Cold chain grate furnace flow simulation.mfx (10.3 KB)
Dear developers and users of MFiX,
I am currently using MFiX-CGP to perform a cold-state particle flow simulation of a chain grate furnace. I have encountered some issues with boundary condition definition and initialization, which have troubled me for a long time. The front view of my 3D chain grate furnace geometry model is shown in Fig.1.
Model description: The blue line on the left represents the particle inlet boundary, the red line at the top represents the flue gas outlet boundary, the red line on the right represents the ash/slag outlet boundary, the black line represents the adiabatic rear arch, the inclined orange line at the bottom represents the moving grate, and the other white lines represent the water-cooled walls.
Problem description: The model dimensions are 11 m × 16 m × 4 m. Initially, a 150 mm thick coal particle fuel bed needs to be stacked above the grate. As the simulation starts, the fuel bed moves with the grate, and the ash/slag is discharged from the ash outlet. Meanwhile, particles need to be continuously injected from the left inlet; these particles will fall onto the grate and move together with the grate.
Current issue:
- Unable to define the boundary conditions for the bottom inclined grate and the adiabatic rear arch.
After building the 3D geometry and importing it into MFiX as an STL file, MFiX only recognizes it as a single 3D entity.
If I define the walls (Fig.2), I can only select all faces of the entire geometric model for definition. When I try to define the inlet and outlet boundaries, I cannot define them separately because the inlet/outlet boundaries lie on the same plane as their adjacent walls. I later chose to extend the inlet and outlet wall surfaces outward individually, which successfully allowed me to define the inlet and outlet boundaries, as shown in Fig.3.
However, I really cannot figure out how to define the bottom inclined boundary as a no‑slip wall with a specified velocity. Also, how can I accurately identify the adiabatic rear arch inside the model and define it as an adiabatic wall? Is there any method to achieve this? I tried importing all the faces that make up the geometric entity, which would allow me to define each face separately, but MFiX does not seem to recognize the shape enclosed by these faces as a valid 3D geometric entity, so I cannot run the simulation.
Problem 2: How can I initialize a 150 mm thick fuel bed stacked above the grate?
As far as I know, during initialization, particle stacking can only be done by specifying a rectangular (cuboid) region using coordinates. Given that my grate is inclined, how can I achieve this?
I hope everyone can provide some answers. Thank you!
