Research On Hydrodynamic Characteristics Of Bump Foilgas Aerodynamic Bearing Rotor System

Bump foil bearing supported by elastic surface is a self-acting hydrodynamicbearing. With the combination of high temperature solid lubrication technology, it hasmany outstanding features: high speed, non-polluting, adaptive, wide operatingtemperature range, simple structure, high stability, and long life. Foil bearing has broadapplication prospects and huge economic value in the field of aerospace, defense,precisive manufacturing, and low temperature refrigeration. However, due to thecomplexity of the structure and gas-elastic coupling, the static and dynamicperformance has been in the process of continuous improvement.Considering gas compressibility and foil deformation, theoretical analysis model ofthe first generation bump foil gas bearing has been establisehed. Reynolds equation andfilm thickness equation are coupled through pressure and solved by Relaxation IterationMethod and Finite Difference Method. The gas pressure distribution, film thickness andload-capacity of bump foil bearing are in good agreement with the experimental data ofrelevant reference, and the model is proved to be accurate.The static characteristics are discussed including the relation between speed,length-diameter ratio and gas film pressure, thickness, load capacity, attitude angle andfriction torque. The distribution rules of film pressure and thickness are comparedbetween foil bearing and traditional rigid bearing, it is revealed that foil bearing hashigher load capacity and stability.Differential equations of bump foil bearing dynamic coefficients were deducted byperturbation method with air lubrication Reynolds equation accounting for aircompressibility, foil deformation and foil friction. Finite Difference Method andRelaxation Iteration Method were applied to calculate the dynamic coefficients. Withthe results compared to the published experimental data, the model was proved to becorrect and accurate. The variation rules of dynamic characteristics of bump foil bearingwere obtained with different speeds, eccentricity ratios, perturbation frequency ratios,length-diameter ratios, foil deformation numbers and friction coefficients.This paper has established the dynamic equation of bump foil bearing-Jeffcott rigidrotor system. The Newmark-β method was used to analyze the effect of speeds,eccentricity ratios, unbalance, clearance, foil deformation and foil friction onhydrodynamic characteristics, which provides theoretical basis for the design andanalysis of foil bearing-rotor system.