[infrared]

Hello, I performed a diesel combustion case with the following configuration:

- Cylindrical domain with impingement on the wall, where the inlet nozzle is placed vertically at the center of the top wall.
- The boundary conditions are initialized as top_wall, bottom_wall, inlet, and outlet.
- The temperatures were set as follows: wall temperature at 500K, vessel temperature at 1000K, and diesel temperature at 338K.
- Vessel pressure is 4 MPa.
- Oxygen is 21% of the air.
- The domain has a diameter of 40 mm and a height of 20 mm, with the inlet diameter being 1 mm.
- The mesh was set to 200x12x64 cells, with a denser configuration near the bottom wall.
- The combustion model is PaSR, using the LES turbulence model and the reactingFoam solver.
- Diesel is continuously injected into the domain.
- The file structure for this case is as follows:
/0 directory: contains alphat, mass fractions, p, T, U, Ydefault.
/constant directory: contains polyMesh, chemistryProperties, combustionProperties, reactions, thermo.compressibleGas, thermophysicalProperties, and turbulenceProperties.
/system directory: contains blockMeshDict, controlDict, FOBilgerMixtureFraction, fvSchemes, and fvSolution.

The problem is that I cannot see any flame in the temperature distribution from this combustion case, as shown in the attachment.

T70.jpg

Is there any issue with the setup I’ve provided above? Any suggestions and comments would be greatly appreciated. Thank you for your kindness.

Best regards,
Ir

[GeekCFD]

Hi Rohmawati,
Can you please share the case setup, particularly the constant and system directories?
It is otherwise difficult to comment on the problem if one doesn't have access to the files.

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Thanks,
GeekCFD

[infrared]

Originally Posted by GeekCFD

Hi Rohmawati,
Can you please share the case setup, particularly the constant and system directories?
It is otherwise difficult to comment on the problem if one doesn't have access to the files.

-------------------------
Thanks,
GeekCFD

Hi @GeekCFD,

Thank you for your response. After carefully checking the case, I found that the problem was that I forgot to define the O2 amount (0.21) in the 0 directory. I successfully ran the case using biodiesel (C17H34O2) as the fuel, but I couldn't observe any flame for the case using diesel (C7H16 or C12H26) as the inlet fuel.

The setups were similar, as I ran them in a constant volume with the fluid impinging on the bottom wall. Here is the file structure of the case:

*0 directory*: alphat, C7H16 or C12H26 or C17H34O2 (depending on the fuel variation), CO2, H2O, k, N2, nut, O2, p, rho, T, U, Ydefault.

*constant directory*: polyMesh, chemistryProperties, combustionProperties (PaSR), reactions (complete and incomplete combustion), thermo.compressibleGas, thermophysicalProperties, transportProperties, turbulenceProperties (LES).

*system directory*: blockMeshDict, controlDict, FOBilgerMixtureFraction, fvSchemes, fvSolution.

Here is the temperature comparison of diesel and biodiesel at the same time, but no flame was visible for the diesel case.

Your response and suggestions are greatly appreciated. Thank you in advance.

[GeekCFD]

Hi Rohmawati,
Sorry for the late reply. I was quite busy last month.

I had a look at your case, and I think there are a few things that could be causing the issue:

1. Reaction Mechanism and Species Properties:
Make sure to update the 'reactions' file and the species properties in the 'thermophysicalProperties' file when switching from biodiesel to diesel. These files might still have values which were originally set for biodiesel. Plus, I’d recommend using a more detailed mechanism like GRI or a similar setup to ensure an accurate representation of diesel combustion.

2. Initial and Boundary Conditions (Possible Major Issue):
Double-check that the initial and boundary conditions are realistic for diesel combustion. For instance, the initial temperature near the injection zone might need to be higher due to diesel's lower volatility compared to biodiesel. Sometimes, the initial conditions might be such that no significant heat generation or fuel spread occurs, which would prevent combustion from initiating.


Please take a look at these points and see if they help resolve the issue. If possible, please share the relevant files from your case setup (like the constant and system directories) so I can better debug the problem.

Let me know if you need any further assistance.


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Best regards,
GeekCFD