Dear Tom and Ken and all,
what you describe is the classical dual fuel mode which works, but not
really well.
Diesel and PG timing is not the same, PG should have more advance.
Ken´s (and my ) Listers are easy due to the huge plug in the prechamber.
So both diesel and spark can have their own timing.
This doesn´ t apply to many engines!
Rolf
Am 13.10.2012 15:49, schrieb Thomas Reed:
Dear Ken and all
Sounds below like you have it nailed.
One option used in the past is to always have the diesel present at idle
injection level, and then add producer gas to whatever power is required. Uses
more diesel, but provides great stability for igniting the too low cetane
number producer gas.
Tom Reed
On Oct 13, 2012, at 5:10 AM, Ken Boak<[email protected]> wrote:
Dear Tom, and Greg,
Thankyou for clarifying that it is the ~50% nitrogen content in producer gas
that gives it a high octane number, and the simple rule of thumb that links the
octane number and the maximum compression ratio.
Having read IISc literature about running converted diesel engines on wood gas
at 17:1 CR, this inspired me to continue with the conversion project of the
Lister type engine at All Power Labs, so that it could be run at it's stock
compression ratio of 17:1 on wood gas.
The conversion involved keeping the original diesel injector and fitting a
spark plug through a side port, which gave direct access to the spherical
combustion chamber.
The rationale behind this conversion, was to allow the diesel engine to be
started and run as a diesel, providing immediate thermal, pneumatic and
mechanical energy, which could be used to start up the downdraft gasifier.
When the gasifier was producing good, engine grade gas, the diesel fuel could
be shut off, the woodgas introduced to the air intake through a mixing valve
and the engine would continue to run in spark ignition mode on woodgas.
This approach seems to make absolute economic sense, where the engine would
only be started and run for 5 minutes or so on diesel (or biodiesel, WVO) and
for the remainder of the daily duty would be run on wood gas.
The small team working on the Lister conversion project at the April weekend
workshop, found that the 6hp engine and alternator was still capable of
generating 2.5 kWe electrical power in wood gas mode at 600 rpm - hardly any
power derating from what it could achieve at 600 rpm in diesel mode.
The Lister type engine is a simple durable engine, still produced, sold and in
common usage around the developing world. It's basic construction lends itself
to this simple spark ignition conversion so that it can benefit from the much
reduced running costs offered by woodgas operation.
regards
Ken Boak
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