PIV Measurements of Flow in Recirculation Cavities at the Inlet of a Centrifugal Compressor

,Because of the necessity of mass flow range as large as possible on turbocharger compressors to match different engine regimes, the surge and stall phenomena, that limit the operational range at low mass flow, need to be controlled. Numerous active and passive devices exist in order to reduce or suppress their occurrence. A method that has been proven to work and is commonly used consists of recirculation passages that extract high entropy flow from the tip of the blades to reduce blockage in the blades. The compressor used in the study features a ported shroud connected by a slot to the main passage that removes part of the flow near the inducer and mixes it upstream into the inlet. In order to understand the mechanism and assess the flow patterns in the recirculation channels, PIV measurements were carried out in the inlet region. Data was collected along a compressor speedline and allows understanding of the flow in the channels and its interaction with the incoming flow for different operating regimes of the compressor.