Mid Turbine Frame Axial Load Isolation
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Solution Overview
Problem
Current mid turbine frame designs face challenges in rotor containment and load transfer during a turbine shaft shear event, requiring improvements in safety and load transfer efficiency.
Innovation Solution
The design incorporates a mid turbine frame with an interturbine duct and load transfer spokes that allow axial movement and load path independence, ensuring load transfer from the turbine disc to the engine case during a shaft shear event, utilizing an interturbine duct with inner and outer shrouds and radial members to manage loads effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the mid turbine frame is designed to support bearings and transfer loads, then load transfer capability is improved, but the complexity of ensuring rotor containment and load transfer during shaft shear events increases
Solution Approach 1:
The mid turbine frame is segmented into an inner case and an outer case, allowing independent load paths. The inner case supports bearings while the outer case provides rotor containment during shaft shear events, dividing the complex load transfer function into manageable segments.
Solution Approach 2:
The interturbine duct assembly acts as an intermediary structure between the turbine rotor and the mid turbine frame. It provides a load transfer path during shaft shear events without requiring direct connection between the rotor and the complex mid turbine frame structure.
2Reliability
If the interturbine duct upstream edge is positioned closer to the turbine disc, then rotor containment during shaft shear events is improved, but the risk of interference with rotating components increases
Solution Approach 1:
The interturbine duct assembly is designed to move axially relative to the mid turbine frame during shaft shear events. This dynamic positioning allows the duct upstream edge to contain the rotor while maintaining sufficient clearance to avoid interference with rotating components under normal operating conditions.
Solution Approach 2:
The solution addresses the clearance problem by introducing axial movement capability, transforming a static positioning problem into a dynamic one. The interturbine duct can shift axially to provide containment when needed while maintaining safe clearance during normal operation.
3Stability of the object's composition
If the mid turbine frame cases are connected by multiple spokes, then structural stability is improved, but the complexity of the load transfer system increases
Solution Approach 1:
The load transfer system is segmented into independent paths: one through the spokes connecting inner and outer cases, and another through the interturbine duct assembly. This segmentation allows each path to be optimized for its specific function while reducing the complexity of the overall system.
Solution Approach 2:
Different parts of the mid turbine frame have different structural qualities optimized for their specific functions. The spokes provide radial stability and load transfer, while the interturbine duct assembly provides axial load transfer and rotor containment, with each component having the appropriate local structural properties for its role.
4Strength
If the interturbine duct is designed with inner and outer shrouds separated by struts, then load transfer capability is improved, but the device complexity increases
Solution Approach 1:
The interturbine duct assembly with its inner and outer shrouds connected by struts serves multiple functions: it provides a load transfer path during shaft shear events, maintains rotor containment, and supports the aerodynamic flow path. This multi-functionality reduces the need for separate specialized components.
Solution Approach 2:
The load transfer function and the aerodynamic duct function are merged into a single integrated assembly. The struts that provide structural load transfer capability also serve as part of the aerodynamic structure, eliminating the need for separate load transfer mechanisms.
Data Source
AI summary
A gas turbine engine mid turbine frame having an inner case supporting at least one bearing and at least three spokes extending radially outwardly to an outer case, the mid turbine frame having an interturbine duct extending through the mid turbine frame, the interturbine duct spaced axially closer to an upstream turbine disc than a bearing supporting structure of the mid turbine frame and mounted axially slidingly relative to the bearing supporting structure to substantially isolate the bearing supporting structure from axial loads, for example such as disc loads incurred in the unlikely event a turbine disc shaft shears within the engine.