Honeycomb Filter Surface Layer Zero Film Thickness Design
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Solution Overview
Problem
Honeycomb filters used in diesel engines experience an abrupt increase in pressure drop due to the flaking of surface layers caused by separation vortices, leading to reduced performance and potential damage.
Innovation Solution
A honeycomb filter design with zero film thickness in the inlet peripheral region and a tapered surface layer to prevent flaking, combined with a manufacturing method that forms a protective film to prevent slurry adherence in these areas, ensuring the surface layer is not formed in regions prone to vortex-induced flaking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a surface layer is formed on the inner surface of inlet opening cells to prevent PM invasion, then surface filtration is improved and pressure drop increase is prevented, but the surface layer flakes off due to separation vortices causing abrupt pressure drop increase
Solution Approach 1:
The patent removes the surface layer from the inlet peripheral region where separation vortices occur, while maintaining it in other regions. This extraction of the problematic portion eliminates the flaking issue caused by vortex-induced stress while preserving the filtration function in stable regions.
Solution Approach 2:
The surface layer is selectively applied only to specific regions of the inlet opening cell inner surface, specifically excluding the inlet peripheral region. This creates local quality differentiation where the surface layer provides filtration where stable but is absent where vortices cause flaking.
2Reliability
If a surface layer is formed to trap PM at the beginning of PM-trapping action, then depth filtration is prevented and porosity is maintained, but flaking occurs under high-speed high-loading conditions
Solution Approach 1:
The inlet opening cell inner surface is segmented into different regions: the inlet peripheral region where the surface layer is removed to prevent flaking, and other regions where the surface layer is maintained for filtration. This segmentation allows different functional requirements to be met in different zones.
Solution Approach 2:
The patent converts the harmful effect of separation vortices (which cause flaking) into a design criterion by identifying and removing the surface layer from the vortex-affected inlet peripheral region, thereby eliminating the flaking problem while maintaining filtration elsewhere.
3Reliability
If the surface layer is formed uniformly across the entire inner surface, then filtration coverage is maximized, but flaking is induced by separation vortices in the inlet peripheral region
Solution Approach 1:
The surface layer application is made non-uniform by excluding the inlet peripheral region, creating local quality differentiation. This allows the surface layer to provide filtration where stable while avoiding regions where vortices cause flaking and subsequent collapse.
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 prevents the flaking of surface layers, maintaining filter performance and reducing pressure drop fluctuations, even under high-speed and high-loading conditions.
Implementation Method 1
generation of separation vortexes of the exhaust emission flow in the vicinity of the inlets of the respective inlet opening cells. The negative pressure of the separation vortex induces flaking of the surface layer
Implementation Method 2
In the surface filtration, the PM is trapped by the surface of the porous partition walls
Implementation Method 3
In the depth filtration, the PM invading the pores of the porous partition walls is trapped by the inside of the porous partition walls
Implementation Method 4
The surface layer has substantially zero film thickness in an inlet peripheral region that represents an area extended from the open inlet of the inlet opening cell
Data Source
AI summary
The honeycomb filter is constructed as a diesel particulate filter having a filtration function for filtering out the particulate matter included in an exhaust emission of a diesel engine. The honeycomb filter has a honeycomb structure as a base and inlet opening cells with surface layers formed on respective inner surfaces thereof. The surface layer has zero film thickness in an inlet peripheral region. Separation vortexes are generated in the inlet peripheral regions. The zero film thickness of the surface layers in the inlet peripheral regions naturally causes non-flaking of the surface layers induced by the separation vortexes generated in the inlet peripheral regions and thereby leads to non-production of flakes. In the non-existent condition of flakes, the overall surface layers are not collapsed by collision of the flakes.