Effect of different blade numbers on the radial force of pump as turbine in transient process

In order to analyze the influence of the number of blades on the radial force characteristics of pump as turbine during the variable flow rate transition process, six impellers with different number of blades are designed. On the basis of verifying the correctness of the numerical calculation method by the external characteristic experiment, the steady and unsteady numerical simulation of each scheme is carried out by ANSYS-CFX software, the radial force characteristics on impellers with different schemes are compared and analyzed. The results show that during the transition process of variable flow rate, the radial force vector and its fluctuation range on the impeller gradually decreases with the increase of the number of blades. The radial resultant force obviously increases with the increase of time in the transition to large flow rate, and obviously decreases with the increase of time in the transition to small flow rate. The dominant frequency of the radial force is equal to leaf frequency, and the pulsation amplitude of the radial force of Z9 is the minimum in both transition processes. In the transition process of variable flow rate, when the number of blades is Z9, the efficiency is the highest, the radial force on the impeller is the minimum, and the pulsation amplitude of the radial force is also the smallest, so for this pump as turbine, the value of blade number equals 9 is the optimal. © 2021, Turbomachinery Society of Japan. All rights reserved.