Theoretical Flow-Models for Externally Pressurized Gas Bearings

1969 ◽  
Vol 91 (1) ◽  
pp. 181-193 ◽  
Author(s):  
H. Mori ◽  
Y. Miyamatsu
Keyword(s):  
Shock Wave ◽  
Load Capacity ◽  
Operating Conditions ◽  
Gas Bearings ◽  
Flow Models ◽  
Thrust Bearings ◽  
Pressure Distributions ◽  
In Series ◽  
Pressure Changes ◽  
Wide Operating

In order to make clear the characteristics of externally pressurized gas bearings, several mathematical flow-models are constructed by making proper chains of fundamental and elemental flow-patterns and pressure changes for circular thrust bearings with single central supply hole. The suggested flow-models, which are the combination of rather simple elements to make the mathematical analysis easy, are quite effective to explain the pressure distributions, the load capacity, and the rate of flow observed experimentally over wide operating conditions. And also, these flow-models make it possible to understand the effects of the inherent compensation, the so-called restrictions in series and the occurrence of shock wave.

Multiphysics Modeling of a Tilting Pad Thrust Bearing: Comparison Between White Metal and Polymeric Layered Pads

2011 ◽  
Author(s):  
R. Ricci ◽  
S. Chatterton ◽  
P. Pennacchi ◽  
A. Vania
Keyword(s):  
Load Capacity ◽  
Vertical Axis ◽  
Operating Conditions ◽  
Standard Size ◽  
White Metal ◽  
Oil Film ◽  
Thrust Bearings ◽  
Pressure Distributions ◽  
Tilting Pad ◽  
Polymeric Layer

Oil-film tilting pad thrust bearings are mainly used in supporting the high axial load of the turbine shaft in vertical hydroelectric units or smaller axial loads of turbo machines. The trend for these applications is to replace the white metal with a polymeric material layer such as PTFE or PEEK, improving the bearing performances and extending its operating conditions. This leads to a reduction of the bearing overall dimensions as a consequence of the load capacity increase. Apart the friction and the resistance to chemical attacks properties of the polymeric layer, the main cause on the improved performances of the bearing is the compliance of the pad layer. In particular the polymeric layer reduces the typical pad crowning allowing a more uniform pressure distribution over the pad and a reduction of its maximum value with respect to Babbitt metal pads. Therefore, the design of layered pad requires a deeper investigation such as thermoelastohydrodynamic (TEHD) analyses, including oilthermal effects and bearing thermal deformation. In the paper, the performance of Babbitt metal and polymeric layered pads of standard size offset-pivoted tilting pad thrust bearings of vertical axis units are compared using a multiphysics software able to manage simultaneously the mechanical, the thermal and the fluid problems. Layer and pad deformation, temperature and pressure distributions, and oil-film thickness have been analysed for different operating conditions. The model has been validated using experimental data available in literature.

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.

Analysis of Starved Thrust Bearings Including Temperature Effects

1987 ◽  
Vol 109 (3) ◽  
pp. 395-401 ◽  
Author(s):  
A. Artiles ◽  
H. Heshmat
Keyword(s):  
Film Thickness ◽  
Thrust Bearing ◽  
Load Capacity ◽  
Operating Conditions ◽  
Geometrical Parameters ◽  
Two Dimensional ◽  
Thrust Bearings ◽  
Direct Iteration ◽  
Finite Thrust ◽  
Raphson Iteration

A method of analysis is described treating starvation in finite thrust bearing pads. A variable-size finite difference mesh is used to represent the two-dimensional temperature and pressure fields. A combination of Newton-Raphson iteration, direct iteration, and column matrix methods are used to solve for the start-of-film and minimum film thickness as well as the coupled two-dimensional energy and Reynolds equations. A parametric study describes the performance characteristics of the tapered land thrust bearing (flowrates, extent of fluid film, temperature rises, load capacity and torque) for different minimum film thicknesses and levels of starvation. This study considered variations in the geometrical parameters such as pad aspect ratio (L/R2=1/3, 1/2, 2/3) and extent of the pad (β=27, 42, and 57 deg) with an optimum taper ratio (β1/β=0.8). It is found that the effects of starvation are fairly small near the flooded condition but accelerate rapidly below the 50 percent starvation level. The start of the film (θ1) depends mostly on the level of starvation, and is essentially independent of the geometrical parameters, operating conditions or film thickness.

The Effects of Temperature and Inertia on Hydrostatic Thrust Bearing Performance

1971 ◽  
Vol 93 (2) ◽  
pp. 307-312 ◽  
Author(s):  
L. L. Ting ◽  
J. E. Mayer
Keyword(s):  
Load Capacity ◽  
Operating Conditions ◽  
Performance Estimation ◽  
Rotational Inertia ◽  
Adiabatic Flow ◽  
Thrust Bearings ◽  
Adiabatic Theory ◽  
Bearing Life ◽  
Load Carrying ◽  
Effects Of Temperature

The effects of the lubricant rotational inertia and the temperature on the performance of parallel stepped hydrostatic thrust bearings have been investigated. Expressions for pressure and temperature distributions and load carrying capacities are obtained under adiabatic flow conditions. Satisfactory correlation between theory and experiment has been observed especially when the bearing speed is high. In order to insure the increase of load capacity as speed increases, the ratio of step location to bearing radius must be chosen no less than a limiting value which depends on the other geometry and operating conditions of the bearing. Since the bearing performance estimation by adiabatic theory is conservative, the design criteria provided will be practical and useful if long bearing life is essential.

CFD Thermohydrodynamic Analysis of 3-D Sector-Pad Thrust Bearings With Rectangular Dimples

2013 ◽  
Author(s):  
C. I. Papadopoulos ◽  
L. Kaiktsis ◽  
M. Fillon
Keyword(s):  
Carrying Capacity ◽  
Thermal Effects ◽  
Computational Study ◽  
Load Capacity ◽  
Operating Conditions ◽  
Load Carrying Capacity ◽  
Performance Indices ◽  
Thrust Bearings ◽  
Load Carrying ◽  
Texture Design

The paper presents a detailed computational study of flow patterns and performance indices in a dimpled parallel thrust bearing. The bearing consists of eight pads; the stator surface of each pad is partially textured with rectangular dimples, aiming at maximizing the load carrying capacity. The bearing tribological performance is characterized by means of Computational Fluid Dynamics (CFD) simulations, based on the numerical solution of the Navier-Stokes and energy equations for incompressible flow. Realistic boundary conditions are implemented. The effects of operating conditions and texture design are studied for the case of isothermal flow. First, for a reference texture pattern, the effects of varying operating conditions, in particular minimum film thickness (thrust load), rotational speed and feeding oil pressure are investigated. Next, the effects of varying texture geometry characteristics, in particular texture zone circumferential/radial extent, dimple depth and texture density on the bearing performance indices (load carrying capacity, friction torque and friction coefficient) are studied, for a representative operating point. For the reference texture design, the effects of varying operating conditions are further investigated, by also taking into account thermal effects. In particular, adiabatic conditions and conjugate heat transfer at the bearing pad are considered. The results of the present study indicate that parallel thrust bearings textured by proper rectangular dimples are characterized by substantial load carrying capacity levels. Thermal effects may significantly reduce load capacity, especially in the range of high speeds and high loads. Based on the present results, favorable texture designs can be assessed.

Effect of Operating Conditions on the Elastohydrodynamic Performance of Foil Thrust Bearings for Supercritical CO2 Cycles

2016 ◽  
Vol 139 (4) ◽  
Author(s):  
Kan Qin ◽  
Ingo H. Jahn ◽  
Peter A. Jacobs
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Supercritical Co2 ◽  
Load Capacity ◽  
Fluid Phase ◽  
Operating Conditions ◽  
Inertia Force ◽  
Fluid Structure ◽  
Thrust Bearings ◽  
Foil Bearings

In this paper, a quasi-three-dimensional fluid–structure model using computational fluid dynamics for the fluid phase is presented to study the elastohydrodynamic performance of foil thrust bearings for supercritical CO2 cycles. For the simulation of the gas flows within the thin gap, the computational fluid dynamics solver Eilmer is extended, and a new solver is developed to simulate the bump and top foil within foil thrust bearings. These two solvers are linked using a coupling algorithm that maps pressure and deflection at the fluid structure interface. Results are presented for ambient CO2 conditions varying between 0.1 and 4.0 MPa and 300 and 400 K. It is found that the centrifugal inertia force can play a significant impact on the performance of foil thrust bearings with the highly dense CO2 and that the centrifugal inertia forces create unusual radial velocity profiles. In the ramp region of the foil thrust bearings, they generate an additional inflow close to the rotor inner edge, resulting in a higher peak pressure. Contrary to the flat region, the inertia force creates a rapid mass loss through the bearing outer edge, which reduces pressure in this region. This different flow fields alter bearing performance compared to conventional air foil bearings. In addition, the effect of turbulence in load capacity and torque is investigated. This study provides new insight into the flow physics within foil bearings operating with dense gases and for the selection of optimal operating condition to suit CO2 foil bearings.

scholarly journals Feasibility of Gas Bearings for Small High-Performance Aircraft Gas Turbines

1969 ◽  
Author(s):  
P. W. Curwen
Keyword(s):  
Gas Turbines ◽  
High Speed ◽  
High Performance ◽  
High Stress ◽  
Construction Materials ◽  
Operating Conditions ◽  
System Stability ◽  
Gas Generator ◽  
Gas Bearings ◽  
Thrust Bearings

High temperatures, pressures, and speeds of future Army propulsion systems will impose severe, perhaps intolerable, operating requirements on oil-lubricated engine bearings. Accordingly, air-lubricated (gas) bearings are being investigated as a possible approach to alleviating the lubrication problems. This paper presents results of a study to apply gas bearings to a two-spool gas generator for an advanced 4.5-lb/sec engine. It is shown that gas-lubricated journal and thrust bearings can be designed to carry the maximum loads imposed by flight and landing conditions. Additionally, the resulting engine configuration has promising attributes of compactness and mechanical simplicity. Potential problem areas are identified to be rotor-bearing system stability, LP-spool balancing, and LP-spool seal leakage. One area where feasibility has not been established is durability of the bearing construction materials. Material testing at the high-temperature, high-stress operating conditions of the bearings, including the effects of momentary high-speed bearing contacts, is urgently needed so that the question of material feasibility can be critically assessed.

Bump-Type Foil Bearings and Flexure Pivot Tilting Pad Bearings for Oil-Free Automotive Turbochargers: Highlights in Rotordynamic Performance

2015 ◽  
Author(s):  
Keun Ryu ◽  
Zachary Ashton
Keyword(s):  
High Performance ◽  
Load Capacity ◽  
Mechanical Efficiency ◽  
Outer Diameter ◽  
Gas Bearings ◽  
Thrust Bearings ◽  
Foil Bearings ◽  
Thermal Growth ◽  
Tilting Pad ◽  
Tilting Pad Bearings

Oil-free turbochargers require gas bearings in compact units of enhanced rotordynamic stability, mechanical efficiency, and improved reliability with reduced maintenance costs compared with oil-lubricated bearings. Implementation of gas bearings into automotive turbochargers requires careful thermal management with accurate measurements verifying model predictions. Foil bearings are customarily used in oil-free microturbomachinery because of their distinct advantages including tolerance to shaft misalignment and centrifugal/thermal growth, and large damping and load capacity compared with rigid surface gas bearings. Flexure pivot tilting pad bearings are widely used in high performance turbomachinery since they offer little or no cross-coupled stiffnesses with enhanced rotordynamic stability. The paper details the rotordynamic performance and temperature characteristics of two prototype oil-free turbochargers; one supported on foil journal and thrust bearings and the other one is supported on flexure pivot tilting pad journal bearings and foil thrust bearings of identical sizes (OD and ID) with the same aerodynamic components. The tests of the oil-free turbochargers, each consisting of a hollow rotor (∼0.4 kg and ∼23 mm in outer diameter at the bearing locations), are performed for various imbalances in NVH (i.e, cold air driven rotordynamics rig) and gas stand test facilities up to 130 krpm. No forced cooling air flow streams are supplied to the test bearings and rotor. The measurements demonstrate the stable performance of the rotor-gas bearing systems in an ambient NVH test cell with cold forced air into the turbine inlet. Posttest inspection of the test flexure pivot tilting pad bearings after the hot gas stand tests evidences seizure of the hottest bearing, thereby revealing a notable reduction in bearing clearance as the rotor temperature increases. The compliant flexure pivot tilting pad bearings offer a sound solution for stable rotor support only at an ambient temperature condition while demonstrating less tolerance for shaft growth, centrifugal and thermal, beyond its clearance. The current measurements give confidence in the present gas foil bearing technology for ready application into automotive turbochargers for passenger car and commercial vehicle applications with increased reliability.

An Experimental Study on Externally Pressurized Supersonic Gas Thrust Bearings

1985 ◽  
Vol 107 (1) ◽  
pp. 122-127 ◽  
Author(s):  
Yutaka Miyake ◽  
Takehiko Inaba ◽  
Naoshige Kubo ◽  
Jun-ichi Takeoka
Keyword(s):  
Experimental Study ◽  
Flow Rate ◽  
Load Capacity ◽  
Experimental Results ◽  
Static Characteristics ◽  
Thrust Bearings ◽  
Pressure Distributions ◽  
Theoretical Predictions ◽  
New Type ◽  
Good Agreement

Externally pressurized supersonic gas thrust bearings whose generation of load capacity is substantially independent of the viscosity of working fluids, have been proposed and analyzed by the authors. This report presents the experimental results of the static characteristics of this new type of bearings. The experimental results including load capacity, stiffness, mass flow rate, and pressure distributions in the bearing clearance, generally show a good agreement with the theoretical predictions and verify the validity of this new bearing. The effect of an orifice to improve the stiffness is also examined. Some problems which should be solved to put the bearing in practical use are pointed out.

Prediction of the Operating Temperature of Thrust Bearings

1981 ◽  
Vol 103 (1) ◽  
pp. 97-106 ◽  
Author(s):  
J. H. Vohr
Keyword(s):  
Heat Balance ◽  
Laboratory Tests ◽  
Operating Temperature ◽  
Field Measurements ◽  
Operating Conditions ◽  
Thrust Bearings ◽  
Pressure Distributions ◽  
Lubricant Flow ◽  
Wide Range ◽  
Balance Analysis

An analytical method is described for predicting the operating temperature of thrust bearings of the size and speed typically found in large vertical machinery. The method involves evaluating the various mechanisms by which heat is transferred from the bearing and balancing this heat loss against the calculated heat generated by viscous shearing. This heat balance analysis is combined with a comprehensive bearing computer program which evaluates bearing pressure distributions, bearing pad deflection, lubricant flow and lubricant temperature rise within the bearing film. Predicted bearing operating temperatures show excellent agreement with laboratory tests and with field measurements over a wide range of bearing sizes and operating conditions.

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