Turbine Bucket Closure Assembly Axial Insertion
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Solution Overview
Problem
In known turbine engines, the assembly of the final axial entry bucket is hindered by tightly fitting shrouds, requiring costly dovetail closure inserts that increase operating stresses and complicate the assembly process.
Innovation Solution
A rotor wheel assembly with a leading and trailing auxiliary bucket and a closure bucket, featuring integral covers with angled edges, allows for axial insertion of the closure bucket without a dovetail insert, utilizing a keyway and retaining pin for secure attachment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If tightly fitting shrouds are used to maintain continuous circumferential coupling of buckets, then reliability of bucket coupling is improved, but ease of operation deteriorates because the closure bucket cannot be inserted axially
Solution Approach 1:
The closure bucket assembly is segmented into multiple components: a closure bucket, a closure shroud, and a retainer. The retainer is a separate component that secures the closure bucket to the rotor wheel after axial insertion, allowing the shroud to have a standard tight-fitting configuration while the retainer provides the securing function that would otherwise require a complex integrated solution.
Solution Approach 2:
The retainer acts as an intermediary component between the closure bucket and the rotor wheel. It mediates the connection by engaging with both the closure bucket and the rotor wheel, providing a simple axial insertion path while ensuring secure attachment, thus resolving the conflict between easy insertion and reliable coupling.
2Reliability
If a dovetail closure insert is used to secure the closure bucket, then reliability of closure bucket attachment is improved, but device complexity increases and operating stresses increase
Solution Approach 1:
The complex dovetail closure insert is extracted from the system and replaced with a simpler retainer component. The retainer is a straightforward axial insertion piece that secures the closure bucket without requiring the complex dovetail geometry, thus reducing device complexity while maintaining attachment reliability.
Solution Approach 2:
The retainer is designed as a simple, inexpensive component compared to a dovetail closure insert. It serves its purpose of securing the closure bucket during operation and can be easily replaced if needed, providing a cost-effective solution that reduces both device complexity and operating stresses.
3Reliability
If a dovetail closure insert is used to secure the closure bucket, then reliability of closure bucket attachment is improved, but loss of time increases due to difficult and time-consuming assembly
Solution Approach 1:
Instead of using a complex insert to secure the bucket, the approach is inverted: a simple retainer is used that allows axial insertion of the closure bucket, and the retainer itself becomes the securing element. This inversion of the traditional approach dramatically reduces assembly time while maintaining reliable attachment.
Data Source
AI summary
A rotor wheel assembly has a rotor wheel including a plurality of dovetail slots. The rotor wheel assembly includes a bucket closure assembly having a leading auxiliary bucket with a dovetail coupled to a dovetail slot and an integral cover having a back side edge oriented at a first angle relative to the rotor wheel rotation axis. The bucket closure assembly includes a closure bucket having a dovetail coupled to a dovetail slot and an integral cover having a front side and a back side edge, where the back side edge is oriented to a second angle and the front side edge is parallel to the back side edge of the leading auxiliary bucket. The bucket closure assembly includes a trailing auxiliary bucket having a dovetail coupled to a dovetail slot and an integral cover having a front side edge parallel to the back side edge of the closure bucket.