Variable Inlet Guide Vanes in a Turbocharger Centrifugal Compressor: Local and Global Study

Engine downsizing is potentially one of the most effective strategies being explored to improve fuel economy. A main problem of downsizing using a turbocharger is the small range of stable functioning of the turbocharger centrifugal compressor at high boost pressures.

Several stabilization techniques were studied to increase the compressor operating range without sacrificing the compressor efficiency. The paper presents an experimental study of one of these techniques, the axial variable inlet guide vanes (VIGV). Test rigs were put up to conduct two different experiments. The first was to study the effect of pre- rotation generated by VIGVs on the overall compressor performance and the second to determine the pressure loss through the VIGVs and to analyze the flow downstream the VIGV system using LDA (laser Doppler Anemometry) measurement.

The experimental studies have shown the advantageous of VIGVs in extending the stable functioning of the compressor associated with lower efficiency levels at middle and high flow rates. The efficiency drop at particular points of functioning of low flow rate was explained by the non symmetric flow downstream the VIGVs at high vane setting angles. Moreover the results showed that the angle of rotation of flow didn't change at a distance of two times the impeller diameter inlet of the turbocharger compressor, downstream the VIGV system.