Abstract
Increasing quality demands of combustion engines require, amongst others, improvements of the engine’s acoustics and all (sub)components mounted to the latter. A significant impact to the audible tonal noise spectrum results from the vibratory motions of fast-rotating turbocharger rotor systems in multiple hydrodynamic bearings such as floating bearing rings. Particularly, the study of self-excited non-linear vibrations of the rotor-bearing systems is crucial for the understanding, prevention or reduction of the noise and, consequently, for a sustainable engine acoustics development. This work presents an efficient modeling approach for the investigation, optimization, and design improvement of complex turbocharger rotors in hydrodynamic journal bearings, including floating bearing rings with circular and non-circular bearing geometries. The capability of tonal non-synchronous vibration prevention using non-circular bearing shapes is demonstrated with dynamic run-up simulations of the presented model. These findings and the performance of our model are compared and validated with results of a classical Laval/Jeffcott rotor-bearing model and a specific turbocharger model found in the literature. It is shown that the presented simulation method yields fast and accurate results and furthermore, that non-circular bearing shapes are an effective measure to reduce or even prevent self-excited tonal noise.
Highlights
The recent development of combustion engines shows a clear trend towards “downsizing”, i.e., the reduction of quantity and/or volumetric size of the cylinders and an increased demand of higher specific power of such new engines together with lower carbon dioxide emissions
[19], Laval/Jeffcott-rotor whereathe usually linear elastic and damped bearings Laval/Jeffcott-rotor were replaced by plain where the usually linear elastic and damped bearings were replaced by plain hydrodynamic bearings hydrodynamic bearings with circular geometry which introduce non-linear bearing forces
We show that non-circular change the onset subsynchronous effects
Summary
The recent development of combustion engines shows a clear trend towards “downsizing”, i.e., the reduction of quantity and/or volumetric size of the cylinders and an increased demand of higher specific power of such new engines together with lower carbon dioxide emissions. These requirements may only be achieved by using highly efficient turbocharger systems. A special case of disturbing turbocharger noises are tonal noises which result from imbalance-excited or self-excited resonances of the rotor-bearing system. In [1] it was demonstrated how the subjective perception of tonal turbocharger noises can be assessed objectively
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