Influence Of Fluid Exciting Force In A Low Specific Speed Centrifugal Pump On The Dynamic Characteristics Of The Rotor

Low-specific-speed centrifugal pump with small flow and high head characteristic is widely used in petrochemical,coal chemical,nuclear power and pharmaceutical industries.With the continuous development of the process industry,the development of centrifugal pump with high head and high power.The unsteady flow inside the centrifugal pump is more complex,and the fluid exciting force generated by the complex unsteady flow inside the centrifugal pump will intensify the vibration of the centrifugal pump.In this paper,the unsteady numerical of the whole flow field of the low-specific-speed centrifugal pump was carried out,and the fluid exciting force acting on the impeller was loaded on the rotor structure,so as to study the influence of fluid exciting force in the low-specific-speed centrifugal pump on the dynamic characteristics of the rotor.The main research contents are as follows:(1)The fluid domain and solid domain models of low-specific-speed centrifugal pump were established.And FLUENT was used for unsteady flow calculation.ANSYS Workbench was used for rotor dynamics calculation.(2)Based on the numerical simulation results of the whole flow field of the model pump,the pressure pulsation analysis in the low-specific-speed centrifugal pump was carried out,and the analysis results can be obtained as follows: The main frequency of pressure pulsation is the passage frequency of long and short blades,and the secondary frequency is the passage frequency of long blades.The more the centrifugal pump deviates from the rated operating condition,the more uneven the pressure pulsation distribution in the guide vane passage.The main frequency and the secondary frequency of the pressure pulsation in the centrifugal pump are related not only to the number of impeller blades but also to the speed of the centrifugal pump.The inlet pre-whirl speed has little effect on the pressure pulsation in the centrifugal pump.(3)A comparative study on pressure pulsation and external characteristics of low-specificspeed centrifugal pump was carried out.The results showed that the main frequency of pressure pulsation obtained in the experiment was the passage frequency of long blade,and the secondary frequency was the passage frequency of short and long blade.Moreover,the amplitude of pressure pulsation in the main frequency was much larger than that in the secondary frequency.The external characteristic curves obtained by experiment and numerical simulation are basically consistent,and the error is within the allowable range,which verifies the accuracy of numerical simulation.(4)The characteristics of fluid exciting force on impeller under unsteady flow were analyzed.The results show that the main frequency of the fluid exciting force acting on the impeller is the axial frequency,and the secondary frequency is the passage frequency of the long and short blades.The smaller the flow rate is or the higher the speed is,the greater the fluid exciting force acting on the impeller will be.The larger the inlet pre-whirl velocity,the smaller the amplitude of the fluid exciting force acting on the impeller.(5)The critical speed of the centrifugal pump rotor system was calculated,the analysis of modal vibration was made,and the bearing vibration characteristic was analyzed after loading the fluid exciting force.The results show that the critical speed of wet state is more accurate than that of dry state.The vibration of centrifugal pump rotor system mainly comes from the fluid exciting force generated by unsteady flow.