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Comparing 3 types of nozzles


newbieforge

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Having recently gotten my gas forge into a state where it is working reasonably well, my next steps will be to optimize the burners, with the goal of being able to reliably get welding temperature.

As Frosty pointed out to me in another topic, my forge is also a bit underpowered. I have been using the front 10" of the forge, with at most two (out of four) 3/4" burners lit. The interior diameter is 10.5" which means each burner services roughly 430 cubic inches. This is above the recommended minimum of 300 cubic inches per burner. Based on this, I am working on a new 1" burner design. As a 1" burner is equivalent to two 3/4" burners, I should be able to replace one of the existing 3/4" burners to bring the world back into balance, and get welding heat.

Furthermore, my burners have terrible nozzles. I forged them roughly from 1" pipe, at barely red heat. I was dealing with the chicken and egg problem of needing a forge to forge the burner nozzles, so I had to fake it. These nozzles are very ugly, but they have worked well enough for now. But I think they can be made better, and so this is the first area I worked on.

Improving Existing 3/4" Burners
I made two new nozzles for testing. Both nozzles are made from cheap cast iron plumbing couplings. One is from a straight 3/4" coupling; the other is from a 3/4" to 1". I used my Chinese 7x12 mini lathe to bore out 1:12 (5 degrees) tapers in one end of each coupling, leaving the thread on the other end.

post-25178-0-25766600-1351665746_thumb.j

The thread then lets me screw the nozzles onto a threaded pipe nipple. This is different than the classic Reil burner design, where the pipe nipple threads are cut off, requiring you to use a set screw to attache the forged nozzle in place.

The following web site was a great help to me when building these burners:
http://metalcast.boo....us/reil_1.html

As in these instructions, the output orifice is drilled into the side of the brass 1/8" pipe nipple, with a 0.040" diameter (#60 drill bit).

The New Nozzles

post-25178-0-85471900-1351662467_thumb.j post-25178-0-07049800-1351662470_thumb.j

Nozzle A - my original badly forged piece of 1" pipe
Nozzle B - straight 3/4" coupling, with one end bored out to a 1:12 taper
Nozzle C - 3/4" to 1" coupling, with the 1" end bored out to a 1:12 taper

Test Setup

post-25178-0-27343200-1351662981_thumb.j post-25178-0-44307500-1351663399_thumb.j post-25178-0-02557300-1351663402_thumb.j

The leg vise is holding a burner by the tube. The burner is connected to a 20lbs propane tank, via a 0-30psi regulator. The regulator has a 0-30psi pressure gauge. The burner tube is a 3/4" by 8" long black pipe nipple.

Test Procedure

The basic idea was to see what each nozzle does at different pressures, and at different flame types (oxidizing, neutral and reducing).

Flames:
The oxidation type of the flame can be adjusted using the choke on the back of the burner.

To adjust the flame type, I first put Nozzle C (3/4" to 1" coupling) on the burner, and set the gas pressure to 5psi. For the oxidizing flame, I opened the choke right up, letting the burner suck in the maximum amount of air. In this setting, the flame was a bright blue stream with some orange streaks further away from the nozzle. For a neutral flame, I adjusted the choke so that the "tongue" in the middle of the flame started showing some green at the furthest tips away from the nozzle. For reducing flame, I set the choke nearly closed so that the flame tongue became a more transparent greenish blue with a blue transparent halo further away from the nozzle.

Pressures:
I tested at various gas pressures: <1psi, 1psi, 5psi, 10psi, 15psi and 30psi.

With the <1psi tests, I intended to see how each nozzle performed at very low pressure. When working, I'd never use pressure this low but I thought it would be interesting to see what the nozzles do anyway.

The 30psi tests were interesting, because these high pressures may actually be useful to get very intense heat in the forge.

At each flame type and pressure, I took a photo of the flame coming out of the burner. I used the manual mode on my DSLR camera, with exposure set to f2.8 and 1/160 shutter. Using the same exposure settings for each photo will allow a fairly objective comparison of each flame's characteristics.

Test Results

These images show the flame produced by each nozzle type.

post-25178-0-24132700-1351663496_thumb.j post-25178-0-87149800-1351663497_thumb.j post-25178-0-32805800-1351663500_thumb.j

Here are the same images, but rearranged to compare the oxidizing, neutral and reducing flames from each nozzle.

post-25178-0-19573500-1351664124_thumb.j post-25178-0-61599900-1351664121_thumb.j post-25178-0-59527800-1351664126_thumb.j

If there is no photo for an oxidation/pressure setting, then it means that the nozzle would not hold a flame at that setting. Nozzles A and B had trouble holding flames at higher pressures.

In all these image sets, you can clearly see how the shape and colour of the flame are affected by the gas pressure and choke setting.

Comments & Notes

Nozzles A (forged from 1" pipe) and B (3/4" coupling) both performed poorly at higher pressure with the choke set for an oxidizing flame. I suspect that these nozzles held the flame too weakly at high pressure, and the blast of air that the burner inhales at high pressure just blew out the flame.

Nozzle B worked ok at pressures up to 23-24psi, but any higher and it did not hold a flame. Also at very low pressure, Nozzle B developed a "woop woop woop" where the flame jumped in and out of the burner tube.

Nozzle A out-performed Nozzle B at high pressures. Nozzle A (the badly forged 1" pipe) had no problem holding a flame at high pressure, as long as the choke was set to reducing or neutral flame. Like Nozzle B, it could not hold a flame when the choke was wide open.

The flame shape from Nozzles A and B was less consistent than Nozzle C. The flame from Nozzle C was almost always nice and straight.

Nozzle C was the best of all three. It was impossible to make the burner blow itself out, no matter how high or low the gas pressure, or what the choke setting was. At extremely low pressure, where the gauge was showing 0psi and the regulator was just about completely closed, the nozzle held a nice smooth flame. At pressure above 30psi, where the regulator was cranked way up, the burner still held a solid flame.

At around 10psi and above, all the burners made a pleasing roar. At 30psi, the roar from Nozzle C was almost deafening. I can't wait to hear what a 1" burner sounds like at 30psi.

Needless to say, I will be making a lot more of Nozzle C for my 3/4" burners. My next test this week will be to put new nozzles on the existing burners, and then see what kind of temperatures I can get inside the forge.

Nozzle C type burners are nice because the cast iron plumbing part costs a couple of dollars, and machining out the taper takes about 5 minutes.

Looking to the future, I am already working on scaling up the 3/4" burner design to a 1" burner. When ready, I will test it in a similar manner as described above. Here are some nozzles I've already machined in preparation:

post-25178-0-25958900-1351664440_thumb.j

On the left is the 3/4" to 1" coupling which we've already seen. It is here to compare sizes with the 1" nozzles. In the middle is a 1" to 1-1/4" coupling. The 1-1/4" end has been bored out to 1:12 taper. On the right is a straight 1" coupling, with one end bored out. Based on these test results, I would predict that the 1" to 1-1/4" coupling will perform the best. (The 1" to 1-1/4" coupling is galvanized, and I am aware that galvanized parts are bad. I do plan to burn off the galvanization in good ventilation before doing anything else with it.)

That's it for now. My search for a better understanding of forge burners continues...

Comments, questions and criticisms welcomed.

All the best
Markus

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I applaud your efforts and am certainly not criticizing your extensive research and work so please don't take this as such - but I believe effective insulation and refractory lining is more important that refining burner design to the gnat's ear. This is evidenced by relatively simple systems that just dump gas into a blown system - if the fuel mix is correct and there are sufficient BTU's then you'll get a good enough flame to heat the inside of the box to welding heat. Of course, you are working with a venturi burner, which is more sensitive to tuning effects (one of the reasons I gave up on them about 20 years ago and went to a blower). One thing you have clearly shown is that basic pipe fittings work quite well for the application.

I'll probably be flamed for uncharitable comments so congrats on your continuing education into building burners.

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HWooldridge,
Thanks for replying. No risk of flaming from me. If there are better directions I could be headed, I'd rather know sooner than later, so I can save my effort. However I have to admit, I have fun whenever I mess around with burners, no matter what... :)

Your point on the importance of good insulation and refractory lining is well taken. My forge has 2" of kaowool, coated with ITC-100. I am thinking about putting in another layer to reduce the volume, and improve insulation.

I read about blowers, and I know a lot of people use them and make money with them. Are you able to get a neutral atmosphere with your electric blower?

Back before I had built anything, I had read about the need for neutral and reducing forge atmospheres. The Venturi / induction type burners provided a pretty easy way to do that. I understood that with blowers (and I may be completely wrong, please correct me if I am!) the atmosphere will be oxidizing because of all the extra air being pushed into the forge.

All the best
Markus

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Yes, you can get a neutral atmosphere (or anything else) by using a needle valve to control the mix. I run the regulator at 5 lbs and the blower at full speed without a damper then control the flame characteristics with the valve. It doesn't take much adjustment to make a rich atmosphere by introducing a bit more fuel.

2" of kaowool and ITC is a good start - I should think you will reach welding temps if the BTU's are sufficient.

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Actually a blown burners is much EASIER to get a neutral to reducing atmosphere than with a aspirated burner!

Since the system is much less dependent on lack of back pressure or getting the venturi just right you can adjust the air from gosh awful oxidizing all the way down to barely burning with way too much gas---for each level of gas input.

You adjust your aspirated burner's air way down and it will want to start huffing.

Don't know where you got the idea that blown burners couldn't get neutral atmospheres.

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macbruce,
That's an interesting idea. I didn't think of varying the orifice size to balance the air flowing into the back of the burner. I'd be interested to try it... wouldn't that be really tricky to tune? Are you willing to share any plans or dimensions for this kind of burner, that work well?

You're right, messing with air gates can be finicky. At some point I'll simplify the choke, so that it can be tuned and then fixed in position. On the other hand, the T-Rex burners have adjustable chokes and they have developed a reputation of being "the best in class" for as far as atmospheric burners go.

All the best
Markus

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Markus: A naturally aspirated burner is harder to tune up front but once it is it's easy to adjust as the fuel: air ratio remains the same increasing or decreasing the fuel pressure just turns the heat up or down. A gun/blown burner is easy to construct but requires more hassle adjusting the fire up or down, turn up the air and you need to turn the gas up to maintain your desired air: fuel ratio.

In either case it requires tuning and an eye for cause and effect, one is just front end the other is back end. One costs more and is tied to electricity, the other is less expensive and is self powering but is a lot more finicky to get working properly.

I haven't messed with a linear burner since Ron and I were messing with the things years ago. His design works and work well. I like mine because I have them down pat and they're a little more robust in operation. Meaning they're less affected by outside breezes. I don't know if Ron makes a 1" burner so I don't know if he has specifics on his site. I do like a mig contact tip as a gas jet for a couple reasons. They're cleaner than a drilled hole so the propane enters the tube in a cleaner more uniform stream. Aligning them down the tube is really easy, just look up the tube and adjust with a screw driver. (gently bend them) Tuning is as easy as moving them closer to the throat for less induced air (richer burn) or farther back for more induced air (leaner burn) No chokes necessary if you're patient.

Frosty The Lucky.

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macbruce,
That's an interesting idea. I didn't think of varying the orifice size to balance the air flowing into the back of the burner. I'd be interested to try it... wouldn't that be really tricky to tune? Are you willing to share any plans or dimensions for this kind of burner, that work well?

You're right, messing with air gates can be finicky. At some point I'll simplify the choke, so that it can be tuned and then fixed in position. On the other hand, the T-Rex burners have adjustable chokes and they have developed a reputation of being "the best in class" for as far as atmospheric burners go.

All the best
Markus


All the burners I use now are variants of Mr Zoeller's. I reckon fitting a gate to the air intake for carburizing would be easy or a needle valve on the gas line to make an oxidizing flame such as I have is no biggie. I just use the needle valves on my 3 burner to isolate them if needed. Can't remember but I used either an .030 or .035 mig tip threaded into a 1/8'' pipe for the orifice. Note: you must swage down 1/8 pipe slightly in order to thread it for 1/8 npt...............

http://www.google.com/url?sa=t&rct=j&q=zoeller%20burner&source=web&cd=1&cad=rja&sqi=2&ved=0CC0QFjAA&url=http%3A%2F%2Fwww.zoellerforge.com%2Fflare.html&ei=UNeRUM_PM-iyigLkmID4DA&usg=AFQjCNEHNOQPjiOb8cBpvQecQCZ0w5DFhQ
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I found the easiest way to align my gas stream was by using water. Its easy to see when the stream shoots out of the center of the flared nozzle. I did observe a big difference in the stream of water when the oriface was just a drilled hole in the tube vs a mig welding tip. It was a much smoother, more stable stream with the mig tip.
My burners run stable from 1psi (idle circuit) up to 40-50 psi or whatever i have the regulator set at, usually around 6 to10 psi.

Is this all alot if tinkering for nothing, who knows but it sure is fun playing with it especially in the cold winter.

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Frosty,

I've been following Ron's work on burners quite closely. It's nice to talk to someone who is so close to the source.

Thanks for pointing out that you can tune the burner by moving the jet along the burner axis, without a choke. I hadn't picked up on that. This gives me some ideas; I think I can simplify my burners quite a lot.

I like these burners for the reasons you mentioned -- they don't require external power, they are cheap to make, and they don't require re-tuning when you change the gas pressure. The price of these advantages is that they are trickier to get working... but, that is something in which I'm willing to invest some time to learn.

Ron does discuss some 1" and larger burners, called the Mongo series, here: http://ronreil.abana.org/design1.shtml#TheMongo

I think that with some experimenting, it should be possible to scale up the Reil 3/4" burner to be a 1" burner, or even larger. The operating principle is the same.

All the best
Markus

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Frozenforge,

Is this all alot if tinkering for nothing, who knows but it sure is fun playing with it especially in the cold winter.


You nailed it, I will definitely I agree that it is a lot of tinkering, but not always for nothing. :)
This is very well-explored territory. It's also a mentally stimulating and fun activity to take the mind off the day-to-day grind. :D

All the best
Markus
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