Semi-floating Bearing Research Articles

Literature Research on Experimental Investigations of Automotive Turbocharger Rotordynamics

Contemporary turbochargers are high-speed rotating devices, commonly supported by full floating bearings or semi-floating bearings. Depending on the size and operational speed of the turbocharger, rotordynamics significantly changes. Industrial turbochargers are operating below 20.000 RPM and their rotor weight is substantial, leading to quasilinear rotordynamics behaviour. By contrast, automotive turbochargers are rotating up to 300.000 RPM with non-linear rotordynamics characteristics. Due to this non-linearity, rotor movement is intense, and bearing load is dynamically changing all the time. The consequence is reduced lifespan of the turbocharger. In this paper, the effect of changing bearing clearances, as well as the differences between semi-floating and full floating bearing constructions will be described based on journal papers scientific publications on the topic. Also, the damping and whirling phenomenon inside a bearing system will be investigated and presented in a comprehensive literature research on automotive turbocharger rotordynamics.

Modelo lineal para la identificación de velocidades críticas en un turbocompresor de MCIA

Linear models to identify critical points of operation depend largely on linear coefficients representing film lubrication, in which the shaft is supported, and the exciting forces of the shaft. However, the magnitudes of the coefficients of the oil film determined in rotational dynamics studies of small turbochargers (TC) still have great uncertainty. In present paper the linear coefficients of the film hydrodynamic lubrication in automotive turbocharger with semi-floating bearings have been estimated using different methodologies. These methodologies are based on the resolution of the film lubrication Reynolds equation using different approaches. These approaches are short bearing and long infinite bearing. Different tests have been made with various magnitudes with a synchronous frequency to generate excitation forces on the compressor and turbine wheels. At the end, the input parameters of the model (linear coefficients of the lubrication film and synchronous forces) are fitted in order to predict the measured orbit described by the shaft tip on the compressor side. The main critical operation points have been identified by a Campbell diagram. These points are related with the synchronous frequencies of the shaft. The obtained results have been compared with experimental measurements.