Cooling of a turbine blade

Abstract: Structure with elements includes a main body (21) of the element used in a gas stream and a plurality of fluid passage (25,26). Each outlet (27, 28) of the fluid passage (25,26) openes in the surface of the main body (21). Coolant fluid flows through the passage and from each outlet (27, 28) to cover the surface in a fluid film. A first one of the fluid passages is arranged to discharge the coolant fluid from the outlet (27, 28) in the direction of the gas stream (23) on the surface. The coolant fluid also flows from an outlet (28) of a second one of the fluid passages (26) toward the gas stream and lies adjacent and close to the first outlet (27) of the first fluid passage (25).

Description: The present invention concerns a structure suitable for use as a turbine blade or turbine nozzle and is particularly concerned with the cooling of such a blade or nozzle. In a gas turbine, if the gas temperature is high during a first stage of the turbine, the efficiency for generating electric power increases. However, in order to raise the gas temperature for the first stage of the turbine, the heat-durability of the turbine blade and turbine nozzle should also be increased. As a method for raising the heat-durability of the gas turbine, film cooling by fluid on the blade surface is well known. Fig. 1 is a schematic diagram of the turbine blade of the gas turbine according to the prior art. The turbine blade consists of a main body 1 of the blade and a base 2 to attach the main body to a rotor (not shown in Fig. 1). Fig. 2 is a sectional plan of line K-K of Fig. 1. Fig. 3 is a sectional plan of the J-J line of Fig. 1. As shown in Fig. 2 and Fig. 3, three coolant passages 3a, 3b, 3c are formed in the base 2 and the main body 1. The three coolant passages are connected to a supply source of cooling fluid. The cooling fluid in the coolant passage 3a, 3b, 3c executes convective cooling through the base 2 and the main body 1. When the cooling fluid flows through the coolant passage 3a, 3b, they flow out through a plurality of outlets 8 on the loading edge 4, side wall 5, other side wall 6, tip 7. The cooling fluid in the coolant passage 3c flows out through outlets 10 on the trailing edge 9. The outlet of coolant passage is normally formed as an ellipse. Fig. 4 is a schematic diagram of the outlet of the coolant passage on the blade surface according to the prior art. Fig. 5 is a sectional plan of line L-L of Fig. 4. As shown in Fig. 4 and Fig. 5, in the outlet 8 passing through the side wall 5 and the other side wall 6, the center line 12 of the outlet of the coolant passage is inclined in the direction of the gas stream 11 on the surface of the wall 5 (6). The cooling fluid flowing from the outlet 8 is mixed with the gas stream 11 flowing over the surface at high speed, and cools the surface by forming a film-like layer over it. As a method for setting the outlet on the surface, plural lines of the outlets 8 perpendicular to the direction of the gas stream 11 may be set as shown in Fig. 6 and Fig. 7. In order to supplement the outlets 8 on the upstream side, the outlets 8 on the downstream side, whose position is different from the position of the outlets on the upstream side, are set as shown in Fig. 8. In order to strengthen the film cooling effectiveness of the spread of the fluid, the diameter of the outlet 13 is gradually increased as it reaches the surface as shown in Fig. 9A and Fig. 9B. Alternatively, as shown in Fig. 10, the outlet 13 is opened at fixed intervals as it reaches the surface, thus resembling a staircase. However, in the film cooling method in which the center line 12 of the coolant passage is inclined in the direction of the stream, the following problem occurs. The cooling fluid flowing from the outlet 8 has a high Kinetic energy stream that crosses the direction of the gas stream flowing along the surface. Therefore, as shown in Fig. 11, a separation of the coolant as the cooling fluid flows up in a columnar shape occurs. As a result, the gas stream 11 is divided by a pillar 14 of cooling fluid flowing from the outlet 8 and rolls up in the downstream area of the pillar 14. This makes it is difficult for the fluid film to cover the surface 5 (6) and therefore film cooling effectiveness is reduced. When the outlet is shaped as shown in Fig. 9B and Fig. 10, the fluid film covers only 70% of the surface interval between neighbouring outlets. In addition, the pressure of the fluid flowing from the outlet is low because of the wide outlet 13. Therefore, in the downstream area of the outlet 8 on the surface 5 (6), the gas stream 11 mixes with the cooling fluid 14, and the film cooling effectiveness is low. According to the prior art method shown in Figs. 12A and 12B, the direction of the coolant passage is inclined in a direction different from the direction of the gas stream along the surface (i.e., the "lateral direction"). In this method, the fluid diffuses laterally in the direction of the gas stream. In short, the flowing fluid diffuses only along the lateral area in the direction of the gas stream. The film cooling effectiveness of the fluid for the area downstream is therefore low. Another prior art structure is shown in Figs. 13A and 13B, the outlet is shaped as a diffusion type in addition to the specific feature of Figs. 12A and 12B. In this method, the center line of the diffusion part is inclined in the lateral direction similar to the center line of the outlet of the coolant passage. Therefore, the film cooling effectiveness of the fluid over the downstream area is low in the same way as shown in Figs. 12A and 12B. Further relevant background art is disclosed in each publication EP-0373175, with respect to which the claims of the present specification are characterised and US 5382133. EP-0373175 discloses an aerofoil for a gas turbine engine turbine rotor blade or stator vane is subject to film cooling by means of multiple rows of small cooling air exit apertures in the exterior surface of the blade or vane Each exit aperture is supplied with cooling air through at least two holes extending from the aperture through the wall of the blade or vane to interior chambers or passages The holes are mutually intersectng and their intersection forms the exit apertures and defines a flow constriction for controlling the flow rate of cooling air through the holes and out of the aperture. If the holes' centrelines intersect behind the plane of the exterior surface by an optional distance, the flow constriction is spaced apart from the exit aperture and is within the wall thickness, the exit aperture being enlarged. These film cooling hole configurations reduce the liability of the holes to block up due to contamination by environmental debris. US 5382133 discloses a film cooling passage through the external wall of a hollow airfoil having in serial flow relation a metering section and a diffusing section, the diffusing section characterized in that it has four inward facing surfaces that define a passage having a generally rectangular cross-section and an outlet over which a hot gas stream flows in a downstream direction. One of the surfaces of the diffusing section is generally downstream of the other surfaces, and this surface defines a section of a circular cylinder. It is an object of the present invention to provide a structure with elements that are able to suppress the roll up of the gas stream for the fluid downstream of each outlet on the surface of the main body. It is another object of the present invention to provide a structure with elements which are able to uniformly spread the cooling fluid over a wide area of the surface as a fluid film. According to a first embodiment of the present invention, there is provided a structure comprising a main body for use in a gas stream, having the features of claim 1. Further according to a second embodiment of the present invention there is provided a structure comprising a main body for use in a gas stream having the features of claim 5. A structure useful as a turbine blade will now be described, by way of example only, with reference to the accompanying figures, in which: Fig. 14A is a schematic diagram of the outlet of the coolant passage on the surface of the blade according to a first embodiment of the present invention. Fig. 14B is a sectional plan of line A-A of Fig. 14A. Fig. 15A is a schematic diagram of the outlet of the coolant passage on the surface of the blade according to a second embodiment of the present invention. Fig. 15B is a sectional plan vie on the line B-B of Fig. 15A Fig. 16A is a schematic diagram of the outlet of the coolant passage on the surface of the blade according to a third embodiment of the present invention. Fig. 16B is a sectional plan of line C-C of Fig. 16A Fig. 17A is a schematic diagram of the outlet of the coolant passage on the surface of the blade according to a fourth embodiment of the present invention. Fig. 17B is a sectional plan of line M-M of Fig. 17A. Fig. 18A is a schematic diagram of an outlet of a coolant passage on surface of the blade according to a fifth embodiment of the present invention. Fig. 18B is a sectional plan of line D-D of Fig. 18A. Fig. 19A is a schematic diagram of the outlet of the coolant passage on the surface of the blade according to a sixth embodiment of the present invention. Fig. 19B is a sectional plan of line E-E of Fig. 19A. Fig. 20A is a schematic diagram of the outlet of the coolant passage on the surface of the blade according to a seventh embodiment of the present invention. Fig. 20B is a sectional plan of line M-M of Fig. 20A. Fig. 21A is a schematic diagram of the outlet of the coolant passage on the surface of the blade according to an eighth embodiment of the present invention. Fig. 21B is a sectional plan of line N-N of Fig. 21A. Fig. 22A is a schematic diagram of the outlet of the coolant passage on the surface of the blade according to a ninth embodiment of the present invention. Fig. 22B is a sectional plan of line 0-0 of Fig. 22A. Fig. 23 is a schematic diagram of the turbine blade including the coolant passage according to the first embodiment. Fig. 24 is a graph comparing the cooling efficiencies of the structures embodied in the present invention and the prior art. Fig. 14A is a plan of an outlet of a coolant passage on the surface of the turbine blade according to a first embodiment of the present invention. Fig. 14B is a sectional plan of line A-A of Fig. 14A. In Figs. 14A and 14B, material 21 represents a main body such as the turbine blade or the turbine nozzle. The high temperature gas stream 23 flows over one surface 22 of the main body 21. In the main body 21, a plurality of main passages (first outlet 27 of coolant passage 29) 25 and a plurality of subpassages (second outlet 28 of coolant passage 30) 26 are set. Each section of the main passage 25 and the sub passage 26 is shaped as an circular. The first outlet 27 and the second outlet 28 are mutually located along a direction perpendicular to the direction of the gas stream 23 on the surface 22. The cooling fluid flows from the first outlet 27 through the first coolant passage 29 and from the second outlet 28 through the second coolant passage 30. A center line 31 of the first coolant passage 29 is inclined to the downstream side in relation to the direction of the gas stream 23. A center line 32 of the second coolant passage 30 is inclined to the upstream side in relation to the direction of the gas stream 23. The first coolant passage 29 and the second coolant passage 30 are connected to a supply section of the cooling fluid (not shown). Preferably, the section size of the first outlet 27 is larger than the section size of the second outlet 28. Preferably, an inclination angle of the first coolant passage 29 facing downstream is smaller than an inclination angle of the second coolant passage 30 facing upstream. Furthermore, the spaces between the first outlets 27, whose direction is perpendicular to the direction of the gas stream 23, are preferably less than three to five times the diameter of the circular of the passage 25. In the above-mentioned structure, the cooling fluid flows from the first outlet 27 to the downstream side in relation to the direction of the gas stream 23. The cooling fluid flows from the second outlet 28 to the upstream side on the surface 22. In this case, the cooling fluid flowing from the second outlet 28 collides with the gas stream 23 passing along side of the first outlet 27. Therefore, the gas stream 23 does not roll up the pillar of the cooling fluid flowing from the first outlet 27. In short, the pillar of cooling fluid easily settles on the downstream side and the cooling fluid film spreads widely along the downstream area. Furthermore, the cooling fluid from the second outlet 28 mixes with the gas stream 23 and the temperature of the gas stream drops. The low temperature gas stream flows on the space between the neighbouring first outlets 27. Therefore, cooling for the space between neighbouring first outlets 27 is executed and the surface temperature distribution in the direction perpendicular to the direction of the gas stream is made uniform. Fig. 15A is a plan of an outlet of a coolant passage on the surface of the turbine according to a second embodiment of the present invention. Fig. 15B is a sectional plan of line B-B of Fig. 15A. In structure of the second embodiment in Figs. 15A and 15B, two second outlets 28 are located on both sides of the first outlet 27. The two center lines of the two second outlets 28 mutually cross on the upstream side of the first outlet 27 based on the direction of the gas stream 23. The direction of this intersecting flow opposes the direction of the gas stream, which is rolled up. In the second embodiment, the efficiency of the cooling fluid from the second outlet increases. In short, the gas stream 23 roll-up of the cooling fluid flowing from the first outlet 27 is avoided. The cooling fluid film certainly spreads on the downstream side from the first outlet 27. Fig. 16A is a plan of an outlet of a coolant passage on the surface of the turbine blade according to a third embodiment of the present invention. Fig. 16B is a sectional plan of line C-C of Fig. 16A. In the structure of the third embodiment, the second outlets 28 are respectively arranged downstream from the arrangement line of the first outlets 27 in addition to the structure of the first embodiment. As in the first embodiment, the cooling fluid flowing from the second outlet 28 collides with the gas stream 23 passing along side of the first outlet 27. Therefore, the gas stream 23 roll-up of the pillar of the cooling fluid flowing from the first outlet 27 does not occur. The cooling fluid film thus widely spreads over the downstream area. Furthermore, the cooling fluid from the second outlet 28 mixes with the gas stream 23 and the temperature of the gas stream drops. The low temperature gas stream flows over the space between neighbouring first outlets 27. Cooling of the space between the neighbouring first outlets 27 is thus executed. Fig. 17A is a plan of an outlet of a coolant passage on the surface of the turbine blade according to a fourth embodiment of the present invention. Fig. 17B is a sectional plan of line M-M of Fig. 17A. In the structure of the fourth embodiment, two second outlets 28 (26) are located on both sides of the first outlet 27 (25). Two center lines 32 of the two second outlets 28 are parallel to the center line 31 of the first outlet 27. The cooling fluid flowing from the second outlets 28 obstructs the gas stream 23 passing on both sides of the first outlet 27. As a result, the gas stream 23 roll-up the fluid flowing from the first outlet 27 is avoided. Accordingly, the pillar of the cooling fluid easily settles on the downstream area and the cooling fluid film spreads widely and uniformly on the downstream area. In the four above-mentioned embodiments, the center line 31 of the first coolant passage 25 is inclined to the downstream side relative to the direction of the gas stream 23, and the center line 32 of the second coolant passage is inclined to the upstream side or the downstream side. However, the center line 31 of the first coolant passage 25 may be inclined to the upstream side and the center line 32 of the second coolant passage may be inclined to the downstream side or the upstream side. In this case, the cooling fluid flowing from the first outlet collides with the gas stream and the cooling fluid flowing from the second outlet obstructs passage of the gas stream. Therefore, the gas stream roll-up of the cooling fluid is avoided. Furthermore, the temperature of the gas stream drops and this gas stream flows downstream from the first outlet. The fluid film therefore settles uniformly on the downstream side. Fig. 18A is a plan of an outlet of a coolant passage on the surface of the turbine blade according to a fifth embodiment of the present invention. Fig. 18B is a sectional plan of line D-D of Fig. 18A. In the fifth embodiment, the second outlet 28 is located between the neighbouring two first outlets 27 and a center line 32 of the second coolant passage 26 is inclined along a direction perpendicular to the direction of the gas stream 23. The cooling fluid flowing from the outlet 28 obstructs the gas stream 23 passing on both sides of the first outlets 27. As a result, the gas stream 23 roll-up of the cooling fluid flowing from the first outlet 27 is avoided. Accordingly, the pillar of the cooling fluid easily settles on the downstream side and the cooling fluid film spreads widely on the downstream area. Fig. 19A is a plan of the outlet of the coolant passage on the surface of the turbine blade according to a sixth embodiment of the present invention. Fig. 19B is a sectional plan of line E-E of Fig. 19A. In the sixth embodiment, two second outlets 28 (26) are located on both sides of the first outlet 27 (25). The two center lines of the two second coolant passages 26 intersects at a position above the first outlet 27. The upper position departs from the first outlet 27 after a predetermined distance. Therefore, cooling fluid flowing from the outlet 28 obstructs the gas stream 23 passing on both sides of the first outlet 27. As a result, the gas stream 23 roll-up of the cooling fluid flowing from the first outlet 27 is avoided. Accordingly, the pillar of the cooling fluid easily settles on the downstream side and the cooling fluid film spreads widely on the downstream area. Fig. 20A is a plan of a coolant passage on the surface of the turbine blade according to a seventh embodiment of the present invention. Fig. 20B is a sectional plan of line M-M of Fig. 20A. In the seventh embodiment, the first coolant passage 50 is inclined in the lateral direction of the downstream side of the gas stream 23. The second coolant passage 60 is inclined to the upstream side on the surface 22. In the structure of the seventh embodiment, the cooling fluid flows from the first outlet 52 toward the lateral direction of the downstream side. On the other hand, the cooling fluid flows from the second outlet 62 toward the upstream side. In this case, the cooling fluid flowing from the second outlet 62 suppresses the roll-up of the gas stream 23 of the cooling fluid flowing from the first outlet 52. In addition, the cooling fluid flowing from the second outlet 62 mixes with the gas stream 23. Therefore, the cooling fluid film uniformly spreads in the lateral direction on the surface 22. Furthermore, the cooling fluid flows from the first outlet 52 in the lateral direction of the downstream side. Therefore, the cooling fluid film widely spreads toward the lateral direction of the downstream side. Fig. 21A is a plan of a coolant passage on the surface of the turbine blade according to an eighth embodiment of the present invention. Fig. 21B is a sectional plan of line N-N of Fig. 21A. In the eighth embodiment, the first coolant passage 50 is inclined to the lateral direction of the downstream side of the gas stream 23. The second coolant passage 60 is inclined to the lateral direction of the upstream side. The direction of the center line 54 of the first coolant passage 50 is parallel to the direction of the center line 64 of the second coolant passage 60 on the surface 22. In the structure of the eighth embodiment, the cooling fluid flows from the first outlet 52 toward the lateral direction of the downstream side. On the other hand, the cooling fluid flows from the second outlet 62 toward the lateral direction of the upstream side. In this case, the cooling fluid flowing from the second outlet 62 suppresses the roll-up of the gas stream 23 of the cooling fluid flowing from the first outlet 52. In addition, the cooling fluid flowing from the second outlet 62 mixes with the gas stream 23. Therefore, the cooling fluid film is uniformly spread in the lateral direction on the surface 22. Furthermore, the cooling fluid flown from the first outlet 52 flows from the first outlet 52 toward the lateral direction of the downstream side. Therefore, the cooling fluid film widely spreads in the lateral direction of the downstream side. Fig. 22A is a plan of a coolant passage on the surface of the turbine blade according to ninth embodiment of the present invention. Fig. 22B is a sectional plan of line 0-0 of Fig. 22A. In the ninth embodiment, the first coolant passage 50 is inclined in the lateral direction of the downstream side of the gas stream 23. The second coolant passage 60 is inclined in the lateral direction of the upstream side. Furthermore, the center line 54 of the first coolant passage 50 intersects the center line 64 of the second coolant passage 60 at more than 90 degrees. In the structure of the ninth embodiment, the cooling fluid flows from the first outlet 52 in the lateral direction of the downstream side. On the other hand, the cooling fluid flows from the second outlet 62 in the lateral direction of the upstream side. In this case, the cooling fluid flowing from the second outlet 62 suppresses the roll-up of the gas stream 23 of the cooling fluid flowing from the first outlet 52. In addition, the cooling fluid flowing from the second outlet 62 mixes with the gas stream 23. Therefore, the cooling fluid film spreads uniformly in the lateral direction on the surface 22. Furthermore, the cooling fluid flows from the first outlet 52 in the lateral direction of the downstream side. Therefore, the cooling fluid film widely spreads in the lateral direction of the downstream side. Fig. 23 is a schematic diagram of the turbine blade including the coolant passage to which the first embodiment is applied. As shown in Fig. 23, the turbine blade consists of a main body 41 of the blade and a base 42 to connect the main body 41 to a rotor (not shown). A plurality of coolant passages are formed in the base 42 and the main body 41. Each entrance of the coolant passage leads to a path of cooling fluid in the rotor. The cooling fluid flows through the coolant passage in the base 42 and the main body 41 and flows out from each outlet 46, 47. In Fig. 23, the first outlet 46 and the second outlet 47 are mutually arranged along a direction perpendicular to the direction of the gas stream on the leading edge 43, body wall 44 and other wall 45. In this case, a center line of the first outlet 46 is inclined to the downstream side of the gas flow. A center line of the second outlet 47 is inclined to the upstream side. It is better that size of the first outlet 46 is equal to or larger than size of the second outlet 47. Fig. 24 is a graph comparing the cooling efficiencies of the structures embodied in the present invention and the prior art. In Fig. 24, X1 represents the film cooling efficiency of the outlet of the prior art shown in Fig. 7; X2 represents the film cooling efficiency of the outlet of the prior art shown in Fig. 8; X3 represents the film cooling efficiency of the outlet of the present invention shown in Figs. 15A and 15B. According to the graph, the cooling efficiency of the present invention is greater in comparison with the prior art.

Claims: A structure useful as a turbine blade comprising a main body (21) for use in a gas stream (23), a plurality of fluid passages (25, 26) in the main body (21), each fluid passage having an outlet (27, 28) opening on a surface (22) of the main body (21), wherein fluid can flow from each outlet to cover the surface in a fluid film, the fluid passages (25, 26) include each of a first fluid passage (25) arranged to direct fluid to flow in the direction (23) of flow of the gas stream and a second fluid passage (26) arranged to direct fluid to flow in substantially the opposite direction to that of the gas stream, characterised in that the outlet (28) of the second fluid passage (26) is spaced from the outlet (27) of the first fluid passage (25) along a direction perpendicular to the gas stream on the surface (22) to suppress roll up of the gas stream for the fluid flowing from the first fluid outlet (27). The structure according to claim 1, wherein the area of the outlet (28) of the second fluid passage (26) is smaller than area of the outlet (27) of the first fluid passage (25). The structure according to claim 2 wherein the center line of the first fluid passage (25) is inclined to the downstream side of the gas stream (23) on the surface (22), and the center line of the second fluid passage (26) is inclined to the upstream side of the gas stream. The structure according to claim 1, wherein the main body (21) is a turbine blade or a turbine nozzle of a gas turbine. A structure suitable for use as a turbine blade or turbine nozzle comprising a main body (21) for use in a gas stream (23), the main body (21) having first and second fluid passages (50, 60), and an outlet opening on a surface (22) of the main body (21), so that fluid can flow from the outlet (52, 62) to cover the surface in a fluid film, characterised in that each fluid passage (50, 60) has a separate outlet (52, 62), and in that the first fluid passage (50) is arranged so that fluid can flow along a predetermined direction lateral to the gas stream, and the second fluid passage (60) is arranged to discharge the fluid in substantially the opposite direction to that of the gas stream next to the outlet (52) of the first fluid passage (50) so as to suppress roll up of the gas stream for the fluid flowing from the outlet (52) of the first fluid passage (50). The structure according to claim 5, wherein the center line of the second fluid passage (60) is parallel to the direction of the gas stream (23). The structure according to claim 5, wherein the center line of the second fluid passage (60) is inclined in the lateral direction with respect to the gas stream (23)and does not intersect a centre line of the first fluid passage (50). The structure according to claim 5, wherein the center line of the second fluid passage (60) intersects the centre line of the first fluid passage (50) at more than 90 degrees. The structure according to claim 5, wherein the main body (21) is a turbine blade or a turbine nozzle of a gas turbine.

Inventors: IKEDA KAZUTAKA, ISHII JUNJI, KOGA AKINORI, IKEDA, KAZUTAKA, ISHII, JUNJI, KOGA, AKINORI
Applicants: TOSHIBA KK, KABUSHIKI KAISHA TOSHIBA
Application year: 1997
Main classification: F01D5
IPC codes: F01D5