Trade-off between thermal performance and fatigue life of grooved thrust bearings in steam turbines using an FSI-based approach

Abstract

Thrust bearings are essential for maintaining the axial stability of steam turbine rotors under continuous high-load operation. At the Tenayan coal-fired power plant, repeated thrust bearing overheating caused several unit trips despite lubrication flow improvements and material replacements. This study investigates the thermo-mechanical behavior and fatigue life of thrust bearings with and without surface grooving modification using a numerical approach based on one-way fluid–structure interaction (FSI) and fatigue analysis. Hydrodynamic pressure and temperature distributions obtained from lubrication flow simulations were applied as loading conditions in transient structural and fatigue analyses. The results show that surface grooving significantly improves thermal performance by reducing the maximum operating temperature from 543.7 K (270.6 °C) in the non-grooved bearing to 360.7 K (87.5 °C) in the grooved configuration, indicating enhanced lubricant distribution and heat dissipation. In addition, the grooved bearing exhibits lower equivalent stress and deformation. However, fatigue analysis reveals that the minimum fatigue life decreases from 25,793 cycles in the non-grooved bearing to 1,476 cycles in the grooved design due to localized stress concentration at the groove edges. These findings demonstrate a trade-off bet†ween thermal performance and structural durability, underscoring the need for an optimized groove geometry in steam turbine thrust bearing applications.