The best of the best burners!

Discussion in 'Burners and their construction' started by OMM, Jun 8, 2019.

  1. OMM

    OMM Silver

    Quickly in my head I multiply it by 2.2. Or multiply it by 2 and then add 1 for every 7 to get miles per hour.
    => 18 miles an hour with gusts 25 miles an hour.
  2. PatJ

    PatJ Silver Banner Member


    Those melt times match that of the Morgan commercial furnace for a repeat melt, and given your low mass furnace, that makes sense.
    I had a lot of discussion in the past with ironsides about how fast iron could be melted in my furnace, and ironsides was confident that I would never match the melt times of the Morgan furnace with my burner/furnace arrangement.
    At the time I was using my high mass furnace, and so that was a safe assumption on his part.

    My melt times are far better with my new lower mass furnace, but still don't match a ceramic blanket furnace design, and I am ok with that, and happy with the times I am getting.

    During all of my drip-style burner tests, I was also getting fuel dripping out of the bottom of the furnace, and I came to the realization that the drip-style burner really does not do a very good job of vaporizing the fuel compared to a siphon nozzle burner.

    One of the times that ironsides posted for an iron melt was 57 lbs iron in 100 minutes using 4.1 gallons of waste oil from cold start, which is about 1.75 minutes per pound of iron.

    I fully believe the siphon nozzle burner burns fuel more efficiently and hotter (especially during the initial stages of the melt) than a drip-style burner, and so your coupling the siphon nozzle burner with a ceramic blanket furnace and getting melt times of approximately 1 minute per lb of iron makes sense.
    I don't recall anyone else using a drip-style burner with a ceramic blanket furnace, and I think that is an optimum situation.

    Congrats on that melt time.
    Its very impressive.
    Some research on your part has paid off in spades, and you have broken the Morgan glass ceiling (or matched it at least), and it was predicted by those knowledgeable in iron that those figures would never be matched.

    Happy 4th everyone.
    I am working today and tomorrow, but off to the lake Saturday and Sunday for some R & R.

    So was this melt at 3 gal/hr?
  3. PatJ

    PatJ Silver Banner Member

    I know of a great spot for your furnace.
    Nice little neighborhood in a cove, next to a power line, without a lot of neighbors around (my house).

    I will clear out a spot for it.

    I guess I need to turn down my compressed air from 30 psi to perhaps 10 psi (or less).

    Tobho Mott likes this.
  4. Melterskelter

    Melterskelter Silver Banner Member

    It was closer to 2 gal per hour, but I did not measure exactly. But I burned less than 5 gal in 2 hours. Next time I will be more careful about measuring. In my defense, I had unexpected visitors. I love having visitors, mind you, but I do find it distracting to answer questions, make sure they are safe, all the while monitoring the furnace, not forgetting to add ferrosilicon (for fluidity especially and as cheap insurance for very uniformly soft castings), making sure pouring temps are right, keeping an eye on the weather, keeping well hydrated, skimming well and timely, monitoring fuel level and adding when needed, not kicking the power cord to the blower like I did yesterday causing impressive rolling black smoke ete etc....

    Sounds great! If we could get 4 or 5 furnaces all running at once we could pour more or less continuously!

    You might see what your setup does with lower pressure setting on atomization. It would be interesting to hear what you learn. Will your experience be similar to mine or not? We’ll see.

  5. PatJ

    PatJ Silver Banner Member

    That white paper that I posted a link to keeps coming to mind.
    In it, the guy tried pulsing the fuel pressure with a siphon-nozzle burner, and he got perhaps a 30% improvement in melt times.

    The reason for the improvement, he stated, was something to do with increasing the surface area of the hottest burning part of the flame (I can't remember the exact wording).
    My slant on it is that it is akin to blowing smoke rings, or perhaps smoke rings fractured into lots of tiny parts, and thus a great increase in surface area of the hottest part of the flame.

    Lowering the compressed air pressure changes the fuel droplet size, and so by a similar measure, you may be doing something similar to pulsing the fuel pressure, ie: increasing the area of the hottest burning part of the flame.

    The Delavan white paper about siphon nozzle burners mentions that the finest atomization does not necessarily created the hottest flame.

    This is really great news.
    Once of my initial beefs with melting iron was the long melt times, but these times are quite reasonable, and economical too for iron in my opinion.

    From the white paper "Fuel Nozzles for Oil Burners" by E. O. Olson, Chief Engineer,
    Delavan Fuel Meteing Products Operation.

    A 1.00 GPH nozzle operating at 100 psi, spraying No. 2 fuel oil breaks the fuel up into droplets, which have an average diameter of approximately .002 inch (50 microns).
    That means that one gallon of fuel is broken up into something like 55,000,000,000 droplets, ranging in size from .0002" to .010" diameter.
    By this process the surface area is increased by approximately 3800 times.
    The resultant area of one gallon of fuel is approximately 690,000 square inches.

    An oil burner is a combustion machine.
    Its purpose is to promote efficient combustion of oil fuel.
    Mechanically speaking, there are several different types of oil burners, such as vaporizing pot type, low pressure gun type, high pressure gun type, and several types of rotary burners.

    The fundamental processes upon which all of these different burners are based are the same, however.
    The process of combustion may be thought of in the following steps:

    1. The oil must be vaporized, since all combustible matter must be converted to a vapor or gas before combustion can take place. This is usually accomplished by the application of heat.

    2. The oil vapor must be mixed with air in order to have oxygen present for combustion.

    3. The temperature of the mixture must be increased above the ignition temperature.

    4. A continuous supply of air and fuel must be provided for continuous combustion.

    5. The products of combustion must be removed from the combustion chamber.

    Droplet Size:

    To summarize, the droplet size is dependent upon the following factors:

    1. The droplet size is usually larger in the higher discharge rates, assuming the same pressure. That means that a 10.00 GPH nozzle will have larger droplets in its spray than a 5.00 GPH
    nozzle with the same spray angle at the same pressure.
    That is one of the reasons for using multiple adapters and two or three nozzles instead of one to improve combustion.

    2. The droplet size is smaller in the wider spray angles.
    A 45° spray will have larger droplets in it than an 80° spray.

    3. High viscosity fuel produces larger droplets in a spray than low viscosity fuel at the same pressure.

    4. A nozzle with a rough orifice finish produces larger droplet size than a nozzle with a good finish.

    5. Increasing the fuel pressure on the nozzle reduces the droplet size.

    6. Nozzle design is a very important determinant of droplet size in the spray.
    The smallest possible droplet size is not necessarily the most desirable.

    Good droplet size distribution to produce efficient, quiet fires is determined by nozzle design.

    Last edited: Jul 4, 2019
  6. OMM

    OMM Silver

    I actually found (during testing Diesel) that working with the finer mist fuel actually was leaving unburnt.

    I’m going to make another Kwiki and reverse the fuel to the Mig tip. I’m going to try to use the turbine combustion air to adomize hopefully just enough and in the burn tube to add more combustion air.

    The Kwiky uses A quarter inch copper water pipe. I’m going to run this down the middle of quarter inch brass pipe. The brass pipe and the copper pipe i’m going to run this inside half inch iron pipe. Both the brass pipe and the iron pipe will be providing combustible air. Just a different speeds/psi. I figure slightly larger droplets in a high-pressure Vortx will keep the droplets dropping and being so fine escaping has gas.

    Has anybody ever built a furnace like an upside down cyclone?
    Last edited: Jul 4, 2019
  7. Melterskelter

    Melterskelter Silver Banner Member

    I looked again at Delevan’s recommendations for atomizing air and find it interesting that they recommend pressures between 3 and 5 PSI. SIPHON.pdf

    I think I started right out with increased atomizing pressure hoping to siphon more fuel which I “figgered” should equal more heat. In retrospect I think that higher atomizing pressure may well be counterproductive. In fact, I wonder if using a yet larger burn tube than my current 2” one might allow slower velocity of combustion air and thus be better. I also think on another iteration I would try to set my nozzle further inside the tube so it was further from the internal furnace chamber as that would allow combustion to begin closer/at the opening of the burner tube.

    The same might be said for excessive fuel flow. There must be an ideal point where fuel flow is not so much as to require unnecessarily rapid combustion air flow to keep up with the fuel and yet provides optimal heat to melt metal. Too much fuel requires too rapid flow speed of combustion air and pushes the cool portion of the flame too far into the furnace delaying development of full combustion temperature.

    So if I were to make a new burn tube I might try a larger 3 or 3.5” tube, place my nozzle 4 to 6 inches from the opening of the tube, run atomizing air as low as possible—-around 2-4 PSI and fuel flow around 2GPH by continuing to pressurize it to about 8PSI and see what happens. Might be great or not. But that is my best present guess as to how to improve burner performance. FWIW.

  8. PatJ

    PatJ Silver Banner Member

    I know from experimentation that if the spray nozzle is pulled too far back in the burner tube, it will impinge on the burner tube and start to drip.
    You can also start to get combustion in the burner tube, which will turn it red hot (a condition I find unacceptable).

    Also I have found that if the compressed air is dialed back too far, you can also get dripping, but I have not tried dialing back the compressed air with a fully hot furnace.

    It also may be important to note that the delavan/hago nozzles are used for heating systems that typically discharge into a large open combustion chamber (with no curves).
    This is not at all like what we use with a furnace (in my opinion), but it is certainly worth experimenting with a siphon nozzle at 3-5 psi just to verify what it will do.
    The defining limit is when you dial back the compressed air until you get dribbling and puddling of fuel in the furnace.
    If I dialed back the compressed air to 3-5 psi, I would also do this in total darkness and pay close attention to the radiant temperature/glow of the furnace interior, so make sure that the combustion process was not getting colder visibly, ie: the furnace surfaces start to go darker in color.

    I have tried fuel flow rates up to 10 gal/hr, and they did not seem to run very hot.
    It was much like melter describes, where you are pushing an enormous amount of ambient combustion air into the furnace, and there is not enough time for that much fuel and air to combine and combust properly. The excessive combustion air seems to cool the furnace.

    I tried a large burner tube (3") with dual siphon nozzle burners in it, but it did not work well.

    If I were going to try something else, I would use dual pressure-style or siphon-nozzle burners at 180 degrees.
    I tried this once before, but I did not know how to tune a burner at the time.
    I am pretty satisfied with the simplicity and the function of one oil burner at this time though.

    If I went to a larger furnace, for perhaps a #100 crucible, then I would definitely use dual burners at 180 degrees.

  9. Jason

    Jason Silver Banner Member

    Right on Pat! Bell curve.. EVERYTHING operates on a curve. Lean any furnace, any burner arrangement, any lawnmower to peak EGT temp and that's it. Any extra fuel will naturally cool things down. If someone wants to burn 10gallons an hour, it doesn't necessarily mean it will be hotter. Just more thirsty. Once a furnace is built, that's it. The dimensions are fixed and once you lean it to peak temp, I don't care if you put nine blowers and 4 fuel nozzles on it, it will not burn hotter. Anything else is just locker room prick envy. I wrote a lengthy post one time about how we operate piston aircraft and the relationship of fuel mixture to EGT's.... In short, after you level off, you lean it until it won't get any hotter. That's all you will get out of her. PERIOD. If you want your equipment to have a nice long life, you enrichen the mixture to cool the EGT's slightly. This combined with careful monitoring of cylinder head temps and you make TBO. All of this is predicated on fixed combustion chamber sizes. This applies to our furnaces. Until we have morphing combustion chambers, you get what you get. (I heard some auto companies are putzing with varying combustion chamber size through the use of fancy crankshafts whatever that's worth:rolleyes:) Reminds me of cadillac's 4,6,8 POS in the early 80's.

    If I was a betting man, the guys selling the high dollar melting furnaces are ages behind in technology compared to half the crap most of us run in our backyards. That stuff was designed decades ago and I seriously doubt they continued dumping money in R&D. The stuff gets hot, melts metal and that's it. The stuff I see on the market looks like it's from the 1940's. No magic there.

    I believe the compressed air, while variable, changes the end result very little. It only provides the motive force to move fuel. You can only suck so much fuel which leads a person to have to dump more combustion air to keep it lit. All the while dealing with the fixed dimension of the furnace. More importantly how much you can burn and get out to make space for the incoming mix. I built my kwiky and got it to reliably move fuel at 20psi, and then I see the next guy bitching his takes 50psi to get it to spray fuel! Point being, it comes down to how the thing is built, how that tip is shaped and a couple other things too. The compressed air moves the fuel, that's it's only job. The belle curve is for the furnace, not the burner, not the blower or force used to move fuel.
    Once you find that peak EGT, you aren't going hotter on that furnace unless you go nuclear, change your fuel or teach it to morph into something it's not.

    I can't speak of droplet size, I'm not that smart, but it seems to me there is a reason a fuel injector sprays gasoline at the size it does. In a perfect world, oil or diesel probably require something entirely different. We seek something that will accomplish both tasks. Lot's of give and take and nothing is or will ever be perfect.;)
  10. PatJ

    PatJ Silver Banner Member


    I agree with just about everything you say.

    One minor clarification though.
    Some folks use the compressed air for a siphon effect to draw fuel from the fuel tank and deliver it to the nozzle tip.
    I use a pressurized fuel tank, and so the compressed air in the nozzle is not moving the fuel from the tank to the nozzle, but rather the fuel is being pushed to the nozzle by the tank pressure.
    Melter uses a fuel pump to deliver fuel from his fuel tank to the nozzle.

    So really the compressed air is being used to mechanically break up the fuel in the nozzle and as it exits the nozzle, and the spin vanes give the atomized fuel a spinning motion as it enters the air stream.

    The pressure-style delavan does not used compressed air, but rather uses about 100 psi of pressure from a gear pump to both deliver fuel to the nozzle, and provide enough energy to cause the fuel to break up into droplets as it exits the nozzle (like a perfume sprayer).

    But yeah, there is definitely a sweet spot for fuel/air mixture that seems to be determined by the furnace size.
    I first noticed it on Clarke's furnace at Soule, and I asked him what his fuel flow was, since he was getting very fast melts.
    He told me something in the 3 gal/hr range, or perhaps a little less, and that is when it hit me, and I discovered the law of physics that states "Less is More".
    At first I thought Clarke was bs'ing me, but it turned out to be true.

    Last year I re-discovered (proved to myself) that what Clarke said was true (ie: use 3 gal/hr) during my multi-valve flow tests.
    And then melter said he was also using something in the 3 gal/hr range.
    And I think ironsides often is in that range.

    Sometimes what would appear to be obvious is not (at least not to me anyway).

    Jason likes this.
  11. OMM

    OMM Silver

    To be fair, when you say 3 gallons per hour, how many cubic feet are inside your furnace? And then I would suspect you would have to subtract the crucible.
  12. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    This is the issue. I think Andy mentioned this before, but internal volume of the furnace and the volumetric flow will locally cause the combustion gas to approach the flame propagation speed of the fuel and ultimately limit how much fuel can be burned in the furnace. This in part is why people have noted that oil burners like more internal furnace volume.......because there is a lot of energy in the fuel, requires a lot of air....which will produces high internal velocities.

  13. Melterskelter

    Melterskelter Silver Banner Member

    And that is why slowing down the flow rate of the air fuel mix can allow higher temps in a given furnace.

    A given burner tube size limits the low end speed possible that still achieves near complete slightly reducing combustion for a given fuel flow rate. So, using one burner tube size for testing fuel flow rates and air mixes does not test a potentially important factor. I’ll admit that it is much more difficult to vary burn tube diameter for testing. That does not diminish its potential importance.

    Similarly, location of the nozzle as far back in the burn tube as practical can simulate some of the recognized pre-combustion benefits of the Ursutz. The trick is to find the spot that just heats the tube to about 1000 degrees and to use stainless so you don’t burn up your tip. If you look into your furnace it is possible to see that the air fuel mix may not actually start to combust for a few inches after it leaves the tube. That is true in spades when cramming lots of fuel with lots of high speed combustion air and even higher speed compressed air. Ideally the mix would be actually burning at the moment it enters the furnace and have time to burn before it leaves.

    Ultimately complex theoretical discussions are settled at the test bench.

    Mark's castings likes this.
  14. PatJ

    PatJ Silver Banner Member

    I suspect that it may be as much a surface area thing as a volume thing.
    Basically you will have X square inches of hot furnace surface that can be heated by the burning oil.

    At some point as you increase the fuel flow, you will begin to wash the surface with partially burned fuel, and you will cool the surface.
    You can witness this effect at night in total darkness while running the furnace.

    If the surface is at its maximum temperature, it transfers maximum energy into the crucible, and also assists with completing the vaporization and combustion process, especially when using a drip style burner, but also with a spray burner.


    There is definitely a cold spot in front of the burner tube, and this is the area where the abient temperature fuel and air have entered the furnace and have not yet started to burn.
    This area is basically at ambient temperature, and this can only be changed by using an Ursutz type arrangement, or some variant on that method.

    As far as velocity, this is where the dual burner tube helps, since it would have half the velocity in each burner tube as a single burner.

    The flame distribution is much more smooth with a dual burner at 180 degree arrangement, but I think this mainly effects the early part of the melt when the furnace is not totally radiant.

    I think the dual 180 degree burner setup is the ultimate setup, and almost certainly the most efficient setup, but for me, there is just too much plumbing for any potential gain when using a dual 180 degree burner arrangement.

    The fuel/air stream that enters the furnace with a single burner tube strikes the back wall and is deflected upwards along the wall at about a 45 degree angle. This is where a dual burner arrangement at 180 degrees would help.

    Some photos below.

    This is a single burner arrangement with its inherent uneven heating distribution.

    This is a dual burner arrangement with a far more even flame distribution.
    Notice that due to the air velocity being 1/2 of a single burner tube, the wall climbing is essentially eliminated. I am not convinced that the wall climbing effect is a big deal, but you can see the difference between the two configurations.


    Last edited: Jul 5, 2019
    OMM, Jason and Tobho Mott like this.
  15. OMM

    OMM Silver

    Pat, I thoroughly impressed with your observation with duel burners and single burner. But... i’m wondering if the combustion air pressure was increased if a more cyclone affect would generate a full 360° burn?

    I for sure see cutting everything in half could be more balanced.

    Today I just witnessed a 1 foot wide NG burner that had a 39” reach that I had a 3 foot diameter hot face from the displacement. It was more of a forge set up.
    Last edited: Jul 9, 2019
  16. PatJ

    PatJ Silver Banner Member

    The fixed rate for melting iron seems to be between 2 and 3 gal/hr, and so that fixes the amount of combustion air you can input into the furnace.
    For my Toro leaf blower, I use the "low" setting, and so whatever that amount of air is, it is what combusts about 2.75 gal/hr of diesel.

    OMM likes this.
  17. OMM

    OMM Silver

    Here’s my next question... still sticking with diesel and waste oil burners.

    I see some guys reduce the diameter at the end of the burn tube and I see some guys increase the diameter at the end of the burn tube. On one hand it would speed up the combustion air and on the other hand it would slow it.

    I’m sure there is more to it calculations, like absence of the diameter of the burner nozzle.

    @PatJ since you are literally a drip stream, do you find your combustion air carrying the stream or does it just drip out the end of your burn tube? If you increased your leaf blower to a higher speed and decreased the diameter you could be providing the same CFM just carrying the fuel stream a little better/faster.

    I suspect once it hits the furnace it will just be travelling at a higher speed and displacing within the large volume no different, except it might carry the flame two revolutions instead of one.

    Anybody‘s thoughts on this matter?
  18. Jason

    Jason Silver Banner Member

    I'm burnt out... Melt some metal! Then screw with it later.:p:D
  19. OMM

    OMM Silver

    I hope I’m not burning you out Jason? I was told maybe another week or two until I get the brick.

    Then I’ll probably be questioning you on your flux’s... and lifting tools.... and maybe how are you anneal to make things more machinable.

    Edit: I believe I’ve started two relevant threads on this forum...And I believe the members (including yourself) providing good relevant experience and education have landed these thread in the high viewing. Your experience and knowledge (and others participating) I’m sure it is where the following is derived from. You may have a silent following here. I know for sure I don’t!
    Last edited: Jul 14, 2019
  20. Jason

    Jason Silver Banner Member

    lol... Those that follow me are just in it for the laughs. I'm not a fluxer as I do pretty much no aluminum. Lifting tools are easy, I'm sure you weld so that'll be a no brainer for you. Be warned, crucibles pooch out and get a bit fatter when hot and full of metal. So keep that in mind when ya build your tools. Brian Oltreg on YouTube had a cool one tool solution that lifts and pours. Sadly we cant get him to give up the file for cutting it out on the plasma...:mad: Its good for #10 and smaller crucibles. I make artsy fartsy stuff so no annealing either. That's where the steamers around here will be helpful I bet. Some day when I'm an old fart, I'll have to make cool toys like that. At the moment, I need to sell my crap. Wife wants a stainless steel swimming pool so I gotta raise a lotta cash. Maybe I could sell some dirty bath water like that bimbo. You see that goofy shit? 19yr old twit sells 500jars of dirty bathwater for 30bucks a whack. Our society is F$@ked..

Share This Page