Strength analysis of remaining bolts as several connection bolts of hydro-turbine head cover in failure
GE Xinfeng1*, XU Xu1, SHEN Minghui2, TAN Linjie1, QIAN Julin3, ZHANG Changzheng1
1. College of Energy and Electrical Engineering, Hohai University, Nanjing, Jiangsu 211100, China; 2. Xinxiang Power Supply Company, State Grid Henan Electric Power Co., Xinxiang, Henan 453002, China; 3. Fuchunjiang Hydropower Plant, State Grid Xinyuan Co. Ltd., Tonglu, Zhejiang 311504, China
Aiming at severe accidents such as flooding hydropower plant caused by broken connection bolts of head cover in hydro-generator units, the geometrical and mechanical models of head cover and connection bolts of a hydro-turbine in a hydropower plant were established and analyzed by using finite element method. Based on the finite element method in Ansys, the static element force equilibrium equations were solved numerically, and the stress distribution in the bolts were determined under va-rious working conditions. Firstly, a normal case was established, i.e. the bolt strength was analyzed when all the bolts engaged properly under runaway condition. Then, a few bolt failure cases were taken into consideration to determine the strength of the remaining bolts, namely, the cases where there are 1, 2, 4 and 8 bolts failed which can be distributed 90?symmetrically, side by side and 180?apart. Results show that the maximum stress level in the remaining bolts increases after several bolts are broken due to uneven distribution of the bolts along the circumferential direction. Specially, the more the bolts are broken and the closer the broken bolts are distributed, the less the strength of the remaining bolts is. When the number of failed bolts is 4 and they are distributed side by side, the maximum stress level of the remaining bolts is as high as 744.03 MPa, which is very close to the bolt allowable stress 744 MPa. When the number of failed bolts is 8 and they are positioned side by side, the maximum stress is increased by 19.69% and arrives at 776.21 MPa, which is far beyond the allowable stress, clearly the safe operation of the hydropower plant will be under threat.
GE Xin-Feng-*,XU Xu-,SHEN Ming-Hui- et al. Strength analysis of remaining bolts as several connection bolts of hydro-turbine head cover in failure[J]. Journal of Drainage and Irrigation Machinery Engin, 2019, 37(7): 600-605.
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