As long the are no oxygen and the co2 hit hot carbon the will be gas made.
This can pretty much be from the nozzles to the grate,but it’s called the reduction corne/tube so much will happen there.
You can have the reduction zone more over the restriction if you rise the nozzles higher.
It will then be more like a FEMA or WK and no reduction tube/corne is needed.
At idle (low demand) everything happens high, above the restriction. The lower part is nothing but drag. Apart from risk making tar when the internal temperature lowers you will end up with a tight and packed charbed over time.
At full throttle (high demand) oxygene will be pulled down low and start consuming char to make gas. Pulled down deep enough it will even start consuming your gas and the gasifier will overheat.
I will never forget Mr Wayne’s quote from years back: “Vehicle gasification is a constant battle - work vs fuel size”.
Yes, what do you think, it would be easier to just insert a plate into the tube and make holes for restriction
In my old books it says that the gas should have the cone for the reduction to continue a bit under restriction and that the heat should be better maintained with a cone, but at the same time shows pictures of units that do not have the cone, does it work just as well without it?
I wuld disagree with the theory that the cone adds to heat retaining. Charcoal and ash are far better insulators thain steel and in the cone design, you heat the steel but if there is no cone you heat charcoal.
The gas will naturaly flow in a cone shape out trugh the restriction. The shape, size and position of the grate will help shape the actual glowing cone.
I built a gasifier similar to JOs with no cone and no grate. Gas went in the restriction then in a huge charcoal filled chamber. The goal was to extend the turndown ratio with that reserve char. And it worked just fine.
Actualy, now that you mentioned, l still have that gasifier. It ran a 109hp 1.6l engine but I will probably modify it to power my 8hp sawmill.
Ok, so you think I can make a generator that looks like this, no con neither over nor under restriction, it would be much easier.
Security filters, do you use them?
What do I need for gauges to control the gas in the car, temp on the wood container, what else do you have?
Absolutely. Are you planing on going without a grate?
The restriction is more thain a hole in a plate thugh. You want a thick hevy ring of solid metal there, at least a kilo in weight. One reason is this is the hottest part of the gasifier. It will deteriorate over time and you need some spare mass.
Second reason is once the masive restriction heats to yelow hot, it acts like a flywheel to the performance of the gasifier. Smooths its gas output quality when demand changes.
I used to have a condensate trap just prior to the engine but now l just have a towel sack filter. Soot or even ash will not destroy a engine in a hour and if l wuld detect dust in the suply pipe l wuld act. But the simple sack filter is preety much bullet proof.
Instrumentation, it depends. To tell the truth the only reliable instrumentation l ever had was the O2 sensor stock on my Chevy and MB. I installed DIY vacuum guages but didnt work well on my MB, maybee l might revisit this someday thugh.
I am certainly not paying 220€ for a pair of vacuum guages thats for sure… that is the ptlrice here.
Best instrument is your feel, and experiances. But otherwise l wuld say vacuum guages are kind of the most important ones as far as actual instruments go.
Thanks Kristijan.
The unit I built now is without grate, but I saw when I last fired it up that the cone under restriction, was just red, doubting it will hold.
What else do you have for filters, do you have hay filters too?
Jan, I did some maintence this weekend and learned something new I didn’t expect. I reached down with my hand through the restriction and found even the walls of the upside-down cone below the restriction had a smoth protective slag coating. Just saying.
Ok, I hope it will take a while then, but I have welded the cone with mig and regular thread (flux) from both sides.
Where did you find your restriction?
It’s an old bearing racer from a waste bin at work.
Got my stainless steel filter today, the pieces are 0.3x0.6 meters, it is best to make a pipe in sheet metal with holes in, and have these filters on the outside.
Or should I make a frame and place in an oil drum, and in this way divide it in the middle, will be larger area in that way.
Soooo, NOW I understand more about the WK and the ‘heat flywheel’ youall talk about. This piece of metal has to be yellow hot? This is very hard duty for any kind of metal. Can we replace it another material? Silicon carbide can survive yellow heat for a long time. I know, because foundry crucibles are made from it. But expensive. Would it be possible to use a big clinker/slag chunk with a hole chipped in the middle, so that it is a donut/toroid shape? This would be free, for us, and I think maybe almost as durable as SiC. Just thinking.
Rindert
A nother thing the WK does that is helpfull… lots of heat recovery and when its most neaded. If you think about it, hotest air will enter in the gasifier when there is least of it: at idle. And there its most important to maintain the heat!
Yellow hot, preety much, at least from what l saw sticking my wiskers in a empty hopper 
but you have to realise at the point where the restriction is the athmosphere is neutral, mostly reducing. Its not the heat that destroys the metal, its the oxigen. Not a lot of it at this point. Plus, steel will form a protective lair over it.
It cant run forever, but even a ring forged out of half inch squere rod will last some time, just doesent add much of ths flywheal effect. Tryed.
Hi Jan,
you asked several times about going directly to a fabric filter without a cyclone and what is the reason to give slightly better filtration results.
The reason is that without a cyclone there are more coarse dirt particles in the gas that build a filter cake on the fabric filtering the fine particles better.
With a cyclone, there are more or less just fine particles in the gas left that may easier find its way through the fabric filter.
But: As Max said, you need to protect the fabric under all circumstances from glowing particles!
And you need a larger total area of filter fabric and of course more dirt is collecting in this filter housing.
Vesa Mikkonen in Finland uses just a fabric filter without a cyclone with good results in his setup.
http://ekomobiili.fi/Tekstit/english_etusivu.htm
Kind regards,
Til
That I ask about fabric filters is precisely that in the old books, they describe that the cleaning with fabric filters will be better even if the large particles are included, and with fiberglass filters there should be no problem with glowing particles.
Hi Jan,
yes the cleaning is better because (and no even with) of the large particles. It is all about the filter cake on the fabric, that does the biggest part of the filtration process. With larger particles, it is less dense and less likely to clog, and it will easier fall off from time to time. The fabric itself is more or less just there to support the filter cake.
But even with fiberglass it should be well protected against glowing particles. They can ignite the filter cake, don’t forget it is not just ashes but fine charcoal and soot. So even fiberglass can be destroyed.
So at least the flow of incoming gas in the filter housing has to be directed in a way that it doesn’t hit the filter directly. This is Vesa Mikkonen’s experience (see link in my last posting), he has burned some of his filters. Here are two videos of his system, in case you don’t know it:
Regards,
Tilman
What filters do you have and are you satisfied with this?
I do not know what to use, would like something that does not generate a lot of soot in the suction tube.
If I’m going to run with the cyclone and a hay filter, which hay is best, oat straw or very fine grass, (these are the varieties I have.)
After all, I can do as Kristijan and have a towel to start with at the suction, to see how much is going through.
