Gas turbine rotor imbalance due to the effect of the added mass of the oil layer in the plain bearing

Аuthors

Dunaev V. I.^1*, Bataev A. V.^2**, Stepanov M. S.^1***

1. Kuban State Technological University, Krasnodar, Russia
2. Branch of the Maykop State Technological University in the village of Yablonovsky, Republic of Adygea, Russia

*e-mail: dunayev1964@bk.ru
**e-mail: alex.bunyakin@mail.ru
***e-mail: m.s.stepanov@mail.ru

Abstract

In technical diagnostics of turbomachines, the problem of analyzing their vibration spectrum arises. One must identify and numerically evaluate the dynamic impact magnitudes and frequencies of each component, which together constitute the entire vibration spectrum. Since plain bearings are installed in turbomachines, both in the drive and in the centrifugal compressor, the dynamics of oil film flow between the shaft and the bearing shell is of interest. The oil flow velocity is close to the peripheral velocity at the shaft surface (over ten meters per second), while the shaft displacement amplitude is tens of microns, comparable to the oil film thickness. Therefore, the added mass effect (in the aero-hydro-elastic approximation) during shaft “floating” in the lubricating layer is very significant and contributes to the overall vibration background. The paper presents modeling results and numerical estimates of this effect. The model assumptions isolate this effect by neglecting viscosity and compressibility of the lubricating layer (ideal fluid approximation). The cyclic imbalance caused by the added mass effect produces shear stresses in the bearing shell, accumulating fatigue damage and reducing bearing service life.

Keywords:

plain bearing diagnostics; oil film hydrodynamics; added mass effect; turbomachine rotor imbalance

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