油盘直径和高度对火旋风特征影响的试验研究

Experimental research on influence of fire source heights and diameters on characteristics of fire whirls

为考察油盘直径和高度对航空煤油火旋风特征的影响,利用四面边墙夹缝式火旋风试验装置,对地面到0.8 m高度,直径0.1,0.15和0.2 m池火形成的火旋风进行试验研究。首先利用Rankine涡理论,分析质量燃烧速率和速度环量的定量关系,探讨火旋风的气动平衡机制;再由电子天平记录的燃料质量随时间变化曲线,得到准稳定阶段火旋风质量燃烧速率;利用摄像机记录的火焰连续图像,获得火焰时平均高度。理论分析表明,就给定半径的油盘而言,在假定涡核半径与油盘半径之比不变的情况下,质量燃烧速率与速度环量成线性关系。分析试验数据发现,无量纲质量燃烧速率及无量纲火焰高度随无量纲油盘高度的增加均呈现负指数递减趋势,并逐渐趋于相近的常值。

To investigate the influence of fire source diameters and heights on the characteristics of aviation fuel fire whirls,fire whirls of three different fire sources with diameters of 0. 1,0. 15 and 0. 2 m from zero to 0. 8 m in height were studied experimentally in a square enclosure consisting of four tempered glass panels. Rankine vortex theory was used to analyze the quantitative relationship between mass burning rate and velocity circulation and to explain the air dynamic balance mechanism of fire whirls. On the basis of mass-time variation curve recorded by an electronic balance,mass burning rate data were obtained for different heights in their quasi-steady periods of fire whirls were obtained. Taking the advantage of the continuous whirl fire flame image sequences recorded by a camera,data on time-averaged flame heights in their quasi-steady periods of these experiments were acquired. Theoretical analysis indicated that for a given diameter fire source,under the assumptions that the diameter ratio between the fire whirl core and the fire source was fixed,a linear relationship exists between the mass burning rate and the velocity circulation.Then,through analysis of these experimental data,it was found that the non-dimensional mass burning rates and the non-dimensional flame heights both decreased exponentially first with the non-dimensional fire source heights and eventually approached a close constant.