Fan Assembly Blade Flutter Mitigation via Selective Reinforcement

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Solution Overview

Problem

Fan blade flutter in turbine engines leads to reduced efficiency and shorter blade life due to high cycle fatigue, as existing technologies fail to effectively manage the natural frequency of blades.

Innovation Solution

A fan assembly with a reinforcing member that contacts a subset of blades, increasing their stiffness and altering their natural frequency, thereby reducing flutter and fatigue.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a reinforcing member contacts a subset of blades to alter natural frequency, then blade flutter and fatigue are reduced, but device complexity increases

Engineering Contradiction:

Improveblade lifeVSAvoidfan assembly structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The reinforcing member is designed to contact only a subset of blades rather than all blades, segmenting the reinforcement approach. This selective reinforcement reduces the complexity compared to reinforcing all blades while still achieving sufficient flutter reduction and fatigue mitigation for improved blade life.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The reinforcing member provides localized reinforcement to specific blades that are most susceptible to flutter. By applying reinforcement only where needed rather than uniformly across all blades, the design achieves effective flutter reduction while minimizing overall structural complexity.

Inventive Principle:

Principle #3Local quality

2Object-affected harmful factors

If a reinforcing member is added to alter blade natural frequency, then flutter is reduced, but manufacturing complexity increases

Engineering Contradiction:

ImproveflutterVSAvoidfan assembly manufacturing

Core Design Contradiction:

Object-affected harmful factorsVSEase of manufacture

Solution Approach 1:

The reinforcing member is configured to contact only a subset of blades, which simplifies the manufacturing process compared to reinforcing all blades. This segmented approach reduces the amount of material and assembly steps required while still achieving effective flutter reduction.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The reinforcing member provides partial reinforcement to a subset of blades rather than complete reinforcement to all blades. This partial action is sufficient to achieve the desired flutter reduction while minimizing manufacturing complexity and cost.

Inventive Principle:

Principle #16Partial or excessive 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 enhances turbine engine efficiency by minimizing fan blade flutter, leading to longer blade life and improved performance by selectively reinforcing blades to alter their natural frequency.

Implementation Method 1

A tuning notch referenced at 50 is defined in the back of a blade root 42 to tune the natural frequency of the blade 32

Methodology Applied

Scientific EffectNatural frequency tuning: Resonance

Implementation Method 2

Fan blade flutter in turbine engines leads to reduced efficiency and shorter blade life due to high cycle fatigue

Methodology Applied

Scientific EffectFlutter: Flutter

Data Source

PatentUS8469670B2Fan assembly

Publication Date: 2013.06.25 ROLLS ROYCE CORP

AI summary

A fan assembly is disclosed herein. The fan assembly includes a fan operable to rotate about an axis. The fan includes a hub and a plurality of blades extending radially from the hub relative to the axis. The fan also includes a reinforcing member positioned adjacent to the fan along the axis. The reinforcing member contacts a predetermined subset of less than all of the plurality of blades.