Radial Loading Fastener for Gas Turbine Rotor Stability
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Solution Overview
Problem
In gas turbines, thermal transients cause rabbeted joints to become unloaded, leading to rotor imbalance and vibrations due to differential thermal expansion, necessitating costly rebalancing or replacement.
Innovation Solution
A fastener system comprising a bolt with threaded ends and two sleeves that impart radial loads when tightened, ensuring alignment and stability between rotor wheels and spacers, eliminating the need for rabbeted joints.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If rabbeted joints are used to connect rotor wheels and spacers, then assembly is simplified, but thermal transients cause the joints to become unloaded leading to rotor imbalance and vibrations
Solution Approach 1:
The connection system is segmented into multiple functional components: a bolt for axial loading, and two sleeves (inner and outer) for radial loading. This segmentation allows each component to address specific functional requirements independently, with the sleeves providing continuous radial contact to prevent joint unloading during thermal transients while the bolt handles axial fastening.
Solution Approach 2:
The inner and outer sleeves act as intermediary elements between the bolt and the rotor wheel/spacer assembly. These sleeves transmit and distribute the radial loads, ensuring continuous contact and preventing direct unloading of the rabbeted joints during thermal expansion and contraction cycles.
2Strength
If rabbeted joints are used between wheels and spacers, then structural connection is achieved, but differential thermal expansion causes joint unloading and rotor imbalance
Solution Approach 1:
The sleeve system is designed to dynamically adapt to thermal transients. The sleeves can expand and contract radially in response to thermal changes, maintaining continuous contact with the rotor wheel and spacer surfaces. This dynamic adjustment prevents joint unloading and maintains rotor balance during thermal expansion and contraction cycles.
Solution Approach 2:
The sleeves are designed with specific geometric parameters (tapered surfaces, cylindrical sections) that allow them to change their load distribution characteristics in response to thermal parameters. As temperature changes, the sleeves adjust their contact pressures and distribution patterns to maintain stable joint engagement and prevent rotor imbalance.
3Force
If conventional bolts are used for fastening, then axial loading is provided, but radial loading capability is insufficient to prevent joint unloading
Solution Approach 1:
The fastening function is segmented into two independent load paths: axial loading handled by the bolt, and radial loading handled by the two sleeves. This segmentation allows each component to be optimized for its specific function, with the sleeves providing the necessary radial loading capability that conventional bolts cannot provide.
Solution Approach 2:
The invention merges the axial fastening function (bolt) with the radial loading function (sleeves) into a single integrated fastening system. This combination creates a comprehensive solution that simultaneously provides both axial and radial load resistance, preventing joint unloading under all operating conditions including thermal transients.
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 fastener system maintains rotor balance, reduces vibrations, and simplifies assembly and disassembly by providing self-centering and additional torque, eliminating the need for rabbets and line reaming.
Implementation Method 1
The first and second sleeves are configured to impart an outwardly radial load when the at least one nut is tightened on the bolt
Data Source
AI summary
A fastener is provided including a bolt having at least one threaded end, a first sleeve configured to fit over the bolt, and a second sleeve configured to fit over the first sleeve. At least one nut is configured to cooperate with threads in the threaded ends of the bolt. The first and second sleeves are configured to impart an outwardly radial load when the nuts are tightened on the bolt.