横向风条件下线性火焰热特性

Thermal Properties of Line Fire Under Cross Wind

通过搭建横向风下线性火焰燃烧的实验装置,对线性火焰下游壁面处温度以及辐射热流进行了研究。结果表明,壁面温度随无量纲下游距离增加而减小,且呈分段函数分布。量纲分析和数据拟合表明,无量纲辐射热流随着无量纲下游距离增加而减小。计算结果表明,辐射分数随着风速的增加而略微减小。考虑到火焰浮力和环境风动量的共同作用,依据火焰附壁长度,将火焰分为浮力主控区和动量主控区,建立了一种修正的线性火焰对下游壁面热辐射的预测模型,模型预测与实验结果吻合较好。

An experimental device of line fire under cross wind was built,and experimental simu-lation was conducted to study the hot gas temperature and radiant heat flux near the ground surface along the downstream direction.It is found that the gas temperature and the radiant heat flux decrease as the downstream distance increases.The horizontal length of the flame was suggested as the characteristic length for the dimensionless downstream distance and the dimensionless radiant heat flux.Data fitting shows that the gas temperature and the dimensionless radiant heat flux can well fit the dimensionless downstream distance.The radiative fraction,inversely calculated by the radiant heat fluxes at five measurement positions,shows a slight decrease as the cross-wind speed increases.Due to the coupled effect of wind momentum and flame buoyancy,the whole flame was divided into the momentum-and buoyancy-controlled regions with the flame drag length as the boundary,and then a revised model was developed to predict the thermal radiation from the line fire to the ground surface in the downstream direction.The model prediction agrees well with the experimental measurement.