The grooves are 12-13mm wide, I usually be careful not to touch the grate when I clean underneath, so not too much falls down and destroys the charcoal above the grate.
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As you say , it is necessary to test the idea , not just to “siphon” , but also to be clear with the theory.Kristjan, if everyone agrees with you, there is no development and soon you will have nothing to think about, so the debate can go on. I will try to show my understanding of the pressure conditions in the gasifier , the lowest pressure is at the restriction orifice and extends steadily up to the filter , further up the hot pipe the pressure rises , at the nozzles in the upper part it is already relatively high , only slightly lower than the ambient air pressure , occasionally it even exceeds it , this happens after a high load , when we stop in front of a traffic light, the gas starts to escape at the air intake and the pyrolysis gases flood the hot zone, which cools rapidly, so that the tar gases soon have a chance to pass through the reduction. For example, when there is a smaller WK below, I assume that in this part the pressure still does not exceed the pressure of the outside air so it still enters through these nozzles and maintains the reduction process. It is true that the charcoal will be consumed in the hot pipe , but as the volume of pyrolysis gases and steam in the gasifier decreases, fresh air will start to flow to the upper nozzles and pyrolysis will continue,…
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Yes I agree that the gasifier mainly runs in a vacuum mode of operation from the intake draw of the engine in different inches of water vacuum in the different areas of gasifier. And it can develop a positive pressures in the hopper because of the moisture causing steam. I have not witnessed steam/smoke coming out my gasifier air intake. Only at complete engine shut down and it takes awhile. But it is a long way of piping and passage ways to my intake opening to the nozzles.
But in theory if the steams positive pressures is more then the engine idle vacuum and idle velocity being created then it would be possible for the smoke inside the hopper to go backwards into the nozzles momentarily. Humm.
I think this is why the WK Gasifier restriction opening is not a long tube. But after the opening it opens up into a larger area what we call the Charcoal reserves and goes to the grate. Humm. More thinking. Okay the temperature at the nozzles hot lobe area is running somewhere in the 2000 to 3000 degrees f. That lobe is usually above the restriction opening. This is when I am running highway speed 50 mph. About 1300 degree f. plus at the grate. When I am driving hard and at 75 mph. The lobe is now at the restriction opening and going through, the reserves of my Charcoal are being used up. I am at this point over pull my gasifier. Temperature at the grate? I have had it to 1760 degrees f. At 1800 degrees f the stainless steel would probably melt down. Yes I have warped the grate a little bit. Okay now I come to a slow down speed and I pull off and stop, but still idling the engine.
I think in this situation no tar gases could possibly make it through the restriction zone with out being converted.
But if I tried that samething with my gasifier not fully warmed up? Tar would make it passed the charcoal bed possibly. I am not going to test this.
Now if there was extra nozzles just above the restriction zone that would open up only at engine idle that might stop the tar from going through and not be converted.
Kinda safety on the gasifier and help with idling and take off hesitation problems all in one. This would definitely be good on the Imbert gasifier for sure.
Bob
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Mr Robert , I hope you understand what I mean , that there is always air coming through the lower nozzles , because they are always in the vacuum zone and always have an open air inlet , and the inlet to the upper ones is opened when the flow is increased , I guess this would work without a floating valve . Jo says she has it done at Mazda. When you mention the imbert , I agree with you , I would place the lower nozzles a little above the narrowest part of the hot zone and the upper nozzles higher up in the wider part.
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Oh okay the air flow for lower nozzles open all the time and upper nozzles air flow can be open or closed. Now the drawing makes more since.
Bob
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Tone, this was during building process of the Mazda gasifier back in 2017.
5 lower nozzles in an 8" firetube and 10 upper nozzles in a 10". The upper air manifold still missing.
I’ve been running this gasifier almost every day ever since. If I were to change anything that would be making the lower nozzles smaller. I’m propably pulling oxygen a little too deep at high demand.
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Nice design JO, is the nozzles holding the plates in place?
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Yes, that’s right. Nozzles screwed in with brackets holding the heat shield plates.
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Hi Jo , you say you have too much air coming in at the lower nozzles , as I read from your posts you have separate inlet pipes from the exchanger , separate for the upper nozzles , separate for the lower nozzles , so you have the option of restricting the inlet to the lower section , as it doesn’t matter if the flow is restricted by the size of the nozzles or by the throttle in the inlet pipe . What is the cross-section of the nozzles?
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Tone, I have no valve for the lower manifold apart from the main air inlet valve. Only the upper manifold can be switched off separately.
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I apologize Jo, but in your sketch you can see a separate inlet for the upper and lower nozzles, but after reviewing the pictures you only have an inlet in the lower part forward in the upper and a connection to the pipe from the outside, hmm … with minor intervention it is feasible to separate inlets
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DAM!!! I just went through 300+ postings to find this picture and maybe some more that would have answered a question I have. It wasn’t until I got to # 1 that I realized I was looking in JO’s Volvo. I was looking to find where he routed the air to the top row of nozzles, so I KNEW I was dealing with the build that had two sets of nozzles. At least I wasn’t in the VW build. TomC
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@Tone and @TomC.
This pic may answer your questions.
The lower manifold feeds the upper manifold via a valve, which I no longer use. Found out the lower nozzles supply enough air as is, and the top row starts blowing when pulling hard on the gasifier - self regulating.
Edit: Just to make it clear - I wouldn’t do this again. If you for some reason want two levels of nozzles it would be a lot less complicated to feed booth rows from the same manifold. I would settle for no more than 10-15% nozzle capacity in the bottom row though.
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What if you insert inserts with a smaller diameter into the existing openings of the lower nozzles?
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That would certainly add velocity. Joni has prescribed I always narrow the tips of an oversized tube to the desired nozzle diameter.
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Yes, that was my initial thinking.
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JO; Is there anyway you could close the lower nozzles and run on the upper nozzles. Wouldn’t that make the Mazda more like the VolVo gasifier?? I think I proved to myself that a gasifier with more and larger nozzle openings and higher above the restriction gives a much more powerful engine. TomC
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I think it allows us to open the restriction a little more with out allowing tar to make it pass the hot restriction zone. There is also a higher larger hot lobe above the restriction zone. Also the final pyrolysis is now higher in the top of the firetube and up into the hopper. My hopper temperature is around 130° f, a little hotter then most. At half empty it is 140° f in my hopper.
Bob
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Easiest way would be to plug them, but I’m not sure I want to. It runs so sweet in the low end, idles forever and cranks right back on woodgas every time after sitting. Perfect for what I’m mostly using it for.
Now that I have a proper Sunday car I can uttilize it, whenever I feel like collecting speeding tickets 
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Okay so you have your truck gasifier tuned for more of a work truck not mainly highway running truck. Wayne has his Dodge V-10 truck like that mainly working on the farm and slow idling checking out the cows hauling big hay rolls to feed the cows.
This is very important for wood gasification drivers to know what type of driving they are planning on doing. You are working in the forest hauling lots of loads of wood home. More slow road driving then your Volvo Sunday driver at mostly highway speeds cruising down the highway.
So lower nozzles slower driving and higher nozzles to the restriction opening for high speed driving on your gasifier. Great information here for the DOW members.
Now I change my original 12" firetube that had 12" from the nozzles to the restriction opening with a restriction opening 7 1/4", the new fitetube with the nozzles to restriction opening 9 3/4". With a 7 1/2" opening. The distance from the grate to the restriction opening is about the same as the original build. I did move my grate up to 3/4" it was at 1 1/2" clearance from the bottom of the gasifier to the grate. My nozzle were moved down 1 1/2" deeper into the firetube. Total of 3" from the top of the firetube this is to stop the heat cracking of the top of the fire tube welds that formed in the old original firetube top plate. I now have a 7 1/2" restriction opening. No hesitating at stops lights or spot signs.
This has now really got me thinking with my 4X4 Jeep built I am doing. I will be doing a lot of slow drive into the mountains to the mining claims I work. I drive twelve miles to some of them slow gravel roads. And some just off the highway to claims but it is 30 to 100 plus miles highway driving at 60 mph to get there on others with hauling equipment. You can see why I want to drive on wood. Spend all my mining profits up in just gasoline getting there and back.
Bob
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