Sensitivity analysis of the dynamic characteristics of thrust bearings
Gregory Bregion Daniel1; Leonardo Carpinetti Vieira1; Katia Lucchesi Cavalca1
1 UNICAMP
doi:10.20906/CPS/USM-2016-0042
Resumo
The hydrodynamic bearing has an important role in rotating machinery, because its characteristics can directly affect the dynamic behavior of the rotor. On other hand, the behavior of the thrust bearing depends on several parameters, namely, clearance, oil film temperature (or viscosity), oil film minimum thickness and loading. Certainly relative velocity is also an important parameter, however in this paper the focus is mainly on the oil film thickness and the experimental validation of the dynamic coefficient of stiffness. To reproduce the complete rotating system, an accurate modeling of the bearings is, then, mandatory. Here, a turbochager thrust bearing is represented by a thermohydrodynamic model and inserted in the numerical model of the turbocharger rotor as equivalent dynamic coefficients of stiffness and damping. To proceed with the experimental validation, an experimental set up is assembled in order to measure axial load and displacement of the shaft for several rotation speeds. The numerical simulation of the experimental set up is accomplished and the results are compared. However, uncertainties related to the assembling and, mainly, to some measurements are found to propagate up to the final estimation of the oil film thickness and, consequently, the stiffness coefficient. Facing this problem, a statistical analysis of the experimental results is fundamental to establish a confidence bound of the parameters estimation. The confidence limits conditions were, then, numerically simulated and interesting results about the parameters sensitivity are reached. At this point, the experimental validation of the bearing model is presented in terms of mean value and standard deviation, considering Gaussian distribution for the uncertainties.
Palavras-chave: thrust bearing; sensitivity analysis; turbochager application