Numerical Simulation Of The Whole Bulb Turbine Runner&Fluid-structure Coupling Vibration Analysis Of Its Blades

Bulb tubular power plant is one of the most effective forms to develop low-head hydropower resources. To ensure the stable and safe operation of the units, it is very important to study the vibration problems of runner blades caused by hydraulic excitation. In this paper, based on a prototype single unit in bulbs tubular power plant, the three-dimensional geometrical model was established. Based on computational fluid dynamics(CFD), the numerical simulation research under various conditions was carried out, the flow field structural features inside the turbine and the dynamic pressure of characteristic monitoring points were obtained; At the same time, based on fluid-structure interaction (FSI) method of the sound field and the weak coupling method, vibration characteristics of turbine blades in various factors and the problems of the flow-induced vibration on runner blades were studied. The main results are as follows:(1) By researching CFD theory comprehensively and using of existing computing conditions, the appropriate calculation methods for the numerical simulations of the bulb turbine internal flow field were put forward combined with operation features of bulb turbine.(2) Based on ANSYS-Workbench platform, the full-body channel fine model including the three-dimensional twisted runner blades, guide vanes and the bulb were established. Considering the features of the flows, the entire turbine flow field is divided into several parts, each part was meshed by the professional software ICEM, which achieved the consensus of the computational efficiency and accuracy.(3)With the slip grid technique, the detached eddy simulation (DES) turbulence model and PISO algorithm were chosen to carry out the unsteady flow field numerical simulation in the design condition and the small opening condition respectively. The flow characteristics inside the turbine and the dynamic pressure of the characteristic monitoring points on the flow channel and the bulb body were obtained in these two conditions, which provided a basis to study the vibration characteristics of the unit.(4) Based on the FSI theory of the sound field and modal analysis method, the vibration characteristics of the runner blades were analyzed under different media and conditions, which demonstrate the key factors affecting the vibration characteristics of the runner blades.(5) Considering hydraulic excitation is the main factor causing the vibration of turbine unit, the weak coupling method was chosen for the turbine runner blades coupling calculation in this paper. The results reflected the process of the fluid induced vibration of the runner blades, and by analyzing the dynamic response of the single blade, the main features of the runner blade flow-induced vibration was revealed.