Rotor Mast Clamping Structure for Ducted Fan Tip-Gap Stability
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Solution Overview
Problem
Ducted fan systems face limitations in thrust generation due to unfavorable flow characteristics caused by the mixing of air through the fan and the gap between the blade tips and the duct, which reduces the pressure differential and overall thrust, and require increased out-of-plane stiffness to prevent catastrophic fan movement.
Innovation Solution
A rotor assembly with enhanced out-of-plane stiffness is achieved by applying a clamping force through components disposed between the hub and the mast bearing, using a combination of a rotor mast, mast bearing, cuff, and conical rings to distribute compressive forces and increase stiffness, allowing for improved stability and thrust performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the tip gap between the blade tips and the duct is minimized to maximize thrust, then thrust generation is improved, but the risk of catastrophic fan contact increases due to forces causing fan movement relative to the duct
Solution Approach 1:
The rotor assembly is divided into functionally distinct components: the rotor hub, rotor mast, mast bearing, and cuff. This segmentation allows each component to be optimized for its specific function while working together as a integrated system that addresses both thrust generation and stability requirements
Solution Approach 2:
The patent implements a dynamic stiffness solution by introducing a cuff and mast bearing assembly that can adapt to operational forces. The cuff fits over the rotor mast and works with the mast bearing to dynamically adjust the structural characteristics of the rotor assembly during operation, allowing the system to maintain stability while accommodating the forces that cause fan movement
2Reliability
If the rotor mast is made more rigid to prevent fan movement, then fan stability is improved, but the complexity of the rotor assembly increases
Solution Approach 1:
The cuff and mast bearing functions are merged into a single integrated assembly that fits over the rotor mast. This combination consolidates multiple functions (structural reinforcement, bearing support, and alignment) into one component package, reducing the number of separate parts while achieving the desired rigidity and stability
Solution Approach 2:
The cuff is designed to fit over the rotor mast in a nested configuration, with the mast bearing assembly positioned within the cuff structure. This nesting approach allows multiple functional elements to be housed within each other, minimizing the overall space required and reducing assembly complexity while maintaining the structural integrity needed for fan stability
Data Source
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AI summary
A rotor assembly (108) configured to increase the stiffness of a rotor mast. The rotor assembly includes the rotor mast (124), a rotor hub (126), a mast nut (132), a mast bearing (128), and a cuff (130) disposed between the mast nut and the mast bearing. The cuff is captured and compressed between the mast nut and the inner race (136) of the mast bearing along an uninterrupted load path that extends between the mast nut and the mast bearing.