Humidity

[Bruce Bowling]

> 
> The discussions on humidity appear to be based on the assumption that
> power output increases with humidity.  This is not supported by many years
> of testing and, in fact, engine performance tests correct test results for
> humidity and reflect the fact that power goes down as humidity goes up.
> Water injection was intended to serve as a means to eliminate knock and
> will increase power output on a knocking engine by eliminating the knock
> (or if allows more spark advance to be used without knock).  The best
> discussion of this I have seen is in Obert's classic text "Internal
> Combustion Engines and Air Pollution" on p. 299 in the third edition.
> 
> Name:		J. W. Hodgson
> 

I agree - the formulisms I have seen which predict air density shows
that air density increases with a decreasing vapor pressure.

Look at:
 
   http://efi332.eng.ohio-state.edu/bowling/fi.html

and play with the value of the relative humidity number, while watching
the computed vapor pressure and air density.

- Bruce


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                 Bruce A. Bowling
                 Staff Scientist
   Thomas Jefferson National Accelerator Facility
    12000 Jefferson Ave - Newport News, VA 23606
                 (804) 249-7240
bowling at cebaf.gov  http://devserve.cebaf.gov/~bowling
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