If i build a down draft char gas maker- can i install a single nozzle up through the bottom of the unit, or is the nozzer come through the side of the unit.Do the gas come out below the grate, how far from the grate should the nozzle be, Or how big diameter pluming and nozzle for a 1.8 pontiac vibe, You think. THANKS
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I’d go with a Mako style charcoal gasifier. Air jacket and nozzles. I’m eventually going to make one for the 2011 GMC using a car rim as the air jacket. Pipe nozzles to thread in and replace.
The Mako S1 from the Gengas book says with 4 14mm nozzles it could power a 2 Liter to a 4 Liter engine, so I think with 3 of those nozzles, or 4 of some 1/2" steel pipe nozzle you’d be able to power the 1.8 on the Pontiac and have good heat to crack moisture in the charcoal. I think the area below the nozzles on the Mako S1 was 14" diameter by 14" deep to the grate. They didn’t even use that thick of a pipe for the hearth, I want to say it was 3mm thick or around that, almost 1/8".
You could basically build it like a WK burn tube with nozzle tips or like an Imbert without a restriction. Preheat is always good but isn’t as necessary for charcoal. Bumpa Gary and Bobmac are basically doing that.
Mako nozzles pointed a little bit downwards to keep slag from building up in front of them.
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THANKS much CODY i will check that out once i find the gengas book, I am not premium member Yet. THOUGH thats a lot of good info, or probley enough,Like you said,those replaceable screw in nozzles idea i like TOO. I was thinking about that as i was typing, why a wk burn tube set up should work, it burns pure charco now though only below the nozzles, should work with a little exra thick metal around the nozzle area of the burn tube,Or fire crete few inches above and below the nozzles. and some scew in nozzles, maybe small water drip.
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The nozzles will keep the worst of the heat away from the walls. I’d say if you wanted to go thick you could use 1/4" tube and use 2" long nozzles, I’d start with 4 1/2" pipe nozzles. Buy some plumbing couplers and cut them in half with a chop saw and then you’ve got your threads for the pipe nozzles. You’d think the cast iron couplers don’t weld in but I’ve used them a lot.
If you use moistened charcoal you won’t need water drip, it’ll keep the heat down.
You should still have a cooling rail condensate tank but it’ll mostly be just water with some soot in it.
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Thanks again CODY, I will check that gen gas unit , i am copying the notes you gave me, back too bed for know , or i won’t get my dakota finished, its taking shape though, well the gasifier end of it anyway, the cab corners need under coating and a little mig welding metal fab next,or no end in sight,Dang salt eats up older vehicles from michigan salt roads.THANKS AGAIN for all the tech notes. I could get building with that great information.
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hello kevin, here some copies from the swiss gengas book from tilman (search under Til )…
slag build up in charcoal gasifiers, different constructions
and crossdraft, where the problem comes up that the slags leads the heat too much to the shell of the gasifier , and so the protecting effect from coal around the hot area exists not more…and further creates disturbs with gas-flow…
therefore i like the design of eddy ramos (ramosedmundo) with his nozzle that enters from the bottom, so less possible heat stress for the nozzle i would say…
easy water drip installation, the water cannot flow the gasifier when forgotten to close the valve…
the slag build up makes the form of a crater and from my modest insight this protects the nozzle , further one can make some heat resistant stones around the nozzle for prevent nozzle contact with the really hot area…
what i would modyfie at this design: i would not make the gas outlet on the top of the gasifier, but in about maybee 30 cm over the nozzle to avoid too much coal dry out…but of course than is needed a additional cooler…
.in the swiss book is also claimed that high speed air flow must not be connected with cross-draft design…
English-Manual-V3-PDF.pdf (2.1 MB)
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Thanks giorgio, its not in english, though what are them black sock looking area near in inlet nozzles/ I see the exit pipe half way up the side of the charco drum, is that a good way too pull the gas out. Looks like a slotted pipe maybe on the exit plumming.
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Kevin the black splotches are to show where the reaction is flowing
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the black "socks " is the slag build up during operation…
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I like that we are back talking about nozzle’s again as i would like to ask if anyone else is having the the results that i have had using a Hexoloy silicon carbide nozzle ? has anyone else run it for hundreds of hours like i have ? i did not keep an accurate running time but i must be well over 400 hours of run time , would be interesting to know if someone has put any miles or hours on one .
Just in case you did not know i have had one of these Hexoloy tubes in my updraft gasifier since i think it was Aug 2018 that i ran on a regular basis on a 7KW generator , no water drip or cooling of any kind , fed from the bottom of a 55gallon drum vertically and allowing the slag and ash to build up around the nozzle and only cleaning out when i see that the 1 inch dia of the nozzle is closing up due to slag build up , and in that time the only damage to the Hexoloy was down to me sliding a bar up from underneath to clear away some of the molten slag that had formed partially blocking off the nozzle , other than that i saw no degradation of the Hexoloy nozzle at all .
I have not done any building or running of gasifiers since middle of last year due to things going on over here at the moment but hope to get back to building a cross draft downdraft one soon .
Dave
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I only put a few hours on the silicon carbide nozzle I tried. I think your experience is the benchmark Dave.
I would point out that Larry Dobson used silicon carbide extensively in his designs.
I think silicon carbide is ideal for the tolerating the heat and is well proven in that role (thinking of silicon carbide turbo charger wheels). I chipped the one I used too, that was my only complaint and why I don’t think I’ll use them.
@giorgio thanks for that picture! The slag patterns are important design criteria! Especially with very small engines where flow restriction has a large effect. Notice how the horizontal nozzle is essentially blocked. The other implication is that these gasifiers are expected to run hot enough to produce slag. Makes sense as conversion efficiency goes up with heat.
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Vertical nozzle;
I wonder why Dave and Eddy and Koen have such good success with vertical nozzles, yet they aren’t found in the literature? Every time I’ve tried them they plug… Perhaps there is a minimum engine size for them? Maybe hardwood charcoal only?
And Eddy is using a 17mm nozzle for a 3.6l engine! Should be making a lot of slag. Notice he says he tried a larger nozzle and it didn’t work as well. But Gary Gilmore was using 17mm nozzles with 6hp engines. Makes me feel like I’m missing something:)
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Eddy uses whatever wood he can get to make charcoal, nuts and limbs and scrap boards.
Maybe it’s the velocity preventing blockages and moves it over to volcano around it.
Another design that’s worked well is Don Mannes and Jeff’s open bottom design. Has a big grate and just sucks up as much air as it wants. That’s closer to WW2 and Pre WW2 updraft gasifiers. Only issue is you need an enclosure at the bottom to catch ash and embers.
The Flute updrafts also tend to have slag volcanoes, I’d get very brittle slag partially blocking the holes but just poking with a bent coat hanger solved that. Worst case scenario was when I’d melted a nail right in front of the hole and had to scrape it out.
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lots a good air feed air nozzle / charco gasifier designs rehashing, I am taking notes now for later, though i do want build a good working compact charco gas unit,ASAP. Got too try black ,I gess -? ^
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Flute updrafts:
When I’ve used a flute that is surrounded with charcoal it heats up and preheats the air so that slag plugs it up.
When I used flute nozzles in my forges, they are protected on all sides except the air openings and they stay cool, so the air stays cool and the heat is far enough away from the mild steel flute that they last and last and no slag actually sticks to them.
Notice the fire brick is melted in this pic of a forge flute. Small nuggets of slag also form a kind of gravel that will block the openings over time.
I’ve never had a flute nozzle fail. I have had them completely covered in glass/slag when customers ran them insanely hot… but the mild steel was fine. These are .095 wall mild steel tubes. This one has over a hundred hours.
Closeup:
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maybe because they choose to force the air into their gasifiers at high speed! it seems that the faster the air enters the more the focus of heat deviates from the tip of the nozzle
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“it seems that the faster the air enters the more the focus of heat deviates from the tip of the nozzle”
This hasn’t been true in my limited experience. How far the hottest zone (and therefore slag) is from the nozzle tip has been all about air pre-heat. The liquid cooled nozzles with cool air inlet has a hot zone 30mm or so from the tip, which means the slag doesn’t plug the nozzle. When a hot nozzle is used, like the tungsten carbide example in post 436, the super heated air allows the hot combustion zone to move up and surround the nozzle. This even when the velocity is fairly high.
I suspect the bottom nozzle arrangements that work share some traits;
**fairly massive construction, (like a Pederick plate)
**limited protrusion.
The more the nozzle protrudes the more 360 degree circulating heat it is subjected to, which results in more air preheat which brings the hot zone closer to the nozzle, which preheats the air even further, etc.
The more the nozzle protrudes the further the hot end is from the mass heat sink and the greater the heat gradient is along the nozzle assembly.
The nozzles that protrude into the fuel from the side will always struggle with limiting the heat.
In post 451 I did an experiment with a bottom located nozzle of high velocity that protruded 3 inches. It plugged with slag quickly. What I wish I had done is remounted it WITHOUT protrusion like so many of the bottom nozzles and tried it again, all other variables the same.
Max the Gasman and MattR move the nozzle out of the glowing char and solve the problem another way.
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i wonder what will happen with a horizontal nozzle like gohin poulenc style, when one goes with the vehicle downhill or steep uphill…in way that the nozzle tip points upwards for a longer time because of the terrain situation…?? steam explosion in the nozzle? bad cooling?..
this question raises up for me with the motorcultivator, when i work with the reversible plow…one wheel lays deeper because it runs in the grove made by the plow, turning back the other wheel lays deeper…also the field is not completely flat, but a bit hilly…
nozzle slooped downwards like chuck´s design will avoid this problems…if it is a problem??
ciao giorgio
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Cody, where did you see that the Pederick had “two or three” nozzle holes, versus just one?
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I’ll have to hunt down the drawing, but there’s sort of an X Ray diagram of a Pederick in the old manuals.
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