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-   -   How to set an equilibrium-Air model (http://www.cfd-online.com/Forums/cfx/21313-how-set-equilibrium-air-model.html)

jorge sancho June 6, 2005 05:51

How to set an equilibrium-Air model
 
Hello, I am trying to set an Air equilibrium model for a hipersonic case. The air will be reacting and disociating, but i am going to consider that the reaction time is too fast compared to residence time of the fluid. I have all the properties for reacting Air at equilibrium as tables, like Cp(P,T), and i wish to set up a model with them. Do anyone know how to do that?

khalid sultan June 6, 2005 12:32

Re: How to set an equilibrium-Air model
 
Find a scheme to apply; that is, what spieces will be assumed to be present and there elementary reaction equations (i.e. H2=H+H, O2=O+O, CO2 = CO+O, . . . , so on). Each of these elementary rxns has an equilibrium constant (normally function of temp.) which must be obtained (if in table => fit these to polynomials.). The air must be thereafter considered as a mixture of these species (mole fractions) with properties that are obtained from those of the individual species, T=T_i, P = sum(P_i), R = sum(R_i*Y_i), M = sum(M_i*X_i), Y_i = (X_i*M_i)/M. where P_i: partial pressure of species i

R_i: gas constant " " "

X_i: mole fraction " " "

Y_i: mass " " " " and M is the molecular weight.

and then p = (\rho)*R*T

hoping it would help.

jorge sancho June 6, 2005 12:41

Re: How to set an equilibrium-Air model
 
Thanks, i did it in fact, and i have these all the resultant properties for the mixture in tables. The problem is to implement that in CFX, i think is using the RPG tables formats. But i am still working on understanding them. As soon i got a solution i will post it. Regards Jorge


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