Honeycomb Filter with Variable Cell Cross-Sectional Areas
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Solution Overview
Problem
Conventional honeycomb filters face challenges in maintaining high PM capturing efficiency and reducing pressure loss, especially in compact designs for high emission vehicles, where PM particle number regulation is stringent and pressure loss increases due to uneven gas flow and PM accumulation.
Innovation Solution
A honeycomb filter design with two types of exhaust gas introduction cells having different cross-sectional areas, where each exhaust gas emission cell has an equal or larger cross-sectional area than the second exhaust gas introduction cell, ensuring moderate gas flow and preventing local pressure increases, along with a ratio of length to diameter of less than 1.0 to distribute gas flow evenly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the honeycomb filter is shortened to reduce size and improve fuel economy, then the length-to-diameter ratio decreases, but PM capturing efficiency deteriorates due to insufficient residence time and uneven gas flow distribution
Solution Approach 1:
The honeycomb filter is segmented into multiple sections along its longitudinal direction, with each section having cells of different cross-sectional areas. This segmentation allows the filter to maintain compact overall length while providing varied flow paths that enhance PM capturing efficiency through distributed filtration zones.
Solution Approach 2:
Different sections of the honeycomb filter have locally optimized cell cross-sectional areas. The first section has cells with a first cross-sectional area, while the second section has cells with a second cross-sectional area that is 0.5 to 1.5 times the first area. This local quality variation ensures uniform gas flow distribution and maintains high PM capturing efficiency despite the shortened overall length.
2Ease of manufacture
If cells have uniform cross-sectional area throughout, then manufacturing is simplified, but gas flow becomes uneven causing localized PM accumulation and increased pressure loss
Solution Approach 1:
The honeycomb filter employs local quality variation by dividing cells into different sections along the longitudinal direction. The first section has cells with a first cross-sectional area, while the second section has cells with a second cross-sectional area (0.5-1.5 times the first area). This gradual transition in local cell dimensions ensures uniform gas flow distribution, prevents localized PM accumulation, and reduces pressure loss while remaining manufacturable using standard extrusion processes with sectioned dies.
3Ease of operation
If the cross-sectional area of emission cells is made larger, then gas flow resistance decreases, but the filter volume increases reducing compactness
Solution Approach 1:
The emission cells have their cross-sectional area varied locally along the longitudinal direction. The first section has cells with a first cross-sectional area optimized for initial gas flow acceptance, while the second section has cells with a second cross-sectional area (0.5-1.5 times the first area) that reduces flow resistance. This local optimization allows the filter to maintain compact overall volume while ensuring low gas flow resistance through progressive area increase in the flow direction.
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 enhances PM capturing efficiency and reduces pressure loss by distributing gas flow evenly and allowing for wide, thin PM accumulation, maintaining low pressure loss even after significant PM accumulation.
Implementation Method 1
capture PMs in exhaust gas
Implementation Method 2
PM accumulation on cell walls
Data Source
Figure 1
Figure 2(a)~2(b)
Figure 3(a)~3(b)
AI summary
The present invention provides a honeycomb filter being compact in spite of being used for high emission vehicles, maintaining a high PM capturing efficiency to satisfy severe emission regulations, and reducing the pressure loss. The honeycomb filter of the present invention includes porous cell walls and exhaust gas emission cells each having an plugged end, wherein the honeycomb filter has a ratio of the length to the diameter (length/diameter) of less than 1.0; the exhaust gas introduction cells include first exhaust gas introduction cells and second exhaust gas introduction cells each having a larger cross sectional area than each first exhaust gas introduction cell in a direction perpendicular to the longitudinal direction of the cells; each exhaust gas emission cell has an equal or larger cross sectional area than each second exhaust gas introduction cell in a direction perpendicular to the longitudinal direction of the cells; and the total volume of the exhaust gas introduction cells is larger than the total volume of the exhaust gas emission cells.