Study On Particle Flow Of The Screw Discontinuous Quantitative Feeding Performance

The screw feeder is the main unit of mechanized transportation in various departments of industry and agriculture.It can reduce labor intensity,improve work efficiency and has a wide range of applications.By means of screw feeding device,the discontinuous quantitative feeding of particulate materials can effectively isolate the external environment and improve the safety production efficiency.Discontinuous quantitative feeding by screw is one of the new development directions of the application of screw conveying technology,which has broad prospects in agricultural production.In this paper,two typical agricultural products,soybean and millet,were selected as the object of discontinuous feeding.The characteristics of particle flow in helical discontinuous feeding were studied to solve the problems of poor quantitative accuracy and low stability of helical discontinuous feeding.The main research contents and conclusions are as follows:(1)Theoretical analysis of particle flow characteristics of typical agricultural products with screw discontinuous feeding.The particle characteristics of typical agricultural products soybean and millet were analyzed.According to the characteristics of screw discontinuous feeding,the particle flow stability,feeding accuracy and its influencing factors were studied.Based on the analysis of particle contact force,the relationship between particle flow stability and contact force type,size and its change was studied.Through the analysis of screw discontinuous feeding between particles,particles and screw,particles and trough.The contact force between the screw and the trough is different,and the contact force is proportional to the particle radius or equivalent radius.On the basis of determining the size of the screw discontinuous feeder,the accuracy of the screw feeding is analyzed based on the single-loop feeding quantity,and the screw speed and material density are proportional to the single-loop feeding quantity.(2)Simulation and analysis of soybean particle flow characteristics with screw discontinuous feeding.The process of soybean particle screw discontinuous feeding was was carried out by rotating 60 degrees intermittently.The contact force between particles,the contact force between particles and screw,the contact force between particles and the trough under different rotating speeds,different discharging modes,different feeding modes and different screw were analyzed.The results show that with the increase of speed,the three contact forces in the choke scetion increase correspondingly,and the particle flow stability is the best at 120 rpm.The setting of the feeding device not only increases the contact force between the particles in the choke section,but also greatly improves the stability of the particle flow in the feeding section.The contact force between particles and screw is the largest and the stability of particle flow is the strongest when the single screw is set up with the dividing device,compared with the other three kinds of screw.In continuous preparation,the particles are relatively loose,which is not conducive to the stability of feeding.In one preparation,the contact force of particles is larger,the fluctuation of single-loop feeding volume is smaller,and the stability of particle flow and feeding accuracy are significantly improved.(3)Simulation and analysis of the flow characteristics of millet and mixed particles with screw discontinuous feeding.The screw discontinuous feeding process of millet particles and soybean millet mixed particles was simulated by intermittent rotation of 60 degrees.Based on the contact force curve of particles,the distribution characteristics of the contact force of the screw discontinuous feeding particles under different rotating speeds,different discharging modes and mixed particles were compared.The simulation results show that the contact force is the largest when the screw speed is 240 rpm,but with the continuous discharging of particles,the contact force will drop sharply;when the dividing device is set up,the distribution and peak value of contact force increase,which improves the stability and consistency of the screw discontinuous feeding particle flow;when the mass of 1:1 mixing particle is compared with the single feeding millet or soybean,its particle group and machine The contact force between particles is similar to that of individual millet particles.(4)Construction and experimental study of screw discontinuous feeding test system.A new screw discontinuous feeding machine was made by upgrading and improving the screw discontinuous feeding test system.The screw discontinuous feeding experiment was carried out for millet and soybean mixed particles.The effects of spiral speed,discharging device,millet and mixed particles on the screw discontinuous feeding were analyzed.The results showed that the standard deviation of single-loop discharging rate was the smallest when the rotating speed was 90 rpm,and the single-loop discharging rate of mixed particles was 0.49.The relative standard deviation is 10.3 %,which is less than that of a single millet particle.The stability and accuracy are improved obviously.The above conclusions have important guiding role and application value for further research and development of screw discontinuous feeder for agricultural products.