Research Papers: Hydrodynamic Lubrication

On the Controllability and Observability of Actively Lubricated Journal Bearings With Pads Featuring Different Nozzle-Pivot Configurations

[+] Author and Article Information
Jorge G. Salazar

Department of Mechanical Engineering,
Technical University of Denmark,
2800 Kgs. Lyngby, Denmark
e-mail: jgsal@mek.dtu.dk

Ilmar F. Santos

Department of Mechanical Engineering,
Technical University of Denmark,
2800 Kgs. Lyngby, Denmark
e-mail: ifs@mek.dtu.dk

1Present address: Department of Mechanical Engineering, University of La Frontera, Temuco 4780000, Chile.

2Corresponding author.

Contributed by the Tribology Division of ASME for publication in the JOURNAL OF TRIBOLOGY. Manuscript received October 1, 2015; final manuscript received February 5, 2016; published online October 10, 2016. Assoc. Editor: Daejong Kim.

J. Tribol 139(3), 031702 (Oct 10, 2016) (17 pages) Paper No: TRIB-15-1356; doi: 10.1115/1.4033053 History: Received October 01, 2015; Revised February 05, 2016

The fundamental properties of an actively lubricated bearing (ALB) from a control viewpoint are investigated, i.e., the stability, controllability and observability. The ALB involves the addition of an oil injection system to the standard tilting-pad journal bearing (TPJB) to introduce constantly and/or actively high pressurized oil into the rotor-pad gap through, commonly, a single radial nozzle. For the work goal, a four degrees-of-freedom (DOFs) ALB system linking the mechanical with the hydraulic dynamics is presented and studied, comprising: (i) the vertical journal movement, (ii) the pad tilt angle, (iii) the vertical pad movement—due to the pivot flexibility, and (iv) the controllable force as the hydraulic DOF. The test rig consists of a rigid rotor supported by a single rocker-pivoted rigid pad. A thorough parametric study is carried out by investigating the effects of: (a) nozzle-pivot offset, (b) pivot flexibility, and (c) bearing loading on these control basics in order to determine the pad with the best control characteristics. Different nozzle-pivot offsets can be set by varying the positioning of either the injection nozzle or the pivot line. The influence of the pivot compliance on the bearing dynamics is assessed by benchmarking the results obtained with the flexible pivot against the rigid pivot. Three different bearing loads are studied. According to the results, the proposed configurations, especially the offset-pivot pad with slight offsets, improve the bearing control characteristics by introducing an extra mechanism to access the system states. The loading condition modifies the stability, controllability, and observability, while the pivot flexibility highly affects the ALB dynamics.

Copyright © 2017 by ASME
Your Session has timed out. Please sign back in to continue.


Santos, I. F. , 1994, “ Design and Evaluation of Two Types of Active Tilting Pad Journal Bearings,” The Active Control of Vibration, C. R. Burrows , and P. S. Keogh , eds., Mechanical Engineering Publications Limited, London, pp. 79–87.
Hagg, A. C. , 1946, “ The Influence of Oil-Film Journal Bearings on the Stability of Rotating Machines,” ASME J. Appl. Mech., 13(3), pp. A211–A220.
Santos, I. F. , 1995, “ On the Adjusting of the Dynamics Coefficients of Tilting-Pad Journal Bearing,” Trans. Tribol., 38(3), pp. 700–706. [CrossRef]
Santos, I. F. , and Russo, F. , 1998, “ Tilting-Pad Journal Bearing With Electronic Radial Oil Injection,” ASME J. Tribol., 120(3), pp. 583–594. [CrossRef]
Haugaard, A. M. , and Santos, I. F. , 2010, “ Elastohydrodynamics Applied to Active Tilting-Pad Journal Bearings,” ASME J. Tribol., 132(2), p. 021702. [CrossRef]
Cerda Varela, A. , Bjerregaard Nielsen, B. , and Santos, I. F. , 2013, “ Steady State Characteristics of a Tilting Pad Journal Bearing With Controllable Lubrication: Comparison Between Theoretical and Experimental Results,” Tribol. Int., 58, pp. 85–97. [CrossRef]
Cerda Varela, A. , and Santos, I. F. , 2015, “ Dynamic Coefficients of a Tilting Pad With Active Lubrication: Comparison Between Theoretical and Experimental Results,” ASME J. Tribol., 137(3), p. 031704. [CrossRef]
Santos, I. F. , and Scalabrin, A. , 2003, “ Control System Design for Active Lubrication With Theoretical and Experimental Examples,” ASME J. Eng. Gas Turbines Power, 125(1), pp. 75–80. [CrossRef]
Santos, I. F. , Nicoletti, R. , and Scalabrin, A. , 2004, “ Feasibility of Applying Active Lubrication to Reduce Vibration in Industrial Compressors,” ASME J. Eng. Gas Turbines Power, 126(4), pp. 848–854. [CrossRef]
Nicoletti, R. , and Santos, I. , 2003, “ Linear and Non-Linear Control Techniques Applied to Actively Lubricated Journal Bearings,” J. Sound Vib., 260(5), pp. 927–947. [CrossRef]
Nicoletti, R. , and Santos, I. , 2005, “ Frequency Response Analysis of an Actively Lubricated Rotor/Tilting-Pad Bearing System,” ASME J. Eng. Gas Turbines Power, 127(3), pp. 638–645. [CrossRef]
Nicoletti, R. , and Santos, I. , 2008, “ Control System Design for Flexible Rotors Supported by Actively Lubricated Bearings,” J. Vib. Control, 14(3), pp. 347–374. [CrossRef]
Varela, A. C. , and Santos, I. F. , 2014, “ Tilting-Pad Journal Bearings With Active Lubrication Applied as Calibrated Shakers: Theory and Experiment,” ASME J. Vib. Acoust., 136(6), p. 061010. [CrossRef]
Santos, I. F. , and Nicoletti, R. , 1999, “ THD Analysis in Tilting-Pad Journal Bearings Using Multiple Orifice Hybrid Lubrication,” ASME J. Tribol., 121(4), pp. 892–900. [CrossRef]
Santos, I. F. , and Nicoletti, R. , 2001, “ Influence of Orifice Distribution on the Thermal and Static Properties of Hybridly Lubricated Bearings,” Int. J. Solids Struct., 38(10), pp. 2069–2081. [CrossRef]
Haugaard, A. M. , and Santos, I. F. , 2010, “ Multi-Orifice Active Tilting-Pad Journal Bearings-Harnessing of Synergetic Coupling Effects,” Tribol. Int., 43(8), pp. 1374–1391. [CrossRef]
Haugaard, A. M. , and Santos, I. F. , 2010, “ Stability of Multi Orifice Active Tilting-Pad Journal Bearings,” Tribol. Int., 43(9), pp. 1742–1750. [CrossRef]
Salazar, J. G. , and Santos, I. F. , 2015, “ Exploring Integral Controllers in Actively-Lubricated Tilting-Pad Journal Bearings,” Proc. IMechE Part J, 229(7), pp. 835–848. [CrossRef]
Salazar, J. G. , and Santos, I. F. , 2015, “ Feedback-Controlled Lubrication for Reducing the Lateral Vibration of Flexible Rotors Supported by Tilting-Pad Journal Bearings,” Proc. IMechE Part J, 229(10), pp. 1264–1275. [CrossRef]
Springer, H. , 1980, Dynamic Characteristics of Sliding Bearings With Movable Segments, Vol. 381, VDI-Berichte, pp. 177–184.
Santos, I. F. , 1996, “ Theoretical and Experimental Identification of the Stiffness and Damping Coefficients of Active-Tilting Pad Journal Bearings,” Identification in Engineering Systems, M. Friswell , and J. Mottershead , eds., The Cromwell Press Ltd., Swansea, UK, pp. 325–334.
Dmochowski, W. , 2007, “ Dynamic Properties of Tilting-Pad Journal Bearings: Experimental and Theoretical Investigation of Frequency Effects Due to Pivot Flexibility,” ASME J. Eng. Gas Turbines Power, 129(3), pp. 865–869. [CrossRef]
Wilkes, J. , and Childs, D. , 2012, “ Tilting Pad Journal Bearings—A Discussion on Stability Calculation, Frequency Dependence and Pad and Pivot,” ASME J. Eng. Gas Turbines Power, 134, pp. 991–1006. [CrossRef]
San Andres, L. , and Tao, Y. , 2013, “ The Role of Pivot Stiffness on the Dynamic Force Coefficients of Tilting Pad Journal Bearings,” ASME J. Eng. Gas Turbines Power, 135(11), p. 112505. [CrossRef]
Wilkes, J. C. , and Childs, D. W. , 2013, “ Improving Tilting-Pad Journal Bearing Predictions Part II: Comparison of Measured and Predicted Rotor-Pad Transfer Functions for a Rocker-Pivot Tilting-Pad Journal Bearing,” ASME J. Eng. Gas Turbines Power, 135(1), p. 012503. [CrossRef]
Schweitzer, G. , Maslen, E. H. , and Keogh, P. , 2009, Magnetic Bearings, Springer, Berlin, Heidelberg.
Aguirre, L. A. , 1995, “ Controllability and Observability of Linear Systems: Some Noninvariant Aspects,” IEEE Trans. Educ., 38(1), pp. 33–39. [CrossRef]
Hendricks, E. , Jannerup, O. E. , and Sørensen, P. H. , 2005, Linear Systems Control, Technical University of Denmark, Lyngby, Denmark.
Hamdan, A. , and Nayfeh, A. , 1989, “ Measures of Modal Controllability and Observability for First- and Second-Order Linear Systems,” J. Guid. Control Dyn., 12(3), pp. 421–428. [CrossRef]
Park, U. S. , Choi, J. W. , Yoo, W.-S. , Lee, M. H. , Son, K. , Lee, J. M. , Lee, M. C. , and Han, S. H. , 2003, “ Optimal Placement of Sensors and Actuators Using Measures of Modal Controllability and Observability in a Balanced Coordinate,” KSME Int. J., 17(1), pp. 11–22. [CrossRef]
Laub, A. J. , Heath, M. T. , Paige, C. C. , and Ward, R. C. , 1987, “ Computation of System Balancing Transformations and Other Applications of Simultaneous Diagonalization Algorithms,” IEEE Trans. Autom. Control, 32(2), pp. 115–122. [CrossRef]
Junkins, J. L. , and Kim, Y. , 1991, “ Measure of Controllability for Actuator Placement,” J. Guid., Control, Dyn., 14(5), pp. 895–902. [CrossRef]
ISO/IEC, 2008, “ Guide to the Expression of Uncertainty in Measurement (GUM:1995),” ISO, Geneva, Switzerland, ISO/IEC Guide No. 98-3, p. 120.


Grahic Jump Location
Fig. 1

Scheme of a simplified ALB consisting of: a passive lubrication system, ⑤ low pressure pump + ③ sprinklers; an active lubrication system, ① high pressure pump + ② servovalve + ④ injection nozzles. Both lube systems are connected to the same ⑥ reservoir.

Grahic Jump Location
Fig. 2

Sketched view of the pad-injector section. ①: pad, ②: pivot, ③: injector, ④: housing body, ⑤: o-ring seal, and ⑥: nozzle conical inlet wall.

Grahic Jump Location
Fig. 3

Different tilting pads with pressurized oil injection nozzle: (a) offset-nozzle pad, Θnozzle<0.5, Θpivot=0.5, (b) centered-nozzle pad, Θnozzle=Θpivot=0.5, (c) offset-pivot pad, Θnozzle=0.5, Θpivot>0.5, and (d) comparison of an offset-nozzle pad with a centered-nozzle pad

Grahic Jump Location
Fig. 4

Three DOFs rigid rotor-single rigid pad system. Pad with rocker-pivot and injection nozzle. ξ: vertical journal movement; θ: pad tilt angle; and η: pad vertical displacement.

Grahic Jump Location
Fig. 5

Sensors placement for DOFs measuring: (a) measuring of journal displacement ξ, (b) measuring of pad tilt angle θ and pad vertical displacement η, and (c) measuring of controllable forcefc

Grahic Jump Location
Fig. 6

Root locus plot for the system under 1400 N

Grahic Jump Location
Fig. 7

ALB test rig with centered-nozzle pad. ①: servovalve, ②: AC motor, ③: electromagnetic shaker, ④: rotor, ⑤: levered arm, ⑥: load cell, and ⑦: displacement sensor (not seen).

Grahic Jump Location
Fig. 8

Comparison of theoretical (Theo) against experimental (Exp) FRFs of the system with pad #C under different loading conditions. Journal displacement as output variable, y1=ξ.

Grahic Jump Location
Fig. 9

Theoretical FRFs for all pads. Bearing applied load of 1400 N. △: pad #N2, □: pad #N1, ◯ : pad #C, ⋄: pad #P1, and ▽: pad #P2. Solid line (–): flexible pivot and dashed line (- -): rigid pivot.

Grahic Jump Location
Fig. 10

Comparison of pressure profiles and their circumferential centroids for the centered-nozzle pad. (a) Hydrodynamic pressure profile, (b) hydrodynamic + constant hydrostatic pressure profile, and (c) variable hydrostatic pressure profile. Injector placed at origin. Circumferential injector limits ± 1.7 deg.

Grahic Jump Location
Fig. 11

Stiffness and damping force coefficients for the ALB with different pads obtained under the studied operational condition. Bearing load of 1400 N; single pad configuration and flexible pivot.

Grahic Jump Location
Fig. 12

Calibration function for the hydraulic system under the studied operational conditions. Controllable force fc as a function of control signal u. ◇: 700 N of bearing load, κH = 95 N/V. ◯: 1400 N of bearing load, κH = 80 N/V. □: 2800 N of bearing load, κH = 70 N/V.

Grahic Jump Location
Fig. 13

Theoretical FRFs. Bearing applied load of 700 N. △: pad #N2, □: pad #N1, ◯: pad #C, ◇: pad #P1, ▽: pad #P2. Solid line (–): flexible pivot and dashed line (- -): rigid pivot.

Grahic Jump Location
Fig. 14

Theoretical FRFs. Bearing applied load of 2800 N. △: pad #N2, □: pad #N1, ◯: pad #C, ◇: pad #P1, ▽: pad #P2. Solid line (–): flexible pivot and dashed line (- -): rigid pivot.




Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In