scholarly journals Numerical and experimental study on air thrust foil bearing performance with improved structural model based on real-time taper inlet height

2020 ◽  
Author(s):  
Fangcheng Xu ◽  
Liukai Hou ◽  
Bin Wu ◽  
Zeda Dong ◽  
Yongliang Wang
Keyword(s):  
Film Thickness ◽  
Real Time ◽  
Test Data ◽  
Gas Turbines ◽  
Structural Model ◽  
Load Capacity ◽  
Thickness Distribution ◽  
New Model ◽  
Bearing Load ◽  
Simulation Results

Abstract Air thrust foil bearings are key bearings of micro turbo-machinery (such as micro gas turbines, turbo blowers, and air compressors). The bearing load capacity is affected by many factors, and the taper inlet height of bearing structure is closely related to the load capacity. In many previous literature the taper inlet height, as a constant value, was used to calculate film thickness distribution. However, the reality is that the foil will be squeezed by the pressure generated between runner disk and top foil, which makes taper inlet height change during iteration. Therefore, the actual bearing taper inlet height should be chosen properly instead of the constant taper inlet height when iterating. In this paper, an improved computational model of film thickness for adjusting the taper inlet height in real-time is proposed. The relationship between the maximum bearing load capacity and taper inlet height at different rotor speeds of two models is obtained through numerical simulation. It is found that the optimal taper inlet height of the new model is larger than that of the old model. Three types of bearings with different taper inlet height (20μm, 70μm, 114μm) had been tested and the maximum load capacity at different rotor speeds had been obtained. Finally, test data and the simulation results of the two models are compared. It is found that the simulation results of the two models are quite different when the taper inlet height is near the optimal taper inlet height, and the new model is more agree well with the test data.

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.

Numerical Investigation for Characteristics and Oil-Air Distributions of a Tilting-Pad Journal Bearing Under Different Loads

2020 ◽  
Author(s):  
Aoshuang Ding ◽  
Xuesong Li
Keyword(s):  
Film Thickness ◽  
Journal Bearing ◽  
Viscosity Ratio ◽  
Cavitation Model ◽  
Tilting Pad ◽  
Sst Model ◽  
Bearing Load ◽  
Simulation Results ◽  
Bearing Loads ◽  
Tilting Pad Journal Bearing

Abstract This paper analyses the flow characteristics and oil-air distributions of oil flows in a tilting-pad journal bearing under different bearing loads. This titling-pad journal bearing is working at 3000 rpm rotation speed and its minimum film thicknesses have been measured under different loads from 180 kN to 299 kN. Based on the previous researches of this bearing under 180 kN, the gaseous cavitation and low-turbulence flow exists in this bearing flow. A suitable gaseous cavitation model and the SST model with low-Re correction are used in the film flow simulations. With the rotor and pads assumed to be rigid, the dynamic mesh and motion equations are applied to simulate the motions of the rotor and the rotations of the pads. Based on the simulation results under different bearing loads, the simulated minimum film thicknesses agrees well with the measured data. It indicates that the simulation results can catch the film geometries and flows correctly. With the load increasing, the rotor moves closer to the loaded pads and the minimum film thickness decreases. Taking the effect of boundary layers into consideration, the turbulence has a negative relationship with the film thickness and decreases in the loaded area under higher bearing load. It can be verified by the simulated lower turbulent viscosity ratio distributions in the loaded pads. In the unloaded area, both the film thickness and turbulence viscosity ratio are positively related to the bearing loads. Thus, the higher bearing load may lead the flow to be more different in the loaded and unloaded area, and the turbulence in the loaded pads may transfer to laminar in the end. As for the oil-air distributions, in the unloaded pads, with the bearing load increasing, the simulated air volume fraction increases in the unloaded pads with lower pressure. It should be caused by the higher film thickness of the unloaded pads under higher loads. In sum, the flow turbulence and cavitation process changes with the bearing load. With a higher load, the cavitation becomes more in the unloaded pads and the flow changes sharper from the high-turbulence unloaded area to the low-turbulence loaded area. As the simulation results is in good accordance with the experimental data, the SST model with low-Re correction and the gaseous cavitation model are verified to be suitable for bearing film simulations under different loads.

Thermal Management and Rotordynamic Performance of a Hot Rotor-Gas Foil Bearings System: Part 2—Predictions Versus Test Data

2010 ◽  
Author(s):  
Luis San Andre´s ◽  
Tae Ho Kim ◽  
Keun Ryu
Keyword(s):  
Test Data ◽  
Gas Turbines ◽  
Computational Models ◽  
Energy Transport ◽  
Structural Model ◽  
Test System ◽  
Forced Response ◽  
Rotor Speed ◽  
Foil Bearings ◽  
System Operating

Implementation of gas foil bearings (GFB) in micro gas turbines relies on physics based computational models anchored to test data. This two-part paper presents test data and analytical results for a test rotor and GFB system operating hot. A companion paper (Part 1) describes a test rotor-GFB system operating hot to 157°C rotor OD temperature, presents measurements of rotor dynamic response and temperatures in the bearings and rotor, and including a cooling gas stream condition to manage the system temperatures. The second part briefs on a thermoelastohydrodynamic (TEHD) model for GFBs performance and presents predictions of the thermal energy transport and forced response, static and dynamic, in the tested gas foil bearing system. The model considers the heat flow from the rotor into the bearing cartridges and also the thermal expansion of the shaft and bearing cartridge and shaft centrifugal growth due to rotation. Predictions show that bearings’ ID temperatures increase linearly with rotor speed and shaft temperature. Large cooling flow rates, in excess of 100 L/min, reduce significantly the temperatures in the bearings and rotor. Predictions, agreeing well with recorded temperatures given in Part 1, also reproduce the radial gradient of temperature between the hot shaft and the bearings ID, largest (37°C/mm) for the strongest cooling stream (150 L/min). The shaft thermal growth, more significant as the temperature grows, reduces the bearings operating clearances and also the minimum film thickness, in particular at the highest rotor speed (30 krpm). A rotor finite element (FE) structural model and GFBs force coefficients from the TEHD model are used to predict the test system critical speeds and damping ratios for operation at increasing shaft temperatures. In general, predictions of the rotor imbalance show good agreement with shaft motion measurements acquired during rotor speed coastdown tests. As the shaft temperature increases, the rotor peak motion amplitudes decrease and the system rigid-mode critical speed increases. The computational tool, benchmarked by the measurements, furthers the application of GFBs in high temperature oil-free rotating machinery.

Surface Finish and Clearance Effects on Journal-Bearing Load Capacity and Friction

1959 ◽  
Vol 81 (2) ◽  
pp. 245-252 ◽  
Author(s):  
F. W. Ocvirk ◽  
G. B. DuBois
Keyword(s):  
Experimental Data ◽  
Film Thickness ◽  
Surface Finish ◽  
Journal Bearing ◽  
Load Capacity ◽  
Journal Bearings ◽  
Oil Film ◽  
Bearing Clearance ◽  
Bearing Load

A method of relating surface finish to minimum oil-film thickness and the corresponding load capacity of plain journal bearings is presented with supporting experimental data. The effect of clearance on load capacity and friction are shown on graphs indicating an optimum bearing clearance.

Improvements to the Analysis of Gas Foil Bearings: Integration of Top Foil 1D and 2D Structural Models

2007 ◽  
Author(s):  
Luis San Andre´s ◽  
Tae Ho Kim
Keyword(s):  
Film Thickness ◽  
Gas Turbines ◽  
Load Capacity ◽  
Structural Models ◽  
Underlying Structure ◽  
Fe Model ◽  
Foil Bearings ◽  
Damping Coefficients ◽  
Minimum Film Thickness ◽  
Stiffness And Damping

Gas foil bearings (GFBs) find widespread usage in oil-free turbo expanders, APUs and micro gas turbines for distributed power due to their low drag friction and ability to tolerate high level vibrations, including transient rubs and shaft misalignment, static and dynamic. The static load capacity and dynamic forced performance of GFBs depends largely on the material properties of the support elastic structure, i.e. a smooth foil on top of bump strips. Conventional models include only the bumps as an equivalent stiffness uniformly distributed around the bearing circumference. More complex models couple directly the elastic deformations of the top foil to the bump underlying structure as well as to the hydrodynamics of the gas film. This paper details two FE models for the top foil supported on bump strips, one considers a 2D shell anisotropic structure and the other a 1D beam-like structure. The Cholesky decomposition of the stiffness matrix representing the top foil and bump strips is performed off-line prior to computations coupling it to the gas film analysis governed by Reynolds equation. The procedure greatly enhances the computational efficiency of the numerical scheme. Predictions of journal attitude angle and minimum film thickness for increasing static loads and two journal speeds are obtained for a GFB tested decades ago. 2D FE model predictions overestimate the minimum film thickness at the bearing centerline, while underestimating it at the bearing edges. Predictions from the 1D FE model compare best to the limited tests data; reproducing closely the experimental circumferential wavy-like minimum film thickness profile. The 1D top foil model is recommended due to its low computational cost. Predicted stiffness and damping coefficients versus excitation frequency show that the two FE top foil structural models result in slightly lower direct stiffness and damping coefficients than those from the simple elastic foundation model.

scholarly journals The Increase in Thickness Uniformity of Films Obtained by Magnetron Sputtering with Rotating Substrate

2016 ◽  
Vol 3 (3) ◽  
pp. 100-104 ◽  
Author(s):  
D. Golosov ◽  
S. Melnikov ◽  
S. Zavadski ◽  
V. Kolos ◽  
J. Okojie
Keyword(s):  
Experimental Data ◽  
Thin Films ◽  
Magnetron Sputtering ◽  
Film Thickness ◽  
Thickness Distribution ◽  
Model Error ◽  
Film Deposition ◽  
Substrate Rotation ◽  
Titanium Thin Films ◽  
Simulation Results

The titanium thin films obtained by magnetron sputtering with the rotating substrate at different distances between the substrate and magnetron centers were studied with regard to the uniformity of the film thickness distribution. On the basis of the experimental data obtained, the model for the magnetron film deposition during substrate rotation was developed. The analysis of the simulation results shows that the model error is not greater than 10%.

Hydrodynamic Analysis of Compliant Foil Bearings With Modified Top Foil Model

2011 ◽  
Author(s):  
Fangcheng Xu ◽  
Zhansheng Liu ◽  
Guanghui Zhang ◽  
Liang Xie
Keyword(s):  
Film Thickness ◽  
Pressure Distribution ◽  
Structural Model ◽  
Thickness Distribution ◽  
Hydrodynamic Analysis ◽  
Foil Bearings ◽  
Stiffness Model ◽  
The One ◽  
The Mathematical Model ◽  
Gas Bearing

The mathematical model of film thickness is developed with considering the compressibility of the gas and the deformation of the foil in this paper. By employing the Newton-Raphson method and the finite difference method, the compressible gas lubricated Reynolds equation and the film thickness equation are solved coupling together. The static characteristics such as pressure distribution and film thickness distribution for equivalent bump foil stiffness model are obtained to verify the validation of the proposed method. The gas film thickness model is modified by modeling the top foil as the one dimension curved beam, to meet the case of the real physical model. The numerical results of this modified structural model are compared with the other finite element top foil models. It indicates that the pressure distribution for bump foil gas bearing is in good agreement with the test data.

scholarly journals Control the deposition uniformity using ring cathode by DC discharge technique

2019 ◽  
Vol 15 (32) ◽  
pp. 57-67
Author(s):  
Kadhim A. Aadim
Keyword(s):  
Film Thickness ◽  
Direct Current ◽  
Discharge Plasma ◽  
Thickness Distribution ◽  
Experimental Results ◽  
Dc Discharge ◽  
Deposition Uniformity ◽  
Simulation Results

Simulation of direct current (DC) discharge plasma usingCOMSOL Multiphysics software were used to study the uniformityof deposition on anode from DC discharge sputtering using ring anddisc cathodes, then applied it experimentally to make comparisonbetween film thickness distribution with simulation results. Bothsimulation and experimental results shows that the deposition usingcopper ring cathode is more uniformity than disc cathode

scholarly journals Rational Design and Porosity of Porous Alumina Ceramic Membrane for Air Bearing

Membranes ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 872
Author(s):  
Jianzhou Du ◽  
Duomei Ai ◽  
Xin Xiao ◽  
Jiming Song ◽  
Yunping Li ◽  
...  
Keyword(s):  
Film Thickness ◽  
Ceramic Membrane ◽  
Load Capacity ◽  
Porous Alumina ◽  
Ceramic Membranes ◽  
Alumina Ceramic ◽  
Air Bearing ◽  
Supply Pressure ◽  
Simulation Results ◽  
Gas Supply

Air bearing has been widely applied in ultra-precision machine tools, aerospace and other fields. The restrictor of the porous material is the key component in air bearings, but its performance is limited by the machining accuracy. A combination of optimization design and material modification of the porous alumina ceramic membrane is proposed to improve performance within an air bearing. Porous alumina ceramics were prepared by adding a pore-forming agent and performing solid-phase sintering at 1600 °C for 3 h, using 95-Al2O3 as raw material and polystyrene microspheres with different particle sizes as the pore-forming agent. With 20 wt.% of PS50, the optimum porous alumina ceramic membranes achieved a density of 3.2 g/cm3, a porosity of 11.8% and a bending strength of 150.4 MPa. Then, the sintered samples were processed into restrictors with a diameter of 40 mm and a thickness of 5 mm. After the restrictors were bonded to aluminum shells for the air bearing, both experimental and simulation work was carried out to verify the designed air bearing. Simulation results showed that the load capacity increased from 94 N to 523 N when the porosity increased from 5% to 25% at a fixed gas supply pressure of 0.5 MPa and a fixed gas film thickness of 25 μm. When the gas film thickness and porosity were fixed at 100 μm and 11.8%, respectively, the load capacity increased from 8.6 N to 40.8 N with the gas supply pressure having been increased from 0.1 MPa to 0.5 MPa. Both experimental and simulation results successfully demonstrated the stability and effectiveness of the proposed method. The porosity is an important factor for improving the performance of an air bearing, and it can be optimized to enhance the bearing’s stability and load capacity.

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