A Theory of an Externally Pressurized Circular Thrust Gas Bearing With Consideration of the Effects of Lubricant Inertia

1963 ◽  
Vol 85 (2) ◽  
pp. 304-309 ◽  
Author(s):  
Haruo Mori
Keyword(s):  
Velocity Distribution ◽  
Pressure Distribution ◽  
Elliptic Function ◽  
Load Capacity ◽  
Hydrodynamic Theory ◽  
Pressure Curve ◽  
Parabolic Shape ◽  
Parallel Surfaces ◽  
Gas Bearing ◽  
Theoretical Results

A hydrodynamic theory, with consideration of the effects of compressibility and inertia of the lubricant, is applied to externally pressurized gas bearings which consist of circular and parallel surfaces. The ordinary velocity distribution in a bearing clearance with a parabolic shape is changed to a velocity distribution with a shape of elliptic function due to the effect of lubricant inertia. The pressure distribution in this case differs from the ordinary pressure curve calculated without consideration of inertia, but the load capacity seems to be almost the same in both cases. The theoretical results agree in general with the experimental results reported in a previous publication [3].

A Theory of Lubrication by Microirregularities

1966 ◽  
Vol 88 (1) ◽  
pp. 177-185 ◽  
Author(s):  
D. B. Hamilton ◽  
J. A. Walowit ◽  
C. M. Allen
Keyword(s):  
Closed Form ◽  
Analytical Solutions ◽  
Load Capacity ◽  
Face Seal ◽  
Lubrication Mechanism ◽  
Surface Asperity ◽  
Parallel Surfaces ◽  
Theoretical Results

This paper describes a theory of liquid lubrication applicable to parallel surfaces, such as the surfaces of a rotary-shaft face seal. The lubrication mechanism presented is based on surface microirregularities and associated film cavities. Closed-form analytical solutions are obtained giving load capacity as a function of speed, viscosity, and surface-asperity dimensions. The theoretical results agree qualitatively with load capacity determined experimentally for three asperity distributions.

Theory of Externally Pressurized Circular Thrust Porous Gas Bearing

1965 ◽  
Vol 87 (3) ◽  
pp. 613-620 ◽  
Author(s):  
H. Mori ◽  
H. Yabe ◽  
T. Ono
Keyword(s):  
Porous Media ◽  
Porous Material ◽  
Pressure Distribution ◽  
Permeability Coefficient ◽  
Load Capacity ◽  
Bearing Surface ◽  
Porous Bearing ◽  
Parallel Flows ◽  
Flow Through ◽  
Gas Bearing

The externally pressurized circular thrust gas bearing with porous bearing surface is analysed here theoretically. The authors use “permeability coefficient” which identifies the characteristic of porous media, and introduce the concepts of the “equivalent clearance” and the “effective restricting thickness” of the porous layer so that the flow through the porous material can be analyzed in both axial and radial directions, and the flow in the porous material and the bearing clearance may be considered as two parallel flows connected with each other. The analysis coincided qualitatively as well as quantitatively with the results of the experiments concerning the pressure distribution and the load capacity.

Foil Gas Bearing With Compression Springs: Analyses and Experiments

2007 ◽  
Vol 129 (3) ◽  
pp. 628-639 ◽  
Author(s):  
Ju-ho Song ◽  
Daejong Kim
Keyword(s):  
Loss Factor ◽  
Load Capacity ◽  
Underlying Structure ◽  
Equivalent Viscous Damping ◽  
Foil Bearings ◽  
Foil Bearing ◽  
Different Types ◽  
Structural Loss ◽  
Compression Springs ◽  
Gas Bearing

A new foil gas bearing with spring bumps was constructed, analyzed, and tested. The new foil gas bearing uses a series of compression springs as compliant underlying structures instead of corrugated bump foils. Experiments on the stiffness of the spring bumps show an excellent agreement with an analytical model developed for the spring bumps. Load capacity, structural stiffness, and equivalent viscous damping (and structural loss factor) were measured to demonstrate the feasibility of the new foil bearing. Orbit and coast-down simulations using the calculated stiffness and measured structural loss factor indicate that the damping of underlying structure can suppress the maximum peak at the critical speed very effectively but not the onset of hydrodynamic rotor-bearing instability. However, the damping plays an important role in suppressing the subsynchronous vibrations under limit cycles. The observation is believed to be true with any air foil bearings with different types of elastic foundations.

An Assessment of the Value of Theory in Predicting Gas-Bearing Performance

1961 ◽  
Vol 83 (2) ◽  
pp. 195-200 ◽  
Author(s):  
S. Cooper
Keyword(s):  
Steady State ◽  
Slip Velocity ◽  
Reynolds Equation ◽  
Energy Equation ◽  
Experimental Methods ◽  
Experimental Results ◽  
Theoretical Investigations ◽  
Gas Bearing ◽  
Theoretical Results

The object of the paper is to indicate the value of theoretical investigations of hydrodynamic finite bearings under steady-state conditions. Methods of solution of Reynolds equation by both desk and digital computing, and methods of stabilizing the processes of solution, are described. The nondimensional data available from the solutions are stated. The outcome of an attempted solution of the energy equation is discussed. A comparison between some theoretical and experimental results is shown. Experimental methods employed and some difficulties encountered are discussed. Some theoretical results are given to indicate the effects of the inclusion of slip velocity, stabilizing slots, and a simple case of whirl.

scholarly journals Lubrication Analyses of Cam and Flat-Faced Follower

Lubricants ◽  
2019 ◽  
Vol 7 (4) ◽  
pp. 31 ◽  
Author(s):  
Hazim U. Jamali ◽  
Amjad Al-Hamood ◽  
Oday I. Abdullah ◽  
Adolfo Senatore ◽  
Josef Schlattmann
Keyword(s):  
Film Thickness ◽  
Pressure Distribution ◽  
Surface Deformation ◽  
Numerical Study ◽  
Point Contact ◽  
Radius Of Curvature ◽  
Operating Cycle ◽  
Essential Step ◽  
Parabolic Shape ◽  
Principal Factors

The principal factors that affect the characteristics of contact problem between cam and follower vary enormously during the operating cycle of this mechanism. This includes radius of curvature, surface velocities and applied load. It has been found over the last decades that the mechanism operates under an extremely thin film of lubricant. Any practical improvement in the level of film thickness that separates the contacted surfaces represents an essential step towards a satisfactory design of the system. In this paper a detailed numerical study is presented for the cam and follower (flat-faced) lubrication including the effect of introducing an axial modification (parabolic shape) of the cam depth on the levels of film thickness and pressure distribution. This is achieved based on a point contact model for a cam and flat-faced follower system. The results reveal that the cam form of modification has considerable consequences on the level of predicted film thickness and pressure distribution as well as surface deformation.

Centrifugal Effects in Hydrostatic Porous Thrust Bearing

1979 ◽  
Vol 101 (3) ◽  
pp. 381-385 ◽  
Author(s):  
R. S. Gupta ◽  
V. K. Kapur
Keyword(s):  
Pressure Distribution ◽  
Thrust Bearing ◽  
Load Capacity ◽  
Bearing Material

In this analysis the customary neglected centrifugal effects on the performance of hydrostatic porous thrust bearing with incompressible lubricant has been studied and the effects of their interaction of pressure distribution and load capacity illustrate the possibility of replacement of the nonporous bearing material by porous one.

Experimental Identification of Dynamic Force Coefficients for a 110 mm Compliantly Damped Hybrid Gas Bearing

2014 ◽  
Author(s):  
Adolfo Delgado
Keyword(s):  
Load Capacity ◽  
Excitation Frequency ◽  
Dynamic Test ◽  
Inlet Pressure ◽  
Dynamic Force ◽  
Metal Mesh ◽  
Gas Bearings ◽  
Force Coefficients ◽  
Test Parameters ◽  
Gas Bearing

Compliant hybrid gas bearings combine key enabling features from both fixed geometry externally pressurized gas bearings and compliant foil bearings. The compliant hybrid bearing relies on both hydrostatic and hydrodynamic film pressures to generate load capacity and stiffness to the rotor system, while providing damping through integrally mounted metal mesh bearing support dampers. This paper presents experimentally identified force coefficients for a 110 mm compliantly damped gas bearing using a controlled-motion test rig. Test parameters include hydrostatic inlet pressure, excitation frequency, and rotor speed. The experiments were structured to evaluate the feasibility of implementing these bearings in large size turbomachinery. Dynamic test results indicate weak dependency of equivalent direct stiffness coefficients to most test parameters except for frequency and speed, where higher speeds and excitation frequency decreased equivalent bearing stiffness values. The bearing system equivalent direct damping was negatively impacted by increased inlet pressure and excitation frequency, while the cross-coupled force coefficients showed values an order of magnitude lower than the direct coefficients. The experiments also include orbital excitations to simulate unbalance response representative of a target machine while synchronously traversing a critical speed. The results indicate that the gas bearing can accommodate vibration levels larger than the set bore clearance while maintaining satisfactory damping levels.

ASSESSMENT OF MULTALL AS CFD CODE FOR THE ANALYSIS OF TUBE-AXIAL FANS

2021 ◽  
pp. 1-12
Author(s):  
Piero Danieli ◽  
Massimo Masi ◽  
Giovanni Delibra ◽  
Alessandro Corsini ◽  
Andrea Lazzaretto
Keyword(s):  
Experimental Data ◽  
Steady State ◽  
Velocity Distribution ◽  
High Speed ◽  
State Of The Art ◽  
Stable Operation ◽  
Pressure Curve ◽  
Analysis Tool ◽  
Low Speed ◽  
Axial Fans

Abstract This work deals with the application of the open source CFD code MULTALL to the analysis of tube-axial-fans. The code has been widely validated in the literature for high-speed turbomachine flows but not applied yet to low speed tutbomachines. The aim of this work is to assess the degree of reliability of MULTALL as a tool for simulating the internal flow in industrial axial-flow fan rotors. To this end, the predictions of the steady-state air flow field in the annular sector of a 315 mm tube-axial fan obtained by MULTALL 18.3 are compared with those obtained by two state-of-the-art CFD codes and experimental data of the global aerodynamic performance of the fan and the pitch-wise averaged velocity distribution downstream of the rotor. All the steady-state RANS calculations were performed on either fully structured hexahedron or hexa-dominant grids using classical formulations of algebraic turbulence models. The pressure curve and the trend of the aeraulic efficiency in the stable operation range of the fan predicted by MULTALL show very good agreement with both the experimental data and the other CFD results. Although the estimation of the fan efficiency predicted by MULTALL can be noticeably improved by the more sophisticated state-of-the-art CFD codes, the analysis of the velocity distribution at the rotor exit supports the use of MULTALL as a reliable CFD analysis tool for designers of low-speed axial fans.

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