不同来流下火旋风的实验研究

已有的实验研究和数值模拟表明:火旋风存在一种中空燃烧的状态.本文通过燃烧风洞,对不同来流影响下的火旋风进行分析研究.通过一个置于大型燃烧风洞中的边角开有切向进风口的六边形小尺寸火旋风发生模型,应用热电偶测温和皮托管测速以及电子数据采集系统,对该模型内的温度分布数据和速度分布数据进行采集.通过燃烧风洞改变来流速度的大小,分析不同来流速度下火旋风内部的温度分布、速度分布和持续时间,研究来流速度对火旋风内部燃烧结构的影响、火旋风旋转速度的影响以及持续时间的影响.研究表明:来流改变了火旋风内部的燃烧结构,促进了中空燃烧状态的形成.中空燃烧状态有一个中心的低温区域.在中心低温区域温度最低时,火旋风持续时间最长.来流增强了火旋风的整体转动,并且加剧了火旋风的螺旋状上升.

An Experimental Study on Fire Whirl under Various Air Inflow Velocities

Previous experimental and numerical results showed that a hollow combustion state exists in a fire whirl. In this paper, experiments were conducted to study the fire whirl influenced by various air inflows in the wind tunnel of State Key Laboratory of Fire Science. A hexagonal test rig was used to simulate the formation of a fire whirl. Thermocouples and Pitot tubes were used to measure the temperatures and air inflow velocities, and the electronic data acquisition system was applied to acquire data of the temperatures and velocity distributions in the model rig. The temperature distributions, velocity distributions and durations under various air inflow velocities of wind tunnel were analyzed. Influences of air inflow velocities on internal combustion structure, rotation velocity and duration of fire whirl were studied. Results show that air inflows alter the internal combustion structure and urge the formation of a hollow combustion state for which there exists a low temperature region. When the temperature of this region reaches the lowest point, the duration of the fire whirl will be the longest. Air inflows strengthen the overall rotation and enhance the helical rise of the fire whirl.