【作者】 孟兆新；

【导师】 曹军；

【作者基本信息】 东北林业大学 ， 机械设计及理论， 2011， 博士

【摘要】 木材生产过程中木材干燥是能耗最大的工序。随着木材干燥技术的提高以及木材干燥设备系统集成度的增加,木材干燥过程中不同性质或状态的材料相互影响以及不同物理域的耦合作用,干燥系统越来越复杂,迫切需要引入木材干燥过程与设备的先进分析方法、设计模型和设计思想。本文针对木材干燥系统的多场耦合现象与设计优化问题,提出了实际工作状态下木材干燥系统的多场耦合建模与分析方法；以提高木材干燥性能为目的,进行了多系统整体优化与导流装置设计研究,并进行了试验验证。基于Reynolds时均方程建立了干燥窑的空气流动模型,构建干燥窑内空气流动与换热的基本控制方程。建立了木材干燥过程的水分迁移模型和热传导方程,完成了对木材干燥过程的机理性描述。提出了木材干燥窑的热力耦合模型和流-固耦合模型,利用数值方法对木材干燥的多场耦合方程进行了求解,得到了干燥窑内流体和温度的宏观分布。为更进一步研究木材干燥过程的微观特性,建立了木材微观结构的元胞自动机模型,采用元胞自动机的自组织局部规则模拟了干燥过程中木材的水分迁移微观机理,为实现多场环境木材干燥系统的性能表征、复杂动态性能的仿真及设计优化等工程目标提供了可能。考虑到木材干燥过程中存在多种不确定性,基于随机摄动技术定量计算了木材的材料随机性、尺寸随机性和导流板对干燥过程的影响,以概率思想表达了木材实际干燥过程所带来的随机差异对其干燥过程和性能的影响,获得了对木材干燥过程最为关键的参数组合。为优化木材干燥系统的整体性能,将多场一体化优化方法引入木材干燥系统的宏观参数优化中。基于随机摄动分析获得的信息,建立了木材干燥系统的优化模型,设计了木材干燥系统的多学科优化算法。优化结果表明,通过优化得到了较为合理的干燥参数组合,优化了木材干燥系统的性能。为更进一步提高干燥窑内气体流动均匀性和增强干燥效果,进行了导流板结构的拓扑优化。建立了导流板拓扑优化模型,对模型进行了求解。导流板结构拓扑优化的结果表明,优化以后的导流板输出风速有了较大提高,材堆的风速均匀性也得到了改善。设计了导流装置模拟试验机进行木材干燥的试验研究。试验测试结果表明,导流装置大幅改善了干燥窑内的介质循环风速均匀性,为干燥性能的提高提供了有效途径。更多还原

【Abstract】 Wood drying is the largest energy consumption process in the production of wood products. With the improvement of wood drying technology and significant increasing of wood drying equipment, the interaction of materials with different quality or state and coupling of different physical domains increases in wood drying process, which shows a more and more complex trend. It is necessary to introduce advanced analytical methods, design models and design ideas for equipment and process of woods drying.This paper focuses on the multi-field coupling and design optimization of wood drying system, and presents the modeling and analysis method for wood drying system under working state. To improve the performance of wood drying, an overall Multi-disciplinary Design Optimization and design of guiding device is proposed, and a test experiment is performed.Considering the physical model of the drying kiln, the air flow model in the drying kiln is established based on the Reynolds equations. The basic equations for air flow and heat transfer of the drying kiln is built. The moisture movement and heat conduction equation of the wood drying process is presented, and the mechanistic description of the wood drying process is proposed.The thermal-mechanical and fluid-structure coupling models of the drying kiln are proposed. The multi-field models are solved by numerical methods, and macro distribution of flow and temperature are obtained. To further study microscopic properties of wood drying process, a cellular automaton model of the wood micro-structure is presented. The micro moist Lire moving mechanism of wood drying is simulated by the self-organizing local rules of cellular automaton, which provides supports for the expression of multi-physics environment, complex dynamic simulation and design optimization of wood drying system.Considering the uncertainty in wood drying process, the influence of randomness of wood material and size, and guiding plate on the drying process is quantitatively calculated using stochastic perturbation technique. The random differences to drying process are described based on the probability theory. The most critical parameters of the wood drying process are obtained.To optimize the overall performance of the wood drying system, the Multi-disciplinary Design Optimization method is introduced into the parameters optimization of the wood drying system. Using the results of perturbation analysis, an optimization model for wood drying is established. The multi-disciplinary design optimization algorithm is designed. The multidisciplinary design optimization results show that reasonable drying parameters are obtained through optimization and the optimal performance of the system of wood drying is achieved.To further improve the uniformity of air flow in the drying kiln and enhance drying effect, the structural topology optimization guiding plate is conducted. The topology optimization model of the guiding plate is established. The results of topology optimization of the guiding plate show that the output air speed of the guiding plate is increased, and the uniformity of the air speed is improved.A simulation tester with guiding device is designed to conduct experimental study of wood drying. Experimental results show that the guiding device significantly improved the uniformity of speed of media circulation, which provides an effective way for the improvement of drying performance.更多还原