Hello everyone!
I want to try a simple reaction with mfix.（C+O2=CO2）I have two problems.
First，I can’t find solid carbon in the species database, and I can’t find the carbon a1-a7 when I add the new species, so I borrowed the carbon a1-a7 from some other people’s cases on the forum.It’s OK.
Second，Since this is a heterogeneous reaction, I set the reaction rate in usr_rates_des.f imitating the case in the user manual. But I didn’t see any CO2 generation. I increased the temperature, but it was still useless.
So I want to ask what went wrong.
Attach my case.
thank you very much!
----Li
c_2021-10-20T141303.889123.zip (777.3 KB)
Hi Li -
Carbon is in the species database (“Burcat”) in a few different forms
It’s also in there as ‘diamond’ but searching for ‘carbon’ doesn’t find that
Finally, amorphous carbon / lampblack is present as well but is not considered a solid. If you click the ‘G’ and ‘L’ buttons next to ‘Phase’ the search will be expanded to all phases.
Since C is a variable used in MFiX, the symbol C cannot be used directly - you can change the alias and the red message will go away.
I think the reason you are not seeing any reactions happen is that in your initial condition, no carbon is present - I only see nitrogen, oxygen and CO2
Try adding some carbon to the IC. It might also help to enable the stiff chemistry solver.
Hope this helps,
– Charles
You have Carbon (you call it ash) in the solids phase.
The issue is the reaction rates depends on A-i which is not defined, so it is zero and DES_RATE is also zero. Note that you can also get garbage values if you don’t initialize a variable.
If you set a non-zero value for A_i it should work.
DES_RATES(Rx1) = (A_i*k_so*c_O2) / (ONE + K_H*p_O2 + KS*p_O2)
1 Like
Sorry, indeed there is carbon in the solids phase, which I didn’t see. Thanks Jeff.
– Charles
That’s it, thank you very much
That’s it, thank you very much！