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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I’ll have to hunt down the drawing, but there’s sort of an X Ray diagram of a Pederick in the old manuals.
Here’s the picture, circled around the Flame Plate.
In the center is the Lighting Plug, and on either side are two air inlets. I wouldn’t see the need for two air inlets if there isn’t more than one nozzle hole. These were sized up for cars and trucks, and to evenly burn the fuel. It makes sense to have three or so holes spread out to get an even usage of fuel.
The Flame Plate has an antechamber where air and moisture can preheat so it’s assured to enter the reaction as steam and make better H2 instead of simply cooling the reaction down.
It’s also logical to light from the center, all you have to do is light one hole and it’ll spread to the rest.
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i found this, dont know if it is helpful…
cody, i believe you are always around the clock available for the forum…
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I use the forum on my phone mostly, so I am always a swipe away! I usually check a couple times per hour.
If I could post while sleeping I’m sure I would.
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Thanks, had seen you or someone post those previously, good diagrams. Not sure I’m convinced of multiple nozzles holes yet though. The two air inlets, and of different lengths, are confusing to me as well.
Have been interested in the Pederick because it seemed to have a good reputation for reliability, in the 40’s. Hammer-simple design. I can see the water boiling off that heavy plate, cooling the plate and providing vapor through the nozzle(s?) for the reaction.
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I just personally don’t see why they would have had two air inlets, one being with water addition, with just one nozzle hole in the center. Especially for a bigger truck, it’s better to have a few small-medium sized jets than to have one big honking jet. Less CO2 made and the reaction is a shorter distance. Big nozzles give a chance for the velocity to not be correct at idle. Sort of a charcoal gasifier’s own version to a Turn-Down Ratio, except instead of tar it’s just making impotent gas.
And having three smaller jets gives you a more even use of the fuel. I know with the Flute updrafts it appeared that you could get the charcoal level a fair bit lower than a Simple-Fire or a central single nozzle.
I think this would have made a decent cross-draft gasifier, would have had a sort of Delta shaped active zone.
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i remember dark somewhere in the forum was a photo of the 3 nozzle holes, but not remember where…maybee those were needed to distribute cooling over the plate, and arguments like cody says…
or the 3 air inlets combined with one nozzle hole was needed for better distribution of cooling the plate by incoming air…?
or different designs for heavier trucks or cars…?
a photo gallery from the public part of the forum would be helpful to find pictures easier…
who can do this?
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on the cut- drawing is only to see one nozzle hole, the lightning plug is closed during operation…on the right air feed pipe is not to see a nozzle hole on the opposite site( on the fire plate)…
maybee the left pipe has his entrance deeper near the bottom for some reason because of water dripping on this side?
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interesting…
Read this i would suggest…
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