| The dynamic pressure was used as an important factor in silo designed.There is not pay much attention to the dynamic pressure during discharging when designing the large diameter squat silo in China’s specification.With the increasing height of the large-diameter squat silo,in particular,the large diameter squat silo with the height-diameter ratio greater than 1.0 will generate ruinous dynamic pressure when discharging,resulting in the silo instability.A new type of squat silo with double side chutes was advised by the national natural science foundation of China(51578216)"research on silo lateral pressure mechanism based on energy conversion".To research and analysis dynamic pressure and flow pattern of the silo by model test and numerical simulation.The dynamic pressure would compare with the double sidedraw silo and the central discharge from the bottom.To verify the effect of the double sidedraw silo with chutes on reducing dynamic pressure and improving flow pattern.The major works are as follows:Firstly,according to the data about the double sidedraw squat silo of ZhongMou agricultural in ZhengZhou City,we use plexiglass to make a scale model silo with the chutes,meanwhile,the central discharge from the bottom and the double sidedraw silo were made.To verify the accuracy of the test,the static pressure of three working conditions was measured and compared with the theoretical value.The dynamic pressure and overpressure coefficient of three working conditions were compared,and the distribution rule of the maximum overpressure point was analyzed.The results show that the maximum overpressure coefficient reaches 2.35 on the central discharge from the bottom,this position is at the 7/11 depth of the silo.The maximum overpressure coefficient reaches 1.6 on the double sidedraw,this position is at the 1/11~2/11 depth of the silo.The maximum overpressure coefficient reaches 1.43 on the double sidedraw with the chutes,this position is at the 1/11~2/11 depth of the silo.Secondly,the dynamic pressure of the pressure ear region,the static region and the flow region would analyzed by the eccentric discharge specification.The results show that the maximum overpressure coefficient of pressure ear region reaches 1.6 and 1.43 on the double sidedraw and the double sidedraw with the chutes.The maximum overpressure coefficient of static region reaches 1.44 and 1.22 on the double sidedraw and the double sidedraw with the chutes.The overpressure is more obvious in the pressure ear region.Thirdly,to build the numerical model of double sidedraw with the chutes by PFC3 D that belongs to Discrete Element.To verify the correctness of the numerical model,the static and dynamic pressures were simulated and compared with experimental results and theoretical values.The results show that the base and the contact between the base and the cylinder wall has effect on the pressure of the numerical model.The maximum overpressure coefficient reaches 1.42 at the numerical model discharging,this position is at the 2/11 depth of the silo.The overpressure curve of numerical simulation agrees with the experimental results.Finally,to compare and analysis the flow patterns of three working conditions.To establish numerical model and compared with experimental flow patterns through PFC3 D.The relationship between flow patterns and dynamic pressure was analyzed through dynamic arch theory.The results show that it is mass-flow at the initial stage,and the flow patterns translate pipe flow when the storage drops to the 6/11 depth of silo on the central discharge from the bottom.The duration of mass-flow accounts for about 5/12 of the whole discharging process.The duration of mass-flow is relatively short on the double sidedraw and the double sidedraw with the chutes.It accounts for about 1/8-1/7 of the whole discharging process.There are obvious flow region and static region on the the double sidedraw and the double sidedraw with the chutes.The dynamic pressure on the mass-flow is greater than that on the pipe flow and funnel flow. |
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