Something on pressure regulators...

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Mr.B
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Something on pressure regulators...

Post by Mr.B » Tue Oct 17, 2006 3:38 pm

The main reason, as I see it, that pressure regulators and valveless PJ dont mix has to do with resonance. As the PJ is breathing in and out, the fuel line(propane) joins in the rhytme as the fuel is held back and released as the pressure changes in the engine. The membrane in the regulator dempens the pulse, which results in bad fuel delivery. Maybe one could device a simple tube configuration that reflects the wave....Or maybe a buffer tank at the low pressure end of the regulator..

Eric
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re: Something on pressure regulators...

Post by Eric » Tue Oct 17, 2006 3:58 pm

It has more to do with flow.

Most regulators are meant for low volume uses like grills. A typical 40,000 BTU grill will take 10 hours to empty a 20 pound propane tank, where a typical pulsejet will take on the order of 10 minutes.

Eric
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larry cottrill
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re: Something on pressure regulators...

Post by larry cottrill » Tue Oct 17, 2006 4:38 pm

Of course, I only build small engines, but I always use a regulator with a needle valve feeding through about 2 metres of rubber hose and have never had any problems getting engines to run just fine with it. It is a somewhat specialized design: low pressure (the 26 PSIG shown is its maximum setting) and high flow (oversize pad & seat and large internal passages). It was designed for compressed air use and I re-fitted it with a standard propane barb.

I think Eric is correct; the bad reputation propane regulators have is probably due to inadequate sizing and/or poor planning of the fuel setup. I have no idea how big an engine I could run with this rig, but I would guess probably not very large, even if the needle valve were removed from the flow path. But it's more than adequate for small engines like my FWEs.

L Cottrill
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Good_propane_regulator_setup_crop1.jpg
A more-than-adequate propane regulator and control valve setup for testing small engines. 26 PSI shown here is maximum pressure setting. Photo Copyright 2004 Larry Cottrill
Good_propane_regulator_setup_crop1.jpg (69.66 KiB) Viewed 3506 times

Jonny69
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re: Something on pressure regulators...

Post by Jonny69 » Fri Oct 20, 2006 6:23 pm

My variable regulator runs from 0-60psi and its great for running my 2" exhaust valved jet. It's just a matter of getting the right regulator and I think I got lucky when I bought that one. It probably wouldn't run much bigger than that but then the gas wouldn't come out the bottle much faster either as it would freeze., you'd need to syphon out liquid ideally.

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