Rotordynamic Analysis of an Oil-Free Turbocharger Supported on Lobed Gas Foil Bearings—Predictions versus Test Data

Sim, Kyuho; Lee, Yongbok; Kim, Tae Ho

doi:10.1080/10402004.2014.937885

Cited by 27 publications

(21 citation statements)

References 17 publications

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“…And the representative ones among them are the GFJBs supported by double-layer bump foil, 16 circumferential separated bump foil, 17 three-pitch tile foil, 18 and bump foil with variational stiffness. 19 From the point of applying mechanical preload, the multiwedged GFJB, 20 GFJB with thin shims, 21,22 and GFJB with flexure pivot tilting pads 23 were invented. Since the modified bump foil usually means the higher manufacturing cost, the introduction of metal shims is a cheap and effective way to improve the performance.…”

Section: Introductionmentioning

confidence: 99%

Study on the performance of gas foil journal bearings with bump-type shim foil

Feng

Ren

2020

Proceedings of the Institution of Mechanical Engineers, Part J:

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The upscaling of turbomachinery using gas foil journal bearings (GFJBs) is limited because of their limited load capacity and dynamic stability. The improvement potential of shim foil inserted under the bump foil of such bearings is investigated in terms of better bearing performance. The arch height difference Δ hb between the shim foil and bump foil can be zero or not to attain the different effect. By considering the local hardening structural stiffness and an Initial installation clearance due to the shim foil, the static and dynamic characteristics of the novel bearing were calculated through the finite difference method (FDM) and perturbation method, respectively. In the analysis, a modified bump stiffness model considering the variable foil thickness was established, and a 2 D thick plate model was adopted for the top foil. The characteristics of novel GFJB with and without preload were compared with the traditional bearing. The results indicate that the load capacity and direct stiffness of the novel GFJB with shim foil can be increased largely, especially when there is a preload (Δ hb≠0). And the improvement is reinforced as the increment of Δ hb. Moreover, the stability threshold speed ( STS) of rotor supported by the novel GFJBs is enhanced by the preload, which means better stability. In addition, an air compressor test has also been conducted to verify the improved supporting performance of novel bearings. Based on this study it is convinced that the addition of shim foil under a GFJB's bump foil can be of practical interest in the quest of enhanced load capacity and dynamic stability. Moreover, the installation of shim foil is not affected by the working environment and could even be retrofited on the existing GFJBs.

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Section: Introductionmentioning

confidence: 99%

Study on the performance of gas foil journal bearings with bump-type shim foil

Feng

Ren

2020

Proceedings of the Institution of Mechanical Engineers, Part J:

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“…For decades, many literatures have been published to study the influence of waviness error on the sliding bearings (Hargreaver, 1991; Hassan, 1998; Iwamoto and Tanaka, 2005; Wubin et al , 2015; Lukas et al , 2017; Jian et al , 2018; Ma et al , 2019), but few studies have been conducted on the foil bearings. Sim et al (2014) compared the traditional and three-lobe journal foil bearing on an oil-free turbocharger, and found that the changed film thickness caused by non-circular wedge greatly affected the rotor dynamic performance. However, the relevant research on GFCB based on the manufacturing roundness error is still lacking, so the influence law is studied systematically in this paper.…”

Section: Introductionmentioning

confidence: 99%

Effect of roundness error on the performance of novel gas foil conical bearings

Feng

Ren

2020

ILT

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Purpose The purpose of this paper is to study the effect law of roundness error on the properties of gas foil conical bearing (GFCB), and the performance of bearings with different non-circular sleeve shapes are calculated. Design/methodology/approach For the bump-type GFCB, the nonlinear bump foil stiffness model and 1-D beam top foil stiffness model are built. On this basis, the finite element method and finite difference method are used to solve the Reynolds equation and the film thickness equation coupled, and the static and dynamic properties of GFCB are calculated. The effect law of sleeve roundness error on the static performance under different conditions is obtained. Moreover, the dynamic stiffness and damping characteristics under different errors are also studied. Findings The roundness error will decrease the load capacity and friction torque of GFCB, and increase the attitude angle. The error effect is more dramatic when there is larger eccentric, small nominal clearance, larger error value and more error lobes, and the static performance exhibits a periodic change in the circumferential direction. The roundness error can also decrease the direct stiffness and cross-coupled damping of GFCB, while the cross-coupled stiffness increases largely, which will reduce the bearing stability. Originality/value The roundness error adversely affects the static and dynamic characteristics of GFCB, which should be concerned by bearing designers, researchers and academicians. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-01-2020-0019/

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“…At present, domestic and foreign scholars have conducted a significant amount of theoretical research on the nonlinear stability and dynamic characteristics of gas bearings (10,11) . Owing to the assumptions of the lubrication theory model and simplification of the calculation model, the theoretical calculation method cannot accurately reflect the nonlinear coupling relationship between the dynamic pressure and static pressure diffusion effects of gas bearings (12)(13)(14) . The combination of theoretical calculations and experimental tests is also scarce in the research, which results in the calculation of the dynamic bearing capacity and stiffness damping of the gas film deviating from the true value, and therefore large errors (11,15,16) .…”

Section: Introductionmentioning

confidence: 99%

Study on dynamic characteristics of gas films of spherical spiral groove hybrid gas bearings

Cui

Zhang

Guo

et al. 2019

Proceedings of the Institution of Mechanical Engineers, Part J:

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According to the gas film force variation law, when the bearing axis is slightly displaced from the static equilibrium position, displacement and velocity disturbance relation expressions for the gas film force increment are constructed. Moreover, combined with the bearing rotor system motion equation, calculation model equations for the gas film stiffness and damping coefficients are established. The axial and radial vibration and velocity of the gas bearings during operation are collected. The instantaneous stiffness and damping coefficients of the gas film are calculated by the rolling iteration algorithm using MATLAB. The dynamic changes in the gas film stiffness and damping under different motion states are analyzed, and the mechanism of the gas film vortex and oscillation is studied. The results demonstrate the following: (1) When the gas bearing is running in the linear steady state in cycle 1, the dynamic pressure effect is enhanced and the stability is improved by increasing the eccentricity; when the gas supply pressure is increased, the static pressure effect is enhanced and the gas film vortex is reduced, but the oscillation is strengthened. (2) With the increase in rotational speed, the gas film vortex force gradually exceeds the gas film damping force, and the stability gradually worsens, causing a fluctuation in the gas film stiffness and damping, following which singularity occurs and a half-speed vortex is formed. Meanwhile, the gas film oscillation is intensified, and the rotor enters the nonlinear stable cycle 2 state operation. (3) As the fluctuation of the film force increases, the instantaneous stiffness and damping oscillation of the film intensifies, most of the stiffness and damping coefficients exhibit distortion, and the rotor operation will enter a chaotic or unstable state. Therefore, the gas bearing stiffness and damping variation characteristics can be used to study and predict the gas bearing operating state. Finally, measures for reducing the vortex and oscillation of the gas film and improving the stability of the gas bearing operation are proposed.

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Rotordynamic Analysis of an Oil-Free Turbocharger Supported on Lobed Gas Foil Bearings—Predictions versus Test Data

Cited by 27 publications

References 17 publications

Study on the performance of gas foil journal bearings with bump-type shim foil

Study on the performance of gas foil journal bearings with bump-type shim foil

Effect of roundness error on the performance of novel gas foil conical bearings

Study on dynamic characteristics of gas films of spherical spiral groove hybrid gas bearings

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