Compliant CMC Blade Track Interface for Gas Turbine Sealing
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Solution Overview
Problem
Existing systems face challenges in mitigating high local stresses at the interface between ceramic matrix composite (CMC) and metallic structures in gas turbine engines due to differences in thermal expansion coefficients, leading to potential surface damage and cooling air leakage.
Innovation Solution
A compliant structure is introduced, featuring a CMC blade track assembly with a metallic hanger and a wavy spring clip configuration that redistributes load, centers the CMC blade track, and controls cooling air leakage by using a wavy washer and clip assembly to accommodate differential thermal expansion and provide sealing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a rigid connection is used between CMC and metallic structures, then structural strength is improved, but high local contact stresses and surface damage occur due to differential thermal expansion
Solution Approach 1:
A compliant structure acts as an intermediary element between the CMC blade track and the metallic hanger. This compliant structure includes a spring clip and wavy washer that accommodate differential thermal expansion while distributing contact stresses, preventing surface damage to both the CMC and metallic components.
Solution Approach 2:
The compliant structure changes its physical parameters (shape, position) in response to thermal expansion differences. The spring clip and wavy washer deform elastically to absorb dimensional changes, maintaining a stable interface between components with different thermal expansion coefficients.
2Object-affected harmful factors
If a compliant structure is introduced to reduce local stresses, then surface damage is mitigated, but device complexity increases
Solution Approach 1:
The compliant structure utilizes flexible metallic elements (spring clip and wavy washer) that deform to accommodate thermal expansion. These flexible components replace complex multi-part assemblies while providing the necessary compliance and stress distribution functions.
Solution Approach 2:
The solution employs a composite assembly combining CMC blade track with metallic compliant structure (spring clip and wavy washer). This hybrid construction leverages the high-temperature properties of CMC while using the ductility and elastic properties of metals to manage thermal stresses.
3Productivity
If sealing measures are added to control cooling air leakage, then operational efficiency is improved, but device complexity increases
Solution Approach 1:
The compliant structure performs multiple functions simultaneously: it provides mechanical compliance to accommodate thermal expansion, distributes contact stresses to prevent surface damage, and creates sealing surfaces to control cooling air leakage. This multi-functionality eliminates the need for separate sealing components.
Solution Approach 2:
The spring clip and wavy washer are integrated with the hanger and blade track assembly, combining structural support, compliance, and sealing functions into a unified structure rather than separate components.
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 solution effectively reduces local contact stresses and minimizes cooling air leakage, enhancing the operational efficiency and longevity of gas turbine engine components by ensuring proper alignment and thermal compatibility between CMC and metallic components.
Implementation Method 1
a spring arrangement resulting in load redistribution that leads to reduced local contact stresses
Implementation Method 2
provide sealing around the CMC structure to control cooling air leakage
Data Source
AI summary
A structure providing compliance and sealing between ceramic or ceramic composite (CMC) part and a metallic part has an interface component for centering the CMC part in the metallic part, thus reducing thermal stress motion of the CMC component. In gas turbine engine applications, the structure comprises a CMC blade track inserted in a clip placed within a metallic hanger. The clip provides for radial compliance and secures controlled leakage of cooling air required to ensure that acceptable temperatures are maintained for the metallic structures. A washer is positioned adjacent to the clip provide for axial orientation of the blade track.