Application of fluid-structure interaction technique for the TEHD lubrication problems of the bidirectional thrust bearings

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Application of fluid-structure interaction technique for

the TEHD lubrication problems of the bidirectional

thrust bearings

Liming Zhai, Zhengwei Wang, Yongyao Luo, Zhongjie Li, Xin Liu

To cite this version:

Application of fluid-structure interaction technique for the

TEHD lubrication problems of the bidirectional thrust

bearings

Liming Zhai1, 2_{, Zhengwei Wang}1, 2, *_{, Yongyao Luo}1, 2_{, Zhongjie Li}1, 2_{, Xin Liu}1, 2

ISROMAC 2016 International Symposium on Transport Phenomena and Dynamics of Rotating Machinery Hawaii, Honolulu April 10-15, 2016 Abstract

Thrust bearing lubrication involves fluid-thermal-structural interactions between the oil film, the pad and the runner collar. This study used the FSI technique to investigate the lubrication characteristics of a bidirectional thrust bearing for several typical operating conditions to analyze the influences of the operating conditions and the thrust load on the lubrication characteristics. The results show only a very small part of heat is dissipated through the pad and collar, while most of the heat is carried away into the fresh oil by the film flow. The heat out of the inner radius surface, trailing surface and outer radius surface account for almost 80 percent of the total heat transferred into the pad. The heat transfer coefficients on the pad surfaces are quite uneven with the largest on the leading surface and the least on the trailing surface. The eddies in the space between the adjacent two pads result to the larger heat transfer coefficients on the leading surface and less on the trailing surface.

Keywords

Bidirectional thrust bearing — TEHD — FSI — Heat transfer

1 _{State Key Laboratory of Hydroscience and Engineering, Tsinghua University, Beijing, China} 2 _{Department of Thermal Engineering, Tsinghua University, Beijing, China}

*Corresponding author: wzw@tsinghua.edu.cn

INTRODUCTION

The thrust bearings are one of the most crucial components in large hydropower units which greatly affects units’ safe and stable operation. A thrust bearing includes a thrust collar, a mirror plate and several pads. The rotor load is transferred to each pad through the thrust collar and the mirror plate, and then to the base. A very narrow clearance between the mirror plate and each pad is filled with the lubricating oil during operation.

The lubrication of large thrust bearings is the thermal-elastic-hydrodynamic (TEHD) problem. During operation, high pressure is formed in the oil film between the mirror plate and the pad which support the thrust load. In addition, the oil film is heated by viscous friction which leads to the temperature gradient in the pad and collar (or mirror plate). Thus, the high pressure in the film will result in mechanical deformation on the pad and collar, while temperature gradient in the pad and collar will cause the thermal deformation. In turn, the total deformation will change the oil film thickness and affect the pressure and temperature distribution in the film. Luo et al. [1] theoretically and experimentally analyzed the applications and operating conditions of thrust bearings with different centrally supporting structures and various operating conditions. Huang et al. [2] [3] and Wu et al. [4] conducted experiments on a bidirectional thrust bearing in a test rig and verified 3D TEHD numerical results. They solved the Reynolds equation, the energy equation, the film thickness equation for the film with assumpted inlet temperatures and then the heat conduction equation and the elastic