Problematic Pulse Jet!

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Problematic Pulse Jet!

Post by projectpulser1 » Tue Nov 27, 2012 4:13 pm

Hi there,

A group of us were given a project to create a working pulsejet. We used popular sites and knowledge from people that had done similar projects in the past and from this we created a pulsejet (see dimensions on engineering drawing). We had problems getting the pulsejet actually going, with splutters of life but nothing actually self-perpetuating.

Here are a few details:

The petal valve material is made from spring steel of thickness 0.25mm (we're thinking maybe this is too thick, but may not be our only problem).

The fuel is propane and is mixed in the combustion chamber which is fed through the valve plate (see attached picture).

The dimensions of the pulsejet are given in the engineering drawing below, and it could be that they are fundamentally wrong, which would point to the fact that the pulsejet needs air to be forced through the valve petals. It seems to be stalling when the air source is moved away (even though it sounds close to resonance).

It's difficult to describe and hence there will be a youtube link soon after this post to actually show what noises it is making, obviously ignoring the noise of the leafblower in the background.

We have used a copper spacer within the assembly of the valve plate, petals and gas supply (see attached drawing) but do not know if this is of any benefit, as it may restrict the volume of air entering the combustion chamber.

We'd be grateful for any help or insight would massively be appreciated. We need to get the bugger going!

Valve Plate
(301.79 KiB) Downloaded 179 times
Our Valve Design
(257.53 KiB) Downloaded 170 times
Valve Plate Assembly
(306.14 KiB) Downloaded 165 times
Engineering Drawing
(192.33 KiB) Downloaded 165 times
Valve plate and combusion chamber glowing.
Jet of Flame exiting through exhaust
Blue Flame - correct gas and air mixture?

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Re: Problematic Pulse Jet!

Post by MANOLO » Mon Dec 31, 2012 7:59 pm

hello these valves are not well made ​​... the entrance is small .. the stop valve must have other degrees, and the most appropriate fuel is kerosene and gasoline ...
in have a person named lopez, is a complete load of pulsejets expert.
is experiencing a life spent in computations. especially the big pulses. are invited to enter the forum and ask lopez. English and Spanish admit. greetings.

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Re: Problematic Pulse Jet!

Post by luc » Thu Feb 07, 2013 12:23 am


Sorry I missed this one looking at the original date it was published ...

For the valve, .25mm = .0098" which I don't think is too thick. In fact, I would say the valve is too thin for an engine that size. My pulse jet was probably 1/3 scale of your engine and it ran very well with .018" (.46mm) thick valve.

One thing I did spot looking at your picture, IF the picture was taken while the engine is not running of coarse, is what looks to be a gap between your valve and the valve plate which would mean the engine's chamber is not close. If this picture was taken from a passive engine (Not running) ... Well, that's a BIG NO NO. The valve MUST be well seated on the plate when the engine is not running.

Next to this ;

1) Make shure your engine is well welded with no holes and a good way to find out is tap the engine's tail pipe with duct tape and fill the engine with water, mark any found holes and weld them close. I've noted you seems to use some sort of clamps and I hope it is not to hold the air inlet to the combustion chamber, because here too that's a NO NO. Pulse jets need to be perfectly closed with NOT A SINGLE holes other then the valves and exhaust, otherwise, any other holes, even as small as a pin head, WILL screw your acoustic and the engine won't run.

2) Start with an engine having an exagerated to long tail pipe, for it is much easier to start with a too long tail pipe then too short, and you can always cut later.

3) Kerosene, gasoline or Propane makes no difference other then the fuel delivery system. This is why I prefer propane for it self pressurise. If you later feel the engine need more fuel, you can then turn the propane bottle upside down and feed the engine with liquid propane.

And that's about it I would say ...

Experience and history has demonstrated that with "Valved" pulse jets, even if you have made alot of mistakes in your design and fabrication, if your engine is totally close with extra tail pipe and you give it air, fuel and sparks ... IT WILL do shit load of noise ... ;-)

Good luck ... ;-)
Designer & Inventor

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