| High temperature gas cooled reactor(HTGR)is the fourth generation of nuclear reactor which will be developed in China in the next fifty years.Because of its intrinsic safety characteristics,it has been recognized by the international nuclear energy community.It is very important to separate the coated fuel particles according to the sphericity by using the inclined vibrating plate in the fuel element manufacturing of HTGR.However,the current separation equipment can’t meet the development needs of HTGR in terms of accuracy and efficiency.With the development of computer technology,discrete element method(DEM)has become an effective method to predict and analyze the dynamic characteristics of particle system.In this study,the separation mechanism of coated fuel particle sphericity separation equipment is studied by DEM numerical simulation,and the optimized separation process parameters as well as new equipment design scheme are proposed.The main research contents are as follows:(1)The geometric model of real coated nuclear fuel particles based on super-ellipsoid was established,and the separation mechanism and characteristic of nuclear fuel particles in inclined vibration separation equipment were studied by DEM numerical simulation.The super-ellipsoid particle model of DEM was used to model the real coated fuel particles according to their sphericity and size distribution.A quantitative analysis method was proposed to evaluate the separation result.The separation characteristics of particles with different sphericity on IVP were studied by this analysis method.Based on DEM,the relationship between amplitude and frequency of inclined IVP was studied,and the relationship was connected by comprehensive factor of frequency and amplitude.On this basis,the effects of different operating parameters,feeding parameters and physical parameters on the results of particle separation were explored,and the optimal design parameters of IVP were obtained.The simulation results showed that using the optimal design parameters could greatly improve the feeding rate of the existing separation equipment,and the separation accuracy could reach more than 99%.(2)A new type of feeding system with stable,efficient and large flow rate for coated fuel particles was designed,and its effectiveness was verified by DEM numerical simulation.The feeding system consisted of a feeding hopper to control the feeding rate and a multi-layer multichannel feeder to control the particle distribution.The accuracy of the hopper model and DEM algorithm was verified by hopper experiment,and the influence of different filling height,particle diameter,hopper half angle and outlet diameter on mass flow rate was obtained by numerical research.The distribution and movement characteristics of the particles in the feeder are studied,and it is proved that the feeder can meet the feeding requirements of the separation equipment.(3)A new type of conveyor belt sorting equipment was developed,which could avoid the efficiency reduction caused by the violent movement of particles in the traditional inclined vibration separation equipment.The optimal equipment design and process operation parameters are obtained by DEM numerical simulation.Each process parameter was individually controlled to study its influence on separation.The effects of inclination angle,belt speed,sliding friction coefficient,restitution coefficient and rolling friction coefficient between belt and particles on the separation of coated nuclear fuel particles were studied by orthogonal experiments,and the optimum equipment design and process operating parameters were obtained.This study provides an effective research method for particle sphericity separation,and provides an optimized scheme for high temperature gas cooled reactor particle separation system,which provides guidance for the manufacture of particle separation equipment. |
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