CO gas flow patterns in a medium-scale semi-enclosed experimental tunnel following a methane explosion

To investigate how obstacles influence methane explosion evolution in semi-enclosed roadways, a mesoscale system was built to examine overpressure and CO migration under the coupled effects of the methane concentration (7.5%, 9.5%, and 11.5%) and obstacle position (4380, 8380, and 12,005 mm). The CO pathways are reconfigured via downstream vortices and pressure-induced recirculation, which produces bimodal concentration curves and delays concentration decay. The effects are concentration dependent: at 9.5%, strong turbulence promotes secondary combustion, leading to a surge in CO production; at 11.5%, sustained secondary combustion causes abnormal CO elevation; and at 7.5%, combustion is suppressed, with front obstacles quenching primary combustion. At 9.5%, a mid-placed obstacle (8380 mm) optimally disturbs flow and modulates pressure waves, enhancing CO transport and peak concentration. This reveals synergistic mechanisms between obstacle position and methane concentration.