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Reacting Flow – Error when importing Chemkin input file into Fluent

    • jm15411

      Hello! I am having an issue when importing a chemkin input file into fluent. My simulation setup is described below:

      • Turbulence Model: Realizable k-epsilon
      • Species Model: Species Transport with Eddy Dissapation - Volumetric reaction

      I downloaded the chemkin input file from a source online. Then I uploaded the file along with the thermodynamic and transport equation files. The files all loaded correctly. During the simulation, the file failed, and outputted the chem.out file. This file showed the following information:

          POSF10325                                      3.04E+27   -2.6  2464148.4                                                                                                                                                                                          
            Error...product array full, cannot add...0.5H
            Error...product array full, cannot add...1.5CH3
                    add keyword "MAXSP=" to the REACTION line to increase the limit.
                    where is the max number of reactants or products in a reaction.
                    Example: REACTION    MAXSP=8

      I am aware that the maximum number of species in both the product and reactants is limited to 6. However, I also know I should be able to add a line to the "REACTIONS"  line using "MAXSP=12". I editted the chemkin input file to the following.


      After saving and uploading the file, I recieved an error in fluent saying the following:

      Reading volumetric reaction mechanism file ...
      Invalid UNIT data, maxsp, at line no. 47.
      Invalid UNIT data, maxsp, at line no. 47.
      Species  found at line no. 47 is not in the species list.
      Species  found at line no. 47 is not in the species list.

      0: mpt_accept: error: accept failed: No such file or directory

      The fl process could not be started.

      I know and am confident that line 47 is the "REACTION      MAXSP=12" line, however I cannot figure out why this is an issue and how to fix it. Any solutions or thoughts would be much appreciated. Thanks in advance!

    • Swathi V. V.
      Ansys Employee


      May I know the Fluent version you are using. Since Fluent uses the Chemkin libraries for mechanism import starting R17.0, the limitation of  6 product species is not applicable. Can you try to read in the mechanism without the MAXSP variable? 

      You can ignore the error message in the .out file for now. This message should be cleaned up the latest releases. I would recommend you to use the latest version of Fluent.

    • jm15411

      Hello and thank you for your response!

      The version of Fluent I am using is Fluent 2020 R2.

      When I upload the Chemkin file without the "MAXSP", it loads and allows the simulation to run, however I saw the error mesage above in the chem.out file and was worried it would result in inaccurate resutls.

      So just for clarification, you are saying that the error I am recieveing in the chem.out file is a fictional error and that there is actually no issue at all in running the simluation as far as the chemical reactions go as defined by the chemkin file?

      Thank you very much for your insight. It is much appreciated! I look forward to your response!

    • jm15411

      Hello again, to provide more information of this issue, I tried running the same simualtion in Fluent 2022 R1 and got the same errors in the chem.out file along with the following statement in the TUI after loading the Fluent file:


      CHEMKIN features will be unavailable (see chem.out)


      > CHEMKIN features will be unavailable (see chem.out)


      Hopefully this is helpful in diagnosing the issue. Thank you for the support!


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