Learning Forum

[ZoeYuan]

Hi,

I am using the species module in ANSYS Fluent and tried to import CHEMKIN mechanism into my module. I added the mechanism according to the steps described in User Manual. However, the import failed and I got an error message (see below).

The screenshot of species solver and the CHEMKIN mechanism import section are attached as below:

Can anyone tell me how to solve this issue please? Many thanks.

Regards,

Zoe

[DrAmine]

Hard to say. What do the files which are created on reading tell?
Is it an encrypted mechanism? You can attach the data so that non ANSYS staff can check.

[ZoeYuan]

Hi Amine,

Many thanks for your reply.

The CHEMKIN mechanism I used was from the following website: https://www.detchem.com/mechanism It's about the detailed surface chemistry of C3H6/CO oxidation and NO reduction on Pt/Rh based catalyst. There is no gas-phase reaction. 

Regards,

Zoe

 

[DrAmine]

If there is no gas phase reactions how can you explain the screenshot you posted? We need a gas phase mechanism to full the import? What did you import there? Have you looked into the files I was mentioning? Can you just attach what you trying to add?

[ZoeYuan]

Hi Amine,

To answer your questions: 

1&2. The mechanism file for gas-phase is attached as below. I only defined the elements and species in this file in order to complete the import. 

3. I am not quite sure the files that you were mentioning refers to which file. 

4. I didn't find out where can I attach files in this discussion and I can only insert the screenshot. The screenshots of the surface mechanism I used are attached as below. If possible, would you please tell me how to attach a file in the discussion? Many thanks.

Regards,

Zoe

[DrAmine]

Can you provide a university email address?

[DrAmine]

Thanks. Check your inbox. 

[ZoeYuan]

Hi,

I have successfully imported the CHEMKIN mechanism into Fluent and tried to run a transient simulation in a single-channel model with this mechanism. However, the model doesn't converge at all and shows error message as below. I don't quite understand what cause the 'Invalid cp (000000e+00 J/kgK) for chemkin-import at temperature 1.#QNAN0 K' in the error message, because I have checked the thermodynamic data file and it looks alright. Do you have any suggestions on how to solve this issue? Thank you very much.

Regards,

Zoe

[DrAmine]

Again look in the out files generated when mechanisms and thermo data is read into Fluent.

[ZoeYuan]

Hi Amine,

Thanks for your reply.

I have checked the out files when the mechanisms and thermo data was imported into Fluent. It shows that there is no error with the input files. Also, I have noticed that when I run the model as steady state, the model works and no such error message appear; while if I switch it to transient simulation, it will give error message as above, saying that 'Invalid cp for chemkin-import at temperature NaN'. 

Regards,

Zoe

[DrAmine]

What happens if you run steady and then within same session switch to transient? Does it show the error message?

[ZoeYuan]

Hi Amine,

I just made a mistake of the basic settings for the steady state simulation, so just ignore my previous message. 

I tried another time to run as steady state and it shows the same error message as below.

Regards,

Zoe

[ZoeYuan]

I have uploaded the out files when imported the mechanism into Fluent as above. 

Regards,

Zoe

[DrAmine]

I am sorry as ANSYS Staff I cannot download any attachments.

[DrAmine]

Mehanism and Thermo files were containing mistakes. After correction both files can be read properly in to 2019R2.

[ZoeYuan]

Hi Amine,

Many thanks for your reply. I don't quite understand what you mean by 'mechanism and thermo files containing files'? 

Regards,

Zoe

[DrAmine]

mistakes. Typo.

[mehdib9170]

Hi,

I'm facing the same problem but I don't know how to correct the mistakes in my mechanism file. Even more, I'm not sure what the mistakes are.

I would really appreciate it if you could help me. 

P.S. my file is an ENCRYPTED FILE.

[ZoeYuan]

Hi,

Have you tried using the latest version ANSYS 19.2? It might be helpful. 

Regards,

Zoe

[ZoeYuan]

Hi,

I am modelling catalytic surface reaction using imported CHEMKIN mechanism in a single-channel model via ANSYS Fluent. The mechanism describes the oxidation reaction of CO, C3H6 and H2 as well as NO reduction by CO over catalyst surface site. 

At the channel inlet, different mole fractions for species: O2, C3H6, H2, H2O, CO2, CO, NO were defined. At the channel wall, the reaction was activated with the surface area washcoat factor set as 70. 

The simulation was set as transient simulation with gradually increased inlet temperature. After some iterations, the simulation finished without any errors with good convergence. I checked the species molar fraction at the outlet and noticed that there are reactions taking place. However, when plotting the contour of Kinetic Rate of Reactions, the reaction rate is zero for all the reactions. It is so weird, because there are definitely some reaction occuring. Take the CO conversion for example, the CO conversion efficiency obtained from simulation versus temperature is shown as below. CO is gradually consumed with temperature increasing; while related reaction rate is zero see screenshot attached below. Can anyone tell me is there anything wrong with my initial setting please?

Regards,

Zoe

[Ch Qian]

I am using ansys fluent to simulate the catalytic oxidation of co on a pt surface. I uploaded the kinetic file and the thermodynamic file. But ansys always reports an error and shows that it can't be uploaded. So I would like to ask if there is a syntax error in my files or because the version is too low. I am using ansys 18.0. Can anyone tell me is there anything wrong with my file?

 

Here is my reaction mechanism document.

REACTIONS MWOFF KJOULES/MOLE   
O2 + (Pt) => O2(Pt)                           5.000E-02  0.000      0.000 
    STICK 
O2(Pt) => (Pt) + O2                           5.243E+11  -0.069     19.573 
O2(Pt) + (Pt) => O(Pt) + O(Pt)                8.325E+13  -0.000     39.933 
O(Pt) + O(Pt) => O2(Pt) + (Pt)                4.444E+21  0.000      264.067 
    COV / O(Pt)                               0.000E+00  0.000      -88.200 / 
CO + (Pt) => CO(Pt)                           8.400E-01  0.000      0.000 
    STICK 
CO(Pt) => (Pt) + CO                           7.635E+12  -0.139     143.145 
    COV / CO(Pt)                              0.000E+00  0.000      -29.300 / 
CO2 + (Pt) => CO2(Pt)                         3.193E-03  -0.035     2.686 
    STICK 
CO2(Pt) => (Pt) + CO2                         1.894E+10  0.139      21.855 
CO(Pt) + O2(Pt) => CO2(Pt) + O(Pt)            4.124E+13  0.069      9.494 
    COV / O(Pt)                               0.000E+00  0.000      44.100 / 
CO2(Pt) + O(Pt) => CO(Pt) + O2(Pt)            2.910E+23  -0.069     272.506 
    COV / CO(Pt)                              0.000E+00  0.000      29.300 / 
CO(Pt) + O(Pt) => CO2(Pt) + (Pt)              4.764E+13  0.069      101.361 
    COV / CO(Pt)                              0.000E+00  0.000      -29.300 / 
CO2(Pt) + (Pt) => CO(Pt) + O(Pt)              6.297E+20  -0.069     140.239 
    COV / O(Pt)                               0.000E+00  0.000      44.100 / 
END