水轮机顶盖螺栓受力特性研究

Stress characteristics of top cover bolts of hydraulic turbine

顶盖螺栓是连接水轮机顶盖与座环的重要连接件,顶盖螺栓的安全状态是水电站安全运行的重要保障。以某轴流式水轮机作为研究对象,建立了全三维流体模型和水轮机顶盖及螺栓结构模型,采用流固耦合方法将顶盖过流面压力分布水压力传递给水轮机顶盖,对现场电站螺栓采用中空测力传感器进行现场试验,将螺栓不同截面的等效应力分布与试验结果进行验证,研究表明:顶盖水压力随着水头和导叶开度的增大而增大,最大水头大开度工况顶盖总轴向压力值达到最大;螺栓不同位置截面应力分布不均,螺栓同时承受着轴向应力与弯曲应力,螺栓头部、螺栓与螺纹交接处相比螺栓比螺栓中部截面受力大;不同位置螺栓受力变化趋势一致验证了顶盖耦合面的水压力为轴对称分布的特性;开机时螺栓受力比停机时增加明显,较低负荷振动区,顶盖螺栓受力有所提升,在稳定运行区螺栓受力保持稳定;停机及三个稳定运行工况下数模计算的结果和现场试验吻合,验证了有限元计算的准确性,中空测力传感器能够比较准确的反应螺栓的轴向受力。

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.