bearing rigidity on characterisitics of natural vibration of shaft system in hydroturbine generating unit
BAI Bing, ZHANG Li-Xiang, ZHAO Lei
(1. Department of Engineering Mechanics, Kunming University of Science and Technology, Kunming, Yunnan 650051, China; 2. The First Research Institute of 134 Department of Xinhang Military Company, Xinxiang, Henan 453049, China)
To study the characteristics of the lateral natural vibration of the main shaft system in hydroturbine generating unit, with the finite element method the main shaft system was discretized; and with energy method the dynamic equation was obtained. Based on simplified actual parameters, with MATLAB software, fixed frequencies, mode shapes and critical speed of rotation of the shaft system were calculated and influences on critical speed caused by changes in the guide bearing rigidity were analyzed. The results show that when only one guidebearing rigidity is changed, up guidebearing has little influence on critical speed; however, the down bearing and the water guidebearing greatly affect the critical speed. There occurs a “saturated” phenomenon, that is to say, the critical speed remains unchanged when the rigidity reaches or exceeds a certain value. If the rigidity of the three guidebearings is increasing simultaneously, the critical speed can be increased significantly. Change in the up guidebearing has little effect on the modes in the first three orders; Change in the down guidebearing and water guidebearing will result in an opposite mode in a certain mode. It can be concluded that it is necessary to fully consider the effect caused by the guidebearing rigidity in evaluating the critical speed of the shaft system.
BAI Bing,ZHANG Li-Xiang,ZHAO Lei. bearing rigidity on characterisitics of natural vibration of shaft system in hydroturbine generating unit[J]. Journal of Drainage and Irrigation Machinery Engin, 2013, 31(4): 318-324.
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