Flow Structure and Stability of a Turbocharger Centrifugal Compressor
This document deals with the aerodynamic behavior and stability of small-scale centrifugal compressors. The flow structure, the formation of secondary flows, and the stability of the compressor system are investigated experimentally. In order to achieve good measurement accuracy and comparability, the experiments are performed in a true-scale and an up-scaled compressor model. A special focus is put on the influences of low Reynolds numbers and large relative tip clearances as these effects are dominant features of small-scale applications and lead to a deterioration of compressor performance. It is found that the flow structure in the vaneless diffuser does not correspond to the classical jet wake model as the tip gap flow is altering the flow pattern. Based on these findings, a modified three-zone flow model which includes tip leakage flows is proposed. Furthermore, in a stability analysis, the trajectory and the destabilizing behavior of the tip vortex are investigated.