Multi-Material Bushing Assembly for Thermal Expansion Mismatch
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Solution Overview
Problem
Existing journal bearing bushings in gas turbine engines face challenges in efficiently managing thermal expansion and material compatibility between rotating and stationary structures, leading to potential wear and reduced performance.
Innovation Solution
A multi-section, multi-material bushing assembly is introduced, featuring a stainless steel mount with a specific thermal expansion coefficient, a bronze bearing, and an optional sleeve with a low thermal expansion coefficient, which together provide a material bridge to accommodate thermal expansion differences and enhance durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single-material bushing is used, then the structure is simple, but it cannot accommodate thermal expansion differences between rotating and stationary structures
Solution Approach 1:
The bushing is divided into multiple sections with different materials (e.g., bronze bearing surface, stainless steel intermediate layer, aluminum or magnesium mount). Each section serves a specific function: the bronze provides low-friction bearing contact, the stainless steel accommodates thermal expansion, and the lightweight mount integrates with the stationary structure. This segmentation allows the bushing to handle thermal expansion differences while maintaining structural integrity.
Solution Approach 2:
The bushing employs composite construction with dissimilar materials bonded together. The bronze bearing surface is bonded to a stainless steel intermediate layer, which is in turn bonded to a lightweight alloy mount. This composite structure combines the low-friction properties of bronze with the thermal expansion characteristics of stainless steel and the weight savings of lightweight alloys, creating a multi-functional component that addresses multiple requirements simultaneously.
2Weight of moving object
If dissimilar materials are used for rotating and stationary structures, then weight reduction is achieved, but thermal expansion incompatibility causes wear
Solution Approach 1:
A stainless steel intermediate layer is introduced between the bronze bearing surface and the lightweight alloy mount. This intermediate layer acts as a mediator that accommodates thermal expansion differences between the dissimilar materials. The stainless steel's thermal expansion coefficient bridges the gap between bronze and lightweight alloys, preventing stress concentration and material incompatibility issues that would lead to wear and failure.
Solution Approach 2:
The bushing design incorporates materials with specifically selected thermal expansion coefficients. The stainless steel intermediate layer has a thermal expansion parameter that is compatible with both the bronze bearing surface and the lightweight alloy mount, allowing the assembly to expand and contract uniformly with temperature changes without causing differential stress or wear.
3Reliability
If a multi-material bushing is used, then wear is reduced, but manufacturing complexity increases
Solution Approach 1:
The bushing is manufactured as separate sections (bearing surface, intermediate layer, mount) that can be produced using optimized processes for each material. This segmentation allows each component to be manufactured independently with appropriate techniques, then assembled through bonding. This approach reduces manufacturing complexity compared to attempting to create a monolithic multi-material component, while still achieving the wear resistance benefits of dissimilar materials.
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 bushing assembly effectively reduces wear and enhances the durability of gas turbine engine components by managing thermal expansion and ensuring material compatibility, thereby improving the overall performance and longevity of the engine.
Implementation Method 1
a stainless steel mount with a specific thermal expansion coefficient, a bronze bearing, and an optional sleeve with a low thermal expansion coefficient, which together provide a material bridge to accommodate thermal expansion differences
Data Source
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AI summary
An assembly (10) for a gas turbine engine includes a rotating structure (12), a stationary structure (14) and a bushing (16). The rotating structure (12) extends axially along and is rotatable about a centerline (18). The stationary structure (14) extends circumferentially about the rotating structure (12). The stationary structure (14) is configured from or includes stationary structure material with a coefficient of thermal expansion between 10 µin/in-°F (18 µm/m-°C) and 15 µin/in-°F (27 µm/m-°C). The bushing (16) is radially between the rotating structure (12) and the stationary structure (14). The bushing (16) includes a mount (46) and a bearing (48) within the mount (46). The mount (46) is configured from or otherwise includes mount material with a coefficient of thermal expansion between 9 µin/in-°F (16.2 µm/m-°C) and 10 µin/in-°F (18 µm/m-°C). The mount material contacts the stationary structure material. The bearing (48) is configured from or includes bearing material, where the bearing material is engaged with and rotatably supports the rotating structure (12). The bearing material is or includes copper.