Abstract
The leakage flow paths in the sidewall gaps of centrifugal pumps are of significant importance for numbers of effects. The paper is concerned with the transient flow in the leakage flow paths with wear ring clearance variation. For this purpose, numerical simulations of the whole pump were carried out. The grid dependence and yplus check were performed first. Additionally, experimental data of performance characteristic and pressure fluctuation inside the sidewall gap was used to validate the numerical results. The transient velocity fields inside the sidewall gaps during one blade passage period were simulated. And the leakage through the wear ring gap was obtained for all operating points investigated. To have a better idea of attenuation and propagation of pressure inside the sidewall gap, the unsteady pressure distributions in the gap were calculated. Additionally, the surfaces of the impeller were divided into four parts. The fluid force on each part was expressed as a percentage of the total radial force. Through comparing the flow fields, the pressure distributions, and the radial force between the pumps with different wear ring clearances, the effects of the wear ring clearance were discussed in detail. The results can be used to guide the optimum design of the pump sidewall gaps.
Highlights
Leakage flow paths between the rotating impeller and the stationary housing play an important role in centrifugal pumps
Uy and Brennen [4] and Adkins and Brennen [5] indicated that the leakage flow from the impeller outlet to the front sidewall gap can produce great hydraulic forces, which can take up 70 percent of the total radial force and 30 percent of the total tangential force
Guinzburg et al [6] investigated the influence of the gap size between the shroud and the casing on the hydraulic force, and the results show that the decreasing leakage gap size can increase the force
Summary
Leakage flow paths between the rotating impeller and the stationary housing play an important role in centrifugal pumps. The gaps in the leakage flow paths can greatly affect pump performance. A larger gap size can decrease the disk friction and increase the leakage flow rate, according to the study conducted by Gulich [1]. Increasing the length and surface roughness of the gap clearance will increase the pump losses and reduce the leakage flow rate [2]. The swirling flow and nonuniform pressure distribution induced by the leakage in the sidewall gaps are the main sources of the radial force [3]. Uy and Brennen [4] and Adkins and Brennen [5] indicated that the leakage flow from the impeller outlet to the front sidewall gap can produce great hydraulic forces, which can take up 70 percent of the total radial force and 30 percent of the total tangential force. Hsu and Brennen [7] presented the effect of swirl at the leakage path inlet on unsteady hydraulic force, which indicated that the increasing swirl can make the forces unstable
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