Thanks Tone, more to study this weekend 
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And yes, work takes up most of our time. So , in general, make sure you like your work
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Hi Tone, not sure how you will connect the upper tubes in the bottom part of the drawing to exit the gases. Looking forward to see how you do it.
My Question is, how many cm or inches is the bottom nozzle holes from the end of the charcoal to the grate exit out the bottom?
In theory you need time and distance of the gases to travel in the hot charcoal lobe for the reaction of everything to change from carbon dioxide to carbon monoxide and H20 vapor to hydrogen and to form methane gases.
I have always figured at the very least to have 7 inches or about 18 cm of charcoal mass to prevent a heater effect in the gasifier of extra oxygen burning up good woodgases or chargases going through the grate.
This is on my WK Gasifiers with 5.2 liter engine. On my Flute Charcoal Gasifier it is 6 inches of charcoal from the nozzles to the grate. On this unit my grate can be moved up or down for its needs on what size genset I am using.
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Thanks for the drawing Tone, I donāt understand but hopefully Iāll learn something.
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Hi Tone, looks great, very interesting.
I would avoid stainless flexible pipes though, they are very prone to cracking.
If you find a flex copper pipe i guess it will hold up better.
But as in your drawing, a long stainless flex pipe, as long as possible, maybe put in a āloopā would minimize the stress on it?
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If I may mention a concern of mine. Those pipes have many similarities with ss expansion bellows and the bellows are prone to cracking after x amount of heat cycles / expansions and attached to a semi swinging grate (the pipe will stiffen it up quite a bit but you will get the swinging perpendicular to the pipe) you get many small movements. With that said my guess is you would probably get a few years out of it but it should probably be changed out as a service thing before cracking / snapping off, we donāt want anything happening to you Tone 
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I think it looks great, there is a lot of critical welds if I understand the air/gas paths correctly, may I ask what you planned to seal the flanged bottom with?
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Haha Gƶran, you beat me to it with a few seconds 
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Hi Johan, seems we think alike?
And you beat me with thisā¦
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I just had an idea about the flanged bottom, Tone, while you have a few water connections already perhaps ārollā a square pipe to size and welded to he gasifier part with inlet and outlet next to each other and have a water cooled seal.
Just throwing an idea out there without much thought put in to it but you probably already have an idea about the seal.
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Before I start making a new unit, I will have help from you.
- Length adapted to engine, adapted to maintain 800c to lower edge of core tube to avoid re-formation to co2.
- Length between nozzle and throttle adapted to engine, throttle replaceable.
- Diameter of core tube adapted to engine.
- Length and diameter of nozzles adapted to engine, and to build up an ash protection against hearth tube, which means that thick hearth tube is not needed and heat is maintained.
- Insulation to retain the heat, also insulate the bottom edge of the hopper, (the tar)
- Cone wood transport.
- Perforated plate for circulation of condensation.
- Movable roster.
- High withdrawal of gas.
- Drain condensation water.
- Inlet air with shutdown, no preheating of air inside to avoid heat loss in the hearth and avoid leakage of air into the gas.
- Single wall on the hopper for as large a cooling surface as possible.
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It took me a coffee or two before I realised it is not a design from Tone but yours Jan. Looks like a Ben Peterson. Preheat/ keep the heat is crucial to have a gasifier working IMHO. Speed at the nozzles might not be that important, lower is less friction. Again, only my opinion, let the daily drivers comment on that.
Not an expert, but if you preheat your air the heat is not lost and it cools the steel mantel.
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Iām grateful for all the answers, Iāve only read about how to do it in books, which doesnāt mean itās right.
As I understand it, the diameter of the nozzles determines how much air comes in, not too much, and not too little.
The length means that the fire tube does not get too hot, I have driven for 3-4 years with only 2mm walls.
I think preheating is good, but not taking the heat from the core tube. and there are more places where you can get a heat leak.
My idea.
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Goran, Johan, with the Fergie gasifier, I have a similar joint of the gasifier cover with the lower part, here I simply use the sealing compound for the gearbox 350 Ā°C, because the plate-to-plate connection is 100% tight.
I will activate the lower nozzle on the hanging grate if there is resistance through the gasifier, on the outside I will add a throttle screw that will fit into the hole where the copper or stainless steel flexible pipe will be connectedā¦
I want to achieve and maintain a high temperature in the form of a ball in the hot zone, which spreads upwards when consumption is high, but when consumption is low, it descends towards the grid and decreases. The hot gases are light and rise upwards, and the vacuum of the engine pulls them downwards, so the ring of nozzles creates a spherical shape in the glowing zone. If we want to have a gasifier that can work for a long time with a small load, the hot ball must shrink and as such maintain a high temperature, so here we need a narrower area and a small cross-section of the air nozzles. We all know that a big problem is the sticking of wooden pieces that they enter a narrower hot area, so it is important for a wood gasifier that the wood is converted into charcoal already higher in the funnel, so I advocate higher nozzles in a wide area and, of course, a hot funnel heated with hot gas. Heating the funnel at least half way has more advantages, in addition to more intense pyrolysis, the hot walls prevent very moist gases from going down, but propel them up again, but among other things, the tar gases are also well heated and thus do not cool the reduction process much. As you can see, I am drawing a gasifier with a lower and wider shape, because I think that this shape is less susceptible to wood jamming and, most importantly, that the hot zone is deep in the middle. The lower demountable plate - the bottom of the ash compartment - will not be insulated, as a layer of ash will quickly accumulate inside, which will act as insulation, and otherwise the hot gases will move to the side and up, but if the gasifier is mounted on the caisson of the truck, put a fireproof plate underneath.
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Thank you, Tone. Lots of good information. Several things I never thought about. I like posts like that.
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One wonder, is there really any distinct reduction space needed?
Neither Tone nor JO seems to have it, and JO tried to make a reduction, but there was no difference, Tone can idle for a long time without any problems.
How does it actually work?
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Hi Jan, a distinct reduction area is not needed, especially if theres enough heat, this zone takes place by itself where oxygen is no longer available.
Itās more of the old āit should be this wayā thoughts to build in the reduction area in a decided space.
But both works, with pros and conās, its mostly a way to concentrate the heat in the restriction, burning of all left over oxygen, the problem often with decided reduction area is to keep it hot enough.
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If I continue to thinkā¦
Goran nicely stated that when the core is heated enough, the gasification process of WOOD should take place by itself without additional air, but since heat losses occur, this does not happen and we fall into a vicious circle. There is a large expansion of the pyrolysis gases at the top, they raise the pressure in the funnel and push down through the hot zone with charcoal, so it cools down quickly and the moist tar gases can escape the conversion if the āworkingā temperature is not maintained below. Since we are here in an area with a higher negative pressure, outside air has the possibility to enter this part, there is also a possibility that the pyrolysis gas also enters through the upper nozzles and mixes with fresh air lower down in the double wall of the hot zone and is thus āblownā into dense area with fine charcoal mixed with ash and here the conversion is guaranteedā¦
When I think about the size of the air nozzles, I first have to ask myself, what proportion of air must be brought to a certain volume of gas produced? I havenāt seen this information anywhere yet. We have to imagine a gasifier with an optimal load that produces, say, 1000 liters of gas per minute, which is enough for a 2l engine at full load at 4000 rpmā¦ how much air does the gasifier capture at that time? Is it 10%, or more, or less than the amount of gas? This proportion probably depends on heat losses, wood humidity, air humidity,ā¦ and in reality this proportion changes considerably, especially when the load changes,ā¦
If we compare a wood gasifier with a gasoline carburetor, we see that a good car carburetor is double, consisting of precisely positioned nozzles for idling in the throttle area, precise nozzles for higher loads in the venturi taper,ā¦ well, for a wood gasifier, it is similar logic.
When I compare the start-up of the gasifier and the start-up of a cold engine, I see that the engine needs enrichment of the mixture (choke), so the gasifier also needs additional air for quick heating at start-up. Mr. Wayne uses a special tube that he pushes deep into the hot zone area and fires into the core through that tube, thatās how I do it, well, because I have a portable air blower, I blow air through that tube directly into the core, and thatās how I get a quick boost. During the new construction of the gasifier, I plan to install such a pipe from the side at an angle of 45Ā° and after start-up I would pull it out of the hot areaā¦
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Iām hoping that when you build this new gasifier that you record the construction step by step like in the WK book or like Marcus did with the WK build videos. Iām not real good with theory but I can build anything Iām shown.
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Good reasonings Tone.
There are several publications up in the DOW Library which precisely calculate by molecular balances the the amount of atmospheric oxygen needed for complete chemical conversion.
VesaM. in his book adds in thermal balance equations.
He at least acknowledges the results will still be just guidelines.
Too many secondary factors come into play.
You referred to the effects of from a cold state to a warmed up; stabilized state. Huge!
You also refer to the effects of the system loading internal flows draw. Huge!
Then the effects of air let in humidity . . .
The effects of in-place char working temperature affecting all . . .
Etc. Etc. Etc.
The most practical for us to control imho is system working temperatures. Requires active managements for a good wood gasifier.
Regards
Steve Unruh
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Tone, you make an important point about the variability of gasifier operation.
Iāve been reading up on wood/char/producer gas characteristics and how to tune engines to best run on those kinds of fuels.
Flame speed of the product gas ends up being a critical measure of the gas mix as it puts a soft ceiling on the engineās RPM.
The flame speed is affected by LOTS of variables, some of which are determined by the gasifier: N2 dilution, Hydrogen fraction, Lean/rich ratio, gas pressure, temperature, turbulence and others. A key take away is that even the best gasifierās output will be low flame speed as compared to gasoline. You just arenāt going to red line an engine on wood!
I found a bunch of papers but this one was the best:
Laminar Burning Velocities Of Gas Mixtures
It covers a lot of different fuel types, many of which are undiluted versions of our chargas, like from FT process or what not, but it touches on producer gas as well. The paper lays bare how variable flame speed can be.
Higher temps are good, higher pressure is bad (unfortunate because chargas can run much higher compression), high hydrogen fraction is good, CO2 is bad, N2 is less bad. Rich is faster than lean but unfortunately the fastest speeds are rich to the point of wasting fuel. Even pure stoch ratios are below peak flame speeds. Lean mixes burn slow.
What I read confirms Mattās practical experience with chargas and water drip: it produces much more powerful gas vs wood. I say āpowerfulā but it isnāt necessarily about the energy density of gasā¦ itās that the higher hydrogen fraction and lower N2 dilution allows combustion to complete at higher RPMs, IE faster flame speed. There are subtilties but more RPM is more horses.
Iāve looked at engines as well. The most obvious mods are earlier ignition (bump the timing!!) and higher compression (time to cut metal!). Higher compression works against flame speed but increases efficiency and power at a given RPM and fuel charge. Higher compression will also boost temperatures in the cylinder which may offset the lower flame speed attributed solely to pressure. To increase compression, Iād shave the cylinder heads (3-4mm+!!) and machine in valve relief pockets to the piston. Those are not modifications for the faint of heart but double in a basic shop, especially a smaller engine intended for a generator. Valve lash can help a bit as well once an optimal working RPM is figured out. Itās a small but measurable factor and one I need to study more to really understand.
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interesting design, toneā¦only thing i am not really convinced is the air connection of the bottom nozzleā¦from my sight would be better a stiff nozzle, and in the grate you have a bigger hole , where the nozzle goes through, in way that the swinging grate has enough space without touching the nozzleā¦on the nozzle is welded a disc , that covers the bigger hole in the grate, some millimeters higher as the grate, so the grate can move freeā¦on this disc can also build up a little ash cone for nozzle protection, as you have on your fergie designā¦
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