You probably noticed that I drew the bottom of the hot zone a little differently, well, I did it for two reasons, the first is to get a space under the air entering the nozzle for a barrier, which I would add to reflect the radiation from above and additionally preheat the air for the lower nozzle. Another purpose is the thermal expansion of the lower plate, I think that with this shape it would considerably reduce the forces generated in the middle, well, even the ash slide would have a certain slope.
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Tone, I notice this drawing is a bit different from your current hearth. You’re still using a restriction in the tractor. Will this design not require a restriction and instead use the bottom nozzle as the final cracking of tars, using the reduction tube as a way to funnel them to said bottom nozzle?
Or is the restriction so large it isn’t noticed as one anymore?
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now its early and i have not had coffee yet, but let me blab out a thought here quick. With the air being let in to the lower nozzle, and the lower plate is already somewhat preheating, is the air coming through the nozzle not being expanded by this lower plate radiant heat coming up from underneath? thus adding more preheat to the air coming out of the nozzle and displacing the air somewhat, pushing the air up into the fuel above? it would be a miniscule amount, maybe less then a inch but still a somewhat upward force? i hope that made sense
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thierry, i have had the same problem with my mower for harvesting grain…because of the narrow end of the milk vessel- upside down- the gas flow was restricted by ashes after about 30 minutes and creates problems…i resolved with a insertion of a reduction area "basket with cuts around…so it becomes double walled in sense that the coal in this area not touches more the outer sheet…this makes a bypass effect, if one part clogs up the gas find easily another way, and also ashes can go away easier…since this modification works well …two days ago tillering with the same gasifier -1 for 2- 6 hours without disturbs.
simil to tones reduction basket design…
ciao giorgio
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Thanks for all the answers guys. I’m going to take some pictures at the end of the week to better visualize my current setup.
Thierry
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In the video I posted a few days ago, you can see how the restrictor tube glows, especially the lower part above the bottom where the lower nozzle is installed. This heat greatly overheats the middle of the floor plate and this causes the expansion of the material and the lower part radiates the heat into the fresh air intake, if I were to add a thin sheet 1 cm away from the floor plate, it would stop the radiation, and with that it would also heat up itself, well, the air traveling towards the middle nozzle has to travel a long way and in the meantime it gets very hot,… I’m babbling a bit,… @ForbiddenTuna Cody, the restrictor opening is now a restrictor tube, on the tractor the lower part is identical to the one in the pictures. @Norman89 Marcus, while you make coffee in the morning, I make it after lunch for our family and we both read posts on this forum. 
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Tone, I never realised your firetube is only 8" dia. Is the tractor gasifier the same size? With the size of your fuel it’s probably a good thing.
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JO, it is the same on the tractor, except that the upper part is even wider, about 13 inches
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Tone,
If I understand everything. Perhaps add ash insulation to floor plate and lower nozzle hat.
Rindert
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JO if l understand correstly, the gasifier on the picture is the new one, wich l belive he ment to put on the BCS mower. The one on the tractor is much bigger.
What surpriced me thugh, Tone sayd to me the other day his nozzes are just 4mm. Seems real small
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I published the data here, or rather in the next few contributions,…
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tone´s bottom cleaning nozzle…it is of course not a hot leak, that steals gas…but it produces gas because it is surrounded by charcoal…like as a little charcoal one nozzle gasifier…
the incoming air burns away and produces a little reaction area, surrounded by the reduction coal area, consumes the coal, so the upper coal (and ashes) glides down…
my simple, not very scientific understanding…
ciao giorgio
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Really? Even on the bigger tractor 13" gasifier? Maybe it helps penetrate the small fuel and the bottom nozzle keeps enough temp up down low to be able to handle the rich mixture of steam and CO2.
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I bought some material to make a variable geometry gas mixer, you may remember the sketch I posted. There is no time for that at the moment, the nice weather calls me to work outside.
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Tom recently said that it would be good to edit the posts, but I’m so confused that I forget where I left off, confusion in my head, confusion in the workshop, confusion on the forum, well, this post would fit here…
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Hi Tone, here is a drawing of what a bigger WK Gasifier combined with your fixed vertical preheat grate tubes. The difference is the lower incoming air would be 2" valve controled inside the 4" intake pipe that can be closed also, not shown. Yes this gasifier will run bigger engines. The lower nozzes have a distance of 6" to the out side of the grate tubes from the 8 nozzles. Under the nozzle pipe is a heat sink for cooling it.
No detail of the WK Gasifier shown working parts.
I also put some ash protection on top of the lower nozzle head as menioned and the ash protection below the nozzle. This will also protect the lower welds of the vertical tubes.
Bob
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You have drawn the restrictor tube facing upwards, in this way the gases generated above would have the possibility to escape past the operating area of the lower nozzle, which is not good, the restrictor tube must extend so deep that it covers the openings of the lower nozzle, at least that’s what I think.
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Here I lowered the lower the pipe for the 8 nozzles holes to 2" from 4" where it was. The restection pipe is now 4" into the vertical pipe grate. This will now protect the upper welds on the pipes and cause the charcoal to move down to be closer to the lower nozzles.
Bob
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Bob, imagine a flow of gases traveling from higher to lower pressure, the highest pressure is the air pressure that is at the nozzle openings, and the lowest is in the area around the grate and extends through the gaps to the coal and ash that comes through the restrictor tube from the top . If the end of the restrictor pipe is high above the lower nozzle, the gases from the top have quite a chance to flow under the lower edge of the restrictor pipe towards the grate, and the lower nozzle will remain high up with ash and fine coal, and thus a rather high negative pressure must be created in order for this clean and make the charcoal glow. The pressure difference determines the amount of air on the nozzles, if you want a hot bottom operation and gasification of the coal, you must prioritize the bottom nozzle over the top ones. Well, otherwise it is easy to lengthen or shorten the restrictor tube and thus optimize the operation.
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Good morning
here is a sketch of my current gasifier. it is designed to run on charcoal. I installed a restriction (about 14 cm) as a precaution to crack the water vapor and any volatile coming from imperfectly cooked charcoal
the nozzle is adjustable in height. the grid has been replaced by a height-adjustable iron disc. I am considering replacing the metal disc (the one that acts as the grid) with a lower nozzle like that of Tone
I hope to get a more regular smoother gas flow (less drag)
your advice will be welcome
Thierry
I will post photos as soon as the temperature allows it. here -30 c with winds of 80 to 90 km/h this weekend
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