when i stated that these engines can be run in dual fuel mode, my intension or reasoning is as follows
1. they can be run in dual fuel mode, but not optimally
2. some provision will have to be made to admit the alternate fuel, such as carburation for alcohol, vaporizor for propane, etc
3. some form of overspeed control would be prudent
4. timing alteration should be used
for these engine's most forms of alternate fuels have sufficiently high octane ratings so as to not autoignite in the compression cycle, propane, alcohol, methane fit this group. all of these fuels have a lower btu rating and some have a marked difference in flame propagation over diesel fuel. So optimally timing would have to be altered.
in a basic sense, admitting the alternate fuel into the intake stream the fuel will not ignite until the diesel fuel is injected, having the extra alternate fuel allows the engine to speed up and in doing so the govenor tailors back the diesel that is injected and therefore control engine speed. Some engines can run upwards of 95% alternate fuel and 5% diesel pilot fuel.
it is unlikely in my opinion that the listeroid, petteroids and changfa's will tolerate much more than 80% alternate fuel, likely less than 75%, by tolerate i mean run reliably.
so basically in dual fuel mode it is my contention that running at a 50/50 mix would allow for good govenor control, stable engine operation and negate most of the need to alter the engine timeing. This is running in dual fuel mode but not optimally.
it comes down to how close you wanna slice the thing, how efficient you want or need to be.
to me having the option of dual fuel allows the use of other fuels as extenders to the pilot fuel, and therefore to me some sacrifice in efficiency is tolerable.
for instance
rape seed press it into oil, and use as a fuel straight up or as biodiesel
take the cake and ferment it to alcohol and carburate it as an alternative fuel in dual fuel mode
feed the mash to the pig, and then take the pigcrap to the methane generator, methane to the engine in dual fuel mode
the end slurry goes back to the field as fertilzer and the cycle is complete
is each point in the cycle maximized in efficiency? decidedly no
is the overall system efficiency acceptable? probably yes
if i were to set up a listeroid for a definite purpose dual fuel engine, such as with alcohol, then i would jet a carb and mount it, and also incorporate a hoof govenor to aid in control of the carburator, i would then alter the timeing to optimize power at the max ratio that the engine would tolerate and still operate reliably (run without miss)
even after all the work i am not sure the gains efficiency would offset the expense and complexity, and i would have an engine locked into one alternate fuel which might be fine if i had a large and steady source of the alternate fuel (in this case alcohol)
personally i believe this is the overriding beauty of the listeroid etc, because they can be made to produce useful power using a variety of fuels
giving me many options, which lessons my dependence on diesel fuel.
bob g
