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Old   May 15, 2007, 21:42
Default diesel spray and combustion with EGR
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Hello everybody,

I want to calculate diesel spray and combustion problem with various EGR conditions:

1. I set Unpremixed/Diffusion EBU LATCT 2. I write the reaction C12H26 + 18.5O2 -> 12CO2 + 13H2O. 3. For O2 Fixed-Fraction I specify the value depending on my EGR condition. (for example, without EGR-0.233) 4. In molecular properties for scalars I add CO2(r)and H2O(r) as active scalars. 5. In Additional scalars->Initialization, I specify Initial Mass Fractions for O2, N2, CO2(r) and H2O(r) depending on my EGR conditions. N2 always will be 0.767 right? Because if I write the reaction like C12H26+18.5(O2+3.76N2)->12CO2+13H2O+69.56N2 the N2 content is equal on the left hand side and the right hand side. But when we initialize Air for additional scalars we have to specify N2 mass fraction as 0.767, is it right? Is this procedure correct?

Please share your knowledge

Appreciate it
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Old   May 16, 2007, 04:34
Default Re: diesel spray and combustion with EGR
Klaas Klever
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1- 4 sounds reasonable (don't forget to define a scalar for C12H26).

Although the overall mass flow of N2 won't change (if we neglect NOx formation), the mass fraction at the inlet and the outlet will differ as you add mass with your fuel.

However, your initial conditions are only the starting point for the iterations (I assume you are running steady-state). They should not affect the solution, only the time it takes to reach that solution. The more important setting for the result is the scalar mass fractions in the boundary conditions.

hope that helps.
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