Wall Flow Filter with Segmented Catalytic Coating for Low Backpressure
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Solution Overview
Problem
Existing wall flow filters face challenges in achieving high catalytic activity while maintaining filtration efficiency and minimizing exhaust gas back pressure, which are crucial for effectively reducing particulate emissions from gasoline engines.
Innovation Solution
A wall flow filter design with specific catalytic coating zones applied in separate steps, where the first and third coatings extend over 55 to 96% of the filter length, and the second and fourth coatings over 10 to 40%, using a pressure difference reversal to remove excess coating suspension, ensuring balanced catalytic activity and minimal back pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the filter is coated with a catalyst in such a way that the catalyst penetrates the porous walls (in-wall coating), then the catalytic activity is improved, but the filter's backpressure increases significantly
Solution Approach 1:
The patent applies different coating types to different regions of the filter: in-wall coating is applied only to the first 30% of the channel length from the inlet, while overlay coating is applied to the remaining 70%. This local differentiation allows the filter to have high catalytic activity where particles are most concentrated (inlet region) while maintaining low backpressure in the outlet region where particles have already been filtered
Solution Approach 2:
The filter channel length is segmented into two functional zones: a first section (0-30% of length) with in-wall coating for high catalytic activity, and a second section (30-100% of length) with overlay coating for low backpressure. This segmentation allows each zone to perform its specific function optimally without compromising the other
2Reliability
If a wall-flow filter is used to remove soot particles, then filtration efficiency is improved, but the backpressure increases
Solution Approach 1:
The overlay coating is applied with a thickness that increases along the channel length from the inlet, being thinnest at the inlet and thickest at the outlet. This gradient design provides sufficient filtration efficiency while minimizing backpressure by reducing flow resistance in the inlet region where pressure drop is most critical
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 filter achieves improved catalytic activity and filtration efficiency with only a slight increase in exhaust gas back pressure, surpassing the performance of prior art filters in terms of catalytic activity and filtration efficiency.
Implementation Method 1
As the exhaust gas passes through the wall, the particles are trapped
Implementation Method 2
The catalyst promotes the chemical conversion of various exhaust gas components to form harmless products such as carbon dioxide and water
Data Source
Figure 1~2b
Figure 2c~3
Figure 4~5
AI summary
The present invention is directed to a wall-flow filter which is used in particular in exhaust gas systems of vehicles driven by gasoline engines. The filter has a three-way activity and filters fine particles, which result from the combustion of gasoline, from the exhaust gas stream. The invention also relates to a method for producing a corresponding filter and to the preferred use thereof.