Design And Research Of Hydraulic System Of A Test Rig For A Large Thrust Bearing Lubricated By Oil

Thrust bearing,as the core component of the nuclear reactor coolant pump,is used to carry the axial thrust of the RCP,which is the key to the safe operation of the RCP.At present,most of the domestic RCP depends on the import,so the localization of thrust bearing has become an important part of accelerating the independent construction of the RCP in China.The mainly reason of backwardness in domestic bearing manufacturing technology is the lack of relevant key test technology and test equipment in the bearing industry.It is very important to develop a stable and reliable thrust bearing rig for research the influencing factors of thrust bearing performance,improve the manufacturing technology of thrust bearing,and test the rationality and reliability of thrust bearing design.In this paper,the thrust bearing test rig can simulate the load applied to the thrust bearing when the impeller rotates under complex operating conditions,its loading process and accuracy play a decisive role in the accuracy of the test results.Therefore,improving the loading characteristics of the test rig has become the focus of this research.This paper discusses the development status of thrust bearing test rigs in the domestic and foreign,and the four loading methods commonly used in test rigs.The structure and test process of the bearing test rig with the structure and working principle of the loader device were briefly introduced.According to the specific technical requirements of the hydraulic system of the test rig,the loading force control system is defined as the focus of this research.The control mode and pressure regulation mode of the hydraulic system are analyzed,and the closed-loop loading force control system with servo proportional valve,loader and force sensor as the core is determined.A schematic diagram of the hydraulic system is designed which includes the loading system,the hydrostatic bearing system and the oil return system.Calculate the parameters of the main components of the hydraulic system,and select the type and determine the specification parameters.In this paper,the transfer function of the closed-loop loading force control system is derived,and its stability is judged by the Bode diagram.The dynamic response simulation model of the main components and the entire closed-loop loading force control system was built using the Amesim software platform,and the dynamic characteristics and steady-state error of the system were analyzed.Because the system cannot meet the technical requirements of rapidity and accuracy,the system is calibrated by fine-tuning PID parameters,and the result of system calibration meets the technical requirements.In order to reduce the hydraulic shock,this paper adopts the force/position hybrid control and the open/closed-loop switching control method respectively,and compares the advantages and disadvantages of the two control methods.The results show that with these two control methods,the response speed and loading accuracy of the system meet the technical requirements,and the hydraulic shock is also reduced.After comparison,the force/position hybrid control is better than the open/closed-loop switching control in system performance,and the open/closed-loop switching control is better than the force/position hybrid control in actual implementation.Considering the actual production,it is finally determined to adopt the open/closed-loop switching control.This paper further research the influence of open-loop gain and cylinder dynamic orifice size on system performance under open/closed-loop switching control.The results show that reducing the opening ring gain and increasing the damping hole can reduce the hydraulic impact of the system,but the damping hole should not exceed 2mm.