World’s fastest air bearings

A team at Belgian university KU Leuven has made a shaft that runs at 1.2 million rotations per minute, which is 133 times faster than the maximum rpm of a Ferrari 458 Italia.

The shaft, which is 6mm in diameter, is suspended in aerodynamic radial bearings, so that it floats on a thin layer of air that is only a few micrometres (one-thousandth of a millimetre) thick.

Due to the fact that the shaft does not touch any other parts, there is no wear, even at 1.2 million rpm. Multiplying rpm with shaft diameter yields that the shaft surface reaches a speed of 377m/s, or Mach 1.1 (1.1 times faster than the speed of sound), a world record in self-acting air bearing technology.

The speed of air bearings is usually limited by instabilities, but the researchers solved this problem by developing a special damping mechanism. Moreover, in contrast to aerostatic air bearings, which operate on a compressed-air supply, this air bearing is aerodynamic (or self-acting) and thus develops sufficient bearing pressure from its own rotation. This is particularly beneficial as the self-pressurising system can operate autonomously.

These high-speed bearings will be used in turbos, small gas turbines, compressors and micro-milling cutters. Turbos that operate with air bearings have less friction and are thus more efficient than the current types, which use oil bearings or ball bearings.

Using these bearings in compressors ensures oil-free compressed air, which is important for applications in the medical sector and food industry. Small gas turbines will be used for domestic cogeneration and as auxiliary engines (range extenders) for electric cars.