The rate of lump coal is one of main factors that affects the price of raw coal. The coal mines always puzzle themselves about how to control rate of lump coal effectively. At present, the rate of lump coal is measure...The rate of lump coal is one of main factors that affects the price of raw coal. The coal mines always puzzle themselves about how to control rate of lump coal effectively. At present, the rate of lump coal is measured mainly by manual operation. The process is inaccurate and the efficiency is low. In this paper, a diameter classification method is proposed to measure the size of lump coal based on image processing.展开更多
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 i...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.展开更多
提高高炉炉料结构中块矿配比对降低铁水生产成本具有重要作用,而天然块矿一般湿度较大,天然块矿在入高炉前有必要进行干燥。以块矿为研究对象,通过实验研究了干燥介质温度、流速和块矿粒度对块矿的干燥特性的影响。结果表明,升高干燥温...提高高炉炉料结构中块矿配比对降低铁水生产成本具有重要作用,而天然块矿一般湿度较大,天然块矿在入高炉前有必要进行干燥。以块矿为研究对象,通过实验研究了干燥介质温度、流速和块矿粒度对块矿的干燥特性的影响。结果表明,升高干燥温度、提高空气流速、减小块矿粒度可以有效缩短块矿干燥时间,提高干燥效率,适宜的干燥工艺条件为:干燥气体温度400℃,干燥气体流速12 m^(3)/h;在此基础上对块矿干燥进行了动力学分析,发现与Henderson and Pabis模型、Lewis模型相比,Page模型与实际干燥水分比MR-时间曲线吻合程度最高。同时得到了干燥介质温度T、流速V与干燥水分比MR的干燥动力学方程。发现干燥过程依次出现升速干燥、恒速干燥、第一降速干燥和第二降速干燥4个阶段,且升速干燥和恒速干燥过程时间相对较短,分别为干燥总时间的5%和10%。展开更多
The lung is an important organ that takes part in the gas exchange process. In the study of gas transport and exchange in the human respiratory system, the complicated process of advection and diffusion (AD) in airway...The lung is an important organ that takes part in the gas exchange process. In the study of gas transport and exchange in the human respiratory system, the complicated process of advection and diffusion (AD) in airways of human lungs is considered. The basis of a lumped parameter model or a transport equation is modeled during the inspiration process, when oxygen enters into the human lung channel. The quantitative measurements of oxygen are detached and the model equation is solved numerically by explicit finite difference schemes. Numerical simulations were made for natural breathing conditions or normal breathing conditions. The respiratory flow results for the resting conditions are found strongly dependent on the AD effect with some contribution of the unsteadiness effect. The contour of the flow rate region is labeled and AD effects are compared with the variation of small intervals of time for a constant velocity when breathing is interrupted for a negligible moment.展开更多
文摘The rate of lump coal is one of main factors that affects the price of raw coal. The coal mines always puzzle themselves about how to control rate of lump coal effectively. At present, the rate of lump coal is measured mainly by manual operation. The process is inaccurate and the efficiency is low. In this paper, a diameter classification method is proposed to measure the size of lump coal based on image processing.
基金The funding was supported by National Natural Science Foundation of China(No.51974294).
文摘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.
文摘提高高炉炉料结构中块矿配比对降低铁水生产成本具有重要作用,而天然块矿一般湿度较大,天然块矿在入高炉前有必要进行干燥。以块矿为研究对象,通过实验研究了干燥介质温度、流速和块矿粒度对块矿的干燥特性的影响。结果表明,升高干燥温度、提高空气流速、减小块矿粒度可以有效缩短块矿干燥时间,提高干燥效率,适宜的干燥工艺条件为:干燥气体温度400℃,干燥气体流速12 m^(3)/h;在此基础上对块矿干燥进行了动力学分析,发现与Henderson and Pabis模型、Lewis模型相比,Page模型与实际干燥水分比MR-时间曲线吻合程度最高。同时得到了干燥介质温度T、流速V与干燥水分比MR的干燥动力学方程。发现干燥过程依次出现升速干燥、恒速干燥、第一降速干燥和第二降速干燥4个阶段,且升速干燥和恒速干燥过程时间相对较短,分别为干燥总时间的5%和10%。
文摘The lung is an important organ that takes part in the gas exchange process. In the study of gas transport and exchange in the human respiratory system, the complicated process of advection and diffusion (AD) in airways of human lungs is considered. The basis of a lumped parameter model or a transport equation is modeled during the inspiration process, when oxygen enters into the human lung channel. The quantitative measurements of oxygen are detached and the model equation is solved numerically by explicit finite difference schemes. Numerical simulations were made for natural breathing conditions or normal breathing conditions. The respiratory flow results for the resting conditions are found strongly dependent on the AD effect with some contribution of the unsteadiness effect. The contour of the flow rate region is labeled and AD effects are compared with the variation of small intervals of time for a constant velocity when breathing is interrupted for a negligible moment.
