Impact of volute inlet cross-section on the hydraulic turbine radial force

Radial force is one of the important factors affecting the operation stability of the hydraulic turbine. Alternating radial force loading on the hydraulic turbine shaft successively can induce a certain deflection, and other problems like vibration. The volute parameters are closely related to the radial force performance of the hydraulic turbine. In this paper, the volute of a single-stage hydraulic turbine was redesigned, and the ANSYS-FLUENT software was used to study the radial force performance of the hydraulic turbine of different volute inlet cross-sections. And also the changes of the turbine performance were analyzed. The results show that the radial force increases linearly with the increase of the volute inlet cross-section diameter. When the volute inlet cross-section diameter is greater than a critical value, there is a slow decline of the radial force. The relative position between the tongue and the resultant radial force direction is between 60°~90° at a low flow rate, and about 110°~150° at a high flow rate. The flow across the tongue region has a strong influence on the distribution of the radial force. Furthermore, the turbine efficiency with the redesign of the volute is higher than that of the original one.