Turbine Interstage Seal Segments for Field Maintenance
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Solution Overview
Problem
Existing interstage seals in multi-stage turbines are not field maintainable, require significant work to replace, and complicate access to internal components, while also necessitating high-cost, high-performance alloys due to exposure to hot gases, and are not suitable for flange bolted rotor architectures.
Innovation Solution
A sealing system with near flow path seal segments that transfer centrifugal load to forward and aft stage buckets, featuring support webs and retention mechanisms for radial and axial engagement, allowing for field replacement and reduced material costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional mechanical seals are used between turbine stages, then fluid leakage is reduced and rotor wheels are protected from hot gases, but the seals are not field maintainable and require substantial work to replace
Solution Approach 1:
The sealing system is divided into multiple discrete seal segments that can be independently replaced. Each seal segment is a separate component that can be removed and replaced individually during field maintenance, eliminating the need to disassemble the entire seal system. This segmentation enables field maintainability while maintaining reliable sealing performance across all stages.
Solution Approach 2:
The seal segments are designed with flexible mounting mechanisms that allow them to be dynamically adjusted and replaced without permanent installation. The segments can be quickly installed and removed from the turbine stages, enabling field maintenance operations. This dynamic design transforms the seal system from a static, permanent installation to a maintainable, replaceable component system.
2Reliability
If traditional seals are used, then fluid leakage is reduced, but access to internal components becomes more difficult and additional components like spacer wheels are required
Solution Approach 1:
The sealing function is extracted from complex assemblies and integrated directly into the bucket structure. The seal segments are mounted directly on the buckets without requiring additional spacer wheels or complex support components. This extraction simplifies the overall device complexity by eliminating unnecessary intermediate components while maintaining reliable sealing performance.
Solution Approach 2:
The bucket structure serves multiple functions: it provides the turbine blade structure, supports the seal segments, and facilitates assembly. By making the bucket multi-functional, the design eliminates the need for separate support components like spacer wheels. This universality reduces device complexity while maintaining seal reliability.
3Reliability
If static seals with axial extensions are used, then sealing is achieved, but rotor wheels are not isolated from hot gas path requiring higher performance alloys at high cost
Solution Approach 1:
The seal segments act as intermediary components that are mounted on the buckets rather than requiring the rotor wheels themselves to be isolated from hot gases. This intermediary approach allows standard materials to be used for the rotor wheels while the seal segments provide the necessary thermal isolation. This reduces material costs by eliminating the need for expensive high-temperature alloys in the rotor wheel structure.
4Reliability
If traditional seals are used, then sealing is achieved, but assembly and disassembly of flange bolted rotor architectures is complicated
Solution Approach 1:
The sealing system is segmented into discrete components that can be independently assembled and disassembled from the flange bolted rotor architecture. This segmentation allows the seal segments to be installed and removed without requiring complete disassembly of the rotor assembly, significantly easing the assembly operation while maintaining reliable sealing performance.
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 sealing system enhances system efficiency, reduces secondary airflow, and allows for cost-effective fabrication and maintenance, including field replacement, while maintaining robustness and power density, and is compatible with flange bolted rotor architectures.
Implementation Method 1
The sealing component configured to provide for substantially all the centrifugal load from the sealing component to be transferred to the forward stage turbine bucket and the aft stage turbine bucket
Data Source
AI summary
A sealing system for a multi-stage turbine includes multiple interstage seal segments disposed circumferentially about a turbine rotor wheel assembly and extending axially between a forward turbine stage and an aft turbine stage. Each of the interstage seal segments includes a forward end portion including an outer seal surface and an inner support face, an aft end portion, including an outer seal surface and an inner support face and a main body portion extending axially from the forward end portion to the aft end. The main body portion includes at least two support webs coupling the outer seal surfaces and the inner support faces. The outer seal surfaces are configured to be retained in a radial direction by a land support on each of a forward and aft stage turbine buckets, such that substantially all the centrifugal load from the multiple interstage seal segments is transferred to the forward and aft stage turbine buckets. A method of assembling the sealing system is disclosed.