Help with my uglier stick, I'm about to burn it

[Johnneysul]

This is my first time posting a request so forgive if my questions sound dumb. I came to pulsejets a few months ago from something else I was working on and started setting fire to various plumbing fittings etc. using information I picked up around the internet, (I had not found this site), while it was fun nothing I made ran. I then came here and saw the Ugly Stick and thought someone designed this with me in mind. I cut up my previous attempts and, within no time, I had a straight uglier stick, which is very close to the dimensions in the drawing.
Well it’s been about 3 weeks and many tins of gas later and it still wont go. I read of all these others that have it running perfectly where it starts without air and almost runs without fuel and all I get is growls and bangs and lots of flame.
I’ll explain – it is very close to the correct dimensions, the inlet side of the combustion chamber is not as bell-shaped as the tail side but these are just the fittings I had. I have rounded all of the edges, the inlet is copper pipe and I have flared the end, all of the rest is made from iron fittings. My gas line is 4mm i.d. copper and I have used all different kinds of ends suggested in the forum from flattened to round. I have tried it all the way from the end of the inlet right into the cc in small stages. My air supply is normally a hot air gun but I also have compressed air. My gas supply, which I think must be where my problem lies, is from a blow torch which has 600cc ( 350g) tins of propane. I have followed the starting suggestions given in other threads and I can get it to a strong growl ( but not very loud) and beyond this it turns into a series of very loud bangs at the frequency of my spark, about 3 per second, this is with a fresh tin of gas turned up full. I think it can put out about 3 liters of gas per hour (compared to a 50lb Lockwood takes about 20 gal/hour I believe) and I am wondering if this is way-off the mark of getting it running. I am find it difficult getting an un-regulated gas cylinder fitting, all I can find are ones that are fixed regulators at about 4psi and I read that these are not much good.
I am about to throw my hat at it, I would burn it but I don’t have enough gas left, by the way, the 600cc tin of gas is costing 6.50 euros ( about $8.00 I think ) so it would be quite costly to run much of an engine on these little tins. Any help or suggestions would be great as I am stuck.

[Mike Everman]

Hi John, welcome.
First thing is first, you are definitely not getting enough fuel. It sounds like it wants to go, but you can't turn it up high enough.
I know fittings are hard to get, so you've got to get creative with a barbie tank.
*I recommend you do not do anything I'm about to suggest!*
Disclaimers out of the way, I personally would take the regulator off and butcher it to get the fitting, and adapt that down to whatever hose you have.

The 4mm feed should be OK, pinched, and I've had some good luck with a sharp 90 degree bend in the end, then long enough to just reach the CC. The attached stinger was .187" od, and even bent back on itself a bit. It was submerged so it sprayed at the CC head from the inside.

What is the ID of your intake, and any other dimensions?

[mk]

Jhonneysul,

As Mike Everman already pointed out, you are not getting enough fuel flow out of your propane cartouche. Besides his suggestion, I can only advice you to switch to 5 or 11 kg propane bottles, commonly used for BBQs, campers, burners etc.

In fact, the cartouche layouts are flawed in a way you cannot fix. That means, the opening or straw which pinches the bottle is just of too small size, i.e. diameter. You can only tweak behind this connection, which would not improve anything, because the system inherent flow restriction is just too high. Most likely, also the needle valve - which you are probably using in-line, right? - would restrict fuel flow too much.

Besides the things mentioned above, small canisters would not allow for a large heat (energy) draw, causing the vapour pressure to drop too fast. Well, that's just another system inherent flaw, when using pressurized (gaseous) fuels, but it can be solved somehow by using larger reservoirs. Herein, even when only running an "ugly stick" or similar sized pulse-jet, you would notice some cooling of such larger bottles mentioned above.

Last but not least, for your own health, do not try to mess with the cartouche connection joints or catouches themselves! Which e.g. means the onews used in your current fueling system!

EDIT: Spelling and grammar. What else.

[vhautaka]

How much gas do such cartouches actually give? If a camping stove can easily make 10k btu, that would mean half a pound per hour propane vapor?

What about liquid? I bet those little cans don't have safety features to prevent that.

[Mike Everman]

We have to assume that this combustor is very inefficient, so assuming an SFC of 4 or 5 and thrust of 1 lb, you obviously need to be able to deliver 4 or 5 lb of gas per hour as a guess.

[Johnneysul]

Thanks for the advice. Woult the fixed pressure regulators ( about 4psi ) that we use on gas cookers and BBQs be good enough for a PJ of this size, I can get one of these, a bit pricy, but if it was likely to work I would try it. Could anyone give an estimate as to how much fuel an Ugley Stick would consume per hour?.

Once again, thanks for the help. This is a great site - keep up the good work.

JohnneySul

[Johnneysul]

Thanks Mike, you had my question answered before I could even ask it.

JohnneySul

[mk]

When using propane bottles of that 5+ kg size, it has been mentioned and found several times, that it is best to get rid of any pressure regulator. One or another type of the latter is used commonly for any type of equipment. Without much explanation here, we do not want some of common designs in line, when we have a pulse-jet at the end.
Please search the forum for detailed explanations.