Honeycomb Structure with Slit Charging Material for Thermal Shock Resistance
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Solution Overview
Problem
Existing honeycomb structures used as catalyst carriers and heaters in vehicle exhaust systems face issues with uneven temperature distribution and poor thermal shock resistance, particularly due to excessive current flow in metal heaters and limitations in ceramic materials' thermal expansion coefficients, leading to damage and cracking.
Innovation Solution
A honeycomb structure with a charging material having a strength of 500 kPa or more and a Young's modulus of 1500 MPa or less, containing silicon carbide aggregates and silicon oxide, with a porosity of 20-90% and thermal expansion coefficient ratio between 0.6 to 1.5, and featuring slits with a neck material to bond aggregate particles, which improves thermal shock resistance and inhibits temperature unevenness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a metal heater is used to raise catalyst temperature, then heating efficiency is improved, but excessive current flows through the heater causing damage to power source circuit
Solution Approach 1:
The patent introduces a ceramic heater as an intermediary heating element between the power source and the catalyst. The ceramic material provides appropriate electrical resistance to limit current flow while still generating sufficient heat, thus protecting the power source circuit from excessive current damage while maintaining effective catalyst heating capability.
Solution Approach 2:
The patent changes the material parameter of the heater from metal to ceramic, which fundamentally alters the electrical resistance characteristic. This parameter change enables the heater to operate at high voltage without excessive current flow, solving the reliability issue while maintaining heating effectiveness.
2Reliability
If a ceramic material is used as catalyst carrier, then thermal shock resistance is improved, but uneven temperature distribution occurs when voltage is applied
Solution Approach 1:
The patent segments the ceramic structure by forming multiple slits that extend through the thickness of the catalyst carrier. These slits divide the ceramic body into multiple segments, allowing differential thermal expansion and contraction, thereby reducing thermal stress and improving thermal shock resistance while maintaining uniform temperature distribution.
Solution Approach 2:
The patent creates a composite structure by filling the slits with charging material that has different thermal expansion properties than the ceramic matrix. This composite design allows the structure to accommodate thermal expansion differences, reducing thermal stress and improving both thermal shock resistance and temperature distribution uniformity.
3Reliability
If charging material is charged into slits, then thermal expansion stress is reduced, but shearing stress is generated at the boundary causing damage to charging material
Solution Approach 1:
The patent optimizes the physical and mechanical parameters of the charging material, including its strength, elasticity, and thermal expansion coefficient. By carefully selecting and controlling these parameters, the charging material can accommodate thermal expansion stress without generating excessive shearing stress at the boundary, thus preventing damage while maintaining stress resistance.
Solution Approach 2:
The patent applies different material properties to different regions of the structure. The charging material in the slits has specific local properties (strength, elasticity, thermal expansion) that are optimized for stress accommodation, while the ceramic matrix maintains its structural integrity. This local quality differentiation allows the system to handle thermal expansion stress without damaging the charging material.
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
The proposed honeycomb structure effectively prevents damage from thermal stress, maintains mechanical strength, and ensures even heating by controlling thermal expansion and stress distribution, enhancing its performance as both a catalyst carrier and heater.
Implementation Method 1
a honeycomb structure which is a catalyst carrier and also functions as a heater when a voltage is applied thereto
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
There is disclosed a honeycomb structure which is a catalyst carrier, also functions as a heater when a voltage is applied thereto, can inhibit an unevenness of a temperature distribution, and is excellent in thermal shock resistance. The honeycomb structure includes a honeycomb structure body 4 and a pair of electrode members 21 disposed on a side surface 5 of the honeycomb structure body 4, each of the pair of electrode members 21 is shaped in the form of a band extending in a cell extending direction of the honeycomb structure body 4, and in a cross section perpendicular to the extending direction of cells 2, one electrode member 21 is disposed on a side opposite to the other electrode member 21 via a center of the honeycomb structure body 4, one or more slits 6 opened in the side surface 5 are formed in the honeycomb structure body 4, the honeycomb structure body 4 has a charging material 7 charged into the at least one slit 6, the charging material 7 contains aggregates and a neck material, and a ratio (α2/α1) of a thermal expansion coefficient α2 of the charging material 7 to a thermal expansion coefficient α1 of the honeycomb structure body 4 is from 0.6 to 1.5.