Development Of Foil Thrust Bearing Test Rig

Abstract

Oil lubricated bearings have been widely used in variety of turbo machinery, though it has its own limitations such as thermal degradation of oil over temperature, complicated oil lubrication system and their maintenance. Commercial application of the air foil bearing (AFB) in Microturbomachinery have been acknowledged. Microturbomachinery term is used in applications with shaft power less than 1000KW and shaft diameter less than 100mm. Microturbomachinery has demanded light weighted, compact, extreme temperature and high speed operation. DN number for oil lubricated bearings and rolling element bearings is very less when compared to foil bearings. Absence of external pressurizing and lubricating system makes the system light and compact. Simple construction, low friction drag and reliability at high speed operations are few more advantages of the foil bearings. With all these advantages, foil bearings appears to be the one of the most effective techniques for Microturbomachinery. With the relentless demand for machines capable of operating at greatest speeds, high power densities and temperatures, foil gas bearings represent an enabling technology for advanced oil free system. While air foil journal bearings have been advanced significantly in past decades, very few literature data are available and not much experimental work has been conducted on foil thrust bearings.There is comparatively less information on air foil thrust bearings due to challenges in design, manufacturing and assembly. This research focuses on development of foil gas thrust bearing test rig which will operate at high temperature and speed. The test rig developed is equipped with thermocouple, optical probe, load cell which provides temperature, axial load, torque and high speed data by using NI labview. Design, manufacturing and assembly of air foil thrust bearing are detailed. The test rig has a push/pull mechanism which makes the stiffness measurement much easier. By evaluating parameters such as load capacity, steady state temperature, structural stiffness, and start stop friction torque will help to enhance the performance of the air foil thrust bearing.