Influence of Turbocharger Bearing Design on Observed Linear and Nonlinear Vibration

Abstract

Automotive turbochargers are known to have operation into the self-excited unstable vibration 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 bushing 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 current and future improved bearing design modifications. The current results, for a series of custom fixed geometry journal bearings, show a shift in the frequencies of the two unstable modes for the no load operating condition. These results can be compared to the linear analysis predicted instability frequencies to better understand the actual response of the high speed turbocharger. This paper documents the spectrum content for three different bearing designs and compares the results to a stock floating bush journal bearing result for the same no load operating condition.

Classification of Design Methodologies to Minimize Vibrations in Gears and Bearings in the 21st Century: A Review

“…Kirk R et al [127] studied the dynamic characteristics of three custom, fixed bore, bearing designs in a turbocharger of a 3,9 L 130 HP diesel engine. They obtained the two-mode frequency for the different bearings, and they compared it with the initial stock floating bush bearing.…”

Numerical investigation of subsynchronous vibration in floating ring bearings

“…The advantages of FRBs have attracted researchers to investigate its characteristics and to improve their performance. [1][2][3][4][5] Of all the issues studied, two major problems concerned researchers the most: the decrease of ring-to-shaft speed ratio at high shaft speed and the characteristics of subsynchronous vibration. Researchers who have focused on the ring-to-shaft speed ratio, experiment measurement, and Reynold equation solution are the major methods.…”

“…On the other hand, researchers have conducted experiments or used dynamics to analyze the shaft subsynchronous vibration characteristics. Kirk et al 3,14,15 experimentally investigated the vibration and report some of the subsynchronous frequency on their turbocharger test rig. Recently, some researchers have noted the interaction of the oil film and shaft and predicted the shaft-bearing system by simultaneously calculating the fluid dynamics of the lubricant film and the dynamic response of the shaft.…”