Attenuation of the Amplitude Vibration Level by Using Nonlinear Active Control Techniques Applied to a Hybrid Short Journal Bearing Using a Particular Rotor-Bearing System Configuration

Results of theoretical investigations on stability characteristics of an actively controlled hydrodynamic journal bearing are presented. Proportional, derivative and integral controls are adopted for a hydrodynamic journal bearing with an axial groove. Furthermore, a cavitation algorithm, implementing the Jakobsson-Floberg-Olsson boundary condition, is adopted to predict cavitation regions in a fluid film more accurately than the conventional analysis, which uses the Reynolds condition. Using the bearing's linear dynamic coefficients, which are evaluated from the perturbation method, the stability characteristics of a rotor-bearing system are investigated using the Routh-Hurwitz criteria. It is shown that the instability threshold speed of a rotor-bearing system can be greatly increased and the unbalanced responses of the system can be markedly decreased by both proportional and derivative control of the bearing. Results show that active control of a hydrodynamic journal bearing can be adopted for stability improvement and reduction of the unbalanced whirl amplitude of a rotor-bearing system.

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Nonlinear Dynamics of Flexible Rotors Supported on Journal Bearings—Part I: Analytical Bearing Model

Journal of Tribology ◽

10.1115/1.4037730 ◽

2017 ◽

Vol 140 (2) ◽

Cited By ~ 3

Author(s):

Mohammad Miraskari ◽

Farzad Hemmati ◽

Mohamed S. Gadala

Keyword(s):

Journal Bearing ◽

Nonlinear Coefficient ◽

Journal Bearings ◽

Flexible Rotor ◽

Dynamic Coefficients ◽

Flexible Rotors ◽

Rotor Bearing ◽

Bearing Force ◽

Derivatives Of ◽

Bearing System

To determine the bifurcation types in a rotor-bearing system, it is required to find higher order derivatives of the bearing forces with respect to journal velocity and position. As closed-form expressions for journal bearing force are not generally available, Hopf bifurcation studies of rotor-bearing systems have been limited to simple geometries and cavitation models. To solve this problem, an alternative nonlinear coefficient-based method for representing the bearing force is presented in this study. A flexible rotor-bearing system is presented for which bearing force is modeled with linear and nonlinear dynamic coefficients. The proposed nonlinear coefficient-based model was found to be successful in predicting the bifurcation types of the system as well as predicting the system dynamics and trajectories at spin speeds below and above the threshold speed of instability.

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Nonlinear Vibration Prediction of a Highly Flexible Rotor Supported by an Axial Groove Journal Bearing Considering Journal Angular Whirling Motion

Volume 7B: Structures and Dynamics ◽

10.1115/gt2019-90951 ◽

2019 ◽

Author(s):

Nuntaphong Koondilogpiboon ◽

Tsuyoshi Inoue

Keyword(s):

Nonlinear Vibration ◽

Ball Bearing ◽

Journal Bearing ◽

Flexible Rotor ◽

Large Disk ◽

Subcritical Bifurcation ◽

Whirling Motion ◽

Vibration Prediction ◽

Rotor Bearing ◽

Bearing System

Abstract In this study, the difference in dynamic behavior of the rotor-bearing system supported by the bearing model that considers both lateral and angular whirling motions of the journal (model A), and the model that considers only lateral whirling motion (model B) is investigated. The rotor model consists of a slender shaft, a large disk and two small disks supported by a self-aligning ball bearing and an axial groove journal bearing of L/D = 0.6. Three positions of the large disk: 410, 560, and 650 mm measured from the ball bearing, are investigated. Numerical integration of the rotor-bearing system which is modally reduced to the 1st forward mode is performed at above the onset speed of instability until either a steady state journal orbit or contact between the journal and the bearing occurs to identify the bifurcation type. Numerical results using model A indicate subcritical bifurcation with the contact between the journal and the inboard side of the bearing in all three large disk positions, whereas those of model B indicate subcritical bifurcation when the large disk position is at 410 mm, and supercritical bifurcation is observed in the other two cases. Lastly, the experiments at the same three large disk positions are performed. Subcritical bifurcation with the contact between the journal and the inboard side of the bearing is observed in all large disk positions, which conforms with the calculation result of model A. As a result, model A is essential in nonlinear vibration analysis of a highly flexible rotor system.

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Nonlinear Dynamics Analysis of Tilting Pad Journal Bearing-Rotor System

Shock and Vibration ◽

10.1155/2011/213742 ◽

2011 ◽

Vol 18 (1-2) ◽

pp. 45-52 ◽

Cited By ~ 3

Author(s):

Jiayang Ying ◽

Yinghou Jiao ◽

Zhaobo Chen

Keyword(s):

Nonlinear Dynamics ◽

System Dynamics ◽

Journal Bearing ◽

Rotor System ◽

Moment Of Inertia ◽

Dynamics Analysis ◽

Tilting Pad ◽

Rotor Bearing ◽

Tilting Pad Journal Bearing ◽

Bearing System

The nonlinear dynamics theory is increasingly applied in the dynamics analysis of tilting pad journal bearing-rotor system. However, extensive work on system dynamics done previously neglects the influence caused by the moment of inertia of the pad. In this paper, a comparison is made between the responses of the rotor in the bearings with and without pad inertia effect. Taking the Jeffcott rotor system as an example, the characteristics of bearing-rotor system, such as bifurcation diagram, cycle response, frequency spectrum, phase trajectories, and Poincaré maps, were attained within a certain rotation rate range. The pivotal oil-film force of tilting pad journal bearing was calculated by database method. The results directly demonstrate that considering the influence of the pad moment of inertia, system dynamics characteristics are found more complicated when rotor-bearing system works around natural frequency and system bifurcation is observed forward when rotor-bearing system works on high-speed range.

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Dynamic Behaviors of a Rotor-Bearing System under Base-Transferred Shock Excitations Considering Journal-Bearing Clearance

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.29-32.703 ◽

2010 ◽

Vol 29-32 ◽

pp. 703-708 ◽

Cited By ~ 1

Author(s):

Shao Hua He ◽

Ping Hao Zhang ◽

Xin Yue Wu

Keyword(s):

Journal Bearing ◽

Inhibitory Effect ◽

Time Varying ◽

Transient Responses ◽

Oil Film ◽

The Past ◽

Bearing Clearance ◽

Rotor Bearing ◽

Residual Response ◽

Bearing System

The past researches on the transient responses of rotor-bearing systems under shock excitations paid little attention on impact-contact-rub forces which would arise when taking journal- bearing clearance into account, and these forces’ influences on the overall responses remain unknown until now. In this paper, models of impact-contact force, rub force and oil-film force in a rotor-bearing system were built respectively. Numerical calculation was performed to obtain time-varying responses of those forces while the system suffers base-transferred shock excitations. Influences of those forces on system overall responses were investigated. The main conclusion is that the rub force has no obvious influence on the system responses during shock lasting time, whereas it shows an obvious inhibitory effect on the residual response, making time-varying amplitudes be smoother. Rub force maybe bigger in x direction than in y direction although shock energy in x direction is less than in the y direction. Influences of the oil-film force on response is similar to that of rub force but more severely. It has obvious influences on overall responses both during shock lasting time and residual time.

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Journal Bearing Rotor Speed Effect on Dynamics Coefficients and Film Pressure

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.274.320 ◽

2013 ◽

Vol 274 ◽

pp. 320-323

Author(s):

Nai Wen Hu ◽

Guang Bin Yu ◽

Xue Mei Wu ◽

Chang Sheng Hu ◽

Zhi Gang Qu ◽

...

Keyword(s):

Thermal Instability ◽

Journal Bearing ◽

Pressure Effect ◽

Rotor Speed ◽

Film Pressure ◽

Dynamic Coefficients ◽

Rotor Bearing ◽

Speed Effect ◽

Analytical Expressions ◽

Bearing System

The dynamic coefficients and film pressure effect in rotor-bearing systems may lead to an unstable station. The mechanism of the dynamic coefficients and film pressure induced thermal instability in the rotor-bearing system has been studied. The journal bearing model is adopted for the derivation of analytical expressions. The results show that the rotor speed has some effect on bearing dynamic coefficients and film pressure.

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Nonlinear Vibration Prediction of a Highly Flexible Rotor Supported by an Axial Groove Journal Bearing Considering Journal Angular Whirling Motion

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.4044761 ◽

2020 ◽

Vol 142 (4) ◽

Author(s):

Nuntaphong Koondilogpiboon ◽

Tsuyoshi Inoue

Keyword(s):

Nonlinear Vibration ◽

Journal Bearing ◽

Rolling Element Bearing ◽

Flexible Rotor ◽

Large Disk ◽

Subcritical Bifurcation ◽

Whirling Motion ◽

Vibration Prediction ◽

Rotor Bearing ◽

Bearing System

Abstract The difference in dynamic behavior of the rotor-bearing system supported by the bearing model that considers both lateral and angular whirling motions of the journal (model A), and the model that considers only lateral whirling motion (model B) is investigated. The rotor model consists of a slender shaft, a large disk, and two small disks supported by a self-aligning rolling element bearing (REB) and an axial groove journal bearing (JB) of length-to-diameter ratio (L/D) = 0.6. Three positions of the large disk: 410, 560, and 650 mm measured from the REB, are investigated. Numerical integration of the rotor-bearing system which is modally reduced to the first forward (FWD) mode is performed at above the onset speed of instability until either a steady-state journal orbit or contact between the journal and the bearing occurs to identify the bifurcation type. Numerical results using model A indicate subcritical bifurcation with the contact between the journal and the inboard (IB) side of the bearing in all three large disk positions, whereas those of model B indicate subcritical bifurcation when the large disk position is at 410 mm, and supercritical bifurcation is observed in the other two cases. Finally, the experiments at the same three large disk positions are performed. Subcritical bifurcation with the contact between the journal and the IB side of the bearing is observed in all large disk positions, which conforms with the calculation result of model A. Hence, model A is essential in nonlinear vibration analysis of a highly flexible rotor system.

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Nonlinear Vibration Analysis of a Flexible Rotor Supported by a Journal Bearing Considering Journal Angular Motion

Volume 8: 31st Conference on Mechanical Vibration and Noise ◽

10.1115/detc2019-97404 ◽

2019 ◽

Author(s):

Nuntaphong Koondilogpiboon ◽

Tsuyoshi Inoue

Keyword(s):

Nonlinear Vibration ◽

Ball Bearing ◽

Journal Bearing ◽

Angular Motion ◽

Experimental Result ◽

Flexible Rotor ◽

Large Disk ◽

Rotor Bearing ◽

Bearing Force ◽

Bearing System

Abstract The effect of bearing length to diameter (L/D) ratio and large disk position on nonlinear vibration (limit cycle and bifurcation type) of a flexible rotor-bearing system is investigated. The rotor consists of a shaft modeled by 1-D finite elements (FE), two small disks and a large disk. It is supported by a self-aligning ball bearing and an axial-groove journal bearing with L/D ratio of 0.4 and 0.6. Two large disk positions: 340 and 575 mm measured from the ball bearing are investigated. The journal angular motion, which is essential for the highly flexible rotor but typically not considered in the previous nonlinear vibration literature; is considered in nonlinear bearing force calculation. The degrees of freedom (DOF) of the rotor-bearing system are reduced to those of the node that the nonlinear journal bearing force and moment act on by real mode component mode synthesis (CMS) that retains only the 1st forward and backward modes. Shooting method and Floquet multiplier analysis are applied to the reduced rotor-bearing system to obtain limit cycles and their stability of each bearing L/D ratio and large disk position case. Numerical results indicate that supercritical Hopf bifurcation only occurs in the case of L/D = 0.4 and large disk position 575 mm, otherwise subcritical occurs. However, if the typical bearing model that does not consider journal angular motion is used, the bifurcation type for the case of L/D = 0.6 with large disk position 575 mm will change to supercritical. Lastly, the experiments with the same L/D ratio and large disk position investigated in the calculation are performed as a validation. The experimental result of each case shows the same bifurcation type as the calculation result using the bearing model that considers the journal angular motion.

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Active control of multi-input hydraulic journal bearing system

Journal of Physics Conference Series ◽

10.1088/1742-6596/744/1/012062 ◽

2016 ◽

Vol 744 ◽

pp. 012062

Author(s):

Jen-Chen Chuang ◽

Chi-Yin Chen ◽

Jia-Ying Tu

Keyword(s):

Active Control ◽

Journal Bearing ◽

Bearing System

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Experimental Measurements of Actively Controlled Bearing Damping With an Electrorheological Fluid

Volume 4: Manufacturing Materials and Metallurgy; Ceramics; Structures and Dynamics; Controls, Diagnostics and Instrumentation; Education; IGTI Scholar Award; General ◽

10.1115/99-gt-017 ◽

1999 ◽

Cited By ~ 1

Author(s):

John M. Vance ◽

Daniel Ying

Keyword(s):

Active Control ◽

Electrical Power ◽

Companion Paper ◽

Squeeze Film ◽

Control Logic ◽

Response Curves ◽

Rotor Bearing ◽

Er Damper ◽

Er Fluid ◽

Bearing System

Selection criteria and design evaluations of several types of bearing dampers with active control for application to aircraft engines were described in a companion paper (Vance, Ying, and Nikolajsen, 1999). A disk type electrorheological (ER) damper was chosen for further study and testing. The results of the tests and the final conclusions of the study are described in this paper. Experimental results including stiffness and damping coefficients are presented for the ER bearing damper with two types of ER fluid, 350 CS and 10 CS (centistokes) viscosity. The vibration attenuation performance of the ER damper was measured on a rotordynamic test rig in the form of free vibration decay, rotor orbits, and runup unbalance responses. The results show that the ER fluid with lower viscosity has the better characteristics for rotordynamic applications. It was found that ER fluids produce both Coulomb and viscous damping. If only the damping is considered, the Coulomb type is less desirable, but with active control it can also achieve control of rotor stiffness as analyzed in Vance and San Andres (1999). A feedback control system was developed and applied to the ER damper with the objective of improving the overall rotordynamic performance of the rotor bearing system, considering both vibration amplitudes and dynamic bearing forces. A “bang-bang” (on and off) simple control logic was found to work better in practice than more sophisticated schemes. The measured runup responses of the rotor-bearing system with this control approximated the desired vibration response curves fairly well. The tests highlighted some of the practical considerations that would be important for aircraft engine applications, such as the ER fluid limitations, the electrical power supply requirements, the electrical insulation requirements, the nonlinear relationship between the voltage and the damping, and the relative benefits of active control. It is concluded that active control of bearing damping is probably not a practical improvement over the passive squeeze film dampers currently used in most aircraft gas turbine engines.

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