Honeycomb Structure with Gradient Partition Wall Thickness
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Solution Overview
Problem
Honeycomb structures with hexagonal cells face issues of cell twist and lower mechanical strength, which affect their temperature elevation property and catalyst loading efficiency, particularly when used as catalyst carriers for exhaust gas purification from internal combustion engines.
Innovation Solution
A honeycomb structure with thicker partial cell partition walls and gradually increasing thickness towards the outer peripheral wall, along with roundish sectional shapes at intersection points, enhances isotactic fracture strength and thermal shock resistance, allowing for uniform catalyst loading and reduced catalyst usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the partition wall thickness is made smaller to reduce cost, then the amount of catalyst used can be reduced, but the mechanical strength and temperature elevation property deteriorate
Solution Approach 1:
The partition walls are designed with non-uniform thickness, being thicker at the outer peripheral wall and thinner toward the inner side. This local variation in thickness allows the outer peripheral region to maintain high mechanical strength while the inner region uses less material and catalyst, resolving the contradiction between reducing catalyst amount and maintaining mechanical strength.
2Quantity of substance
If the cell sectional shape is changed from tetragon to hexagon to reduce catalyst amount, then catalyst loading efficiency is improved, but cell twist occurs easily and mechanical strength decreases
Solution Approach 1:
The hexagonal cell structure is implemented with varying partition wall thickness, where the outer peripheral partition walls are thicker than inner ones. This local thickness variation provides enhanced structural support at the vulnerable outer regions, preventing cell twist while maintaining the hexagonal shape's catalyst loading efficiency advantages.
Solution Approach 2:
The partition wall thickness is made asymmetric within the hexagonal cell structure, with the outer peripheral walls being thicker than the inner walls. This asymmetric thickness distribution compensates for the inherent instability of hexagonal cells and prevents cell twist during canning and operation.
3Strength
If the partition wall thickness is made larger at outer peripheral cells to prevent cell twist, then mechanical strength is improved, but heat capacity increases and temperature elevation property deteriorates
Solution Approach 1:
The partition wall thickness is optimized with a gradient distribution, being thicker only at the outer peripheral wall where mechanical strength is needed, and thinner toward the inner side where heat capacity should be minimized. This localized thickness variation allows the structure to gain mechanical strength where needed without increasing overall heat capacity, thus maintaining temperature elevation property.
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A honeycomb structure 1 comprising porous partition walls 13 forming a plurality of cells 3 extending between the two end faces and an outer peripheral wall 19 formed integrally with the partition walls 13, wherein the cells 3 comprise complete cells 5 having a hexagonal, complete cell section and partial cells 7 present at the outermost portion of the plurality of cells and having an incomplete cell section not forming a hexagon, the honeycomb structure satisfying at least one of the relationships (1) to (4).