Wall-flow Honeycomb Filter Asymmetric Cell Area Ratio
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Solution Overview
Problem
Wall-flow honeycomb filters face challenges in balancing high catalyst loading with high particulate storage capacity while maintaining low backpressure, as the application of washcoats on porous walls can decrease effective flow area and increase pressure drop.
Innovation Solution
The filter design features a ceramic monolith with cross-shaped inlet cell clusters and separate inlet and outlet cells, allowing for a higher ratio of combined cross-sectional area of inlet cells to outlet cells, and differential washcoat application on inlet cluster walls and filtering walls to maintain low backpressure and high particulate storage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If washcoat is deposited within the pores of the porous walls, then the effective flow area of the inlet cells is largely unaffected, but the storage capacity of the filter decreases because the pores are filled partially or entirely with the washcoat
Solution Approach 1:
The filter structure is segmented into two distinct functional zones: inlet cells with high porosity (40-80%) for particulate storage and outlet cells with low porosity (0-20%) for catalysis. This segmentation allows each zone to be optimized independently, enabling high catalyst loading in outlet cells without compromising the storage capacity of inlet cells.
Solution Approach 2:
Different porosity characteristics are assigned to different locations within the filter structure. Inlet cells are designed with high porosity to maximize particulate storage capacity, while outlet cells are designed with low porosity to accommodate high catalyst loading. This local differentiation resolves the contradiction between storage capacity and catalytic function.
2Reliability
If the washcoat is deposited on the porous walls, then the catalytic activity is enhanced, but the effective flow area of the inlet cells decreases, resulting in an increase in pressure drop
Solution Approach 1:
The filter structure is segmented into two distinct functional zones: inlet cells with high porosity (40-80%) for particulate storage and outlet cells with low porosity (0-20%) for catalysis. This segmentation allows each zone to be optimized independently, enabling high catalyst loading in outlet cells without compromising the storage capacity of inlet cells.
Solution Approach 2:
Different porosity characteristics are assigned to different locations within the filter structure. Inlet cells are designed with high porosity to maximize particulate storage capacity, while outlet cells are designed with low porosity to accommodate high catalyst loading. This local differentiation resolves the contradiction between storage capacity and catalytic function.
3Stress or pressure
If the ratio of inlet cell area to outlet cell area is increased, then the backpressure is reduced, but the standard checkerboard pattern with equal cross-sectional areas is abandoned
Solution Approach 1:
The filter structure transitions from the symmetric checkerboard pattern with equal inlet and outlet cell areas to an asymmetric configuration where inlet cells have a combined cross-sectional area 0.5 to 2.0 times that of outlet cells. This asymmetry optimizes flow distribution and reduces backpressure by providing a larger inlet area for exhaust gas entry.
Solution Approach 2:
The cell area ratio parameter is changed from the standard 1:1 ratio to a range of 0.5 to 2.0 times, optimizing the balance between backpressure reduction and manufacturing feasibility. This parameter adjustment resolves the contradiction between performance optimization and manufacturing complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design achieves a high catalyst loading with reduced backpressure and increased particulate storage capacity by separating filtration and catalytic functions, allowing for effective particulate filtration and catalysis without significant increases in backpressure.
Implementation Method 1
The filter may be catalyzed to reduce pollutants such as hydrocarbons and CO from the flow prior to the flow exiting the filter
Data Source
Figure 1
Figure 2
Figure 3~4A
AI summary
A wall-flow honeycomb filter comprising a ceramic monolith (102) having a plurality of porous walls (114) formed therein. The plurality of porous walls (114) define a plurality of inlet cells (110) and a plurality of outlet cells (112) extending between an inlet end face (106) and an outlet end face (108) of the monolith. The inlet cells (110) are open at the inlet end face (106) and plugged at or near the outlet end face (108). The outlet cells (112) are open at the outlet end face (108) and plugged at or near the inlet end face (106). The monolith (102) has a ratio of a combined cross-sectional area of the inlet cells (110) to a combined cross-sectional area of the outlet cells (112) greater than 1. The monolith (102) has at least one inlet cell cluster (120) which contains an N x M group of inlet cells (110), N and M being integers greater than 1, each inlet cell cluster (120) consisting of a plurality of inlet cells (110) separated by inlet cluster walls (124).