Analysis and Test of a Robust Sector Thrust Bearing for a Cryogenic Turboalternator

2001 ◽  
Vol 123 (4) ◽  
pp. 768-776
Author(s):  
G. F. Nellis ◽  
M. V. Zagarola ◽  
H. Sixsmith
Keyword(s):  
Thrust Bearing ◽  
Large Temperature ◽  
Cryogenic Temperatures ◽  
Inertial Effects ◽  
Test Results ◽  
Viscous Effects ◽  
Reliable Operation ◽  
Restoring Force ◽  
Thrust Bearings ◽  
Leakage Flows

The miniature turboalternator associated with a reverse-Brayton cryocooler requires geometrically simple, self-acting thrust bearings capable of reliable operation over a large temperature range and insensitive to secondary leakage flows. In order to meet this need, a robust sector thrust bearing has been developed. This thrust bearing is different from a classic stepped sector thrust bearing in that the restoring force at cryogenic temperatures originates primarily from inertial effects while at higher temperatures its restoring force is related primarily to viscous effects. This paper describes the analysis and initial test results for a prototypical robust sector thrust bearing.

Evaluating Thermal Performance of a PTFE-Faced Tilting Pad Thrust Bearing

2003 ◽  
Vol 125 (2) ◽  
pp. 319-324 ◽  
Author(s):  
Sergei B. Glavatskih
Keyword(s):  
Thrust Bearing ◽  
Friction Torque ◽  
Outer Diameter ◽  
Test Results ◽  
Operating Characteristics ◽  
Thrust Bearings ◽  
Ptfe Composite ◽  
Temperature Distributions ◽  
Tilting Pad ◽  
Bearing Friction

This paper compares and analyses operating characteristics of equalizing tilting pad thrust bearings with babbitt and polytetrafluoroethylene (PTFE) composite facings. Each bearing arrangement included six pads with an outer diameter of 228.6 mm and 60 percent offset. The babbitted bearing was typical of design in general use. A PTFE composite was applied instead of the babbitt to a similar bearing. Bearings were tested at different load-speed combinations in the fully flooded mode. Pad temperature distributions, collar temperatures and bearing friction torque were continuously measured. Test results show that the PTFE composite provides excellent thermal insulation so that pad thermal crowning is eliminated. PTFE-faced bearings operate with lower power loss and slightly higher collar temperatures compared to similar babbitted bearings.

Inertial contributions to friction measurements in thrust bearings

2021 ◽  
pp. 135065012110653
Author(s):  
Jonathon K. Schuh
Keyword(s):  
Scaling Laws ◽  
Thrust Bearing ◽  
Friction Reduction ◽  
Textured Surface ◽  
Fluid Inertia ◽  
Viscous Effects ◽  
Navier Stokes Equation ◽  
Moving Plate ◽  
Thrust Bearings ◽  
Lubricated Sliding

Surface textures decrease friction in lubricated sliding contact. Traditionally, the friction reduction for a given textured surface is determined by using the Reynolds equation, which neglects fluid inertia. However, as the separation and relative motion between the surfaces increase, inertia can affect the measured tangential and normal forces for flow over a textured surface, and thus cause the coefficient of friction to differ from the purely viscous, Stokes flow prediction. Here, the increase in torque and normal force between a moving plate and stationary textured surface, which simulates a textured thrust bearing, are calculated as a function of the Reynolds number in the thin film limit. The predictions for a non-textured thrust bearing are compared to fully 3-D numerical simulations of the incompressible Navier-Stokes equation, and the predictions for textured thrust bearings are compared to experimental data given in the literature. Good agreement is seen between the predictions and the data, validating the predicted scaling laws. This work also suggests that inertia can be used as a secondary effect to reduce friction in lubricated sliding, and textures that take advantage of the inertial effects will have lower friction than textures that only use purely viscous effects.

scholarly journals Measurements Versus Predictions for a Hybrid (Hydrostatic Plus Hydrodynamic) Thrust Bearing for a Range of Orifice Diameters

2019 ◽  
Vol 141 (6) ◽  
Author(s):  
Dara W. Childs ◽  
Paul Esser
Keyword(s):  
High Speed ◽  
Thrust Bearing ◽  
Fluid Film ◽  
Orifice Diameter ◽  
Axial Stiffness ◽  
Test Results ◽  
Flow Rates ◽  
Face To Face ◽  
Thrust Bearings ◽  
Inner Radius

A fixed-geometry hybrid thrust bearing is investigated with three different supply orifice diameters, (1.63, 1.80, and 1.93 mm). The test rig uses a face-to-face thrust-bearing design, with the test bearing acting as the rotor loading mechanism. A hydraulic shaker applies the static axial load, which is reacted by a second (slave) thrust bearing. The rotor is supported radially by two water-lubricated fluid-film journal bearings and is attached to a 30.6 krpm motor via a high-speed coupling with very low axial stiffness. Thrust bearings are tested for a range of supply pressures (5.17, 10.34, and 17.34 bars), fluid film thicknesses, and speeds (7.5, 12.5, and 17.5 krpm). The water-lubricated test bearings have eight pockets, with feed orifices located centrally in each pocket. Experimental results are compared to predictions from a bulk-flow model, showing generally good agreement. Thrust-bearing inlet supply and inner radius flow rates all decreased with decreasing orifice diameters and bearing axial clearances. In most cases, the bearings with larger orifice diameters exhibit higher recess pressure ratios, operating clearances, and flow rates. An optimum hybrid thrust-bearing orifice diameter will depend on the conditions of individual applications. Larger orifices generally provide larger operating clearances and higher stiffnesses, but also require higher flow rates. For most applications, a compromise of bearing performance parameters will be desired. The test results and comparisons presented will aid in sizing orifice diameters for future hybrid thrust-bearing designs and in validating and improving models and predictions.

Performance Characteristics of Tilting Pad Thrust Bearings at High Operating Speeds

1976 ◽  
Vol 98 (1) ◽  
pp. 81-88 ◽  
Author(s):  
J. W. Capitao
Keyword(s):  
Power Loss ◽  
Thrust Bearing ◽  
Experimental Program ◽  
Test Results ◽  
Transition Range ◽  
Thrust Bearings ◽  
Laminar To Turbulent Transition ◽  
Turbulent Transition ◽  
Tilting Pad ◽  
Bearing Loads

A full scale experimental program was conducted to investigate the influence of fluid film turbulence on the performance of the tilting-pad, self-equalizing type thrust bearing. Test results include data on centrally pivoted, 6-pad, 381-mm (15-in.) and 432-mm (17-in.) O.D. bearings operating with shaft speeds up to 10000 rpm and bearing loads ranging up to 3.447 MPa (500 psi). Data collected include bearing metal temperatures, bearing power loss, and observation of the laminar to turbulent transition range.

scholarly journals Run-Up Simulation of a Semi-Floating Ring Supported Turbocharger Rotor Considering Thrust Bearing and Mass-Conserving Cavitation

Lubricants ◽  
2021 ◽  
Vol 9 (4) ◽  
pp. 44
Author(s):  
Christian Ziese ◽  
Cornelius Irmscher ◽  
Steffen Nitzschke ◽  
Christian Daniel ◽  
Elmar Woschke
Keyword(s):  
Reynolds Equation ◽  
Energy Equation ◽  
Thrust Bearing ◽  
Three Dimensional ◽  
Reliable Prediction ◽  
Two Phase ◽  
Hydrodynamic Bearings ◽  
Thrust Bearings ◽  
Run Up ◽  
The Impact

The vibration behaviour of turbocharger rotors is influenced by the acting loads as well as by the type and arrangement of the hydrodynamic bearings and their operating condition. Due to the highly non-linear bearing behaviour, lubricant film-induced excitations can occur, which lead to sub-synchronous rotor vibrations. A significant impact on the oscillation behaviour is attributed to the pressure distribution in the hydrodynamic bearings, which is influenced by the thermo-hydrodynamic conditions and the occurrence of outgassing processes. This contribution investigates the vibration behaviour of a floating ring supported turbocharger rotor. For detailed modelling of the bearings, the Reynolds equation with mass-conserving cavitation, the three-dimensional energy equation and the heat conduction equation are solved. To examine the impact of outgassing processes and thrust bearing on the occurrence of sub-synchronous rotor vibrations separately, a variation of the bearing model is made. This includes run-up simulations considering or neglecting thrust bearings and two-phase flow in the lubrication gap. It is shown that, for a reliable prediction of sub-synchronous vibrations, both the modelling of outgassing processes in hydrodynamic bearings and the consideration of thrust bearing are necessary.

An Accurate Solution of the Gas Lubricated, Flat Sector Thrust Bearing

1977 ◽  
Vol 99 (1) ◽  
pp. 82-88 ◽  
Author(s):  
I. Etsion ◽  
D. P. Fleming
Keyword(s):  
Film Thickness ◽  
Thrust Bearing ◽  
Load Capacity ◽  
Thickness Distribution ◽  
Maximum Load ◽  
Accurate Solution ◽  
Operating Conditions ◽  
Thrust Bearings ◽  
Practical Design ◽  
Minimum Film Thickness

A flat sector shaped pad geometry for gas lubricated thrust bearings is analyzed considering both pitch and roll angles of the pad and the true film thickness distribution. Maximum load capacity is achieved when the pad is tilted so as to create a uniform minimum film thickness along the pad trailing edge. Performance characteristics for various geometries and operating conditions of gas thrust bearings are presented in the form of design curves. A comparison is made with the rectangular slider approximation. It is found that this approximation is unsafe for practical design, since it always overestimates load capacity.

FROUDE’S LAW OF SIMILITUDE – CONTEMPORARY AND FUTURE SEAKEEPING TESTING

2021 ◽  
Vol 153 (A2) ◽  
Author(s):  
R P Dallinga ◽  
R H M Huijsmans
Keyword(s):  
Model Test ◽  
Scale Effects ◽  
Higher Order ◽  
Air Pressure ◽  
Test Results ◽  
Viscous Effects ◽  
Two Phase ◽  
Scale Models ◽  
Non Linear

Historically “scale effects” in the interpretation of tests with scale models in waves using Froude’s Law of Similitude are mostly associated with viscous effects. Nowadays, with a much more complete modelling of reality and a focus on higher order non-linear phenomena, scaling of model test results implies a wider range of assumptions than the validity of Froude’s Law. Our contribution to the conference is a visionary review of contemporary and future problems in the interpretation of these tests. In this context we will discuss the developments in test techniques, including the development of a new Two-Phase Laboratory facilitating seakeeping and sloshing tests at reduced air pressure.

The Effect of Macro-Roughness on the Performance of Parallel Thrust Bearings

1950 ◽  
Vol 163 (1) ◽  
pp. 149-161 ◽  
Author(s):  
M. E. Salama
Keyword(s):  
Thrust Bearing ◽  
Prime Factor ◽  
Thrust Bearings ◽  
Rational Explanation ◽  
Film Lubrication ◽  
Effect Of Surface

This work was initiated to investigate the effect of surface macro-roughness on the performance of the parallel-faces thrust bearing and, at the same time, to find a rational explanation of its behaviour. The problem is treated both theoretically and experimentally and the main result arrived at indicates that macro-roughness is a prime factor in the behaviour of the bearing, as it provides passages which both feed the surfaces with the lubricant and allow the formation of hydrodynamic films so that the performance corresponds closer to that for film lubrication. Further work on micro-roughness is proceeding.

Static and Dynamic Characteristics of Aerostatic Circular Porous Thrust Bearings (Effect of the Shape of the Air Supply Area)

2000 ◽  
Vol 123 (3) ◽  
pp. 501-508 ◽  
Author(s):  
S. Yoshimoto ◽  
K. Kohno
Keyword(s):  
Porous Material ◽  
Dynamic Characteristics ◽  
Thrust Bearing ◽  
Aerostatic Bearing ◽  
Bearing Surface ◽  
Static And Dynamic Characteristics ◽  
Thrust Bearings ◽  
Porous Bearing ◽  
Air Supply ◽  
Bearing Design

Recently, graphite porous material has been used successfully in an aerostatic bearing. In actual bearing design, it is often necessary to reduce the thickness of porous material to make the bearing smaller. However, a reduction in thickness results in a reduction in the strength of the porous material. In particular, when the diameter of porous material is large, it is difficult to supply the air through the full pad area of porous material because it deforms. Therefore, in this paper, two types of air supply method (the annular groove supply and the hole supply) in a circular aerostatic porous thrust bearing are proposed to avoid the deflection of the bearing surface. The static and dynamic characteristics of aerostatic porous bearing with these air supply methods are investigated theoretically and experimentally. In addition, the effects of a surface restricted layer on the characteristics are clarified.

On the performance of foil thrust bearing with misaligned bearing runner

2017 ◽  
Vol 69 (2) ◽  
pp. 105-115 ◽  
Author(s):  
Abdelrasoul M. Gad
Keyword(s):  
High Speed ◽  
Thrust Bearing ◽  
Approximation Technique ◽  
Hydrodynamic Effect ◽  
Stable Operation ◽  
Content Type ◽  
Thrust Bearings ◽  
Load Carrying ◽  
Foil Thrust Bearing ◽  
Stiffness And Damping

Purpose Compliant foil thrust bearings are promising bearings for high-speed oil-free turbomachinery. However, most previous experimental and numerical approaches to investigate the performance of these bearings have ignored the effect of bearing runner misalignment. Therefore, this paper aims to evaluate the effects of static and dynamic angular misalignments of the bearing runner on the performance of a gas-lubricated foil thrust bearing. Design/methodology/approach The bearing runner is allowed a maximum angular misalignment that produces a minimum gas film thickness as low as 20 per cent of the nominal clearance. Then, the variations of bearing load carrying capacity, viscous power loss and stiffness and damping coefficients of the gas film with runner misalignment are thoroughly analyzed. The flow in the gas film is modeled with compressible Reynolds equation along with the Couette approximation technique, and the deformation of the compliant bearing is calculated with a robust analytical model. Small perturbations method is used to calculate the force and moment dynamic coefficients of the gas film. Findings The results show that misaligned foil thrust bearings are capable of developing a restoring moment sufficient enough to withstand the imposed misalignments. Furthermore, the enhanced hydrodynamic effect ensures a stable operation of the misaligned bearing, and the results highlighted the role of the compliant bearing structure to maintain foil bearing prominent features even at misaligned conditions. Originality/value The value of this study is the evaluation of the effects of runner angular misalignments on the static and dynamic characteristics of Generation II bump-type foil thrust bearing.

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