A theoretical-experimental comparison of the synchronous response of a bowed rotor in five different sets of fluid film bearings

Abstract

A comparison of theoretical and experimental synchronous unbalance responses of a bowed Jeffcott rotor in fluid film bearings has been completed. A transfer matrix method was used to predict theoretically the response of a 25·4 mm shaft in fluid film bearings and results were compared to data from a previous experimental study. Four bearing types were used: two axial groove, pressure dam, tilting pad and four-lobe. Very good agreement was found for all bearing types at the rotor critical speed (3000 rpm). Differences less than 15% in peak response were found and the theoretical and experimental peaks were found to occur within 200 rpm. Worst agreement was found for the preloaded four-lobe bearings and this disagreement was found for speeds other than the critical speed. Also, for equal bow and unbalance the tilting pad and four-lobe bearings were found to produce the least and most damping at the critical speed, respectively. Previous to this time a comparison of theoretical and experimental synchronous responses of a rotor system representing industrial turbomachines has not been published, nor has a comparative study of the different bearing types.