预点火湍流对正戊烷云雾爆炸参数的影响

摘要

In this paper we investigated the influence of the pre-ignition turbulence intensity on the explosion parameters of n-pentane mists. By using 0.4, 0.6 and 0.8 MPa of pneumatic pressure spray, we obtained n-pentane mists with the Sauter mean diameter (SMD) of 21.21, 14.51 and 8.64 μm, and at the same time, the pre-ignition turbulence intensity under different pneumatic pressures. Then, in a 20 L mists explosion parameter measuring system for experimental research, we aquired the influence of the pre-ignition turbulence on the evaporation rate, the peak explosion overpressure, the explosion pressure rise rate and the ignition delay time of n-pentane mists. The results showed that, the average turbulence velocity of the enviromental fluid field was zero. The smaller the droplet size was, the more obvious was the increase of the evaporation rate of the mists with the increase of the turbulence intensity. At the same time, for the SMDs of 14.51 and 21.21 μm, the peak pressure and the maximum pressure rise rate increased more obviously with the SMD of 8.64 μm, and the explosion intensity was significantly strong, suggesting the existence of a transition range. For the SMDs in the range of 8?22 μm, the mean square turbulence velocity in 1.0?4.0 m/s was the low growth stage of the flame propagation delay time, whereas that in 4.0?6.2 m/s was the high growth stage. The turbulence intensity and the flame propagation delay time exhibited a linear growth in both stages.%以正戊烷云雾为研究对象，进行预点火湍流对云雾爆炸参数影响规律的实验研究。首先通过不同气动压力进行喷雾，获得平均特征直径（SMD）分别为 21.21、14.51 和 8.64 μm 的正戊烷云雾，并得到不同气动压力预点火的湍流均方根速度；随后在 20 L 云雾爆炸参数测量系统中实验获得预点火湍流对正戊烷云雾蒸发速率、爆炸超压峰值、压力上升速率和火焰传播延迟时间的影响。结果表明：(1) 对于圆柱形罐体对称式双喷头分散系统，流场环境可近似认定为零平均速率湍流场；在0.4、0.6和0.8 MPa的气动压力喷雾50 ms的分散作用下，在100～250 ms内，湍流均方根速度在1.0～6.2 m/s范围内，平均湍流积分尺度在40～72 mm范围内，湍流最大湍流尺度的雷诺数在8 000～15 000范围内，柯尔莫哥洛夫微尺度在0.03～0.1 mm范围内；(2) 对于较小的液滴群，随湍流强度的增加，液滴群的蒸发速率有更为明显的提升；(3) 对比云雾三种SMD，粒径8.64 μm的超压峰值与最大压力上升速率随湍流强度增长趋势更显著，并发生爆炸强度显著提升现象，即存在“转变区域”（transition range）现象；(4) 对于SMD在8～22 μm范围内，湍流均方根速度处于1.0～4.0 m/s时为火焰传播延迟时间的低增长阶段，湍流均方根速度处于4.0～6.2 m/s时为火焰传播延迟时间的高增长阶段，湍流强度与火焰传播延迟时间在相应的两个湍流强度阶段范围内呈线性增长。