School of Mechanical Engineering, Department of Industrial and Physical Pharmacy, Purdue University, West Lafayette, Indiana 47907, USA.
AAPS PharmSciTech. 2013 Mar;14(1):339-51. doi: 10.1208/s12249-012-9917-x. Epub 2013 Jan 17.
In this work, a single tablet model and a discrete element method (DEM) computer simulation are developed to obtain the angular circulation speed of tablets in a vibratory tablet coating pan for range of vibration frequencies and amplitudes. The models identify three important dimensionless parameters that influence the speed of the tablets: the dimensionless amplitude ratio (a/R), the Froude number (aω2/g), and the tablet-wall friction coefficient, where a is the peak vibration amplitude at the drum center, ω is the vibration angular frequency, R is the drum radius, and g is the acceleration due to gravity. The models predict that the angular circulation speed of tablets increases with an increase in each of these parameters. The rate of increase in the angular circulation speed is observed to decrease for larger values of a/R. The angular circulation speed reaches an asymptote beyond a tablet-wall friction coefficient value of about 0.4. Furthermore, it is found that the Froude number should be greater than one for the tablets to start circulating. The angular circulation speed increases as Froude number increases but then does not change significantly at larger values of the Froude number. Period doubling, where the motion of the bed is repeated every two cycles, occurs at a Froude number larger than five. The single tablet model, although much simpler than the DEM model, is able to predict the maximum circulation speed (the limiting case for a large value of tablet-wall friction coefficient) as well as the transition to period doubling.
在这项工作中，开发了一个单片剂模型和离散元法 (DEM) 计算机模拟，以获得在振动片剂包衣锅中片剂的角循环速度，涵盖了一系列的振动频率和振幅。这些模型确定了影响片剂速度的三个重要无量纲参数：无量纲振幅比 (a/R)、弗劳德数 (aω²/g) 和片剂-壁摩擦系数，其中 a 是滚筒中心的峰值振动幅度，ω 是振动角频率，R 是滚筒半径，g 是重力加速度。模型预测，片剂的角循环速度随这些参数的增加而增加。随着 a/R 值的增加，角循环速度的增加率观察到减小。角循环速度在片剂-壁摩擦系数值约为 0.4 后达到渐近值。此外，发现片剂开始循环时，弗劳德数应大于一。随着弗劳德数的增加，角循环速度增加，但在较大的弗劳德数下变化不大。倍周期发生在弗劳德数大于五的情况下，此时床的运动每两个周期重复一次。虽然单片剂模型比 DEM 模型简单得多，但它能够预测最大循环速度（片剂-壁摩擦系数较大值的极限情况）以及倍周期的转变。
