Study On The Hydraulic Performance And Radial Gap Size Of The Full-flow Pump

The full-flow pump directly arranges the pump impeller inside the rotor of the motor to integrate the motor and the pump.Therefore,the full-flow pump is also called a motor pump.When the full-flow pump is working,the impeller rotates with the rotor.The water flows through the inner cavity of the rotor,and the rotor of the motor is in the fluid.The rotor of the motor belongs to the wet rotor.The full-flow pump has the characteristics of compact structure,flexible installation,simple pump room,etc.It is used more and more in engineering.However,there is a working gap between the stator and the rotor of the full-flow pump motor.There is gap backflow in the gap.The gap backflow can play the role of heat dissipation on the one hand,and affect the flow field of the impeller inlet on the other hand,and increase the friction of the motor rotor.The loss causes the hydraulic performance parameters of the full-flow pump to change.The change law has not been fully grasped so far.Therefore,the influence of the size of the gap on the flow rate of the full-flow pump gap.The hydraulic performance of the pump and the internal flow characteristics are considered to be the innovation and development of flow pumps are of great significance.In this paper,a full-flow pump was designed based on the axial pump model.Then the model pump was manufactured separately.The CFD technology was used to simulate the internal flow field of the common axial flow pump and the full-flow pump.The pump model test was carried out using a high-precision hydraulic mechanical test bench.The inflow characteristics and hydraulic performance of the axial flow pump and the full-flow pump with the gap d=0.65mm were compared and analyzed.The numerical simulation results were compared with the model test results to verify the accuracy of the numerical calculation.On the basis of the initial gap d=0.65mm full-flow pump,the size of the throttling gap d was changed.Then six schemes of d=0.4mm,1mm,1.5mm,2mm and 2.5mm were calculated,and the six schemes were coherent.The hydraulic performance and internal flow field characteristics of the flow pump under three characteristic conditions(Q=210L/s,Q=390L/s,Q=50L/s)were compared and analyzed.Finally,the axial-flow pump and the full-flow pump with the gap d=0.65mm(Q=270L/s,Q=390L/s,Q--470L/s)were subjected to unsteady calculation and radial distribution.The pressure pulsation of the axial distribution monitoring points was compared and analyzed.Through this research,it was found that compared with the ordinary axial flow pump,the efficiency of the full-flow pump in design condition is nearly 7%,the lift is nearly 0.23m,and the maximum lift in the saddle area is also reduced by 15%.The main reason is that the friction loss of the wet rotor disk of the ful-flow pump is large,which leads to the increase of the shaft power.Secondly,the flow field of the impeller inlet was deteriorated due to the backflow of the gap,which causes the impeller lift to decrease.The higher the lift,the larger the backflow of the gap and the more obvious the drop of the impeller.As the gap size increases,the friction loss of the rotor disk is basically unchanged,and the efficiency of the full-flow pump decreases.The efficiency of the maximum gap at the design flow rate reduced by about 1.8%compared with the minimum gap.Through unsteady calculation analysis,it was found that the pressure pulsation characteristics of the full-flow pump are similar to those of the axial flow pump.The pressure pulsation amplitude is slightly smaller than that of the axial flow pump,and the main frequency of the pressure pulsation is still the leaf frequency.