In this paper, an improved foil dynamic model with bending moment included is proposed to determine the effective stiffness of foil structure. The results are compared to published experimental data. | Journal of Science & Technology 130 (2018) 001-006 Research on Effects of Geometry Parameters on Stability Zone of a Rotor Supported by Foil-Air Bearings Using an Improved Foil Model Nguyen Minh Quan*, Pham Minh Hai, Dinh Van Phong Hanoi University of Science and Technology, No. 1, Dai Co Viet, Hai Ba Trung, Hanoi, Viet Nam Received: August 27, 2018; Accepted: November 26, 2018 Abstract Foil-air bearings have been drawing much scientists’ attention to application into high-speed rotating machines for environmentally friendly performance. Due to their compliant foil structure, foil-air bearings are able to resist being seized-up (because of high heat or centrifugal effect), thereby lengthening their service time. However, during working time, foil-air bearings are supposed to demonstrate their non-linear effects that need investigating, especially on rotor’s performance. In this paper, an improved foil dynamic model with bending moment included is proposed to determine the effective stiffness of foil structure. The results are compared to published experimental data. From that, influences of some geometry parameters on rotor’s stability are investigated based on a model of turbocharger with foil-air bearings. Keywords: foil-air bearing, effective stiffness, non-linear dynamics 1. Introduction1 Nevertheless, the bump shape was presumed to remain circular even after load exertion. Furthermore, top foil and all the bumps are assumed to stay in contact all the time while there may be some zones where aerodynamic pressure can be lower than ambient pressure. Foil-air bearings (FAB) have been widely studied and applied into turbomachinery thanks to their outstanding advantage [1,2]. For conventional air selfacting bearing, the radial clearance needs to be small enough for air pressure generation; however, seizing can occur because shaft growth (due to high temperature) can surpass this clearance. This kind of hard contact can be avoided by soft contact between shaft .
