Variable Nozzle Turbocharger Vane Torque Reversion
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Solution Overview
Problem
Variable nozzle turbochargers with cambered vanes experience aerodynamic torque reversion, affecting controllability, particularly when the nozzle throat area is small, leading to negative torque, which complicates the functionality of the actuator assembly and unison ring.
Innovation Solution
Optimizing the vane design by positioning the pivot point between 0.25 and 0.45 times the vane length from the leading edge, locating the local extreme of curvature within specific ranges, and ensuring a flow incidence angle of at least 5° in the closed position, while using composite curves for the airfoil surfaces, reduces aerodynamic torque reversion and enhances controllability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If cambered vanes are used in variable nozzle turbocharger, then aerodynamic performance is improved, but aerodynamic torque reversion occurs causing negative torque when nozzle throat area is small
Solution Approach 1:
The patent modifies the geometric parameters of the vane, specifically positioning the pivot point between 0.25 and 0.45 times the vane length from the leading edge, and designing the airfoil surfaces with composite curves having specific curvature characteristics. These parameter changes eliminate torque reversion while preserving aerodynamic performance.
Solution Approach 2:
The patent employs composite curves for the airfoil surfaces with specifically designed curvature characteristics. The inner airfoil surface has a convex section followed by a concave section, while the outer airfoil surface has a concave section followed by a convex section. This curvature design prevents torque reversion by optimizing the flow incidence angle.
2Reliability
If vane pivot point is positioned optimally, then torque reversion is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The patent specifies the pivot point position as a range (0.25 to 0.45 times the vane length from the leading edge) rather than a single precise value. This range-based specification maintains torque consistency while providing manufacturing tolerance, reducing the stringency of precision requirements.
3Reliability
If flow incidence angle is increased to at least 5 degrees, then torque reversion is minimized, but device complexity increases
Solution Approach 1:
The patent achieves the required flow incidence angle of at least 5 degrees through the curvature design of the airfoil surfaces. The composite curves with convex and concave sections naturally guide the exhaust gas flow to achieve the desired incidence angle without requiring additional mechanical components or complex control mechanisms.
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
The optimized vane design ensures consistent positive torque and improved operational controllability, minimizing torque reversion and enhancing turbocharger efficiency by maintaining a positive torque orientation regardless of vane position, thus improving overall engine performance.
Implementation Method 1
consistent positive torque
Implementation Method 2
exhaust gas flow
Data Source
AI summary
There is provided a turbocharger with a variable nozzle assembly having a plurality of cambered vanes positioned annularly around a turbine wheel, each vane (20) being pivotable around a pivot point (Pp) and being configured to have a leading edge (Ple) and a trailing edge (Pte) connected by an outer airfoil surface (2) and an inner airfoil surface (4), said outer airfoil surface (2) being substantially convex and said inner airfoil surface (4) having a convex section at the leading edge (Ple) which has a local extreme (Pex) of curvature and transitions into a concave section towards the trailing edge (Pte). The positions of the pivot point (Pp) and the local extreme (Pex) are set such that, even when the vanes are placed in a closed position, the exhaust gas stream exercises a positive torque on the vanes which tends to open the nozzle.