SEDL / STP / STP1077-EB / STP19102S

Cavitation Monitoring of Hydroturbines with RMS Acoustic Emission Measurement

Derakhshan, O
engineers, Tennessee Technological UniversityEngineering Laboratory, Tennessee Valley Authority, CookevilleNorris, TNTN

Houghton, JR
engineers, Tennessee Technological UniversityEngineering Laboratory, Tennessee Valley Authority, CookevilleNorris, TNTN

Jones, RK
engineers, Tennessee Technological UniversityEngineering Laboratory, Tennessee Valley Authority, CookevilleNorris, TNTN

March, PA
engineers, Tennessee Technological UniversityEngineering Laboratory, Tennessee Valley Authority, CookevilleNorris, TNTN

Pages: 11    Published: Jan 1991

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Abstract

Acoustic Emission measurements are shown to be a reliable indicator of cavitation pressure pulses. The method of display is the root mean square, RMS, of the AE signal integrated over 1 second that is proportional to the average cavitation energy. An inexpensive AE transducer, amplifier, filter, and RMS circuit is described with a gain of 22 dB and a frequency range of 10 kHz to 1.25 MHz. Data from two laboratory controlled cavitation experiments is presented. The system is tested on two TVA hydroturbines. Kaplan-type and Francis-type turbines had a similar shaped increased RMS AE curve with wicket gate opening but the numerical maximum values are different in each hydroturbine installation. A real-time continuous RMS AE monitor is recommended on each hydroturbine for the evaluation and control of cavitation erosion.