Z wrote:
Not to say that I disagree, but I think that is
definitely an open question. There are
two pieces to the overall efficiency equation,
first, combustion efficiency, (efficiency
of converting chemical potential energy to heat),
second, thermodynamic efficiency
(efficiency of converting heat energy to
mechanical work).
There is no question that rotary engines will
never equal reciprocating engines in
the realm of combustion efficiency, for the
reasons others have already stated.
However, it is important to remember that the
thermodynamic efficiency of the rotary
engine cycle is considerably better than that of
the piston engine cycle. This was one
of the things which helped spur interest in the
rotary engine in the first place. With
properly timed intake and exhaust (allowing full
extraction of the available heat energy
during the expansion phase), the greater
thermodynamic efficiency of the conventional
rotary cycle is more than capable of offsetting
the lower combustion efficiency.
If you go beyond this and start talking about
using the intake air itself to cool
the rotors and rotor housings, the achievable
overall efficiency of the rotary
configuration in fact considerably exceeds that
which can be realized in a piston
engine, a fact which the Moeller rotary has
already demonstrated.