Hi All,
I am trying to simulate Methane combustion in high pressure system. The case is laminar. Now, the moment I trun on volumetric reactions after simulating cold flow, I get this error:
routine = phi2y
location = 1
message = non-positive species sum
****** END ISAT_ABORT **************
I am using GRI 3.0 mechanism.
Thank you
Regards,
Anmol
Will the model run without the chemistry? Check the mesh quality & resolution, then move onto boundary conditions etc. When models fail it's best to remove anything complex (chemistry in this case) and then build back up.
Hi,
Thank you for your message. So, I am simulating a case for Methane combustion in a high-pressure system. The simulations were fine with the Fluent's 3 steps mechanism for Methane combustion but the moment I switch to another mechanism (from some paper, hardcoded into fluent) I get the above-mentioned error.
Thank you
Best,
Anmol
Check the mechanism and that it balances. Can you post the set up of the reactions?
Hi,
Thank you for your message. The Mechanism I am using is as follows:
1. CH3 + HCO = CH4 + CO 8.41E+13 0.0 0.0
2. CH2O + CH3 = CH4 + HCO 2.12E+04 2.8 5860.0
3. HCO + M = CO + H + M 5.75E+16 -1.0 17000.0
4. HCO + OH = CO + H2O 2.90E+12 0.0 0.0
5. CO + O2 = CO2 + O 3.12E+10 0.0 47700.0
6. CO + OH = CO2 + H 1.93E+14 -0.6 331.8
Duplicate
7. CO + OH = CO2 + H 7.37E+04 2.0 -355.7
Duplicate
8. CO + O (+M) = CO2 (+M) 2.35E+10 0.0 2384.0
Low /1.27881E+25 -2.79 4191.0/
H2O/12.0/ CO2/3.6/ CO/1.75/
9. HCO + O = CO2 + H 3.82E+10 0.0 0.0
10. HCO + O = CO + OH 2.14E+16 0.0 0.0
11. CO + HO2 = CO2 + OH 1.26E+06 2.1 17942.6
12. CH3 + HO2 = CH4 + O2 6.33E+12 0.0 0.0
13. CH3 + O2 = CH2O + OH 2.16E+11 0.0 8940.0
14. CH3 + H2O2 = CH4 + HO2 6.33E+02 2.5 5180.0
15. H + O2 = O + OH 2.32E+16 -0.7 17041.0
16. HO2 + OH = H2O + O2 2.23E+134 -40. 34800.0
Duplicate
17. H + H2O2 = H2O + OH 5.82E+14 0.0 3970.0
18. H2O2 + O = HO2 + OH 5.94E+08 2.0 3970.0
19. HO2 + OH = H2O + O2 2.82E+16 -1.8 60.0
Duplicate
20. HO2 + OH = H2O + O2 1.79E+85 -22. 26900.0
Duplicate
21. HO2 + OH = H2O + O2 3.74E+69 -17. 32900.0
Duplicate
22. HO2 + OH = H2O + O2 5.59E+12 2.0 40000.0
Duplicate
23. H2O2 + OH = H2O + HO2 4.78E+11 0.0 427.0
Duplicate
24. H2O2 + OH = H2O + HO2 2.85E+41 -7.0 37600.0
Duplicate
25. CH3 + H (+M) = CH4 (+M) 1.05E+17 -0.6 383.0
Low /2.17162E+34 -4.76 2440.0/
TROE /0.783 74.0 2941.0 6964.0/
CH4/2.0/ H2O/6.0/ CO2/2.0/ CO/1.5/
26. CH3 + O = CH2O + H 1.41E+13 0.0 0.0
27. CH2O + O = HCO + OH 1.20E+16 0.0 3540.0
28. CH2O + HO2 = H2O2 + HCO 2.64E+12 0.0 8000.0
29. CH2O + OH = H2O + HCO 2.49E+09 1.1 -447.0
30. CH2O + O2 = HCO + HO2 3.65E+18 0.0 40000.0
31. 2 O + M = O2 + M 6.25E+16 -1.0 0.0
32. H + O + M = OH + M 1.98E+18 -1.0 0.0
33. H + O2 (+M) = HO2 (+M) 5.43E+11 0.4 0.0
Low /3.75013E+21 -1.4 0.0/
TROE /0.5 1e-30 1e+30 0.0/
H2O/11.89/ CO2/2.18/ CO/1.09/ O2/0.85/
34. H + HO2 = H2O + O 5.99E+10 0.0 671.0
35. 2 OH (+M) = H2O2 (+M) 1.21E+15 -0.4 0.0
Low /9.04468E+14 -0.584 -2293.0/
TROE /0.7346 94.0 1756.0 5182.0/
H2O/6.0/ CO2/3.6/ CO/1.75/
36. HO2 + O = O2 + OH 9.55E+15 0.0 0.0
37. H + HO2 = 2 OH 1.20E+15 0.0 295.0
38. 2 HO2 = H2O2 + O2 3.54E+13 0.0 12000.0
Duplicate
39. 2 HO2 = H2O2 + O2 5.46E+10 0.0 -1630.0
Duplicate
40. CH4 + O = CH3 + OH 1.82E+10 1.5 8600.0
41. CH4 + OH = CH3 + H2O 4.60E+08 1.6 3120.0
42. H + OH + M = H2O + M 9.32E+23 -2.0 0.0
43. 2 OH = H2O + O 1.90E+02 2.4 -2110.0
44. H + HCO (+M) = CH2O (+M) 7.71E+11 0.5 -260.0
Low /8.89016E+23 -2.57 1425.0/
TROE /0.7824 271.0 2755.0 6570.0/
CH4/2.0/ H2O/6.0/ CO2/2.0/ CO/1.5/
45. H2O + HCO = CO + H + H2O 1.17E+18 -1.0 17000.0
46. HCO + O2 = CO + HO2 4.67E+07 0.8 -727.0
Also, other than the non-positive species sum error, I am also getting a dasac failure at certain temperatures.
Thank you
Best,
Anmol
Try removing the duplicates: if you have two reactions with different rates the solver can't work out which one to use.
