Great Job so far Brian G.!!
You haven't said what fuel type you intend to use. This will make a difference with how you configure your reduction tube/air jets/grate height. The default GEK has a 6" high reduction cone with the"ash" grate set 1.5" below. This results in an inverted cone shaped column of char/charcoal 7.5" high to create the thermal/chemical reduction area ( all of the produced gases must pas through this area). You could probably used a piece of 3-3 1/2" SS exhaust pipe of a late model diesel PU to make this. You Will need a grate to hold the charcoal up and out of the ash that will settle to the bottom. It Will have to be rotatable or shake able to sift the ash through the charcoal.
Keep it up. Looking real good. Steve Unruh

Thanks Steve.

I intend on using pine wood for fuel. Pine is quite abundant in the national forest and with a $30 permit from the forest service I can cut 3 cords of timber. I haven't figured out yet how fine it needs to be cut though. I can chop down to 1" blocks fairly easily, but having seen that many people are using wood pellets it had me thinking of trying to shred it in some fashion. Again... I haven't thought that far into the future yet.

I have a 3" x 8" reduction area, though it has no taper. It can be seen in the background of my picture with the fan above. As for the grate, thus far I have not built one however I'm going to get to working on it soon. Since the reduction area is a 3" diameter, I have it sitting ~4" below the center line of the nozzles. Also, my nozzles are on a diameter of ~6" and I plan on getting the grate to sit ~4" below the bottom of the reduction area. All those diameters are loosely based upon Table 5-2 "Imbert Nozzle and Hearth Dimensions" in the Handbook of Biomass Downdraft Gasifier Engine Systems.


Thanks again!
--brian

brian wins the prize for most produced with the least resources. so i'm going to send him the new stainless sheet reduction bell and tar fence. it only seems fair . . .

his currently straight pipe one will be really senstive to flow rate. even with the cast 3" top 4" bottom bells, they are somewhat easy to overpull. you can tell when you are overpulling with the long TC probe that comes with the kit. poke it in under the reuduction bell. if you see the temp go over 700C, you are starting to pull your redution down onto the grate, as it is not fiinishing in the bell. if you really overpull, the temp will cliimb further. you can also see this by your paint burning off the gas cowling at the grate level.

(continued)

remember, the notion with the bell taper is that the taper outwards compensates for the reduced cross-sectional area as the fuel size is reducing. the goal seems to be to keep the velocity about constant, while the porous structure of the pathway is reducing in area. thus your flow potential / pressure drop through the bed remains about the same across all parts of it.

my current best guess on the taper that achieves this is a 1:2 taper, over a length twice that of the top constriction diameter. i think historic bells are too open, and thus result in flow favoring the walls, losing more heat than necessary. the fluidyne straight tube i believe is too far in the other direction, and thus has little potential for flow rate variation.

we've built a bunch of different proportioned bells to test this. but have yet to get to the testing.

j

brian, if you are pulling 3/4-1" of h2o vac, you have plenty of vac for a first one. or to clarify, if that is the vac after the reactor, adn before the filter, then you are ok. actually, i think it might be a bit high, given the straight reduction tube you are using. those are easy to overpull. they have a narrow band of proper flow it seems. you might have anemic gas as you are overpulling and reduction is not finishing. or it could be a ton of other things. you are starting with a charcoal prefill, right?

and yes, the white is steam. you always get this on start up as the moisture is being boiled out of the charcoal. then you will continue to get it if you fuel is too moist. anythign other than very dry fuel will greatly complicate your early runs. new pellets straight out of a new bag will work, but you will likely get quite a bit of tar. such is the usual experience. but you will get gas.

to make things easier, you can also start it by putting a cup or so of diesel fuel on the charcoal prefill stack. light this, let it get glowing, then fill biomass on top. the diesel will continue to vaporize off for a bit, which will help your flame strength in the beginning, and better transition into your regular gas. you can see this very clearly by the color of the flame.

jim

to clarify, the diesel vaporizing off is into your gas stream, not out the top of the reactor. this is the cheating method of starting. you put enough liquid fuel on the fuel stack that as it heats up it just vaporizes and goes out your gas out. a very crude vapor carburetor. yes, a bit embarassing. but it works nearly everytime.

just don't use gasoline. the whoosh on starting is more than you want. alcohols can be similar. diesel or kerosene are nice. store bought charcoal lighter would work too. that really what its doing too. it vaporizes with heat and then burns, creating more heat until proper pyrolysis begins, and then those gases burn. so using it to light a gasifier is nearly a label correct application!

while doing this, point out to the newbies gathered around your fire, how vaporizing is different pyrolysis, though the products of both are burable gasses. this is the core of understanding the difference between the combustion of liquids and the combustion of solid biomass. two very different routes. but both lead to gas.

Hi I live in denver, I have lots of metal working friends and spare motors and such - how are you doing, could I help? I would love to see one of these things working.

Hi, I live in Fraser (next door to Winter Park) and I bought a GEK 3 from AllPowerLabs. I have been working on assembling it, and then am going to use it to power my 1974 VW Thing. I can hardly wait to see this one of these things working too. Making enough right size charcoal granules for the filter bed is the last major thing on my list, plus a details list. With any luck, I might fire it this week!
Frank