Nested Flexible Shaft Coupling for High-Speed Misalignment
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Solution Overview
Problem
Existing gas turbine engines face misalignment issues between high speed shafts due to manufacturing and assembly tolerances or maneuver deflections, leading to excessive loads and premature failure, which current flexible couplings like bellows or splines fail to adequately address.
Innovation Solution
A high speed shaft flexible coupling design featuring a smaller diameter flexible shaft contained within a larger diameter primary shaft, with a torque transfer feature at the end, allowing for misalignment tolerance without contact except at the transfer point, reducing system length and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a traditional flexible coupling (bellows or spline) is used to tolerate misalignment between shafts, then misalignment capability is improved, but system length increases and cost increases
Solution Approach 1:
The flexible shaft is nested within the hollow extension of the rigid shaft, with the flexible shaft having a smaller diameter than the hollow shaft. This allows the flexible coupling functionality to be integrated within the existing shaft structure, eliminating the need for external bellows or spline couplings and thereby reducing overall system length while maintaining misalignment tolerance capability
2Adaptability or versatility
If a traditional flexible coupling (bellows or spline) is used to tolerate misalignment between shafts, then misalignment capability is improved, but cost increases
Solution Approach 1:
The flexible shaft is nested within the hollow extension of the rigid shaft, integrating the flexible coupling functionality into the shaft structure itself. This eliminates the need for separate, expensive flexible coupling components such as bellows or splines, thereby reducing manufacturing cost while maintaining misalignment tolerance
Solution Approach 2:
The invention merges the functions of the rigid shaft and flexible coupling into a single integrated structure. The hollow extension of the rigid shaft and the nested flexible shaft work together as a unified torque transmission system, eliminating the need for separate flexible coupling components and reducing overall system cost
3Adaptability or versatility
If a flexible shaft is used to connect two high speed shafts, then misalignment tolerance is improved, but rotor system stiffness decreases
Solution Approach 1:
The shaft system is segmented into two distinct functional portions: a rigid shaft portion for maintaining structural stiffness and support, and a flexible shaft portion for tolerating misalignment. The rigid shaft with its hollow extension provides the necessary structural backbone, while the nested flexible shaft provides misalignment tolerance, allowing each segment to optimize its specific function
Solution Approach 2:
Different portions of the shaft system have different mechanical properties optimized for their specific functions. The rigid shaft portion maintains high stiffness for structural support, while the flexible shaft portion has reduced stiffness to allow misalignment accommodation. This local differentiation of mechanical properties allows the system to simultaneously achieve both stiffness and flexibility where needed
Data Source
AI summary
A gas turbine engine in which a long length-to-diameter (L/D) flexible shaft is used to connect two high speed shafts in order to tolerate misalignment. In order to reduce the overall system length, a smaller diameter flexible shaft is contained within but not in contact with a larger diameter primary turbomachinery shaft such that the smaller flexible shaft adjoins to the primary shaft aft of the primary shaft bearing. This design reduces a length of the overall system and reduces additional cost associated with a flex bellows or spline.