Perforated Exhaust Pipe Absorbing Thermal Expansion
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Solution Overview
Problem
Exhaust systems for internal combustion engines face challenges in managing thermal stresses between pipes and housings with different materials and expansion coefficients, leading to costly manufacturing requirements and noise issues due to sliding seats.
Innovation Solution
The pipe is designed with targeted perforations to increase elastic flexibility, allowing it to absorb thermal expansion forces through elastic deformation, enabling fixed connections at both ends and eliminating the need for sliding seats, thus simplifying installation and reducing noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a sliding seat is used to allow the pipe to move in the longitudinal direction, then thermally induced stresses are avoided, but manufacturing expense increases and noise is generated
Solution Approach 1:
The pipe wall is designed with variable thickness: thicker at the end areas for strength and stability, and thinner in the middle section for flexibility. This parameter change allows the pipe to absorb thermal expansion through elastic deformation without requiring a sliding seat, thus avoiding the manufacturing complexity and noise issues while maintaining thermal stress management
Solution Approach 2:
The pipe is designed to be dynamically flexible in the longitudinal direction through the thinner middle section, allowing it to expand and contract with temperature changes. This dynamic capability replaces the need for a sliding seat mechanism, simplifying the design while maintaining thermal stress management
2Reliability
If a sliding seat is used to allow the pipe to move in the longitudinal direction, then thermally induced stresses are avoided, but device complexity increases
Solution Approach 1:
The pipe wall thickness is varied along its length, creating a flexible middle section that can deform elastically to accommodate thermal expansion. This eliminates the need for a sliding seat mechanism, significantly reducing device complexity while maintaining the ability to manage thermal stresses
Solution Approach 2:
The sliding seat mechanism is completely removed from the design. Instead, the pipe itself is designed with inherent flexibility through variable wall thickness, extracting the thermal stress management function from a separate mechanical component and integrating it into the pipe structure
3Ease of manufacture
If the pipe is fixedly connected to the housing at both end areas, then installation is simplified and stability is improved, but thermal expansion forces must be absorbed
Solution Approach 1:
The pipe wall thickness is optimized to create a flexible middle section that can absorb thermal expansion forces through elastic deformation. This allows both end areas to be fixedly connected to the housing for simplified installation and improved stability, while the variable thickness design provides the necessary compliance to handle thermal expansion
Solution Approach 2:
The thinner middle section of the pipe acts as a pre-designed cushioning element that absorbs thermal expansion forces before they can transmit to the fixed connections. This beforehand cushioning allows rigid fixed connections at both ends while protecting the system from thermal stress
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 enhances manufacturing efficiency, stability, and noise reduction by allowing the pipe to absorb thermal expansion forces elastically, enabling symmetrical assembly and reducing the risk of plastic deformation damage.
Implementation Method 1
the flexibility of the pipe can be designed in a targeted manner, so that thermally induced longitudinal expansion forces between the pipe and the housing can be absorbed largely through elastic deformation
Implementation Method 2
Relatively great temperature differences may occur between an exhaust-carrying pipe on the inside and the housing on the outside. Additionally or alternatively, the pipe and housing may be made of different materials having different thermal expansion coefficients
Data Source
AI summary
An exhaust-carrying component (2) of an exhaust system (1) for an internal combustion engine is provided, in particular for a motor vehicle. The component (2) includes a pipe (4) through which exhaust gas can flow from one longitudinal end (6) to the other longitudinal end (7) and which has between its longitudinal ends (6, 7) a longitudinal section (8), the wall (9) of which is provided with perforations (10). The component (2) also has a housing (5) which surrounds the pipe (4) in a circumferential direction and to which the pipe (4) is fixedly connected in both one end area (11) having a longitudinal end (6) and in another end area (12) having the other longitudinal end (7). In order for the component (2) to nevertheless be able to resist the thermal stresses that occur during operation, the perforations (10) are designed so that the longitudinal section (8) can absorb thermal longitudinal expansion forces between the pipe (4) and the housing (5) through elastic deformation.