[learner1111]

Hello Convergent Science,

I've been trying to run a combustion case whose fuel injection tempurature is very low, around 100K. I keep seeing energy convergence problems, such as.

ERROR: Something is wrong in function get_temp_from_table_massfrac: upper_energy_value must be greater than lower_energy_value!
upper_energy_value is -nan(ind), and lower_energy_value is -nan(ind).

So I wonder if there is anything that I should pay particular attention when running such a case. Should model parameters be anything different from those in regular IC engine cases?

Thanks

[Pndsc]

I would check your case setup pretty carefully - somewhere theres a "minimum temperature in domain" limiter.

Check also your gas simulation parameters for the critical temperature and the contents of your therm.dat file for species whose data does not go below 0 celsius - checking a few likely suspects (O2, N2) their property curves end at 300K for the therm.dat file I'm using.

I'd suggest you get in touch with tech support to see if they can help you out with therm.dat (and maybe mechanism?) files for cryogenic species.

[Yaju]

Hi learner1111,

Try using the following in your inputs.in (real gas properties and critical condition data):

*
*
3                       eos_flag                     Equation of state: 0=ideal gas, 1=Redlich-Kwong, 2=Redlich-Kwong-Soave, 3=Peng-Robinson.
1                       real_gas_prop_flag           0=Thermodynamic quantities are only function of T, 1=Thermodynamic quantities are only function of both T and P.
*
"crit_conditions.dat"   crit_temp                    Filename for gas species critical properties.
"crit_conditions.dat"   crit_pres                    Filename for gas species critical properties.
"crit_conditions.dat"   acentric_factor              Filename for gas species critical properties.
*
*

Here the "crit_conditions.dat" file contains critical condition data for all your relevant species. For the species which are not listed in this file, the code is going to use the DEFAULT line. Below is an example:

# species      crit_temp      crit_pres      acentric_factor 
DEFAULT        133.0          3.77e+6        0.035          
N2             126.19         3.3978e+6      0.039          
O2             154.58         5.043e+6       0.025          
CH4            190.6          4.61e+6        0.011          
CH2O           408.0          6.59e+6        0.253          
C2H2           308.3          6.138e+6       0.19           
C2H3           308.3          6.138e+6       0.19           
C2H4           282.5          5.06e+6        0.089          
C3H4           402.4          5.63e+6        0.215          
C6H12          504.03         3.14e+6        0.28           
C7H16          540.2          2.74e+6        0.349          
C10H22         617.8          2.11e+6        0.489          
CO             134.45         3.49875e+6     0.066          
CO2            304.18         7.38e+6        0.2373         
HO2            728.0          22.0e+6        0.0            
H2             33.18          1.3e+6         -0.216         
H2O            647.0          22.064e+6      0.344          
H2O2           728.0          22.0e+6        0.0            
NO             180.0          6.48e+6        0.588          
JP10           698.0          3733000.0      0.035