Influence of Wall-Attached Vortices on the Pump Installed in the Suction Pipe of an Open Intake

Wall-attached vortices in pump intake commonly appear and damage the stability of the whole pump station. Revealing the effects of these vortices on the pump performance is crucial for safe operation. In this paper, scale-adaptive simulation based on the shear stress transport k-ω model was performed on a pump intake with an axial-flow pump installed in the suction pipe. Three submergences (3.0, 4.0, and 4.67 DL, where DL is the bell mouth diameter) and three flow rates (0.8, 1.0, and 1.2 Qd, where Qd is the design flow rate) were studied. It was demonstrated that the intake vortex structures were significantly different in the cases with and without the pump being installed. Under different conditions, the backwall vortices appeared first, then floor vortices and the sidewall vortices appeared at last. It was found that only backwall vortices entered the impeller. The strength of the vortices increased as the flow rate increased. The fluctuation of head and efficiency was related to the nonaxial inflow at impeller inlet. In order to evaluate the influence of backwall vortices, the entropy loss coefficient based on entropy theory was defined. It was found that, although flow separation occurred on the blades, the main source of entropy production was backwall vortices.