I think he means compressed natural gas (methane). Liquid methane is
alittle out of the realm of practicality. You cannot get liquid methane
unless the temp is under -116 degF and then it's like 620 psi (strange but
true: if you continue to compress methane and keep it above -116degF it will
never liquify, yet it's density will be higher than that of the liquid). I
think the pressures for commercial CNG systems are running around 2500psi.
This is becoming more common now a days. The big advantage for the home
handyman convertion is that if you tap into your house gas system,
(requiring a suitable compressor) you can fill up road tax free, that is
until enough people do it then the gov will figure a way to take care of the
new menace.
LP at 70 deg F is around 110 psi, or like 170 psi at 100 deg F.
> Propane is normally used
>since other acceptable gasses, butane for instance, will self freeze when
>required to evaporate at an engine demand rate.
This is only true if your drawing vapor off of the tank. The bigger problem
is that if your operating in cold climate the vapor pressure of n-Butane
or iso-Butane could go to zero (gage) and you'd never get anything out of
the tank. Butane boils at around +30 deg F. This would necessitate a tank
heater or a pump to get it out of the tank if below +30 F. LP's boiling
temp is like -44 deg F.
>The systems usually require a special cylinder or vehicle tank with a dip tube
>into the liquefied gas and have a preheating device to ensure the engine
>breathes no liquid.
True, but the vaportizer/regulator job is to proved a very small negative
pressure of LP vapor to the carb. It isn't so much a preheat as it is
simply to keep the vaporizer from freezing up. Two types, either run engine
coolant thru it or the other type has a large set of fins and you place it
in the cooling air outlet, if an air cooled engine. I believe that on a CNG
system the regulator unit must provide a very small posative pressure to the
carb. For safety reasons, this necessitates a more complex system.
>They are far less polluting and wearing on the engine but can tolerate
>compression ratios well above that even obtainable on aviation gasoline, the
>fork lift trucks invariably use propane because they run in enclosed buildings.
True, not to mention that you can change the oil on an LP engine and it
looks new. I reuse it in one of my old beater trucks.
>Power is slightly down on gasoline but its well under 10%.
Fuel consumption/cost, in $'s per mile, is a little higher than with
gasoline. ( or whatever your local currency & distance units are!)
Try it, you'll like it!
je
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