CMC Rotor Disk Tapered Bore Design
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Solution Overview
Problem
Conventional gas turbine engine rotor disk designs, particularly those using high temperature superalloys, face challenges in incorporating Ceramic Matrix Composites (CMC) due to geometric constraints that lead to excessive hoop growth and stress issues, which are not effectively addressed by existing CMC designs.
Innovation Solution
A CMC disk design featuring a rail integrated with the hub that tapers to a rail inner bore, allowing for a larger innermost bore radius, reduced weight, and improved stress balance, while maintaining the continuity of internal stress-carrying fibers, replacing the conventional rim and teardrop-like bore structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a conventional thin mid-section bore geometry is used in rotor disks, then self-retention capabilities are improved through minimization of excessive hoop growth, but the geometry does not lend itself to Ceramic Matrix Composites (CMC) manufacturing
Solution Approach 1:
The invention changes the geometric parameters of the bore from a thin mid-section conventional shape to a large radius bore with optimized dimensions. This parameter change allows CMC materials to be manufactured while still providing sufficient hoop growth control, as the larger radius geometry inherently reduces stress concentration and allows for the integration of CMC airfoils and rails.
Solution Approach 2:
The invention integrates CMC materials into the rotor disk structure, including CMC airfoils extending from a CMC hub and CMC rails defining the bore geometry. This composite material approach enables the manufacturing of complex geometries that would be difficult with conventional materials, while maintaining the necessary mechanical properties for hoop growth control.
2Weight of moving object
If CMC materials are used in rotor disks, then weight is reduced and stress resistance is improved, but complex attachment areas and integration with conventional structures become more difficult
Solution Approach 1:
The invention merges the attachment structures directly into the CMC rail body, creating an integrated design where the rail itself forms the attachment areas. This eliminates separate attachment components and simplifies the overall structure, as the CMC rail with its tapered bore and platform section provides both structural support and attachment functionality in a unified component.
Solution Approach 2:
The invention segments the rotor disk into distinct CMC components (hub, airfoils, rails) that can be manufactured separately and then assembled. This segmentation allows each component to be optimized for CMC manufacturing while maintaining overall system integration, reducing the complexity of creating monolithic CMC structures with complex attachment areas.
3Volume of moving object
If a large innermost bore radius is implemented in CMC disks, then packaging benefits and weight reduction are achieved, but stress distribution patterns change requiring new design approaches
Solution Approach 1:
The invention applies local quality by creating a tapered bore geometry where the rail thickness varies along the bore length, being thicker at certain sections and thinner at others. This non-uniform local structure optimizes stress distribution in different regions, allowing the large bore radius to provide volume benefits while the localized thickness variations maintain appropriate stress levels where needed.
Solution Approach 2:
The invention uses curved and tapered geometries in the rail bore design, transitioning from straight cylindrical sections to tapered sections with optimized curvature. These curved transitions help distribute stresses more evenly around the large bore radius, preventing stress concentration at sharp corners or abrupt geometry changes while maintaining the volume benefits of the large bore.
Data Source
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AI summary
A rotor disk (64A, 64C) for a gas turbine engine (20) includes a ceramic matrix composite (CMC) hub (68A, 68C) and a rail (80A, 80C) integrated with the CMC hub opposite the multiple of CMC airfoils (66A, 66C), the rail defines a rail (80A, 80C) platform section (84) that tapers to a rail inner bore (82). A corresponding rotor module (62) is also provided.