Wear analysis and performance optimization of drum blade in mining coal gangue with shearer

Highlights

• The coupling model of spiral drum was established by discrete element method.

• The wear depth of blade is obtained through simulation and industrial experiment.

• A multi-objective model was constructed to solve performance optimization problem.

• Optimal drum structure parameters and kinematic parameters were obtained.

Abstract

Drum blades play an important role in the process of coal seam cutting. The blade wear failure will directly reduce the production efficiency of the shearer, and it is difficult to repair, and the replacement cost is high. Therefore, the shearer blade wear is analyzed, and its performance optimization is crucial. The Archerd model of EDEM (Engineering Discrete Element Method) software is used to study the wear of MG2 × 55/250BW thin seam shearer drum blade. The coupling model of the drum with different traction speeds, drum rotational speeds, blade spiral angles and coal walls with different gangue firmness coefficients are established respectively. The wear law of the blade is obtained through simulation analysis. Combined with the analysis of actual working conditions, a multi-objective optimization model was constructed based on blade wear and careful consideration of coal loading rate, productivity, cutting area, and cutting specific energy consumption. The optimal drum structure parameters and kinematic parameters were obtained through a genetic algorithm. The results show that: when the drum cuts coal with a firmness coefficient of 3.5 under the following condition: the spiral angle is 11.56°, the rotational speed is 80.65 r/min, and traction speed is 4.23 m/min, the coal loading rate is 41.65%, the productivity is 206.37 t/h, the maximum cutting area is 1217.0 mm², the cutting specific energy consumption is 0.8612 kW·h/m³, and the blade wear reaches a minimum of 0.25416 nm. This method takes the wear amount as the main factor and comprehensively considers the drum performance to optimize the parameters of the spiral drum, which has strong theoretical and guiding significance for the design of the shearer drum and coal mining.

Introduction

China's mining of medium and thick coal seams has reached the leading technical level [1], but there are still difficulties in mining thin coal seams. The main reasons are that the mining space of thin coal seams is relatively small, manual operations are difficult, the mining efficiency is low, and the economic income cannot make ends meet, resulting in serious abandonment of thin coal seams [2], [3]. In the total output of coal mining, the mining amount of thin coal seam is only 10.4% [4], and the mining condition of the thin coal seam is shown in Fig. 1.

Besides, the working condition of the thin coal seam is complex, including faults, gangues, hard rock particles and other conditions, which have various effects on the drum, resulting in serious impact wear and friction wear. In the coal mining process, the picks directly contact the coal wall, and they are easy to wear, but they are easy to replace as well; and the blades are severely worn during coal loading and coal transportation. After failure, they will seriously affect the cutting performance of the drum, and replacement or repairing is troublesome, so the blade wear failure will greatly reduce the production efficiency. In order to reduce the friction and wear of the blade and improve the production efficiency and cutting performance of the shearer, domestic and foreign scholars have done the following research on the spiral drum.

In the 1990s, Hurt. K et al.[5] used the shearer cutting test bench to cut coal and rock. By analyzing the wear degree of the pick, the service life of the pick is predicted, and different working conditions were set to explore its cutting efficiency. In 1995, O. Z. Hekimoglu et al. [6] analyzed the force on the pick at all positions on the drum and found that the wear of the end plate pick was more serious through the relationship between force and wear. In 1997, Yang et al. [7] studied the wear of the end plate pick base under the condition of oblique cutting of shearer drum and reduced the wear of the end plate pick base and improved the coal breaking efficiency of the drum by welding the sweeping teeth on the end plate. In 2005, John P. Loui et al. [8] used the finite element method to study the transient heat transfer of the pick when cutting coal and rock and found that the surface temperature of the pick is greatly affected by the drum rotational speed and the friction between the pick and the coal and rock. Excessive temperature will cause the material to soften, and it is easier to wear and age the parts. In 2007, Tao Rong et al. [9] improved the spiral drum parameters through parametric design and programming to reduce the wear of spiral drums under complex load. In 2012, Chao et al. [10] found that the spiral drum is extremely vulnerable to wear and failure when the shearer is mining in a complex geological structure. To change this undesired scenario, the theoretical analysis and transformation of the spiral drum were carried out to improve the reliability of the shearer. In the same year, Li et al. [11] judged the grinding of pick at different positions by weighing the quality of spiral drum pick before and after mining coal by changing the distribution angle and arrangement structure, the failure forms and wear causes of different parts of the pick were compared and analyzed, and the reliable improvement scheme was put forward. In 2016, Liu [12] analyzed the form of the interference between the pick and coal and studied the influence law on the pick wear from the aspects of the working level, structural parameter variation and cutting form. In 2017, Shi et al. [13] computed the interference between the gear seat of the spiral drum and the coal rock through MATLAB (Matrix Laboratory) software, and the cause of the wear of the gear seat at the end of the drum is analyzed. In 2019, Zhao et al. [14] used ANSYS to analyze the wear of drum blades, obtained the wear parts and analyzed the causes of wear, and fitted the wear trajectory equation through MATLAB, which provided a reference for blade additive repair. Since Cundall [15] proposed the discrete element method, scholars at home and abroad have gradually used the discrete element software [16], [17], [18] to study the friction and wear problems: Chen et al. [19] combined the discrete element method with the wear model to study the wear problems of the feeding belt of the reclaimer, so as to reduce the wear of the feeding belt. In 2008, according to the Archard wear model, Jerzy Rojek et al. [20] used the discrete element analysis method to establish the model of pick cutting coal and rock. The wear situation of pick cutting in coal mining is predicted, and the change process of pick shape caused by wear is explored. In 2017, Ma [21] adopted the discrete element software EDEM to explore the cutter wear characteristics of shield machines under different soil cover thicknesses and cutter head forms and the wear differences at different positions. In 2019, Zhang [22] and Yang [23] conducted numerical simulation research on the blade wear behavior of screw conveyor by using the discrete element method and obtained the severest wear part, wear distribution and wear law of spiral blade.

Through theory, experiment, computer simulation and other methods, the above scholars have done a lot of research work on the wear of spiral drum and achieved considerable results. However, for the more complex working conditions, especially for the thin coal seam rich in gangue, the spiral drum blade will face the test of coal and rock medium mutation and load fluctuation. Adjusting the blade angle and designing the blade with higher conveying efficiency and lower wear amount needs to be studied.