Turbocharger Synchronous Vibration Control on High Speed Balancer: Test and Prediction

Abstract

Current trends for advanced automotive engines focusing on downsizing, better fuel efficiency and lower emissions have led to several changes in turbocharger bearing systems design and technology. Automotive turbochargers are running faster under high engine vibration level. Vibration control is becoming a real critical issue and turbocharger manufacturers are focusing more and more on new and improved balancing technology. This paper deals with turbocharger synchronous vibration control on high speed balancers. In a first step the synchronous rotordynamics behavior is identified. The developed fluid bearing code predicts bearing rotational speed (in case of fully-floating design), operating inner and outer bearing film clearances and bearing force coefficients. A rotordynamics code uses this input to predict the synchronous lateral dynamic response of the rotor-bearing system by converging with bearing eccentricity ratio. The rotor-bearing system model is validated by shaft motion test data on high speed balancer (HSB). It shows that only one of the peaks seen on the synchronous G level plot collected in a high speed balancer can be explained by rotordynamics physics. A step-by-step structural dynamics model and analysis validated by experimental frequency response functions provides robust explanations for the other G level peaks. The synchronous vibration response of the system “turbocharger-HSB fixture” is predicted by integrating the predicted rotordynamics rotational bearing loads on the structural dynamics model. Numerous test data show very good correlation with the prediction, which validates the developed analytical model. The “rotordynamics – structural dynamics model” allows deep understanding of turbocharger synchronous vibration control as well as optimization of the high speed balancer tooling.