Influence of wall roughness on cavitation performance of centrifugal pump

Weihui Xu,Zhihao Huang,Xiaoke He,Weishu Wang,Xiao Hou

doi:10.1007/s40430-021-03023-3

Abstract

Cavitation is a phenomenon that occurs easily during rotation of fluid machinery and can decrease the performance of a pump, thereby resulting in damage to flow passage components. To study the influence of wall roughness on the cavitation performance of a centrifugal pump, a three-dimensional model of internal flow field of a centrifugal pump was constructed and a numerical simulation of cavitation in the flow field was conducted with ANSYS CFX software based on the Reynolds normalization group k-epsilon turbulence model and Zwart cavitation model. The cavitation can be further divided into four stages: cavitation inception, cavitation development, critical cavitation, and fracture cavitation. Influencing laws of wall roughness of the blade surface on the cavitation performance of a centrifugal pump were analyzed. Research results demonstrate that in the design process of centrifugal pumps, decreasing the wall roughness appropriately during the cavitation development and critical cavitation is important to effectively improve the cavitation performance of pumps. Moreover, a number of nucleation sites on the blade surface increase with the increase in wall roughness, thereby expanding the low-pressure area of the blade. Research conclusions can provide theoretical references to improve cavitation performance and optimize the structural design of the pump.

Highlights

In the local area of pump flow passage during operation, transporting liquid is vaporized to bubbles when the absolute pressure of liquid is lower than the vapor pressure under current temperature
To verify the accuracy of numerical simulation on flow law in the internal flow field of a centrifugal pump, the test results of the external characteristics of the pump were compared with the predicted results in numerical simulation under constant conditions
Considering the influences of grid size on meshing quality, we can view the numerical simulation results in high accordance with the rated values of characteristic parameters, which proves the reasonability of the model setting and reliability of the calculated results. These results enable us to analyze the influences of wall roughness on the cavitation process

Summary

Introduction

In the local area of pump flow passage during operation, transporting liquid is vaporized to bubbles when the absolute pressure of liquid (generally water) is lower than the vapor pressure under current temperature. Breakage of bubbles occurs exceptionally on the surface of the flow passage and may form a high-speed microjet at the boundaries of solids. When the shock pressure produced by the implosion of bubbles is stronger than the ultimate mechanical strength of materials, pits that are micrometers big in diameter are formed on the solid wall. These pits accumulate continuously and develop into sponge-like plastic deformation and fall off. Roughness is an important physical factor that influences cavitation performance of hydraulic machinery and relevant studies are mainly based on axial flow pump and pump turbine [9,10,11]. Effects of roughness on the operation of hydraulic machinery remain unknown

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