50 replies to this topic

[tlreif]

kcrucible, on 18 August 2010 - 10:10 AM, said:

But is a longer flame any better? The point of the burner is to combust a given quantity of fuel fully. If that happens, the same number of BTUs should be added to the forge, regardless of the velocity. If anything, I'd think that a slower flame is better because the hot gas will linger in the melting/forge chamber longer, pushing the heat into the material you're working rather than shooting out of the exhaust/front... less dragon's breath.

Higher velocity has the advantage that it should make it easier to get enough oxygen to fully combust, but I don't think that the velocity of the air/fuel/flame itself is neccessarily an advantage? Maybe I'm wrong. Happy to be corrected by people with actual experiance of the difference instead of just theory!

Yes I understand your theory. I thought that as well when I was first playing around with this. However I have found that these burners that I am using are very efficient. I use less gas and produce more heat with my forge than many I have seen. Maybe it is just dumb luck on my part. IDK. But I made a 2 burner forge using a 12 inch diameter helium balloon tank. IT has 2 inches of kaowool with a 1/4 inch of satonite and ITC 100 coating that. So my chamber is roughly 8 inches wide by 12 inches long. I acheive forge welding temp at 3.5 psi and I can turn off one burner and go below 1 psi to use the forge as a heat treating oven and have complete control of temp. If you wish I can take some pics and post them. Also with your burner flare you need to be able to adjust it up or down the burner tube to find the sweet spot.

http://www.scribd.co...eating-Handbook


The volume of the fuel is a product of psi and the orifice diamter. Velocity is just how fast it's moving and a byproduct of the first two + size of the container, right? At the same pressure and jet size, the same number of BTUs is being put into the forge as far as I can tell.







Yes, after I moved the tip up things got better. I'd had it up at this point before, but because of other problems it wasn't obvious that it was an improvement until after I could get the flame stable.





I'd thought I'd done the 1:12 ratio, but maybe I misunderstood what it meant. I'd found one website that described it as a doubling of size over the course of 12 of the sizes. ie. if starting from 1" diameter, it becomes a 2" diameter after 12". When manufacturerd to those specs I was not able to keep the flame lit at decent pressures. This might be because my flare was too short to hit the "magic width" where the velocity of the exit gasses would match the flame burn rate.


Last night I widened up the outer sections of the flare (effectively decreasing the ratio I guess) and introduced turbulance inside it to create a hybrid flare/flame holder. This is working very well, though with a shorter flame than I'm sure you're used to. But so long as the same number of BTUs is output, I can't complain.

It works ok up until I start hitting the higher end of my regulator, at which point I'm not pulling enough oxygen to fully combust the fuel. This is where flaring out the air intake or using a venturi tube might come in handy. Still investigating.

[kcrucible]

Oh, the irony. Just on a lark I decided to just screw on a 1" -> 1 1/4" pipe reducer rather than my flare or flame holder and see what would happen. I started analyzing the form factor and thought it might do ok... the turbulence-inducers are mostly outside of the jet stream and definitely supplimentary to the cross-sectional area of the pipe, so no velocity limiters inside the burner tube which would choke it down. The net result: It is the best flame holder I've used with literally no work at all.

The widening allows the gas to slow and the threads at the end induce enough turbulance to keep the flame from burning back into the tube until there simply isn't enough gas to combust at all. At high pressures it gets to quite a roar and I'm getting a better air mix all the way up... no orange except for the occasional dust-burn. It might improve slightly if I taper up the threads so that the lower-most threads don't stick quite as far into the pipe, but don't know if I should bother (and maybe I'll ruin the magic!) At a little over 3 dollars I can afford to replace them periodically if I need to.


That said, if I were to paint my burner with 2000 degree paint, would that help limit corrosion on the burner end, or would it just get burnt off and/or degraded? Anyone have any experiance with high-temp paint?

[tlreif]

kcrucible, on 19 August 2010 - 07:30 PM, said:

Oh, the irony. Just on a lark I decided to just screw on a 1" -> 1 1/4" pipe reducer rather than my flare or flame holder and see what would happen. I started analyzing the form factor and thought it might do ok... the turbulence-inducers are mostly outside of the jet stream and definitely supplimentary to the cross-sectional area of the pipe, so no velocity limiters inside the burner tube which would choke it down. The net result: It is the best flame holder I've used with literally no work at all.

The widening allows the gas to slow and the threads at the end induce enough turbulance to keep the flame from burning back into the tube until there simply isn't enough gas to combust at all. At high pressures it gets to quite a roar and I'm getting a better air mix all the way up... no orange except for the occasional dust-burn. It might improve slightly if I taper up the threads so that the lower-most threads don't stick quite as far into the pipe, but don't know if I should bother (and maybe I'll ruin the magic!) At a little over 3 dollars I can afford to replace them periodically if I need to.


That said, if I were to paint my burner with 2000 degree paint, would that help limit corrosion on the burner end, or would it just get burnt off and/or degraded? Anyone have any experiance with high-temp paint?

You can use High temp paint. It will work just fine. I powder coat mine and just the base has dulled no other visible signs of heat. I will be posting some pics and a thread on what I have done with my forges.

[kcrucible]

tlreif, on 19 August 2010 - 07:43 PM, said:

You can use High temp paint. It will work just fine. I powder coat mine and just the base has dulled no other visible signs of heat. I will be posting some pics and a thread on what I have done with my forges.

Excellent. I look forward to seeing them.

[kcrucible]

Finished my paint job etc... the burner is complete. When I get a chance to hook it up to a tank and let er fly I'll post an action shot.


I think I should have done a pre-burn of the pipe before painting. I think the oils, etc, burnt off at the end of trying to cure the paint and coated it with soot. I used a Mr. Clean magic eraser on it to verify that the color was still there. It'll never be "perfect like new", but I'm kinda liking this aged look anyway. Every time I see it I think "Half-Life" due to the orange color (it was supposed to be red.)

[kcrucible]

Well, this is probably the last post I'll need to make under this particular heading. A picture of the burner "in-action." I'm seeing a bit more yellow than I had prior to the paint job. It got more pronouced the longer that the burner ran and I saw a little smoke curling out of the end. I suspect that it's still outgassing from the paint job and burning some of the fumes so not really a fuel/air question at this point.


Low pressure




High Pressure

[tlreif]

Hey thats looking good! Now its time to put it to work! Do you have the forge built yet?

[Fe-Wood]

Thats What I'm talk'in about... Looks good

[kcrucible]

Thanks guys.


Foundry/Forge is only partly built at this point. Need a bit more TLC on the shell then cast the refractory. I have all of the lid forms pretty much built. The lower forms need more work, as well as a bit more welding to secure the burner, etc.





In case it's not obvious, the black steel ring is screwed onto the top (with a few welds) for strength and to get a good lifting surface. The ring is at the bottom of the lid. There's a steel bar welded onto the forge port lip to rest items on so that it doesn't abuse the castable, and the castable will extend from that point another few inches before it opens up into the heating chamber. The crescents on the top are for exhaust (with a healthy dose of castable around it to help protect the metal shell.) Top is mostly kastolite except for a strip of inswool down the center strip. Designed it such that the area directly over the forge ports (and a crucible in the base) is opposed by insulating material so that the heat doesn't radiate out into space. There is a small dome overtop of the center for strength/support and should have the interesting effect of being an infra-red mirror focussing the heat into a smallish area like a magnifying glass bringing it up to heat that much faster.

The two bits welded together underneath form the bottom, and will have basically a hollow cylinder of kastolite 30 (abou 1.25") wrapped in 2" of inswool. The burner inlet is obvious. There's a spill hole on the opposite wall (spilling straight down doesn't seem good to me, and this lets me put more insulation underneath.)


I'm envisioning a tube coming off the handle to the vertical and pivoting on that point so that I can swing the top out of the way. Whether that comes to pass I strongly suspect is up to the various weights of the parts.

All of the ports have plugs that can be inserted/overlayed so that I can bottle up the furnace for a slow annealing process. Longer pieces could be accomodated by adding an insulated pipe sitting on top of one/both of the crescents.

Or at least that's the plan. I'm a feature-guy. I crave flexibility just in case I ever want to try something different than my initial use. We'll see how it all pans out!

[Sweany]

I love it when a plan comes together!

[kcrucible]

Sweany, on 30 August 2010 - 09:23 AM, said:

I love it when a plan comes together!

Heheh. Metal-working on unconventional but common materials to create something dangerous? Check!


The Low-pressure picture above was actually Mid-pressure. At Low pressure I was getting a lot of huffing. Yesterday I ground down the exit theads in a taper (innermost threads almost gone, etc, etc) to reduce turbulance and back pressure. Now, in conjunction with the choke, I can dial it ALL the way down to where it's just a blue wispy flame that rises. It's very cool.


Work continues on the furnace body. Welded on a pipe collar to the base, a bit on conduit onto the steel arm to use as a pivot, build up the forge port shelf to be a bit more substatial and installed sheet metal screws at various points to try to keep the refractory from sliding out (wouldn't that be embarrassing?) I've got my lid's forms made, so now just wrapping up the paint job on the top before doing some casting.


In any event, thanks to all who helped me get over the hump!