I need help with tuning a propane burner.

Gallery, Projects and General > How do I??

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vtsteam:

--- Quote from: S. Heslop on March 28, 2013, 01:20:48 PM ---
--- Quote from: vtsteam on March 27, 2013, 07:42:41 PM ---Pure guesswork , but looks to me like your square air opening is too far back to benefit from the gas jet, so the jet isn't pulling much air in.

--- End quote ---

I don't understand why opening the choke would blow the flame out in this instance.

Maybe I could try rolling a flare.

--- End quote ---

My guess was that you don't have enough oxygen mixing in. The flame is yellow and moves out away from the burner nozzle as you increase pressure because it is trying to mix with air beyond the burner before it can combust. Opening still further blows it out.

My guess is also that the gas orifice you built is located too far forward to draw in much air from your air ports. That's why it's so rich.

If you move the orifice back or move the ports forward you will draw in more air (I believe) and should have a leaner flame and one that stays more attached as you open the gas tap further.

Look at Lionel Oliver's burner referenced by Steve Huckss above. Notice that the orifice (a tiny drilled hole) Is located considerably aft of the air port holes. Now look at your topmost photograph of your own burner. Where is the air port in relation to your jet orifice?

I believe that the higher the gas pressure, the further forward a port needs to be to draw well. As you increase your gas, your ports are (in my estimate) reducing the amount of incoming air, rather than increasing it.

Again, all guesswork on my part.

S. Heslop:

--- Quote from: vtsteam on March 28, 2013, 01:36:19 PM ---
--- Quote from: S. Heslop on March 28, 2013, 01:20:48 PM ---
--- Quote from: vtsteam on March 27, 2013, 07:42:41 PM ---Pure guesswork , but looks to me like your square air opening is too far back to benefit from the gas jet, so the jet isn't pulling much air in.

--- End quote ---

I don't understand why opening the choke would blow the flame out in this instance.

Maybe I could try rolling a flare.

--- End quote ---

My guess was that you don't have enough oxygen mixing in. The flame is yellow and moves out away from the burner nozzle as you increase pressure because it is trying to mix with air beyond the burner before it can combust. Opening still further blows it out.

My guess is also that the gas orifice you built is located too far forward to draw in much air from your air ports. That's why it's so rich.

If you move the orifice back or move the ports forward you will draw in more air (I believe) and should have a leaner flame and one that stays more attached as you open the gas tap further.

Look at Lionel Oliver's burner referenced by Steve Huckss above. Notice that the orifice (a tiny drilled hole) Is located considerably aft of the air port holes. Now look at your topmost photograph of your own burner. Where is the air port in relation to your jet orifice?

I believe that the higher the gas pressure, the further forward a port needs to be to draw well. As you increase your gas, your ports are (in my estimate) reducing the amount of incoming air, rather than increasing it.

Again, all guesswork on my part.

--- End quote ---

Ah that makes sense.

I just tried out making a flare out of a bit of scrap pipe and it made a fair bit difference, but still not ideal. I'm letting the garage air out for a bit then i'll try moving the orifice back. The brass bit is loose in the steel tube and can slide back a bit, although i'd need to hold it aligned by hand myself. If it works out I could figure out a more permanent solution.

Come to think of it, I could make a whole new part to hold mig tips as orifices.

S. Heslop:
I think I finally got it working. Had to order a new pin chuck for smaller microdrills. Got it online for a few reasons. I'd heard that Eclipse brand were still the best around but the one I got is far from that. It was out of concentricity by at least 2 millimeters, and i'm lucky I had a 4 jaw chuck to get it better aligned.

Drilled out a 0.6mm gas orificie and here it's running at about half a bar pressure.

Thanks for the help though everyone. I think I better understand how these things work now.

DaveH:
It isn't quite so easy designing burners for natural gas as it was for coal gas.
A good place to start maybe to have a look at a Natural gas Bunsen burner with a flame retainer.
:beer:
DaveH

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