Numerical simulation of the influence of elbow inlet passages on the hydraulic characteristics of vertical axial-flow pumps

In order to investigate quantitatively the influence of elbow inlet passages on the hydraulic characteristics of axial-flow pumps and achieve performance prediction, the time-averaged Navier-Stokes equations and standard turbulence model were adopted to simulate the three-dimensional flow field of an elbow inlet passage with an axial-flow pump. The characteristic curves of discharge vs. head, power and efficiency of the pump were obtained and compared with those obtained under standard flow conditions. Within the range of computed discharges and under the flow conditions supplied by the elbow inlet passage, the head and efficiency of the pump dropped averagely by 8.62% and 5.74%, respectively, while the shaft power approximately increased by 3.56%. The efficiency at the best efficiency point (EFP) dropped by 5.99% and the corresponding discharge decreased by 8.59%. Through computation and comparison of five design schemes of elbow inlet passage, it is found that swirl angles at the outlet section of elbow inlet passage correlate closely with pump performance and the maximum difference of the pump efficiency can be as high as 4.34% at a certain discharge. Hence, for the purpose of guaranteeing high efficiency and safety operation of pump, more attentions should be paid to the optimization of hydraulic design of inlet passages and object-oriented design of pump to improve flow conditions of pump and reduce effect of inlet passage on pump hydraulic performance.