Active Control of Hydrodynamic Gas Film Bearings with Piezo-Actuator

流体动力气膜轴承用于支撑高速旋转机械，如气体膨胀机、涡轮泵、高速电机等。特别是阶梯式气体轴承，由于其结构简单，承载能力高，稳定性高，被广泛应用于此类机械。然而，传统的阶梯式气膜轴承对于外加载荷（如脉冲载荷）的突然变化阻尼能力较低。本研究的目的是利用压电式作动器主动控制台阶高度，开发一种新型的液力阶梯式推力气膜轴承。设计了实验装置，其中转速范围为0rpm ~ 30000rpm，轴由内置式高速电机旋转。垫片数量为6个，垫片延伸角为55度。，垫片外径为30mm，施加载荷范围分别为1.5kg ~ 2.62kg。这些变量是由流体动力润滑理论确定的，包括台阶上的惯性效应。目前，设备的旋转部分已经完成，包括轴承面在内的定子正在制造中。采用这种类型的轴承，可以通过压电作动器改变步进高度来主动控制气膜的阻尼能力。另一方面，在广泛的工作条件下，从理论上研究了阶梯推力气体轴承的静态和动态特性。从数值结果出发，阐明了步进液膜惯性和气膜可压缩性对轴承特性的综合影响。

Hydrodynamic 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 aime of this resarch is to develop a new type of hydrodynamic stepped thrust gas film bearings by use of the piezo-type actuators to control activily the step height. The experimental apparatus was designed, in which the range of rotational speed is from 0rpm to 30000rpm and the shaft is rotated with built-in-type high speed motor. The number of pads is six, the pad extent angle is 55deg., the outer diameter of pad is 30mm, the range of applied load is from 1.5kg to 2.62kg, respectively. These variables were determined by the hydrodynamic lubrication theory including the inertia effects at the step. At the present step, the rotating part of apparatus has been completed, and the stator including bearing surface is now under manufacturing. Using such type of bearing, the damping capacity of gas film can be controled actively with varying the step hight through piezo-actuator.On the other hand, the static and dynamic characteristics of stepped thrust gas bearings are theoretically examined for a wide range of operating conditons. 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.