风速对不同结构红松针叶床层失水系数影响的室内模拟研究  

Laboratory study of the effects of wind speed on drying coefficient of fuelbeds composed of Korean pine needles with varied structure

作　　者：张运林[1] 孙萍[1] 胡海清[1] 张俪斌 ZHANG Yunlin;SUN Ping;HU Haiqing;ZHANG Libing(Northeast Forestry University, Harbin 150040, Heilongiiang, China)

机构地区：[1]东北林业大学,黑龙江哈尔滨150040

出　　处：《中南林业科技大学学报》2018年第3期51-58,共8页Journal of Central South University of Forestry & Technology

基　　金：国家自然科学基金项目(31370656)

摘　　要：以红松针叶床层为例,研究风速对其失水系数的影响,为在更多的可燃物类型、更多样的可燃物床层结构和更大的风速范围研究风速对可燃物失水系数的影响提供支持。以当年凋落的红松针叶为材料,设置不同的风速和床层密实度,在实验室内近恒温湿条件下,每隔0.5 h测定一次针叶床层的含水率,获得含水率动态数据。根据Simard平衡含水率模型,计算各床层的失水系数。利用方差分析研究风速和密实度对失水系数的影响,确定影响因子。以密实度为分类条件,拟合红松针叶床层失水系数和风速之间的关系,建立相应模型,分析风速对失水系数的影响。结果表明:不同风速时红松针叶床层失水速率的差异随床层含水率的下降而减少。不同风速、不同密实度时红松针叶床层的失水系数在0.2到1.2 h-1之间。失水系数与风速呈非单调形式:无风时失水系数均值在0.4 h-1左右,从无风到有风,失水系数增加,在风速2 m·s-1或3 m·s-1时达到极值,极值均值在0.9 h-1左右,然后随风速增加而下降。随着密实度增加,失水系数有降低趋势。风速、密实度及其两者的交互作用都对红松针叶床层的失水系数有极显著影响。所得最佳模型形式为k=a+bw/w3+cw2+dw+e,不同密实度的红松针叶床层的平均绝对误差分别为0.002 0、0.057 4、0.734 0 h-1,平均相对误差分别为0.6%、8.1%、10.6%。风速对红松针叶床层失水速率具有极显著影响,该影响在高含水率阶段大于低含水率阶段。红松针叶床层失水系数随风速先增后降,变化幅度与床层密实度有关,用风速的一次多项式和三次多项式之商拟合效果最好。The effects of wind speed on drying coefficient of fuelbed composed of Korean pine needles were analyzed in the study.The aim of the study is to provide more information to better understand the wind effect on fuel desorption for more fuel types,more diversed fuelbed structures and wider wind range.Korean pine needles fallen at collecting year were collected from Northeast Forestry University Maoershan Experimental Forest.Wind speed was set at 0,1,2,3,4 m·s^-1 and fuelbed compactness set at 0.015 8,0.023 6,0.031 6.Three replica were used for each combination of wind speed and fuelbed compactness.Totally 45 fuelbeds were constructed using Koean pine needles with oven dried mass determined before construction and moisture conditioned by soaking and drying indoor for a period.The size of fuelbed was 20 era by 20 cm by 2 cm.For each combination of wind speed and compactness,the three fuelbeds with corresponding compactness were placed on a rack some distance to fans to allow wind speed on the surface of the fuelbeds to equal to the set wind speed.These fuelbeds were weighted every half hour for a successive run of 10 hours.Ambient temperature and humidity were also measured at the same time,Fuel moisture contents were determined after the end of the experiments.Assuming a constant drying coefficient for each fuelbed in the experiment and equilibrium moisture content is in the form of Simard model,the drying coefficients of each fuelbed were estimated.Variance analysis was employed on the effects of wind speed and fuelbed compactness on drying coefficient.Data fittings were conducted over the drying coefficients and wind speeds for each fuelbed compactness separately.Results show that the differences of drying rates of Korean pine needle fuelbeds under different wind speeds decreased with fuelbedmoisture.Dying coefficients of the fuelbeds under vared wind speed ranged from 0.2 h11 to 1.2 h^-1.The relationship between drying coefficient and wind speed was not monotonous.Drying coefficients were around 0.4 hl for zero

关 键 词：风速 失水系数 时滞 含水率 红松 可燃物 

分 类 号：S762.2[农业科学—森林保护学]