Wall Flow Filter Pore Segmentation for Pressure Loss
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Solution Overview
Problem
Wall flow type exhaust gas purification filters experience increased pressure loss due to catalyst loading, which degrades gas permeability and reduces the effectiveness in purifying NOx, CO, and HC from internal combustion engines.
Innovation Solution
The filter features a honeycomb structure with specific pore size distribution, where large pores (15 µm to 200 µm) and small pores (0.1 µm to 8 µm) are strategically designed to absorb catalysts in small pores, maintaining gas passage in large pores, thereby minimizing pressure loss and ensuring efficient purification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a catalyst is loaded on the partition walls of a wall flow type exhaust gas purification filter, then the purification effectiveness for NOx, CO, and HC is improved, but the gas permeability of the partition walls is degraded causing increased pressure loss
Solution Approach 1:
The partition walls are segmented into two distinct pore size regions: small pores (0.1-8 μm) that serve as catalyst support and large pores (15-200 μm) that serve as gas passages. This spatial segmentation allows the catalyst to be effectively loaded while maintaining gas permeability through the larger pores that remain unclogged.
Solution Approach 2:
Different regions of the partition walls are given different functional qualities: the small pore regions are optimized for catalyst absorption and chemical reactions, while the large pore regions are optimized for gas flow with minimal resistance. This local differentiation resolves the contradiction between catalyst loading and gas permeability.
2Quantity of substance
If the opening ratio is reduced by the thickness of the catalyst coat layer, then the catalyst loading capacity is improved, but the gas permeability is reduced causing increased pressure loss
Solution Approach 1:
The pore structure is segmented into small pores for catalyst accommodation and large pores for gas flow. This allows high catalyst loading density in small pores while the large pores maintain sufficient cross-sectional area for gas permeability, preventing pressure loss increase despite thick catalyst layers.
Solution Approach 2:
The solution transitions from a single-dimensional pore size approach to a two-dimensional pore size distribution approach. By utilizing both small and large pores simultaneously in different spatial regions, the system achieves high catalyst capacity without compromising gas flow pathways.
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 effectively suppresses the rise in pressure loss after catalyst loading, allowing for efficient purification of exhaust gases while maintaining filter strength and permeability.
Implementation Method 1
the catalyst is absorbed selectively in the small pore region
Data Source
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AI summary
There is provided a wall flow type exhaust gas purification filter is provided with a honeycomb structure having porous ceramic partition walls 12 and plugging portions disposed in one side opening end portions of predetermined cells and the other side opening end portions of the other cells. In the exhaust gas purification filter, when an average pore size is obtained for each region of 1/3 mm × 1/3 mm in a range of 10 mm2 in an arbitrary cross section perpendicular to a surface of the partition walls 12, a large pore region having an average pore size of 15 µm or more has an area of 0.1 mm2 or more, and a small pore region having an average pore size of 8 µm or less has an area of 0.1 mm2 or more.