Vibro-acoustical Behavior of a Turbocharger Housing Excited by Oil-film Induced Rotor Oscillations

Abstract

This paper deals with the interaction of the turbocharger housing and the rotor to reveal the acoustic phenomena which are excited by the oil whirl/whip instabilities. Therefore, a flexible multibody model is built up for the rotor subsystem which is supported in floating ring bearings. The flexibility of the housing subsystem is taken into account by considering it as a modally reduced structure within the multibody simulation model. Primarily, the two subsystems are simulated sequentially. The first step gives the oil film forces during a typical run-up simulation of the rotor subsystem if the bearing shell deformation is neglected. In a second step, the obtained oil film forces are applied at the decoupled housing structure to analyze the vibro-acoustics of the turbocharger in detail. The vibro-acoustical behavior is judged by the occurring housing amplitudes which are predominantly influenced by the mounting concept of the turbocharger on the engine. It is found out that the subsynchronous excitation due to the oil films can be magnified through the housing structure in a quite wide speed range which is the main excitation mechanism affecting the acoustics of turbochargers. Finally, the run-up simulation is performed for the coupled subsystems of rotor and housing where the oil film forces are also dependent on the local deformation of the bearing housing.