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HELP NASA CEA CODE
I am using Nasa CEA code for calculating Isp for different Ae/At
ratios with chamber pressure of 1000 psi. Problem is Isp should have a peak at optimum expansion condition i.e. when Pexit= Patm but with increasing Ae/At ratios Isp's are increasing although the PexitPatm. Can anybody who has used the code help me ? Warm Regards Vaibhav |
#2
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HELP NASA CEA CODE
Vaibhav wrote...
I am using Nasa CEA code for calculating Isp for different Ae/At ratios with chamber pressure of 1000 psi. Problem is Isp should have a peak at optimum expansion condition i.e. when Pexit= Patm but with increasing Ae/At ratios Isp's are increasing although the PexitPatm. Can anybody who has used the code help me ? If you overexpand a convergent-divergent nozzle beyond ideal conditions (i.e., when Pexit Patm), the exit velocity will indeed be greater than the ideal exit velocity. However, you need to account for the "base pressure" thrust loss, Aexit * (Patm - Pexit). This drag term grows with overexpansion and it prevents overexpanded thrust from exceeding the ideal thrust. Note: There are limits to how much viscous attachment effects allow a nozzle to be overexpanded. Eventually, the flow will separate from the divergent wall. Regards, Jeff Berton |
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