Effects of VNT and IGV association on turbocharger centrifugal compressor performances

Abstract

Turbochargers are today widely used to improve performances of internal combustion engines. The compressor's characteristics are important because they govern the fresh air quantity introduced to engine cylinder and consequently determine the air/fuel ratio which governs the combustion quality. Generally, the best engine-turbocharger matching is achieved by using the variable geometry technique. This paper studies the effects of VNT (Variable Nozzle Turbine) and IGV (Inlet Guide Vanes) combination on compressor's characteristics. However, except the industrial compressor cases, the flow direction adjustment at the entry of automotive compressor is not yet applied in spite of the high rotational speed. An experimental investigation coupled with a numerical study is used to achieve this work. The IGV technique shows a real improvement of the compressor's characteristics over its whole operating range but without adjusting the look of the efficiency curve at large opening of turbine nozzle blades because power and diffuser loses remain important.