How many chemical reactions could be set in MFix at most?

MFiX How to
#1

Hello everyone,

I am doing some work about ammonia combustion and I need to reduce the chemical mechanism, so I want to know how many chemical reactions could be set in MFix at most.

I have found that chemical mechanisms with less than 50 elementary reactions (50*2=100 reactions at most) can be calculated normally in MFix, but when I try a mechanism with 67 elementary reactions (134 reactions are required), an error occurs (I have attached the relevant file below, and the error information is in err.txt).

I’m not sure whether this error is related to my settings, or more than 100 chemical reactions could not be set in MFix. I checked the user guide and other materials, but I didn’t get any useful information.

I know that some CFD software like Fluent may be more suitable for dealing with complex chemical reactions, but my further work will involve particles, and I really enjoy using MFix for gas-solid flow calculation, so I want to use MFix for my work.

So is 100 chemical reactions really the upper limit of mfix? If not, how can I modify my file?

Thank you very much!

Pan

NH3_Okafor.mfx (45.7 KB)
usr_properties.f (36.1 KB)
usr_rates.f (51.5 KB)
err.txt (4.3 MB)

#2

The limit is set to 100 reactions.

You can increase this limit by modifying line 53 in mfix/model/param_mod.f

INTEGER, PARAMETER :: DIMENSION_RXN = 100

(say set DIMENSION_RXN = 200)

Since you are writing reactions rates to vtk file, you also need to increase nrrmax on line 25 of mfix/model/rxns_mod.f:

INTEGER, PARAMETER :: nrrmax = 100

(again, say nrrmax=200)

We currently have a known issue with the solver not building if we copy param_mod.f into the project directory, so you will need to modify the original file for now.

#3

Thank you very much! Now it works, and this is very helpful for my reduction work!