Oh Steve, I have been waiting for you to chime in. I thought you would have a definitive answer to my problem. I have just wasted about 3 hours of good shop time running through various computation, but nothing that seems real to me based on my previous experience. I have one more in mind to make but I’ll do it tonight while TV is blocked out with political BS. TomC
3 Likes
Tom, I calculated 6% of your restriction area devided by 10 nozzles and came up with 9.3 mm nozzle dia. Seems reasonable to me.
4 Likes
Thank you JOl I remembered you said 8% also and that is where I started. I got diameter equals .424 inches. Your 9.3 I think comes out to diameter of .37 inches. Both sound possible and I believe you said the 8% was for small engines so your .37 inches sounds good. That was the calculation I referred to when I said I would calculate one more after working in the shop Thank you again for taking the time. I know a meter is about a yard plus. but as I calculate I have no idea what the numbers are saying until I get to the end and go to a program that converts metric to what ever my system is called — besides confusing. Possible pictures to follow. TomC
3 Likes
New Imbert build ( with Max’s suggestions )
The fire tube nozzles not welded in yet and the back end will be cut off and the entrance to the orfice belled before air shroud is installed.
Grate with angle iron bars to hold ash and two tabs so the grate can be removed.
Bottom side of the reduction bell with tabs to hold the removable grate ( why I have a removable grate I don’t know, but the man said-- I think )
The space between the two end rings will be filled with ash all around top to bottom of the reduction bell. The holes will add ash to the area when running.
Reduction bell with grate installed.
Reduction bell installed in fire tube ( restriction goes on top of reduction bell and it will be 4.5 inches from the nozzles.)
TomC
16 Likes
Wow Tom this looks so nice.
Are your nozzles removeable?
A nother question is on the char slope, its hard to say off a picture, but it seems you have the imaginary angle from nozzle tip to restriction of less thain 60°. Am l correct?
1 Like
I like it Tom, looking forward to following the build of your gasifier, and learn about the Imbert style. I like how the V grate bars can hold ash to help insulate from the heat.
Bob
3 Likes
Looking good Tom!
A couple of questions though.
What’s the bell inner dia?
What purpose does the upper end ring serve?
3 Likes
Looking good
I like that the nozzles could be changed for different sizes to optimize
I welded 5/8" nuts on the inside of the fire tube and have seen no erosion of the threads after 3000 miles
5 Likes
Kristijan; [quote=“KristijanL, post:486, topic:1225”]
Are your nozzles removeable?
[/quote]
Yes The nuts get welded to the outside of the fire tube and the nozzles screw into the nuts— I will probably have to change the orfice in the nozzles before I am done.[quote=“KristijanL, post:486, topic:1225”]
A nother question is on the char slope,
[/quote]
The reduction bell is just dropped in and not really at the height it will be in the finished product. There will be a restriction laying on top of the bell which will also change the angle— I go by the nozzle circle and restriction diameter in the book. Not necessarily the angle alone. TomC
6 Likes
Good morning JO; [quote=“JO_Olsson, post:488, topic:1225”]
What’s the bell inner dia?
[/quote]
5.5 inches. I built it a couple of years ago when Max was working with me and how the dimensions of it came to be evades me right now.
Not really sure it was all that necessary. Without it, the char/ash would have filled that space, except if the restriction ring was full diameter it would have held the char up out of the insulation area around the reduction bell. The only thing I understood for sure is, it needs a good insulation around the reduction bell to hold as much heat as long as possible. TomC
1 Like
It’s not up to me but why not just put the restriction on top of the bell without the upper ring. Make the top of the bell accept a loose fit restriction that can be changed out. Not only between wide or narrow but also tall - short. That will allow you to adjust the oxidation/reduction volume ratio.
Without the upper ring the space outside the bell will be easy to fill with ash and will insulate the reduction even better. Less heat will be conducted towards the outer tube.
I’m glad you decided to go ahead with a new build. Keep the pictures coming. You know we love pictures.
4 Likes
JO you asked the diameter of the reduction bell. Could that have been decided based on a theory you put forth about the diameter of a ball in the reduction zone should be 1/3 that of the oxidation zone? ( maybe volume instead of diameter).
The top plate on the reduction bell? With out that, I would have had to make a disk the diameter of the fire tube with a recess in the center to hold a replaceable restriction ring. That disk would have covered the entire ash area thus stopping char/ash from filling in. With this design, I have the slots in the reduction bell below the upper ring where ash can come in. This could have been done with a disk that you have suggested. I will have a replaceable restriction that can be changed out and raise if necessary. For lowering the restriction, I have left myself a little room but any more than that and I will have to change the pins that hold the reduction tube up in the fire tube and lower the entire reduction bell including the top ring. The restriction stays on top of that ring. TomC
3 Likes
Tom, it looks like you are set this gasifier up to be able to really do some fine tuneing if it is needed. Good job on thinking this all out.
Is this unit going to have preheated air from the muffler of the truck?
Are you going to hot gas filter the gas with a mantle filter setup and use slyclone filters?
What is the spacing measurements in the grate?
Bob
3 Likes
Yes, 1/3 by volume. That was something I read by DJ. I don’t remember where but might be a good number to aim for.
With your adjustment possibilities that ratio can be fine tuned. Also easily compensated for later on by fuel size.
Maybe something I don’t understand. To me it seems a small disk on top of the bell to hold the restriction could be an inch or so shy from the firetube wall. Plenty of room for ash to fall down. I even prefilled/stuffed that void with white ash from start.
3 Likes
Nice job so far Tom. What is the spacing between your grate angles? How did you make those nozzles? Stainless bolts with holes drilled through?"
2 Likes
Bob; yes it should be versatile. The hard part will be to decide to adjust the nozzles, the restriction, the restriction height, or wood size. My old one was flared many times along with a second gasifier I had built and I kept switch things, mostly nozzles, until the one gave the best gas. That one went in the truck.
I am no longer a fan of preheat. My present preheater weighs about 100 lb and I am out to put the truck on a diet, so the preheat is going. It was made out of about 15 ft of 3" exhaust pipe formed and covered with 4" pipe to make a counter flow heat exchanger.
I had a shop roll me a new cyclone filter so of course I will use that. Thinking about a bag filter and a box around the bag and cyclone for heating the gas going up to the engine. Key word— thinking.
The bars are spaced 3/8 th’s apart. I am going for more ash and less char. No room for slip char so this may be problematic. My old grate was 3/8 th rebar spaced about 3/8 apart and it worked although there was a little room for slip char. TomC
5 Likes
Hi JO. That 1/3 theory looks pretty good but I am not going to actually calculate it because they are not round balls, but more elliptical shape. Just eyeballing it and I feel good.
I am really bad about being consistent on my wood size. With my chunkier if I’m chunking a 1 1/2 in. limb it will probably be about 3 in. long If I am chunking 3 in limbs it is 2 in long and I feed them all in at the same time.
That top disk. Making the disk like you mention, is a problem because the center opening of the reduction bell is 5 1/2 inches and the restriction will be at least 4 3/4 in so no room for a complete restriction ring recess in the top disk. I did think of making the top disk go out to the fire tube with 4 long openings along the wall. The way I did it I think was what Max had suggested with those slots in the top of the reduction bell. I will be able to fill the volume around the reduction bell on start up through those slots. The book says those slots will keep the area full. TomC
4 Likes
Tom, when you hit the magic grate height position there will be no problem with ash plugging. I had problemms with that but, the grate plugged big time after just about 50 miles, then l moved the grate about half a inch up and no proublems for at least 2000 miles now. Its amazeing how much difference just half an inch does.
The 3/8" looks good grate spaceing.
Will you make a hot or cold sack filter? I made both, l am a big fan of them.
Cold sack filter requires more surface (becouse the water in the gas makes a tight cake on the sack, this allso adds to better filtration). But the hot filter does seem to be self cleaning, the dust falls off when enough is collected.
Allso, a hot filter keeps the cooler clean. Thats a big plus
7 Likes
Thanks for the tip on the grate. I have most everything moveable, but I’m not sure, I understand things as well as you and JO where you know to adjust the grate, or make the reduction volume smaller or change wood size. The nozzle orfice size and the restriction dia. will be adjustable without removing the hopper but anything else will require cleaning out the hopper and removing it. I HATE doing that.
The “PLAN” is for the gas to come out of the gasifier, then through a cyclone, into a bag filter, and then to the cooling rails. After the cooling rails and hay filter, the gas will go into a box around the cyclone and bag filter, to pick up some heat and lower the humidity of the gas. Then on up to the engine for possibly a paper filter. I have been running for a couple of years now with only a cyclone and hay filter and I haven’t really had a problem with soot, but if I can eliminate it and moisture in the pipe to the engine— I might – heavy on the “might” do this. TomC
4 Likes
Hi, Tom!
10. of November 2016
Eaven if my malfunctioning “conveyor-belt” does not reach you,
I want to stop malinformation to be put to others:
A paperfilter for woodgas should never be put in a motorcompartment!
It has to be placed in the same envelope as the cyclone, in order to be
warm and kept dry by reheated gas, before streamed through it at all,
at startups!
After that, if the gas again goes through cold tubes to the motorcompartment,
no damage will happen to the filter!
5 Likes