The simulator rotor-bearing system was operated while positioned in various orientations. Subsequent testing was completed to demonstrate the capabilities of miniature thrust foil bearings as well. A good correlation between measurement and analysis is observed. Very short rotor acceleration times from rest to maximum speed were also measured. A parallel test simulator has been used to accumulate over 1000 start-stop cycles to demonstrate the life of the bearing and coating. Based on this successful testing, it is expected that the goal of developing oil free turbochargers and small turbojet engines that operate at high speeds with long life will be achieved.
The requirements for high performance, long-life bearings for this new class of machines are severe. Conventional rolling element bearings are severely challenged by the speed and load capacity required. Additionally, unless the process fluid can be used as a lubricant, an external lubrication system will almost certainly.
Eliminating the oil-lubricated bearings and associated supply system will simplify the rotor system, reduce system weight, and enhance performance but will increase internal bearing compartment temperatures, which will ultimately require bearings capable of operating at temperatures approaching 650°C and at high speeds and loads. Besides surviving the extreme temperatures and speeds, the oil-free bearings will also need to accommodate the shock and vibration conditions experienced in mobile applications.
The feasibility of applying compliant foil bearings to small turbojet engines has been demonstrated under a wide range of temperature, shock, load, and speed conditions. Tests to 150,000 rpm, at bearing temperatures above 260°C, under shock loading to 90g and rotor orientations including 90 deg pitch and roll, were all completed successfully. Under all conditions tested, the foil bearing supported rotor remained stable, vibrations were low, and bearing temperatures were stable. Overall, this program has provided the background necessary to develop a completely oil-free turbojet or high efficiency turbofan engine.
Reference
Isomura, K., Murayama, M., Yamaguchi, H., Ijichi, N., Asakura, H., Saji, N., Shiga, O., Takahashi, K., Tanaka, S., Genda, T., and Esashi, M., 2002, “Development of Microturbocharger and Microcombustor for a Three-
Dimensional Gas Turbine at Microscale,” ASME Paper No. GT-2002-3058.
Post time: Jun-28-2022