The Analysis Of Flow Field And Influence Of Top Foil Deformation To Performance Of Gas Foil Bearings

Gas foil bearing (GFB) has been widely used in high-speed gas turbines, but its low-load capacity has limited its implications, and many researchers have made effort to improve its load capacity by optimize its structures. Until now, there are four generation of bump-type gas foil bearings, and its load capacity has been largely improved. Optimizing structures of GFB needs to forecast the static and dynamic performance accurately, which is on the basis of flow field analysis of GFB.The main content and conclusions of this paper are shown below:(1) Considering top foil deformation and air compressibility, a model is built to forecast static performance of GFB by coupling Reynolds equation and gas film equation, and modeling results have shown good agreement with NASA's experimental data. The influences of parameters to load capacity and stability have been researched under the modeling results.(2) A model with pressure far field is built to analyze 3-D flow field of GFB, and modeling result has shown good agreement with other reference. Besides, flow field and pressure distribution at bearing's end, which is different from researches before. On the basis of 3-D flow field analysis, flow fields under different parameters of GFB have been analyzed to research their influence mechanism to load capacity and stability.(3) A model without considering top foil deformation and another model with considering top foil deformation have been built to research the influence of top foil deformation to load capacity and stability of GFB. Results show that top foil deformation leads to lower load capacity and lower stability at high rotating speed. In order to study the mechanism of influence of top foil, the flow field with top foil deformation has been analyzed, results show:the channels formed by top foil deformation increased air-flow resistance and decrease air motion at tangential direction, accordingly, ending leakage mass flow rate is increased.(4) Parameters of top foil have been researched to investigate their influence to static performance of GFB. Considering the second generation GFB has adopted subsections axially, the stiffness of bump foil at end of GFB has been studied. Beside, ending air feed pressure has also been studied.(5) Under the analysis of influence of parameters of top foil, stiffness of bump foil at end, ending air feed pressure, optimizations have been made to improve load capacity and stability of GFB.