Leitinger wood gasifier

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#241

I think the restriction is closer to 9cm. So 3,5". I found the whole alubox is allso a preheater now :grinning:

At a normal idle the engine feeds just on offgas. The air inlet valve stays closed. When it stops offgasing, the charbed is too cool to give good gas. At least thats what l think.

Perhaps my new non return valve is allso partialy responcible. It has a heavyer flap thus needs a bit more vacuum to lift. Will try to dissasemble it for a test and see what happens.
I think the main difference betwen my and your system is your hayfilter.
First lll set the idle higher, then lll go for a longer drive. Perhaps the charbed didnt set as it shuld yet…

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#242

Don’t know what you have on your engine for an idle air control, but mine was doing what you say yours is. I drove with the left foot running the brake and the clutch and the right foot was always working the accelerator to keep it revved and running. I took my IAC off and cleaned the little pentle and the pocket it sits in with a little wire brush and now it seats and works like it is suppose to. TomC

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#243

Hi, Kristijan!
15.9.2016

First, clean your gasoline idle components; they may be sooty.
Trim the gasoline idle to work flawlessly!

…

You have to see the gas/air mixing fundamentals:

Availability decides what ratio the mix will contain.

You have a little “chamber” abowe the single throttle in a “T-mixer”.

The gasgenerator has an unrestricted access to this “chamber”.

At idle, mix consumption is very low.

When the air flap and the “gas plant” have equal flowresistances

you will get 50/50 mix. (volume-wise)

But the flow resistance of the gasplant can be postive or negative!

Only a few cm H2O turns the mixing ratio upside down!

…

After a full speed drive to stop and idle, the gas can
be eliminated of the nitrogen component. (no primary air intake)

This means that the gas becomes 2 times “richer”.

The mix can be 33% richer than normal,
provided the mix ratio stays the same 50/50.

As you see, this will not happen with a T-mixer!

…

On the other hand, at idle, the intake manifold will have a

vacuum of 500 — 700 cm H2O! ; 5m — 7m H2O!

Now, if you have a mixing pot between the intake manifold

and 2 ganged throttles, one for air, one for gas,

You will maintain equal flow resistaces for both gas and air,
independent of what the gasifier happens to do…

…

And on higher power out-take, you can use a manually operated
air flap ahead of the twin throat body in a traditional way.

You will have some of the benefits of two systems, with a little effort.

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#244

Hi, Kristijan!
15.9.2016

During the building you declaired, that your restriction plane is just point-welded with a few spots, and easily knocked free as needed!

Now, if this does not hold, add an extra plane leaning on the current one with screwable from abowe bolt-legs. (trimming)

Cut it in two parts to pass the nozzles and fit them together when in place.

It needs not to be perfectly tight; the main part of the “dirty” process is already done a bit higher.

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#245

Max,

as always, you meke sence.
The idle servo was bad for some time now. Got worse with woodgas thugh.

You have good memory! l can do what ever l want with it. But what do you soggest? Seting it higher or make it narrower?

l set the idle from 750 to 1200 rpm today. What a difference! Much nicer and longer idle.
Anyway, burned 2 hoppers today and it looks like the gas gods are starting to smile. I saw ash in the aspit for the first time today! So looks like the grate is in a better position. I used biger fuel. The charbed seems nice and loose.
The holes in performance l fill with a quick on/off to the petrol pump. A squirt of gasoline and the ride is smooth again.

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#246

Hi, Kristijan!
16.9.2016

Yes, higher RPM gives a bit of relief, but does not solv the fundamental problem described in mess. 243!

I think the gasgods are waiting for a decisive move to handle their product right!
…

But to get a better product, the oxidation volume has to be decreased.

Keep the current plane (mess. 244), and put an adjustable plane abowe it.

This will spare you of internal gasifier work.

Make 2 (two) identical 4–5mm thick SS plates, tightly scraping the firetube walls. Center hole diameter = 100mm.

Cut the plates exactly in half. Bolt the lower halves to the upper halves in 90 degrees horizontally when inside and in place. Bolt holes syncronized and bored outside, before assembling inside. Slight desyncronizing (45*) can help pressing and tightening to the wallsides…

This “packags” of 4 (four) halves needs additionally to have 4 (four) adjustable legs (bolts) so the height to the nozzles can be adjusted. SS or acid proof! As far out in the perphery as possible, but still turnable.

The trim (adjusting) bolts need to have the heads ~reasonably high abowe the new plane to give trim length.
They need corresponding nuts welded on the bottom side of this new plane.

Initial height = 65 mm from the nozzle centers.

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#247

Max,

l was thinking for a while what is the purpose of two plates cut in half. You are suggesting that becouse of the nozzles? If so, that isnt nessesery. If you look at post 33 the nozzles can be easyly removed or adjusted.

What if l just cut a 4cm long pice of 8.5cm pipe and weld it on top of the existing restriction plane? Sort of like Arvid showed on post 21. Thain l screw out the nozzles to achive the 60* slope and thats it.
But shuld the grate thain allso be set higher?

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#248

Maybe you have already experimented with bigger fuel? (less oxidation surface area). Works for me. Less work wood prepping. Some chunks as big as 2,5 - 3". I would never have thought this was possible in an 8" firetube, but it is :grin:
(of cource some are always a bit smaller)

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#249

Hi, Kristijan!
16.9.2016

2 half-circle plates + 2 half-circles turned 90 degrees makes a pattern which can be used for sqeesing the edges tight to the cylindrical walls with slightly unsyncronized boltholes
(45 degrees)

The height of a “loose” plane can be adjusted by turning the 4 legbolts. The 2+2 half-circle package is less prone to wrigle by thermal expansion and shrinking.
Less work inside the gasifier.

A welded tube is a welded tube, and a tube is a “bottleneck”.

The active cone dimensions are found on mess. 235.

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#250

JO,
Yes, l did. And it looks like this solved the too big oxidation zone (wich you have to if l remember right).
The gasifier now runs a bit hotter and consumes more fuel. But l ran out of dry hardwood so was burning bulkier chestnut. The change of drag in the hearth can now be seen on tha airmix walve. Much more open while driveing.

I was thinking JO what is the difference in our desighs that changes the performance of our gasifiers, since we have such a similar design. One is your hayfilter and two l just realized that l dont have a hopper condensor. That might be the reason why l have so much offgas! The steam doesent go to the condensate tank but trugh the charbed, giveing strong gas and cooling the charbed. Not much l can do about that thugh…

Max now l understand. Will drive for a few more hoppers and if that doesent work well, change some things.

Anyway, l emptied the gasifier today. No sign of ash in the reduction! What a relif. Char looks good and beans size. But still very litle sliped char eaven thugh l made the grate slots a bit biger. I think the platform cooshins the vibration of the road, thus less char is slipping.

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#251

That might be an important difference. Without checking I think I remember steam has 1800 times larger volume than liquid water. Not counting what the negative pressure adds.
On the other hand the cooler pulls H2O together again and should even that out. On the third hand you get additional water from the oxidation ??? And then there is the extra cooling effect??? Read somewhere there is no reduction going on below 650 C or something.
I don’t really know what’s what. I think it’s easier to just experiment and drive to try get a feel for what works best.

To me it seems we over all have very simular performance except for the off-gas. Who knows, I might have it too, only sucked up by my large volume.

About the small amount of char slipping. Isn’t that a good thing as long as you don’t get constipated ? I get only about a small shovel (1 - 2 L) from 300 km of driving.

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#252

Agree on everything. Althugh steam in the gas isnt such a oroblem, like you have sayd, the cooler shuld take it out, the problem is steam reacts endothermicaly with hot char, giveing very rich gas and cool charbed. It takes a few seconds so there is enough oxigen to heat it up again, and for the richer gas to come to the engine ad takeoffs, but l got used to hit the hybrid button for a second to eaven the hole.

The char not sliping a great thing! More char, more water can get hcracked meaning less gets in the gas. One kg of char one liter of water.
Well in that case we are about the same, l got about 1l of char after 300km. Was expecting a lot more!

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#253

Just got to 1000km of DOW today! Things run much better now. At this point lm not sure l realy want to change anything on the gasifier. Just use big fuel and thats it. There seems to be no slag or sliping char, the ash goes where it is suposed to go. Performance is good, althugh hybriding on crossroads is a must. Condensate is nice and clear, no soot or tar. I am waiting for the fiberglass fabric (found a dealer for the non sun shine let trugh stuff) other theings are more or less in order.
The alubox is insulated with rockwoll and tiday we went on a trip to a weather station near us, the gasifier was still hot after quite a few hours of standing still. No need for a relight.
I allso found out a guy lives about 100 km south of me that legaiysed a woodgas pickup, so lll pay him a visit some day now and report to you guys.
I allso experianced a puff in a hose for the first time today. My gas hose is lightly put on the T-mixer so in such a case it just blows apart. No harm done, exept l had to burn dyno to drive to a place l culd fix it.

The question, why does such puffs eaven hapoen? What triggers them?

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#254

What level was your feedstock at?

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#255

Hi All,
I used 1/4" rods, ends cut at 45 degrees. Top space is 5/8", bottom space 1/4" after a few stabs at dimensioning. I thought of using a 60 degree angle but thought I’d lose too much storage space. I also was using what I had, a 24" diam pressure tank that already had been cut to length (height). My unit is quite tall so I wanted to keep it shorter. I did have some blocks sticking to the wires so I installed a shaker on the outside and ran it on a timer, once every 15 min for 15 sec or so. Never had a blockage after that although I had a couple of blocks stick here and there. However my next unit will be a smaller diam with 60 degree slope.
If you want to see my build pics go to Small engines, click on “My first small engine run” and go to comment 153, June 2012.
Pepe

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#256

Congratulations to your 1000 km. Seems you got things tuned in.
I’ve never had any puffs that I know of, but I think they are more likely to happen when your timing is retarded or if some intake bildup happens to get stuck not allowing an inlet valve to shut tight.

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#257

Arvid l dont remember for sure but it wasnt empty.

Pepe, l use about the same pattern, but at a 60* slope. I thod l had bridgeing, but as it turnrd out, it wasnt the top that was problematic, but the bottom. Looks like when l hit a bump the constipated reduction got a bit loose. No problems now.

JO, the timeing l didnt touch, althugh l wuld realy like to, but the leaking valve is possible.

A nother problem showed up thugh… it seems the engine consumes fuel eaven with fuel pump off. Sure, l burn some while startup and hybrid, but it seems to much. looks like the injectors still let fuel trugh becouse of high vacuum. So l was thinking to put a swich on the injectors. That way they shuld always be closed. The question now is culd l hook all on one swich or shuld l make 4 swiches? Any thods?

#258

I believe Arvid is thinking of hopper puffs. I thought you meant intake puffs.

I know of only one person who has discovered fuel syphoning and that was Herb Hartman on his Caddy. I think that was tbi. It’s unlikely (but not impossible) on your mpfi.
If it was me I would experiment with putting a small valve on the fuel line before cutting into any wires.

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#259

Yes I was Jo.

You have to have oxygen to have a puff of any kind… personally I’d call that a back fire if it happened after the grate.

I’m not a fan of that flex tube at all… they can develop pin holes

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#260

l dont realy undertand this system. There are 3 hoses goeing from the fuel tank. one for fuel, second for vapor suction (?) but the third? There is allso a container trugh wich one of the hoses go. Culd someone explayn how does this mpfi work? I got the basics but things get complicated.

JO you use a valve sistem?