单侧缝竖形槽道内的火旋风中心区域特性

The primary characteristics of fire whirls in vertical square channels with a lateral seam

火旋风的本质是一种有燃烧反应的有旋流动,为了进一步了解其发生机理,采用大尺寸的(2.0 m×2.0 m×15.0 m)火旋风发生装置进行了实验.该装置为单侧缝、底部有小开口的竖形槽道,并采用大涡模拟技术对底部有3个小开口的情况进行了数值模拟,还分别对底部无小开口、底部有三侧全打开、有1个和2个小开口的情况进行了数值模拟研究.得到了除在底部三侧全打开时没有火旋风形成,其他情况皆能形成火旋风的结果.在能形成火旋风的情形下,得到了火旋风的中心温度和轴向速度随高度的分布规律,同时发现火旋风的旋转中心偏离几何中心以及火旋风的火焰顶端不连续的特征.

A fire whirl is simply a vortex flow with combustion. To understand the mechanism generating fire whirls, large scale experiments were conducted in a vertical square channel （2.0 m ×2.0 m ×15.0 m） with a lateral seam. They were also simulated with computational fluid dynamics （CFD） using fire dynamics simulator （FDS） version 4.07 which includes a method for large eddy simulation. To investigate the primary characteristics of fire whirls, five cases were simulated, each using a different bottom vent. It was found that when three edges at the bot- tom of the channel connect with the ambient a fire whirl cannot be produced. The other four cases produced one. In those cases, the distribution rule of temperature and axial velocity of the fire whirl at the channel centerline with the changing of height was presented. Next, the observed shifting of the central axis of the fire whirl from the channel＇s centerline was analyzed. It was also noted that the positions of the top of the flame in the fire whirl were incontinuous.