基于控制容积干缩模型的X射线法测算木材含水率分布  

Measurement of Wood Moisture Content Distribution by X-Ray Method Based on Control Volume Shrinkage Model

作　　者：吕嘉莉 涂登云[1] 胡传双[1] 王先菊 王清文[1,3] 周桥芳[1] LüJiali;Tu Dengyun;Hu Chuanshuang;Wang Xianju;Wang Qingwen;Zhou Qiaofang(Key Laboratory of Bio-Based Materials and Energy of Ministry of Education,South China Agricultural University,Ghuangzhou 510642;College of Electronic Engineering,South China Agricultural University,Ghuangzhou 510642;Institute of Biomass Engineering,South China Agricultural University,Ghuangzhou 510642)

机构地区：[1]华南农业大学生物基材料与能源教育部重点实验室,广州510642 [2]华南农业大学电子工程学院,广州510642 [3]华南农业大学生物质工程研究院,广州510642

出　　处：《林业科学》2023年第11期76-84,共9页Scientia Silvae Sinicae

基　　金：广东省自然科学基金项目“热-湿-力多场耦合控制的木材压缩密实化路径及调控”(2023A1515010502);国家自然科学基金面上项目“胶合层积高频加热弯曲定型机理及其流变学特性”(32271783)。

摘　　要：【目的】构建木材控制容积干缩模型,采用X射线法测量木材剖面密度,计算含水率分布,为科研和生产测定木材含水率及其分布提供技术支撑。【方法】将绝干前木材沿厚度方向划分控制容积,引入木材全干干缩率参数并依据木材干缩原理计算绝干后木材控制容积厚度,利用木材剖面密度确定控制容积密度,完整构建求解绝干前木材控制容积含水率计算模型。模型中绝干前木材控制容积含水率、绝干后木材控制容积厚度和密度等变量高度耦合,通过开发迭代算法并在Matlab软件中编制计算程序求解以上变量,该算法以绝干后木材实际厚度为约束条件不断修正木材全干干缩率,有效避免因全干干缩率引入值与真实值偏差带来的计算误差。同时,开展毛白杨木材对流干燥试验,利用本研究方法测算不同干燥阶段木材含水率分布,并与木材实际平均含水率(称重法)以及假设木材厚度方向均匀干缩法测算的含水率分布进行对比分析。【结果】本研究方法测算的木材平均含水率与称重法测量的木材平均含水率非常接近,二者相关系数的平方(R2)在0.9992以上。本研究方法与均匀干缩法相比,在FSP(纤维饱和点)以上时2种方法测算的木材含水率分布一致;在FSP以下时本研究方法测算的木材含水率在试件表层相对较低、芯层相对较高,芯、表层含水率梯度较大。木材分别干燥45、69和134 h时,本研究方法测算的芯、表层木材含水率差分别为22.61%、15.65%和5.58%,均匀干缩法测算的芯、表层含水率差分别为18.06%、11.51%和4.27%,2种方法的绝对偏差分别为4.55%、4.14%和1.34%,差异较明显。相比均匀干缩法,干燥时间为45、69和134 h时,本研究方法测算的木材含水率分布其精度分别提高3.80%、6.00%和4.04%。【结论】本研究构建的控制容积干缩模型充分考虑含水率分布引起的非均匀干缩,可弥补均匀干缩【Objective】The shrinkage model of wood control volume is established,the wood profile density measured by Xray method is used to calculate the moisture content distribution,which provides a new method for the calculation of wood moisture content distribution.【Method】The wood before oven drying is divided into control volume along the thickness direction,the oven-dry shrinkage parameter is introduced,the thickness of the wood control volume after oven drying is calculated according to the wood shrinkage principle,the density of the control volume is calculated by the wood profile density,and the calculation model for computing the moisture content of the wood control volume before oven drying is constructed.In the calculation model,the moisture content of the wood control volume before oven drying and the thickness and density of the wood control volume after oven drying are highly coupled.Therefore,the results of the above variables are computed by developing an iterative algorithm and compiling a calculation program in Matlab software.The algorithm takes the actual thickness of the wood after oven drying as the constraint condition to continuously correct the oven-dry shrinkage parameter of the wood,it can effectively avoid the calculation error caused by the deviation between the introduced value of oven-dry shrinkage and the real value.At the same time,this study carried out Populus tomentosa in the convective drying test of wood,the calculation method of this study is used to calculate the moisture content distribution of wood in different drying stages,and compared with the actual average moisture content of wood(weighing method)and the moisture content distribution calculated by method of assuming uniform shrinkage in the thickness direction of wood.【Result】The average moisture content of wood measured by the calculation method in this study is very close to that measured by the weighing method,and the correlation coefficient square(R2)is more than 0.9992.Compared with uniform shrinkage method t

关 键 词：干缩模型 X射线法 含水率分布 控制容积 迭代计算 

分 类 号：S781.71[农业科学—木材科学与技术]