Peter,
Yet another option… Make a temporary cooler- after the cyclone, a long pipe will do, you just want to get the temp low enough to keep from melting down a central vac fan,.
a shop vac will work if the gas does NOT flow past he brushes
Hooked up to a dimmer switch, and using Manometer you can find where where it makes gas or doesn’t 
I think it will.TerryL
Here is a picture of an ejector that I built with pipe from the hardware store… it pulls pretty good for what I use it for (a pellet fired unit). There is a piece of 1/4" copper tubing that goes from the back of the elbow to where the 3/4" pipe starts. I used a manometer on a plug at the bottom of the 2" elbow to tell me how long to make the copper tube on the inside. I trimmed the copper tubing until I saw the vacuum start to decrease.
Another area I have wanted to explore is the use of an “air amplifier” as an ejector… it is based on the Coanda effect where the compressed air is fed around the perimeter of the pipe rather than the center. Anyways, these things are precision made and pricey, and I have not figured out how to make one with pipe fittings, so I am still using the Venturi effect and the good old ejector.
I added another picture because I have swapped some parts around. The second picture is what I am using today…
what were you running in it for fuel?
Terry, Good idea, but i am getting water in the cyclone. I don’t think anything downstream will be the cure. From talking to all of you guys, i think the problems are related to the gasifier temperature.
Thanks, Peter
Gary, How much air pressure must you maintain to operate your ejector?
Peter
Hi Arvid, I was running dried oak chunks cut & broken up from 4x4 blocking. Was wondering if i should use kiln dried framing lumber for my next test. I do have an unlimited supply of new framing lumber cut offs.
Peter
Peter, I built an air ejector and it worked fine on my 1st FEMA fireup for a while. However towards the 2 hour mark I noticed a decrease in air velocity and started losing my flare so I cranked up the pressure gradually getting up to 60 or more psi with little effect on increasing the flare velocity. HUH???
As usual I did a tear down to ferret out the problem(I’ve got pics if I can figure out how to download to the site, If not I’ll try to email them to you. I found the ejector was clogging up with FEMA tar creating turbulence and destroying pull (lift, if you’re a pilot). That was before I had a blower fan built, but I reasoned the fan wasn’t going to fare much better with an open top 6" fire tube downdraft FEMA. That’s when I started building my fluidyne gasifier.
My advice in your present stage is to continue using the blower until you get a clean gas tar free gas.
Pepe
There is a 1/16" hole drilled in the 1/2" copper cross piece that the air is fed into ( it can be seen if you look close). This high velocity air stream creates a very low pressure area that normal ambient air pressure( high air pressure relatively speaking) pushes the air through the system. Good old Bernoulli effect.
The gunk build up is like ice on a wing surface and it destroys lift (pull).
Pete, Kiln dried lumber still has about 6 to 15 % moisture content( depending on humidity, stored inside or out, air temp, etc) and being soft wood does not have the BTU per pound value that dried hardwood has. Softwood will however produce a good gas. I’m not sure if more tars are associated with soft wood, I haven’t used it in a gasifier yet. My preference is hardwood. I haven’t run an ICE yet but I’m soooo close. I just had to fix all my little problems before I tarred up the valve train, etc in my almost sacrificial, 8 HP, B&S, elec start snow blower. Pepe
Hi Pepe, just a note about the hardwood / softwood thing. Hardwood is denser than softwood, but at the same moisture level they both have the same BTUs per pound. A pound of softwood takes up more room than a pound of hardwood. You will get less distance out of a hopper full of softwood, but you are using the same pounds per mile. As far as tar goes, I’ve always heard that pine has tar in it and to avoid it for stoves etc. but that seems to be unfounded. Wayne runs almost exclusively pine, heating his house and running the trucks. Never a tar/creosote issue. He can run any species, even tried some paulownia wood recently, which did great.
Pepe, Thanks for the pictures. You are right, i think that i will stick with the fan for now. Too many changes at once ----- tempting, but not good for learning.
Peter
Peter,
I do think you getting anywhere near the velocity you need to make gas, The water in the cyclone in mostly caused by the low temp you are getting as a result of the low velocity.
You can read this, It should make it clear for ya.
http://www.driveonwood.com/sites/default/files/pdf/SuperficialVelocity.pdf--Superficial%20Velocity.pdf
To repeat the essentials…
It’s an Imbert… You must have…
A full char bed - Grate overflowing with it, Surrounding area as well. There are pictures showing Char up around the reduction bell! Good dry, clean, and of the wood species you are going to run is best. Otherwise store bought Natural Charcoal… Not Briquettes will work.
Dry wood 20% moisture or less
No Leaks.
Velocity… Gotta have it. Just like jn Cubic Inches, no substitute.
Without it ya got yourself a Meat Smoker - Jungle Fogger.
Once you get the suction thing worked out, try it like it is.
I think you will be surprised.
There are things I would look at tweeking but not before doing the above
Have fun
TerryL
Chris, Whereas i have a supply of framing lumber, do you see any problems associated with dialing my unit in on this fuel?
Peter C
Terry, Your advise is well taken ------ will do !! Headed for the shop to start modifications.
Thanks, Peter
Peter, if you want to try using compressed air to evacuate the gas, here are the measurements for the ejector setup I have been using. I hit it with 10-20 PSI, but I think the SCFM has more to do with the performance because it works on the VOLUME of air being moved. The PSI it just a measurement of the air that does not comfortably fit through the 1/4" copper tube. With 10 PSI, it will draw several inches of water.
Hi Gary, That looks like a good idea. I think i will experiment with it and compare the performance to my fan. May as well try everything!!
Thanks Peter
The only “unusual” part to make is the 3/4" fitting that needs to be tapped about half way on the inside using a 3/8 NPT tap. Since I have the tap, I started with a 3/4" plug and drilled it through, then tapped both sides of the hole so I could screw in the air fitting on the outside and the brass to 1/4 copper on the inside. The black junk on the copprt tube is tar that I could not easily scrape off. Tar will collect on the outside of the copper tube, but the end should not block or stop up unless things are really bad.
Gary, no problem with the tapping. What did you use for a flare nozzle?
Thanks Peter
Its 1-1/2" pipe, but you could use 2" or larger. the silver thingy is a hose clamp on it to hold a thermocouple for measuring gas temperature
Thanks Gary
Peter