scholarly journals A New Analysis Tool Assessment for Rotordynamic Modeling of Gas Foil Bearings

2010 ◽  
Author(s):  
Samuel A. Howard ◽  
Luis San Andre´s
Keyword(s):  
Power Loss ◽  
High Speed ◽  
Structural Deformation ◽  
Analysis Tool ◽  
Test Rig ◽  
Contributing Factors ◽  
Foil Bearings ◽  
Rotordynamic Coefficients ◽  
Foil Bearing ◽  
Analytical Tools

Gas foil bearings offer several advantages over traditional bearing types that make them attractive for use in high-speed turbomachinery. They can operate at very high temperatures, require no lubrication supply (oil pumps, seals, etc), exhibit very long life with no maintenance, and once operating airborne, have very low power loss. The use of gas foil bearings in high-speed turbomachinery has been accelerating in recent years, although the pace has been slow. One of the contributing factors to the slow growth has been a lack of analysis tools, benchmarked to measurements, to predict gas foil bearing behavior in rotating machinery. To address this shortcoming, NASA Glenn Research Center (GRC) has supported the development of analytical tools to predict gas foil bearing performance. One of the codes has the capability to predict rotordynamic coefficients, power loss, film thickness, structural deformation, and more. The current paper presents an assessment of the predictive capability of the code, named XLGFBTH©. A test rig at GRC is used as a simulated case study to compare rotordynamic analysis using output from the code to actual rotor response as measured in the test rig. The test rig rotor is supported on two gas foil journal bearings manufactured at GRC, with all pertinent geometry disclosed. The resulting comparison shows that the rotordynamic coefficients calculated using XLGFBTH© represent the dynamics of the system reasonably well, especially as they pertain to predicting critical speeds.

scholarly journals A New Analysis Tool Assessment for Rotordynamic Modeling of Gas Foil Bearings

2010 ◽  
Vol 133 (2) ◽  
Author(s):  
Samuel A. Howard ◽  
Luis San Andrés
Keyword(s):  
Power Loss ◽  
High Speed ◽  
Structural Deformation ◽  
Analysis Tool ◽  
Test Rig ◽  
Contributing Factors ◽  
Foil Bearings ◽  
Rotordynamic Coefficients ◽  
Foil Bearing ◽  
Analytical Tools

Gas foil bearings offer several advantages over traditional bearing types that make them attractive for use in high-speed turbomachinery. They can operate at very high temperatures, require no lubrication supply (oil pumps, seals, etc.), exhibit very long life with no maintenance, and once operating airborne, have very low power loss. The use of gas foil bearings in high-speed turbomachinery has been accelerating in recent years although the pace has been slow. One of the contributing factors to the slow growth has been a lack of analysis tools, benchmarked to measurements, to predict gas foil bearing behavior in rotating machinery. To address this shortcoming, NASA Glenn Research Center (GRC) has supported the development of analytical tools to predict gas foil bearing performance. One of the codes has the capability to predict rotordynamic coefficients, power loss, film thickness, structural deformation, and more. The current paper presents an assessment of the predictive capability of the code named XLGFBTH©. A test rig at GRC is used as a simulated case study to compare rotordynamic analysis using output from the code to actual rotor response as measured in the test rig. The test rig rotor is supported on two gas foil journal bearings manufactured at GRC with all pertinent geometry disclosed. The resulting comparison shows that the rotordynamic coefficients calculated using XLGFBTH© represent the dynamics of the system reasonably well especially as they pertain to predicting critical speeds.

Design Space of Foil Bearings for Closed-Loop Supercritical CO2 Power Cycles Based on Three-Dimensional Thermohydrodynamic Analyses

2015 ◽  
Vol 138 (3) ◽  
Author(s):  
Daejong Kim
Keyword(s):  
Power Loss ◽  
Closed Loop ◽  
Ambient Pressure ◽  
Three Dimensional ◽  
Measured Data ◽  
Analysis Tool ◽  
Power Cycles ◽  
Foil Bearings ◽  
Foil Bearing ◽  
Flow Turbulence

The closed-loop Brayton cycle with supercritical CO2 (S-CO2) as an operating fluid is an attractive alternative to conventional power cycles due to very high power density. Foil gas bearings using CO2 are the most promising for small S-CO2 turbomachinery but there are many problems to address: large power loss due to high flow turbulence, lack of design/analysis tool due to nonideal gas behavior, and lack of load capacity when they are used for large systems. This paper presents high-level design/analysis tool involving three-dimensional (3D) thermohydrodynamic (THD) analyses of radial foil bearings considering real gas effect and flow turbulence inside the film. Simulations are performed for radial foil bearing with 34.9 mm in diameter and lubricated with CO2 and N2 under various ambient conditions up to above 40 bar gauge pressure. The simulation results using the turbulence model still underpredict the measured data in open literature. However, the error between the prediction and measurements decreases as either speed or ambient pressure increases. In addition, general behavior of substantial increase in power loss with ambient pressure agrees with the measured data. The simulation results indicate the importance of detailed THD analysis of the foil bearings for prediction of power loss under severe turbulent condition. A conceptual layout of rotor system for 10 MWe S-CO2 loop is also presented along with realistic rotor weight and bearing load. A hybrid foil bearing with diameter of 102 mm is suggested for gas generator rotor, and its power losses and minimum film thicknesses at various operating conditions are presented.

Turbulent Flow Foil Bearings for Cryogenic Applications

1995 ◽  
Vol 117 (1) ◽  
pp. 185-195 ◽  
Author(s):  
Luis San Andres
Keyword(s):  
High Speed ◽  
Excitation Frequency ◽  
Liquid Oxygen ◽  
Dynamic Force ◽  
Foil Bearings ◽  
Rotordynamic Coefficients ◽  
Numerical Predictions ◽  
Foil Bearing ◽  
Rotor Support ◽  
System Life

Fluid film foil bearings are an innovative bearing technology proposed for rotor support in cryogenic turbomachinery. These bearings offer system life and rotor speeds currently unachievable with rolling element bearings alone. An isothermal analysis for the turbulent bulk-flow of a variable properties liquid in a foil bearing with a simple elastic matrix is introduced. Numerical predictions compare the static and dynamic force performance of a three pad foil bearing with a rigid surface bearing for a high speed application in liquid oxygen. The major advantages of the foil bearing are immediately apparent, namely linearity in the load versus eccentricity curve, uniform rotordynamic coefficients, and overall unsurpassed stability conditions. The effects of excitation frequency and the foil structural damping on the dynamic force coefficients are discussed.

An experimental investigation of a microturbine simulated rotor supported on multileaf gas foil bearings with backing bump foils

2017 ◽  
Vol 232 (9) ◽  
pp. 1169-1180 ◽  
Author(s):  
Bo Zhang ◽  
Shemiao Qi ◽  
Sheng Feng ◽  
Haipeng Geng ◽  
Yanhua Sun ◽  
...  
Keyword(s):  
High Speed ◽  
Preliminary Test ◽  
Journal Bearings ◽  
Rotating Machinery ◽  
System Stability ◽  
Test Rig ◽  
Thrust Bearings ◽  
Foil Bearings ◽  
Simulated System ◽  
First Time

Two multileaf gas foil journal bearings with backing bump foils and one set of gas foil thrust bearings were designed, fabricated, and used in a 100 kW class microturbine simulated rotor system to ensure stability of the system. Meanwhile, a preliminary test rig had been built to verify the simulated system stability. The rotor synchronous and subsynchronous responses were well controlled by using of the gas foil bearings. It is on the multileaf gas foil bearings with backing bump foils that the test was conducted and verified for the first time in open literatures. The success in the experiments shows that the design and fabrication of the rotor and the gas foil bearings can provide a useful guide to the development of the advanced high speed rotating machinery.

Rotordynamics Performance of Hybrid Foil Bearing Under Forced Vibration Input

2017 ◽  
Author(s):  
Daejong Kim ◽  
Brian Nicholson ◽  
Lewis Rosado ◽  
Garry Givan
Keyword(s):  
Impulse Response ◽  
High Speed ◽  
Load Capacity ◽  
Supply System ◽  
Forced Response ◽  
Experimental Results ◽  
Lateral Acceleration ◽  
Foil Bearings ◽  
Foil Bearing ◽  
Gas Supply

Foil bearings are one type of hydrodynamic air/gas bearings but with a compliant bearing surface supported by structural material that provides stiffness and damping to the bearing. The hybrid foil bearing (HFB) in this paper is a combination of a traditional hydrodynamic foil bearing with externally-pressurized air/gas supply system to enhance load capacity during the start and to improve thermal stability of the bearing. The HFB is more suitable for relatively large and heavy rotors where rotor weight is comparable to the load capacity of the bearing at full speed and extra air/gas supply system is not a major added cost. With 4,448N∼22,240N thrust class turbine aircraft engines in mind, the test rotor is supported by HFB in one end and duplex rolling element bearings in the other end. This paper presents experimental work on HFB with diameter of 102mm performed at the US Air force Research Laboratory. Experimental works include: measurement of impulse response of the bearing to the external load corresponding to rotor’s lateral acceleration of 5.55g, forced response to external subsynchronous excitation, and high speed imbalance response. A non-linear rotordynamic simulation model was also applied to predict the impulse response and forced subsynchronous response. The simulation results agree well with experimental results. Based on the experimental results and subsequent simulations, an improved HFB design is also suggested for higher impulse load capability up to 10g and rotordynamics stability up to 30,000rpm under subsynchronous excitation.

Rotordynamic Performance of a Shaft With Large Overhung Mass Supported by Foil Bearings

2016 ◽  
Vol 139 (4) ◽  
Author(s):  
Nguyen LaTray ◽  
Daejong Kim
Keyword(s):  
High Speed ◽  
Foil Bearings ◽  
Speed Test ◽  
Foil Bearing ◽  
Stable Conditions ◽  
Bending Mode ◽  
Mode Vibration ◽  
Lift Off ◽  
Compact Design ◽  
Bearing System

This work presents the theoretical and experimental rotordynamic evaluations of a rotor–air foil bearing (AFB) system supporting a large overhung mass for high-speed application. The proposed system highlights the compact design of a single shaft rotor configuration with turbomachine components arranged on one side of the bearing span. In this work, low-speed tests up to 45 krpm are performed to measure lift-off speed and to check bearing manufacturing quality. Rotordynamic performance at high speeds is evaluated both analytically and experimentally. In the analytical approach, simulated imbalance responses are studied using both rigid and flexible shaft models with bearing forces calculated from the transient Reynolds equation along with the rotor motion. The simulation predicts that the system experiences small synchronous rigid mode vibration at 20 krpm and bending mode at 200 krpm. A high-speed test rig is designed to experimentally evaluate the rotor–air foil bearing system. The high-speed tests are operated up to 160 krpm. The vibration spectrum indicates that the rotor–air foil bearing system operates under stable conditions. The experimental waterfall plots also show very small subsynchronous vibrations with frequency locked to the system natural frequency. Overall, this work demonstrates potential capability of the air foil bearings in supporting a shaft with a large overhung mass at high speed.

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.

scholarly journals Rotor dynamic experimental investigation of an ultra-high-speed permanent magnet synchronous motor supported on a three-pad bidirectional gas foil bearing

2019 ◽  
Vol 11 (9) ◽  
pp. 168781401987536
Author(s):  
Wenjie Cheng ◽  
Zhikai Deng ◽  
Ling Xiao ◽  
Bin Zhong ◽  
Wenbo Duan
Keyword(s):  
Permanent Magnet ◽  
High Speed ◽  
Permanent Magnet Synchronous Motor ◽  
Synchronous Motor ◽  
Rotor System ◽  
Permanent Magnet Motors ◽  
Foil Bearings ◽  
Foil Bearing ◽  
Ultra High Speed ◽  
Rotor Dynamic

With a 10-kW, 120,000-r/min, ultra-high-speed permanent magnet synchronous motor taken as a prototype, experimental research is conducted on the rotor dynamic behaviours of a three-pad bidirectional gas foil bearing high-speed motor rotor system. Load-carrying properties of the three-pad bidirectional gas foil bearing are analysed, and natural frequencies of conical and parallel whirling modes of the elastically supported rotor are calculated based on an appropriate simplification to the stiffness and damping coefficients of the gas foil bearings. The prototype passes through a 90,000-r/min coast-down experiment. Experiments show that there are violent subsynchronous whirling motions that are evoked by the gas foil bearing–rotor system itself. The cause of shaft orbit drift is analysed, and the corresponding solution is put forward. The theoretical analysis and experimental results can offer a useful reference to the bearing–rotor system design of ultra-high-speed permanent magnet motors and its subsequent dynamic analysis.

CFD Assessment of Rotordynamic Coefficients in Labyrinth Seals

2014 ◽  
Author(s):  
Sai S. Sreedharan ◽  
Giuseppe Vannini ◽  
Hiteshkumar Mistry
Keyword(s):  
High Speed ◽  
Test Results ◽  
Active Magnetic Bearings ◽  
Test Rig ◽  
Labyrinth Seals ◽  
Cfd Simulations ◽  
Flow Solver ◽  
Rotordynamic Coefficients ◽  
Pressure Test ◽  
Dynamic Seal

Seals used in high speed centrifugal compressors are prone to generate rotordynamic (RD) instabilities. To further understand their influence, a CFD based approach is developed. The objective of the current study is to numerically investigate and characterize the RD coefficients, representative of the dynamic seal forces. Experiments were carried out at high pressure test rig (up to 200 bar seal inlet pressure) which runs at 10000 RPM and has a high pre-swirl (about 0.9) along the same direction of rotor rotation. The rotor shaft in the experiment was instrumented with active magnetic bearings (AMBs) to linearly excite the rotor at three different frequencies: 28 Hz, 70 Hz and 126 Hz. Each frequency is characterized by amplitude of vibration and a phase. CFD simulations were carried out using commercial flow solver, using similar boundary conditions as that of experiments. The paper describes details of CFD model and its comparison against experiments. Numerical results show reasonable agreement of RD coefficients with test results. This job has to be considered as a first approach to CFD methodology applied to annular seals for the authors.

Reducing Gear Windage Losses From High Speed Gears

2000 ◽  
Author(s):  
Don D. Winfree
Keyword(s):  
Power Loss ◽  
High Speed ◽  
Total Power ◽  
Fort Worth ◽  
Trial And Error ◽  
Test Rig ◽  
Cost Overruns ◽  
Basic Set ◽  
Drive Trains ◽  
Reducing Gear

Abstract Windage losses in gearboxes account for a large portion of the total power loss in high-speed drive trains. Very little actual data has been collected specifically quantifying these losses. Traditional techniques to measure the effects of baffles in high speed gearing applications have been done by trial and error on very complex systems. This trial and error technique is used throughout the gearing industry to solve problems without isolating each individual gear windage effect. These solutions are usually sub-optimum. They cause time-consuming delays and cost overruns in many programs. This paper describes a gear baffle test rig that was built to quantify and minimize the gear windage losses in high-speed drive trains. These tests were conducted at the Lockheed Martin Aeronautics Company, Fort Worth Texas Facility. The intent of the gearbox baffle test rig was to isolate and measure the windage effects on a single high-speed bevel gear with various baffle configurations. Results of these tests were used to define a basic set of ground rules for designing baffles. Finally the set of ground rules was used to design an optimum baffle configuration.

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