The fact that you get better power under load is probably linked to the design of the gasifier. At low load, the glow zone is probably not surrounding the entire “firetube”, so the “dead gases” like CO2 and H2O can pass trugh by the walls. At high load the glow zone enlarges, making it harder for the dead gases to sneak trugh.
And tars. They will sneak trugh too…
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That sounds like a good explanation.
This is an earlier picture before I enlarged the holes and I turn it with the holes facing down.
I didn’t center up the hole locations good enough so the first one leaves a pretty big space between the wall of the fire tube and the last hole is very close to the back wall.
The fire tube is around 8 inch diameter so pretty big for the size of my generator but it probably didn’t even need this burn tube. I didn’t want to waste that much unusable charcoal to fill it all the way with charcoal but maybe I should have. The Simple Fire doesn’t use a burn tube (firetube) but it can’t have damp fuel either but it’s updraft.
Would NO BURN TUBE solve this problem where the CO2 and H2O can sneak through or is this always going to be a problem with such a low load?
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no burn tube makes the problem greater, because more easier umidity and eventually tar from not well charred pieces can pass by…
i see no sense in the flute nozzle here - from my sight…you get a longer fire, like a stripe, but less ball sized, so beside the stripe undesired things can bypass…
for your small engine size a single nozzle from besides, placed immediately over your burn tube with a massive metal head, let say two inches and a 12 or 14 mm hole inside, welded on a piece of pipe, works really well…look at my thread of the “red bear mower”…there is all demonstrated in pictures…
for the nozzle tip look for some round thick piece and drill a hole inside…
from my sight a single nozzle creates more a ball sized fire in front of the nozzle tip…
when the coal has too much umidity, firing 10 or 15 minutes with open lid, how said earlier…
further observe coal size, how others have explained…
than should work fine your gasifier…
eventually improving welding quality…do you weld outdoor?
ciao giorgio
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Thanks Giorgio. Your build was what I originally was using as a guide for this one. I went with the flute nozzle because that’s what was lasting the longest for me with my Simple Fire but the same size pipe in this one melted after just a few runs.
That could explain why this one run better when the original pipe flute melted and I kept using it as basically a straight pipe although that quickly continued melting.
This is from further back in this thread with your (Giorgio’s) measurements and the nozzle placement. I’ll start looking around for a big chunk of solid round metal or maybe figure out how to use the Hexoloy silicone carbide piece I got a while back and never used.
Yes, I weld outside. I don’t have a good place indoors that I can safely weld so real gas shielded mig welding is not really an option (plus my only welder capable of that has a broken wire feeder) so flux core wire feed welding or old fashioned stick welding is what I have been using. Brazing I also did outside but I’m out of oxygen and brazing rods. I have gotten a lot better at welding but not as good as I would like. When everything is working right, the flux core welder can do pretty good but it’s easy to get pockets of flux especially when trying to fill a big hole like the end of the pipe.
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brian, i am also a outdoor welder, with 1,5 mm elektrodes and 3 batteries connected to 36 volt and iron wire as resistance…i have no space inside, and for smokes is healthier doing it outdoor.
the problem doing outdoor is the eye adaption… too much sunlight comes also in the mask and the eyes need longer time to adapt and at least to see something through the cobalt glass…in a darker room the adaption of the eyes happens more quickly…
so , not having a room inside for welding, i have modyfied my welding mask how to see on the foto
i added some stuff besides and on the top…dark paint inside is very important…
it is a incredible difference how much i can observe the welding work with the modyfied mask…
also i use only a piece of cardboard for little fine weldings , for example on the nozzle tip of my water cooled nozzle for exact aiming the points where i will touch with the electrode…
( using a mask in this case till you see something , the electrode is everywhere but not there were you like)
the procedure is: going with the electrode near the aimed point, move the cardboard in front of the eye, touch the point, weld, leave the electrode, leave the cardbord a bit aside that one eye can see the welded point, and aim immediately the next point with the electrode, what ignites immediately on the still glowing further point…, always looking before igniting the electrode that you have the cardboard between to shield your eyes…
this works really for fine weldings when it is quickly done in way that the slag on the electrode and welding point not can get hard…so it ignites immediately again and again and makes a fine, valid seam of good connected welding points on small surfaces and also on thin metal…i weld also 1 mm metal sheet in this way with 1,5 mm electrodes, i take away the electrode immediately after igniting and having made a point, so the metal burns not away…only a short touch…every second a touch or so…so finer the metal, so shorter the touch…
helpfull when you weld thin metal sheet , what normally burns away, is to fix it on a thicker metal, so the heat is absorbed partially from the thicker metal…in this way i can also weld my band saw blades what are thinner as 1 mm.
for the grounding i use a grip pliers…
helpfull is when you work in the shade , maybee under a piece of roof metal fixed over your head, avoiding to have to much sunshine where you work…
hope this is helpful…
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This comment got both a like and a bookmark. Being able to see what I’m trying to weld is a problem working outside. I’ve thought about modifying my welding helmet with something to block the light from getting behind it but never did. I can’t count the number of nice weld beads I have made in the wrong spot because I can’t see good enough to keep it in the right location.
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i will also add a observation…i tried a water bubbler on my stationary unit for to see if it can catch dust out…it bublles really nice, but the gas absorbs water umidity and the engine runs really very weak without load…first i thought, maybee some connection is not thight and false air goes in the system, but changing the air-mix not helps, so i think it was the umidity from the bubbler…the coal in the hopper was dry.
leaved the bubbler , it runs fine like always…
a good example how important is relative dry charcoal, also for easier starting it makes a difference…
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I am a charcoaler as well and I have learned a little over the past three years. I grind my charcoal to 1/2 inch/13mm and screen it through a 1/4/6.5mm screen. Anything that passes the screen goes into bio-char. A lot of my char comes from the wood stove and must be separated from the ash but this always leaves a ash haze on the coal. For a long time I just ignored that and still got decent gas but then I started washing it off… Took a long time to dry that way and didn’t work as well as the very dry unwashed to I started drying it in my wood dryer. Now I believe it’s about optimum. Of course this is a couple extra steps and extra time and if I had to work a job or had other pressing constraints on my time I would probably not do it. But it does result in a better fuel.
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Sooo many variables, eh? That’s what makes it fun;)
I didn’t realize your engine was so small. I agree with the other posts that you likely have too much nozzle area for your engine, especially at light load as you observed.
Are you getting any slag? Ideally you would be right on the edge of a slag/clinker problem, which would verify that your reaction zone is up to temperature.
I have the same size engine and I’ve avoided downdraft because I want to maximize the reaction temp and make lots of slag. This seems to mitigate a lot of other problems; water, low quality char, and bridging mainly.
Running hot meant switching to a liquid cooled nozzle. It’s nice to not ever worry about the nozzle again.
I switched to 1/2 inch max char size to increase it’s reactivity, which the small engine liked.
Since water is unavoidable for me, I also use fiberglass filters so the damp gas doesn’t cause too much restriction in the filter.
Smaller char, smaller nozzle, smaller reduction zone??
I’m watching your downdraft experience with interest!
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I probably should have saved the flute nozzle but decided to cut it off for the next test.
I put the charcoal back in and added another bucket of ungraded charcoal on top just to fill it up fuller. The charcoal it used should have been smaller pieces and the top layer wouldn’t be used yet.
I refilled my propane torch and it lit up really fast. The gasoline torch would have done the same but the propane is more convenient. The open nozzle had a direct path to the charcoal so it ignited fast.
I was running the generator on gasoline to power the blower so I moved the blower from the filter (suction side) to the nozzle and almost instantly could get a flare.
I hooked up the hose and turned off the gasoline. Within maybe a minute or two the gasoline was used up and I was able to adjust the air mixture to be running on charcoal. The engine was running faster than it had been and powered the miter saw almost as good as it does on gasoline.
There was a couple drops of water in the collection jar and the filter but that was likely still there from the last run.
I didn’t run it very long this time but I’d say the nozzle was the main problem. It’s running at least as good as it ever has. To be fair, all of the charcoal should have been pretty dry and, except for the last bucket, it was all a lot smaller size but there was a noticeable increase in power this time.
Thanks to everyone’s help I’m calling it fixed. I do need to change the way the top lid is held down and I want to build a better grinder for the charcoal but I can quit using so much gasoline again.
OH, I forget to answer the slag question. Yes, it does make slag but I haven’t cleaned out the fire tube recently so I don’t know how much might be in it now.
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Your going to want to maybe build a water cooled nozzle like Giorgio and Chuck have , In the mean time you could try grinding out a little of the thread on a 1 inch galv bush till you get a plug fit to push the Hexoly into it , then you can screw that onto a 1 inch pipe or reduce down to the size your working with .
Dave
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I did look at the Hexoloy piece I have and a 1" coupler but my generator isn’t close enough to the compressor anymore so I didn’t try grinding the coupler to fit that Hexoloy. Plus, I didn’t know if this was going to fix the problem but it looks like it did.
I asked Gary about his water cooled, copper nozzle. He was pretty sure he BRAZED the hottest sections but probably just soldered the rest of it. His water cooled nozzle was on the Simple Fire that he showed me running his log splitter. It was set up to feed the humid air from the water tank back into the nozzle but he also used the exhaust gas to help cool it. I’d really like to try making a water cooled nozzle but, if I get the Hexoloy nozzle on this one, I might use the water cooled nozzle on the Simple Fire. I haven’t used that gasifier more than a couple times since I built this down draft gasifier and that was because I needed it to build parts for this new one. I do plan to use the Simple Fire since it is more portable than the bigger down draft one. It still works good but my main use was for the generator which is now hooked to the new one but I have run the log splitter on the Simple Fire.
My plan now is to use the new gasifier to power the generator for running the wood working tools.
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Sounds like success.
Liquid cooled nozzle:
For stationary gasifiers I think they are a great choice. The cooler can be little more than a bucket of coolant. Never think about your nozzle again.
Giorgio demonstrated a nozzle build recently from SS. I build mine from mild steel. If you cool them with glycol like your car they won’t rust.
They don’t have to be copper, that would add a lot of unnecessary time and expense maybe.
If you angle them downward a little they thermo-syphon readily and any slag tends to puddle under the end instead of blocking it.
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brian, i am cleaning my fire tube -reduction area after every run…so the ash and dust is away for the next start…cleaning only by use of the shaker grate or taking out with the kind of rake i have through the double clean out port…it must not be emptied the whole gasifier, i take out only till clean coal comes out.
before starting is good do a bit poking with a rod in the fire tube, so it becomes more compakt and bigger hollow spaces are disappearing.
the measures of the fire tube of the design from the columbia project pdf for motors from about 500ccm - 1000ccm
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I needed to fill up my air compressor tank again so I fired up the gasifier. Took a little while to get the air mixture right at full load but then it run the compressor pretty good.
Then I cut up a little more firewood using the miter saw.
Then…
I had some sawdust laying around and the glowing opening to the nozzle was right there so I fed it some of the sawdust. Didn’t make a noticeable difference in the sound of the generator but sucked the sawdust right in. I gave it several handfulls of the sawdust before I shut it down.
This run caught some more water but it has been raining and the humidity is pretty high. Run good anyway so I guess I’ll just accept that it is going to condense some water. The tank was getting pretty hot so I probably should get the better charcoal processing grinder built but I’m glad to be able to run the generator without gasoline. I did use a little gasoline to get the generator running and a little at the end but all the work was done using the charcoal collected from the furnace.
I keep collecting more charcoal from the furnace. Got one smaller barrel (15 gallons) filled and the bigger one almost filled again.
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Not directly related to this build yet but I just spent a long time looking for this so figured I would post the links here for future reference.
That one has some information on Tone’s aluminum cooling “necklace”
Then the fan on the top of the hopper.
And this is what I was most interested in:
This fuzzy picture was a screenshot of the above video. If I’m not mistaken, this is a multipurpose chimney. It can vent off excess moisture and it looks like it might be the safety “POOF” lid.
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I’ve always wanted a flapper valve exhaust but never found the right engine to put one on. I thought the chimney might be a good reason to get/build one so I drew up an idea.
Then I thought this could just be overcomplicating things especially when my gasifier is stationary. Now I’m thinking just a pipe plugged with something maybe held down with a spring or springs or maybe just a big cork and a chain to keep it from getting lost or becoming a projectile if/when it poofs.
Having a separate safety exit for the gas would allow me to clamp my lid down tight without worrying about leaks or worse. Being able to easily vent the smoke and steam should help dry out the damp charcoal.
I found a pipe about 2-1/4" ID but I’m worried I will just end up with another place for a leak. The lid hasn’t gotten too hot to touch but it does get hot and I’m not sure how to seal it good enough but not too good.
I’m just going to leave it alone for now.
I think, if there was a poof, the nozzle is going to shoot glowing charcoal out instead of (or in addition to) pushing the lid up. That wasn’t a big deal when the gasifier was outside but glowing pieces of charcoal would be a bad thing where it is now. I usually put the cap on it to kill the generator now because it shoots flames out that nozzle if I just shut off the generator.
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Had a new idea for the chimney cap. Thinking about casting one out of aluminum which I’m not really set up to do right now but would like to be.
This has taken several tries to get the size right to fit the pipe I have. The idea is to have a pocket for a stove rope gasket.
While it should be possible to make a pattern with hand tools alone, I have a CNC router that hasn’t been used in a while so I thought I’d try using that to make the pattern. It isn’t as rigid as I’d like so I kept the depth shallow and figure I can cut it out by hand following the outline.
The block of wood is programmed as a 4" wide x 5" tall block and all the depths are set to cut only 1/8" deep. The starting block of wood can be bigger than that but the zero point is set at the lower left corner of that size block.
The estimated cut time is 10 minutes but that isn’t always accurate. My tool (a 1/8" bit) won’t cut the draft for the pattern so that will need to be done by hand.
Loading the Gcode program into the software it estimates only a little over half the time at 5 minutes 19 seconds but that isn’t always accurate either.
Once I located all the tools, the actual cut time was 6 minutes and 11 seconds.
Testing the fit it looks like it could work. It will need cut out, sanded, and probably a coat of shellac before it can be cast. Of course, my casting sand, crucible, and other foundry tools are 10 miles away right now. I’ll also need to cut and weld some pieces as the hinge and some way to attach a spring but I’m closer than I was this morning.
I won’t be surprised if I mess up and need to rebuild the pattern or run into other problems but getting a foundry set back up and figuring out how to use it should open up a lot of possibilities like the ash clean out cover I was thinking about before.
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Brian, I’d try one with smaller holes.
Jakob North had a similar problem in his downdraft and he found the jets were too big. Too big a jet and it makes more CO2 than CO.
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Thanks Cody. Right now I have just a single open nozzle with the opening 3/4" inside at the fire but still just 1/2" going in.
Next time I take it apart I’ll try grinding and pounding a 1/2" pipe in the end. That should give it an even thicker nozzle in the hottest zone.
It’s working pretty good but it runs good at very low loads but takes a little while (few seconds) to get to full power when a bigger load like the compressor or miter saw is turned on. Maybe the bigger nozzle is letting more air flow when the draw increases than it can handle until more of the charcoal is burning.
The other possible problem could be too big of charcoal. I need to make a new charcoal grinder that will process it faster and make more of the smaller pieces. Mine is slow (hand crank powered) and has too much space for the larger pieces to get through.
I’m happy with it and keep using it but it could still work better. I never did rip the engine apart and try to adjust the timing a little and have considered taking the head off and either shaving a little off or trying to find a thinner gasket. I still use it and it works so I hate to mess around too much and risk messing it up though.
I keep looking at the sawmill so close and want to try running it on the gasifier. Just don’t have the pipes to get the gas closer to it and then add a flexible hose that could travel with the carriage and engine. It’s about the same size engine as the generator but needs to spin fast enough to keep the clutch engaged. I would need to build another adapter to fit that engine and have a good filter so it doesn’t suck up the fine sawdust it throws while cutting.
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