Coupling Shaft Segmentation for Gas Turbine Gear Stress
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Solution Overview
Problem
Advanced gas turbine engines face challenges in reducing stresses caused by misalignments and managing vibrations in epicyclic gear trains due to the need for flexible couplings to maintain ideal gear orientations amidst engine deflections.
Innovation Solution
A coupling shaft assembly with a forward and aft coupling shaft section, including interface splines, a convolute for stiffness, and an oil distribution system to facilitate torque transfer and vibration segregation, connected to an epicyclic gear system, which integrates a slip-joint and oil management features to support modular construction and compact design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If flexible couplings are used to connect the gear train to rotating shafts, then stresses due to misalignments are reduced, but device complexity increases
Solution Approach 1:
The coupling shaft is divided into multiple sections (first coupling shaft section, second coupling shaft section) connected by a slip joint. This segmentation allows each section to independently accommodate misalignments while reducing stress, without requiring a completely flexible coupling design.
Solution Approach 2:
The slip joint enables relative movement between the first and second coupling shaft sections, allowing the coupling shaft to dynamically adapt to misalignments and engine deflections. This dynamic adjustment reduces stresses while maintaining a relatively simple overall structure compared to fully flexible couplings.
2Adaptability or versatility
If a coupling shaft assembly with multiple sections and slip joints is used, then adaptability to misalignments is improved, but manufacturing precision requirements increase
Solution Approach 1:
By segmenting the coupling shaft into multiple sections with a slip joint, the patent distributes the adaptability function across separate components. Each section can be manufactured with standard precision, and the slip joint provides the necessary movement capability without requiring ultra-precise manufacturing of individual parts.
Solution Approach 2:
The slip joint acts as an intermediary element between the first and second coupling shaft sections. It mediates the connection while allowing relative movement, thereby providing adaptability to misalignments without transferring high precision requirements to the manufacturing of the shaft sections themselves.
3Reliability
If oil distribution features are integrated into the coupling shaft sections, then reliability is improved, but device complexity increases
Solution Approach 1:
The oil distribution features are merged directly into the coupling shaft sections, combining the torque transmission function and lubrication function into a single integrated component. This eliminates the need for separate lubrication systems, thereby improving reliability through better lubrication while avoiding the complexity of additional separate lubrication devices.
Solution Approach 2:
The coupling shaft sections are designed with multi-functionality, serving both as torque transmission elements and as oil distribution channels. The oil distribution features are formed as integral parts of the shaft sections, allowing a single component to perform multiple functions without increasing overall device complexity.
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 coupling shaft assembly effectively reduces stresses and vibrations, enabling efficient torque transfer while maintaining gear alignment and facilitating modular engine construction with reduced weight and complexity.
Implementation Method 1
a convolute (40) for stiffness
Implementation Method 2
an oil distribution system to deliver lubrication
Implementation Method 3
a number two bearing assembly (38B) at a second end of the low pressure turbine shaft (50)
Data Source
Figure 1
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AI summary
A coupling shaft assembly (62) for a gas turbine engine (20) includes a forward coupling shaft section (64) with a forward interface spline (68) and a forward mid shaft interface spline (68) and an aft coupling shaft section (66) includes an aft mid shaft interface spline (72) and an aft interface spline (74). The aft mid shaft interface spline (72) is engageable with the forward mid shaft interface spline (70).