Application of multi-leaf foil bearings in high-speed turbo-machinery

Abstract. Foil bearings are self-acting hydrodynamics bearings used to support lightly loaded high speed rotating machinery. The advantages that they offer to process fluid lubricated machines usingworking fluid as a lubricant (ambient air) physically non-contacting high speed operation. Foil bearings have been considered as an alternative to conventional bearings with the capacity to cater for high-speeds and hostile environment (high temperature). However, the lack of load carrying capacity at relatively lower speeds limits their applications in heavy turbo machinery and as such are highly suitable in lightly loaded, high speed turbo machinery like small gas turbines.This paper discusses the design and assessment of dynamic characteristics in terms of load carrying capabilities as a function of speed, gap between the bearing and the runner as well as shape of foils for an air foil thrust bearing. The effects of various bearing parameters like foil thickness, number of foils fixed circumferentially and along the axis of rotation and with foil geometry configuration. Characteristics of performance defined essentially in terms of load carrying capabilities and static stiffness have been used for evaluation. Experiments were conducted both for angular foils (with inner edge height less than outer edge height) and square foils by varying number of foils. The experimental results shows that the effect of foil configuration enhances the load carrying capabilities of air foil thrust bearing.

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Application of Gas Foil Bearings in China

Applied Sciences ◽

10.3390/app11136210 ◽

2021 ◽

Vol 11 (13) ◽

pp. 6210

Author(s):

Yu Hou ◽

Qi Zhao ◽

Yu Guo ◽

Xionghao Ren ◽

Tianwei Lai ◽

...

Keyword(s):

High Speed ◽

Low Cost ◽

Small Scale ◽

Environmental Friendliness ◽

Wear Resistant Coatings ◽

Foil Bearings ◽

Foil Bearing ◽

Turbo Machinery ◽

Principle Theory ◽

Rotor Dynamic

Gas foil bearing has been widely used in high-speed turbo machinery due to its oil-free, wide temperature range, low cost, high adaptability, high stability and environmental friendliness. In this paper, state-of-the-art investigations of gas foil bearings are reviewed, mainly on the development of the high-speed turbo machinery in China. After decades of development, progress has been achieved in the field of gas foil bearing in China. Small-scale applications of gas foil bearing have been realized in a variety of high-speed turbo machinery. The prospects and markets of high-speed turbo machinery are very broad. Various high-speed turbomachines with gas foil bearings have been developed. Due to the different application occasions, higher reliability requirements are imposed on the foil bearing technology. Therefore, its design principle, theory, and manufacturing technology should be adaptive to new application occasions before mass production. Thus, there are still a number of inherent challenges that must be addressed, for example, thermal management, rotor-dynamic stability and wear-resistant coatings.

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Gas-Dynamic Foil Bearings Application in High-Speed Turbines

Journal of Konbin ◽

10.2478/jok-2013-0109 ◽

2015 ◽

Vol 27 (1) ◽

pp. 99-108 ◽

Cited By ~ 1

Author(s):

Bolesław Giemza ◽

Emil Nowiński ◽

Marek Domański

Keyword(s):

High Temperature ◽

High Speed ◽

Foil Bearings ◽

Gas Dynamic ◽

Aviation Technology ◽

Turbo Machinery

Abstract Authors present the general characteristics of the gas-dynamic foil bearings in the paper. The short analysis of the application and possibilities of using gas-dynamic bearings in turbo machinery, especially in the aspect of aviation technology were described. Authors also pointed out possible directions of development and gas-dynamic foil bearings application in high-speed turbines, especially working in high temperature.

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Rotordynamic Performance of a Rotor Supported on Bump Type Foil Gas Bearings: Experiments and Predictions

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.2718233 ◽

2006 ◽

Vol 129 (3) ◽

pp. 850-857 ◽

Cited By ~ 36

Author(s):

Luis San Andrés ◽

Dario Rubio ◽

Tae Ho Kim

Keyword(s):

High Speed ◽

Critical Speed ◽

Load Capacity ◽

Test System ◽

Foil Bearings ◽

Rotor Imbalance ◽

Synchronous Motion ◽

Damping Characteristics ◽

Rotor Surface ◽

Stiffness And Damping

Gas foil bearings (GFBs) satisfy the requirements for oil-free turbomachinery, i.e., simple construction and ensuring low drag friction and reliable high speed operation. However, GFBs have a limited load capacity and minimal damping, as well as frequency and amplitude dependent stiffness and damping characteristics. This paper provides experimental results of the rotordynamic performance of a small rotor supported on two bump-type GFBs of length and diameter equal to 38.10mm. Coast down rotor responses from 25krpm to rest are recorded for various imbalance conditions and increasing air feed pressures. The peak amplitudes of rotor synchronous motion at the system critical speed are not proportional to the imbalance introduced. Furthermore, for the largest imbalance, the test system shows subsynchronous motions from 20.5krpm to 15krpm with a whirl frequency at ∼50% of shaft speed. Rotor imbalance exacerbates the severity of subsynchronous motions, thus denoting a forced nonlinearity in the GFBs. The rotor dynamic analysis with calculated GFB force coefficients predicts a critical speed at 8.5krpm, as in the experiments; and importantly enough, unstable operation in the same speed range as the test results for the largest imbalance. Predicted imbalance responses do not agree with the rotor measurements while crossing the critical speed, except for the lowest imbalance case. Gas pressurization through the bearings’ side ameliorates rotor subsynchronous motions and reduces the peak amplitudes at the critical speed. Posttest inspection reveal wear spots on the top foils and rotor surface.

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

Proceedings of the Institution of Mechanical Engineers Part J Journal of Engineering Tribology ◽

10.1177/1350650117725463 ◽

2017 ◽

Vol 232 (9) ◽

pp. 1169-1180 ◽

Cited By ~ 5

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.

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Analysis of high speed permanent magnet synchronous motor rotor supported by air foil bearings

International Journal of Applied Electromagnetics and Mechanics ◽

10.3233/jae-171157 ◽

2019 ◽

Vol 59 (2) ◽

pp. 755-764

Author(s):

Hao Lin ◽

Haipeng Geng ◽

Tingchen Du ◽

Xiangming Xu ◽

Yanyan Zhang ◽

...

Keyword(s):

Permanent Magnet ◽

High Speed ◽

Permanent Magnet Synchronous Motor ◽

Synchronous Motor ◽

Foil Bearings

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Rotordynamics Performance of Hybrid Foil Bearing Under Forced Vibration Input

Volume 7A: Structures and Dynamics ◽

10.1115/gt2017-65233 ◽

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.

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

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.4034918 ◽

2016 ◽

Vol 139 (4) ◽

Cited By ~ 2

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.

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Compliant Foil Bearings Technology and Their Application to High Speed Turbomachinery

Tribology Series - Thin Films in Tribology, Proceedings of the 19th Leeds-Lyon Symposium on Tribology held at the Institute of Tribology, University of Leeds ◽

10.1016/s0167-8922(08)70411-5 ◽

1993 ◽

pp. 559-575 ◽

Cited By ~ 17

Author(s):

H. Heshmat ◽

P. Hermel

Keyword(s):

High Speed ◽

Foil Bearings

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Influence of geometric parameters on the bump foil bearing performance

Proceedings of the Institution of Mechanical Engineers Part J Journal of Engineering Tribology ◽

10.1177/1350650119887043 ◽

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.

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