Wedge Key Bucket Locking for Turbine Rotor Stress Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing turbine engines face challenges in securely coupling buckets to a rotor wheel assembly, particularly due to the use of twist locks which increase costs and operating stresses, and fail to achieve tight coupling at bucket platforms to raise natural frequencies and reduce dynamic stresses.
Innovation Solution
A rotor wheel assembly with dovetail slots and notches, and a wedge key system where the wedge key has a locking taper, allowing for secure axial and circumferential coupling of buckets, reducing the need for twist locks and enabling frictional contact forces to maintain tight coupling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If twist locks are used to prevent axial shifting of buckets, then buckets are secured on the rotor wheel, but operating stresses increase and cost increases
Solution Approach 1:
The patent removes the twist lock component entirely from the system. Instead of using twist locks to prevent axial shifting, the invention uses a closure bucket with dovetail that mates with a dovetail slot in the rotor wheel, eliminating the need for separate locking mechanisms and thereby reducing operating stresses while maintaining bucket security.
Solution Approach 2:
The patent inverts the traditional approach by making the closure bucket itself the primary securing mechanism rather than using separate locks. The closure bucket's dovetail structure provides both the sealing function and the mechanical securing function, reversing the conventional role assignment where buckets are secured by separate locking components.
2Reliability
If twist locks are used to secure buckets, then axial shifting is prevented, but device complexity and cost increase
Solution Approach 1:
The patent extracts and removes the twist lock component from the assembly system. The closure bucket with its dovetail structure replaces the function of twist locks, simplifying the overall device by eliminating separate locking mechanisms and reducing assembly complexity.
Solution Approach 2:
The closure bucket serves multiple functions: it seals the gap between adjacent buckets, prevents axial shifting through its dovetail-mate slot mechanism, and provides structural support. This multi-functionality eliminates the need for separate twist lock components, reducing device complexity.
3Stability of the object's composition
If integral covers are extended between adjacent buckets, then vibratory response is dampened and natural frequencies increase, but tight coupling at bucket platforms is prevented
Solution Approach 1:
The patent incorporates preliminary coupling features in the form of dovetails and dovetail slots that are pre-configured to engage when the closure bucket is installed. This preliminary action ensures tight coupling at the bucket platforms before operational loads are applied, enabling the integral covers to effectively dampen vibratory response while maintaining strong coupling.
Solution Approach 2:
The closure bucket acts as an intermediary element that bridges the gap between adjacent buckets with integral covers. Its dovetail structure mediates the connection, enabling both tight coupling for strength and proper positioning for vibratory response control.
4Reliability
If keys are used to secure buckets in dovetail slots, then buckets are locked in position, but closure bucket insertion is prevented by integral covers
Solution Approach 1:
The patent inverts the traditional key-in-groove locking mechanism. Instead of using separate keys to lock buckets, the closure bucket itself has a dovetail that mates with a dovetail slot in the rotor wheel, providing locking through the closure bucket's own structure rather than through separate keys.
Solution Approach 2:
The closure bucket serves as both the sealing element and the locking element. Its dovetail structure provides the locking function traditionally performed by separate keys, while its presence in the assembly enables both sealing and securing functions simultaneously.
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
This solution reduces operating stresses, enables accurate standing assembled vibration testing, and increases bucket natural frequencies, thereby enhancing turbine engine performance and reducing assembly complexity and costs.
Implementation Method 1
a frictional contact force is generated between the first bucket and the wedge key, and the second bucket and the wedge key
Implementation Method 2
a wedge key system where the wedge key has a locking taper
Data Source
AI summary
A rotor wheel assembly includes a rotor wheel having a plurality of dovetail slots spaced circumferentially about a peripheral surface of the rotor wheel. The rotor wheel also has a plurality of notches formed in the peripheral surface. The rotor wheel assembly includes at least one bucket having an integral cover, an airfoil, a dovetail, and a platform having a first surface and an opposite second surface. The first surface of the platform includes a keyway. The keyway has an opposing tapered surface oriented at a first angle relative to the first surface of the platform. Furthermore, the rotor wheel assembly includes a wedge key having first face that is oriented substantially parallel to the first surface of the platform and an opposite second face that is oriented at the first angle relative to the first face, such that the second face is substantially parallel to the taper surface.