Fan Disk Windage Shield Anchor System Differential Expansion

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Solution Overview

Problem

Gas turbine engines face stress and fretting issues due to thermal and mechanical expansion rate differences between components, particularly between the windage shield and fan disk, leading to potential damage and reduced performance.

Innovation Solution

The use of an anchor system comprising a bushing, washer, fastener, and fastener retainer, which allows for axial load maintenance and minimizes stress by spacing components apart, enabling differential expansion while maintaining alignment and reducing radial loads on the fastener.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If the windage shield is rigidly coupled to the fan disk, then alignment and structural integrity are maintained, but stress and fretting increase due to differential thermal and mechanical expansion

Engineering Contradiction:

Improvealignment stabilityVSAvoidstress in fastener

Core Design Contradiction:

Stability of the object's compositionVSStress or pressure

Solution Approach 1:

The anchor system is divided into separate functional elements: a fastener for connection, a bushing for spacing, and a washer for load distribution. This segmentation allows each component to address specific requirements - the fastener maintains alignment while the bushing and washer accommodate differential expansion, resolving the contradiction between rigid alignment and stress reduction.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The bushing acts as an intermediary element between the windage shield and fan disk, providing a controlled interface that allows differential expansion while maintaining alignment. The bushing absorbs expansion differences through its material properties and geometry, preventing direct stress transmission to the fastener while preserving the relative positioning of the components.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Strength

If components are rigidly connected, then structural strength is maximized, but fretting occurs due to differential expansion

Engineering Contradiction:

Improvestructural strengthVSAvoidfretting

Core Design Contradiction:

StrengthVSObject-generated harmful factors

Solution Approach 1:

The bushing and washer are positioned in advance to create clearance and compliance in the connection system. This beforehand cushioning allows the components to accommodate differential expansion without generating harmful fretting stresses, while the fastener maintains the necessary structural connection. The design anticipates expansion differences and provides a mechanism to absorb them before damage occurs.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Stress or pressure

If the anchor system allows differential expansion, then stress is minimized, but alignment may be compromised

Engineering Contradiction:

Improvestress in fastenerVSAvoidalignment

Core Design Contradiction:

Stress or pressureVSStability of the object's composition

Solution Approach 1:

Different parts of the anchor system have different functional qualities: the fastener provides rigid connection for alignment, the bushing provides compliant spacing for expansion accommodation, and the washer distributes loads. This local differentiation of properties allows the system as a whole to achieve both alignment stability and stress minimization simultaneously.

Inventive Principle:

Principle #3Local quality

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 effectively minimizes stress and fretting between the windage shield and fan disk, ensuring consistent performance and longevity of the gas turbine engine by allowing for differential thermal and mechanical expansion while maintaining alignment and low radial loads on the fastener.

Implementation Method 1

Harmful stresses may form in the windage shield during operation of the gas turbine engine. These stresses may result from high rotational speeds of the fan assembly or from differences in thermal and mechanical expansion rates between the windage shield and the fan disk.

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 2

The bushing may be located in the second anchor-receiving space and arranged to extend out of the anchor receiving space toward the first component to engage the first component. The washer may be positioned to engage the bushing along the installation axis to locate the second anchor-receiving space between the washer and the first component.

Methodology Applied

Scientific EffectMechanical spacing:

Data Source

PatentUS11193375B2Attachment of piloting feature

Publication Date: 2021.12.07 ROLLS ROYCE CORP

AI summary

A fan assembly for use in a gas turbine engine of an aircraft includes a fan disk having a number of fan blades and a windage shield coupled to the fan disk to move therewith. The fan assembly supplies air for use in the engine. The windage shield rotates with the fan disk during operation of the gas turbine engine and directs air supplied by the fan blade.