Evaluation of transient temperature characteristics of tilting pad bearing by simplified calculation method

Abstract

In this study, we intended to make the prediction method of the transient characteristics of the flooded lubrication tilting pad bearings, and we developed the high speed calculation method with reasonable accuracies assuming the use by designers. Instead of solving the Reynolds equation and the energy equation simultaneously such as THL analysis, a method of simply calculating the oil film reaction force and temperature by using a database was employed. Based on this method, the average temperature of the shaft, pad, and housing in the time step is calculated every moment, and finally the changes over time in the bearing gap and oil film temperature can be obtained in seconds. In addition, we measured the bearing temperature with a test bearing bored 100 mm in diameter under conditions where the transient temperature exceeds the steady temperature to validate the analysis. In the transient state, the bearing gap decreases remarkably just after starting, and then gradually increases toward convergence. We considered it as a factor that the temperature rise of the shaft and pad with small heat capacity is large and their outer diameter and thickness change rapidly due to thermal expansion, while the temperature rise of the housing with large heat capacity is small and its inner diameter change gradually. We considered those mechanizm in the analysis. Also, the thermal expansion of the housing is considered to be suppressed by the casing or something, thus the deformation is multiplied by the hot clearance coefficient. When the value was set to 0.4, though the errors between the measured and the analyzed tempreratures at steady and maximus points increase as the mean pressure increases, both errors are minimized and they are within 5 deg. C under the test conditions. Although the sensitivity of the mean pressure is high, the analysis can predict the transient temperature with reasonable accuracy in short calculation time.