Experimental Investigations of the Disturbed Inlet-Flow Structure Caused by Mixing Geometries and Its Influence on the Performance of a Turbocharger Centrifugal Compressor

Abstract

One solution for reducing the nitrogen oxide emissions of diesel engines is the Low-Pressure-Exhaust-Gas-Recirculation method. This solution involves gathering exhaust gas from behind the turbine and mixing it with the aspirated fresh air upstream of the turbocharger compressor. This in turn tends to result in an inhomogeneous inflow into the compressor affecting the distribution of the velocity, the total pressure and the total temperature. The efficiency of the centrifugal compressor is influenced by this strongly disturbed inflow. In this paper the consequences of different mixer geometries developed for this application are examined. Experimental investigations are carried out in order to understand the flow processes of the disturbed inlet-flow structure and the associated effects on the efficiency of the compressor. These different mixer geometries are investigated for different mass flow ratios. These inflow conditions are then compared to a straight, undisturbed inflow and an elbow inlet. The aim is to decide which one of these mixing geometries is most appropriate.