| As the main "going global" brand of China’s nuclear power,Hualong-1 and its auxiliary equipment are required to have advanced,economic,mature and reliable technical characteristics of three generations of nuclear power.The Hualong-1 VNA system(ventilation duct system of nuclear auxiliary building)undertakes the important task of discharging filtered gas from nuclear island plant,and has the discharge function of safety related CAV system(annular space ventilation system)and VFL system(nuclear fuel building ventilation system).In Hualong-1 nuclear power project,"obstacle" measurement and positioning technology and robot equipment are inseparable from micro gyroscope.The research on sensitivity and robustness of MEMS gyroscope is an important support to ensure the realization of technology and normal operation of equipment.In this paper,the dynamic equations of VNA system with various nonlinear and complex factors are established,and the dynamic response and safety performance of the system under various working conditions are analyzed.For the micro gyroscope system,this paper analyzes the sensitivity and robustness of the gyroscope based on the dual drive double detection four degree of freedom micro gyroscope model which is caused by the large deformation of the elastic beam of the driving module.The main research work and achievements are as follows:1.According to the actual engineering environment,a simplified VNA system dynamic model is established.The differential transformation method is applied to solve the natural vibration characteristics of multi-point constrained variable cross-section riser structure for the first time.The results show that: 1)compared with the pipe with constant outer diameter,the second-order and above second-order mode shapes of the pipeline with quadratic outer diameter function move up and the frequency is reduced;2)the "limit" effect of large constraint stiffness forces the low-order mode with high constraint stiffness to jump to the higher-order mode with low constraint stiffness;3)the near center symmetric elastic constraint layout scheme can make the vibration mode of the system present half stable and half bending The form of music.These results are rarely reported in the previous literature,which can provide theoretical support for the design of VNA pipeline and the layout of guide bracket.2.The vortex induced vibration model of VNA system is established,and the stability of the system is studied.It is found that the internal flow velocity does not cause flutter instability.The results show that: 1)in the different range of internal flow parameters,the vibration response under two frequency locking conditions will have different change rules;2)when different nonlinear stiffness parameters are selected,there is a specific set of amplitude and average velocity in pulsation The internal velocity makes the system jump back and forth frequently between almost periodic motion and periodic motion.This study is helpful to put forward the index requirements for the gas velocity in the pipeline in the overall design of VNA system,so as to ensure that the pipeline works in the response range of the stable solution.3.The dynamic behavior of VNA system under the action of internal velocity,vortex induced force and foundation excitation is studied.This paper presents an optimization design idea that the guide bracket is placed at the high elevation of the nuclear island shell,and the linear stiffness of each guide constraint is greater than the nonlinear stiffness as much as possible,which can avoid the violent oscillation near the response extreme value caused by the multi frequency excitation of seismic load under the design and accident conditions,and ensure the service life of the equipment.4.According to the technical requirements and standard specifications of the third generation nuclear power plant Hualong-1,the overall assembly model of the VNA system of the nuclear power unit is optimized and designed based on the qualitative analysis results of the nonlinear dynamics of the system.1)Through the simulation calculation,the safety performance of the equipment under the design and accident conditions is improved,and the relative dangerous parts of each structure of the system are determined;2)the requirements in the later use process are proposed;3)a group of optimized design schemes of the support in the VNA system engineering are proposed,which can effectively reduce the problem of insufficient bearing capacity of the weld.The structural design scheme can meet the important needs of the state in the independent research and development of the third generation nuclear power auxiliary equipment.5.In this paper,the dynamic equations of multi degree of freedom micro gyroscope considering the stiffness nonlinearity in two driving directions are established.The dynamic response of the system under the condition of main resonance is solved by using the multi-scale method,and the resonance characteristics of the system are analyzed.The results show that: 1)only when the nonlinear stiffness of the driving module is large,the dynamic characteristics of the drive and detection module will be significantly affected;2)the hardening characteristics of the nonlinear system show an atypical feature of bending down to the right;3)the amplitude jump phenomenon of the output response and the unstable multi solution region occur outside the working bandwidth of the drive module and the detection module,but within the bandwidth 4)the sudden change of working environment will lead to frequency drift,and then cause the change of resonance parameters in the system.The results show that this structure is helpful to the robust design of the system,but at the same time,the working conditions and processing errors in the nuclear island should be fully considered and corresponding error compensation should be made.6.The partial bifurcation analysis of multi degree of freedom micro gyroscope system is carried out,and the influence of system parameters and structural physical parameters on environmental robustness is discussed.The results show that: 1)in order to ensure that the micro gyroscope used in the special environment of nuclear power plant can have a large stable output response,the amplitude of electrostatic driving force should be taken as large as possible in the stable region on the premise that the driving voltage should not exceed the pull-in voltage;2)in order to maintain high robustness to the environment and strong resistance to sudden changes in external conditions during the system operation,it is necessary to At the same time,the amplitude of electrostatic force and the damping coefficient between the driving module and the elastic beam of the decoupling frame are increased to ensure the motion stability of the system.The research content closely fits the theoretical analysis with the optimization of engineering parameters,which is helpful to the further optimization of micro gyroscope structure.The above work has opened up the dynamic research field of VNA system of the third generation nuclear power Hualong-1 auxiliary equipment.By combining theoretical analysis with practical conditions,a new nuclear power exhaust duct structure is designed,and the nonlinear dynamic characteristics of the VNA system are revealed.This study can provide engineering reference for VNA system of Hualong-1 reactor,and provide theoretical basis for similar structures in other fields.At the same time,the research in this paper extends the nonlinear dynamics research of multi freedom micro gyroscope,and combines the system parameter analysis and robust design optimization closely.This research can provide theoretical support for the measurement and positioning technology in nuclear power engineering and the multi degree of freedom micro gyroscope product design applied in the robot equipment in the plant. |
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