www.pulse-jets.com

hi all, i built a pipewood engine for a science fair project. I got it to run with a constant flow of air and got it to run for like 2 sec without air, and thats it. anyone know whats wrong?

probably not enough fuel

How are you suppling the fuel, and what are using to start it (spark/flame, compressed air/vacuum)? ... i got one of these running a few months ago for high school senior research. I'll try to upload some pics by saturday the 5th

Even after correcting the chamber size, i couldn't get it to work, but i put in a fuel injector using brakeline fittings threaded through the chamber to use propane. Normal USA propane valves, after the regulator, thread in to the brake line perfectly.
Not to scale...

Ben wrote:Your fueling rig may be taking up too much of the volume of the chamber or area of the intake.

I wrote:Not to scale

1/8 inch after a reducer. .19 out of .63 area (2-d) taken up, also I have the intake the same size as the tail pipe. solved the problem of me finding a reducer 2 to 3/4. Plus the chamber length is a 1/2 in. longer in length from the edited length in the other forum. Sorry bad picture.

The intake looks shorter than plan. If you've made it 1" pipe, it may need to be a bit longer still, which changes other lengths, etc. Simple rules are meant to fall, but like Ben says, really give what already works a fair shot.

Preserving an L/D ratio of 6.25 or so on the intake may be more important than the intake length being 1/7 the over-all, but I haven't tried the 1" intake.

The pipe fittings are so crappy for flow, really, it's the main reason to go with a straight pipe and a smaller diameter intake; it's the most forgiving layout.

I'm curious. Pulsejets seem to always be discussed in leignth (maintaining the ratios); Why not volume? We are expanding gas in 3 dimensions. second, how have these ratios come about: mathmatical/trial and error? I have always use trial and error.

attache' wrote:I'm curious. Pulsejets seem to always be discussed in leignth (maintaining the ratios); Why not volume? We are expanding gas in 3 dimensions. second, how have these ratios come about: mathmatical/trial and error? I have always use trial and error.

To put it simply (perhaps too simply), pulsejets are acoustical devices. Their functioning is to a large extent governed by the laws of acoustics. They work best when the gases inside display resonant behavior, meaning that their pulsations resemble a standing wave pattern. For that to happen, the shocks (places of pressure transition) have to be at certain distances from each other. That is why lengths are usually more important than sections and volumes.

True. Organ tuners becoming rocket scientists, interesting. I am on the board of directors for a theator organ society. Never saw the parallel. Thanks