Turbomachine Cavity Mistuning for Vibration Reduction
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Solution Overview
Problem
Turbomachines, such as centrifugal compressors and turbines, face challenges in controlling rotor disk excitation due to resonant vibrations caused by upstream stator wakes, flow inhomogeneities, and acoustic pulsations, leading to high cycle fatigue and potential failure, with current solutions either limiting operational flexibility or requiring additional fluid resources.
Innovation Solution
The introduction of blade-like elements, such as grooves or ridges, within the cavities adjacent to the impeller hub and cover in turbomachines to intentionally mistune acoustic modes, reducing acoustic pulsations and minimizing vibratory responses by modifying the boundary conditions of gas-filled cavities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If blade-like elements are added to mistune acoustic modes, then noise and vibration are reduced, but device complexity increases
Solution Approach 1:
The cavity boundary is segmented by adding discrete blade-like elements (grooves or ridges) at specific circumferential positions. These segmented features create localized impedance variations that mistune the acoustic modes without requiring complete restructuring of the entire cavity, thus reducing complexity while achieving noise and vibration reduction.
Solution Approach 2:
Instead of modifying the entire cavity uniformly, blade-like elements are placed only at specific local positions where they most effectively interact with the acoustic modes. This localized modification achieves the desired mistuning effect with minimal added complexity, as only specific regions of the cavity boundary are altered.
2Reliability
If blade-like elements are introduced to reduce acoustic pulsations, then component life is extended, but manufacturing complexity increases
Solution Approach 1:
The blade-like elements are designed as simple geometric features (grooves or ridges) that can be manufactured using conventional machining or molding processes. These features are inexpensive to add and do not require complex tooling or multi-step manufacturing procedures, making them cost-effective despite extending component life through vibration reduction.
Solution Approach 2:
The manufacturing approach leverages changes in geometric parameters (depth, width, spacing of grooves or ridges) rather than fundamental changes in material composition or manufacturing process. By adjusting these parameters, the desired acoustic mistuning is achieved using standard manufacturing capabilities, maintaining ease of fabrication.
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 effectively reduces noise signature and potential excitation of adjacent bladed disks or impellers, extending the life of turbomachine components by minimizing resonant vibrations and high cycle fatigue without compromising operational performance.
Implementation Method 1
The bladed elements are positioned to mistune the cavities to minimize acoustic pulsations in the cavities
Implementation Method 2
reducing acoustic pulsations and minimizing vibratory responses by modifying the boundary conditions of gas-filled cavities
Implementation Method 3
effectively reduces noise signature and potential excitation of adjacent bladed disks or impellers, extending the life of turbomachine components by minimizing resonant vibrations and high cycle fatigue
Data Source
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AI summary
An arrangement for intentionally mistuning a cavity formed adjacent an impeller in a turbomachine, the arrangement including at least two bladed elements defined within a perimeter of a casing wall adjacent the impeller, wherein the bladed elements are configured to mistune cavity acoustic modes to minimize acoustic pulsations in the cavity.