EP2725194A1 - Turbine rotor blade of a gas turbine - Google Patents

Abstract

The turbine blade has a root portion, a platform and an aerofoil that is mounted on platform and is formed by a pressure side wall and a suction side wall and has an outer surface. The pressure side wall and suction side wall meet at a leading edge and a trailing edge. The suction side wall defines portion of radially outward surface of aerofoil and overhang at aerofoil tip that has maximum overhang length that is between 5% and 20% of axial chord length of blade and is located between 15% and 40% of suction surface length from leading edge. An independent claim is included for a rotor stage of turbine.

Description

The invention relates to a turbine rotor blade of a gas turbine with a blade profile formed in the radial direction (relative to an engine axis of the gas turbine) or in the longitudinal direction of the blade and with a blade tip. As a blade tip is referred to in the context of the present invention, the radially outer end of the turbine rotor blade.

The invention furthermore relates not only to rotor blades, but also to stator blades, wherein the blade tip in the case of stator blades is defined as a radially inner end of the blade.

In the prior art, it is known that at the radial gap between the rotor blades and a housing or between stator blades and a hub caused by the pressure difference from the blade pressure side to the blade suction side leakage mass flow. In this case, solutions have been proposed which reduce this leakage mass flow and / or reduce the negative influence of a forming blade tip vortex on the turbine aerodynamics.

To improve the flow over the blade tips of the rotors mainly circumferential sealing edges (squealer), but partly also overhangs on the blade tip (Wingletausführungen) are provided. Squealer constructions ( US 2010/0098554 A1 ) but only a small improvement in aerodynamics. The winglet construction according to US 7,118,329 B2 has an overhang to the pressure side near the blade trailing edge and a circumferential sealing edge on the blade tip with an opening on the blade trailing edge. The construction according to US 6,142,739 has a suction and pressure side overhang, which is very small near the blade leading edge and overhangs along the blade skeleton line to the blade trailing edge more and more. Furthermore, this construction has an opening of the blade tip cavity at the trailing edge.

On the one hand, the solutions known from the prior art bring only slight aerodynamic advantages, on the other hand, the overhangs (winglets) are dimensioned in such a way that in particular, they are poorly supported by the thin blade trailing edge and affect the mechanical strength of the blade.

The invention has for its object to provide a turbine rotor blade of the type mentioned, which allows for a simple structure and simple, inexpensive to manufacture an optimization of the leakage mass flow and has a good component strength.

According to the invention the object is achieved by the combination of features of claim 1, the dependent claims show further advantageous embodiments of the invention.

According to the invention, it is thus provided that the blade tip has at least on its suction side, starting from a stagnation point on the blade leading edge up to an intersection of the suction-side profile line of the blade with a trailing edge circle, an overhang (winglet). The overhang at the stagnation point and at the intersection with the trailing edge circle is substantially zero and reaches its maximum value at about 40% of the run length of the suction side profile line.

Thus, according to the present invention, there is provided a flow-optimized construction which is advantageous in terms of the strength of the blade, in which the aerodynamic losses are minimized.

It is particularly favorable if the size of the suction-side overhang (vertical distance from the suction-side profile line) reaches approximately 45% of the diameter of the maximum circle T _max which can be inscribed in the blade profile.

In a particularly favorable embodiment of the blade according to the invention is further provided that the blade tip on its pressure side, starting from a stagnation point on the blade leading edge to an intersection of the pressure side profile line of the blade with the trailing edge circle, also has an overhang (winglet), which at the stagnation point and is substantially zero at the intersection and which has a maximum value at about a run length between 20% and 60% of the total run length of the pressure side profile line.

To improve the flow and to further reduce the leakage mass flow, it may furthermore be favorable that a peripheral sealing edge is formed at the radially outer edge region of the blade (in the case of a rotor blade) or at the radially inner edge region in the case of a stator blade. This can, for example, have a substantially rectangular cross-section, so that a depression / cavity is formed in the middle region of the blade tip.

The sealing edge can furthermore preferably have a region with a reduced height or a region with a height of zero, which is provided in the region of the suction-side overhang between a running length of the suction-side profile line of 10% to 30%. Thus, an opening is formed through which an inflow of the boundary layer close to the housing can take place on the blade tip.

It is particularly advantageous to dimension the height and the width of the sealing edge as a function of a blade tip gap. The radial height may be between half of the blade tip gap and the triple blade tip gap. With regard to the width of the sealing edge, this can be formed between the triple blade tip gap and the sixfold blade tip gap.

With regard to the height of the overhang (winglets) in the radial direction, it can be particularly favorable if this height amounts to a maximum of 10% of the radial length of the blade profile. A preferred value is 5%. This means that about 90% to 95% of the blade profile is formed unchanged and that only the outer 10 or 5% of the length of the blade profile is provided with the overhang or winglet according to the invention.

In order to further optimize the flow conditions, it may be favorable to make the transition from the blade profile to the overhang (winglet) rounded.

Furthermore, it may be advantageous to provide the edge region of the overhang (winglets) at the radial end at an angle. This angle is defined in a plane spanned by a radial vector from the sealing edge to the engine axis and a vector normal to the sealing edge. The angle then forms between a tangent to the outer sealing edge surface and the radial vector. That's it Particularly favorable when the tangent to the pressure-side sealing edge of the blade at an angle between 10 ° and 50 ° directed away from the blade and at the suction-side sealing edge at an angle of 10 ° to 50 ° at a running length 0.1≤s≤0 3 is directed toward the blade and is directed away from the blade at a travel length of between 0.4≤s≤1 at an angle between 10 ° and 50 °.

• Durch die relative schnelle Verkleinerung des großen saugseitigen Überhangs im Bereich (b) entsteht eine konkave Schaufelspitzenform. Das führt dazu, dass der Schaufelspitzenwirbel stromab einen immer größeren Abstand zur Schaufel gewinnt.
• Als Folge wird der Schaufelspitzenwirbel von der saugseitigen Schaufelumströmung entkoppelt und interagiert nicht oder nur sehr wenig mit dem sich in diesem Bereich entwickelnden Sekundärströmungswirbel. Diese Entkopplung trägt maßgeblich zur Wirkungsgradverbesserung der Schaufelspitzenströmung durch das Winglet bei.
• Der Überhang des Winglets reduziert den treibenden Druckgradienten zwischen Druckseite und Saugseite und verringert damit den Leckagemassenstrom.
• Die Öffnung der umlaufenden Dichtkante des Winglets sorgt für eine Einströmung von relativ kalter gehäusenaher Luft in die Kavität des Winglets. Die Trajektorie dieser Zuströmung (Stromlinienkrümmung) bewirkt einen Druckgradienten in Richtung Druckseite der Schaufel. Hierdurch wird eine weitere Reduktion des Leckagemassenstromes erzielt. Weiterhin verringert die aufströmende relativ kalte Luft die Kühlungsanforderungen für das Winglet.
• Die Form (Tangentenwinkel) der umlaufenden bzw. unterbrochenen Dichtkante ist in Abhängigkeit der Profillauflänge so gestaltet, dass an gewünschten Positionen Strömungsablösungen hervorgerufen werden (z.B. Druckseite) und an anderen Positionen (z.B. Saugseite) Strömungsablösungen vermieden werden.

The winglet construction according to the invention has the property to improve the overflow of the turbine blade tips so that the leakage mass flow through the blade tip is reduced (improved efficiency in the rotor) and at the same time the outflow in the rotor blade tip is equalized in terms of the outflow angle (efficiency improvement in the downstream blade rows). These advantages are achieved by the following flow-mechanical effects:

• Due to the relatively rapid reduction of the large suction-side overhang in region (b), a concave blade tip shape is formed. This results in the blade tip vortex gaining an ever greater distance downstream of the blade downstream.
• As a result, the blade tip vortex is decoupled from the suction-side blade flow and does not interact or interacts very little with the secondary flow vortex developing in this region. This decoupling contributes significantly to the efficiency improvement of the blade tip flow through the winglet.
• The overhang of the winglet reduces the driving pressure gradient between the pressure side and the suction side and thus reduces the leakage mass flow.
• The opening of the peripheral sealing edge of the winglet provides for a flow of relatively cold air close to the housing into the cavity of the winglet. The trajectory of this inflow (streamline curvature) causes a pressure gradient in the direction of the pressure side of the blade. As a result, a further reduction of the leakage mass flow is achieved. Furthermore, the influx of relatively cold air reduces the cooling requirements for the winglet.
• The shape (tangent angle) of the circumferential or interrupted sealing edge is designed as a function of the profile run length so that flow detachments are caused at desired positions (eg pressure side) and at other positions (eg suction side) flow separation can be avoided.

Fig. 1

eine schematische Darstellung eines Gasturbinentriebwerks gemäß der vorliegenden Erfindung,

Fig. 2

eine vereinfachte Draufsicht auf den Endbereich der erfindungsgemäßen Schaufel,

Fig. 3

eine Ansicht, analog Fig. 2, mit Angabe der Schnittlinien der Fig. 4 bis 6,

Fig. 4 bis 6

Teil-Schnitte gemäß den Schnittlinien in Fig. 3,

Fig. 7

eine Darstellung, ähnlich Fig. 5, mit Angabe der Definitionen zur Bemessung des Schaufelendbereichs,

Fig.8, 9

stirnseitige Ansichten, analog den Fig. 2 und 3, zur Darstellung des erfindungsgemäßen Überhangs,

Fig. 10, 11

Dickenverteilungen des saugseitigen und druckseitigen Überhangs bezogen auf die Lauflänge der saugseitigen bzw. druckseitigen Profillinie,

Fig. 12

eine perspektivische stirnseitige Ansicht, analog den Fig. 2 und 3, mit Darstellung der Dichtkante,

Fig. 13

eine Draufsicht auf die Darstellung gemäß Fig. 12 mit Strömungslinien,

Fig. 14

eine Schnittansicht, analog den Fig. 4 bis 6, mit Darstellung des Strömungsverlaufs, und

Fig.15

eine Draufsicht zur Verdeutlichung des in Fig. 14 gezeigten Strömungsverlaufs.

In the following the invention will be described by means of an embodiment in conjunction with the drawing. Showing:

Fig. 1

a schematic representation of a gas turbine engine according to the present invention,

Fig. 2

a simplified plan view of the end portion of the blade according to the invention,

Fig. 3

a view, analog Fig. 2 , indicating the cutting lines of the 4 to 6 .

4 to 6

Partial cuts according to the cutting lines in Fig. 3 .

Fig. 7

a representation, similar Fig. 5 , specifying the definitions for the design of the blade end area,

8, 9

frontal views, analogous to Fig. 2 and 3 , for the representation of the overhang according to the invention,

10, 11

Thickness distributions of the suction-side and pressure-side overhang with respect to the run length of the suction-side or pressure-side profile line,

Fig. 12

a perspective frontal view, analogous to Fig. 2 and 3 , with representation of the sealing edge,

Fig. 13

a plan view of the illustration according to Fig. 12 with streamlines,

Fig. 14

a sectional view, analogous to 4 to 6 , with representation of the flow course, and

Figure 15

a plan view to illustrate the in Fig. 14 shown flow pattern.

The gas turbine engine 10 according to Fig. 1 is a generalized example of a turbomachine, in which the invention can be applied. The engine 10 is formed in a conventional manner and comprises in succession an air inlet 11, a fan 12 circulating in a housing, a medium pressure compressor 13, a high pressure compressor 14, a combustion chamber 15, a high pressure turbine 16, a medium pressure turbine 17 and a low pressure turbine 18 and a Exhaust nozzle 19, which are all arranged around a central engine axis 1.

The intermediate pressure compressor 13 and the high pressure compressor 14 each include a plurality of stages, each of which includes a circumferentially extending array of fixed stationary vanes 20, commonly referred to as stator vanes, that radially inwardly from the engine casing 21 in an annular flow passage through the compressors 13, 14 protrude. The compressors further include an array of compressor blades 22 projecting radially outwardly from a rotatable drum or disc 26 coupled to hubs 27 of high pressure turbine 16 and mid pressure turbine 17, respectively.

The turbine sections 16, 17, 18 have similar stages, comprising an array of fixed vanes 23 projecting radially inward from the housing 21 into the annular flow passage through the turbines 16, 17, 18, and a downstream array of turbine rotor blades 24 projecting outwardly from a rotatable hub 27. The compressor drum or compressor disk 26 and the blades 22 disposed thereon and the turbine rotor hub 27 and the turbine rotor blades 24 disposed thereon rotate about the engine axis 1 during operation.

The Fig. 2 shows an end view of an embodiment of a turbine rotor blade according to the invention 24. It is understood that the frontal Surface is not flat, but part of a cylinder jacket around the engine axis 1. To simplify the illustration, the end surface is in each case flat in the following figures.

The Fig. 2 thus shows an inventive design of the rotor blade tip in plan view. Here, a feature of the invention, the special shape of the suction-side overhang 30. The inventive design of the suction-side overhang 30 is by means of Fig. 8 and 10 described in more detail. Two reference points, namely the stagnation point at the blade leading edge (under 2D approach) LE and the intersection of the suction-side profile line with the trailing edge circle TE, are used to describe the suction-side winglet overhang. Between these two reference points, the dimensionless run length s is defined along the suction-side profile line, so that s (LE) = 0 and s (TE) = 1. Along s, the winglet overhang T _w (s) is defined as a thickness distribution, ie as a vertical distance to the suction-side blade profile line. In this case, the thickness distribution with the maximum profile thickness T _{max of} the blade tip (diameter of the largest circle 31 that can be inscribed in the blade profile) is made dimensionless.

In order to utilize the aerodynamic effects of the suction-side overhang 30, the thickness distribution in Fig. 10 especially advantageous. At the two reference points LE and TE, the thickness distribution is close to 0 (no significant overhang 30 is present). Starting from the point LE, the overhang 30 increases only very slowly along s. From approx. S = 0.1, there is a rapid increase in the thickness distribution, range (a), up to the maximum T _{w, max} , which is approximately 40% of the run length s = 0.4, or approximately in the area of the narrowest cross section (throat) of the blade passage between adjacent blades is reached. Between approx. 0.5 <= s <= 0.7, range (b), the thickness distribution decreases rapidly to approx. 20% T _{w, max} and finally slowly returns to 0% until s = 1, range ( c). Furthermore, in Fig. 10 two further thickness distributions (dashed lines shown), which thus narrow an area for the particularly advantageous design of the suction-side overhang 30.

In the 8 and 9 If a blade profile 29 is shown as a dashed line, this line corresponds to the blade profile under the winglet 30 at 90% of the blade height. Line 38 shows the contour of the suction-side overhang ( Fig. 8 ) while the line 39 the contour of the pressure-side overhang ( Fig. 9 ) shows. The reference numeral 31 indicates the circle which can be inscribed in the region of the maximum thickness of the cross section of the blade profile 29. The reference numeral 32 shows the trailing edge circle.

As in the Fig. 2 and 3 illustrated, the edge of the overhang 30 is formed in the form of a sealing edge 33, which is carried out substantially circumferentially. It has, as will be described below, an opening 34 ( FIGS. 12 and 13 ). While in Fig. 8 the suction-side overhang is shown and explained in detail, shows the Fig. 9 the pressure-side overhang with its contour 39.

The Fig. 4 to 7 each show sectional views along the in Fig. 3 shown cutting lines.

The thicknesses of the overhangs on the suction side and the pressure side are in the 10 and 11 shown. The course is in each case applied over a dimensionless running length s, which extends from the stagnation point on the blade leading edge LE along the suction or pressure-side profile line to the intersection of the profile line with the trailing edge circle TE. The size of the overhang T _w (s) is normalized to the diameter of the maximum circle T _max which can be inscribed in the blade profile. It follows at which points in each case the maximum values are provided particularly favorable. The dashed lines in the 10 and 11 show a preferred design range, while the solid line represents an optimized solution.

• Einen relativ kleinen, aber signifikanten druckseitigen Überhang T_w(s), der, wie in Fig. 9 und 11 gezeigt, zwischen 0≤s≤0,2 sehr klein ist, von s=0,2 bis s=0,6 bis auf sein Maximum von 15% T_max anwächst und schließlich von s=0,6 bis zur Schaufelhinterkante abfällt, sodass der druckseitige Überhang bei s=1 tangential an den Hinterkantenkreis übergeht. Eine günstige Gestaltung des druckseitigen Überhanges kann mittels der gestrichelten Kurven in Fig. 11 eingegrenzt werden.
• Eine Öffnung, zumindest aber eine Verringerung der Höhe d der umlaufenden Dichtkante im vorderen Bereich des saugseitigen Überhangs zwischen ca. s=0,1 und s=0,3, wie in Fig. 12 und 13 gezeigt.
• Eine mittels des Rotorschaufelspitzenspaltes (nominal im Normalbetrieb) t definierte Höhe d der umlaufenden bzw. unterbrochenen Dichtkante auf dem Winglet von ca. 0,5t≤d≤3t (siehe Fig. 7).
• Eine mittels des Rotorschaufelspitzenspaltes t definierte Breite b der umlaufenden bzw. unterbrochenen Dichtkante auf dem Winglet von ca. 3t≤b≤6t (siehe Fig. 7).
• Eine Höhe h des Winglets von nicht mehr als 10 % der mittleren Höhe des Rotorschaufelprofiles. In besonders günstiger Ausführung sollte h∼5% der mittleren Höhe des Rotorschaufelproflies betragen (siehe Fig. 7). Dabei ist h als der radiale Abstand der Wingletspitze von dem radialen Schaufelprofilschnitt anzusehen, bei dem die Aufweitung des Schaufelprofils in das Winglet deutlich beginnt.
• Einen stetigen, mit angemessenen Radien R (bzw. geeigneten Kurvenformen) abgerundeten, sanften Übergang zwischen dem Wingletüberhang und dem Schaufelprofil (siehe Fig. 7).
• Einen von der Profillauflänge s abhängigen, beispielhaft mittels der Schaufelschnitte A:A, B:B und C:C in Fig. 7 definierten Winkel β zwischen der Tangente an der äußeren Dichtkante 35 und dem Radialenvektor 36, sodass die Tangente an der Druckseite stets von der Schaufel mit einem Winkel zwischen 10°≤β_DS≤50° weg zeigt und die Tangente an der Saugseite zwischen 0,1≤s≤0,3 zu der Schaufel mit einem Winkel zwischen 10°≤β_ss≤50° hin zeigt, jedoch zwischen 0,4≤s≤1 stets mit einem Winkel von 10°≤β_SS≤50° von der Schaufel weg zeigt.

As shown in the figures, the rotor blade tip has the following preferred structural properties in order to minimize the effect of the rotor tip gap leakage flow on the turbine efficiency:

• A relatively small but significant pressure-side overhang T _w (s), which, as in Fig. 9 and 11 between 0≤s≤0,2 is very small, from s = 0,2 to s = 0,6 increases to its maximum of 15% T _max and finally decreases from s = 0,6 to the blade trailing edge, so the pressure-side overhang at s = 1 tangential goes to the trailing edge circle. A favorable design of the pressure-side overhang can by means of the dashed curves in Fig. 11 be limited.
• An opening, but at least a reduction in the height d of the circumferential sealing edge in the front region of the suction-side overhang between about s = 0.1 and s = 0.3, as in FIGS. 12 and 13 shown.
• A defined by the rotor blade tip gap (nominal in normal operation) t height d of the circumferential or interrupted sealing edge on the winglet of about 0.5t≤d≤3t (see Fig. 7 ).
• A width b defined by the rotor blade tip gap t of the circumferential or interrupted sealing edge on the winglet of about 3t≤b≤6t (see Fig. 7 ).
• A height h of the winglet of not more than 10% of the mean height of the rotor blade profile. In a particularly favorable design h~5% should be the average height of the rotor blade profiled web (see Fig. 7 ). H is to be regarded as the radial distance of the winglet tip from the radial blade profile section, in which the widening of the blade profile into the winglet clearly begins.
• A smooth, smooth transition between the winglet overhang and the blade profile, rounded off with appropriate radii R (or appropriate curve shapes) (see Fig. 7 ).
• One dependent on the profile run length s, for example by means of the blade sections A: A, B: B and C: C in Fig. 7 defined angle β between the tangent to the outer sealing edge 35 and the radial vector 36, so that the tangent to the pressure side always pointing away from the blade at an angle between 10 ° ≤β _DS ≤50 ° and the tangent to the suction side between 0.1 ≤s≤0.3 points to the blade at an angle between 10 ° ≤β _ss ≤50 °, but always between 0.4≤s≤1 with an angle of 10 ° ≤β _SS ≤50 ° away from the blade shows.

To clarify the above statements thus show the 4 to 6 each sectional view according to Fig. 3 from which the preferred embodiments result. In particular, the show 4 to 6 the respective angles β between the tangent 35 and the radial vector 36. The Fig. 7 again clarifies the dimensional definitions and also schematically illustrates the housing 40 and the blade tip gap 37.

From the Fig. 12 to 15 again gives a representation of the flow conditions. The Fig. 13 shows in particular an inflow through the opening 34 and a flow through the blade tip gap 37. Accordingly, the FIGS. 14 and 15 for clarity, an example of a blade tip-splitting vortex 41 forming as well as a secondary flow vortex 42.

LIST OF REFERENCE NUMBERS

1

Engine axis

10

Gas turbine engine / core engine

11

air intake

12

fan

13

Medium pressure compressor (compressor)

14

High pressure compressor

15

combustors

16

High-pressure turbine

17

Intermediate pressure turbine

18

Low-pressure turbine

19

exhaust nozzle

20

vanes

21

Engine casing

22

Compressor blades

23

vanes

24

Turbine rotor blades

26

Compressor drum or disc

27

Turbinenrotornabe

28

outlet cone

29

Bucket profile (below the winglet at approx. 90% bucket height)

30

Overhang / winglet

31

Circle (with maximum diameter inscribable in the blade profile)

32

Trailing edge circuit

33

sealing edge

34

Opening of the sealing edge

35

Tangent at the sealing edge

36

Radial vector at the sealing edge

37

Blade tip clearance

38

Contour of the suction-side overhang

39

Contour of the pressure-side overhang

40

Housing end wall of the turbine rotor

41

Blade tip clearance vortex

42

Secondary flow vortices

DS

pressure side

SS

suction

LE

Stagnation point at the blade leading edge

TE

Intersection of the suction or pressure side profile line with the trailing edge circle

b

Width of the sealing edge

d

Height of the sealing edge

H

Height of the overhang (winglet)

R

Rounding radii between overhang (winglet) and blade profile

s

yardage

t

Height of the blade tip gap

T _max

maximum blade profile thickness

T _w

Overhang (winglet) size

T _{w, max}

maximum overhang (winglet) size

Claims (10)

Turbine rotor blade of a gas turbine with a blade tip, wherein the blade tip at least on its suction side (SS), starting from a stagnation point (LE) at the blade leading edge to an intersection (TE _SS ) of the suction side profile line of the blade (24) with a trailing edge circle (32) an overhang (30) which is substantially zero at the stagnation point (LE) and at the intersection (TEss) and which has a maximum value at about 40% of the run length (s) of the suction-side overhang (30). Bucket according to claim 1, characterized in that the maximum value of the suction-side overhang (30) is formed substantially in the region of the narrowest cross-section of the blade passage. Shovel according to claim 1 or 2, characterized in that the blade tip on its pressure side (DS), starting from a stagnation point (LE) at the blade leading edge to an intersection (TE _DS ) of the pressure side profile line of the blade (24) with a trailing edge circle ( 32) has an overhang (30), which at the stagnation point (LE) and at the intersection (TE _DS ) is substantially zero and which has a maximum value at about a run length (s) of 20% to 60% of the run length (s) of the pressure side Overhang (30). Blade according to one of claims 1 to 3, characterized in that at the radially outer edge region of the blade (24) has a peripheral sealing edge (33) is formed. Blade according to claim 4, characterized in that the sealing edge (33) in the region of the suction-side overhang (30) between a run length (s) of 10% and 30% has a reduced or reduced to a value of zero height (d). Blade according to claim 5, characterized in that the reduced height (d) of the sealing edge (33) forms an opening (34) extending between 10% and 30% of the run length (s) of the sealing edge (33). Blade according to one of claims 4 to 6, characterized in that the sealing edge (33) has a radial height (d) of 0.5t≤d≤3t, where t is the blade tip gap (37) provided in the operation and / or that the Sealing edge (33) has a width (b) of 3t≤b≤6t. Bucket according to one of claims 1 to 7, characterized in that the height (h) of the overhang (30) is at most 10%, preferably 5% of the radial length of the blade profile (29). Bucket according to one of claims 1 to 8, characterized in that the transition from the blade profile (29) to the overhang (30) is rounded. Shovel according to one of claims 1 to 9, characterized in that an angle (β) between a tangent (35) at the outer edge of the overhang (30) and a radially extending, with respect to an engine axis (1) extending vector (36) is formed so that the tangent (35) on the pressure side (DS) of the blade (24) at an angle (β _DS ) of 10 ° ≤β _DS ≤50 ° directed away and on the suction side (SS) between 0, 1≤s≤0.3 with an angle (β _SS ) of 10 ° ≤β _SS ≤50 ° towards the blade (24) and between 0.4≤s≤1 with an angle of 10 ° ≤β _SS ≤ 50 ° from the blade (24) directed away.

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