Turbine Engine Rotor Blades with Intentional Mistuning for Flutter Control
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Solution Overview
Problem
Turbine engines face instability issues due to flutter, a self-excited vibration of blades caused by structural-dynamic and aerodynamic forces, leading to high-cycle fatigue and potential blade loss, particularly at subsonic and supersonic speeds.
Innovation Solution
Implementing intentionally mistuned blades with specific airfoil distribution patterns and intentional mistuning features, such as altered natural frequencies and mode shapes, to disrupt self-excited fluid structure interactions and mitigate flutter risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If blades are tuned to identical natural frequencies, then aerodynamic performance is optimized, but flutter instability occurs due to self-excited vibrations
Solution Approach 1:
The patent applies asymmetry by intentionally creating non-uniform blade tuning characteristics. Specifically, at least one blade is designed with different natural frequencies or mode shapes compared to other blades in the set. This asymmetric distribution of tuning parameters disrupts the synchronous vibration patterns that cause flutter, while maintaining acceptable aerodynamic performance through careful selection of the mistuning strategy.
Solution Approach 2:
The patent implements local quality by applying mistuning selectively to specific blades rather than uniformly across all blades. The mistuning can be localized to particular regions of the blade (such as tip mass additions or root modifications) or applied to specific blades within the set, allowing targeted disruption of flutter mechanisms while preserving aerodynamic efficiency in critical regions.
2Reliability
If blades are intentionally mistuned to disrupt self-excited vibrations, then flutter margin is enhanced, but aerodynamic performance may be impacted
Solution Approach 1:
The patent employs parameter changes by systematically varying blade tuning parameters such as natural frequencies, mode shapes, or mass distribution. These parameter variations are controlled and optimized to achieve sufficient flutter margin improvement while minimizing the impact on aerodynamic performance. The mistuning parameters are selected based on analytical models and experimental validation to balance stability and performance requirements.
3Ease of manufacture
If all blades are made identical, then manufacturing is simplified, but high-cycle fatigue and blade loss risk increase due to synchronized flutter vibrations
Solution Approach 1:
The patent applies asymmetry by introducing deliberate variations in blade tuning parameters while maintaining overall geometric similarity. This approach preserves most manufacturing benefits of uniformity (such as simplified tooling and assembly procedures) while introducing sufficient variability to prevent synchronized flutter vibrations that lead to high-cycle fatigue and blade loss.
Solution Approach 2:
The patent implements segmentation by dividing the blade population into groups with different tuning characteristics. Rather than making each blade completely unique, blades are segmented into categories (e.g., baseline blades and mistuned blades, or groups with different mass additions), allowing standardized manufacturing processes for each segment while achieving the diversity needed to prevent flutter-induced fatigue.
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
Enhances flutter margin and reduces aerodynamic performance impacts by strategically mistuning blades to control vibrations, thereby improving engine stability and efficiency.
Implementation Method 1
flutter, a self-excited vibration of blades caused by structural-dynamic and aerodynamic forces
Data Source
AI summary
A rotor blade system. The rotor blade system includes a rotor and a plurality of blades coupled to the rotor. The plurality of blades are arranged in an airfoil distribution pattern. The airfoil distribution pattern includes one or more baseline blades and one or more intentionally mistuned blades including an intentional mistuning feature.