Blade, blade ring, blade ring segment and turbomachine

Abstract

A blade (10) for a turbomachine is provided. In at least one cross section disposed orthogonally to a longitudinal blade axis, an outer surface of the blade forms a curve () that runs continuously on the inflow side along an at least approximate ellipse (E) between a first separation point (P.sub.1) and a second separation point (P.sub.2). On the pressure side 12, the curve () has an inflection point W. A distance of the second separation point (P.sub.2) from the inflection point W along the curve is at least exactly equal, at least twice as great, at least three times as great, or even at least five times as great as a distance of the second separation point (P.sub.2) from the first separation point (P.sub.1) along the at least approximate ellipse (E). Also described is a blade ring having at least one blade of this kind, as well as a turbomachine.

Claims

1. A blade for a turbomachine, the blade comprising: at least one cross section disposed orthogonally to a longitudinal blade axis, an outer surface of the blade forming a curve running continuously on an inflow side along an ellipse between a first separation point and a second separation point along the ellipse or without any abrupt changes in curvature approximately along the ellipse; the first separation point, the curve separating from the ellipse, toward a suction side and, at the second separation point, toward a pressure side, in each case without any abrupt changes in curvature; in addition, the curve having an inflection point on the pressure side; and a first distance of the second separation point from the inflection point along the curve being at least exactly equal or greater as a second distance of the second separation point from the first separation point along the ellipse; wherein the first distance is at least five times as great as the second distance.

2. The blade as recited in claim 1 wherein the first distance is at most ten times as great as the second distance.

3. The blade as recited in claim 1 wherein the first distance is at most eight times as great as the second distance.

4. The blade as recited in claim 1 wherein the ellipse defines an angle between a first tangent at the first separation point and a second tangent at the second separation point of at least 70.

5. The blade as recited in claim 4 wherein the angle at least 80.

6. The blade as recited in claim 4 wherein the angle at least 90.

7. A blade ring comprising an inner ring and the blade as recited in claim 1.

8. A blade ring segment comprising the blade as recited in claim 1.

9. A turbomachine comprising a compressor stage or turbine stage comprising the blade ring segment as recited in claim 8.

10. An aircraft engine or turbofan aircraft engine comprising the turbomachine as recited in claim 9.

11. A blade for a turbomachine, the blade comprising: at least one cross section disposed orthogonally to a longitudinal blade axis, an outer surface of the blade forming a curve running continuously on an inflow side along an ellipse between a first separation point and a second separation point along the ellipse or without any abrupt changes in curvature approximately along the ellipse; the first separation point, the curve separating from the ellipse or the approximate ellipse, toward a suction side and, at the second separation point, toward a pressure side, in each case without any abrupt changes in curvature; in addition, the curve having an inflection point on the pressure side; and a first distance of the second separation point from the inflection point along the curve being at least exactly equal or greater as a second distance of the second separation point from the first separation point along the ellipse; wherein a hollow body at least in the region of the at least one cross section has a maximally occurring wall thickness between the first and second separation point of at most 110% of twice a small half-axis of the ellipse or being at least 90% of the small half-axis.

12. The blade as recited in claim 11 wherein the hollow body at least in the region of the at least one cross section has a maximally occurring wall thickness between the first and second separation point of at most 105% of twice the small half-axis or being at least 95% of the small half-axis.

13. The blade as recited in claim 11 wherein the maximally occurring wall thickness between the first and second separation point is at most 2 mm.

14. The blade as recited in claim 11 wherein the maximally occurring wall thickness between the first and second separation point is at most 1.5 mm.

15. The blade as recited in claim 11 wherein the maximally occurring wall thickness between the first and second separation point is at most 1 mm.

16. The blade as recited in claim 11 wherein in at least one portion of the longitudinal blade axis, each cross section orthogonal to the longitudinal blade axis has the at least one cross section.

17. The blade as recited in claim 16 wherein the at least one portion extends at least one third, at least one half, or at least two thirds of the length of the blade.

18. A blade ring comprising an inner ring and the blade as recited in claim 11.

19. A turbomachine comprising a compressor stage or turbine stage comprising the blade ring segment as recited in claim 18.

20. An aircraft engine or turbofan aircraft engine comprising the turbomachine as recited in claim 18.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Preferred exemplary embodiments of the present invention will be described in greater detail below with reference to the drawing. It is understood that individual elements and components may be combined in ways other than those described. Reference numerals for mutually corresponding elements are used throughout the figures and, as the case may be, are not respecified for each figure.

(2) In the schematic drawing,

(3) FIG. 1: shows the characteristic curve of an outer surface of a blade in accordance with a specific embodiment of the present invention in cross section together with a corresponding functional representation of the curvature profile of the outer surface;

(4) FIG. 2: pressure profiles on the pressure side and suction side in a comparison of conventional blades and inventive blades;

(5) FIG. 3: a detail view from a cross section through an exemplary inventive blade at the inflow region thereof including an outer and an inner surface; and

(6) FIG. 4 shows highly schematically the blade ring and turbomachine having the blades as in FIG. 1

DETAILED DESCRIPTION

(7) In the lower portion, FIG. 1 schematically shows an outer surface of an exemplary inventive blade 10 in a cross section orthogonally to a longitudinal blade axis. Blade 10 has a suction side 11 and a pressure side 12; an indicated primary flow direction X is from left to right in the figure.

(8) In the cross section perpendicularly to the longitudinal blade axis, the outer surface of the illustrated blade forms a closed curve which runs on the inflow side along an ellipse E that, in accordance with the aforementioned definition, also includes an approximate, respectively almost ellipse; in the illustrated example, ellipse E is formed as a circle. The shared portion of the curve and of ellipse E ends toward the suction side of the blade at a first separation point P.sub.1 where curve separates from the ellipse (in the indicated through-flow direction). Following in the opposite direction (thus, toward suction side 11 of the blade), curve separates from ellipse E at a second separation point P.sub.2; thus, in this direction, the shared portion of curve and of ellipse E ends at second separation point P.sub.2. Along the shared portion and at separation points P.sub.1 and P.sub.2, curve is free of any abrupt changes in curvature, i.e., even in the regions of separation points P.sub.1 and P.sub.2, there is no abrupt change, respectively no discontinuity in the curvature profile of curve .

(9) A first tangent T.sub.1 to curve at first separation point P.sub.1 and a second tangent T.sub.2 to curve at second separation point P.sub.2 form an angle in which the ellipse is located; this angle, whose opposite angle is characterized in FIG. 1 as , is more than 90 here.

(10) In the illustrated cross section, blade 10 thereby forms an obtuse, inflow-side leading region.

(11) On the outflow side, thus in the trailing region of the blade, curve runs in the example shown between a third separation point P.sub.3 and a fourth separation point P.sub.4 continuously along another ellipse K, which, in the illustrated exemplary embodiment, is formed as a circle, similarly to ellipse E. Curve separates from further ellipse K toward pressure side 12 at third separation point P.sub.3 and, toward suction side 11, at fourth separation point P.sub.4. In the illustrated, advantageous specific embodiment, the small half-axis (thus, here, the radius) of ellipse E (likewise formed as a circle) is at most three times, at most two and a half times, or even at most twice as great as the small half-axis (here, the radius) of further ellipse K.

(12) Starting from the inflow-side leading region, respectively first separation point P.sub.1, the curve changes the curvature direction thereof (for the first time) along the continuation path thereof at an inflection point W on pressure side 12 of blade 10. This is readily discernible by the curvature profiles of curve illustrated in the upper portion of FIG. 1: Function graph K.sub.D, illustrated as a solid line in the figure, shows the curvature of curve in the area of pressure side 12, in each case as a function of an extent x of blade 10 at the outer surface thereof in indicated primary flow direction X, and function graph K.sub.S plotted as a dashed line represents the curvature of curve on suction side 11 of the blade. The first zero crossing of function graph K.sub.D marks inflection point W on pressure side 12 of blade 10. As is discernible in the figure, the distance of second separation point P.sub.2 from the inflection point that is measured along curve is greater than the distance of second separation point P.sub.2 from first separation point P.sub.1 that is measured along curve .

(13) Thus, on pressure side 12, inflection point W is spaced relatively far from the inflow-side leading region. This makes it possible to minimize changes, respectively differences in the pressure profile: This is discernible in FIG. 2, where the pressure on the suction side and on the pressure side are each plotted as a function whose variable x represents the extent of blade 10 at the outer surface thereof in primary flow direction X. Graphs p.sub.D,1 and p.sub.S,1 plotted as solid linesfor the pressure side and, respectively the suction sideshow the pressure profile of a conventional blade where the inflow-side leading region runs along a circular path, and the outer surface toward the pressure side separates from the circular path at an inflection point. Namely, graph p.sub.D,1 shows that a pronounced change in pressure occurs on the pressure side (relative to primary flow direction X) downstream of a stagnation point in the inflow region of the blade (thus, downstream of a point where the gas flowing through has the highest pressure and a velocity of zero).

(14) On the other hand, the inflection point located further downstream in accordance with the present invention results in a pressure profile as shown by dashed-line graphs p.sub.D,2 and p.sub.S,2 for the pressure side, respectively the suction side. Specifically, graph p.sub.D,2 shows a pressure differential that is significantly reduced in comparison to conventional profile p.sub.D,1. This makes it possible to avoid a pressure-side separation, thereby enhancing efficiency.

(15) FIG. 3 shows a detail view of a cross section through an exemplary inventive blade 10 at the inflow region thereof. As is discernible, the blade is formed in the region as a hollow body. The outer surface of the blade extends continuously between a first separation point P.sub.1 and a second separation point P.sub.2 along an ellipse E, which is formed as a circle here. A first tangent T.sub.1 to outer surface at first separation point P.sub.1 and a second tangent T.sub.2 to outer surface at second separation point P.sub.2 form an angle in which the ellipse is located; this angle, whose opposite angle is characterized in the figure as , is more than 90 here.

(16) At every point of the outer surface, the blade has a wall thickness that is defined in each case as the minimum distance to a point on the inner surface of the hollow body; FIG. 3 characterizes a maximally occurring wall thickness S of the blade between first and second separation point P.sub.1, P.sub.2. A maximum wall thickness of this kind is preferably at most 110%, preferably at most 105% of twice the small half-axis of ellipse E; in the illustrated example, S is exactly equal to twice the small half-axis of ellipse E, which, in the case of the ellipse formed as a circle, is the diameter thereof.

(17) Maximum wall thickness S may preferably be at most 2 mm, at most 1.5 mm or at most 1 mm.

(18) A blade 10 for a turbomachine is described. In at least one cross section disposed orthogonally to a longitudinal blade axis, an outer surface of the blade forms a curve which runs continuously along an ellipse E between a first separation point P.sub.1 and a second separation point P.sub.2. On pressure side 12, curve has an inflection point W. A distance of second separation point P.sub.2 from inflection point W along the curve is at least exactly equal, at least twice as great, at least three times as great, or even at least five times as great as a distance of second separation point P.sub.2 from first separation point P.sub.1 along ellipse E.

(19) Also described in a highly schematicized view in FIG. 4 is a blade ring 110 having an inner ring 118, at least one blade 10, as well as a turbomachine 100. The cross section can extend over at least a third or more of the longitudinal axis of the blade 10.

REFERENCE NUMERAL LIST

(20) 10 blade 11 suction side 12 pressure side 100 turbomachine 110 blade ring 118 inner ring opposite angle to the angle between tangents T.sub.1 and T.sub.2, in which ellipse E is located curve formed from the outer surface of the blade, in cross section E ellipse (on the inflow side) K ellipse (on the outflow side) K.sub.D curvature profile of the outer surface on pressure side 12 K.sub.S curvature profile of the outer surface on suction side 11 p.sub.D,1 inflow-side pressure profile in the case of a conventional blade on the pressure side p.sub.D,2 inflow-side pressure profile in the case of a blade 10 according to the present invention on pressure side 12 p.sub.S,1 inflow-side pressure profile in the case of a conventional blade on the suction side p.sub.D,2 inflow-side pressure profile in the case of a blade 10 according to the present invention on pressure side 11 P.sub.1 first separation point P.sub.2 second separation point P.sub.3 third separation point P.sub.4 fourth separation point S maximum wall thickness of the blade between the first and second separation point T.sub.1 first tangent T.sub.2 second tangent X indicated primary flow direction