[Gasification] Engine knock

[Peter Singfield]

I believe your both talking different model diesels.

The old style Listers are but 16 to one -- and low RPM -- the ones so
common in Australia and New Zealand are the much more modern air cooled --
higher RPM -- much higher compression.

The old are all indirect combustion -- the newer direct injection.

It is extremely easy to change the compression -- lower or higher -- for
the old models -- just machine the clean out plug accordingly.

Precombustion model should tolerate tar much better. As it is fast and easy
to take out plug and clean chamber on the old style Listers.

>Gas is easy to make for a demo, but try relying on you 
>system every day for the rest of your life, as some people will need to do 
>very soon.

You best figure on reliably operating 4 hours per day -- not 24/7!!

The ORMAT ORC will keep looking better and better ---

Peter

At 08:10 PM 2/6/2007 +1300, you wrote:
>Hi Jim,
>
>You need clarification:
>
>> nearly every diesel I know of is over 16:1.  especially if they are
>> non turbo, they are usually going to be 18:1 or more.
>
>This is the lean burn principle incorporated into modern diesel engines, to 
>squeeze more power out of lighter engines, or to increase the output from 
>smaller engines, which if were naturally aspirated would be operating at 
>16-17:1.  The other factor to consider, is that these smaller high 
>compression (22:1) engines all get their extra power at higher RPM 
>generating power (3,000 RPM), and this piston speed exceeds the flame speed 
>of producer gas.
>
>> but i of course could be very wrong.  I've yet to dual fuel
>> a diesel, but everyone here seems to not have problems.
>
>I am not aware of any other commercial expertise on this list that is duel 
>fuelling diesel engines, and if they are, then they will all be operating at 
>compression ratios of under 17:1.
>
>
>> listers, which are relatively low compression, are over 16:1.  i think
>> they are 18:1, and indirect injection/precombustion usually.
>
>Listers are not likely to be 18:1, as all the Listers we worked with were 
>16:1. I am not aware of any Listers with pre-combustion chambers, but some 
>of their older engines may have such features. I have a number of their 
>engine manuals, and will see if I can find reference to them.
>
>> so can you give us some of your experience with woodgas detonation in
>> diesels in dual fuel mode?  especially in indirect
>> injection/precombustion chamber engines.
>
>No, because we could not gasify engines over 16-17:1 compression ratio, 
>because of the detonation problems, unless the gas/air mixture was so weak, 
>it was a waste of time doing it.  If you have not followed previous 
>discussions of our work on this forum Jim, Fluidyne worked very closely with 
>Listers here in New Zealand, for power generation in the Pacific Islands, 
>and were the only company to receive their approval to maintain engine 
>warranties.
>
> > all the diesel engines i
>> have lined up to wood gas dual fuel are of this type.  my heart might
>> break if i learn they are no go.
>
>Better a broken heart than  going bankrupt.
>
>> i'm confused by this doug.  as you know, thermodynamic efficiency has
>> a direct relationship to compression ratio.  we gain efficiency the
>> higher we can compress before combustion.  this was the main "a ha"
>> that led away from early atmospheric pressure internal combustion
>> engines.  mechanical friction becomes a smaller fraction of total
>> cycle energy the higher compression goes.  and more importantly, the
>> delta T we can mine goes higher the higher pressure under which the
>> original combustion happens.
>
>You miss the difference Jim.  Diesel is injected into the cylinder pressure, 
>not compressed like producer gas to it's spontaneous ignition temperature , 
>which coincides with about 16:1. purpose built gas engines are all around 
>the 12.5:1 ratio, so I expect the engine designers have checked out all your 
>theories.   I did not set these rules, they are straight out limitations set 
>by the gas chemistry, and the forces applied to them. You may wish to 
>disregard what I say, but nothing can change my comments, which are based on 
>many thousands of engine hours observing producer gas fuelled engines.
>
>> if we had a fuel that could run at 100:1, and a motor that would stay
>> together, that would be a very high efficiency motor.
>
>There is a big gap to apply theoretical calculations to the manufacture of 
>producer gas, and,it's application in engines. The advise I give to every 
>one, is to first learn to make gas correctly, then use a standard spark 
>ignition engine to create your motive power. Learn the limitations before 
>you try to design gasification systems to overcome the limitations, and if 
>this sounds to easy, then take note of how much money has been wasted 
>chasing rainbows! Gas is easy to make for a demo, but try relying on you 
>system every day for the rest of your life, as some people will need to do 
>very soon.
>
>Doug Williams,
>Fluidyne Gasification.
>
>