EP1849960A2

EP1849960A2 - Turbine blade having internal cooling passage

Info

Publication number: EP1849960A2
Application number: EP07008241A
Authority: EP
Inventors: Ryou c/o Hitachi Ltd Intellectual Property Group Akiyama; Yasuhiro c/o Hitachi Ltd Intellectual Property Group Horiuchi; Shinya c/o Hitachi Ltd Intellectual Property Group Marushima
Original assignee: Hitachi Ltd
Current assignee: Hitachi Ltd
Priority date: 2006-04-27
Filing date: 2007-04-23
Publication date: 2007-10-31
Also published as: JP2007292006A; EP1849960A3

Abstract

A turbine blade can be provided which enhances efficiency of a gas turbine by being efficiently cooled and has a high degree of reliability.

The turbine blade includes an internal cooling passage (4,5,7a-7f), and a plurality of projections (16) on a blade ventral side wall surface and a rear side wall surface of the cooling passage on a blade trailing edge side (13) thereof or a plurality of portions (e.g., cylindrical pin fins extending from the blade trailing edge side (13) ventral side wall surface to the blade trailing edge side rear side wall surface) connecting the blade ventral side wall surface with the rear side wall surface. The projections (16) or the portions are arranged so as to have different passage resistances depending on a position on the wall surfaces on the blade trailing edge side. This reduces the necessary amount of the cooling medium while performing efficient cooling.

Description

Background of the Invention

1. Field of the Invention

The present invention relates to a turbine blade having an internal cooling passage.

2. Description of the Related Art

A gas turbine is an apparatus in which fuel and air compressed by a compressor are mixedly burned by a burner to obtain a high temperature and high pressure working gas, which drives a turbine, thereby providing rotational energy. This rotational energy is used as power source to provide electric energy using a generator or to drive a pump or the like.
Recently, a combined cycle which combines a gas turbine with a steam turbine has been largely expected to increase its efficiency. Examples of means for increasing the efficiency include promoting the increased temperature-pressure ratio of a working medium.
In addition, attention is focused on a humid air turbine (HAT) power-generating plant which intends to increase efficiency by adding moisture to intake air of a gas turbine. This plant adds moisture to air for burning to increase humidity, which increases energy potential. This intends to increase output of the gas turbine, thereby increasing the thermal efficiency of the power-generating plant.
The heat load of a turbine high-temperature portion tends to increase from year to year because of increased temperature of a gas turbine working gas or of high-temperature gas added with moisture.
A turbine blade is one of the high-temperature components of a turbine. The turbine blade is provided with an internal hollow cooling passage, through which a cooling medium is allowed to flow, thereby cooling the blade material to a level not higher than a permissible temperature. The bleed air or discharged air of the compressor is frequently used as the cooling medium. If the air from the compressor is used, since an increase in the flow rate of cooling air implies a reduction in amount of burning air, the efficiency of a gas turbine is lowered. Thus, it is desirable that the turbine blade be efficiently cooled with a smaller amount of air.
To efficiently cool the turbine blade, it is necessary to promote heat transfer in the cooling passage. To promote heat transfer, it is effective to make an air flow on a heat transfer surface turbulent or to destroy a boundary layer, which involves a method where a large number of projections or obstacles are provided on the cooling surface inside the blade. Examples of paying attention to cooling the trailing edge of a turbine blade include e.g. JP-A-6-137102 , which discloses the following techniques. A gas turbine moving blade has pin fins provided on a to-be-cooled portion on the trailing side thereof. To enhance an effect of cooling the vicinity of the trailing edge side tip of the moving blade, the moving blade has a plurality of cooling air passages whose outlets are radially arranged in the trailing edge portion thereof. In addition, to enhance efficiency of cooling the same vicinity, the gas turbine moving blade is provided with a partition plate to direct a portion of cooling air to the tip side of the blade. JP-A-5-156901 discloses a configuration in which to cool the trailing edge side of a gas turbine moving blade having pin fins in a to-be-cooled portion on the trailing edge of the blade, cooling air is fed from the blade-tip side and root side of the a pin fin installed area.

Summary of the Invention

However, the configuration of radially arranging the outlets of the plurality of cooling passages in the trailing edge portion of the blade insufficiently cools to-be-cooled portions other than the trailing edge portion of the blade. Increasing the number of the cooling passages increases the necessary amount of cooling air, lowering the efficiency of the gas turbine. Reducing the number of the cooling passages enlarges the diameters thereof, which leads to a slower flow rate. Thus, an effect of cooling portions other than the pin fin installed portion is reduced. The configuration where the partition plate is provided to direct a portion of cooling air to the tip portion of the blade can slightly increase the amount of cooling air fed to the trailing edge side tip portion of the blade. However, since most of the cooling air flows out from the root side of the blade, the cooling air does not reach the tip portion of the blade, that is, it cannot cool the vicinity of the trailing edge side tip of the blade. The configuration where the cooling air is fed from the tip side and root side of the blade makes it difficult for the cooling air to flow in the vicinity of the intermediate area between the tip side and root side of the blade. This area cannot be sufficiently cooled. That is to say, the configuration of a cooling passage of a blade is desired which sufficiently cool the entire to-be-cooled portion of the trailing edge portion of the blade.
It is an object of the present invention to provide a high reliable turbine blade which is efficiently cooled without lowering the efficiency of a gas turbine.
According to an aspect of the present invention, there is provided a turbine blade which includes an internal cooling passage and a plurality of projections on a blade ventral side wall surface and a rear side wall surface of the cooling passage on a blade trailing edge side thereof or a plurality of portions connecting the blade ventral side wall surface with the rear side wall surface, wherein the projections or the portions are arranged so as to have different passage resistances depending on a position on the wall surfaces on the blade trailing edge side.
The present invention can provide a turbine blade that can enhance efficiency of a gas turbine by being efficiently cooled and has a high degree of reliability.

Brief Description of the Drawings

Fig. 1 is a longitudinally cross-sectional view of a turbine moving blade according to a first embodiment of the present invention.
Fig. 2 is a cross-sectional view of the turbine moving blade 1 taking along line A-A of Fig. 1.
Fig. 3 is an enlarged view of a cooling passage 7f and a blowout section 13 of the turbine moving blade 1 depicted in Fig. 1.
Fig. 4 is a longitudinal cross-sectional view of a turbine moving blade according to a second embodiment of the present invention.
Fig. 5 is an enlarged view of a cooling passage 7f and a blowout section 13 of the turbine moving blade 1 depicted in Fig. 4.
Fig. 6 is a longitudinal cross-sectional view of a turbine moving blade according to a third embodiment of the present invention.
Fig. 7 is an enlarged view of a cooling passage 7f and a blowout section 13 of the turbine blade 1 depicted in Fig. 6.
Fig. 8 is a longitudinal cross-sectional view of a turbine stationary blade according to a fourth embodiment of the present invention.

Detailed Description of the Preferred Embodiments

The present invention can be applied to the moving blade or stationary blade of a gas turbine. The following embodiments use compressor bleed air or discharged air is used as a cooling medium by way of example.

(First Embodiment)

A first embodiment of the present invention will be described in detail with reference to Figs. 1, 2 and 3. Fig. 1 is a longitudinal cross-sectional view of a turbine moving blade according to the embodiment of the present invention. The turbine moving blade 1 includes a shank section 2 located on the root side thereof and a blade section 3 located on the tip side thereof. Hollow cooling passages 4, 5 are provided to extend from the inside of the shank section 2 to the inside of the blade section 3. Compressor bleed air or discharged air is fed to the cooling passages 4 and 5 through cooling medium supply holes 14 and 15, respectively. Incidentally, direction 12 denotes a blade trailing edge side.
The cooling passage 4 is partitioned by partition walls 6a, 6b into cooling passages 7a, 7b, 7c in the blade section 3. The cooling passages 7a, 7b, 7c together with a tip bent portion 8a and a lower end bent portion 9a form a serpentine cooling passage which is a fold passage. The cooling passage 5 is partitioned by partition walls 6c, 6d into cooling passages 7d, 7e, 7f in the blade section 3.
The cooling passages 7d, 7e, 7f together with a tip bent portion 8b and a lower end bent portion 9b form a serpentine cooling passage.
A blowout section 13 is provided on the trailing edge side of the cooling passage 7f to allow the cooling air flowing in the cooling passage 5 to flow to the outside of the blade. A plurality of pin fins 16 is provided in the blowout section 13 so as to be integral with the blade. The present embodiment uses the pin fins 16 which are each formed almost cylindrical.
Cooling air is fed from a rotor disk (not shown) carrying the turbine moving blade 1 to the supply holes 14, 15 and internally cools the moving blade 1 while passing through the cooling passages 4, 5. Most of the cooling air flowing into the supply hole 14 flows out through a blowout hole 11 provided at the tip of the moving blade. Most of the cooling air flowing into the supply hole 15 flows out to the outside from a blowout section 13 provided at the trailing edge of the moving blade.
The turbine moving blade 1 of the present embodiment includes six cooling passages in total to cool the blade section 3: three passages extending from the blade root side toward the blade tip side and three passages extending from the blade tip side toward the blade root side. With such a large number of the passages, since a sectional area per one passage is small, the flow velocity of cooling air is fast as compared with the reduced number of the passages, which provides the enhanced effect of cooling the blade section 3. To provide a sufficient cooling effect, it is desirable that a turbine moving blade used in the same application as that of the present embodiment be provided with four or more passages in total which include passages extending from the blade root side to the blade tip side and from the blade tip side to the blade root side for cooling the blade section 3.
The turbine moving blade 1 of the present embodiment includes two cooling systems in total of cooling passages of cooling the blade section 3: the cooling passage 4 adapted to feed cooling air from the supply hole 14 and the cooling passage 5 adapted to feed cooling air from the supply hole 15. A sufficient amount of cooling air must be supplied to the supply hole of each system. Therefore, if the number of the cooling systems of the cooling passage is increased, the necessary amount of cooling air to be supplied is increased. The compressor bleed air or discharged air, which is a portion of a working medium, is often used as cooling air. Thus, the increased necessary amount of cooling air leads to a reduction in amount of burning air to be supplied to a burner, which lowers the efficiency of the gas turbine.
Since the present embodiment can suppress the total number of the cooling systems to as small as two, an amount of supply cooling air is small, which can enhance the efficiency of the gas turbine. Taking into consideration the efficiency of the gas turbine, it is desired that the total number of cooling systems be two or less in total for the turbine blade used in the same application as in that of the present embodiment.
Fig. 2 is a cross-sectional view of the moving blade taken along line A-A of Fig. 1. Direction 22 denotes the blade trailing edge side. The pin fin 16 is an almost-circular constituent element which extends from the blade ventral side wall 28 to the blade rear side wall 29.
Fig. 3 is an enlarged view of the cooling passage 7f and blowout section 13 of the turbine moving blade 1 depicted in Fig. 1. Flows 18, 19a-19e denote the flows of cooling air. A portion of cooling air is led as flow 18 to the blade trailing edge side tip by the cooling passage 7f. While the cooling air is led as flow 18 to the blade tip, a portion of flow 18 gradually flows to the outside as flows 19a-19d from the blowout section 13.
In the case of a turbine blade (not provided with a cooling passage 7f) provided with pin fins in an area corresponding to the cooling passage 7f, most of cooling air blowing out from the blowout section 13 flows out as blade root side flows 19a-19c and a little cooling air reaches the blade tip side. Thus, the high-temperature portion in the vicinity of the blade trailing edge side tip cannot be sufficiently cooled, which lowers reliability of the turbine blade.
In contrast, in the present embodiment, the cooling passage 7f is provided on the blade leading edge side of the blowout section 13 provided with the pin fins. With this configuration, more air can be more reliably led to the blade trailing edge side tip portion as compared with the gas turbine blade not provided with the cooling passage 7f. That is to say, since the flaw volumes of the cooling air of the downstream side of flow 18 and flows 19d, 19e are increased, the effect of cooling the portion to be cooled by the flows is increased. This lowers the metal-temperature of the to-be-cooled portion, thereby enhancing reliability of the turbine blade. In addition, even the blade trailing edge side tip portion that the cooling air is hard to reach can be cooled efficiently; therefore, an amount of supplying cooling air can be reduced, which further enhances the efficiency of the gas turbine.
In the embodiment, the blade root portion is provided with large pin fins 16b whereas the blade tip portion is provided with small pin fins 16a. Thus, the passage resistance of the cooling medium encountered when the cooling medium blows out to the outside from the area provided with the large pin fins 16b, which is the blade root side area of the blowout section 13, can be made larger than that from the area provided with the small pin fins 16a. In short, the flow volume of flows 19a-19c can be made small whereas the flow volume of flows 19d, 19e can be made large. With this configuration, more air can be more reliably led to the blade trailing edge side tip portion as compared with the turbine blade provided with pin fins 16 having almost the same size. That is to say, this configuration can provide two effects, an improvement in reliability of the turbine blade and an improvement in efficiency of the gas turbine, similar to the effects obtained by providing the cooling passage 7f.
Incidentally, the passage resistance of the present embodiment means how difficult it is for the cooling air to flow in the blowout section 13 when the cooling air flows from the cooling passage 7f through the blowout section 13, which is the area provided with the pin fins 16, to the outside.
In the embodiment, a large pin fin means that the cross-section area of its surface almost parallel to the surface (the blade ventral side wall 28 or the blade rear side wall 29) provided with the pin fin 16 is large. Similarly, a small pin fin means that the cross-section area of the pin fin 16 is small. A ratio of the cross-section area of the large pin fin to that of the small pin fin should be optimally designed based on the cooling capacity required by the upstream side and downstream side of arrow 18. The ratio is generally selected from about 1.4 to 4.0. When the cross-sectional shape of the pin fin is circular as in the embodiment, about 1.4 to 4.0 corresponds to about 1.2 to 2.0 in a ratio between circular diameters.
In the embodiment, in view of increasing the cooling capacity of the blade trailing edge side tip portion, the small pins 16a are provided on the blade tip side. If the cooling capacity of other portions such as the blade root side and the like is intended to be increased, it is conceivable that the pin fins 16 at appropriate portions are made larger or smaller.

(Second Embodiment)

A second embodiment of the present invention will be described with reference to Figs. 4 and 5. Fig. 4 is a longitudinal cross-sectional view of a turbine moving blade 1 according to the second embodiment of the present invention. Fig. 5 is an enlarged view of a cooling passage 7f and a blowout section 13 of the turbine moving blade 1 depicted in Fig. 4.
In the present embodiment, the number of pin fins 16 per unit area, i.e., the installation density of the pin fins 16, of a part in a blowout section 3 is made different from that of another part in the blowout section 3. Specifically, the installation density of pin fins 16c in an area (on the blade tip side) corresponding to passages of flaws 19d, 19e in the blowout section 13 is made lower than that of pin fins 16d in an area (on the blade tip side) corresponding to passages of flows 19a-19c in the blowout section 13.
With this configuration, the passage resistance of a cooling medium encountered when the cooling medium is blown out to the outside from the area provided sparsely with the pin fins 16c, which is the blade root side area of the blowout section 13, is made smaller than that from the area provided with the pin fins 16d. That is to say, the flow volume of flows 19a-19c is small whereas the flow volume of flows 19d, 19e is large. In addition, with this configuration, more air can be more reliably led to the blade trailing edge side tip portion as compared with the turbine blade having entire the same installation density of pin fins 16. That is to say, this configuration can provide two effects, an improvement in reliability of the turbine blade and an improvement in efficiency of the gas turbine, similar to the effects obtained by the turbine blade of the first embodiment.
The present embodiment changes intervals between the pin fins 16 to be arranged. The interval ratio should be optimally designed based on the cooling capacity required by the blade tip side and the blade root side. The interval ratio is generally selected from about 1.1 to 2.0 by way of example.
In the embodiment, in view of increasing the cooling capacity of the blade trailing edge side tip portion, the installation density of the pin fins 16c installed on the blade tip side is made small. If the cooling capacity of other portions such as the blade root side and the like is intended to be increased, it is conceivable that the density of the pin fins 16 at appropriate portions are made larger or smaller.

(Third Embodiment)

A third embodiment of the present invention is described with reference to Figs. 6 and 7. Fig. 6 is a longitudinal cross-sectional view of a turbine moving blade according to the third embodiment of the invention. Fig. 7 is an enlarged view of a cooling passage 7f and a blowout section of the turbine moving blade 1 depicted in Fig. 6.
In the present embodiment, the installation density and size of the pin fins 16 of a part in a blowout section 13 is made different from those of another part in the blowout section 13. Specifically, small pin fins 16e and large pin fins 16f are provided on the blade tip side and blade root side, respectively, of the blowout section 13 and the installation density of the small pin fins 16e is made smaller than that of the large pin fins 16f. The configuration described above can provide an improvement in reliability of the turbine blade and an improvement in efficiency of the gas turbine as described in the first and second embodiments. The turbine blade of the present embodiment includes the pin fins having the different sizes and further different installation densities. Therefore, the turbine blade of this embodiment can provide the larger effects than those of the first and second embodiments.
The gas turbine moving blade 1 has been thus far described taking the turbine blade as an example. However, the application of the present invention is not limited to the moving blade. A fourth embodiment describes a gas turbine stationary blade embodying the invention.

(Fourth Embodiment)

A fourth embodiment of the present invention is described with reference to Fig. 8. Fig. 8 is a longitudinal cross-sectional view of a turbine stationary blade according to the fourth embodiment of the present invention.
A turbine stationary blade 61 includes cooling passages 67a, 67b inside a blade section 63. Direction 72 denotes a blade trailing edge side, direction 85 denotes a blade root side, and direction 86 denotes a blade tip side. The cooling passages 67a and 67b are partitioned by a partition wall 66. A plurality of pin fins 76 are provided in a blowout section 73 on the blade trailing edge side of the cooling passage 67b. Flows 64, 65, 79a-79e denotes flows of cooling air.
The cooling air fed from a cooling air supply hole 74, flowing in the cooling passage 67a in the blade tip side direction, and flows out from a blowout hole 83. The cooling air fed from a cooing air supply hole 75 flows in the cooling passage 67b toward the blade tip side. Flow 65 toward the blade tip side branches into flows 79a, 79b, 79c, 79d, 79e, which cool the blowout section 73 and flow out to the outside of the blade.
In the turbine stationary blade 61 of the present invention, metal temperature rises particularly in the vicinity of a blade central vicinity area 87. Thus, it is desired that much cooling air be fed to the vicinity of the area 87 in the blowout section 73 which is a trailing edge side area of the turbine stationary blade 61.
In the embodiment, small pin fins 76a are installed in the area 87 and large pin fins 76b are installed in the other areas in the blowout section 73. With the configuration described above, the passage resistance of cooling air flowing out as flow 79c from the area 87 can be made lower than that as flow 79a, 79b, 79d, 79e from the other areas, thereby feeding a sufficient amount of cooling air.
As described above, cooling capacity for the area 87 where metal temperature rises particularly on the blade trailing edge side can be enhanced, thereby enhancing cooling efficiency of the turbine stationary blade 61. Therefore, this embodiment can provide two effects, an improvement in reliability of the turbine blade and an improvement in efficiency of the gas turbine.
In the present embodiment, the size of the pin fin 76 in an area of the blowout section 73 is made different from that in the other areas, whereby the passage resistance of cooling air flowing out through the area from the blowout section 73 is made different from that through the other areas. However, it is conceivable that the passage resistance in an area of the blowout section 73 is made different from that in other areas by other methods of, e.g., making the installation density in an area different from that in other areas.
In the embodiments described above, the sizes or installation densities of the pin fins 16 are made different from each other depending on the areas. This makes it easy for cooling air to reach an area where it is otherwise difficult for the cooling air to reach, such as the blade trailing edge side tip portion or the like, or an area which particularly needs to be cooled. Thus, the turbine blade is effectively cooled. The effective cooling is achieved by providing areas in the blowout section provided with the pin fins, the areas being high and low in passage resistance of the cooling air flowing out from the blowout section. That is to say, if the passage resistances can be made different from each other depending on flowing-out portions of the cooling air in the blowout section, the two effects can be provided, an improvement in reliability of the turbine blade and an improvement in efficiency of the gas turbine.
Allowing the pin fins 16 to have different sizes and/or different installation densities depending on areas is to allow them to have different pin fin installation areas per unit area on the blade ventral side wall or on the blade rear side wall. The turbine blade configured as described above can provide the two effects mentioned above.
The pin fin 16 used in the embodiments described above is formed almost cylindrically to be integral with the blade but the present invention is not limited to this pin fin. For example, a triangular fin which extends from the blade ventral side wall 28 to the blade rear side wall 29 may be used as a structure which plays the same role as the pin fin 16. In addition, projections may be provided on the blade ventral side wall 28 or the blade rear side wall 29. In conclusion, it is needed only to use a structure capable of increasing passage resistance of cooling air flowing out from the blowout section 13 to the outside.

Claims

A turbine blade comprising:
an internal cooling passage (4,5,7a-7f); and

a plurality of projections (16) on a blade ventral side wall surface and a rear side wall surface of the cooling passage (7f) on a blade trailing edge side (13) thereof or a plurality of portions connecting the blade ventral side wall surface with the rear side wall surface;
wherein the projections (16) or the portions are arranged so as to have different passage resistances depending on a position on the wall surfaces on the blade trailing edge side (13).
The turbine blade according to claim 1, wherein installation areas, per unit area, of the projections (16) or the portion on each of the wall surfaces are different from each other depending on the position on the wall surfaces on the blade trailing edge side (13), whereby the passage resistances are different from each other depending on the positions on the wall surfaces on the blade trailing edge side (13).
The turbine blade according to claim 1, wherein the projections (16) or the portions are almost cylindrical members connecting both the wall surfaces on the blade trailing edge side (13) and installation densities of the almost cylindrical members are different from each other depending on the position on the wall surfaces on the blade-trailing edge side (13).
The turbine blade according to claim 1, wherein the projections (16) or the portions are almost cylindrical members connecting both the wall surfaces on the blade trailing edge side (13) and cross-section areas of surfaces of the almost cylindrical members almost parallel to the wall surface on the blade trailing edge side (13) are different from each other depending on the position on the wall surfaces on the blade trailing edge side (13).
The turbine blade according to claim 1, wherein the passage resistance on the blade tip side (3) is lower than that on the blade root side (2).
The turbine blade according to claim 1, further comprising a cooling passage (7a) which is adjacent to a blade leading edge side of an area having the projections (16) or the portions and is adapted to lead a cooling medium from a blade tip side (3) to a blade tip portion (8a).
The turbine blade according to claim 1,
wherein the cooling passage is provided with an inlet (14,15)at a blade root portion (2) thereof and with at least one outlet (13) at a blade trailing edge portion thereof, and
wherein the turbine blade includes:
a first cooling passage (7a,7b,7c) which is a combination of a passage (7a) allowing a cooling medium to flow from a blade root side (2) to a blade tip side (3) and a passage (7b) allowing the cooling medium to flow from the blade tip side (3) to the blade root side (2) and which is used to cool from a root side (2) of a blade section to a tip side (3) thereof; and

a second cooling passage (7f) which is adjacent to a blade leading edge side of an area having the projections (16) or the portions and is adapted to lead a portion of or all of the cooling medium from a blade root side (2) to a blade tip portion (3).
A method of cooling a turbine blade including an internal cooling passage (4,5,7a-7f), and a plurality of projections (16) on a blade ventral side wall surface and a rear side wall surface (13) of the cooling passage on a blade trailing edge side thereof or a plurality of portions connecting the blade ventral side wall surface with the rear side wall surface,
wherein the projections (16) or the portions are arranged so as to have different passage resistances depending on a position on the wall surfaces on the blade trailing edge side (13).
A gas turbine provided with a turbine blade including:
an internal cooling passage (4,5,7a-7f); and

a plurality of projections (16) on a blade ventral side wall surface and a rear side wall surface of the cooling passage on a blade-trailing edge side (13) thereof or a plurality of portions connecting the blade ventral side wall surface with the rear side wall surface;
wherein the projections (16) or the portions are arranged so as to have different passage resistances depending on a position on the wall surfaces on the blade trailing edge side (13).