Mid-turbine frame with threaded spoke tensioning
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Solution Overview
Problem
The existing mid-turbine frames in gas turbine engines face challenges in efficiently supporting bearing loads and routing air between high and low-pressure turbine stages while maintaining compactness and power density, with existing designs often compromising on axial length and structural integrity.
Innovation Solution
A mid-turbine frame design featuring an outer and inner frame case connected by hollow spokes with threaded tie rods and retaining nuts, allowing for adjustable tension and reduced manufacturing tolerances, which supports bearing loads and routes air efficiently between turbine stages, maintaining compactness and power density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional rigid connection methods are used between frame cases, then structural strength is maintained, but manufacturing precision requirements increase and assembly difficulty increases
Solution Approach 1:
The patent changes the connection parameter from rigid fixed connection to adjustable threaded connection. The tie rods with threads allow the spoke length and tension to be adjusted, accommodating manufacturing tolerances while maintaining structural strength. This parameter change enables the structure to adapt to dimensional variations without compromising integrity.
Solution Approach 2:
The patent introduces dynamic adjustability to the connection system. The threaded tie rods allow for tension adjustment after assembly, transforming a static rigid connection into a dynamically adjustable one. This enables the structure to accommodate manufacturing variations and maintain optimal performance under different operating conditions.
2Reliability
If traditional fixed spoke tension design is used, then structural simplicity is maintained, but reliability decreases under varying operating conditions
Solution Approach 1:
The patent makes the spoke tension dynamic and adjustable rather than fixed. The threaded connection allows tension to be adjusted during assembly and potentially during operation, enabling the structure to maintain reliability under varying thermal and mechanical conditions. This dynamic capability significantly improves reliability without adding excessive complexity.
Solution Approach 2:
The patent enables parameter adjustment of spoke tension to adapt to different operating conditions. The threaded tie rods allow the tension parameter to be modified based on thermal expansion, mechanical loading, and other operational variables, thereby maintaining optimal structural performance and reliability across different scenarios.
3Length of moving object
If axial length is reduced for compactness, then power density increases, but structural integrity may be compromised
Solution Approach 1:
The patent uses adjustable tie rod tension as a key parameter to maintain structural integrity in a compact design. By optimizing and adjusting the tension in the shortened spokes, the design achieves compact axial length while maintaining or even enhancing structural integrity through controlled pre-stress in the tie rods.
Data Source
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AI summary
A mid-turbine frame located in a gas turbine engine axially aft of a high-pressure turbine and fore of a low-pressure turbine includes an outer frame case, an inner frame case, and at least a first spoke connecting the outer frame case to the inner frame case. The first spoke includes a tie rod having a first threaded surface and a connector having a second threaded surface. The first and second threaded surfaces overlap partially but not completely.