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Continuous mining is one of the development goals for metal mines, and the application of coal mining equipment represented by shearers provides a reference for continuous mining. However, rock in metal mines is generally harder than coal, making cutting difficult. Improving the surrounding rock conditions is an important way to improve the applicability of the drum for hard rock cutting. Therefore, this article explores the correlation between drum-cutting performance and surrounding rock boundary conditions, aiming to obtain surrounding rock boundary conditions that can help improve drum-cutting performance. To achieve the goal, a model of a shearer drum and hard rock is established using finite element software. With the model, hard rock cutting was simulated and the stress distribution on rock mass, deformation of rock mass, and drum cutting force during the cutting process under different confining pressures were analyzed. Relations between drum cutting force and confining pressure on rock mass were obtained. Then, drum cutting force under different free surfaces of rock mass are studied and the positions of free surface on rock mass that help to reduce the drum cutting force were summarized. According to the research, when the rock mass is under uniaxial compression, drum cutting force increases with the confining pressure on the rock mass; In addition, the free surfaces on the rock mass are proved to be helpful to reduce the drum cutting force. The research content lays the foundation for the boundary conditions required to reduce drum-cutting force in metal mining. [ABSTRACT FROM AUTHOR]

The extremely poor loading performance of a thin coal shearer drum affects the mining efficiency in thin seam mining seriously on account of the restriction by the complicated mining environment and seam thickness. The coal loading performance of the drum is influenced by several complex factors, such as motion parameters and structural parameters, including the structure and form of the hub. The form of the drum hub is cylindrical in general, and in order to study the influence of the hub form on the coal loading rate of the drum, seven drums with different hub forms and structures were designed. The influence of the complexity of hub structures on the coal loading performance was studied by discrete element method (DEM) simulation in this paper. The change curves with the research object of different drums, such as coal loading rate, velocity field distribution, and contact force between fallen coal particles, were obtained. The results showed that the conical hub drum can improve the coal loading performance than the cylindrical hub drum, and the curve-shaped hub drum had a more obvious promotion on the coal loading performance. The coal loading rate increased first and then decreased with the increase of hub cone angle. Compared with the conical hub drum, the curve-shaped hub drum can not only improve the coal loading rate, but also has a larger space containing coal. This study has proposed a drum with a new form hub which could increase the coal loading rate, and the methods and conclusions provide the guidance for drum hub design. [ABSTRACT FROM AUTHOR]

AbstractSpherical and flaky particles are mixed during hard rock tunneling. In particular, flakey particles are difficult to load, resulting in conveying machines that have difficultly operating efficiently. Based on the characteristics of flakey particles and the present conveying structures, such as star wheels, three new conveying structures are introduced in this paper, and the parameters related to the conveying ability are evaluated with theoretical analysis. Then, the flow and trajectory of particles under different conveying structures and the difference in their working capabilities were investigated with the help of the discrete element method (DEM). Finally, conveying machines with different conveying structures are made with 3D printing technology and experiments for validation of the conveying ability are performed. The results show that the conveying structures can be divided into two categories: those with a rotational speed proportional to the loading rate and those with the opposite condition. The propulsion status has a stable loading phase with a long time period relative to the non-propulsion status. The findings can be used to guide conveying machine designs, and they can be helpful for the enhancement of the working ability in conveying particles with flakey shapes. [ABSTRACT FROM AUTHOR]

The cutting unit of a mining shearer is composed of a drum, gear transmission and hydraulic height adjusting mechanism. To obtain the dynamic characteristics of crucial components in the coal cutting process, a model of a drum cutting coal was constructed using LS-DYNA. The model of gear transmission was constructed with Adams, and a model of the hydraulic height adjusting system was constructed with AMESim. Data transmission and co-simulation of these three models were implemented with MATLAB. Changes of the meshing force, acceleration and amplitude–frequency characteristics of key gears under different conditions were obtained. From the research, we conclude that it is effective and feasible to apply the multi-software co-simulation used by this paper to research a complex mechanical–hydraulic system such as a shearer cutting unit; supports from a hydraulic cylinder can decrease the meshing force of gears to some extent; and the meshing force of gears increases significantly as the mining height of the drum increases. [ABSTRACT FROM AUTHOR]