Segmented Turbine Bucket with Single-Lobe Joint
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Solution Overview
Problem
Turbine bucket assemblies in gas turbine engines face limitations due to material constraints, particularly in high-temperature environments, where the length of airfoil portions and dovetail sizes require increased materials, leading to higher costs and maintenance challenges, and varying forces necessitate specific material properties that are not adequately addressed by existing designs.
Innovation Solution
A segmented turbine bucket assembly with a single-lobe joint, featuring a ceramic matrix composite tip segment, a titanium aluminide root segment, and a superalloy turbine wheel, allowing for differential thermal expansion and heat resistance, enabling reduced structural loading, easier repair, and cost-effective operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the length of the airfoil portion of the buckets is increased to facilitate enhanced performance, then the operating capacity of the engine is improved, but the size of the dovetails and dovetail slots must be increased, leading to higher material costs and manufacturing complexity
Solution Approach 1:
The airfoil is divided into multiple segments (first airfoil segment, second airfoil segment, third airfoil segment) that can be manufactured separately and then assembled together. This segmentation allows each segment to be optimized independently and reduces the overall complexity of manufacturing the entire long airfoil, while still achieving the desired enhanced operating capacity.
Solution Approach 2:
Different portions of the airfoil are made from different materials with varying properties. The root portion uses a first material, the mid portion uses a second material, and the tip portion uses a third material. This composite approach allows optimization of each region for its specific functional requirements, reducing the need for oversized dovetails while maintaining performance.
2Strength
If the size of the dovetails and dovetail slots is increased to retain longer buckets, then the structural integrity is improved, but the material costs and manufacturing difficulty increase
Solution Approach 1:
By segmenting the airfoil into multiple portions that can be manufactured separately, the patent reduces the manufacturing difficulty associated with producing long, complex dovetail structures. Each segment can be manufactured with standard-sized dovetails, and the assembly process simplifies the overall manufacturing challenge.
Solution Approach 2:
Different materials are used in different portions of the airfoil based on local quality requirements. This allows optimization of material properties in regions experiencing different stresses and temperatures, improving structural integrity without requiring uniformly increased dovetail sizes throughout the entire airfoil.
3Reliability
If different materials are used in different portions of the airfoil to address varying forces, then the performance is improved, but the manufacturing complexity and cost increase
Solution Approach 1:
The patent applies different materials to different portions of the airfoil based on local quality requirements. The root portion uses a first material optimized for high stress and heat, the mid portion uses a second material, and the tip portion uses a third material. This localized material selection improves performance by ensuring each region has the appropriate material properties, while the modular segmentation approach helps manage manufacturing complexity.
Solution Approach 2:
By segmenting the airfoil into distinct portions that can be manufactured separately from different materials, the patent makes the implementation of material variation more manageable. Each segment can be manufactured from its designated material using standard processes, and the assembly process integrates these different materials while controlling overall complexity.
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 design reduces structural loading, facilitates easier maintenance, permits operation at higher temperatures, and allows for the use of lighter materials, thereby enhancing the performance and durability of turbine bucket assemblies while minimizing repair costs and downtime.
Implementation Method 1
the root segment material and the turbine wheel material having lower heat resistance and higher thermal expansion than the tip segment material
Data Source
AI summary
A turbine bucket assembly and turbine system are disclosed. The turbine bucket assembly includes a single-lobe joint having an integral platform, the joint having a first axial length; a segmented airfoil having a root segment extending radially outward from the platform and a tip segment coupled to the root segment, the tip segment having a second axial length, which is less than the first axial length; and a turbine wheel defining a receptacle with a geometry corresponding to the single-lobe joint and being coupled to the single-lobe joint. The tip segment includes a tip segment material, the root segment includes a root segment material, and the turbine wheel includes a turbine wheel material, the root segment material and the turbine wheel material having a lower heat resistance and a higher thermal expansion than the tip segment material.