Patent attributes
A turbocharger having a turbine housing defining a chamber for receiving exhaust gas, and a nozzle leading from the chamber. Exhaust gas flows from the nozzle through a turbine wheel in the chamber and changes direction from a radially inward direction in the nozzle to an axial direction downstream of the turbine wheel. A divider in the nozzle divides the nozzle into first-stage and second-stage nozzles. The divider has an upstream surface to guide exhaust gas through the first-stage nozzle and an opposite downstream surface to guide exhaust gas flowing through the second-stage nozzle. An axially slidable tubular piston, disposed in the turbine housing, has a radially inner surface extending along the axial direction and a non-flat upstream end surface. The piston also includes a curved flow-guiding surface causing the exhaust gas to change direction. In a closed position, the piston abuts the divider to close the second-stage nozzle.
