Exhaust Mixer with Curved Transition Surface for Thermal Stress
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Solution Overview
Problem
Existing mixers for exhaust systems of internal combustion engines face challenges in withstanding thermal and mechanical loads, leading to potential cracking due to uneven stress distribution during thermal expansion.
Innovation Solution
A mixer design featuring a continuously concave first transition surface between the inner and outer wall surfaces, along with a radially increasing radius of curvature, and a flexible support structure that allows for radial movement, minimizes stress concentrations and facilitates thermal expansion without creating excessive local stresses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the mixer body is rigidly connected to the exhaust system components, then structural stability is improved, but thermal expansion stresses cause cracking during thermal cycles
Solution Approach 1:
The support area is segmented into distinct functional zones: a mixer connection area for attaching to the mixer body, a pipe connection wall for exhaust system integration, and a mixer body support wall providing structural support. This segmentation allows each zone to independently handle specific stresses and movements, preventing crack propagation across the entire structure during thermal expansion cycles.
Solution Approach 2:
The transition surface between the inner wall surface and outer wall surface is designed with a continuously concave curvature, eliminating sharp corners and edges. This curved geometry distributes thermal expansion stresses uniformly across the transition zone, preventing stress concentration that would lead to cracking during repeated thermal cycles.
2Ease of manufacture
If the transition surface has sharp edges or corners, then manufacturing is simplified, but stress concentrations develop during thermal expansion
Solution Approach 1:
The transition surface employs a continuously concave curved geometry instead of sharp edges or corners. This design smoothly connects the inner wall surface to the outer wall surface, distributing thermal expansion stresses uniformly and eliminating stress concentration points that would initiate cracks during thermal cycling.
3Strength
If the support structure is rigid, then mechanical strength is improved, but flexibility to accommodate thermal expansion is reduced
Solution Approach 1:
The support structure is divided into a pipe connection wall and a mixer body support wall, allowing differential movement and thermal expansion in each zone while maintaining overall structural integrity. This segmentation provides both rigidity for strength and flexibility for accommodating thermal changes.
Solution Approach 2:
The continuously concave transition surface creates a flexible yet strong connection between wall surfaces, allowing the structure to bend and expand thermally without compromising mechanical strength. The curved geometry acts as a stress-distributing element that maintains structural integrity during thermal cycles.
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 design ensures a stable and durable mixer that can withstand multiple thermal expansion cycles without cracking, maintaining a gas-tight connection and efficient mixing of exhaust gases with reactants.
Implementation Method 1
corner or edge areas which are subject to strong mechanical stress during the unavoidable thermal expansion of the mixer body
Data Source
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AI summary
A mixer for an exhaust system of an internal combustion engine comprises a mixer body (12) with a plurality of flow deflection elements (16) extending radially outwards from a mixer body center (14) with respect to a mixer longitudinal axis (L), and a support area (22) adjoining the mixer body (12) radially outwards and surrounding the mixer longitudinal axis (L) in a ring-like manner, wherein the support area (22) comprises: - a mixer connection area (24) for connecting the mixer (10) to an exhaust system component to be positioned adjacent to the mixer (10), - a pipe connection wall (30) adjoining the mixer connection area (24) with an inner wall surface (32), - a mixer body support wall (34) adjoining the mixer connection area (24), supporting the mixer body (12) and surrounded radially outwards by the pipe connection wall (30) with an outer wall surface (36),- a first transition surface (40) adjoining the outer wall surface (36) and the inner wall surface (32), wherein the first transition surface (40) between the inner wall surface (32) and the outer wall surface (36) is substantially continuously concave and axially limits an annular pipe receiving space (38) formed between the pipe connection wall (30) and the mixer body support wall (34).