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Help needed for calculating Specific Impulse

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Old   September 20, 2000, 23:30
Default Help needed for calculating Specific Impulse
Dongsuk Chae
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Hi guys,

I recently work on nozzle flows of various geometries by CFD method. Reading related papers, I found that Isp(specific impulse) of nozzles is expressed by the ratio of an ideal specific impulse. I'm wondering how we obtain the idela specific impulse of a given nozzle. Plz, suggest me the method or related papers and books. Thanks in advance.
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Old   September 21, 2000, 03:44
Default Re: Help needed for calculating Specific Impulse
A. Taurchini
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By definition specific impulse is


where T is total thrust and mf is the mass of expelled propellent. Now the calculation of thrust depends on which kind of propulsion you use. For example if your nozzle is for a rocket system, then (in adapted condition : pext=pamb)

T= mf Vext

where Vext is the exhaust velocity that depends essentially from which kind of fuels and oxydizers you use. For this case is obviously


This is valid ONLY for rocket system. If you need more informations mail back. Bye.

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