On the down draft design I have found this if you put no restiction open in below the nozzles or nozzle the ash will build this formation or the gases to flow through. Every time I have dug out the charcoal/ash area I have noticed this on my 2" nozzle with a 3/4" in side it. What I call the ash formation after the nozzle seemed to form but not the same way each time I cleaned it out. It would take a few runs to form this and the gas production would become better after it formed.
With a reduction opening pathway aready there I noticed my gas production was good with a fresh clean out.
I noticed with matt’s gasifier design and the way he designed his fire harth area he has pre shaped it already so just a little ash to fill in is all that is needed. Check out the lower area below the nozzle and the shape.
And yes you need some much charcoal after the gases are produced for cooling and enough volume too of charcoal.
Even in a WK Gasifier this is happing but it takes longer. Sometimes a few loads of wood with shorter driving range. This is what we call the charbed must settle in. But there is ashes involed in this too. When we use our prob rod to check the condition of our char bed we should be very carful probing straight down to the grate to check the tightness of the carbed. And not just raming the rod down in there like you can do with a Imbert design. The Imbert has a pre formed matal shape to its design in the fire tube harth.
Hey they all work just fine. But how you handle that area firetub after it takes shape is what helps the gasifier to make good start up gases and running.
Bob
I tried a few different things with the idea of avoiding that.
Temperatures that are turning ash to slag are higher than required.
Not optimal.
Other places are cooler than desired.
Water tars CO2 not being efficiently reduced in these places.
Good design minimizes the cool and hot spots.
Operating in as narrow a turn down range of flows also improves efficiency.
From a strictly stationary plant perspective the " reactor " should have a single operating range it functions at to reduce slagging and unreacted feed.
This is not how a mobile gasifier works so most of my tinkering leads to bigger and bigger machines and gas cleaning cooling heat recycling systems that are completely impractical for anything other than a plant that feeds a gasometer.
All thats on me and my choices.
I’m just sharing some opinions and thinking out loud as I am formulating a new experiment ( feel free to ignore me lol )
As a possible benefit of the updraft, I would expect an updraft charcoal gasifier to handle a greater range of engine sizes and speed changes over a downdraft due to the flexibility of the reaction zone size.
Thats why I have the V shaped chamber to force the flows to the center.
Yes I have studied your design and that V shape is actally a type of restiction opening shape the gases are flowing at a much high rate of speed in the bottom and it helps clean the extra unneeded ashes out and completes the gasification prosses. In my old gasifier I had 2 V’s one on each side for the ashes to go, but they just pretty much sat there. I know now it should have been more like your V shape. This was after my restriction opening. Mine worked but was a pain to clean it out when it was full of ash. It is fun and great when you find the right combination in metal bending shapes that works and it is a real K.I.S.S. in design.
This to me is my main goal in any gasifier build. And it is very hard for me to do. Keeping It Silly Simple.
Bob
Oh no not me. I look at everything everyone is doing even the beginers here at DOW. You never know when someone might try something a little different and it works. Just look at all the recorded discoveries on this site of things that have worked.
Bob