Turbocharger

Abstract

A variable-geometry turbocharger comprising a bearing housing which supports a turbine impeller rotatably, a turbine housing in which a scroll channel for supplying exhaust gas to the turbine impeller is formed, and an exhaust nozzle which can change the flow velocity and flow angle of the exhaust gas to be supplied from the scroll channel to the turbine impeller side, wherein the exhaust nozzle is equipped with a pair of exhaust gas introduction walls which form an exhaust gas channel, and a plurality of nozzle vanes which are arranged between the pair of exhaust gas introduction walls and supported rotatably on the periphery of the turbine impeller, and wherein the nozzle vane has a high pressure-side wall surface facing the scroll channel and is provided in such a manner that the bearing housing side of the high pressure-side wall surface is closer to the turbine impeller than the turbine housing side, and the nozzle vane moves to the turbine housing side or pushes the exhaust gas introduction wall on the turbine housing side so that the clearance between the exhaust gas introduction wall provided on the turbine housing side, out of the pair of exhaust gas introduction walls, and the nozzle vane is narrowed when the turbine impeller is rotating.

Description

technical field [0001] The present invention relates to turbochargers. [0002] This application claims the priority of Japanese Patent Application No. 2008-284140 for which it applied in Japan on November 5, 2008, The content is used here. Background technique [0003] Conventionally, there is known a bearing housing that rotatably supports a turbine rotor, a turbine housing in which a vortex flow path for supplying exhaust gas to the turbine rotor is formed, and a flow rate of the exhaust gas supplied from the vortex flow path to the turbine rotor side. and a variable capacity turbocharger having an exhaust nozzle with a variable flow angle (for example, refer to Patent Document 1). [0004] The exhaust nozzle of the variable-capacity turbocharger of Patent Document 1 is equipped with a movable nozzle on a pair of parallel walls (exhaust gas introduction walls) between the spiral chamber (swirl flow path) and the impeller (turbine rotor). Nozzle vanes (nozzle fins). In ...

AI Technical Summary

Problems solved by technology

[0017] However, even when the nozzle vane has a convex shape in this way, the nozzle vane is also arranged at a position relatively close to the exhaust gas introduction wall provided on the bearing housing side, and there is no connection with the exhaust gas inlet wall provided on the turbine housing side. When the gap between the introduction walls becomes large

In this case, as described above, the loss that occurs when the exhaust gas that passes through the gap on the turbine housing side flows into the turbine rotor side is compared to the loss that occurs when the exhaust gas that passes through the gap on the bearing housing side flows into the turbine rotor. The loss is relatively larger, and the turbine efficiency in the latter case is lower than that of the former

As a result, the turbine efficiency drops

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