| Centrifugal charging pump is one of the core power equipment of pressurized water reactor nuclear power plant,which belongs to nuclear safety level II equipment.The equipment has the characteristics of high head and high speed,and plays an important role in nuclear power system.Therefore,the analysis of the dynamic characteristics of the centrifugal charging pump is of great significance for ensuring the stability and safety of nuclear power plant units.In this paper,the full flow field model and rotor dynamics model of the charging pump in a nuclear power plant are constructed.The steady and unsteady flow field calculation and the rotor vibration characteristics calculation are carried out under dry and wet condition,and the cooling fan is analyzed by fluid-solid coupling technology.The specific work is as follows:1.Based on CFD numerical simulation,the fluid domain of the twelve-stage pump group was established,the steady characteristics of the internal flow field of the pump under small flow rate condition was analyzed.The distribution of pressure field,velocity field and turbulent kinetic energy of the whole unit of the pump under steady state were revealed.Taking the first three impellers as the unsteady research object,the unsteady characteristics of the flow field in the charging pump were analyzed,and the pressure fluctuation characteristics of the impellers and guide vanes were obtained.The transient radial excitation force acting on the impeller and rotor was obtained,and its frequency components were also explored.2.Based on the rotor dynamics software,the rotor under dry and wet condition was modeled,and the dynamic characteristics of the impeller seal clearance of the charging pump are analyzed by CFD method.The stiffness and damping coefficients of the impeller ring seal and guide bearing were fitted,and the influence of the liquid ring seal on the dynamic characteristics of the pump rotor was explored.By comparing the modal shapes and critical speeds under the two states,the effects of fluid annular seal and fluid softening on the rotor were preliminarily summarized.The natural frequency increase effect caused by the increase of the equivalent stiffness of the support point caused by the annular seal is more obvious than the frequency reduction effect caused by the softening effect of the impeller filling liquid.The rotor is changed from a ‘dry’ flexible rotor to a ‘wet’ rigid rotor.3.The vibration monitoring program of the field pump was developed,and the peak frequency of the power spectrum function curve of the vibration data was calculated by using the monitoring data.The natural frequency of the system when the rotor was working in a rigid state was determined,and the correctness of the established rotor dynamics model was verified.It provides a clear analysis path for the dynamic modeling simulation and model verification of the full-stage charging pump.4.Under the action of unbalanced mass,the displacement response of impellers at all levels under ’ dry and wet ’ state was explored,and the maximum radial displacement position and axis trajectory under two states were obtained respectively.5.The modal analysis of the cooling fan under different working conditions was carried out,and the stress and deformation of the fan after fluid-solid coupling were analyzed when considering the action of the external flow field.The comparative analysis shows that there is stress concentration in the ’ drilled ’ fan,and the position of the lost blade is obtained,and the rotor vibration response in the extreme flight state is also evaluated.The vibration analysis results show that the vibration variation of the rotor caused by the partially detached plastic blades in the rotor is small,and the fault is not easy to be detected.In a word,the work of this paper can provide technical support for the dynamic analysis and vibration troubleshooting of the charging pump rotor. |
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