Error in reducing an mechanism file

[Debojit Sharma]

Hello everyone,

I am trying to reduce a mechanism file in  . YAML Cantera format. 

However, I am facing some errors in calculating sensitivities for many species, as can be seen in the screenshot. In addition, I am getting an error in the thermodatabase as well. The error message is as follows:

***************************************************************************************

For species HOCHO, discontinuity in h/RT detected at Tmid = 1500
        Value computed using low-temperature polynomial:  -22.992822585416665
        Value computed using high-temperature polynomial: -22.199627374374998


For species HOCHO, discontinuity in s/R detected at Tmid = 1500
        Value computed using low-temperature polynomial:  42.802369494994956
        Value computed using high-temperature polynomial: 42.0724991710496

***************************************************************************************

I would appreciate it if I could get some suggestions on rectifying these errors, as I am very new to the Cantera environment.

Thanks and regards,

Debojit Sharma.

[Steven DeCaluwe]

Hi Debit,

The error message means that the polynomials used to calculate the thermo properties for HOCHO do not produce a smooth and continuous value across the entire temperature rage.  

The behavior is covered in some detail here, but in short: your input file gives parameters to specify thermo properties across two temperature ranges.  In your case, these two ranges overlap at T_mid = 1500 K.

Cantera checks the polynomials to make sure they give continuous results at the mid point for S/R, h/RT, and C_p/R.  

As shown in the Jupyter notebook, you can plot these values and try to diagnose the reason for the discontinuity (In the notebook example, the problem was fixed simply by shifting T_mid to a lower value (note this may or may not work in your case).

Best regards,

Steven 

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