Simulation and experiment of the effect of clearance of impeller wear-rings on the performance of centrifugal pump

Abstract

The effect of clearance of impeller wear-rings on the performance of a centrifugal pump was investigated numerically and experimentally. The whole flow field model including front and back shrouds of pump was designed so as to accurately calculate the head and efficiency of the centrifugal pump. Based on RNG k-ε turbulence model, three wear-rings schemes were established, and the effects of clearance of impeller wear-rings on the hydraulic efficiency and mechanical efficiency of the centrifugal pump was analyzed, chiefly from the turbulent kinetic energy, vorticity and radial force angles. According to the results, it can be drawn that the head and total efficiency of the centrifugal pump increase as the clearance value of wear-rings narrows. The following reasons may account for it: firstly, as the clearance value of wear-rings declines, the turbulent kinetic energy and energy dissipation decrease within the impeller, and the impact of secondary flow at the inlet of impeller on the mainstream weakens slowly, which leads to a lower hydraulic loss, thus a higher hydraulic efficiency; secondly, radial force decreases with the clearance value of wear-rings, so the eccentric whirl of centrifugal pump is dampened, which results in a lower mechanical loss and a higher mechanical efficiency; thirdly, the front shroud leakage diminishes with the clearance value of wear-rings, therefore, the volume loss is reduced and volume efficiency improved. Finally, the first wear-ring scheme of impeller is adopted after comprehensive comparison of these three wear-ring schemes, because its efficiency is highest and it satisfies the requirements of the engineering application.