Study on the Complex Erosion Characteristics and Specific Influencing Factor Mechanism in a Francis Hydraulic Turbine

Abstract

Sediment erosion of hydraulic turbines has gradually become a key factor affecting their long-term stable operation. There are many different factors that can cause erosion in the Francis hydraulic turbine; among them, the vortex occurs in the turbine, which is also a negative factor for the unit. In this paper, the purpose is to study the complex erosion characteristics and specific influencing factor mechanism. The method is based on numerical simulation, combined with the verification data on site. Research results show that the differences in flow patterns among various components correspond to the erosion distribution of the unit at the same location, indicating that local flow patterns affect the unit’s erosion. The highest total erosion rate is on the surface of the runner at 1.08 × 10−3 kg·s−1·m−2. The erosion rate on the guide vane wall is second highest, also at 9.8 × 10−4 kg·s−1·m−2. The total erosion rate in the clearance is lower than that on the guide vane wall at 7.03 × 10−4 kg·s−1·m−2. The lowest total erosion rate is found in the draft tube at 2.57 × 10−4 kg·s−1·m−2. The effect of local vortices not only exacerbate the microscopic damage on the blade surface but also leads to a more obvious nonuniform erosion distribution, especially at the clearance, where erosion is more severe. The vortex in the guide vane passage alters the particle trajectory at the guide vane outlet, increasing the erosion in the guide vane clearance. Similarly, the vortex in the draft tube increases particle rotation, enhancing erosion on the draft tube wall. Research indicates that eliminating vortices is beneficial for reducing sediment erosion within the unit. The research results provide a theoretical basis for the optimization design of Francis hydraulic turbine.