Dynamic Performances of Foil Bearing Supporting a Jeffcot Flexible Rotor System Using FEM

Abstract

Aerodynamic bearings have received considerable attention in recent decades and are increasingly being used in applications where high speed, low loads and high precision are required. Aerodynamic applications mainly concern auxiliary power units (APU) and air-conditioning machines (ACM). From the industrial point of view, the static and dynamic characteristics of these bearings rotating at very high speed must be determined. According to the literature, studies carried out on this type of bearing consider the elastic deformations of the foils due to the pressure generated in the air film. The linear approach is from time to time adopted for the prediction of the dynamic behavior of these bearings, which is not always justified. This paper aims to present a step towards a better mastery of the non-linear dynamic behavior of a flexible rotor-air bearing system. We will focus on finite element modeling (FEM) of the non-linear isothermal elasto-aerodynamic lubrication problem in the case of a radial bearing operating in a dynamic regime. We will present the effects of rotational speed, unbalance eccentricity, and rotor mass on the non-linear response of rigid and compliant bearings. We use a partitioned approach which treats fluid and structure as two computation domains solved separately; reducing the development time needed for a monolithic code which is difficult to manage when the geometries or the physical properties of the problem to be treated become complex.

Comparative study on tribological behavior of foil journal bearings with micro pocket

“…The thin air film is developed due to hydrodynamic action in the small clearance between the shaft and the bearing surface [4]. The significant advantages of foil bearing are: capability to operate under extreme environmental conditions, lightweight due to thin flexible structure, environment friendly and less maintenance cost [5,6]. However, there are various power and frictional loss in high-speed machinery.…”

Analysis of misalignment characteristics for textured foil journal bearing based on multigrid method

“…As a significant support component inside microsmall turbo-machineries [1], gas foil journal bearing (GFJB) has been widely recognized [2] for its high reliability and prolonged environmental durability. However, except for some novel power systems, such as additional gas supply [3,4] or hybrid magnetic bearing [5], the journal in GFJB is only supported by gas self-developing pressure.…”

“…However, realizing these objectives requires accurately obtaining the foil's local deformation. Hence, in previous studies, one finite element model needs to be first selected to mesh the foil structure, such as linear or nonlinear spring element [2,8,24], Euler beam element [1,3], plate element [5,10,13], or shell element [7]. On this basis, by superimposing the stiffness matrices of different foil components [13] or introducing the contact mechanics method [1,7], the fluidsolid coupling results of GFJB can be obtained.…”

“…On this basis, by superimposing the stiffness matrices of different foil components [13] or introducing the contact mechanics method [1,7], the fluidsolid coupling results of GFJB can be obtained. Meanwhile, coupling the above results with the rotor dynamics equations can further obtain the shaft center trajectory [2] or elucidate bifurcation characteristics. In addition, the effect of the rarefied gas [13] and viscous dissipation [21] was also explored to describe the flow features accurately in GFJB.…”

Calculation of Dynamic Coefficients of Air Foil Journal Bearings Using Time-Domain Identification

“…The air foil bearing is a self-acting hydrodynamic bearing that uses ambient air as the lubricant and has a flexible surface. It has the advantages of low power consumption, no need for an additional lubrication system, good temperature resistance, and high-speed performance [1][2][3][4]. Therefore, it is environmentally friendly and widely used in green technology such as air cycle machines in aircraft, turboexpanders for cryogenic applications, turbochargers, and micro gas turbine engines [3].…”