Elektra I Jet Engine Builders Web Log

This Web log is to encourage building and experimenting with the world's cheapest working pulsejet engine: the Elektra I(TM) - total cost in brand-new materials: Under $10.00 US, not counting the spark plug.

Want to build your own Elektra I pulsejet, with help from designer Larry Cottrill? Then this page is for you!

Thursday, July 15, 2004

Regulated Propane Fuel Supply

Here's a picture of my working version of a small-engine propane vapor supply. The only thing that doesn't show up very well here is the small T-handle of the needle valve, which is protruding just to the right of the fuel hose connection. As you can see, the regulator is fairly compact, yet it is a high-volume design, with very large internal port area, quite different from the design of welding regulators. You could use a large capacity propane grille regulator, as long as you can attach an output pressure gauge. I had to provide the propane stem and needle valve [from Menards] and the gauge, which is just an old one I had lying around. A lower range gauge would actually be better, for more accurate settings. The hose is from Menards, and was designed for water hookup to kitchen ice makers; the fittings have rubber O-rings, which means it isn't necessary to wrench them tight to get a perfect seal.

The 26 PSI shown on the gauge is NOT what I ended up with to run Elektra - it's just showing the maximum pressure to which this unit can be set. I am able to run Elektra I with 10 or 15 PSIG, and it would probably run with even less, with this type of regulator. So you can see that the output of the regulator does not need to be high pressure, as long as it is capable of significant gas flow.

Another way to say this is that the idea is to make sure the regulator isn't the flow-limiting element; rather, you want an adjustable low pressure setting that allows a good range of needle valve settings for fine control. As described in the earlier article about the intake details, the propane is delivered early in the intake air stream of the engine, to provide adequate path length for mixing. This method works wonderfully in the case of Elektra I.


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