stockmaker Posted February 28, 2017 Share Posted February 28, 2017 Andy98, I only have one comment and it is about the proposed new fan. First of all I would like to say I am impressed with your work. I know you have done a great deal of research on this, and I am not going to debate you on your findings, because I can not. But I am concerned that the PC fan you are planing to purchase will not have near enough power for your needs, they are just little guys that run quietly for years in a a box full of electronics. Double check your numbers before buying, and be sure you have a decent DC power supply to power it, and best of luck. Quote Link to comment Share on other sites More sharing options...
Andy98 Posted February 28, 2017 Author Share Posted February 28, 2017 2 hours ago, WoodnMetalGuy said: I wonder if you'd have better control with a regulator in the feed rather than trying to control the gas with a partially opened ball valve. And an unrelated question - what's up with all the funnels hanging on the fence in the background? -- Dave Hi, 1) Control probably would be better - but I doubt it's necessary. It's regulated (at the gas main) which is all of 40ft away, so I suspect my pressure will be pretty constant (there isn't a tank that will deplete or change temperature). Also, I think an adjustable regulator for such a low pressure range would be hard to source. 2) The funnels were a (largely unsuccessful) water toy for my kids. They pour water into them, or use the hose. Seemed like it should be fun, but in reality they just like to use the hose and don't seem to care what, exactly, they are filling/soaking. Cheers, Andy Quote Link to comment Share on other sites More sharing options...
Andy98 Posted February 28, 2017 Author Share Posted February 28, 2017 16 minutes ago, stockmaker said: Andy98, I only have one comment and it is about the proposed new fan. First of all I would like to say I am impressed with your work. I know you have done a great deal of research on this, and I am not going to debate you on your findings, because I can not. But I am concerned that the PC fan you are planing to purchase will not have near enough power for your needs, they are just little guys that run quietly for years in a a box full of electronics. Double check your numbers before buying, and be sure you have a decent DC power supply to power it, and best of luck. Hi, thanks for your comments. The fan in question is a beefy unit, actually, not your typical fan by any means. To illustrate, I picked this typical cheapo 40mm fan for comparison. The fan I'm considering is: Almost 3x the depth of a typical fan (2.8cm vs 1cm). That should allow the blades to be more "scoopy", so to speak, which makes sense to me as what you'd need for higher static pressures. It Is 4.5x faster (18000 rpm vs 4000rpm) - which means it's not only bulk moving more air, it means there are higher tip speeds involved. It draws almost 10x the current (0.43A vs 0.05) and thus higher wattages as well (5W vs 0.4) It's almost 3x louder (54dB vs 20) So, assuming the manufacturer isn't outright lying about their fan performance specs, then it should be able to keep up with the draft inducer I tested with. The draft inducer appears to have a lower static pressure max (~1inWC vs almost 2 for the PC fan) but for sure has a much higher CFM in free air (the video shown has the draft inducer running with it's opening gated down to about 10% of max - it makes waaay more air than I need). I'm not sure what else I could be missing here - but of course there could be something. At this point I think I've proven enough things out that it's a reasonable next step, and if it turns out not to work then I'm out less than $40 anyway and can revert back to the draft inducer. Finally, I'd rather take a shot at the PC fan than continue to invest in the draft inducer. To finish the draft inducer approach I still would need to make a weather resistant housing for it, get better ducting, get some proper HVAC reducers, and make a better gate valve. There is at least $20-30 worth of materials required there and probably about 6 hours work. The PC fan, if it works, will give me a clean solution with a lot fewer hassles. It'll be easier to setup, store, etc....plus I'll be able to modulate the speed better. ..and I'll have fun building the PWM circuit. Quote Link to comment Share on other sites More sharing options...
Latticino Posted February 28, 2017 Share Posted February 28, 2017 From the video it appears that you have too much fuel/air flow for your nozzle diameter. The mixture appears to be moving away from the burner faster than the flame front is burning back. Visually it does not look like you are getting complete combustion, but you may be further in the chamber. I believe that you are right that you will get batter combustion as the forge heats up, but you will likely have some trouble turning down the system to low fire. I also agree that some form of metering valve is better for the gas line. Generally I would suggest a globe type valve at least 1 size smaller than your line size (for good valve authority) for the gas and a gate or butterfly valve for the air side. Quote Link to comment Share on other sites More sharing options...
Andy98 Posted February 28, 2017 Author Share Posted February 28, 2017 28 minutes ago, Latticino said: I believe that you are right that you will get better combustion as the forge heats up, but you will likely have some trouble turning down the system to low fire. Thanks - it's funny, I will likely have to transition from worrying about not enough output to dealing with too much. It'll take me a while to accept that concept - but I guess that makes sense given the total BTUH potential I calculated. I went with the ball valve simply because someone else had used one in their NG build - but I did have it mostly closed already, so if I do need to meter it down further I won't have have a lot of precision. I'll look into globe valves. The NG hose is 3/8" and the output pipe is 1/2" - are you suggesting a 1/4" globe valve then? Quote Link to comment Share on other sites More sharing options...
Latticino Posted February 28, 2017 Share Posted February 28, 2017 Just beware that you might have too much gas/air output for your burner outlet, but not for your forge volume/insulation/thermal mass. You might need a larger burner flare to get the most from your burner. It's all about relative velocity. 1/4 should be good for control authority provided you have enough pressure. Control valves are a tradeoff also. I'd try a larger flare first Quote Link to comment Share on other sites More sharing options...
Andy98 Posted March 23, 2017 Author Share Posted March 23, 2017 On 2/28/2017 at 4:35 PM, Andy98 said: So, assuming the manufacturer isn't outright lying about their fan performance specs, The fan is here. I'm not saying they lied about the specs, but they are at least extremely optimistic.There may be one of these fan units that produces the specified fan performance curve but the one they shipped me does not. I purchased an "R" class fan, and it performs like "P" class curve (the fan is labelled as being an "R" unit): In my burner, I measure the unit as producing ~6cfm - spec curve suggests more like ~16. I also measure the fan to produce a static pressure of ~1inH20 - spec says 1.8. All that said, the fan is still sufficient - at least according to measurements in my garage. 6 cfm is close to my original performance spec. I did make an improvement to the fan: I inserted a layer of tape around the inside of fan's housing (basically sealing the housing to the fan blades a bit better) and that upped the performance to 8cfm. So, I'm disappointed that I won't have as much headroom with the fan as I wanted but the good news is that it should still work and if it doesn't, then upsizing to 1" pipe from the 3/4" I'm at now should give me significantly more airflow in any case. I'm tempted to buy the parts just to test that out. Temporary mounting and ugly green painter's tape aside, this could be pretty elegant for a blown burner: Next post: Electronics. Quote Link to comment Share on other sites More sharing options...
Andy98 Posted March 23, 2017 Author Share Posted March 23, 2017 I've also made progress on the electronics front to control the fan speed. I had two viable solutions: Approach #1: Off the shelf parts Note that R1 in there is really a 0-5k pot, but LTSpice doesn't model that. That circuit will produce a 25kHz PWM signal with a duty cycle between approx 5-98%. To get it to 100% you'd need a trim pot and tweak the R2 resistance up. The trick is making sure you don't get something like a 110% duty cycle, because that will actually cause it to produce something like a 12.5kHz PWM at ~50% duty cycle. It should be relatively easy to tune when connected to the fan, and represents about $4 worth of parts. I post it here for posterity. Approach #2: Microprocessor Instead of the circuit above, I built a PWM controller using an ATTiny85 that takes voltage input from a 0-10k resister, and outputs that as a 25kHz PWM wave. The code came from here - it's straightforward once you decode it. I used an Arduino Uno as the ISP/programmer. Both of these things were pretty new to me, so that was fun to try. It worked great! On the bench at least, I have a working circuit that, according to a USB logic analyzer I was able to borrow from a friend is giving me a perfect 25kHz PWM signal, with a range of around 1-100%. It doesn't do full zero. I could modify the program to make that work, but I don't think it's necessary so I'll leave it be for now. This was about $3 worth of parts. There will likely be another $5 worth of stuff required: I'll need a barrel connector to plug the power in, a connector for the fan wires, a regulator to produce 12VDC for the fan, and another one to produce 5VDC for the microprocessor circuit. I would have needed those with the other circuit too. Lack of (portable) power supplies is preventing me from testing the PWM circuit with the actual fan, and from testing the entire burner in the forge. Frustrating. But I should be able to get that all setup this weekend, and then I'll have to wait for cooperative weather to see how it runs. I'm optimistic that the result will be about the same as the previous test with the draft inducer. I think the draft inducer in my video was running at about 6-7cfm, which is what the fan can produce. Fingers crossed. Quote Link to comment Share on other sites More sharing options...
stockmaker Posted March 26, 2017 Share Posted March 26, 2017 Hi Andy, nice work on your blower. I had a thought that you need to be aware of. With the fan that close to the torch body it will be susceptible to forge heat when it is turned off after a long run. The heat will chimney up the torch pipe and could possibly melt or warped your fan blades. Of course I don't know how you are going to mount the burner or if it will be removable but just watch it during testing. Quote Link to comment Share on other sites More sharing options...
Andy98 Posted March 26, 2017 Author Share Posted March 26, 2017 4 hours ago, stockmaker said: Hi Andy, nice work on your blower. I had a thought that you need to be aware of. With the fan that close to the torch body it will be susceptible to forge heat when it is turned off after a long run. The heat will chimney up the torch pipe and could possibly melt or warped your fan blades. Of course I don't know how you are going to mount the burner or if it will be removable but just watch it during testing. Yes - good point! My burner is side mount, so that should be somewhat helpful. I'm also not going to put an off switch on the fan it, so that should help me remember to do something smart to keep it from melting before I shut off the air. I probably will end up removing either the entire burner, or the non-metal parts of the burner, after use. Should be straightforward, if a little annoying. Hopefully this week will be test run #2. I also wanted to say that Digikey is awsome: They will happily either ship me a replacement fan, or refund me the cost of the fan. I have found an even more powerful unit (this one) that I might replace it with. Will depend on how things go this week. Quote Link to comment Share on other sites More sharing options...
Andy98 Posted March 29, 2017 Author Share Posted March 29, 2017 I was able to put all the pieces together and give it a run today. Bright sunlight out, so hard to see what's going on. My synopsis: Success! I don't think I need a stronger blower. I don't understand why it's sputtering. I think/guess I had it too lean with the blower too high. I think the sputtering is due the gas velocity being too high. Apologies in advance, I took a lot of video. First the good: Here is the forge running at a really, really low setting. The noise on the video that sounds like high-rate-gas-flow is actually the fan. The NG flow noise is undetectable. For some reason the camera also seems to be exagerating the fan noise. Running at idle like this, the forge was almost silent compared to the usual street noise around me. Next up, forge running at about 90%. The exposure on this one was a little wonky. The forge lining was getting into lemon yellow in person, and the refractory floor tile had that slick melty look to it. I think this is hot enough to weld in? This next one is really long, and unless you are really interested in this you might want to skip it. In this video I am adjusting the flow, trying to get a feel for things. I've noted in the video description what I was doing. Most interesting part is probably around 2:00 minutes when I bring it all the way down to a rolling flame. So that's the thing running, and I think it's doing pretty well. What I don't understand, is the sputtering. Here is the forge starting up from cold - note how much it sputters. It actually went out a few times. I could make the forge go out at will by turning up the blower. I didn't know if the forge was stuttering because the gas velocity was too low, or if it was too high. I now have the opinion that it was too high, and the mix was too lean, but I would really appreciate feedback and advice from others. So, there you go! Obviously I need to package up the electronics, but I think this is a success.Next time I get it in my head to try an electronics related project, I have to remind myself that I hate soldering. I'd appreciate any feedback, onions, advice, observations others might have. I don't really know what I'm looking at, honestly and can use the help. Quote Link to comment Share on other sites More sharing options...
Buzzkill Posted March 30, 2017 Share Posted March 30, 2017 6 hours ago, Andy98 said: I'd appreciate any feedback, onions, advice, observations others might have. I don't really know what I'm looking at, honestly and can use the help. I'm fresh out of onions at the moment, but I do have an observation. I never saw you adjust the gas flow in any of the videos. When you speed up the fan you are changing the fuel to air ratio. If you do not increase the fuel flow as you speed up the fan then you will start to burn very lean if you can keep it burning at all. A lean flame will cause significant scale to show up on steel inside the forge and an extremely lean flame will not burn as hot due to the excess air. It looks like you have a ball valve for fuel adjustment. It's probably already been mentioned, but a needle valve will be much better suited to the application. For forced air/gas burners I bring the fuel and air up together and then play with the air to get the desired forge atmosphere. For me that's a slightly rich (reducing) flame. You can tune by ear once you get used to it. The flame should produce a continuous roar. Turn the air flow up and down to find out where the flame is the loudest. Once you find that, cut the air back just slightly and that should give you a mildly reducing flame. Quote Link to comment Share on other sites More sharing options...
Andy98 Posted March 30, 2017 Author Share Posted March 30, 2017 3 hours ago, Buzzkill said: I'm fresh out of onions at the moment, Oops! That gave me a good laugh. Of course I'm looking for opinions but will take onions if they are offered. 3 hours ago, Buzzkill said: I'm fresh out of onions at the moment, but I do have an observation. I never saw you adjust the gas flow in any of the videos. When you speed up the fan you are changing the fuel to air ratio. Yes, understood. When I did adjust the gas a bit to see what effect that had on things, but that gas ball valve I am using needs two hands to make a small adjustment, so I didn't get that on video. I was trying to get a handle on what adjusting the gas does to the performance, and then separately what adjusting the air does to the performance. Once the forge was hot, I did fiddle with trying to get the forge into a good operating mode. I think I can forge at that low idle setting. It was quite hot, plus quiet. Then the 90% setting is, I figure, where I'd need to be to weld. I have some other videos in the middle, in each case I'd tune it to try and get some orange flame out the door. The ball valve is a giant pain and I'm going to replace it with something better (probably needle valve), just trying to source something reasonable at the moment. I didn't do it already because I'm trying to limit my investment in each step with the (until now) expectation that I'd have to abandon this at some point. 3 hours ago, Buzzkill said: You can tune by ear once you get used to it. The flame should produce a continuous roar. Turn the air flow up and down to find out where the flame is the loudest. Once you find that, cut the air back just slightly and that should give you a mildly reducing flame. In the 90% video, would you consider that a "continuous roar"? Or just high-frequency-sputtering? I'm thinking in that video it's sputtering and falls into the "ok" but "not great" category but if you have an onion I'd hear it Quote Link to comment Share on other sites More sharing options...
Buzzkill Posted March 30, 2017 Share Posted March 30, 2017 3 hours ago, Andy98 said: In the 90% video, would you consider that a "continuous roar"? No, that sounded more like a rapid pulse. Full disclosure here - I've never built a natural gas powered forge. When I used forced air it was with propane, but I don't think there should be a significant difference in the sound of a properly burning flame. Someone with NG forge experience may be able to verify that though. Until you change out that ball valve I'd be hesitant to make too many other changes. One simple thing you could do in the meantime is move the burner tube further in and out of the forge body to see if that changes the behavior of the flame, but somehow I doubt that will eliminate the pulsing flame you have. As a general rule only change one thing at a time so that you can be confident what the problem was when you get it sorted out. Quote Link to comment Share on other sites More sharing options...
Andy98 Posted March 30, 2017 Author Share Posted March 30, 2017 2 hours ago, Buzzkill said: One simple thing you could do in the meantime is move the burner tube further in and out of the forge body to see if that changes the behavior of the flame Unfortunately that's easier said than done. I have to change out the burner support holder - the 3/4" pipe is just slightly too large to fit, so it's pushed in as far as I can push it and that makes the end of the mixer tube end about 1/2" into the outer layer of kaowool. Quote Link to comment Share on other sites More sharing options...
Buzzkill Posted March 30, 2017 Share Posted March 30, 2017 Hmm. Well, have you tried lighting it outside the forge with a flare on the end of it? Of course you want final tuning to be done where it will be used, but if the pulsing stops outside the forge then you'd have an idea that the pulsing has something to do with the burner orientation and/or forge chamber dimensions. If the pulsing remains then you can eliminate that factor and focus on fuel/air delivery and burner construction. Quote Link to comment Share on other sites More sharing options...
Andy98 Posted April 3, 2017 Author Share Posted April 3, 2017 On 3/30/2017 at 2:26 PM, Buzzkill said: have you tried lighting it outside the forge with a flare on the end of it? Good suggestion. I don't have a usable flare at the moment, which is annoying. I did try lighting it without the flare, and I could not get a sustained burn (no surprise) but it did make me realize that at low fan speeds my gas velocity is below the flame-speed and the flame front moves into the mixing tube, while at high fan speeds I can easily blow out the flame (without a flare). I presume that's normal for blown burners? The burner gets crazy hot if the flamefront is inside the mixing tube. Would a more typical blown burner have a minimum blower speed that is always above the flame speed? Quote Link to comment Share on other sites More sharing options...
Latticino Posted April 3, 2017 Share Posted April 3, 2017 15 minutes ago, Andy98 said: Would a more typical blown burner have a minimum blower speed that is always above the flame speed? Yes, all burners have a minimum fuel/air mixture flowrate that is at or just above the flame speed. However some have burner "end conditions" (flares, multiport burner outlets, flame retention ring nozzles...) that attempt to isolate the burner mixing tube from the flame front by use of a radical velocity change. To the best of my knowledge these extend the stable operating characteristics of a given burner. These are not in great favor typically on NA burners, as they invariably add a bit of flow restriction and consequent friction which reduces the ultimate capacity of the burner, but are not as significant for a typical forced air burner. No idea how they would impact yours. Quote Link to comment Share on other sites More sharing options...
Buzzkill Posted April 3, 2017 Share Posted April 3, 2017 2 hours ago, Andy98 said: I don't have a usable flare at the moment, which is annoying. I did try lighting it without the flare, and I could not get a sustained burn (no surprise) but it did make me realize that at low fan speeds my gas velocity is below the flame-speed and the flame front moves into the mixing tube, while at high fan speeds I can easily blow out the flame (without a flare). After watching the videos and listening to the sound of the flames again I'm fairly convinced that the staccato sound happens when your flame is burning inside the tube rather than at the end as it should. There were several brief moments when the flame sounded "right" to me and that always coincided with visible flames inside the forge at the burner port. The chopped sound of the flame returned as the visible flame inside the forge disappeared again. The flame should be burning at the end of the tube, not inside it. Once that gets hot then the ignition of the fuel/air mix will continue inside the tube even if you turn up the gas and air. If that happens then you have to wait for the tube to cool down again before another attempt. The flare doesn't need to be anything special for testing purposes. All you're trying to do is hold the flame at the end of the burner tube for now. If you have threads on the end you can use a bell reducer (with the large end one size bigger than your pipe) temporarily just to try to get a stable flame and see if the pulsing/staccato flame goes away. You can also "roll your own" from non-galvanized sheet metal such as stove pipe. Again, we aren't planning on a permanent flare here for use in the forge. Quote Link to comment Share on other sites More sharing options...
Andy98 Posted April 4, 2017 Author Share Posted April 4, 2017 20 hours ago, Buzzkill said: After watching the videos and listening to the sound of the flames again I'm fairly convinced that the staccato sound happens when your flame is burning inside the tube rather than at the end as it should I took some of the earlier videos and watched them frame-by-frame and it does look like the flame front is spreading backwards, but it's hard to tell because it happens it happens in just two frames. I did, however, just discover that my phone will do 240fps high-speed video so I should be able to get some good slow-mo of the flame front next time. So I think you're right - but I can't riddle out why the burner wasn't getting hot in those original videos. In all those videos I posted, the burner stayed nice and cool (with one brief exception). It wasn't until a test run on Sunday, video of which I have not posted, that the hot-burner became a problem. It still looked to me like the burner was putting itself out rather than sustaining a burn inside the mixing tube. I guess it's possible it burned all the way back to where the gas/air was not mixed well enough to burn? Then it goes out until the next slug reaches the hot forge and reignites? 20 hours ago, Buzzkill said: Once that gets hot then the ignition of the fuel/air mix will continue inside the tube even if you turn up the gas and air. I'm really glad you mentioned that. That is a really good point, and is completely non-obvious to me (but makes total sense). It explains a lot of what happened on my most recent test run. I guess I have to be really careful, especially when starting the unit up when the temptation/need for slower flow is the highest. If I put all the pieces together then I guess: When the gas velocity is lower than the flame speed I get sputtering but the burner tube stays cool since the flame puts itself out. When the gas velocity is high then I get regular burning but can blow the flame out. When the gas velocity is such that somewhere in the mixing tube it's exactly the same as the flame speed I get burning in the mixing tube and an overheating burner. ...I'm starting to think that the 3/4" burner needs to run at a much higher rate than my forge really requires. All of this does point to a high-power fan being a good thing - it would not only let me have higher velocities in the 3/4", but would surely be necessary if I try a 1/2" burner. BTW, thanks again for taking the time to watch and respond - I appreciate the help immensely! Quote Link to comment Share on other sites More sharing options...
Buzzkill Posted April 4, 2017 Share Posted April 4, 2017 There are enough differences between what you are attempting to do and what I did that I'm not comfortable making any definitive statements based on what I'm seeing. I'm looking at a process of elimination here to see where the deficiency is. If we can eliminate the shape, size, and orientation of the burner port in the forge then we can move to the fuel and air mixing and delivery. I also used a 3/4 inch pipe as my final tube into the forge, my forge body was a disposable helium tank, and I believe my forge chamber dimensions were smaller than what you show. However, I was using propane rather than natural gas. The air was supplied by a bouncy house blower (way more than needed) and regulated by a gate valve. I also had larger diameter pipe where the gas was introduced into the system, more pipe length between the fuel inlet and the end of the burner, and a couple "bends" in the piping (one 45 degree and one 90). As I understand it, NG mixes with air better than propane does, so you may not need those features to ensure good fuel/air mix, but I wouldn't rule it out. I was able to turn down to a very low flame and still have it stable with my setup. I did have to keep the flame at a moderate level until the forge interior heated up a bit to avoid flameout, but once the interior started glowing I could turn it up pretty much as far as I wanted without flame stability issues. Still, if I were you I'd change one thing at a time to try to nail down where the issue lies. I'd want to eliminate the forge itself as any part of the equation before moving on, so that's why I recommended trying a flare outside the forge before making any other changes. Quote Link to comment Share on other sites More sharing options...
Andy98 Posted April 5, 2017 Author Share Posted April 5, 2017 7 hours ago, Buzzkill said: Still, if I were you I'd change one thing at a time to try to nail down where the issue lies. I'd want to eliminate the forge itself as any part of the equation before moving on, so that's why I recommended trying a flare outside the forge before making any other changes. I agree with everything you've said, and the course of action you have suggested. It'll take me a while to progress it. It occurs to me that we do have one more piece of info: The burner performance with the draft inducer (from my Feb 28 post's video) vs the PC Fan. The draft inducer appears to be running sputter free (to me). That is a single (but big) variable change: same burner, mounting, and forge - different blower. Quote Link to comment Share on other sites More sharing options...
Buzzkill Posted April 5, 2017 Share Posted April 5, 2017 16 hours ago, Andy98 said: The draft inducer appears to be running sputter free (to me). That is a single (but big) variable change: same burner, mounting, and forge - different blower. Good point. Your PC fan may be able to move enough volume of air, but it may not have the required static pressure for the burner to function correctly. It should be easy enough to try a different air source to verify if that's the main issue. I was (am) kind of hoping the PC fan thing would work for you. It's a much quieter option than anything I've used to date. Quote Link to comment Share on other sites More sharing options...
Andy98 Posted April 7, 2017 Author Share Posted April 7, 2017 On 4/5/2017 at 1:34 PM, Buzzkill said: Your PC fan may be able to move enough volume of air, but it may not have the required static pressure for the burner to function correctly. New information: I did try augmenting the blower with a hairdryer. It clearly increased the airflow, but didn't change the sputter. It was a short test, and it was done while the mixing tube was overheating, but my conclusion at the time was that the extra air didn't help at all. Random chatter - might be super boring to others: I know the burner can produce gas flow rates both above, and below, the flame propagation speed outside of the forge (when I ran it flareless, I couldn't get a sustained burn but I could clearly get it to point where it was too fast and would blow out my lighter, and then too slow where it would light and the flame would go straight into the mixing tube). Back of the envelop calcs, rooted in my measured actual value of ~6cfm (no NG) has my fuel&gas velocity at ~800cm/sec, and the flame speed is something like <60cm/sec from what I can research. So even if the burner became 90% less efficient in the forge, I'm still above flame propagation speed when running full out. I'd speculate that the draft inducer was running at a much higher rate than my PC fan is capable of (150%-200%?) of what my PC fan can do. It was leaving a dark spot on the impact wall even while the rest of the forge was really hot. I am wondering if the momentum of the fan is a problem. The rotating part of the PC fan is really light, whereas the draft inducer is a lot heavier (not heavy, but heavier). If there were pressure shock-waves then the PC fan might be speeding up and slowing down rapidly and imperceptibly? It also occurs to me that for the draft inducer, I have a 2" by 3' duct run. That entire duct will be filled with (slightly) pressurized air, potentially acting as a buffer. I do not have that on the PC fan build. Or the fan speed control could be misbehaving and not actually running the fan at a constant rate. Or it really is something that's happening in the forge itself, and that the effect goes away at high enough flow rates (draft inducer). My current plan for immediate next steps (hopefully this weekend): Get a reducer to use as a flare and see how the burner performs outside of the forge. Get some high speed video of the fan blades and the flame. Replace my burner mount with something larger so that I can move the end of the burner forward into the forge. Do a better job lighting the burner so I don't let the burner tube get hot. In any case, so long as I can at least replicate my first run then the burner is working, and I do intend to use it whether I can make it better or not. Quote Link to comment Share on other sites More sharing options...
Latticino Posted April 7, 2017 Share Posted April 7, 2017 IMHO you are still missing a key step that has been suggested by several parties: install an appropriate valve that can meter your gas supply adequately. For the level of stability you are expecting from your air supply, your gas needs to be similar to assure overall operation. There is a good reason that almost all well built commercial gas fired pieces of equipment are fitted with gas pressure regulators. Quote Link to comment Share on other sites More sharing options...
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