Stress characteristics of top cover bolts of hydraulic turbine

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Journal of Vibration and Shock ›› 2021, Vol. 40 ›› Issue (17) : 55-62.

GE Xinfeng1, ZHANG Jing1, ZHU Shuangju2, QIAN Julin3, ZHAO Lei2, #br# ZHENG Shengyi1, ZHENG Yuan1, XU Xu1, BINAMA Maxime1

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Abstract

Top cover bolt is an important connector between top cover and seat ring of a hydraulic turbine.The safety state of top cover bolt is the important guarantee for safe operation of hydropower station.Here, a certain axial-flow hydraulic turbine was taken as the study object, and a full 3-D fluid model and a top cover-bolt structure model of the hydraulic turbine were established.The water pressure distribution on the flow surface of the top cover was transferred to the top cover using the fluid-solid coupling method.The hollow force sensor was used to do field tests of bolts on site.The calculation results of equivalent stress distributions of bolts’ different cross-sections were verified with test results.The study showed that the top cover water pressure increases with increase in waterhead and guide vane opening, the total axial compression value of top cover reaches the maximum under the condition of maximum waterhead and large opening; stress distributions of bolt’s cross-sections at different positions are uneven, and bolt bears both axial stress and bending stress; stresses of bolt head and joint between bolt and screw thread are larger than that of bolt middle section; the change trend of stresses at bolt’s different positions reveals water pressure on the top cover coupling surface being axisymmetric; when the turbine starts, bolt stress increases more obviously than that when it halts, top cover bolt stress increases obviously in the lower load vibration zone, and it is stable in the stable operation zone; the numerical simulation results under 3 stable operation conditions are consistent to the field test results, so the correctness of the finite element calculation is verified and the hollow force sensor can more accurately reflect top cover bolt’s axial stress.

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top cover bolt / fluid-solid coupling / stress characteristics / hollow force sensor

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GE Xinfeng, ZHANG Jing, ZHU Shuangju, QIAN Julin, ZHAO Lei, ZHENG Shengyi, ZHENG Yuan, XU Xu, BINAMA Maxime. Stress characteristics of top cover bolts of hydraulic turbine[J]. Journal of Vibration and Shock, 2021, 40(17): 55-62

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