Forced Air Propane Burner

Discussion in 'Burners and their construction' started by cojo98v6, Nov 12, 2018.

  1. cojo98v6

    cojo98v6 Copper

    I fabricated a quick simple burner for my new small furnace. I had a small squirrel cage fan laying around that used for the air source, not sure on the specifications, runs on 110v. The outlet was 1.25" X 2.5". I made a transition out of 18ga sheet metal and welded this together. The transition was down to a 1.25" square. I took a small length of SS 1.25" tubing and formed a square at the end. I then took a 1" SS tube and flared the end to 1.25" to transition to the larger tube. TIG welded this all together and screwed it to the fan. I found I needed the flare even inside the furnace as the flame would keep blowing out.
    For the fuel inlet I made a 1/4" NPT bung to weld to the 1.25" tube. I then took a 1/4" pipe nipple and threaded the inside both ends to 1/8" NPT. This allowed me to thread the propane hose adapter on one side and a plug on the other side. I drilled a #57 hole in it, same as the Reil burner or Oliver upwind burner uses.
    I purchased an adjustable regulator so I can adjust the fuel amount, surprisingly it does not use much pressure as I though that it would.

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  2. DavidF

    DavidF Administrator Staff Member Banner Member

    The blower/burner is straight up steam punk in my books..
    I mean that in a good way :cool:
     
  3. PatJ

    PatJ Silver Banner Member

    Are those TIG welds?
    Welding thin sheet metal can be a bit of a trick with stick welding.
     
  4. cojo98v6

    cojo98v6 Copper

    The flare is really thin SS, I do plan on going back and making one in thicker SS as this one gets very bright red.

    I did build a Reil burner first as I wanted a furnace that used no electricity for simplicity, but it seamed to run just too rich and could hot enough to my liking. The forced air version was a much better choice in my opinion.


    Hmm, you know, I didn't realize that until you pointed it out. I was going to paint it hi-temp black, but I really dig the steam punk and now that you point that out, I'm going to leave it as is. Thanks!

    Yes, this is all TIG welded. I just cut pieces of carbon steel .030 MIG wire and used that as my filler rod for this thin sheet metal. I used this filler on the SS tube and it gave it a rust color, kind of strange.
     
  5. oldironfarmer

    oldironfarmer Silver Banner Member

    A induced draft burner can sure get hot enough and roar nicely if you get the air adjusted right. Maybe you're tuyere is too small for the heat you want.

    Cool burner. I mean hot burner.
     
  6. PatJ

    PatJ Silver Banner Member

    Did it work?
    We need videos/photos.
     
  7. cojo98v6

    cojo98v6 Copper

    Did not think of this. That might have been my problem.

    Yes, got to try it out this weekend worked great. It takes me 2-3 attempts to get it to stay lite, but once fired it burns great. I feel it would melt brass easily as it melted the aluminum fairly fast.

    Here are some vids lighting and running in the furnace.



     
  8. PatJ

    PatJ Silver Banner Member

    Looks like it worked well.
    I assume you are going to pull the burner tube back out the tuyere a bit so it does not get so hot?

    People melt iron with propane and forced combustion air.
     
  9. Rasper

    Rasper Copper

    That is a very nice piece of work.

    I wonder about your blower description. From your photograph it looks like it's a centrifugal blower. An unusual one.

    I agree with Pat J about pulling the burner back. I would try pulling it back to where none of your flare is inside the furnace. The flare will last longer. Whatever works.

    Richard
     
  10. Zapins

    Zapins Silver

    I'm no know-it-all expert but I can't help but feel this burner has been built at a strange angle. Why is the #57 hole at a 90 degree angle to the air tube? Usually they are parallel inside the air tube so the gas shoots directly into the furnace with the blower air swirling around the propane tube. The way it is set up now the gas will mix and become a burnable fuel/air mix inside the tube rather than mixing and becoming burnable inside the furnace body. Mixing inside a tube will allow the flame to burn inside the tube rather than inside the furnace. Maybe that's why you are having sputtering issues as the flames are getting sucked inside the tube?

    Also, that flare inside the furnace will definitely burn away within a few uses. You shouldn't need a flare inside the furnace to get it working, something needs tweaking!
     
  11. Tobho Mott

    Tobho Mott Silver Banner Member

    I think the tiny gas hole and it being aimed straight down the burner tube are just needed to activate the venturi effect in naturally aspirated burners. I'm not seeing how the direction it enters at would lessen the mixing of the air and gas, when you consider the blower on this burner is going to send the gas right down the tube anyhow.
    My burner runs on forced air, and although I only use propane for preheat, it dumps into the burner tube at a 90 (with no tiny orifice needed), much like in Lio's original plans on BYMC for the Brute and Hot Shot.

    Definitely agree about pulling that burner back out of the furnace bore though; it'll burn up pretty quickly that way, I would think.

    Jeff
     
  12. cojo98v6

    cojo98v6 Copper

    Well my thought on this was that the fan/blower would going to push the air down the tube no matter what, so I was not worried about where the gas entered in, don't have specs on it, but it moves a good amount of air. It was done as more of a convenience for welding. I don't get any combustion inside the tube, I have to cover the fan/blower inlet to even have a chance of lighting it. Then I slowly remove the cover, this is when the flame blows out. I have to turn the gas up really high at first, give full air, then I can reduce back the propane.

    I have to do some modifying on the furnace to allow the flare to be pulled back. I originally made this furnace for the Reil burner with no flare, but I was disappointed in its performance. I'll try and pull the burner tube back without the flare and see what happens. I think the blower/fan just puts out too much air and flare is acting more of a flame catcher. But I'm no expert either, so just a thought. I'll do some suggested tweaking and see what happens.
     
  13. Jason

    Jason Silver Banner Member

    Nice plenum for that blower. I'm still using an old ketchup bottle. :oops:
     
    Tobho Mott likes this.
  14. Joe Avins

    Joe Avins Copper

    Just a thought from a total newbie: you might try adding a speed controller of some sort to the blower. You described the flame problem as "the flame blows out", so try not blowing so hard. (Maybe some other form of flow restriction before investing the time and money in a speed controller, like a piece of cardboard partially covering the inlet.
     
  15. cojo98v6

    cojo98v6 Copper

    The blower is brushless, so when I tried using a controller it didn't work very good. It caused it to surge when slowed down. Its a good idea you had, just did not work in my case. I use a piece of sheet metal to cover the inlet and slowly remove once I light it.

    Thanks for the input.

    Corey.
     

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