Gas Turbine Fan Blade Mistuning for Flutter Stability
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Solution Overview
Problem
Gas turbine engine fans experience fan flutter, a self-excited vibration phenomenon that can lead to fatigue failure if not adequately minimized, particularly in the design of composite fan blades.
Innovation Solution
The fan design incorporates two sets of fan blades with organic matrix composite bodies and varying leading edge members, where the first set has a lighter leading edge member compared to the second set, with specific mass distributions and volumes to reduce flutter while maintaining aerodynamic efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If all fan blades have uniform leading edge member mass, then manufacturing is simpler and cost is lower, but fan flutter occurs leading to fatigue failure
Solution Approach 1:
The patent applies local quality by varying the leading edge member mass specifically at certain blade positions rather than uniformly across all blades. The leading edge members have different masses localized at specific locations around the fan circumference, creating non-uniform mass distribution that disrupts flutter patterns while maintaining uniform aerodynamic properties.
Solution Approach 2:
The patent implements asymmetry by deliberately creating non-uniform mass distribution in the leading edge members of adjacent blades. This asymmetric mass variation breaks the symmetry that would otherwise allow coherent flutter vibrations to develop across all blades, thereby reducing flutter risk.
2Reliability
If leading edge member volume is reduced to lower mass, then flutter is reduced, but structural strength may be compromised
Solution Approach 1:
The patent applies local quality by concentrating the mass variation specifically in the leading edge members rather than throughout the entire blade structure. This localized mass adjustment allows flutter control without significantly impacting the overall structural integrity of the blade, as the core structural elements remain unchanged.
Solution Approach 2:
The patent implements preliminary action by designing the leading edge members with predetermined mass variations before assembly. The mass distribution is carefully planned and fixed during manufacturing, ensuring that the structural strength requirements are met while achieving the desired flutter reduction effect.
3Reliability
If blade mass is varied to reduce flutter, then aerodynamic performance may be affected, but flutter stability is improved
Solution Approach 1:
The patent applies local quality by restricting mass variations to the leading edge members only, while maintaining uniform aerodynamic surfaces and profiles across all blades. This localized modification ensures that the aerodynamic flow characteristics remain consistent, preserving aerodynamic efficiency while achieving flutter reduction through the mass variation.
Solution Approach 2:
The patent implements segmentation by separating the mass variation function from the aerodynamic function. The leading edge members are treated as distinct elements that can be independently varied in mass without affecting the uniform aerodynamic geometry of the blade surfaces, thus decoupling flutter control from aerodynamic performance.
Data Source
AI summary
A fan for a gas turbine engine, the fan comprising a first set of fan blades and a second set of fan blades arranged circumferentially around a hub. Each of the fan blades of the first and second set comprises an organic matrix composite body and a leading edge member connected to the body. The leading edge member of the first set of fan blades has a mass less than the leading edge member of the second set of fan blades.