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Is there any equation for minimum area ratio (Throat area (At)/ Combustion Chamber area (Ac) ) required for choked flow in convergent nozzle (just like equations for minimum Pressure ratio and Temperature ratios)?

While searching online for minimum Area ratio required, most of them are related to CD nozzle. But in my case I'm looking for Convergent nozzle only so that I can get an estimate how wide combustion chamber should be to the exhaust area.

I tried to derive equation from mass flow continuity equation but it is dependent on flow velocity inside combustion chamber which is generally assumed to be near zero. (and I got stuck here.)

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  • $\begingroup$ Mass flow and velocity should help... $\endgroup$ – Solar Mike Apr 5 '19 at 4:56
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Of course there is, you can find it on the NASA webpage:

https://www.grc.nasa.gov/www/k-12/airplane/astar.html

You can demonstrate the equation with mass flow conservation equation (continuity), ideal gas law and isentropic relations.

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  • $\begingroup$ Thanks for reply but the link you provided , is for CD nozzle. There area ratio is throat area to divergent exhaust area. But I'm looking for just convergent nozzle. Here I need area ratios of combustion chamber and convergent exhaust area. So, basically my question is about how much convergent nozzle needs to be converged just to have choked flow for given pressure and temperature ratios. $\endgroup$ – SRD Apr 15 '19 at 0:14
  • $\begingroup$ You can use the same formula for the convergent zone by using the inlet Mach. The ration will then be A_inlet/A_throat. $\endgroup$ – user20096 Apr 15 '19 at 9:29

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