Silicon Carbide Honeycomb Filter Outer Wall Thickness Design
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Solution Overview
Problem
Existing ceramic honeycomb filters for diesel engine exhausts face issues with cracking and melting due to thermal shock from uneven PM burning and rapid temperature changes, which current structural modifications fail to adequately address.
Innovation Solution
The silicon carbide honeycomb filter is designed with honeycomb segments having an outer peripheral wall thickness between 1.5 and 9 times that of the cell walls, and a cross-sectional shape with an octagonal configuration and linear chamfers, along with vacant intersection spaces to alleviate thermal stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the cell wall thickness is reduced to suppress pressure loss and increase PM accumulation capacity, then pressure loss decreases and PM accumulation increases, but the structure becomes more susceptible to cracking and melting under thermal stress
Solution Approach 1:
The patent applies different wall thicknesses to different parts of the honeycomb structure. The outer peripheral wall thickness is set to 1.05-1.30 times the average cell wall thickness, creating a thicker outer layer that resists thermal stress while maintaining thin inner walls for low pressure loss. This local differentiation allows the structure to simultaneously achieve low flow resistance and high thermal shock resistance.
2Strength
If bonding material layers are added to bond honeycomb segments, then structural integrity improves, but thermal stress concentration increases at bonding locations
Solution Approach 1:
The patent pre-designs the outer peripheral wall thickness before thermal stress occurs, setting it to 1.05-1.30 times the average cell wall thickness. This preliminary structural preparation ensures that the outer walls can withstand thermal expansion and stress concentration at bonding locations during regeneration, preventing cracking before it occurs.
3Reliability
If the outer peripheral wall thickness is increased to suppress cracking, then thermal stress resistance improves, but pressure loss increases
Solution Approach 1:
The patent carefully controls the outer peripheral wall thickness to be within 1.05-1.30 times the average cell wall thickness. This precise local differentiation provides sufficient thermal stress resistance while minimizing the impact on flow resistance, achieving an optimal balance between structural integrity and fluid flow performance.
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 cracking and melting while maintaining heat conduction and preventing pressure loss, thereby enhancing the structural integrity and performance of the honeycomb filter under thermal stress.
Implementation Method 1
maintaining heat conduction
Implementation Method 2
under thermal shock due to the uneven burning of PM during regeneration, the rapid temperature change of an exhaust gas, etc.
Data Source
AI summary
A silicon carbide honeycomb filter constituted by honeycomb segments each comprising cell walls forming cells defining pluralities of flow paths longitudinally extending between both end surfaces, plugs sealing end surfaces of the cells alternately in a checkerboard pattern, and an outer peripheral wall, bonding material layers filling lattice gaps between the honeycomb segments for bonding them, and a skin layer covering the bonded honeycomb segments, the thickness of the outer peripheral wall being more than 1.5 times and 9 times or less that of the cell walls.