Learning Forum

[194106015]

 am simulating a case where the oxidizer and fuel are supplied with mass fluxes of 400 and 100 microns in width, respectively. I am employing species transport with volumetric reactions to capture both premixed and diffusion flames in the combustion zone. I am using a detailed reaction mechanism with 38 species and 127 reactions.

When using the laminar flow model with FR/No-TCI, the results are somewhat similar to the experimental data and simulation data available in the literature, although the exact flame structure is not replicated (using only a stiff chemistry solver).

However, when using any turbulent model with FR/ED, combustion is not occurring (using a direct source chemistry solver). I need to use turbulent model.

Could you please assist me with this issue?

[Ren]

Hello, Neeraj,

If the flow is indeed turbulent, then the FR/ED model is applicable. To numerically ignite the mixture, follow these steps:

1. run the calculation for some number of iterations, say, 100, to establish some mixing of the reactants.
2. define a small region in the expected flame region using, e.g., a region cell register, patch a high enough temperature (e.g., 2000 K) in this region. In addiiton, patch a reasonable value for a product species (e.g., co2 or h2o) mass fraction.

 

[194106015]

Thanks for the response. I will do what you mentioned and let you know, 

[194106015]

 

Hello Sir, I ran the simulation for around 100 iterations then gave a patch with 2000K temp and ran again. You can see the attached residual plot , after another 100 iterations the solution is getting converged without the combustion taking place. I have attached the temperature and velocity plots also for your reference. also what i noticed reactions are also not happening as heat of reaction in whole domain is zero. 

Another point: I just tried the same process with FR/No-TCI turbulent model. In that case whole domain is at 4000K( after around 1000 iterations)

 

Thanks

 

[Ren]

If using FR/No-TCI, you need to activate the "Stiff Chemistry Solver" in the Species Model dialog box.

The velocity magnitude looks relatively low. Can you show me a contour plot of the turbulent viscosity ratio?

[194106015]

I have updated the mass flux values at inlets. These values are more releastic . Followed the same process. The domain's bottom side is axis and top side is symmetry.  Now showing mirror plane of axis.

 

Attached turbulent viscosity plots also. 

 

Thanks 

[194106015]

For your reference i have attached case and data files https://drive.google.com/drive/folders/11IdHWPQgp5eVTmofEGXoIwEpghCtvAcI?usp=drive_link

[Ren]

We are not allowed to download files.

The turbulent viscosity is very low meaning the flow is predominantly laminar.

Please tell me the mass flow rate, mixture composition and temperature of each inlet.