Re: GAS-L: Internal Combustion with Producer Gas

[Peter Singfield <snkm@btl.net>]

Tom;

Bare with me here -- 

Yes -- we all know producer gas has a high very high octane - and a very 
low cetane number. But why can't spark ignition be done at the 16 to 18:1
compression ratios of the standard diesel -- why must it be reduced to 12:1??

That my friend is the question -- not whether spark ignition works. We know
it works.

But why only at 12 to 1 maximum??

When combined with diesel injection -- it works at regular compression levels.

There is two reasons it would be nice not to have to reduce compression
ratios in that "standard" diesel.

One -- higher efficiencies.

Two -- much lest retrofitting.

Do you grasp what we are trying to derive here yet?? 

Prof. Parikh/Shashikantha has stated that twelve to one is the highest
optimal compression ratio for spark ignition.

I am simply trying to deduce why.

My "theory" is that direct spark ignition of the charge is not suitable
(Based on Prof.Parikh/Shashikantha actual observations!) -- ergo am
suggesting spark then flame ignition -- which more closely approximates
fuel injection ignition. Ergo -- then we could stay at those higher
compression ratios.

Can you understand any of this?? Sorry -- I have this habit of thinking
people are following my thought patterns. Maybe I jumped ahead to fast??

Hopefully -- the repetition above of what I am trying to discuss here can
be understood now???

So -- lets try again ---- 

Peter/Belize

At 08:53 AM 5/3/00 EDT, you wrote:
>Dear Peter et al:
>
>Duh.  You said :
>
> Obviously there is an ignition problem with just "spark". The diesel
> principle is injection of a fuel into an atmosphere heated to the flash
> point of that fuel with enough oxygen present to accomplish combustion.
>
>WRONG WRONG!  No problem with "spark", except the trouble of converting.
The 
>trouble with not converting is (1) you continue to use 20% diesel and (2)
you 
>are always tempted to trash the gasifier and use pure diesel.  If you
convert 
>to spark you'll be OK.
>
>Maybe my earlier message was unclear.  The reason the producer gas doesn';t 
>ignite in pressure ignition is that it has a very high octane - and a very 
>low cetane number.  Ergo, you can use spark ignition or pilot diesel.  
>
> Lots of labs are now using "spark converted diesel" engines.  See Prof. 
>Parikh/Shashikantha excellent paper at recent ASME meeting based on
SHshi's 8 
>year thesis.  Can you post Mrs. P?  
>
>                ~~~~
>
>
>>Pure hydrogen is far richer than producer gas with all that nitrogen.
>
>Wrong.  Pure hydrogen contains 300 Btu/scf and producer gas is typically 150 
>Btu/scf.  Not "far" richer, but a factor of two for sure.  
>
>FUel injection is of course out of the question, since compressing the weak 
>producer gas - or the hydrogen (unless at tank pressure) would be 
>prohibitively expensive.
>
>                                            ~~~~~~~
>
>This is a major "mechanical" adaptation. I simple wonder why compression
>must be lowered when running producer gas only -- when it does not need to
>be when running a small amount of diesel??
>
>Probably doesn't need to be reduced, due to the reduced charge, even at the 
>high CR.  BUt I hope we hear form Prof. P. on why she thinks 11-3 CR is 
>optimum.  
>
>I presume one can add an extra head gasket to reduce CR?
>
>YOurs truly,       TOM REED
>  >>
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