Error analysis in the determination of the dynamic coefficients of tilting pad journal bearings

In this work, a method for the determination of the systematic error affecting the computation of dynamic coefficients of Tilting Pad Journal Bearings (TPJB) is described. This statistical method is applied to the coefficients obtained for a 5-pad TPJB with 280 mm diameter. Experimental activity was carried out on an advanced experimental test rig specifically designed for investigations on large size high-performance bearings for turbomachinery. The adopted configuration has the test article (TA) floating at the center of a rotor supported by two rolling bearings. The TA is statically loaded by a hydraulic actuator and excited by two orthogonal hydraulic actuators with a single tone or multitone dynamic load. The linear coefficient computation method is based on the dynamic measurement of forces, accelerations and relative displacements of rotor and bearing. The analysis of the acquired data is carried out in the frequency domain, after signal Fast Fourier Transform (FFT) computation. Along with a description of the experimental setup and of the main characteristics of the sensors used for data acquisition, this paper presents a statistical technique for the estimation of the systematic error and a comparison with the random error.