Dynamic Characteristics Of Water-lubricated Guide Bearing And Optimization Design Of Rotor Dynamics For Reactor Coolant Pump

The nuclear reactor coolant pump(RCP)is the core of the nuclear power plant and the only high-speed rotating equipment in the primary circuit system as the key equipment to control the coolant circulation in the nuclear reactor island.The RCP not only operates under extremely complicated operating conditions,but also requires long-term continuous operation without failure.Bearing plays an important support component in the rotating parts of the RCP.In the design process,not only the bearing capacity and lubrication performance should be considered,but also the effect of the bearing on the dynamic characteristics of the rotor system should be analyzed,so the dynamic characteristics of the bearing and the reliability of rotor system dynamics design play a crucial role to guarantee the safe and stable operation of the RCP.Combined with the Science and Technology planning project of Sichuan Province"Research on optimal design theory and method of RCP based on multidisciplinary"and the project entrusted by enterprises,this paper takes the"rotor-support system"of a shaft-sealed RCP as the research object,and the method of numerical simulation was used to analyze the influence of geometric parameters on the dynamic characteristics of water-lubricated guide bearing.On this basis,the influence of the water-lubricated guide bearing on the rotor dynamics of the RCP and the optimization of the geometric parameters of the water-lubricated guide bearing were further analyzed.The main research content and results are as follows:(1)Analysis of the influence of geometric parameters on the dynamic and static characteristics of the water-lubricated guide bearing of the RCP.Taking the geometry parameters of the bearing as variables,the influences of the geometric parameter(eccentricity,aspect ratio,radius gap)on the static characteristics(bearing capacity,power loss,the maximum liquid film pressure,the minimum liquid film thickness)and dynamic characteristics(stiffness coefficient and damping coefficient)of water-lubricated guide bearing of RCP under different working conditions were analyzed by numerical simulation.The results show that the static characteristic index values of the water-lubricated guide bearing increase with the increase of eccentricity,aspect ratio and rotate speed,and decrease with the increase of radius gap under both normal and accident conditions,while the index values of static characteristics under accident conditions are smaller than those under normal conditions.The influence of geometric parameters on the dynamic characteristics of the water-lubricated guide bearing is greater at high rotate speed,while their magnitude range basically does not change with the change of geometric parameters.The stiffness coefficient is basically kept in the magnitude range of 10~8,and the damping coefficient is basically kept in the magnitude range of 10~7.(2)Based on the orthogonal test method,the sensitivity analysis and optimization of geometric parameters for the dynamic characteristics of the water-lubricated guide bearing of the RCP were conducted.Taking bearing capacity,power loss and stiffness coefficient as the optimization objectives,sensitivity analysis of eccentricity,aspect ratio,radius clearance and rotate speed is carried out to explore the primary and secondary relationship of their influences on the dynamic characteristics of the water-lubricated guide bearing and the optimal combination of geometric parameters.The results show that the aspect ratio is the most vital factor affecting the bearing capacity and stiffness coefficient,and the rotate speed is the most crucial factor affecting the power loss.Under the design speed of the RCP,the optimal geometric parameters combination for improving bearing capacity of bearing’system and reducing power loss is suggested as follows:eccentricity of 0.4,aspect ratio of 0.9,and radius gap of 0.2mm.In order to ensure the stiffness of the bearing,the optimal combination of geometric parameters is suggested as follows:eccentricity of 0.7,aspect ratio of 1.1,and radius clearance of 0.15mm.(3)Analysis of influence of geometric parameters of water-lubricated guide bearing on rotor dynamic characteristics of RCP.Based on the dynamic characteristics of water-lubricated guide bearing,the modal analysis and harmonious response analysis of the rotor of RCP are carried out to obtain the natural frequency and vibration mode changes of the rotor of RCP under different geometric parameters of water-lubricated guide bearing,and the influence of geometric parameters on the dynamic characteristics of the rotor of RCP is analyzed.The results show that the geometric parameters of the water-lubricated bearing have a weak influence on the modal vibration of RCP,and the vibration direction of each component is basically the same.The critical speed of the rotor system is mainly affected by the aspect ratio,followed by the influence of the radius gap.The geometrical parameters of the water-lubricated bearing have little effect on the vibration frequency of the RCP rotor harmonic response vibration graph,but it has an effect on the amplitude of the vibration direction.Rotation speed is the biggest factor that affects the vibration amplitude of shafting,and the influence of eccentricity is the smallest.The research results of this project have been successfully applied to the localization of a large shaft-sealed RCP,and the key technical problems of the optimal design of the geometric parameters of the water-lubricated guide bearing and the comprehensive optimization of the rotor dynamics of the RCP have been solved,which proves that the research methods and techniques adopted are feasible and reliable.