Performance analysis of a fully textured hybrid circular thrust pad bearing system operating with non-Newtonian lubricant Satish C. Sharma, Saurabh K. Yadav n Department of Mechanical and Industrial Engineering, Tribology Laboratory, Indian Institute of Technology, Roorkee 247667, India article info Article history: Received 12 October 2013 Received in revised form 25 March 2014 Accepted 13 April 2014 Available online 23 April 2014 Keywords: Hybrid thrust bearings Parallel surfaces Surface texture Non-Newtonian lubricant abstract The present paper deals with the theoretical investigation of the influence of dimple geometry on fully textured hybrid thrust pad bearing and operating with non-Newtonian lubricant. The modified Reynolds equation which governs the flow of non-Newtonian lubricant in the clearance space has been solved using Finite Element Method. The simulated results indicate that the values of load carrying capacity, frictional power loss, maximum pressure and fluid film stiffness coefficient are significantly affected by the behavior of lubricant. The results presented in the study are expected to aid in determining the optimum value of dimple diameter and depth for the optimum bearing performance. & 2014 Elsevier Ltd. All rights reserved. 1. Introduction Fluid film thrust bearings are widely used to support axial thrust in heavy machineries. The lubricant film in these bearings not only prevents direct metal to metal contact but also aids in reducing friction coefficient and wear. The performance of these bearings greatly depends on the type of compensating device used in the bearing system. A flow control device provides pressure drop between the supply manifold and recess. Accordingly, differ- ent types of compensating devices have been developed such as membrane, capillary, orifice, constant flow valve (CFV) etc. The most commonly used hybrid thrust bearing compensated with capillary is shown in Fig. 1. In recent decade, many researchers focused their interests on the study of the influence of surface texture on the performance of fluid film thrust bearing system. They proved experimentally and theoretically that the surface texture has a positive influence on load carrying capacity, frictional power loss and wear resistance [1–3]. In 1966 Hamilton et al. [1] presented that for hydrodynamic bearing, microdimples on the bearing surface acts as microbearing. Since 1996 Etsion and coworkers [3–10] have been investigating thoroughly the effect of texture on the bearing performance parameters. In recent years many studies showed that in these microdimples, micro-cavitation takes place in the opposite side of motion and a fluid film pressure rise takes place in the direction of the motion which is larger than the average fluid film pres- sure generated in a particular area without microdimple. Qui and Khonsari [2] studied that the depth of these microdimples sig- nificantly affects the performance of the bearing. They also studied the influence of cavitation pressure on load carrying capacity and showed that optimum dimple dimensions must obtain the max- imum load carrying capacity. The validity of Reynolds equation for microdimple depends on surface geometry and ratio of micro- dimple depth, microdimple diameter. Kraker et al. [11] showed that apart from increase in pressure and cavitation effect, the surface texture may result into convective inertia effect which cannot be handled by Reynolds equation. Therefore, they com- puted the value of convective flow factors by using Navier–Stokes equation and added them into Reynolds equation. A large number of very small sized microdimples are textured on the bearing surface. In order to harness the effect of microbearings, a very fine mesh is therefore required near the microdimple which leads to a high computational time. Therefore, many studies [12–16] have been carried out to reduce computation time. Kraker et al. [12] studied the surface texture by using multiscale modeling method. They analyzed the local flow effects for a single cell using Navier– Stokes equation and directly added them to Reynolds equation. Pie et al. [13] presented a multiscale method for modeling surface texture in hydrodynamic lubrication. Further, they showed that the use of Finite cell method significantly reduced the computational time and computational storage significantly, when compared with finite element method and the results of FCM had also good agreement with existing theoretical and experimental studies. There are many studies that suggest different shapes of dimple for the texture. But the most commonly used geometry for an improved bearing performance is spherical. Etsion and co- workers [3,7,8] investigated the effect of dimple geometry on the Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/triboint Tribology International http://dx.doi.org/10.1016/j.triboint.2014.04.013 0301-679X/& 2014 Elsevier Ltd. All rights reserved. n Corresponding author. Tel.: þ91 9760011910. E-mail addresses: sshmefme@iitr.ac.in (S.C. Sharma), saurabhme.iitr@gmail.com (S.K. Yadav). Tribology International 77 (2014) 50–64