Turbocharger vibration shows nonlinear jump.

Automotive turbochargers are known to operate into the self-excited unstable region. In the past these instabilities have been accepted as unavoidable, but recent developments in analysis and instrumentation may make it possible to reduce or eliminate them. A test stand has been developed at Virginia Tech to measure the vibrations of a 3.9 liter diesel engine stock turbocharger with both stock floating ring journal bearings and also custom design fixed geometry bearings. Vibration spectrum content clearly identifies the shaft instabilities and provides the basis for additional evaluation of future improved bearing design modifications. The current results, for custom fixed journal bearings, have clearly revealed a distinct jump with associated shift in the spectrum frequency content. This paper will document the recent tests of custom design fluid film bearings that have experienced this nonlinear jump condition. [ABSTRACT FROM PUBLISHER]