Factors influencing the dust-blocking effect of air curtains during the fully mechanized excavation of working faces
XIA Dingchao;LYU Pin;DU Peng;WANG Jinyue
目前综掘工作面粉尘污染的研究多集中于单一因素对综掘工作面风幕阻尘效果的影响，而未充分考虑各因素间的交互作用，使得压风分流技术的工程应用效果欠佳。为明确附壁风筒径向出风距离、径向出风比及轴向出风距离对风幕阻尘效果的影响，以潘三矿810西翼机巷综掘工作面为研究对象，运用Fluent软件对径向出风距离为10～25 m、径向出风比为0.6～0.9及轴向出风距离为6～12 m条件下的风流分布和粉尘扩散情况进行数值模拟。结果表明：① 随着径向出风距离增大，径向涡流风幕在巷道内的转变更充分，综掘机司机前端的风流分布越均匀，更有利于形成风速方向均指向工作面的轴向阻尘风幕。当径向出风距离为10 m时，距工作面7 m断面内涡流特性明显，风速方向紊乱；当径向出风距离为25 m时，距工作面7 m断面内，风流分布趋于均匀，风速方向均指向工作面，形成了能够覆盖全断面的轴向阻尘风幕。② 随着径向出风比增大，整流风筒轴向风流风量减小，轴向风流风速和射流强度降低，轴向风流对综掘工作面前端气流的扰动减弱；径向出风比越大，越有利于形成风流方向指向工作面且能覆盖全断面的轴向阻尘流场，即轴向阻尘风幕。③ 径向涡流风幕的阻尘能力随径向出风比的增大先增强后减弱，轴向阻尘风幕的阻尘能力随径向出风比的增大而不断增强。④ 在采取压风分流风幕阻尘技术后，当压风总量为300 m3/min，吸风量为400 m3/min，附壁风筒径向出风距离为20 m，径向出风比为0.9，整流风筒轴向出风距离为8～10 m时，能很好地将粉尘聚集在吸尘口附近，达到高效控尘除尘的目的。在810西翼机巷综掘工作面进行现场测试，测点风速和粉尘质量浓度实测值与模拟值基本一致，高浓度粉尘被有效阻控于工作面前端，隔尘效果较为明显，验证了数值模拟的有效性。
Prevalent research on dust pollution during fully mechanized excavation has mainly focused on the impact of individual factors on the effectiveness of air curtains in fully mechanized excavation sites. However, scant research has been devoted to the interaction between factors, because of which pressure-induced air diversion technology has not been adequately applied to this context.To investigate the impact of the radial distance of the outlet of air, the ratio of this outlet, and the distance between the outlet and the wall-coated air duct on the effectiveness of dust blocking by air curtains, the authors of this study consider the excavation of the working face of the 810 west wing machine tunnel at the Pansan Mine . We used Fluent software to numerically simulate the distribution of wind flow and the diffusion of dust under a distance of the radial outlet of air of 10-25 m, a ratio of the outlet of 0.6-0.9, and an axial distance of the outlet of 6-12 m.The results showed that: ① As the distance of the radial outlet of air increased, the radial vortex air curtain transforms more fully in the tunnel . The wind flow at the front end of the excavation operator was more evenly distributed, and the wind speed was directed toward the working face such that this was more conducive to the formation of an axial dust-blocking air curtain.When the radial distance of the outlet of air was 10 m, vortical characteristics became apparent within a distance of 7 m from the working surface, and the direction of wind became disordered. When the radial distance of the air outlet was 25 m, the wind flow tended to be uniform within 7 m of the working surface, and its direction was evenly distributed toward the working surface. This led to the formation of an axial dust-blocking wind curtain that could cover the entire section.② As the ratio of the radial outlet of air increased, the volume of axial airflow of the rectifier air cylinder decreased to reduce the velocity of axial airflow and the intensity of the jet. This in turn reduced the disturbance caused by the axial airflow to that at the top of the mechanized working face that was being excavated. A higher ratio of the radial outlet of air was more conducive to the formation of an axial dust-blocking flow field, with the wind directed toward the working surface and covering the entire section. This led to an axial dust-blocking air curtain. ③ The dust-blocking ability of the radial vortical air curtain initially increased and then decreased as the ratio of the radial outlet of air increased. Its ability then continued to improve as the ratio was further increased. ④ We implemented the dust-control technology based on the air curtain with forced ventilation-induced diversion. When the pressure-induced volume of air was 300 m3/min and the volume of air suction was 400 m3/min, the distance between the radial outlet of air and the attached wall of the air duct was 20 m. The ratio of the radial outlet of air, and the distance between this outlet and the air duct of the rectifier was 8-10 m. The air curtain was able to collect dust near the port of the dust suction for efficient dust control and removal.We conducted an on-site test of the fully mechanized excavation working face of the 810 west wing machine tunnel. The empirically measured data of wind speed and dust mass concentration at measuring points and the results of numerical simulations were consistent with each other. Highly concentrated dust was blocked at the front end of the working face, and its isolation was noticeable. This confirms the effectiveness of the numerical simulations.
fully mechanized excavation working face;dust blocking by air curtain;long-pressure and short-extraction system;wall-mounted air duct;forced ventilation-induced diversion;airflow distribution;dust diffusion