基于CFD的新型风幕控尘装置的模拟研究及其应用

针对传统风幕控尘装置设备多、空间小、掘进机移动不便等诸多不足之处,⌒进行了优化设计。为确保新型风幕控尘装置的实际应用效果,指导现场防尘系统设计,确定抽出式风机风筒安设位置,依(山西某矿掘进巷道工作面1:1建立了物理几何模型,并利用计算流体动力学(CFD)进行模拟。根(湍流模型特性及流体运动特点,选取拉格朗日法离散相模型对掘进巷道粉尘浓度分布进行了模拟分析并进行现场实践。结果显示,所选物理几何模型参数设置合理,拟合精度达到预测要求;加装新型风幕控尘装置前后,粉尘浓度下降对比明显;距底板2.1 m处安设抽出式风机风筒时,系统降尘效果显著。     

Effects of radial air flow quantity and location of an air curtain generator on dust pollution control at fully mechanized working face

To better understand the effects of radial air flow quantity and the location of air curtain generator on dust pollution control, the 2–109₂ fully mechanized working face in Xinzhi coal mine (Huozhou Coal Electricity Group Co., Ltd., Shanxi, China) was numerically simulated in the present study. A full-scale physical model of the working face was established; then, based on airflow-dust particle two-phase flowing characteristics, the k-ε-Θ-k_p mathematical model was constructed. The comparison between simulation results and field measurements validated the model and the parameter settings. Furthermore, the effects of ventilation parameters on airflow migration and dust diffusion were numerically investigated using FLUENT. The results show that the increase of the radial air flow quantity (denoted as φ) and the distance of the air curtain generator from working face (denoted as d_w) is beneficial to the formation of a dust-control air curtain. At a constant d_w, the dust diffusion distance (denoted as D) decreases with the increase of φ. At a constant φ, D decreases with the increase of d_w when a dust-control air curtain is formed; otherwise, the increase of d_w leads to the increase of D. By analyzing the simulation results, the optimal ventilation parameters for 2–109₂ fully mechanized working face and those working faces under similar production conditions are determined as: φ = 240–270 m³/min and d_w = 20–30 m.     

A study on the dust control effect of the dust extraction system in TBM construction tunnels based on CFD computer simulation technology

In order to control dust in a tunnel boring machine (TBM) construction tunnels, this paper, in combination with field measurements, applies CFD computer simulation technology to study the dust control effect of TBM construction tunnels under different dust extraction flow rates. Firstly, the dust extraction system is closed, and the result of the simulation show that the dust diffuses to the entire TBM working area within 181 s, indicating the necessity of having a dust extraction system in the tunnel. Secondly, the dust extraction system is open and under the original dust extraction flow rate of Q_e = 8 m³/s, the overall dust diffuses to the entire working area L_o = 130 m, and the full-face dust diffusion distance is L_f = 47.54 m. Then the study was carried out with the setting of 2 m³/s ≤ Q_e ≤ 14 m³/s. The results show that: when Q_e ≤ 8 m³/s, the full-face dust diffuses to 47.54–71.84 m; when Q_e > 8 m³/s, the full-face dust can be controlled at 42.81–46.34 m; and when Q_e = 8 m³/s, the full-face dust control effect is better, and the average dust concentration in the tunnel is as low as 12.25 mg/m³, indicating that the original dust extraction system has a better design. The field measurement results verify that the CFD computer simulation results are accurate.     

Formation mechanisms of a dust-removal air curtain in a fully-mechanized excavation face and an analysis of its dust-removal performances based on CFD and DEM

A high concentration of dust in a fully-mechanized excavation face is a serious threat to the safety of production underground and miners’ health. This paper discusses the use of a novel air curtain generator and proposes a novel dust control and prevention technique. Based on the k-ε two-equation turbulence model, Hertz-Mindlin model and the CFD-DEM coupled interface compiled with C++ language, this paper firstly constructs a simulation model of the coupling between airflows and dust in a fully-mechanized excavation face, and then simulates the airflow fields and dust fields under forced/exhaust ventilation conditions with and without a novel air curtain generator being utilized. The results show that when only the forced/exhaust ventilation was used, a high concentration of dust spread throughout the entire tunnel space and no effective air curtain was formed. Furthermore, after the air curtain generator was turned on, as the radial-to-axial forced air ratio (P_FQ) increased, the horizontal vortex in the front of the head-on section weakened gradually, and the originally disordered airflows behind the heading machine moved uniformly towards the head-on section. As the P_FQ further increased, the distance (d) between the formed air curtain and head-on section decreased overall; through a curve fitting, this relationship can be written as: d = ?5.247 ln(P_FQ) + 13.569. When the P_FQ > 5:5, the average negative-pressure-induced dust-exhaust capacity increased, the distance between the formed air curtain and the head-on section decreased, and the re-entrainment of dust did not take place in a straightforward manner. Finally, some field measurements were carried out in order to validate the simulated results, with the subsequent comparison showing that the numerical simulated results were basically accurate.     

Study of high-pressure air curtain and combined dedusting of gas water spray in multilevel ore pass based on CFD-DEM

In order to solve the problem of dust pollution caused by ore unloading in ore pass, this paper, taking Li Lou Mining as a case study, conducted the wind speed variation law in the fluid domain and the impact of the collision between the ore in the unloading process on the fluid to determine the key dust control point based on the CFD-DEM coupling software. By Fluent software, the air curtain dust-proof efficiency under the action of unloading airflow is analyzed, and the relationship between the dust-control wind speed and the impinging airflow is known. And an experimental model of gas water spray is established to analyze the effect of spray dust removal. By analyzing the impact airflow and dust migration caused by ore unloading and the effect of air curtain dust control through numerical simulation, it can be seen that when the ore discharging quantity M_o = 4000 kg, the dust production is mainly concentrated in the fourth middle section. By high-pressure air shield assisting dust removal, dust diffusion can be better controlled when the ratio of impact wind speed of ore pass wellhead (denoted as λ) to high-pressure air curtain wind speed (denoted as ζ) is at least 1:8. When the dust removal effect is optimal, the ratio δ of the water supply amount q_l and the gas supply amount Q_g is determined by the gas water spray dust control experimental platform.     

Experimental investigation and CFD simulation of multiphase flow behavior in air reverse circulation drilling

In reverse circulation (RC) down-the-hole hammer (DTH) drilling, hole cleaning has a great impact on reducing accidents and improving efficiency. There is a technical difficulty in RC drilling to select the minimum air influx while keeping cuttings discharged smoothly according to different water invasion conditions. A novel experimental device was used to study the physics of multiphase flow associated with the cleaning process. Air influx required for cuttings transport was measured under different conditions in Rate of Penetration (ROP), cuttings diameter, and water yield, and influence among three factors were revealed. Furthermore, the computational fluid dynamic (CFD) method simulated and analyzed multiphase flow behavior. The results show that factors of ROP, cuttings diameter, and water yield obviously impact minimum air influx during the cuttings transport process. The accuracy and credibility of CFD method have been confirmed on account of reasonable agreement with experimental data (a relative error of less than 14% is achieved). The CFD simulation of multiphase transport reveals that cuttings velocity and pressure drop could be influenced by ROP, cuttings diameter, and water yield. Therefore, these factors should be carefully characterized during air RC drilling and hole cleaning to maximize the efficiency of cuttings transport.     

Research on mine dust suppression by spraying: Development of an air-assisted PM10 control device based on CFD technology

In order to solve the serious pollution problem of PM10 in a fully mechanized mining face, focusing on the drum cutting process which produces the most dust, a new type of shearer sprayer is developed in the paper. At present, it is difficult for a single spray device to meet the dust control demands of a mine. Therefore, in combination with the airflow-carrying-droplet mechanism, a fan is added to the shearer’s spray device to develop an air-assisted PM10 control device. A No. III nozzle is optimally chosen following the spray experiments, and CFD software is used for a numerical simulation of the 4307 fully mechanized mining face of the Bailu Coal Mine. According to the airflow and spraying field distribution, it is observed that when the spray device’s pressure is 8 MPa, the spraying field’s microscopic parameters are more conducive to the settling of PM10 by the mist droplets. The PM10 data measured at 1^#-3^# measuring points of the 4307 fully mechanized mining face of the Bailu Coal Mine have shown that the best PM10 settling effect is at a spraying pressure of 8 MPa. The PM10 concentrations at 1#-3# measure points were reduced to 0.987 mg/m³, 0.405 mg/m³ and 0.262 mg/m³ respectively, with the dust control rate being above 90%. Thus the serious PM10 pollution problem in a fully mechanized mining face has been solved effectively.