[whysoserious]

Why there is a difference of NOx value among emissions.out, passive.out and species.out? which one is recommended?

[SamWijey]

CONVERGE provides you different mechanisms to calculate NOx. Thermal NOx is calculated using extended Zeldovich mechanism and is using passive species. The hard-coded reactions are used to calculate the production of NO and is reported in passive.out. The same NO value is reported in emissions.out with a multiplier of 1.533 (user can change this value).
To obtain the above values, you do not need to solve detailed chemistry. But if you have a detailed chemistry mechanism and NOx chemistry is included in that mechanism, then you get another output in species.out. This output records the mass of each species in your chemical mechanism.
The NO value from species.out and passive.out might not match due to the fact that they use different reaction rates. Further, the value given in species.out depends on the concentration of other species in the chemical mechanism.
What value to look at when comparing to experimental data depends on what quantity is available as measured data (NO, NO2 or NOx).

[whysoserious]

Originally Posted by SamWijey

CONVERGE provides you different mechanisms to calculate NOx. Thermal NOx is calculated using extended Zeldovich mechanism and is using passive species. The hard-coded reactions are used to calculate the production of NO and is reported in passive.out. The same NO value is reported in emissions.out with a multiplier of 1.533 (user can change this value).
To obtain the above values, you do not need to solve detailed chemistry. But if you have a detailed chemistry mechanism and NOx chemistry is included in that mechanism, then you get another output in species.out. This output records the mass of each species in your chemical mechanism.
The NO value from species.out and passive.out might not match due to the fact that they use different reaction rates. Further, the value given in species.out depends on the concentration of other species in the chemical mechanism.
What value to look at when comparing to experimental data depends on what quantity is available as measured data (NO, NO2 or NOx).

Thank you for your reply.

From what I learn, the NOx value reported in passive.out is only the production of NO by Zeldovich mechanism. And the NOx value in emissions.out includes NO, NO2, N2O and so on. That's why a multiplier is necessary. Right?

But, why the multiplier is 1.533 since the portion of NO in NOx is usually large? how to change the multiplier?

Best regards.

[SamWijey]

This multiplier of 1.533 is the ratio of molar mass of NO2 to NO. Hence its a simple way of converting the NO mass produced by the Zeldovich mechanism to NO2. However if you know the majority of the measured NOx is NO (which is typically the case for most ICE applications) simply look at the value from passive.out or divide the emissions.out value by 1.533.

In CONVERGE v2.4 you can change this value in emissions.in