NO model vs post processing in coal combustion,CFX
I am modeling coal combustion in a reactor with swirl flow and I want to analyze the amount of NOx emission in the outlet of my reactor.
I have used fuel gas oxygen reactions, not the HCN NO PDF ones, and used post processing. but the amount of mass fraction of NO in the outlet is not added to the summation of mass fraction of all species in the outlet. meaning that NO.mf = 0.67, sum(all mass fractions including NO)=1.67, sum(all mass fractions excluding NO)=1.
So I thought maybe this method is the wrong way and there there might be another way to consider NO analysis as the main reactions while solving not in post processing.
In the tutorial for coal combustion, I see the post processing is used to study NO mass fractions and in the can combustor tutorial, NO model is used in terms of using CFX library and HCN NO PDF reactions without any post processing.
My question is are these two, post processing and NO model, two different methods in CFX? which one is more accurate and you suggest to use?
The post-processor solves the same transport equation after momentum, enthalpy etc. It is one-way coupled. So, if there is no feedback, it should be okay.
Thermal NO is the classic example. I have much experience with gaseous combustion, lesser with coal. So, I can give no final recommendation. You may just try both and compare.
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