Richard Riley wrote:

On 3 Oct 2005 10:06:32 -0700, wrote:
:
:How does liquified methane (at high pressure, ambient temperature) look
:to power a conventional internal combustion engine, or perhaps even a
:methane fuel cell?

Basically, it looks about the same as gasoline. It does have lower
emissions, so it does well where regulations force low emissions
standards. In my area they use it for city busses. But for aircraft,
I don't see much advantage. For a fuel cell it has to be reformed to
H2 and C02, that means more equipment and more weight - but you'd have
to do that with any hydrocarbon.
:
:I think that methane requires somewhere around 3700 psi to compress it
:into a liquid at normal temperature, surely there's got to be some
:carbon-fibre reinforced, aluminum polyester-lined composite tank
:technology available nowadays that can handle the pressures necessary
:to handle non-cryo liquified methane, without being prohibitively heavy
:for an aircraft. Methane has a motor octane rating of around 130 in a
iston engine too, and you certainly won't be needing a fuel pump, just
:a good strong pressure regulator / phase change heat
:exchanger/gassifier at the tank's output valve to feed a direct fuel
:injection metering system for the engine. You could probably employ the
hase change heat exchanger as a clever way to air-condition the cabin
:too! (just make damn sure of no leaks)

I'm just not seeing that you get much in exchange for the weight and
cost of the high pressure tanks. Gasoline is pretty good stuff.

Yes, not bad, but not perfect. Reciprocating ic engines typically
are 25% efficient overall, thanks to mechanical losses and un used
heat thrown out with the exhaust.

If an electric motor is 75% efficient with hi frequency small coils
and can regenerate braking and if we could recombine O2 and H2 to
make water and electricity directly, along with maybe steam rocket
exhaust, you might see an improvement, especially with elecro motor
wheels rotors that are tailored for speed so they need not
transmissions. Their only weight is in the magnets, coils, and
switching controllers.

Magnetoheterodynamic generators are quite efficient, I hear. If we
could use one to drive 2electric contra rotors using motor
torque to set pitch, we might get somewhere.

I personally think a huge low pressure H2 fuel tank might provide
zero cost lift, so H2 might yet be more efficient than even our
wildest imaginings, so long as we use anti static plastic film tanks
and squeezable bouyancy bladders, like fish do.

Much is to come in the future.