基于CFD-DEM的稻谷通风阻力数值模拟与试验

为探究稻谷通风中谷层阻力的变化规律,基于离散元理论,构建了2个品种稻谷颗粒的数值模型,采用CFD-DEM耦合模拟了垂直圆管约束中的稻谷颗粒群在不同风速及谷层深度下通风阻力的变化规律。结果表明:在表观风速一定时,谷层阻力随谷层深度的增加而非线性增加(R20.99);当谷层深度一定时,谷层阻力随表观风速的变化关系可表达为二次多项式形式(R20.98);不同品种的稻谷在相同条件下谷层阻力变化趋势相同,数值不同,长粒型较短粒型谷粒通风阻力小。通过搭建试验装置,对模拟结果进行了试验验证,成对t检验(α=0.01)结果表明差异不显著,数值模拟与试验结果吻合,证明应用CFD-DEM方法数值模拟稻谷通风阻力是可行的,获得的拟合方程可用于谷仓通风阻力计算,指导就仓干燥系统管网设计及风机的选配。

Numerical Simulation and Experiment on Paddy Ventilation Resistance Based on CFD-DEM

To explore the change rule of paddy layer ventilation resistance, guiding the tube network of ventilation drying warehouse design and fan selection, a numerical model of two varieties of paddy was constructed based on discrete element theory. The changing regulation of ventilation resistance of paddy at a series of wind velocities and paddy layer depths in a vertical tube was simulated by the coupled CFD-DEM model. The results showed that, when the apparent wind speed was constant, the resistance of paddy layer showed nonlinear increasing (R2>0.99) relationship with the increase paddy layer depth; when paddy layer depth was constant, the resistance of paddy layer showed a quadratic nonlinear increasing (R2>0.98) relationship with the increase of the apparent wind speed. Different varieties of paddy were under the same condition, and the layer resistance had the same change trend, but the numerical values was different, the ventilation resistance of long grain type was smaller than short grain type. By building test equipment, the simulation results of the experimental verification, paired t test results showed no significant difference was found, and the numerical simulation and experimental results agreed. The results testified that the numerical simulation of ventilation resistance in paddy was feasible by the method of CFD-DEM. The fitting equation obtained can be used for calculating barn ventilation resistance and guiding the tube network of in store drying system design, fan selection, paddy ventilation resistance simulation and engineering practice.In the design and operation on barn drying system, the apparent wind speed is appropriate at 0.2~0.3 m/s, paddy layer depth is not more than 1.5 m, the difference of grain type should be considered when calculating the ventilation resistance.