Research On Theory Of Shearer Drum Cutting Coal And Cutting Dynamics

The drum-type shearer has become the key machinery facility in mechanization of coal mining,which plays an important role in that field.The research on the interaction between the pick and coal will facilitate further study on the cutting performance of drum,as well as improve the working efficiency,the stability and the life of the shearer.Consequently,it is significant for optimal design of drum to investigate the micro break of the coal and the performance of the pick at different cutting parameters.This subject is about the study on the coal cutting process of pick and drum,whose main work was as follows.Firstly,the discrete element model of coal was established by means of PFC3 D software based on understanding the mechanical properties of coal.The uniaxial compression test and Brazilian tensile test were carried out to measure the mechanical properties of the model,which had mated the real coal.Then,the solid model of the point attack pick was built utilizing UG software,imported into PFC3 D,and the simulation of linear cutting process at different cutting depths was implemented and the reliability of the model has been validated.Secondly,the influences of the cutting angle and the cutting linear velocity to the micro break of coal,the load of the pick and the specific energy were investigated respectively at 5 mm,10 mm and 15 mm of cutting depths.In addition,the model of double-pick cutting coal was built to analyze cutting mechanism and cutting performance at different cutting modes.Besides,coal cutting tests have been simulated at 5 mm,10 mm,15 mm and 20 mm of cutting depths and 30 mm,40 mm,50 mm,60 mm and 70 mm of linear spacing by means of double-pick,from which the micro break ofcoal,the load of the pick and the specific energy were discussed as well.Last,the rotational cutting model of pick and drum were modeled to investigate the effect of rotational speed and traction speed of pick/drum to cutting performance.The following are the conclusions of this dissertation according to the investigation above.The validity of the results of numerical simulation and the reliability of the numerical model of coal were validated by means of regression analyses via comparison with the results of theoretical calculation.The shear break of coal increases with the increasing of the cutting linear velocity,while the cutting angle influences the measure of micro break and the direction of the crack propagation.The cutting force and the specific energy are both first decrease then increase with the increasing of the cutting linear velocity.In summery,the cutting linear velocity should be in a range from 3 to 4 m/s,and the cutting angle be from 45 to 50 degree for a good cutting performance.The interaction of picks weakens and the shearing action from pick to coal enhances with the growing of the linear spacing,and the load of pick increases as well.The optimal ratio of cutter spacing and cutting depth should be in a range of3.5~4 with the least specific energy.The load of drum grows with the increasing of the traction speed,while that value first decreases then increases with the growing of the rotational speed.The forces acting on the drum were optimal at60 r/min of rotational speed and 2 m/min of traction speed,which was identical with the simulation results of rotational cutting process of pick.The specific energy grows with the increasing of the traction speed,while first decreases then increases with the growing of the rotational speed.The specific energy was least at 50 r/min of rotational speed and 5 m/min of traction speed with the highest cutting efficiency.