Numerical Analysis Of Hydrodynamic Characteristics Of Submersible Axial Flow Pumps With Unequal Blade Placement Angle

The angle of impeller blade for large and medium-sized axial flow pump is mostly adjustable.Because of the manufacturing accuracy,installation quality of blade,and loosing of the fastening bolts of blade during the operation etc.,the angle of each impeller blade of the submersible axial flow pump is not consistent.The inconsistency of impeller blade angle will greatly affect the hydrodynamic characteristics of pump system,when serious may cause vibration,blade cavitation or energy loss of the flow pump,even affect the safe operation and service life of pump.Therefore,it is necessary to carry out research on the influence of non-equal vane placement angle on the performance of axial flow pump.The research object in this paper is submersible axial flow pump.CFX software is used to numerically calculate steady and unsteady flow fields for the original scheme and 12 calculation schemes.The hydrodynamic characteristics of submersible axial flow pump system for each scheme is comparatively analyzed,which mainly including the comparative analysis of external characteristics,such as axial flow pump efficiency,head and shaft power,the comparative analysis of the flow patterns of the impeller inlet and outlet sections,the diffusion sections and outlet sections of the guide vane,and comparative analysis of the pressure pulsation characteristics of the monitoring points at the inlet and outlet of the impeller and the outlet of the guide vane,as well as the comparative analysis of the impeller transient radial force,axial force and shaft power.When the impeller blade is placed with non-equal angle,the main research conclusions are as follows:(1)The efficiency and head curve of the axial flow pump will be offset,and the shaft power will change regularly.When the positive angle of single blade or interphase blade increases,the efficiency curve of axial flow pump shifts to the direction of large flow rate,and the head and axial power increase.When the negative angle of blade angle increases,the efficiency curve of axial flow pump shifts to small flow direction,and the head and shaft power decrease.(2)The blade angle is not consistent,will increase the impeller blade pressure surface pressure,as well as suction surface inlet and outlet low pressure range,increase the blade work,more prone to cavitation.The pressure and velocity of each characteristic section have great influence on the flow uniformity of axial flow pump.Where the diffuser angle of the guide vane is larger,the range of the low-velocity area and the flow-off area on the rim side is significantly reduced.There are a large number of vortex areas at the outlet of the guide vane,the vortex intensity of each part of the guide vane is deepened,the range is increased and the vortex position changes.(3)The peak value of each measuring point at the impeller inlet and outlet increases,and the peak difference of trough increases with the increase of angle,and the pressure fluctuation is not uniform.When the angle changes too much,the main frequency or harmonic frequency becomes low frequency.The low-frequency pulsation at the outlet of the guide vane increases significantly.When the positive angle of the single blade increases,the pressure pulsation at each measuring point at the outlet of the guide vane increases,especially at the measuring point on the hub side.When the positive angle of the interphase blade increases,the pulsation amplitude at the hub increases,and vice versa.(4)When the positive angle of the blade placement angle increases,the pressure in each channel of the impeller changes unevenly,and the pressure on the surface of each blade changes unevenly,which in turn causes the shaft power to fluctuate.(5)The transient radial force and axial force of impeller have obvious changes.The change of single blade angle will greatly increase the transient radial force and amplitude of impeller.When the placement angle of single blade or interphase blade increases,the transient axial force of impeller increases,and the amplitude may increase significantly.On the contrary,the transient axial force of the impeller decreases continuously,and the amplitude becomes smaller.