Flow Simulation And Analysis For The Rotor Chamber And The Collecting Tube Of A Rotor-jet Pump

The rotor-jet pump,also known as Pitot pump or the rotating-casing pump,falls into the category of very low specific speed pumps.The rotor-jet pump is featured by unique hydraulic components and operation characteristics.Relative to other single-stage centrifugal pumps,the rotor-jet pump adapts well to the requirements of low flow rate and high pump head.In recent years,the performance of the rotor-jet pump has been consistently improved;moreover,the pump structure has been optimized.Nevertheless,existing knowledge of the principles of the rotor-jet pump is far from adequate.Reliable design methods for the hydraulic components of the rotor-jet pump are still under investigation.Reliability and operation stability of rotor-jet pump products need to be further improved.Insufficient understanding of complex flows in the rotor-jet pump is a main factor hindering the technical advancement of the rotor-jet pump.This dissertation put emphasis on this subject.Considering the deficiency of available flow measurement techniques in the presence of the flows in the rotor-jet pump,computational fluid dynamics(CFD)was used as the primary instrument here.The major contents of the dissertation are following:(1)The operation principles and structural characteristics of the rotor-jet pump were briefly introduced.A comparison was implemented between the rotor-jet pump and other low-specific-speed pumps.Methods for studying inner flows of the rotor-jet pump were analyzed.The feasibility of applying numerical simulation in studying the flows in the rotor-jet pump was verified.(2)The geometric model of a rotor-jet pump,as well as the flow domain model,was constructed.Grids were used to spatially discretize the flow domain.The commercial CFD software was used as the solver for the governing equations of the flow considered.(3)Flows in the pump chamber and the collecting tube were analyzed based on numerical results obtained.Distributions of static pressure and velocity were compared for different flow rates;in particular,the disturbance of the collecting tube to the flows in the pump chamber was explained.Turbulent parameters were investigated as well for different flow rates.(4)Regarding the configuration of the guide plate in the collecting tube,flow factors were analyzed.Flow parameter distributions near the guide plate in the collecting tube were illustrated.The forces exerted on the whole collecting tube were calculated.The factors influencing the operation stability of the collecting tube were explained.The major conclusions obtained in the present study are as follows.(1)In the rotating chamber,both velocity and static pressure increase with the radial distance from the pump axis.In contrast,along the axial direction,the variation is fairly slight.Inlet flows at the collecting tube inlet are irregular,arousing high energy loss.(2)Around the collecting tube,intricate flow structures are witnessed.The intrusion of the collecting tube imposes an adverse effect on the averaged flow parameters in the rotating chamber,as is clearly evident at large flow rates.(3)The collecting tube influences the turbulent parameter distributions in the chamber.High turbulent kinetic energy occurs at the collecting tube inlet.Meanwhile,along the perimeter of the collecting tube,turbulent kinetic energy increases with the radial distance from the pump axis.(4)The force exerted on the collecting tube in the pump axis direction is considerably larger than its counterparts in the other two directions,as lends a support to the reason of the practical rupture of the collecting tube.The static pressure distribution near the guide plate varies apparently with the variation in the flow rate.