Study On The Noise Source Identification And Noise Reduction Of The Four-axis Variable Trajectory Equal-thickness Vibrating Screen

Coal is the primary energy in China. The direct utilization of the poor-quality raw coal with high-content ash and sulfur may cause serious environmental pollution and waste of resources. Coal preparation is the most economical and effective method for high-quality coal utilization. The screening process as well as the corresponding widely-used vibrating screen is the key to coal preparation. However, during the vibrating screen operations, a strong noise would be created, which results in serious noise pollution, making coal preparation operators with severe serious occupational hearing loss, restricting the sustainable development of coal industry in our country.The Large radiated noise problems of the large vibrating screen was focused on in the dissertation, with the model of the four-axis variable trajectory equal thickness vibrating screen as a carrier, the research system of the vibrating screen of noise source identification and noise reduction were proposed, and the correctness of the system was proved theoretically. Through which was provide to design and manufacture more static vibrating screen The main work completed and the results obtained are summarized as follows:In this dissertation, the basis of summarizing and analyzing the research status of the noise source identification and noise reduction of the vibrating screen at home and abroad, and based on the working principle of the four-axis variable trajectory track, the vibration transmission path of the vibrating screen was analyzed, the mechanism of various kinds of radiation noise of vibrating screen was expounded, and the characteristics of the radiation noise signal of four-axis variable trajectory equal-thickness vibrating screen radiation noise signal with non- stationary period and time variation were determined, the mechanism of various kinds of radiation noise of vibrating screen was expounded, and the characteristics of the radiation noise signal of four-axis variable trajectory equal-thickness vibrating screen radiation noise signal with non- stationary period and time variation were determined.By using four kinds of analysis techniques(i.e., sound pressure measurement, three dimensional sound intensity measurement, wavelet transform and independent component analysis), the radiation noise of the vibrating screen was studied further Based on the analysis of the sound pressure signals obtained from the field measurements, the main frequency bands of the radiation noise of the four axis variable track were obtained; Through three-dimensional sound intensity measureme- nt, the sound intensity distribution map of four-axis variable trajectory equal-thickness vibrating screen was obtained, the image of the noise source was obtained, and further according to the contribution of each component to the radiation noise of the whole vibration screen, the noise source is sorted; with method of wavelet transform, the time-frequency characteristic of the four-axis variable trajectory equal-thickness vibrating screen radiated noise signal was obtained, and the noise source identification was studied by analyzing the characteristics of the signal; Finally, the blind signal separation of the noise signal from the measured four-axis variable trajectory equal-thickness vibrating screen was made by the ICA technique, and the independent component of the main noise source was obtained.By using the FEM modal analysis technique, the modal analysis was carried out on the four-axis variable trajectory equal-thickness vibrating screen machine and its main components. Through the structure optimization, the side-plate and the rear-baffle in the sensitive frequency range of the modal density were reduced, and the model frequency is beyond the blind source separation of independent component corresponds to the frequency of half power bandwidth, thus reducing the chance of the resonance, and the radiation noise of the vibrating screen can be reduced.