A study on fire plume behaviour in cross-winds.

侧风中火羽行为的研究。

• 批准号: 16310109
• 负责人: OKA Yasushi
• 金额: $ 9.98万
• 依托单位: Yokohama National University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 2004
• 资助国家: 日本
• 起止时间: 2004 至 2005
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-16310109/
• 关键词: fire plume; cross wind; merged fame; trajectory position; temperature width of fire plume; 温度場; 温度幅

On the basis of the experimental study using a single fire source and/or multiple fire sources focusing on the flame shape and fire plume behavior in the presence of crosswinds, the following conclusions were obtained.(1)Dimensionless formula for the apparent flame height of an inclined flame under the influence of cross-wind has been developed based on the modified dimensionless heat release rate, Froude number and equivalent length of burner. An empirical formula also has been developed to predict the flame tilt angle considering the burner shape. This model is derived from the balance of mass fluxes of wind and hot current, combined with centreline properties of a fire plume.(2)An empirical formula for predicting the position of an inclined fire plume axis by applying the logistic function including the variables expressed by the combination function of heat release rate and crosswind velocity was proposed. A new formula for estimating the velocity along the inclined fire plume axis … More using the values of the temperature rise, crosswind velocity and travelling distance was developed based on the assumption that there is a virtual ceiling at the upper limit of the height that the hot current can reach. Further, the behaviour of this hot current, influenced by the crosswind, closely resembles the ceiling jet that flows under this virtual ceiling. This correlation is useful, and it is applicable for the estimation of the velocity along the fire plume axis irrespective of the presence of a crosswind.(3)The section shape of the inclined fire plume was experimentally clarified based on the plume width defined by temperature. In addition, it was shown that the temperature distribution in the inclined fire plume was expressible as the sum of two kinds of Gaussian distributions, one is temperature distribution directory carried from the fire source and the other is carried from the upstream by the cross-winds.(4)The reproducibility of the fire plume properties in the cross-winds was examined by using two kinds of CFD codes. It became clear that the height of the continuous flame and the position of the fire plume axis were able to be reproduced to some degree by applying the combustion model and by devising the method of setting the heat release rate. Two kinds of CFD codes showed mutually different results. Moreover, the temperature decreasing properties along the inclined fire plume were different with the experimental results.(5)The empirical formulae for predicting the apparent flame height, the position of an inclined fire plume and the temperature decreasing along an inclined fire plume for a single fire source were examined whether it was possible to apply by comparing them with the experimental results with multiple fire sources in cross-winds. Less

通过对侧风作用下单火源和多火源的火焰形态和羽流行为的实验研究，得出以下结论。（1）基于修正的无因次热释放率、弗劳德数和燃烧器当量长度，推导了侧风影响下倾斜火焰表观火焰高度的无因次计算公式。考虑燃烧器形状，还建立了预测火焰倾角的经验公式。该模型是从风和热气流的质量通量平衡出发，结合火羽流的中心线特性建立的。(2)An提出了一个用热释放速率和风速的组合函数表示的Logistic函数预测倾斜火羽轴线位置的经验公式。倾斜火羽流轴向速度沿着分布的新公式 ...更多信息 基于热流可达高度上限处存在虚拟天花板的假设，利用温升、风速和行进距离的值，此外，这种热流的行为，受风的影响，非常类似于在这个虚拟天花板下流动的天花板射流。这种相关性是有用的，它适用于估计的速度沿着火羽轴线，而不考虑存在的一个障碍。（3）根据温度定义的羽流宽度，实验确定了倾斜火焰羽流的截面形状。此外，还发现倾斜火羽流中的温度分布可以表示为两种高斯分布之和，一种是火源携带的温度分布方向，另一种是侧风从上游携带的温度分布方向。（4）采用两种CFD程序对侧风作用下的火灾羽流特性进行了再现性研究。很明显，连续火焰的高度和火羽轴线的位置能够在一定程度上通过应用燃烧模型和通过设计热释放速率的设置方法来再现。两种计算流体动力学程序显示了相互不同的结果。此外，倾斜火羽流沿沿着的降温特性与实验结果也存在差异。（5）通过与侧风中多火源实验结果的比较，验证了单火源下火焰高度、倾斜羽流位置和沿沿着方向温度下降的经验公式是否适用。少