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A bulk-flow model of angled injection Lomakin bearings
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A bulk-flow model for determination of the leakage and dynamic force characteristics of angled injection Lomakin bearings is presented. Zeroth- and first-order equations describe the equilibrium flow for a centered bearing and the perturbed flow for small amplitude rotor motions about the equilibrium position, respectively. The computational analysis accounts for the flow interaction between the injection orifices, the feed circumferential groove and the film lands through adequate Bernoulli-type relationships at the interfaces. The influence of the holes and the groove is considered with a one control-volume model in the groove and coupled with an existing bulk-flow program for annular pressure seals. Flow turbulence is accounted for with turbulent shear stress parameters and Moody's friction factors. The zeroth- and first-order flow equations are solved numerically using a robust computational method. Comparisons between predictions and experimental results for a tangential-against-rotation injection Lomakin bearing configuration show that the current bulk-flow model predicts well the leakage and the direct stiffness and damping force coefficients. Trends for the cross-coupled stiffness coefficient with respect to the rotor speed and the supply pressure are correct, but quantitative agreement remains poor despite the introduction of an additional groove-film land parameter in an effort to improve the determination of the important circumferential velocity at the film land entrance. A parameter investigation evidences the effects of the groove geometry on the Lomakin bearing leakage and dynamic force coefficients. The orifice injection angle in the groove does not have a sensible influence on the leakage and the direct rotordynamic coefficients, yet it is the main design parameter considering the Lomakin bearing stability characteristics, through the determination of the cross-coupled stiffness coefficient. This confirms the promising stabilizing effect of the tangential-against-rotation injection configuration. Besides the impact of the orifice injection angle, the analysis shows that, given the operating conditions and the film lands geometry, the static and dynamic force characteristics of the Lomakin bearing depend on two typical groove numbers defined from the groove geometry parameters. The analysis also shows that the film land clearance and length have a larger impact on the Lomakin bearing performance than its groove depth and length.
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Includes bibliographical references (leaves 90-93).
Issued also on microfiche from Lange Micrographics.
Soulas, Thomas Antoine Theo (2001). A bulk-flow model of angled injection Lomakin bearings. Master's thesis, Texas A&M University. Available electronically from
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