1D LFS calculation failed

zwu249 · November 28, 2020, 10:32

Hi, I am using CONVERGE chemistry tool to calculate laminar flame speed (LFS) to generate a LFS table for PRF92 fuel. I uses the default settings for the solve setup. I ran many cases, however, a small number of cases failed (especially for cases with 1500K, the upper bound of the initial temperature) . I got zero LFS values for these cases, i.e. they are not converged. I have tried two methods learned from this forum, (1) change the cutoff temp, (2)add a hidden.in file to change the time limit to 10000. Neither of them worked. Given that the mechanism is good for LFS calculation, someone can tell me which solver parameter I can change to get converged result. Thanks in advance.

Kamlesh Patel · December 1, 2020, 06:26

Hello,

Could you please try the following?

1.Use the solver settings from the example case. Load example cases>>One D simulation >> Laminar flame speed >> Newton Solver.
2.Check if the initial conditions are reasonable. Do you have test data available for these conditions?
3.Try altering the anchor temperature and Initial number of grid points

Case limit time is a regular feature in v3.0 and also has an option to automatically adjust the anchor temperature for each cases. Could you please try your case in v3.0 and see if they are still failing?

Thanks,

zwu249 · December 3, 2020, 00:48

Hi, Kamlesh, thank you for you answer! I increased the initial number of grid points, the problem is resolved now.

November 28, 2020, 10:32	1D LFS calculation failed	#1
zwu249 New Member Johnny Join Date: Nov 2015 Posts: 26 Rep Power: 10	Hi, I am using CONVERGE chemistry tool to calculate laminar flame speed (LFS) to generate a LFS table for PRF92 fuel. I uses the default settings for the solve setup. I ran many cases, however, a small number of cases failed (especially for cases with 1500K, the upper bound of the initial temperature) . I got zero LFS values for these cases, i.e. they are not converged. I have tried two methods learned from this forum, (1) change the cutoff temp, (2)add a hidden.in file to change the time limit to 10000. Neither of them worked. Given that the mechanism is good for LFS calculation, someone can tell me which solver parameter I can change to get converged result. Thanks in advance.

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December 1, 2020, 06:26		#2
Kamlesh Patel New Member Kamlesh Patel Join Date: Oct 2020 Posts: 2 Rep Power: 0	Hello, Could you please try the following? 1.Use the solver settings from the example case. Load example cases>>One D simulation >> Laminar flame speed >> Newton Solver. 2.Check if the initial conditions are reasonable. Do you have test data available for these conditions? 3.Try altering the anchor temperature and Initial number of grid points Case limit time is a regular feature in v3.0 and also has an option to automatically adjust the anchor temperature for each cases. Could you please try your case in v3.0 and see if they are still failing? Thanks,

December 3, 2020, 00:48		#3
zwu249 New Member Johnny Join Date: Nov 2015 Posts: 26 Rep Power: 10	Hi, Kamlesh, thank you for you answer! I increased the initial number of grid points, the problem is resolved now.