How does this work?

[Mark]

http://cgi.aol.ebay.com/ws/eBayISAPI.dl ... gory=57114
I was wondering if there was a simple propane fuel pump that would drive a tiny piston, (something like those toy planes with a fuselage pumed up with air that drives a piston/propellor for short jaunts),and admix methanol with the escaping propane?
It would be nice to pull/draw methanol into the picture without a potentially "tastes flamey" fireball heat, don't want to pressurize any more fuel than I need at any one time.
Propane for the pressure head and methanol for the majority of the fuel if possible.
Mark

[cbromano]

This looks to me to only inject methanol into a full size LP tank. If you could find fittings to convert it down to a small, mostly empty, disposible LP tank, 8 fl of methanol would become the main fuel and the LP would expand to maintain its vapor pressure. Better yet- use a small can of O2 that is for basic welding sets. The left hand thread would be a pain in the butt to convert from but it could be done.

If your not actually talking about injecting methanol into the tank of propane, why don't you just set something up like the antique perfume atomisers. Salvage one of those hoses they use for camping and splice a T fitting in the middle with barbs and hose clamps. Let the bottom part of the tube lead into a regular tank of methanol. Control the methanol flow by changing the level of the tank with relation of the fitting.

CB Romano

[Mike Everman]

How beautiful! The whole concept of using a propane tank for liquid fuel, and pressurizing it with propane is genius!
Who needs nitrogen now? Aren't those tanks at 250 psi or so?

Chris or Rescyou, if you're here, what pressure are those PWM fuel injectors expecting?

[Mike Everman]

Better yet- use a small can of O2

Hey, take it to the rocket forum, buddy. ;-P

[resosys]

Chris or Rescyou, if you're here, what pressure are those PWM fuel injectors expecting?

I'm not sure what the limits are, but the fuel rail on my car is at 100psi. It can easily handle 125psi. Fuel injectors probably won't work for pulsejets due to the high heat. Standard NOS or other solenoid valves with some PWM may do the job ahead of a nice little spray nozzle and they are rated at much higher than 250.

I'm still not sure what's so wrong with a fuel pump and pressurized fuel loop?

I may be missing something though. It's happened before.

BTW, I turned 33 today, so there's no telling where I'm headed.

Chris

[Mike Everman]

Happy bday, man! And yeah, pumps are good too. I just like the idea, 'cause you need a stout tank, and we're used to them sitting around with pressurized fuel in them, and think nothing of it. I also like that it automatically has propane available for starting, or running pneumatic actuators and such. (I think that last bit was Bruno's idea from a while ago.)

[Mark]

I'm no chemist, but I was wondering if you added methanol to liquid propane would they become intimate, you know when you add two liquids together, they often don't float one above the other? Would it become a kind of acetone/acetylene soda pop slurry, where when it was ejected into the open air with less pressure, the propane bubbles out of solution.
I was thinking since you have the compressed liquid propane, why not have it run a little pneumatic piston or tubine-like pump and incorporate methanol in with the escaping propane, freezy cold and good for thrust and perhaps cooling certain parts of the engine if need be.
If you just wanted a small amount of fuel, "seems" you could just get some thick plumbing pipe of say 1 inch diameter and cap both ends and take the methanol off the bottom and admit a gaseous propane pressure at the top.
Certainly you would want to fill it completely with alcohol and then have a tiny copper tubing bring pressure to the pipe/crude fuel tank. I hate the idea of any oxygen getting in and for some reason reacting with the pressurized fuel. This really is just an idea for a small, small engine.
I would rather just draw/suck methanol using a propane driven piston like the toy Air Hogg plane that uses air pressure. If you had an initial heat source, perhaps methanol could be used like water in a steam engine, and the hot alcohol vapor sprayed into the engine. From then on, the heat from the pulsejet could drive the steam engine/fuel injector.
Just some half baked thoughts....
The more I experiment with my little Logan, the more ideas evolve on how to feed it fuel. One thing is for certain though, I want is safe and simple! My older brother from time to time mocks me when I say something is too hard or difficult or worth the bother. He chides me and says, "OK, I know you don't want to have to drill more than one hole, like those jam jars." I'm aiming for something as simple as those putt-putt boats to be honest. I have even wondered about somehow using putt-putt action as a fuel pump. Then you could have a pulsejet fuel injection for a puslejet engine.
I made a small improvement on the fueling last night, I put a large needle valve into the fuel tank/fuel line. It's so funny to see the fuel pushed from the nose through the 1/8 inch plumbing pipe and over to the side port where it gets ingested, albeit wastefully. No pressurized propane or traditional fuel injection at all, really it's just fuel getting pushed down a long straw bleeding pressure from the combusion chamber. I like it because it always works when I go out to start it and it's no moving parts, not even with the "high tech fuel injection system." ha

[Bruno Ogorelec]

I was thinking since you have the compressed liquid propane, why not have it run a little pneumatic piston or turbine-like pump

Some 25 years ago I designed a pulsejet with powered valve. It ran on propane. Since propane is stored under considerable vapor pressure, I thought of using a small piston engine – like a double-acting steam engine, really -- to drive a valve to and fro. The amount of propane that powered one movement was the amount that was exhausted from the piston engine into the combustion chamber, so that the valve driver was also a fuel metering unit.

Like all my engines, this one had two combustion chambers, so that valve movement to one side fed one, and the return movement fed the other chamber. It was a very neat design of the engine, giving valve loiter in the closed position. Unfortunately, I lost all drawings. I can’t recall the exact design. Too long ago.

I only remember it had a piston sliding along a shaft with detent stops. A few weeks ago I wrote to a number of forum members for ideas on pneumatic actuators that would do this, but did not get very far. This could be a beautiful thing, because you could use relatively heavy, heat-resistant poppet valves like those used in piston engines, but the frequency could still be high, because the valves would be positively driven independently from combustion pressure.

[sparks]

It´s late now and i´m tired so i may be completely wrong.
One thing that pops up in my head is membranes.
On some of my ultra-low-tech stirling engines i used membranes instead of piston/cylinder.
They are fast (not much mass in movement), eliminates possible leaks and flexible (works OK with less tan perfect precision).
Something to think about i guess.....

[Mike Everman]

No, not wrong. You can use an aneroid from an old altimeter. It's a disk with concentric waves in it to make it more flexible out of plane.

[Bruno Ogorelec]

I am almost certain that a membrane-type 'valve' can only be used to control fuel supply -- e.g. by pushing and a pulling needle valve. Any membrane would quickly use its desired properties under the conditions existing in a pulsejet. But, I could be wrong.

[Mark]

http://cgi.aol.ebay.com/ws/eBayISAPI.dl ... gory=57114
I was wondering if there was a simple propane fuel pump that would drive a tiny piston, (something like those toy planes with a fuselage pumed up with air that drives a piston/propellor for short jaunts),and admix methanol with the escaping propane?
It would be nice to pull/draw methanol into the picture without a potentially "tastes flamey" fireball heat, don't want to pressurize any more fuel than I need at any one time.
Propane for the pressure head and methanol for the majority of the fuel if possible.
Mark

I just got a reply from the seller. The device is used in the propane industry to help eliminate moisture to prevent regulator freeze-ups. "Basically it does the same thing as putting dry gas [methanol] in your automobiles gas tank." A small amount of methanol is injected into the tank.
I wonder how thirsty a little model engine would be if you removed the glowplug and got it cycling using propane with a fitting that screwed into the glowplug hole? Then perhaps use the shaft to pump your methanol along with the captured exhaust of the propane feeding it all into your pulsejet?
Half baked again and sleepy. My brother has a very tiny piston/propellor engine he showed me once that runs on CO2 I think, I should posit the question to him. I think it is even smaller than the .010 he has, if my memory serves. I have a pneumatic screwdriver and a few other air compressor driven devices, maybe if I could take one apart, or adapt it, it would be fun to drive it on propane "IF" it was safe.
T'would be funny to hear the charming sound of a pneumatic lug wrench blended with the sound of a pulsejet. Even funnier would be to rev it up and let it die down over and over, throttling the thrust.
Here's something, don't know if it would be good or if any of you have used these before?http://www.bing.de/english/products/type08020.html
Mark

[cbromano]

I find the simple method of mixing propane and methanol in the same tank extremely attractive. Unlike CO2 or N2, vaporizing propane in the tank would maintain a constant even pressure of about 120psi at 20 deg C. The other advantage is that it would be a way to connect a high-pressure fuel injector to the jet without needing an external pump.

If my high school chemistry serves me right, the propane and methanol would mix but not react. As the volume of liquid inside the tank dropped the propane would boil off to even the pressure back out. I figure there would be a few problems though.

As the propane vaporized the concentration of liquid propane in the methanol would drop. That drop might affect the amount of fuel needed to keep the engine running. The solution would be to add as little propane as possible so it would not affect the combustion of methanol or to add excess propane so the drop in concentration would be negligible.

Am I right in these observations?

I have an idea of using an iron pipe with end caps as a tank. In one end cap I would tap a hole to accept a valve. Since the valve has 3/8 in threads it will fit onto a propane tank. I figure fill the tank mostly with methanol then screw a propane bottle onto it. With the propane tank inverted fill up the tank the rest of the way. I would like to try this idea in the jet I am building. I have never run one before so I don’t actually know how much fuel it will consume. The local hardware store sells 6 in length of threaded pipe. I was looking at going for the 1.5in dia. pipe but is that too big?

CB Romano

[evildrome]

I'd be careful about building your own pressure vessels. There are very strict engineering codes for building such things. These rules are the result of many years of 'suck it & see' followed by trips to the infirmary. And thats just boiler design, not things that hold combustables.

If you're going to use home made pressurised vessels, stand behind something substantial while you fill them & then, don't move them. Better yet, get a hydraulic pressure tester, fill your vessel with water & pressure test to 150% of what you expect. This is how they test compressor tanks.


Cheers,

Wilson.

[Hank]

Hello- Reading this string of input boiled down in my mind the thought that
perhaps a diaphram pump actuated by the pressure pulse of the intake may be the way to go for those so inclined. Consider that most pre-fuel injection American manufacture gasoline automobile engines utilized a diaphram type fuel pump, most actuated by an eccentric cam lobe and a push rod. These pumps were (are) good for a failure-usage of about 100k
miles.
Mylar was mentioned in several threads on the previous incarnation of this site.
Hank