Research Papers: Multiphase Flows

Study of Erosive Cavitation Detection in Pump Mode of Pump–Storage Hydropower Plant Prototype

[+] Author and Article Information
Tine Cencîc

Sôske Elektrarne Nova Gorica,
5000 Nova Gorica, Slovenia

Marko Hoĉevar, Brane Ŝirok

Faculty of Mechanical Engineering,
University of Ljubljana,
1000 Ljubljana, Slovenia

Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received February 4, 2013; final manuscript received November 21, 2013; published online March 11, 2014. Assoc. Editor: Olivier Coutier-Delgosha.

J. Fluids Eng 136(5), 051301 (Mar 11, 2014) (11 pages) Paper No: FE-13-1075; doi: 10.1115/1.4026476 History: Received February 04, 2013; Revised November 21, 2013

An experimental investigation has been made to detect cavitation in a pump–storage hydropower plant prototype suffering from leading edge cavitation in pump mode. Vibrations and acoustic emission on the housing of the turbine bearing and pressure fluctuations in the draft tube were measured and the corresponding signals were recorded and analyzed. The analysis was based on the analysis of high-frequency content of measured variables. The pump–storage hydropower plant prototype has been operated at various input loads and Thoma numbers. Several estimators of cavitation were evaluated according to a coefficient of determination between the Thoma number and cavitation estimators. The best results were achieved with a compound discharge coefficient cavitation estimator that is based on the discharge coefficient and several rms estimators: vibrations, acoustic emission, and pressure fluctuations. The compound discharge estimator was set as a product of the rms estimator and the squared discharge coefficient. Cavitation estimators were evaluated in several intervals of frequencies; the best frequency interval for the vibration sensor on the turbine cover was from 24 to 26 kHz, for the vibration sensor on the guide vane 36–40 kHz, for the acoustic emission sensor on the turbine cover 140–145 kHz, and for the pressure fluctuation sensor in the draft tube wall 130–150 kHz.

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Fig. 1

The power house of pump–storage hydro power plant Avce

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Fig. 2

Schematics of occurrence of cavitation on the prototype in pump mode: Area A (left), (right) the figure shows the cavitation erosion on the blades that had the highest cavitation erosion damage

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Fig. 3

Influence of the discharge value on the flow velocity triangle in pump mode of operation at the impeller inlet

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Fig. 4

Installation of sensors (detail 1 of the Fig. 1) showing (left) view from side and (right) view from top (AE acoustic emission sensor, ACC1 and ACC2 accelerometers 1 and 2, PS pressure sensor)

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Fig. 5

Schematics of a pump turbine Avce runner, draft tube, and downstream reservoir

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Fig. 6

Results of measurements of vibrations, acoustic emission, and pressure fluctuations, showing dependence of measured variables on three intervals of discharge coefficients

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Fig. 7

Discharge coefficient cavitation estimator (DE) for different cavitation sensors

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Fig. 8

Normalized spectra of fluctuations of acceleration ACC1 and ACC2. Shown are five different intervals of frequencies.

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Fig. 9

Normalized spectra of fluctuations of accelerations AE and PS. Shown are five different intervals of frequencies.

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Fig. 10

Discharge coefficient cavitation estimator (DE) of accelerations ACC1 and ACC2 at selected frequency intervals. Shown is coefficient of determination R2.

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Fig. 11

Discharge coefficient cavitation estimator (DE) of acoustic emission AE and pressure PS at selected frequency intervals. Shown is coefficient of determination R2.




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