Planetary Gearbox Sacrificial Bushing for Plain Bearing Failure
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Solution Overview
Problem
Planetary gear boxes in gas turbine engines face challenges with high mechanical and thermal loads, leading to potential rapid failure and secondary damage due to plain bearing failures, which can result in unstable operation and safety risks.
Innovation Solution
Incorporating a sacrificial bushing designed to spatially separate the plain bearing from the planet gear, made from materials with lower melting and stiffness points than the planet gear, which can absorb and dissipate thermal loads, thereby limiting damage and preventing crack propagation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a plain bearing is used for the planet gear, then high power density is achieved, but the planet gear is vulnerable to rapid damage spread under high mechanical and thermal loads
Solution Approach 1:
The planet gear is segmented into two functional parts: the gear body (providing structural strength and power transmission) and the bushing (providing bearing function and damage absorption). This segmentation allows each part to be optimized for its specific function, resolving the contradiction between power density and damage resistance.
Solution Approach 2:
The bushing acts as an intermediary element between the plain bearing and the planet gear body. It absorbs thermal and mechanical loads, preventing direct heat transfer and damage propagation to the gear body, thus maintaining reliability while enabling high power density operation.
2Strength
If high-strength materials are used for the planet gear, then strength is improved, but thermal conductivity increases leading to faster heat spread
Solution Approach 1:
Different materials with complementary properties are used in different locations: high-strength material for the gear body and low thermal conductivity material for the bushing. This local differentiation resolves the contradiction by providing strength where needed while blocking heat spread in critical areas.
Solution Approach 2:
The planet gear assembly uses a composite structure combining high-strength steel (gear body) with thermally insulating materials (bushing). This composite approach allows simultaneous achievement of high strength and thermal management, preventing the heat spread problem associated with monolithic high-strength materials.
3Reliability
If the bushing is designed as a sacrificial part, then protection against secondary damage is achieved, but the device complexity increases
Solution Approach 1:
The bushing is designed as a disposable sacrificial component that absorbs damage and can be replaced independently of the expensive planet gear body. This approach provides secondary damage protection while keeping the overall system simple, as the bushing integration requires minimal additional structural complexity.
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 sacrificial bushing effectively reduces the risk of secondary damage and enhances the robustness of the planetary gear box by limiting the spread of damage and reducing the likelihood of catastrophic failures, ensuring safer operation under high loads.
Implementation Method 1
If the bushing melts during operation on account of thermal loads, the generation of heat due to the failure of the plain bearing is—at least for a certain period of time—limited
Implementation Method 2
Through softening or melting of the bushing material, a further temperature increase in the failing plain bearing is slowed down or a drop in temperature is brought about
Data Source
AI summary
The invention relates to a planetary gearbox in a gas turbine engine wherein a plurality of planetary gears are each mounted on a planetary gear bearing journal by a slide bearing, characterized in that a bushing is arranged in an inner bore of at least one planetary gear, which bushing spatially separates the sliding surface of the slide bearing from the inner bore of the planetary gear and the bushing is designed as a replacement part, in particular as a sacrificial part. The invention also relates to a gas turbine engine.