[Yuqi]

Hello guys,

I am trying to model fluid flow through a converging diverging nozzle with dissociation and recombination reactions accounted. From example, the fluid is water vapor (the product for H2 + O2 combustion, assume the combustion process is completed before they enter the nozzle) at 3000K, the dissociation already occurs before entering the nozzle, and recombination will occur down the road due to expansion, so is there a way to do this in ansys fluent? I was recommended to use CHEMKIN, and I need to define all chemical kinetics under different temperatures then import into fluent, but I do not have any experience on that before.
Therefore, it would be great to have some instructions from people who has this kind of experiences.
Much appreciate for any help in advance.

[LuckyTran]

It's not that you have to learn chemkin, what you need first and foremost is to define the chemical kinetics.

M. Burke has a pretty comprehensive H2/O2 mechanism [doi:10.1002/kin.20603] it's the most comprehensive one that I know of. If you do any reacting stuff for H2/O2, chances are you will not escape Burke's kinetic mechanism. Check it out and see if it suits your needs. You can ask him for the chemkin files directly (I got them from him).

[Yuqi]

Originally Posted by LuckyTran

It's not that you have to learn chemkin, what you need first and foremost is to define the chemical kinetics.

M. Burke has a pretty comprehensive H2/O2 mechanism [doi:10.1002/kin.20603] it's the most comprehensive one that I know of. If you do any reacting stuff for H2/O2, chances are you will not escape Burke's kinetic mechanism. Check it out and see if it suits your needs. You can ask him for the chemkin files directly (I got them from him).

Hello, Thank you so much for your response and info. I am more interested in how to define chemical kinetics in ANSYS FLUENT. So far what I have done is turned on the SPECIES in the model and use Finite-Rate/Eddy-Dissipation, volumetric reaction. The Chemical solver is set to None-explicit Source. Then I define the mixture is H2O, H, OH (eg, only one chemical kinetics H20=H +OH). In mixture edit-reaction, I created only 1 reaction as I mentioned, with pre-exponential factor 3.49e15, activation energy 440,000 j/kgmol, and temperature component is 0. Here, I do not know how to set up the Rate exponent for each species, and the Mixing rate(the default is A=4 and B=0.5), also the third-body efficiencies.

I am not even sure that I'm on the right track, and if you know a better way of doing this please help. Just in case if you have questions about why I set up like that, here are some extra info down below:

1) If I use Eddy-Dissipation, I do not have the option define the activation energy, temperature exponent, etc...
2)If the Chemical solver is set to "Relax to Chemical Equilibrium", "No fuel species for the chemical time-scale have been selected in teh integration paramaters panel", where in this case I do not have fuel/oxidizer species.
3)Ultimately, I want the chemical kinetics(dissociation/recombination reactions) depend on the pressure and temperature inside the CD nozzle, so I randomly set up some numbers for Rate Exponents and third-body efficiencies, the result at the outlet of the nozzle is just pre-defined species concentration at a lower temperature which the dissociation shouldn't happen, in other words, they should all recombine and only have H2O.
4) Per my post, I only need the dissociation and recombination reactions setup in FLUENT, so I am not interested in the combustion process.
5)I'm Using ANSYS WB 19.0

Much appreciate for your help.