CNG Vehicle in Perth, bit of an update

[Seth]

Hmm, ran a gaseous CNG injected Dodge Neon in school.  Rail pressure was
150 to 200 psi. If I can convert correctly, that's ~ 1.0-1.3
megapascals. Container was used at 3600 psi. I believe it was carbon
fiber wrapped polyethylene.  Might have been PTFE, I can't
remember.Walls of pressure vessel were ~1.5 inches thick, mostly
plastic. Engine ran at 10.0 and 14.5 to one compression ratio. (swapped
pistons one year) 14.5:1 produced excessive NOX, without a drastic
increase in power.Don't rmember hom much ignition advance it used, but
it could take lots before pinging. Had a problem at WOT with flooding. 
Gaseous CNG displaced enough air to flood out. Had to engineer an
electronice "ramp in" for the throttle. Acceleration enrichment ( in the
stock ECU) was what did it, IIRC. 

pics are here:

http://vri.etec.wwu.edu/viking_25.htm

-Seth

Bill the arcstarter wrote:
> 
> Mike wrote:
> 
> >Now this is interesting :)
> >
> >The ford they run is a six cylinder, (4.2L?) and runs the *same* fuel rail
> >as the original petrol variant. The additions are:-
> >
> >a.     Injectors are high flow methanol units supplied by Bosch, I
> >       will try to get a part number. Note: They operate at 200KPa
> >       fuel rail pressure and the fuel rail is only dense gas (methane
> >       mostly) at that pressure.
> 
> So thats about 28 psi.  Pretty tame.
> 
> >
> >b.     Standard ECU was reprogrammed to take the larger injectors other
> >       controls are unchanged - AFAIK - but will check.
> 
> Easy so far.
> 
> The volumetric stoich for methane is 1:10, which means it will displace
> about 1/11th of the original (gasoline) air charge.  This means I'd expect a
> reduction in power at the crank, unless this is compensated for via timing,
> compression ratio, turbo  etc to exploit the 130 octane.
> 
> >c.     There's no fuel pump, high or low pressure, though might still be
> >       in the vehicle... Not sure if there's a safety run/stop solenoid
> >       valve.
> 
> Bet there is!
> 
> >
> >d.     Two stage pressure regulator, drops from tank 20MegaPascals to
> >       the 200KPa used by the injectors.
> 
> 20 Meg = 3000 psi.  Must be a special unit.
> 
> >
> >e.     Regulator is plumbed with hot water from cooling system as the
> >       methane has a small amount of water (hope there's no hydrates)
> >       when it comes from the refinery. Nothing to worry about its just
> >       that its enough to ice up the regulator on higher flows...And I
> >       suppose a single stage 20MPa to 200KPa might not be so stable ?
> 
> Heat would also be to supply specific heat requirements due to changing the
> pressure by about 20 million pascals. >:)
> 
> >f.     Injectors only work for 60,000 Kms before failing. Reason suggested
> >       by Ford is that they are designed for fluid with that cushioning
> >       effect - running dense gas makes them wear and fatigue more.
> >
> >g.     Vehicle doesn't have dual fuel capability, injection system being
> >       tuned/setup/fixed only for CNG.
> 
> Nope.  All Ford parts fail at 60,000 Kms. :( (JUST KIDDING but it does
> explain a few things...)
> 
> >h.     Not sure of size of tank, will check out later this week if at all
> >       possible, I udnerstand wall thickness is 1/2" though and *HEeaVY*.
> >
> >There is some suggestion that a suitable solvent could be found for methane
> >in a storage format similar to acetylene tanks (Acetone I think, or is this
> >just acetone to wet the catalyst the acetylene sits on in the tank) ?
> >
> 
> Now you're getting somewhere.  So does anyone know of a good solvent/solute
> for methane?
> 
> Acetylene tanks are filled with some sort of porous substance soaked in
> acetone.  The gas is dissolved into the acetone at relatively low pressures,
> like 150 psi etc.
> 
> Acetylene is sort of weird - supposedly it will self decompose at pressures
> above 15 psi.  This being said - nobody has been able to explain (to me) how
> the acetylene in the high pressure side of the regulator is immune from this
> effect.
> 
> -Bill
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