Detuner Torsional Frequency Tuning for Generator Rotors
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Solution Overview
Problem
Current methods for tuning the frequency of a rotating body's torsional mode are invasive, expensive, and can cause stress or unwanted lateral frequency changes, as they require decoupling and modifying the rotor or its components, which is not easily reversible and affects other connected objects.
Innovation Solution
A detuner is added as an undamped torsional vibration absorber to the overhung shaft connected to the rotating body, allowing for adjustments in stiffness and inertia to shift the torsional natural frequency without affecting the main rotor, enabling precise tuning while maintaining the system's assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If large shrunk-on rings are added or removed to shift the torsional natural frequency, then the frequency can be adjusted, but the process requires decoupling the rotor from the prime mover and involves expensive, irreversible modifications
Solution Approach 1:
The invention separates the frequency tuning function from the main rotor by introducing an independent detuner component. This detuner is a separate inertia element that can be independently adjusted without modifying the rotor itself, thus segmenting the tuning function from the main structure and avoiding complex decoupling and remachining operations.
Solution Approach 2:
The detuner acts as an intermediary element between the prime mover and the rotor. By adjusting the detuner's inertia, the torsional natural frequency of the rotor can be shifted without directly modifying the rotor or requiring decoupling operations. The detuner mediates the frequency adjustment function while leaving the main system intact.
2Manufacturing precision
If mass is added to the rotating body to tune the torsional frequency, then the frequency can be shifted, but the frequency of other connected objects is also affected causing stress levels or lateral frequency changes
Solution Approach 1:
The detuner is designed as a separate, isolated inertia element that affects only the torsional mode of the rotor through controlled coupling. This segmentation ensures that the mass addition for frequency tuning does not directly impact the rotor or other connected components, thereby avoiding unwanted stress and lateral frequency changes in the connected objects.
Solution Approach 2:
The detuner provides localized frequency adjustment capability specifically targeted at the rotor's torsional mode. By concentrating the inertia adjustment function in a separate detuner component rather than adding mass directly to the rotor, the solution achieves local quality improvement - precise torsional frequency control without affecting the global characteristics of connected objects.
3Manufacturing precision
If machining is performed on the rotating body or coupling to remove stiffness or inertia, then the frequency can be adjusted, but the process is not easily reversible and requires significant expense and downtime
Solution Approach 1:
The detuner provides a dynamic, adjustable solution for frequency tuning. Instead of permanent, irreversible machining operations, the detuner's inertia can be adjusted by adding or removing mass from the detuner itself, allowing the system to adapt to different frequency requirements. This dynamic adjustment capability makes the tuning process reversible and flexible.
Solution Approach 2:
The invention changes the approach from modifying structural parameters (stiffness through machining) to adjusting inertial parameters (mass of the detuner). This parameter change allows for non-invasive, reversible frequency tuning by simply adding or removing mass from the detuner component without affecting the rotor or coupling structures.
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 precise tuning of the torsional frequency without significant impact on the main system, reducing costs and downtime, and avoids stress or lateral frequency issues, enabling effective management of resonant responses by moving frequencies away from electrical grid harmonics.
Implementation Method 1
adding a detuner to act as an undamped torsional vibration absorber
Data Source
Figure 1
AI summary
A solution is provided for tuning the frequency of a torsional mode of interest of a rotating body (100) (such as a generator rotor (100) torsional mode) by adding a detuner (106) to act as an undamped torsional vibration absorber. The detuner (106) may be coupled to an overhung shaft (105) extending from the rotating body (100). The detuner (106) may be modular, therefore weight can be added or subtracted easily from the detuner (106) in order to adjust the stiffness and/or inertia of the overhung shaft (105). This change in stiffness and/or inertia yields a torsional frequency of oscillation in the overhung shaft (105) substantially similar to the natural frequency of the torsional mode of interest of the rotating body (100), therefore forcing the frequency of the torsional mode of interest of the rotating body (100) above or below its torsional natural frequency.