Finite element analysis of gas bearings for oil-free turbomachinery
Keywords:
Gas bearings, rotordynamics, stability, finite element modelAbstract
Further advancements in high performance turbomachinery operating at extreme temperatures mandate the development of gas film bearing technology to procure compact units with improved efficiency in an oil-free environment. A novel finite element (FE) procedure to model thin film gas bearings follows. The FE model incorporates a novel class of high order shape functions ensuring computational efficiency and numerical stability even at (infinity) high speed bearing numbers. The method does not rely on cumbersome schemes for evaluation of advection flow terms in the Reynolds equation nor introduces artificial diffusion into the numerical solution. A computational FE program forwards predictions for the static performance and dynamic force coefficients of an externally pressurized gas bearing for ready application to an automotive turbocharger. The predictions show the strong effects of excitation frequency on the dynamic force coefficients and the onset of a hydrodynamic instability at moderately low rotor speeds. The analysis of predictions evidences the benefits and limits of rigid surface gas bearings for oil-free turbomachinery.
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