From what I understand, they did as Kristjan says first, then someone came on the moderator, who uses the entire hopper surface as a condensation surface. At the same time, they changed the incoming air so that it would not go past the hearth and cool it, it is a bit doubtful when you see how well JO’s Volvo is doing.
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Jan, I’ve given this a bit more thought. I recall deciding it was better to have a layer of insulating preheat air outside the firetube, than heating rising woodgas leaving the gasifier.
Also, with only a 4" restriction in a 12" firetube the ash crust-cone reaches all the way up to the heatshields. Heatshields are even spaced a few mm from the firetube wall.
I guess we will never know what’s really most heat economical. I still have slight hesitation symphtomes, but I believe it also has to do with my 12" firetube is pushing limits and borderline overkill for my power needs.
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Bob, the water you mention is actualy rail condensate. Gives you a good example how much water the poor heart has to deal with…
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Yes, I have two thoughts of what we call moisture in the gasifer. One is gas moisture and the other is liquid moisture. The gas moisture H2O is closer because of it’s state it is in to being converted and having it’s oxygen stripped away by the white hot burning charcoal and converting to H2. Now the moisture that is in liquid form can not do this until it reaches a gases moisture form to be converted H2O gas to H2. This takes a lot of energy. That will cool down the white hot charcoal in the fire tube. We already have way to much H2O liquid more then we need in a WOOD gasifer. So it only makes sense to get rid of it and not past it through the firetube.
This is where the hopper with tubing on the out side of it works so well. The created steam is turn back into water and drained off.
Now you can do two things with the tar being created drain most of it off with the water or burn this fuel up and make more gases out of it.
This is what the old mantel monorator Imbert were doing. The problem was the cooling effects and poor efficiencies it had.
Make as much H2 as possible and Carbon monoxide that comes from burning some of the tar.
One person I know is doing this in his WK Gasifier. Al Frick design his lid to drip some of the tar back into the center of his firetube. He is getting more miles for a pound of wood by doing this.
Getting rid of the unneeded water and still have wet gases coming out the end of the gasification prosses is the goal. The soot is wet easier to collect it. The firetube running at the optimum temperatures 1360 to 1500°f plus or minus or 737.8 to 815.6 ° c at the grate.
In the firetube between 2000 to 2500 ° f or 1093.3 to 1371.1 ° c plus or minus of the hot charcoal lobe.
My conclusion is this have we created the perfect gasifer yet? No, but we are working on it on DOW.
Bob
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You wrote good explanations. I’m literally a beginner in the world of gasification, but I don’t want to be too smart.
Facts I rely on:
- wood consists of 50% C, 44% O and 6% H by molecular weight
-if the reaction is triggered under certain laboratory conditions, the process of hydrogen oxidation takes place, which gives energy, which is then consumed by the reduction process where 24% CH4 and 74% CO are formed and some oxygen remains
-in order to approach the ideal conditions, it is necessary to retain as much energy as possible in the interior, which is used in the upper part for drying and preheating the wood, and the highest concentrated heat is in the reduction zone.
-addition of fresh air is necessary to achieve the conditions, but this impairs the efficiency of the gas.
In my opinion, WK has very well concentrated energy for reduction but the cold upper part weakens its gas and condensation of water vapor is a necessary evil.
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I agree Tone, this is where Kristijan insulated hot hopper worked. With the addition of the cooling tubes on the outside of the hopper and condensation tank to drain off the water.
The insulation around the lower part of the gasifer like JO is doing and a larger drop out area.
Preheating the air into the nozzles. Minimizing the heat loses out of the gasifer and putting the heat to work with pyrolysisation of wood in the hopper is a big plus.
This is my goal on the WK build I’m building now. We are getting closer to a very efficient gasifer. If we don’t melt it down on the inside in the firetube area. It is all about controlling the heat, the velocities, frequencies and chemical change in the gases that is going on inside the gasifer in the firetube reactor with a vaccum and postive atmospheric contiinuelessly changing involvement.
In wood gasification the number one problem is to over come the excess of H2O.
In a Charcoal Gasifer it is the lack of H2O is the problem.
You want a fast start up, and a good clean rich gas, and free of tar at all times. Preheating intake air helps with this.
The turn down ratio built into the WK Gasifier is one plus. Having a 25.4 cm / 10 in. minimum firetube for smaller engines, 30.4 cm / 12 in. for larger engines.
The larger firetube allows heat to go up into the hopper and for wood to feed into the firetube from the hopper above easier less chance of bridging.
Heat shielding in the firetube area to protect from high heat.
From the nozzles down to the grate to maintain a good charcoal bed with a reserve.
After the restriction opening slow the velocities down and after the grate slow the velocities down more larger drop box area to catch soot.
Use this area to preheat incoming air.
Keeping the gases moisture wet to collect soot.
Just some of the things I want to take into consideration in building my next gasifer.
Bob
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https://youtu.be/xGVuQJrN_yc
I don’t know if it will work, this is supposed to be a gas-air mixer, where the gas flow would determine the amount of air
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Looks a lot like the Lego version Chris built a while back
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Ha, but he overtook me in the patent, only this one has a gas flap unilaterally clamped so that the gas flow opens it according to the flow. 
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Also yours will hold up better and last longer then the Lego version. Cheap plastic.
Bob
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Only one way to know! Let’s here it purr!
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So does this behave like the ww2 era throttles for producer gas powered cars? I notice those throttles always have two butterfly valves that move in tandem so I can only assume it adds air as it adds more producer gas.
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Bob, actually, Lego uses the “good” plastic!! will still melt… 
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Today is the day for the test run, the system operated for 4 hours under a load of 3 - 4 kW, the operation was stable.
Is it normal for the hay in the filter to get wet, or is this a sign of an oversized pipe in the firebox?
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Congratulations Tone!
Chips for fuel? What do they look like? Size, shape?
Is that bucket hopper condensation? If so, what prevents air to get sucked into the hopper?
Wet hay is certainly normal, and a good thing as soot sticks to it even better. At shutdown some of the soot will get washed down as condensation drips down.
What’s the size of the motor and generator (kW) ?
Lot’s of questions. I feel like @TomC 
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Thanks Jo, the engine is an older Kubota 400, newer models are expected to have 7.5 kW at 3200 rpm, this probably less. In the experiment, the generator rotates 2300 rpm and produces about 3.5 kW. The rated power of the generator is 5kVA. When testing only on diesel fuel, I slightly increase the load by 0.5 kW, so the power when working on wood gas is reduced by 13%, otherwise these are the first measurements, which excites me.
A basket in a bucket, … I don’t understand that question. Do you mean the filter?
The fuel is wood chips of all sizes and shapes.
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Thanks Tone!
That’s incredible performance.
You run a small amount of diesel for ignition, right? How many % do you estimate the consumption is?
At 1:05 you show us a bucket of what looks like hopper juice - tary condensation. If the hopper drain drips into a bucket, how do you prevent air to sneak in? Most of us use a sealed container.
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If the tube is under water I don’t know that could produce enough vacuum in the hopper to pull it up the 2 foot is so to the hopper, pressure would probably equalize and as condensate fills the tube it slowly pushes out. Just a guess
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Yeah, that’s right, as Marcus wrote, I had the hose clogged at first, but when the water came out, I put it in a bucket. There are automatic siphons for air conditioners.https://sl.capaparda.com/sifon-za-klimatsko-napravo-naprava-in-vrste-15435
This one, as you said, Jo, there is oil for ignition, I limited the injection pump so that the unloaded engine still worked with difficulty, I estimate 10%, and the speed adjustment lever is set to max, so the oil is constantly dosed, unless the engine exceeds the revs, you can easily see in the clip when I reduce the setting for a moment, the engine immediately stalls and I have to turn off the heater to recover.
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