Asymmetric Electrode Honeycomb Structure for Thermal Stress Reduction
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Solution Overview
Problem
Honeycomb structures used for particulate filtration and electrical heating face issues with crack generation due to thermal stress from uneven temperature distribution during particulate combustion, exacerbated by the Negative Temperature Coefficient (NTC) characteristic of the materials, which increases current flow to hotter areas.
Innovation Solution
The honeycomb structure incorporates a pair of electrode layers disposed asymmetrically, with one layer closer to the outflow end face than the center, to reduce temperature differences and thermal stress, facilitating efficient particulate burning and removal while preventing crack formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the honeycomb structure is electrically heated to burn particulates, then particulate removal efficiency is improved, but thermal stress causes cracks in the honeycomb structure
Solution Approach 1:
The patent applies asymmetry by positioning electrode layers asymmetrically on the honeycomb structure. Specifically, the electrode layers are disposed closer to the outflow end face than to the inflow end face, creating an asymmetric electrical heating pattern that reduces temperature differential and thermal stress across the structure, thereby preventing cracks while maintaining particulate combustion efficiency
2Use of energy by stationary object
If the honeycomb structure material has NTC characteristic, then electrical conductivity is improved, but temperature difference increases leading to higher thermal stress
Solution Approach 1:
The patent addresses the NTC characteristic issue by using asymmetric electrode positioning. The asymmetric arrangement ensures that even though current naturally flows more to hotter areas (NTC effect), the overall temperature distribution remains more uniform because the heating pattern compensates for this tendency, reducing peak temperature differences and associated thermal stress
3Productivity
If combustion heat transmits from inlet side to downstream side, then particulate combustion is achieved, but larger temperature difference generates thermal stress
Solution Approach 1:
The patent applies inversion by reversing the conventional heating pattern. Instead of heating primarily from the inlet side where particulates enter, the electrode layers are positioned closer to the outflow end face. This inverted heating pattern reduces the temperature gradient along the flow direction, allowing particulate combustion to occur while minimizing thermal stress from excessive temperature differences
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 suppresses crack generation and enhances electrical control, ensuring efficient particulate combustion and removal while maintaining structural integrity.
Implementation Method 1
electrically heating the honeycomb structure as a filter, combustion of the particulates
Implementation Method 2
when the material of the honeycomb structure portion has NTC characteristic, a current easily flows to a higher temperature side
Data Source
AI summary
A honeycomb structure including a honeycomb portion having porous partition walls extending from an inflow end face to an outflow end face, an outermost peripheral wall, and a pair of electrode layers on a side surface of the honeycomb portion. Each electrode layer extends in a direction of the cells. One electrode layer is disposed on a side opposite to the other electrode layer across a center of the honeycomb portion in a cross section orthogonal to the extending direction of the cells. The honeycomb structure portion includes first cells opened on the inflow side and plugged on the outflow side, and second cells opened on the outflow side and plugged on the inflow side. A middle of each length of the pair of electrode layers is closer to the outflow side than a middle position of a length of the honeycomb portion in the extending direction of the cells.