By installing obstacle plates with different opening shapes in an experimental pipeline, the combined effect of vertical concentration gradients and obstacle shapes on methane-air explosion characteristics was experimentally investigated. The presence of obstacles and concentration gradients induced turbulent flame instabilities, which promoted the positive feedback between the combustible gas flow and combustion process. The combustion process caused the upstream lean methane, lighter than the unburned gas, to propagate through the obstacle and hence bubble-like local disturbances were generated in the central area downstream of the obstacle. Under the action of transverse waves, a "gap" appeared in the lower part of the flame front, and the flame front appeared concave. The effect of the concentration gradient and obstacles on the methane explosion gradually weakened, and hence the wrinkled flame surface gradually stabilized. Results show that the square-shaped opening affected the flame propagation and explosion evolution most significantly. As the concentration gradient increased, the combined effect undermined the positive feedback mechanism, and the maximum explosion overpressure and maximum rate of pressure rise were reached for the square-shaped opening at a low concentration gradient (0.5 %), while for the circular-shaped and quadrant-shaped openings the maximum values were reached at a higher concentration gradient (1.0 %). The effect of obstacles was more significant than the effect of concentration gradients with respect to the flame propagation velocity and rate of pressure rise.

通过在实验管道中安装具有不同开口形状的障碍板，实验研究了垂直浓度梯度和障碍物形状对甲烷-空气爆炸特性的综合影响。障碍物和浓度梯度的存在导致湍流火焰不稳定，从而促进了可燃气体流量与燃烧过程之间的正反馈。燃烧过程导致上游的贫甲烷（比未燃烧的气体轻）通过障碍物传播，因此在障碍物下游的中央区域产生了气泡状的局部扰动。在横波的作用下，火焰前沿的下部出现“间隙”，火焰前沿呈凹形。浓度梯度和障碍物对甲烷爆炸的影响逐渐减弱，因此起皱的火焰表面逐渐稳定。结果表明，方形开口对火焰的传播和爆炸演变的影响最大。随着浓度梯度的增加，组合效应破坏了正反馈机制，在低浓度梯度（0.5％）下，方形开口达到了最大爆炸超压和最大压力上升率，而圆形开口则达到了最大爆炸超压和最大压力上升率。象限形开口最大浓度梯度（1.0％）达到最大值。在火焰传播速度和压力上升速率方面，障碍物的影响比浓度梯度的影响更为显着。