Repairable Bushing and Pin for Mid-Turbine Frame Stator
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Solution Overview
Problem
Gas turbine engine stators, particularly mid-turbine frame stators, face challenges due to high temperatures and stresses, leading to fastener wear and the need for extensive disassembly or engine removal for replacement or repair.
Innovation Solution
A repairable bushing and pin system is introduced, where the bushing is press-fit into a boss on the stator, and a pin is partially inserted into the bushing, allowing for re-boring and replacement without full disassembly, using cobalt and nickel-cobalt alloys for durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fasteners are used to couple the stator to the casing, then the stator can be securely mounted, but the fasteners wear due to high temperatures and stresses, requiring replacement
Solution Approach 1:
The fastening system is divided into separate components: a bushing press-fit into the boss and a pin retained in the bushing. This segmentation allows the pin to be replaced independently without replacing the entire stator assembly, addressing wear while maintaining secure mounting.
Solution Approach 2:
The fastening system uses interference fit parameters (press-fit bushing with specific dimensional tolerances) to create a secure connection that can withstand high temperatures and stresses. The engagement length of the pin (0.5 to 1.5 times the bushing diameter) is optimized to provide sufficient holding strength.
2Productivity
If fasteners are replaced due to wear, then the stator can continue to function, but extensive disassembly or removal of the engine is required
Solution Approach 1:
The bushing and pin are designed as separable components that can be accessed and replaced independently. The pin can be removed and replaced without removing the stator from the engine or disassembling the entire engine, enabling quick maintenance while maintaining operational continuity.
Solution Approach 2:
The pin is extracted as a separate replaceable component from the bushing-stator assembly. This allows the worn pin to be removed and replaced without taking out the entire fastening system or engine, significantly reducing maintenance time and effort.
3Device complexity
If the stator is designed with integrated fasteners, then the structure is simpler, but repair requires extensive disassembly
Solution Approach 1:
The fastening system is segmented into a bushing (press-fit into boss) and a pin (retained in bushing), creating a modular structure that is both simple to manufacture and easy to repair. The pin can be accessed and replaced independently while the boss and stator remain intact.
Solution Approach 2:
The bushing acts as an intermediary component between the boss and the pin. This intermediary structure provides a retained environment for the pin, allowing the pin to be easily replaced while maintaining a simple overall stator structure without requiring complex integrated fastener 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 solution enables the stator to be securely mounted and repaired without disassembling the entire engine, reducing maintenance complexity and extending the life of the engine components.
Implementation Method 1
The bushing may be press fit within the boss
Data Source
AI summary
A gas-turbine engine is provided comprising a high-pressure turbine, a low-pressure turbine aft of the high-pressure turbine, and a housing around the low-pressure turbine and the high-pressure turbine. A stator may be disposed between the low-pressure turbine and the high-pressure turbine with a boss formed on the stator. A bushing may be retained in the boss with a pin coupled to the housing and partially within the bushing. A method of mounting a full-ring stator is also provided, the method including the steps of inserting a bushing into a boss of the full-ring stator by press fitting, and inserting a pin into the bushing of the full-ring stator.