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
Abstract：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.
葛新峰*,徐旭,沈明辉,檀林杰,钱巨林,张昌振. 水轮机顶盖部分螺栓断裂后剩余螺栓的强度分析[J]. 排灌机械工程学报, 2019, 37(7): 600-605.
GE Xinfeng*, XU Xu, SHEN Minghui, TAN Linjie, QIAN Julin, ZHANG Changzheng. Strength analysis of remaining bolts as several connection bolts of hydro-turbine head cover in failure. Journal of Drainage and Irrigation Machinery Engin, 2019, 37(7): 600-605.
[1]楼文高. 船用柴油机气缸盖固定螺栓强度的可靠性分析[J]. 渔业机械仪器,1993,20(106):21-24. LOU Wengao. Reliability analysis of strength of fixed bolts for cylinder head of marine diesel engine[J]. Fishery machinery and instrument,1993,20(106):21-24.(in Chinese)[2]张续钟,刘思靓,马建峰. 混流式水轮发电机顶盖螺栓的安全性设计方法[J]. 小水电,2017(5):25-28. ZHANG Xuzhong,LIU Siliang,MA Jianfeng. Safety design method for top bolt of Francis turbine generator[J]. Small hydro power,2017(5):25-28.(in Chinese)[3]Association of German Engineers. Systematic calculation of high duty bolted joints: VDI 2230 Part 1[S]. Duesseldorf, Germany: Verein Deutscher Ingenieure, 1977.[4]蓝秀琼,陈建华. 汽车用高强度组合螺栓断裂失效分析[J]. 机械强度,2018,40(5):1263-1265. LAN Xiuqiong, CHEN Jianhua. Fracture failure analysis of a auto high strength assembling bolt[J]. Journal of mechanical strength, 2018,40(5):1263-1265.(in Chinese)[5]王熙婷. 螺栓联接接触问题有限元分析[J]. 工业技术创新,2017,4(6):11-14. WANG Xiting. Finite element analysis on the contact issue of bolt connection[J]. Industrial technology innovation, 2017,4(6):11-14.(in Chinese)[6]田彤辉,袁杰红,王青文. 基于有限元模型的螺栓法兰连接结构冲击失效实验方案研究[C]//第27届全国结构工程学术会议论文集(第Ⅱ册). 2018:7.[7]石虹. 高强度螺栓失效若干因素的研究[D]. 沈阳:东北大学, 2012.[8]刘献良,张路,赖云亭,等. 电站连接螺栓断裂失效分析[J]. 理化检验(物理分册),2018,54(10):778-781. LIU Xianliang, ZHANG Lu, LAI Yunting, et al. Failure analysis on fracture of connecting bolts in a power plant[J]. Physical testing and chemical analysis(part A: physical testing), 2018,54(10):778-781.(in Chinese)[9]施刚,石永久,王元清,等. 端板连接高强度螺栓受力特性试验研究[J]. 东南大学学报(自然科学版),2004,34(3):375-378. SHI Gang, SHI Yongjiu, WANG Yuanqing,et al. Experimental study on bolt resistance for structural steel extended end-plate connections[J]. Journal of Sou-theast University(natural science edition), 2004,34(3):375-378.(in Chinese)[10]李振强. 兆瓦级风力发电机高强度螺栓联接静力学性能分析[D]: 长沙:湖南大学, 2013.[11]陈世杰,扬帆,黄辉,等. 立式轴流泵装置叶片区压力脉动数值分析[J]. 流体机械,2019,47(2):17-22. CHEN Shijie, YANG Fan, HUANG Hui, et al. Numerical analysis of pressure fluctuation of the blade region in vertical axial-flow pumping system[J]. Fluid machi-nery, 2019,47(2):17-22.(in Chinese)[12]哈尔滨大电机研究所. 水轮机设计手册(水轮发电机组设计手册第一部分)[M]. 北京:机械工业出版社, 1976.
