Comprehensive performance analysis of a shearer drum in a complicated seam based on discrete element method

Drum of Shearer undertakes the main function of coal falling and loading, and its performance directly affects the working efficiency of the shearer. Therefore, in order to realize the analysis of the performance of the shearer drum, the MG2 × 55/250-BW shearer drum was the engineered object. Combining the physical and mechanical properties experiment results of coal samples, the coupling model of the drum cutting in complex coal seam was established using discrete element method. The falling-coal characteristics of the spiral drum were studied under different working conditions, and the falling-coal trajectories of the coal and rock particles were fitted. Based on a virtual prototype, the variations of the coal loading rate and lump coal rate with different design parameters were determined by studying the falling-coal effect and loading performance of the drum. Considering the drum performance, multi-objective optimization theory was used to determine the optimal operating and structural parameters. The results indicate that, in the process of drum cutting, the cutting depth has the most significant effect on the coal loading rate, while, the blade spiral angle has the least significant. Moreover, with the increase of the cutting depth of drum and the traction speed, the lump coal rate increases. While, with the increase of the drum rotation speed and the blade spiral angle, the lump coal rate decreases. It is found that when the cutting depth of the drum is 597 mm, the traction speed is 5.4 m/min, the drum rotation speed is 104.8 r/min, and the blade spiral angle is 12° the performance of the drum is optimal. Compared with the falling-coal trajectories before optimization, the displacements of the coal and rock particles ejected along the optimal falling-coal trajectories increase in the coal loading direction. The loading rate and lump coal rate of the drum increase by 6.05% and 12.27%, respectively. The load fluctuation of the drum decreases, and the productivity increases.

Numerical simulation of coal wall cutting and lump coal formation in a fully mechanized mining face

It is difficult to accurately calculate the lump coal rate in a fully mechanized mining face. Therefore, a numerical simulation of the coal wall cutting process, which revealed the crack expansion, development, evolution in the coal body and the corresponding lump coal formation mechanism, was performed in PFC2D. Moreover, a correlation was established between the cutting force and lump coal formation, and a statistical analysis method was proposed to determine the lump coal rate. The following conclusions are drawn from the results: (1) Based on a soft ball model, a coal wall cutting model is established. By setting the roller parameters based on linear bonding and simulating the roller cutting process of the coal body, the coal wall cutting process is effectively simulated, and accurate lump coal rate statistics are provided. (2) Under the cutting stress, the coal body in the working face underwent three stages—microfracture generation, fracture expansion, and fracture penetration—to form lump coal, in which the fracture direction is orthogonal to the cutting pressure chain. Within a certain range from the roller, as the cutting depth of the roller increased, the number of new fractures in the coal body first increases and then stabilizes. (3) Under the cutting stress, the fractured coal body is locally compressed, thereby forming a compact core. The formation and destruction of the compact core causes fluctuations in the cutting force. The fluctuation amplitude is positively related to the coal mass. (4) Because the simulation does not consider secondary damage in the coal, the simulated lump coal rate is larger than the actual lump coal rate in the working face; this deviation is mainly concentrated in large lump coal with a diameter greater than 300 mm.

Numerical Simulation of Coal Wall Cutting and Lump Coal Formation in a Fully Mechanized Mining Face

It is difficult to accurately calculate the lump coal rate in a fully mechanized mining face. Therefore, a numerical simulation of the coal wall cutting process, which revealed the crack expansion, development, evolution in the coal body and the corresponding lump coal formation mechanism, was performed in PFC. Moreover, a correlation was established between the cutting force and lump coal formation, and a statistical analysis method was proposed to determine the lump coal rate. The following conclusions were drawn from the results. (1) Based on a soft ball model, a coal wall cutting model was established. By setting the roller parameters based on linear bonding and simulating the roller cutting process of the coal body, the coal wall cutting process was effectively simulated, and accurate lump coal rate statistics were provided. (2) Under the cutting stress, the coal body in the working face underwent three stages—microfracture generation, fracture expansion, and fracture penetration—to form lump coal, in which the fracture direction was orthogonal to the cutting pressure chain. Within a certain range from the roller, as the cutting depth of the roller increased, the number of new fractures in the coal body first increased and then stabilized. (3) Under the cutting stress, the fractured coal body was locally compressed, thereby forming a compact core. The formation and destruction of the compact core caused fluctuations in the cutting force. The fluctuation amplitude was positively related to the coal mass. (4) Because the simulation did not consider secondary damage in the coal, the simulated lump coal rate was larger than the actual lump coal rate in the working face; this deviation was mainly concentrated in large lump coal with a diameter greater than 300 mm.

Numerical Simulation of Coal Wall Cutting and Lump Coal Formation in a Fully Mechanized Mining Face

It is difficult to accurately calculate the lump coal rate in a fully mechanized mining face. Therefore, a numerical simulation of the coal wall cutting process, which revealed the crack expansion, development, evolution in the coal body and the corresponding lump coal formation mechanism, was performed in PFC2D. Moreover, a correlation was established between the cutting force and lump coal formation, and a statistical analysis method was proposed to determine the lump coal rate. The following conclusions were drawn from the results. (1) Based on a soft ball model, a coal wall cutting model was established. By setting the roller parameters based on linear bonding and simulating the roller cutting process of the coal body, the coal wall cutting process was effectively simulated, and accurate lump coal rate statistics were provided. (2) Under the cutting stress, the coal body in the working face underwent three stages—microfracture generation, fracture expansion, and fracture penetration—to form lump coal, in which the fracture direction was orthogonal to the cutting pressure chain. Within a certain range from the roller, as the cutting depth of the roller increased, the number of new fractures in the coal body first increased and then stabilized. (3) Under the cutting stress, the fractured coal body was locally compressed, thereby forming a compact core. The formation and destruction of the compact core caused fluctuations in the cutting force. The fluctuation amplitude was positively related to the coal mass. (4) Because the simulation did not consider secondary damage in the coal, the simulated lump coal rate was larger than the actual lump coal rate in the working face; this deviation was mainly concentrated in large lump coal with a diameter greater than 300 mm.

Numerical Simulation of Coal Wall Cutting and Lump Coal Formation in a Fully Mechanized Mining Face

It is difficult to accurately calculate the lump coal rate in a fully mechanized mining face. Therefore, a numerical simulation of the coal wall cutting process, which revealed the crack expansion, development, evolution in the coal body and the corresponding lump coal formation mechanism, was performed in PFC. Moreover, a correlation was established between the cutting force and lump coal formation, and a statistical analysis method was proposed to determine the lump coal rate. The following conclusions were drawn from the results. (1) Based on a soft ball model, a coal wall cutting model was established. By setting the roller parameters based on linear bonding and simulating the roller cutting process of the coal body, the coal wall cutting process was effectively simulated, and accurate lump coal rate statistics were provided. (2) Under the cutting stress, the coal body in the working face underwent three stages—microfracture generation, fracture expansion, and fracture penetration—to form lump coal, in which the fracture direction was orthogonal to the cutting pressure chain. Within a certain range from the roller, as the cutting depth of the roller increased, the number of new fractures in the coal body first increased and then stabilized. (3) Under the cutting stress, the fractured coal body was locally compressed, thereby forming a compact core. The formation and destruction of the compact core caused fluctuations in the cutting force. The fluctuation amplitude was positively related to the coal mass. (4) Because the simulation did not consider secondary damage in the coal, the simulated lump coal rate was larger than the actual lump coal rate in the working face; this deviation was mainly concentrated in large lump coal with a diameter greater than 300 mm.