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Old   March 5, 2006, 13:45
Default Dear all, I am going to add N
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saeid kheradmand
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Dear all,
I am going to add Nox prediction (zeldowich) to achen bomb.
Is it neccessary to edit the source code? (is it possible by just editing dictionaries?)
thank you for your time.
regards
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Old   March 6, 2006, 03:11
Default This is a very weird question.
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Niklas Nordin
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This is a very weird question.
You are going to add a NOx mechanism to
a case??? So will you be able to use it
on only the aachen bomb case then?
Anyways.....

If you are planning to use dieselFoam,
then you will use the chemkin-interface and
in that case it has already been done.
If you look at the mechanism chem.inp_15
you'll find its already in there.
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Old   March 6, 2006, 04:45
Default Dear Dr Nordin Thank you for
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Dear Dr Nordin
Thank you for your answer
I dont want to use mechanism like chem.inp-15 (I have used it and it worked).
I am going to use a one step reaction
fuel+oxidant=co2+h2o
and
a simplified Nox mechanism that d(NO)/dt depeneds on O2 and N2.
sorry for the weird questions(cases like achen bomb)
regards
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Old   March 6, 2006, 05:01
Default Ok, so you do not want to use
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Ok, so you do not want to use Zeldovich,
since you're planning to bolt on NOx to the
global fuel conversion rate.

Then I'd suggest you just
use 2 reactions in chem.inp.
one for the fuel conversion rate
and one for the NO, like
NO + NO = N2 + O2
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Old   March 6, 2006, 05:19
Default thank you very much. I will d
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thank you very much.
I will do that and compare with complex mechanism.
than you
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Old   September 30, 2013, 13:54
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how to calculate fuel nox in openfoam
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Old   May 25, 2015, 17:27
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Hello everyone,

I would like to post-process NOx formation by considering only the global species concentrations for 1-step irreversible methane combustion.

From what I have understood and read I came to the following conclusion.
The formation of thermal NO_x according to the extended Zeldovich mechanism is given by
O + N_2 \rightleftharpoons  N + NO  \quad k_f^1 = 1.8*10^8 e^{-38370/T} \quad  k_b^1 = 3.8*10^7 e^{-425/T} \\

N + O_2 \rightleftharpoons  O + NO \quad  k_f^2 = 1.8*10^4 T e^{-4680/T} \quad  k_b^2 = 3.81*10^3 T e^{-20820/T} \\

N + OH \rightleftharpoons   H + NO \quad  k_f^3 = 7.1*10^7 e^{-450/T} \quad  k_b^3 = 1.7*10^8 e^{-24560/T} \\
with rate constants in m^3/mol-s

The rate of formation of [NO] is then given by
\frac{d[NO]}{dt} \: = \: k_f^1 [O] [N_2] +  k_f^2 [N] [O_2] + k_f^3 [N] [OH] - k_r^1 [NO] [N] - k_r^2 [NO] [O] - k_r^3 [NO] [H]

which under the quasi-steady assumption for [N] can be simplified to
\frac{d[NO]}{dt} \quad = \quad 2 \: k_f^1 \: [O] \: [N_2] \quad  \frac{\left(1-\frac{k_b^1 \: k_b^2 \: {[NO]}^2}{k_f^1 \: [N_2] \: k_f^2  \: [O_2]}\right)}{\left(1+\frac{k_r^1 \: [NO]}{k_f^2 \: [O_2] \: + \:  k_f^3 \: [OH]}\right)} \quad (mol/m^3-s)

with equilibrium concentration of [O] given by [O] = 3.97*10^5 T^{-1/2} e^{-31090/T}\: [O_2]^{1/2} mol/m^3
and the concentration of [OH] is given by [OH] = 2.129*10^2 \:  T^{-0.57} \: e^{-4595/T} \: [O]^{1/2} \: [H_2O]^{1/2} mol/m^3 using partial equilibrium approach.

Therefore, the concentration of [NO] can be obtained by solving the following scalar transport equation with \phi = [NO] and S_{[NO]} = M_{NO} \frac{d[NO]}{dt}
\underbrace{ \frac{\partial{\rho \phi}}{\partial t}}_{Transient \ term} +   \underbrace{ \nabla \cdot (\rho \vec u \phi )}_{Convection \ term}   =\underbrace {\nabla \cdot (\rho D \nabla \phi )}_{Diffusion \ term} +   \underbrace {S_{\phi}}_{Source \ term}\\

So, basically to successfully post-process NOx formation in OpenFOAM we need to solve the scalar transport equation for [NO] with a spatially varying source term which depends upon the concentration of [NO].
Can someone suggest a possible way of doing this. This is a non linear equation and would need to be solved iteratively. I want to implement this in OF but do not know where to start from. Any ideas please ??
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Old   June 18, 2015, 04:14
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Hello, I have successfully implemented thermal NOx formation using scalarTransportFoam. The results are qualitatively very good when compared to Fluent, however quantitatively they differ by a constant factor. I am not able to understand where I go wrong. Any suggestions ??
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