Airfoil for a turbine stator or turbine rotor of an axial flow gas turbine

Abstract

The invention relates to an airfoil (AF) comprising: - a suction side wall (SW) and a pressure side wall (PW), both side walls (PW) extending from a leading edge (LE) to a trailing edge (TE) and from an inner end (IE) of the airfoil to an outer end (OE) of the airfoil, - at least one plenum (FP1) for a coolant (CM), - at least two cooling circuits (CC1-CC5) in the suction side wall and / or the pressure side wall and in fluid connection with the first plenum (FP1), - wherein each cooling circuit comprises a plurality of channel segments (CS), in the outlet region, the arrangement of the respective cooling circuit in the most downstream channel segment (CS) opens into one of the suction side wall or the pressure side wall of the airfoil, wherein in the overlap region (PR) of the airfoil, where the channel segments of different cooling circuits overlap, the channel segments of the different cooling circuits are arranged alternately in a regular arrangement.

Description

Technical Field

[0001] This invention relates to an airfoil for turbine stator or turbine rotor blades of an axial flow gas turbine.

[0002] In gas turbines, the airfoil components of the turbine rotor and stator blades play a crucial role in converting the energy of the hot working gas into mechanical work. The reliability and efficiency of a gas turbine largely depend on the reliability and efficiency of the turbine rotor and stator blades used in its turbine section.

[0003] In recent decades, and even today, gas turbine inlet temperatures have increased and continue to increase in order to achieve higher gas turbine efficiency. Therefore, there has been and continues to be a need to improve cooling efficiency so that turbine blades and stator blades can withstand the high temperatures of the working gas for as long as possible. Existing technologies already include a wide variety of cooling concepts to meet these two requirements. An example is disclosed in US 7,717,675 B1, which illustrates so-called near-wall cooling of a turbine blade airfoil. According to this disclosure, several supply channels supply a cooling network extending in multiple principal chord directions located in the suction and pressure sidewalls of the blade. Furthermore, the leading edge of the airfoil is cooled by means of several nozzle cooling ducts. Additionally, EP 2,472,062 B1 discloses cooling channels extending from the leading edge to the trailing edge of the airfoil. It also discloses US 2022 / 0333490 A1 for cooling the trailing edge of a turbine blade. Background Technology

[0004] Since the trend toward higher turbine inlet temperatures and longer turbine blade and impeller life remains unbroken, new solutions are needed that can achieve even higher turbine temperatures and / or longer lifespans for these components, especially their airfoils. Furthermore, the airfoils must be able to operate continuously with limited operational risk in the event of foreign object damage (FOD). Summary of the Invention

[0005] Based on this, the object of the present invention is to provide a turbine blade or turbine blade airfoil for a gas turbine that has improved performance in terms of coolant consumption, durability, lifespan and / or FOD capability.

[0006] The solution is an airfoil with the features described in claim 1. Specifically, the airfoil of the present invention is for a turbine stator or turbine rotor blade of a gas turbine.

[0007] include:

[0008] - Suction sidewalls and pressure sidewalls, which guide the hot working gas of the gas turbine. When the airfoil is used in the gas turbine, the two sidewalls extend from the leading edge to the trailing edge in the chordal direction of the gas turbine, and from the inner end to the outer end of the airfoil in the radial direction of the gas turbine.

[0009] - At least one pressure supply chamber for coolant extending radially.

[0010] - At least two cooling circuits in the suction sidewall and / or the pressure sidewall, and the at least two cooling circuits are fluidly connected to a first pressure supply chamber in the at least one pressure supply chamber.

[0011] -Each cooling circuit includes an outlet region and a plurality of channel segments extending along a chord direction, wherein in the outlet region, the corresponding cooling circuit is arranged in the most downstream channel segment leading to one of the suction sidewall or the pressure sidewall of the airfoil.

[0012] The outlet regions of the different cooling circuits are separated from each other relative to the chord direction of the airfoil.

[0013] In the overlapping region of the airfoil, the channel segments of different cooling circuits overlap, and the channel segments of the different cooling circuits are arranged alternately, preferably in a regular arrangement, so as to simultaneously cool the overlapping region of the airfoil.

[0014] One advantage of this cooling scheme for airfoils is the highly efficient use of coolant while achieving adequate cooling of the airfoil, even when used in the first stage of the turbine section of a stationary heavy-duty gas turbine. This reduction in coolant volume can be used to improve gas turbine efficiency and / or increase the working gas temperature. By also positioning the coolant outlet region significantly downstream of the leading edge, i.e., at a greater chordal distance from the leading edge, the available pressure ratio of the coolant increases, allowing for optimized coolant distribution along the chord.

[0015] The arrangement of channel segments of different cooling circuits in overlapping areas can be regular and / or irregular. One understanding of a regular arrangement is that the order of the channel segments of different cooling circuits is always the same along the span. Therefore, another understanding of a regular arrangement is that the density of channel segments is constant within a corresponding range of the airfoil's span. For example, since the heat load from the hot working gas may be higher at the outer (or inner) end of the airfoil than at the middle span, the density of the channel segments near the outer end is constant, but also higher than the density of the channel segments at the middle span. This regular arrangement allows for a balanced distribution of the locally required cooling capacity across the affected cooling circuits. Nevertheless, a regular arrangement can also be understood as the same radial distance between the channel segments of different cooling circuits.

[0016] In summary, this invention allows for improved cooling efficiency by using coolant flow in multiple regions along the chord direction of the airfoil. First, in the leading edge region, a high temperature differential occurs, requiring the coolant pressure to meet foreign object damage criteria, and a low pressure differential is maintained between the coolant feed and the hot working gas pressure at the stagnation point. Second, the heating of the coolant during cooling of the leading edge does not completely consume its cooling capacity; therefore, the coolant can be used further downstream of the leading edge to convectively cool other chord regions of the airfoil. This results in further heating of the coolant, leading to higher cooling efficiency, and ultimately to increased efficiency of gas turbines equipped with turbine stators or rotors incorporating such airfoils.

[0017] For clarity, it should be noted that the terms "radial direction," "axial direction," and "circumferential direction" refer to the machine axis of the gas turbine when the airfoil is assembled therein. The "chord direction" is generally a combination of axial and circumferential, and depends on the predetermined cross-section of the airfoil and its blade angles. The spanwise direction of the airfoil is the same as the radial direction.

[0018] The terms "upstream" and "downstream" both refer to the main flow direction of the hot working gas. This is the case when these terms are associated with the surface of the sidewall or the entire airfoil. Alternatively, these terms refer to the flow direction of the coolant. This is the case when they are associated with a channel section or cooling circuit.

[0019] The term "overlap" must be understood as such that in the chord region under consideration, cooling channels of different cooling circuits are arranged at different spanwise heights, that is, in this region, the cooling channels of different cooling circuits are arranged at different distances from the inner end of the airfoil.

[0020] According to a first preferred embodiment, a pressure chamber is arranged in the leading edge region of the airfoil. The pressure chamber extends radially between the inner and outer ends of the airfoil. This allows for effective and efficient cooling of the airfoil region subjected to the highest heat load during operation. Furthermore, the different cooling circuits are arranged with channel inlets in the most upstream channel sections, wherein most, preferably all, channel sections are arranged in the same region relative to the chord direction, i.e., along the chord direction. Preferably, the affected channel inlets are arranged relative to the chord in the leading edge region, and most preferably opposite the airfoil leading edge. This results in a higher density of cooling channels with more cooling circuits in the chord region of the airfoil where the heat load is higher, and a lower density of cooling channels with fewer cooling circuits in the chord region of the airfoil where the heat load is lower.

[0021] In a highly preferred embodiment, when viewed in cross-section of the airfoil, the upstream channel segment of the respective channel section is L-shaped, having a first sub-segment starting from the first pressure chamber, a turning segment below the stagnant area at the leading edge, and a second sub-segment extending in the chord direction along the respective sidewall. This geometry of the upstream channel segment of each cooling circuit results in a thinner boundary layer in the coolant flow due to the change in flow direction, thereby leading to enhanced heat transfer. Utilizing this enhanced heat transfer is most advantageous in the leading edge where the heat load is highest during operation.

[0022] More preferably, each channel segment in the downstreammost channel section of the corresponding channel is arranged at the downstream end of the corresponding channel section. Cooling circuits lead to the suction sidewalls respectively. And wherein, for at least one cooling circuit, preferably for each cooling circuit, an outlet pressure chamber is arranged near its outlet, which interconnects the downstreammost channel segments of the corresponding cooling circuit, and the outlet pressure chamber extends radially between the inner and outer ends of the airfoil.

[0023] Advantageously, for at least one cooling circuit, preferably for each cooling circuit, an intermediate pressure chamber is arranged, which interconnects the channel sections of the respective cooling circuits. The intermediate pressure chamber extends radially between the inner and outer ends of the airfoil.

[0024] The use of outlet pressure chambers and / or intermediate pressure chambers promotes different fluid distributions and allows for further improvements in cooling efficiency. Furthermore, the use of pressure chambers enables the regulation of coolant flow and a uniform coolant flow distribution along the spanwise direction. However, the invention also includes the possibility of not using pressure chambers, in which the fluid is redistributed in the middle of the pressure chamber.

[0025] Another advantage of using the outlet pressure chamber and / or intermediate pressure chambers becomes apparent when single or multiple channel sections are defective, such as when at least partially or completely blocked by dust and / or other particles carried by the coolant, or when a channel section is not covered due to damage from foreign objects. In these cases, the channel sections arranged further downstream remain effective because other parallel channel sections connected via the outlet pressure chamber and / or intermediate pressure chambers serve as bypasses for the defective channel sections. This increases the reliability of the airfoil in defective conditions and extends its lifespan.

[0026] In a highly preferred embodiment, some channel sections of one of the at least two cooling circuits are arranged between the surface of a) the pressure sidewall or suction sidewall and b) the outlet pressure chamber or intermediate pressure chamber of the other of the at least two cooling circuits. This allows for suitable cooling of different regions of the airfoil to accommodate localized thermal loads. Consequently, a more uniform thermal temperature distribution can be achieved along the chord direction of the airfoil, which increases the airfoil's lifespan.

[0027] In a preferred embodiment, the number of channel segments located upstream of the intermediate or outlet pressure chamber in the corresponding cooling circuit differs from the number of channel segments located downstream of the same pressure chamber. This allows for suitable cooling of different chordal regions of the airfoil for localized thermal loads. Consequently, a more uniform thermal temperature distribution can be achieved along the chordal direction of the airfoil, which increases the airfoil's lifespan. This allows for a high degree of flexibility in the cooling scheme for efficient and effective cooling of the airfoil.

[0028] In another advantageous embodiment, the outlet regions of at least two cooling circuits are located on the same sidewall or different sidewalls of the airfoil.

[0029] More preferably, some of the channel segments are positioned at a distance from the surface of the corresponding sidewall, these channel segments being designated not to cool the corresponding sidewall; that is, the distance is greater than the distance between the channel segments designated for cooling the corresponding sidewall and the surface of the sidewall. Similarly, some channel segments or sub-segments may extend through the reinforcing ribs of the airfoil connecting the suction sidewall and the pressure sidewall. These features enable the supply of less heated coolant to locations on the airfoil that are further from the pressure chamber than the most upstream channel segment of at least one cooling circuit.

[0030] In a highly preferred embodiment of the invention, at least two cooling circuits comprise three, four, or five cooling circuits, and each of the channel segments is assigned to one of the three, four, or five cooling circuits, and / or at least one pressure chamber comprises a second pressure chamber. Thus, the cooling scheme of the present invention can be applied multiple times in different areas of the same airfoil to multiply its advantages of reducing coolant consumption and improving cooling efficiency.

[0031] Preferably, when viewed in cross-section, each outlet region has a chord length not longer than 20% of the axial chord of the airfoil, and / or wherein the chord distance between two adjacent outlet regions is at least 30% of the axial chord in the case of two cooling circuits, or at least 20% of the axial chord in the case of three cooling circuits, or at least 15% of the axial chord in the case of four or five cooling circuits.

[0032] Of course, the channel section is arranged in a near-wall cooling configuration in the suction sidewall and / or pressure sidewall, and / or the outlet is implemented as a thin-film cooling hole. The use of the invention is not limited to its application only on the pressure side of the airfoil.

[0033] Since the cooling scheme of the present invention includes many channel segments in the overlapping area of ​​the airfoil, the diameter of which is typically between 0.3 and 3.0 mm, the preferred manufacturing method is an additive manufacturing process, particularly by laser powder bed fusion. This results in a single airfoil design that avoids the modular designs known in the prior art that increase the amount of assembly work.

[0034] A turbine rotor blade or turbine stator blade includes an airfoil element according to any one of the preceding claims.

[0035] Other embodiments, features, and advantages of the present invention will become clearer from the following detailed description taken in conjunction with the accompanying drawings, which illustrate the principles of the invention by way of example. Attached Figure Description

[0036] Figure 1 For the cross section passing through the airfoil member according to the first exemplary embodiment of the present invention,

[0037] Figure 2 This is a schematic perspective view of the airfoil component according to the first embodiment.

[0038] Figure 3 A schematic cross-section through the airfoil member according to a second exemplary embodiment of the present invention, and

[0039] Figure 4 It shows Figure 3 Details X. Detailed Implementation

[0040] Figure 1 A cross-section through an airfoil AF according to a first exemplary embodiment of the invention is schematically shown. The planes of the cross-section are arranged perpendicular to the radial direction RD. Figure 2 ).thus, Figure 1 The outline of the airfoil AF is shown, which also represents the surface of the airfoil AF. This surface comes into contact with the hot working gases of the gas turbine during operation.

[0041] Similar to conventional airfoils of existing known turbine blades or turbine stator blades of gas turbines, the airfoil comprises a suction sidewall SW and a pressure sidewall PW, which merge together at the leading edge LE and trailing edge TE of the airfoil AF, while the terms "front" and "back" refer to the flow direction of the hot gas working of the gas turbine.

[0042] Perpendicular to this, in the radial direction, the airfoil AF, as well as the suction sidewall SW and pressure sidewall PW, leading edge LE, and trailing edge, also extend spanwise from the inner end IE to the outer end OE. When the airfoil AF is part of a turbine blade (not shown), a platform is typically arranged at the inner end IE. In the same manner, when the airfoil AF is part of a turbine blade (also not shown), platforms are typically included at the inner end IE and the outer end OE. These platforms are also referred to as shrouds. The chord direction CD extends from the leading edge LE to the trailing edge TE and is arranged in the plane of the cross-section.

[0043] Next, we will refer to Figure 1 and Figure 2 The invention will be explained in more detail below. A first pressure chamber FP1 is arranged in or immediately adjacent to the leading edge LE, which can be supplied with coolant in a conventional manner, such as compressor air. According to a first exemplary embodiment of the invention, the airfoil AF includes four cooling circuits, namely first, second, third, and fourth cooling circuits CC1, CC2, CC3, and CC4; however, the basic idea of ​​the invention can be implemented with only two cooling circuits. Each of them includes multiple channel segments CS. Cooling circuits CC1, CC2, CC3, and CC4 are located on the pressure side of the airfoil AF and, therefore, in the pressure side wall PW, as a near-wall cooling configuration. The channel segments CS generally extend in the chordal direction CD.

[0044] Although the channel cross-sections CS of different cooling circuits are shown as lines of different styles in all figures, it must be understood that these lines should represent conventional cooling channels or pathways in the airfoil AF, preferably having circular, elliptical, or rectangular shapes. Typical diameters of cooling channels range from 0.3 mm to 3.00 mm, depending on the airfoil size and localized cooling requirements. Rectangular shapes offer a larger surface area and a larger cross-section.

[0045] Four cooling circuits CC1-CC4 are arranged in the upstream channel section CSU, which is connected to the first pressure chamber FP1. Their channel inlets CI are preferably all arranged in the same chord region and, according to the exemplary embodiment shown, are arranged next to the leading edge LE. Downstream of the channel inlets, the upstream channel section CSU extends along the chord in the pressure sidewall directly below the surface of the airfoil. In this configuration, and during operation, the coolant flowing through these sections effectively cools the corresponding sidewall portions.

[0046] Conversely, the sub-segments NCC of the channel sections CS of the third cooling circuit CC3 and the fourth cooling circuit CC4 are arranged at a greater distance from the surface than the channel sections CS of the first cooling circuit CC1 and the second cooling circuit CC2. These sub-segments are designed not to effectively cool the sidewalls. Their purpose is to transfer the already heated coolant to the chord region without heating or with the lowest possible heating, where the coolant can still be used to cool the sidewalls.

[0047] Each of the downstream channel sections CSD of the four cooling circuits CC1-CC4 terminates at an outlet OT, which is located in the surface of the airfoil AF. Preferably, the outlet OT can be implemented as a conventional film cooling hole. The outlet OTs of the different cooling circuits CC1-CC4 are distributed along the chord direction CD, as shown in the figure. Figure 2 .

[0048] like Figure 1 The arrangement of the channel section CS shown appears multiple times at different spanwise altitudes of the airfoil AF. Figure 2 The diagram schematically illustrates the stacking of these arrangements, with other arrangements having fewer channel segments interspersed between them. Thus, the outlets OT of the same cooling circuit CC1-CC4 are arranged in an extended row. The area where the outlets OT of the same cooling circuit are arranged has a relatively short dimension in the chord direction. This area (also referred to herein as the outlet area OR) preferably has a dimension of at most 20% of the chord length AF of the airfoil. Depending on the number of cooling circuits, the chord distance between outlet areas is at least 15%, 20%, or 30% of the total chord length. Thus, when the outlets OT of channel segments are located in the same outlet area, the channel segments belong to the same cooling circuit.

[0049] Alternatively, when the channel sections are connected via outlet pressure chambers EP1-EP4 and / or intermediate pressure chambers IP2-IP4, the channel sections belong to the same cooling circuit. Cooling circuit CC1 includes only outlet pressure chamber EP1, while cooling circuits CC2, CC3, and CC4 each include one outlet pressure chamber EP2, EP3, EP4 and one intermediate pressure chamber IP2, IP3, IP4. Each cooling circuit may have more intermediate pressure chambers. Figure 1 , Figure 3 and Figure 4 In the diagram, outlet pressure chambers EP1-EP5 and intermediate pressure chambers IP2-IP4 are shown as solid circles, and... Figure 2 The diagram shows a thick line extending in the longitudinal direction between the inner (IE) and outer (OE) terminals. In this case, each cooling circuit is separated from the other cooling circuits.

[0050] As in Figure 2As exemplarily and schematically shown, the sub-segments of the upstream channel sections CSU of all four cooling circuits CC1, CC2, CC3, and CC4 overlap in the overlapping region PR, wherein, according to the invention, they are arranged in an alternating, preferably regular pattern along the spanwise direction. The feed chamber is not in... Figure 2 As shown in the image. It should be mentioned that... Figure 1 The fact that all the upstream channel segments of the four cooling circuits in the overlapping region PR are arranged at the same distance toward the pressure side surface, so that they all contribute (at least to a similar degree) to cooling the wall region, is not reflected.

[0051] There is another overlapping region between outlet regions OR1 and OR2, and between outlet regions OR2 and OR3, but with a progressively decreasing channel segment density each time. The patterns in the different overlapping regions OP can also differ, and therefore, the density of the channel segments CS for the cooling sidewalls can differ in the different chord regions: in the intermediate region IR2 arranged between outlet regions OR1 and OR2, the density of the channel segments designated for the cooling sidewalls is lower than that in the overlapping region PR. This also applies to the other intermediate regions IR3 and IR4, where intermediate regions IR2, IR3, and IR4 include channel segments of the same density between their intermediate pressure chambers IP2, IP3, IP4 and their outlet pressure chambers EP2, EP3, EP4, which are designated as cooling sidewalls. It is noteworthy that in the downstream intermediate region, in this example in IR4, the different cooling circuits do not overlap. Cooling of the cooling channels occurs.

[0052] In the region of an outlet pressure chamber, the channel segments of other cooling circuits may not be arranged inside the airfoil, as described above, but rather also close to the surface. This is exemplarily shown at location QW, where the upstream channel segment CSU of the second cooling circuit CC2 is located between the surface of the outlet pressure chamber EP of the first cooling circuit CC1 and the pressure sidewall PW.

[0053] like Figure 2 As shown, the number of channel segments counted longitudinally upstream of the outlet pressure chamber differs from the number of channel segments in the same cooling circuit located downstream of the corresponding pressure chamber.

[0054] Cooling of the suction sidewalls SW and / or the remaining areas (e.g., trailing edge TE) can be performed in a conventional manner, for example, as shown in the prior art.

[0055] Turning to a second exemplary embodiment of the invention, Figure 3A cross-section through another airfoil element AF is schematically shown. Features identical to those in the first exemplary embodiment will not be described again. Hereinafter, only the differences from the first exemplary embodiment will be described in detail.

[0056] Compared to the first exemplary embodiment, the second exemplary embodiment includes a second feed chamber FP2 in the intermediate chord region between the leading edge LE and the trailing edge TE. This second feed chamber FP2 is connected to a fourth cooling circuit CC4 and replaces the feed chamber FP1 only for the fourth cooling circuit CC4. Another difference is that no cooling circuit includes an intermediate chamber.

[0057] The next difference is that two cooling circuits CC3 and CC5 are also arranged on the suction sidewall SW, thus creating another overlapping area OP directly downstream of the leading edge LE. Another difference is that the third cooling circuit CC3 includes a channel section with three sub-segments CSS1, CSS2, and CSS3. The first sub-segment CSS1 is located in the suction sidewall SW, used to cool the corresponding area, and is no longer located on the pressure side. The second sub-segment CSS2 serves as a transfer channel to guide coolant from the airfoil's suction side to the pressure side, and the third sub-segment CSS3 again serves as a cooling channel in the mid-chord region of the pressure sidewall PW, then merges into the outlet pressure chamber EP of the third cooling circuit CC3. Thus, the upstream channel section of the third cooling circuit CC3 includes three sub-segments CCS1-CSS3. The second sub-segment CSS2 is located in the reinforcing rib SR, which connects the suction sidewall SW and the pressure sidewall PW, and separates the two supply pressure chambers FP1 and FP2 from each other.

[0058] Figure 3 Detail X in Figure 4 The two features are repeated at a larger scale to clearly illustrate them. First, the structure of the uppermost channel segment CSU comprises the first sub-segment FL and the second sub-segment SL, as well as the turning section between them. Each of the uppermost channel segments CSU, and therefore each of the first sub-segments FL, has a channel inlet CI at the pressure chamber FP1. These channel inlets are again arranged in the same chordal direction region as the leading edge LE of the airfoil AF, i.e., in the region where... Figure 3 and Figure 4 In the cross-section shown, the channel inlets CI are located in the inner surface forming the pressure chamber FP1, such that they are opposite the leading edge LE. The first sub-segment FL is quite short and extends perpendicular to the wall of the leading edge LE. The turning segments function similarly to the impact channel segments with increased heat transfer capacity. Therefore, the structure shown is highly advantageous when applied to areas with the highest heat load (i.e., in the leading edge). This avoids nozzle cooling at the leading edge, which also helps to save coolant. Thus, when viewed in cross-section, the four upstream channel segments CSU are L-shaped.

[0059] Secondly, in the region of the outlet pressure chamber EP1, the channel section of the second cooling circuit CC2 is located between the surface of the outlet pressure chamber EP1 of the first cooling circuit CC1 and the pressure sidewall PW. In this case, the downstream channel section CSD of the first cooling circuit CC1 and the upstream channel section CSU of the second cooling circuit CC2 do not merge with each other; they are arranged offset in the spanwise direction.

Claims

1. An airfoil (AF) for a turbine stator or turbine rotor blade of a gas turbine. include: - Suction sidewall (SW) and pressure sidewall (PW), the suction sidewall (SW) and the pressure sidewall (PW) are used to guide the hot working gas of the gas turbine. When the airfoil (AF) is used in the gas turbine, the two sidewalls (SW, PW) extend from the leading edge (LE) to the trailing edge (TE) in the chord direction (CD) of the gas turbine, and from the inner end (IE) of the airfoil to the outer end (OE) of the airfoil in the radial direction (RD) of the gas turbine. - At least one pressure supply chamber (FP1, FP2) for coolant (CM) extending in the radial direction (RD). - At least two cooling circuits (CC1-CC5) in the suction sidewall (SW) and / or the pressure sidewall (PW), and the at least two cooling circuits (CC1-CC5) are fluidly connected to the first pressure supply chamber (FP1) in the at least one pressure supply chamber (FP1, FP2). -in, Each cooling circuit (CC1-CC5) includes an outlet region (OR1-OR5) and multiple channel segments (CS) extending in the chord direction (CD), wherein in the outlet region, the corresponding cooling circuit (CC1-CC5) is arranged in the downstream channel segment (CS) leading to one of the suction sidewall (SW) or the pressure sidewall (PW) of the airfoil (AF). The outlet regions (OR1-OR5) of the different cooling circuits (CC1-CC5) are separated from each other relative to the chord direction (CD) of the airfoil (AF). In the overlapping area (PR) of the airfoil (AF), the channel segments (CS) of different cooling circuits (CC1-CC5) overlap, and the channel segments (CS) of the different cooling circuits (CC1-CC5) are arranged alternately, preferably in a regular arrangement, so as to simultaneously cool the overlapping area of ​​the airfoil.

2. The airfoil (AF) according to claim 1. in, The first pressure chamber (FP1) is arranged in the leading edge region of the airfoil (AF), and the first pressure chamber (FP1) extends in the radial direction (RD) between the inner end (IE) and the outer end (OE) of the airfoil (AF).

3. The airfoil (AF) according to claim 1 or 2. in, Each of the different cooling circuits arranged in the uppermost channel section (CSU) has a channel inlet (CI), wherein most, preferably all, of the channel inlets are arranged in the same area along the chord direction, preferably in the area where the leading edge (LE) is located, and most preferably opposite the leading edge (LE) of the airfoil (AF).

4. The airfoil (AF) according to claim 1 or 3. in, In the cross-section of the airfoil, the upstream channel segment (CSU) of the corresponding channel segment is L-shaped and has a first sub-segment (FL) starting from the first pressure chamber (FP1), a turning segment below the stagnation area of ​​the leading edge, and a second sub-segment (SL) extending along the corresponding sidewall (PW, SW).

5. The airfoil (AF) according to any one of the preceding claims. in, Each channel segment (CS, CSD) in the downstreammost channel section of each cooling circuit (CC1-CC5) leads to the suction sidewall (SW) or the pressure sidewall (PW) through an outlet (OT); and wherein, for at least one cooling circuit (CC1-CC5), preferably each cooling circuit (CC1-CC5) has an outlet pressure chamber (EP) arranged near the outlet (OT), the outlet pressure chamber (EP) interconnecting the downstreammost channel segments (CSD) of the corresponding cooling circuit (CC1-CC5), and the outlet pressure chamber (EP) extends radially between the inner end (IE) and the outer end (OE) of the airfoil (AF).

6. The airfoil (AF) according to claim 5. in, Some channel sections of the channel section (CS) of one of the at least two cooling circuits (CC1-CC5) are arranged between the surface (SE) of the corresponding sidewall (SW, PW) and the outlet pressure chamber (EP) of the other circuit (CC2, CC1) of the at least two cooling circuits (CC1-CC5).

7. The airfoil (AF) according to any one of the preceding claims. in, For at least one of the cooling circuits (CC1-CC5), an intermediate pressure chamber (IP2-IP5) is provided, which interconnects the channel segments (CS) of the respective cooling circuits (CC1-CC5), and the intermediate pressure chamber extends in the radial direction (RD) between the inner end (IE) and the outer end (OE) of the airfoil (AF).

8. The airfoil (AF) according to claim 5, 6 or 7. in, The number of channel sections (CS) located upstream of the intermediate pressure chamber (IP) or outlet pressure chamber (EP) is different from the number of channel sections (CS) located downstream of the same pressure chamber (IP, EP).

9. The airfoil (AF) according to any one of the preceding claims. in, The outlet areas (OR1-OR5) of the at least two cooling circuits (CC1-CC5) are located in the same sidewall (SW, PW) and / or in different sidewalls (SW, PW).

10. The airfoil (AF) according to any one of the preceding claims. in, Some of the channel segments (CS) or sub-segments (NCC, CCS2) are positioned at a certain distance from the surface (SE) of the corresponding sidewall (SW, PW) and are designated not to cool the corresponding sidewall (SW, PW), i.e., their distance is greater than the distance between the channel segments designated for cooling the corresponding sidewall and the surface of the sidewall.

11. The airfoil (AF) according to any one of the preceding claims. in, The at least two cooling circuits include three, four, or five cooling circuits (CC1-CC5), each cooling circuit including multiple channel sections (CS), and / or The at least one pressure supply chamber (FP1, FP2) includes a second pressure supply chamber (FP2).

12. The airfoil (AF) according to any one of the preceding claims. Each exit region (OR1-OR5) has a chord length not exceeding 20% ​​of the axial chord of the airfoil (AF), and / or the chord distance between two adjacent exit regions (OR1-OR5) is In the case of two cooling circuits (CC1-CC5), at least 30% of the axial chord, or In the case of three cooling circuits, it is at least 20% of the axial chord, or In the case of four or more cooling circuits, it is at least 15% of the axial chord.

13. The airfoil (AF) according to any one of the preceding claims. in, The channel section (CS) is arranged in the suction sidewall (SW) and / or the pressure sidewall (PW) in a near-wall cooling configuration, and / or the outlet (OT) is implemented as a film cooling hole (FCH).

14. The airfoil (AF) according to any one of the preceding claims. in, The airfoil (AF) is monolithically manufactured and / or manufactured by additive manufacturing processes, particularly by laser powder bed fusion.

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