Effect of Splitters in Recirculation Channels on Performance of Turbocharger Compressors Used in Gasoline Engines- A CFD Study

Abstract

Turbochargers used in gasoline engines have their compressor outlet directly coupled to the engine inlet via the throttle valve. On sudden closing of the throttle, the compressor outlet is blocked, and the compressed air has no path to exit resulting in a compressor surge. Compressor recirculation valves are used to connect the outlet of the compressor to the inlet to recirculate excess air and thus reduce the compressor surge. Under normal operating conditions, when the valve is closed, the channel connecting the compressor inlet and the valve causes an inlet disturbance resulting in the reduction of compressor efficiency. Hence a steady state CFD analysis of a gasoline engine turbocharger compressor modelled with a recirculation channel at the inlet was conducted. The channel connecting the compressor inlet and the recirculation valve was observed to cause inlet aerodynamic disturbance resulting in a drop in compressor efficiency by 1%. To overcome this problem, splitters were used in recirculation channels and 80% recovery of loss was observed with the use of splitters.