High Speed Gas Bearing System with Actively Controlled Clearance

气膜轴承用于支承高速旋转机械，如气体膨胀机、涡轮泵、高速电机等，特别是阶梯式气体轴承因其结构简单、承载能力高、稳定性好而被广泛应用于此类机械。然而，传统的阶梯式气膜轴承存在着对冲击载荷等突变载荷阻尼能力低的缺点，本研究的目的是开发一种新型的动压阶梯式止推气膜轴承，利用压电驱动器主动控制阶梯高度。设计了转速范围为10000 ~ 40000 rpm的实验装置，轴采用内置式高速电机旋转。焊盘的数量为六个，焊盘延伸角度为58 °，垫块外径为32 mm，施加载荷分别为1.5 ~ 2.0kg。这些变量是由流体动力润滑理论，包括惯性效应的步骤。使用这种类型的设备，气膜的弹簧和阻尼能力可以主动控制与变化的台阶高度。另一方面，阶梯推力气体轴承的静态和动态特性的理论研究，为广泛的操作条件。从数值结果来看，流体的综合作用。阐明了台阶处的油膜惯性和气膜的可压缩性对轴承特性的影响。

Gas film bearings are used for supporting high-speed rotating machinery such as gas expander, turbo-pomp, high-speed motor and so on. Especially, stepped gas bearings are widely used for such machinery because of their simple structure, high load carrying capacity and high stability. However, conventional type of stepped gas film bearing has disadvantage of low damping capacity for sudden changes of applied load, for example, impulsive load.The aim of this research is to develop a new type of hydrodynamic stepped thrust gas film bearings by use of the piezo-type actuators to control actively the step height. The experimental apparatus was designed, in which the range of rotational speed is from 10000rpm to 40000rpm and the shaft is rotated with built-in-type high speed motor. The number of pads is six, the pad extent angle is 58deg., the outer diameter of pad is 32mm, the applied loads are 1.5kg to 2.0kg, respectively. These variables were determined by the hydrodynamic lubrication theory including the inertia effects at the step. Using such type of apparatus, the spring and damping capacity of gas film can be controlled actively with varying the step height.On the other hand, the static and dynamic characteristics of stepped thrust gas bearings are theoretically examined for a wide range of operating conditions. From the numerical results, the combined effects of fluid. film inertia at the step and compressibility of gas film on the bearing characteristics were clarified.