DEVELOPMENT OF AERODYNAMIC BEARINGS FOR ULTRA MICRO TURBOMOCHINE ROTATING AT ULTRA HIGH SPEEDS

近来，随着工业产品的尺寸变得越来越小，强烈地需要具有高输出密度的小型发电机。在20世纪90年代中期，MIT提出了可以以100万rpm旋转的超微型燃气轮机作为便携式发电机，从那时起，许多研究人员积极研究了该领域的各种问题。使用超微型气体涡轮机的便携式发电机具有与锂电池相比可以产生高一个数量级的功率密度的优点，因此被认为是下一代便携式电源。在这些超微型燃气轮机中，通常使用空气动力轴承，这是由于低摩擦、高速时的优异稳定性和高温环境的能力。为了解决上述问题，提出了一种改进的气动轴承稳定性方法，并对该方法进行了理论分析和实验验证，结果表明，该方法能有效地提高气动轴承的稳定性， 关于我们 根据2004年的计算结果，设计并制造了一种带浮动衬套的人字形槽空气动力轴承。为了实现浮动瓦的柔性支承，试验了两种不同的支承方法。一种是浮动衬套，使用人字形槽产生的加压空气。另一种是由薄的柔性箔支撑的浮动衬套。进行实验以确认这些建议的轴承的稳定性。因此，我们得到了以下结论。（1）.所提出的具有浮动衬套的空气动力轴承可以在50万rpm以上的速度下稳定地支撑轴。（2）人字形槽的粘性效应产生的压缩空气能够支撑浮动衬套的重量，因此，由于浮动衬套的作用，轴即使水平放置也能够稳定地旋转。在这些实验中，由于空气涡轮机的功率限制，我们无法使轴旋转超过50万转/分。在不久的将来，我们计划通过使用超音速喷嘴使轴旋转超过50万rpm。少

Recently, small sized power generators with high output density have been strongly required as the sizes of industrial products are getting smaller. In the middle of 1990's, MIT have proposed ultra-micro gas turbines which could rotate at 1 million rpm as a portable power generator and, since then, many researches have actively studied various issues on this area. Portable power generators using an ultra micro gas turbine have the advantage that they can produce one order higher power density compared with lithium battery and, hence, are considered to be a next generation of portable power source. In these ultra-micro gas turbines, aerodynamic bearings are usually used due to low friction, excellent stability at high speeds and the capability for high temperature environment. Accordingly, aerodynamic bearings with higher stability are necessary for these devices to improve gas turbine performances.In order to solve the above problem, we proposed the improved method of stability of aero … More dynamic bearings and planed to develop an aerodynamic bearing which could rotate at speeds over 1 million rpm.Based on the calculated results conducted in 2004, a herringbone grooved aerodynamic bearing with a floating bush was designed and manufactured. In order to flexibly support the floating bush, two different methods were tested. One is a floating bush using pressurized air generated by herringbone grooves. The other is a floating bush supported by thin flexible foils. The experiment was conducted to confirm the stability of these proposed bearings. As a result, we obtained the following conclusions.(1).The proposed aerodynamic bearings with a floating bush could stably support the shaft at speeds over 0.5 million rpm.(2).The pressurized air generated by the viscous effect of herringbone grooves could support the weight of a floating bush and, hence, the shaft could stably rotate even when it was horizontally set due to the effect of a floating bush.In these experiments, we could not rotate the shaft over 0.5 million rpm because the power limitation of air turbine. In the near future, we plan to rotate the shaft over 0.5 million rpm by using the supersonic nozzles. Less