www.pulse-jets.com

I built a pulsejet. Calculated the volumes, lengths and diameters. Even calculated thrust that its going to create.





But it does not seem to work without compressed air. Also compressor's flow may be weak. I know that huge amount of air and fuel should be needed. But my project resonates at somehow lower values. Should I send in air as much as I can and find new resonation point ?

Ignition is achieved, it starts but stops when we cut compressed air going to air intake.

View My Video

Here is attemt to start. Please help

I think you need more fuel to get it to sustain. Btw, you don't need a flare on a expanded tailpipe. A 2nd thing to try is to add a bit more length to the straight part of your tailpipe, this might give you a lower idle setting. Try more fuel first obviously

metiz wrote:I think you need more fuel to get it to sustain. Btw, you don't need a flare on a expanded tailpipe. A 2nd thing to try is to add a bit more length to the straight part of your tailpipe, this might give you a lower idle setting. Try more fuel first obviously

Do you mean that,
-remove the flange out from exhaust pipe
-add this lost 20 mm length to straight narrow part to the end of U turn that means begining of exhaust cone
-use more fuel.

Can the pressure of compressor cause problem ? Because when I send in more fuel it just flames out of the exhaust pipe quietly as I remember. But I didnot try to work with much fuel though.

The flange is pretty pointless so removing it would be a good idea. you could try adding that length to the straight part of the tailpipe, yes. If you use more fuel to get your engine up to idle you'll need more air.

metiz wrote:The flange is pretty pointless so removing it would be a good idea. you could try adding that length to the straight part of the tailpipe, yes. If you use more fuel to get your engine up to idle you'll need more air.

But the air we are sending is limited with the capacity of compressor. So I doubt that It is not capable of sending high flow of air. Also we don't have leaf blower If we manage to start it up without compressor by removing flange and adding length to tailpipe will we need higher air anyways ?
What length can you estimate for the added part ? I'm thinking of cutting out flange and adding 100 mm to straight narrow section that comes after U turn. Also, if we lengthen the 45 mm diameter section (tailpipe's out to air) by adding 60-70 mm of 45 mm diameter of pipe after cutting out flange, will it give the same effect as lengthening narrower 34 mm diameter by 100 mm ?

100mm sounds about right for a first try. If you start the engine up without air and it is running, you won't need air to keep it sustaining (at least, that's the idea)

adding more length to the tailcone will not be the same as adding to the tailpipe. I'd say try the tailpipe first. Btw, what kind of injector are you usin, how far is it in? It COULD just be an injector problem

We drew extruded (both sides) 3 1,5 mm holes to a 8 mm diameter steel pipe.. (Thats total of 6 1,5 mm diameter holes) Holes facing towards the sides (rectangular to flow). We use LPG. Both injector and spark approximately 20 mm away from combustion chamber in and out cones.
It looks like this:

Here is overall sight.

(blue) You probably need only 2 fuel holes pointing back into the engine that are 1mm in diameter. (or 0.71mm if available)

(red)It may help to place a 16mm diameter bar in the intake until it runs on its own. Lockwoods require alot of starting air, no way around that.

Today we cut out the flange out of exhaust tailcone. It got its steady state (with compressor sadly) quickly than before but as we stop compressor air, it stops. We will try to replace injector as you said and add 100 mm length to straight 34 mm diameter exhaust section. Try try try

http://www.youtube.com/watch?v=9o1RaB4pjLw

here is second try. We cut out the exhaust flange. Problem still occurs

Has the fuel injector been modified?

We will try that today, Holes will be looking backwards, does it affect that much ? Also, just 2 holes seem a bit less ? Anyways, we will construct what you have adviced

Fewer holes increase fuel stream pressure/velocity. Fuel velocity pointed into the engine pulls in more fresh air, and helps to mix better.