On the effect of pad clearance and preload manufacturing tolerances on tilting pad bearings rotordynamic coefficients

Tilting pad bearings (TPB) are commonly used in high-speed and high-power turbomachines, due to its contributions in avoiding rotor instabilities. Studies related to the estimation of dynamic coefficients have been carried out considering a uniform value of the geometric parameters (clearance, pre-load) for all bearing pads. These assumptions give a reasonable agreement on the direct coefficients prediction while, recently, some discrepancies have been found on the cross-coupled coefficients. In this work, a numerical study is devised to analyze the influence of the pre-load and clearance variations from pad to pad, due to manufacturing tolerances, on the dynamic coefficients prediction. The numerical code for the estimation of the dynamic coefficients uses the finite element method to integrate the Reynolds's equation through a perturbation approach. Variations on the pre-load and clearance for each bearing's pad were performed, producing plots quantifying the sensitivity of the tilting pad bearing cross coupled coefficients to manufacturing tolerances.