Effects of shear stiffness in top foil structure on gas foil bearing performance based on thick plate theory

Fei, Xu; Liu, Zhansheng; Zhang, Guanghui; Cao, Zhixuan

doi:10.1177/1350650112468071

Cited by 19 publications

(12 citation statements)

References 17 publications

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“…A few studies that have already been conducted indicate that the top foil deflection plays an important role in determining the performance of GFTBs. 9,10,16,18,27 Hence, foil deflection must be considered in the structural model.…”

Section: Static Characteristics and Experimental Validationmentioning

confidence: 99%

Parametric study on static and dynamic characteristics of bump-type gas foil thrust bearing for oil-free turbomachinery

Feng

Liu

Guo

et al. 2015

Proceedings of the Institution of Mechanical Engineers, Part J:

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Gas foil bearings have bright application prospects in oil-free turbomachinery such as aircraft air cycle machines, compressors and gas turbines. To extend the applicability of foil bearings to high-speed and heavy-load systems, the axial force produced primarily by the pressure difference between the turbine and compressor sides must be taken into consideration. The thrust disc of the rotor is typically used to sustain the axial force and maintain the attitude of the rotor in a rotor-bearing system. In an analytical model used to predict the performance of gas foil thrust bearings (GFTBs), fluid–structure interaction must be considered because of the coupling effects of hydrodynamic lubrication and the compliance of bearing surface. In this study, a link-spring structural model was employed to calculate the equivalent vertical stiffness of the bump foil. This model exhaustively considered the effect of three factors: flexibility of the bump foil, interactions between bumps, and frictional forces at the contact surfaces. In addition, top foil deflection that directly affects film thickness is calculated using a finite-element shell model. The static and dynamic characteristics of GFTBs were predicted after solving the steady-state Reynolds equation and two linearized dynamic coefficient equations which were obtained with perturbation method by using finite-difference method. The structural deformation equation was substituted into the Reynolds equations in the calculation process. The calculated static load was compared with the published experimental data, and the results validated the theoretical analysis. Thereafter, the static and dynamic characteristics including impact of rotational speed, initial minimum film thickness and the ratio of the inlet to outlet film thicknesses were analyzed. Parametric studies were also conducted to evaluate the effect of different structural parameters of the bump foil and journal tilting on the static characteristics of GFTBs. Because the proposed analytical model is completely algebraic, it can be easily programmed for accurately and effectively investigating the performance of GFTBs.

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Section: Static Characteristics and Experimental Validationmentioning

confidence: 99%

Parametric study on static and dynamic characteristics of bump-type gas foil thrust bearing for oil-free turbomachinery

Feng

Liu

Guo

et al. 2015

Proceedings of the Institution of Mechanical Engineers, Part J:

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“…San Andres 13 analyzed the hydrodynamic performance of GFJB by integrating two different finite element models of top foil. Xu 14 discussed the effect of shear stiffness in the top foil structure based on a thick plate theory.…”

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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“…22 Many authors have presented AFB models with a structural model of the top foil. [23][24][25][26][27][28][29] These models have been used to investigate the influence of the top foil on the AFB performance. The most common studies are on the effects of top foil sagging, i.e.…”

Section: Introductionmentioning

confidence: 99%

Transient and steady state behaviour of elasto–aerodynamic air foil bearings, considering bump foil compliance and top foil inertia and flexibility: A numerical investigation

Nielsen

Santos

2017

Proceedings of the Institution of Mechanical Engineers, Part J:

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This work gives a theoretical contribution to the problem of modelling air foil bearings considering large sagging effects in the calculation of the non-linear transient and steady state response of a rigid rotor. This paper consists of two parts: the development of a miltiphysics model of the air foil bearing, and a numerical parameter study of a rigid journal supported in an air foil bearing with a partially supported top foil. The mathematical model of the air foil bearing is centred around the finite element models of both the air film and the top foil structure. These finite element models utilise two types of eight-node isoparametric elements. The rotor is modelled as a rigid body without rotational inertia, i.e. as a journal. The bump foil is included via a bilinear version of the simple elastic foundation model. This paper introduces the bilinear simple elastic foundation model, which combined with the top foil structure model, enables a separation of the top foil and the bump foil. A phenomenon associated within areas of the top foil is where the aerodynamic pressure is sub-ambient. The parameter study investigates the performance of three air foil bearings with partially supported top foils and one air foil bearing with a fully supported top foil. The steady state responses of a journal supported by these air foil bearings are investigated for varied rotational speeds and journal unbalances as well as the top foil sagging in the unsupported area. The study reveals that sub-harmonic vibrations associated with a large journal unbalance can be eliminated by a proper design layout of the bump foil, i.e. placement of the unsupported area. The positive effect is attributed to ‘equivalent shallow pockets’ formed by the sagging top foil.

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Effects of shear stiffness in top foil structure on gas foil bearing performance based on thick plate theory

Cited by 19 publications

References 17 publications

Parametric study on static and dynamic characteristics of bump-type gas foil thrust bearing for oil-free turbomachinery

Parametric study on static and dynamic characteristics of bump-type gas foil thrust bearing for oil-free turbomachinery

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

Transient and steady state behaviour of elasto–aerodynamic air foil bearings, considering bump foil compliance and top foil inertia and flexibility: A numerical investigation

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