Forced Air Ribbon Burner Orientation

[ToMang07]

So I finally have a burner cast, and the rest of the supplies for the forge are finally in..... took a month to get a bag of Castolite, lol

Anywho, the last thing I can't decide on is the orientation of the burner. I have seen these 3 in 99% of the forges out there. (A, B, or C)

B seems to be the best option, as it is the least likely to blow directly on your work, however it would be the hardest to cut and cast into the forge body.
 

NOT LOOKING for debate as to the size of the forge. This is strictly about the orientation of the burner.

[Latticino]

B for the win, as far as I'm concerned.  Cutting the rectangle into the forge skin is the same no matter which option you choose.  Cutting the frax blanket is super easy with a very sharp thin knife (I use a fillet knife).  Even casting the interior is pretty easy if you put a form in first.  If you already have your ribbon burner, just wrap it in plastic and put it in place further into the forge temporarily while you cast the interior.  If you need to tweak you can always rasp the Kastolite a bit before it gets fired.  

Of course the ribbon burner should have a shorter flame, so all of the options should be acceptable regarding flame impingement on work, depending on what you decide to forge.  The real question is how well you can distribute the flame/gas mixture over the full 18" (you will need a fairly advanced mixing block design as well as creative baffles IMHO) and just how much propane you will need to use to keep the system from backfiring.  I assume you are going with a forced air system?

When finished you don't want the ribbon burner to project into the forge that far for any options.  I personally like the face of the burner to align with the outer edge of the castable and let the castable act as a bit of an integral flare.

Not going to debate you on the forge size.  I think Albert Paley's was almost that big, and he ran propylene/air (and a Nazel B6) if I remember correctly.

[ToMang07]

Yeah, I suppose I should have spent an extra minute getting the model square.... I was more demonstrating where they get placed versus how deep, so my bad on that, I would have the burner face flush with the inner casting as well.

I do have the burner cast. Of course, this is all experimental, taken from firsthand experience; advice; and research all discombobulated into what my brain filters into a myriad of confusing information, lol

The burner is long, but skinny. I'm hoping the increased air flow from my blower will compensate for the distance the air/gas mixture needs to travel. I have a 3"/272cfm Forge blower, and a long 2" pipe with baffle to mix the gas mixture. The way I look at it is even if I need to run it at 4psi it's still running on 1/3 less pressure than my (venturi-style) small forge does.

[tinkertim]

B works for me!

Tink!

[Buzzkill]

3 minutes ago, ToMang07 said:

The way I look at it is even if I need to run it at 4psi it's still running on 1/3 less pressure than my (venturi-style) small forge does.

Note that 1/3 pressure does NOT mean 1/3 fuel used.

I'm interested to see how the burner works out for you.  I don't think I've ever seen one that long and narrow in action.

[tinkertim]

Hi Tom,
I don't think you can compare PSI for a Venturi setup and a Forced-Air setup, as you will have different sized Gas orifices, so Apples Vs Oranges.

It is more down to the Fuel/Air ratio in your Fuel/Air Mix (FAM) and the volume of FAM you can combust within your forge per unit time (eg. per Second). The more volume of FAM you have combusting per second, the more heat you will generate (within the limits of Propane combustion parameters).

Tink!

[ToMang07]

Longest I've seen is 14", but they had 3 rows of holes. I'm hoping the smaller holes will allow enough pressure to build to fill the whole chamber and distribute it evenly.

It's an experiment, for sure! lol

[Latticino]

The old Johnson gas forges with the metal ribbon burners were extremely long (over 14" for sure).  Been over 30 years since I used one, so can't really remember too much about it, but a lot were sold so I guess they worked.  The ones I saw used natural gas and I think some kind of slide gate for closing off outlet holes when not in use.  Memory a bit fuzzy from back that far though.

41 minutes ago, Buzzkill said:

Note that 1/3 pressure does NOT mean 1/3 fuel used

Not even with the same burner assembly given the equation for pressure and fluid velocity (which is directly proportional to flowrate in a fixed diameter pipe/duct) has a squared factor, and that isn't even accounting for orifice conditions.