Variable Nozzle Turbocharger

Abstract

The shape, of a vane for use in a variable nozzle assembly of a turbocharger was designed, including a step of defining a camberline curve and a thickness curve by means of two Bézier curves having a certain number of control points, and a step of applying computational fluid dynamics analysis and a Design of Experiments methodology for optimizing the setting of the control points to improve performance of the vane. As result, a distinct vane shape as shown in the drawings was obtained.

1 . A turbocharger with a variable nozzle assembly having a plurality of vanes ( 20 ) positioned annularly around a turbine wheel, wherein
 the shape of each vane ( 20 ) is defined by a first surface ( 1 ) defining a leading edge (LE), a second surface ( 2 ) defining a trailing edge (TE), a third surface ( 3 ) connecting the first and second surfaces on a radially outer side of the vane, and a fourth surface ( 4 ) connecting the first and second surfaces on a radially inner side of the vane,   the midpoints between the third surface ( 3 ) and the fourth surface ( 4 ) define a substantial part of the camberline of the vane, and   the thickness at a specific point of the vane is twice the distance between the specific point and the camberline in a direction perpendicular to a chord Connecting the leading edge (LE) with the trailing edge (TE),   characterized in that   said camberline falls within the bounds of a virtual envelope defined by first Bézier curves, wherein each first Bézier curve has six control points Y 1 , Y 2 , Y 3 , Y 4 , Y 5 , Y 6  which are set to be equally spaced over the length (L) of said chord in ascending order towards the trailing edge (TE), each control point Y 1 , Y 2 , Y 3 , Y 4 , Y 5 , Y 6  is shifted from the chord by a distance which is x-times the length (L), and x falls within the following ranges:
 −0.1≦x≦0.1 for control point Y 1 , 
 −0.033≦x≦−0.027 for control point Y 2 , 
 0.09≦x≦0.13 for control point Y 3 , 
 0.04≦x≦0.054 for control point Y 4 , 
 0.03≦x≦0.05 for control point Y 5 , and 
 −0.1≦x≦0.1 for control point Y 6 ; and 
   the thickness (Th) of the vane is given at each specific point of said third surface ( 3 ) or said fourth surface ( 4 ) by a thickness curve that falls within the bounds of a virtual envelope defined by second Bézier curves, wherein each second Bézier curve has five control points T 1 , T 2 , T 3 , T 4 , T 5  which are set to be equally spaced over the length (L) of said chord in ascending order towards the trailing edge (TE), each control point T 1 , T 2 , T 3 , T 4 , T 5  is shifted from the chord by a distance which is y-times the length (L), and y falls within the following ranges:
 0.03≦y≦0.09 for control point T 1 , 
 0.09≦y≦0.18 for control point T 2 , 
 0.02≦y≦0.05 for control point T 3 , 
 0.03≦y≦0.056 for control point T 4 , and 
 0≦y≦0.025 for control point T 5 . 
   
   
   
       2 . A turbocharger according to  claim 1 , wherein x and y meet at least one of the following equations:
 x≦0.12, preferably x≦0.11 for control point Y 3 ,   x≦0.04 for control point Y 5 ,   y≦0.7, preferably y≦0.5 for control point T 1 , and   y≦0.16, preferably y≦0.13 for control point T 2 .   
   
   
       3 . A turbocharger according to  claim 1 , wherein each of the first surface and the second surface has the shape of a truncated ellipse. 
   
   
       4 . A turbocharger according to  claim 1 , wherein the length of said third surface ( 3 ) or said fourth surface ( 4 ) is not less than 0.8 times, preferably 0.9 times the length (L) of the chord. 
   
   
       5 . A turbocharger according to  claim 1 , wherein each vane is pivotable around a pivot point (P), said pivot point (P) being located at a position which meets the following expressions:
 0.25<Mp<0.45, preferably 0.30<Mp<0.40, and   −0.10<DYp<0, preferably −0.06<DYp<−0.02,   wherein Mp is the distance between the pivot point and the leading edge in the direction of the chord divided by the length of the chord, and DYp is the distance between the pivot point and the chord in a direction perpendicular to the chord divided by the length of the chord, with negative values of DYp representing a pivot point which is more on the radially inner side of the vane.   
   
   
       6 . A turbocharger according to  claim 1 , wherein the length (L) of said chord 19.5 mm or less, preferably 19.0 mm or less, more preferably 18.5 mm or less. 
   
   
       7 . A method of designing the shape of a vane ( 20 ) for use in a variable nozzle assembly of a turbocharger, said method comprising the following steps:
 defining a camberline curve of the vane by using a first Bézier curve which has at least six control points;   defining a thickness curve by using a second Bézier curve which has at least five control points;   setting the shape of the vane based on the camberline curve and the thickness curve; and   applying computational fluid dynamics analysis and a Design of Experiments methodology for optimizing the setting of the control points to improve performance of the vane.