Abstract:

In order to investigate the effects of obstacle number on the characteristics of vented gasoline-air mixture explosions, a series of contrast experiments were conducted under three different initial gasoline vapor concentrations in terms of the obstacle number, the conclusions show that: (1) There existed three typical pressure peaks denoted as p_v, p_max, and p_neg during the gasoline-air mixture explosions in a semi-opened pipe, and the magnitude of p_v was just associated with the fracture constant of the polyethylene film at the pipe exit but not with the obstacle number, while the magnitudes of p_max and the absolute values of p_neg increased with the growth of obstacle number, and the time to obtain the p_max was not fully dependent on the obstacle number. (2) During the initial flame propagation process, the flame remained a “finger-like” shape, while disturbed by the obstacles, the flame fronts became distorted, and they were accelerated to change from laminar flame to turbulent flame. And finally the flame fronts formed a “mushroom-like” shape outside the pipe, and the more obstacles, the more significant the “mushroom-like” shape. (3) The obstacles had significant effects on the flame acceleration, and the maximum flame speeds increased with the growth of the obstacle number. (4) Overpressure and flame propagation of the explosion process of gasoline-air mixture explosions had a positive feedback coupling relationship between incentives, they promoted with each other during the evolution of explosions, and the coupling relation became more significant with the growth of obstacle number. (5) The effects of obstacle number on the enhancement of p_max and maximum flame speeds for initial gasoline vapor concentrations of 1.3% and 2.1% were more obvious than that of 1.7%.

Key words: gasoline-air explosions, obstacle number, explosion overpressures, flame speeds, turbulent flow, mixtures, experimental validation

摘要：

为了研究障碍物数量对油气泄压爆炸传播特性的影响，选取了高（2.1%）、中（1.7%）、低（1.3%）3种初始油气浓度，在半开口全透明有机玻璃管道内进行了一系列油气泄压爆炸对比实验。结果表明：①半开口管道内油气爆炸超压曲线存在3个典型的压力峰值p_v、p_max、p_neg；其中p_v的大小只与封口材料破裂常数有关，与障碍物数量无关，而p_max的数值大小和p_neg的绝对值大小随着障碍物数量的增大而增大，但是到达p_max的时间长短不完全由障碍物数量决定；②火焰在传播初期以比较规则的“指尖形”火焰传播，当受到障碍物的扰动之后火焰锋面的规则形状会受到破坏，加快火焰形态从层流到湍流的转捩，并最终在管道外部形成“蘑菇状”火焰，并且管道内障碍物数量越多，这种“蘑菇状”火焰越明显；③障碍物对油气爆炸火焰传播具有显著的加速效应，而且随障碍物数量的增大，这种加速效应越明显，获得的最大火焰速度越大；④油气爆炸过程的爆炸超压和和火焰传播具有正反馈激励的耦合关系，二者在爆炸演变过程中互相促进，这种耦合关系随着障碍物数量的增大体现得越明显。⑤障碍物数量对油气爆炸p_max和火焰传播速度的增大作用在高浓度（2.1%）和低浓度（1.3%）工况下比中间浓度（1.7%）时体现得更加显著。

关键词: 油气爆炸, 障碍物数量, 爆炸超压, 火焰速度, 湍流, 混合物, 实验验证