A comparison of modal analyses of foil-air bearing rotor systems using two alternative linearisation methods

Bonello, Philip; Pourashraf, T.

doi:10.1016/j.ymssp.2021.108714

Cited by 13 publications

(3 citation statements)

References 24 publications

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“…Discrepancies between this OSSV and the OSSV obtained by transient analysis have been reported [14,15]. Additionally, Bonello and Pourashraf [16] have shown the inability of Lund's method to detect certain instabilities due to the omission of state variables associated with the foil and air film domains. In 2014, Bonello and Pham [17] presented a model which allows the simultaneous solution of the governing equations.…”

Section: Introductionmentioning

confidence: 85%

A Numerical Analysis of the Nonlinear Dynamics of Shimmed Conical Gas Foil Bearings

Sarrazin

Liebich

2023

Applied Sciences

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Conical gas foil bearings (CGFBs) have the potential to halve the number of necessary bearings in a conventional rotor system supported by gas foil bearings. Transient simulations of gas foil journal bearings and gas foil thrust bearings have proven their necessity to accurately predict the safe operating range of such bearings. This work presents the first transient model able to simulate the three-dimensional dynamics of CGFBs. The static behaviour of a single CGFB with a uniform bearing clearance is compared to a CGFB modified by thin metal shims and the resulting advantages of shimmed CGFBs are discussed. An investigation of the linear stability behaviour shows that the axial load of the bearing determines the stability of the equilibrium position. Furthermore, three transient simulations demonstrate the capability of the presented model to describe the nonlinear dynamics of a shimmed CGFB such as the occurrence of stable limit cycles and self-excited sub- and super-synchronous vibrations with and without a rotor unbalance. Additionally, waterfall diagrams are used to investigate the frequency response for different rotational speeds. The novel findings of this work are the importance of a non-uniform bearing clearance for the functionality of a CGFB and the identification of the axial force as a critical factor in maintaining bearing stability. These findings are specific to CGFBs and have not been discussed or mentioned in previous works.

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Section: Introductionmentioning

confidence: 85%

A Numerical Analysis of the Nonlinear Dynamics of Shimmed Conical Gas Foil Bearings

Sarrazin

Liebich

2023

Applied Sciences

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“…The study concludes that predicting modal properties in different cases is closely related to direct linearization. In literature, 19 the low dynamic viscous coefficient of air means that airfoil bearings offer limited damping at high speeds and may be susceptible to hydrodynamic instability. Therefore, it is necessary to perform dynamic design and analysis to ensure safe rotor operation.…”

Section: Introductionmentioning

confidence: 99%

Identification of dynamic coefficients of gas foil bearings by simulated excitation based on coupled fields

Cheng,

Zhu,

et al. 2024

Advances in Mechanical Engineering

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The dynamic coefficients (dynamic stiffness coefficient and dynamic damping coefficient) of gas foil bearings (GFBs) are important for transient dynamics calculation and stability analysis of the GFBs-rotor system. Although the perturbation method can be used to calculate the dynamic coefficients, it can only consider a single whirl ratio. Moreover, the whirl ratio is assumed and not practical. Therefore, this paper proposes an identification method of dynamic coefficients of GFBs by simulated excitation. Firstly, based on single journal-single GFB model considering gas-structure interaction by coupled fields, harmonic excitations were applied to the rotor to obtain the shaft orbit. Next, frequency response function method and equivalence coefficient method were used to identify dynamic coefficients. The former method is suitable for the case where response and excitation are same frequency, namely linear problem. The latter method is fit for the situation in which the response has multiple frequency components, namely nonlinear problem. Finally, examples were carried out, and the results from different methods were compared and analyzed. This research work lays a theoretical foundation for the design of the GFBs-rotor system.

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“…This method enables the dynamic coefficient method to obtain the onset instability speed results consistent with the time-domain method. Bonello and Pourashraf [21] showed that the modal analysis of a rotor supported by an air foil bearing using the bearing dynamic coefficient method has good accuracy in comparison with the direct linearization method proposed in [22].…”

Section: Introductionmentioning

confidence: 99%

Calculation of Dynamic Coefficients of Air Foil Journal Bearings Using Time-Domain Identification

Feng

Liu

et al. 2023

Lubricants

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Dynamic coefficients of a bearing are basic elements of rotor dynamics analysis. At present, there are still some issues in the calculation of the dynamic coefficient of air foil bearing. In this paper, the dynamic coefficients of the air foil bearing are calculated by time-domain identification. This method does not need to linearize the system equations, so it is generally applicable to different models for air foil bearings. Using the established method, this paper verified the calculation results using the foil model with axial uniform deformation for the first time, and the influence of the foil model on the dynamic coefficients was studied. The calculation results of the foil models with axial uniform deformation and axial independent deformation have significant differences. Furthermore, the accuracy of the dynamic coefficient method for different disturbance amplitudes was compared. The results indicate that the dynamic coefficient method has good accuracy over a large disturbance range.

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A comparison of modal analyses of foil-air bearing rotor systems using two alternative linearisation methods

Cited by 13 publications

References 24 publications

A Numerical Analysis of the Nonlinear Dynamics of Shimmed Conical Gas Foil Bearings

A Numerical Analysis of the Nonlinear Dynamics of Shimmed Conical Gas Foil Bearings

Identification of dynamic coefficients of gas foil bearings by simulated excitation based on coupled fields

Calculation of Dynamic Coefficients of Air Foil Journal Bearings Using Time-Domain Identification

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