Buzzkill Posted November 13, 2023 Share Posted November 13, 2023 (edited) I’ve been tinkering around with naturally aspirated ribbon burners for a few years now. In that time I’ve tried quite a few different configurations regarding the number, diameter, and length of the ports. There are a few generalizations I’ve gleaned in that time, but I wanted to zero in on the specifics a little better. Recently I’ve learned enough CAD to emulate AFB’s vortex inducer, so I started looking for a good combination of that inducer and a burner block that gives me good results. Specifically the characteristics I’m after are as follows: Able to reach forge welding temperatures in a reasonable amount of time. Relatively quiet. I like to be able to have a conversation near the forge while it's running. Can turn down to low pressure after forge welding without backfiring or burning in the plenum. At least as fuel efficient as a single port burner with the same mixing tube diameter. Everything I’ve made and tested recently has been cast using Tabcast 94. It’s not bad, but there is a fair amount of aggregate material in it (similar to Kastolite), which makes vibrating the castings pretty much a necessity. The finish is not quite as smooth as I’d like either. A couple minutes after firing up the first burner option I decided to set up a type K thermocouple to monitor temperatures. All of these are using an AFB inspired vortex inducer of the appropriate size for the mixing tube. The first one tested employed a .030 MIG tip for the jet. The ports are 3/16” in diameter and 1.5” long. I forgot to record the number of ports, but I can provide that if anyone is interested. The PSI shown is what I set it to at the time listed to the left. I recorded the temperature in degrees Celsius because my PID controller only displays degrees C. Time Temp (C) PSI Dragon’s Breath 13:20 70 5 Minor 13:30 960 10 No change 13:40 1170 15 No significant change 13:45 1252 5 Minor 13:50 1203 3 Backfire/burning in plenum immediately At this point I switched to a 0.6 mm 3d printer nozzle for the jet, but left everything else the same. There was no dragon’s breath at any pressure, and it was so far from being acceptable that I just recorded the temperature at max pressure. Time Temp (C) PSI Dragon’s Breath 1109 21 None Switched to a ½” mixing tube with appropriate inducer, but still with the 0.6 mm 3d printer nozzle. Again, no dragon’s breath observed and it was not suitable for further testing. Time Temp (C) PSI Dragon’s Breath 1063 21 None Changed to a 0.8mm 3d printer nozzle with ¾” mixing tube. Time Temp (C) PSI Dragon’s Breath 14:30 490 5 None 14:35 940 10 None 14:40 1051 15 None 14:45 1145 20 minor 14:50 1235 5 barely visible 14:55 1165 N/A Backfired immediately when pressure dropped below 5 psi At this point I decided to try a different plenum/burner block combination that had given me unsatisfactory results previously. I ran a rod through all the full length ports to ensure they were clear before testing this time. Originally there were 189 ports, but due to the fragility of the 3d prints I had fewer full length ports. I believe I still have about 185 functional ports which are 1/8” in diameter and about 3” long. The info below was gathered using the same vortex inducer, 0.8mm 3d printer nozzle, and ¾” mixing tube. Time Temp (C) PSI Dragon’s Breath 15:10 545 5 None 15:15 905 10 Barely visible 15:20 1030 15 Slight 15:25 1126 20 Small/moderate 15:30 1201 20 No change 15:35 1235 20 No change 15:40 1260 20 No change 15:45 1280 5 Slight 15:50 1229 2 small/lazy 15:55 1150 1 no change 16:00 1099 0 forge off 16:05 814 For those that don’t want to do the conversions, 1260 degrees C is 2300 degrees F. That combination of inducer and burner block has provided the results I was looking for, so I’m not sure how much more experimenting I’ll do at this time. However, to satisfy my own curiosity I may run the last burner setup again with a Frosty T setup instead of a vortex inducer to see if there is much of a difference for NARB’s. I may also run it again using a single port configuration with the vortex inducer. I suspect a single port will get hotter faster than the ribbon burner. Edited November 13, 2023 by Buzzkill grammar Quote Link to comment Share on other sites More sharing options...
Buzzkill Posted November 27, 2023 Author Share Posted November 27, 2023 Although there seems to be less than cyclonic enthusiasm for this topic, I did a few more experiments, so I'll post a more summarized version. I attempted to use the vortex inducer on a single port 3/4" burner with a small flare on the end using a .8 mm 3d printer nozzle. I couldn't keep it lit unless I covered about 80% of the air intake, so I abandoned that test and installed a 1 mm 3d printer nozzle. This performed much better. I went through similar pressures for about the same amount of time shown in my previous post above. I was able to reach 1275 degrees C after working up to 20 psi in 5 minute increments and there was a moderate orange dragon's breath (about 6 to 8 inches past the front of the opening). Surprisingly, I was also able to turn this setup down to 1 psi after being at forge welding temperature without it burning back into the mixing tube. Next I tried the 1 mm 3d printer nozzle on the 3/4" mixing tube with the vortex inducer and the burner block using 180+ 1/8" diameter ports that are about 3" long. I abandoned this fairly quickly. The dragon's breath was significant and mostly blue even at 20 psi. Next I moved to a Frosty T setup, but still with the 1 mm 3d printer nozzle. This was not fine tuned and the end of the nozzle was only about 1/3 into the opening when viewed from the side. I stayed with the 1/8" diameter port burner block. This still produced a lot of blue dragon's breath so it was abandoned quickly as well. After that I replaced the 1 mm with a .8 mm 3d printer nozzle, but kept the Frosty T 3/4" setup. I ran this at 20 psi immediately without stepping up in 5 psi increments. Dragon's breath was slight and orange. After 20 minutes the forge had gone from 681 C to 1247 C. Finally I switched back to the vortex inducer, but still with the .8 mm 3d printer nozzle and 3/4" mixing tube on the same NARB burner block. In about 15 minutes at 20 psi the forge went from 970 C to 1240 C with a little more dragon's breath than the Frosty T. I was running out of propane at this point so the experiments ended. So here's my conclusions: 1) I need to refurbish my forge, and it's more of a heat sink than I originally thought. 2) It appears that my NARBs cause a reduction in induced air compared to a single port burner whether using a vortex inducer or a Frosty T. 3) The enhanced performance of a vortex inducer is significantly diminished or eliminated on a NARB with lots of ports. 4) I could reach about the same temps with a NARB as I did with a single port burner, but the single port got there more quickly (but also with a larger jet orifice). 5) Although I really like the performance of a vortex inducer, I like the quiet ribbon burner more. Quote Link to comment Share on other sites More sharing options...
Brian Hibbert Posted November 27, 2023 Share Posted November 27, 2023 4 hours ago, Buzzkill said: Although there seems to be less than cyclonic enthusiasm for this topic, I did a few more experiments, so I'll post a more summarized version. Don't think that no one is reading or interested. I don't comment on this post or most of Mikey's because I don't know enough to even ask good questions, but I do read these "basic research" posts with interest. Please keep us informed of your progress. When I start thinking of a forge build, I'll be looking at experiments like yours to see if I want to go that route or stick with the more traditional Frosty burner... Quote Link to comment Share on other sites More sharing options...
Frosty Posted November 27, 2023 Share Posted November 27, 2023 I'm reading Buzz, I don't have anything to say because I don't normally work with that depth of data so I can't interpret it usefully. Given enough time and a light might come on. I do have one thought based on performance and symptoms rather than your data. First, yes lose excess thermal mass in the forge. Second. The reason your experiments show reduced combustion air induction isn't jet size, position, etc. it's back pressure from the burner block, increase the number of outlets in the block. Your induction should improve. Frosty The Lucky. Quote Link to comment Share on other sites More sharing options...
Buzzkill Posted November 27, 2023 Author Share Posted November 27, 2023 I agree in the sense that I think the size, number, and length of the outlets (ports) affect the amount of friction and therefore the back pressure that is created. However, I've not made a NARB yet, regardless of the number, size, or length of holes, where the flames on the ribbon burner were tuned the same as when I used the same T and mixing tube for a single port burner. The NARBs always seem to run a bit richer for me. It's entirely possible I'm doing something different/wrong compared to other people, but I've always had to find a way to reduce the fuel or increase the air to get my NARBs running the flames I want. This burner head is already huge - about 3 by 7 inches with more than 180 holes, and frankly I don't think I have the necessary motivation to go through the entire process of casting it again. I really like the small diameter ports for a couple reasons: 1) The burner is super quiet. The fuel coming out of the jet orifice makes more noise than the flames inside the forge, and 2) I can turn the burner down to the point where nothing registers on the pressure gauge after being at forge welding temperatures without it backfiring or burning back into the plenum. Since I can reach forge welding temps with it, I can check off all the most important features (to me) in a burner. Part of me really wants to experiment more, but another part wants to heat and beat some steel. Quote Link to comment Share on other sites More sharing options...
Scott NC Posted November 27, 2023 Share Posted November 27, 2023 Those that you least suspect, are paying attention. Quote Link to comment Share on other sites More sharing options...
Frosty Posted November 28, 2023 Share Posted November 28, 2023 Of course the NARB burns differently than the same inducer as a single nozzle burner. Mine all run slightly richer on a NARB than in the other forge. I think the guys making NARBS successfully have discovered a lot of the factors I was playing with don't really mean much at a home built level. Length of outlet nozzle through the block for example. It isn't nearly as important than I thought. Heck a couple test blocks and mine were working well enough I only made the two in refractory though I do think of things I wanted to try but I discovered age and arthritis takes a lot of the fun out of anvil time. So I hang out and pass what I can along. Frosty The Lucky. Quote Link to comment Share on other sites More sharing options...
Hefty Posted December 11, 2023 Share Posted December 11, 2023 This one slipped past me, but I'm reading with interest now! I'm currently building a small forge with the intention of then overhauling my larger forge to run a NARB and I've also played with my own version of AHB's 3D printed inducer, but I haven't made a burner block yet. Just to clarify, whether running the vortex inducer or a T, the burner block with the best results for avoiding back burning has been a deeper block (3"?) with approx 180 x 1/8" holes? Hopefully this could make an appropriate starting point for me to start planning mine. Quote Link to comment Share on other sites More sharing options...
Buzzkill Posted December 11, 2023 Author Share Posted December 11, 2023 You have it right. There didn't seem to be much difference between a T burner "top end" and an AFB inspired vortex inducer on the NARB burner block I used. There is a noticeable difference as a single port burner though. For several sessions I got absolutely no burn back into the plenum and no "poof" when shutting off the fuel when using the block that has over 180 ports which are about 3 inches long - even after being at 1280 C. However, since then I have had a little "poof" when I turn off the gas. I still can turn the pressure down to the point where it doesn't register on the gauge after being at forge welding temp without it backfiring or burning back into the plenum though. The down side is it is a large, heavy burner head, and all those small diameter holes make it a challenge to cast and clean. I made a disposable 3d printed mold form for the burner head. Once I vibrated in the refractory and placed the plenum I put the whole thing in a plastic bag for a day or so. My next step was to put the whole thing on the 3d printer bed and heat it to 100 C for about a day before removing the plastic bag and letting it set another day or so (with heat). After that I cut off all the exterior plastic, built a small fire, and moved the burner block and plenum gradually closer to the fire and then eventually in it. It was a several hour process, but ultimately the burner was in the middle of the fire with coals under it, and the plastic all burned out fairly well. It was still worthwhile to run a rod through all the holes I think. That's not exactly the prescribed method given by the manufacturer, but it seems to have resulted in a solid burner head with no cracks (yet). Quote Link to comment Share on other sites More sharing options...
Frosty Posted December 12, 2023 Share Posted December 12, 2023 I went through a long curing and firing process for my first NARB then abbreviated it considerably on the second after reading testimonials from users on a website about refractories. I bookmarked the site but when I checked back it'd moved onto something completely different refractory based. When I looked closer it turned out to be a blog and as chaotic as any. That sucked, that thread was full of really useful experiences but . . . <sigh> What I learned was Kastolite-30 is formulated for minimal cure time to put it to work furnace liner. The users in the blog most commonly fired it as gunnite into HOT furnace liners as a patch and it was known for lasting at least as long as the liner. I never tried casting small dia. nozzle, burner blocks, I had to sift out the larger aggregate to get good castings with crayon size nozzles. The big trick I learned for NARB 2 was pealing the wrappers off the crayons so they melted and burned out without residue. I don't have a 3D printer though may have access to one more recently if I were interested in further experiments. Unfortunately arthritis is keeping me off the anvil so making new burners and forges has become sort of a thought experiment thing anymore. Sucks but I'm not going to complain about living this long. Frosty The Lucky. Quote Link to comment Share on other sites More sharing options...
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