Fluidyne Pioneer

I began to build a Pioneer and quit several times this decade.
Always found something else to do with my time

This time will be different. ( I hope lol )

So thoughts:
Because the design can crack tar I can run low quality char torrified wood.
Using preheat I can keep the low hearth rate flow hot enough to produce clean gas.
Using steam injection I can flatten the temperature spikes at high hearth load.
In the middle operational range there should be enough moister still locked in the cellulose to provide some Hydrogen to increase the flame speed of he fuel

Anyone else ever played with this and what did you find?

Doug Williams sent me a few email back in the day when this PDF files was new.
One hell of a nice fellow, but he never talked about what he thought I could do with his design, he just said it works within its range and not to screw with it.


My basic impression of the Fluid-dyne is it is just a good basic Imbert style gasifier that has been produced and proven. 12-15 years ago Doug was very active in our Yahoo Woodgas forum. I think this design can be modified up or down if you follow the Imbert chart.TomC


I much agree with TomC’s opinion.

Wallace I personally sort out the woodgasifier types into broad stroke categories.
First the fuel sizing/type. DougW insists his are for WOOD! MSW, Ag wastes, poo’s, peat, fossil coal and charcoal need not apply.
Now in wood fueled chunked types then three broad operational characteristics categories:
Small active internal volume systems then very dependent on fast narrow range of gasses flow through rates: Inberts/GEKS/Victories/Williams/Mikonnen and others.
Then large active volume systems with moderate broader range of internal gasses flow rates: WK and a few others. Mnn. PowerHearth and maybe Canadian Greg Mannings systems.
Then figgging huge (ALL) active area systems with super high internal temperatures and very low internal gasses flow rates. Larry Dobson and others that follow actual fluidized bed principals.

Once you operate a bunch it all starts to make sence.
Ha! Just like IC piston engines. Once you greasy knuckles know, you will never screw with Wankel and other woo-woo poorer thermal designs.

Steve Unruh


I want a charcoal system that does not require such a tightly controlled feed stock.

Chasing and idea my friend…

One option to get by with a more variable feed stock is to use a clean and consistent feed stock in a small diameter central cylinder with the torrified stuff surrounding and slowly migrating into the good consistent reaction zone as in the Brandt style gasifier.

Sounds reasonable Bruce, but why separate the two fuels when you can cook the fuel a product that’s dry if not completely uniformly cooked to charcoal.

I get the impression no one likes this idea.
Making quality charcoal has got to be more trouble to make than to build a gasifier that does not care so long as the material is bare minimum torrified.

Here is an interesting read on the subject.

Its less energy intensive to make the torrified wood.

So lets say I cook some chunks at 400F for an hour in a kiln.
Some will become char because I lack the scale and sophistication to uniformly char.
So why bother being uniform at all as long as its all 3% or less moister with some of the offending volatiles cooked off it should be great fuel to run in a down draft gasifier, maybe even a cross draft if designed correctly.

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If I remember right wayne’s first units were a modified fema that relied of partially chared or torrified wood. Someone correct me if I’m wrong. So does that mean that torrified wood overcomes the drawbacks of a fema?

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Sorry, I’m lost. What exactly is it you want to do??

You started out wanting a Fluidyne gasifier. That is a good thing. Now you are talking about some “half processed” charcoal. The direct gasification of wood into woodgas is much easier than making, processing and sizing charcoal. Charcoal is best for small single cylinder engines or small vehicles where you spend time off the vehicle preparing the char and then a simplifier on the vehicle.TomC

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FEMA was designed to be an expedient means to keep small agricultural equipment and trucks moving in an emergency.

My FEMA was tar factory, but in hind sight I would have liked to try that to see if it helps. .

Too me a FEMA gasifire is like Rhubarb hat, it will keep the heat off for a while, but its no long term solution.

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Sorry TomC:
In my thoughts area at the very beginning I was discussing what I thought was a good idea I have mulled about for a long time with.
A gasifire for Charcoal, only one not too choosy for its fuel with the ability to deal with tar from a low grade partial chard fuel.

Torrified wood does not need to be processed as long as making charcoal.
It’s hydrophobic and does not rot so storage is easy.
It’s more energy dense than wood but retains over 90% of the energy the of fuel wood.

It’s potential easier fuel to process since it can be cooked up in about an hour per batch at 400F.
Maybe this means I could make it in a continuous process if I made a clever retort that allowed the feed stock to slide in one the top and pulled from the bottom like a coke battery on its side.

The pioneer itself is simple and small.
Add some preheat ideas hijacked from the GEK and maybe I could widen its turn down ratio and improve its performance.

So why not take the Fluidyne or such and run your tariffed wood in it. I’m not sure what you mean by the “pioneer”? You mention it but then put up a video of the Fluidyne.TomC

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Pioneer class is the model the gasifier is based on, Fluidyne is the company.

When I click on the link I get a PDF file and short write up on it with design specs.
What do you get when you click the link?
Maybe something is wrong with the link.?

I don’t have any torrified wood and I don’t have a pioneer class gasifier.

Before I build it I want some feedback from others who have tried these things and experimented with the feed stock, preheating air and fuel bunker as well as steam injection to control the reaction.
I think thermal runaway is a real possibility just like a regular charcoal unit would face.
I have read a few places about extremely dry feed stocks causing thermal runaway in the GEK, and Greg Manning talked about it in his early preheated design too.

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Ive never looked at that PDF but that looks nothing short of an Imbert. What makes this special?

The grate is similar to ours where we are rotating it on a shaft radially.

We have built very elaborate air preheats and went to simpler designs you can only heat the air up so much, and it heats up very fast. We now have a simpler baffling system and are getting the same results as before. Where we differ from any one else is our reduction system. Our reduction is now fours times the spec on the imbert chart with a hybrid cross draft grate. Our jetting is tuned slightly to match the fuels we specifically test with. The Imbert chart is just for reference, no fuels run the same pine vs hardwood vs other softer woods. Chip size, moisture, air preheating, and other aspects play a whole other part in your tuning.

To get fuels to flow in any small gasifier grate flow vs your upper raw fuels flow must match. Adding the grate and hopper agitators will correct these things and get your machine to flow. However, it must be tuned as well. The better tuned the machine the better the agitator will work.

We did try creating the void very early on to stop bridging. This was the very first rev of what was the Evolution design at the time and why we had the bump out in the mid section. It didnt seem to make a difference and I wanted to try different designs. So we kept this bump out to create other designs and this has evolved into what you see today, its now there to simply make room for our jet system and to allow a place to add insulation.

Our conical / tapered hearth is also tuned for flows at combustion. This combined with our reduction bell is sort of like the hour glass hearth systems, but we are retaining the void around the reduction bell for natural insulation build up. From here our bell also has a tapered top and is also shaped like an hour glass, its no longer an inverted cone. The side walls of our reduction have revisions for carbon build up along the outer perimeter, the lower portion then transitions from down draft to cross draft to eliminate packing, The grate design and agitator are also components needed for this work.

Pull your gas out from the side like a cyclone in reverse. This does two things, it helps distribute heat evenly while also aiding in dropping your heavy debris. Our new system with tank we hardly even need the centrifugal filter any more and this may go away in the future.

So I guess at the end of the day for a gasifier to flow, we need to consider fuel first, then design around it. Denser fuels need less reduction then less denser fuels, smaller fuels need less great spacing. A dense fuel like a wood pellets need longer jetting, jet openings typically are smaller as well. But you can always open them up. Pellets will flow well going into the combustion zone but are more prone to grate clogging. Chipped fuels are less dense so all the above are just the opposite, however, if a hopper agitator is used this will eventually effect things down stream.


Hi Wallace,
I started with the FEMA, read about its short comings and tried my hand at the fluidyne design. It’s as Matt says basically built to imbert dimensions. Nothing wrong with that except the 1/2" nozzle dimension and other refinements like preheated air, monorator hopper. SU advised me to start with 1/4" nozzles and increase if needed. I still run 1/4" nozzles with good results. In my vid I had neglected to fully weld the reduction tube to the flange, thus you see the redhot area on the shell. This also is called an internal leak allowing gas to by pass the reduction zone and diluting the finished gas resulting in a lower quality gas and “passing through some tars”. Then I caught up on my reading and learned about preheat, etc and went into my present imbert build. Here’s a few pics and vids of my fluidyne. By the way I used tree branches from 1" dia to 3" dia, cutting them as long as their diameter. I use this same size for my GEK variant and it works well. Check out the rest of my posts once you’re on the site.
I would relegate the fluidyne to experimenter status and move on to the imbert as I did. How were you going to preheat your air. Same question I asked myself, so I went whole hog on my present unit. Yes it’s more involved, but it is time well spent on a proven design and a great learning experience. You’ll get a better quality operation and gas, imho. I was able to salvage much of the fluidyne to move on. Good luck in your quest. Don’t hesitate to ask questions, we’ve all been there at some point.

The large plate holding the grate interferes with the free flow of gas and a “cool” spot which may inhibit reduction therefore gas quality. I used a “just big enough” round washer on the next tear down.

Note the FEMA in the left background. It was good for getting into gasification and back into welding, but has many drawbacks, notably tar production. The fluidyne seemed a logical step up in terms of ease of build, but as I said, still not taking advantage of preheat, etc.

Checkout my journey in the Forum, “My first small engine run”. Hope this helps.


Matt the Pioneer is nothing special, its just small, adjustable and has a track record of working.

Matt, how do you accomplish your air preheat?
It should be easy to run a counter flow system and achieve 60%-70% heat transfer without much trouble ( on par with a medium efficiency furnace with the same thermal output ).
We managed much higher numbers at large scale at my former employer running a Bessemer based converter ( and you want see a dust load ).

I need to look at your videos to see if I can understand some of the other ideas you bring to the table.

And thank you Pepe for showing off your system, Its nice to be able to pick your brains and get suggestions too.


haha unfortunately I cant show all. Open sourcing dont work, people still steal your work. Once we get patents Ill open up more.

But for the preheat its really nothing special. The pictures the CAD model of the current Flex R1 much simpler, yes it could be better like our older versions but for the amount of work and cost, this is the better option and works good enough and it has performance advantages over the older version as well.

On older versions we had two air preheat systems. First stage had a very elaborate baffling that wrapped around the reduction zone, we added the secondary system later on (pictured below). When we evolved to the next generation systems we scrapped this primary preheat and left this secondary preheat system in its place.

Where the advantage of this is and why I believe we dont need it to be that elaborate. At lower loading the air is entering at a slow velocity giving it plenty of time to absorb heat. This aids in adding to the turndown ratio. At higher loading, the air velocity is increased but will absorb less heat. Not an issue because at higher loading the machine has no issue maintaining temperature. In the higher loading the air does not get as much heat and is denser. This is good because it helps the machine breath better at higher loading.

See pictures below, this can be adapted to the Fluidyne quite easily as it is a similar design. Ill try and find pictures of the exterior jetting.


On the Fluidyne design leave it as is with the exception of making that reduction zone much bigger. Build it with the same desing concepts but open that up after the restriction and give it a good 6 to 8 inch skirt. The grate on the center shaft like that you can then make it so you can adjust it to different levels.

If you can build it so you can do this on the fly you will need to start out with it all the way up and tune it down. Ive been down this road, and once its adjusted down its not very easy to bring it back up.


Pepe I was thinking about your design and the leak internally,

Ever try some converter clay to plug it up?
Its rated for far higher temperatures and you can chip it out after ( refractory material used for plug in metallurgical furnaces so the plug has to come out for tapping )

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This is the only picture I could find of the jet piping. We no longer hard pipe, we use JIC fittings with the SS flex hose.


Great insights on the temperature of the air needing to be higher at a low flow and lower at high flow.

Thank you very much Matt.
This is very useful information.

The CAD drawing seems to show two sets of Tyvers ( not sure about the spelling of that )one set above the hearth restriction ( where I would expect ) and one below.