Two-Stage Acoustic Method for Paddle Wheel Parameter Determination
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Solution Overview
Problem
Accurately measuring and determining mechanical parameters, such as damping and stiffness, of integrally manufactured paddle wheels, which exhibit complex vibration modes and time-variant properties due to mistuning and aerodynamic effects.
Innovation Solution
A method involving two excitation stages: first, using a multi-frequency acoustic sweep signal to measure the system response, and second, selectively exciting specific frequencies with a sine signal to determine mechanical parameters like damping and stiffness based on amplitude and phase responses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If purely frequency-based measurement methods are used, then the measurement process is simple, but the measurement precision is insufficient for integrally manufactured paddle wheels
Solution Approach 1:
The measurement process is divided into multiple sequential stages: initial frequency-based screening to identify resonance frequencies, followed by targeted time-domain measurements at specific frequencies. This segmentation allows the complex measurement task to be broken down into manageable steps, each optimized for specific parameter determination.
Solution Approach 2:
A preliminary frequency-based measurement is performed first to identify the natural frequencies and vibration modes of the paddle wheel. This preliminary information guides the subsequent time-domain measurements by indicating which frequencies require detailed analysis, thereby optimizing the overall measurement process.
2Measurement precision
If traditional single-frequency excitation is used, then the measurement process is straightforward, but it cannot capture the complex vibration modes and mistuning effects
Solution Approach 1:
The measurement system applies periodic excitation signals at multiple discrete frequencies, systematically sweeping through the frequency range to excite different vibration modes. This periodic multi-frequency approach ensures comprehensive coverage of all relevant vibration characteristics while maintaining a structured measurement process.
Solution Approach 2:
The excitation frequency parameter is varied across multiple discrete values during the measurement process. By changing the excitation frequency and observing the system response at each frequency, the method captures the full vibration behavior including mistuning effects and different mode shapes that would be invisible at a single frequency.
3Measurement precision
If high excitation amplitudes are used to improve signal detection, then the measurement sensitivity increases, but the object may experience fatigue-causing vibrations
Solution Approach 1:
The measurement uses partial action by applying excitation only at specific discrete frequencies rather than continuous broadband excitation. This allows concentrated energy at measured frequencies to achieve sufficient signal-to-noise ratio while minimizing total energy input and avoiding excessive vibrations that would cause fatigue.
Solution Approach 2:
The system substitutes mechanical contact-based excitation with acoustic field excitation using loudspeakers. This non-contact method reduces mechanical stress and friction at contact points, thereby minimizing fatigue-causing vibrations while still providing sufficient excitation energy for accurate measurement.
4Measurement precision
If multiple measurement points are used to capture all vibration modes, then the measurement completeness improves, but the measurement complexity and data processing burden increase
Solution Approach 1:
Different measurement points are strategically selected based on the local vibration characteristics of each blade. By placing sensors at locations that are most sensitive to specific vibration modes and mistuning effects, the system achieves comprehensive mode characterization with a reduced number of measurement points, optimizing the balance between completeness and complexity.
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 allows for precise determination of mechanical parameters, effectively addressing the challenges of mistuning and time-variant properties in integrally manufactured paddle wheels, thereby improving the accuracy of vibration analysis and reducing fatigue-causing vibrations.
Implementation Method 1
exciting the object with a multi-frequency signal; detecting a first response signal of the object
Implementation Method 2
system response is measured at selected measuring points on the blades of the blisk and by laser vibrometry
Data Source
Figure 1~3
Figure 4~6
AI summary
The invention relates to a method comprising the steps: - first exciting of the object by means of a multi-frequency signal; - detecting a first response signal of the object at one or more measurement points on the object; - transforming the first response signal from a time range to a frequency-dependent range; - selecting from one or more frequencies on the basis of the frequency-dependent range; - second exciting of the object on the basis of the selected frequencies; - detecting a second response signal of the object at one or more measurement points of the object; - determining a mechanical parameter on the basis of the second response signal.