Investigations on Large Turbine Bearings Working Under Transitional Conditions Between Laminar and Turbulent Flow

Abstract

The report deals with investigations on large turbine bearings, a tilting pad bearing, and an elliptical bearing. In special cases, the maximum babbitt temperatures show a sudden leap, caused by a slight change of the operating conditions. According to the test results, the temperatures do not change within the whole bearing, but only in a region near the minimum gap width. As proved by comparative theoretical investigations, the reason for this temperature leap is a local transition between laminar and turbulent flow, changing the thermal conductivity within the oil film to a high degree. Thus, the consideration of thermal diffusion in the energy equation is essential for precalculating this phenomenon. As a consequence of locally high surface temperatures, considerably large thermoelastic deformations are observed at both test bearings. For this reason the comparative calculations are based upon measured gap width profiles.