The combined effects of methane draft pressure and heat wind pressure on airflow behavior in parallel roadways: an experimental study

Abstract

ABSTRACT Most previous studies have mainly investigated the independent effect of methane draft pressure (MDP) or heat wind pressure (HWP) on airflow behavior in tilted ventilated roadways. However, once high concentrations of methane accumulate in a high-temperature-tilted roadway in deep wells, two additional forces – the MDP and the HWP – are generated simultaneously. To investigate the combined impacts of MDP and HWP on airflow characteristics (i.e., the wind speed, oxygen concentration, and airflow temperature) in parallel roadways, a 1/30 experimental platform equipped with a heating device that can adjust airflow temperature is constructed. With an inclination angle of 60°, airflow direction changes several times in upward ventilation, while airflow direction remains unchanged throughout the experiment in downward ventilation, and the curves of the wind speed in both branches show roughly the same trends but in opposite directions. The experimental results indicate that the height difference is a necessary factor for the generation of MDP and HWP and that the combined effects of MDP and HWP lead to a phenomenon of airflow oscillation in upward ventilation while resulting in airflow circulation in downward ventilation. In addition, the airflow temperature in the main branch is varied (from 45°C to 15°C, 25°C, and 35°C) to investigate its influence on airflow behavior in upward ventilated tilted roadways. As airflow temperature in the main branch increases, the maximum and minimum wind speeds measured in the main branch remain unchanged, and the corresponding values are 0.79 m/s and 0.08 m/s, respectively; the values of wind speed in the side branch stabilize at the early stage of ventilation as well. It can be concluded that airflow behavior changes slightly as airflow temperature increases when the main branch is filled with high concentrations of methane because the density difference caused by high concentrations of methane is more significant than that caused by small temperature differences.