Numerical research on viscous oil flow characteristics inside the rotor cavity of rotary lobe pump

Abstract

In order to reveal the influence of medium viscosity on flow characteristics in rotary lobe pump, the flow of five media with different viscosities, ranging from 1 (cst) to 110 (cst) has been studied in this paper. Based on the dynamic mesh model and the deformation technology of local grid reconstruction, the effects of viscosity, gap structure and speed on flow rate and pressure were investigated by transient numerical simulation, which were also verified by experiments. The results show that the viscosity has a significant influence on the performance of rotary lobe pump. With the increase in viscosity, the flow of fluid in rotor cavity tends to be steady. And the viscosity force could hinder the leakage flow of the medium in rotor cavity to some extent. The change in viscosity of the fluid medium would affect its outlet flow rate, and the outlet flow rate of 110 (cst) medium is 40% higher than that of the 1 (cst) medium. As the rotational speed is reduced from 400 (r/min) to 100 (r/min), the outlet flow rate decreases by 95% at 11 (cst) and by 80% at 72 (cst). Additionally, compared with the fixed gap structure, the gradient gap structure can effectively optimize the flow pulsation in the low-viscosity fluid, which reduces the pressure fluctuation by more than 30%.