Test of new naturally aspirating burner

Discussion in 'Burners and their construction' started by metallab, Oct 6, 2020.

  1. metallab

    metallab Copper

    Normally I use a forced draft burner, but, seeing some videos on Youtube (e.g. BigstackD), they make a simple burner of a 'bell' adapter, a pipe nipple and a flare. And want to use it in a forge as well.
    So I ordered these parts (SS 316) online and put a 12mm pipe in it with a small 0.5mm orifice, which I already use normally with my forced air burner.

    It appears to work OK, but I see that the flame is partly inside the tube which gets very hot and makes a low frequency 'thundering and roaring' noise.

    I did not test it in the furnace yet as I have to attach the set screw to fasten the gas pipe to the burner.

    What do you guys think about it ? Here a video.

    (if you don't see anything, hover over the top half of the screen)
  2. You'll get a completely different result when the burner is installed into a furnace chamber too, due to the sealed volume the burner fires into.
    DavidF likes this.
  3. FishbonzWV

    FishbonzWV Silver

    It appears the flame is all the way down in the tube.
    My burner would do that when I lit it with the gas pressure too low. I would turn it off and re-light it with more pressure so the flame was not burning in the tube. It will get red hot if you burn it like that.
  4. rocco

    rocco Silver

    Depending on how I light it, one of my burners will burn inside the tube, there are two ways I deal with it, either increase the fuel pressure or block off the air flow a little until the flame is burning properly, once the flame sets up properly at the flare, it stays there even if I decrease the fuel pressure or allow full air flow.
  5. FishbonzWV

    FishbonzWV Silver

    Once mine was burning at the orifice, I could never get it to advance to the end.
    3/4" x 8" black pipe.
  6. rocco

    rocco Silver

    I have two burners, very similar in design (Reil style) and dimensions, but one will burn in the tube, the other one never does, even when I light it from the inlet side.
  7. Fasted58

    Fasted58 Copper

    OP's .5mm orifice (about .020"), the orifice may not be large enough for the amount of primary air. Or, like Rocco said restrict inlet air, masking tape will work in a pinch. The large reducer coupling on the hot end may work well for a forge burner but not necessarily inside a foundry furnace. A straight pipe coupling should work OK. I replaced my original 3/4" x 1" hot end coupling w/ a straight 3/4" coupling for the furnace, still had to grind the threads out in a taper to get it to light outside the furnace. The factory straight coupling would burn back in the pipe. These are fickle beasts.

    With a 3/4" x 1" coupling hot end, 0.035 MIG tip and open primary air this burner ran over 40 psi gas and would rip as a forge burner.

    Shown is my low fire set up for starting the slow curing of refractory and later the ITC-100HT coating. 3/4" straight coupling, 0.023" MIG tip and restricted (w/ tape) primary air. 2-3 pounds gas pressure. Huge difference.

    That ain't a lotta primary air.


    I'd think the OP may wanna try a straight coupling hot end flare, restrict primary air and dabble with orifice sizes. Just my 0.02 worth.
    Last edited: Oct 6, 2020
    DavidF likes this.
  8. metallab

    metallab Copper

    Thanks, but I tried inserting a smaller (3/4") tube inside the burner tube which fixed the burning inside the tube issue and the tube did not get hot anymore. I'll continue experimenting with this. BTW, the orifice is larger than 0.5mm, probably 1mm.

    When using inside a furnace, I just unscrew the flare.
    Last edited: Oct 6, 2020
  9. metallab

    metallab Copper

    I updated it.

    Now it works much better with a 3/4" inner tube to prevent burning inside the 1" pipe. And I have fixed the gas tube to the bell.

    (same link as OP, but updated from 1:33 on. If you don't see anything, hover over the top half of the screen)

    Its behavior is much like the 'standard Youtube burner' as most burners in videos there look like this, based on 'Reil burner'.

    Today the sound was much smoother than yesterday (beginning of video).
    Last edited: Oct 7, 2020
    Tobho Mott likes this.
  10. OMM

    OMM Silver

    Can you make this a standard YouTube video? I tried to follow your link. It's just too slow.
  11. metallab

    metallab Copper

    Then it is your internet connection. Youtube won't help that.
  12. Tobho Mott

    Tobho Mott Silver Banner Member

    How you host it is your business, but FWIW this 5 minute video took 48 minutes to play for me as well, in 3-5 seconds bursts of action punctuated by long buffering pauses. That made it a bit hard to follow what you were saying. Maybe it's Ontario's internet connection.

    But it looks like the burner is working pretty good, congrats!

  13. rocco

    rocco Silver

    It almost seems like your video is being throttled, I have no trouble live steaming HD broadcasts or simultaneously viewing multiple youtube videos while your video loaded fairly quickly for me, it does not load smoothly, there a few brief pauses in the video as my system waits for it to load, not a normal experience for me with most other video sources.
    I don't know if this is a coincidence or not but OMM, Tobho, and I are all in Ontario Canada so it's possible we're all using the same Internet service provider and that's where the problem lies.
    Last edited: Oct 17, 2020
  14. I guess my otherwise good internet connection is too slow also since it won’t load the video. The connection is great for everything else.

  15. Jason

    Jason Gold

    Video streamed fine for me.
  16. Petee716

    Petee716 Silver Banner Member

    Me too. I've had trouble with Metallabs vid in the past though. But the last few months or so have been fine.
  17. metallab

    metallab Copper

    Maybe that your ISP throttles streaming video from other sources than Youtube or possibly Vimeo. Well, I used to put them on Youtube, but a few years ago the conditions changed and they censor some videos which occasionally end behind an adult wall, despite no tits or other sexual related content is in my vids. So I host my own videos without any problem.
  18. master53yoda

    master53yoda Silver Banner Member

    the flame location in a burner is where the velocity of the fuel mixture slows down to the flame spread rate. The reason the smaller pipe solved the problem is that it increased the velocity of the fuel mix. Assuming the original burner was air ratio correct, if you increased the fuel and added more air too the original burner it would have moved the flame to the end of the burner.

    Also burners adjusted in open air almost never fire the same in a furnace due to the back pressure created in the furnace.
    Flame spread varies depending on back pressure and other turbulence causing intrusions in the burner. as a starting point it is about 50m/s 0r 160 ft /sec velocity for propane or natural gas.

    Art B
    Last edited: Oct 24, 2020 at 11:20 AM
  19. metallab

    metallab Copper

    Indeed, the innert ube increases flame speed. And in a furnace I use my new burner without flare while in open air with flare. But I don't get the temperature which I reach with forced air. Until now I did not reach iron casting temperatures (1400 C) with naturally aspirated burners, while a forced air burner gets 1550 C in my smaller furnace.
  20. master53yoda

    master53yoda Silver Banner Member

    A burner inside the furnace reduces the amount of air that a naturally aspirated burner can draw due to the back pressure. One of the reasons for forced air is to overcome the back pressure. You probably couldn't get enough air naturally to the burner in the furnace to reach maximum flame temp, it is also possible with a blower to get to much air which reduces the flame temp, any air over that required to cleanly burn the fuel will reduce the flame temp.

    Art B

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