Squeeze Film Operation of Thrust Bearing Operating with Shear-Thinning Lubricants

2022 ◽  
pp. 103-114
Author(s):  
Vivek Kumar ◽  
Vatsalkumar Ashokkumar Shah ◽  
Kuldeep Narwat ◽  
Satish C. Sharma
Keyword(s):  
Thrust Bearing ◽  
Shear Thinning ◽  
Squeeze Film

Additively Manufactured Compliant Hybrid Gas Thrust Bearing for SCO2 Turbomachinery: Design and Proof of Concept Testing

2021 ◽  
Author(s):  
Bugra Ertas
Keyword(s):  
Thrust Bearing ◽  
Nonlinear Behavior ◽  
Squeeze Film ◽  
Outer Diameter ◽  
Proof Of Concept ◽  
Unit Load ◽  
Rotating Speed ◽  
Load Carrying ◽  
New Type ◽  
Turbomachinery Design

Abstract The following paper presents a new type of gas lubricated thrust bearing fabricated using additive manufacturing or direct metal laser melting (DMLM). The motivation for the new bearing concept is derived from the need for highly efficient supercritical carbon dioxide turbomachinery in the mega-watt power range. The paper provides a review of existing gas thrust bearing technologies, outlines the need for the new DMLM concept, and discusses proof of concept testing results. The new concept combines hydrostatic pressurization with individual flexibly mounted pads using hermetic squeeze film dampers in the bearing-pad support. Proof-of-concept testing in air for a 6.8" (173mm) outer diameter thrust bearing was performed; with loads up to 1,500 lbs (6.67kN) and a rotating speed of 10krpm (91 m/s tip speed). The experiments were performed with a bent shaft resulting in thrust runner axial vibration magnitudes of 2.9mils (74microns) p-p and dynamic thrust loads of 270 lbs (1.2kN) p-p. In addition, force deflection characteristics of the bearing system are presented for an inlet hydrostatic pressure of 380psi (2.62MPa). Results at 10krpm show that the pad support architecture was able to sustain high levels of dynamic misalignment equaling 6 times the nominal film clearance while demonstrating a unit load carrying capacity of 55psi (0.34Mpa). Gas-film force-deflection tests portrayed nonlinear behavior like a hardening spring, while the pad support stiffness was measured to be linear and independent of film thickness.

Lubricant Selection for Minimum Traction in Elastohydrodynamic Lubrication Line Contacts During Accelerated Motion—A Numerical Approach

2017 ◽  
Vol 139 (5) ◽  
Author(s):  
Niraj Kumar ◽  
Punit Kumar
Keyword(s):  
Elastohydrodynamic Lubrication ◽  
Shear Thinning ◽  
Numerical Approach ◽  
Squeeze Film ◽  
Accelerated Motion ◽  
Line Contacts ◽  
Traction Coefficient ◽  
Minimum Variation ◽  
Starting Speed ◽  
Transient Thermal

Transient thermal elastohydrodynamic lubrication (EHL) line contact simulations are carried out to study the traction behavior during accelerated motion considering realistic shear-thinning behavior. Using three lubricants with different inlet viscosity and shear-thinning parameters, the application of present analysis for lubricant selection is demonstrated. Owing to squeeze film action, the film evolution is delayed, and EHL traction during acceleration is found to increase much above the designed value. This effect decreases with increasing starting speed. The most shear-thinning test oil considered here yields the lowest traction coefficient with minimum variation in its value desirable for smooth and vibration-free operation.

Additively Manufactured Compliant Hybrid Gas Thrust Bearing for SCO2 Turbomachinery: Experimental Evaluation & Fluid-Structure Model Predictions

2021 ◽  
Author(s):  
Bugra Ertas ◽  
Keith Gary ◽  
Adolfo Delgado
Keyword(s):  
Thrust Bearing ◽  
Load Capacity ◽  
Ideal Gas ◽  
Squeeze Film ◽  
Outer Diameter ◽  
Structure Model ◽  
Unit Load ◽  
Free System ◽  
Fluid Structure ◽  
Process Gas

Abstract The following paper presents test results and advances an analytical predictive fluid-structure model for a new type of gas lubricated thrust bearing fabricated using direct metal laser melting (DMLM). The concept in the present study is a compliant hybrid gas thrust bearing using external pressurization to increase load carrying capacity, where the testing in the present study only focused on steady state static performance. The need for the bearing concept comes from enabling highly efficient supercritical carbon dioxide (sCO2) turbomachinery by replacing oil-lubricated bearings with process gas lubrication. Leveraging the process gas for bearing lubrication results in lowered bearing power loss [1], simplified mechanical design, and allows for novel oil-free hermetic drivetrains resulting in an efficient emission-free system [2,3]. The new concept utilizes hydrostatic pressurization on individual tilting pads flexibly mounted with hermetic squeeze film dampers (HSFD). The paper focuses on tests of a 173mm outer diameter gas thrust bearing in air up to 10krpm and hydrostatic inlet pressures to 365psi (2.52MPa). The present work advances a fluid-structure thrust bearing model using an isothermal ideal-gas based Reynolds flow equation coupled to a lumped stiffness element possessing axial and rotational degrees of freedom. The rotating testing demonstrated load capability of 1,816 lbs (8.1KN), which equates to a thrust bearing unit load of 67psi (0.46 MPa). Load capability was shown to increase with increasing hydrostatic inlet pressure while the increase in thrust runner speed revealed a small decrease in load capacity.

Additively Manufactured Compliant Hybrid Gas Thrust Bearing for sCO2 Turbomachinery: Design and Proof of Concept Testing

2020 ◽  
Author(s):  
Bugra Ertas
Keyword(s):  
Thrust Bearing ◽  
Nonlinear Behavior ◽  
Squeeze Film ◽  
Outer Diameter ◽  
Proof Of Concept ◽  
Unit Load ◽  
Load Carrying ◽  
Final Design ◽  
New Type ◽  
Turbomachinery Design

Abstract The following paper presents a new type of gas lubricated thrust bearing that utilizes additive manufacturing or also known as direct metal laser melting (DMLM) to fabricate the bearing. The motivation for the new bearing concept is derived from the need for highly efficient supercritical carbon dioxide (sCO2) turbomachinery in the mega-watt power range. The paper provides a review of existing gas thrust bearing technology, outlines the need for the new DMLM concept, and discusses proof of concept testing results. The new concept combines hydrostatic pressurization with individual tilting pads that are flexibly mounted using hermetic squeeze film dampers (HSFD) in the bearing-pad support. This paper describes the thrust bearing concept and discusses the final design approach. Proof-of-concept testing in air for a 6.8” (173mm) outer diameter thrust gas bearing was performed; with thrust loading, up to 1,500 lbs (6.67kN) and a thrust runner speed of 10krpm (91 m/s tip speed). The experiments were performed with a bent shaft resulting in thrust runner axial vibration magnitudes of 2.9mils (74microns) p-p and dynamic thrust loads of 270 lbs (1.2kN) p-p. In addition, force deflection characteristics and stiffness coefficients of the bearing system are presented for an inlet hydrostatic pressure of 380psi (2.62MPa). Results at 10krpm show that the pad support architecture was able to sustain high levels of dynamic misalignment equaling 6 times the nominal film clearance while demonstrating a unit load carrying capacity of 55psi (0.34Mpa). Gas-film force deflection tests portrayed nonlinear behavior like a hardening spring, while the bearing pad support stiffness was measured to be linear and independent of gas film thickness.

scholarly journals Thrust Bearing with Rough Surfaces Lubricated by an Ellis Fluid

2014 ◽  
Vol 19 (4) ◽  
pp. 809-822
Author(s):  
A. Walicka ◽  
E. Walicki ◽  
P. Jurczak ◽  
J. Falicki
Keyword(s):  
Pressure Distribution ◽  
Analytical Solutions ◽  
Carrying Capacity ◽  
Reynolds Equation ◽  
Thrust Bearing ◽  
Equations Of Motion ◽  
Squeeze Film ◽  
Load Carrying Capacity ◽  
Load Carrying ◽  
Plastic Fluid

Abstract In the paper the influence of bearing surfaces roughness on the pressure distribution and load-carrying capacity of a thrust bearing is discussed. The equations of motion of an Ellis pseudo-plastic fluid are used to derive the Reynolds equation. After general considerations on the flow in a bearing clearance and using the Christensen theory of hydrodynamic rough lubrication the modified Reynolds equation is obtained. The analytical solutions of this equation for the cases of a squeeze film bearing and an externally pressurized bearing are presented. As a result one obtains the formulae expressing pressure distribution and load-carrying capacity. A thrust radial bearing is considered as a numerical example.

A compressible flow model for the air-rotor–stator dynamics of a high-speed, squeeze-film thrust bearing

2010 ◽  
Vol 655 ◽  
pp. 446-471 ◽  
Author(s):  
J. E. GARRATT ◽  
K. A. CLIFFE ◽  
S. HIBBERD ◽  
H. POWER
Keyword(s):  
Compressible Flow ◽  
High Speed ◽  
Reynolds Equation ◽  
Flow Model ◽  
Thrust Bearing ◽  
Finite Amplitude ◽  
Squeeze Film ◽  
Axial Position ◽  
Rotor Support ◽  
Rotor Stiffness

A compressible air-flow model is introduced for the thin film dynamics of a highly rotating squeeze-film thrust bearing. The lubrication approximation to the Navier–Stokes equations for compressible flow leads to a modified Reynolds equation incorporating additional rotation effects. To investigate the dynamics of the system, the axial position of the bearing stator is prescribed by a finite-amplitude periodic forcing. The dynamics of the squeeze-film are modelled in the uncoupled configuration where the axial position of the rotor is fixed. The coupled squeeze-film bearing dynamics are investigated when the axial position of the rotor is modelled as a spring-mass-damper system that responds to the film dynamics. Initially the uncoupled squeeze-film dynamics are considered at low operating speeds with the classical Reynolds equation for compressible flow. The limited value of the linearized small-amplitude results is identified. Analytical results indicate that finite-amplitude forcing needs to be considered to gain a complete understanding of the dynamics. Using a Fourier spectral collocation numerical scheme, the periodic bearing force is investigated as a nonlinear function of the frequency and amplitude of the stator forcing. High-speed bearing operation is modelled using the modified Reynolds equation. A steady-state analysis is used to identify the effect of rotation and the rotor support properties in the coupled air-flow–structure model. The unsteady coupled dynamics are computed numerically to determine how the rotor support structures and the periodic stator forcing influence the system dynamics. The potential for resonant rotor behaviour is identified through asymptotic and Fourier analysis of the rotor motion for small-amplitude, low-frequency oscillations in the stator position for key values of the rotor stiffness. Through the use of arclength continuation, the existence of resonant behaviour is identified numerically for a range of operating speeds and forcing frequencies. Changes in the minimum rotor–stator clearance are presented as a function of the rotor stiffness to demonstrate the appearance of resonance.

Performance of textured spherical thrust hybrid bearing operating with shear thinning and piezoviscous lubricants

2021 ◽  
pp. 135065012110313
Author(s):  
Nitin Agrawal ◽  
Satish C Sharma
Keyword(s):  
Power Loss ◽  
Reynolds Equation ◽  
Thrust Bearing ◽  
Strong Dependence ◽  
Shear Thinning ◽  
Flow Equation ◽  
Textured Surfaces ◽  
Bearing Surface ◽  
Fluid Film Bearings ◽  
Hybrid Bearing

Improving the lubricating performance of tribo-pairs using engineering textured surfaces has been the main focus of tribology research in recent years. The use of a suitably designed micro-texture on the bearing surface may have a beneficial effect on the performance of fluid film bearings. In the present paper, a mathematical model of a hybrid spherical thrust bearing is developed considering the effect of shear thinning and piezoviscous behaviour of a lubricant. The modified Reynolds equation for a hybrid spherical thrust bearing configuration together with a restrictor flow equation for a capillary restrictor is solved using a finite-element method. In this work, the effect of various micro-textures shapes (spherical, circular, conical and square) and non-Newtonian lubricant behaviour having shear thinning and piezoviscous effects are analysed. The numerically simulated result shows a strong dependence on the combined effect of shear thinning and piezoviscous lubricant behaviour and a chosen geometric shape of a texture. The frictional power loss is seen to reduce nearly by 24.05%, and the stiffness gets enhanced by 11.08%.

Squeeze Film Flow Between Arbitrary Two-Dimensional Surfaces Subject to Normal Oscillations

1978 ◽  
Vol 100 (3) ◽  
pp. 316-322 ◽  
Author(s):  
J. A. Tichy ◽  
M. F. Modest
Keyword(s):  
Thrust Bearing ◽  
Analytic Solution ◽  
Film Flow ◽  
Oscillation Amplitude ◽  
Reynolds Numbers ◽  
Lubrication Theory ◽  
Squeeze Film ◽  
Two Dimensional ◽  
Surface Geometry ◽  
Inertia Effects

An analytic solution is presented for squeeze film flow with smooth, arbitrary, two-dimensional surface geometry. One surface undergoes sinusoidal oscillation toward the other. The oscillation amplitude is much smaller than the film thickness, which is in turn much smaller than the bearing length. The solution improves on the lubrication theory due to the inclusion of inertia effects. The solution to an illustrative problem is presented—the thrust bearing. The velocity field, pressure distribution and load differ significantly from those predicted by lubrication theory. The results show the lubrication solution for load and pressure to be in error by over 100 percent for Reynolds numbers as low as 5.

Additively Manufactured Compliant Hybrid Gas Thrust Bearing for sCO2 Turbomachinery: Experimental Evaluation and Fluid-Structure Model Predictions

2020 ◽  
Author(s):  
Bugra Ertas ◽  
Keith Gary ◽  
Adolfo Delgado
Keyword(s):  
Thrust Bearing ◽  
Load Capacity ◽  
Inlet Pressure ◽  
Squeeze Film ◽  
Outer Diameter ◽  
Structure Model ◽  
Free System ◽  
Fluid Structure ◽  
Process Gas ◽  
Load Carrying

Abstract The following paper presents rotating test results and advances an analytical predictive fluid-structure model for a new type of gas lubricated thrust bearing fabricated using direct metal laser melting (DMLM). The bearing concept in the present study is a compliant hybrid gas thrust bearing that uses external pressurization to increase load carrying capacity, where the testing campaign in the present study was only focused on steady state static performance. The need for the bearing concept comes from enabling highly efficient supercritical carbon dioxide (sCO2) turbomachinery by replacing oil-lubricated bearings with process gas lubrication. Leveraging the process gas of the turbomachine for bearing lubrication results in lowered bearing power loss [1], simplified mechanical design, and allows for novel oil-free hermetic drivetrains resulting in an efficient emission-free system [2,3]. The new concept utilizes hydrostatic pressurization on individual tilting pads flexibly mounted with hermetic squeeze film dampers (HSFD). The paper focuses on rotating tests of a 173mm outer diameter gas thrust bearing in air up to 10krpm and hydrostatic inlet pressures to 365psi (2.52MPa). The influence of thrust runner speed and bearing inlet pressure on force deflection characteristics and load carrying capability of the gas film were experimentally evaluated. The present work also advances a predictive fluid-structure thrust bearing model using an isothermal ideal-gas based compressible Reynolds flow equation directly coupled to a lumped stiffness element possessing axial and rotational degrees of freedom. The rotating testing demonstrated load capability of 1,816 lbs (8.1KN), which equates to a thrust bearing unit load of 67psi (0.46 MPa). Gas film force-deflection curves reveal a nonlinear relationship between thrust load and film clearance. Comparison of film thickness values with the predictive model show good agreement under high load and inlet pressure, however deviate as load and pressure decrease. Load capability was shown to increase with increasing hydrostatic inlet pressure while the increase in thrust runner speed revealed a small decrease in load capacity.

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