【作者】 张瑞雪；

【导师】 曹军；

【作者基本信息】 东北林业大学 ， 控制理论与控制工程， 2010， 硕士

【摘要】 木材是全球应用最广的工程材料之一。木材干燥是一个复杂的强耦合非线性动力学系统,在干燥过程中存在外界的干扰和模型的不确定性,如何建立有效的干燥模型是木材干燥的重要基础研究内容之一,也是实现干燥全自动控制,提高干燥质量,减少能量消耗,缩短干燥时间的先决条件。对干燥一定树种的木材来说,当其他影响干燥速率的因素(如空气温度、湿度、板材厚度)相对恒定时,空气流速与木材干燥的速率存在某一关系,循环风速也是木材干燥的一个重要因子,正确选用循环风速,不仅对干燥速度和干燥质量有较大影响,而且可使能耗大幅度降低。本文针对实验室用顶风式木材干燥窑的内部气流循环分布规律和影响因素进行了研究,探讨了木材干燥窑内的风速因子对干燥窑性能的影响重要性。将计算流体力学CFD(Computational Fluid Dynamics)方法引入木材干燥窑建模及仿真的研究中,对其建立了三维稳态的模型,进行了数值仿真计算(使用FLUENT计算流体力学软件)。计算结果给出了合理的流场分布,并与实验值进行了对比,并用所做的实验数据对仿真模拟结果进行了对比分析,验证了所采用的CFD模型的可行性与准确性。在以上研究的基础上,进一步预测了实验室用顶风式木材干燥窑内部空气的速度场的分布情况,分析了实验室用顶风式木材干燥窑在风机给定不同风速时的空气流动特性,同时又讨论了各工况下的平均风速(?)值、均方差σ值和变异系数V值,进一步对比分析研究了所建立的顶风式木材干燥窑模型的最优风速指标。本文的研究结果表明：通过实验数据与模型仿真结果的比较,验证了所建立的木材干燥窑的CFD模型的可行性与准确性,因此该CFD模型亦可用于不同干燥阶段的速度、温度、湿度及压力场的仿真模拟研究。通过对各工况的对比计算分析得出,风机给定气流速度为3m／s时的变异系数较低即气流循环分布的均匀性优于其他情况,并且各测点的气流速度均在资料给定的最佳速度范围内,因此综合各种因素考虑认为,对于所建立的实验室用顶风式木材干燥窑的CFD模型,在七种工况中,工况4(即风机给定风速为3m／s)为最优情况,此仿真结果对顶风式木材干燥窑的初始风机给定风速的选取及干燥控制技术的改进有一定的参考和指导意义,提高我国的节能干燥窑的科技水平,为改进木材干燥窑不同干燥时期窑内温湿度、速度等的信息检测与仿真技术提供了一种新的方法。更多还原

【Abstract】 Wood is one of the most popular engineering materials. Wood drying is a strong coupling, nonlinear and complex dynamic system, and external interference and model uncertainty exists during the drying process. So how to create an effective model of drying is an important foundation study of wood drying, and it is also the pre-condition of realizing full automatic control of drying, improving drying quality, reducing energy consumption and reducing the drying time. The operating procedure of a certain species of wood drying, when the other factors that affect the drying rate (such as temperature, humidity, plate thickness) is relatively constant, the air flow and the timber dry has some relations. The airflow velocity is also an important factor of wood drying, so the correct selection of airflow velocity, not only has to the drying velocity and the drying quality affects greatly, moreover may cause the energy consumption to reduce large scale.The distribution of air speed and the influence factors of it in the laboratory-type wood drying kiln were studied in this essay and a discussion on the importance of airflow velocity factor to the wood drying kiln is conducted for developing improved designs with respect to ventilation efficiency. In his paper, CFD (Computational Fluid Dynamics) method will introduce modeling and simulation of wood drying kiln research. Three dimension model of wood drying kiln is simulated used commercial using software of FLUENT. The computation gives related computing velocity field. With results of simulation compared with experimental data have done, the feasibility and veracity of numerical simulation by software of FLUENT to wood drying kiln is validated. Then internal air velocity distributions are forecasted, meantime different airflow velocities which the fan given are analyzed. Besides, it is also discussed the average airflow velocity v,mean square errorσand coefficient of variation V in different conditions, further comparative analysis of the wood drying kiln in the best airflow velocity indicators.The results indicate that experimental data by comparison with the simulation results to verify the established CFD method of wood drying kiln of the feasibility and accuracy. Therefore, the CFD model can be used for different stages of drying rate, temperature, humidity and pressure field simulation study. Through the comparison of the various conditions calculation and analysis, when airflow velocity is 3m/s,the coefficient of variation is smaller and the airflow distribution is better. Therefore, comprehensive consideration of various factors that the defiance of established laboratory-type wood drying kiln model, the condition 4 (then a given wind velocity 3m/s) for the optimal situation in the seven research conditions. The simulation results of the wood drying kiln fan for a given wind velocity there is some reference and selection guide, then optimal control of wood drying and improving the technological level of energy-saving drying kiln. And for wood drying kiln temperature and humidity in different kiln drying time and speed information detection and simulation provides a new way.更多还原