Particulate Filter Coat Layer Particle Size Optimization
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Solution Overview
Problem
The catalyst coat layer in particulate filters for internal combustion engines increases pressure drop due to its narrow flow paths, which is a challenge in exhaust gas purification systems.
Innovation Solution
A wall-flow type particulate filter design is implemented with a coat layer containing a first and second inorganic oxide, where the mean particle diameter of the first oxide is larger than the second, and their weight ratio is maintained between 10% to 50%, reducing the void fraction and thus widening the flow paths for exhaust gas, thereby minimizing pressure drop.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a catalyst coat layer is formed on the base material to provide exhaust gas purification function, then the exhaust gas purification capability is improved, but the pressure drop increases due to narrow flow paths
Solution Approach 1:
The invention changes the particle size parameters of inorganic oxides in the coat layer, specifically using a mixture of fine particles (0.1-10 μm) and coarse particles (10-100 μm) with controlled weight ratios. This parameter optimization reduces void fraction to 30-70%, thereby widening flow paths and reducing pressure drop while maintaining purification function
Solution Approach 2:
The invention uses a composite coat layer structure combining two types of inorganic oxide particles with different size ranges. The fine particles provide catalytic activity while the coarse particles create larger inter-particle voids that serve as flow paths, achieving both purification and low pressure drop characteristics
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 configuration effectively reduces the increase in pressure drop while maintaining the exhaust gas purification function, allowing for efficient PM capture and gas component purification.
Implementation Method 1
the catalyst coat layer causes flow paths for exhaust gas to be narrow, thereby increasing pressure drop
Implementation Method 2
a catalyst coat layer formed on the base material... contains a catalyst (e.g., a catalyst metal such as Pt, Pd, and Rh) capable of oxidizing or reducing exhaust gas components
Implementation Method 3
capable of oxidizing or reducing exhaust gas components
Implementation Method 4
capable of oxidizing or reducing exhaust gas components
Implementation Method 5
PM is captured in the porous partitions
Data Source
AI summary
A wall-flow type particulate filter includes: a wall-flow type base material; and a coat layer formed on the base material. The base material includes: an inlet cell open only at an exhaust gas inlet end; an outlet cell open only at an exhaust gas outlet end; and a partition partitioning the inlet and outlet cells and having multiple pores through which the inlet and outlet cells communicate with each other. The coat layer is provided for the wall surfaces of the pores and contains a first inorganic oxide and a second inorganic oxide. The mean particle diameter Da of the first inorganic oxide is larger than the mean particle diameter Db of the second inorganic oxide. The weight ratio of the second inorganic oxide is designed to be from 10% to 50% inclusive when the total weight ratio of the first inorganic oxide and the second inorganic oxide is 100%.