基于三维图像分析的浮力扩散火焰几何与辐射特性研究

火焰几何特性和辐射特性是刻画火灾规模及其危害的重要参量。利用三维火焰重构技术,获取了丙烷浮力扩散火焰的火焰高度、表面积、体积和火焰面元视角系数的变化规律。结果表明,三维重构的火焰能够表征真实火焰形态的动态变化。平均火焰表面积和体积均可较好地拟合为热释放速率的幂函数,火焰表面积热释放速率随火焰热释放速率的增加趋于常数。平均火焰高度、表面积和体积与火焰外部平均辐射热流之间具有较好的幂函数关系,且拟合指数随着与火源距离的增大而减小。此外,将点源、圆柱辐射模型和火焰面元积分方法得到的辐射计算值与辐射测量值进行比较,发现火焰面元积分方法能够更好地预测火焰外围的瞬时和平均辐射热流分布。

Study on the geometric and radiative characteristics of buoyant diffusion flame based on 3D image analysis

The flame geometry and radiation characteristics are important parameters in describing the scale of fire and its hazards. In this paper, the three-dimensional measurement method was used to obtain the variations of flame height, surface area, volume and flame view factors of propane buoyant diffusion flame established on circular fire sources. The results showed that the three-dimensional reconstructed flame could represent the dynamic variations of the instantaneous flame shape. The time-averaged flame surface area and flame volume could be fitted well with the fire heat release rates by simple power functions. The heat release rate per unit flame surface area approached a constant value with the increase of the heat release rate. The time-averaged flame height, surface area and volume could be correlated well with the mean radiative heat flux outside the flame by simple power functions. The fitted power tends to decrease with the increase of the distance from the fire source. In addition, the predicted radiative heat fluxes by the point source, cylindrical radiation models and three-dimensional flame panel integration method were compared with the measurement results. It was shown that the three-dimensional flame panel integration method could better predict the instantaneous and mean radiative heat flux distributions around the flame.