Experimental Estimation of Equivalent Damping Coefficient of Thrust Bearings

A specific class of rotary machines is the high rotation turbochargers, to automotive application, wherein the shaft is continually subjected to axial forces of different magnitudes due to gas flows in the turbine and the compressor. These forces are supported by axial lubricated thrust bearings. The thrust bearings are modeled through equivalent stiffness and damping coefficients and the objective of the work is to get good estimates of these coefficients, comparing simulated results with experimental results. The stiffness coefficient is first obtained by small perturbation around the equilibrium position and used in a finite element model of the system at specific rotational speeds, and this value is compared to experimental results. Then, the damping coefficient is estimated, by running an optimization problem on this parameter, to approximate the simulated dynamic response of the system to experimental results of the turbocharger excited by an impact hammer, where both the displacement and force were measured.