| Scraper conveyor is the key equipment of fully mechanized coal mining equipment.Scraper conveyor working environment is bad,and scraper chain is easy to produce large dynamic tension and fatigue fracture accident,which affects the stability of the whole fully mechanized mining system.In the process of transportation,the load of scraper conveyor is large,and the scraper conveyor is affected by the falling impact of coal bulk,the inconsistency between the speed of bulk and scraper,and the regular movement of coal particles.Therefore,in the static and dynamic analysis of scraper conveyor,the distribution of coal bulk on the scraper conveyor,the movement characteristics of coal bulk in the transportation process and the characteristics of bulk can not be ignored.At the same time,in the actual production,the scraper conveyor often needs to stop or start with load,which produces a huge impact on the structural strength of the scraper chain.In this paper,based on the Discrete Element Method(DEM)and Multi-body Dynamics(MBD),the rigid discrete coupling model of scraper conveyor was established.The advantages of EDEM in dealing with particle problems and Recur Dyn in dealing with complex motion and force problems between geometric bodies were brought into play at the same time.The rigid discrete coupling kinematics effect of scraper conveyor under complex working conditions was explored.The main research contents are as follows:(1)The running state of scraper conveyor in stable condition,emergency shut-up and full load start condition was simulated,and the formation of bulk flow,distribution and mass accumulation characteristics of coal bulk on scraper conveyor under these three complex conditions were studied,which laid the foundation for further research on movement characteristics of coal bulk on scraper conveyor and mechanical characteristics of scraper conveyor;(2)Under stable transportation conditions,the vibration loosening and compacting effect,vibration delamination phenomenon and its formation mechanism of coal bulk on the scraper conveyor were analyzed.The results show that,the porosity among coal particles at the bottom of the middle trough increased from 0.4116 in the stable transportation stage to 0.4631 close to the coal output stage,indicating that the coal bulk accumulation had changed from compaction to loose.In the stage of compaction and stable transportation of coal bulk,the stratification phenomenon between different particle sizes was obvious,and at the same time,the percentage of small particles in different positions was used to describe the stratification phenomenon quantitatively,to explain the degree of separation of different particle sizes,and also found that the stability of the movement state of small particles was from top to bottom,which is the foundation for exploring the internal mechanism of the whole separation behavior.Finally,from the point of view of energy,the particle filling mechanism was used to explain the vibration stratification phenomenon of coal bulk.In addition,the filling mechanism of coal particles was proved by the change of average velocity and average torque of coal particles.This study can not only lay a foundation for further exploring the formation of material flow and the transport efficiency of scraper conveyor from the perspective of compactness change of coal bulk,but also make a certain contribution to improve the research of complex kinematic characteristics of bulk from the perspective of delamination movement of coal particles with different sizes;(3)On the premise of analyzing the formation of coal bulk transportation in scraper conveyor,the mechanical characteristics of load chain link were studied.From two aspects of the theoretical calculation and the analysis of simulation results,the changes of contact force of chain link under stable transportation,emergency shutdown and full-load startup conditions were explored.The results show that,under stable transportation,the contact force between links fluctuated periodically,and the contact force near the coal baffle was greater due to the accumulation of coal,and its value fluctuated in the range of 0.328-122.557 k N;the main factor affecting the contact force of chain link under emergency shutdown was the speed of chain,and its value fluctuated in the range of 0.745-77.602 k N;under the condition of full load start-up,and not at the moment of start-up,the contact force between scraper chains increased abnormally due to the starting speed and coal accumulation,and the contact force changed periodically with the maximum value of 161.328 k N.When the chain was stuck,the two scraper chains would produce a huge tension difference,accompanied by the torsional vibration of the scraper and the aggregation of coal particles.This study can directly reflect the mechanical characteristics of scraper chain under complex working conditions and the influencing factors of the characteristics,and provide a theoretical basis for solving the problems of chain sticking or chain breaking of scraper chain in actual working conditions. |
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