Experimental Versus Theoretical Characteristics of a High-Speed Hybrid (Combination Hydrostatic and Hydrodynamic) Bearing

1993 ◽  
Vol 115 (1) ◽  
pp. 160-168 ◽  
Author(s):  
K. Alan Kurtin ◽  
D. Childs ◽  
Luis San Andres ◽  
K. Hale
Keyword(s):  
High Speed ◽  
Load Capacity ◽  
Test Facility ◽  
Navier Stokes ◽  
Radial Clearance ◽  
Hydrodynamic Bearing ◽  
Speed Test ◽  
Discharge Coefficients ◽  
Hybrid Combination ◽  
Numerical Predictions

The high-speed test facility designed and installed at Texas A&M to study water lubricated journal bearings has been successfully used to test statically an orifice compensated five-recess-hybrid (combination hydrostatic and hydrodynamic) bearing for two radial clearance configurations. Measurements of relative-bearing position, torque, recess pressure, flow rate, and temperature were made at speeds from 10,000 to 25,000 rpm and supply pressures of 6.89 MPa (1,000 psi), 5.52 MPa (800 psi), and 4.14 MPa (600 psi). For speeds of 10,000 and 17,500 rpm, the bearing load capacity was also investigated. A pitching instability of the bearing limited the number of test cases. A 2-dimensional, bulk-flow, Navier-Stokes numerical analysis program was used for all theoretical performance predictions. Orifice discharge coefficients used in the program were calculated from measured flow and pressure data. Reynolds numbers for flow within the bearing lands due to shaft rotation and recess pressurization ranged from 6700 to 16,500. Predictions sensitivity to ±10 percent changes in the input parameters was investigated. Results showed that performance prediction sensitivities are high for changes in discharge coefficients and negligible for changes in relative roughness. The numerical predictions of relative bearing position, recess pressure, flowrate, and torque are very accurate, provided the selected orifice discharge coefficients are correct.

Aerothermal Measurements and Predictions of an Intermediate Turbine Duct Turning Vane

2015 ◽  
Author(s):  
Martin Johansson ◽  
Jonathan Mårtensson ◽  
Hans Abrahamsson ◽  
Thomas Povey ◽  
Kam Chana
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
High Speed ◽  
Test Facility ◽  
Spanwise Direction ◽  
Tip Leakage Flow ◽  
Current Configuration ◽  
Speed Test ◽  
Intermediate Turbine Duct ◽  
Numerical Predictions

Flow in a turbine duct is highly complex, influenced by the upstream turbine stage flow structures, including tip leakage flow and non-uniformities originating from the upstream HPT vane and rotor. The complexity of the flow makes the prediction using numerical methods difficult, hence there exists a need for experimental validation. This paper presents experimental data including both aerodynamic and heat transfer measurements within an intermediate turbine duct. These have been conducted in the Oxford Turbine Research Facility, a short duration high speed test facility enabling the use of an engine sized turbine, operating at the correct non-dimensional parameters relevant for aerodynamic and heat transfer measurements. The current configuration consists of a HPT stage and a downstream duct including a turning vane, for use in a counter rotating turbine configuration. With a stator-to-stator vane count of 32-to-24, instrumentation was installed on three adjacent intermediate turbine duct vanes and endwalls to investigate its influence. Flow phenomena such as trailing edge wakes and vortex structures from the upstream HPT vane travels through the rotor and forms an inlet condition to the intermediate turbine duct with tangential variations. Time-averaged experimental data show this effect to be distinguishable although varying in the spanwise direction. Comparisons with results from numerical predictions are included to further analyse the flow through the 1.5 stage.

A High Speed Test Rig Capable of Running at 190,000rpm to Characterize Gas Foil Thrust Bearings

2018 ◽  
Author(s):  
Nguyen T. LaTray ◽  
Daejong Kim
Keyword(s):  
High Speed ◽  
Thrust Bearing ◽  
Load Capacity ◽  
Test Facility ◽  
Frictional Torque ◽  
Test Rig ◽  
Speed Test ◽  
Compliant Structure ◽  
Bearing Load ◽  
Speed Up

This paper details the design and performance of a high-speed (up to 190,000rpm) gas foil thrust bearing (GFTB) test rig to measure bearing load capacity. Several GFTB test rigs were reported in the literature for operating speed up to 90krpm. A few recently presented works show successful runs at 135krpm for testing gas thrust bearing with viscoelastic support and 130krpm tilting pad thrust bearing with compliant structure. However, a GFTB test rig for speed range over 100krpm has not been reported. At high speed operation, the gas film thickness of the GFTB is around a few microns which makes it difficult to achieve in testing. In many cases, the measured thrust load from experiments is well below the predicted data due to difficulty in testing and instrumentation. Difficulty in validating the actual load capacity of the bearings leads to increasing the thrust bearing size to ensure sufficient load capacity in actual applications, which results in higher power consumption. This work presents detail feature of a novel GFTB test rig and test results of 38mm GFTB. The developed test rig runs up to 190krpm and measures bearing load capacity, frictional torque and temperature across bearing ID and OD. The test rig is suitable for testing GFTB with OD from 30 mm to 40 mm. The test facility successfully tests a 38 mm GFTB to its predicted load capacity of 75N (110kPa).

Measurements Versus Predictions for the Dynamic Impedance of Annular Gas Seals—Part II: Smooth and Honeycomb Geometries

2002 ◽  
Vol 124 (4) ◽  
pp. 963-970 ◽  
Author(s):  
M. P. Dawson ◽  
D. W. Childs
Keyword(s):  
Control Volume ◽  
Test Facility ◽  
Radial Clearance ◽  
Cell Width ◽  
Volume Model ◽  
Numerical Predictions ◽  
Dynamic Impedance ◽  
Honeycomb Seals ◽  
Gas Seals ◽  
Honeycomb Cell

Results are presented from tests conducted using an experimental test facility to measure the leakage and dynamic impedance of smooth and honeycomb straight-bore annular gas seals. The test seals had a 114.3 mm (4.500 in.) bore with a length-to-diameter ratio of 0.75 and a nominal radial clearance of 0.19 mm (0.0075 in.). The honeycomb cell depth for both seals was 3.10 mm (0.122 in.), and the cell width was 0.79 mm (0.031 in.). Dynamic impedance and leakage measurements are reported using air at three supply pressures out to 1.72 Mpa (250 psi), three speeds out to 20,200 rpm, and exit-to-inlet pressure ratios of 40% and 50%. Comparisons to the predictions from the two-control-volume model of Kleynhans and Childs [1] are of particular interest. This model predicts that honeycomb seals do not fit the conventional frequency independent model for smooth annular gas seals. The experimental results verify this new theory. Numerical predictions from a computer program incorporating the new two-control-volume model of Kleynhans and Childs [1] correlate well with both measured seal leakage and dynamic impedances for the honeycomb seals.

Influence of geometric parameters on the bump foil bearing performance

2019 ◽  
Vol 234 (7) ◽  
pp. 1017-1026
Author(s):  
Sadanand Kulkarni ◽  
Soumendu Jana
Keyword(s):  
Carrying Capacity ◽  
High Speed ◽  
System Development ◽  
Load Capacity ◽  
Radial Clearance ◽  
Load Carrying Capacity ◽  
Foil Bearings ◽  
Foil Bearing ◽  
Load Carrying ◽  
Lift Off

High-speed rotating system development has drawn considerable attention of the researchers, in the recent past. Foil bearings are one of the major contenders for such applications, particularly for high speed and low load rotating systems. In foil bearings, process fluid or air is used as the working medium and no additional lubricant is required. It is known from the published literature that the load capacity of foil bearings depend on the operating speed, viscosity of the medium, clearance, and stiffness of the foil apart from the geometric dimensions of the bearing. In case of foil bearing with given dimensions, clearance governs the magnitude of pressure developed, whereas stiffness dictates the change in radial clearance under the generated pressure. This article deals with the effect of stiffness, clearance, and its interaction on the bump foil bearings load-carrying capacity. For this study, four sets of foil bearings of the same geometry with two levels of stiffness and clearance values are fabricated. Experiments are carried out following two factor-two level factorial design approach under constant load and in each case, the lift-off speed is measured. The experimental output is analyzed using statistical techniques to evaluate the influence of parameters under consideration. The results indicate that clearance has the maximum influence on the lift-off speed/ load-carrying capacity, followed by interaction effect and stiffness. A regression model is developed based on the experimental values and model is validated using error analysis technique.

Theory Versus Experiment for the Effects of Pressure Ratio on the Performance of an Orifice-Compensated Hybrid Bearing

1998 ◽  
Vol 120 (4) ◽  
pp. 930-936 ◽  
Author(s):  
P. Mosher ◽  
D. W. Childs
Keyword(s):  
High Speed ◽  
Stokes Equations ◽  
Load Capacity ◽  
Dynamic Stiffness ◽  
Pressure Ratio ◽  
Navier Stokes ◽  
Rotordynamic Coefficients ◽  
Wide Range ◽  
Bearing Load ◽  
Hybrid Bearing

This research investigates the effect of varying the concentric recess pressure ratio of hybrid (combination hydrostatic and hydrodynamic) bearings to be used in high-speed, high-pressure applications. Bearing flowrate, load capacity, torque, rotordynamic coefficients, and whirl frequency ratio are examined to determine the concentric, recess-pressure ratio which yields optimum bearing load capacity and dynamic stiffness. An analytical model, using two-dimensional bulk-flow Navier-Stokes equations and anchored by experimental test results, is used to examine bearing performance over a wide range of concentric recess pressure ratios. Typically, a concentric recess pressure ratio of 0.50 is used to obtain maximum bearing load capacity. This analysis reveals that theoretical optimum bearing performance occurs for a pressure ratio near 0.40, while experimental results indicate the optimum value to he somewhat higher than 0.45. This research demonstrates the ability to analytically investigate hybrid bearings and shows the need for more hybrid-bearing experimental data.

scholarly journals High-Speed Flow in an Annular Cascade With Tip Clearance: Numerical Investigation

1998 ◽  
Author(s):  
E. S. Politis ◽  
K. C. Giannakoglou ◽  
K. D. Papailiou
Keyword(s):  
High Speed ◽  
High Reynolds Number ◽  
Tip Clearance ◽  
Navier Stokes ◽  
High Speed Flow ◽  
Numerical Predictions ◽  
Simulated Experiment ◽  
Speed Flow ◽  
High Reynolds ◽  
Annular Cascade

The high-speed flow in an annular cascade with two tip clearance sizes is numerically modeled using a Navier-Stokes solver and the high-Reynolds-number k-ε turbulence model. The numerical predictions should be regarded as complementary to the experimental work conducted in the NTUA annular cascade facility, designed for studying tip-clearance effects in compressor cascades. In the numerically simulated experiment, the stationary blades are mounted on the casing and the tip clearance is formed between them and the spinning hub. The purpose of the present paper is to scrutinize flow trends identified during the measurements and elucidate the flow patterns in the blade passage for rotating and stationary hub.

Turbulent Flow, Flexure-Pivot Hybrid Bearings for Cryogenic Applications

1996 ◽  
Vol 118 (1) ◽  
pp. 190-200 ◽  
Author(s):  
Luis San Andres
Keyword(s):  
High Speed ◽  
Energy Transport ◽  
Load Capacity ◽  
Equations Of Motion ◽  
Liquid Oxygen ◽  
Hydrodynamic Bearings ◽  
Numerical Predictions ◽  
Tilting Pad ◽  
Direct Stiffness ◽  
Stiffness And Damping

The thermal analysis of flexure-pivot tilting-pad hybrid (combination hydrostatic-hydrodynamic) bearings for cryogenic turbopumps is presented. The advantages of this type of bearing for high speed operation are discussed. Turbulent bulk-flow, variable properties, momentum and energy transport equations of motion govern the flow in the bearing pads. Zeroth-order equations for the flow field at a journal equilibrium position render the bearing flow rate, load capacity, drag torque, and temperature rise. First-order equations for perturbed flow fields due to small amplitude journal motions provide rotordynamic force coefficients. A method to determine the tilting-pad moment coefficients from the force displacement coefficients is outlined. Numerical predictions correlate well with experimental measurements for tilting-pad hydrodynamic bearings. The design of a liquid oxygen, flexure-pad hybrid bearing shows a reduced whirl frequency ratio and without loss in load capacity or reduction in direct stiffness and damping coefficients.

Rotordynamic Performance of Hybrid Air Foil Bearings With Regulated Hydrostatic Injection

2017 ◽  
Vol 140 (1) ◽  
Author(s):  
Behzad Zamanian Yazdi ◽  
Daejong Kim
Keyword(s):  
High Speed ◽  
Friction And Wear ◽  
Heat Dissipation ◽  
Load Capacity ◽  
Substantial Improvement ◽  
Maximum Speed ◽  
Foil Bearings ◽  
Speed Test ◽  
The Past ◽  
Foil Bearing

Air foil bearing (AFB) technology has made substantial advancement during the past decades and found its applications in various small turbomachinery. However, rotordynamic instability, friction and drag during the start/stop, and thermal management are still challenges for further application of the technology. Hybrid air foil bearing (HAFB), utilizing hydrostatic injection of externally pressurized air into the bearing clearance, is one of the technology advancements to the conventional AFB. Previous studies on HAFBs demonstrate the enhancement in the load capacity at low speeds, reduction or elimination of the friction and wear during starts/stops, and enhanced heat dissipation capability. In this paper, the benefit of the HAFB is further explored to enhance the rotordynamic stability by employing a controlled hydrostatic injection. This paper presents the analytical and experimental evaluation of the rotordynamic performance of a rotor supported by two three-pad HAFBs with the controlled hydrostatic injection, which utilizes the injections at particular locations to control eccentricity and attitude angle. The simulations in both time domain orbit simulations and frequency-domain modal analyses indicate a substantial improvement of the rotor-bearing performance. The simulation results were verified in a high-speed test rig (maximum speed of 70,000 rpm). Experimental results agree with simulations in suppressing the subsynchronous vibrations but with a large discrepancy in the magnitude of the subsynchronous vibrations, which is a result of the limitation of the current modeling approach. However, both simulations and experiments clearly demonstrate the effectiveness of the controlled hydrostatic injection on improving the rotordynamic performance of AFB.

Measurements Versus Predictions for the Dynamic Impedance of Annular Gas Seals: Part 2 — Smooth and Honeycomb Geometries

2001 ◽  
Author(s):  
Matthew P. Dawson ◽  
Dara W. Childs
Keyword(s):  
Control Volume ◽  
Test Facility ◽  
Radial Clearance ◽  
Cell Width ◽  
Volume Model ◽  
Numerical Predictions ◽  
Dynamic Impedance ◽  
Honeycomb Seals ◽  
Gas Seals ◽  
Honeycomb Cell

Results are presented from tests conducted using an experimental test facility to measure the leakage and dynamic impedance of smooth and honeycomb straight-bore annular gas seals. The test seals had a 114.3 mm bore with a length-to-diameter ratio of 0.75 and a nominal radial clearance of 0.19 mm. The honeycomb cell depth for both seals was 3.1 mm, and the cell width was 0.79 mm. Dynamic impedance and leakage measurements are reported using air at three supply pressures out to 1.72 MPa, three speeds out to 20,200 rpm, and exit-to-inlet pressure ratios of 40% and 50%. Comparisons to the predictions from the two-control-volume model of Kleynhans and Childs [1] are of particular interest. This model predicts that honeycomb seals do not fit the conventional frequency independent model for smooth annular gas seals. The experimental results verify this new theory. Numerical predictions from a computer program incorporating the new two-control-volume model of Kleynhans and Childs [1] correlate well with both measured seal leakage and dynamic impedances for the honeycomb seals.

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