1 University of technology, Electromechanical Engineering Department, Baghdad, Iraq.

2 University of Baghdad, College of Engineering, Aeronautical Engineering Dept. Baghdad, Iraq.

3 Ministry of Higher Education and Scientific Research ,Studies and Planning and Follow Up Directorate Baghdad, Iraq.


Improving the essential factors of rotor bearing system are the aim of this study. In addition to the presence of two ball bearings to support the rotor, two additional fluid film journal bearings have been used as an external damping sources. The ANSYS Mechanical APDL 18.0 was used to model rotor bearing system with existence of two additional fluid film journal bearings. Matlab software has been used to achieve the analytical solution. The results clearly showed that the maximum response displacement strongly decreasing and the critical speed has been enhance by using an external damping source as well as the stability of rotor bearing system has been improved due to increasing damping of rotor system where the response displacement decreasing by 99% and critical speed increasing by 0.6% when using an external damping sources. The position of damping source has an important effect on the maximum response displacement and the more decreasing value of response displacement has been achieved when the damping source become as close as possible to the disk position.


[1].Y. Kang, Y. P. Chang, J.W. Tsai, L.H. Mu and Y. F. Chang,” An investigation in stiffnesseffects on dynamics of rotor-bearing-       foundation systems”,  doi:10.1006/jsvi.1999.2719, Journal of Soundand vibration, 231(2), 343-374, 2000.
[2] J. A. Vazquez, L. E. Barrett and R. D. Flack,   “Including the Effects of Flexible Bearing Supports in Rotating Machinery”, International       Journal of Rotating Machinery, Vol. 7, No. 4,  pp. 223-236, 2001.
[3] D. P. Fleming , J. T. Sawicki , J.V. Poplawski” Unbalance response prediction for  accelerating rotors with load-dependent  nonlinear bearing stiffness”, NASA/TM-2005-      213801, 2005
[4] G. S. Navarro, F. L. Medina and A. C. Amado,”Unbalance compensation in a rotor-  bearing system by dynamic stiffness control and     acceleration scheduling”, Proceedings of ISMA  2010, International Conference on Noise and  Vibration Engineering including USD2010;      Leuven, Belgium, 20 - 22 September , 2010.
[5] X. Zhang, K. Gao, Z. Shen, and Y. Xie, “The vibration characters analysis of tube   compressor” Proceedings of the 5th  International Conference on Civil Engineering      And Transportation, Guangzhou, China,      Published by Atlantis Press, 2015.
 [6] J. Yao, J. Gao, Y. Zhang, and W.Wang,”The  dynamic analysis of two-rotor three-bearing   system”, Hindawi Publishing Corporation,      International Journal of Rotating Machinery, Vol. 2015, Article ID 342636, 15 pages,, 2015.
[7] M. Eftekhari”The effect of damping and  stiffness of bearing on the natural frequencies of  rotor bearing system”, International Journal of       Engineering Vol. 30, No. 3, 448-455 ,  Iran,  doi: 10.5829/idosi.ije.2017.30.03c.15, 2017
[8] C. J. Paul, K. Srividya, M. Nagaswapnasri, K. K. Dondapati and L. Camarini, “Effect of oil  viscosity over critical frequencies in rotor      bearing systems” International Journal of  Engineering Research and Technology. ISSN      0974-3154 Vol. 11, No. 2, pp. 307-317, 2018.
[9] ANSYS Help Topics Mechanical APDL  Documentation Version 18.0. 2018.