Aerochargers are better than a twin screw!! hahaha ;-)

[Greg Hermann]

At 2:13 PM 10/15/01, Stephen Webb wrote:
>> loss in the motor due to the higher backpressure on it, you are STILL
>> getting more total useful work (flywheel HP plus compressor HP) out of a
>> given amount of  fuel burned (or amount of air breathed) because of the
>> higher overall expansion ratio which exists in the motor/turbo system.
>
>Ahh, I see.
>
>To some extent it seems like we would care less about how much work is
>extracted from the turbine, though.  Since the work you extract from the
>turbine is not being used to drive the car, but to add more air to the
>engine, you can't be justified in counting it, can you?

Well--compared to robbing (otherwise useful) power from the crank to drive
the compressor--it _does_ have a point. And that point shows up in the fact
that turbo engines will generally yield better bsfc than supercharged
engines do.

Another interesting illustration of this is the old turbo-compound
multi-row radial aero engines--in which they actually geared exhaust
turbines to the crank so as to boost output ! IIRC, both Lockheed and
Curtis Wright did this one .

The comment about the waste gate wasting a lot of potential energy is true,
and IS one of the more powerful aruments in favor of VATN turbos.

Greg


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