Superchargers increase the over all HP load on the engine
because the HP required to drive them comes from the output
shaft.

Consequently supercharged engines burn more gas than
turbo charged engines for a give HP output.
Turbochargers make use of the otherwise 50% waste energy
in the exhaust.

Turbochargers also require power from the engine to produce boost, but this power comes from the
exhaust. It is very true that a portion of the power is obtained by reclaiming exhaust energy that
would otherwise be wasted, but the turbine does increase the backpressure on the engine quite
significantly, creating an additional parasitic load on the engine. The "art" of turbocharger
matching is in finding a combination of turbocharger parameters that minimizes the parasitic load
while still providing the desired boost characteristics. In a poorly matched turbo (or even a
well-matched turbo operating away from its best regime), the turbine inlet pressure can exceed the
compressor outlet pressure.

Not arguing that the turbocharger can be more fuel efficient than a supercharger, and that the
turbo certainly makes more sense in an aviation application. Since we sell supercharged engines,
I'm a little sensitive to the common misperception that turbochargers give their boost "for free,"
when in fact they do create a parasitic loss of significant magnitude.

Jonathan Lauter
Rotary Power Marine Corporation
516-656-5685
www.rotarypowermarine.com

How is it going Jon? Are the supercharged version of the marine
rotary engines selling well?

Paul Lamar

 
The AirCraft Rotary Engine NewsLetter.  Powered by Linux.
ACRE NL web site. http://home.earthlink.net/~rotaryeng/            
Copyright 1998-2002 All world wide rights reserved.