Research On The Characteristics Of Bump Foil Aerodynamic Bearings

Bump foil aerodynamic bearing is widely used in aerospace high-speed rotatingmachinery, which has the advantages of high limit speed, high load capacity, adaptivestable and so on. The characteristics of bump foil aerodynamic bearing is the main basisof the engineering design, which have been widely studied under different rotation andstructural parameters at home and abroad. With the development of bump foilaerodynamic bearing applications, foil materials and processing technology, and thesubstantial increase in rotor speed, the influence of lubrication gas properties, foilmechanical properties and micro-flow effect is more prominent. The present paper iscarried out in above background.Firstly, taking Hydresil-type bump foil aerodynamic bearing (journal) for the study,established the Reynolds equation and the film thickness equation which contain withfoil deformation, used the finite difference method to coupling the two equations foriterative solution. In the range of the gas physical properties variation along with thetype and the temperature, numerical method was used to study the influence of thegas-solid characteristic parameters, such as lubrication gas viscosity （4.21×10-6-4.46×10-5Pa s）, the modulus of elasticity (70-340Gpa) and bump foil material Poisson’sratio (0.15-0.45), on the bearing gas film thickness distribution, pressure distributionand the carrying capacity. Results show that, as the viscosity increases, the bearing loadcapacity increases by50%-75%; as the elastic modulus and Poisson’s ratio increase, thebearing load capacity y increases by5%-10%and30%-40%respectively.Secondly, on the basis of two-equation bearing model, using the small disturbancemethod deduction perturbation equation, obtaining the dynamic characteristicparameters by using the finite difference to solve perturbation equation. Results showthat, as the viscosity increases, the dynamic stiffness coefficient reduces by10%-50%,the dynamic damping coefficient increases by about25%-60%; as the bearing foilmaterial elastic modulus increases, the dynamic stiffness coefficient increases by30%-50%, the dynamic damping coefficient in the y direction gradually increases, by about10%, in the x direction gradually decreases, by about10%.Then, based on ANSYS Workbench, a two-way fluid-structure coupling simulation analysis method was established, and the slip velocity model was used to describemicro-scale flow boundary slippage effect, the influence of different slip properties ofthe journal surface and the foil surface on bearing characteristics was studied. Resultsshow that the bearing capacity is strongest when the journal surface without slippingand the foil surface with slipping, whereas the weakest. Contrast analysis of thedifference in static characteristic such as film pressure and film thickness of bump foilaerodynamic bearing and rigid surface bearing was conducted under the same slipboundary. Results show that the slip boundary has greater influence on the rigid bearing.And then analyzed the effects of the slip boundary on the performance of bump foilaerodynamic bearing with parameters such as lubrication gas viscosity, eccentricity,radius clearance and speed.Results of this study may be a useful reference for the bump foil aerodynamicbearing engineering design.