CMC Turbine Clamping Assembly Thermal Expansion Design
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Solution Overview
Problem
Metallic fasteners used to couple ceramic matrix composite (CMC) turbine nozzles in gas turbine engines experience thermal expansion issues, leading to reduced clamping force at high temperatures, which can result in combustion gas leakage and efficiency loss.
Innovation Solution
A clamping assembly comprising a shaft and two sets of clamps, where the shaft and clamps are designed to thermally expand at a greater rate than the CMC materials, maintaining or increasing clamping force by using a key with a flange and pin to secure the clamps in place, ensuring a dovetail connection that retains the turbine nozzles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If metallic fasteners are used to couple CMC turbine nozzles, then the nozzles can be securely fastened together, but the clamping force decreases at high temperatures due to differential thermal expansion
Solution Approach 1:
The patent changes the material parameters of the fastening system by using a metallic key with a coefficient of thermal expansion greater than the CMC nozzles. This parameter change ensures that as temperature increases, the key expands more than the nozzles, maintaining contact pressure and clamping force throughout the operating temperature range.
Solution Approach 2:
The patent explicitly utilizes differential thermal expansion between the metallic key and CMC nozzles. The key is designed with a higher coefficient of thermal expansion than the CMC material, so that thermal expansion of the key compensates for any loss of clamping force, ensuring continuous contact and secure fastening at elevated temperatures.
2Strength
If the shaft thermally expands at a greater rate than the clamps, then clamping force is maintained or increased at high temperatures, but the structural design becomes more complex
Solution Approach 1:
The shaft is designed with a higher coefficient of thermal expansion than the clamps, creating a deliberate differential expansion relationship. As temperature rises, the shaft expands more than the clamps, which actively maintains or increases the clamping force on the turbine nozzles, converting thermal expansion from a potential problem into a beneficial effect.
Solution Approach 2:
The clamping assembly incorporates dynamic adaptability through the differential thermal expansion mechanism. The system automatically adjusts the clamping force in response to temperature changes, with the shaft's greater expansion dynamically compensating for thermal effects, eliminating the need for complex active control systems.
3Ease of manufacture
If metallic fasteners are used, then assembly is straightforward, but combustion gases may escape between turbine nozzle segments at high temperatures
Solution Approach 1:
The metallic key's greater thermal expansion ensures continuous contact with the turbine nozzle segments across the entire operating temperature range. This prevents gaps from forming that could allow combustion gas leakage, while the simple insertion assembly process maintains ease of manufacture.
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 clamping assembly effectively maintains or increases clamping force at higher temperatures, preventing combustion gas leakage and enhancing the efficiency of the gas turbine engine by ensuring secure coupling of turbine components.
Implementation Method 1
The shaft thermally expands at the same or at a greater rate than the first and the second pluralities of clamps
Data Source
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AI summary
A clamping assembly (100) includes a shaft (112), a first plurality of clamps (104), and a second plurality of clamps (106). Each of the first and second pluralities of clamps (104, 106) includes a first wall (118, 126), a second wall (120, 128) extending outwardly from the first wall (118, 126) in a first direction, and a third wall (122, 130) extending outwardly from the first wall (118, 126) in a second direction. Each first clamps (104) are longitudinally spaced apart by second clamps (106). The second walls (128) of the first clamps (104) are transversely spaced from the second walls (120) of the second clamps (106). The first and the second walls (118, 120, 126, 128) collectively define a first slot (134) that receives the shaft (112). The first and the third walls (118, 122, 126, 130) collectively define a second slot (108) for receiving adjacent turbine CMC components.