Patent Application
20240318560
This application claims priority to European Patent Application No(s). 23163634.1, filed on Mar. 23, 2023, the disclosure(s) of which is(are) incorporated herein by reference in its(their) entirety.
The present invention relates to a blade for a gas turbine, a blade assembly for a gas turbine, and to a gas turbine.
Description of the Related Art
Blades and vanes of a gas turbine, in particular, blades and vanes in a turbine part of the gas turbine, are subject to high thermal loads. Therefore, it is common to cool the blades and vanes by means of a cooling fluid, such as compressed air delivered by a compressor of the gas turbine. The cooling fluid, typically, is conducted to an interior cavity of the blade or vane and discharged to an outer surface of the blade through cooling holes extending between an inner surface that defines the interior cavity and the outer surface of the blade.
Since individual regions of the outer surface of the blade are exposed to different temperatures, the positions where the individual cooling holes open to the outer surface of the blade are distributed over the outer surface of the blade. As a consequence, at least some of the cooling holes may have a central axis that extends inclined relative to the inner surface of the blade. Hence, an aperture of the cooling hole on the inner surface may have locally very small radii. Depending on a stress field within the blade, high mechanical stress may locally occur in the region of the aperture of the cooling hole.
A turbine blade with cooling holes that extend inclined relative to an inner surface of the blade is disclosed, for example, in US 2015/0 226 069 A1.
It is one of the objects of the present invention to provide improved solutions for cooling a blade of a gas turbine. In particular, it is an object to minimize local mechanical stress in the region of a cooling hole of a blade for a gas turbine.
To this end, the present invention provides a blade in accordance with claim 1, a turbine blade assembly in accordance with claim 14, and a gas turbine in accordance with claim 15.
According to a first aspect of the invention, a blade for a gas turbine includes an outer surface, an inner surface that defines a cavity for receiving a gaseous cooling fluid, and a cooling hole foot formed on the inner surface. The cooling hole foot includes a first foot surface that extends inclined relative to a base surface region of the inner surface surrounding the cooling hole foot. The blade further includes a cooling hole extending between the first foot surface of the cooling hole foot and the outer surface to discharge cooling fluid from the cavity to the outer surface. A central axis of the cooling hole extends transverse to the first foot surface.
According to a second aspect of the invention, a turbine blade assembly includes a rotor disk and a plurality of the blades according to the first aspect of the invention. The blades are coupled to the rotor disk, wherein each of the plurality of blades is coupled to the rotor disk, e.g., by means of a root.
According to a third aspect of the invention a gas turbine includes the turbine blade according to the first aspect of the invention.
It is one of the ideas of the present invention to provide a cooling hole foot on the inner surface of the blade, wherein the cooling hole foot has first surface that extends inclined relative to a region or portion of the inner surface surrounding the cooling hole foot. A cooling hole that connects the cavity defined by the inner surface and an outer surface of the blade extends from the first surface of the cooling hole foot to the outer surface with its central axis being transverse to the first surface of the cooling hole foot and, thus, inclined to the surface region of the inner surface surrounding the cooling hole foot. Thereby, locally small radii in the aperture of the cooling hole on the first surface of the cooling hole foot are mainly avoided. For example, if the cooling hole has a circular cross-section, the aperture of the cooling hole on the first surface of the cooling hole foot may have a circular or substantially circular circumference. Consequently, local stress concentrations are reduced which helps in increasing the lifetime of the blade.
The outer surface of the blade may include, for example, at least one of an outer surface of an airfoil, an outer surface of a platform connected to the airfoil, and an outer surface of a coupling structure of the blade.
The inner surface of the blade defines a cavity or hollow space within the blade. Between the inner surface and the outer surface, massive material, e.g., a metal material, is provided that forms a blade wall. The cooling holes extend through the blade wall. The cavity is configured to be in fluid communication with a source of pressurized cooling fluid. For example, the blade may include a channel opening into the cavity. A thickness of the blade wall between the inner and the outer surface may be dimensioned to withstand the local mechanical and thermal loads. Generally, the inner surface may be a curved surface or, at least, may include curved surface regions.
The cooling hole foot, which is also referred to only as “foot” in the following, is a local, discrete topographic element formed integrally with the inner surface. Hence, a region of the inner surface surrounding the foot may be flat or curved and is named herein as base surface region. The foot includes a first foot surface, which may, for example, be flat or planar, and extends inclined relative to the base surface region.
The cooling hole provides a fluid connection between the cavity and the outer surface of the blade. The cooling hole extends between the first foot surface and the outer surface of the blade. Hence, the cooling hole forms an inner aperture on the first foot surface and an outer aperture on the outer surface of the blade. A central axis of the cooling hole extends inclined relative to the base surface region of the inner surface and transverse to the first foot surface. Therefore, mechanical stress on the inner surface of the blade in the region of the inner aperture is reduced since a glancing intersection between the cooling hole and the inner surface is avoided.
Further embodiments of the present disclosure are subject of the further subclaims and the following description, referring to the drawings.
According to some embodiments, the first foot surface may be flat or planar. “Even” or “planar” or “flat”, in this context, is not limited to perfectly even surfaces but may also include surfaces having a small curvature, e.g. with a radius of curvature greater than 0.05 m, preferably greater than 0.1 m, and particularly preferable greater than 0.5 m. A flat or essentially flat surface provides the benefit, that occurrence of local small radii in the aperture formed by the cooling hole in the first foot surface can be further prevented.
According to some embodiments, the cooling hole foot is formed as a projection or boss protruding from the base surface region of the inner surface. For example, the first foot surface may form a ramp emerging from the base surface region. By providing the foot as a projection, i.e., by adding material or land on the inner surface of the blade, weakening of the wall thickness is avoided.
According to some embodiments, the cooling hole foot may include a curved second foot surface emerging from the base surface region and extending inclined to the first foot surface. The second foot surface and the first foot surface may face away from each other and, together, may form a substantially wedge-shaped element or a dormer. An intersecting edge between the first and the second foot surface may be oriented along a radial or span direction of the blade, i.e., transverse to an axis of rotation of the rotor disk, which is typically a direction along which high loads occur due to centrifugal forces. Thereby, the influence of the foot on a flux of forces within the blade is advantageously reduced.
According to some embodiments, a first intersecting line between the first foot surface and the base surface region may be a straight line. This straight line, optionally, may extend along the radial direction of the blade. Thereby, the influence of the foot on a flux of forces within the blade is advantageously reduced further.
According to some embodiments, a second intersecting line between the second foot surface and the base surface region may be a curved, i.e., arc shaped line.
According to some embodiments, the second foot surface has a convex curved main portion and a transition portion connecting the main portion and the base surface region, wherein the transition portion is curved convex or concave. For example, the second foot surface may have generally the shape of a bell curve. By forming the second foot surface as a curved surface, a smooth transition between the base surface region of the inner surface and the foot is achieved which further reduces mechanical stress in the region of the foot.
According to some embodiments, an intersecting edge between the first foot surface and the second foot surface may be arc shaped. Thereby, a transition between the base surface region of the inner surface and the foot thereby is optimized in terms of reducing mechanical stress in the region of the foot.
According to some embodiments, the intersecting edge may extend along a span or radial direction of the airfoil, the span or radial direction extending from a root end towards a tip end of the blade. As mentioned above, thereby, the influence of the foot on a flux of forces within the blade is advantageously reduced.
According to some embodiments, the cooling hole may have a circular cross-section. Since the central axis of the cooling hole extends transverse to the first foot surface, the inner aperture of the cooling hole is circular or substantially circular. Thereby, locally small radii are avoided and, consequently, local stress concentrations are reduced.
According to some embodiments, the cooling hole may have diameter within a range between 0.3 mm to 5 mm. According to some embodiments, the cooling hole may have diameter within a range between 0.6 mm to 1.5 mm.
According to some embodiments, a first angle between the central axis of the cooling hole and the base surface region of the inner surface may be greater than 0° and smaller or equal to 45°. According to some embodiments, the first angle may be in a range between 5° and 30°.
According to some embodiments, a second angle between the first foot surface and the central axis of the cooling hole may be within a range between 70° and 110°. In particular, the second angle may be within a range between 85° and 95°. Hence, the central axis of the cooling hole extends perpendicular or substantially perpendicular to the first foot surface. Thereby, occurrence of locally small radii at the inner aperture of the through hole can be further reduced.
According to some embodiments, the blade may include an airfoil extending along a span or radial direction between a platform end and a tip end, and along a chord direction between a leading edge and a trailing edge, wherein the airfoil has an outer surface that forms, between the leading edge and the trailing edge, a suction side surface and an opposite pressure side surface. The outer surface of the blade, hence, may be formed, at least partially, by the outer surface of the airfoil.
According to some embodiments, the blade may include a platform protruding transversely from the outer surface of the airfoil at the platform end. The platform, for example, extends along a circumferential direction and along the axial direction. The circumferential direction extends transverse to the span or radial direction and transverse to the axial direction. The platform may include an upper surface that faces towards the tip end of the airfoil, a lower surface that is oriented opposite to the upper surface, and an end face that connects the upper and the lower surface. The upper surface of the platform may be connected to the outer surface of the airfoil by a transition surface that may, optionally, have a concave curvature. The outer surface of the blade, therefore, may include the upper surface, the lower surface, and the end face of the platform, and, if provided, the transition surface.
The outer surface of the airfoil and the upper surface of the platform form a hot gas washed surface, when the blade is employed in a turbine part of the gas turbine.
According to some embodiments, the blade may include a root connected to the platform protruding from the platform along the radial direction. The root may have, for example, a firtree shaped cross section and, generally, is configured to couple the blade to the rotor disk, which may include a complementary shaped recess or groove. The outer surface of the blade may also include an outer surface of the root. Optionally, the root may include a channel that is in fluid communication with the cavity that may, for example, mainly extend within the airfoil.
According to some embodiments, the cooling hole may extend between the first foot surface and the outer surface of the airfoil. According to further embodiments, the cooling hole may extend within the platform between the inner surface and the end face of the platform facing away from the airfoil.
According to some embodiments, the blade may include a plurality of cooling holes, and multiple cooling hole foots may be formed on the inner surface. In this case, each of the cooling hole foots includes a first foot surface that extends inclined relative to a respective base surface region of the inner surface surrounding the respective cooling hole foot. At least some of the plurality of cooling holes extend between the first foot surface of a respective cooling hole foot and the outer surface, the central axis of the respective cooling hole extending transverse to the respective first foot surface. That is, there may be provided cooling holes that extend directly between the inner surface and the outer surface of the blade. Those cooling holes may be named, for example, first cooling holes. Further, there may be provided second cooling holes each of which extending between a first foot surface of a respective foot and the outer surface. For example, at least one of the second cooling holes may extend between a first foot surface of a respective foot and the outer surface of the airfoil. Additionally, or alternatively, at least one of the second cooling holes may extend between a first foot surface of a respective foot and the end face of the platform.
According to some embodiments, the gas turbine may comprise a compressor configured to compress a working fluid, a burner receiving compressed working fluid from the compressor and configured to burn a fuel to heat the working fluid, and a turbine including the blade, wherein the turbine stage is configured to expand the working fluid causing the turbine blade assembly to rotate. Hence, the blade may form part of the turbine, for example, as a rotating blade or a stationary vane. As a working fluid, the compressor may suck air from the environment, and the compressed air may be used for combustion of the fuel in the combustor or burner. As a fuel, liquid fuel, such as kerosene, diesel, ethanol, or similar may be used. Alternatively, gaseous fuel such as natural gas, fermentation gas, hydrogen, or similar can be used.
The features and advantages described herein with respect to one aspect of the invention are also disclosed for the other aspects and vice versa.
With respect to directions and axes, in particular, with respect to directions and axes concerning the extension or expanse of physical structures, within the scope of the present invention, an extent of an axis, a direction, or a structure “along” another axis, direction, or structure includes that said axes, directions, or structures, in particular tangents which result at a particular site of the respective structure, enclose an angle which is smaller than 45 degrees, preferably smaller than 30 degrees and in particular preferable extend parallel to each other.
With respect to directions and axes, in particular with respect to directions and axes concerning the extension or expanse of physical structures, within the scope of the present invention, an extent of an axis, a direction, or a structure “crossways”, “across”, “cross”, or “transversal” to another axis, direction, or structure includes in particular that said axes, directions, or structures, in particular tangents which result at a particular site of the respective structure, enclose an angle which is greater or equal than 45 degrees, preferably greater or equal than 60 degrees, and in particular preferable extend perpendicular to each other.
Within the scope of the present invention, the term “blade” is intended to cover both, a rotating blade and a stationary vane.
For a more complete understanding of the present invention and advantages thereof, reference is now made to the following description taken in conjunction with the accompanying drawings. The invention is explained in more detail below using exemplary embodiments, which are specified in the schematic figures of the drawings, in which:
In the figures like reference signs denote like elements unless stated otherwise.
The compressor 310 of the gas turbine 300 may draw air as a working fluid from the environment and compress the drawn air. The compressor 310 may be realized as centrifugal compressor or an axial compressor.
The compressed air is supplied to the combustor 320 for combustion of a fuel, such as natural gas, hydrogen, diesel, ethanol or similar. Further, a part of the compressed air is supplied as a gaseous cooling fluid to high-temperature regions of the gas turbine 300 for cooling purposes. The burner or combustor 320, by use of the compressed air, burns fuel to heat the compressed air.
The turbine 330 includes a plurality of blade assemblies 200, each comprising a rotor disk 210 to which a plurality of turbine blades 100 are coupled. The turbine 330 further includes a plurality of turbine vanes 335.
The rotor disk 210, generally, may have the form of a ring and, at its outer circumference, includes multiple coupling interfaces 230 for coupling the blades 100 to the disk 210. As exemplarily shown in
As shown in
The airfoil 110 may extend along radial or span direction R between a platform end 12 and a tip end 13. With regard to an axial or chord direction, that extends transverse to the radial direction, the airfoil 110 may extend between a leading edge 14 and a trailing end 15. An outer surface 1a of the airfoil 110, between the leading edge 14 and the trailing edge 15, may define a pressure side surface 1p and a suction side surface 1s being oriented opposite to the pressure side surface 1p.
As schematically shown in
The outer surface 1a of the airfoil 110, in particular, the pressure side surface 1p and the suction side surface 1s, each may be connected to the upper surface 120a of the platform 120 via a transition surface 120t. As exemplarily shown in
The root 130 is connected to the lower surface 120b of the platform 120 and protrudes from the lower surface 120b of the platform 120 along the radial direction R. As exemplarily shown in
Hence, generally, the blade 100 extends in the radial direction R between a root end 101, e.g., an end of the root 130 facing away from the airfoil 110, and a tip end 102, e.g., being the tip end 13 of the airfoil 110. An outer surface 100a of the blade 100 is formed by the outer surface 1a of the airfoil 110, the transition surface 120t, the upper and lower surfaces 120a, 120b and the end face 120c of the platform 120, and an outer surface of the root 130.
As visible from
As shown in
The cooling holes 2 may have a circular cross-section. A diameter 24 of the cooling holes 2 may lie within a range between 0.3 mm to 5 mm, in particular, within a range between 0.6 mm to 1.5 mm.
As shown in
To reduce the peak stresses or, in other words, the so called notch effect in the inner surface 100i in the region of inclined cooling holes 2, a cooling hole foot 1 is formed on the inner surface 100i as shown in
As schematically shown in
The cooling hole 2, which central axis 20 extends inclined relative to the base surface region 100b of the inner surface 100i, is formed so as to extend between the first foot surface 11a of the cooling hole foot 1 and the outer surface 100a of the blade 100. A first angle a1 between the central axis 20 of the cooling hole 2 and the base surface region 100b of the inner surface 100i is greater than 0° and smaller or equal to 45°. For example, the first angle a1 may be in a range between 5° and 30°. As visible best in
In the example of
Although the present invention has been explained above in connection with a blade 100 rotating with a rotor disk 210, it is not limited to this configuration. The “blade” including the cooling foot and the cooling hole extending from the cooling foot to the outer surface may also be a stationary vane.
Although specific embodiments have been illustrated and described herein, it will be appreciated by those of at least ordinary skill in the art that a variety of alternate and/or equivalent implementations exist. It should be appreciated that the exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration in any way. Rather, the foregoing summary and detailed description will provide those skilled in the art with a convenient road map for implementing at least one exemplary embodiment, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope as set forth in the appended claims and their legal equivalents. Generally, this application is intended to cover any adaptations or variations of the specific embodiments discussed herein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 23163634.1 | Mar 2023 | EP | regional |
