yes i had that issue with a green limb it burned the end to nothing in a few minutes the problem i have is i need a 1 inch nozzle but i have to someway seal it inside the 3 inch as i quickly found to much air gets to the charcoal and burning/making heat i was unsure of what this onan genset would need as far as nozzle size until i ran it to see it ran ok on 1/2 but sounded very resticted
on the full 3 inch it gets too hot and melted the gas hose to the engine but aluminum might work but i was afraid it would melt without wood being in front facing the heat the water would be in a chamber around the 1inch pipe blocked by the wood/aluminum i think that some water would leak around the aluminum and wood and turn to steam/c02 that was mentioned as being beneficial in cooling like water drip
Short video of 10 hour inspection of an early nozzle.
Video:
Nozzle removal for 10 hour inspection
Ryan, shows the rock wool flange and gasket in action for quick take outs and experimentation. I’ve re-used the same gasket several times without difficulty. The key seems to be the large surface area of the mating surfaces. This reduces the psi on the rock wool so it doesn’t break down.
The heat distribution is evident in the insulation burn off pattern.
No apparent degradation after ten hours on this nozzle (no breakdown on any of them so far).
This flat faced nozzle is especially easy to construct. You can forge the end down to meet the inner tube or you can weld a flat plate to the end of the outer tube.
Chuck from Sandy, Oregon
I’ve been thinking of making a crossdraft charcoal gasifier for my Sierra. I’ve looked at the Pegasus book and they prescribe a nozzle velocity of 80m/s.
Using @k_vanlooken spreadsheet it says I should use roughly a 25mm nozzle if I were to go with a single nozzle.
I used Eddy Ramos’ equation from his guide and got the same answer.
Did I use Koen’s chart wrong? The only factors I modified were engine liters, velocity to 80, and number of nozzles to 1.
Just wanted to make sure my math was correct.
4,3 vs 4.3 ?
I think might work…
Here it is with 4,3. I believe with 4.3 it turned it into a date and not a figure so it threw the whole thing off.
It suggests a 5mm nozzle but I don’t think that would power my truck 
There must be a mistake. I dont think 80m/s is even phisicly possible eith engine draw alone.
Thats 180mph! Usualy its somewhere in the neighbourhood of 25m/s
I saw the number in the Pegasus book regarding crossdraft charcoal gasifiers. Maybe they mean the maximum air velocity?
Basically either way the spreadsheet and Eddy’s formula lead me to a 25mm nozzle regarding my engine size.
25mm sounds about right yes.
Do give your plan a big thod thugh… In my opinion crossdrafts are not worth the effort. They can be a tad lower thain a updraft yes but thats where the benefits end. Big problem is they are ash collectors and require periodical emptying. Not a problem on a small genny where you burn a found or two a hour. But on a full size vehicle you are looking at emptying the dust and slag filled burnzone every second or third hopper…
I may go for a diagonal downdraft then. At least at that point the slag would hopefully be beneath the grate in the ash dump.
I would go updraft but I’m worried the form factor would be unfriendly to an updraft. I want to build it with a 55 gallon solid drum sideways welded to part of a 100lb propane tank lower. 55 gallon drum laying sideways being the hopper. It will prevent from obstructing my view in the truck but not compromise capacity.
Hi Cody, stay with vertical walls for the hopper into the nozzles area. Why because I have found charcoal will flow better. This is why I have scrapped my barrel shaped hopper with vertical sides. Most of the charcoal stayed in the hopper and made a worm hole. I tried a screw augur still did not work well. The one I am using now a small barrel works great right down to the last few inches of charcoal in the hopper. If you a worrying about seeing out the back of the vehicle, get some big side mirrors and use your center mirror to look at the gauges on the gasifer. Only vertical hopper walls for me forget the 60° slope and all that stuff, the charcoal will hang up because of moisture in the hopper.
Bob
Well my theory is since I intend to mount it on a reece hitch luggage rack that it would have enough wiggle room to shake the hopper around during turns and bumps in the road.
I really don’t want to cut holes in the bed for the Sierra plus it’s still getting full inspections. I’m not sure when I’ll have the Mazda done so I’m planning out the Sierra’s conversion.
I put a 2×4 under the gasifer and shook it up and down and twiddle it fast and slow on the gasifer the charcoal just stayed in place for the most part. This cut my run time down too a few minutes I figured instead of 30 or more minutes if driving. It would only last 30 minutes running on my small Genset. Just saying straight walls are the only way to go for me and the wider the opening to the nozzles the better.
Bob
I value your advice Bob, and I took a look at your “Gasifier that wanted to be”. Mine is a slightly different shape in my head. I drew it out just to show how it could be if I made it updraft. I noticed with the Swedish Motorcycle gasifier it had an L shaped hopper extension, not entirely surprising considering a bike can go at least a little sideways but I’m sure that wasn’t the intention of the design to wait for a turn to shake some over.
I will still have straight up and down hearth walls, and I will probably leave a good length so it has a good distance for the gas to cool down on itself. If it doesn’t work out I can remove the sideways hopper and just use a normal barrel vertically.
A coworker said he is giving me two steel Semi Truck tanks, I may use one of those instead of a barrel depending on the shape they’re in. He told me he only swapped them out for aluminum ones because he’s doing a total overhaul of an International Harvester and wants it all to look new.
Depending on the form of the semi truck tanks I could maybe just do a sideways gasifier with an extra long flute.
On that design I would put a augur in the bottom of the gasifer hopper so when it turns it will pull the fuel to the center from both sides and in to the fire tube.
Bob
Thought I would bring this thread back from the depths.
I’m wanting to build a svedlund for the Sierra, as a stop gap or maybe permanent reactor. I’m basically hedging my bets against my raw wood gasifier for it.
I have plenty of that 5/8" thick walled 2" DOM tubing, but I was wondering if I should leave it as an open ended nozzle pointing down, or cap it with heavy plate and use it as a central air entrance and drill a series of holes, 6 pointing outwards in a ring and one pointing down through the plate. I would use at least a 6" length of the tubing to give it mass against heat. My main concern with open ended is if I don’t have enough space between the nozzle and the grate it could just blast a hole through said grate, a common issue with the Gragas units.
Ceramic blanket liner for the heat insulating hearth, treated with Sodium Silicate water glass to harden the outside. Maybe a Refractory Mortar slurry glaze going over that for more durability.
I can use half of my 100lb propane tank and use some of my undesirable 55 gallon drums as the hopper, this would save the other half of the tank for my genset Gasifier.
I can attach the nozzle in using a coupler welded into the wall of the reactor, and an elbow to point it down. Would make servicing the grate easier.
The ring of holes in the tubing would prevent a blast effect and make more of a plane like a ring nozzle would do, but it would also put more of the nozzle in the hot zone and it would sit in the hot zone while shutting down. Maybe I’m over thinking this? If I use my same engine grade sized charcoal then the density could prevent the blast effect.
Report on tungsten carbide nozzle experiment:
Context:
I’m experimenting with slagging charcoal updraft gasifiers with a downward angled single nozzle. The idea is to maximize the reaction temp by using undersized nozzles that produce high inlet velocity. The high reaction temperature gives good conversion numbers, very fast startup, and fuel size, quality, and moisture tolerance.
I’ve had good success with liquid cooled nozzles but they require coolant infrastructure.
I’ve used silicon carbide nozzles but they are relatively fragile and not well suited to slag.
I routinely use flute nozzles in my forges but running with slag tends to plug them quickly.
Experiment:
This experiment used a tungsten carbide drill guide/insert of 8.5mm ID, swagged into a stainless pipe. The engine was 212cc generator at 3600 rpm. The nozzle size is intentionally small for high velocity and slagging.
18% moisture softwood charcoal made using flame cap hot method, 1 inch minus, dust included, in a 16 gallon gasifier.
No water drip.
Results:
Gasifier startup to combustible (engine will run) gas approx 1 minute. Generator would take a 1100 watt load in about 2 minutes.
The nozzle progressively plugged over a thirty minute run, dropping in output until it wouldn’t run at all. The nozzle assembly ran at red heat, and while the tungsten carbide was unaffected, the stainless tube softened enough for the tip to droop. The hot nozzle assembly preheated the air and the slag moved up until was actually surrounding the nozzle and built up inside it.
Water was misted into the nozzle while at full output to see if additional hydrogen could be generated and the nozzle cooled, but adding water only degraded performance as there was significant water in the charcoal.
The results are very predictable and are maybe only noteworthy in that a liquid cooled nozzle of identical ID with the same fuel and engine will run unattended for 8+ hours at the same output.
The cool inlet air keeps the slagging zone away from the nozzle by maybe an inch so the nozzle stays clear.
Obviously, a larger tungsten carbide nozzle matched to the engine to prevent slagging (1/2 to 3/4 inch?) would likely not have the same problems.
Hi Chuck , i had been running "Tungsten Carbide " as the first attempt to make a long lasting nozzle back in about 2014 ( i think ) That was pure Tungsten carbide i got out the scrap bin from a company my brother used to do work for in the UK it was VERY heavy and solid when going through customs Xray machines at airports i was stopped at every single check point as it shows as a black object that was very very dense it was about 25mm OD with a 13mm id ,I ran that for about 2 weeks in one of my updraft units with no problem at all apart from the standard fire brick i had mounted it in turning to glass , i will see if i can find it in the shed and get you a photo , no problem with hole blocking up or excessive slag around the vertically mounted Nozzle .
i also have silicon carbide nozzles ranging from 10 mm id up too 25 mm id and again never had it build up inside of the hole only on the outside thus giving it a layer of protection till when it becomes time to break it off , i have also managed to chip bits off when being a bit too heavy handed .
These are a couple of pics i just took of another silicon carbide nozzle with a 10mm id that i ran for 2 months around 120 hours run time roughly .
Ps forgot to mention also no cooling egr or water drips at all . the last nozzle went in updraft in 2018 still in there working as a vertical up draft
Dave
I run 1/2 inch NPT thick wall SS pipe in ours. Engine range is 200 cc to 450 cc. I keep the nozzle out of the charcoal and dont have any of these issues. The tip of the nozzle only sticks in a 1/2 inch. Its also surrounded by a thick wall 1 inch NPT couple that the nozzle assembly is threaded into. So there is a gap between it and the nozzle. Atomized water injection works flawlessly and is very consistent with the way we are doing it now. The water never pools in the nozzle it immediately evaporates and we inject more than 1 drip per second, its more like 2 to 3 drips per second. So combination of all these things are why it works you cant do just one part, it wont work. The smaller high velocity jet is why I can back that thing out of there.
I should note yes slag can still form but never in the nozzle. But we just check it before you light. If there is one there we just dig em out. No biggy. Id rather do that than fiddle with constant ash and condensate removal any day 
Dave, thanks for the pics.
I had a lot of slag build up on my silicon carbide nozzles and they tended to break when I tried to clean them up.
How much slag are you getting with your setup, not running water? I get a lump the size of my hand after an 8 hour run, which I have to clean out or performance degrades. I always assumed the vertical nozzle would be more susceptible to slag, not less. Does the slag just run down beside the nozzle?
Slag tolerance is really important to me as I want everything to survive without water drip.