[Gasification] Producer gas injection through spark plug?

[doug.williams]

Hi Jonathan,

You ask:

> However it crossed my mind that this method of injection may make the 
> engine
> much more tolerant of tar in the gas.  If the gas injection bypasses the
> valves entirely won't the issue of tar gumming up valves be solved?  And
> what tar is in the gas should be combusted in the engine and not 
> accumulate
> on the inner surfaces within the cylinder.
>
> As so many of the problems of running engines on "woodgas" are caused by
> "tarry" gas won't this solve that problem?

Without a doubt, if we could bypass the valve train, all out troubles would 
be over, at least for the engines. However, the problem then becomes 
transfered to the pre-engine systems, because we still have to cool the gas, 
creating condensate, and compress it before offering it up to the engine 
injectors. You could not rely on suction alone to pull in the volume of gas 
through such a small injector.
>
> I'm not saying that woodgas should be "tar" rich only that maybe if this
> method of injection is used than not so much an elaborate and expensive
> filtration method are necessary or also that fluctuations in tar levels at
> different engine loads may not be of as much of a concern.

Tar really is a good engine fuel, so long as the engine never stops and 
cools off!! Tar filtration is still very much a "black art", but cooling is 
worth all you can spend on it to increase the volumetric efficiency, and get 
the water out.

> Others please comment or note where tar might still be an issue or cause
> problems if this method of injection is used.  Assuming that the fuel 
> lines
> themselves going to the engine aren't affected.

I can assure you that trying to run tar gas through a colder horizontal pipe 
of a size that would connect to an injector, will block with both tar and 
dust. Engines have been designed to run on tar, and were discussed at length 
on this forum, but I have no experience myself with these type of engines.

 If tar did become the fuel, I think you would create an emission problem, 
and I guess, more suited to very slow speed application. With tar present, 
you also have the moisture, so the flame speed would be very slow, and as an 
after thought, would need a glow-plug, or hot bulb ignition. A spark plug 
would not be suited to this type of contaminated gas, as it will foul very 
quickly. Tar in the gas also makes the engine run much hotter, so you will 
need to consider a larger capacity engine radiator system.
Hope this helps.
Doug Williams,
Fluidyne Gasification.

>
>
> Jonathan Pratt
>
>
>
>
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