| Centrifugal pumps are widely used in many fields,such as hydraulic,aerospace,chemical,fire protection and so on.As a key equipment,the pressurized medium is delivered to the various production steps and operating units of the system,which is the "heart" of the fluid delivery system,and its performance directly affects the overall operation of the system.Centrifugal pumps are divided into single-stage and multi-stage centrifugal pumps according to the impeller stage.Multi-stage centrifugal pumps have the characteristics of large flow rate and high head,but the structure of the impeller stages is complicated.Due to the flow interference and unstable flow between the impeller stages,It have a greater impact of hydraulic and vibration performance.The hydraulic characteristics and vibration performance are important indicators to measure the performance of the centrifugal pump.Therefore,analyzing the flow field characteristics and vibration characteristics of the multistage centrifugal pump is of great significance for the safe and stable operation of the equipment.Because the design of traditional centrifugal pumps seldom considers the matching relationship between the impellers of all stages,it is difficult to accord the performance requirements of multistage centrifugal pumps by simply relying on the speed coefficient method.On the basis of not changing the shape of the overcurrent parts,the clocking effect of adjusting its circumferential position has gradually become a new direction to improve the performance of multistage centrifugal pumps.In this paper,the clocking effect on the performance of multistage centrifugal pumps is studied.The influence of clocking effect on pump external characteristics obtained through experiments.The influence of clocking effect on pump internal flow and pump vibration characteristics analyzed by numerical simulation.The brief research contents of this article are described below:(1)Through external characteristic experiments on multi-stage centrifugal pumps,it is found that as the flow rate increases,the pump head gradually decreases,and the efficiency increases first and then decreases.The results of numerical calculation are compared with the experimental results.The maximum deviation of calculation head and experimental head is 2.4%,and the maximum deviation of calculation efficiency and experimental efficiency is 10%.The experiment and numerical simulation are in good agreement,which verifies the accuracy,reliability and applicability of numerical simulation method.(2)The internal flow field of the multistage centrifugal pump was numerically calculated based on CFX by designing 9 different schemes.It is found that the clocking effect will affect the internal flow of the pump:changing the static pressure distribution,reducing pressure pulsation,reducing local turbulent kinetic energy,and reducing fluid medium flow loss,thereby improving the hydraulic performance of the multistage pump.(3)The fluid vibration force and equivalent dynamic characteristics of the rotor were calculated for each scheme of the full flow field,and then the vibration simulation calculation of the multistage centrifugal pump was performed based on the commercial software Ansys Workbench.It is found that clocking effect has little effect on the axial force distribution and amplitude of the multi-stage pump,which reduces the radial force,the vibration displacement of the rotor,and the structural deformation of the pump shaft.Thus,the vibration characteristics of the multistage pump are improved. |
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