Methods for vibro-acoustic diagnostics of turbine cavitation

Bajic, Branko

doi:10.1080/00221680309499932

Cited by 17 publications

(11 citation statements)

References 4 publications

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“…e vibroacoustic method has received extensive attention from domestic and foreign scholars because of its real-time performance, strong anti-interference, lower operation cost, and wider acceptance. Bajic and Keller [13,14] conducted a series of experiments for early detection of cavitation in a hydro turbine by the vibroacoustic diagnostics. With a certain number of accelerometers and sound pressure gauges installed on the guide vane, cover, and draft tube, the cavitation location on the impeller blade was obtained.…”

Section: Introductionmentioning

confidence: 99%

Detection of Inception Cavitation in Centrifugal Pump by Fluid‐Borne Noise Diagnostic

Zhao

Dai

2019

Shock and Vibration

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This paper presents an experimental methodology that is capable of sensitively detecting the cavitation inception in a centrifugal pump. Firstly, with a centrifugal pump of ns=117 as research object, the cavitation performance, the bubble pattern distribution at impeller inlet, and the vibration and noise were synchronously measured at different flow conditions each with several cavitation coefficients. The change laws of total level of vibration and noise signals throughout the cavitation process were emphatically investigated. After comparing the sensitivity and reliability of different detection methods, the method based on overall sound pressure level of liquid-borne noise is found to present high sensitivity to cavitation. Secondly, by comparing the affected 1/3 octave spectrum by changing flow and cavitation coefficients, the highly sensitive frequency band to cavitation was obtained. Then, a new inception cavitation detection method was proposed based on Pauta principle. Finally, the method was verified through an ultra-low-specific speed pump (ns=25). The results show that the total pressure level of liquid-borne noise increases firstly and then decreases with the development of cavitation. The broadband SPL of liquid-borne noise between 2000 and 3000 Hz can be used to detect the inception cavitation, and the cavitation detection threshold is determined as 1.0%.

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Section: Introductionmentioning

confidence: 99%

Detection of Inception Cavitation in Centrifugal Pump by Fluid‐Borne Noise Diagnostic

Zhao

Dai

2019

Shock and Vibration

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“…Chini et al 12 measured the vibration signal of the centrifugal pump in cavitation and non-cavitation conditions and proposed a method for online instantaneity monitoring of cavitation in centrifugal pump. Bajic 13 carried out a multidimensional monitoring research to the cavitation of the turbine and realized accurately recognizing the position of the cavitation. Based on this, cavitation characteristic development trend can be predicted.…”

Section: Introductionmentioning

confidence: 99%

Research on cavitation acoustic characteristics of centrifugal pump based on fluid-acoustic field coupling method

Zhao

Dai

et al. 2018

Advances in Mechanical Engineering

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In order to study the change rules of interior acoustic field with the development of cavitation, this article presented a method that through comparing the experiment results with numerical simulation results in cavitation bubbles' distribution images under different cavitation coefficients to optimize the accuracy of acoustic field simulation using computational fluid dynamics combined with the Lighthill acoustic analogy. First, a closed visual testing system was established based on pump product test system and high-speed photography. Second, the cavitation performance under the rated operating condition was calculated using different cavitation models, in order to obtain both pump cavitation performance curve and distribution of cavitation bubbles. Next, based on the external characteristics experiment and highspeed photography experiment, the appropriate cavitation model for unsteady numerical calculation was selected. On the basis of vapor volume fraction distribution and the cavitation performance curve, four different typical points representing different cavitation coefficients were selected for further analyses. The direct boundary element method was used to calculate the variation characteristics of cavitation-induced noise at different cavitation coefficients. Finally, the peak-to-peak value of pressure fluctuation coefficient is defined as E, and the pressure pulsating frequency domain signals were analyzed to further study the influence of pressure pulsation on acoustic field. The results show that the effect of pressure pulsation on noise is mainly focused on the discrete eigenvalues, and as for the broadband noise, the influence is not obvious. With the development of cavitation, axial passing frequency, 10-to 100-Hz frequency band, and 1000-to 3000-Hz frequency band show an increasing trend, while blade passing frequency and its harmonic frequencies show a decreasing trend. At the onset of cavitation, 1000-to 3000-Hz frequency band has the highest sensitivity for cavitation detection.

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“…Bajic [6] carried out vibro-acoustic analysis of cavitation signals and succeeded to correlate the power of the signal of interest (SOI) and the intensity of cavitation for a given machine operating point. The vibro-acoustic signal power I(P) can be modeled as a sum of the powers of each cavitation mechanism SOI Im:…”

Section: A Methodologies Developed So Farmentioning

confidence: 99%

Cavitation Aggressiveness Estimation in Hydro Turbines Based on Cyclostationary Modeling

Marinho

Barúqui

2016

BJIC

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This work proposes a new methodology of detection and identification of erosive cavitation in hydro turbines, which is based on cyclostationary modeling of the cavitation induced vibrational signals. Different cavitation types cause damage to different turbine parts and induce different vibrational signatures, which can be employed to identify and locate the cavitation. Additionally, the cavitation aggressiveness can be estimated using the measured power of vibrational signal. High frequency accelerometers picked up the signals from two real turbines under normal operation. The methodology was implemented in software and a specific hardware was developed to run the software locally. Signals were synthesized in accord with the cyclostationary modeling and employed to validate the proposed methodology. Results obtained from real signals were similar to the ones obtained from synthetic signals, and corroborate the feasibility of this methodology in cavitation monitoring systems.

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Methods for vibro-acoustic diagnostics of turbine cavitation

Cited by 17 publications

References 4 publications

Detection of Inception Cavitation in Centrifugal Pump by Fluid‐Borne Noise Diagnostic

Detection of Inception Cavitation in Centrifugal Pump by Fluid‐Borne Noise Diagnostic

Research on cavitation acoustic characteristics of centrifugal pump based on fluid-acoustic field coupling method

Cavitation Aggressiveness Estimation in Hydro Turbines Based on Cyclostationary Modeling

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