Seal Assembly Using Shape Memory Alloy for Gas Turbine Clearance Control
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Solution Overview
Problem
Existing rotor seals in gas turbine engines face challenges in maintaining consistent seal clearance and minimizing leakage across varying operating conditions, including temperature and rotational speed changes, which can lead to increased wear and reduced seal life.
Innovation Solution
The use of shape memory alloys (SMAs) or bimetallic materials in the seal assemblies to control seal clearance throughout the operational range, ensuring a more constant leakage rate by maintaining a consistent gap size despite temperature and speed variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional rotor seals are used in gas turbine engines, then the seal structure is simple and easy to manufacture, but the seal clearance varies significantly with temperature and rotational speed changes leading to increased leakage
Solution Approach 1:
The patent applies parameter changes by incorporating shape memory alloy (SMA) materials that change their physical dimensions in response to temperature variations. The SMA component expands or contracts automatically with temperature changes, compensating for thermal expansion of other seal components and maintaining consistent seal clearance throughout the operating temperature range, thereby resolving the contradiction between seal clearance consistency and structural simplicity
Solution Approach 2:
The patent uses composite materials by integrating shape memory alloy with traditional seal assembly components. This composite approach combines the temperature-responsive properties of SMA with the mechanical strength and sealing capabilities of conventional materials, creating a seal assembly that maintains reliable performance across varying operating conditions while managing structural complexity
2Reliability
If conventional rotor seals are used, then the manufacturing process is straightforward, but leakage increases due to varying seal clearance under different operating conditions
Solution Approach 1:
The shape memory alloy component automatically adjusts its dimensions based on temperature changes without requiring complex active control systems. This passive parameter change mechanism maintains consistent seal clearance and controls leakage effectively, while the manufacturing process remains relatively straightforward by incorporating the SMA component into the existing seal assembly fabrication流程
3Reliability
If seal clearance is reduced to minimize leakage, then leakage decreases, but wear increases due to tighter tolerances under varying operating conditions
Solution Approach 1:
The shape memory alloy dynamically adjusts the seal clearance parameter in response to temperature variations, ensuring that the clearance remains within optimal ranges throughout operation. This prevents excessive clearance that would cause leakage while avoiding overly tight clearance that would cause wear, thereby extending seal life by maintaining balanced clearance conditions
Solution Approach 2:
The patent introduces dynamic adaptability to the seal assembly through the shape memory alloy component that automatically responds to temperature changes. This dynamic adjustment capability allows the seal to maintain optimal clearance characteristics under varying operating conditions, preventing both leakage and wear issues that plague static seal designs
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 approach results in a more consistent seal performance, reduced leakage, and extended seal life by maintaining a stable seal clearance across the range of operating conditions.
Implementation Method 1
a portion of one of the rotor and the stator being formed of (i) a shape memory alloy or (ii) a first metal and a second metal, the second metal having a coefficient of thermal expansion different from the first metal
Data Source
AI summary
A seal assembly for a rotary machine. The seal assembly includes a rotor and a stator. The rotor is rotatable about a rotational axis and has a rotor seal face. The stator has a stator seal face. The stator seal face is positioned opposite the rotor seal face and faces the rotor seal face with a gap therebetween. A portion of one of the rotor and the stator is formed of (i) a shape memory alloy or (ii) a first metal and a second metal with the second metal having a coefficient of thermal expansion different from the first metal. The seal assembly is characterized by a seal clearance compliance ratio (SCCR) from 20% to 90%.