[RiccardoCFD]

Hi everyone,
I'm trying to simulate a natural gas spark ignition engine, using the SAGE detailed chemistry solver. I started using the GRI 3.0 mechanism but, after SAGE is activated,the simulation proceeds at an extremely slow pace. That's why I've decided to use a much simpler mechanism for CH4 combustion, with only 6 species and 2 reactions.

My question is: is it possible to start the simulation from a restart just before spark timing (or just before SAGE activation) with a different mech.dat file? I tried to change the mech.dat, by writing down the new reactions and keeping all the species I had with the previous mechanism in the SPECIES section (since they had been tracked up to that moment) but it doesn't seem to work.

Thanks in advance

[jhuang]

Hi Ricardo, in this case, you can use the restart mapping by setting mapflag to 2 in inputs.in. It will use your last restart file as mapping file to initialize the simulation. Please make sure that all the species in the simple mechanism are included in the original mechanism. Thanks.

[SamWijey]

Hello,

CONVERGE is used to do NG simulations using GRI-Mech 3.0 quite frequently. The slow down that you are seeing might be related to non-optimized case setup. If you can email your case setup to support@convergecfd.com we can take a look at it and give you some pointers to run faster.

Thanks,