Hi guys, I’m Ron from Australia. Fantastic site this is, after a lot of reading I’ve been bitten by the woodgas bug again! I built one ten years ago with little idea of what I was doing and only fired it up last week knowing now that the dimensions are way off, but it still held a flare for an hour & 40 minutes using poor quality wood and no filter at all. That was exciting for me haha.
Now I’m in the process of learning from that one to build something better but I’m stuck on the hearth side of things. I’m building it to suit a 4 litre 6 cylinder ford falcon ute so… this is my question: with the imbert dimensions available on this site it mentioned matching dimensions with horse power but this Ute is 240hp on petrol (obviously much less on wood) I’m just not sure which figure to aim for, like what flow rate would best suit that engine, also the restrictor sizes seem much larger than other designs I’ve been reading about. I’m eager to get out with the grinder and welder but decided to cave and ask for a little help, it’s easy to get a little lost with so much information available. Any guidance would be much appreciated thanks
Welcome Ron, My suggestion to every one, is to join the premium side of the site to get the full experience. That way you can see all our builds, and ask about all the details of WK systems, which are better suited for mobile wood gas. You will save many times over in wasted time,and materials over the superscription cost. Again welcome.
Welcome Ron,
What Al and Pepe said. A gasifier about the size of a Dakota WK should fit your needs. Maybe slightly smaller restriction to begin with, to be on the safe side.
Welcome Ron. I’m one of the few Imbert guys on here. I don’t know where you got the idea that the dimensions are based on horsepower— there is hp and there is hp. There is hp in farm tractors which is powertake off. Then there is hp in automobiles which some day I will tell you what all we had to do to get a figure for a car engine. So lets forget that idea.
I will have to go back in my notes to get the exact table you need. Ok I opened my notes from years ago and first off came to a pamphlet that is in DOW’s library, FAO72. From my notes, page 61 has a drawing of a Imbert type gasifier with reference to the dimensions. Then through out the pamphlet are calculations for most pertinent dimensions. Most dimensions are based on the displacement of the engine and the anticipated RPM to be run at. Beware that many times the dimensions are in metrics-- kind of mind boggling if you aren’t use to it.
Another good book is Handbook of Biomass Downdraft Gasifier Engine Systems by Thomas Reed
Just for quick reference, I have a 4.3 Liter engine running 2000 rpm. I had 5 nozzles, the diameter of the nozzle tips was 9 inches, the restriction is 4 3/4 inch below the nozzle tips, and the restriction is 4 1/2 inch dia, , the grate is 4 inch below the restriction. My notes are not clear on the nozzle orifices, I did a lot of changing around. Hope this helps TomC
Thanks Tom that does help, the chart that I was looking at didn’t mention engine capacity hence the confusion, I’ll attach a pic. I will definitely have a look through the articles that you suggested also being Aussie we are used to jumping between metric and imperial as both are commonly used. Even though we went metric in the early 70’s. This engine of mine is torque and happy at low revs so 2000rpm would be it’s average cruising revs to use while getting the sizing close as I can. I do like to experiment and I sure don’t expect to get it right first go, cheers
G’day Ron , and welcome back to the world of wood and charcoal , really hope you manage to get your ute on wood gas real soon .
PS hope your in Victoria
Dave
Thanks Richard, that good to hear it was a success. I did notice the gas output, so if I calculated the total volume an engine would inhale at max desired rpm would I divide that in half assuming the air gas ratio would be around 1:1?
Ron, the factor of two–wood gas to air only comes into play just before it enters the manifold. You do have to remember on a four cycle engine, it pumps air on one half the revolutions, the other rev’s it is compressing, and power strokes. I’m trying to say in calculating the volume of air going through the gasifier divide the rpm by 2.
I might mention that two years ago I drove my truck down to Argos. Iast year I was finishing up a rebuild for the trip again when I burned my shop up. I spent all year rebuilding my shop and am trying to get my truck ready for this year. TomC
Thats an unfortunate set back with your shop, and yes I half my numbers when working out total volume allowing for the 4 stroke cycle. So a 4 litre engine @ 3000rpm will take in 360 cubic meters per hour total volume (air+fuel)
So at a 1:1 ratio that’s 180 cm/hour and still below the max output on the chart. Or 120 cm/hour @ 2000rpm so the chart gives an expected hp? Even though it’s a 240hp engine the flow rates seem to match. Even at a 700rpm idle it works out to 42 cm/hour @ 1:1 ratio which is within the limits, I think I’m on the right track with it but unless I’m missing something, cheers
I come up with 129.6 cubic meters per hour for a 4l engine at 3000 rpm. What size does it need to be.? That’s more math than I can do tonight… I will add that’s using max gasman math.
Hi Ron , pleased to hear your close but if its a race you want your gonna win hands down i’m afraid as i live up in the hills on Mount Dandenong and so will struggle to get anywhere on wood gas, apart from downhill of course its getting back up that would be my problem , but give me a shout if your ever stuck for items to use in your builds as i have a friend with a scrap yard that would also like to see you on the road .
Hi mate, with some more reading I’ve realised that with the maths you used your 129.6 is exactly 72% of my 180.
That 72% is to allow for real world cylinder filling. I learned that from finding the calculations on Dutch johns site so thanks for the lead! Always learning
That sounds great dave cheers! I go to pick a part quite a bit, that would be sort of near you. My local scrap dealer is about to close down he is getting too old for it so I’d love to find another to sort through! There used to be a good one at mt Evelyn but I think the council put a stop to the public sales side of it. When I get to building the cooler I will definitely like to see what he has, I’ve already put a large hay filter together. Thanks
Hi Ron , yes the council stopped Brian selling from his yard to the public , but if you were to contact me letting me know when you were down this way we can exchange numbers and meet up at the yard , it is of course very hit and miss as to what is available as nearly everything gets weighed in and off to china most weeks now days , although the more interesting bits nearly always find there way into the shed over the road for when we get the time to do something with it .
Dave
I was about to propose DJs site, but you already found it. It houses all the math you need. You can calculate any dimension gesifier with his formulas.
Ron, you’re probably already aware. Just a quick reminder.
I remember Wayne once mentioned making those gasifier calculations is like aiming your gun using a microscope
The numbers are all about max output. Still, the most important thing is to make the gasifier small enough not to make tar at idle. You just have to accept what ever upper limit you get. At some point you will have to back off and let go of the pedal not to overheat the gasifier.
I run a 2000 kg 4 cyl vehicle. 120 hp on gasoline. Whenever going fast I add some gasoline. I fueled up last fall going for inspection. About 5,000 km later the guage still shows 60%.
What I’m trying to say is that 90% of the time we’re not using the available performance anyway. Since a gasifier probably can’t be built that can satisfy all our needs, the best we can do is to make it cover the low end.
I know, I’m only repeating what Wayne has been telling us for years, but it’s still worth mentioning now and then.
That’s very good advice thank you, that does make a lot of sense to have the gasifier well in its range at idle so Im aiming to make the nozzles and restrictor adjustable with in that ballpark but undersized for your reason, hearing from others experiences is the best info to get
its getting back up that would be my problem , but give me a shout if your ever stuck for items to use in your builds as i have a friend with a scrap yard that would also like to see you on the road .