Research On The Structure Design Of The Distributor Of The Downgraded Shallow Circular Silo And Its Influence On The Ventilation Effect

The risk and uncertainty of the global grain market have increased significantly,which has brought great challenges to China’s grain production.At present,more than half of China’s food consumption is non ration food,mainly including meat,eggs,milk and oil.Its production and transformation are inseparable from soybeans.Therefore,the food security in the new era should not only ensure the food security of staple food,but also strive to ensure the safety of soybean.Domestic soybean storage is mostly shallow silo storage.The phenomenon of automatic grading of soybeans after flowing into the shallow silo is serious,which leads to uneven distribution of porosity in the grain pile,resulting in high local temperature in the grain pile,which is not conducive to the long-term storage of grain.In order to alleviate the phenomenon of automatic grading of grain when entering the shallow silo,some shallow silo at home and abroad use the distributor,which partially alleviates the phenomenon of automatic grading of grain.However,there are still some problems in the process of use,such as uneven distribution of grain and deficient application effect.In view of the above problems,the main research contents of this thesis are as follows:1.Based on the measurement of the intrinsic parameters of real soybean particles,the soybean non spherical particle model has been reconstructed,and the discrete element simulation parameters of soybean are calibrated and optimized with the angle of repose as the response value.The results show that the optimal main simulation parameters are soybean-soybean collision recovery coefficient 0.292,soybean-steel static friction coefficient0.487 and soybean-soybean static friction coefficient 0.409.2.Taking the porosity distribution uniformity and ventilation effect as the optimization indicators,this thesis designs and optimizes a new type of shallow silo distributor structure,which is mainly composed of overflow barrel,sliding arm,chute,baffle and motor.By adjusting the parameters such as the rotation speed of distributor,the number of sliding arm,the grain blanking point can be adjusted.At the same time,the discrete element simulation software is used to simulate the grain pile stacking process under different feeding modes,obtain a static grain pile close to the real grain pile,and further analyze the distribution laws of porosity in the grain pile.It is found that when the number of arms of the feed distributor structure is six and the rotating speed is 6（RPM）,the porosity distribution in the grain pile is more uniform.3.The ventilation process of static grain pile is studied by using DEM-CFD coupling calculation method,and the parameters such as ventilation uniformity and cooling rate of grain pile when different distributor structure are selected for feeding are deeply compared and analyzed.When the structure of the feed distributor is six arms and the rotating speed is 6（RPM）,the ventilation effect of the grain pile is the best.the ventilation uniformity of grain pile is higher,up to 0.9127,and the cooling rate of grain pile is higher,up to 0.7048（℃/ h）.4.By comparing and analyzing the changes of the experimental values of the temperature of each layer of the grain pile,the coupling calculation results and the calculation results of the traditional method,it is found that the results of the coupling calculation method can better reflect the flow and heat transfer laws inside the real grain pile.which verifies the accuracy of the numerical simulation results.At the same time,it is proved that it is feasible to optimize the shallow silo distributor by using the numerical simulation method with porosity distribution uniformity and ventilation effect as the optimization indicators.After comprehensively considering the two indicators of grain pile porosity distribution uniformity and ventilation effect,the results show that the optimal distributor structure is six and the optimal rotating speed is 6（RPM）.The innovation in this study is to design a new type of shallow silo distributor,and simulate and analyze the influence of distribution characteristics of porous media on heat transfer based on DEM-CFD coupling calculation method.It provides a basis for effectively solving the automatic grading of grain and optimizing the process of grain storage.