Vibration of an automotive turbocharger - a case study

Almost all rotors of automotive turbochargers exhibit strong sub-harmonic vibrations as well as the more usual unbalance vibrations found in other rotating machines. These vibrations are undesirable as they cause noise (rumble) and can be of large amplitude, causing rotor-stator rub. The purpose of this case study is to conduct a trouble-shooting exercise to discover the origin of these sub-harmonic vibrations. The findings are of general significance to a range of rotating machines and a simple unified linear theory is presented to explain the dual phenomena of oil whirl and oil whip.