jseaman
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Joined: February 2017
Posts: 14
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Post by jseaman on Jan 27, 2019 11:19:26 GMT -5
I dug out my CT26 propane powered jet engine I built ~18 months ago today and got it fire up again. With a new 5 pin relay for the buzz coil, a fresh spark plug and a bit of encouragement with a leaf blower it ran again. A couple of things:
1. It seemed to fluctuate rather than maintain a steady flow like it used too, short of stripping it all down and checking things out, any thoughts on what would make it a little wobbly?
2. It sustained quite well with up to 10psi but every time I tried my crude afterburner it extinguished. This is just a regulated propane feed through a single pipe into the outlet but guess it may need a ring or something to stop it blowing out the main jet?
Any help welcomed
James
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jseaman
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Posts: 14
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Post by jseaman on Jan 27, 2019 11:21:26 GMT -5
A couple of pics ...
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Post by racket on Jan 27, 2019 15:48:38 GMT -5
Check your propane supply , you need seperate"systems" to prevent possible "fluctuations"
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jseaman
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Post by jseaman on Jan 27, 2019 18:01:45 GMT -5
Thanks, I've got regulators for the feed to the jet and the afterburner and it's stable pressure (57kg tank)
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Post by racket on Jan 27, 2019 18:32:36 GMT -5
What do you mean by "regulators"??
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jseaman
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Post by jseaman on Jan 28, 2019 4:57:06 GMT -5
You can see on of them in the picture (enhanced version attached), it's a gauge with variable valve so I can regulate the propane feed into both the jet and afterburner. I was wondering if the afterburner was igniting in the exhaust and sending a pressure wave back in to stall the jet but it feels more like it slowly stalls than fails with a bang.
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BFTO
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Post by BFTO on Jan 28, 2019 7:09:15 GMT -5
You have a pressure regulator on the bottle? Dimensions on the compressor/turbine and dimensions on the AB?
I see that you have the delivery tube at the primary zone and tangent, that can contribute to some problem to.
Did the turbine work good without AB?
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ausjet
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Post by ausjet on Jan 28, 2019 8:27:42 GMT -5
If your running both off one bottle, so as soon as you turn on the afterburner, the propane pressure for your gas producer will drop substantially and rpm will fall
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Post by racket on Jan 28, 2019 15:55:45 GMT -5
Most regulators don't have sufficiently large enough flows for our engines , also they have bits inside them that can be problematic , its found that replacing regulators with simple needle valves can cure a lot of problems.
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jseaman
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Posts: 14
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Post by jseaman on Jan 28, 2019 16:52:52 GMT -5
Thanks for all the comments. I'll check to see if I get a pressure drop when I turn the afterburner on, that does seem to make sense with the symptoms actually
I think it was 60mm exit from the turbine (just a stock unit), 47mm inducer and 65mm exducer on the turbo
Is it better to have the gas parallel with airflow rather than perpendicular?
Turbine is fine without the AB fired
No regulator on the bottle, just straight to my mini regulators for each (with a shut off valve and one way valve)
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Post by racket on Jan 28, 2019 18:36:32 GMT -5
The propane needs to be injected at 90 degrees to airflow .
Regulators always seem to give troubles , its generally advised to throw them away and use a needle valve , often just the cylinder shutoff v/v , .........with 2 regulators in the system you're bound to have problems
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jseaman
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Post by jseaman on Jan 29, 2019 6:58:16 GMT -5
Oh so the current set up is correct then for propane injection on the ab?
The regulators are working perfectly on the jet, it lights at low pressure then I increase boost by increasing gas supply, very happy with that. Just the afterburner to sort
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BFTO
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Post by BFTO on Jan 29, 2019 7:38:42 GMT -5
Can you draw a simple drawing on how you introduce the propane in the gas producer and AB?
And what happens if you run the gas producer and then open the flow to the AB (without light it off)? change in RPM?
Try to use two bottles and separate systems and needlevalves that racket propose, I use the same but with diesel and you get good control of the engine.
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jseaman
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Joined: February 2017
Posts: 14
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Post by jseaman on Jan 29, 2019 11:05:01 GMT -5
Sure, hopefully the crude attachment will show the set up. I have a 47kg bottle which runs thorough two separate lines (just a T piece) and hits two regulators. One is opened for the jet and the other is for the ab. I can pop a second bottle on easily enough to see what happens. In terms of the gas flow control, I'm very happy with the current set up, not sure why I'd change to a different valve? I'm struggling with this one: "And what happens if you run the gas producer and then open the flow to the AB (without light it off)? change in RPM? " Do you mean, light the jet and allow propane into the exhaust but not fire the spark plug in the exhaust? If so, it extinguishes the jet. Or have I misunderstood the question?
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miuge
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Post by miuge on Jan 29, 2019 16:04:25 GMT -5
Sounds like it's the regulators causing the problems, fluctuation and extinguishing of the flame, replace them with simple ball valves or needle valves as suggested. Been there...
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