Self-Excited Vibration Evaluation for Tube Bundles
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Solution Overview
Problem
Existing methods for evaluating self-excited vibration in tube bundles, particularly those with U-shaped tubes, fail to accurately account for friction damping between the tubes and support members, leading to inadequate suppression of vibrations along the flow direction.
Innovation Solution
A self-excited vibration evaluation method that includes time history response analysis to simulate changes in vibration amplitude while varying the negative damping ratio, calculating the critical flow velocity based on the minimum negative damping ratio at which divergence occurs, and accounting for friction damping between the tube bundle and support members.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If friction damping between tube bundle and support member is not taken into account, then the evaluation method is simple, but the accuracy of self-excited vibration evaluation deteriorates
Solution Approach 1:
The patent introduces a friction damping ratio parameter to characterize the friction damping effect between the tube bundle and support member. By adding this parameter to the vibration evaluation model, the accuracy of self-excited vibration prediction is improved without significantly complicating the overall evaluation methodology.
Solution Approach 2:
The patent uses an equivalent friction damping ratio as an intermediary parameter to represent the complex friction interaction between tubes and support members. This intermediary approach simplifies the modeling of friction effects while maintaining evaluation accuracy, avoiding the need for detailed contact mechanics analysis.
2Device complexity
If pressing force at support points is assumed to be zero, then the calculation is simplified, but the friction force for suppressing vibration is not accounted for
Solution Approach 1:
The patent changes the assumption about pressing force by introducing a friction damping ratio parameter that implicitly accounts for the pressing force effect. This allows the model to capture vibration suppression mechanisms without explicitly calculating pressing forces at each support point, maintaining computational simplicity while improving reliability.
Solution Approach 2:
The equivalent friction damping ratio parameter serves itself to represent both the friction force magnitude and its vibration suppression effect. This self-service approach eliminates the need for separate pressing force calculations while maintaining the physical realism of friction-based vibration suppression.
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 evaluates and suppresses self-excited vibrations by considering friction damping, preventing damage from unstable hydroelastic vibrations in tube bundles, especially in steam generators, by determining the maximum friction damping ratio that can be applied without causing vibration.
Implementation Method 1
such vibration phenomenon along the flow direction is suppressed by a friction force between the tubes and the anti-vibration bar
Implementation Method 2
self-excited vibration (hydroelastic vibration) may occur
Data Source
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AI summary
A self-excited vibration evaluation method for evaluating self-excited vibration of a tube bundle arranged in a fluid so as to be supported by a support member includes: for each of at least one eigenmode of the tube bundle, a time history response analysis step of performing time history response analysis of simulating a change in vibration amplitude of the tube bundle, while changing a negative damping ratio corresponding to an excitation force of the fluid; a critical flow velocity calculation step of calculating a critical flow velocity of the fluid on the basis of a minimum negative damping ratio at which the change of the vibration amplitude of the tube bundle diverges in the time history response analysis; an input step of inputting an expected flow velocity of the fluid; and an evaluation step of evaluating the self-excited vibration of the tube bundle for each eigenmode by comparing the expected flow velocity of the fluid with the critical flow velocity.