53 / 2023-05-15 21:27:55

Research on the Air Flow Stability Characteristics in Turning Mine Tunnels

air flow field; turning angle; average velocity; stable distance; mine ventilation

There are many heterogeneous tunnels in underground coal mines, such as turns and sudden changes in tunnel sections, which lead to local airflow turbulence, and the the accurate measurement and monitoring of underground ventilation airflow was seriously influenced. In addition, due to the airflow turbulence, harmful gases may accumulate in tunnels , which can easily induce to serious accidents.. Up to now, the airflow distribution and dynamic monitoring of airflow in straight tunnels have been researched extensively by many scholars and beneficial results have been obtained. However, there was little research on the energy loss and airflow stability characteristics under complex flow fields. The spatial location of points similar to the average wind speed in the turning tunnel have been analyzed by scholars using experimental methods, but there was limited research on the distribution characteristics of the flow field in the turning tunnels, the feature of the average ventilation velocity, and the relationship among the stable distance of the airflow and the turning angle and airflow velocity.

So in view of the current problems that the airflow stablity feature in turning tunnel was unclear and the online ventilation system was difficult to accurately measure in turning tunnel, the 3D physical model and airflow flow dynamics model of turning tunnels in mines were established and researched in this paper. The ventilation velocity was supposed to be 1m/s, 2 m/s, 3 m/s, 4 m/s, and 5 m/s, and the turning angles was supposed to be 0°, 15°, 30°, 45°, 60°, 75°, and 90° respectively.The influence of different turning angles and airflow velocities on the characteristics of the airflow field in turning tunnels were studied by CFD numerical methods. The average velocity distribution after turning was analyzed and characteristic indicator representing the stable distance of airflow was proposed and the influence factors were obtained. A mathematical model was constructed among airflow velocity, turning angle, and stable distance of the airflow field and a precise measurement scheme for the air volume in turning tunnels was proposed. The research results indicate that the air flow showed turbulence at the turning field, with higher inner wind speed and lower outer wind speed and after the turning field, the inner ventilation velocity was lower while the outer ventilation velocity was higher; the average ventilation velocity showed irregular circular shape at turning field and gradually recovers to the same average ventilation velocity distribution in a straight tunnel; The turning angle and airflow velocity were the key factors that influenced the distribution of airflow  field and the airflow stable distance; At the same ventilation velocity, the airflow stable distance of the airflow field gradually increased as the turning angle increasing, but the increasing trend decreased, the relationship between the airflow stable distance and the turning angle fitted in a logarithmic function trend; At the same turning angle, the airflow stable distance of the airflow field gradually increased as the increasing of the ventilation velocity, but the increasing trend slowly decreased, the relationship between the airflow stable distance and the ventilation velocity fitted in a trend of exponential function. The relevant results can provide guidance for conducting precise measurement of ventilation systems in turning tunnels of coal mines.