Journal of Mechanical Engineering

Effect of Roughness on Journal Bearing Performance with Non-Newtonian Fluids

K.  Jagannath, Mechanical  and  Manufacturing  Engineering ,M.I.T Manipal, India

Abstracts

The present study investigates the effect of surface roughness properties on the steady-state  and  dynamic  characteristics  of  hydrodynamic  journal  bearing using  non-Newtonian  lubricants  obeying  power-law  model.  An  analytical expression for average film thickness is obtained and introduced in the modified Reynolds  equation.  The  resulting  differential  equation  is  then  solved  by  the finite difference method with a successive over-relaxation scheme. The modified Reynolds equation with rough surfaces having Gaussian distribution has been solved  using  the  non-linear  transient  approach  to  determine  the  stability parameters  considering  longitudinal,  transverse  and  isotropic  roughness patterns.  The  equation  of  motion  is  then  solved  by  the  fourth-order  Runge- Kutta  method.  The  results  are  compared  with  established  results  for  smooth bearings.  It  is  found  from  the  detailed  analysis  that  roughness  parameter considerably influences stability of journal bearings. Stability is highest when the bearing is rough than journal. Surface pattern orientation of bearings has an important role in determining the stable running of a bearing. Improvement
in  stability  not  only  depends  on  whether  the  surfaces  have  isotropically, longitudinally,  or  transversely  oriented  surface  but  also  on  the  variation  in the  roughness  between  journal  and  bearing.  Transversely  oriented  surface with  rough  bearing  gives  higher  stability.  Lower  L/D  ratios  (short  bearing) gives better stability characteristics. Non-Newtonian effects cause the maximum film pressure to increase. It is observed from the pressure distribution that for different values of flow behavior index, non-Newtonian lubricants show flatter pressure  distribution  which  is  advantageous  for  bearings  subjected  to oscillatory  loads.

Keyword: Non-Newtonian lubricants, Stability, Journal bearings, roughness orientation.

References: 
[1] Ram Turaga, Sekhar, A. S. and Majumdar, B. C. (1999).  The effect of roughness parameter on the performance of hydrodynamic journal bearings with rough surfaces  Tribology International, 32, 231-236.
[2] Ram Turaga, Sekhar, A. S. and Majumdar, B. C. (2000).  Non-linear transient stability  analysis of  a  rigid  rotor  supported  on  hydrodynamic  journal bearings with rough surfaces  Tribology transactions, vol. 43, 3, 447-452.
[3] Wang, P., Keith, T. G.  and Vidyanathan, K.  (2002).  Combined surface roughness  pattern and  non-Newtonian  effects  on  the  performance  of dynamically loaded journal bearings  Tribology transactions, vol. 45, 1, 1-10.
[4] Wang-Long Li, Cheng-I Weng and Jang-I Lue. (1996).  Surface roughness effects  in  journal  bearings with  non-Newtonian  lubricants   Tribology transactions, vol. 39, 4, 819-826.
[5] Nadir Patir and Cheng, H. S. (1978).  An average flow model for determining effects  of  three  dimensional  roughness  on  partial  hydrodynamic lubrication  Transactions of ASME, 100, 12-17.
[6] Nadir Patir and Cheng, H. S. (1979).  Application of average flow model to lubrication between rough sliding surfaces  Transactions of ASME, 101, 220-229.
[7] Akers A, Michaelson, S. and Cameron, A. (1971).  Stability contours for a whirling journal bearing  Trans. of ASME, Journal of Lub. Tech. 93, 177-190.
[8] Raghunandana, K. and Majumdar, B. C. (1999).  Stability of journal bearing systems using non-Newtonian lubricants: A nonlinear transient analysis Tribology International, 32, 179-184.