Basic Gasifier Build

[PyroJoe]

Reed Valves? moving parts? blasphemy!

Just picking. Thanks for the good suggestions.

The first few runs with the engine will tell more of the related parameters.

After running a few calcs and seeing the result, there is a small chance the gasifier may start weakly pulsing on its own(with a reasonable sized draft pipe).

Either way, the good news is the most friable ash/ember material should be nearest the grate, so whatever (engine) backflow pulse available should hit that area first.

My hunch is that the fuel in the flame tube will muffle the backflow pulse before reaching the inlet pipe. In a perfect world one could almost make the flame tube into a Bodine Reflector(fig.3). Wish someone could explain Bodines lambda notations. Looks like the single tic mark is 1/2 lambda, and the double tic mark maybe a 1/4 lambda?

One background problem is the (engine intake) venturi action for such a large secondary source (1.2" I.D. fuel pipe). In some preliminary pipe"T" testing I notice when the main intake flow starts pulling the secondary flow into the stream, the primary intake air flow is reduced. She will be a "tight rope walk" adjusting the parameters.

Just have to see how it goes.

[PyroJoe]

Right on schedule,
Cut & fit lower plate, installed tabs, cut pass through on lid. Tab fitted to flame tube. Reasonably happy with the results. The thin walled flame tube stiffend considerably when installed through the lid and lower plate. Pictures to be posted tomorrow.

[PyroJoe]

Here is the latest, after the welding is finished will paint with some high temp. paint. Red or black?

vturbine, does your gasifier preheat the inflow air?

[PyroJoe]

Here is an idea for pre-heating the inflow air if needed. Involves running the intake pipe through the cap and into the bottom of the flame tube. Adds about another 5" of convection/draft length, but does take away from the cross section area of the lower flame tube.

[vturbine]

Here is the latest, after the welding is finished will paint with some high temp. paint. Red or black?

vturbine, does your gasifier preheat the inflow air?

Looking good!

Joe, I haven't built a gassifier yet. My furnaces and burners are clean heat producers, not gassifiers. The info I gave you in the other thread, though, has all the information it takes for a practical home-built design for a non-retort gassifier. Those are: the Gengassidan website site and the Pope's gassifier website referenced in the other thread.

To answer your question from a guessing point of view, I don't think preheating the air will make a big difference. Air is denser when colder, and therefore provides more oxygen per unit volume. On the other hand, in those other designs, air is also preheated, anyway, and your vertical heated inlet may assist with draft. So, just try it and see!

ps. Your use of propane cylinders is similar to what I have imagined doing -- using the scrounged condemned 40 lb cylinder the originally contained the gas I used to test out the Grim draft and turbine. It's empty now and ready for other uses. I'll be unscrewing the valve and filling it with water before cutting. But I have a few other things I want to do before working on wood gas generators. Perhaps you'll have a workable design before I have to think about it!

[PyroJoe]

Probably be best to test this inlet design first, before cutting a hole in the side of the housing and flame tube. Easy to change the cap and do minor surgery later if needed.

I think this could be built with a single propane tank, I just had two of them lying around, one already had been cut. If she works and functions well, will post as built dimensions. Many scrap metal yards have old tanks like these to be had at reasonable prices. The important factor is as you have stated, to fill with something inert to avoid a nasty bang.

[PyroJoe]

Pulled and repaired water well pump this weekend. Will try to make up time over the week. Found a nice coupler to fit the lower cap, should make adjustments to the intake pipe much easier.

[PyroJoe]

Here are some shots of the coupler and the lower cap. The coupler is interesting in that it has a constant outside diameter. Cut a hole in the lower cap and slipped the coupler halfway through (not welded at time of picture). This will allow quick changes to the intake pipe length going up into the flame tube. Also allows quick changes of the exterior intake pipe lengths.

[PyroJoe]

A little set back this morning, was adjusting the intake pipe to center better in the flame tube when heard a tale tell "tink". the weld holding the coupler to the cap had failed. Sad, sad, as that weld had passed the water leak test . The cap is cast, so re-welded with a wider bead on the cast side. Some casts hold a weld better than others, I would say this is somewhat a medium type, can hold a weld but not withstand significant mechanical stress/strain.

Another leak test and welding some pin holes shut, and back on track. After some careful measuring, cut the internal intake pipe to 4" inside the flame tube.

Cut and welded the exhaust pipe. Another leak test, weld more pin holes, leak tested good.

Still short on ash supply, sometime this week will need to have a mesquite cook-off.

After some review there is a much easier solution for a grate system. Won't even have to create a hole through the housing, it just slips over the intake pipe and can be agitated by using a handle welded to the coupler.

The fuel charge above the intake pipe is approx 18", so I can use a fuel charge of either 3 charges of 6" height or 2 at a 9" height. Think the 6" charges would probably be best. If I make the heavy plunger 6" tall, I can tell by the plunger depth when the next charge needs to be added. At re-charge there will be nearly 4 charges in process.

Still have to pour the plunger, will use a piece of pipe a little less than the flame tube diameter (pipe capped on the bottom) and pour the 6" length with heavy metal.

(yes, thats a soccer ball in the background to the right. They call the grass "coastal" in this region, it is currently growing past the 30" mark. Just a few weeks ago the field appeared lifeless. Will soon be enlisting the help of Barbados black bellies to help with the over production of bio-mass )

[PyroJoe]

Here is the basic idea of the simplified grate system. It slides over the intake pipe and a slot in the grate fits a weld nub on the intake pipe. rotating the cap will agitate the grate.
(this was done in autocad with shademode set to conceptual.....text added in paintbrush)

[Viv]

Hi Mate

Coming along nicely now, cant wait to hear the results of your first burn

Viv

[PyroJoe]

Thanks Viv,
No tellin' what the first burn has in store, figure it will be a fiery run away or a slow smoke and smolder. Maybe some fluctuations between until things are adjusted.

[PyroJoe]

Plunger constructed, weighing in at 7.5 lbs. The steel cylinder is only half full of lead. Another Pb pour would bring it up to 15 lbs. Using as is for initial runs. Slides down the flame tube with almost no resistance.

[PyroJoe]

Didn't get a picture of the grate before install, but is reasonably represented by the illustration. Here is a shot down the Flame Tube showing the grate. Not the best of alignments. Maybe try laser alignment to the tenthousandths on the next build.

[PyroJoe]

Neighbors burning brush piles this weekend, was able to harvest plenty of ash. Finished up late last night, still need a handle for agitating the grate. No runs as of yet. Getting close.