Mayf said (snip. . . ) "Oh, hydrogen as a fuel is rather inefficient because
it takes as much energy to release the hydrogen from the water molecule as
it makes in recombining with oxygen. I prefer a more efficient fuel".
Mayf...from an efficiency point I agree with you. But as an LSR fuel (which
I thought you were discussing) I'm not sure I follow your reasoning. Since
it is already in gaseous form there are no molecule separating efficiencies
to deal with. And since a motor is a heat-expansion pump the fuel's heat of
combustion and molecule size is what determines best power.
The following are the calculated heats of combustion in Kcal/32 grams of
oxygen. Of the non-oxygen bearing fuels hydrogen is the highest.
Benzene = 79.9
Octane = 90.5
Methanol = 104
Hydrazine = 124
Hydrogen = 136
Nitromethane = 404
(source was a Hot Rod article by Dr. Dean Hill many years ago. The date has
been lost, I just kept the notes)
"...Lastly, the ad mentioned the Turbinator as having an external combustion
engine. ...my old texts and nowhere do they ever mention the Brayton Cycle
as an external combustion process".
I agree (but not seeing your source) I think the point was that since
combustion takes place in a combuster (a container on the outside of the
turbine) and then the expanding gases are discharged to act on the turbine
blades, it might be considered "external". I think of axial flow turbines as
IC but I guess a "combuster" chamber could be considered external.
-Elon
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