Honeycomb Structure Uneven Coat Layer Pressure Loss
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Solution Overview
Problem
Honeycomb structures used in diesel particulate filters face challenges in preventing pressure loss when trapping particulate matter, as either large pore diameters allow clogging or small diameters restrict particulate matter from reaching the catalyst, leading to ineffective combustion and increased pressure loss, especially at low exhaust gas temperatures.
Innovation Solution
A honeycomb structure with a porous substrate and a porous coat layer having an uneven surface to increase the catalyst's contact area, where the coat layer's average height of protrusions is 20 to 300 µm, and the average gap between protrusions is 30 µm to 10 mm, with an average pore diameter of 0.1 to 20 µm, inhibiting microparticles from entering the pores and ensuring effective particulate matter combustion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the pore diameter of the partition walls is increased, then the pressure loss before particulate matter deposition is reduced, but particulate matter enters the pores and causes clogging, increasing pressure loss
Solution Approach 1:
The partition wall structure is segmented into two distinct layers: a base layer with larger pores for maintaining low pressure loss, and a surface coat layer with smaller pores for preventing particulate matter clogging. This segmentation allows each layer to perform its specific function optimally without compromising the other.
Solution Approach 2:
Different pore size characteristics are applied to different regions of the partition wall: the base layer has larger pores (10-100 μm) for efficient gas flow, while the surface coat layer has smaller pores (0.1-10 μm) for particulate matter filtration. This local differentiation of properties resolves the contradiction between flow efficiency and clogging prevention.
2Reliability
If the pore diameter of the partition walls is decreased, then pressure loss due to particulate matter deposition is inhibited, but passages in the walls become narrow, increasing pressure loss before deposition
Solution Approach 1:
The partition wall is divided into functional segments: a thick base layer (0.5-2.0 mm) with large pores that dominates the flow characteristics and maintains low pressure loss, and a thin surface coat layer (10-100 μm) with small pores that provides clogging resistance. The base layer's larger cross-section compensates for the narrow passages in the coat layer.
Solution Approach 2:
The surface coat layer applies small pore sizes (0.1-10 μm) locally at the gas inlet side where particulate matter concentration is highest, providing targeted protection against clogging without requiring the entire partition wall to have small pores, thus maintaining overall flow efficiency.
3Loss of energy
If a coat layer is added to inhibit microparticles from entering pores, then pressure loss before deposition is suppressed, but particulate matter does not enter the pores and contact with the catalyst, reducing combustion effectiveness
Solution Approach 1:
The coat layer is designed with specific local properties: small pores (0.1-10 μm) for preventing microparticle entry and maintaining low pressure loss, combined with a rough uneven surface (protrusions of 20-300 μm height) that increases surface area and promotes particulate matter accumulation and catalyst contact, enabling effective combustion.
Solution Approach 2:
The coat layer surface is made three-dimensional with protrusions and unevenness rather than flat, increasing the surface area by 1.05 to 10 times. This dimensional change provides more contact points for particulate matter and catalyst interaction, compensating for the reduced pore penetration while maintaining low pressure loss.
4Productivity
If the surface area of the catalyst is increased to improve combustion, then more particulate matter can be combusted, but the structure becomes more complex
Solution Approach 1:
Instead of increasing catalyst surface area by adding multiple layers or complex structures, the invention uses surface roughness (protrusions of 20-300 μm height) on the coat layer to increase the effective surface area by 1.05 to 10 times. This dimensional approach achieves high combustion efficiency while maintaining a simple two-layer structure.
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 pressure loss and ensures efficient combustion and removal of trapped particulate matter by preventing clogging while maintaining a sufficient catalyst surface area, even at low temperatures.
Implementation Method 1
a porous coat layer disposed on a surface of the partition walls to inhibit microparticles from entering
Implementation Method 2
in order to combust and remove trapped particulate matter
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 3~6
AI summary
A honeycomb structure includes: a porous substrate having porous partition walls separating and forming a plurality of cells functioning as fluid passages, a porous coat layer disposed on a surface of the partition walls to inhibit microparticles from entering, a surface of the coat layer having an uneven shape to increase a surface area, and plugging portions for plugging cells so that a fluid flowing into the structure from an opening portions on one end side of predetermined cells maypass through the partition walls and flows out from opening portions on the other side of the other cells to allow the gas to flow through the partition walls and the coat layers. The honeycomb structure can inhibit the pressure loss from increasing upon trapping particulate matter in exhaust gas and can effectively combust and remove the trapped particulate matter.