Study On Stall Flow Characteristics And Generation Mechanism In Diffuser Vane Of Centrifugal Pump

Centrifugal pumps are prone to stall at low flow rate because of their positive diffusivity and large curvature of blades.Rotating stall is a common and dangerous form of stall.For vaned centrifugal pump,because of its special structure,unstable flow phenomena such as rotational stall are more likely to occur,resulting in Hump of pump flow head curve,low frequency pressure fluctuation,hydraulic excitation force,flow noise and other hazards.In view of the research situation that the main concern at home and abroad is placed inside the centrifugal pump impeller and the rotational stall in the vane is ignored,the main focus of this study is on the diffuser vane channel inside the vane centrifugal pump.This study based on the experimental test and numerical simulation results,the three-dimensional flow inside the vane channel of a vane centrifugal pump was studied.The main research contents include:?1?Numerical simulation of the pump in the whole working condition,systematically studied the influence of the vane on the performance of the centrifugal pump and the production interval of the hump area.?2?The mechanism of the internal rotation stall of the vane of the vane-type centrifugal pump is analyzed systematically,and the flow characteristics,development and propagation law are analyzed by the method of determining the rotational stall of the cross-power spectrum.?3?Comparing the internal flow characteristics of the impeller with and without diffuser vanes,and analyzing the influence of the vanes on the internal flow characteristics of the impeller.?4?Applying the Omega vortex identification method to identify the internal vortex of the diffuser vane channel in the characteristic working point of the hump area,and explore the development law of the vortex and the cause of the rotating stall.?5?Applying vortex volume integral to analyze the loss of different parts of the vaned diffuser centrifugal pump and explore the initial of the hump area.?6?A single variable analysis is carried out on the number of vanes and radial gap parameters,and the influence of the geometric parameters of the centrifugal pump on the rotational stall in the vanes is discussedThe results show that:?1?The vaned diffuser centrifugal pump will produce "hump"phenomenon in small flow conditions,and the diffuser vane in the non-hump section will have little effect on the internal flow of the impeller,but it will flow in the flow path of the impeller in the hump area corresponding changes have occurred.The flow state in the impeller flow channel of the peak section becomes better,and the flow state in the impeller of the trough section deteriorates.Corresponding changes occur in the internal loss of the fluctuating diffuser vane in the hump area.The loss curve and the hump curves are similar.?2?Under small flow conditions,the internal flow of the diffuser vanes is complicated,and the number of stalled cells will increase with the decrease of operating conditions,but the fluctuation frequency generated by the rotating stall will not be consistent with the change of operating conditions.In some operating conditions,there may be multiple forms of stall group motion in the diffuser vane.For example,the fixed stall and the rotating stall will occur simultaneously in the 0.35Q₀ working condition,when the stall cells rotates in the flow channel,it exhibits the characteristics of non-synchronous rotation.?3?By analyzing the vortex structure with strong rotation,it is found that the relative position of the vortex in the diffuser vane flow channel changes with the change of the operating conditions,and the vortex direction also changes.In the flow channel,it mainly exists in the form of streamwise vortex,circumferential vortex and spanwise vortex.?4?The factors affecting the inflow condition of the vane and the radial gap are studied.It is found that the stall type of the stall cell inside the vane is affected by both the number of vanes and the number of stalls.In this study,when the number of vanes is 9,the number of stalls is 3,and when the number of stalls is not an integral multiple of the number of vanes,the number of vanes only affects the rotation frequency of the stalls,and does not change the stall form of the cells;the radial gap changes the distribution pattern,rotation mode,rotation direction and pressure pulsation of the stall cells in the diffuser vane flow channel.