Parametric Study of Bump Foil Gas Bearings for Industrial Applications

2011 ◽  
Author(s):  
Oscar De Santiago ◽  
Luis San Andres
Keyword(s):  
Computational Models ◽  
Load Capacity ◽  
Dynamic Performance ◽  
Scaling Up ◽  
Industrial Applications ◽  
Working Fluid ◽  
Metal Foil ◽  
Gas Bearings ◽  
Foil Bearings ◽  
Process Gas

Gas bearings are an appealing technology for rotor support due to their inherent characteristic of oil-free operation. Elimination of lubricant brings also the possibility of designing the bearings for operation within the flow path of thermal machines and even using the process gas as working fluid for the bearing. Among several gas bearing technologies, foil bearings are the most common ones currently found in applications such as small compressors for aircraft pressurization, microturbines, and other small turbomachinery. Broad application of foil gas bearings to date is precluded due to their limited load capacity. Presently, scaling up of foil bearings requires expensive testing due to limitation of validated computational models of the fluid flow in the bearing coupled to the mechanical behavior of the metal foil and underlying corrugated structure. Recent work in this area shows that calibrated models are now available in the open literature and it is possible to predict more accurately the performance of the bearings at non-conventional sizes. The objective of this work is to present a study of the most relevant parameters of foil bearings affecting their static and dynamic performance and aimed at scaling them up for industrial applications currently not considered for them. The paper presents a calibration of the computational model to previous tests by independent researchers and discusses simple rules for scaling up the bearing components. Finally, the paper presents a feasibility study of application of foil gas bearings to a generic centrifugal compressor for industrial use.

Three-Dimensional Turbulent Thermo-Elastohydrodynamic Analyses of Hybrid Thrust Foil Bearings Using Real Gas Model

2016 ◽  
Author(s):  
Fangcheng Xu ◽  
Daejong Kim
Keyword(s):  
Power Generation ◽  
Power Loss ◽  
Closed Loop ◽  
Load Capacity ◽  
Three Dimensional ◽  
Analysis Tool ◽  
Real Gas ◽  
Gas Bearings ◽  
Foil Bearings ◽  
Flow Turbulence

Environment-friendly power generation systems are active area of research. Among many systems, closed loop Brayton cycles using super critical CO2 (S-CO2) is attractive alternative to conventional power cycles due to very high efficiency and power density. When converting low temperature thermal energy such as waste heat to electrical power, closed loop organic Rankine cycles (ORC) using refrigerants are very popular. Large utility scale systems adopting S-CO2 or ORC cycles require traditional bearing systems with dry gas seals, but small systems with shaft power less than 1MW are best suited with gas bearings lubricated with the cycle fluids. Foil gas bearings, which have been successfully applied to the air blowers/compressors and small power generation gas turbines, are the best candidate for the small S-CO2 or ORC cycle systems. However, design/analysis tool of the foil bearings with these non-ideal gases is rare. In addition, thrust foil bearings are technically more challenging compared to radial foil bearings due to low load capacity and large power loss due to high flow turbulence. This paper presents high level analysis tool involving three-dimensional thermo-hydrodynamic analyses of hybrid thrust foil bearings employing real gas effect and flow turbulence inside the film. The pressure distribution, temperature distribution, load capacity, film thickness, and power loss of 154mm hybrid thrust foil bearings are presented.

A Comparison of the Steady-State and Dynamic Performance of First- and Second-Generation Foil Bearings

2010 ◽  
Author(s):  
M. J. Conlon ◽  
A. Dadouche ◽  
W. M. Dmochowski ◽  
R. Payette ◽  
J.-P. Be´dard
Keyword(s):  
Steady State ◽  
Experimental Evaluation ◽  
First Generation ◽  
Second Generation ◽  
Load Capacity ◽  
Dynamic Stiffness ◽  
Dynamic Performance ◽  
Foil Bearings ◽  
Foil Bearing ◽  
Stiffness And Damping

Oil-free foil bearing technology has advanced intermittently over the years, driven by research efforts to improve both steady-state and dynamic performance characteristics, namely: load capacity, stiffness, and damping. Bearing designs are thus classified according to “generation”, with first-generation bearings being the most primitive. This paper presents an experimental evaluation of a first- and a second-generation foil bearing, and aims to provide the high-fidelity data necessary for proper validation of theoretical predictive models of foil bearing performance. The aforementioned test bearings were fabricated in-house, and are both 70mm in diameter with an aspect ratio of 1; bearing manufacturing details are provided. The work makes use of a facility dedicated to measuring both the steady-state and dynamic properties of foil bearings under a variety of controlled operating conditions. The bearing under test is placed at the midspan of a horizontal, simply-supported, stepped shaft which rotates at up to 60krpm. Static and dynamic loads of up to 3500N and 450N (respectively) can be applied by means of a pneumatic cylinder and two electrodynamic shakers. The bearings’ structural (static) stiffnesses are highly nonlinear, and this affects the accuracy of the dynamic coefficient determination. Both dynamic stiffness and damping are found to vary nonlinearly with excitation frequency, and are over-predicted by a structural experimental evaluation — the film plays an important role in bearing dynamics. The second-generation bearing is found to have a higher load capacity, dynamic stiffness, and damping than the first-generation bearing.

A Fully Coupled Fluid-Structure-Interaction Model for Foil Gas Bearings

2012 ◽  
Author(s):  
Wei Zhang ◽  
Abbas A. Alahyari ◽  
Louis Chiappetta
Keyword(s):  
Load Capacity ◽  
Fluid Structure Interaction ◽  
Interaction Model ◽  
Working Fluid ◽  
Performance Parameters ◽  
Fluid Structure ◽  
Gas Bearings ◽  
Structure Interaction ◽  
Gas Bearing ◽  
Fully Coupled

Foil gas bearings are self-acting, compliant-surface hydrodynamic bearings that usually use air or other process gas as their working fluid or lubricant. Foil gas bearings are made of one or more bump foils, which are compliant surfaces of corrugated metal, and one or more layers of top foil. Because foil gas bearing performance parameters, such as load capacity, are dominated by foil material and foil geometric designs, numerical models have been developed to predict the bearing’s performance based on these characteristics. However, previous models often simplify bump foil as elastic foundation with constant stiffness and neglect top foil altogether. Further, they typically use the Reynolds equation to simplify the fluid solution. In this study, ANSYS software is used to build a 3D, fully-coupled, fluid-structure-interaction model for a foil gas bearing to predict key performance parameters such as load capacity and journal attitude angle. The model’s results show good agreement with previously published test data. This not only demonstrates the feasibility of 3D fully coupled fluid-structure-interaction model for a conventional foil bearing using commercial codes, but also shows modeling capability for future generations of foil gas bearing.

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.

A Fully Coupled Fluid–Structure Interaction Model for Foil Gas Bearings

2016 ◽  
Vol 139 (2) ◽  
Author(s):  
Wei Zhang ◽  
Abbas A. Alahyari ◽  
Louis Chiappetta
Keyword(s):  
Load Capacity ◽  
Fluid Structure Interaction ◽  
Interaction Model ◽  
Working Fluid ◽  
Performance Parameters ◽  
Fluid Structure ◽  
Gas Bearings ◽  
Structure Interaction ◽  
Gas Bearing ◽  
Fully Coupled

Foil gas bearings are self-acting, compliant-surface hydrodynamic bearings that usually use air or other process gas as their working fluid or lubricant. Foil gas bearings are made of one or more bump foils, which are compliant surfaces of corrugated metal, and one or more layers of top foil. Because foil gas bearing performance parameters, such as load capacity, are dominated by foil material and foil geometric designs, numerical models have been developed to predict the bearing's performance based on these characteristics. However, previous models often simplify bump foil as elastic foundation with constant stiffness and neglect top foil altogether. Further, they typically use the Reynolds equation to simplify the fluid solution. In this study, ansys software is used to build a 3D, fully coupled, fluid–structure interaction (FSI) model for a foil gas bearing to predict the key performance parameters such as load capacity and journal attitude angle. The model's results show good agreement with previously published test data. This not only demonstrates the feasibility of 3D fully coupled fluid–structure interaction model for a conventional foil bearing using commercial codes, but also shows modeling capability for future generations of foil gas bearing.

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

2015 ◽  
Vol 138 (4) ◽  
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 (TCs) 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 TCs requires careful thermal management with accurate measurements verifying model predictions. Gas foil bearings (GFBs) 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 (FPTPBs) 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 TCs; one supported on foil journal and thrust bearings and the other one is supported on FPTP journal bearings and foil thrust bearings of identical sizes (outer diameter (OD) and inner diameter (ID)) with the same aerodynamic components. The tests of the oil-free TCs, each consisting of a hollow rotor (∼0.4 kg and ∼23 mm in OD at the bearing locations), are performed for various imbalances in noise, vibration, and harshness (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. Post-test inspection of the test FPTPGBs 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 FPTPGBs 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 GFB technology for ready application into automotive TCs for passenger car and commercial vehicle applications with increased reliability.

Parametric Studies on Static and Dynamic Performance of Air Foil Bearings with Different Top Foil Geometries and Bump Stiffness Distributions

2006 ◽  
Vol 129 (2) ◽  
pp. 354-364 ◽  
Author(s):  
Daejong Kim
Keyword(s):  
Spatial Variation ◽  
Linear Stability ◽  
Load Capacity ◽  
Dynamic Performance ◽  
Dynamic Force ◽  
Stability Analyses ◽  
Foil Bearings ◽  
Analytical Studies ◽  
Different Types ◽  
Stiffness Distribution

Experimental and analytical studies on air foil bearings have been performed extensively over the past decades, and significant improvement in load capacity and rotor dynamics stability have been reported. Often, advanced air foil bearings are believed to have complicated bump foil structure to provide unique underlying support mechanism, which in turn make the bearing very stable and have high load capacity. However, all the analytical studies on air foil bearings so far assume a circular profile of top foil with uniform bump stiffness distribution because detailed information on bump stiffness distribution and overall bearing shape is not known to the public. This paper investigates load capacities and rotordynamic performances of two different types of air foil bearings, e.g., circular cylindrical bearings with single continuous top foil and noncircular preloaded bearings with three top foil pads. Within the two subcategories, stiffness variations along axial and circumferential directions were given to have a total of four types of air foil bearings with different overall bearing shapes and stiffness distributions. Overall static and dynamic performance of the four different types of air foil bearings are presented and compared via calculations of load capacities and dynamic force coefficients, modal stability analyses, and time domain orbit simulations. The major difference of load capacities comes from the overall bearing shape (circular continuous foil or preloaded three pad) rather than spatial variation of bump stiffness within the bump foils. Preloaded three-pad bearings have significantly reduced load capacity compared to the circular bearings because of small pad arc length. Rotordynamic performance is also much more sensitive to the overall bearing shape than spatial variation of bump stiffness and damping within the bump foils. The linear stability analyses predict modal natural frequencies very close to those from the orbit simulations. However, onset speeds of instability from these two approaches are quite different, manifesting the limitation of the linear stability analyses. The orbit simulations show the three-pad bearings have higher onset speeds of instability than circular bearing (47,000rpm versus 24,000rpm).

scholarly journals Numerical Homogenization of Multi-Layered Corrugated Cardboard with Creasing or Perforation

Materials ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 3786
Author(s):  
Tomasz Garbowski ◽  
Anna Knitter-Piątkowska ◽  
Damian Mrówczyński
Keyword(s):  
Computational Models ◽  
Load Capacity ◽  
Torsional Stiffness ◽  
Numerical Homogenization ◽  
Corrugated Board ◽  
3D Geometry ◽  
Corrugated Cardboard ◽  
Numerical Tools ◽  
Packaging Industry ◽  
Theoretical Considerations

The corrugated board packaging industry is increasingly using advanced numerical tools to design and estimate the load capacity of its products. This is why numerical analyses are becoming a common standard in this branch of manufacturing. Such trends cause either the use of advanced computational models that take into account the full 3D geometry of the flat and wavy layers of corrugated board, or the use of homogenization techniques to simplify the numerical model. The article presents theoretical considerations that extend the numerical homogenization technique already presented in our previous work. The proposed here homogenization procedure also takes into account the creasing and/or perforation of corrugated board (i.e., processes that undoubtedly weaken the stiffness and strength of the corrugated board locally). However, it is not always easy to estimate how exactly these processes affect the bending or torsional stiffness. What is known for sure is that the degradation of stiffness depends, among other things, on the type of cut, its shape, the depth of creasing as well as their position or direction in relation to the corrugation direction. The method proposed here can be successfully applied to model smeared degradation in a finite element or to define degraded interface stiffnesses on a crease line or a perforation line.

Foil Gas Bearing With Compression Springs: Analyses and Experiments

2007 ◽  
Vol 129 (3) ◽  
pp. 628-639 ◽  
Author(s):  
Ju-ho Song ◽  
Daejong Kim
Keyword(s):  
Loss Factor ◽  
Load Capacity ◽  
Underlying Structure ◽  
Equivalent Viscous Damping ◽  
Foil Bearings ◽  
Foil Bearing ◽  
Different Types ◽  
Structural Loss ◽  
Compression Springs ◽  
Gas Bearing

A new foil gas bearing with spring bumps was constructed, analyzed, and tested. The new foil gas bearing uses a series of compression springs as compliant underlying structures instead of corrugated bump foils. Experiments on the stiffness of the spring bumps show an excellent agreement with an analytical model developed for the spring bumps. Load capacity, structural stiffness, and equivalent viscous damping (and structural loss factor) were measured to demonstrate the feasibility of the new foil bearing. Orbit and coast-down simulations using the calculated stiffness and measured structural loss factor indicate that the damping of underlying structure can suppress the maximum peak at the critical speed very effectively but not the onset of hydrodynamic rotor-bearing instability. However, the damping plays an important role in suppressing the subsynchronous vibrations under limit cycles. The observation is believed to be true with any air foil bearings with different types of elastic foundations.

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