DClaville Posted March 11, 2011 Share Posted March 11, 2011 I have just finished a new forge burner for a vertical welding forge I will build soon it is a 1" burner main burner tube is 30cm long 1" stainless steel pipe the mixing chamber is 1 1/4" pipe 18cm long with 3 milled 25mm wide 7,5cm long slots the choke sleeve is 1 1/2" pipe flared at the end for smoother air flow the 1" pipe was also flared for a smooth inside where it meets the 1 1/4" mixing chamber so there's no hindrance to the venturi effect. sprayed a bit of Ford blue on it just for kicks the flame holder is just black pipe and just for testing the forge i will build will have the shape for a flame holder cast in it. here is a few pics here is a few vids testing it it is running with a 0,8mm MIG welding tip for the gas injector whatya think? will it be big enough for a 30cm tall by 20cm round vertical chamber ? I have been thinking would it have made a difference (improvement maybe) with the burning and gas/air mixing if i had made say 6 slimmer slots for air intake?? and is the step down in size from the 1 1/4" to 1" "mixing chamber to burner tube" enough or will more, say 1 1/2 mixing chamber for a 1" burner be even more efficient?? all thoughts and input much appreciated cheers. Quote Link to comment Share on other sites More sharing options...
kcrucible Posted March 12, 2011 Share Posted March 12, 2011 Based on the video, I don't think you're getting enough air mixed with the propane initially, which is why the flame is predominantly yellow (propane mixing/burning with the air later.) In my experiance, moving the tip much further into the slots helps a lot with this. Somewhere between 1/4" and 1/2" shy of the slot's end. Basically, you'll get better vaccume, which pulls more air into the tube, letting it burn a bit hotter. In my opinion, the "mixing chamber" is primarily just an air inlet. Mixing happens in the tube proper. As long as you have a surface area of the slots as big as the cross sectional area of the pipe you've got plenty of capacity. A larger diameter mixing chamber, just allows you to grow the slot area, really. I think you're fine as far as that goes. Push the tip forward 2-3" and see what happens. I think you'll be surprised at the difference. At least, it helped my design signifigantly. Quote Link to comment Share on other sites More sharing options...
Nakedanvil - Grant Sarver Posted March 12, 2011 Share Posted March 12, 2011 Kcrucible is right. You want maximum velocity at the choke-point in the venturi. I think you're losing too much velocity with the gas so far away. It's no longer a jet, it has fanned out by the time it gets to the choke-point. Quote Link to comment Share on other sites More sharing options...
DClaville Posted March 12, 2011 Author Share Posted March 12, 2011 AHA! so thats the problem will have to make a new longer injector thanks you Kcrucible and Grant will report back when I get it done Quote Link to comment Share on other sites More sharing options...
Nakedanvil - Grant Sarver Posted March 12, 2011 Share Posted March 12, 2011 The venturi principle is hard to visualize. We're no trying to use the gas to push air through the pipe, That only works to a limited extent. In a venturi the high velocity jet crates a partial vacuum which pulls* the air in. The higher the velocity at the choke-point in the venturi, the better the vacuum. With your air control open, you should be able to get a lean blue flame. *I know, (technically) it's actually atmospheric pressure that "pushes" the air in. Quote Link to comment Share on other sites More sharing options...
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