Experimental Study Of Water Jet Cavitation Noise

As new technology, cavitating water jet is used in many industry fields, such as coal-mining, petroleum-mining, cleaning, water treatment and so on.The generating system of submerge cavitating water jet and the testing system of cavitation noise are built, which is necessary to carry out the experimental study. The cavitation noise with different structural cavitating nozzles at different standoff are collected with a hydrophone under the same experimental conditions.Cavitation noise is weakly random signals with high frequency. Analyzing the collected experimental signals with self-adapting filtering treatment, wavelet entropy analysis, wavelet energy numerical analysis and power spectrum intensity estimation, the capability and the frequency characteristics of the cavitation noise generated by cavitating nozzles with different structure are investigated.Cavitation noise is filtered with the self-adapting filtering treatment. The filtered signal with adjustable digital filter is sent to the adaptive noise canceller where the signal is subtracted by the signal collected under the cavitation condition. The exported cavitation noise near to the reality is attained.Cavitation noise is analyzed with the technology of wavelet entropy. To get the wavelet entropy frequency spectrums of the cavitation noise datum with different nozzles, a piece of cavitation noise is inserted to the system noise taken as a main signal. According to the spectrum, the stable frequency range of the nozzles is obtained.The energy of the cavitation noise is numerically analyzed with the wavelet energy numerical analysis. The cavitation noise datum is decomposed with three-scale and 8 wavelet packages to compute the noise energy of different standoff. The wavelet packages with the signals of cavitation noise are found. These wavelet packages are analyzed with power spectrum intensity estimation to find the frequency characteristic of the cavitation noise with different nozzles.The above four analyzing methods were programmed with the software of Matlab. The datum of the cavitation noise were computed and analyzed successfully with the program. The cavitation efficaciously taken place in the cavitating water jet is verified from different aspects, and some datum is obtained. The datum is fit with the software of Origin. The energy amplitude of the cavitation noise is obtained at different standoff with different nozzles.The results of experimental study show that the cavitating capability of water jet generated by the No.2 nozzle with oscillating cavity is greater than No.3, No.4 and No.0. The optimal standoff of No.2 is 30mm. The cavitation noise energy of No.2 is 10 times more than other three nozzles, whose frequency is 10～160KHz。...