CNG Vehicle in Perth, bit of an update

[Bill the arcstarter]

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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