Bill Clawson wrote:
> Hi All,
>
> Since our chamber pressure on KISS was designed to be about 300 PSI and air
> pressure is running at 14.7 PSI, wouldn't the ideal ratio of nozzle area to
> throat area be about 20:1? All our engines seem to have less than this
> expansion ratio and I was wondering why.
Area ratio /= pressure ratio... they are related by a fairly ugly equation:
Ae/At = [2/(y+1)^(1/(y-1)) * (Pc/Pe)^(1/y) /
sqrt{(y+1)/(y-1) * [1-(Pe/Pc)^((y-1)/y)]}
where y is the ratio of specific heats, Cp/Cv.
For Pc/Pe of 20, Ae/At is in the range of 3-4 for reasonable gamma.
Doug
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