近年来，随着大型水轮机组不断投入运行，电站对机组运行稳定性的要求不断提高，深入研究水力非定常流动及其对机组结构和运行性能的影响具有重要意义。本研究对大型轴流转桨式水轮机的活塞杆断裂现象进行分析，通过数值模拟和现场实测的方法开展水力、结构和运行特性的研究，在理论计算方法和工程应用研究方面取得了有益的经验和突破，在提高机组安全稳定运行的科学研究中取得了重要进步。 应用现代CFD技术深入研究了轴流转桨机组流道内部的流动特性及水力激励特性。多个稳态工况的定常流动计算得到的效率和非定常流动计算得到的压力脉动混频幅值与实测结果进行了比较。计算与实测的水轮机水力效率基本吻合，计算和实测的关键点压力脉动混频幅值基本一致。机组在高水头小开度工况压力脉动幅值突然增大，研究发现小开度时活动导叶与桨叶之间无叶区的漩涡流是造成这种现象的主要原因。 应用弱流固耦合方法深入研究了水力激励作用下的轴流转桨式水轮机桨叶操作机构多体系统桨叶、活塞杆等关键部件的动力特性。重点分析六个桨叶绕自身枢轴水力扭矩的非定常、非均匀、非同步特性，应用弱流固耦合和面接触力传递分析技术进行了桨叶操作机构多体系统的动应力计算，获得了多个运行工况水力激励作用下的桨叶、活塞杆、转轮体等关键部件的动应力和位移云图，活塞杆的应力集中部位与实际断裂部位吻合。 发展了基于轴流转桨机组实际运行特性和动力特性理论计算结果的运行区划分理论方法。全面分析了机组在线振动、摆度和水压力实测数据，结合CFD计算结果，发现导叶出口压力脉动可作为表征该机组水力稳定性的主要依据；在计算得到的活塞杆动应力谱的基础上，预测了活塞杆的疲劳寿命，绘制了不同运行工况下的活塞杆疲劳寿命等值线图。在活塞杆疲劳寿命和导叶出口压力脉动分布基础上，划分了该轴流转桨式水轮机的运行区，电站机组运行实践证明运行区划分合理可靠。
In recent years, a great number of large scale hydraulic turbines were put into production. Much attention is paid to higher operating stability of turbine unit. It is of great importance to study hydraulic instability as well as its effect on unit structure and operating performance. Analysis on failure of piston rod for a large scale Kaplan turbine is carried out in this paper. Numerical simulation and field measurement were used to study hydraulic instability, structure response and operation characteristics. The results are helpful to improve the stability and safety of the unit. The internal flow pattern and pressure pulsation in Kaplan turbine were intensively investigated using modern computational fluid dynamics (CFD) technology. The calculated turbine hydraulic efficiency for steady state and pressure pulsation for unsteady state agreed well with measured data. The amplitude of pressure pulsation increases suddenly when the turbine unit operates under high head and small guide vane opening condition. It is found that the movement of vortexes in non-blade region between guide vanes and blades caused the relative high pressure pulsation under small guide vane opening. The dynamic characteristics of blades and piston rod were further calculated using weak fluid-structure interaction method for multi-body blade-control system of Kaplan turbine, with emphasis on the unsteady, asymmetrical and unsynchronized characteristics of hyduaulic torques along blade shank for six blades. The structure response of multi-body blade-control system was computed based on fluid-structure interaction and surface contact technology. The dynamic stresses and displacement nephogram of blade, piston rod and runner hub induced by hydraulic instability were obtained. The stress concentration in piston rod agrees well with actual fracture position. A theoretical method was developed to partition Kaplan turbine operating region based on operation characteristics obtained by field measurement and dynamic characteristics obtained by numerical simulation. A thorough analysis of online measurement data and CFD results show that pressure pulsation at guide vane outlet can be used as the main index of stability for the Kaplan turbine. The fatigue life of piston rod was predicted based on dynamic stress spectrum obtained by finite element analysis. The contour of piston rod fatigue life was plotted. The operating region of the Kaplan turbine was partitioned according to fatigue life of the piston rod and pressure pulsation at guide vane outlet. The operating region was proved to be reasonable and reliable by the operating practice of the power station.
