• Tribology and Lubricants
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• v.17 no.2
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• pp.116-123
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• 2001

A theoretical analysis has been undertaken to show the influence of bearing geometry on the steady state characteristics of air lubricated spherical tilting pad bearings. The geometry variations considered are the number of pads, the eccentricity ratio, the direction of load, and the preloading. Dynamic characteristic equations are derived with pad assembly method.

• Tribology and Lubricants
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• v.17 no.2
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• pp.97-108
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• 2001

This paper describes the development of performance analysis technique for a leaf-type gas lubricated fail bearing. Stiffness coefficient and frictional damping due to the slip between all contacts of leaves are evaluated for various leaf structures. The fluid film thickness and pressure distribution are computed but it is not considered the elastic deformation by film pressure. The analysis results include the effects that the curvature radius and the length of leaf and the friction coefficient have on the static and dynamic characteristics of the foil bearings.

• Tribology and Lubricants
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• v.18 no.5
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• pp.364-370
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• 2002

In this paper, numerical analyses were undertaken to calculate the static and dynamic performances of step-pocket, inward pumping spiral grooved, outward pumping spiral grooved and herringbone grooved bearings. For each bearing, optimal values for various design parameters were obtained to maximize the load capacity and the stiffness and bearing performances were calculated. The optimized performances of these bearings were compared to conclude that the performance of step-pocket bearing is better than the other bearings.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1999.06a
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• pp.291-296
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• 1999

This study presents a method for determining stiffness and damping coefficients of 30% U slider-air bearings by using perturbation method, and shows that this method is more accurate than steady state method according to the comparison of those with the modal analysis method. Through a generalized lubrication equation, which based on linealized Boltzmann equation, the static and dynamic pressure distributions are calculated by finite volume method.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2001.06a
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• pp.231-235
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• 2001

This paper has been presented the dynamic effect by the journal speed. eccentricity and source positions in order to overcome the defects of air bearing such as low stiffness and damping coefficient. Choosing the two row source position of air bearing is different from previous investigations in the side of pressure distribution of air film by the wedge effects. These optimal chooses of the two row source positions enable us to improve the performance of the film reaction force and loading force as making the high speed spindle. The results of investigated characteristics may be applied to precision devices like ultra-precision grinding machine and ultra high speed milling.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1999.06a
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• pp.156-161
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• 1999

new bearing concept, the wave journal bearing, has been developed to improve the static and dynamic performances of an air-lubricated hydrodynamic journal bearing. This concept features waves on bearing surface. In this study, we present the solution of the compressible Reynolds equation valid for arbitrary Knudsen numbers. Straight wave journal bearing is investigated numerically. The performances of straight wave bearing are compared to the plain journal bearing over relatively wide range of bearing number and eccentricity. The wave journal bearing offers better stability than the plain journal bearing under a13 bearing numbers covered in this study. The bearing load and stability characteristics are dependent on the geometric parameters such as the amplitude and the starting point of the wave relative to the applied load. Under the condition of Knudsen number)0.01, we can not ignore the effect of slip for journal bearing.

• Tribology and Lubricants
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• v.17 no.1
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• pp.28-32
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• 2001

A new bearing concept, the wave journal bearing, has been developed to improve the static and dynamic performances of an air-lubricated hydrodynamic journal bearing. This concept features waves on bearing surface. In this study, we present the solution of the compressible Reynolds equation valid for arbitrary Knudsen numbers. Straight wave journal bearing is investigated numerically. The performances of straight wave bearing are compared to the plain journal bearing over relatively wide range of bearing number and eccentricity. The wave journal bearing offers better stability than the plain journal bearing under all bearing numbers covered in this study. The bearing load and stability characteristics are dependent on the geometric parameters such as the amplitude and the starting point of the wave relative to the applied load. Under the condition of Knudsen number＞0.01, we can not ignore the effect of slip for Journal bearing.

• Tribology and Lubricants
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• v.10 no.1
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• pp.46-55
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• 1994

The static and dynamic analysis of air lubricatied tilting pad journal bearing which considers tilting effect of each pad, preload but which neglects pad inertia effect and deflection are performed. A direct numerical method is used in evaluating the static characteristics such as load carrying capacity, friction force and small peturbation method is used for calculation of dynamic characteristics. Stiffness and damping coefficients are compared with the variation of the preload. And these coefficients are slightly decreased with increased compressibility number under the constant bearing load carrying capacity.

• 유체기계공업학회:학술대회논문집
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• 2002.12a
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• pp.453-458
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• 2002

The feasibility study on supporting a turbocharger rotor on air foil bearing is investigated. Based on finite difference method and Newton-Raphson method, the static equilibrium position of a turbocharger rotor is predicted. And using finite difference method and perturbation method, dynamic characteristics of air foil bearings are calculated. Rotordynamic analysis is performed by finite element method, with collaboration of calculated stiffness and damping of foil bearing. The effect of compliance and clearance of bump foil bearing on the oil-free turbocharger is investigated in terms of rotordynamics. And the critical speeds, eccentricity ratio, vibration amplitude, and stability are considered. It is demonstrated that foil bearings offer a rlausible replacement for oil-lubricated bearings in turbocharger.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2001.11a
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• pp.197-203
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• 2001

In this paper, numerical analyses were undertaken to calculate the static and dynamic performances of step-pocket, inward pumping spiral grooved, outward pumping spiral grooved and herringbone grooved bearings. For each bearing, optimal values for various design parameters were obtained to maximize the load capacity and the stiffness and bearing performances were calculated. The optimized performances of these bearings were compared to conclude that the performance of step-pocket bearing is better than the other bearings.