Research On Structure Radiant Noise Of Rotary Machines And The Mechanism To Control It

With the development of industry, the kinds and numbers of rotary machine continuously increase. Lots of rotary machines bring strong noise when they rotate. As the result of the noises, the people feel very annoyance in their daily life. Many researchers have taken much efforts to reduce the noise. With decades years research and experience, we have summarized many theories of reducing equipment noise and successful experience, acquired lots of useful achievements. Many equipment designers and manufacturers broken new fields of noise research, developed numerous low noise mechanical products and impelled this field developing and perfecting continually.The frame radiated noise is one of the major noise resources of rotary machines, especially for gear case which has close shell and vibrating screen which works in vibrating ways, the frame radiated noise energy account for more than 90% of total sound energy. So if we could not successfully resolve the problem, the noise of rotary machines would never be effectively controlled. Although there are much research in the field, most research only deal with special machine, special part in some way. It is short of systematicness and popularity. In view of this case, the paper mainly studied sound radiation properties of structure, sound source identification methods, main factors affecting frame radiated noise and the common way to control the noise radiated by rotary machines. The detail research shows as fellows:(1) Study on sound radiation properties of box-shape structure. Taking gear case as research object, we studied the sound radiant efficiency of complex box-shape structure under practical stimulation by experiment, mainly observed the difference of sound radiant efficiency between the complex structure under practice stimulation and the known simple structure. By experiment, we found that the variation of gear case radiant efficiency with frequency keep accordance with that of simple one as a whole, but the radiant efficiency of gear case will go beyond any calculation result of empirical formula when the frequency is below 250Hz. We also found that stimulation changes affect radiant efficiency little by varying speed experiment, and it can be ignored in engineering calculation. The rectangle structures as gear case, possess characters of both plane and ball, and their sound radiant efficiency lie between plane and ball region. So we propose that the mean of radiant efficiency of plane and pulse ball region can act as that of this kind of structure in practice.(2) Sequential distinguish of structure sound resource in complex sound field. We studied the sound source identification methods in complex sound field andinproposed the sequential sound source identification method. In the practicality point of view, we mainly studied the details of the former two layers. We proposed the means of near field measurement correction and far-near-field fuzzy distinguish synthesis according to if fixed evaluation points exist. The method advanced in precision. We also proposed a reformed surface speed method based on the problems of surface speed method in engineering application. This method can make sure the structure radiant sound status in total noise and the detail phonate part quickly and correctly.(3) Study on the control mechanism of structure noise radiated from rotary machines, we build a common model of rotary machine structure noise analysis relied on the general characters of rotary machines. Based on this model, we analyzed various influence factors to structure radiant noise using the union of revolution and numerical calculation method. We found that the joint stiffness between the rotor and the frame is the most sensitive parameter of structure radiant noise by calculating and analyzing. Moreover, each parameter's effect is mutual compensatory. We advanced a general valid method to reduce the structure radiant noise of rotary machines based on the analysis results. At last, we tested the analysis results by model experiment.