【目的】研究Rothermel林火蔓延速率预测模型及另外2种以Rothermel模型为核心的蔓延速率预测模型对南方8种典型森林地表死可燃物的适用性,为林火蔓延速率预测提供理论支撑和指导。【方法】以南方地区8种典型速率地表死可燃物为对象,根...【目的】研究Rothermel林火蔓延速率预测模型及另外2种以Rothermel模型为核心的蔓延速率预测模型对南方8种典型森林地表死可燃物的适用性,为林火蔓延速率预测提供理论支撑和指导。【方法】以南方地区8种典型速率地表死可燃物为对象,根据研究对象的野外实际条件,在东北林业大学帽儿山实验林场风洞实验室内,构建不同可燃物床层含水率、载量及高度的可燃物床层,每种可燃物在平地无风条件下进行36次点烧试验,共288次点烧,记录每种可燃物类型不同配比条件下的蔓延速率。通过直接使用Rothermel模型、重新估计Rothermel模型参数、对Rothermel模型形式改进后自建模型的对比,得到最合适的预测模型。【结果】 1)平地无风条件下,南方8种典型森林地表死可燃物床层最大蔓延速率为0.55 m ·min -1 ,平均蔓延速率由大到小依次为:华山松、云南松、毛竹、柳杉、杉木、马尾松、麻栎及青冈栎。2)直接使用Rothermel模型预测的林火蔓延速率误差较大,平均绝对误差为0.18 m ·min -1 ,平均相对误差为70.0%。3)重新估计参数后的Rothermel模型及自建模型,预测的可燃物蔓延速率精度显著提高,平均绝对误差分别为0.04、0.037 m ·min -1 ,平均相对误差分别<18%、16.45%。4)重新估计参数的Rothermel模型与自建模型的预测误差的差异不显著,其中自建模型的预测值与实测值的 R 2 变化在0.71~0.90,平均为0.80。【结论】对南方8种典型森林的地表死可燃物类型,在平地无风条件下,重新估计参数的Rothermel模型及自建模型的预测精度相近,但自建模型可能更简单易用,可预测平地无风条件下可燃物地表火蔓延速率。展开更多
To investigate the charring rate of timber beams exposed to three-side fire, a total of fifteen new and used Douglas-Fir timber beams in four groups exposed to three-side fire were experimentally studied, together wit...To investigate the charring rate of timber beams exposed to three-side fire, a total of fifteen new and used Douglas-Fir timber beams in four groups exposed to three-side fire were experimentally studied, together with the finite element analyses of the temperature distribution in the beam section. The durations of fire exposure were 0 (on a test piece), 10, 15, 20 and 30 min, according to the ISO 834 standard fire curve. The charring depth of each timber beam was calculated by averaging the values at one-third and two-thirds along each cross section to give the charring rate of timber beams. It was found that the timber beam's charring rate reduces as the duration of fire exposure increases and the vertical charring rate is slightly higher than the horizontal one. The areas of beam sections reduce due to charring and the strength and stiffness of the pyrolysis layer near the charring edge decrease owing to the high-temperature. The average horizontal and vertical charring rates are 0.98 and 1.08 mm/min, respectively. To take into account the difference between the test furnace temperature curve and the ISO 834 stand- ard fire curve, some corrections were made for these data to yield the solution for charring rate. With the help of the finite element software ANSYS, the temperature distribution of the wood's cross-section was analyzed. The longer the exposure time is, the greater the effect of density will impose on the distribution of temperature, but the moisture content has no effect.展开更多
文摘【目的】研究Rothermel林火蔓延速率预测模型及另外2种以Rothermel模型为核心的蔓延速率预测模型对南方8种典型森林地表死可燃物的适用性,为林火蔓延速率预测提供理论支撑和指导。【方法】以南方地区8种典型速率地表死可燃物为对象,根据研究对象的野外实际条件,在东北林业大学帽儿山实验林场风洞实验室内,构建不同可燃物床层含水率、载量及高度的可燃物床层,每种可燃物在平地无风条件下进行36次点烧试验,共288次点烧,记录每种可燃物类型不同配比条件下的蔓延速率。通过直接使用Rothermel模型、重新估计Rothermel模型参数、对Rothermel模型形式改进后自建模型的对比,得到最合适的预测模型。【结果】 1)平地无风条件下,南方8种典型森林地表死可燃物床层最大蔓延速率为0.55 m ·min -1 ,平均蔓延速率由大到小依次为:华山松、云南松、毛竹、柳杉、杉木、马尾松、麻栎及青冈栎。2)直接使用Rothermel模型预测的林火蔓延速率误差较大,平均绝对误差为0.18 m ·min -1 ,平均相对误差为70.0%。3)重新估计参数后的Rothermel模型及自建模型,预测的可燃物蔓延速率精度显著提高,平均绝对误差分别为0.04、0.037 m ·min -1 ,平均相对误差分别<18%、16.45%。4)重新估计参数的Rothermel模型与自建模型的预测误差的差异不显著,其中自建模型的预测值与实测值的 R 2 变化在0.71~0.90,平均为0.80。【结论】对南方8种典型森林的地表死可燃物类型,在平地无风条件下,重新估计参数的Rothermel模型及自建模型的预测精度相近,但自建模型可能更简单易用,可预测平地无风条件下可燃物地表火蔓延速率。
基金supported by the National Natural Science Foundation of China (Grant No. 51178115)the Priority Academic Program Development of Jiangsu Higher Education Institutions
文摘To investigate the charring rate of timber beams exposed to three-side fire, a total of fifteen new and used Douglas-Fir timber beams in four groups exposed to three-side fire were experimentally studied, together with the finite element analyses of the temperature distribution in the beam section. The durations of fire exposure were 0 (on a test piece), 10, 15, 20 and 30 min, according to the ISO 834 standard fire curve. The charring depth of each timber beam was calculated by averaging the values at one-third and two-thirds along each cross section to give the charring rate of timber beams. It was found that the timber beam's charring rate reduces as the duration of fire exposure increases and the vertical charring rate is slightly higher than the horizontal one. The areas of beam sections reduce due to charring and the strength and stiffness of the pyrolysis layer near the charring edge decrease owing to the high-temperature. The average horizontal and vertical charring rates are 0.98 and 1.08 mm/min, respectively. To take into account the difference between the test furnace temperature curve and the ISO 834 stand- ard fire curve, some corrections were made for these data to yield the solution for charring rate. With the help of the finite element software ANSYS, the temperature distribution of the wood's cross-section was analyzed. The longer the exposure time is, the greater the effect of density will impose on the distribution of temperature, but the moisture content has no effect.
