Latest forge - dual blown burner

Atlas Knife Company

Atlas Knife Company

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Feb 16, 2010
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For a long time, it's been believed that a large, high speed centrifugal blower is needed for a blown burner. Normally, it's a Dayton producing 178CFM. Here is a tested and proven 200k burner running off a 12vdc blower at 20 watts. A simple and cheap pwm speed controller adjusts the blower speed, instead of a gate valve.IMG_20200109_111525_735-980x980.jpg PhotoPictureResizer_200109_193608626_crop_1764x1891-882x946.jpg

18" shell, 16" long x 5" chamber
Single 45CFM blower with .062" orifice @ 20 PSI producing 200k BTU (too big) split into two channels
It runs fine down to about 25k BTU
Plicast LWI 24 chamber
 
lanternnate said:
What are you seeing for temps you can hold consistent at the low end and high end?
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That's a great question. If it were warmer outside, I'd let it run for a few hours to level out and see. For now, this is more discovery of what actually works for a blown burner, as well as testing the Plicast refractory.

PS Deker pointed out a math error on my behalf and this burner is lot bigger than needed. I calculated for a 6" chamber instead of 5".
 
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Atlas Knife Company said:
That's a great question. If it were warmer outside, I'd let it run for a few hours to level out and see. For now, this is more discovery of what actually works for a blown burner, as well as testing the Plicast refractory.

PS Deker pointed out a math error on my behalf and this burner is lot bigger than needed. I calculated for a 6" chamber instead of 5".
Click to expand...

Very excited to follow along. I love my Graham, but this is super interesting. Would the speed controller be compatible with a PID setup?
 
Nice basic working forge. Once the cast liner gets soaked, they will hold the heat very evenly.

Stack firebricks as needed to make the front and back ports.

Just a comment on the photo:
I would NOT run the power cord across the forge top as shown.
 
Atlas Knife Company said:
Single 45CFM blower with .062" orifice @ 20 PSI producing 200k BTU
Click to expand...
A question please. Most places I've seen with blower type burners use 1/4" nipple or 1/8" nipple running at very low PSIG, perhaps 2 psig or so. You've got this burner with a .062" jet at 20 PSIG. I can see the same amount of gas going thru, high pressure thru a small hole vs low pressure thru a much larger hole. Is there an advantage to using a small jet with high pressure? Perhaps the high pressure thru the small hole does a better job of atomizing the gas thus allowing better mix with air for better burn? I'd like to hear your comments please.

Is that 1" black iron pipe? Doesn't look large enough for 1-1/4", but can't really tell. Comment please.

Ken H>
 
While I am sure it works fine, I see no need for the orifice either. a 1/8" pipe nipple ( or 1/4" would be just as good. Perhaps he gets a bit more adjustment finesse by having the gas pressure vary over 1-20PSI instead of varying over 1-5PSI.
 
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Stacy E. Apelt - Bladesmith said:
While I am sure it works fine, I see no need for the orifice either. a 1/8" pipe nipple ( or 1/4" would be just as good. Perhaps he gets a bit more adjustment finesse by having the gas pressure vary over 1-20PSI instead of varying over 1-5PSI.
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Yes, having an abundance of 20 PSI regulators, I can get a finer control with 0-20 than 0-5 PSI. There is no need for a secondary needle valve to adjust it with this setup. The bonus to this setup is that the smaller orifice does a great job of mixing the fuel/air in a much shorter tube than other designs.
 
Stacy E. Apelt - Bladesmith said:
Nice basic working forge. Once the cast liner gets soaked, they will hold the heat very evenly.

Stack firebricks as needed to make the front and back ports.

Just a comment on the photo:
I would NOT run the power cord across the forge top as shown.
Click to expand...

No, don't run with the power cord over the shell. Haha

As far as soaking, this casting is very similar to IFB or wool and doesn't need any extra soak time like Kastolite does.
 
lanternnate said:
Very excited to follow along. I love my Graham, but this is super interesting. Would the speed controller be compatible with a PID setup?
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I would guess not, at least not with this setup. The fan is too close to the chamber to turn off the fan. That said, it could easily be redesigned to move the fan further away and turn on/off like any other PID controlled fan
 
I have found that injecting the propane mid stream of the air is best. You can get a laminar flow with this kind of set up. I think this is why high pressure blowers work so well, thy help break up the laminar flow lines and promote mixing. With laminar flow if propane is introduced right at the edge of a pipe it can flow in an unmixed layer till it reaches the burner flare (aka flared refractory in a blown forge).
 
Atlas Knife Company said:
Yes, having an abundance of 20 PSI regulators, I can get a finer control with 0-20 than 0-5 PSI. There is no need for a secondary needle valve to adjust it with this setup. The bonus to this setup is that the smaller orifice does a great job of mixing the fuel/air in a much shorter tube than other designs.
Click to expand...
Thank you for input. I had wondered if putting gas in thru an orificde at higher presssure wouldn't allow better atomizing and miing of gas than going thru a plain pipe nipple. Without needle valve you adjust flame with pressure alone?
Ken H>
 
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