Variable geometry turbocharger

Abstract

Provided is a variable geometry turbocharger, comprising: a turbine rotor; and a variable nozzle mechanism for adjusting the flow of exhaust gas from a scroll flow passage formed on the outer peripheral side of the turbine rotor to the turbine rotor. The variable nozzle mechanism includes: a nozzle vane provided in an exhaust gas flow passage for guiding exhaust gas from the scroll flow passage tothe turbine rotor; a support wall that forms a flow passage wall of the exhaust gas flow passage on one side in an axial direction of the turbine rotor and that supports the nozzle vane in a cantilever manner such that the nozzle vane is turnable; and a non-support wall that forms a flow passage wall of the exhaust gas flow passage on the other side in the axial direction. A pressure surface-sideedge part of an end surface of the nozzle vane on the non-support wall side has a non-support wall-side straight portion formed into a straight shape.

Description

technical field [0001] The present disclosure relates to variable capacity turbochargers. Background technique [0002] The variable capacity turbocharger uses the variable nozzle mechanism to adjust the flow of exhaust gas from the vortex flow path in the turbine casing to the turbine rotor, thereby changing the flow velocity and pressure of the exhaust gas flowing to the turbine blades, and improving the supercharging effect . [0003] In recent years, efforts have been made to improve the response in the low-speed region of the engine by enhancing exhaust gas restriction, etc., and a higher response of the turbocharger is expected. When the engine is accelerated, the opening degree of the nozzle vanes of the variable nozzle mechanism is reduced to increase the exhaust pressure, thereby increasing the number of rotations of the turbine rotor. Such as Figure 21 As shown, when the opening of the nozzle vane is small, the loss of leakage flow (hereinafter referred to as ga...

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Problems solved by technology

like Figure 21 As shown, when the opening of the nozzle vane is small, the loss of leakage flow (hereinafter referred to as gap flow) leaking from the gap between the end surface of the nozzle vane and the flow path wall increases, and the efficiency decreases, so the rotation will be delayed. increase in number

[0004] On the other hand, although the efficiency can be improved by reducing the gap between the end surface of the nozzle vane and the flow path wall, if the gap is excessively reduced, the nozzle vane will block (stick, not rotate)

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