Modeling of Catalytic Convertor

Introduction

-A workshop to demonstrate how to model porous media in FLUENT

-Workshop models a catalytic convertor. Nitrogen flows in though inlet with an uniform velocity 22.6 m/s, passes through a ceramic monolith substrate with square shaped channels, and then exits through the outlet.

-Substrate is impermeable in Y and Z directions, which is modeled by specifying loss coefficients 3 order higher than in X direction

 

Starting Fluent in Workbench

1. Open the Workbench (Start > Programs > ANSYS 12.0 > ANSYS Workbench)
2. Drag FLUENT into the project schematic
3. Change the name to Catalytic
4. Double click on Setup
5. Choose 3D and Double Precision under Options and retain the other default settings

Import Mesh

This starts a new Fluent session and the first step is to import the mesh that has already been created:

1. Under the File menu select Import> Mesh
2. Select the file catalytic_converter_125k.msh.gz and click OK to import the mesh
3. After reading the mesh, check the grid using Mesh>Check option

or by using Check under Problem Setup>General

Setting up the Models

1. Select Pressure Based, Steady state solver Problem Setup>General>Solver
2. Specify Turbulence model

Problem Setup > Models > Viscous

Double click and select k-epsilon (2 eqn) under Model and Realizable under k-epsilon model and retain the default settings for the other parameters

1. Make sure that the Energy Equation is disabled

Problem Setup > Models> Energy

Materials

Define the materials.

Problem Setup > Materials

1. Click on air to open Create/Edit Materials panel
2. Click on FLUENT Database…> Select nitrogen(n2) from the list > Copy
3. Click on Change/Create

Fluid Zone Conditions

Under Problem Setup >Cell Zone >Double click on part-in under Zone

– Select Material Name : nitrogen

– Default values for other settings

– Click to OK

Similarly, visit to part-out Zone and select the same settings as above

 

Fluid Zone Conditions (2)

Under Problem Setup ->Cell Zone ->Double click on part-catalyst under Zone

– Select Material Name : nitrogen

– Select and click on Porous Zone

– Under Direction-1 Vector, specify as: 1, 0, 0

– Under Direction-2 Vector, specify as: 0, 1, 0

– Specify as per GUI under Viscous Resistance and Inertia Resistance

– Default values under Power law Model and Porosity

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