scholarly journals Pressure Profile Measurements Within the Gas Film of Journal Foil Bearings Using an Instrumented Rotor With Telemetry

2020 ◽  
Vol 142 (3) ◽  
Author(s):  
Karim Shalash ◽  
Jürg Schiffmann
Keyword(s):  
Frequency Domain ◽  
Journal Bearing ◽  
Pressure Profile ◽  
Foil Bearings ◽  
Foil Bearing ◽  
Pressure Profiles ◽  
Fundamental Understanding ◽  
The Rich ◽  
Bearing Behavior ◽  
Circumferential Pressure

Abstract Foil bearings are strong candidates to support oil-free turbomachinery. Although foil bearings are a widely used technology, models describing their behavior are not validated using the film pressure, which is the fundamental variable of any fluid film bearing. This paper presents pressure profiles measured within the gas film of a journal foil bearing. The pressure is measured using an instrumented rotor with embedded pressure probes and wireless telemetry. The measurements yield the simultaneous circumferential pressure profiles at two axial positions inside the bearing. Proximity probes on the bearing allowed the measurement of the corresponding rotor orbits. The bearing under investigation is a bump-type compliant journal bearing, with a nominal diameter of 40 mm, an L/D = 1, and was tested up to 37.5 krpm. Load-displacement and break-away tests were performed on the test bearing in order to identify bearing parameters necessary for reproducibility. The pressure profiles are compared to a frequency domain foil bearing model. This paper is a step toward further fundamental understanding of the foil bearing behavior and the validation of the rich modeling literature.

scholarly journals Pressure Profile Measurements Within the Gas Film of Journal Foil Bearings Using an Instrumented Rotor With Telemetry

2019 ◽  
Author(s):  
K. Shalash ◽  
J. Schiffmann
Keyword(s):  
Frequency Domain ◽  
Journal Bearing ◽  
Pressure Profile ◽  
Foil Bearings ◽  
Foil Bearing ◽  
Pressure Profiles ◽  
Fundamental Understanding ◽  
The Rich ◽  
Bearing Behavior ◽  
Circumferential Pressure

Abstract Foil bearings are strong candidates to support oil-free turbomachinery. Although foil bearings are a widely used technology, models describing their behavior are not validated using the film pressure, which is the fundamental variable of any fluid film bearing. This paper presents pressure profiles measured within the gas film of a journal foil bearing. The pressure is measured using an instrumented rotor with embedded pressure probes and wireless telemetry. The measurements yield the simultaneous circumferential pressure profiles at two axial positions inside the bearing. Proximity probes on the bearing allowed the measurement of the corresponding rotor orbits. The bearing under investigation is a bump type compliant journal bearing, with a nominal diameter of 40mm, an L/D = 1, and was tested up to 37.5 krpm. Load-displacement and break-away tests were performed on the test bearing in order to identify bearing parameters necessary for reproducibility. The pressure profiles are compared to a frequency domain foil bearing model. This paper is a step towards further fundamental understanding of the foil bearing behavior, and the validation of the rich modelling literature.

The Effects of Oil Supply Pressure at different Groove Position on Temperature and Pressure Profile in Journal Bearing

2013 ◽  
Vol 66 (3) ◽  
Author(s):  
Mohamad Ali Ahmad ◽  
Salmiah Kasolang ◽  
R. S. Dwyer-Joyce ◽  
Aidah Jumahat
Keyword(s):  
Journal Bearing ◽  
Pressure Profile ◽  
Diameter Ratio ◽  
Radial Load ◽  
Oil Supply ◽  
Supply Pressure ◽  
Pressure Profiles ◽  
Hydrodynamic Journal Bearing ◽  
Temperature And Pressure ◽  
Length To Diameter Ratio

The effects of oil supply pressure on the temperature and pressure at different groove locations on a hydrodynamic journal bearing were investigated. A journal with a diameter of 100 mm and a ½ length-to-diameter ratio was used. The supply pressure was set to 0.2, 0.5, and 0.7 MPa at seven different groove locations, namely, -45°, -30°, -15°, 0°, +15°, +30°, and +45°. Temperature and pressure profiles were measured at speed values of 300, 500, and 800 rpm with 10 kN radial load. The results show that the change in oil supply pressure simultaneously reduced the temperature and increased the pressure profile.

scholarly journals Compliant Foil Journal Bearing Performance at Alternate Pressures and Temperatures

2008 ◽  
Author(s):  
Robert J. Bruckner ◽  
Bernadette J. Puleo
Keyword(s):  
Journal Bearing ◽  
Load Capacity ◽  
Ambient Pressure ◽  
Operating Conditions ◽  
Test Program ◽  
Foil Bearings ◽  
Current Test ◽  
Foil Bearing ◽  
Development Risk ◽  
Highly Loaded

An experimental test program has been conducted to determine the highly loaded performance of current generation gas foil bearings at alternate pressures and temperature. Typically foil bearing performance has been reported at temperatures relevant to turbomachinery applications but only at an ambient pressure of one atmosphere. This dearth of data at alternate pressures has motivated the current test program. Two facilities were used in the test program, the ambient pressure rig and the high pressure rig. The test program utilized a 35 mm diameter by 27 mm long foil journal bearing having an uncoated Inconel X-750 top foil running against a shaft with a PS304 coated journal. Load capacity tests were conducted at 3, 6, 9, 12, 15, 18, and 21 krpm at temperatures from 25°C to 500°C and at pressures from 0.1 to 2.5 atmospheres. Results show an increase in load capacity with increased ambient pressure and a reduction in load capacity with increased ambient temperature. Below one-half atmosphere of ambient pressure a dramatic loss of load capacity is experienced. Additional lightly loaded foil bearing performance in nitrogen at 25°C and up to 48 atmospheres of ambient pressure has also been reported. In the lightly loaded region of operation the power loss increases for increasing pressure at a fixed load. Knowledge of foil bearing performance at operating conditions found within potential machine applications will reduce program development risk of future foil bearing supported turbomachines.

The Effect of Oil Supply Pressure on the Circumferential Pressure Profile in Hydrodynamic Journal Bearing

2013 ◽  
Vol 315 ◽  
pp. 809-814 ◽  
Author(s):  
Mohamad Ali Ahmad ◽  
Salmiah Kasolang ◽  
Rob Dwyer-Joyce ◽  
Nik Rosli Abdullah
Keyword(s):  
Journal Bearing ◽  
Hydrodynamic Lubrication ◽  
Pressure Profile ◽  
Journal Bearings ◽  
Maximum Pressure ◽  
Oil Supply ◽  
Supply Pressure ◽  
Machine Elements ◽  
Hydrodynamic Journal Bearing ◽  
Circumferential Pressure

In hydrodynamic lubrication, the pressure condition of the fluid is critical to ensure good performance of the lubricated machine elements such as journal bearings. In the present study, an experimental work was conducted to determine the effect of oil supply pressure on pressure profile around the circumference of a journal bearing. A journal diameter of 100mm with a ½ length-to-diameter ratio was used. The oil supply pressure was set at three different values (0.3, 0.5, 0.7 Mpa) and the circumferential pressure results for 400, 600 and 800 RPM at different radial loads were obtained. It was observed that the maximum pressure values were affected by changes in oil supply pressure.

Experimental and Numerical Investigation of the High-Speed Instability of Aerodynamic Foil Journal Bearings for Micro Turbomachinery

2012 ◽  
Author(s):  
Kei Somaya ◽  
Toru Yamashita ◽  
Shigeka Yoshimoto
Keyword(s):  
High Temperature ◽  
High Speed ◽  
First Generation ◽  
Journal Bearing ◽  
Journal Bearings ◽  
Orbit Method ◽  
Foil Bearings ◽  
High Speeds ◽  
Foil Bearing ◽  
Excellent Stability

Foil bearings have been attracting considerable attention for their applications to micro turbomachinery, such as blowers and compressors, because of their excellent stability at high speeds and durability in high-temperature environments. This paper investigates experimentally and numerically the high-speed instability of a rotor supported by small aerodynamic foil journal bearings. Two types of foil journal bearings were prepared: a first-generation bump-type foil bearing and a dimple-type foil bearing; these consist of a top foil and a support foil with bumps or dimples, respectively. The dynamic characteristics of a support foil using the frequency response and the threshold speed of instability at high speeds were measured experimentally. Furthermore, the numerical threshold speed of instability was obtained using the nonlinear orbit method. It was confirmed experimentally and numerically that a 6 mm diameter rotor with a mass of 4.7 g supported by either of the two types of foil journal bearing treated in this paper could rotate stably at speeds of more than 760,000 rpm.

Evaluation of Foil Bearing Performance and Nonlinear Rotordynamics of 120kW Oil-Free Gas Turbine Generator

2013 ◽  
Author(s):  
Daejong Kim ◽  
An Sung Lee ◽  
Bum Seog Choi
Keyword(s):  
Frequency Domain ◽  
Gas Turbine ◽  
Turbine Rotor ◽  
Gas Generator ◽  
Turbine Generator ◽  
Element Analysis ◽  
Foil Bearings ◽  
Foil Bearing ◽  
Nonlinear Transient ◽  
Stiffness And Damping

This paper presents design approach of air foil bearings (AFBs) for 120kWe gas turbine generator, which is a single spool configuration with gas generator turbine and alternator rotor connected by a diaphragm coupling. Total four radial AFBs support the two rotors, and one set of double acting thrust foil bearing is located inside the gas generator turbine. The rotor configuration results in eight degree of freedom (DOF) rotordynamic motions, which are two cylindrical modes and two conical modes from the two rotors. Stiffness of bump foils of candidate AFB was estimated from measured structural stiffness of the bearing, and implemented to computational model for linear stiffness and damping coefficients of the bearing and frequency-domain modal impedances for cylindrical and conical modes. Stiffness of the diaphragm coupling was evaluated using finite element analysis and implemented to non-linear rotordynamic analyses of entire engine. Analyses show conical mode of turbine rotor is the main source of instability of entire engine when AFB clearance is not selected properly. Optimum AFB clearance is suggested from frequency domain modal analyses and nonlinear transient analyses.

Dynamic Characteristics of a High-Speed Rotor With Radial and Axial Foil-Bearing Supports

1981 ◽  
Vol 103 (3) ◽  
pp. 361-370 ◽  
Author(s):  
L. Licht ◽  
W. J. Anderson ◽  
S. W. Doroff
Keyword(s):  
Support System ◽  
Dynamic Characteristics ◽  
High Speed ◽  
Journal Bearing ◽  
Foil Bearings ◽  
Flexible Support ◽  
Foil Bearing ◽  
Experimental Apparatus ◽  
Asymmetric Rotor

An asymmetric rotor (19N; 4.3 lb), supported radially and axially by compliant bearings (foil bearings), is subjected to severe excitation by rotating unbalance (43 μm.N; 6100 μin.oz) in the “pitching” mode, at speeds to 50,000 rpm. The resilient, air-lubricated bearings provide very effective damping, so that regions of resonance and instability can be traversed with impunity, with amplitudes and limit-trajectories remaining within acceptable bounds. A novel journal bearing is introduced, in which a resilient support is furnished by the outer turn of the coiled foil-element, initially bent to form an open polygon. The experimental apparatus and procedure are described, and the response of the rotor and flexible support system are copiously documented by oscilloscope records of motion.

scholarly journals High Pressure Performance of Foil Journal Bearings in Various Gases

2008 ◽  
Author(s):  
Maxwell H. Briggs ◽  
Joseph M. Prahl ◽  
Robert Bruckner ◽  
Brian Dykas
Keyword(s):  
Carbon Dioxide ◽  
High Pressure ◽  
Atmospheric Pressure ◽  
Power Loss ◽  
Journal Bearing ◽  
Brayton Cycle ◽  
Foil Bearings ◽  
Foil Bearing ◽  
Peak Pressures

Foil bearings offer several advantages over traditional oil-lubricated bearings in closed Brayton Cycle (CBC) systems, such as those proposed for long-term space power generation. Proposed CBCs require foil bearings to use an inert gas lubricant at pressures as high as 3.0 MPa as the bearing lubricant. The High Pressure Rig (HPR) at the NASA Glenn Research Center is used to measure foil bearing power loss using potential CBC working fluids at and beyond proposed CBC peak pressures. In the current study foil journal bearing power loss is measured in helium, nitrogen, and carbon dioxide from atmospheric pressure to 4.83 MPa and at shaft speeds from 10 krpm to 42 krpm. Bearings operating in helium show no increase in power loss with increasing pressure for the conditions tested. Bearings operating in nitrogen show increases in power loss with increasing pressure at speeds above 19 krpm, while increases in bearing power loss during carbon dioxide testing were seen at 15 krpm. At speeds above these thresholds, power loss is shown to increase more rapidly in carbon dioxide than in nitrogen. Results suggest that bearing power loss performance is dependent on both gas density and shaft speed.

Experimental Identification of Force Coefficients of Large Hybrid Air Foil Bearings

2013 ◽  
Vol 136 (3) ◽  
Author(s):  
Yu Ping Wang ◽  
Daejong Kim
Keyword(s):  
Frequency Domain ◽  
Linear Perturbation ◽  
Frequency Domain Method ◽  
Impulse Responses ◽  
Significant Progress ◽  
Rotating Shaft ◽  
Foil Bearings ◽  
Stiffness Coefficients ◽  
Foil Bearing ◽  
Reliability Performance

Foil bearing technology using air or gas as a lubricant has been around since the mid-1960s, and it made significant progress in its reliability, performance, and applications. Even if significant progress has been made to the technology, the commercial applications to relatively large machines with journal shaft diameter bigger than 100 mm was not reported. This paper presents dynamic characteristics of a hybrid (hydrodynamic + hydrostatic) air foil bearing (HAFB) with a diameter of 101.6 mm and a length of 82.6 mm. The test rig configuration in this work is a floating HAFB on a rotating shaft driven by electric motor, and the HAFB is under external load. HAFB stiffness coefficients were measured using both (1) time-domain quasi-static load-deflection curves and (2) frequency-domain impulse responses, and HAFB damping coefficients were measured using only impulse responses. The HAFB direct stiffness coefficients measured from both methods are close to each other in the range of 4∼7 MN/m depending on speed, load, and supply pressure, but frequency domain method shows larger scatter in the identified coefficients. HAFB coefficients simulated with the linear perturbation method using a bump stiffness matched to the load-deflection characteristics at 18,000 rpm show reasonably good agreements with experimentally measured values.

Evaluation of Foil Bearing Performance and Nonlinear Rotordynamics of 120 kW Oil-Free Gas Turbine Generator

2013 ◽  
Vol 136 (3) ◽  
Author(s):  
Daejong Kim ◽  
An Sung Lee ◽  
Bum Seog Choi
Keyword(s):  
Frequency Domain ◽  
Gas Turbine ◽  
Turbine Rotor ◽  
Gas Generator ◽  
Turbine Generator ◽  
Element Analysis ◽  
Foil Bearings ◽  
Foil Bearing ◽  
Nonlinear Transient ◽  
Stiffness And Damping

This paper presents a design approach of air foil bearings (AFBs) for a 120 kWe gas turbine generator, which is a single spool configuration with gas generator turbine and alternator rotor connected by a diaphragm coupling. A total of four radial AFBs support the two rotors, and one set of double acting thrust foil bearing is located inside the gas generator turbine. The rotor configuration results in eight degree of freedom (DOF) rotordynamic motions, which are two cylindrical modes and two conical modes from the two rotors. Stiffness of bump foils of candidate AFB was estimated from measured structural stiffness of the bearing, and implemented to the computational model for linear stiffness and damping coefficients of the bearing and frequency-domain modal impedances for cylindrical and conical modes. Stiffness of the diaphragm coupling was evaluated using finite element analysis and implemented to nonlinear rotordynamic analyses of the entire engine. Analyses show the conical mode of the turbine rotor is the main source of instability of the entire engine when AFB clearance is not selected properly. Optimum AFB clearance is suggested from frequency domain modal analyses and nonlinear transient analyses.

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