Hi there,
I am having a simple box geometry (2D). I am using a reduced CHEMKIN mechanism for n-heptane for the combustion purpose. The initial conditions are as follows.
Initial mixture mass concentration:
nC7H16: 0.028
N2: 0.745
O2: 0.227
Initial temperature: 1000 K
Initial Pressure: 42 bar
There is a uniform mixture of air and fuel in the 5mm x 10mm box. I am using ANSYS Fluent to solve the combustion problem.
Model used: Species Model
Reaction: Volumetric with Eddy dissipation concept.
When I run the unsteady simulation, the ignition always starts from the wall and it propagates to the middle of the box. It takes significant time to reach to the centre. For almost 7 milliseconds, there is no ignition at the middle of the box.
Can anybody suggest me why is this happening ? If the mixture is uniform throughout, it should ignite at the middle also. Please help me with the problem.
The temperature plot is attached herewith.
Thanks a lot in advance.
Hello Sir,
Do you think it will help me to solve the problem ? I will definitely try with laminar finite rate chemistry. Please let me know if you have anymore suggestions. I really appreciate your response.
Thanks,
Parth
Hi,
When you use Laminar finite rate chemistry , switch off the turbulence models.
Also, what kind of thermal conditions did you apply for the walls?
Hello Sir,
I am using no slip boundary condition and at wall I set as 0 heat flux. I think the problem is due to viscosity. Inviscid flow gives me proper results. Are these Inviscid solutions reliable for real life situations ?
Is there any way to get proper results with turbulence model on ?
Thanks,
Parth
So, did you give viscosity as constant for the species? If so, change it to mass weighted mixing law calculation.
You can also change other params like thermal conductivity to follow mass weighted mixing law.
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