Gas Turbine Rotor Blades with Density Mistuning Plugs
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Solution Overview
Problem
Gas turbine engine blades are susceptible to destructive vibrations such as flutter and forced response, which can lead to blade damage, particularly when all blades have identical vibration frequencies, making them prone to increased flutter susceptibility.
Innovation Solution
The introduction of mistuning plugs made of different materials and densities, which are inserted through the blade tips or external surfaces to alter the resonance frequencies of the blades without changing their airfoil shape, thereby reducing flutter effects and maintaining aerodynamic performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If all blades on a rotor are identical in terms of their vibration frequencies, then manufacturing simplicity is maintained, but flutter susceptibility increases
Solution Approach 1:
The patent applies local quality by inserting mistuning plugs at specific locations on selected blades (typically near the blade root or along the span) to create localized mass variations. This allows most of the blade to remain uniform for easy manufacturing, while specific local regions have modified properties to achieve the desired frequency differentiation and reduce flutter susceptibility.
Solution Approach 2:
The patent changes the mass parameter of selected blades by inserting plugs made of materials with different densities than the blade material. By carefully selecting plug material density, size, and position, the natural frequencies of individual blades are adjusted to create intentional mistuning across the rotor, thereby reducing flutter while maintaining overall manufacturing simplicity.
2Reliability
If mistuning plugs are inserted into blade tips or external surfaces to alter resonance frequencies, then flutter resistance is improved, but device complexity increases
Solution Approach 1:
The patent implements the nesting principle by placing mistuning plugs inside hollow cavities or bores that are drilled into the blade structure. The plugs are nested within the blade's internal volume or surface features, allowing mass modification without adding external protrusions or significantly complicating the overall blade geometry. This minimizes aerodynamic interference while achieving the desired frequency tuning.
3Reliability
If mistuning plugs are used to create structural mistuning, then flutter susceptibility is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies preliminary action by pre-drilling precisely positioned holes or cavities in the blades during the blade manufacturing process, before the mistuning plugs are inserted. These pre-prepared receptacles are located at optimal positions calculated to achieve the desired frequency tuning. By establishing the precise geometry and location upfront, the subsequent plug insertion requires less precision, as the critical positioning has already been established during controlled manufacturing operations.
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 mass mistuning of blades using density-different plugs effectively reduces flutter-induced stress and maintains the aerodynamic integrity of the airfoil shape, enhancing the structural strength and operational stability of the rotor.
Implementation Method 1
alter the resonance frequencies of the blades
Implementation Method 2
The plurality of blades are divided into a set of first frequency blades and a set of second frequency blades
Data Source
Figure 1~2
Figure 3
Figure 4~6
AI summary
A rotor (10) for use in a gas turbine engine (110) includes a wheel (12) and a plurality of blades (16). The wheel (12) is arranged about an axis of the gas turbine engine for rotation. The plurality of blades (16) are arranged around the wheel and extend radially outward from the wheel to interact with gases flowing through the engine. A first blade (16) comprises a first material and has a first external surface (22), a second external surface (24) opposite the first external surface to define a leading edge (32), a trailing edge (34), a pressure side (36), and a suction side (38) of the first blade, a first hole (42) extending through the first external surface and into the first blade in a direction normal to the first external surface; whereby a first plug (18) is located in the first hole and has a first outer surface (50) flush with the first external surface of the first blade such that the first outer surface is exposed to the gases surrounding the rotor, and the first plug comprises a second material that is different than the first material of the first blade.