Unsteady Calculation And Vibration Analysis Of The Francis Runner With Splitter Blades In Sandy Water

China is a country with abundant water resources. As the development hydropower gradually shifted to the west of China, the study of turbine erosion has become a hot topic in recent years because of the high sediment content of mountainous rivers. Francis turbine runner with splitter blades is a new type of turbine which has been designed in recent years.Its effect in significantly slowing down the turbine erosion in rivers with high sediment content has been proved. However, the study of the internal flow conditions and its stability are still insufficient.A Francis turbine runner with splitter blades was selected as the research object. Through3 D modeling and CFD technology, the unsteady flow in this turbine was calculated under three conditions. The internal flow conditions and pressure pulsation were analyzed.The erosion and the stability of this turbine were predicated.Major works completed in this study are as follows:1. According to existing wooden form drawings, the volute, stay ring, runner and draft tube of the turbine were three-dimensionally modeled by UG. The established 3D model was introduced into the ICEM CFD to partition various parts, generate grids and check their quality.2. The processed mesh files of various flow components were imported into CFX to set the boundary conditions and solution conditions. And then, the unsteady flow in this turbine was numerically simulated under three conditions.3. The calculated results were processed to extract the pressure and sediment distributions under different conditions. The simulated results were converted from the time domain to frequency domain by using the Fast Fourier Transform(FFT) method.4. According to the extracted data, the internal flow conditions of the Francis turbine with splitter blades were analyzed, and the effect of pressure pulsation on the stability of the turbine was analyzed, too. The results show that sediment concentration decreases with the increasing of flow rate in the volute and guide vanes. On the leading side of the blade,sediments mainly distribute at the runner band near the outlet edge due to gravity. At the suction side of the long blade, there is an area with high sediment concentration at the center of the blade, while this high concentration area is located at the center of the outlet edge for short blades. The sediment distribution in the draft tube is affected by vortexes. There are solid vortexes at part load and rated load conditions, while there are hollow vortexes at over load conditions. The stability of the turbine is mainly affected by low-frequency pressure pulsation in the draft tube. There is a middle-frequency pressure pulsation at the volute and guide vanes and a high-frequency pressure pulsation at the runner which main frequency is the multiple of the blade number.