# vol25no4pa2

TJES: Muhsin IA. The Effect of Pads Number and Their Tilt Angles on the Bearing  Stiffness. Tikrit Journal of Engineering Sciences 2018; 25 (4): 6-9.
APA: Muhsin, I. A. (2018). The Effect of Pads Number and Their Tilt Angles on the Bearing  Stiffness. Tikrit Journal of Engineering Sciences, 25(4), 6-9.

KeywordsTribology, tilted pads journal bearing, bearing stiffness and stability.

Tikrit Journal of Engineering Sciences (2018) 25(4) 6- 9 The Effect of Pads Number and Their Tilt Angles on the Bearing  Stiffness

 Ibrahim Ali Muhsin Mechanical Eng. Dept., College of Eng., Tikrit University/ Iraq.

Abstract

In this work a plain (conventional) and a tilted bad bearings are analyzed and studied (both have the same dimensions and work conditions). Three, four and five pads models are studied.  The pads are fixed circumferentially in a manner each two close pads are separated with an angle that is the same for all the close pads. Each pad is pivoted in its leading edge and is facilitated to be tilted around this pivot with small angles. This study was achieved for three values of tilting angles.  These angles are, 0.01o, 0.011o and 0.012o. Two dimensions’ form of Reynolds equation is used and solved numerically then the stiffness coefficients had been calculated. A comparison had been done between the stiffness coefficients values for the two models (tilted pads and conventional bearings). The results of this comparison was found that (for n = 0.4), are, +28%, +275%, +270 % and -100% for Ksr, Krr, Kss and Krs respectively.  It was noticed that the values of the principal coefficients Krr and Kss are increased significantly while the cross coupling coefficient, (Krs) is decreased significantly and (Ksr) is increased slightly. And this is a positive sign for stability improvement. Also it was found that increasing the tilt angle (delta) cause an increase of the stiffness coefficients values. These increases (for n = 0.4 and changing the tilt angle from 0.010 to 0.011 then to 0.012 respectively) are, Krr=+50%, +47%, Kss = +40%, +32%, Ksr = +33%, +42%, and Krs = +15%, +20%. And since increasing the values of the cross coupling coefficients make the bearing stability worse, so increasing the tilt angle is not a preferable method for improving stability. Changing the number of pads is a better solution and it was found that three pads bearing is the best among them.

## Download Full-Text PDF

References

   Qiu ZL. A theoretical and experimental study on dynamic characteristics of journal bearings.  Ph.D. Thesis: Wollongong University; Wollongong NSW 2522, Australia: 1995.

  Glienicke J, Han D-C, Leonhard M. Practical determin-ation and use of bearing dynamic coefficients. Tribology International 1980; 13 (6): 297-309.

  Balupari RS. Validation of finite element program for journal bearing static and dynamic properties.  MSc. Thesis. University of Kentuky; Lexington, USA: 2004.

  Andres L. Dynamics of a rigid rotor-fluid film bearing system.  MSc. Thesis. Texas A&M University; Texas, USA: 2000.

  Martelli F, Manfrida G. A new approach to the theoretical calculation of the dynamic coefficients of tilting-pad bearings. Wear 1981; 70 (2): 249-258.

  Majed RH. Load line direction and bearing length effects on the tilting 4-pad bearing performancePerformance. Engineering and Technol-ogy Journal 2009; 27 (9): 1691-1700.