有风条件下倾斜柱体池火视角系数模型与计算

View Factor Model and Calculation of Inclined-Cylinder Pool Fire in Wind

采用倾斜柱体模型计算有风情况下池火燃烧过程的热辐射,是评估池火灾危险性较为可靠的模型。但是,由于倾斜柱体的视角系数无法解析计算,其应用受到了严重限制。根据视角系数的定义,本文将倾斜柱体分成侧面与水平椭圆顶面两部分,分别推导了池火辐射对周围任意朝向斜柱体中心线方向观测点的视角系数计算公式。之后对池火灾辐射表面进行合理离散化,数值计算了任意倾角池火灾的周围任意点视角系数,讨论了由于火焰倾斜对水平面上视角系数等高线的影响,并进一步分析了距离、高度以及火焰长度对视角系数的定量影响规律。

Under the circumstance of wind blowing, it is much reliable to calculate the heat radiation and to evaluate the risk of pool fire by adopting the inclined cylinder model. However, for the inclined cylinder, its view factor cannot be solved analytically, which limited the use of the pool fire inclined cylinder model. Thus in the present study, the cylinder is divided into two separated parts, i.e., the up elliptic plane and the surface bounded by the up elliptic plane and the pool on the ground. View factor calculation equations for these two different parts were derived for any space point which pointing to the central directrix. By performing discretization to these two different parts, the view factor value for cylinder with any arbitrary obliquity can then be numerically calculated from any space points. Finally, the effect the wind induced fire incline on the contour of view factors on the ground was investigated. The influences of the flame length as well as the distance and height of the observation point were explored.