Jet Questions

Unread postAuthor: meatballs » Thu May 17, 2007 8:34 pm

I sort of understand how a valveless pulse jet works, but could anyone give me an explanation so i understand it better? i'm thinking i want to try to build a small version of this:
http://www.home.no/andreas.sunnhordvik/English/mechanical/valveless_e.htm
could it be possible to make this out of steel or iron pipe, maybe using one inch and two inch pipe? Any ideas how much power that might generate?
any info would be greatly appreciated
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Unread postAuthor: Freefall » Thu May 17, 2007 11:59 pm

How does it work? Ok, here goes...
(sorry, text will have to do, so feel free to ask lots of questions)

Let's start with the basics. Air is mixed with fuel and ignited. Expanding gases are forced out at high speed, producing thrust.

OK, that covers one cycle.

Let's take the typical valveless pulsejet and assume that both arms are the same length. What happens?
Hot gases are forced out. As the gases cool, some air is drawn back in. But since both pipes are the same length, there's no imbalance. The gases are sucked back in, but much of the already-burned gas stays in the chamber.

Now, let's go back to the typical design with unequal arm lengths.
When the combustion cycle is complete, the gases again cool down, drawing fresh air back into the chamber. BUT since the arms are different lengths, there is a larger moving mass of hot gas on one side than on the other. This imbalance carries the combusted gas out of the chamber, making room for fresh air.

When designed properly, a small portion of the exhaust will fail to leave the chamber, thus providing an ignition source for the newly replenished mixture. Mixture ignites, and the cycle repeats.
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Unread postAuthor: Pete Zaria » Fri May 18, 2007 12:56 am

Freefall's explanation is a pretty good one. Here's some reading material. The first one has step-by-step diagrams explaining the operating cycles of the valveless pulsejet.

http://www.home.no/andreas.sunnhordvik/ ... less_e.htm

http://en.wikipedia.org/wiki/Valveless_pulse_jet

http://www.pulse-jets.com/

Peace,
Pete Zaria.
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Unread postAuthor: meatballs » Fri May 18, 2007 2:45 pm

thankyou both, very helpful. i understand much better now. do you think it might be feasible to build such a device out of metal pipe and fittings?
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Unread postAuthor: spudzinger » Fri May 18, 2007 5:27 pm

Most valveless pulsejets ive seen are custom made if pipe and it is all welded. What type of "metal pipe and fittings" are you talking about?
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