Turbine Interstage Seal Segmentation for Field Maintenance
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Solution Overview
Problem
Current interstage seals in gas turbines are not field maintainable, require significant work to replace, and complicate access to internal components, leading to inefficiencies and increased costs due to the need for high-performance alloys and additional components like spacer wheels.
Innovation Solution
A sealing system with multiple interstage seal subsystems featuring near flow path seal segments, forward and aft coverplates that extend radially to buckets, and axial retention rings, allowing for easy assembly and replacement, and accommodating flange bolted rotor architectures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional mechanical seals are used between turbine stages, then fluid leakage between stages is reduced and turbine rotor wheels are protected from hot gases, but the seals are not field maintainable and require substantial work to replace
Solution Approach 1:
The seal is divided into multiple independent segments that can be individually replaced. Each seal segment is a separate component that can be accessed and replaced without removing the entire seal assembly or disassembling blade rows, enabling field maintenance while maintaining sealing effectiveness.
2Reliability
If traditional mechanical seals are used between turbine stages, then fluid leakage is reduced, but the shape of the seals makes access to internal components more difficult
Solution Approach 1:
The segmented design allows technicians to access and replace individual seal segments without removing the entire seal assembly. This modular approach maintains effective sealing while improving accessibility for maintenance operations.
3Manufacturing precision
If traditional mechanical seals are used, then proper axial and radial alignment is achieved, but additional components such as spacer wheels are required
Solution Approach 1:
The seal segments are integrated directly with the turbine wheel structure, eliminating the need for separate spacer wheels and alignment components. The seal segments themselves provide the necessary axial and radial alignment features, reducing overall system complexity while maintaining precision.
4Ease of manufacture
If static seals with axial extensions are used, then the seal structure is simplified, but turbine wheel rims are not isolated from hot gas path requiring higher performance alloys
Solution Approach 1:
The seal segments create effective barriers between stages that isolate turbine wheel rims from the hot gas path. This segmentation approach provides thermal protection comparable to more complex designs while maintaining structural simplicity and using standard materials.
Data Source
AI summary
A sealing system for a multi-stage turbine includes multiple first interstage seal subsystems disposed circumferentially about a rotor wheel shaft of the multi-stage turbine and extending axially between a first turbine stage and a second turbine stage of the multi-stage turbine. Each of the first interstage seal subsystems includes multiple near flow path seal segments. The first interstage seal subsystem also includes a forward coverplate disposed axially between a first turbine wheel of the first turbine stage and the near flow path seal segment and an aft coverplate disposed axially between the near flow path seal segment and a second turbine wheel of the second turbine stag. Further, each of the forward coverplate and the aft coverplate extends radially to a first stage bucket and a second stage bucket respectively.