基于玻璃化转变理论的稻谷籽粒干燥应力数值模拟及爆腰声发射法研究

项目名称： 基于玻璃化转变理论的稻谷籽粒干燥应力数值模拟及爆腰声发射法研究

项目编号： No.31471618

项目类型： 面上项目

立项/批准年度： 2015

项目学科： 农业科学

项目作者： 吴中华

作者单位： 天津科技大学

项目金额： 78万元

中文摘要： 稻谷爆腰降低稻米品质和经济价值。为了抑制爆腰，当前稻谷往往采用低温干燥，导致干燥机生产效率低、能耗高，限制了我国稻谷机械化干燥的推广。课题拟发展一种稻谷高温快速干燥新工艺，以实现稻谷高效、保质干燥。为此，课题从玻璃化转变角度，研究新工艺所涉及的籽粒爆腰产生机理、模拟预测、动态无损检测和精细控制。建立基于玻璃化转变理论的干燥应力模型，采用适体坐标网格和动网格技术提高模拟精度；模拟热风干燥过程中籽粒内部应力的时空分布，并根据内功-断裂能评定标准预测爆腰形成时间及位置，阐明爆腰产生的细观损伤机制。提出了一种基于声发射的籽粒爆腰的动态无损检测方法；通过研究稻谷干燥裂纹的声发射模式和特征，探索基于声发射的稻谷爆腰预警机制及干燥过程精细控制方法。结合数值模拟和声发射法，研究高温缓苏抑制稻谷爆腰机理和条件，以突破稻谷低温干燥限制，设计和优化稻谷高温快速工艺；进行稻谷高温干燥小试实验，评价实际干燥效果。

中文关键词： 稻谷干燥；应力；爆腰；玻璃化转变；声发射

英文摘要： Fissuring reduces rice quality and its economic value. To prevent fissuring, the low-temperature drying processes of paddy rice are often applied and this technology causes a low productivity and high energy consumption of the dryer, which hiders the wide application of artificial drying in China. This project aims at developing a high temperature drying technology for paddy that yields higher quality, improved productivity and lower energy consumption relative to current low-temperature drying processes. To realize this aim, a series of fundamental studies will be conducted on the generation mechanisms, prediction, dynamic and nondestructive testing, and fine control of fissuring by considering the glass transition process of paddy rice during process. We establish the rice drying stress model based on the glass transition theory and improve the model validation by applying the body-fitted coordinates mesh and dynamic mesh technologies. By carrying out numerical simulation of the hot air drying process, the spatial and temporal distribution of internal stresses in rice kernel during the drying process will be obtained; thus where and when fissures will form can be determined according to the internal work-fracture energy assessment criterion. The model will allow prediction of fissuring during the drying process, and identifying the micromechanical damage mechanisms leading to breakage of the rice kernels. We will propose a new dynamic, nondestructive testing method to quantitatively determine the rice fissures using the acoustic emission method. By studying the acoustic emission patterns and characteristics of rice fissuring during the drying process , it will be possible to develop an early warning system for fine control of the drying process. By combining the new stress model with the acoustic emission method, We will study the mechanism and function of the high-tempering in preventing rice fissuring, which will permit better design and optimization of the high temperature fast drying technology for paddy rice. Finally, small scale experiments of the proposed high-temperature drying method for paddy rice will be conducted to validate the model and test the control scheme. The actual drying effects will be also evaluated.

英文关键词： Rice drying;Stress;Fissure;Glass transition;Acoustic emission