Exhaust Filter Pre-stressed Layer Thermal Stress
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Solution Overview
Problem
Exhaust aftertreatment filters for diesel engines experience separational fracture and cracking due to differential thermal expansion between the hotter central core and cooler outer periphery during regeneration, leading to reduced effectiveness and shorter lifespan.
Innovation Solution
A pre-stressed layer with a higher coefficient of thermal expansion than the filter body is bonded to the outer periphery, providing compressive axial stress to counteract the tensile stress caused by thermal cycling, thereby preventing fractures and extending the filter's lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the filter body undergoes thermal cycling during regeneration, then the trapped contaminant particulate is burned-off, but differential thermal expansion causes separational axial tensile stress leading to fracture and cracking
Solution Approach 1:
A pre-stressed layer is applied to the outer periphery of the filter body before thermal cycling occurs. This layer is pre-compressed to generate a compressive stress that counteracts the tensile stress generated during thermal expansion, preventing fracture and cracking before they can occur during regeneration cycles
Solution Approach 2:
The pre-stressed layer is designed with specific material properties including a coefficient of thermal expansion greater than the filter body and a compressive strength exceeding the tensile stress generated during thermal cycling. These parameter changes enable the layer to effectively counteract the harmful tensile stresses
2Reliability
If a pre-stressed layer with higher coefficient of thermal expansion is bonded to the outer periphery, then compressive axial stress is provided to counteract tensile stress, but device complexity increases
Solution Approach 1:
The pre-stressed layer is applied only to the outer periphery of the filter body where the tensile stress occurs during thermal cycling, rather than modifying the entire filter structure. This localized application reduces the increase in device complexity while maintaining effectiveness
Solution Approach 2:
The filter body is enhanced by bonding a pre-stressed layer with different material properties (higher coefficient of thermal expansion and compressive strength) to the outer periphery. This composite structure combines the filtering capabilities of the original body with the stress-resistant properties of the pre-stressed layer
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 pre-stressed layer effectively reduces the risk of axial tensile stress-induced fractures, enhancing the filter's durability and longevity by maintaining structural integrity during regeneration cycles.
Implementation Method 1
pre-stressed layer 32 is formed of a material having a greater coefficient of thermal expansion than filter body 18, such that pre-stressed layer 32 undergoes greater thermal contraction than filter body 18 upon cooling below the noted thermal bonding temperature, to provide pre-stressed layer 32 with the noted anti-separational axial compressive stress
Implementation Method 2
pre-stressed layer 32 is thermally bonded to filter body 18 at outer periphery 20 at a thermal bonding temperature preferably, but not necessarily, greater than the regeneration temperature
Data Source
AI summary
An exhaust aftertreatment filter has a pre-stressed layer bonded to the filter body at the outer periphery and compressively axially pre-stressed in an opposite axial direction to separational axial tensile stress to counteract the latter during regenerative heating, to minimize separational fracture and cracking.