Cavitation erosion detection method based on acoustic emission

Abstract

The invention discloses a cavitation erosion detection method based on acoustic emission, which comprises the following steps: utilizing an acoustic emission sensor to collect an acoustic emission signal in unit time length during cavitation erosion development; performing wavelet decomposition on the acoustic emission signal according to set layer number to obtain a wavelet coefficient and relevant degree of the cavitation erosion and frequency range where the wavelet coefficient is located, and denoising the wavelet coefficient according to the relevant degree and the set layer number; performing signal reconstruction by utilizing the wavelet coefficient after denoising, and obtaining a reconstruction signal; setting parameter estimating threshold and counting time interval of the reconstruction signal; calculating acoustic emission event number and acoustic emission even average energy of the reconstruction signal; and judging plastic deformation and mass loss condition during cavitation erosion development according to the acoustic emission even number and the acoustic emission even average energy. The cavitation erosion detection method based on the acoustic emission performs denoising according to the characteristics of the acoustic emission signal and utilizes a simple estimating parameter to represent the development condition of plastic deformation and mass loss during cavitation erosion.

Description

technical field [0001] The invention relates to a method for directly detecting cavitation erosion, in particular to a method for detecting cavitation erosion based on acoustic emission technology. Background technique [0002] When the local pressure of the liquid is low enough, cavitation will occur; the process of causing damage to the surface of the solid material when the cavitation collapses is called cavitation erosion. Cavitation is a common form of damage to fluid machinery: slight cavitation causes the surface of the material to lose its luster and produces pits; severe cavitation causes the material to become loose or even fall off, affecting the operating state of the fluid machinery. First of all, in order to avoid severe cavitation, it is necessary to monitor the occurrence of cavitation and adjust the operating status of hydraulic machinery; secondly, to avoid severe cavitation, it is necessary to repair the surface of fluid machinery before it occurs, and the...

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Problems solved by technology

At present, research on cavitation state monitoring has been paid attention to. Common cavitation monitoring methods monitor cavitation phenomena through noise and structural vibration and other physical quantities to monitor cavitation indirectly. On-line Monitoring Method and Diagnosis Device for Corrosion Damage" provides an indirect cavitation monitoring method by monitoring the cavitation coefficient of fluid machinery, the pressure pulsation in the flow channel, the energy characteristics of fluid machinery, and the working water head. Monitoring and Diagnosis System" (Source: Water Conservancy and Hydropower Technology, 2002, 33(7): 17-20) uses pressure pulsation, efficiency and cavitation noise to monitor cavitation indirectly, and the literature "Cavitations monitoring and diagnosis of hydropower turbine online based on vibration and ultrasound acoustic" (Source: Proceedings of the Sixth International Conference on Machine Learning and Cybernetics, 2007: 19-22) monitors cavitation indirectly using cavitation-induced vibration and ultrasound pairs; however these are associated with cavitation The corresponding relationship between the physical quantities and cavitation erosion is not clear, so it is difficult to accurately estimate the state of cavitation erosion by indirect monitoring methods based on these physical quantities

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