针盘式粉碎机圆柱齿钉二维绕流数值模拟

为了分析针盘式粉碎机静圆柱齿钉的气动力学特性,利用计算流体力学(diesel engine emission experiments,CFD)方法,对粉碎机中二维单圆柱齿钉的绕流问题进行研究。在进行计算之前,采用均匀来流中的圆柱绕流问题对计算模型进行验证,并且对数值计算中的网格和时间步长独立性均进行了算例考核。结果表明:在雷诺数小于200的范围内,流动出现3种不同的流态;在稳定分离区中圆柱齿钉上的附着涡最大长度约等于齿钉直径,且附着涡随雷诺数增加出现了消亡的现象;在不稳定泄涡区流动只在较小的雷诺下呈现出周期性,圆柱齿钉上受到流体周期性的升力和阻力均很小,在较大雷诺数下,流动的无量纲频率增加,且不再由单个频率主导,出现了一个频带;在不稳定泄涡区的无量纲频率比均匀来流中的圆柱绕流情况小一个数量级。该文为研究粉碎机圆柱齿钉在高雷诺数下的受力情况提供了参考。

Numerical simulation of flow around circular cylinder in pin pulverizer

In order to investigate the aerodynamic performance of circular cylinders in a pin pulverizer, the computational fluid dynamics method was applied in the study of flow past a circular cylinder nail in a 2D model. The problem of flow around a circular cylinder in uniform inflow was used to verify the correctness of the computational model. The independence of mesh and time step were also investigated. The results showed that flows could be classified into three flow regimes when Reynolds numbers varied within 200. In the stable separating regime, the max length of closed wakes was approximately equaled to the diameter of the cylinder, and the wakes would vanish as the increasing of Reynolds number. In the unstable vortex shedding regime, periodical vortices shedding occurred at low Reynolds numbers. Lift force and drag force on the cylinder were small. As Reynolds number grew, the dimensionless frequency increased and different frequency components appeared. The dimensionless frequency was one order of magnitude smaller than that of the flow around a cylinder in uniform inflow. It lays the foundation of the research on the problem of flow around cylinders at high Reynolds numbers.