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On controlling the film thickness in self-acting foil bearings
SYSTEMATIC
ABSTRACTS
OF CURRENT
LITERATURE
pocket bearing offers the best load-carrying capacity. It is significantly higher than that of a bearing with the spiral grooved pattern under the conditions investigated. Zero-load Stability of Rotating Externally Pressurised Gas-lubricated Journal Bearings. D. P. Fleming, R. E. Cunningham and W. Jo Anderson, JOLT, 92 Ser. F, (2) (1970) 325-335; 7 figs., 13 refs. A small eccentricity analysis was performed for a bearing having two feeding planes each of which is assumed to be a line source. Numerical results were obtained for a range of bearing numbers, pressure ratio, feeding parameter and orifice recess volume by means of a digital computer. Steady-state load, attitude angle and stability data were obtained. Stability decreased markedly with increasing recess volume. There was no correlation between stability and steady-state attitude angle for any of the cases studied. Fair agreement was obtained with available experimental data. Steady-state Experiments on Rotating ExternaIly Pressurised Air-Iubricated Journal Bearings. R. E. Cunningham, D. P. Fleming and W. J. Anderson, JOLT, 92 Ser. F, (2) (1970) 336345; 11 figs., 8 refs. Experimental load, stiffness and attitude data for externally pressurised air journal bearings are compared with two small eccentricity perturbation theories. Loadcarrying capacity is generally less than predicted, attitude angles vary with shaft speed as predicted but are generally larger in magnitude. Measured air mass flow through the bearings agreed well with calculated values. Helical-grooved Journal Bearing Operated in Turbulent Regime. C. Y. Chow and J. H. Vohr, JOLT, 92 Ser. F, (2) (1970) 346-358; 16 figs., 3 tables, rg refs. An analysis based on the linearised lubrication theory, developed by Ngand Pan, is presented. The data presented include the bearing performance at the steady state, the stiffness and damping coefficients and the critical mass of the journal in both linear and turbulent regimes. To facilitate design, these data are computed for optimum geometries to provide maximum radial stiffness at various Reynolds numbers. The effect of external pressurised supply of lubricant is shown in the performance curves. On Controlling the Film thickness in Selfacting Foil Bearings. A. Eshel,JOLT, 92 Ser. F, (2) (1970) 359-362; 4 figs., 2 refs. Some factors useful in overcoming excessive
223
air gaps in foil bearings are investigated. Theoretical prediction curves allowing the calculation of the air gap as a function of corner angle change in radius of curvature and the molecular mean free path are presented. Dynamic Response of a Double Squeeze-film Thrust Plate. T. Chang, C. I-I. T. Pan and H. G. Elrod, JOLT, 92 Ser. F, (2) (1970) 363-369; 5 figs., 11 refs. The dynamic response of a double squeezefilm thrust plate was analysed theoretically. When the squeeze frequency is higher than a critical frequency the synchronous response is 180 deg. out of phase with the squeeze motion which enhances squeeze action and increases the load capacity and stiffness. The converse is true when the squeeze frequency is lower than the critical frequency. The harmonic solution for the dynamic response without linearisation agrees well with the exact numerical solution. The linearised harmonic solution has only qualitative agreement with the exact numerical solution. Thermal Behaviour and Friction in Journal Bearings. A. Nica,JOLT, 92 Ser. F, (3) (1970) 373-380; 13 figs., 10 refs. A study of thermal behaviour and friction in journal bearings. Good agreement is found between theoretical results and experimental data on thermal behaviour of the lubricant film. Theoretical predictions for minima of friction torque and the mechanisms of heat dissipation in bearings are considered to verify the assumptions used. Means of cooling bearings efficiently, as well as the role of the divergent zone in the process, are discussed. The Hybrid Boost Bearing-a Method of Obtaining Long Life in Rollins-contact Bearing Applications. D. F. WiIcock and L. W. Winn, JOLT, 92 Ser. F, (3) (1970) 406-414; IO figs., 6 refs. A new bearing concept is described which offers the almost unlimited life of the fluidfilm bearing combined with the free-starting, stopping and oil-system failure characteristics of the rolling-element bearing. The hybrid boost bearing is envisaged as having applications in jet engines to extend bearing life and in land turbine equipment as a means of providing high overload capacity. Data on this advanced design will be available soon. Rigid-body Rotor Dynamics-Dynamic Unbalance and Lubricant Temperature Changes R. H. Badgley and J. F. Booker, JOLT, 92 Ser. F, (3) (1970) 4r5-424; 11 figs., 14 refs. The work described provides a means for evaluating the effects of dynamic unbalance in relatively short rigid rotors. For the rotor Wear, 17 (1971) 219-227
ABSTRACTS
OF CURRENT
LITERATURE
pocket bearing offers the best load-carrying capacity. It is significantly higher than that of a bearing with the spiral grooved pattern under the conditions investigated. Zero-load Stability of Rotating Externally Pressurised Gas-lubricated Journal Bearings. D. P. Fleming, R. E. Cunningham and W. Jo Anderson, JOLT, 92 Ser. F, (2) (1970) 325-335; 7 figs., 13 refs. A small eccentricity analysis was performed for a bearing having two feeding planes each of which is assumed to be a line source. Numerical results were obtained for a range of bearing numbers, pressure ratio, feeding parameter and orifice recess volume by means of a digital computer. Steady-state load, attitude angle and stability data were obtained. Stability decreased markedly with increasing recess volume. There was no correlation between stability and steady-state attitude angle for any of the cases studied. Fair agreement was obtained with available experimental data. Steady-state Experiments on Rotating ExternaIly Pressurised Air-Iubricated Journal Bearings. R. E. Cunningham, D. P. Fleming and W. J. Anderson, JOLT, 92 Ser. F, (2) (1970) 336345; 11 figs., 8 refs. Experimental load, stiffness and attitude data for externally pressurised air journal bearings are compared with two small eccentricity perturbation theories. Loadcarrying capacity is generally less than predicted, attitude angles vary with shaft speed as predicted but are generally larger in magnitude. Measured air mass flow through the bearings agreed well with calculated values. Helical-grooved Journal Bearing Operated in Turbulent Regime. C. Y. Chow and J. H. Vohr, JOLT, 92 Ser. F, (2) (1970) 346-358; 16 figs., 3 tables, rg refs. An analysis based on the linearised lubrication theory, developed by Ngand Pan, is presented. The data presented include the bearing performance at the steady state, the stiffness and damping coefficients and the critical mass of the journal in both linear and turbulent regimes. To facilitate design, these data are computed for optimum geometries to provide maximum radial stiffness at various Reynolds numbers. The effect of external pressurised supply of lubricant is shown in the performance curves. On Controlling the Film thickness in Selfacting Foil Bearings. A. Eshel,JOLT, 92 Ser. F, (2) (1970) 359-362; 4 figs., 2 refs. Some factors useful in overcoming excessive
223
air gaps in foil bearings are investigated. Theoretical prediction curves allowing the calculation of the air gap as a function of corner angle change in radius of curvature and the molecular mean free path are presented. Dynamic Response of a Double Squeeze-film Thrust Plate. T. Chang, C. I-I. T. Pan and H. G. Elrod, JOLT, 92 Ser. F, (2) (1970) 363-369; 5 figs., 11 refs. The dynamic response of a double squeezefilm thrust plate was analysed theoretically. When the squeeze frequency is higher than a critical frequency the synchronous response is 180 deg. out of phase with the squeeze motion which enhances squeeze action and increases the load capacity and stiffness. The converse is true when the squeeze frequency is lower than the critical frequency. The harmonic solution for the dynamic response without linearisation agrees well with the exact numerical solution. The linearised harmonic solution has only qualitative agreement with the exact numerical solution. Thermal Behaviour and Friction in Journal Bearings. A. Nica,JOLT, 92 Ser. F, (3) (1970) 373-380; 13 figs., 10 refs. A study of thermal behaviour and friction in journal bearings. Good agreement is found between theoretical results and experimental data on thermal behaviour of the lubricant film. Theoretical predictions for minima of friction torque and the mechanisms of heat dissipation in bearings are considered to verify the assumptions used. Means of cooling bearings efficiently, as well as the role of the divergent zone in the process, are discussed. The Hybrid Boost Bearing-a Method of Obtaining Long Life in Rollins-contact Bearing Applications. D. F. WiIcock and L. W. Winn, JOLT, 92 Ser. F, (3) (1970) 406-414; IO figs., 6 refs. A new bearing concept is described which offers the almost unlimited life of the fluidfilm bearing combined with the free-starting, stopping and oil-system failure characteristics of the rolling-element bearing. The hybrid boost bearing is envisaged as having applications in jet engines to extend bearing life and in land turbine equipment as a means of providing high overload capacity. Data on this advanced design will be available soon. Rigid-body Rotor Dynamics-Dynamic Unbalance and Lubricant Temperature Changes R. H. Badgley and J. F. Booker, JOLT, 92 Ser. F, (3) (1970) 4r5-424; 11 figs., 14 refs. The work described provides a means for evaluating the effects of dynamic unbalance in relatively short rigid rotors. For the rotor Wear, 17 (1971) 219-227