Wall Flow Filter Hexagonal Inlet Square Outlet Geometry
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional wall flow type exhaust gas purification filters face issues with increased pressure loss and potential cracking due to particulate matter accumulation, as the existing designs compromise on filtration area and strength at the intersection points of partition walls, leading to thermal stress concentration.
Innovation Solution
The design enhances the filtration area and opening ratio of inflow-side cells while maintaining a large opening diameter for outflow-side cells, featuring hexagonal and square cross-sectional shapes with specific geometric configurations and dimensions to distribute thermal stress, thereby reducing pressure loss and preventing cracks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the opening ratio of inflow-side cells is increased to reduce clogging, then the filtration area increases, but the opening ratio of outflow-side cells decreases leading to increased pressure loss
Solution Approach 1:
The patent applies different cross-sectional shapes to different cell types: inlet opening cells have a substantially hexagonal cross-section while outlet opening cells have a substantially square cross-section. This local differentiation allows optimization of each cell type's function - hexagonal cells provide better filtration area and PM accumulation capacity, while square cells maintain lower pressure loss at the outlet stage.
2Quantity of substance
If different cross-sectional areas and shapes are used between inflow-side and outflow-side cells to increase filtration area, then PM accumulation capacity improves, but the partition walls become thinner at intersecting parts reducing strength
Solution Approach 1:
The patent introduces asymmetric cross-sectional shapes - hexagonal for inlet cells and square for outlet cells. This asymmetry creates different geometric properties at different locations of the filter, allowing the inlet side to maximize PM accumulation while the outlet side maintains structural integrity with thicker effective partition walls.
Solution Approach 2:
Different cross-sectional geometries are assigned to different regions: hexagonal sections at the inlet provide larger perimeter-to-area ratio for better filtration, while square sections at the outlet provide more uniform stress distribution and thicker effective wall sections at intersection points.
3Loss of energy
If partition walls are made thinner to increase cell opening ratio, then initial pressure loss decreases, but thermal stress concentration at intersecting parts causes cracks
Solution Approach 1:
The asymmetric design with hexagonal inlet cells and square outlet cells creates different stress distribution patterns. The square outlet cells have partition walls that intersect at more favorable angles and with greater effective thickness, providing stress relief zones that prevent crack propagation from thermal loading.
Data Source
AI summary
A wall flow type exhaust gas purification filter includes a honeycomb structure body and plugging portions. Four inlet opening cells having a substantially hexagonal shape in cross section surround one outlet opening cell having a substantially square shape in cross section, where one side of an inlet opening cell and one side of the outlet opening cell have a substantially same length and are substantially parallel and adjacent to each other. Distance a between the partition wall defining a first side of the outlet opening cell and the partition wall defining an opposed second side is in a range of exceeding 0.8 mm and less than 2.4 mm, and distance b between the partition wall defining a third side of the inlet opening cell and the partition wall defining an opposed fourth side has a ratio to the distance a in a range exceeding 0.4 and less than 1.1.