Turbomachine Bladed Disc Intentional Mistuning for Flutter Stability
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Solution Overview
Problem
Existing methods for voluntarily detuning bladed wheels in turbomachines are ineffective in adapting to variable and unpredictable vibratory phenomena during operation, such as flutter, leading to potential instability and damage.
Innovation Solution
A method that selects an eigenmode of vibration with nodal diameters, determines blade displacements for stationary deformation waves, and introduces projections or notches on the disk to separate these waves, creating a frequency disparity and thus introducing voluntary detuning tailored to specific operational vibratory issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If systematic voluntary detuning is applied to all bladed wheels, then frequency disparity is achieved, but the detuning cannot adapt to variable and unpredictable vibratory phenomena during operation
Solution Approach 1:
The patent applies dynamics by making the detuning configuration adaptive to operational conditions. The method involves selecting a specific eigenmode with k nodal diameters, determining blade displacements for stationary deformation waves, and positioning projections or notches based on the identified mode shape. This allows the detuning to dynamically adapt to the actual vibratory phenomena occurring during operation, rather than applying a fixed systematic detuning to all blades.
Solution Approach 2:
The patent applies local quality by positioning projections or notches only on specific blades where they are most effective. Instead of uniformly detuning all blades, the method identifies the eigenmode characteristics and places detuning features only on blades corresponding to vibration nodes or specific positions in the mode shape. This localized approach optimizes the detuning effect for the specific vibratory phenomenon while reducing overall complexity.
2Reliability
If projections or notches are added to the disk to separate standing waves, then voluntary detuning is achieved, but the device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the detuning intervention into discrete, localized features (projections or notches) on the disk. Rather than modifying the entire disk geometry, the method segments the intervention to specific locations corresponding to blade positions. This segmentation reduces the overall complexity by limiting modifications to only the necessary areas.
Solution Approach 2:
The patent applies partial action by implementing detuning only where it is most effective - on specific blades corresponding to the identified eigenmode characteristics. The method determines the exact positions of vibration nodes and antinodes, and places projections or notches only at the optimal locations, rather than applying detuning uniformly across all blades. This partial approach achieves the necessary frequency disparity with minimal geometric modification.
3Manufacturing precision
If detuning is applied during design phase, then frequency distribution can be optimized, but it cannot address unpredictable vibratory phenomena that occur during operation
Solution Approach 1:
The patent applies preliminary action by identifying and analyzing the eigenmode characteristics before implementing the detuning. The method involves selecting the target eigenmode with k nodal diameters, determining the blade displacements for stationary deformation waves, and identifying which blades correspond to vibration nodes. This preliminary analysis ensures that the subsequent geometric modifications are precisely targeted to address the specific vibratory phenomenon.
Solution Approach 2:
The patent applies feedback by using the identified eigenmode characteristics to guide the detuning configuration. The method determines the displacement of blades for each stationary deformation wave, identifies blades where vibration antinodes of one wave correspond to vibration nodes of the other, and positions projections or notches accordingly. This feedback loop ensures the detuning is optimally positioned to separate the standing waves and achieve frequency disparity for the specific operational conditions.
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
This approach allows for adaptive detuning that stabilizes the bladed wheel by modifying the disk geometry, avoiding systematic detuning and directly impacting the blades, thereby enhancing aero-elastic damping and reducing the risk of vibratory instability.
Implementation Method 1
select an eigenmode of vibration of the bladed wheel with k nodal diameters... determining the displacement of the blades over the entire circumference of the bladed wheel for each of the two stationary deformation waves of the same frequency... providing a projection or a notch in the disk of the bladed wheel facing each of the blades thus determined, so as to separate the two standing waves of deformation at a frequency
Implementation Method 2
Such a frequency disparity makes it possible to stabilize the bladed wheel with respect to flutter by increasing its aero-elastic damping
Data Source
Figure 1
Figure 2a~2b
Figure 3a
AI summary
The present invention relates to a method (100) for intentionally mistuning a turbine blade of a turbomachine (10), by providing raised portions (31) or slots (32), the position of which is calculated on the basis of a vibration analysis of the disk (steps a) to d)).