Variable Geometry Turbocharger Nozzle Vane Clearance Reduction
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Solution Overview
Problem
Existing variable geometry turbochargers face challenges in reducing clearance between nozzle vanes and wall surfaces to prevent leakage and ensure efficient turbocharging, especially when thermal deformation occurs, leading to potential sticking issues.
Innovation Solution
The design incorporates a nozzle vane accommodating unit with variable nozzle vanes that have a distal end surface inclined towards the inner diameter side due to a fitting gap between the nozzle shaft and shaft hole, utilizing a clearance reduction promotion portion to increase the inclination angle and maintain a sealing property even during thermal deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the clearance between nozzle vanes and wall surfaces is reduced to prevent leakage loss, then turbocharging efficiency is improved, but the nozzle vanes may stick when thermal deformation occurs
Solution Approach 1:
The nozzle vane is designed with asymmetric thickness distribution, where the end portions have a greater thickness than the center portion. This asymmetric geometry creates different clearance characteristics at different locations, allowing the end portions to maintain sealing contact with the wall surfaces while the center portion maintains movement freedom, thus preventing sticking during thermal deformation
Solution Approach 2:
Different portions of the nozzle vane are given different thickness properties - the end portions have increased thickness for sealing contact with wall surfaces, while the center portion has reduced thickness for maintaining movement capability. This local differentiation of properties resolves the contradiction between sealing efficiency and movement reliability
2Speed
If the opening degree of nozzle vanes is reduced to increase turbine revolutions during engine acceleration, then turbocharging response is improved, but leakage loss through clearances increases
Solution Approach 1:
The nozzle vane employs non-uniform thickness distribution with thicker end portions and thinner center portion, creating localized sealing zones at the ends while maintaining flow passage in the center. This allows the vane to achieve small opening degrees for rapid response without excessive leakage through the clearances
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively reduces leakage flow and enhances turbocharging efficiency while preventing nozzle vanes from sticking due to thermal deformation, ensuring optimal performance and reliability.
Implementation Method 1
exhaust gas from an engine acts on a turbine rotor through inside of a scroll chamber formed in a turbine casing and a plurality of variable nozzle vanes
Implementation Method 2
exhaust gas from an engine acts on a turbine rotor through inside of a scroll chamber
Implementation Method 3
when components adjacent to the nozzle vane are thermally deformed by combustion gas
Data Source
AI summary
An object is to is to reduce a leakage flow by reducing a clearance between an end surface of a nozzle vane, forming a variable nozzle mechanism of a variable geometry turbocharger, and a wall surface facing the end surface, and prevent the nozzle vane from being stuck due to contact of the end surface.A variable geometry turbocharger includes a nozzle shaft 49 which protrudes on one of the both end surfaces 58 of a nozzle vane 45 and rotatably supports the nozzle vane 45, a shaft hole 53 in which the nozzle shaft 49 fits with a gap in between, a distal end surface 57 of the nozzle vane with which a clearance is reduced when the nozzle vane 45 which has received exhaust-gas pressure is inclined toward an inner diameter side due to a fitting gap formed between the shaft hole 53 and the nozzle shaft 49 fit to each other, the clearance being formed between the distal end surface 57 and a wall surface 59a of another one of the parallel walls, and a clearance reduction promotion portion 65 which promotes reduction of the clearance with an increased inclination angle of the distal end surface 57 or an increased exhaust-gas-affected surface of the nozzle vane 45.