Tilting-Pad Journal Bearings With Active Lubrication Applied as Calibrated Shakers: Theory and Experiment

Abstract

In recent years, a continuous research effort has transformed the conventional tilting-pad journal bearing (TPJB) into a mechatronic machine element. The addition of electromechanical elements provides the possibility of generating controllable forces over the rotor as a function of a suitable control signal. Such forces can be applied in order to perform parameter identification procedures “in situ,” which enables evaluation of the mechanical condition of the machine in a noninvasive way. The usage of a controllable bearing as a calibrated shaker requires obtaining the bearing specific frequency dependent calibration function, i.e., the transfer function between control signal and force over the rotor. This work presents a theoretical model of the calibration function for a TPJB with active lubrication. The bearing generates controllable forces by injecting pressurized oil directly into the bearing clearance. The injected flow is controlled by means of a servovalve. The theoretical model includes the dynamics of the hydraulic system using a lumped parameter approach, which is coupled with the bearing oil film using a modified form of the Reynolds equation. The oil film model is formulated considering an elastothermohydrodynamic lubrication regime. New contributions to the mathematical modeling are presented, such as the inclusion of the dynamics of the hydraulic pipelines and the obtention of the bearing calibration function by means of harmonic analysis of a linearized form of the controllable bearing constitutive equations. The mathematical model is used to study the relevance and effects of different parameters on the calibration function, aiming at providing general guidelines for the active bearing design. Finally, experimental results regarding the calibration function and the usage of the studied bearing as a calibrated shaker provide insight into the possibilities of application of this technology.

A 3D Approach for THD Lubrication in Tilting Pad Journal Bearing—Theory and Experiment

“…Varella [15] and Nielsen [16], and described in the following sections. The geometrical terms labeled on Fig.1 are the journal radius, the pad radius, ℎ 0 the assembled radial clearance of the bearing, ℎ the pad thickness, the pad tilt angle deflection, the angular position of the pivot, the pad length and the pad angular span.…”

“…Varela [15] incorporates improvements in the mechatronic system that controls the servo oil injection valves in the test system developed by Nielsen [16] and obtained a theoretical model considering TEHD lubrication and modeled…”

Active tilting-pad journal bearings supporting flexible rotors: Part I – The hybrid lubrication

“…which can be experimentally characterized or theoretically calculated as presented in [41]. This approach has been utilized in works such as [21,22,42].…”

Non-Invasive Parameter Identification in Rotordynamics via Fluid Film Bearings: Linking Active Lubrication and Operational Modal Analysis

“…The idea of using controllable fluid film bearings as a "non-invasive calibrated shaker" to aid rotordynamic testingsimilar to the usage of active magnetic bearings [32][33][34][35][36] -was first mentioned in [4], preliminarily exploited in [37] and more deeply investigated in [38]. In [38] the experimental characterization of the active fluid film forces were carried out in the frequency domain using a pair of actively lubricated tilting-pads. The application of ALBs as a calibrated shaker with the goal of determining the frequency response function (FRF in m/N) of a rotordynamic system was demonstrated.…”

“…The majority of the results shown in the literature focus on vibration control [5][6][7], enhancement of bearing damping properties [26], compensation of cross coupling effects [27], enlargement of stability range of rigid [21] and flexible rotors [24,27], and compensation of thermal effects [28][29][30][31]. The idea of using controllable fluid film bearings as a "non-invasive calibrated shaker" to aid rotordynamic testingsimilar to the usage of active magnetic bearings [32][33][34][35][36] -was first mentioned in [4], preliminarily exploited in [37] and more deeply investigated in [38]. In [38] the experimental characterization of the active fluid film forces were carried out in the frequency domain using a pair of actively lubricated tilting-pads.…”