I've built a version of the Reil burner based on a drawing by Rupert Wnig. Mine uses a 1.4" i.d. SS burner tube and 2 to 1-1/4 reducer coupling and Tweco tips. For my version I built a butterfly choke out of a short piece of
2" SS nipple. Initial open air test burns show that the thing lights and runs and I can get reasonable flame control with the choke although I can't get the nice symmetrical and consistent flares that Reil shows on his site. I am surprised, too, that even with 15-20 psi gas pressure the burner like alot of choke, i.e. nearly closed. My question is this. How do you select the tip or jet size. With a .8mm tip the burner sometimes wanted to burn inside the burner tube which I know is probably because the tip was too small. I tried one drilled out to .055" and another drilled out to .065" and this moved the flame out to the end of my burner tube. But, how do you optimize the jet size? I've thoroughly researched the Reil site (a bit difficult to navigate) but couldn't find any advice on this. Others say that they started small and worked their way up but how do you know when you're there? Strangely, too, I tried a few nozzle flares that I machined, and get about the same results with or without them in open air. I still haven't made the perfect one yet though with the theoretical 2 x i.d. length and
I built one pretty much copying Brian Booorman's design at
. The only thing I did different was my reducer bell was 1 1/4 at the wide end (I couldn't find one that went to
1.5 in) and I didn't attach the nipple at the back where you would use a choke (I don't have a choke of any kind). And I'm pretty sure I drilled a #60 hole (I don't know the actual diameter in inches or mm) and left it at that. You said you couldn't get the "nice symmetrical and consistent flares that Reil shows," if you mean the flame isn't even, make sure the jet is in the center of the pipe and pointed straight down it. I also had to move my flared nozzle in and out to find the best place to put it. I don't know how my burner runs as far at efficiency and I'm not real sure how rich/lean it burns, but its hot and clean enough to forge weld steel, so it's good enough for me.
My experience is that tip size only determines mixture. If you have too large an orifice for your venturi, even with the choke fully open you'll never even get it neutral. (Mind this is affected by the flare, which adds a bit of back pressure. A short flare will burn much leaner than a proper one.) Too small an orifice and velocity will be slow because the intake will be so choked off with respect to the diameter of the burner tube.
A good flame is a short inner cone of blue color. Not a lazy green (or worse yet, yellow tip due to carbon burning) flame, which is too rich. A thin purple flame is lean, with a good burner you can push it very lean indeed without it blowing out. Others, particularly with bad flares or none at all, have a certain flame velocity and mixture limit: an open-end pipe can be used as a burner for very slow flames, and it can burn neutral. The low flame velocity is unstable and it might start fwooping. If it fwoops once too hard, the flame will kick up in the tube and burn near the intake (no good). At higher gas pressure, you have to reduce air flow (choke) to keep velocity down, otherwise the flame will blow off. So you add a flare, and suddenly this little pressure step at the end allows burning at very high velocities, even fully lean. The technical name is a flame holder, and if it's not holding the flame (at the shoulder formed between the end of the burner tube and the flare), you can know right there it's not burning right.
I suspect you could've done as well with the smaller tip, just at higher pressure and more choke. This boosts up the velocity, while giving more lean headroom (if you need an oxidizing atmosphere or extra flame temperature). It also reduces maximum power, as only so much propane is coming in.
Try. Typical sizes are #57 for a 1" pipe, .030 for 3/4", .022" for 1/2" conduit (no venturi needed), etc. I'd guess 1/16" for 1 1/2" pipe.
Bah, I've never made a proper flare in my life. I just bend some sheetmetal (24ga. works good) around a size smaller pipe then spring this on the burner tube. No taper, the step between inside of burner tube and flare (i.e., pipe thickness) holds the flame. (BTW, a perfectly smooth burner tube doesn't work. It needs the abrupt step.) I let it hang out about i.d. past the end. I'd never go with 2 x i.d., with a taper I suppose it might work but it's just too much hot sheetmetal. Wasteful of the heat and whatnot. However, anything shorter than i.d. will be unstable, burn extra lean, etc. Make sure it's easy to replace, it WILL turn to scale in half an hour, particularly if you're melting bronze or something.
Note: no flare is necessary if your furnace/forge's tuyere is a tight fit to the burner tube.
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Thanks for the thorough response. I had not picked up on the fact in my own reading that when properly working the flame actually burns inside the flare just off the "step" formed by the wall of the burner tube and the body of the flare. I (and a few others whose results I have been studying) have been trying to get the flame out of the burner tube and the flare.
I to have a through the large end of the reducer two holes for the gas line. Is the flame tip end flared ? This is important to keep it alive. Not to much, but an obvious flair helps. Once the furnace is hot the flame can't go out. While cold it can be tough.
Mart> I built one pretty much copying Brian Booorman's design at
Got it working. I settled on a Tweco drilled/reamed out to .063". This was the max size for a neutral flame at 25 psi with the choke fully open on my design. I made just a simple flare as you suggested - just a 2" length of slip-over SS pipe. The thing really roars and now wants all the air my choke can give it above 25 psi. It now runs consistently with control of the choke from a few psi all the way up to 35 psi. It does burn inside the flare now which gets red hot but the burner pipe stays cool. Next step is to ram the refractory in my completed furnace shell.
I've built several Reil burners, and find the following details useful:
Fuel gas is 1/8 inch pipe size, with a tee in the middle of the reducer bell. Both ends project through the bell; one end is capped and the other end connects to a 1/8 inch needle valve and then the supply hose. The nozzle is a 1/8 inch solid steel plug with a drilled orifice. Easy to change orifice sizes by switching plugs. Number 57-58-59 drill sizes seem to be ok for 1-1/2 inch pipe size - you can experiment until the flame looks good. Obviously, gas pressure affects this size. I find that 15 to 10 psi propane is ok for me. Dave .
Why 35psi.? I can melt cast iron with the Wenig Monster Burner using
20 to 22 psi of propane. Up to a certain point I think the more fuel and air you pour to it it goes out the exhaust vent and does little too improve melt times, as its going by too fast to be readily absorbed and radiated back to the crucible to do much good. IMHO Ruperts Monster burner is the best designed burner, its economical and works great. Visit my website:
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