不同外部辐射热流下小尺寸原木燃烧特性实验研究  

Experimental investigation of the burning behavior of small logs with various external radiative heat fluxes

作　　者：胡皓玮 祁桢尧 时敬军 纪杰[1] HU Haowei;QI Zhenyao;SHI Jingjun;JI Jie(State Key Laboratory of Fire Science,University of Science and Technology of China,Hefei 230026,China)

机构地区：[1]中国科学技术大学火灾科学国家重点实验室,合肥230026

出　　处：《清华大学学报（自然科学版）》2022年第6期1023-1030,共8页Journal of Tsinghua University(Science and Technology)

基　　金：国家重点研发计划项目(2020YFC1522800)。

摘　　要：木材因其优异的隔热性能、力学强度和观赏价值而被广泛应用于建材、家具和工艺品中。作为一种可燃材料,木材的燃烧过程会经历热解、点燃、炭化与开裂。目前对于木材燃烧特性的研究,样本通常选用均质的人造板材或避开缺陷的原木。但实际情况下,不同树种结构各异,制备而成的原木板表面的纹理分布不均匀,同时原木中还存在木节等结构缺陷,这些因素都可能影响原木板材的燃烧过程。该文在火焰蔓延量热仪下开展小尺寸原木板材燃烧实验,使用3种树种(辐射松、白松、杉木)的原木,比较了不同外部辐射热流下原木的燃烧特性,获得了不同树种的典型燃烧行为、热释放速率曲线和点燃特性。结果表明,不同树种、不同纹理、结构缺陷(木节)会影响原木的燃烧行为。随着外部辐射热流的增加,原木的点燃时间缩短,热释放速率峰值增加。在该文实验工况范围内,外部辐射热流15 kW/m^(2)时原木点燃时间的重复性差异最大约35%,高于均质人造板材,体现了原木结构非均质性对其燃烧特性的影响,但这一差异随外部辐射热流的增加而减小。对于同一树种,疏、密纹理样本的燃烧特性存在差异,辐射松疏、密纹理原木点燃时间差值最大可达500 s以上,且平行于纹理方向上的炭化速率高于垂直于纹理方向上的。杉木中含有大量木节,低外部辐射热流条件下木节的存在会导致点燃时间缩短、热释放速率峰值增加。Wood is widely used in building materials, furniture and handicrafts due to its excellent thermal insulation properties, mechanical strength and ornamental value. However, wood is a combustible material that undergoes pyrolysis, ignition, charring and cracking. Most current studies on the burning characteristics of wood have used relatively homogeneous artificial boards or logs without defects. However, in practical applications, wood structures vary among different species, the wood surface grain is not uniform, and there are many structural defects in the logs, such as knots. These factors cause the wood burning characteristics to differ significantly from that of a homogeneous board. This study experimentally investigated the burning of small logs made of white pine, radiata pine and Chinese fir. The burning behaviors were compared with different external radiative fluxes with measurements of the burning phenomenon, heat release rate, and ignition characteristics. The results show that the wood species, the grains and the defects(knots) all affect the wood burning characteristics. Increasing the external heat flux reduces the ignition time and increases the peak heat release rate. In the range of operating conditions in this paper, the difference of the log ignition time at the external radiative heat flux of 15 kW/m^(2) in the repeated tests is about 35%, which is higher than that of the homogeneous artificial wood. This trend indicates the effect of structural heterogeneity on the combustion characteristics of logs, but this difference decreases with the increase of the external radiative heat flux. For the same tree species, the combustion characteristics of sparse and dense grain samples are different. The highest ignition time difference is more than 500 s, and the charring rate is higher in the direction parallel to the grain than in the direction perpendicular to the grain. The Chinese fir contains a large number of knots, which can reduce the ignition time and increase the peak heat release rate at the

关 键 词：木材燃烧 原木 纹理 木节 炭化 

分 类 号：X959[环境科学与工程—安全科学]