Bellowed Ball-Joint Flexural Interface for Low-Stiffness Duct Motion
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Solution Overview
Problem
Current ball-joint systems in turbine engine bleed air ducting systems compromise dynamic performance due to increased weight from rigidity requirements under dynamic loading, while flexibility is needed under thermal loading, leading to inefficiencies in vibration and thermal expansion management.
Innovation Solution
A pre-loaded, compliant bellowed spherical flex-joint with a kinematic ring and flared tube design that includes ramped backing rings and spring-energized flexures, providing a zero-backlash interface to reduce frictional forces and rotational stiffness, allowing for constrained kinematic geometry and reduced reaction loading during assembly and thermal growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If ball-joints or axial-joints are used in the duct to provide flexibility under thermal loading, then thermal expansion capability is improved, but system weight increases due to rigidity requirements under dynamic loading
Solution Approach 1:
The patent employs a bellows component with corrugated walls that provides thermal expansion flexibility through its flexible structure. The bellows can accommodate thermal growth and dynamic movements without requiring heavy rigid joints, thereby reducing system weight while maintaining adaptability to thermal loading conditions.
Solution Approach 2:
The joint assembly incorporates dynamic elements including the bellows with convolutions that can flex and expand, and a friction ring that allows controlled movement. This dynamic design enables the system to adapt to thermal expansion and vibration without the weight penalty of static rigid ball-joints or axial-joints.
2Strength
If rigid ball-joints are used to maintain structural integrity under dynamic loading, then structural strength is improved, but frictional forces and rotational stiffness increase, compromising dynamic performance
Solution Approach 1:
The friction ring serves as an intermediary element between the bellows and the rigid joint components. It mediates the interaction by providing a controlled friction interface that allows rotational movement while maintaining structural integrity, thereby reducing harmful frictional forces and rotational stiffness compared to direct rigid joint connections.
Solution Approach 2:
The patent changes the friction parameter by using a friction ring with specific material properties and surface characteristics. This controlled friction interface allows the joint to maintain structural strength while enabling smooth rotational movement, reducing the harmful effects of excessive friction and rotational stiffness.
3Reliability
If heavy rigid joints are used to ensure durability under dynamic loading, then reliability is improved, but the system's ability to manage vibration and thermal expansion deteriorates
Solution Approach 1:
The joint assembly is segmented into multiple functional components: the bellows for thermal expansion accommodation, the friction ring for controlled movement, and the rigid fittings for structural strength. This segmentation allows each component to specialize in one function, ensuring durability while maintaining adaptability to vibration and thermal expansion.
Solution Approach 2:
The joint assembly uses composite construction combining flexible bellows material with rigid fitting materials, and a friction ring with specific material properties. This composite approach ensures both durability under dynamic loading and adaptability to thermal and vibrational conditions by leveraging the strengths of different materials.
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 solution effectively minimizes frictional forces and rotational stiffness, enhancing the system's ability to manage thermal expansion and vibration, thereby reducing operational loads and improving the durability of the bleed air ducting system.
Implementation Method 1
spring-energized flexures, providing a zero-backlash interface to reduce frictional forces and rotational stiffness
Implementation Method 2
flexibility under thermal loading
Data Source
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AI summary
A turbine engine duct assembly (80) including a joint assembly (86) having an outer shroud (100), a bellows (106), a flared tube (120), a backing ring (122), and a kinematic ring (128). The joint assembly provides for dynamic movement of the duct assembly during operation of the engine. Such dynamic movement can be resultant of vibrational forces or thermal expansion of the engine. The joint assembly permits such dynamic movement without excessive system stiffness.