Theoretical Study on Static Performance of Double-Bump Foil Bearings

2021 ◽  
Author(s):  
Fangcheng Xu ◽  
Jianhua Chu ◽  
Wenlin Luan ◽  
Guang Zhao
Keyword(s):  
Finite Element ◽  
Film Thickness ◽  
Thrust Bearing ◽  
Load Capacity ◽  
Static Characteristics ◽  
Thrust Bearings ◽  
Foil Bearings ◽  
Foil Bearing ◽  
Static Performance ◽  
Initial Clearance

Abstract In this paper, single-bump foil models with different thickness and double-bump foil models with different initial clearances are established. The structural stiffness and equivalent viscous damping of double-bump foil and single-bump foil are analyzed by finite element simulation. The results show that the double-layer bump foil has variable stiffness and the displacement of the upper bump is greater than the initial gap when the two-layer bumps contact. A model for obtaining static characteristics of aerodynamic compliant foil thrust bearing is established on the basis of the stiffness characteristics of the double-bump foil. This paper solves gas Reynolds equation, the gas film thickness equation and the foil stiffness characteristic equation via the finite element method and the finite difference method. The static characteristics of the thrust bearings including the bearing pressure distribution, the gas film thickness and the friction power consumption have been obtained. The static characteristics of two kinds of foils have been compared and analyzed, and the effect of initial clearance on the static performance of double-bump foil bearings is studied. The results show that the double-bump foil structure can effectively improve the load capacity of thrust bearing. In addition, the static performance of double-bump foil thrust bearings is between the performance of the single-bump foil bearing and the double-bump foil bearing whose foil’s clearance is zero. The smaller the initial clearance is, the easier it will be to form a stable double-bump foil supporting structure.

The Static Characteristics of Bump Foil Thrust Bearing Considering Tilting Condition

2009 ◽  
Author(s):  
Tae-Young Kim ◽  
Dong-Jin Park ◽  
Yong-Bok Lee
Keyword(s):  
High Efficiency ◽  
Thrust Bearing ◽  
Numerical Models ◽  
Load Capacity ◽  
Static Characteristics ◽  
Thrust Bearings ◽  
Foil Bearings ◽  
Foil Thrust Bearing ◽  
Thrust Pad ◽  
Air Film

Air foil thrust bearings are the critical component available on high-efficiency turbomachinery which needs ability to endure the large axial force. Previous investigations about the static characteristics were obtained over the region of the thin air film using finite-difference method and the characteristics of the corrugated bump foil using finite-element method. Moreover, a recent study demonstrated that bearing performance is sensitive to tilting thrust pad condition. In this study, experimentally measured bearing static characteristics are compared with the numerical model of the foil thrust bearing considering tilting pad condition. Three geometrically different type foil bearings were tested to measure their load capacity under tilting conditions that have continuous angles from zero to 0.0002 rad. These data are presented for use i1n the development of more accurate foil thrust bearing numerical models.

Application of Materials on Foil Thrust Bearings for Micro Turbines

2011 ◽  
Vol 201-203 ◽  
pp. 2759-2762
Author(s):  
Quan Zhou ◽  
Yu Hou ◽  
Ru Gang Chen
Keyword(s):  
Thrust Bearing ◽  
Load Capacity ◽  
Bearing Surface ◽  
Thrust Bearings ◽  
Foil Bearings ◽  
Foil Bearing ◽  
Soft Surface ◽  
Static Part ◽  
Micro Turbine ◽  
Foil Thrust Bearing

Foil bearing that has a soft surface is a kind of air bearing. The performances of foil bearings are greatly affected by the materials of bearing surface, which is called foil element. In order to estimate the performance of foil bearings, two kinds of foil thrust bearings that are made of different materials respectively were tested in a micro turbine system, which contains rotation part and static part. Load capacity and stability of these foil thrust bearings were investigated in experiments. The results show that bearing which contains rubber has higher load capacity and bearing which contains copper foil has higher stability. According to the work in this paper, applications with different requirements can adopt suitable foil thrust bearing.

Analytical Model of Bump-Type Foil Bearings Using a Link-Spring Structure and a Finite-Element Shell Model

2010 ◽  
Vol 132 (2) ◽  
Author(s):  
Kai Feng ◽  
Shigehiko Kaneko
Keyword(s):  
Finite Element ◽  
Film Thickness ◽  
Shell Model ◽  
Analytical Model ◽  
Load Capacity ◽  
Radial Clearance ◽  
Interaction Forces ◽  
Friction Forces ◽  
Foil Bearings ◽  
Foil Bearing

A complete analytical model of bump-type foil bearings taking into consideration the effects of four factors, i.e., the elasticity of bump foil, the interaction forces between bumps, the friction forces at the contact surfaces, and the local deflection of top foil, is presented in this investigation. Each bump is simplified to two rigid links and a horizontally spaced spring, the stiffness of which is determined from Castigliano’s theorem. The interaction forces and the friction forces are coupled with the flexibility of bumps through the horizontal elementary spring. The local deflection of the top foil is described using a finite-element shell model and added to the film thickness to predict the air pressure with Reynolds’ equation. The bump deflections of a strip with ten bumps calculated using the presented model under different load distributions are consistent with the published results. Moreover, the predicted bearing load and film thickness obtained from a foil bearing with a bump circumferential extend of 360 deg also agree very well with the experimental data, especially for predictions with a proper selection of radial clearance (preload of foil structure) and friction coefficients. In addition, the radial clearance and friction force variations in the foil bearing are noted to significantly change the performance of the foil bearing. The predictions demonstrate that the radial clearance of the foil bearing has an optimum value for the maximum load capacity.

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.

Development of Foil Thrust Bearings with Simple Structure for Micro Turbines

2011 ◽  
Vol 368-373 ◽  
pp. 1392-1395 ◽  
Author(s):  
Quan Zhou ◽  
Yu Hou ◽  
Ru Gang Chen
Keyword(s):  
High Speed ◽  
Simple Structure ◽  
Thrust Bearing ◽  
Load Capacity ◽  
Complicated Structure ◽  
Thrust Bearings ◽  
Foil Bearings ◽  
Rotational Systems ◽  
Micro Turbine ◽  
Foil Thrust Bearing

Because of the low power loss and high stability, foil bearings are suitable lubrication components for high speed rotational systems. At present, the foil bearings used in actual applications almost have complicated structure and are hard to manufacture. In this paper, two kinds of foil thrust bearings with simple structure are presented. Configurations of these two foil thrust bearings are introduced; meanwhile, the load capacity and running stability are also tested in a high speed micro turbine. It is shown that viscoelastic supported foil thrust bearing has higher load capacity and hemisphere convex dots supported foil thrust bearing is more stable in high speed operational condition.

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.

Numerical Investigation on the Mixed Lubrication Performance of Water-Lubricated Coupled Journal and Thrust Bearings

2019 ◽  
Author(s):  
Yanfeng Han ◽  
Guo Xiang ◽  
Jiaxu Wang
Keyword(s):  
Friction Coefficient ◽  
Film Thickness ◽  
Thrust Bearing ◽  
Journal Bearing ◽  
Load Capacity ◽  
Hydrodynamic Pressure ◽  
Mixed Lubrication ◽  
Eccentricity Ratio ◽  
Thrust Bearings ◽  
Lubrication Performance

Abstract The mixed lubrication performance of water-lubricated coupled journal and thrust bearing (simplified as coupled bearing) is investigated by a developed numerical model. To ensure the continuity of hydrodynamic pressure and flow at the common boundary between the journal and thrust bearing, the conformal transformation is introduced to unify the solution domain of the Reynolds equation. In the presented study, the coupled effects between the journal and thrust bearing are discussed. The effects of the thrust bearing geometric film thickness on the mixed lubrication performance, including the load capacity, contact load and friction coefficient, of the journal bearing are investigated. And the effects of the journal bearing eccentricity ratio on the mixed lubrication performance of the thrust bearing are also investigated. The simulated results indicate the mutual effects between the journal and thrust bearing cannot be ignored in the coupled bearing system. The increasing thrust bearing geometric film thickness generates a decrease in load capacity of journal bearing. There exists an optimal eccentricity ratio of journal bearing that yields the minimum friction coefficient of the thrust bearing.

Link-Spring Model of Bump-Type Foil Bearings

2009 ◽  
Author(s):  
Kai Feng ◽  
Shigehiko Kaneko
Keyword(s):  
Experimental Data ◽  
Film Thickness ◽  
Wide Spectrum ◽  
Load Capacity ◽  
Ambient Air ◽  
Radial Clearance ◽  
Interaction Forces ◽  
Friction Forces ◽  
Foil Bearings ◽  
Foil Bearing

The field experiences of gas foil bearings (GFBs) from the 1960s prove that GFBs offer several advantages over traditional oil bearings and rolling element bearings. They have the potential to be applied in a wide spectrum of turbomachinery. Bump-type foil bearings, which are considered as the best structure for GFBs, can be simply described as a hydrodynamic bearing utilizing the ambient air as the lubricant and a smooth shell supported by a corrugated bump foil as the bearing surface. However, the performance predictions of bump-type foil bearings are difficult due to mechanical complexity of the support elastic structure, especially for the effects of four factors, elasticity of bump foil, interaction forces between bumps, friction forces at contact surfaces, and local deflection of top foil. In this investigation, an analytical model of bump-type foil bearings considering the effects of all above factors is presented. In this model, each bump of the bump strip is simplified to two rigid links and a horizontally spaced spring, whose stiffness is determined from Castigliano’ theorem. Then, interaction forces and friction forces can be coupled with the bump flexibility though the horizontal elementary spring. The local deflection of top foil is described using a Finite Element model and added to the film thickness for the pressure prediction with the Reynolds’ equation. The bump deflections of a strip with ten bumps under different load distributions are calculated with the presented model and the predictions show consistency with published results. Moreover, the predicted bearing load and film thickness of a full bump-type foil bearing using this model are very close to the experimental data. Also, radial clearance and friction force variations in the foil bearing are noted to change the stiffness of bump significantly. And the predictions from the calculation with a proper selection of radial clearance and friction coefficients show extremely good agreement with the experimental data. The assumption of minimum reachable film thickness is based on experimental data to determine the load capacity of bearing. The results demonstrate that the radial clearance of foil bearing has an optimum value for the maximum load capacity.

Effect of Foil Geometry on the Static Performance of Thrust Foil Bearings

2018 ◽  
Vol 140 (8) ◽  
Author(s):  
Gen Fu ◽  
Alexandrina Untaroiu ◽  
Erik Swanson
Keyword(s):  
Film Thickness ◽  
Load Capacity ◽  
Optimization Technique ◽  
Three Dimensional ◽  
Leading Edge ◽  
Numerical Approach ◽  
Sensitivity Study ◽  
Rotating Speed ◽  
Foil Bearings ◽  
Foil Bearing

Gas foil bearings can operate in extreme conditions such as high temperature and high rotating speed, compared to traditional bearings. They also provide better damping and stability characteristics and have larger tolerance to debris and rotor misalignment. Gas foil bearings have been successfully applied to micro- and small-sized turbomachinery, such as microgas turbine and cryogenic turbo expander. In the last decades, a lot of theoretical and experimental work has been conducted to investigate the properties of gas foil bearings. However, very little work has been done to study the influence of the foil bearing pad configuration. This study proposes a robust approach to analyze the effect of the foil geometry on the performance of a six-pad thrust foil bearing. In this study, a three-dimensional (3D) computational fluid dynamics (CFD) model for a parallel six-pad thrust foil bearing is created. In order to predict the thermal property, the total energy with viscous dissipation is used. Based on this model, the geometry of the thrust foil bearing is parameterized and analyzed using the design of experiments (DOE) methodology. In this paper, the selected geometry parameters of the foil structure include minimum film thickness, inlet film thickness, the ramp extent on the inner circle, the ramp extent on the outer circle, the arc extent of the pad, and the orientation of the leading edge. The objectives in the sensitivity study are load capacity and maximal temperature. An optimal foil geometry is derived based on the results of the DOE process by using a goal-driven optimization technique to maximize the load capacity and minimize the maximal temperature. The results show that the geometry of the foil structure is a key factor for foil bearing performance. The numerical approach proposed in this study is expected to be useful from the thrust foil bearing design perspective.

Effects of wedge curvature on performances of foil thrust bearing and the profile design in compressor system

2020 ◽  
pp. 135065012097552
Author(s):  
Hao Li ◽  
Haipeng Geng ◽  
Lei Qi ◽  
Lu Gan
Keyword(s):  
Reynolds Equation ◽  
Thrust Bearing ◽  
Dynamic Performance ◽  
Testing System ◽  
Thrust Bearings ◽  
Foil Bearings ◽  
Foil Bearing ◽  
Set Up ◽  
Foil Thrust Bearing ◽  
Excellent Stability

Foil thrust bearings have attracted considerable attention in small-sized turbo machines with its excellent stability, high compliance, temperature durability. Geometric structure play an important role on the performance of foil thrust bearings. However, the current research on the structure mainly focuses on the underlying foil type, such as bump foil, protuberant bump. In fact, the foil profile, especially in the convergent region has significant influence. In this paper, foil thrust bearings were classified into convex, slope and concave types according to the profile curvature. A numerical model of six pads foil thrust bearing was established by combining the shell model and Reynolds equation. The static and dynamic performance of thrust bearings with different curvature was calculated. The results showed that the convex convergent possessed higher capacity and was not sensitive to displacement disturbance. A stiffness testing system for thrust foil bearing was set up, and the results verified that the foil with convex wedge had higher stiffness. The experiment also indicated that all the thrust foil bearings had typical damping hysteresis. The axial force of a 10 kW on-board compressor was calculated. Based on the conclusion of this paper, the design scheme of curvature value β = 0.6 and gas thickness h2=15 µm was given in consideration of bearing capacity and machining robustness.

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