In a turbocharger for diesel engines, a high pressure ratio and a wide operation range are required to achieve extemely low exhaust emissions. In the present study, the ring groove arrangement was adopted to enhance a flow range in a centrifugal compressor of automobile turbocharger. The upstream groove was located at the casing wall of the suction pipe and the downstream groove was located at the shroud casing wall near the leading edge of the splitter blades, where both grooves were connected by an annular bypass. According to the numerical results calculated by using ANSYS-CFX code, it becomes clear that the ring groove arrangement is effective for supression of separation at the leading-edge of main blade even in small flow rates. The reverse flow appeared on the shroud casing is sucked out from the downstream groove, and the recirculation flow was formed in the groove arrangement. The flow incidence at the main blade leading edge is reduced surccessfully by about 5〜7 degrees due to the increased incoming flow rate.
