Patent Description:
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 <CIT>.

<CIT> discloses a turbine vane comprising an inner surface on which an inward protrusion is formed, wherein an inclined cooling hole extends between the inward protrusion and an outer surface of the vane.

Documents <CIT>, <CIT>, <CIT>, and <CIT> disclose further turbine blades comprising a protrusion on an inner surface of a blade wall and a cooling hole that extends through the blade wall and the protrusion.

It is one of the objects of the present invention to provide improved solutions for cooling a blade or vane 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 or vane for a gas turbine. To this end, the present invention provides a blade or vane in accordance with claim <NUM>, a turbine blade assembly in accordance with claim <NUM>, and a gas turbine in accordance with claim <NUM>.

According to a first aspect of the invention, a blade or vane 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 or vane 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 or vane 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 or vane, 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 or vane 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 or vane.

The outer surface of the blade or vane 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 or vane.

The inner surface of the blade or vane defines a cavity or hollow space within the blade or vane. Between the inner surface and the outer surface, massive material, e.g., a metal material, is provided that forms a blade or vane wall. The cooling holes extend through the blade or vane wall. The cavity is configured to be in fluid communication with a source of pressurized cooling fluid. For example, the blade or vane may include a channel opening into the cavity. A thickness of the blade or vane 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 or vane. The cooling hole extends between the first foot surface and the outer surface of the blade or vane. Hence, the cooling hole forms an inner aperture on the first foot surface and an outer aperture on the outer surface of the blade or vane. 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 or vane 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 invention 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 <NUM>, preferably greater than <NUM>, and particularly preferable greater than <NUM>. 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 the invention, 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 or vane, weakening of the wall thickness is avoided.

According to the invention, the cooling hole foot includes 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 or vane, 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 or vane is advantageously reduced.

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 the invention, an intersecting edge between the first foot surface and the second foot surface is 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 blade or vane, the span or radial direction extending from a root end towards a tip end of the blade or vane. As mentioned above, thereby, the influence of the foot on a flux of forces within the blade or vane 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 <NUM> to <NUM>. According to some embodiments, the cooling hole may have diameter within a range between <NUM> to <NUM>.

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 <NUM>° and smaller or equal to <NUM>°. According to some embodiments, the first angle may be in a range between <NUM>° and <NUM>°.

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 <NUM>° and <NUM>°. In particular, the second angle may be within a range between <NUM>° and <NUM>°. 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 or vane 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 or vane, hence, may be formed, at least partially, by the outer surface of the airfoil.

According to some embodiments, the blade or vane 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 or vane, 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 or vane is employed in a turbine part of the gas turbine.

According to some embodiments, the blade or vane 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 or vane may also include an outer surface of the root.

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 or vane may include a plurality of cooling holes, and multiple cooling hole feet may be formed on the inner surface. In this case, each of the cooling hole feet 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 of the blade or vane, 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 or vane. 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 of the blade or vane. 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.

The features and advantages described herein with respect to one aspect of the invention are also disclosed for the other aspects and vice versa.

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.

<FIG> schematically shows a gas turbine <NUM>. The gas turbine <NUM> includes a compressor <NUM>, a combustor <NUM>, and a turbine <NUM>. The turbine <NUM> and the compressor <NUM> may include a common shaft <NUM> so as to be rotatable about a common rotational axis.

The compressor <NUM> of the gas turbine <NUM> may draw air as a working fluid from the environment and compress the drawn air. The compressor <NUM> may be realized as centrifugal compressor or an axial compressor. <FIG> exemplarily shows a multistage axial compressor which is configured for high mass flows of air. The axial compressor may include multiple rotor disks, each carrying a plurality of blades. The rotor disks <NUM> are mounted on the shaft <NUM> and rotate with the shaft about the rotational axis. Compressor vanes <NUM> are arranged downstream of the blades <NUM>. The blades <NUM> compress the introduced air and deliver the compressed air to the compressor vanes <NUM> disposed adjacently downstream. The plurality of compressor vanes <NUM> guide the compressed air flowing from compressor blades <NUM> disposed upstream to compressor blades <NUM> disposed at a following, downstream stage. The air is compressed gradually to a high pressure while passing through the stages of compressor blades <NUM> and vanes <NUM>.

The compressed air is supplied to the combustor <NUM> 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 <NUM> for cooling purposes. The combustor <NUM>, by use of the compressed air, burns fuel to heat the compressed air.

The turbine <NUM> includes a plurality of blade assemblies <NUM>, each comprising a rotor disk <NUM> to which a plurality of turbine blades <NUM> are coupled. The turbine <NUM> further includes a plurality of turbine vanes <NUM>. <FIG> shows a partial view of a blade assembly which will be explained in more detail below. Generally, each rotor disk <NUM> is coupled to the shaft <NUM> to be rotatable with the shaft about the rotational axis. The turbine blades <NUM> are coupled to the respective rotor disk <NUM> and extend radially therefrom. The turbine vanes <NUM> are upstream of the blades <NUM> of the respective rotor disks <NUM>. The turbine vanes are fixed so that they do not rotate about the rotational axis of the shaft <NUM> and guide the flow of combustion gas coming from the combustor <NUM> passing through the turbine blades <NUM>. The combustion gas is expanded in the turbine <NUM> and the turbine blades generate rotational force while being rotated by the combustion gas. The compressor <NUM> may be driven by a portion of the power output from the turbine <NUM> via the shaft <NUM>.

<FIG> shows a blade assembly <NUM> of the turbine <NUM>. As explained above, the blade assembly includes a rotor disk <NUM> and a plurality of blades <NUM>.

The rotor disk <NUM>, generally, may have the form of a ring and, at its outer circumference, includes multiple coupling interfaces <NUM> for coupling the blades <NUM> to the disk <NUM>. As exemplarily shown in <FIG>, the coupling interfaces <NUM> may be formed by grooves. As an example, <FIG> shows grooves that have a cross-sectional shape similar to a firtree.

As shown in <FIG>, the blade assembly <NUM> includes multiple blades <NUM>. <FIG> exemplarily shows a blade <NUM> in a side view. As shown in <FIG> and <FIG>, each blade <NUM> may include an airfoil <NUM>, a platform <NUM>, and a root <NUM>.

The airfoil <NUM> may extend along radial or span direction R between a platform end <NUM> and a tip end <NUM>. With regard to an axial or chord direction, that extends transverse to the radial direction, the airfoil <NUM> may extend between a leading edge <NUM> and a trailing edge <NUM>. An outer surface 1a of the airfoil <NUM>, between the leading edge <NUM> and the trailing edge <NUM>, may define a pressure side surface 1p and a suction side surface <NUM> being oriented opposite to the pressure side surface 1p.

As schematically shown in <FIG>, the platform <NUM> may be a substantially plate shaped structure having an expanse with respect to the axial direction A and with respect to a circumferential direction C that extends transverse to the axial direction A and to the radial direction A. The platform <NUM> is coupled to the platform end <NUM> of the airfoil <NUM> and may protrude from the airfoil <NUM> with respect to the circumferential direction C. As depicted by way of example in <FIG>, the platform <NUM> may include an upper surface 120a oriented towards the tip end <NUM> of the airfoil <NUM> and a lower surface 120b oriented opposite to the upper surface 120a. Further, the platform <NUM> may have an end face 120c connecting the upper and lower surfaces 120a, 120b and being oriented in the circumferential direction C.

The outer surface 1a of the airfoil <NUM>, in particular, the pressure side surface 1p and the suction side surface <NUM>, each may be connected to the upper surface 120a of the platform <NUM> via a transition surface 120t. As exemplarily shown in <FIG>, the transition surface 120t may be a concave curved surface.

The root <NUM> is connected to the lower surface 120b of the platform <NUM> and protrudes from the lower surface 120b of the platform <NUM> along the radial direction R. As exemplarily shown in <FIG>, the root <NUM> may include a firtree shaped cross-section. Generally, the coupling interfaces <NUM> of the rotor disk <NUM> and the roots <NUM> of the blades <NUM> may have complementary cross-sections. As shown in <FIG>, the roots <NUM> and the coupling interfaces <NUM> are interconnected, i.e., they are engaged and interlocked with each other.

Hence, generally, the blade <NUM> extends in the radial direction R between a root end <NUM>, e.g., an end of the root <NUM> facing away from the airfoil <NUM>, and a tip end <NUM>, e.g., being the tip end <NUM> of the airfoil <NUM>. An outer surface 100a of the blade <NUM> is formed by the outer surface 1a of the airfoil <NUM>, the transition surface 120t, the upper and lower surfaces 120a, 120b and the end face 120c of the platform <NUM>, and an outer surface of the root <NUM>.

<FIG> shows a sectional view of the blade <NUM> shown in <FIG>. As visible from <FIG>, the blade <NUM> includes an inner surface 100i that defines a cavity <NUM>. As shown exemplarily in <FIG>, the blade <NUM> may include multiple cavities <NUM>, each being limited or defined by an inner surface 100i of the blade <NUM>. In the following, it is only referred to one single cavity <NUM> to avoid unnecessary repetitions. Generally, one or more cavities may be provided and at least one of the cavities may be configured as described below.

As visible from <FIG>, the cavity <NUM> may extend along the radial direction R. For example, the cavity <NUM> may extend within at least one of the airfoil <NUM>, the platform <NUM>, and the root <NUM> with respect to the radial direction R. The inner surface 100i defining the cavity <NUM> may be curved or, at least, may have curved regions such as concave curved regions as exemplarily shown in <FIG>. The cavity <NUM> is configured to receive a gaseous cooling fluid, e.g., compressed air supplied by the compressor <NUM>.

As shown in <FIG> a plurality of cooling holes <NUM> are formed in the blade <NUM>. The cooling holes <NUM> connect the one or more cavities <NUM> to the outer surface 100a of the blade <NUM> so that cooling fluid can be discharged from the respective cavity <NUM> through the cooling holes <NUM> on the outer surface 100a of the blade <NUM>. Each cooling hole <NUM> forms an outer aperture <NUM> on the outer surface 100a of the blade <NUM> where the cooling fluid is discharged from the cooling hole <NUM>. As shown in <FIG> by way of example only, cooling holes may be positioned at various locations on the outer surface 100a, e.g., in the outer surface 1a of the airfoil <NUM> such as in the leading edge <NUM>, in the trailing edge <NUM>, adjacent to the tip end <NUM>, and within the pressure side surface 1p and the suction side surface (not visible in <FIG>). Cooling hole <NUM> may also be provided in the platform <NUM>, e.g., in the end face 120c as exemplarily shown in <FIG>.

The cooling holes <NUM> may have a circular cross-section. A diameter <NUM> of the cooling holes <NUM> may lie within a range between <NUM> to <NUM>, in particular, within a range between <NUM> to <NUM>.

As shown in <FIG> and with more details in <FIG>, the central axis <NUM> of at least one of the cooling holes <NUM> extends inclined relative to the inner surface 100i. In this case, an inner aperture <NUM> of the hole <NUM> formed on the inner surface 100i would have an oval or elliptic circumference, when the hole <NUM> has a circular cross section. Depending on the angle between the inner surface 100i and the central axis <NUM>, the circumference of the inner aperture <NUM> would include locally small radii. As a consequence peak stresses may develop in the region around the inner aperture.

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 <NUM>, a cooling hole foot <NUM> is formed on the inner surface 100i as shown in <FIG> and with more details in <FIG>.

As schematically shown in <FIG>, the cooling hole foot <NUM> is formed as a projection or boss protruding from the inner surface 100i. Generally, the cooling hole foot <NUM> includes a first foot surface 11a and second foot surface 11b. The first foot surface 11a may be formed flat or planar and extends inclined relative to a base surface region 100b of the inner surface 100i that surrounds the cooling hole foot <NUM>. The second foot surface 11b extends inclined relative to the first foot surface 11a. As exemplarily shown in <FIG>, the second foot surface 11a extends curved emerging from the base surface region 100b. For example, the second foot surface 11b may have a convex curved main portion 11c and a transition portion 11d connecting the main portion 11c and the base surface region 100b, wherein the transition portion 11d is curved convex or concave, as schematically shown in <FIG>. Irrespective of the shape of the second foot surface 11b, as exemplarily shown in <FIG>, an intersecting line <NUM> between the first foot surface 11a and the base surface region 100b of the inner surface 100i may be a straight or substantially straight line. As further shown in <FIG>, an intersecting line <NUM> between the second foot surface 11b and the base surface region 100b of the inner surface 100i may be a curve, e.g., arc shaped line. An intersecting edge 11e between the first foot surface 11a and the second foot surface 11b is arc shaped as exemplarily shown in <FIG>. This configuration of the cooling hole foot <NUM> is advantageous in terms of force flux, i.e., it helps in conducting forces acting along the inner surface 100i in a smooth fashion to reduce local stress concentrations. Optionally, the intersecting edge 11e between the first and second foot surfaces 11a, 11b and or the intersecting line between the first foot surface 11a and the base surface region 100b may extends along the radial direction R of the blade <NUM>.

The cooling hole <NUM>, which central axis <NUM> 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 <NUM> and the outer surface 100a of the blade <NUM>. A first angle a1 between the central axis <NUM> of the cooling hole <NUM> and the base surface region 100b of the inner surface 100i is greater than <NUM>° and smaller or equal to <NUM>°. For example, the first angle a1 may be in a range between <NUM>° and <NUM>°. As visible best in <FIG> and <FIG>, the central axis <NUM> of the cooling hole <NUM> extends transverse to the first foot surface 11a. For example, a second angle a2 between the first foot surface 11a and the central axis <NUM> of the cooling hole <NUM> may lie within a range between <NUM>° and <NUM>°, in particular, between <NUM>° and <NUM>°. Due to the inclined orientation of the first foot surface 11a to the inner surface 100i and the substantially perpendicular extension of the central axis <NUM> of the cooling hole <NUM> to the first foot surface 11a, the cooling hole <NUM> can extend inclined to the inner surface 100i but small local radii are avoided. In the case of a cooling hole <NUM> with a circular cross-section, the inner aperture <NUM> has a circular or substantially circular circumference, as visible best in <FIG> showing a view in a direction parallel to the central axis <NUM> of the cooling hole. An angle between the base surface region 100b of the inner surface 100i and the first foot surface 11a may, for example, lie within a range between <NUM>° and <NUM>°.

In the example of <FIG> and <FIG>, only one of the shown cooling holes <NUM> extends from the cooling hole foot <NUM>. However, it should be understood that multiple cooling hole feet <NUM> can be provided on the inner surface 100i defining the cavity <NUM>. Where the blade <NUM> includes a plurality of cooling holes <NUM> in fluid communication with one cavity <NUM>, multiple cooling hole feet <NUM> may be formed on the inner surface 100i. Each of the cooling hole feet <NUM> may be formed as described above. At least some of the plurality of cooling holes <NUM>, in this case, may extend between the first foot surface 11a of a respective one of the plurality of cooling hole feet <NUM> and the outer surface 100a of the blade. Those cooling holes <NUM> that extend from the cooling hole feet <NUM> each have a central axis <NUM> that extends transverse to the respective first foot surface 11a and inclined to the base surface region 100b surrounding the respective cooling hole foot <NUM>.

<FIG>, by way of example only show a cooling hole <NUM> that extends within the platform <NUM> between the inner surface 100i and the end face 120c of the platform <NUM>. However, the invention is not limited to this case. For example, the cooling hole <NUM> may alternatively extend between the first foot surface 11a and the outer surface 1a of the airfoil <NUM> or between the first foot surface 11a and the outer surface of the root <NUM>. Generally, the cooling hole <NUM> extends between the first foot surface 11a of the cooling hole foot <NUM> and the outer surface 100a of the blade <NUM>.

Although the present invention has been explained above in connection with a blade <NUM> rotating with a rotor disk <NUM>, it is not limited to this configuration. Also a stationary vane may include the cooling foot and the cooling hole extending from the cooling foot to the outer surface.

Claim 1:
A blade (<NUM>) or vane for a gas turbine (<NUM>), comprising:
an outer surface (100a) and an inner surface (100i) that defines a cavity (<NUM>) for receiving a gaseous cooling fluid;
a cooling hole foot (<NUM>) formed on the inner surface (100i), wherein the cooling hole foot (<NUM>) is formed as a projection protruding from a base surface region (100b) of the inner surface (100i) surrounding the cooling hole foot (<NUM>), the cooling hole foot (<NUM>) including:
a first foot surface (11a) that extends inclined relative to the base surface region (100b) of the inner surface (100i), and
a curved second foot surface (11b) emerging from the base surface region (100b) and extending inclined to the first foot surface (11a); and
a cooling hole (<NUM>) extending between the first foot surface (11a) of the cooling hole foot (<NUM>) and the outer surface (100a) to discharge cooling fluid from the cavity to the outer surface (100a), a central axis (<NUM>) of the cooling hole (<NUM>) extending transverse to the first foot surface (11a),
characterized in that an intersecting edge (11e) between the first foot surface (11a) and the second foot surface (11b) is arc shaped.