Hybrid Journal Bearings: Theoretical and Experimental Results

1989 ◽  
Vol 111 (2) ◽  
pp. 265-269 ◽  
Author(s):  
B. Bou-Said ◽  
J. P. Chaomleffel
Keyword(s):  
Journal Bearings ◽  
Global Method ◽  
Pressure Drops ◽  
Fluid Turbulence ◽  
Lubricated Contacts ◽  
Geometric Configurations ◽  
New Type ◽  
Approximation Element ◽  
Viscosity Fluid ◽  
Inertia Forces

The analysis of actual lubrication problems needs to take into account particularities in the flow coming from kinematic conditions and contact geometry. For hybrid journal bearings lubricated by low dynamic viscosity fluid, turbulence and pressure drops due to inertia forces in the recess outlets are phenomena which must be taken into account to compute their working characteristics. A global method of study of lubricated contacts in isothermal laminar or not laminar flow by finite element method is presented. It can solve a great number of lubrication problems. A new type of approximation element for lubrication (Hermitian type) is used because it offers the following advantages: The nonlinearities in lubrication which come from turbulence phenomena, geometrical discontinuities (pressure drops) or boundary conditions (recess pressure) require the derivation of unknown functions. Added interpolations are not necessary to determine these values because the nodal unknowns are the values of the function and its derivatives in the two directions. As the modified Reynolds equation is in Cartesian coordinates, in the case of closed geometries such as journal bearings, joining is done just by nodal identification which guarantees continuity of the pressure and of its derivatives. The validity of this numerical model is realized with an experimental study done with a three recess hybrid journal bearing for different kinematic and geometric configurations. In a general way, experimental and theoretical results are in good agreement.

Modelling Fluid Inertia Forces of Short Journal Bearings for Rotordynamic Applications

1993 ◽  
Author(s):  
A. El-Shafei
Keyword(s):  
Momentum Equation ◽  
Journal Bearings ◽  
Fluid Inertia ◽  
Radial Acceleration ◽  
Damping Characteristics ◽  
Energy Approximation ◽  
Form Model ◽  
Fluid Inertia Effect ◽  
Stiffness And Damping ◽  
Inertia Forces

Abstract It has been recently suggested that fluid inertia may play an important role in the dynamic behavior of rotors supported on journal bearings. This paper presents a model for fluid inertia forces in short cylindrical journal bearings based on an energy approximation. The inertialess velocity profiles predicted by the solution of Reynolds’ equation are inserted in the axial momentum equation multiplied by the axial velocity profile and integrated across the film thickness, to obtain the pressure in short journal bearings including the fluid inertia effect. The pressure is then integrated to obtain the fluid inertia forces. It is shown that the inertia forces thus obtained are proportional to the usual radial, centripetal, tangential and coriolis accelerations of the journal, in addition to a nonlinear radial acceleration. Moreover, it is shown that the inertia forces contribute to the stiffness and damping characteristics of the journal bearings. The inertia coefficients of the bearings are obtained in cartezian and cylindrical coordinates, for both uncavitated and cavitated bearings, and are plotted versus the eccentricity ratio. The model thus obtained is an analytical closed form model for fluid inertia forces in short journal bearings. Such a model is the most suitable for rotordynamic applications, particularly for time transient rotordynamic simulations.

Design Charts for Optimum Bearing Configurations: 2—The Pivoted-Pad Thrust Bearing

1970 ◽  
Vol 92 (4) ◽  
pp. 572-577 ◽  
Author(s):  
R. Bosma ◽  
H. Moes
Keyword(s):  
Thrust Bearing ◽  
Journal Bearings ◽  
Thrust Bearings ◽  
Design Chart ◽  
Design Charts ◽  
Dimensionless Groups ◽  
Minimum Film Thickness ◽  
New Type ◽  
Complete Set ◽  
Film Stiffness

As a followup to an earlier paper in which a new type of design chart for full journal bearings was given a complete set of design charts for pivoted-pad thrust bearings (Michell bearings) shall now be presented. The dimensionless groups of parameters representing minimum film thickness and bearing traction for one single pad, respectively, have been plotted in a new design chart. Some illustrative examples demonstrating how to use the chart for optimization of pivoted-pad thrust bearings have been included. Some attention has also been paid to the stiffness of the film of lubricant. A design chart for film stiffness has been added to this purpose.

The Stability of Self-Acting Gas Journal Bearings With Noncircular Members and Additional Elements of Flexibility

1969 ◽  
Vol 91 (1) ◽  
pp. 113-119 ◽  
Author(s):  
H. Marsh
Keyword(s):  
Stability Boundary ◽  
Journal Bearings ◽  
Satisfactory Explanation ◽  
Unusual Behavior ◽  
Stability Boundaries ◽  
Linearized Theory ◽  
New Type ◽  
The Stability ◽  
Theory And Experiments ◽  
Bearing System

The linearized theory for the stability of self-acting gas bearings is extended to include bearing systems with noncircular members or additional elements of flexibility and damping. The theory offers a satisfactory explanation for the unusual behavior of a bearing system with a three-lobed rotor, including the whirl at low speeds and the whirl cessation. A comparison between the theory and experiments for a flexibly mounted bearing system shows that the theory can be applied to predict the stability boundaries of bearing systems with additional elements of flexibility. A new type of bearing apparatus is proposed in which it would be possible to obtain information about bearing stability without operating at the stability boundary.

Short Bearing Theory Prediction of Inertial Turbulent Journal Orbits

1990 ◽  
Vol 112 (4) ◽  
pp. 643-649 ◽  
Author(s):  
G. Capone ◽  
M. Russo
Keyword(s):  
Nonlinear Equations ◽  
Hydrodynamic Lubrication ◽  
Journal Bearings ◽  
Fluid Particles ◽  
Straightforward Solution ◽  
Rigid Supports ◽  
Inertia Forces

The proposed method enables a straightforward solution of the nonlinear equations of the cylindrical motion of rotors on journal bearings in conditions of unsteady nonlaminar hydrodynamic lubrication taking into account the inertia forces of the fluid particles. The analysis is restricted to the case of rigid supports and rigid symmetrical rotor adopting the short bearing theory. Some meaningful examples of predicted journal orbits are reported for balanced and unbalanced rotors.

Modeling Fluid Inertia Forces of Short Journal Bearings for Rotordynamic Applications

1995 ◽  
Vol 117 (4) ◽  
pp. 462-469 ◽  
Author(s):  
A. El-Shafei
Keyword(s):  
Momentum Equation ◽  
Journal Bearings ◽  
Fluid Inertia ◽  
Radial Acceleration ◽  
Damping Characteristics ◽  
Energy Approximation ◽  
Form Model ◽  
Fluid Inertia Effect ◽  
Stiffness And Damping ◽  
Inertia Forces

It has been recently suggested that fluid inertia may play an important role in the dynamic behavior of rotors supported on journal bearings. This paper presents a model for fluid inertia forces in short cylindrical journal bearings based on an energy approximation. The inertialess velocity profiles predicted by the solution of Reynolds’ equation are inserted in the axial momentum equation multiplied by the axial velocity profile and integrated across the film thickness, to obtain the pressure in short journal bearings including the fluid inertia effect. The pressure is then integrated to obtain the fluid inertia forces. It is shown that the inertia forces thus obtained are proportional to the usual radial, centripetal, tangential and coriolis accelerations of the journal, in addition to a nonlinear radial acceleration. Moreover, it is shown that the inertia forces contribute to the stiffness and damping characteristics of the journal bearings. The inertia coefficients of the bearings are obtained in cartesian and cylindrical coordinates, for both uncavitated and cavitated bearings, and are plotted versus the eccentricity ratio. The model thus obtained is an approximate analytical closed form model for fluid inertia forces in short journal bearings. Such a model is the most suitable for rotordynamic applications, particularly for time transient rotordynamic simulations.

Superadiabatic Lean Catalytic Combustion in a High-Pressure Reactor

2009 ◽  
Vol 7 (1) ◽  
Author(s):  
Wojciech M. Budzianowski ◽  
Ryszard Miller
Keyword(s):  
High Pressure ◽  
Ignition Temperature ◽  
Catalytic Combustion ◽  
Bifurcation Diagrams ◽  
Fuel Conversion ◽  
Pressure Drops ◽  
Elevated Pressures ◽  
New Type ◽  
Thermal Expansion Effect ◽  
Expansion Effect

The isobaric lean catalytic combustion in a high-pressure recuperative reactor in view of gas turbine technologies is examined. A new type of the T/P bifurcation diagram is revealed and elucidated. It is found that the reactor thermally stabilizes at higher pressures. The elevated P to 0.5 MPa extends bifurcation isola for mfin, i.e. each fold is improved by approximately 15%. The thermal and concentration hysteresis bifurcation diagrams are also improved, i.e. the ignition temperature was decreased from 490 to 475 K and the extinction concentration from 177 to 157 ppmv, respectively. The pressure drops are alleviated by the factor of P/P0 slightly corrected for the gas thermal expansion effect. It is also revealed, that the intra-phase mass transfer resistances are reduced at elevated pressures. The fuel conversion pressure dependences are provided for some types of high-pressure reactors.

Frequency Dependent Dynamic Properties of Tilting Pad Journal Bearings: Experimental Results and Uncertainty Analysis

2005 ◽  
Author(s):  
Waldemar Dmochowski ◽  
Jacek Dmochowski
Keyword(s):  
Spectral Density ◽  
Dynamic Properties ◽  
Journal Bearings ◽  
Data Uncertainty ◽  
Dynamic Coefficients ◽  
Power Spectral ◽  
Tilting Pad ◽  
Spectral Density Method ◽  
Tilting Pad Journal Bearings ◽  
Inertia Forces

The paper presents experimentally obtained TPJB response to multifrequency excitation and its comparison with theoretically obtained data. Uncertainty considerations for the results obtained using the power spectral density method are also presented. It has been concluded that inertia forces and pivot flexibility effects are behind the variations of dynamic coefficients with frequency of excitation.

Tribological design of hydrodynamic sliding journal bearings – formulating new functional charts

2005 ◽  
Vol 57 (1) ◽  
pp. 4-11 ◽  
Author(s):  
C. Pandazaras ◽  
G. Petropoulos
Keyword(s):  
Design Methodology ◽  
Reynolds Equation ◽  
Journal Bearings ◽  
Content Type ◽  
Topographic Features ◽  
Operational Characteristics ◽  
Innovative Methodology ◽  
Limited Length ◽  
New Type

PurposeThis paper aims to introduce an innovative methodology for the determination of operational characteristics of journal bearings (j‐bs) through using new type charts based upon a numerical solution of the Reynolds equation.Design/methodology/approachThe present paper proposes the mapping of the behaviour of a smooth, isothermal and hydrodynamic (j‐b) as a first step towards a future representation of the behaviour of j‐b's with limited length and high lubricating clearance with or without macro or micro topographic features operating under high loads, high temperatures and low linear velocities leading to conditions of mixed or boundary lubrication.FindingsThe derived analytical relationships between dimensionless quantities lead to the development of high precision synthetic operational charts regarding sliding j‐b of any given geometry and varying operational characteristics.Originality/valueBy considering the iso‐operational curves which are of a hook form relevant to comparative data becomes directly and rapidly clarified.

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