MOVING BLADE AND TURBOMACHINE

Abstract

A moving blade for a turbomachine, in particular an aircraft engine, is disclosed, having an inner shroud which has a front elongation for forming an axial overlap with an upstream guide blade, and on which at least one flow guide element for deflecting a leakage flow of a cooling air flow in the peripheral direction is situated. The at least one flow guide element is guided beyond a leading edge of the elongation. A turbomachine having a plurality of these types of moving blades is also disclosed.

Description

This claims the benefit of German Patent Application DE 10 2012 206 126.6, filed Apr. 13, 2012 and hereby incorporated by reference herein.

The present invention relates to a moving blade for a turbomachine and a turbomachine.

BACKGROUND

In engine construction it is generally known that the turbine efficiency may be increased when a leakage flow of a cooling air flow which is branched off on the compressor side, for example, is introduced into a hot gas flow between the guide blades and the moving blades. This type of introduction is described in U.S. Pat. No. 7,244,104 B2, for example, which is hereby incorporated by reference herein. In the patent it is proposed to provide a plurality of flow guide elements in the form of ribs or indentations on an upstream or front elongation of a moving blade inner shroud for forming an axial overlap with an upstream guide blade. The flow guide elements are situated on the elongation on the hot gas side, and have a front curved section and a rear axial section on the hot gas side. The curved sections, which extend away from a leading edge of the elongation in an axial direction and merge into the axial sections, are oriented in the direction of rotation. The aim is for the flow guide elements to “blade,” in a manner of speaking, the leakage flow from a root-side cavity in the guide blades into the hot gas flow, and to impart a peripheral speed to the leakage flow corresponding approximately to the peripheral speed of the inner shroud. However, a basic problem in this regard is how the peripheral speed may be imparted to the leakage flow without resulting in a hot gas intake into the cavity on the root side, which could result in overheating of the guide blades and moving blades in the root area.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a moving blade which allows an optimized introduction of a leakage flow into a hot gas flow and effectively prevents a hot gas intake, as well as a turbomachine having improved efficiency.

The present invention provides a moving blade for a turbomachine, in particular an aircraft engine, has an inner shroud having a front elongation for forming an axial overlap with an upstream guide blade, on which at least one flow guide element for deflecting a leakage flow of a cooling air flow in the peripheral direction is situated. According to the present invention, the at least one flow guide element is guided in the axial direction beyond a leading edge of the elongation.

As a result of the at least one flow guide element being guided in the axial direction beyond the leading edge, a speed is imparted early to the leakage flow in the peripheral direction, and thus in the direction of rotation of the moving blade. The leakage flow is introduced with a swirl into a hot gas flow, thus improving the introduction of the leakage flow. Hot gas intake from the hot gas flow in the direction of the cooling air flow is effectively prevented. The at least one flow guide element is preferably integrally formed together with the elongation. The at least one flow guide element may have a linear, curved, wave-like, or other shape. It must be ensured that the flow guide element does not run against an axially opposite guide blade section due to thermal expansion, so that it may be necessary to enlarge an axial distance between the leading edge and the axially opposite guide blade section.

In one exemplary embodiment, the at least one flow guide element is in flush alignment with a hot gas side and with a cooling air side of the elongation. The at least one flow guide element is thus designed as an axial finger, in a manner of speaking. When there is a plurality of flow guide elements spaced circumferentially or peripherally apart, the leading edge has a comb-like shape. The finger-like design has the advantage that, due to the at least one flow guide element, the elongation does not become thicker in the radial direction, but, rather, has a radial extension which has the original thickness or height of the elongation. Thus, an existing radial plate gap is not diminished by the at least one flow guide element, and therefore also does not have to be reset.

In one alternative exemplary embodiment, the flow guide element protrudes beyond the hot gas side and beyond the cooling air side in the radial direction. The at least one flow guide element therefore has a paddle-like shape. Compared to the previously mentioned finger-shaped exemplary embodiment, this exemplary embodiment has the advantage that an effective area of the flow guide element is enlarged. However, for implementing this paddle-like flow element, structural changes for radial gap maintenance may be necessary to prevent the at least one flow guide element from running against adjacent radial guide blade sections or components in the radial direction due to thermal expansion.

In another exemplary embodiment, the at least one flow guide element has a hot gas side section which is guided on the hot gas side. The flow guide element is thus elongated on the hot gas side in a direction away from the leading edge. The aerodynamic action of the flow guide element may be further intensified in this way. Depending on the angular setting of the section on the hot gas side in the axial direction, the leakage flow may be accelerated to a speed in the peripheral direction which is greater than the peripheral speed of the inner shroud, thus ensuring that a speed that is less than or significantly less than the peripheral speed is not imparted to the leakage flow. At the same time, the extension of the at least one flow guide element on the elongation brings about a structural/mechanical stabilization of the elongation, so that the elongation has a reduced cross section, at least in the area of the flow guide element, and therefore may be designed in a weight-optimized manner. Thus, in this exemplary embodiment the at least one flow guide element also acts as a reinforcing structure in the form of a rib. Since the at least one rib-like flow guide element radially outwardly thickens the elongation at least in sections, for radial gap maintenance, structural changes may be necessary which compensate for the diminished original radial distance. For example, for radial gap maintenance it may be necessary to radially inwardly offset the elongation.

In another exemplary embodiment, the at least one flow guide element has a cooling air side section which is guided on the cooling air side. In this way, a swirl is already imparted to the leakage flow in the area of the cooling air side. For accelerating the leakage flow to a speed in the peripheral direction which is greater than the peripheral speed of the inner shroud, the at least one rib-like flow guide element on the cooling air side opposite from the above-mentioned rib-like flow guide element on the hot gas side should be angularly set in the axial direction. Since the at least one rib-like flow guide element radially inwardly thickens the elongation at least in sections, structural changes may be necessary for radial gap maintenance.

In one exemplary embodiment, the at least one flow guide element has a section on the hot gas side and a section on the cooling air side. This type of U-shaped flow guide element has the advantage that the leakage flow is influenced by the at least one flow guide element on the cooling air side, the leading edge side, and the hot gas side.

The section on the hot gas side and the section on the cooling air side are preferably angularly set oppositely with respect to one another, viewed in the direction of rotation. As a result, the leakage flow on the cooling air side and on the hot gas side is acted on by a velocity component in the same direction. In particular, the section on the hot gas side is situated in front of the section on the cooling air side, viewed against the direction of rotation.

In particular due to structural-mechanical and production engineering reasons, it may be advantageous for the section on the hot gas side and/or the section on the cooling air side to be guided over the entire length of the elongation. Due to the stabilizing effect of the at least one flow guide element, it is thus possible to design the elongation to be thinner, at least in sections, and thus in a weight-optimized manner, so that the rotor mass may be reduced.

From the standpoint of radial gap maintenance, it is advantageous when the section on the hot gas side and/or the section on the cooling air side extend(s) in parallel or essentially in parallel to the respective radially opposite guide blade section or component. It is therefore preferred that the section on the hot gas side and/or the section on the cooling air side has/have a constant height. However, the height of the at least one flow guide element may also vary. In that case, however, in order to not adversely affect the separation effect of the plate gap, it is preferred for the at least one flow guide element to be flat on the other side of the leading edge.

The swirl action or aerodynamic effect of the leakage flow may be additionally influenced by the number of flow guide elements per elongation. Thus, in one exemplary embodiment, multiple flow guide elements are situated next to one another on an elongation, viewed in the peripheral direction.

A preferred turbomachine has at least one moving blade row having a plurality of the moving blades according to the present invention. This type of turbomachine is characterized by an improved efficiency compared to a turbomachine having conventional moving blade rows. Significant structural changes to the components adjacent to this moving blade row, such as guide blade rows and systems, are not necessary. Depending on the design of the flow guide elements, only minor structural changes are necessary for gap maintenance or setting the plate gap.

Other advantageous exemplary embodiments of the present invention are the subject matter of further subclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred exemplary embodiments of the present invention are explained in greater detail below with reference to greatly simplified schematic illustrations.

FIG. 1 shows a finger-shaped flow guide element, according to the present invention, of a moving blade;

FIG. 2 shows a paddle-like flow guide element;

FIG. 3 shows an example of other exemplary embodiments of the flow guide element according to the present invention;

FIG. 4 shows another paddle-like flow guide element;

FIG. 5 shows a flow guide element having a section on the hot gas side;

FIG. 6 shows a flow guide element having a section on the cooling air side; and

FIG. 7 shows a flow guide element having a section on the hot gas side and a section on the cooling air side.

DETAILED DESCRIPTION

FIG. 1 shows an axial section of a turbomachine 1 in the area of a guide blade 2 and a downstream moving blade 4. The turbomachine is preferably an aircraft engine, but may also be a stationary gas turbine. Guide blade 2 is fastened at the root side to a housing section or guide blade support ring, and together with a plurality of further guide blades 2 forms a stationary guide blade row which surrounds a rotor hub which rotates about a rotational axis 6. Moving blade 4 is connected at the root side to the rotor hub via a disk element, for example, and together with a plurality of further moving blades 4 forms a moving blade row which rotates with the rotor hub about rotational axis 6. A direction of rotation or peripheral direction is indicated by the arrow denoted by reference character u.

Guide blade 2 has a platform 8 which extends from a blade tip 10 and represents a radial inner delimitation of a hot gas path. A hot gas flow 12 flows axially through the hot gas path (in the x direction). In the exemplary embodiment shown, the hot gas flow flows through turbomachine 1 from left to right. In order to stabilize platform 8, the platform has a plurality of webs 14 situated on a side facing away from blade tip 10. However, if platform 8 has sufficient inherent stability, the webs may be dispensed with

A radially inwardly directed fastening flange 16 for fastening guide blade 2 to a stationary connecting ring surrounding the rotor hub extends from platform 8. Fastening flange 16 is situated at a distance from a trailing edge 18 of platform 8, and together with platform 8 delimits an annular space 20. A peripheral plate 22 is connected to fastening flange 16, and delimits annular space 20 in the direction of the rotor hub, thus dividing annular space 20 into a radially outer cavity and a radially inner cavity.

Moving blade 4 has an inner shroud 24 which is situated between a blade neck 26 or blade shank and a blade 28, and which represents an inner radial delimitation of the hot gas path. In the exemplary embodiment shown, the inner shroud is situated approximately at the same radial position as platform 8. Moving blade 4 and guide blade 2 are situated with respect to one another in the axial direction in such a way that between trailing edge 18 of platform 8 and an outer end face 30 of inner shroud 24 an annular gap 32 is formed, through which a gas exchange between hot gas flow 12 and a hub-side cooling air flow may take place in principle. For practically complete structural sealing of annular gap 32 in the radial direction (y direction), inner shroud 24 has a front elongation 34 for forming an axial overlap with guide blade 2 or with its platform 8. Elongation 34 extends from outer end face 30 in the direction of guide blade 2, and has a length such that it protrudes into annular space 20, i.e., the outer cavity between platform 8 and peripheral plate 22.

To avoid a hot gas intake, a leakage flow 36 of the cooling air flow is blown through annular gap 32 into hot gas flow 12. According to the present invention, at least one flow guide element 38 is provided for introducing leakage flow 36 with a swirl into hot gas flow 12 or for imparting the peripheral speed of inner shroud 24 to leakage flow 36. At the same time, the machine efficiency is improved by the introduction of leakage flow 36, imparted with swirl, into the hot gas flow.

In the first exemplary embodiment shown in FIG. 1, flow guide element 38 is designed as a finger-shaped projection which extends essentially in the axial direction from a leading edge 40 of front elongation 34. The projection, i.e., flow guide element 38, is preferably linear, but may also be concave, for example in peripheral direction u. For a plurality of these types of finger-shaped projections 38, leading edge 40 has a comb-like shape. Flow guide element 38 preferably merges with flush alignment into a hot gas side 42 and into a cooling air side 44 of front elongation 34. In this exemplary embodiment, the projection thus has the same radial extension as front elongation 34, so that flow guide element 38 does not act on a radial plate gap between elongation 34 and web 14 or between elongation 34 and peripheral plate 22. Depending on the axial extension of the at least one flow guide element 38 beyond leading edge 40, for the axial gap maintenance an original axial distance between leading edge 40 and the fastening flange must be increased.

In one exemplary embodiment shown in FIG. 2, flow guide element 38 is designed as a projection on the leading edge side which is guided beyond hot gas side 42 and beyond cooling air side 44 in the radial direction. Thus, this flow guide element 38 has a shape that is paddle-like and in particular half moon-like. In particular, flow guide element 38 has flat outer surfaces. Flow guide element 38 is preferably not angularly set in axial direction x and in radial direction y (axial setting angle and radial setting angle=0°). However, it may also be angularly set in axial direction x and/or in radial direction y (axial setting angle and/or radial setting angle≠0°).

Due to the radial elongation of flow guide element 38 beyond hot gas side 42 and cooling air side 44, compared to the preceding finger-shaped exemplary embodiment according to FIG. 1 the at least one flow guide element 38 according to FIG. 2 has an enlarged effective area for imparting swirl to leakage flow 36. For radial gap maintenance or to prevent flow guide element 38 from running against web 14 and the peripheral plate due to thermal expansion, it may be necessary to radially inwardly offset elongation 34 and peripheral plate 22 with respect to the finger-shaped exemplary embodiment according to FIG. 1. Since the at least one flow guide element 38 also extends in the direction of peripheral plate 22, for an axially symmetrical design of flow guide element 38, peripheral plate 22 must then be radially inwardly offset by twice the distance compared to elongation 34.

Further exemplary embodiments of flow guide element 38 are outlined in FIG. 3. In contrast to the above-mentioned exemplary embodiments according to FIGS. 1 and 2, these exemplary embodiments additionally have a rib-like extension in the direction of a blade neck 26, i.e., a radially outer end face 30, as well as a radially inner end face 46 of blade neck 26. In this regard, these flow guide elements 38 have a head section 48 which extends beyond a leading edge 40 in axial direction x, and a section 50 on the hot gas side and/or a section 52 on the cooling gas side which extend(s) from the head section in the direction of blade neck 26. As indicated by the dashed lines, sections 50, 52 may extend only over a length of elongation 34, or may merge into end faces 30, 46.

If sections 50, 52 are guided only over a length of elongation 34, for structural-mechanical reasons it is preferred that these sections merge into hot gas side 42 or cooling air side 44 in a stepless, for example ramped, manner. If sections 50, 52 extend to blade neck 26, it is preferred that these sections have a constant height or extension in the radial direction. Due to sections 50, 52, the effective area of the at least one flow guide element 38 is further increased compared to the second exemplary embodiment according to FIG. 2, which has a positive effect on the imparting of swirl to leakage flow 36. In addition, in contrast to the preceding exemplary embodiments according to FIGS. 1 and 2, flow guide element 38 is stabilized since it surrounds leading edge 40.

FIG. 4 shows one exemplary embodiment of flow guide element 38 having a section 50 on the hot gas side and a section 52 on the cooling air side which extend only over a length of an elongation 34. Flow guide element 38 surrounds a leading edge 40 in a U-shaped manner, and merges continuously into a hot gas side 42 and into a cooling air side 44. For example, in the side view flow guide element 38 is a flat circular disk which is interrupted by elongation 34 in the area of hot gas side 42 and cooling air side 44. Thus, this paddle-like flow guide element 38 has a full-moon shape, with a head section 48 and two runout sections 50, 52, in a manner of speaking. Due to the elongation of flow guide element 38 on hot gas side 42 and on cooling air side 44, for the same extension in the radial direction this exemplary embodiment has a larger effective area than the exemplary embodiment according to FIG. 2.

The at least one flow guide element 38 is preferably not angularly set in axial direction x and in radial direction y. However, it may also be angularly set, i.e., positively or negatively inclined, in axial direction x or in radial direction y. For radial gap maintenance, elongation 34 and a peripheral plate 22 may be radially inwardly offset, similarly to the exemplary embodiment according to FIG. 2.

FIG. 5 shows one exemplary embodiment of a rib-like flow guide element 38 which extends in axial direction x beyond a leading edge 40 of an elongation 34, the flow guide element with its head section 48 terminating in flush alignment with a cooling air side 44, and with its section 50 on the hot gas side being guided to outer end face 30. As a result, this flow guide element 38 has an L shape in the side view.

Section 50 on the hot gas side preferably has an elongated linear shape with a constant height. This section is angularly set in axial direction x on a hot gas side 42 of elongation 34. Head section 48 is preferably not angularly set in axial direction x.

In this exemplary embodiment, the inclination of section 50 on the hot gas side is such that, viewed against direction of rotation u, section 50 on the hot gas side is situated in front of head section 48. Thus, starting from head section 48, section 50 on the hot gas side exits the plane of the drawing. Due to the inclination, upon exiting the outer cavity, leakage flow 36 is accelerated to a speed u in the peripheral direction which is equal to or slightly greater than the peripheral speed of inner shroud 24.

For radial gap maintenance or for preventing flow guide element 38 from running against web 14 and peripheral plate 22 due to thermal expansion, elongation 34 and a peripheral plate 22 may, if necessary, be radially inwardly offset with respect to the finger-shaped exemplary embodiment according to FIG. 1. Since the at least one rib-like flow guide element 38 is situated on the leading edge side and the hot gas side, and therefore an original radial distance between elongation 34 and peripheral plate 22 is not diminished, peripheral plate 22 may then be radially inwardly offset by the same distance as elongation 34.

FIG. 6 shows one exemplary embodiment of a rib-like flow guide element 38 which extends in axial direction x beyond a leading edge 40 of an elongation 34, the flow guide element with its head section 48 terminating in flush alignment with a hot gas side 42, and with its section 52 on the cooling air side being guided to inner end face 46. As a result, this flow guide element 38 likewise has an L shape in the side view.

Section 52 on the cooling air side preferably has a constant height and a linear design. This section is angularly set in axial direction x on a cooling gas side 44 of elongation 34. Head section 48 is preferably not angularly set in axial direction x.

To accelerate leakage flow 36 to a speed which is approximately the same as or slightly greater than the peripheral speed of inner shroud 24, in this exemplary embodiment the inclination of section 52 on the cooling air side is such that, viewed against the direction of rotation, section 52 on the cooling air side is situated behind head section 48. Thus, starting from head section 48, section 52 on the cooling air side enters the plane of the drawing.

For radial gap maintenance, a peripheral plate 22 may, if necessary, be radially inwardly offset with respect to the finger-shaped exemplary embodiment according to FIG. 1. Since the at least one rib-like flow guide element 38 is situated on the leading edge side and the cooling air side, and therefore an original radial distance between elongation 34 and web 14 is not diminished, elongation 34 does not have to be radially inwardly offset.

FIG. 7 shows a top view of an unwound peripheral section of a moving blade row in the area of a front elongation 34 which is provided with a further exemplary embodiment of flow guide element 38 according to the present invention. According to the illustration in FIG. 3, flow guide element 38 with its head section 48 surrounds a leading edge 40 of elongation 34 on both sides, and via a section 50 on the hot gas side and via a section 52 on the cooling air side is guided to outer and inner end face 30, 46, respectively. Sections 50, 52 preferably have a uniform constant height and a linear design. These sections are inclined in axial direction x, and in particular are oriented with respect to one another in such a way that that they extend diagonally opposite from head section 48 in the direction of end faces 30, 46. Head section 48 is preferably not angularly set in axial direction x.

In this exemplary embodiment, the inclination of sections 50, 52 is such that, viewed against direction of rotation u, section 50 on the hot gas side is situated in front of section 52 on the cooling air side. Thus, starting from head section 48, section 50 on the hot gas side exits the plane of the drawing, and starting from head section 48, section 52 on the cooling air side enters the plane of the drawing. Thus, in the side view this flow guide element 38 has a rib-like, in particular V-like, shape with two oppositely pivoted fork sections 50, 52.

A moving blade for a turbomachine, in particular an aircraft engine, is disclosed, having an inner shroud which has a front elongation for forming an axial overlap with an upstream guide blade, and on which at least one flow guide element for deflecting a leakage flow of a cooling air flow in the peripheral direction is situated, the at least one flow guide element being guided beyond a leading edge of the elongation, and a turbomachine having a plurality of these types of moving blades.

LIST OF REFERENCE NUMERALS

• 1 turbomachine
• 2 guide blade
• 4 moving blade
• 6 rotational axis
• 8 platform
• 10 blade tip
• 12 hot gas flow
• 14 web
• 16 fastening flange
• 18 trailing edge
• 20 annular space
• 22 peripheral plate
• 24 inner shroud
• 26 blade neck
• 28 blade
• 30 outer end face
• 32 annular gap
• 34 front elongation
• 36 leakage flow
• 38 flow guide element
• 40 leading edge
• 42 hot gas side
• 44 cooling air side
• 46 inner end face
• 48 head section
• 50 section on the hot gas side
• 52 section on the cooling air side
• x axial direction
• y radial direction
• u peripheral direction or direction of rotation

Claims

1. A moving blade for a turbomachine comprising:

an inner shroud having a front elongation for forming an axial overlap with an upstream guide blade;

at least one flow guide element for deflecting a leakage flow of a cooling air flow being situated in a peripheral direction, the at least one flow guide element extending in an axial direction beyond a leading edge of the elongation.

2. The moving blade as recited in claim 1 wherein the flow guide element terminates in flush alignment with a hot gas side and with a cooling air side of the elongation.

3. The moving blade as recited in claim 1 wherein the flow guide element protrudes beyond a hot gas side and a cooling air side of the elongation in the radial direction.

4. The moving blade as recited in claim 1 wherein the flow guide element has a hot gas side section on a hot gas side of the elongation.

5. The moving blade as recited in claim 4 wherein the hot gas side is located over an entirety of an axial extension of the elongation.

6. The moving blade as recited in claim 4 wherein the hot gas side section has a constant height.

7. The moving blade as recited in claim 1 wherein the flow guide element has a cooling air side section on a cooling air side of the elongation.

8. The moving blade as recited in claim 7 wherein the cooling gas side is located over an entirety of an axial extension of the elongation.

9. The moving blade as recited in claim 7 wherein the cooling gas side section has a constant height.

10. The moving blade as recited in claim 1 wherein the flow guide element has a hot gas side section on the hot gas side of the elongation, and a cooling air side section on a cooling air side of the elongation.

11. The moving blade as recited in claim 6 the hot gas side section and the cooling air side section are oriented oppositely with respect to one another, viewed in a direction of rotation.

12. The moving blade as recited in claim 10 wherein the hot gas side and/or the cooling air section is located over an entirety of an axial extension of the elongation.

13. The moving blade as recited in claim 10 wherein the hot gas side section and/or the cooling air side section has a constant height.

14. The moving blade as recited in claim 1 wherein the at least one flow guide element includes a plurality of flow guide elements.

11. A turbomachine comprising:

a moving blade row having a plurality of moving blades as recited in claim 1.

12. An aircraft engine comprising the turbomachine as recited in claim 11.