优化设计CVI反应器结构的流体可视化研究

Optimum Design of CVI Reactor Aided by Visualization Research

CVI反应器内气体的输运对基体的沉积速度与沉积质量有重要的影响。本文在研制了一套结构简单、可操作性强的气体流动可视化设备的基础上 ,通过流场模拟研究 ,得到的结果是 :1在底部进气方式中 ,采用涡流器与多孔整流器 ,能消除中心射流与减小上部回流区域 ,扩大反应器的有效使用空间 ;使衬底与气体主流方向成一定的夹角 ,能有效阻止气体边界层的分离。 2在侧向进气方式中 ,气体采用 30°喷嘴与衬底成 30°角喷入 ,能在圆柱形衬底面上形成较理想的边界层 ;增大衬底直径有利于消除反应器内的下部回流区。

Lack of flow visualization in CVI (chemical vapor infiltration) reactor research in China has handicapped optimum design of CVI reactor. We developed the necessary visualization equipment and used it to make real optimum design possible. We found that the best aerodynamic laboratory research thinking available to us helped us much in developing visualization research equipment and in using it in simulation studies to obtain good optimum design of CVI reactor. The two major simulation research results that can be very helpful in CVI reactor optimum design are: (1) CVI reactor whose gas enters vertically upwards at bottom of reactor. The placement of a whirlpool and a rectifier near gas entrance eliminates effectively the formation of center jet, minimizes the top return flow, and enlarges the effective usable space of the reactor. (2) CVI reactor whose gas enters through the sidewall of reactor. When the elliptical cross section of the muzzle where the gas enters into the reactor makes angle of 30° with the axis of the muzzle, the ideal gas boundary layer is formed.Return flow at the bottom of reactor can be reduced by making the diameter of substrate larger.