秸秆固态发酵回转筒内颗粒混合状态离散元参数标定

Calibration of Discrete Element Parameters of Particle in Rotary Solid State Fermenters

为解决秸秆碎料在发酵过程中积热和触氧条件不均的问题,采用离散元法研究回转筒内秸秆颗粒的运动特性。为利用实验值定量对比仿真,基于图像处理法,定量分析实验法和离散元法的滚筒内颗粒混合状态。通过虚拟堆积实验和滚筒内颗粒混合仿真与实验现象进行对比,标定离散元法的颗粒物性参数。结果表明:图像法表征混合状态时,子域大小的划分与颗粒尺寸相关;影响堆积角的主要因素为颗粒间静摩擦因数和密度;影响回转筒内颗粒混合的主要因素为颗粒与壁面粘性系数和颗粒与壁面滚动摩擦因数;验证标定参数结果表明,颗粒参数能用于离散元法描述回转筒内秸秆碎料的运动特性。

In order to solve the problem of accumulated heat and uneven condition of contact oxygen during straw fermentation process, the study of mixing motion of straw modeled by the discrete element method （DEM） was conducted. The accuracy of DEM models depends on the model parameters. Based on the image analysis, quantitative analysis of experiment and DEM method＇ s mixing state were conducted. A calibration process was developed to determine the parameter value by experiment of particle＇ s repose angle and motion. The research results showed that the size of subdomain was related to the particle＇ s size when using the image analysis of mixing characteristics. The size of subdomain affected the resolution of image analysis and it could be set as six times of particle＇ s diameter. The order of factors＇ influence on the staw＇ s repose angle was the coefficient of static friction of particle/particle, the particle density, cohesion coefficient of particle/particle and coefficient of rolling friction of particle/ particle. The order of factors＇ influence on the mixing characteristics of the straw in rotary drum was the cohesion coefficient of particle/wall, the coefficient of rolling friction of particle/wall, coefficient of static friction of particle/wall, coefficient of restitution of particle/wall and coefficient of restitution of particle/ particle. The orthogonal test results were compared with the experiment data. The granular material parameters could be used to describe the mixing characteristics of straw.