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.

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.

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 The Dynamic Characteristics of a Turborotor Simulator Supported on Gas-Lubricated Foil Bearings—Part 2: Operation With Heating and Thermal Gradients

1970 ◽  
Vol 92 (4) ◽  
pp. 650-659 ◽  
Author(s):  
L. Licht
Keyword(s):  
Dynamic Characteristics ◽  
High Speed ◽  
Elevated Temperatures ◽  
Load Capacity ◽  
Temperature Gradients ◽  
Thermal Gradients ◽  
Foil Bearings ◽  
Foil Bearing ◽  
Geometrical Imperfections ◽  
The Stability

A high-speed rotor, supported by gas-lubricated foil bearings, is free from self-excited whirl and displays no loss of load capacity when vibrated at frequency equal half the rotational speed [1]. It is demonstrated here that in addition to tolerance of geometrical imperfections, misalignment, and foreign particles [3, 4], the foil bearing performs well at elevated temperatures and accommodates appreciable temperature gradients. The foil bearing is endowed with superior wipe-wear characteristics, and the flexibility of the foil accounts not only for the stability of the foil bearing but also for its forgiveness with respect to distortion, contamination, and contact.

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

2016 ◽  
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 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 45krpm are performed to measure the lift off speed and to check the 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 transient Reynolds equation along with rotor motion. The simulation predicts that the system experiences small synchronous rigid mode vibration at 20krpm and bending mode at 200krpm. A high speed test rig is designed to experimentally evaluate the rotor-air foil bearings system. The high speed tests are operated up to 160krpm. The vibration spectrum indicates that the rotor-air foil bearing system operates under stable conditions. The experimental waterfall plots also show very small sub-synchronous vibrations with frequency locked to the system natural frequency. Overall, this work demonstrates the potential capability of air foil bearings in supporting a shaft with a large overhung mass at high speed.

Effect of Circumferential Location of Radial Injection on Rotordynamic Performance of Hybrid Air Foil Bearings

2018 ◽  
Author(s):  
Behzad Zamanian Yazdi ◽  
Daejong Kim
Keyword(s):  
Time Domain ◽  
High Speed ◽  
Substantial Improvement ◽  
Reliable Operation ◽  
Foil Bearings ◽  
Damping Coefficients ◽  
Foil Bearing ◽  
Radial Injection ◽  
Parametric Studies ◽  
Stiffness And Damping

Air foil bearings (AFBs) are introduced as promising bearings for oil-free turbomachinery applications. AFBs provide reliable operation at high speed and high temperature with negligible power loss. Hybrid Air Foil Bearing (HAFB) technology utilizes the radial injection of externally pressurized air into the traditional hydrodynamic AFB’s film thickness through orifices attached to the top foil. Previous studies have reported enhancement in the rotordynamic stability of HAFBs compared to traditional hydrodynamic AFBs. HAFBs have several orifices distributed in the circumferential direction. In this study, the effect of the circumferential location of radial injection on the rotordynamic performance of the rotor-HAFB is studied. Analytical and experimental evaluations of the rotordynamic performance of a rotor supported by two single-pad HAFBs are presented. Parametric studies are conducted using three sets of single-pad HAFBs. The circumferential locations of orifices are different for each set. The presented simulation analyses consist of time-domain orbit simulation and frequency-domain modal analysis. Imbalance responses of rotor-HAFB were measured with various orifice locations and the results agree well with predictions. Comparison of the rotordynamic performance of HAFBs with different orifice configurations demonstrate substantial improvement in rotordynamic stability as well as enhancement in the stiffness and damping coefficients of HAFBs by choosing the best circumferential location for radial injection to control rotor eccentricity and attitude angle.

scholarly journals An Assessment of Gas Foil Bearing Scalability and the Potential Benefits to Civilian Turbofan Engines

2010 ◽  
Author(s):  
Robert J. Bruckner
Keyword(s):  
High Speed ◽  
Load Capacity ◽  
Advanced Technology ◽  
Rolling Element Bearings ◽  
Turbofan Engines ◽  
Foil Bearings ◽  
Foil Bearing ◽  
Fuel Burn ◽  
Rolling Element ◽  
Rotor Support

Over the past several years the term oil-free turbomachinery has been used to describe a rotor support system for high speed turbomachinery that does not require oil for lubrication, damping, or cooling. The foundation technology for oil-free turbomachinery is the compliant foil bearing. This technology can replace the conventional rolling element bearings found in current engines. Two major benefits are realized with this technology. The primary benefit is the elimination of the oil lubrication system, accessory gearbox, tower shaft, and one turbine frame. These components account for 8–13% of the turbofan engine weight. The second benefit that compliant foil bearings offer to turbofan engines is the capability to operate at higher rotational speeds and shaft diameters. While traditional rolling element bearings have diminished life, reliability, and load capacity with increasing speeds, the foil bearing has a load capacity proportional to speed. The traditional applications for foil bearings have been in small, lightweight machines. However, recent advancements in the design and manufacturing of foil bearings have increased their potential size. An analysis, grounded in experimentally proven operation, is performed to assess the scalability of the modern foil bearing. This analysis coupled to the requirements of civilian turbofan engines. The application of the foil bearing to larger, high bypass ratio engines nominally at the 120 kN (∼25000 pound) thrust class has been examined. The application of this advanced technology to this system was found to reduce mission fuel burn by 3.05%.

Effect of Circumferential Location of Radial Injection on Rotordynamic Performance of Hybrid Air Foil Bearings

2018 ◽  
Vol 140 (12) ◽  
Author(s):  
Behzad Zamanian Yazdi ◽  
Daejong Kim
Keyword(s):  
Time Domain ◽  
High Speed ◽  
Substantial Improvement ◽  
Reliable Operation ◽  
Foil Bearings ◽  
Damping Coefficients ◽  
Foil Bearing ◽  
Radial Injection ◽  
Parametric Studies ◽  
Stiffness And Damping

Air foil bearings (AFBs) are introduced as promising bearings for oil-free turbomachinery applications. AFBs provide reliable operation at high speed and high temperature with negligible power loss. Hybrid air foil bearing (HAFB) technology utilizes the radial injection of externally pressurized air into the traditional hydrodynamic AFB's film thickness through orifices attached to the top foil. Previous studies have reported enhancement in the rotordynamic stability of HAFBs compared to traditional hydrodynamic AFBs. HAFBs have several orifices distributed in the circumferential direction. In this study, the effect of the circumferential location of radial injection on the rotordynamic performance of the rotor-HAFB is studied. Analytical and experimental evaluations of the rotordynamic performance of a rotor supported by two single-pad HAFBs are presented. Parametric studies are conducted using three sets of single-pad HAFBs. The circumferential locations of orifices are different for each set. The presented simulation analyses consist of time-domain orbit simulation and frequency-domain modal analysis. Imbalance responses of rotor-HAFB were measured with various orifice locations and the results agree well with predictions. Comparison of the rotordynamic performance of HAFBs with different orifice configurations demonstrates substantial improvement in rotordynamic stability as well as enhancement in the stiffness and damping coefficients of HAFBs by choosing the best circumferential location for radial injection to control rotor eccentricity and attitude angle.

Rotordynamics Performance of Hybrid Foil Bearing Under Forced Vibration Input

2017 ◽  
Vol 140 (1) ◽  
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 (FB) 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 4448–22,240 N thrust class turbine aircraft engines in mind, the test rotor is supported by HFB in one end and duplex rolling element bearings (REB) in the other end. This paper presents experimental work on HFB with diameter of 102 mm performed at the U.S. Air force Research Laboratory (AFRL). Experimental works include: measurement of impulse response of the bearing to the external load corresponding to rotor's lateral acceleration of 5.55 g, forced response to external subsynchronous excitation, and high-speed imbalance response. A nonlinear rotordynamic simulation model was also applied to predict the impulse response and forced subsynchronous response. The simulation results agree well with the experimental results. Based on the experimental results and subsequent simulations, an improved HFB design is also suggested for higher impulse load capability up to 10 g and rotordynamics stability up to 30,000 rpm under subsynchronous excitation.

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