# Performance of Tilting Pad Journal Bearings with the Same Sommerfeld Number
## 4 Conclusions  
This study presents the thermo-elastic-hydro-dynamic effect on TPJB performance by comparing seven different sizes of bearings with the same Sommerfeld numbers. The 3D numerical model with TEHD lubrication includes the pad thermal-elastic deformation and pivot stiffness. The numerical results vividly show that the static and dynamic bearing characteristics vary with bearing sizes albeit the Sommerfeld number is identical. This is because the thermal condition affects the bearing geometry and viscosity, which eventually affects the bearing performance. The change of bearing performance is pronounced at higher operating speeds and for larger bearings. This is due to the thermal energy that is generated at high speed and high bearing load conditions. If the heat source supplied from outside the bearing system is ignored (except for the lubricant), the oil film viscous shear heat changes the lubricant viscosity and is simultaneously transferred to the structure around the oil film. The rotating shaft and bearing pads cause thermal deformation,  
Figure 10: Film thickness distribution on pad. which changes the oil film thickness. The changed bearing clearance changes the viscous shear heat again to change the heat transfer conditions to the surrounding structures. These changes interact and generally converge under constant conditions. Hence, it is important to thoroughly forecast the bearing performance accounting for lubricant supply conditions when designing a relatively large bearing with high-speed operation. At higher operating speeds, and possibly for larger bearings, bearing performance and health can be more sensitive to lubrication supply pressure and temperature. Conceptualization, S.-H.J. and J.S. ; methodology, J.S. ; software, S.-H.J. and J.S. ; validation, H.S.Y. ; formal analysis, S.-H.J. ; writing--original draft preparation, S.-H.J. ; writing--review and editing, S.-H.J. ; visualization, J.S. ; supervision, J.S. ; project administration, H.S.Y. ; funding acquisition, J.S. and H.S.Y. All authors have read and agreed to the published version of the manuscript. This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korean government (MSIT) through GCRC-SOP (No. 2011-0030013). The authors  
* _[PERSON] Spring and Damping Coefficients for the Tilting-Pad Journal Bearing._ASLE Trans._ **1964**, \(7\), 342-352. [CrossRef]
* _[PERSON] et al. (1966)_ [PERSON]; [PERSON]; [PERSON]; March, C.N. Paper 3: An Experimental Investigation of the Thermal Equilibrium of Steadily Loaded Journal Bearings. _Proc. Inst. Mech. Eng. Conf. Proc._ **1966**, _181_, 70-80. [CrossRef]
* _[PERSON] et al. (1996)_ [PERSON]; [PERSON]; [PERSON] On the Generalization of Thermohydrodynamic Analyses for Journal Bearings. _[PERSON]_ **1996**, _118_, 571-579. [CrossRef]
* _[PERSON] et al. (1996)_ [PERSON]; [PERSON]; [PERSON] Thermoelastohydrodynamic Analysis of Fixed Geometry Thrust Bearings Including Runner Deformation. _Tribol. Trans._ **1996**, _39_, 555-562. [CrossRef]
* _[PERSON] et al. (1994)_ [PERSON]; [PERSON]; [PERSON] TEMD Analysis for Tilting-Pad Journal Bearings Using Upwind Finite Element Method. _Tribol. Trans._ **1994**, _37_, 771-783. [CrossRef]
* _[PERSON] et al. (1992)_ [PERSON]; [PERSON]; [PERSON] Experimental Study of Tilting-Pad Journal Bearings--Comparison with Theoretical Thermoelastohydrodynamic Results. _[PERSON]_ **1992**, _114_, 579-587. [CrossRef]
* _[PERSON] (1999)_ [PERSON]; [PERSON] Frequency Effects on the TEHD Behavior of a Tilting-Pad Journal Bearing Under Dynamic Loading. _[PERSON]_ **1999**, _121_, 321-326. [CrossRef]
* _[PERSON] (1978)_ [PERSON] The Influence of Bearing Flexibility on the Dynamic Performance of Radial Oil Film Bearings. In Proceedings of the 5 th Leeds-Lyon Symposium on Tribology, Lyon, France, 6-9 September 1978; pp. 311-319. * _[PERSON] (1988)_ [PERSON]; [PERSON] Evaluation of Pivot Stiffness for Typical Tilting-Pad Journal Bearing Designs. _[PERSON]. Vib. Acoust._ **1988**, _110_, 165-171.