Compressor Rotor Blade Thickness Distribution for Flutter and FOD
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Solution Overview
Problem
Gas turbine engine rotor blades face challenges in achieving a balance between weight reduction, maintaining efficiency, and ensuring robustness to withstand foreign object encounters without increasing weight or reducing flow capacity and efficiency.
Innovation Solution
The implementation of a rotor blade design with a location of local maximum thickness distribution and a total camber distribution, which optimizes the throat dimension and camber along the span of the blade to enhance robustness and flutter margin while minimizing weight and maintaining flow capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the overall thickness of the airfoil is increased to provide robustness against foreign object encounters, then the robustness is improved, but the weight of the rotor blade increases
Solution Approach 1:
The patent applies local quality by positioning the maximum thickness of the airfoil at a specific spanwise location (60-90% from the root) rather than uniformly distributing thickness. This concentrates material where it provides maximum robustness against foreign object encounters while minimizing overall weight, resolving the contradiction between strength and weight.
Solution Approach 2:
The patent transitions from considering only overall thickness to optimizing the three-dimensional distribution of thickness along the span. By controlling the spanwise location of maximum thickness and the throat dimension distribution, the design achieves robustness in the critical region without uniformly increasing weight across the entire blade.
2Weight of moving object
If the weight of the rotor blade is reduced, then the weight constraint is satisfied, but the natural vibratory frequencies decrease causing increased flutter susceptibility
Solution Approach 1:
The patent uses local quality by reducing thickness only in regions where it does not critically affect vibratory frequencies, while maintaining or optimizing thickness at spanwise locations that provide robustness. The maximum thickness positioned at 60-90% span creates a stiffening effect that maintains flutter margin even with reduced overall weight.
Solution Approach 2:
The patent changes the geometric parameters of the airfoil, specifically the spanwise location of maximum thickness and the throat dimension distribution, to optimize the balance between weight and vibratory characteristics. This parameter optimization allows weight reduction while maintaining adequate flutter margin.
3Productivity
If the flow capacity is increased, then the productivity is improved, but the efficiency and robustness are reduced
Solution Approach 1:
The patent optimizes geometric parameters including the throat dimension distribution and camber to achieve high flow capacity while maintaining efficiency. The controlled thickness distribution reduces flow separation and maintains favorable pressure gradients, preserving efficiency even at high flow rates.
Data Source
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AI summary
A rotor blade (500) for a compressor of a gas turbine engine includes an airfoil. The airfoil has a span that extends from 0% at the root to 100% at the tip and a mean camber line that extends from a leading edge to a trailing edge. The airfoil has a location of local maximum thickness defined as a ratio of a first arc distance along the mean camber line between the leading edge and a position of the local maximum thickness to a total arc distance along the mean camber line from the leading edge to the trailing edge. A value of the ratio increases from the root to a first position value (542), decreases from the first position value to a second position value and increases from the second position value (544) to the tip (546). The first position value (542) is at a spanwise location within 20% to 50% of the span.