Thermal Features of Compliant Foil Bearings—Theory and Experiments

2000 ◽  
Vol 123 (3) ◽  
pp. 566-571 ◽  
Author(s):  
Mohsen Salehi ◽  
Erik Swanson ◽  
Hooshang Heshmat
Keyword(s):  
Heat Dissipation ◽  
Thermal Characteristics ◽  
Heat Energy ◽  
Effect Of Temperature ◽  
Experimental Program ◽  
Working Fluid ◽  
Simplified Approach ◽  
Foil Bearings ◽  
Foil Bearing ◽  
Cooling Air

The paper presents an analytical and experimental investigation aimed at eliciting the thermal characteristics of air lubricated compliant foil bearings. A Couette Approximation to the energy equation is used in conjunction with the compressible Reynolds equation to obtain a theoretical temperature distribution in the air used as a lubricant. The effect of temperature on the thermal properties of the working fluid is included. In parallel, an experimental program was run on a 100 mm diameter foil bearing operating at speeds up to 30,000 rpm employing cooling air across the bearing. The temperature rise of the cooling air provided an indication of the amount of heat energy conducted across the top foil of the bearing from the hydrodynamic film. The temperatures resulted from some tests are compared with the temperatures predicted by the analysis, and maximum over-prediction of about 19 percent was obtained. This simplified approach provides us with reasonably predicted temperatures. By comparing the theoretical heat dissipation obtained from the analytical predicted temperatures with the amount of heat carried away by the cooling air it was possible to arrive at the relative quantities of heat transferred from the bearing by convection via side leakage and by conduction via the top foil. From these comparisons it was deduced that about an average of 80 percent of the heat energy is carried away by conduction. The transient temperatures of the foil bearing in conducted tests for various speeds and loads are also presented.

Successful Oil-Free Version of a Gas Compressor Through Integrated Design of Foil Bearings

2008 ◽  
Author(s):  
Jonathan L. Wade ◽  
Daniel R. Lubell ◽  
Dennis Weissert
Keyword(s):  
Integrated Design ◽  
Pass Rate ◽  
Working Fluid ◽  
Acceptance Test ◽  
Foil Bearings ◽  
Foil Bearing ◽  
Higher Power ◽  
Bearing Design ◽  
Maintenance Requirements ◽  
Conventional Oil

In the pursuit of higher power density turbomachinery the rotor speeds and temperatures have been increased to the limits of conventional oil lubricated bearings. Additionally, with conventional oil lubricated bearings there is a risk of oil contaminating the working fluid; this is unacceptable for some applications. When properly designed and integrated the foil gas bearing is one option that can easily operate at higher temperatures and DN’s than conventional oil lubricated bearings systems. This is a case study of a small variable speed gas compressor that progressed through a variety of bearing configurations. The compressor was initially designed with ball bearings; the ball bearing design did not meet the compressor life targets for some operating regimes, requiring extra maintenance. The second iteration was to move to a foil bearing design; unfortunately because of design constraints an under-sized bearing was selected. The under-sized foil bearing provided only marginally better unit life, and was much more sensitive in the build process and the acceptance test pass rate fell dramatically. Unique field operation experience showed a variety of failures and successes from a marginal design. Finally, a properly sized foil bearing was integrated into the pump, capitalizing on the foil bearing strengths. With the properly sized foil bearings the pumps have seen a 100% acceptance test pass rate, no field failures, and the pumps are exceeding the desired life without any maintenance requirements.

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.

The Emergence of Compliant Foil Bearing and Seal Technologies in Support of 21st Century Compressors and Turbine Engines

2010 ◽  
Author(s):  
Hooshang Heshmat ◽  
Zhaohui Ren ◽  
Andrew Hunsberger ◽  
James Walton ◽  
Said Jahanmir
Keyword(s):  
Gas Turbine ◽  
Large Scale ◽  
High Efficiency ◽  
Positive Impact ◽  
Experimental Program ◽  
Operating Efficiency ◽  
Turbine Engines ◽  
Foil Bearings ◽  
Foil Bearing ◽  
Face Seals

For energy independence to become a reality, whether through the more effective use of US natural resources such as natural gas or through the continued development of the hydrogen economy, efficient and reliable large-scale compressors are needed to enhance the existing pipeline infrastructure that moves energy storing gases from production sites to end user locations. Oil-free, non-contacting seal and bearing technologies are critical to the successful development of new high efficiency and power dense compressors. Similarly with increasing emphasis on energy conservation, power and propulsion gas turbine engines will require advanced low leakage seals and may take advantage of efficiencies offered by compliant foil gas bearings. When properly applied these oil-free, non contacting technologies will have a positive impact on the operating efficiency and life of compressor and gas turbine engine systems. The overall objective of this paper is to present recent advances in compliant foil bearings and seals that make them attractive for a wide array of systems. The paper documents the design approach that includes analytical trade off studies to establish overall requirements followed by an experimental program to demonstrate the ability of the identified foil technology to meet the machine requirements. A summary of advancements in foil bearing load carrying capacity, size scaling from 6 mm to 150 mm in diameter, the ability to operate under shock loads greater than 40 g as well as under steady side loads with two different gases and finally the ability to operate at temperatures greater than 750 C will be presented. Data will also be presented showing the application of foil bearings to several different machines. Similarly, results from design, fabrication and testing of compliant foil radial and axial face seals will be discussed. Data from axial face seals testing at differential pressures, surface velocities, and normal loads greater than 675 kPa, 350 m/s, and 1100 N respectively will be presented to demonstrate non-contacting performance. Results of subcomponent testing will also be presented to demonstrate the capability of the face seal to accommodate axial excursions of up to 3.8 mm. Compliant foil radial seal testing in sizes ranging from approximately 60 to 215 mm in diameter under differential pressures to 690 kPa and surface velocities to 340 m/s will be presented and compared to prediction. The culmination of the work presented supports the application of compliant foil bearings and seals in a wide array of advanced machinery.

On the Coupling of Foil Bearing Supported Rotors: Part 2 — Experiment

2007 ◽  
Author(s):  
Michael J. Tomaszewski ◽  
James F. Walton ◽  
Hooshang Heshmat
Keyword(s):  
High Speed ◽  
Dynamic Performance ◽  
Experimental Program ◽  
Motor Drive ◽  
Combined System ◽  
Rotor Systems ◽  
Foil Bearings ◽  
Foil Bearing ◽  
Rotor Bearing ◽  
Full Speed

The expanded application of high-speed rotor systems operating on compliant foil bearings will be greatly enhanced with the ability to adequately couple multiple shaft systems with differing bearing systems and dynamic performance. In this paper the results of a successful experimental program are presented. Test results are presented for three different foil bearing coupled rotor systems. First, a coupled 32 kW, 60,000 rpm induction motor drive supported on compliant foil bearings was coupled to an identical 32 kW 60,000 rpm generator rotor and operated to full speed. Next, a high-speed 30,000 rpm capable ball bearing mounted precision spindle was driven to full speed when coupled to a 32 kW foil bearing supported drive motor. Third, the 32 kW, 60,000 rpm foil bearing based motor drive was coupled to a foil bearing supported rotor having a bending critical speed at approximately 29,000 rpm. This combined system was operated successfully to 60,000 rpm. Results of this experimental test program confirm the rotor-bearing system dynamic analysis and demonstrate the feasibility of coupling foil bearing supported rotors to a wide array of other rotor-bearing systems.

Rotordynamic Performance of Hybrid Air Foil Bearings With Regulated Hydrostatic Injection

2017 ◽  
Author(s):  
Behzad Zamanian Yazdi ◽  
Daejong Kim
Keyword(s):  
Friction And Wear ◽  
Heat Dissipation ◽  
Load Capacity ◽  
Substantial Improvement ◽  
Maximum Speed ◽  
Foil Bearings ◽  
The Past ◽  
Foil Bearing ◽  
Current Modelling ◽  
Modelling Approach

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-pads 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 highspeed 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 modelling approach. However, both simulations and experiments clearly demonstrate the effectiveness of the controlled hydrostatic injection on improving the rotordynamic performance of AFB.

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

2017 ◽  
Author(s):  
Gen Fu ◽  
Alexandrina Untaroiu ◽  
Erik Swanson
Keyword(s):  
Film Thickness ◽  
Stokes Equations ◽  
Optimization Technique ◽  
Ambient Air ◽  
Friction Torque ◽  
Load Force ◽  
Working Fluid ◽  
Cfd Model ◽  
Foil Bearings ◽  
Foil Bearing

Gas foil bearings use ambient air as working fluid, which forms the hydrodynamic wedge between the rotor surface and the compliant foil structure, therefore they are oil-free and environmental friendly. Compared to traditional bearings, gas foil bearing can operate in extreme conditions such as high temperature and high rotating speed. 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 micro gas turbine and cryogenic turbo expander. In the previous decades, a lot of theoretical and experimental work have 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 geometry configuration using computational fluid dynamics (CFD). This study proposes a robust approach to analyze the effect of the foil geometry on the performance of a six pads thrust foil bearing. In this study, a 3D CFD model for a parallel six pads thrust foil bearing is built using ANSYS-CFX software. The full Navier-Stokes equations are solved in the fluid domain. Taking into account the rotational periodicity, the computational model is simplified and only one pad of the thrust foil bearing is analyzed. In order to predict the thermal property, the total energy with viscous dissipation is used. Practical boundary conditions are used in the baseline CFD model. The results of the baseline modes is further compared with a modified Reynolds equation solution. 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. A factorial design technique is employed to sample the design space in DOE. The objectives in the sensitivity study are selected as load force and friction torque. 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 force and minimize the friction torque. The results show that the geometry of 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.

Experimental Studies on Foil Bearing With a Sliding Coating Made of Synthetic Material

2015 ◽  
Vol 138 (1) ◽  
Author(s):  
Grzegorz Zywica ◽  
Pawel Baginski ◽  
Slawomir Banaszek
Keyword(s):  
Dynamic Performance ◽  
Experimental Studies ◽  
Thermal Characteristics ◽  
Original Method ◽  
Test Stand ◽  
Antifriction Coating ◽  
Foil Bearings ◽  
Foil Bearing ◽  
Synthetic Materials ◽  
Set Up

The paper discusses the research on foil bearings with antifriction coating manufactured from synthetic materials. The tests were carried out on a special test stand of our own construction, designed with the use of numerical analysis. In the course of the experimental studies, the test stand was set up in two configurations: with one or two foil bearings. The measurements were done, which focused on temperature distributions with the aid of thermocouples and thermovision camera. The measurements were being performed under varying conditions of bearing operation. The conducted experiments permitted to verify the durability, thermal characteristics, and dynamic performance of foil bearings in different configurations. An original method to measure temperature of a top foil has been worked out.

The Integration of Structural and Fluid Film Dynamic Elements in Foil Bearings: Part II — A New Approach to the Problem

1999 ◽  
Author(s):  
Erik E. Swanson ◽  
Hooshang Heshmat
Keyword(s):  
Degrees Of Freedom ◽  
Dynamic Models ◽  
Experimental Program ◽  
Similar Data ◽  
New Approach ◽  
Two Degrees Of Freedom ◽  
Foil Bearings ◽  
Foil Bearing ◽  
Bearing Stiffness ◽  
Phase Angles

Abstract In Part I of this investigation a survey was made to see how the two-tiered construction of foil bearings, consisting as they do of two generically disparate elements, one hydrodynamic in nature and the other following the laws of elasticity, have been modeled in order to obtain integrated values of bearing stiffness and damping. Here a series of experiments is reported showing that serious discrepancies exist between results obtained from conventional dynamic models and test results. A new approach to the problem is here taken in modeling the two-tiered dynamic system of foil bearings. For this purpose a series of analytical solutions were obtained for different spring and dashpot arrangements. A basic approach was taken in considering the foil bearing as consisting of a two-degrees-of-freedom system. Differences in amplitude of vibration and phase angles were plotted for the different models. Similar data were obtained separately for the hydrodynamic and structural regimes. The solutions showed substantial differences in the amplitudes and phase angles between the two domains. It is concluded that treatment of foil bearing dynamics should be based on a two-degrees-of-freedom model. Suggestions are made for an analytical and experimental program to put the technology of foil bearings on a sounder basis than has been the case heretofore.

Development of a Computational Tool to Simulate Foil Bearings for Supercritical CO2 Cycles

2016 ◽  
Vol 138 (9) ◽  
Author(s):  
Kan Qin ◽  
Ingo Jahn ◽  
Rowan Gollan ◽  
Peter Jacobs
Keyword(s):  
Turbulent Flow ◽  
Supercritical Co2 ◽  
Three Dimensional ◽  
Structural Deformation ◽  
Working Fluid ◽  
Computational Tool ◽  
Element Analysis ◽  
Thrust Bearings ◽  
Foil Bearings ◽  
Foil Bearing

The foil bearing is an enabling technology for turbomachinery systems, which has the potential to enable cost efficient supercritical CO2 cycles. The direct use of the cycle's working fluid within the bearings results in an oil-free and compact turbomachinery system; however, these bearings will significantly influence the performance of the whole cycle and must be carefully studied. Moreover, using CO2 as the operating fluid for a foil bearing creates new modeling challenges. These include highly turbulent flow within the film, non-negligible inertia forces, high windage losses, and nonideal gas behavior. Since the flow phenomena within foil bearings is complex, involving coupled fluid flow and structural deformation, use of the conventional Reynolds equation to predict the performance of foil bearings might not be adequate. To address these modeling issues, a three-dimensional flow and structure simulation tool has been developed to better predict the performance of foil bearings for the supercritical CO2 cycle. In this study, the gas dynamics code, eilmer, has been extended for multiphysics simulation by implementing a moving grid framework, in order to study the elastohydrodynamic performance of foil bearings. The code was then validated for representative laminar and turbulent flow cases, and good agreement was found between the new code and analytical solutions or experiment results. A separate finite difference code based on the Kirchoff plate equation for the circular thin plate was developed in Python to solve the structural deformation within foil thrust bearings, and verified with the finite element analysis from ansys. The fluid-structure coupling algorithm was then proposed and validated against experimental results of a foil thrust bearing that used air as operating fluid. Finally, the new computational tool set is applied to the modeling of foil thrust bearings with CO2 as the operating fluid.

Capabilities of Large Foil Bearings

2000 ◽  
Author(s):  
Erik E. Swanson ◽  
Hooshang Heshmat
Keyword(s):  
Gas Turbine ◽  
Thermal Performance ◽  
Experimental Program ◽  
Practical Application ◽  
Test Rig ◽  
Turbine Engine ◽  
Foil Bearings ◽  
Compliant Surface ◽  
Foil Bearing ◽  
Engine Rotor

An experimental program was conducted on a large compliant surface foil bearing to document its performance. This large single pad foil bearing is 100 mm in diameter, and was operated at speeds of up to 30,000 RPM. Operation at 22,000 RPM with a measured load of 4190 N was also demonstrated. During coastdown runs from 30,000 RPM, maximum amplitudes of shaft vibration did not exceed 7.6 μm while passing through the two rigid shaft modes of the system. Thermal performance of the bearing was also in accord with previously documented foil bearings. This testing also demonstrates the practicality of scaling smaller foil bearing designs to the large bearings required for larger turbomachinery. To enhance the practical application of the results, the test rig shaft was designed to simulate a small gas turbine engine rotor.

Sign in / Sign up

Export Citation Format

Share Document