Experimental study on flow characteristics of coal gangue slurry under multiple working conditions

To investigate the flow characteristics of coal gangue slurry in pipelines under multiple operating conditions, a combination of a pilot-scale ring pipe test and numerical simulation was employed. The effects of slurry concentration, flow rate, and pipe diameter on the flow behavior of coal gangue slurry were systematically analyzed. The results indicate that, in straight pipe sections, the resistance loss along the way is positively correlated with the slurry flow rate, and it increases with increasing slurry concentration and decreasing pipe diameter. The resistance loss is greatest in the uphill section, whereas that in the second set of alternating uphill and downhill sections is comparatively lower. In special pipe sections, the resistance loss increases slightly with increasing flow rate and concentration, while it decreases with increasing pipe diameter. Furthermore, the velocity distribution at the inlet cross-section is relatively uniform, whereas at the outlet cross-section it exhibits a "central subsidence" profile due to gravitational effects, with the minimum flow velocity occurring near the pipe wall. An increase in slurry concentration enhances the structural strength of the slurry while maintaining favorable flowability. As the flow rate increases, the “flow core region” becomes more concentrated toward the pipe center and expands in area, accompanied by an enlargement of the low-velocity zone near the pipe wall. In contrast, an increase in pipe diameter leads to a reduction in the area of the “flow core region.” In the uphill and downhill sections, the high-velocity flow region shifts downward and upward, respectively, due to inertial effects; moreover, this phenomenon becomes less pronounced with increasing pipe diameter.