Honeycomb Filter Partition Wall Thickness Design
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Solution Overview
Problem
Honeycomb filters used in diesel engines face issues with thermal shock resistance when catalysts are loaded, leading to potential cracks near inflow and outflow ends due to increased porosity and thinned partition walls, causing pressure loss and engine output issues during regeneration.
Innovation Solution
A honeycomb filter design with specific structural parameters, including alternate disposition of inlet and outlet plugging cells, optimized thermal expansion coefficients, and four-point bending strength, along with ceramic materials, to enhance thermal shock resistance and minimize pressure loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If porosity of the honeycomb substrate is increased or partition wall is thinned to suppress pressure loss, then pressure loss is reduced, but thermal shock resistance decreases causing cracks near inflow and outflow ends
Solution Approach 1:
The partition wall is designed with non-uniform thickness, being thinner at the center and thicker at the peripheral portion. This local variation in thickness allows the central region to have lower flow resistance while the peripheral region maintains higher strength to resist thermal shock and prevent cracks during regeneration.
2Object-generated harmful factors
If catalyst is loaded onto the honeycomb filter to purify exhaust gas, then purification performance is improved, but thermal shock resistance decreases due to increased porosity and thinned partition walls
Solution Approach 1:
The partition wall thickness is varied locally to compensate for the weakening effect of catalyst loading. The thicker peripheral portion provides the necessary mechanical strength to withstand thermal shock during regeneration, while the thinner central portion maintains low flow resistance for effective exhaust gas purification with catalyst.
3Reliability
If uniform temperature distribution is maintained during regeneration, then thermal stress and cracks are prevented, but regeneration efficiency may be reduced
Solution Approach 1:
The non-uniform partition wall thickness creates different thermal mass distribution throughout the filter. The thicker peripheral walls act as heat sinks that absorb and distribute thermal energy, preventing localized hot spots and thermal stress concentrations during rapid regeneration, thus maintaining structural integrity while allowing efficient PM combustion.
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
The design provides high thermal shock resistance, preventing cracks and maintaining low pressure loss even with increased porosity or thinned partition walls, ensuring effective PM filtration and engine performance.
Implementation Method 1
the partition wall functions as a filtration layer and PM in the exhaust gas is trapped by the partition wall
Implementation Method 2
a honeycomb substrate which includes a porous partition wall defining a plurality of cells functioning as fluid channels
Data Source
AI summary
A honeycomb filter, wherein when a thermal expansion coefficient at 300 to 600° C. of a material constituting a honeycomb substrate is indicated by A (×10−6/° C.), the four-point bending strength of the material constituting the honeycomb substrate is indicated by B (MPa), the thickness of a thinnest portion in a portion partitioning outlet plugging cells of a partition wall 1 is indicated by t (mm), the thickness of a portion partitioning an outlet plugging cell and an inlet plugging cell of the partition wall is indicated by WT (mm), and the distance between the center of the outlet plugging cell and the center of the inlet plugging cell adjacent to each other is indicated by CP (mm), a relation of the following equation (1) is satisfied.0.714×WT+0.160≧t/CP≧0.163×A/B+0.105 (1)