Makoto Hemmi

COMPUTATION OF THERMAL DEFORMATION OF THRUST BEARING PAD CONCERNING THE CONVECTION BY NON-UNIFORM OIL FLOW

Tilting-pad thrust bearings are used to support the loads of large rotating machinery, such as water turbine generators. When such machines are in operation, thermal deformation is so extensive that it is comparable to deformation caused by the pressure of the oil film, and it influences the bearing’s performance. So, the temperature distribution in the pad, which determines the thermal deformation, should be calculated correctly. This requires precise estimation of the convection by the ambient oil at the pad’s surfaces, but the complexity of the pad’s shape and ambient oil flow of oil around it makes this estimation difficult. Using CFD (Computational Fluid Dynamics) software, we computed the temperature distribution in the pad by solving the heat transfer in the pad, in the oil and interfaces of them simultaneously. The thermal and stress deformation were then calculated by the FEM code and is used in oil film analysis to determine the characteristics of the bearing. Comparing its results with the experimental ones validated the computational process.Copyright

Calculation of Thermal Deformation of Thrust-Bearing Pad Considering Convection by Non-uniform Oil Flow

We described the characteristics and the calculation procedure of large-scale thrust bearings whose pads are surrounded by the non-uniform flow in an oil bath. The thermal deformation of the pad is comparable to the thickness of oil film, so we need to calculate it precisely. First, we calculated the characteristics of oil film, e. g., the thickness, pressure and temperature distribution. Second, using the temperature distribution in the oil film as one of the boundary conditions, we calculated the temperature distribution in the pad and the oil flowing around the pad using a computational fluid dynamics (CFD) code. Third, taking into account the CFD result, we calculated deformation of the pad by a structural analysis code. We repeated these three steps until the deformation of the pad is converged. The calculated values for the thickness distribution of the oil film between the runner and the pad are consistent with the measured values. This confirms the importance of including the flow conditions in precisely calculating the deformation of the pad, and the computational process we presented is validated.