Variable Nozzle Vane S-Shape Cross Section for Turbocharger Hysteresis
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Solution Overview
Problem
Variable geometry turbochargers face challenges in achieving accurate and stable nozzle control due to hysteresis caused by fluctuating moments acting on nozzle vanes, particularly at low speeds, and require modifications to enhance moments in the opening direction without shifting the rotational center.
Innovation Solution
The nozzle vanes are designed with a blade cross-section featuring a concave portion at the trailing edge and a convex portion at the leading edge, forming a substantially S-shape, which increases the moment in the opening direction and reduces hysteresis by optimizing the flow path area and pressure distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the blade length of nozzle vanes is increased to improve turbine efficiency at low speed, then the efficiency is improved, but the moment balance becomes unstable causing hysteresis in nozzle control
Solution Approach 1:
The invention applies different geometric characteristics to different parts of the nozzle vane blade. Specifically, the pressure surface is designed with a concave curvature radius that is smaller than the suction surface curvature radius, creating localized flow control that optimizes both low-speed efficiency and moment stability without requiring overall blade length increases
Solution Approach 2:
The invention changes the geometric parameters of the blade cross-section, specifically setting the pressure surface concave curvature radius to be smaller than the suction surface curvature radius. This parameter modification alters the flow distribution and pressure distribution across the blade, stabilizing the moment characteristics while maintaining improved turbine efficiency
2Force
If the position of rotational center is shifted to leading edge side to enhance opening moment, then the opening moment is enhanced, but the link mechanism design becomes complex
Solution Approach 1:
Instead of shifting the rotational center position globally, the invention applies localized geometric modification to the pressure surface of the blade. The concave curvature on the pressure surface with a smaller radius than the suction surface creates localized flow acceleration and pressure changes that enhance the opening moment while keeping the rotational center in its original position
Solution Approach 2:
The invention utilizes curved surface geometry, specifically designing the pressure surface with a concave curvature radius smaller than the suction surface curvature radius. This curvature differential creates favorable flow patterns and pressure distributions that generate enhanced opening moments without requiring mechanical redesign of the link mechanism
3Force
If the blade cross-section shape is modified to increase opening moment, then the moment control is improved, but the manufacturing precision requirements increase
Solution Approach 1:
The invention defines specific geometric parameters for the blade cross-section, namely the concave curvature radius of the pressure surface and the curvature radius of the suction surface. By specifying that the pressure surface curvature radius is smaller than the suction surface curvature radius, the invention provides clear manufacturing targets that balance moment enhancement with manufacturability
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 design enhances safety and accuracy in nozzle control by consistently applying a moment in the opening direction, preventing hysteresis and ensuring stable operation even at low speeds, thus improving the efficiency and reliability of the variable geometry turbocharger.
Implementation Method 1
due to the pressure difference between the static pressure acting on the pressure surface 25 of the nozzle vane 15a adjacent to the high pressure side H and the static pressure acting on the suction surface 27 adjacent to the low pressure side U, a moment M (-) is generated in the closing direction
Implementation Method 2
a moment M (-) is generated in the closing direction of the nozzle throat 23 at the leading edge 29 side of the nozzle vane 15a, while a moment M (+) is generated in the opening direction at the trailing edge 31 side
Data Source
Figure 1~2
Figure 3~4B
Figure 5~6
AI summary
In a variable geometry turbocharger including a variable nozzle mechanism, an object is to enhance safety upon malfunction of the variable nozzle mechanism as well as to improve accuracy in the control of the variable nozzle mechanism by applying a moment that acts on the nozzle vanes in an opening direction securely and stably. A variable geometry turbocharger includes a plurality of nozzle vanes 41a disposed at predetermined intervals around a rotational shaft center of a turbine wheel 7 so as to surround an outer circumferential side of the turbine wheel 7 and a variable nozzle mechanism configured capable of changing a blade angle of each of the nozzle vanes 41a, each of the nozzle vanes 41a having a blade cross-section orthogonal to a nozzle shaft 41b of each nozzle vane 41a, the blade cross-section having: a concave portion 53 curved into a concave shape on at least a part of a pressure surface 45 side, the part being disposed at a trailing edge 51 side with respect to the rotational center C; and a convex portion at a leading edge 49 side with respect to the rotational center C, so that a surface shape of the pressure surface 45 side is a substantially S-shape having the concave portion and the convex portion across a boundary at a same longitudinal position as the rotational center.