Numerical Study On The Clocking Effect In A Multistage Centrifugal Pump

The clocking effect has great influence on the hydraulic performance and pressure pulsation for a multistage centrifugal pump.This paper based on the commercial CFD software,a medium specific speed two-stage centrifugal pump was set as the research object,3D unsteady viscous numerical method and standard k-epsilon turbulence model were applied to discuss the clocking effect on a multistage centrifugal pump under design conditions.Main work includes the following two parts:On the one hand,the discussion of rotor clocking effect.This paper kept the first impeller position unchanged and defined that secondary impeller every 5 degree rotating out of a clocking position relative to the first impeller.External characteristics,inner flow,pressure fluctuation,radial force and axial force of impeller and vorticity were analyzed in the multistage centrifugal pump at four different clocking position.The results show that the change of clocking position of impeller influenced the head to 2.9% and the efficiency to 2.4%.Internal flow field distribution in the first impeller was almost not affected by the clocking position,but it could improve the flow field in the outlet of secondary impeller and reduced blade load when the impeller staggered 15°.The impeller clocking position had no influence on pressure fluctuation in the first stage.However the change was relatively obvious in the secondary impeller and volute,which was mainly manifested as the phase deviation and the maximum amplitude reduce 20.21% in the impeller and 7.45% in the volute.The amplitude of radial force at blade passing frequency and vorticity of the secondary impeller decreased after the circumferential position adjustment of the impeller,but it had little influence on the distribution of the axial force.The Research was supported by the National Natural Science Foundation of China(51339005,51279160),Specialized Research Fund for the Doctoral Program of Higher Education of China(20126118130002).On the other hand,the discussion of stator clocking effect.This paper kept volute position unchanged and defined that radial guide vane every 13 degree rotating out of a clocking position relative to the tongue of volute.External characteristics,inner flow characteristics,pressure fluctuation and radial force of impeller were analyzed in the multistage centrifugal pump at four different clocking position.It was found that with the change of clocking position,the head of pump first decreased and then increased and then decreased and efficiency change was just opposite to head;the maximum pump head was 0.39 meter greater than the minimum pump head,the highest efficiency was improved by 0.11% compared with the lowest value.It could also be found that clocking position may affect the velocity and pressure distribution in the first stage and secondary impeller and the influence of the first stage was larger than that of the secondary.Clocking position had no influence on pressure fluctuation of volute,but the change was relatively obvious in radial guide vane,which was mainly manifested as the phase deviation and the maximum amplitude decrease of the pressure pulsation.Reasonable clocking position can change the amplitude of radial force at blade passing frequency and the minimum amplitude was 4.64% smaller than the maximum amplitude.