CMC Turbine Vane Assembly with Metallic Elongated Member
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Solution Overview
Problem
Turbine engines face challenges in assembling ceramic matrix composite (CMC) vanes due to material differences in tensile strength, ductility, thermal conductivity, and brittleness, leading to cracking and separation issues under mechanical and thermal stresses, as well as difficulties in securely connecting CMC airfoils with metal components.
Innovation Solution
A vane assembly design featuring metallic annular rings with cutouts and a ceramic matrix composite vane, where a metallic elongated member is inserted through a hollow portion of the vane and cutouts in the rings, accepting axial loads without transferring radial loads, allowing for thermal expansion and contraction without compressive or tensile loads on the CMC vane.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If ceramic matrix composite (CMC) materials are used for turbine vanes to improve thermal endurance, then thermal resistance is improved, but tensile strength and ductility deteriorate compared to metallic materials
Solution Approach 1:
The patent employs a composite structure combining metallic annular rings with a CMC vane assembly. The metallic rings provide tensile strength and ductility, while the CMC vane provides thermal endurance. This composite approach allows the system to simultaneously achieve high temperature resistance and mechanical strength by leveraging the complementary properties of different materials.
2Temperature
If CMC materials are used for turbine vanes to improve thermal endurance, then thermal resistance is improved, but ductility deteriorates causing cracking under thermal shock
Solution Approach 1:
The metallic annular rings serve as a ductile framework that can accommodate thermal expansion and contraction, protecting the brittle CMC vane from thermal shock-induced cracking. The composite structure allows the metallic components to absorb thermal stresses that the CMC material cannot withstand alone.
3Strength
If metallic body or strut members are added to strengthen the vane structurally, then mechanical strength is improved, but material compatibility problems arise due to dissimilar characteristics in ductility, thermal conductivity, and brittleness
Solution Approach 1:
The vane assembly is segmented into distinct metallic and CMC components rather than creating a fully integrated hybrid structure. The metallic annular rings are separate from the CMC vane, connected through defined interfaces. This segmentation simplifies the material compatibility issues by allowing each material to perform its optimal function in its designated zone.
Solution Approach 2:
The patent creates a composite assembly where metallic rings and CMC vane components work together. Each material is selected for its specific properties: metal for structural strength and thermal expansion accommodation, CMC for thermal endurance. The composite design leverages the strengths of each material while minimizing their weaknesses through proper interface design.
4Ease of manufacture
If CMC airfoils are formed separately and assembled over metal core, then manufacturing flexibility is improved, but assembly security deteriorates due to differential thermal expansion
Solution Approach 1:
The connection between the CMC vane and metallic rings allows for dynamic movement to accommodate thermal expansion. The set screw and locking mechanism create a secure but flexible connection that maintains assembly integrity while permitting the CMC and metal components to expand and contract at different rates without causing failure.
5Ease of operation
If CMC cover elements are slid over metal core, then assembly ease is improved, but structural security deteriorates under cantilevered aerodynamic forces
Solution Approach 1:
The CMC vane is pre-formed with an integrated hollow elongated member that protrudes beyond the vane ends. This preliminary structural feature allows the elongated member to serve as a built-in strengthening element that extends through the metallic rings, providing structural security against aerodynamic forces while maintaining the ease of sliding assembly.
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 enhances the durability and life expectancy of CMC vanes by avoiding radial loads, reducing fatigue cracking, and accommodating differential thermal expansion, thereby improving the mechanical strength and thermal endurance of turbine engine vanes.
Implementation Method 1
allowing for thermal expansion and contraction without compressive or tensile loads on the CMC vane
Implementation Method 2
due to its usually relatively low ductility, ceramic material has a tendency to crack under the impact of severe or suddenly applied thermal shock or stresses
Data Source
AI summary
A vane assembly includes first and second annular metal rings configured to accept a compressed gas flow therebetween. The first and second annular rings each include a cutout portion. The assembly further includes a ceramic matrix composite vane configured as an airfoil having a blunt rounded nose and a flattened and tapered tail. A first radial end of the vane is rigidly disposed on the first annular ring and a second radial end of the vane is slidably disposed within the cutout portion of the second annular ring such that the vane is encompassed by the first and second annular rings. The vane includes a hollow through opening portion extending radially therethrough. Still further, the assembly includes a metallic elongated member disposed within and extending through the hollow portion of vane and through the cutout portion of the first annular ring.