长通道内烟气一维水平蔓延阶段质量卷吸系数的实验研究

EXPERIMENTAL STUDY ON AIR ENTRAINMENT COEFFICIENT DURING ONE-DIMENSIONAL HORIZONTAL MOVEMENT OF FIRE-INDUCED SMOKE IN LONG CHANNELS

长通道型结构内发生火灾时,由于通道侧壁的限制,烟气将很快运动至充分发展阶段,表现为沿通道轴向的一维水平蔓延。该文分析了一维水平蔓延阶段中上部热烟气层和下部冷空气层在分界面处的水平相对剪切运动,以及由此导致的烟气层质量流率的沿程增加。通过联立烟气作一维水平蔓延时的运动速度衰减规律,推导出了长通道型结构内烟气一维水平蔓延过程中的质量卷吸系数关系式。在模拟尺寸长通道实验台中进行了一系列实验,测得到了关系式中的未知参数,包括环境空气温度、一维水平蔓延阶段中两参考截面处的烟气流速、温度和烟气层厚度等,求出了一维水平卷吸系数。

During fires in long channels, due to the restriction of side walls, the fire-induced smoke will rapidly reach the fully developed phase, with the characteristic of an axial one-dimension horizontal movement. It is analyzed for both the relative shear movement at the interface between the upper hot smoke layer and lower cold air layer during the one-dimensional horizontal movement of smoke, and the resulting increase of mass flow rate of the smoke layer. With combining the variation law of smoke velocity, the expression of an air mass entrainment coefficient was established. A series of experiments were carried out in a bench-scale long channel, the parameters in the expression were measured, including the ambient air temperature, and the velocity, temperature and thickness of smoke layers at two reference positions. Based on these experimental results, the horizontal entrainment coefficient was obtained.