Three-dimensional numerical simulation was conducted on a turbocharger centrifugal compressor to study the inlet flow field of the design point and the points near surge at different rotating speeds; inlet guide vanes on the shroud of centrifugal compressor were presented as a flow control method based on the inlet flow field study and verified by experiment. Investigation shows that the pressure difference of the pressure side and suction side of the blade near surge leads to tangential velocity near shroud in the inlet flow field opposite to the impeller rotating direction

and the tangential velocity increases with the growing impeller speed; at the design point

there are two opposite tangential velocity areas before each blade pressure side and suction side and the area of tangential velocity opposite to the impeller rotating direction is not limited to the area near shroud. Inlet guide vanes on the shroud can decrease the tangential velocity opposite to the impeller rotating direction near surge effectively

and experimental result shows that the centrifugal compressor pressure ratio is improved by 3.4% and the efficiency by 3.0% at 90000r/min near surge. The overall performance is improved.