Effects of Different Blade Numbers on Radial Exciting Force of Lobe Pump Rotor

Abstract

In order to clarify the relationship between different blade numbers and radial exciting force of the rotary lobe pump rotor, five rotary lobe pumps with different blade numbers were researched based on the dynamic mesh techniques using RNG k-ε turbulence model and PISO algorithm. The internal flow characteristics in the pump are compared and the influence mechanism of the different blade numbers on the transient flow structure and the exciting force inside the rotor cavity are revealed. Meanwhile, through numerical simulation and experimental verification, the comparative analysis of numerical prediction shows that the relative error is less than 5.6%, and the numerical simulation has higher accuracy. The results show that the number of blade has a significant effect on the flow characteristics and radial exciting force distribution of rotor cavity of the rotary lobe pump. With the increase of the number of blades, the average flow rate and the flow pulsation amplitude of the flow rate at the outlet of the pump are obviously decreased, which effectively inhibits the secondary flow, vortex and the velocity abrupt change between the rotor gaps region of the rotor cavity. The maximum radial exciting force at 6 blade numbers is less 36% than that at 4 blade numbers. A multistage series transition cavity is formed between the high-pressure cavity and the low-pressure cavity when the blades number of 5 and 6 which can effectively reduce the pressure difference between the two sides of the radial gaps. It can reduce the radial leakage, and effectively suppress the instantaneous pressure relief effect caused by the instantaneous opening of the gaps.