I think it is a great idea, Tone. This design of yours might be more sensitive to an optimum size of wood chunk to prevent “constipation”. 
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Thank you Tone. Looking at your drawing I see what Mike is seeing. To little of a restriction opening for Charcoal and fines to flow through.
Let’s talk about the restriction opening, and what is happening here in milliseconds at this opening. This is a very vital point in gasification. It is a high frequency point, vacuum point, heat transfer point, and magnetic point for the gases and their structures to go through. Now we know some gases are bonded to together stronger then others. We will just talk about two gases right now that we are changing. H2O and CO2 in to H2 and CO. I am sure you and everyone knows that the Oxygen is removed from each. The important thing is the flow of Charcoal and fines ash needs to be a continuous movement through the restriction opening with out stopping. To put a picture in your mind. Think how lava flows. I am sure you have seen this on videos. That is what’s happening inside the gasifier. The Air/gas velocity is changing higher and lower all the time.
So looking at the drawing and you will see what Mike and I both see. A spot where all the things above can stop and plugged up. It needs to be larger at the restriction opening.
The drill nozzles is not helping with the restriction opening going up through it.
How about moving the restriction opening up to where the drill nozzle ends and make the pipe and opening larger and changeable for sizes.
Bob
Edit: also I don’t think the center nozzle will hold up to the heat that it will be subjected to. It will probably melt down. The Charcoal is white hot in this area. 2000 to 3000 degrees f.
Bob
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I think someone forgot about such a state of matter as plasma! 
In factory gasifiers for trucks at 100m³ / h, produced in the USSR, there was a limit of only 82 mm and no one complained about constipation and insufficient power (compared to a limit of 150 mm).
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My idea of what happens in the hot zone is that pyrolysis takes place above the glowing embers and pyrolysis gases are produced which rise up the middle below the top and return to the glowing ember zone along the wall , in effect this is how the wood is cooked into charcoal which slides down , these pieces of charcoal gradually get smaller on their way down , as carbon is consumed in the reduction. The smaller and smaller pieces of charcoal mixed with ash will slide towards the restriction orifice where the gas velocity is highest, so this should allow the condensed fragments to move through the restriction orifice as well, but only if the charcoal is still glowing, if it stops glowing higher up in the fire tube, the condensation of the charcoal and ash under the flow of pyrolysis gases will cause a blockage occurring high up in the fire tube.
That’s why it would be good to have the air inlet close to the restrictor and also close to the centre , so the charcoal would always glow in that area and even if too much air came in it would be used up down on the grate to outgas the charcoal dust , a similar effect is used by a Swede in a separate room on the grid , Jan has attached a photo of this somewhere.
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The only way is to build it and test it out on this new design concept. I can hardly wait to see the results. This gasifier will be many pounds of weight lighter which is great for small vehicle cars and trucks
Yes what you said about what goes on above the nozzles is happening.
I have shut my gasifier down after a long run and let it cool for a while so I could look into the top of the fire tube with out so much smoke. Open the hopper lid and let the heat out.
I carefully looked inside with a face heat shield and poking around just above the nozzles were wood brands and not fully cooked into Charcoal. Right at the nozzles it look like Charcoal. But this is my WK firetube. Closed it up by next morning now cold and opened it up the wood brands were now Charcoal just above the nozzles and wood brands were high into the hopper. It would have been more so. If I had not let all the extra heat out. I have done this a few times. Just call me a curious guy and like to observe things that people might not think to look at.
So the gasification cycle starts when wood enters the hopper and ends after the grate or griddle and falls into the ash box. Looking forward to seeing more. Keep asking the questions this is a great thread.
Bob
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Tone, l have done this before
Worked just as good as any other similar sistem. But the way l look at it its actualy possible for this kind of a gasifier to be more dangerous, tar wise. The lower nozzles rob the main jets of air velocity, so more tar can slip trugh the charbed.
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Hello Tone,
I’ve linked to Bob Mac’s explanation.
And he had linked to yours.
Your’s was an excellent explanation of the physical movement processes that must take place within a wood fueled gasifer.
Very good, and clear English by the way.
However . . . your proposed design is too complex for the long term needed temperature environment that must be maintained; to get to; let alone exceed the best practices, peripheral jets gasifiers 72% conversion.
Before metals will crack and fracture: LEAKING!!, they will heats distort change. This changing, disturbing carefully set dimensions.
The two ways found to actually move the woods cell walls freed up mineral ash is gas velocity, blow through, transport.
Or: leaving enough fine sized pea charcoal to allow the ash then as a composite, to flow.
Ash not transported quickly out of the intense heat reduction area will melt forming clinkers.
Then the whole process flows chokes off.
With base woods from under 1% mineral ash to above 7-8% mineral ash it is very hard to manage this one variable in a same use design.
It is the Operator wood sizing; mixing wood species; and by engine RPM and gasifier loading who accommodates variables.
Better than a gasoline carburetor comparing, compare to working piston steam engines.
US/Canadian/British/German used single expansion steam for rail. They had the domestic coal to use less than ideal. Simplicity, durability, was King.
The French did not have the coal to waste. They had to evolve to much more skilled Operator live tuning double expansion rail steam engines.
For large Ocean steamships, they all had to evolve to best efficiency, triple expansion steam engines. No coal deposits or mines out in the Oceans. These systems needed then at least three levels of skills to operate. Oilers/wipers. Fitters/artificers. Master operating Engineers.
DIY wood-to-shaft power best, easiest, to become a better Forester, imho.
Wood for energies is a true Rural thing. To have the Land; to have the trees and brush.
Regards
Steve unruh
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Thanks to all of you who are contributing to this thread, Kristjan you have done great , but the difference is that in the proposed idea the upper nozzles are switched off at low gas consumption, or rather, the float valve in the airflow shuts off the air flow, so the air only flows to the lower nozzles and the temperature is kept high in this reduced area, but when the flow rate is increased, the float valve in the airflow rises and opens the passage to the upper nozzles. I am even thinking of making a smaller WK below with separate air inlet instead of a centre nozzle, thus creating a double WK, small in large, for a wide range of loads.
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Okay I have another question now and it is Why? The WK Gasifiers already have a great Turn Down Ratio built into its design. It will idle for long periods of time and then take off and go the at highway speeds for long periods of time and anything in between. You can even run a genset off a WK Gasifier that will run a full size truck with a V-8 engine pulling a trailer. You can not do with a Imbert or other Gasifier designs.
Bob
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Hi Mr Robert, I think you know the answer , given the particular problems that Marcus , or Jo , or Jan , refer to , we have to admit that there are shortcomings . The WK has a well designed fire tube , which preheats the air well and has a large charcoal stock , which does allow it to run for quite a while with a small amount of circulation , but not too long and it is also sensitive to the size and shape of the fuel , it wouldn’t work best on my fuel of different sizes and shapes. Ever since I started gasification I have been thinking how to build a flexible hot zone so that it is always glowing just above the restriction orifice, and if the demand increases the heat would spread up and apart, with WK there is no such effect as the air is only supplied through nozzles placed high above the restriction orifice, here the heat spreads in and down and at optimum consumption reaches the restriction orifice and the grate.
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I’ve been laying awake thinking about this for a while and since we’re on the subject…
With the deep charbed of a WK, the big nozzles are probably what makes it work so good. It’s been mentioned before, that at idle oxygen is probably slowly pouring down the sides of the firetube, keeping the heat closer to the restriction than it would with tighter nozzles recommended in Imbert specs for example. Doing so, the lower region is more prepared, heat wize, to deal with a sudden blow of steam and CO2 when we suddenly start pulling hard on the gasifier.
I showed raising the restriction in my Volvo gasifier the other day - an effort to help with both hesitation sympthomes and tightness of the charbed. It’s got only 8mm nozzles, 10 of them. I’ve noticed no difference in behaviour so far. I still need to accelerate carefully not to suffer from hesitation. Once past that, there’s plenty of power again.
I belive the tight charbed is somewhat caused by the small nozzles as well. A hard blast of air pentrates the chunks and fraction char faster than desired. Shaking the grate at lightup gives a couple of miles of OK vacuum ratio. After that - back to “normal” tightness again.
Edit: Tone, I think you’re right when It comes to supply oxygen closer to the restriction at low demand, but as I described above I belive there are several ways of doing that.
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One has to ask oneself: Is having in effect a gasifier with two different (interconnected I know) hearth areas in order to optimize performance instead of a reliable/ acceptable compromise worth the extra complexity and trouble that could create? I could see a way to semi-automate this, drawing from either hearth depending on the measured temperature of each charbed. If the (main?) larger charbed is not in full operation (engine idling) for an extended time, would it not then cool off enough to allow weak or even tarry gas to flow through to the engine upon sudden demand? I realize the smaller (secondary?) hearth will still be at proper reduction temperature… I guess you may have to build it to find out, Tone!
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I agree. You won’t know unless you try. It’s made of steel. If one thing doesn’t work you get out the welder, plug up some holes or whatever and try something else. I seldom understand what you guys are talking about design wise but show me a drawing and I can build it and hope it’s right. If not I’ll build a different one.
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What do your charcoal, ash look like under the grate?
Is there any charcoal coming down or is it just ash?
Interesting I listen and try to understand you all.
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Tone, dont get me wrong. I have prooven time and time again im all in for inovation when it comes to gasifiers. Im just trying to give a constructive critic 
Others have well described the problem l see with this. At low demand, there is no new charcoal produced. You burn just the charcoal stored above the “idler” nozzles. Raw wood passes down past the main nozzles and once you hit the throtle, this is essentialy the same as if you had a bridge in the hopper that collapsed. Tar!
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Marble sized char, but with quite a lot of fines and ash mixed in. I slip what I would call a normal amount of char. Maybe even a little more, since I’m forced to shake the grate at every lightup. In avarage about a bucket every 4-500 km or so.
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Mike, we have a saying here and I’m sure there’s an English version. I just don’t seem to remember it right now. Ours goes something like:
“The destination is not the goal. The journey is.”
I’m all for simplicity, but with gasification this means…even if we’re fully aware of how to make things work first try, that would be the end of the journey. Most of us like to experiment.
One would like to think it’s easy to learn from other people’s mistakes, but nothing beats doing them yourself. You learn a lot as you go and get a much better understanding. If you’re really lucky you may even come up something new.
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Ok, I’m so surprised that you can drive with such a small and dense grate, I tried to put o one more net in mine, it got better gas, but got dense pretty fast.
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With the small diameter I think most gasses by-passes the grate to the sides anyway. What’s your restriction size?
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This is a good description, JO, I think this is why i let my truck standing for so long, it just worked reliable til it broke down. For now im more tempted to start a new build on another car than repair the old one, but I have to control myself and do it 
I noticed this when i felt somewhat “jealous” reading on this forum about new builds, experimenting and tinkering, making tings better and better.
Anyways i have some objects to start experimenting on, sooner or later.
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