Study of the Influence of Heat Convection Coefficient on Predicted Performance of a Large Tilting-Pad Thrust Bearing

Abstract

Part of the heat generated by the shearing of the lubricating film during operation of a hydrodynamic bearing is transferred to the bearing components. In the case of the pad, which is usually fully submerged in the lubricating oil, heat is further transferred at the pad free walls to the oil by convection. This mechanism causes a thermal gradient in a pad and, consequently, its thermal deflection. In large hydrodynamic thrust bearings, thermal deflection of the pads is an important phenomenon influencing bearing performance. For such bearings, pad distortion can reach the level of hydrodynamic film thickness and can significantly change the bearing's properties. In this paper, the study of the influence of the heat convection coefficient on the predicted performance of a large hydrodynamic thrust bearing is presented. Two sets of convection coefficients at the pad free surfaces are investigated with the use of thermo-elasto-hydrodynamic (TEHD) calculations. An analysis is carried out for the Itaipu hydro turbine thrust bearing with the outer diameter equal to 5.2 m, which is one of the biggest hydro power plants in the world. The results of the theoretical predictions are compared to the measured data collected during bearing operation.

Numerical analysis of single pad of thrust bearing with the energy equation solved by the characteristic-based split method

“…Little deviation could be found between those two figures, indicating that the original coarser mesh can be used to obtain a mesh-independent solution of the film temperature. The coarser mesh was also used in the analysis done by Wodtke et al, 27 in which the simulation was performed with FDM. This means that the CBS method could obtain steady-state solution of the energy equation with the same mesh density.…”

“…The mesh information and the axial load settings could be found in Table 2. The axial loads of Cases 1 and 2 have the same value described in the work of Wodtke et al 27 The hot oil carry-over coefficients, k mix , for oil-lubricated thrust bearings (Cases 1-4) are assumed to be 0.589 based on the work done by Ettles. 24 For Case 5, k mix is assumed to be 0.6.…”

“…For Cases 1-4, the node number along every coordinate axis is set according to the referenced work. 27 An additional finer mesh is deployed to test the dependence of the simulation on the mesh. For Case 5, the similar mesh structure is adapted.…”

Effect of presence of lifting pocket on the THD performance of a large tilting-pad thrust bearing

“…Detailed description of the model can be found in Refs. [18,19]. The temperature in the lubricated film and in the pad is calculated by solving the 3D energy equation (i.e., the viscosity is varying across the film thickness) and the 3D heat transfer equation, respectively, using the finite difference method.…”

“…1 Itaipu thrust bearing pad and support arrangement [18]. In previous works [18,19], the authors completed TEHD analysis of Itaipu thrust bearing without including hydrostatic recess. Comparison of predictions and measurements revealed that there were results discrepancy, especially in the vicinity of the hydrostatic recess.…”