Research On Numerical Simulation And Control Of The Hot Chamber Ventilation System

In the nuclear industry’s production process,some substances that are hazardous or radioactive to humans and the environment are usually produced.Hot chambers are closed facilities dedicated to handling such hazardous materials.In order to prevent radioactive contaminated air and aerosols from uncontrollably escaping into the laboratory space outside the hot chamber,mechanical ventilation must be used to create a negative indoor pressure.Establishing a hot chamber environment model with high simulation accuracy,and determining the law of indoor negative pressure with flow rate and spatial distribution in the hot chamber ventilation system are the prerequisites for optimizing the hot chamber environment regulation.In this thesis,a single hot chamber is taken as the research object,and the indoor negative pressure is taken as the control target.Based on the Computational Fluid Dynamics(CFD)method,a CFD model of the hot chamber ventilation system is established,and a MATLAB/COMSOL collaborative simulation platform is set up.A CFD based method for identifying hot chamber system is designed.The hot chamber CFD model is converted into a negative pressure prediction mathematical model,and a negative pressure control method for hot chamber ventilation system based on predictive fuzzy PID is proposed.The main research contents of this thesis are as follows:(1)Based on the working mechanism of the hot chamber ventilation system,the basic equations of fluid dynamics,the flow similarity theory,and the standard K-εturbulence model,a geometric model,a grid model,a physical model,and a solver for the hot chamber are established.And a CFD numerical simulation of the hot chamber flow field is conducted.The effects of different hot chamber structures and different ventilation schemes on the pressure and flow field of the hot chamber are analyzed and verified.The numerical simulation results show that the CFD model of the hot chamber is consistent with the working mechanism of the hot chamber ventilation system.The model can be used to obtain the law of the change of negative pressure with the amount of exhaust air and its spatial distribution characteristics,which can provide a reference for the operation control and management of the hot chamber.(2)Based on Live Link?for MATLAB~?,a MATLAB/COMSOL co-simulation platform for the hot chamber ventilation system is built,which realized programming control,data processing,and analysis of the hot chamber CFD model.Subsequent system identification and control experiments are completed based on the co-simulation platform.(3)Based on the hot chamber CFD model,the boundary conditions are used as the input of the hot chamber ventilation system,and the negative pressure is used as the output of the hot chamber.The ARX model structure is adopted,and the recursive least squares method is used to identify the model parameters to obtain the mathematical model of the hot chamber negative pressure prediction.The model is compared and verified with the output of the CFD numerical simulation.According to the evaluation index,the identified model can be considered to reflect the law of the change of negative pressure and meet the requirements of prediction accuracy.(4)The negative pressure controller of the hot chamber ventilation system is designed based on the obtained negative pressure prediction model of the hot chamber.According to the characteristics of the hot chamber ventilation system,the characteristics of PID control,model predictive control and fuzzy PID control are analyzed.In order to improve the quality of negative pressure control of hot chamber,a negative pressure control method of the hot chamber ventilation system based on predictive fuzzy PID is proposed.The experimental results show that this method makes the system has strong adaptability,good robustness,and obvious advantages in comprehensive control effect.