Publication

Field Assessment of Cavitation Detection Methods in Hydropower Plants

François Avellan, Mohamed Farhat
2002
Conference Papers

Abstract

An experimental investigation on Francis turbines suffering from inlet cavitation erosion on the runner blades has permitted to assess several aspects of the actual cavitation erosion detection and prediction methods based on vibrations. Detection tests in three prototypes have consisted in the measurement of vibrations in turbine guide bearing, guide vanes and draft tube during operation. Discussion about RMS levels, auto power spectra and amplitude demodulation results is provided. A dynamic calibration has been carried out using an instrumented hammer. For that, one of the accelerometers has been mounted on the blade and the rest have been kept in their external positions. Frequency response functions between the blade and the remote sensors have been obtained and compared among the machines. The various transmission paths have been investigated.

Official source

https://infoscience.epfl.ch/entities/publication/61d10654-c899-4b70-b727-386e3199b343

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François Avellan, Mohamed Farhat
2002
Conference Papers

Abstract

Official source

https://infoscience.epfl.ch/entities/publication/61d10654-c899-4b70-b727-386e3199b343

About this result

Related concepts (32)

Amplitude modulation

Amplitude modulation (AM) is a modulation technique used in electronic communication, most commonly for transmitting messages with a radio wave. In amplitude modulation, the amplitude (signal strength) of the wave is varied in proportion to that of the message signal, such as an audio signal. This technique contrasts with angle modulation, in which either the frequency of the carrier wave is varied, as in frequency modulation, or its phase, as in phase modulation.

Demodulation

Demodulation is extracting the original information-bearing signal from a carrier wave. A demodulator is an electronic circuit (or computer program in a software-defined radio) that is used to recover the information content from the modulated carrier wave. There are many types of modulation so there are many types of demodulators. The signal output from a demodulator may represent sound (an analog audio signal), images (an analog video signal) or binary data (a digital signal).

Frequency response

In signal processing and electronics, the frequency response of a system is the quantitative measure of the magnitude and phase of the output as a function of input frequency. The frequency response is widely used in the design and analysis of systems, such as audio and control systems, where they simplify mathematical analysis by converting governing differential equations into algebraic equations.