Study of Micro-High Speed Bearings and

Micromachine gas turbines require extremely high rotor speed to realize the same impeller tip speed to the large gas turbines, by very small diameter of the impellers. Hence, the rotordynamics is one of the critical issues. Especially, the bearing speed will exceed the range of experience in any existing turbomachines, and hence the method to achieve the stable operation at the required design speed has not established, yet. The characteristics of variety of bearings will be reviewed, and the issues of the bearing selection and the rotordynamic design will be addressed. 1.0 INTRODUCTION 1.1 New Markets for Micromachine Gas Turbine Generators Recent advances in autonomous robots are causing increase of power requirements. Robots are expanding their capability of complicated movement, and developers are trying to add a lot of new functions to a robot, such as playing trumpet for example. These new functions use more servomotors that increase the total power requirement of a robot. So far, almost all robots use batteries for their power source. Lithium Ion batteries and Nickel-Metal Hydride batteries are the major types of batteries currently used in robots. Battery is well known as a high power density electric source. It is a good power source for applications as robots that require large current to power many servomotors. However, battery has a weakness of low energy density. The continuous operation time is short. These day’s autonomous robots can operate only 30 minutes after half a day of battery recharging. This short operation time will largely limit the application of autonomous robots. A lot of technology improvements have already been achieved over decades for batteries, and the room for large performance improvement is becoming small, now. Isomura, K.; Togo, S.-I.; Tanaka, S. (2005) Study of Micro-High Speed Bearings and Rotor Dynamics for Micromachine Gas Turbines. In Micro Gas Turbines (pp. 7-1 – 7-62). Educational Notes RTO-EN-AVT-131, Paper 7. Neuilly-sur-Seine, France: RTO. Available from: http://www.rto.nato.int/abstracts.asp.