Experimental Study on Low Speed Lubrication Characteristics of Large Tilting Pad Bearings

Abstract

Abstract：For large generator sets, during low-speed operation such as start-stop or low-speed driving, there may be instances where hydrodynamic lubrication can’t be established, leading to boundary lubrication between bearing and the shaft. This situation can result in bearing damage and cause safety incidents. Therefore, it is necessary to study the lubrication characteristics of bearings under low-speed operation. In this paper, the lubrication properties of the unevenly distributed six-pad tilting pad bearings in an in-service unit are analyzed through theoretical calculations. The analysis focuses on parameters such as film thickness and temperature of the bearing pads under low-speed operating conditions. A full-size test bench is set up to examine the lubrication properties of bearings made of two materials - Babbitt alloy and fluoroplastic, and the pads temperatures, film thicknesses, and vibration characteristics of the bearings are tested under actual operating conditions. The test results show that: the 6-pad small wrap angle bearings designed do not have tile burning phenomenon under low-speed working condition (40r/min), the bearing made of fluoroplastic material has lower temperatures compared to those made of Babbitt alloy, with higher pivot film thickness than that of the Babbitt alloy; The bearing pivot film thickness value using VG68 oil is larger than that of VG46, and the values of the temperature of the pad measurement point are larger than that of VG46.This research paper validates the feasibility of the bearing design scheme for this unit and provides data support for the design and safe operation of similar units.