Simulation Study On Transport Characteristics Of A New Type Screw Conveyor For Grain Stacking Based On EDEM

At present,the small and medium-sized non-specialized bulk cargo yards are not equipped with professional bulk cargo stacking equipment for consideration of input cost.Bulk cargo is transported from the wharf front to the yard by dump trucks.The following three processes are often used in the yard: loader machine and excavator combination,dump truck and loader combination,unloading platform and conveyor belt combination.In view of the low efficiency,highly additional energy consumption and inconvenient equipment transition of these three stacking processes for small and medium-sized bulk cargo yards,this paper proposes a new type screw convery for grain staking based on the practical requirements,and takes it as the research object.According to its unique structure and working principle,theoretical analysis and simulation experiments are used to complete the characteristics of horizontal screw conveying with large filling rate,vertical screw conveying with variable cross-section and inclined screw conveying with variable angle in order to obtaining kinematics,mechanics and transportation efficiency characteristics of grain granular materials in complex transportation process and providing theoretical basis and design basis on research and development,popularization and application of equipment.The main contents and innovations of the thesis are as follows:(1)Design the general and key components of the new grain spiral stacker and analyse the key technologies problems.According to the requirements of grain spiral stacker in small and medium-sized bulk cargo yards,the paper has analysed the method to realize the function of the new grain spiral stacker,completed the general scheme and key component of the new grain spiral stacker;elaborated the key technical issues of the stacker in the design and development process through the research on work principle,stacking process and work economy.(2)Study on the characteristics of spiral conveying at large filling rate.According to analyzing the motion of the material particles about horizontal spiral conveying,the variation of the horizontal,circumferential velocity of the single-particle with the distance from the spiral axis have been obtained,and the characteristics of the horizontal spiral conveying of the stacker have been analyzed.The simulation software of discrete element EDEM has been studied the conveying characteristics of the horizontal section of the stacker at different rotating speed,different equivalent filling rates,and large filling rate.The research results show that when the conveying material is small,the conveying effect is the best and the speed energy efficiency ratio is the largest at rotating speed 80r/min;when the equivalent filling rate may be controlled,the efficiency is the highest at the equivalent filling rate about 100%;when a large amount of material is removed from the dump truck to fill the receiving trolley,the energy efficiency ratio decreases as the spiral speed increases,and the low speed cam save power and consume less energy,but the efficiency is lower.(3)Study on the characteristics of variable cross-section vertical spiral transfer.The material average axial velocity has been obtained by the material free surface morphology in the vertical conveying process,through the geometric design and analysis of the transfer port of the horizontal double helix and the vertical single spiral joint,the optimal shape,shape and size of the transfer port have been determined by EDEM simulation;in addition,according to the characteristics of transfer,the simulation technology has been used to obtain the optimal parameters;through the analysis and comparison of the simulation results,the reason why the variable section can improve the conveying efficiency has been explained accurately,and the relationship between the vertical conveying volumetric efficiency of the stacker and the spiral speed has been obtained,finally,completing the study on variable cross-section vertical spiral transfer conveying characteristics.(4)Study on the characteristics of variable angle on inclined spiral conveying.The EDEM simulation experiment was carried out by using the simplified model of the inclined conveyor section of the stacker.The influence of the inclined angle of the spiral conveyor and the screw speed and the pitch on the conveying efficiency was explored.The three factors,inclination,rotation speed and pitch have been analyzed for the effect of mass flow and energy efficiency ratio in the same feed.The results show that the mass flow rate and energy efficiency ratio of inclined conveying decrease with the increase of the inclination angle,and the different angle reduction trends are different;the mass flow rate and energy efficiency ratio of the inclined conveying increase with the spiral rotation speed while the increase and decrease speed is related to the tilt angle;the mass flow rate and energy efficiency ratio of the inclined transport increase with the pitch,but the larger pitch must be better,and the increase is affected by the spiral speed.