# Sum of NO2, N2O and NO bigger than NOx- values

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 May 30, 2018, 04:11 Sum of NO2, N2O and NO bigger than NOx- values #1 New Member   Vladislav Klass Join Date: May 2018 Posts: 2 Rep Power: 0 Hi everybody, How is it possible that the sum of NO2, N2O and NO values in species_mass.out is sometimes bigger than the NOx values in emissions.out, since NOx should contain these 3 species? Is there a different calculation model? Or could anybody explain how these values are calculated? I did not find any information on that in the CONVERGE manual. Here is a link to the trouble making files: https://we.tl/L6oANGgpyi Cheers! Last edited by vladislavklass; May 30, 2018 at 04:14. Reason: Link added

May 30, 2018, 11:41
#2
Member

Shengbai Xie
Join Date: Aug 2016
Posts: 60
Rep Power: 9
Hi,

It is a very good question. Actually, those two NOx are obtained from different models. The one in emissions.out is from the soot model, the Hiroyasu model most probably. It only works well for high-temperature situations and only three reactions are involved. Whereas the other one (NO2+N2O+NO) in species_mass.out is from the detailed combustion model (SAGE) where more reactions and conditions are considered, as long as the mechanism you used is proper. In a nutshell, they are not necessarily equal and you'd better look at the one in species_mass.out if you are confident about your mechanism.

Quote:
 Originally Posted by vladislavklass Hi everybody, How is it possible that the sum of NO2, N2O and NO values in species_mass.out is sometimes bigger than the NOx values in emissions.out, since NOx should contain these 3 species? Is there a different calculation model? Or could anybody explain how these values are calculated? I did not find any information on that in the CONVERGE manual. Here is a link to the trouble making files: https://we.tl/L6oANGgpyi Cheers!
__________________
Shengbai Xie, Ph.D.
Senior research engineer, Application

(608) 230-1563
convergecfd.com

 June 7, 2018, 04:59 #3 New Member   Vladislav Klass Join Date: May 2018 Posts: 2 Rep Power: 0 This really helped me, thank you very much!

June 7, 2018, 14:14
#4
Member

Shengbai Xie
Join Date: Aug 2016
Posts: 60
Rep Power: 9
Sorry, I meant Zeldovich NOX model, not Hiroyasu soot model.

Quote:
 Originally Posted by xieshengbai Hi, It is a very good question. Actually, those two NOx are obtained from different models. The one in emissions.out is from the soot model, the Hiroyasu model most probably. It only works well for high-temperature situations and only three reactions are involved. Whereas the other one (NO2+N2O+NO) in species_mass.out is from the detailed combustion model (SAGE) where more reactions and conditions are considered, as long as the mechanism you used is proper. In a nutshell, they are not necessarily equal and you'd better look at the one in species_mass.out if you are confident about your mechanism. I hope I have answered your question. Thanks!
__________________
Shengbai Xie, Ph.D.
Senior research engineer, Application

(608) 230-1563
convergecfd.com

 Tags combustion, emissions, nox, species