Bearing Support Frangible Tabs for Controlled Outer Race Decoupling

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Solution Overview

Problem

Gas turbine engines face challenges in managing excessive loads and bearing seizures due to the limitations of conventional bolted flange designs, which can reduce engine performance and complicate decoupling of outer races from inner cases, especially in restricted bearing cavities.

Innovation Solution

A bearing support system utilizing frangible tabs and stress concentrators, calibrated to rupture under specific load thresholds, decouples outer races from the structural casing, maintaining structural integrity and reducing the need for large struts that impede engine performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional bolted flange designs are used to secure bearings to the casing, then the structural integrity is maintained, but the engine performance is reduced and the decoupling of outer races from inner cases becomes complicated

Engineering Contradiction:

Improvestructural integrityVSAvoidengine performance

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The bearing support is divided into modular components: outer races, bearing support structure, and frangible tabs. This segmentation allows the outer races to be decoupled from the inner cases through controlled rupture of the frangible tabs, simplifying maintenance while maintaining structural integrity during operation

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Frangible tabs are introduced as intermediary elements between the bearing support and the inner case. These tabs act as a mediator that can be selectively ruptured to decouple the outer races, providing a controlled failure mechanism that simplifies maintenance operations without compromising overall structural integrity

Inventive Principle:

Principle #24Intermediary (Mediator)

2Strength

If large struts are used to support the bearing structure, then the structural strength is increased, but the engine performance is impeded

Engineering Contradiction:

Improvestructural strengthVSAvoidengine performance

Core Design Contradiction:

StrengthVSProductivity

Solution Approach 1:

The design transitions from large struts to frangible tabs with controlled geometric parameters. The tabs are designed with specific thickness, length, and stress concentrator dimensions that provide adequate structural strength during normal operation while enabling controlled rupture under excessive load, eliminating the need for large struts that would impede engine performance

Inventive Principle:

Principle #35Parameter changes

3Volume of moving object

If the bearing support is made compact, then the space in bearing cavities is reduced, but the decoupling mechanism becomes more complex

Engineering Contradiction:

Improvebearing cavity spaceVSAvoiddecoupling mechanism complexity

Core Design Contradiction:

Volume of moving objectVSDevice complexity

Solution Approach 1:

The frangible tabs are integrated directly into the bearing support structure, merging the mounting function and the decoupling mechanism into a single component. This eliminates the need for separate decoupling devices, reducing overall complexity while achieving compact dimensions that fit within restricted bearing cavities

Inventive Principle:

Principle #5Merging (Combining)

4Reliability

If frangible tabs with stress concentrators are used, then the controlled decoupling under excessive load is enabled, but the manufacturing precision requirements increase

Engineering Contradiction:

Improvecontrolled decoupling capabilityVSAvoidstress concentrator precision

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

Stress concentrators are pre-formed into the frangible tabs during manufacturing as intentional weak points. These pre-formed features ensure that under excessive load, the tabs will rupture at predetermined locations, enabling controlled decoupling. The stress concentrators are designed with standard geometric features that can be manufactured with conventional precision

Inventive Principle:

Principle #10Preliminary action

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 solution effectively manages excessive loads and bearing seizures by allowing controlled decoupling of outer races, preserving the structural integrity of service tubes and other components, while maintaining compactness and reducing parts count, thus enhancing engine performance and reliability.

Implementation Method 1

the frangible tabs defining stress concentrators calibrated for rupturing upon at least one of the bearing supports subjected to a load exceeding a load threshold

Methodology Applied

Scientific EffectStress concentration:

Data Source

PatentUS11499447B2Bearing support with frangible tabs

Publication Date: 2022.11.15 PRATT & WHITNEY CANADA CORP

AI summary

A gas turbine engine has: an engine shaft rotatable about a rotation axis; at least two bearings spaced apart from one another along the rotation axis, the at least two bearings having inner races for rotation with the engine shaft, outer races, and rolling elements disposed radially between the inner races and the outer races; a bearing support extending axially along the rotation axis from one of the at least two bearings to the other, the bearing support secured to both of the outer races of the at least two bearings, the bearing support secured to a structural case of the gas turbine engine via frangible tabs.