Bladed Wheel Vibration Reduction via Tangential Shift
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Solution Overview
Problem
Turbomachines experience high vibration levels due to perturbations in the gas flow caused by stationary or moving bladed wheels and obstacles, leading to resonance and instability issues, which are difficult to manage during the design phase and require costly adjustments.
Innovation Solution
A method to reduce vibration levels by modifying the geometric tangential shift of blade stacking axes to minimize the generalized aerodynamic force, using a systematic approach that involves calculating the synchronous forced response and applying geometric shifts to optimize blade configurations, allowing for early corrective measures during the design process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the bladed wheel design is optimized for aerodynamic performance, then aerodynamic efficiency is improved, but vibration levels increase due to wake perturbations and resonances
Solution Approach 1:
The patent applies local quality by modifying the stacking axis configuration specifically in the regions where blades are most susceptible to wake perturbations, rather than uniformly changing the entire blade geometry. This allows aerodynamic performance to be maintained in critical regions while reducing vibration susceptibility in other areas.
Solution Approach 2:
The invention changes the geometric parameters of the blade stacking axis by introducing a tangential shift relative to the radial direction. This parameter modification alters the phase relationship between blade passages and wake structures, thereby reducing resonance conditions while preserving aerodynamic efficiency.
2Object-affected harmful factors
If vibration levels are reduced by modifying blade geometry, then vibration amplitudes decrease, but aerodynamic performance may be compromised
Solution Approach 1:
The patent introduces a dynamic approach by making the stacking axis configuration adaptable - the tangential shift is optimized based on operating conditions such as rotor speed and wake characteristics. This allows the geometry to be optimized for different regimes, maintaining aerodynamic performance across varying operational states while reducing vibrations.
3Object-affected harmful factors
If design iterations are performed to address vibration issues, then vibration control is improved, but development time and cost increase
Solution Approach 1:
The invention implements preliminary action by providing analytical methods and design criteria that allow vibration characteristics to be predicted and optimized during the initial design phase. The stacking axis configuration is determined upfront using the prescribed method, avoiding the need for extensive iterative testing and adjustment that would otherwise be required.
4Object-affected harmful factors
If the stacking axis is shifted tangentially to reduce vibrations, then vibration synchronization with rotor speed is reduced, but blade alignment with flow may be affected
Solution Approach 1:
The patent resolves the contradiction by operating in an additional geometric dimension - the tangential direction. By shifting the stacking axis in the tangential direction rather than altering the radial blade profile, the invention reduces synchronous vibrations while preserving the blade's aerodynamic alignment with the flow in the radial-plane.
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 method effectively reduces vibration levels synchronous with the rotor's rotation speed, maintaining aerodynamic performance and mechanical stability without adding mass, thereby addressing the challenges of resonance and instability in turbomachines.
Implementation Method 1
the synchronous forced response y(ω) on the first bladed wheel is calculated as a function of the harmonic excitation force f(ω) produced by the second bladed wheel or the obstacle
Implementation Method 2
the presence of critical resonances in the machine's operational range
Implementation Method 3
a geometric tangential shift value θ for the stacking axis is determined for each of said p stacked cross sections of one of the two wheels so as to reduce the term corresponding to the generalized aerodynamic force
Data Source
AI summary
A method for reducing vibration levels in a turbomachine including at least a first and a second bladed wheel, due to aerodynamic perturbations that are produced by the second bladed wheel or an obstacle on the first bladed wheel is disclosed. The method includes: defining an initial configuration of the blades; calculating the synchronous forced response on the first bladed wheel as a function of the harmonic excitation force produced by the second bladed wheel expressed in the form of a linear function of the generalized aerodynamic force for the mode considered; determining a geometric tangential shift value θ for the stacked cross sections of one of the two wheels to reduce the corresponding term to the generalized aerodynamic force. The set of cross sections with the tangential shifts thus defines a new configuration of the blades of one of the two wheels.