Retroreflector Fan Blade Flutter Detection in Open Fan Engines
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Solution Overview
Problem
Existing sensors for detecting fan flutter and abnormal blade deflection in aircraft engines are intrusive, provide noncomprehensive measurements, and are difficult to implement in open fan architectures, leading to inefficiencies and safety risks.
Innovation Solution
Employing retroreflectors for contactless measurement of fan blade deflection and flutter using optical emitting and receiving transducers, allowing for long-range, flexible placement and analysis of deflection and flutter through retroreflected radiant flux.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If strain gauges are used to measure fan blade deflection, then contact-based measurement is achieved, but the measurement system becomes intrusive and complex requiring calibration and maintenance
Solution Approach 1:
The patent replaces mechanical contact-based measurement systems (strain gauges) with an optical measurement system using light probes. The optical system measures fan blade deflection by detecting changes in light reflection patterns, eliminating the need for physical contact, calibration, and maintenance while maintaining measurement precision.
Solution Approach 2:
The patent introduces light as an intermediary medium to transfer measurement information from the fan blade to the detection system. The light probe emits light that reflects off the fan blade, and the reflected light carries deflection information, enabling non-contact measurement without direct mechanical interaction.
2Measurement precision
If standard light probes are placed close to fan blade tips for measurement, then non-contact measurement is achieved, but the probe placement becomes difficult in open fan architectures
Solution Approach 1:
The patent uses retroreflectors as intermediary elements mounted on the fan blade surface. These retroreflectors return light along its incident path, allowing the light probe to be positioned at a convenient distance from the fan blade while still obtaining accurate deflection measurements. This eliminates the need to place the probe within inches of the blade tip.
Solution Approach 2:
The patent changes the measurement geometry by introducing retroreflectors that redirect light along its incident path. This allows the probe to be positioned in a different spatial location (not immediately adjacent to the blade tip) while maintaining measurement capability through the retroreflector's light redirection function.
3Measurement precision
If strain gauges are attached to fan blades for measurement, then deflection data is obtained, but the installation impacts fan blade functioning and engine performance
Solution Approach 1:
The patent replaces mechanical attachment methods (straining gauges requiring physical bonding to the blade) with optical measurement using light probes and retroreflectors. This substitution eliminates any physical modification or attachment to the fan blade, ensuring that the blade's aerodynamic properties and mechanical performance remain unaffected while still obtaining deflection measurements.
Solution Approach 2:
The patent uses retroreflectors as non-intrusive intermediaries that can be mounted on the blade surface without affecting its aerodynamic characteristics. The retroreflectors are positioned to reflect light for measurement purposes while minimizing interference with the blade's function, thereby maintaining engine performance.
4Measurement precision
If standard light probes are used for measurement, then non-contact measurement is achieved, but only point-measurements are provided missing comprehensive data
Solution Approach 1:
The patent divides the fan blade into multiple measurement sections by placing retroreflectors at different locations along the blade (e.g., near the root, mid-chord, and tip). Each retroreflector provides measurements for its local section, and combining these segmented measurements gives comprehensive deflection data throughout the entire blade, not just at a single point.
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
Provides comprehensive, safe, and efficient detection of fan blade deflection and flutter, enabling real-time monitoring and preventing structural damage and performance disruptions.
Implementation Method 1
a retroreflector configured to be disposed on a fan blade of an engine
Implementation Method 2
an optical emitting source configured to emit radiant flux toward a retroreflector disposed on a fan blade
Implementation Method 3
an optical receiver configured to detect the retroreflected radiant flux
Data Source
AI summary
A system for preventing abnormal fan blade deflection or fan flutter includes an optical emitting source, an optical receiver, and a retroreflector for attachment to a fan blade of an engine. The system emits radiant flux from the optical emitting source towards the retroreflector when the engine is operating; receives an incident radiant flux from the retroreflector by the optical receiver; determines a deflection value of the fan blade based on the incident radiant flux received by the optical receiver; determines whether the deflection value is greater than or equal to a threshold for deflection of the fan blade to identify abnormal fan blade deflection or fan flutter; and selectively changes a state of the engine when abnormal fan blade deflection or fan flutter is identified.