多孔障碍物对预混火焰传播的影响

以甲烷为代表性气体，研究了半封闭管道中设置多孔障碍物对可燃气体爆炸火焰传播的影响，基于大涡模拟对实验进行了重现，对比了实验与模拟中火焰传播过程的形状、位置及速度，分析了模拟结果中火焰穿过障碍物前后的流场和表面积变化，给出了衡量火焰褶皱程度的指标及算法。结果表明:大涡模拟结果与实验结果有较好的一致性；火焰在存在障碍物的管道内传播，经历层流快速膨胀、受阻回流、湍流快速发展和脉动减速4个阶段，各阶段火焰依次分别呈现加速、减速、二次加速、二次减速的波动变化；当可燃气体在开口与点火位置同端的管道内爆炸，火焰在接近障碍物时，受管道封闭端和障碍物约束显著，而出现脉动回流现象；火焰穿过多孔障碍物后，传播速度骤升至峰值，较未穿过障碍物前的最大速度可增加58.7%；障碍物是导致火焰面破碎以及面积褶皱率增大的直接原因，火焰褶皱率最大可达44.8%，比未穿过障碍物前的最大褶皱率增大39.27%。

Multi-hole obstacles’ effects on premixed flame’s propagation

Taking methane as the representative gas, the effect of setting multi-hole obstacle in semi-enclosed pipe on the flame propagation of flammable gas explosion was studied, and the experiment was reproduced based on the large eddy simulation (LES), the shape, position and speed of flame propagation were compared in the experiment and simulation, the flow field and area change of the flame before and after the obstacle were analyze and then the method of measuring the refractory rate of the flame is proposed. The results show that the LES results are in good consistency with the experimental results. Flame propagation has gone through four stages in the duct, followed by the layer flow bubbles rapid expansion stage, the flame pulsation reflux stage, the turbulent flame rapid development stage, the flame deceleration stabilization stage, in which the speed of the flame fluctuates. After the flame has passed through the multi-hole obstacles, the propagation speed suddenly rises to a peak value, which is 58.7% higher than the maximum speed in front of the obstacle. The discharge vent and ignition are at the same end in the duct, when the flame is near the obstacle, which is effected by the top of pipe and obstacle significantly, and the speed would be negative and the flame will flow back. Obstacles are the direct cause of the broken layer flow bubbles and the increase of area fold rate, the maximum flame fold rate is 44.8% after flame passed the obstacle, which is increased by 36.72%.