Simulation and Test Research on Dynamic Properties of Armoured Face Conveyor under Multi-working Conditions

Author:Jiang Shou Bo

Supervisor:zeng qing liang

Database:Doctor

Degree Year:2018

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Pages:167

Size:18661K

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The armoured face conveyor(AFC)is the only transportation equipment in long wall fully mechanized coal mining face.After decades of products introduction,technology absorption,independent research and development,the technical parameters of domestic AFC in China have approached the similar foreign products.But in terms of reliability,service life,etc.,there are still some gaps between the domestic and foreign AFCs.In addition to the differences in manufacturing levels of the core componets,the unclear research on the dynamic characteristics of the AFC during its operation also contributes to the gaps.In fact,an AFC is a highly coupled,nonlinear,multi-bodies dynamic system.In this system,apart from the chain system between the sprocket and rings,the system also includes gear transmisstion,frictions between scrapers and central grooves,meshing between sprocket and scrapers,etc.All these factors can affect the dynamic properties of the AFC.In addition,the work environment of the AFC is often rather harsh,and different working conditions have a great influence on the dynamic characteristics of the AFC.Therefore,it’s significant to improve its reliability by systematically studying the dynamic properties of an AFC through a combination of theoretical analysis,simulation calculations and experiments under various working conditions.In this dissertation,the kine,atics and dynamics analysis of the chain drive system in an AFC are firstly analyzed.Based on the special conditions of horizontal bending and vertical bending,the kinematics model of the chain transmission system 1s established,and the changes ot chain speed and acceleration are analyzed.Based on the Vogit model,the dynamic models of the chain ring,chain transmission system and AFC are established in turn.By using the AMESim software,the dynamic characteristics of the AFC are analyzed,and the changes of the chain speed and chain tension at four different typical frequencies of the head and rear sprockets of the AFC at different voltage irequencies are analyzed.This part laies foundation for multi-body dynamics analysis of the AFC.Based on the multi-body dynamic method,the simulation model of the chain drive system in the AFC is established in ADAMS software.Various simulations under different chain speed,different terrains and different working resistances are performed to obtain the influences of working conditions on the dynamic properties.Simulation results show that under different chain speed conditions,there is a certaion degree of fluctutation in the loose and tight chains.With the increase of the chain speed,the chain’s fluctuation amplitude tends to increase,and the chain’s longitudinal fluctuations show a periodic variation.This phenomenon is caused by the polygon effect of the chain drive system.As the load increases,the driving sprocket torque also increases significantly,and the driving torque cyclically fluctuates.The cycle of the driving torque is elosedly related to the chain speed,the number ot sprocket teeth and other f’actors.The topographic f’actor has little effect on the contact force at the tight ring edge,but has a greater influence on the contact force between the rings at the loose edge.Based on multibody dynamic analysis,using the finite element method(FEM),influenes of different loads,chain speeds and sprocket number on the chain drive system’s dynamic properties are achieved in the LS-DYNA software.The FEM simulation results show that the amplitude of the contact force is related to the distance between the contact position and the sprocket.The closer the contact position is to the sprocket,the larger the amplitude of the contact force fluctuation and the lower the frequency.As the load increases,the degree and peak value of the contact force at the sprocket mesh increase.When the load increases,the stress concentration area of the sprocket increases significantly,and the chain speed fluctuates more obviously,which shows that increasing the load can reduce the working stability of the chain drive system,increase the wear of rings and sprocket,and ultimately reduce the service life of the AFCs.In addition,the number of sprocket teeth has a certain influence on the dynamic properties of the chain drive system.With the increase of the sprocket teeth number of,the change of the meshing contact force at the sprocket tends to be gentle,the horizontal contact force and the total contact force between the rings decrease,and the vertical contact force increases.Under the condition that the body structure of the AFC is kept under certain working conditions,increasing the number of teeth of the head sprocket and rear sprocket properly can improve the stability of the chain drive system,which rovides theoretical basis for performance improvement and optimization of AFC.The AFC dynamic properties test bench is set up,and strains,rotation speeds of head and rear sprockets,motor phase current under various working conditions are collected.The dynamic properties of the AFC under real conditions are analyzed.Test results show that the test bench is reliable under different working conditions.The strain,speed,and current signals collected by the acquisition module are stable,which can accurately describe the changes of the dynamic properties of the AFC during the test;the differenceof the data of the axial strain data collected by the test bench and the data of the simulation analysis is stable between 30%and 50%,indicating that the results of simulation analysis can reflect the dynamic characteristics of the AFC under practical conditions to a certain extent,providing a reference for the design and application of the AFC.With the increase of the chain speed,the motor frequency conversion signal in the reducer,the shaft and gear engagement signals of the various stages,the scraping frequency between the scraper and central grooves,and the amplitude of the meshing frequency of the sprocket and the chain have increased.At the same time,the polygon effect of the chain drive system tends to increase with the increase of the chain speed,and there is a slight difference of not more than 1%in rotational speed between the head sprocket and sprocket sprocket.Under different terrain conditions,the meshing frequency of the sprocket-chain has the greatest influence on the dynamic properties under ’horizontal bending’ plus ’vertical bending’ compound condition、while the scraping condition beween the scraper and the central groove is afeccted significantly under horizontal bending and vertical bending working conditions.Under the loaded working condition,the amplitude of the scraper and the middle groove greatly increase,which adversely affects the dynamic properties of the AFC.By monitoring the rotational speed difference between the head sprocket and rear sprocket and monitoring the sag of the scrapers,the tension state of the chain of the squeegee conveyor can be effectively monitored.The problems of the chain loose phenomenon and chain breaking due to the loose chain can be avoided,thereby improving the reliability and stability of the AFC.