Experimental verification of frequency effects in tilting pad journal bearing dynamic coefficients

Abstract

In this paper, vibrational frequency effect in dynamic coefficients of tilting pad journal bearing is verified experimentally. Tilting pad journal bearings (TPJB) is applied in various turbomachinery. Accurate evaluation of the bearing characteristics of TPJB is very important to ensure reliability of rotating machinery. To evaluate the stability of such rotating machinery for sub-synchronous vibration accurately, examination of damped vibrational frequency effects in dynamic coefficients of TPJB under various bearing load condition is necessary. In this study, excitation test with test rig of 4pad TPJB with two types of preload or pad offset ratio is carried out in various load condition. Especially, the test condition where the influence of fluid inertia is small is focused. Frequency effect in dynamic coefficients of TPJB is verified experimentally under the test condition. And, thermo-elastic-hydrodynamic-lubrication (TEHL) analysis is carried out. By comparing analytical results to experimental results, good agreement with experimental result and TEHL analytical result is confirmed. In addition, the influence of bearing load, load direction, pre-load or pad offset ratio on frequency effect is confirmed experimentally and analytically. The results that the frequency effect is larger as bearing load is lower (Sommerfeld number is larger), and the influence of pre-load of bearing on frequency effect is small and that of pad offset ratio (pivot position) is large is obtained.