TURBINE SHELL AND GAS TURBINE

Abstract

A turbine blade (40) comprising: a flow profile section (42), a cooling passage (66) which extends in a blade vertical direction within the flow profile section (42), and a plurality of cooling holes (70) formed in a trailing edge portion (47) of the airfoil section (42) such that they are arranged in the blade vertical direction, wherein the plurality of cooling holes (70) communicates with the cooling passage (66) and opens towards a trailing edge end surface (49) of the airfoil section (42) in the trailing edge portion (47), wherein a formation area of ​​the multitude of cooling holes (70) in the trailing edge part (47) has: having a central region (Rm) and an intermediate position (Pm) between a first end and a second end of the flow profile section (42) in the blade vertical direction, wherein the central region (Rm) has a constant index d_mid, which indicates opening densities of the plurality of cooling holes (70), an upstream region (Rup) which is arranged upstream of a flow of a cooling medium in the cooling passage (66) from the central region (Rm) in the blade vertical direction, wherein the upstream region (Rup) has a constant index d_up which indicates the opening densities of the plurality of cooling holes (70), and a downstream region (Rdown) which is arranged downstream of the flow of the cooling medium from the central region (Rm) in the blade vertical direction, wherein the downstream region (Rdown) has a constant index d_down which indicates the opening densities of the plurality of cooling holes (70), where a relationship of d_up < d_mid < d_down is satisfied, wherein each of the indices d_up, d_mid and d_down, which indicate the opening densities, is represented by a ratio D / P of a through-hole diameter D of each of the cooling holes (70), which are arranged such that they penetrate the trailing edge part (47) to an intermediate space P between the cooling holes (70) adjacent to each other in the blade vertical direction, wherein the upstream area (Rup), the middle area (Rm) and the downstream area (Rdown) connect to each other in the blade vertical direction, and wherein the opening densities of the plurality of cooling holes (70) are all uniform and constant in each of the upstream region (Rup), the middle region (Rm) and the downstream region (Rdown) and the opening densities of the plurality of cooling holes (70) change stepwise in the blade vertical direction.

Description

TECHNICAL AREA

[0001] The present disclosure relates to a turbine blade and a gas turbine. BACKGROUND

[0002] It is known that in a turbine blade, a gas turbine or the like, a turbine blade exposed to a high-temperature gas stream or the like is cooled by flowing a cooling medium to a cooling passage formed in one side of the turbine blade.

[0003] For example, patent document 1 discloses a turbine rotor blade equipped with an internal flow passage located in a combustion gas flow passage of a gas turbine, within which a cooling medium flows. In a trailing-edge portion of the turbine rotor blade, a plurality of outlets are arranged in a direction connecting a blade root and a blade tip. The outlets are arranged such that they open towards a trailing-edge tip. The cooling medium, supplied by a delivery passage located in a blade root section of the turbine rotor blade leading to the internal flow passage, is partially discharged from the plurality of outlets arranged in the trailing-edge portion as it passes through the internal flow passage.

[0004] Patent document 2 discloses a blade for a gas turbine engine, comprising an airfoil having a root region, a tip region arranged radially outside the root region, and leading and trailing edges extending between the root region and the tip region. A fairing extends transversely from the tip region of the airfoil, and the airfoil defines internal cooling channels extending between the root region and the tip region. The airfoil includes a wall element adjacent to the trailing edge and a support structure extending from the wall element to the fairing to support the fairing. The support structure allows cooling air to flow from a cooling channel to the trailing edge in a region near the tip region of the airfoil.

[0005] Patent document 3 discloses a component comprising a plurality of cooling channels arranged in two intersecting configurations to form a plurality of cooling channel intersections. Air jet interactions occur at the cooling channel intersections as air flows through the cooling channels. The spacing of the channels in at least one of the configurations is selected such that a predetermined area of ​​intersection density is provided in one or more selected regions of the component.

[0006] Patent document 4 discloses cooled turbine blades comprising two cavities separated by an internal partition along the height of the blade, each supplied with a cooling fluid flow in its lower part, wherein an upstream cavity with radial flow and a downstream cavity are subdivided into two radial tangential flow zones towards the trailing edge, characterized in that the upstream cavity has ribs that facilitate heat exchange and holes in the leading edge, and that the downstream cavity has large-cross-section bridge elements in the middle zone for the radial flow of the fluid, while in the trailing-edge zone with tangential flow to the trailing edge the downstream cavity has small-cross-section bridges supplemented by deflection elements that direct the radial flow tangentially to the openings at the trailing edge, and thereby,that part of the fluid flows are discharged through outlet openings at the upper part of each cavity.

[0007] Patent document 5 discloses that a gas turbine blade has cooling air channels for conventional cooling within the blade and cooling air outlet nozzles connecting the outside of the blade to the cooling air channels. The amount of cooling air expelled from the cooling air outlet nozzles is adjusted according to the temperature distribution of the main flow gas in the gas channel such that the set value is relatively high in a high-temperature zone of the main flow gas and relatively low in a low-temperature zone of the same.

[0008] Patent document 6 discloses that an airfoil for a gas turbine comprises a leading edge, a trailing edge, a tip plate, a first side wall extending radially between an airfoil root and a tip plate, and a second side wall connected to the first side wall at the leading and trailing edges to define a cooling cavity. The side wall extends radially between the airfoil root and the tip plate. The airfoil further comprises several longitudinally spaced trailing-edge cooling slots arranged in a gap extending through the first side wall. The slots are in flow communication with the cooling cavity and are unevenly distributed along the trailing edge, such that the number of slots is greater in at least one section of the trailing edge than in another section. List of patent literature Patent Document 1: JP 2004-225690 A Patent document 2: US 2009 / 0214328 A1 Patent Document 3: US 2007 / 0031252 A1 Patent document 4: EP 0034961 B1 Patent Document 5: JP H08-14001 A Patent document 6: DE 102005026525 A1 SUMMARY Technical Problem

[0009] Incidentally, according to research conducted by the inventors, a temperature and / or pressure distribution can occur in a cooling passage formed within a turbine blade. Therefore, it is assumed that the blade can be cooled more effectively by performing the cooling according to the temperature and / or pressure distribution in the cooling passage. However, patent document 1 does not explicitly disclose that the turbine blade is cooled in accordance with the temperature and / or pressure distribution in the cooling passage.

[0010] In light of the above, it is an object of at least one embodiment of the present invention to provide a turbine blade and a gas turbine that is capable of effectively cooling the turbine blade. Solution to the problem

[0011] According to the present invention, a turbine blade according to independent claims 1 to 4 and a gas turbine according to independent claim 11 are provided. Advantageous modifications are found in dependent claims 5 to 10.

[0012] (1) A turbine blade according to at least one embodiment of the present invention comprises: a flow profile section, a cooling passage extending in a blade vertical direction within the flow profile section, and a plurality of cooling holes formed in a trailing edge part of the flow profile section such that they are arranged in the blade vertical direction, wherein the plurality of cooling holes communicates with the cooling passage and opens towards a surface of the flow profile section in the trailing edge part.A formation area of ​​the plurality of cooling holes in the trailing edge portion comprises: a central region having an intermediate position between a first end and a second end of the flow profile section in the blade vertical direction, wherein the central region has a constant index d_mid indicating the opening densities of the plurality of cooling holes; an upstream region arranged upstream of a flow of a cooling medium in the cooling passage from the central region in the blade vertical direction, wherein the upstream region has a constant index d_up indicating the opening densities of the plurality of cooling holes; and a downstream region arranged downstream of the flow of the cooling medium from the central region in the blade vertical direction, wherein the downstream region has a constant index d_down indicating the opening densities of the plurality of cooling holes.A relationship of d_up < d_mid < d_down is satisfied.

[0013] Because the cooling medium flows into the cooling passage formed within the flow profile section while cooling the flow profile section, a temperature distribution can occur in which the temperature increases downstream of the cooling medium flow. In this regard, in the configuration above (1), because the opening densities of the cooling holes are higher downstream than upstream of the cooling medium flow in the cooling passage, it is possible to increase the delivery flow rate of the cooling medium downstream through the cooling holes, where the temperature of the cooling medium is relatively high. Therefore, it is possible to cool the trailing edge portion of the turbine blade appropriately in accordance with the temperature distribution of the cooling passage.

[0014] (2) A turbine blade according to at least one embodiment of the present invention comprises: a flow profile section, A cooling passage extending in a blade vertical direction within the airfoil section, and a plurality of cooling holes formed in a trailing-edge portion of the airfoil section such that they are arranged in the blade vertical direction and provide convective cooling of the trailing-edge portion, wherein the plurality of cooling holes communicate with the cooling passage and penetrate the trailing-edge portion to open towards a trailing-edge end surface. A relationship d_up < d_down < d_mid is satisfied, where d_mid is an index representing the opening density of the cooling holes in a mid-region, an intermediate position between a first end and a second end of the airfoil section in the blade vertical direction, and d_up is an index representing the position in a region upstream of a flow of a cooling medium in the cooling passage from the mid-region in the blade vertical direction.and d_down is an index located in a region downstream of the cooling medium flow from the central region in the blade vertical direction. A formation region of the plurality of cooling holes in the trailing edge portion comprises: the central region having the intermediate position between the first end and the second end of the flow profile section in the blade vertical direction, wherein the central region has the constant index d_mid, which specifies the opening densities of the plurality of cooling holes; an upstream region located upstream of the cooling medium flow in the cooling passage from the central region in the blade vertical direction, wherein the upstream region is located on an upstream side of the formation region, wherein the upstream region has the constant index d_up, which specifies the opening densities of the plurality of cooling holes; and a downstream region.which is arranged downstream of the flow of the cooling medium from the central region in the blade height direction, wherein the downstream side is arranged in a downstream side of the formation region, wherein the downstream region has the constant index d_down, which indicates the opening densities of the plurality of cooling holes.

[0015] The temperature of a gas flowing through a combustion gas flow passage where the turbine blade is located tends to be higher in the central region than in the regions at the sides of both ends (the first end and the second end) of the flow profile section in the blade's vertical direction. Conversely, because the cooling medium flows in the cooling passage formed within the flow profile section, cooling the section, a temperature distribution can occur in which the temperature increases downstream of the cooling medium flow.In this case, to adequately cool the trailing edge section, it is desirable to maximize the flow rate of the cooling medium through the cooling holes in the central region in the blade vertical direction and to increase the flow rate of the cooling medium through the cooling holes in the downstream region compared to the upstream region of the cooling medium flow in the cooling passage. In this regard, it is possible with the above configuration (2) because the opening densities of the cooling holes in the central region are higher than the opening densities of the cooling holes in the upstream region and the downstream region of the central region. This allows for an increase in the delivery flow rate of the cooling medium through the cooling holes in the central region, where the temperature of the gas flowing through the combustion gas passage is relatively high.Furthermore, in the configuration above (2), because the opening densities of the cooling holes are higher in the downstream region described above than in the upstream region described above, it is possible to increase the delivery flow rate of the cooling medium through the cooling holes into the downstream region, which has a higher cooling medium temperature than the upstream region. Therefore, it is possible to cool the trailing edge portion of the turbine blade appropriately in accordance with the temperature distribution of the cooling passage.

[0016] (3) A turbine blade according to at least one embodiment of the present invention comprises: a flow profile section, a cooling passage extending in a blade vertical direction within the flow profile section, and a plurality of cooling holes formed in a trailing edge portion of the flow profile section such that they are arranged in the blade vertical direction, the plurality of cooling holes communicating with the cooling passage and opening to a surface of the flow profile section in the trailing edge portion. The turbine blade is a rotor blade.A relationship d_tip < d_mid < d_root is satisfied, where d_mid is an index indicating the opening density of the cooling holes in a central region, representing an intermediate position between the end and the root of the airfoil section in the blade vertical direction; d_tip is an index located in a region closer to the end than the central region in the blade vertical direction; and d_root is an index located in a region closer to the root than the central region in the blade vertical direction. Each of the indices d_tip, d_mid, and d_root, which indicate the opening density, is represented by a ratio D / P of a through-hole diameter D of each of the cooling holes, which are arranged such that they penetrate the trailing edge portion to an interval P between adjacent cooling holes in the blade vertical direction.A formation region of the plurality of cooling holes in the trailing edge portion comprises: a central region having the intermediate position between the end and the root of the airfoil section in the blade vertical direction, wherein the central region has the constant index d_mid, which specifies the opening densities of the plurality of cooling holes; an outer end region, which is located closer to the end than the central region in the blade vertical direction and closest to the end in the formation region, wherein the outer end region has the constant index d_tip, which specifies the opening densities of the plurality of cooling holes; and a root region, which is located closer to the root than the central region in the blade vertical direction and closest to the root in the formation region, wherein the root region has the constant index d_root, which specifies the opening densities of the plurality of cooling holes.

[0017] Because a centrifugal force acts on the cooling medium in the cooling passage formed within the flow profile section of the rotor blade due to turbine operation, a pressure distribution can occur in which the pressure increases on the trailing side of the flow profile section within the cooling passage. In this regard, with the configuration (3) above, because the opening densities of the cooling holes are lower at the trailing side than at the trailing side of the flow profile section, it is possible to reduce the variation in the delivery rate of the cooling medium through the cooling holes in the blade vertical direction, even when the pressure distribution described above occurs. Therefore, it is possible to cool the trailing edge portion of the turbine blade appropriately in accordance with the temperature and pressure distribution of the cooling passage.

[0018] (4) A turbine blade according to at least one embodiment of the present invention comprises: a flow profile section, a cooling passage extending in a blade vertical direction within the flow profile section, and a plurality of cooling holes formed in a trailing edge portion of the flow profile section such that they extend in the blade vertical direction and provide convection cooling of the trailing edge portion, the plurality of cooling holes communicating with the cooling passage and penetrating the trailing edge portion to open to a trailing edge end surface. The turbine blade is a rotor blade.A relationship of d_tip < d_root < d_mid is satisfied where d_mid is an index that indicates an intermediate position between an end and a foot of the flow profile section in the blade height direction, having opening densities of the cooling holes in a central region, d_tip is an index that is located in a region closer to the end than the central region in the blade height direction, and d_root is an index that is located in a region closer to the foot than the central region in the blade height direction.A formation region of the plurality of cooling holes in the trailing edge portion comprises: a central region having the intermediate position between the end and the root of the airfoil section in the blade vertical direction, wherein the central region has the constant index d_mid, which specifies the opening densities of the plurality of cooling holes; an outer end region, which is located closer to the end than the central region in the blade vertical direction and closest to the end in the formation region, wherein the outer end region has the constant index d_tip, which specifies the opening densities of the plurality of cooling holes; and a root region, which is located closer to the root than the central region in the blade vertical direction and closest to the root in the formation region, wherein the root region has the constant index d_root, which specifies the opening densities of the plurality of cooling holes.

[0019] The temperature of the gas flowing through the combustion gas passage, where the rotor blade (turbine blade) is located, tends to be higher in the central region than in the regions at the ends (tip and root) of the airfoil section in the blade's vertical direction. Furthermore, due to the centrifugal force acting on the cooling medium in the cooling passage formed within the airfoil section of the rotor blade as a result of turbine operation, a pressure distribution can occur in which the pressure increases at the end of the airfoil section within the cooling passage.In this case, in order to adequately cool the trailing edge portion, it is desirable to maximize the flow rate of the cooling medium through the cooling holes in the central area in the blade vertical direction and to reduce the variations in the delivery flow rate of the cooling medium through the cooling holes between the area located on the end side and the area located on the foot side in the blade vertical direction.

[0020] In this regard, with the configuration above (4), because the opening densities of the cooling holes in the central region are higher than those in the region located closer to the end than the central region (outer end region) and in the region located closer to the base than the central region (base region), it is possible to increase the delivery rate of the cooling medium through the cooling holes in the central region, where the temperature of the gas flowing through the combustion gas passage is relatively high. Furthermore, with the configuration above (4), because the opening densities of the cooling holes in the outer end region described above are lower than in the base region described above, it is possible to reduce the variation in the delivery rate of the cooling medium through the cooling holes between the outer end region and the base region, even when the pressure distribution described above occurs.Therefore, it is possible to cool the trailing edge part of the turbine blade appropriately in accordance with the temperature distribution of the cooling passage and in accordance with the pressure distribution of the cooling passage.

[0021] (5) In some embodiments, in any of the above configurations (1) to (4), the central region has a plurality of cooling holes having the same diameter, and an outer end region and a foot region each have a plurality of cooling holes having the same diameter as the cooling holes in the central region, wherein the outer end region is located closer to an outer end of the airfoil section than the central region, and wherein the foot region is located closer to a foot of the airfoil section than the central region.

[0022] (6) In some embodiments, in any of the above configurations (1) to (5), the surface of the flow profile section is an end surface of the trailing edge part.

[0023] (7) In some embodiments, in any of the above configurations (1) to (6), the plurality of cooling holes are inclined with respect to a plane perpendicular to the blade vertical direction.

[0024] In the configuration above (7), because the multitude of cooling holes are inclined with respect to the plane running directly in the blade's vertical direction, it is possible to elongate the cooling holes compared to a case where the cooling holes are formed parallel to the plane perpendicular to the blade's vertical direction. Therefore, it is possible to effectively cool the trailing edge portion of the turbine blade.

[0025] (8) In some embodiments, in any of the above configurations (1) to (7) the plurality of cooling holes are formed parallel to each other.

[0026] In the configuration above (8), because the multiple cooling holes are arranged parallel to each other, it is possible to form more cooling holes in the flow profile section than in a case where the multiple cooling holes are not parallel to each other. Therefore, it is possible to effectively cool the trailing edge portion of the turbine blade.

[0027] (9) In some embodiments, in any of the above configurations (1) to (8), the cooling passage is a final path of a serpentine flow passage formed within the flow profile section.

[0028] In the above configuration (9), because the multitude of cooling holes communicating with the last leg of the serpentine flow passage are open to the surface of the flow profile section in the trailing edge part, it is possible to adequately cool the trailing edge part of the turbine blade.

[0029] (10) In some embodiments, in any of the above configurations (1) to (9), the turbine blade is a rotor blade, and the cooling passage has an outlet opening formed at one end of the flow profile section.

[0030] In the above configuration (10), because the rotor blade, which serves as the turbine blade, has any of the above configurations (1) to (9), it is possible to adequately cool the trailing edge part of the rotor blade, which serves as the turbine blade.

[0031] (11) In some embodiments, in the above configuration (1) or (2), the turbine blade is a stator blade, and the cooling passage has an outlet opening formed on an inner cover of the flow profile section.

[0032] In the above configuration (11), because the stator blade, which serves as the turbine blade, has the above configurations (1) to (2), it is possible to cool the trailing edge part of the stator blade, which serves as the turbine blade, in a suitable manner.

[0033] (12) A gas turbine according to at least one embodiment of the present invention comprises: the turbine blade according to any of the above configurations (1) to (11) and a combustion chamber for generating a combustion gas which flows through a combustion gas flow passage where the turbine blade is arranged.

[0034] In the above configuration (12), because the turbine blade has any of the above configurations (1) to (11), it is possible to cool the trailing edge part of the turbine blade in a suitable manner. Beneficial effects

[0035] According to at least one embodiment of the present invention, a turbine blade and a gas turbine are provided which are capable of effectively cooling a turbine blade. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a schematic configuration view of a gas turbine in which a turbine blade is applied according to one embodiment. Fig. Figure 2 is a partial cross-sectional view of a rotor blade, which serves as a turbine blade according to one embodiment. Fig. Figure 3 is a cross-sectional view of the rotor blade (turbine blade) shown in Fig. 2, along line III-III. Fig. Figure 4 is a schematic cross-sectional view of the rotor blade (turbine blade) shown in Fig. 2. Fig. Figure 5 is a schematic cross-sectional view of the stator blade, which serves as the turbine blade according to one embodiment. Fig. Figure 6 is a graph showing an example of an opening density distribution of a trailing edge part of the rotor blade (turbine blade) according to one embodiment. Fig. Figure 7 is a graph showing an example of an opening density distribution of the trailing edge part of the rotor blade (turbine blade) according to one embodiment. Fig. Figure 8 is a graph showing an example of an opening density distribution of the trailing edge part of the rotor blade (turbine blade) according to one embodiment. Fig. Figure 9 is a graph showing an example of a temperature distribution of a combustion gas in a blade height direction. Fig. Figure 10 is a graph showing an example of an opening density distribution of the trailing edge part of the stator blade (turbine blade) according to one embodiment. Fig. Figure 11 is a graph showing an example of an opening density distribution of the trailing edge part of the stator blade (turbine blade) according to one embodiment. Fig. Figure 12 is a graph showing an example of an opening density distribution of the trailing edge part of the stator blade (turbine blade) according to one embodiment. Fig. Figure 13 is a graph showing an example of a temperature distribution of the combustion gas in the blade height direction. Fig. Figure 14 is a graph showing an example of an opening density distribution of the trailing edge part of the rotor blade (turbine blade) according to one embodiment. Fig. Figure 15 is a graph showing an example of an opening density distribution of the trailing edge part of the rotor blade (turbine blade) according to one embodiment. Fig. Figure 16 is a cross-sectional view of the trailing edge portion of the turbine blade in the blade height direction according to one embodiment. Fig. Figure 17 is a view of the trailing edge portion of the turbine blade, seen in a direction from a trailing edge to a leading edge of a flow profile section according to one embodiment. Fig. Figure 18 is a schematic view showing a configuration of a cooling passage of a turbine rotor blade according to one embodiment. Fig. Figure 19 is a schematic view showing a configuration of a vortex generator according to one embodiment. Fig. Figure 20A is a schematic view of the turbine rotor blade to explain the basic configuration of the present invention. Fig. Figure 20B is a view showing an opening density distribution of cooling holes of a conventional blade. Fig. Figure 20C is a view showing an example of the opening density distribution of the cooling holes of the basic configuration of the present invention. Fig. Figure 20D is a view showing an example in which the opening density distribution of the cooling holes of the basic configuration of the present invention is corrected. Fig. 20E is a graph of a creep limit curve. Fig. Figure 20F is a view of another example showing the opening density distribution of the cooling holes of the basic configuration of the present invention. DETAILED DESCRIPTION

[0036] Embodiments of the present invention will now be described in detail with reference to the accompanying drawings. However, unless otherwise specified, it is intended that dimensions, materials, shapes, relative positions, and the like of components described in the embodiments are merely illustrative and are not intended to limit the scope of the present invention.

[0037] The basic idea of ​​the present invention will be described below, using a turbine rotor blade as a representative example. A rotor blade 26 of a gas turbine is attached to a high-speed rotating rotor 8 (see Figure 1). Fig. 1) and operates in an atmosphere of high-temperature combustion gas, and therefore a flow profile section 42 is cooled using a cooling medium. As in Fig. As shown in Figure 20A, a cooling passage 66 is formed within the flow profile section 42 of the rotor blade 26, and the cooling medium, supplied from the side of a foot 50, flows into the cooling passage 66 to cool the flow profile section 42 and is discharged into a combustion gas from an end 48 of a final path 60e on the side of a trailing edge 46. Furthermore, the cooling medium flows through the final path 60e and is supplied to a plurality of cooling holes 70, which are formed downstream in the axial direction of the rotor 8 of a trailing edge portion 47 and have openings towards the trailing edge 46. The cooling medium performs convection cooling of the trailing edge portion 47 as it flows through the cooling holes 70 and is discharged into the combustion gas. In addition, with respect to the cooling holes, as disclosed in Patent Document 1, as shown in Figure 20A, the cooling medium is further described in Figure 20A. Fig. 20B, the cooling holes 70, which have the same hole diameter, are arranged at the same interval over the entire length in a blade vertical direction of the trailing edge part 47 with uniform opening densities of the cooling holes 70 in the blade vertical direction. This is an example of the arrangement of conventional cooling holes.

[0038] The cooling medium is heated by the flow profile section 42 during the process of flowing through the cooling passage 66 upstream of the last path 60e and flows into the last path 60e from the side of the trailing edge 46. The cooling medium receives heat from the flow profile section 42 to be further heated during the process of flowing from the base 50 on an inlet side to the end 48 on an outlet side in a flow direction of the last path 60e. Therefore, the temperature of the cooling medium flowing through the last path 60e in an outer end region of the flow profile section 42 increases, which can lead to demanding operating conditions.In the case of the rotor blade 26, a metal temperature close to an operating temperature limit, determined by an oxidation dilution tolerance, is obtained in the outer end region in the blade vertical direction (outer surface in the radial direction) of the flow profile section 42, and it is necessary to cool the flow profile section 42 to avoid exceeding the operating temperature limit. In the case of the conventional blade structure described above, as a result of the heating of the cooling medium, the metal temperature is highest in the outer end region of the last path 60e of the flow profile section 42, lower in the middle region of the flow profile section 42 than in the outer end region, and even lower in the root region than in the middle region.Therefore, from the perspective of overheating of the flow profile section 42 due to heating of the cooling medium, it is desirable to select the opening densities of the cooling holes 70, which are arranged in the blade vertical direction, such that a uniform metal temperature distribution is obtained without an increase in variations in the metal temperature of the corresponding areas. This means that it is desirable to set the opening densities of the cooling holes 70 in the outer end region outside the blade vertical direction of the rotor blade 26, which is a downstream region in the flow direction of the cooling medium, to the densest distribution, to the opening densities of the cooling holes 70 in the middle region to a medium distribution, and to set the opening densities of the cooling holes 70 in the trailing region to the least dense distribution. Based on the idea described above, [Figure 1] shows... Fig. 20C is an example of a schematic view of the cooling holes according to an embodiment of the present invention.

[0039] On the other hand, centrifugal creep strengths in the central and trailing sections of the last path 60e must also be considered. In the case of the rotor blade 26, which is attached to the rotating rotor 8 and rotates with it at high speed, a centrifugal force acts on the airfoil section 42, generating a tensile stress in the blade vertical direction of one blade wall. Fig. Figure 20E shows an example of a creep limit curve for a blade material. The ordinate indicates an allowable stress, and the abscissa indicates a metal temperature. A downward-sloping curve is obtained, indicating that the allowable stress decreases with increasing metal temperature. Creep failure of the airfoil section 42 will not occur in a region below the creep limit curve with low stress. However, the airfoil section 42 can be destroyed by creep failure in a region above the curve with high stress. Creep failure does not occur in the outer end region of the airfoil section 42, where a low centrifugal force acts. However, the possibility of creep failure must be considered for the middle and trailing regions of the airfoil section 42, even if the metal temperature in these regions is lower than in the outer end region.

[0040] Fig. 20D and Fig. Figure 20E each shows an example of a case where the creep resistances become critical in the central region and the base region. A description is provided using a point A1 of the central region and a point B1 of the base region as examples in Fig. 20E. The example shows a state in which point A1 exceeds a creep limit and a state in which point B1 lies within the creep limit. Whether the point lies within the creep limit depends, for example, on the size and wall thickness of the blade, the metal temperature, and the like in a corresponding section. In the case of the example, shown in the present embodiment, because the creep limit is exceeded at a position of point A1 in the central region, it is necessary to lower the metal temperature. This means that the opening densities of the cooling holes 70 in the central region are further increased to enhance cooling, thereby reducing the metal temperature at a position of point A2.On the other hand, if the opening densities of the cooling holes 70 in the central region are increased, the flow rate of the cooling medium flowing through the cooling holes 70 in the central region can be increased, and the flow rate of the cooling medium flowing through the cooling holes 70 in the lower region can be decreased. Therefore, although the metal temperature in the lower region rises to that at point B2 when cooling in the central region is intensified, these opening densities can be selected as long as a position of point B2 lies within the creep limit, as shown in [reference]. Fig. 20E. The outer end region can be adjusted in a similar manner. This means that it is possible to reduce the flow rate of the cooling medium flowing through the cooling holes 70 in the outer end region by reducing the opening density of the cooling holes 70 in the outer end region. It is possible to increase the flow rate of the cooling medium flowing through the cooling holes 70 in the central region in order to enhance cooling in the central region by reducing the flow rate of the cooling medium, without the metal temperature in the outer end region reaching the aforementioned operating temperature limit. Fig. Figure 20D shows an example where the opening densities of the cooling holes 70 have been corrected in such a process. A solid line indicates opening densities after an adjustment, and a dashed line indicates opening densities before an adjustment. It is possible to determine suitable opening densities for the cooling holes in the corresponding areas by confirming that all of the corresponding areas are within the operating temperature limit or the creep limit.

[0041] Next, if the rotor blade 26 has a metal temperature at end 48 that is lower than the operating temperature limit and exhibits a relative range for the metal temperature at end 48, the centrifugal force acting on the cooling medium flowing through the last path 60e can influence the arrangement of the cooling holes 70. An example of this will be described below. As shown in Fig. 20A, the centrifugal force acts on the cooling medium flowing through the last path 60e of the flow profile section 42 in the same direction as the flow direction of the cooling medium. This means that, due to the effect of the centrifugal force, a pressure gradient occurs in the cooling medium, in which the pressure increases from the side of the base 50 to the side of the end 48. Therefore, with an arrangement of cooling holes with uniform opening densities, as shown in Fig. 20B, the flow rate of the cooling medium discharged into the combustion gas from an outlet opening 64 at the end 48 of the flow profile section 42 or from the cooling holes 70 in the outer end region is limited, and the flow rate of the cooling medium supplied to the cooling holes 70 in the middle and bottom regions decreases, which can lead to insufficient cooling of the middle and bottom regions. In this case, it is necessary to gradually reduce the flow rate of the cooling medium discharged into the combustion gas from the outlet opening 64 at the end 48 or from the cooling holes 70 in the outer end region by decreasing the opening densities from the bottom region to the outer end region and to increase the amount of cooling medium supplied to the cooling holes 70 in the middle and bottom regions.By selecting the appropriate opening density of the cooling holes, it is possible to homogenize the metal temperature of the corresponding areas. Fig. Figure 20F shows an example of an opening density distribution of the cooling holes 70, which takes into account the influence of the centrifugal force.

[0042] It is possible to reduce blade damage associated with, for example, oxidation thinning of the trailing edge and creep fracture, and to improve blade reliability by determining the opening densities in the relevant areas based on the ideas described above. The above description is given using the turbine rotor blade as an example. However, the above description is also applicable to a turbine stator blade, except when centrifugal force is not acting. Specific embodiments of the present invention will be described next.

[0043] First, a gas turbine will be described in which the turbine blade is used according to some embodiments.

[0044] Fig. Figure 1 is a schematic configuration view of the gas turbine, in which the turbine blade is applied according to one embodiment. As shown in Fig. Figure 1, the gas turbine 1, comprises a compressor 2 for generating compressed air, a combustion chamber 4 for generating the combustion gas from the compressed air and fuel, and a turbine 6, which is configured to be driven by the combustion gas. In the case where the gas turbine 1 is used for power generation, a generator (not shown) is connected to the turbine 6.

[0045] The compressor 2 has a plurality of stator blades 16, attached to the side of a compressor housing 10, and a plurality of rotor blades 18, mounted on the rotor 8, such that they are arranged alternately with respect to the stator blades 16. Intake air from an air inlet 12 is directed to the compressor 2 and passes through the plurality of stator blades 16 and the plurality of rotor blades 18 to be compressed, resulting in compressed air that has a high temperature and high pressure.

[0046] The combustion chamber 4 is supplied with fuel and compressed air generated by the compressor 2 and burns the fuel to produce combustion gas, which serves as a working fluid for the turbine 6. As shown in Fig. 1, a plurality of combustion chambers 4 can be arranged in the housing 20 centered around the rotor.

[0047] The turbine 6 has a combustion gas flow passage 28, which is formed in a turbine housing 22, and has a plurality of stator blades 24 and rotor blades 26 arranged in the combustion gas flow passage 28. Each of the stator blades 24 is attached to the side of the turbine housing 22. The plurality of stator blades 24, which are arranged in the circumferential direction of the rotor 8, form a stator blade row. In addition, each of the rotor blades 26 is inserted into the rotor 8. The plurality of rotor blades 26, which are arranged in the circumferential direction of the rotor 8, form a rotor blade row. The stator blade row and the rotor blade row are arranged alternately in the axial direction of the rotor 8.In turbine 6, the combustion gas, which flows into the combustion gas flow passage 28, passes from the combustion chamber 4 through the multitude of stator blades 24 and the multitude of rotor blades 26, thereby driving the rotor 8. Consequently, the generator, which is connected to the rotor 8, is driven to produce energy. The combustion gas that has driven the turbine 6 is released to the outside via an exhaust chamber 30.

[0048] In some embodiments, at least both the rotor blades 26 and the stator blades 24 of the turbine 6 are turbine blades 40, which are described below.

[0049] Fig. Figure 2 is a partial cross-sectional view of the rotor blade 26, which serves as the turbine blade 40 according to one embodiment. Fig. Figure 2 shows the cross-section of part of the flow profile section 42 of the rotor blade 26. Fig. Figure 3 is a cross-sectional view of the turbine blade 40, shown in Fig. 2, along line III-III. Fig. Figure 4 is a schematic cross-sectional view of the rotor blade 26 (turbine blade 40) shown in Fig. 2. Fig. Figure 5 is a schematic cross-sectional view of the stator blade 24, which serves as the turbine blade 40 according to one embodiment. In the Fig. 4 and Fig. Part 5 of the turbine blade configuration 40 is not shown. Arrows in the views indicate the flow direction of the cooling medium.

[0050] As shown in the Fig. 2 and Fig. 4, the turbine blade 40, which serves as the rotor blade 26, according to one embodiment, has the flow profile section 42, a platform 80 and a blade root section 82. The blade root section 82 is embedded in the rotor 8 (see Fig. 1) The rotor blade 26 rotates together with the rotor 8. The platform 80 is integrally formed with the blade root section 82. The airfoil section 42 is arranged such that it extends in the radial direction of the rotor 8 (hereinafter referred to simply as the ‘radial direction’) and has the root 50, which is attached to the platform 80, and the end 48, which is arranged on the side opposite the root 50 in the radial direction.

[0051] In some embodiments, the turbine blade 40 can be the stator blade 24. As shown in Fig. Figure 5, the turbine blade 40, which serves as the stator blade 24, has the flow profile section 42, an inner cover 86 arranged radially inside with respect to the flow profile section 42, and an outer cover 88 arranged radially outward with respect to the flow profile section 42. The outer cover 88 is supported by the turbine casing 22, and the stator blade 24 is supported by the turbine casing 22 over the outer cover 88. The flow profile section 42 has an outer end 52, which is arranged on the side of the outer cover 88 (i.e., radially outside), and an inner end 54, which is arranged on the side of the inner cover 86 (i.e., radially inside).

[0052] As shown in the Fig. 2 to 5, the flow profile section 42 of the turbine blade 40 has a leading edge 44 and a trailing edge 46, which in the case of the rotor blade 26 (see Fig. 2 to 4) extends from the foot 50 to the end 48 and in the case of the stator blade 24 (see Fig. 5) extends from the outer end 52 to the inner end 54. Furthermore, the blade surface of the flow profile section 42 is defined by a pressure surface (concave surface) 56 and a suction surface (convex surface) 58 (see Fig. 3), which extend in the blade height direction between the foot 50 and the end 48 in the case of the rotor blade 26 and between the outer end 52 and the inner end 54 in the case of the stator blade 24.

[0053] The cooling passage 66, which extends in the blade's vertical direction, is formed within the flow profile section 42. The cooling passage 66 is a flow passage for the flow of the cooling medium (e.g., air or the like) to cool the turbine blade 40.

[0054] In the exemplary embodiments shown in the Fig. 2 to 5, the cooling passage 66 partially forms a serpentine flow passage 60, which is arranged within the flow profile section 42. The serpentine flow passage 60, shown in the Fig. Sections 2 to 5 have a plurality of paths 60a to 60e extending in the blade vertical direction and arranged in this order from the leading edge 44 to the trailing edge 46. Adjacent paths (e.g., path 60a and path 60b) of the plurality of paths 60a to 60e are connected to each other on the end 48 or the root 50 side. In the connecting section, a backflow passage is formed with a cooling medium flow direction reversed in the blade vertical direction, and the serpentine flow passage 60 as a whole has a meandering shape.

[0055] In the exemplary embodiments shown in the Fig. 2 to 5, the cooling passage 66 is the last path 60e of the serpentine flow passage 60. Of the multitude of paths 60a to 60e that form the serpentine flow passage 60, the last path 60e is typically located most downstream on the side of the trailing edge 46 in the direction of flow of the cooling medium.

[0056] In the case where the turbine blade 40 is the rotor blade 26, the cooling medium is introduced, for example, in an internal flow passage 84 formed within the blade root section 82 and the serpentine flow passage 60, via an inlet opening 62 located on the side of the root 50 of the flow profile section 42 (see Fig. 2 and Fig. 4) and flows successively through the plurality of paths 60a to 60e. Thereafter, the cooling medium, which flows through the last path 60e, which is furthest downstream in the flow direction of the cooling medium of the plurality of paths 60a to 60e, flows to the combustion gas flow passage 28 outside the turbine blade 40 via the outlet opening 64, which is located on the side of the end 48 of the flow profile section 42.

[0057] In the case where the turbine blade 40 is the stator blade 24, the cooling medium is introduced, for example, into an internal flow passage (not shown) formed within the outer cover 88 and the serpentine flow passage 60, via the inlet opening 62, which is located on the side of the outer end 52 of the flow profile section 42 (see Fig. 5) and flows successively through the plurality of paths 60a to 60e. Thereafter, the cooling medium, which flows through the last path 60e, which is furthest downstream in the flow direction of the cooling medium of the plurality of paths 60a to 60e, flows into the combustion gas flow passage 28 outside the turbine blade 40 via the outlet opening 64, which is located on the side of the inner end 54 (the side of the inner cover 86) of the flow profile section 42.

[0058] For example, a portion of the compressed air obtained by the compressor 2 (see) can be used as the cooling medium for cooling the turbine blade 40. Fig. 1) to the cooling passage 66. The compressed air from compressor 2 can be supplied to the cooling passage 66 after it has been cooled by heat exchange with a cold source.

[0059] The shape of the serpentine flow passage 60 is not limited to the shapes shown in the Fig. 2 and Fig. 3. For example, a multitude of serpentine flow passages can be formed within the flow profile section 42 of the turbine blade 40. Alternatively, the serpentine flow passage 60 can be branched into a multitude of flow passages at a junction on the serpentine flow passage 60.

[0060] As shown in the Fig. 2 and Fig. 3. In the trailing edge portion 47 (a portion having the trailing edge 46) of the airfoil section 42, a plurality of cooling holes 70 are formed such that they are arranged in the blade vertical direction. The plurality of cooling holes 70 communicate with the cooling passage 66 (the last path 60e of the serpentine flow passage 60 in the example shown), which is formed within the airfoil section 42, and open towards the surface of the airfoil section 42 in the trailing edge portion 47 of the airfoil section 42.

[0061] The cooling medium, which flows through the cooling passage 66, partially passes through the cooling holes 70 and flows to the combustion gas flow passage 28 outside the turbine blade 40 from the opening of the trailing edge portion 47 of the flow profile section 42. The cooling medium thus passes through the cooling holes 7 and performs convection cooling of the trailing edge portion 47 of the flow profile section 42.

[0062] The surface of the trailing edge portion 47 of the airfoil section 42 can be a surface that includes the trailing edge 46 of the airfoil section 42, or the surface of the blade surface near the trailing edge 46, or the surface of the trailing edge end surface 49. The surface of the airfoil section 42 in the trailing edge portion 47 of the airfoil section 42 can include the surface of the airfoil section 42 in a 10% proportion of the airfoil section 42 on the side of the trailing edge 46, with the trailing edge 46 in a chordal direction that defines the leading edge 44 and the trailing edge 46 (see Fig. 3) contains, be. The trailing edge end surface 49 refers to an end surface with the pressure surface (concave side) 56 and the suction surface (convex side) which intersect at a termination end of the trailing edge 46 downstream in the axial direction of the rotor 8 and are facing downstream in the axial direction of the rotor 8.

[0063] The plurality of cooling holes 70 has a non-constant and non-uniform opening density distribution in the blade height direction. The opening density distribution of the plurality of cooling holes 70 according to some embodiments will be described below. Fig. 6 to 8 and Fig. 14 and Fig. Figure 15 are graphs that each show an example of the opening density distribution of the trailing edge part 47 of the rotor blade 26 (turbine blade 40) in the blade vertical direction according to an embodiment. Fig. 9 and Fig. Figure 13 are graphs, each showing an example of a temperature distribution of the combustion gas in the blade height direction. Fig. Figures 10 to 12 are graphs that each show an example of the opening density distribution of the trailing edge part 47 of the stator blade 24 (turbine blade 40) in the blade vertical direction according to an embodiment. Fig. Figure 16 is a cross-sectional view of the trailing edge part 47 of the turbine blade 40 in the blade height direction according to one embodiment. Fig. Figure 17 is a view of the trailing edge part 47 of the turbine blade 40 according to an embodiment seen in a direction from the trailing edge to the leading edge of the flow profile section.

[0064] In the following description, “upstream” and “downstream” refer accordingly to “upstream of a flow of a cooling medium in the cooling passage 66” and “downstream of the flow of the cooling medium in the cooling passage 66”.

[0065] In some embodiments, the relationship d_up < d_mid < d_down is satisfied, where d_mid is an index indicating the opening densities (hereinafter also referred to as the opening density index) of the cooling holes 70 in the central region having an intermediate position Pm between the first end and the second end, which are both ends of the flow profile section 42 in the blade vertical direction, d_up is the opening density index of the cooling holes 70 in the upstream region, arranged upstream of the central region, and d_down is the opening density index of the cooling holes 70 in the downstream region, arranged downstream of the central region Rm.

[0066] Furthermore, in some embodiments, the above-described opening density index d_mid of the cooling holes 70 in the central region, the above-described opening density index d_up of the cooling holes 70 in the upstream region and the above-described opening density index d_down of the cooling holes 70 in the downstream region satisfy the relationship d_up < d_down < d_mid.

[0067] The present embodiments are described accordingly in the case where the turbine blade 40 is the rotor blade 26 and in the case where the turbine blade 40 is the stator blade 24.

[0068] First, some embodiments of the above-described embodiments in which the turbine blade 40 is the rotor blade 26 are described with reference to the Fig. 4 and 6 to 9 are described.

[0069] In the case where the turbine blade 40 is the rotor blade 26, because the cooling medium flows through the cooling passage 66 from the side of the foot 50 to the side of the end 48 (see Fig. 2 and Fig. 4) where the last path 60e of the serpentine flow passage 60 flows, the "upstream" and "downstream" flow of the cooling medium in the cooling passage 66 correspond accordingly to the side of the foot 50 and the side of the end 48 of the flow profile section 42 in the cooling passage 66. In addition, the first end and the second end, which are both ends of the flow profile section 42 in the blade vertical direction, correspond accordingly to the end 48 and the foot 50.

[0070] In some embodiments, such as those shown by the graphs of the Fig. 6 and Fig. 7, the opening density index d_mid of the cooling holes 70 in the central region Rm having the intermediate position Pm between the end 48 and the foot 50 of the flow profile section 42 in the blade vertical direction, the opening density index d_up of the cooling holes 70 in an upstream region Rup, arranged upstream (the side of the foot 50) from the central region Rm, and the opening density index d_down of the cooling holes 70 in a downstream region Rdown, arranged downstream (the side of the end 48) from the central region Rm, satisfy the relationship d_up < d_mid < d_down.

[0071] In the embodiment according to the graph of Fig. 6, the area in the blade vertical direction of the flow profile section 42 is divided into three areas, which comprise the central area Rm, the upstream area Rup having the root 50 and located closer to the root 50 than the central area Rm, and the downstream area Rdown having the end 48 and located closer to the end 48 than the central area Rm. The opening densities of the cooling holes 70 are then all uniform and constant in each of the three areas, and the opening densities change stepwise in the blade vertical direction.This means that the opening density index d_mid of the cooling holes 70 in the central region Rm is set to a constant opening density index dm at the intermediate position Pm, the opening density index d_up of the cooling holes 70 in the upstream region Rup is set to a constant opening density index dr (provided that dr < dm) at a position Pr between the intermediate position Pm and the foot 50, and the opening density index d_down of the cooling holes 70 in the downstream region Rdown is set to a constant opening density index dt (provided that dm < dt) at a position Pt between the intermediate position Pm and the end 48.

[0072] In Fig. 6. With respect to each of the upstream region Rup, the mid-region Rm, and the downstream region Rdown, the relationship d_up < d_mid < d_down can be satisfied, provided that all opening densities of the cooling holes 70 in the corresponding regions are the same and constant, and that the opening density indices of the cooling holes 70 at radial intermediate positions in the corresponding regions correspond to d_up, d_mid, and d_down. Intermediate positions in the corresponding regions are designated by Pdm, Pcm, and Pum with respect to the upstream region Rup, the mid-region Rm, and the downstream region Rdown. Pdm, Pcm, and Pum can each be an intermediate position of a radial length between a position of the cooling hole 70 located most radially outward and a position of the cooling hole 70 located most radially inward of a corresponding region.

[0073] Alternatively, Pdm, Pcm, and Pum can each be a position of the cooling hole, arranged in a position corresponding to the intermediate number of cooling holes radially arranged in a corresponding area. Furthermore, the cooling holes 70 can each have a hole diameter D that remains the same from the end side 48 to the foot side 50, or cooling holes 70 with varying hole diameters D can be combined. Alternatively, for each of the upstream area Rup, the mid-area Rm, and the downstream area Rdown, an average opening density index in the respective areas can satisfy the relationship d_up < d_mid < d_down when considering cooling holes 70 with different opening densities. The average opening density index in each area represents an index that indicates an average of all opening densities of the cooling holes 70 in that area.

[0074] It is desirable to place the intermediate position Pum of the upstream section Rup at a position that is 1 / 4 L length from foot 50, relative to a total length L between end 48 and foot 50 in the blade vertical direction, and closer to the side of foot 50. It is desirable to place the intermediate position Pcm of the midsection Rm between the position 1 / 4 L length and a position 3 / 4 L length from foot 50. Furthermore, it is desirable to place the intermediate position Pdm of the downstream section Rdown at a position 3 / 4 L length from foot 50, located between end 48 and this position.

[0075] In the embodiment according to the graph of Fig. 7, in the blade-vertical direction of the flow profile section 42, the opening densities of the cooling holes 70 change so continuously that they increase from the side of the foot 50 to the side of the end 48.

[0076] This means that the opening density index d_mid of the cooling holes 70 in the central region Rm is a value of a region that has the opening density index dm at the intermediate position Pm, the opening density index d_up of the cooling holes 70 in the upstream region Rup is a value not less than the opening density index dr at position Pr on the side of the foot 50 and less than the opening density index dm at the intermediate position Pm, and the opening density index d_down of the cooling holes 70 in the downstream region Rdown is a value that is not greater than the opening density index dt at position Pt on the side of the end 48 and is greater than the opening density index dm at the intermediate position Pm.

[0077] Because the cooling medium flows in the cooling passage 66, which is formed within the flow profile section 42 of the rotor blade 26 (turbine blade 40), a temperature distribution can occur in which the temperature increases downstream of the cooling medium flow (the end 48 side), i.e., the aforementioned heating. In this regard, with the rotor blade 26 (turbine blade 40) as described above, by increasing the opening density of the cooling holes 70 downstream (end 48 side) than upstream (root 50 side) in the cooling passage 66, the delivery rate of the cooling medium through the cooling holes 70 downstream (end 48 side), where the cooling medium temperature is relatively high, can be increased.Therefore, it is possible to cool the trailing edge part 47 of the rotor blade 26 (turbine blade 40) in a suitable manner in accordance with the temperature distribution of the cooling passage 66.

[0078] Furthermore, it is possible to relatively reduce the opening densities of the cooling holes 70 for the entire flow profile section 42 by lowering the opening densities of the cooling holes 70 in a sub-region in the blade vertical direction of the flow profile section 42 compared to other regions. Therefore, the pressure of the cooling passage 66 is easily maintained at a high level, which makes it possible to maintain a suitable differential pressure between the cooling passage 66 and the external environment of the turbine blade 40 (for example, the combustion gas flow passage 28 of the gas turbine 1) and to supply the cooling medium to the cooling holes 70 in a simple and effective manner.

[0079] The opening density distribution of the cooling holes 70 in the blade height direction is not limited to that shown by the graphs of the Fig. 6 or Fig. Figure 7 shows that the opening density indices d_mid, d_up, and d_down described above satisfy the relationship d_up < d_mid < d_down. For example, a region in the blade vertical direction of the airfoil section 42 can be divided into more than three regions, and the opening densities of the cooling holes 70 in corresponding regions can change stepwise such that they gradually increase from the side of the root 50 to the side of the tail 48. Alternatively, in the region in the blade vertical direction of the airfoil section 42, the opening densities of the cooling holes 70 can change continuously in some regions and remain constant in some other regions.

[0080] In some embodiments, e.g., as shown by the graph of the Fig. 8, the opening density index d_mid of the cooling holes 70 in the central region, the opening density index d_up of the cooling holes 70 in the upstream region, arranged upstream (the side of the foot 50) from the central region, and the opening density index d_down of the cooling holes 70 in the downstream region, arranged downstream (the side of the end 48) from the central region, satisfy the relationship of d_up < d_down < d_mid.

[0081] In the embodiment according to the graph of the Fig. 8, the area in the blade vertical direction of the flow profile section 42 is divided into three areas, comprising the central area Rm, the upstream area Rup encompassing the root 50 and located closer to the root 50 than the central area Rm, and the downstream area Rdown encompassing the end 48 and located closer to the end 48 than the central area Rm. The opening densities of the cooling holes 70 are then constant in each of the three areas and change stepwise in the blade vertical direction.This means that the opening density index d_mid of the cooling holes 70 in the central region Rm is set to the constant dm at the intermediate position Pm, the opening density index d_up of the cooling holes 70 in the upstream region Rup is set to the constant opening density index dr (assuming that dr < dm) at the position Pr between the intermediate position Pm and the foot 50, and the opening density index d_down of the cooling holes 70 in the downstream region Rdown is set to the constant opening density index dt (assuming that dr < dt < dm) at the position Pt between the intermediate position Pm and the end 48.

[0082] The temperature of the gas flowing through the combustion gas flow passage 28, where the rotor blades 26 (turbine blades 40) are arranged (see Fig. 1) is distributed, as shown, for example, by the graph of the Fig. 9 is displayed, and tends to be higher in the central region, exhibiting the intermediate position Pm between the end 48 and the foot 50, than in the region on the side of the end 48 and the region on the side of the foot 50 of the flow profile section 42 in the blade vertical direction. On the other hand, because the cooling medium flows into the cooling passage 66, formed within the flow profile section 42, while cooling the flow profile section 42, the temperature distribution can occur in which the temperature increases downstream (the side of the end 48) of the flow of the cooling medium.In this case, in order to cool the trailing edge part 47 appropriately, it is desirable to maximize the flow rate of the cooling medium through the cooling holes 70 in the central region Rm in the blade vertical direction and to make the flow rate of the cooling medium through the cooling holes 70 in the downstream region Rdown greater than in the upstream region Rup described above.

[0083] This means, as described above, that the cooling medium is heated during the flow process in the last path 60e, and the metal temperature of the cooling holes 70 at the end 48 of the last path 60e, or in the downstream region Rdown, becomes the highest. However, in the case of a blade where the metal temperature is kept within a range that does not exceed the operating temperature limit, determined by the oxidation dilution tolerance, it is possible to prevent blade damage by selecting the opening density distributions of the cooling holes 70, as shown in Fig. 20C and Fig. 6, to reduce. On the other hand, in the case of a blade that is in the atmosphere of the combustion gas, the combustion gas temperature distribution of the Fig. 9 indicates that the flow profile section 42 has a large heat input from the combustion gas in the central region Rm and therefore the opening density indices of the cooling holes 70 in the central region Rm, shown in Fig. 20C and Fig. 6. The metal temperature of the cooling holes 70 in the central region Rm exceeds the operating temperature limit. In this case, it is necessary to increase the cooling by further increasing the opening density index of the cooling holes 70 in the central region Rm. This means that the delivery flow rate of the cooling medium flowing through the cooling holes 70 into the downstream region Rdown is reduced by decreasing the opening density index of the cooling holes 70 in the downstream region Rdown and by increasing the opening density index of the cooling holes 70 in the central region Rm, which makes it possible to increase the delivery flow rate of the cooling medium flowing through the cooling holes 70 in the central region Rm.Depending on the metal temperature, the opening density distribution can be selected such that the metal temperature of the cooling holes 70 at the end 48 of the last path 60e and in the downstream region Rdown, and the metal temperature in the central region Rm, are within the operating temperature limit by further reducing the opening density index of the cooling holes 70 in the upstream region Rup. Furthermore, the opening density distribution of the cooling holes 70 for each region in the present embodiment can also be selected by ensuring that the predetermined creep resistances in the central region Rm and the upstream region Rup are within the creep limit.

[0084] With the rotor blade 26 (turbine blade 40) according to the embodiment described above, it is possible to increase the delivery flow rate of the cooling medium via the cooling holes 70 in the central region Rm, where the temperature of the gas flowing through the combustion gas flow passage 28 is relatively hot, by making the opening density index d_mid of the cooling holes 70 in the central region Rm larger than the opening density indices d_up, d_down of the cooling holes 70 in the upstream region Rup and the downstream region Rdown described above.Furthermore, with the rotor blade 26 (turbine blade 40) according to the embodiment described above, by making the opening density index d_down of the cooling holes 70 in the downstream region Rdown larger than the opening density index d_up of the cooling holes 70 in the upstream region Rup, it is possible to increase the delivery flow rate of the cooling medium through the cooling holes 70 into the downstream region Rdown, where the temperature of the cooling medium is higher than in the upstream region Rup. Therefore, it is possible to cool the trailing edge portion 47 of the rotor blade 26 (turbine blade 40) appropriately in accordance with the temperature distribution of the cooling passage 66.

[0085] In Fig. 8. With respect to each of the upstream region Rup, the mid-region Rm, and the downstream region Rdown, the relationship d_up < d_down < d_mid can be satisfied, provided that all opening densities of the cooling holes 70 in the corresponding regions are the same and constant, and the opening density indices of the cooling holes 70 at the radially region-wise intermediate positions in the corresponding regions correspond to d_up, d_mid, and d_down. Alternatively, with respect to each of the upstream region Rup, the mid-region Rm, and the downstream region Rdown, the average opening density index in the corresponding regions can satisfy the relationship d_up < d_down < d_mid if the cooling holes 70 with the different opening densities are included. The concepts of the region-wise intermediate positions and the average opening density index in the corresponding regions are as described above.Furthermore, the cooling holes 70 can each have the hole diameter D, which remains the same from the side of the end 48 to the side of the foot 50, or the cooling holes 70, each having the varying hole diameter D, can be combined.

[0086] The opening density distribution of the cooling holes 70 in the blade height direction is not limited to what is shown by the graph of the Fig. 8 is shown as long as the opening density indices d_mid, d_up and d_down described above satisfy the relationship d_up < d_down < d_mid.

[0087] For example, the area in the blade vertical direction of the airfoil section 42 can be divided into more than three areas, and the opening densities of the cooling holes 70 in corresponding areas can change in steps such that they satisfy the relationship described above. Alternatively, for example, the opening densities of the cooling holes 70 in the area in the blade vertical direction of the airfoil section 42 can change continuously in at least some areas. In this case, the opening densities of the cooling holes 70 in some other areas in the blade vertical direction of the airfoil section 42 can be constant.

[0088] Next, some embodiments of the embodiments described above, in which the turbine blade 40 is the stator blade 24, will be described with reference to Fig. 5 and 10 to 13 are described.

[0089] In the case where the turbine blade 40 is the stator blade 24, they correspond because the cooling medium flows through the cooling passage 66 (the last path 60e of the serpentine flow passage 60) from the side of the outer end 52 to the side of the inner end 54 (see Fig. 5), “upstream” and “downstream” of the flow of the cooling medium in the cooling passage 66 correspond to the side of the outer end 52 and the side of the inner end 54 of the flow profile section 42 in the cooling passage 66. In addition, the first end and the second end, which are the two ends of the flow profile section 42 in the blade vertical direction, correspond to the outer end 52 and the inner end 54.

[0090] In some embodiments, e.g., shown by the graphs of the Fig. 10 and Fig. 11, the opening density index d_mid of the cooling holes 70 in the central region having the intermediate position Pm between the outer end 52 and the inner end 54 of the flow profile section 42 in the blade vertical direction, the opening density index d_up of the cooling holes 70 in the upstream region, arranged upstream (the side of the outer end 52) from the central region, and the opening density index d_down of the cooling holes 70 in the downstream region, arranged downstream (the side of the inner end 54) from the central region, satisfy the relationship d_up < d_mid < d_down.

[0091] In the embodiment according to the graph of Fig. 10, the area in the blade vertical direction of the flow profile section 42 is divided into three areas: the central area Rm, the upstream area Rup, which has the outer end 52 and is located closer to the outer end 52 than the central area Rm, and the downstream area Rdown, which has the inner end 54 and is located closer to the inner end 54 than the central area Rm. Furthermore, the opening densities of the cooling holes 70 are constant in each of the three areas and change in a stepwise manner in the blade vertical direction.This means that the opening density index d_mid of the cooling holes 70 in the central region Rm is set to the opening density index dm at the intermediate position Pm, the opening density index d_up of the cooling holes 70 in the upstream region Rup is set to a constant opening density index do (provided that do < dm) at a position Po between the intermediate position Pm and the outer end 52, and the opening density index d_down of the cooling holes 70 in the downstream region Rdown is set to a constant opening density index di (provided that dm < di) at a position Pi between the intermediate position Pm and the inner end 54.

[0092] In the embodiment according to the graph of the Fig. 11, in the blade-vertical direction of the flow profile section 42, the opening densities of the cooling holes 70 change so continuously that they increase from the side of the outer end 52 to the side of the inner end 54. This means that the opening density index d_mid of the cooling holes 70 in the central region Rm is a value of a region having the opening density index dm at the intermediate position Pm, the opening density index d_up of the cooling holes 70 in the upstream region Rup is a value not less than the opening density index do at position Po on the side of the outer end 52 and less than the opening density index dm at the intermediate position Pm, and the opening density index d_down of the cooling holes 70 in the downstream region Rdown is a value not greater than the opening density index di at position Pi on the side of the inner end 54 and greater than the opening density index dm at the intermediate position Pm.

[0093] Because the cooling medium flows into the cooling passage 66, formed within the flow profile section 42 of the stator blade 24 (turbine blade 40), while cooling the flow profile section 42, a temperature distribution can occur in which the temperature increases downstream (the side of the inner end 54) of the flow of the cooling medium, i.e. the heating / warming described above can occur. In this respect, with the stator blade 24 (turbine blade 40) according to the embodiment described above, by making the opening densities of the cooling holes 70 larger at the downstream position (the side of the inner end 54) than at the upstream position (the side of the outer end 52) of the flow direction of the cooling medium in the cooling passage 66, it is possible to increase the delivery flow rate of the cooling medium downstream (the side of the inner end 54) via the cooling holes 70, where the temperature of the cooling medium is relatively high.Therefore, it is possible to cool the trailing edge part 47 of the stator blade 24 (turbine blade 40) in a suitable manner in accordance with the temperature distribution of the cooling passage 66.

[0094] In Fig. 10. Any upstream region Rup, mid-region Rm, and downstream region Rdown can satisfy the relationship d_up < d_mid < d_down, provided that all the opening densities of the cooling holes 70 in the corresponding regions are the same and constant, and the opening density indices of the cooling holes 70 at radially intermediate positions in the corresponding regions correspond to d_up, d_mid, and d_down. Alternatively, for any upstream region Rup, mid-region Rm, and downstream region Rdown, an average opening density index in the corresponding regions can satisfy the relationship d_up < d_mid < d_down if the cooling holes 70 with different opening densities are included. The concepts of intermediate positions and the average opening density index in the corresponding regions are as described above.Furthermore, the cooling holes 70 can each have the hole diameter D, which remains the same from the side of the end 48 to the side of the foot 50, or the cooling holes 70, which each have the varying hole diameter D, can be combined.

[0095] The opening density distribution of the cooling holes 70 in the blade height direction is not limited to what is shown by the graph of Fig. 10 or Fig. 11 is shown, as long as the opening density indices d_mid, d_up and d_down described above satisfy the relationship d_up < d_mid < d_down.

[0096] For example, the area in the blade vertical direction of the airfoil section 42 can be subdivided into more than three areas, and the opening densities of the cooling holes 70 in corresponding areas can change in steps to gradually increase from the side of the inner end 54 to the side of the outer end 52. Alternatively, for example, in the area in the blade vertical direction of the airfoil section 42, the opening densities of the cooling holes 70 can change continuously in some areas and remain constant in some other areas.

[0097] In some embodiments, for example as shown in the graph of the Fig. 12, the opening density index d_mid of the cooling holes 70 in the central region, the opening density index d_up of the cooling holes 70 in the upstream region, arranged upstream (the side of the outer end 52) from the central region, and the opening density index d_down of the cooling holes 70 in the downstream region, arranged downstream (the side of the inner end 54) from the central region, satisfy the relationship of d_up < d_down < d_mid.

[0098] In the embodiment according to the graph of Fig. 12, the area in the blade vertical direction of the flow profile section 42 is divided into three areas: the central area Rm, the upstream area Rup, which has the outer end 52 and is located closer to the outer end 52 than the central area Rm, and the downstream area Rdown, which has the inner end 54 and is located closer to the inner end 54 than the central area Rm. Furthermore, the opening densities of the cooling holes 70 are constant in each of the three areas and change stepwise in the blade vertical direction.This means that the opening density index d_mid of the cooling holes 70 in the central region Rm is set to the constant opening density index dm at the intermediate position Pm, the opening density index d_up of the cooling holes 70 in the upstream region Rup is set to the constant opening density index do (assuming that do < dm) at the position Po between the intermediate position Pm and the outer end 52, and the opening density index d_down of the cooling holes 70 in the downstream region Rdown is set to the constant opening density index di (assuming that do < di < dm) at the position Pi between the intermediate position Pm and the inner end 54.

[0099] The temperature of the gas flowing through the combustion gas flow passage 28, where the stator blades 24 (turbine blades 40) are arranged (see Fig. 1) is as shown, for example, by the graph of the Fig. 13 distributed and tends to have the intermediate position Pm between the outer end 52 and the inner end 54 higher in the central area than in the area on the side of the outer end 52 and the area on the side of the inner end 54 of the flow profile section 42 in the blade vertical direction.

[0100] On the other hand, because the cooling medium flows in the cooling passage 66, formed within the flow profile section 42, while cooling the flow profile section 42, a temperature distribution can occur in which the temperature increases downstream (the side of the inner end 54) of the cooling medium flow. In this case, in order to cool the trailing edge section 47 appropriately, it is desirable to maximize the flow rate of the cooling medium through the cooling holes 70 in the central region Rm in the blade vertical direction and to make the flow rate of the cooling medium through the cooling holes 70 in the downstream region Rdown greater than in the upstream region Rup described above.

[0101] This means, as described above, that the cooling medium is heated during the flow into the last path 60e, and the metal temperature of the cooling holes 70 at the inner end 54 of the last path 60e, or in the downstream region Rdown, becomes the highest. However, in the case of the blade, where the metal temperature is kept within the range that does not exceed the operating temperature limit, determined by the oxidation dilution tolerance, it is possible to prevent damage to the blade by selecting the opening density distribution of the cooling holes 70, as shown in Fig. 10, to reduce. On the other hand, in the case of a blade that is in an atmosphere of combustion gas, which affects the combustion gas temperature distribution of the Fig. Figure 13 shows that the flow profile section 42 experiences a large heat input from the combustion gas in the central region Rm and therefore the opening density index of the cooling holes 70 in the central region Rm, as shown in Fig. 10. The metal temperature of the cooling holes 70 in the central region Rm exceeds the operating temperature limit. In this case, the cooling is improved by further increasing the opening density index of the cooling holes 70 in the central region Rm. This means that the delivery flow rate of the cooling medium flowing through the cooling holes 70 into the downstream region Rdown is reduced by decreasing the opening density index of the cooling holes 70 in the downstream region Rdown and by increasing the opening density index of the cooling holes 70 in the central region Rm, which makes it possible to increase the delivery flow rate of the cooling medium flowing through the cooling holes 70 in the central region Rm.Depending on the metal temperature, the opening density distribution, in which the metal temperature of the cooling holes 70 at the inner end 54 of the last path 60e and in the downstream region Rdown, and the metal temperature in the middle region Rm fall within the operating temperature limit, can be selected by further decreasing the opening density index of the cooling holes 70 in the upstream region Rup.

[0102] With the stator blade 24 (turbine blade 40) according to the embodiment described above, it is possible to increase the delivery flow rate of the cooling medium through the cooling holes 70 in the central region Rm, where the temperature of the gas flowing through the combustion gas flow passage 28 is relatively high, by making the opening density index d_mid of the cooling holes 70 in the central region Rm larger than the opening density indices d_up, d_down of the cooling holes 70 in the upstream region Rup and the downstream region Rdown described above.Furthermore, with the stator blade 24 (turbine blade 40) according to the embodiment described above, by increasing the opening density index d_down of the cooling holes 70 in the downstream region Rdown to a greater size than the opening density index d_up of the cooling holes 70 in the upstream region Rup, it is possible to increase the delivery flow rate of the cooling medium through the cooling holes 70 in the downstream region Rdown, where the temperature of the cooling medium is higher than in the upstream region Rup. Therefore, it is possible to cool the trailing edge portion 47 of the stator blade 24 (turbine blade 40) appropriately in accordance with the temperature distribution of the cooling passage 66.

[0103] In Fig. 12. Any upstream region Rup, mid-region Rm, and downstream region Rdown can satisfy the relationship d_up < d_down < d_mid, provided that all the opening densities of the cooling holes 70 in the corresponding regions are the same and constant, and the opening density indices of the cooling holes 70 at the radially region-wise intermediate positions in the corresponding regions correspond to d_up, d_mid, and d_down. Alternatively, for any upstream region Rup, mid-region Rm, and downstream region Rdown, the average opening density index in the corresponding regions can satisfy the relationship d_up < d_down < d_mid if the cooling holes 70 with different opening densities are included. The concepts of the region-wise intermediate positions and the average opening density index in the corresponding regions are as described above.Furthermore, the cooling holes 70 can each have the hole diameter D, which remains the same from the side of the end 48 to the side of the foot 50, or the cooling holes 70, which each have the varying hole diameter D, can be combined.

[0104] The opening density distribution of the cooling holes 70 in the blade height direction is not limited to what is shown by the graph of the Fig. 13 is shown, as long as the opening density indices d_mid, d_up and d_down described above satisfy the relationship d_up < d_down < d_mid.

[0105] For example, the area in the blade vertical direction of the flow profile section 42 is divided into more than three areas and the opening densities of the cooling holes 70 in corresponding areas can change stepwise in such a way that they satisfy the relationship described above.

[0106] Alternatively, for example, the opening densities of the cooling holes 70 can change continuously in at least some areas in the vertical direction of the airfoil section 42. In this case, the opening densities of the cooling holes 70 can be constant in some other areas in the vertical direction of the airfoil section 42.

[0107] Next, some other embodiments will be described with reference to Fig. 4, Fig. 14 and Fig. 15. In the present embodiments, the turbine blade 40 is the rotor blade 26 (see Fig. 4).

[0108] In some embodiments, for example shown by the graph of the Fig. 14, the opening density index d_mid of the cooling holes 70 in the central region having the intermediate position Pm between the end 48 and the foot 50 of the flow profile section 42 in the blade vertical direction, an opening density index d_tip in the outer end region, arranged closer to the end 48 than the central region, and an opening density index d_root in the foot region, arranged closer to the foot 50 than the central region, satisfy the relationship of d_tip < d_mid < d_root.

[0109] In the embodiment according to the graph of Fig. 14, the area in the blade vertical direction of the flow profile section 42 is divided into three areas: the central area Rm, an outer end area Rtip (end 48) located closer to the end 48 than the central area Rm, and a root area Rroot (root 50) located closer to the root 50 than the central area Rm. Furthermore, the opening densities of the cooling holes 70 are constant in each of the three areas and change stepwise in the blade vertical direction.This means that the opening density index d_mid of the cooling holes 70 in the middle area Rm is set to the constant opening density index dm at the intermediate position Pm, the opening density index d_tip of the cooling holes 70 in the outer end area Rtip is set to the constant opening density index dt (provided that dt < dm) at the position Pt between the intermediate position Pm and the end 48, and the opening density index d_root of the cooling holes 70 in the foot area Rroot is set to the constant opening density index dr (provided that dm < dr) at the position Pr between the intermediate position Pm and the foot 50.

[0110] Because a centrifugal force acts on the cooling medium in the cooling passage 66, formed within the flow profile section 42 of the rotor blade 26, due to the operation of the gas turbine 1, a pressure distribution can occur in which the pressure increases on the end 48 side of the flow profile section 42 in the cooling passage 66. In this regard, because the rotor blade 26 (turbine blade 40), according to the embodiment described above, is designed with a lower opening density of the cooling holes 70 at the end 48 side than at the root 50 side of the flow profile section 42, it is possible to reduce the variation in the delivery flow rate of the cooling medium through the cooling holes 70 in the blade vertical direction, even when the pressure distribution described above occurs.Therefore, it is possible to cool the trailing edge part 47 of the rotor blade 26 (turbine blade 40) in a suitable manner in accordance with the pressure distribution of the cooling passage 66.

[0111] In Fig. 14. With respect to each of the following regions, the base region Rroot, the middle region Rm, and the outer end region Rtip, the relationship d_tip < d_mid < d_root may be satisfied, provided that all opening densities of the cooling holes 70 in the corresponding regions are the same and constant, and the opening density indices of the cooling holes 70 at radially intermediate positions in the corresponding regions correspond to d_root, d_mid, and d_tip. Intermediate positions in the corresponding regions are designated by Prm, Pcm, and Ptm, respectively, with respect to the base region Rroot, the middle region Rm, and the outer end region Rtip. Alternatively, with respect to each of the base region Rroot, the middle region Rm, and the outer end region Rtip, an average opening density index in the corresponding regions may satisfy the relationship d_tip < d_mid < d_root if the cooling holes 70, which have different opening densities, are included.The concepts of the intermediate positions and the average opening density index in the corresponding areas are as described above. Furthermore, each of the cooling holes 70 can have a hole diameter D that remains the same from the end side 48 to the foot side 50, or the cooling holes 70, each with varying hole diameters D, can be combined.

[0112] The opening density distribution of the cooling holes 70 in the blade height direction does not correspond to that shown by the graph of Fig. Figure 14 is limited as long as the opening density indices d_mid, d_tip and d_root described above satisfy the relationship d_tip < d_mid < d_root. For example, the area in the blade vertical direction of the flow profile section 42 can be divided into more than three areas and the opening densities of the cooling holes 70 in corresponding areas can change stepwise such that they satisfy the relationship described above.

[0113] Alternatively, for example, in the area in the blade vertical direction of the flow profile section 42, the opening densities of the cooling holes 70 can change continuously in at least one of the areas. In this case, the opening densities of the cooling holes 70 in all the other areas in the blade vertical direction of the flow profile section 42 can be constant.

[0114] Furthermore, in some embodiments, for example as shown by the graph of the Fig. 15, the opening density index d_mid of the cooling holes 70 in the middle area, the opening density index d_tip in the outer end area, arranged closer to the end 48 than the middle area, and the opening density index d_root in the foot area closer to the foot 50 than the middle area, as described above, satisfy the relationship d_tip < d_root < d_mid.

[0115] In the embodiment according to the graph of Fig. 15, the area in the blade vertical direction of the flow profile section 42 is divided into three areas, which include the central area Rm, the outer end area Rtip with the end 48 located closer to the end 48 than the central area Rm, and the root area Rroot with the root 50 located closer to the root 50 than the central area Rm. Furthermore, the opening densities of the cooling holes 70 are constant in each of the three areas and change stepwise in the blade vertical direction.This means that the opening density index d_mid of the cooling holes 70 in the central area Rm is set to the constant opening density index dm at the intermediate position Pm, the opening density index d_tip of the cooling holes 70 in the outer end area Rtip is set to the constant opening density index dt (provided that dt < dm) at the position Pt between the intermediate position Pm and the end 48, and the opening density index d_root of the cooling holes 70 in the foot area Rroot is set to the constant opening density index dr (provided that dt < dr < dm) at the position Pr between the intermediate position Pm and the foot 50.

[0116] The temperature of the gas flowing through the combustion gas flow passage 28, where the rotor blades 26 (turbine blades 40) are arranged (see Fig. 1) is distributed, as shown for example by the graph of the Fig. 9 is displayed, and tends to be higher in the central region encompassing the intermediate position Pm between the end 48 and the foot 50 than in the region on the side of the end 48 and the region on the side of the foot 50 of the flow profile section 42 in the blade vertical direction. On the other hand, because the centrifugal force acts on the cooling medium in the cooling passage 66 formed within the flow profile section 42 of the rotor blade 26 due to the operation of the gas turbine 1, a pressure distribution can occur in which the pressure on the side of the end 48 of the flow profile section 42 in the cooling passage 66 increases.In this case, in order to cool the trailing edge part 47 appropriately, it is desirable to maximize the flow rate of the cooling medium through the cooling holes 70 in the central area in the blade height direction and to reduce the variation in the delivery flow rate of the cooling medium through the cooling holes between the area located on the side of the end 48 and the area located on the side of the foot 50 in the blade height direction.

[0117] In this respect, with the rotor blade 26 (turbine blade 40) according to the embodiment described above, it is possible to increase the delivery flow rate of the cooling medium via the cooling holes 70 in the central region Rm, where the temperature of the gas flowing through the combustion gas flow passage 28 is relatively high, by making the opening density index d_mid of the cooling holes 70 in the central region Rm larger than the opening density indices d_tip, d_root of the cooling holes 70 in the outer end region Rtip and the foot region Rroot, as described above.Furthermore, because the rotor blade 26 (turbine blade 40) is designed according to the embodiment described above by making the opening density index d_tip of the cooling holes 70 in the outer end region Rtip smaller than the opening density index d_root of the cooling holes 70 in the root region Rroot, it is possible to reduce the variations in the delivery flow rate of the cooling medium through the cooling holes 70 between the outer end region Rtip and the root region Rroot, even when the pressure distribution described above occurs. Therefore, it is possible to cool the trailing edge portion 47 of the rotor blade 26 (turbine blade 40) appropriately in accordance with the pressure distribution of the cooling passage 66.

[0118] In Fig. 15. For each of the following regions, the base region Rroot, the middle region Rm, and the outer end region Rtip, the relationship d_tip < d_root < d_mid can be satisfied, provided that all opening densities of the cooling holes 70 in the corresponding regions are the same and constant, and the opening density indices of the cooling holes 70 at radial intermediate positions in the corresponding regions correspond to d_root, d_mid, and d_tip. The intermediate positions in the corresponding regions are denoted by Prm, Pcm, and Ptm with respect to the base region Rroot, the middle region Rm, and the outer end region Rtip. Alternatively, for each of the base region Rroot, the middle region Rm, and the outer end region Rtip, the average opening density index in the corresponding regions can satisfy the relationship d_tip < d_root < d_mid if the cooling holes 70 with different opening densities are included.The concepts of the intermediate positions and the average opening density index in the corresponding areas are as described above. Furthermore, the cooling holes 70 can each have a hole diameter D that remains the same from the end side 48 to the foot side 50, or the cooling holes 70, each with a varying hole diameter D, can be combined.

[0119] The opening density distribution of the cooling holes 70 in the blade height direction is not limited to what is shown in the graph of the Fig. 15 is shown as long as the opening density indices d_mid, d_tip and d_root described above satisfy the relationship d_tip < d_root < d_mid.

[0120] For example, the area in the blade vertical direction within the airfoil section 42 can be divided into more than three areas, and the opening densities of the cooling holes 70 in corresponding areas can change stepwise such that they satisfy the relationship described above. Alternatively, for example, within the area in the blade vertical direction of the airfoil section 42, the opening densities of the cooling holes 70 can change continuously in at least one of the areas. In this case, the opening densities of the cooling holes 70 in some other areas in the blade vertical direction of the airfoil section 42 can be constant.

[0121] For example, in the embodiments according to the graphs of the Fig. 6, Fig. 8, Fig. 10, Fig. 12, Fig. 14 and Fig. 15 as described above, because the opening densities of the cooling holes 70 in the corresponding areas (the central area Rm, the upstream area Rup and the downstream area Rdown or the outer end area Rtip and the foot area Rroot) become correspondingly constant in the blade vertical direction of the flow profile section 42, the cooling holes in the corresponding areas are easily produced.

[0122] An opening density index of the cooling holes 70 of the turbine blade 40 described above can be, for example, a ratio P / D of an interval P of the cooling holes 70 in the blade vertical direction (see Fig. 16) and the diameter D of the cooling hole 70 (see Fig. 16) can be applied. The diameter D of the cooling hole 70 can be a maximum diameter, a minimum diameter, or an average diameter of the cooling holes 70. Alternatively, the opening density index described above can be a ratio S / P of a wet edge length S of an opening end 72 of the cooling hole 70 to the surface of the flow profile section (see Fig. 17) (this is a perimeter of the opening end 72 on the surface of the flow profile section 42) and the space P between the cooling holes 70 in the blade vertical direction (see Fig. 17) can be assumed. Alternatively, the opening density index described above can be assumed to be the number of cooling holes 70 per unit area (or per unit length) on the surface of the flow profile section 42 in the trailing edge part 47 of the flow profile section 42.

[0123] The cooling holes 70, formed in the trailing edge part 47 of the flow profile section 42 of the turbine blade 40, can have the following feature.

[0124] In some embodiments, the cooling holes 70 can be inclined with respect to a plane perpendicular to the blade's vertical direction. By forming the cooling holes 70 at such an inclination with respect to the plane running directly in the blade's vertical direction, it is possible to lengthen the cooling holes 70 compared to a case in which the cooling holes 70 are formed parallel to the plane perpendicular to the blade's vertical direction. Therefore, it is possible to effectively cool the trailing edge portion of the turbine blade 40.

[0125] In some embodiments, an angle A can be formed between an extension direction of the cooling hole 70 and the plane perpendicular to the blade height direction (see Fig. 16) not less than 15° and not greater than 45° or not less than 20° and not greater than 40°. It is possible to form the relatively long cooling holes 70 while maintaining the ease of manufacturing the cooling holes 70 or while maintaining the strength of the trailing edge portion 47 of the airfoil section 42 if the angle A is within the range described above.

[0126] In some embodiments, the cooling holes 70 can be formed parallel to each other. With this arrangement of multiple cooling holes 70 parallel to each other, it is possible to form more cooling holes 70 in the trailing edge portion 47 of the airfoil section 42 than in a case where the multiple cooling holes 70 are not parallel to each other. Therefore, it is possible to effectively cool the trailing edge portion 47 of the turbine blade 40.

[0127] Next, the relationship between the last path 60e and the opening densities of the cooling holes 70 in the trailing edge portion 47 will be described below. Typically, on a blade, the inner surface of the serpentine flow passage 60 is provided with a vortex 90 to promote heat transfer with the cooling medium. Fig. Figure 18 shows an arrangement of the cooling holes 70 formed near the trailing edge portion 47, and the configuration of the last path 60e of the cooling passage 66, arranged upstream of the flow direction of the cooling medium adjacent to the trailing edge portion 47. The turbulence enhancer 90, which serves as a turbulence-promoting material, is provided on each of the inner wall surfaces 68 of the pressure surface (concave side) 56 and the suction surface (convex side) 58 of the flow profile section 42 from the base 50 to the end 48 in the last path 60e. Similarly, turbulence enhancers (not shown) are also arranged in the serpentine flow passage 60 upstream of the flow direction of the cooling medium from the last path 60e.

[0128] As shown in Fig.19, the vortices 90 in the serpentine flow passage 60 are arranged on the inner wall surfaces 68 of the pressure surface (concave side) 56 and the suction side (convex side) 58 of at least one path of the corresponding paths 60a to 60e and are formed to have a height e with respect to the inner wall surfaces 68 of the vortices 90. In addition, each of the paths 60a to 60e is formed to have a passage width H in a concave-convex direction and for each flow passage the plurality of vortices 90 are arranged radially adjacent to each other in the interval of a space PP.The turbulators 90 are designed such that a ratio (PP / e) of the space PP of the turbulators 90 to the height e, a ratio (e / H) of the height e of the turbulators 90 to the passage width H in the concave-convex direction and an inclination angle of each of the turbulators 90 with respect to the flow direction of the cooling medium from the foot 50 to the end 48 are essentially constant and are arranged such that they achieve optimal heat transfer with the cooling medium.

[0129] However, in the last path 60e, the passage width H is narrower than that of the other paths 60a to 60d. Therefore, it can be difficult to select the vortex height e corresponding to the appropriate ratio (e / H) of the vortex height e to the passage width H of the cooling passage 66, where the aforementioned suitable heat transfer is achieved. This means that, in the case of the last path 60e, compared to the other paths 60a to 60d, the vortex height e may be too small to maintain the appropriate ratio (e / H) of the vortex height e to the passage width H, making it difficult to manufacture the vortex 90. In particular, because the passage width H on the end side 48 is narrower than on the foot side 50, it can be difficult to select the appropriate height e of the swirlers 90.

[0130] Furthermore, the cooling medium flowing in the last path 60e of the serpentine flow passage 60 is heated by the inner wall surfaces 68 of the flow profile section 42 during the downward flow of the corresponding paths 60a to 60d upstream of the last path 60e and is delivered to the last path 60e. Therefore, the metal temperature of the last path 60e is slightly increased, particularly near the end 48 of the last path 60e. Accordingly, a method is employed to prevent the operating temperature limit of the metal temperature of the last path 60e from being exceeded.For example, a flow structure can be selected in which the flow width H gradually narrows from the intermediate position in the blade height direction to the outlet opening 64 at the end 48 of the last path 60e, reducing the flow cross-sectional area and increasing the flow velocity of the cooling medium. It is possible to reduce the flow cross-sectional area of ​​the last path 60e to the outlet opening 64 and increase the flow velocity of the cooling medium in order to promote heat transfer at the last path 60e and prevent the metal temperature of the last path 60e from exceeding the service limit temperature. When such a structure is used, the flow width H tends to decrease near the end 48 of the last path 60e.

[0131] Therefore, the turbulators 90 can be selected which have a relatively large height e relative to the suitable height e of the turbulators 90 with respect to the passage width H in an area where a pressure drop of a cooling fluid flowing through the last path 60e is permitted. This means that the same constant height e can be selected without changing the height e of the turbulators 90 from foot 50 to end 48, even though the turbulators 90 formed in the last path 60e have a lower height e than the turbulators 90 of the other paths 60a to 60d, other than the last path 60e. As a result, the ratio (e / H) of the height e of the vortex 90 to the passage width H of the last path 60e is greater than the ratio (e / H) of the height e to the passage width H, applied to each of the other paths 60a to 60d.By selecting turbulators 90 with a relatively larger height e than a suitable value in the last path 60e, the occurrence of turbulence in the cooling medium in the last path 60e is promoted, and heat transfer with the cooling medium in the last path 60e is further enhanced compared to the other paths 60a to 60d. As a result, the metal temperature of the last path 60e is prevented from exceeding the operating temperature limit.

[0132] On the other hand, if heat exchange in the last path 60e is promoted as described above, the temperature of the cooling medium flowing through the last path 60e is further increased, while the metal temperature of the last path 60e is reduced. The fact that the cooling medium is supplied with a temperature increase to the cooling holes 70, arranged in the trailing edge section 47, can influence the opening density distribution of the trailing edge section 47. This means that the cooling of the last path 60e is improved, and the occurrence of thermal stress or the like is improved by reducing the passage width H in the last path 60e towards the end 48, by increasing the relative height e of the turbulator 90 in the last path 60e compared to the other paths 60a to 60d, or the like.On the other hand, with regard to the temperature increase of the cooling medium supplied to the trailing edge part 47, the opening densities of the cooling holes 70 in the trailing edge part 47 are increased from the intermediate position in the blade height direction to the outlet opening 64 at the end 48 of the last path 60e in order to compensate for the temperature increase of the inflow cooling medium and to reduce an increase in the metal temperature of the trailing edge part 47, which makes it possible to cool the trailing edge part 47 having the last path 60e in a suitable manner.

[0133] Embodiments of the present invention have been described above, but the present invention is not limited thereto and includes an embodiment obtained by modification of the embodiment described above and an embodiment obtained by suitable combination of these embodiments.

[0134] Furthermore, in the present description, an expression of relative or absolute arrangement, such as "in one direction", "along one direction", "parallel", "orthogonal", "centered", "concentric" and "coaxial", should not be understood as meaning only the arrangement in a strictly literal sense, but also encompassing a state where the arrangement is arranged in a relatively different way due to a tolerance or an angle or a distance, while still making it possible to obtain the same function.

[0135] For example, an expression of an identical state, such as "equal," "same," and "uniform," should not be interpreted as referring only to a state in which that characteristic is strictly identical, but should also encompass a state in which a tolerance or difference exists that can still achieve the same function. Furthermore, for example, an expression of a shape, such as "rectangular shape" or "cylindrical shape," should not be interpreted as referring only to the geometrically correct shape, but should also encompass a shape within the range with unevenness or chamfered edges in which the same effect can be achieved.

[0136] As used herein, the expressions “encompass”, “contain” or “have” of a formation element are not exclusive expressions that exclude the presence of other formation elements. Reference symbol list 1 gas turbine 2 compressors 4 Combustion chamber 6 Turbine 8 Rotor 10 compressor housings 12 Air intake 16 Stator blades 18 rotor blades 20 cases 22 turbine housings 24 Stator blades 26 Rotor blade 28 Combustion gas flow passage 30 Exhaust chamber 40 turbine blades 42 Flow profile section 44 Front edge 46 trailing edge 47 Rear edge section 48 End 49 Trailing edge end surface 50 feet 52 Outer end 54 Inner End 56 printing surface 58 Suction surface 60 serpentine flow passage 60a to 60e path 60e Last Path 62 Entrance opening 64 Outlet opening 66 Cooling passage 68 Interior wall surface 70 cooling hole 72 End of opening 80 platform 82 Shovel foot section 84 Internal flow passage 86 Inner cover 88 Outer cover 90 vortex generators PM Intermediate position PCM intermediate position of the midrange Pump intermediate position of the upstream area PDM intermediate position of the downstream area PTM intermediate position of the outer end area Prm intermediate position of the foot area Rtip outer end area Rm middle area Rroot foot area Rup Upstream area Rdown downstream area

Claims

[1] A turbine blade comprising (40): a flow profile section (42), a cooling passage (66) which extends in a blade vertical direction within the flow profile section (42), and a plurality of cooling holes (70) formed in a trailing edge portion (47) of the airfoil section (42) such that they are arranged in the blade vertical direction, wherein the plurality of cooling holes (70) communicates with the cooling passage (66) and opens towards a trailing edge end surface (49) of the airfoil section (42) in the trailing edge portion (47), wherein a formation area of ​​the multitude of cooling holes (70) in the trailing edge part (47) has: having a central region (Rm) and an intermediate position (Pm) between a first end and a second end of the flow profile section (42) in the blade vertical direction, wherein the central region (Rm) has a constant index d_mid, which indicates opening densities of the plurality of cooling holes (70), an upstream region (Rup) which is arranged upstream of a flow of a cooling medium in the cooling passage (66) from the central region (Rm) in the blade vertical direction, wherein the upstream region (Rup) has a constant index d_up which indicates the opening densities of the plurality of cooling holes (70), and a downstream region (Rdown) which is arranged downstream of the flow of the cooling medium from the central region (Rm) in the blade vertical direction, wherein the downstream region (Rdown) has a constant index d_down which indicates the opening densities of the plurality of cooling holes (70), where a relationship of d_up < d_mid < d_down is satisfied, wherein each of the indices d_up, d_mid and d_down, which indicate the opening densities, is represented by a ratio D / P of a through-hole diameter D of each of the cooling holes (70), which are arranged such that they penetrate the trailing edge part (47) to an intermediate space P between the cooling holes (70) adjacent to each other in the blade vertical direction, wherein the upstream area (Rup), the middle area (Rm) and the downstream area (Rdown) connect to each other in the blade vertical direction, and wherein the opening densities of the plurality of cooling holes (70) are all uniform and constant in each of the upstream region (Rup), the middle region (Rm) and the downstream region (Rdown) and the opening densities of the plurality of cooling holes (70) change stepwise in the blade vertical direction. [2] A turbine blade comprising (40): a flow profile section (42), a cooling passage (66) extending in a blade vertical direction within the flow profile section (42), and a plurality of cooling holes (70) formed in a trailing edge portion (47) of the flow profile section (42) such that they are arranged in the blade vertical direction and provide convection cooling of the trailing edge portion (47), wherein the plurality of cooling holes (70) communicates with the cooling passage (66) and penetrates the trailing edge portion (47) to open towards a trailing edge end surface (49), wherein a relationship of d_up < d_down < d_mid is satisfied, where d_mid is an index having opening densities of the cooling holes (70) in a central region (Rm) an intermediate position (Pm) between a first end and a second end of the flow profile section (42) in the blade vertical direction, d_up is an index located in a region upstream of a flow of a cooling medium in the cooling passage (66) from the central region (Rm) in the blade vertical direction, and d_down is an index located in a region downstream of the flow of the cooling medium from the central region (Rm) in the blade vertical direction, and wherein a formation area of ​​the multitude of cooling holes (70) in the trailing edge part (47) has: having the central region (Rm) the intermediate position (Pm) between the first end and the second end of the flow profile section (42) in the blade vertical direction, wherein the central region (Rm) has the constant index d_mid, which indicates the opening densities of the plurality of cooling holes (70), an upstream region (Rup) which is arranged upstream of the flow of the cooling medium in the cooling passage (66) from the central region (Rm) in the blade height direction, wherein the upstream region (Rup) is arranged in an upstream side of the formation region, wherein the upstream region (Rup) has the constant index d_up which indicates the opening densities of the plurality of cooling holes (70), and a downstream region (Rdown) located downstream of the flow of the cooling medium from the central region (Rm) in the blade height direction, wherein the downstream region (Rdown) is located in a downstream side of the formation region, wherein the downstream region (Rdown) has the constant index d_down, which indicates the opening densities of the plurality of cooling holes (70), wherein each of the indices d_up, d_mid and d_down, which indicate the opening densities, is represented by a ratio D / P of a through-hole diameter D of each of the cooling holes (70), which are arranged such that they penetrate the trailing edge part (47) to an intermediate space P between the cooling holes (70) adjacent to each other in the blade vertical direction, wherein the upstream region (Rup), the middle region (Rm) and the downstream region (Rdown) connect to each other in the blade vertical direction, and wherein the opening densities of the plurality of cooling holes (70) are constant in each of the upstream region (Rup), the middle region (Rm) and the downstream region (Rdown) and the opening densities of the plurality of cooling holes (70) change stepwise in the blade vertical direction. [3] A turbine blade comprising (40): a flow profile section (42), a cooling passage (66) extending in a blade vertical direction within the flow profile section (42), and a plurality of cooling holes (70) formed in a trailing edge portion (47) of the airfoil section (42) such that they are arranged in the blade vertical direction, wherein the plurality of cooling holes (70) communicate with the cooling passage (66) and open to a trailing edge end surface (49) of the airfoil section (42) in the trailing edge portion (47), where the turbine blade (40) is a rotor blade (26), wherein a relationship of d_tip < d_mid < d_root is satisfied, where d_mid is an index having opening densities of the cooling holes (70) in a central region (Rm) indicating an intermediate position (Pm) between an end (48) and a foot (50) of the flow profile section (42) in the blade vertical direction, d_tip is an index located in a region closer to the end (48) than the central region (Rm) in the blade vertical direction, and d_root is an index located in a region closer to the foot (50) than the central region (Rm) in the blade vertical direction, wherein each of the indices d_tip, d_mid and d_root, which indicate the opening densities, is represented by a ratio D / P of a through-hole diameter D of each of the cooling holes (70), which are arranged such that they penetrate the trailing edge part (47) to an interval P between the cooling holes (70) adjacent to each other in the blade height direction, and wherein a formation area of ​​the multitude of cooling holes (70) in the trailing edge part (47) has: having the central region (Rm) the intermediate position (Pm) between the end (48) and the foot (50) of the flow profile section (42) in the blade vertical direction, wherein the central region (Rm) has the constant index d_mid which indicates the opening densities of the plurality of cooling holes (70), an outer end region (Rtip) which is located closer to the end than the middle region (Rm) in the blade height direction and closest to the end (48) in the formation area, wherein the outer end region (Rtip) has the constant index d_tip which indicates the opening densities of the plurality of cooling holes (70), and a foot region (Rroot) that is located closer to the foot (50) than the middle region (Rm) in the blade height direction and closest to the foot (50) in the formation area, wherein the foot region (Rroot) has the constant index d_root, which specifies the opening densities of the plurality of cooling holes (70), where the outer end region (Rtip), the middle region (Rm) and the foot region (Rroot) connect continuously to each other in the blade height direction. [4] A turbine blade comprising: a flow profile section (42), a cooling passage (66) extending in a blade vertical direction within the flow profile section (42), and a plurality of cooling holes (70) formed in a trailing edge portion (47) of the flow profile section (42) such that they extend in the blade vertical direction and that they perform convection cooling of the trailing edge portion (47), wherein the plurality of cooling holes (70) communicates with the cooling passage (66) and penetrates the trailing edge portion (47) to open to a trailing edge end surface (49), where the turbine blade (40) is a rotor blade (26), wherein a relationship of d_tip < d_root < d_mid is satisfied, where d_mid is an index having opening densities of the cooling holes (70) in a central region (Rm) indicating an intermediate position (Pm) between an end (48) and a foot (50) of the flow profile section (42) in the blade vertical direction, d_tip is an index located in a region closer to the end (48) than the central region (Rm) in the blade vertical direction, and d_root is an index located in a region closer to the foot (50) than the central region (Rm) in the blade vertical direction, wherein each of the indices d_tip, d_mid and d_root, which indicate the opening densities, is represented by a ratio D / P of a through-hole diameter D of each of the cooling holes (70), which are arranged such that they penetrate the trailing edge part (47) to an interval P between the cooling holes (70) adjacent to each other in the blade height direction, wherein a formation area of ​​the multitude of cooling holes (70) in the trailing edge part (47) has: having the central region (Rm) the intermediate position (Pm) between the end (48) and the foot (50) of the flow profile section (42) in the blade vertical direction, wherein the central region (Rm) has the constant index d_mid which indicates the opening densities of the plurality of cooling holes (70), an outer end region (Rtip) that is located closer to the end (48) than the middle region (Rm) in the blade height direction and closest to the end (48) in the formation area, wherein the outer end region (Rtip) has the constant index d_tip, which indicates the opening densities of the plurality of cooling holes (70), and a foot region (Rroot) that is located closer to the foot (50) than the middle region (Rm) in the blade height direction and closest to the foot (50) in the formation area, wherein the foot region (Rroot) has the constant index d_root, which specifies the opening densities of the plurality of cooling holes (70), where the outer end region (Rtip), the middle region (Rm) and the foot region (Rroot) connect continuously to each other in the blade height direction. [5] The turbine blade (40) according to any one of claims 1 to 4, wherein the central area (Rm) has a plurality of cooling holes (70) of the same diameter, and wherein an outer end region (Rtip) and a foot region (Rroot) each have a plurality of cooling holes (70) having the same diameter as the cooling holes (70) in the middle region (Rm), wherein the outer end region (Rtip) is located closer to an outer end (48) of the flow profile section (42) than the middle region (Rm), and wherein the foot region (Rroot) is located closer to a foot (50) of the flow profile section (42) than the middle region (Rm). [6] The turbine blade (40) according to any one of claims 1 to 5, wherein the plurality of cooling holes (70) are inclined with respect to a plane perpendicular to the blade vertical direction. [7] The turbine blade (40) according to one of claims 1 to 6, wherein the plurality of cooling holes (70) are formed parallel to each other. [8] The turbine blade (40) according to any one of claims 1 to 7, wherein the cooling passage (66) is a final path (60e) of a serpentine flow passage (60) formed within the flow profile section (42). [9] The turbine blade (40) according to any one of claims 1 to 8, where the turbine blade (40) is a rotor blade (26), and wherein the cooling passage (66) has an outlet opening (64) which is formed at one end of the flow profile section (42). [10] The turbine blade (40) according to claim 1 or 2, wherein the turbine blade (40) is a stator blade (24), and wherein the cooling passage (66) has an outlet opening (64) which is formed on an inner cover (86) of the flow profile section (42). [11] A gas turbine (1) comprising: the turbine blade (40) according to any one of claims 1 to 10, and a combustion chamber (4) for generating a combustion gas which flows through a combustion gas flow passage (28) where the turbine blade (40) is arranged.

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