1) The document describes the design and analysis of catalytic converters through computational fluid dynamics (CFD) simulations. 2) Six CAD models of catalytic converters were generated by varying inlet cone length and substrate dimensions. The models were simulated using both ceramic and steel wire mesh substrates. 3) The CFD results were analyzed to compare pressure variation, recirculation zones, and velocity vectors between the different designs. Models with longer inlet cones and steel wire mesh substrates performed better with lower back pressure and fewer recirculation zones.

1. DESIGN AND ANALYSIS OF CATALYTIC CONVERTER
By
Aakash Srivastava 11-1-2-011
Shivam Chaubey 11-1-2-019
Ankan Jyoti Phukan 11-1-2-046
Vivek Raj Pal 11-1-2-051
Ravi Ranjan 11-1-2-075
Under supervision of
Mrs. Sumita Deb Barma
Department of Mechanical Engineering
National Institute of Technology, Silchar

2. 2
INTRODUCTION
• Most effective after treatment for reducing engine
emissions.
• Lowers temperature needed for oxidation of CO and HC
by using catalysts.
• Three way converter reduces NOx in addition to oxidation of CO and HC.
• Substrates used to hold catalyst may be made of Ceramic honeycomb, metallic monolith
or steel wire mesh
• Various minute channels in substrate form honeycombs in which reactions occur.
• Alumina is used as wash coat and holds catalysts including Rhodium, Palladium and
Platinum

3. COMPARISON BETWEEN SUBSTRATES
Factors Ceramic Metal Steel Wire
Thermal
conductivity(W/m-
K)
32 24 16.7
Porosity 0.69 0.91 0.864
Open-frontal
area(%)
69 91 86.4
Manufacturing ease Difficult Difficult Easy
Wall thickness 0.15 mm 0.05 mm 0.114 mm
• Due to manufacturing ease and low thermal mass , steel wire mesh is found better than
the other two

4. PROBLEM STATEMENT
• Compare various catalytic chamber design parameters such as inlet cone length, type of
substrate medium, diameter and length of substrate
• CFD simulations are done on the generated cad models to study the loss of pressure and
re-circulation zones generated
•Methods used
 Varying inlet cone angle
Varying inlet cone length
Varying substrate dimensions
Varying substrate type (Ceramic/Steel Wire Mesh)

5. OBJECTIVES
1. Preparing CAD model for various test cases to be studied
2. Meshing in ICEM CFD followed by CFD simulations in ANSYS FLUENT
3. Post-processing of CFD results to compare different chamber designs on basis of
minimum back pressure and recirculation zones developed
4. Conclusion giving factors that lead to favourable chamber design.

6. LITERATURE SURVEY
• A review paper on Catalytic Converter for Automotive Exhaust Emission by Prof.
Bharat S Patel and Mr.Kuldeep D Patel
• Design, analysis of flow characteristics of catalytic converter and effects of back
pressure on engine performance by Dr. R. Senthil in IJREAT , March 2013
• Design optimization of Catalytic Converter to reduce Particular Matter and Achieve
limited Back Pressure in Diesel Engine by CFD by B.Balakrishna and Srinivasarao
Mamidala
• Modeling and Simulation of different gas Flow Velocity and pressure in catalytic
converter with porous by K.Mohan Laxmi and V.Ranjith Kumar
• Automotive catalytic converters: current status
and some perspectives by J. Kaspar, N. Hickey and Paolo [ELSEVIER]

7. DESIGN CALCULATION
Engine Specification
Shape of Catalytic Converter- Cylindrical
Space velocity- 30000 hr-1
Volume flow rate- 30.615 m3/hr
Catalyst Volume- 1.0205e-3 m3
Type 4 S, SI
Speed 1000 rpm
Bore 100 mm
Stroke 130 mm
Volume flow rate=Space Velocity*Catalyst Volume
Model Diameter of Substrate Length of Substrate
1 100 mm 153.5 mm
Model Diameter of Substrate Length of Substrate
2 80.6 mm 200 mm

8. DESIGN CALCULATION
Model 1.1 1.2 1.3 2.1 2.2 2.3
Inlet diameter 40 mm 40mm 40mm 40mm 40mm 40mm
Outlet
diameter
40mm 40mm 40mm 40mm 40mm 40mm
Substrate
diameter
100 mm 100mm 100mm 80.6mm 80.6mm 80.6mm
Substrate
length
153.5mm 153.5mm 153.5mm 200mm 200mm 200mm
Inlet cone
Length
30mm 40mm 60mm 30mm 40mm 60mm
Outlet cone
Length
40mm 40mml 40mm 40mm 40mm 40mm
• Six different cad models were generated using the above readings

9. CAD MODEL
• CAD models were generated using CATIA V5
Model 1.1 Model 1.2 Model 1.3
Model 2.1 Model 2.2 Model 2.3

10. 10
Unstructured Grid is chosen over Structured Grids
Reasons:
• Less Mesh Generation Time
• Good result accuracy obtained with improved mesh quality
MESHING is done in following phases:
1. Creating surface mesh using Triangular mesh
2. Creating Tetrahedral Volume Meshes
Softwares used for mesh generation includes ICEM-CFD.
Triangular Mesh
Tetrahedral Mesh
MESH

11. MESH
Quantity Stat
Tetrahedral Volume mesh
Surface Mesh (Magnified
View )
Triangular Surface mesh
Quality Stat

12. SOLVER
•Pressure based solver was used.
• A porous medium was used to simulate the effect of substrate.
• Porosity, Inertial resistance and Viscous resistance value was obtained for Ceramic and
Steel wire substrate
• For Ceramic substrate
 Porosity 0.69
 Inertial Resistance(1/m) - 20.414
 Viscous Resistance(1/m2) - 3.864e+7

13. SOLVER
• For steel wire substrate
Equation for pressure loss at varying velocity for 1 m length of substrate was obtained
from Technical Paper
• Comparing with equivalent equation for any homogeneous media
• The following values were obtained
 Inertial Resistance(1/m)- 2.2857
Viscous Resistance(1/m2)- 1.21e+5
Ploss= 1.40v2+2.189v
Ploss=-C2*0.5*p*v2-u/a*v

14. SOLVER SETTINGS
Scale factor = 0.001
Pressure Based solver
Viscous model: Standard k-epsilon, Standard wall function
Convergence tolerance = 0.000001
Cell Zone Condition: Substrate- Porous and laminar Zone
Pressure under relaxation=0.2
Velocity at Inlet= 6.77 m/s
Outlet gauge pressure= 0 Pa
Respective Inertial and Viscous Resistance values
Momentum under relaxation=0.5
Other settings are kept standard and default
Solved in Fluent v6
• 12 CFD simulations were performed : Two for each model depending on Ceramic and
Steel wire substrates used.

15. POST PROCESSING RESULTS
• The post processing of simulation results was done which were then grouped and
interpreted according to following factors
 Pressure Variation through the Catalytic converter
 Recirculation zones produced
 Velocity variation during fluid flow

16. POST PROCESSING RESULTS
Pressure variation when using Ceramic Substrate
Model 1.1 Model 1.2 Model 1.3
Model 2.1 Model 2.2 Model 2.3

17. POST PROCESSING RESULTS
Pressure variation when using Wire Mesh Substrate
Model 1.1 Model 1.2 Model 1.3
Model 2.1 Model 2.2 Model 2.3

18. POST PROCESSING RESULTS
Recirculation zones when using Ceramic Substrate
Model 1.1 Model 1.2 Model 1.3
Model 2.1 Model 2.2 Model 2.3

19. POST PROCESSING RESULTS
Recirculation zones when using Wire Mesh Substrate
Model 1.1 Model 1.2 Model 1.3
Model 2.1 Model 2.2 Model 2.3

20. POST PROCESSING RESULTS
Velocity vectors when using ceramic substrate
Model 1.1 Model 1.2 Model 1.3
Model 2.1 Model 2.2 Model 2.3

21. POST PROCESSING RESULTS
Velocity vectors when using Wire Mesh substrate
Model 1.1 Model 1.2 Model 1.3
Model 2.1 Model 2.2 Model 2.3

22. POST PROCESSING RESULTS
Velocity vectors when using Ceramic substrate
Model 1.1 Model 1.2 Model 1.3
Model 2.1 Model 2.2 Model 2.3

23. POST PROCESSING RESULTS
Velocity vectors when using Wire Mesh substrate
Model 1.1 Model 1.2 Model 1.3
Model 2.1 Model 2.2 Model 2.3

24. POST PROCESSING RESULTS
Pressure variation when using ceramic substrate
Model 1.1 Model 1.2 Model 1.3
Model 2.1 Model 2.2 Model 2.3

25. POST PROCESSING RESULTS
Pressure variation when using Wire substrate
Model 1.1 Model 1.2 Model 1.3
Model 2.1 Model 2.2 Model 2.3

26. POST PROCESSING RESULTS
Back Pressure for Model 1 (Ceramic vs. Wire Mesh Substrate)
Ceramic Back Pressure (Pa)
Model 1.1 181.7
Model 1.2 177.9
Model 1.3 165.93
Wire Mesh Back Pressure (Pa)
Model 1.1 42.4
Model 1.2 41.8
Model 1.3 40.6
150
155
160
165
170
175
180
185
190
195
200
MODEL 1.1 MODEL 1.2 MODEL 1.3
BACK PRESSURE
CERAMIC
35
37.5
40
42.5
45
47.5
50
MODEL 1.1 MODEL 1.2 MODEL 1.3
BACK PRESSURE
WIREMESH

27. POST PROCESSING RESULTS
Back Pressure for Model 2 (Ceramic vs. Wire Mesh Substrate)
270
272.5
275
277.5
280
282.5
285
287.5
290
292.5
295
297.5
300
MODEL 2.1 MODEL 2.2 MODEL 2.3
BACK PRESSURE
CERAMIC
40
42
44
MODEL 2.1 MODEL 2.2 MODEL 2.3
BACK PRESSURE
WIREMESH
Ceramic Back Pressure (Pa)
Model 2.1 288.34
Model 2.2 283.45
Model 2.3 281.8
Wire Mesh Back Pressure (Pa)
Model 2.1 42.7
Model 2.2 42.29
Model 2.3 41

28. CONCLUSION
• We can see from the results that the maximum pressure drop of 288.34 Pa was seen
for Model 2.1 when simulated for Ceramic substrate while the minimum back pressure
was created for Model 1.3 when simulated for Wire Mesh Substrate.
• It was observed that the back pressure decreased with increase in inlet cone length in
each of the cases irrespective of type of substrate.
• Due to recirculation zones formed, there was a marked decrease in amount of gas
passing through the substrate thus reducing the effectiveness of the converter.
• Model 2.3 shows lowest back pressure but due to formation of recirculation zones ,
the converter’s effectiveness should be lowered ,thus, Model 2.2 with wire mesh
substrate is considered the best candidate for further study and development of
converter.