A fully coupled air foil bearing model considering friction – Theory &amp; experiment

Osmanski, Sebastian von; Larsen, Jon Steffen; Santos, Ilmar

doi:10.1016/j.jsv.2017.04.008

Cited by 50 publications

(14 citation statements)

References 50 publications

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“…Although they DOI 10.2478/ama-2019-0001 Investigation of Gas Foil Bearings with an Adaptive and Non-Linear Structure 6 have a fairly simple construction ( Fig. 1), their operation is associated with physical phenomena whose experimental research requires advanced measurement techniques and computer-aided simulations should be conducted using sophisticated numerical models (von Osmanski et al, 2017). To improve the vibrationdamping capability of such bearings, additional elements in the form of thin foils are placed between the journal and the sleeve.…”

Section: Fig 1 the Exemplary Geometry Of The First-generation Foil mentioning

confidence: 99%

Investigation of Gas Foil Bearings With an Adaptive and Non-Linear Structure

Żywica

Bagiński

2019

Acta Mechanica Et Automatica

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The article discusses the results of simulation-based and experimental research carried out on gas foil bearings. Owing to the use of a set of flexible thin foils in such bearings, they exhibit certain beneficial features that cannot be found in other types of bearings. They have nonlinear operational characteristics and allow the dissipation of excess energy, thus reducing the vibration level. Moreover, gas foil bearings can self-adapt themselves to the current operating conditions by changing the shape of the lubrication gap. Therefore, they can be used to improve the dynamic performance of rotors, in particular, those operating at very high rotational speeds. This article explains the mechanisms for changes of stiffness and vibration damping in compliant components of a foil bearing. The results of the analysis of the bearing’s subassemblies using advanced numerical models are presented. They are followed by conclusions that were drawn not only from these results but also from the results of the experimental research. It has been proven that the rotor supported on carefully designed foil bearings is capable of maintaining a low vibration level, even if it operates at a high rotational speed.

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Section: Fig 1 the Exemplary Geometry Of The First-generation Foil mentioning

confidence: 99%

Investigation of Gas Foil Bearings With an Adaptive and Non-Linear Structure

Żywica

Bagiński

2019

Acta Mechanica Et Automatica

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“…When evaluating the displacement of the j-th foil DOF from its equilibrium w j0 , the stiffness and damping of the foil itself should furthermore be considered. Various elaborate foil structure models are available in the literature [4,15,18,22], but the added complexity of these would not benefit the present comparison. Instead, the Simple Elastic Foundation Model (SEFM), as introduced by Heshmat et al [5], is employed with a uniform baseline stiffness derived from the widely applied expression by Walowit and Anno [25]…”

Section: Including the Foil Stiffness And Dampingmentioning

confidence: 99%

The Classical Linearization Technique’s Validity for Compliant Bearings

Osmanski

Larsen²,

Santos

2018

Mechanisms and Machine Science

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The Gas Foil Bearing (GFB) is a promising and environmentally friendly technology allowing support of high-speed rotating machinery with low power loss and without oil or electronics. Unfortunately, GFBs provide limited damping, making an accurate prediction of the Onset Speed of Instability (OSI) critical. This has traditionally been assessed using linearised coefficients derived from the perturbed Reynolds Equation with compliance included implicitly. Recent work has, however, revealed significant discrepancies between OSIs predicted using these techniques and those observed from nonlinear analysis. In the present work, the perturbation method's underlying assumption on the pressure field is investigated by including the hitherto neglected pressurecompliance dependency directly. This leads to an extended perturbation akin to that commonly applied to tilting pad bearings and is shown to predict OSIs with much better agreement to time integration results. The extended perturbation method is cumbersome, but serves to highlight the error introduced when applying the classical perturbation method -as developed for rigid bearings by J. W. Lund -to GFBs.

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“…The calculation of the film thickness follows an iterative procedure with under-relaxation h nþ1 ðÞ ¼ h n ðÞ þ r hfilm h Ã ðÞ À h n ðÞ ðÞ (29) where h Ã ðÞ is the film thickness given by Eq. (28).…”

Section: The Foil Bearing Modelmentioning

confidence: 99%

“…However, the stiffness of the top foil was discarded. Similar structural models were next developed and some of them included the stiffness of the top foil [26][27][28][29][30].…”

Section: Introductionmentioning

confidence: 99%

A New Structural Bump Foil Model With Application From Start-Up to Full Operating Conditions

Arghir

Benchekroun

2019

Journal of Engineering for Gas Turbines and Power

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This paper presents a new structural bump foil model that can handle all operating conditions from start-up to full speed. The model is based on a nonlinear contact algorithm with friction and gaps. The top foil is modeled as a curved beam while bump foil uses a coupled truss model. The model considers the gaps between the bump foil and the bearing casing, between the bump foil and the top foil and between the rotor and the top foil. Thus, any numerical interference between the rotor and the top foil is avoided. A mixed lubrication model is used for the thin film pressures. Following this algorithm, contact pressures appear if the film thickness is less than three times the equivalent roughness of the rotor and of the top foil. Fluid pressures are calculated from numerical solutions of Reynolds equation while contact pressures, if present, are calculated with the model of Greenwood and Williamson. The model is validated by comparisons with the experimental results obtained for start-up operating conditions of a first-generation foil bearing of 38.1 mm diameter with static loads of 10–50 N. Theoretical predictions of the start-up torque and takeoff speed compare well with experimental results. It is also shown how manufacturing bump height errors can explain the differences between theoretical and experimental predictions. Further validations are presented for the same bearing operating at high speeds (30, 45, and 55 krpm) and heavy static loads (up to 200 N). The calculated minimum film thickness and attitude angle are compared with experimental data from the literature.

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A fully coupled air foil bearing model considering friction – Theory & experiment

Cited by 50 publications

References 50 publications

Investigation of Gas Foil Bearings With an Adaptive and Non-Linear Structure

Investigation of Gas Foil Bearings With an Adaptive and Non-Linear Structure

The Classical Linearization Technique’s Validity for Compliant Bearings

A New Structural Bump Foil Model With Application From Start-Up to Full Operating Conditions

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