Bellows Fluid Duct Structure for Axial Stiffness and Bending Flexibility
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Solution Overview
Problem
Conventional flexible fluid ducts for automotive applications face challenges in maintaining high bending flexibility while withstanding high temperatures and pressures, as measures to enhance stiffness in the flow direction often compromise out-of-plane flexibility, leading to stress and assembly difficulties.
Innovation Solution
A fluid duct design featuring bellows with convolutes that wrap around the duct channel by a specific angle, providing a high range of bending flexibility while maintaining stiffness in the flow direction, achieved through a combination of interconnected bellows and non-bellows tube portions, and optimized convolute profiles and arrangements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If conventional bellows are provided with sections that are substantially rigid in the flow direction (by providing convolutes that do not completely encircle the tube or by molding a rib extending in the flow direction), then the tube maintains stiffness in the flow direction, but the bending flexibility in directions either side of the plane of maximum flexibility is reduced
Solution Approach 1:
The bellows structure implements local quality by providing different structural characteristics in different directions: the convolutes are configured to provide rigidity in the flow direction (axial stiffness) while allowing flexibility in radial bending directions. This is achieved through the specific geometry of convolutes that do not completely encircle the tube, creating localized rigid sections that resist axial deformation while permitting lateral bending.
Solution Approach 2:
The bellows employs asymmetric convolute design where the convolutes are positioned and shaped to provide differential structural properties: they create stiffness in the flow direction through their axial arrangement while maintaining flexibility in perpendicular bending directions. The asymmetric placement and shape of convolutes relative to the tube circumference enables this directional differentiation of mechanical properties.
2Stability of the object's composition
If the reduced out-of-plane bending flexibility is caused by the tube rigidifying portions, then the tube maintains flow direction stiffness, but the rigidity of the overall duct increases thus rendering the assembly thereof to complementary coupling elements more difficult
Solution Approach 1:
The design applies local quality by concentrating rigidifying features only where needed for flow direction stability, rather than making the entire tube rigid. The convolutes are strategically positioned and shaped to provide axial stiffness locally while leaving other regions flexible enough for assembly operations, enabling directional control of mechanical properties.
Solution Approach 2:
The bellows structure exhibits dynamic characteristics where its effective stiffness can change based on operational conditions. During assembly, the flexible regions allow easy coupling, while during operation under thermal and pressure loads, the rigidifying portions maintain structural integrity and flow direction stability.
3Strength
If high bending flexibility is provided in the tube, then stresses on the tube and coupling are reduced, but flexibility in the flow direction is enhanced leading to problems associated with elongation of bellows under high temperatures and pressures
Solution Approach 1:
The bellows design implements local quality by creating regions with different mechanical properties: the convolute sections provide flexibility to reduce stress concentrations, while the inter-convolute tube sections and strategically positioned rigidifying features provide flow direction stiffness to prevent elongation under pressure and thermal loads.
Solution Approach 2:
The bellows structure is segmented into alternating flexible and rigid zones. The convolutes create flexible segments that accommodate bending and reduce stress, while the tube sections between convolutes and the rigidifying portions create stiff segments that resist axial elongation. This segmentation allows simultaneous achievement of stress resistance and flow direction stability.
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 3A~3F
AI summary
Provided herein is a fluid duct (2) comprising a tubular base wall (11) surrounding a duct channel and at least one bellows (10) formed along a section of the tubular base wall (11). The bellows (10) comprises a plurality of convolutes (12) having a profile (14) projecting radially from the base wall (11). At least one convolute (12) wraps around the duct channel at a wrap-around angle Ω of between 180° and 720° from a first end (22a) to a second end (22b) of the convolute (12), said second end (22b) being offset in a flow direction F parallel to a centerline C of the duct channel by a non-zero offset distance D from the first end (22a).