Mid Turbine Frame Mechanical Fuse for Gas Turbine Engine
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Solution Overview
Problem
The design of mid turbine frames in gas turbine engines faces challenges in centering bearing housings due to tolerance stack-up and ensuring safe load transfer, particularly under torsional loads, which can lead to bearing seizures and potential engine damage.
Innovation Solution
The implementation of an annular engine casing with inwardly extending bearing support legs, including a mechanical fuse portion with a reduced cross-sectional area to fail under excessive torsional loads, and a seal housing support to maintain shaft centralization, along with a mid turbine frame system featuring concentric main shafts and a U-shaped structure for load transfer and flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a rigid bearing support structure is used to ensure load transfer strength, then the strength and reliability of load transfer is improved, but the ability to accommodate tolerance stack-up and maintain bearing housing centering deteriorates
Solution Approach 1:
The patent introduces a mechanical fuse portion with reduced cross-sectional area in the bearing support leg, changing the structural parameter from uniform to non-uniform. This allows the structure to remain rigid for normal load transfer while providing a controlled failure mode that accommodates tolerance stack-up and prevents catastrophic failure from bearing seizures.
2Reliability
If the bearing support structure is designed to be highly reliable against torsional loads, then the safety against bearing seizures is improved, but the complexity of the structure increases due to additional protective features
Solution Approach 1:
The patent converts the potential harm of bearing seizures into a beneficial controlled failure mode. The mechanical fuse portion is designed to fail predictably under excessive torsional loads, transforming a catastrophic failure scenario into a protective mechanism that sacrifices a non-critical component to save the engine.
Solution Approach 2:
The mechanical fuse portion acts as a disposable protective element that is intentionally designed to fail under extreme conditions. This sacrificial component is simpler and less critical than the bearing support leg itself, providing reliable protection at lower complexity cost.
3Reliability
If the bearing support leg is designed with sufficient torsional strength, then the load transfer reliability is improved, but the ability to prevent catastrophic damage from bearing seizures deteriorates due to rigid load path
Solution Approach 1:
The patent segments the bearing support leg into two distinct portions: a full-strength portion for normal load transfer and a mechanical fuse portion with reduced cross-sectional area. This segmentation creates a controlled weak point that breaks the rigid load path, preventing catastrophic damage while maintaining reliable load transfer under normal conditions.
Data Source
AI summary
A gas turbine engine has an engine casing component, such as a mid turbine frame system, which may includes an outer case surrounding a spoke or strut casing. Load transfer spokes of the spoke casing extend between the outer case and an inner case of the spoke casing. A bearing housing supported by the engine casing may include a fuse arrangement for isolating bearing seizure loads from the engine casing. A seal arrangement may be provided to centralize the rotors after the fuse fails. The mid turbine frame may be provided to have a desired flexibility through the configuration of the casing and bearings in design.