scholarly journals Discussion: “On Fluid Inertia Effects in Infinitely Wide Foil Bearings” (Eshel, A., 1970, ASME J. Lubr. Technol., 92, pp. 490–493)

1970 ◽  
Vol 92 (3) ◽  
pp. 493-493
Author(s):  
K. L. Knox ◽  
T. Sweeney
Keyword(s):  
Fluid Inertia ◽  
Inertia Effects ◽  
Foil Bearings

scholarly journals On Fluid Inertia Effects in Infinitely Wide Foil Bearings

1970 ◽  
Vol 92 (3) ◽  
pp. 490-493 ◽  
Author(s):  
A. Eshel
Keyword(s):  
Film Thickness ◽  
Approximate Solutions ◽  
Fluid Film ◽  
Fluid Inertia ◽  
Inertia Effects ◽  
Foil Bearings ◽  
Lubricating Film ◽  
Fluid Film Thickness ◽  
Fluid Compressibility

Equations for a foil over a lubricating film in which the effects of fluid inertia are taken into account are derived. Approximate solutions showing the effect of inertia and fluid compressibility are obtained. The effect of inertia is to increase considerably the fluid-film thickness.

Dynamic Characterization of an Integral Squeeze Film Bearing Support Damper for a Supercritical CO2 Expander

2017 ◽  
Author(s):  
Bugra Ertas ◽  
Adolfo Delgado ◽  
Jeffrey Moore
Keyword(s):  
High Speed ◽  
Dynamic Performance ◽  
Mechanical Impedance ◽  
Squeeze Film ◽  
Fluid Inertia ◽  
Inertia Effects ◽  
Damping Behavior ◽  
Impedance Testing ◽  
Stiffness And Damping ◽  
Onset Of Cavitation

The present work advances experimental results and analytical predictions on the dynamic performance of an integral squeeze film damper (ISFD) for application in a high-speed super-critical CO2 (sCO2) expander. The test campaign focused on conducting controlled orbital motion mechanical impedance testing aimed at extracting stiffness and damping coefficients for varying end seal clearances, excitation frequencies, and vibration amplitudes. In addition to the measurement of stiffness and damping; the testing revealed the onset of cavitation for the ISFD. Results show damping behavior that is constant with vibratory velocity for each end seal clearance case until the onset of cavitation/air ingestion, while the direct stiffness measurement was shown to be linear. Measurable added inertia coefficients were also identified. The predictive model uses an isothermal finite element method to solve for dynamic pressures for an incompressible fluid using a modified Reynolds equation accounting for fluid inertia effects. The predictions revealed good correlation for experimentally measured direct damping, but resulted in grossly overpredicted inertia coefficients when compared to experiments.

Annular Squeeze Films With Inertial Effects

1983 ◽  
Vol 105 (3) ◽  
pp. 361-363 ◽  
Author(s):  
S. R. Turns
Keyword(s):  
Annular Plate ◽  
Equation Of Motion ◽  
Plate Motion ◽  
Squeezing Flow ◽  
Approximation Technique ◽  
Inertial Effects ◽  
Fluid Inertia ◽  
Governing Equations ◽  
Inertia Effects ◽  
Incompressible Newtonian Fluid

An analysis of the laminar squeezing flow of an incompressible Newtonian fluid between parallel plane annuli is presented in which a successive approximation technique is used to account for fluid inertia effects. An expression for the force generated by the fluid is developed and coupled to the equation of motion for the annular plate. Results are presented from the numerical integration of the governing equations for the plate motion.

Extended Finite Element Analysis of Journal Bearing Dynamic Forced Performance to Include Fluid Inertia Force Coefficients

2012 ◽  
Author(s):  
Luis San Andrés
Keyword(s):  
Finite Element ◽  
Test Data ◽  
Small Amplitude ◽  
Forced Response ◽  
Inertia Force ◽  
Fluid Inertia ◽  
Inertia Effects ◽  
Force Coefficients ◽  
Reaction Forces ◽  
Bearing Stiffness

Reynolds equation governs the generation of hydrodynamic pressure in oil lubricated fluid film bearings. The static and dynamic forced response of a bearing is obtained from integration of the film pressure on the bearing surface. For small amplitude journal motions, a linear analysis represents the fluid film bearing reaction forces as proportional to the journal center displacements and velocity components through four stiffness and four damping coefficients. These force coefficients are integrated into rotor-bearing system structural analysis for prediction of the system stability and the synchronous response to imbalance. Fluid inertia force coefficients, those relating reaction forces to journal center accelerations, are routinely ignored because most oil lubricated bearings operate at relatively low Reynolds numbers, i.e., under slow flow conditions. Modern rotating machinery operates at ever increasing surface speeds to deliver more power in smaller size units. Under these operating conditions fluid inertia effects need to be accounted for in the forced response of oil lubricated bearings, as recent experimental test data also reveal. The paper presents a finite element formulation to predict added mass coefficients in oil lubricated bearings by extending a basic formulation that already calculates the bearing stiffness and damping force coefficients. That is, a small amplitude perturbation analysis of the lubrication flow equations keeps the temporal fluid inertia effects and develops a set of equations to obtain the bearing stiffness, damping and inertia force coefficients. The method does not impose on the cost of the original formulation which makes it very attractive for ready implementation in existing software. Predictions of the computational model are benchmarked against archival test data for an oil-lubricated pressure dam bearing supporting large compressors. The comparisons show fluid inertia effects cannot be ignored for operation at high rotor speeds and with small static loads.

scholarly journals Squeeze-Film Damper Technology: Part 1 — Prediction of Finite Length Damper Performance

1983 ◽  
Author(s):  
J. W. Lund ◽  
A. J. Smalley ◽  
J. A. Tecza ◽  
J. F. Walton
Keyword(s):  
Finite Length ◽  
Gas Turbines ◽  
Squeeze Film ◽  
Fluid Inertia ◽  
Inertia Effects ◽  
Strongly Coupled ◽  
Squeeze Film Damper ◽  
Rotor Systems ◽  
Squeeze Film Dampers ◽  
Calculation Results

Squeeze-film dampers are commonly used in gas turbine engines and have been applied successfully in a great many new designs, and also as retrofits to older engines. Of the mechanical components in gas turbines, squeeze-film dampers are the least understood. Their behavior is nonlinear and strongly coupled to the dynamics of the rotor systems on which they are installed. The design of these dampers is still largely empirical, although they have been the subject of a large number of past investigations. To describe recent analytical and experimental work in squeeze-film damper technology, two papers are planned. This abstract outlines the first paper, Part 1, which concerns itself with squeeze-film damper analysis. This paper will describe an analysis method and boundary conditions which have been developed recently for modelling dampers, and in particular, will cover the treatment of finite length, feed and drain holes and fluid inertia effects, the latter having been shown recently to be of great importance in predicting rotor system behavior. A computer program that solves the Reynolds equation for the above conditions will be described and sample calculation results presented.

Flow in Finite-Width Thrust Bearings Including Inertial Effects: II—Turbulent Flow

1978 ◽  
Vol 100 (3) ◽  
pp. 339-345 ◽  
Author(s):  
B. E. Launder ◽  
M. A. Leschziner
Keyword(s):  
Turbulent Viscosity ◽  
Turbulence Energy ◽  
Finite Width ◽  
Fluid Inertia ◽  
Inertia Effects ◽  
Thrust Bearings ◽  
Inertial Flow ◽  
Transport Effects ◽  
Rate Of Dissipation ◽  
Selection Of

A new set of turbulent resistance laws for hydrodynamic lubricant films has been derived with the aid of a turbulence model which includes transport effects on two turbulence parameters. The model consists of two differential equations for the turbulence energy and its rate of dissipation and a constitutive equation for the turbulent viscosity. The model places no restrictions on the Reynolds number. An efficient finite-difference scheme, based on the integro-differential approach and incorporating the resistance laws and a set of accurate inertial coefficients, is applied to the solution of the turbulent inertial flow in finite-width slider bearings. A selection of predictions is presented for non-inertial and inertial flows. The former are compared with solutions obtained with alternative turbulent lubrication theories. The importance of including fluid inertia effects is demonstrated.

Fluid Inertia Effects in a Non-Newtonian Squeeze Film Between Two Plane Annuli

1999 ◽  
Vol 122 (4) ◽  
pp. 872-875 ◽  
Author(s):  
R. Usha and ◽  
P. Vimala
Keyword(s):  
Carrying Capacity ◽  
Integral Method ◽  
Squeeze Flow ◽  
Squeeze Film ◽  
Load Carrying Capacity ◽  
Fluid Inertia ◽  
Inertia Effects ◽  
Load Carrying ◽  
Analytical Expressions ◽  
Plastic Fluids

An analysis is presented for the laminar squeeze flow of an incompressible powerlaw fluid between parallel plane annuli using the modified lubrication theory and energy integral method. The local and the convective inertia of the flow are considered in the investigation. Analytical expressions for the load carrying capacity of the squeeze film are obtained using both the methods and are compared with those based on the assumption of inertialess flow. It is observed that the inertia correction in the load carrying capacity is more significant for pseudo-plastic fluids, n<1.[S0742-4787(00)00504-X]

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