Honeycomb Structure Bonding Layer Thermal Expansion Mismatch
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional honeycomb structures used in diesel particulate filters (DPFs) are prone to cracking due to thermal expansion coefficient mismatches between bonding layers and honeycomb segments during regeneration processes, leading to reduced thermal shock resistance and increased soot trapping limitations.
Innovation Solution
A honeycomb structure with pillar-shaped segments bonded by a layer containing mica or alumina, where the thermal expansion coefficient of the bonding layer is set to be between 1.3 and 6 times that of the honeycomb segment, and an outer circumference coating layer with a higher thermal expansion coefficient than the bonding layer, to mitigate stress and crack generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the thermal expansion coefficient of the bonding layer is set same as or smaller than the thermal expansion coefficient of the honeycomb segment, then thermal shock resistance is considered to be increased, but cracks are generated in the honeycomb segment during regeneration process
Solution Approach 1:
The patent changes the thermal expansion coefficient parameter of the bonding layer to be larger than that of the honeycomb segment, specifically setting it within 1.05 to 1.35 times the segment's coefficient. This parameter inversion resolves the contradiction by allowing controlled expansion mismatch that prevents crack generation during thermal cycling while maintaining bonding integrity
Solution Approach 2:
The patent explicitly utilizes thermal expansion differences between the bonding layer and honeycomb segment as a protective mechanism. By designing the bonding layer with a larger thermal expansion coefficient, it expands more during heating cycles, creating a protective effect that prevents stress concentration and crack formation in the rigid honeycomb segment structure
2Ease of manufacture
If conventional bonding layers are used with predetermined thermal expansion coefficients, then manufacturing simplicity is maintained, but crack generation occurs during repeated heating and cooling cycles
Solution Approach 1:
The patent modifies the thermal expansion coefficient parameter of the bonding layer material composition to be larger than the honeycomb segment's coefficient. This can be achieved by selecting specific ceramic materials or adjusting compositional ratios, which are standard manufacturing parameters that can be controlled through material selection and formulation without fundamentally changing the manufacturing process
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 reduces crack formation in honeycomb segments, enhances soot trapping capacity, and postpones filter regeneration, thereby improving fuel efficiency and extending the interval between regeneration cycles.
Implementation Method 1
the thermal expansion coefficient of the bonding layer and the thermal expansion coefficient of the honeycomb segment meet a relationship represented by Expression: 1.3
Data Source
Figure 1~2
AI summary
There is provided a honeycomb structure where a crack at honeycomb segments, which constitute a honeycomb bonded assembly, is reduced. A honeycomb structure 100 has a pillar-shaped honeycomb bonded assembly 10 that has a plurality of pillar-shaped honeycomb segments 22 having a porous partition wall 1 defining a plurality of cells 2 extending from an inflow end face 11 as one end face to an outflow end face 12 as another end face and becoming channels for a fluid, and a bonding layer 24 bonding side surfaces of the plurality of honeycomb segments 22, and in the honeycomb bonded assembly 10, at 25 to 800°C, a thermal expansion coefficient of the bonding layer 24 is larger than a thermal expansion coefficient of the honeycomb segment 22.