| Multistage centrifugal pumps are an important fluid machinery in the field of fluid transportation,and are widely used in various fields of the national economy and national defense construction.And multistage centrifugal pumps have the advantages of high head and large flow,but the problems of vibration and noise during operation restrict their development.Rotor-stator interference inside the pump,secondary flow,and non-uniform flow at the blade outlet are the main factors for vibration.Among them,the unsteady pressure pulsation caused by the rotor-stator interference and the vane outlet shedding vortex is the main reason.Changing the outlet shape of the pump impeller blades and reducing the impeller-volute interaction by increasing the radial gap can effectively reduce the unstable flow caused by the interference between the volute and the impeller.A two-stage centrifugal pump with six two dimensional blades is used for this paper.Through numerical simulation and experimental verification,the influence of the change of the blade outlet shape on the performance and pressure pulsation of the two-stage centrifugal pump is analyzed.The main research contents of this paper are as follows:(1)Use UG to establish the full flow field and volute stator structure of two-stage pumps with different blade outlet shapes,and use ANSYS ICEM to mesh the fluid domain and volute solid domain respectively.In order to analyze the performance and pressure results of the two-stage centrifugal pump,the CFX and Workbench software is used to solve the fluid domain and solid domain.The external characteristics and vibration results obtained by numerical simulation are consistent with the experimental results,which confirms the accuracy of the simulation.(2)Through the analysis of the performance and internal flow of the pump with different blade cutting shapes,it is found that the cutting depth has a damage impact on the performance of the two-stage pump,and the head will gradually increase with the increase of the cutting depth.The decrease of the pressure and excessive cutting will damage the performance of the two-stage pump.Turbulent kinetic energy and impeller entropy production will also increase with the increase of the cutting depth.So the loss of the blade will increase.However,the modified scheme increases the surface pressure of the blade,which can effectively ensure the performance stability of the two-stage pump.(3)Through the analysis of the influence of different blade outlet structures on the circumferential pressure pulsation of the two-stage pump volute.It is found that the pressure distribution at the circumferential monitoring point of the volute is periodic.And as the cutting depth increases,the main frequency amplitude decreases continuously.At the same cutting depth,the elliptical outlet shape is better than the V-shaped outlet shape,and the plan of cutting below2 mm depth,the pressure pulsation amplitude,vibration energy and pressure pulsation coefficient of the elliptical outlet shape are better than the V-shaped outlet shape.(4)Under the design conditions,through the analysis of the vibration characteristics of the modified two-stage pump,it is found that the elliptical cutting of 1mm and 2mm has obvious improvement effects on the vibration acceleration frequency domain,vibration intensity,and vibration displacement of the vibration monitoring point.(5)This article explores the influence of different impeller outlet structures on the pressure pulsation and vibration of the two-stage pump from the two dimensions of the blade outlet shape and the impeller cutting depth.However,the impeller cutting depth and the impeller outlet shape are two variables,as well as the outlet angle and The change of cross-sectional area will affect the comprehensive performance of the two-stage pump.Considering factors such as the performance,entropy production,pressure pulsation and vibration,the elliptical cutting 1mm plan has a stable and effective improvement effect,and has a certain engineering practice value. |
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