Nonlinear Stiffness Bracket for Gas Turbine Thermal Growth
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Solution Overview
Problem
Gas turbine engines face challenges in managing thermal growth mismatches between tubes and fixed structures, leading to unsupported tubes that can yield under actuator forces, causing potential damage.
Innovation Solution
A mounting bracket with varying stiffness in different force directions is employed, featuring flanges and bracket legs designed to react actuator forces differently based on direction, providing support and preventing tube stretching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a rigid mounting bracket is used to support tubes, then the actuator force can be properly reacted, but the thermal growth mismatch between tubes and fixed structures cannot be accommodated, causing the tubes to stretch and yield
Solution Approach 1:
The mounting bracket is designed with non-linear stiffness characteristics that allow it to adapt its rigidity based on the direction of applied forces. The bracket exhibits higher stiffness in directions where actuator force reaction is needed and lower stiffness in directions where thermal growth accommodation is required, enabling it to dynamically respond to different operational conditions
Solution Approach 2:
The bracket structure incorporates varying geometric properties at different locations and orientations. Specific features such as the bracket leg geometry and flange configurations create localized stiffness variations, allowing the bracket to be rigid in certain directions while remaining compliant in others, thus simultaneously satisfying both force reaction and thermal growth requirements
2Adaptability or versatility
If the mounting bracket is made more compliant to accommodate thermal growth, then the tubes can move freely, but the actuator force cannot be properly reacted, causing the tubes to hang unsupported and yield
Solution Approach 1:
The bracket's non-linear stiffness characteristic enables it to switch between compliant and rigid states based on loading conditions. Under thermal growth conditions, the bracket remains compliant to allow movement, while under actuator loading conditions, it becomes rigid to properly react forces, thus resolving the contradiction between compliance and strength
Solution Approach 2:
The bracket design changes its effective stiffness parameter depending on the direction and magnitude of applied forces. Through its geometric configuration, the bracket achieves high stiffness in the actuator force direction while maintaining low stiffness in the thermal growth direction, allowing it to satisfy both contradictory requirements simultaneously
3Reliability
If a complex mounting structure is designed to accommodate both force reaction and thermal growth, then both requirements can be met, but the device complexity and manufacturing cost increase
Solution Approach 1:
The mounting bracket is designed as a multi-functional component that simultaneously performs force reaction, thermal growth accommodation, and positioning functions. By integrating multiple functions into a single bracket structure rather than using separate components for each function, the design achieves high reliability while minimizing device complexity and manufacturing cost
4Strength
If the actuator position is rigidly fixed, then the actuator force can be properly reacted, but the tubes experience stretching and fretting due to thermal growth mismatch
Solution Approach 1:
The bracket provides a dynamic support system that adapts its stiffness based on operational conditions. During thermal cycles, the bracket allows tube movement to prevent stretching and fretting, while during actuator operation, it provides rigid support for proper force reaction, thus eliminating both harmful effects
Solution Approach 2:
The mounting bracket acts as an intermediary element between the fixed actuator mounting structure and the thermally growing tubes. It mediates the conflicting requirements by providing conditional support - rigid when needed for force reaction and compliant when needed for thermal accommodation - thus protecting the tubes from both stretching and fretting
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 ensures stable support and reduced tube stretching, maintaining the actuator's position and preventing fretting, while being compact and cost-effective.
Implementation Method 1
The mounting bracket has a first stiffness when a load is applied in a first force direction and has a second stiffness different from the first stiffness when the load is applied in a second force direction opposite the first force direction
Data Source
AI summary
A mounting bracket of a gas turbine engine includes a first mounting flange configured to connect the mounting bracket to a casing of the gas turbine engine, a second mounting flange configured to connect a component to the mounting bracket, and a bracket leg extending between the first mounting flange and the second mounting flange. The mounting bracket has a first stiffness when a load is applied in a first force direction and has a second stiffness different from the first stiffness when the load is applied in a second force direction opposite the first force direction.