Leitinger wood gasifier

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#923

Kristijan, you’re having way too much fun while I’m getting tortured at work.
Ha, I couldn’t help laughing picturing you as the mad scientist in “Back to the future” when I read you were looking down the hopper while reving the engine :smile:

A couple of things crossed my mind:

Max ones quoted a scientific report from the 30s in Germany: “In theory 37% of the woodgas heat leaving the gasifier is possible to exchange into the incoming air”. This should give a hint on the volume ratio. Differences in molecular masses of course not taken into account. BUT, what really offsets the equation is the moisture in the wood. Making steam and force it through the charbed makes the woodgas volume skyrocket until reaching the cooler.
Wayne summarised things years ago: “There are so many parameters”.

Volume and heat again:
Imbert charts are made for none or very mild preheat. With a reasonable preheat we should be able to at least double the nozzle csa. I know my nozzles are a bit tight. Pulling hard on the gasifier the vacuum ratio should increase slightly due to the intense heat in the charbed. Mine is doing the opposite. I belive tight nozzles to be the reason.

So this boils down to what we should aim for:
Preheat, big nozzles, condencing hopper…
… in short a WK gasifier :smile:

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#924

Hi, Kristijan!
3.4.2017

I assume you are now using manual gas mix setting?
If you did not reset the mix going from

Imbert to FEMA (lid open) and backflap + nozzles bypassed, you have had

a very different mixture, when you “compared” gasification modes!!!

If so, you have to redo the comparation!

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#925

Haha Jan, lets reverse that title; Future back from the past!

lll make a video (again :grinning:). Its so interasting. All the surface of the char gets the same amount of oxigen, but the part above the restriction is the onlyone that gloes almost white hot. Shows why is there a restriction in the first place.

My calculation was based on dry wood to dry gas. Ofcorse, realisticly there are so many parameters :wink:

WOW! l did some more math. A volume of ambient air doubles its volume if heated to 300c!!! Time to drill the nozzles. Thanks for the eyeopener!

Max, Yes, l did change the a/f ratio but culdnt duplicate the resaults from FEMA.

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#926

Has someone ever measured the temp of preheated air? Any guess?

#927

I think Carl ones measured his WK around 1000 F (500+ C). But that’s massive WK preheat. Just a WAG on mine is 300 C.

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#928

Hi, Kristijan!
3.4.2017

“Minor” thing, but no cool air flow in the hearth mantel will increase the wall temperature = less loss sideways.

The most intense glow (as you observed) moves downward nearer the restriction opening. This will consequently also increase the temperature in and below the restriction itself.

Instead of “carving up” the nozzle openings, I would, if they are now blowing horizontally, do new ones which are bored with the nozzle tips aiming downwards 60 degrees.

Same hole diameter to retain intensity on low consumtion.

You cannot move nozzles downward, as full power needs a certain oxidation volume to complete before the restriction.

#929

OK that was my WAG allso (based for the calculation above).

Max, what is the purpose of downward turned nozzles?

#930

Hi, Kristijan
3.4.2017
To concentrate the high-glow in the center-low, but still having enough oxidation volume in the fuel during high power demand.

#931

Isnt this about the same as puting nozzles lower?

#932

Hi, Kristijan!
3.4.2017
No! Keeping the nozzlepoints in the current position means conserving a bigger oxidation volume, the 60 degree downblowing tip-holes aims at giving oxygen for the low-power needs forming near the restriction opening.
Still being higher starts the process earlier when the general flow of fuel is high.

#933

Hi JO, The “massive” 3/8 wall fire tube takes 45 minutes or more of highway driving to reach 1000F on inlet air. 400-500F is easy to reach in a 10 mile drive. I use heatexchanger and the old standard WK bottom up air flow on the firetube. What’s interesting is the temps go up when you slow down because of reduced air flow, longer dwell time. I think that helps with turndown ratio.

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#934

Mr. Carl,
Yes, that and weight may be the only small disadvantages with all that metal, but even my little gasifier will use close to half an hour before railtemp levels off. I know I´ve said that before but I´ll try remember to put a probe into my nozzle manifold to see where I´m at air wise. I agree on the turndown ratio.

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#935

even if you calculate incoming and outgoing at the same temperature, you are adding volume by gasifying carbon…
the volume increases after the nozzles by 1,2 ( cool air in and cool gas out )
Its all in the books :grin:

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#936

I know the WK wood gasifier is touch’able on the outside of the unit with its 9 layers of heat salvage.better than most any gasifier for the size of a truck it pulls down the road, Though i have a questain? At what temp will charco in the charbed stop glowing, when calculating the self sustaining oxegen from a certain temperture.??h2

#937

Hi Kevin,
I am not sure if i understand your question correctly, but in my experience;
If no oxygen is admitted, the consumption ( burning away) of the carbon will stop, self heating will seize…

if applying external heat (as i do in the charcoaling process and in the activation process) charcoal will glow but not be consumed (only volatiles will) , i tested that up to 1400ºC.
Only when adding “materials” containing O ( from oxygen) as Ozone, H2O2, CO2… the heat, combined with the glowing charcoal, will deplete the amount of carbon as the C will strip away with an O …
For any O mol, it will strip a C mole and form CO, as long you provide the heat… ( until all C is consumed of course )

Any “free” O will cause an exothermic ( producing heat ) reaction, as where Bound O will cause an endothermic ( absorbing heat energy ) reaction.

The absence of Free O will extinguish the glowing Carbon.

Gasifying is all about balancing exothermic and endothermic reactions

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#938

Thanks Koen for the testing results, would you say tar will crack at high temp areas with out the charco actually glowing slitely below the glowing char, or how far below the depleted oxegen zone on an inbert design as the one you use is the tar still cracking, or at what temp you think.??

#939

Hi Kevin,

I think we now enter the “grey zone” as where each persons observation play’s a role.
But, physically, every tar needs a certain temperature and dwell time with glowing charcoal to be “reduced” or “cracked”
if the transition zone, between oxydation and reduction, is well formed, then only “smoke” will enter the reduction zone and that will be reduced in a constant , irreversible state of gas.
If the transition zone passes liquid Tar ( mostly the heavy tar’s ) then that tar will turn into smoke in the reduction zone and only partial stay gas, rest will be condensed again.

As per initial build from Kristijan, i was very fond with the idea of air injection in the reduction zone, to eliminate the cool down from passing Tar’s, hence keeping the char glowing more profound.

Having a large glowing charcoal bed is, IMO, the most important issue.
Generating sufficient heat to do so, is best accomplished by , again IMO, retaining the heat but without preheating the incoming air.
The best example to confirm that is the statement/observation from Kristijan, that when he opens the lid, the gasifier runs at its best. Hence better airflow, more free O’s going down in the bed.

The dryer the fuel, the easier it gets, (known fact), to compensate for moister, you’l need O to have sufficient combustion.

I am working on a “condensate” entrapment for the charcoaling unit, but this can easy implemented in a gasifier to eliminate some Tar issue’s.

PS. The better i take care about my fuel in my gasifiers, the less smoke i get , So why should that be different with a good woodgasifier once the char bed is well established… ?

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#940

Thanks again Koen for your testing experianced responces, keep up the good work.Were all still learning, i just caint DOW untill i move the spring shackels over on. My truck too replace the rear axel, it must be and older chevy axel but looks like it will work. The only thing good on my texas truck was the body and frame. And i need too move one of my water tanks underneath for better cooling effect, tanks up by gasifier unnessisary in winter long as they are drained after useing, and will likely draw in more water being cooler away from heat exchanger, 3" now till i move.HWWT.

#941

Maybe Arvid and Sabedess could chime in here. As far as I know, their secret weapon is down angled nozzles. But lacking their input I am going to suggest that you make it like the post number 912 with the center nozzle, but; angle your nozzles down as Max suggested. With the angle nozzles the top center of the oxidation zone will not receive the air jets that it receives with the horizontal jets. But that extra jet, would be pointing directly into the center. TomC

#942

Hi, Kristijan!
5.4.2017

It is impossible? to give any specific suggestions based on the status of build now, as you have given no measures; that is “floating” on imaginary level… and video.

Still the 60 degree tips at the current 3 horizontal nozzles.

As for a lightening tube 1" exclusively, start at the top side
and follow the hearth inside, then bending 120 degrees (not too sharp) toward the top of the restriction mouth. Don’t go to the edge of the restriction, stay 1" behind horizontally measuring.
It has been recently approved locally on a Volvo, and it gives rather little start-up smoke.
It first lights foremost charcoal, not wood!

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