I thought it was tight today when it did not work, when I had cleaned the cyclone and would light, I see that I have no carbon left in the fire tube, only a little over the choke restriction.
I have experienced the same thing once before, it seems like it hangs sometimes, so that the charcoal is not enough.
Is that why the fire pipe should be around 30 cm instead of 21 cm that I have, so that it will make more carbon from the wood due to the larger surface area?
3 Likes
Yes, a wider firetube would probably have better fuel flow and less likely to bridge. One reason why small chunks are important in a small gasifier. I remember reading a rule of thumb is that a minimum of four chunks fit within the firetube diameter, which means your chunks shouldnât exceed 2 inches.
You probably watched videos of Wayne exersizing the charbed. If you discover bridging like that or a lot of smoke coming outof the blower, itâs a fast way of restoring the charbed and avoid making tar.
3 Likes
Jan; I should stop suggesting things to you, but that isnât my nature.
FIX YOUR GRATE!!!
The grate is meant to hold the char up in the working section of a gasifier. You are letting the char fall through to the bottom and blow out the exit tube into the cyclone or even down stream from there. TomC
PS. I think I have made other suggestions that you have ignored-- I not going to look back but with out looking them up, I would say they all are important to getting better gass. By worrying about âchar sizeâ, âwood moistureâ, and those other side shows you are just spinning your wheels.
3 Likes
Jan Axelsson when TomC is giving advice it is from the perspective of using a Biggish 4.3 liter engine.
That is 2X the size of the 4 cylinder user guys.
Shame Mile LaRosa has passed and not able to give his real 4.3L Chevy pickup woodgasing experiences too.
He said many times that he preferred his earlier 2.2L GM four cylinders (heâs done both a car and a pickup truck). He went V-6 in the pickup truck for fast highways possible driving.
Things changed for him going from the littler higher revving fours; to the bigger, slower rpm V-6.
Big V-8âs? Thatâd be Mr Wayne Keiths experiences area.
Me doing small aircooled single cylinders to small watercooled three cylinders primarily - even here - SIZE Matters in so many ways. Woodgas ease begins at a 1000cc engine imho. And the bigger engine guys, demanding more cubic gas volumes, developing higher hearth loadings, just seem to have much less troubles.
Ha! Except feeding their fuel hogs. Never enough really dry wood fuel.
Regards
SteveU.
2 Likes
@TomC , this is what mine looks like, do you want me to make the space in the grate smaller?
I have about 15 mm in the middle and 12 mm between the rest of the grate (you have 9.5mm i think), I have also put an edge that holds the carbon on the grate.
Do you not think that coal can be pulled aside as easily as through the grate?
I drive mostly about 30-40 km a day on wood lasts at most 80kmh, it goes down to 60kmh on the uphill slopes.
I would probably make it go faster if I had a restriction of 140,150, instead of the 120mm I have today, But I doubt if I could drive at idle for so long then.
I will try to put in a slightly smaller grid when I clean it next time so weâll see if it will be different. Regards Jan
2 Likes
Jan; Sorry if I came on too strong. lâm not near the expert as many others on here. It is just we are working with the same engine and I am telling you what worked for me. Besides the spacing of the grate bars or openings, you asked about the ââbasketââ edge you put on your grate. I put the grate right up aganst the bottom of the fire tube so that the gas has to go through the hot char before it can go out the tube to the cyclone.
The way you have yours now there is a space between the fire tube end and the top of your âbasketâ that lets gas escape with out going âthroughâ as much char as possible. Raise your grate until the edge of the basket is above the bottom of the fire tube or build the basket up taller. TomC
3 Likes
OK, but it says in all books that the grate should be about 4 "below the fire pipe (R in the drawing), it was only the Russians who had such a good material in the grate so they could put that suit against the fire pipe.
When you have it so high up, you do not burn the grate?
Do you not get any carbon at all in your cyclone?
When you drive your car, does it differ much in speed between the uphills and the flat road?
1 Like
The height of the grate is only dictated by the gas draw! Charcoal above the grate is where the magic happens. Its where the gas gets made. But the reaction is not instant and takes a while to perform fully. You want enaugh charcoal above the grate for all the gases to react and nothing more, to prevent drag and plugging.
Where ever there is heat that is to high for ordinary steel to handle this only means one thing. Not fully reacted gases!
4 Likes
OK, so actually I should have a longer fire tube, maybe 6-7 âunder restriction instead of 4â, because my tube is only 21cm and would be 30cm in diameter, 21cm should keep the heat longer, I have the same flow, as to a 30cm tube?
1 Like
21 cm is the nozzle tip circle or the actual tube?
Edit sorry l just noticed you put measurements on the top skech.
Looking at this all l can say you are starving the gasifier for sure! This is the rough size of a gasifier l had on my Chevy. With a 1.6l engine!
It seems you just cant make enaugh charcoal fast enaugh and burn it, maybee even draw oxigen in the grate.
I wuld leave the grate alone for a moment and focus on somehow expanding the oxidation zone. You cant go wider, you cant go down, but you can go up! A simple solution is you point the nozzles upward some. At a hard pull heat will rush up in the hopper and start to pirolize wood above the firetube, making more charcoa. Idleing and low demand, not much different will happen.
1 Like
Actually, I think 80kmh is enough for me, what I would like is that it was a little stronger.
Think itâs easy to ride with it, would need to put the steering to the petrol pump, so I had it to go too.
1 Like
Hmmm.
Let me point out three issues here.
-
The original Imbertâs assumed a completely across, wall-to-wall All Gasses Must flow through grate. The finished gas was collected below the grate, and above the ash pile then l-o-n-g pathway up, with much slowed velocity (dropping any sucked up ash) at the top of the system level. VesaM. and most-all (MaxG, excepted) of the modern Finn systems Iâve seen pictured do these wall to wall grates too.
TomC picture and uses a gas-pass-through and outer edge gas-by-passing grate. What I am familiar with.
JanA? Yours? How can not unfinished gasses not tunnel through narrow char stack edge and not leave unreduced? Would seem super sensitive to a perfect char bed always maintaining. -
Note that the only âconstantâ in the Imbert chart is maintained internal gases velocity.
Hey. It works.
But other systems with varying internal velocity have now proven to work to. The WK for one. -
Other systems now that can better accommodate the wide range from minimum idle gas, needs to maximum loaded demanded fuel gas needed. The âWâ gas flow hearths.
BenPâs book says for a 4.0L engine woodgas needed 420 to 3360 cubic feet per hour.
Ha! 03:00 AM here. Sorry my brain just ainât able to do the conversion into cubic meters.
And his design (not a W hearth, not a WK) does jam a perimeter fenced grate above the edge level of the reduction tube.
Would use 9 jets. Be much wider oxidization zone. Much deeper reduction zone. ~36 inch ash/soot/char gas upward flow dropping pathway. Not designed for char harvesting. Designed for maximum in-system char use as a fuel within the hearth. Thatâs what Douglas Fir wood (low density conifer) use evolves you into. An energetic âfastâ wood. With low carbons to volatiles ratio. We do not have the hardwoods extra carbons to lose. Need them all in system to heat make and hot free carbons convert all of our volatiles.
S.U.
3 Likes
Sorry Steve, Iâm too bad at English to follw you.
But shows how I have perceived that an imbert looks, what I understand was Finnland banned double-walled wood containers at the end of the war, was because it used more steel and partly because the condensation became much better.
According to my books so is Imbert enough to 200hp, then hands them not to. (I have 198hp).
1 Like
This is a wood carburetor, I think I uploaded the whole book here somewhere, send with a few more pictures so you see better.
2 Likes
The sketch I presented was to show how if the grate is too low, the gas can slip out the side and not come into as much hot char as if the grate was higher and forced the gas âthroughâ the grate.
The grate made of cement re-inforcing ârebarâ, never burned.
All that my cyclone collects is soot.
Of course it slows down going up hill. If you want your truck to go up a hill at 80kmh you will have to have it run something like 95kmh on the flatâ depending how steep the hill is.
In the tableI âImbert Nozzles and Hearth Dia.â you will see there is NO dimension for the distance from the line common to (R) and (H) and the restriction (dh). That is an important dimension because as Kristijan says, âthat is where the magic happensâ. So I understood the drawing to mean (R) was the missing dimension, not the distance to the grate. On our size gasifiers I considered 4 to 6 inches way way too much for the grate to be below the firetube⌠I want the gas forced right through the hot char, not allowing it to slide off the side of the moundâ unless like Steve said, a grate that went from wall to wall of the gasifier and the gas is taken off from under the grate.
I donât understand what you were saying about âmy tube is only 21cmâ and âwould be 30cmâ. If the fire tube is only 21cm (8.27in.), That is not big enough to get the ânozzle tip diameterâ of 9.0in. in and if you went for a ânozzle tip diameterâ of 8.125in. they would not protrude in to the fire tube.
Spent too much time on this now. Got to get back to trying to fix my computer. TomC
1 Like
Thank you for taking your time with me, still trying to understand this, but have not succeeded yet (if I ever do)
I have not found a tube that is 30cm, therefore I took the largest I had, therefore the nozzles are right next to the edge of the tube.
If I were to redo the grate, is it better to move it down 4 "instead of lifting the grate?
That would mean that I got more carbon that the gas must pass, or does the gas become too cold then, so it is re-formed into CO2?
1 Like
Those short nozzles are a problem. The reason why nozzles are long in original lmberts is that there is a insulative ash buildup behind them to protect the firetube from direct heat. Your firetube just draws the heat out from the hearth and dumps it out in the gas wich is bad.
I got around this by making the firetube double walled and passing intake air trugh it. Just like a WK. But l dont think thats a oprion for you. If it is, its probably more work thain building a whole new gasifier.
Have you checked out JOs 8" Rabbit gasifier thread? His grate desigh wuld work great for you because its adjustible by height with a screw. You can start on the bottom and just lift it up 1cm at a time untill you start seeing best performance.
Allso if l remember right his grate never pluged or sliped char.
2 Likes
Do you think there will be any difference?
According to the tests they did after the war, the gas was completely formed after the fire pipe, or rather below 900 degrees C so the reduction stopped.
But it was 30cm tube.
1 Like
Running slowly or with several shutdowns it did plug with ash from time to time. I think with a âblow-throughâ grate, a grate shaker would come in handy. I never got to making one though. I just tapped and twisted the grate a little at lightup with the poker.
I used 1/2" spacing between the bars, but never found the grate slipped too much char.
Did they tell how hard they pulled on the gasifier? At idle I would guess gas is completly formed only an inch below the nozzles. At full blast air is sometimes pulled right through the entire charbed and you wish you had another foot of char depth.
3 Likes
To what are you reffering to? Charcoal depth or double walled firetube?
Double walled firetube, absolutely. Every calorie you can trap in the gasifier is a calorie more in the gas.
Char depth, JO explained it perfectly.
2 Likes