Cooled gas turbine blade with turbulators

Abstract: Leading edge portion turbulators in gas turbine cooled blade are improved so as to enhance cooling performance. Rounded tip portion of leading edge portion cooling passage 3 is approximated by triangular cooling passage 1 having orthogonal turbulators 11, 12 and smoothly curved rear portion thereof of the leading edge portion cooling passage 3 is approximated by square cooling passage 2 having oblique turbulators 13, 14, thus the leading edge portion cooling passage 3 is formed so as to have combination of orthogonal turbulators 21 of the rounded tip portion and oblique turbulators 22, 23 of the smoothly curved rear portion thereof. These rounded portion and rear portion thereof are provided with the respective turbulators having excellent heat transfer characteristics and cooling performance of the leading edge portion is enhanced.

Description: Field of the Invention: The present invention relates to gas turbine cooled blade comprising turbulators as defined by the preamble portion of claim 1, specifically comprising turbulators applied to a blade leading edge portion of a gas turbine cooled blade for enhancing a heat transfer performance. Description of the Prior Art: Fig. 6, being a longitudinal cross sectional view of a prior art gas turbine moving blade, shows arrangement of turbulators in cooling air passages thereof and Fig. 7 is a transverse cross sectional view of the gas turbine moving blade of Fig. 6. In these figures, numeral 30 designates a moving blade and cooling passages 31A, 31B, 31C, 31D and 31E are provided therein so that cooling air 33 is supplied into the cooling passages 31A, 31B and 31E, respectively. The cooling air 33 which has entered the cooling passage 31A is injected from a leading edge portion to effect a shower head cooling 51 as shown in Fig. 7. The cooling air 33 which has entered the cooling passage 31B flows through the cooling passage 31C and further through the cooling passage 31D to be injected from a blade surface to effect a film cooling 52 as shown in Fig. 7. Also, the cooling air 33 which has entered the cooling passage 31E on a trailing edge side is injected through a trailing edge to effect a pin fin cooling 53 as shown in Fig. 7. In each of the cooling passages 31A to 31E, in order to make the cooling air 33 convection-activated and enhance a heat transfer ability, there are provided a multiplicity of oblique turbulators 32, wherein the turbulators 32 are of same shapes arranged obliquely with respect to each of the cooling passages, as shown in Fig. 6. Also, in Fig. 8 showing a longitudinal cross sectional view of another example of prior art gas turbine moving blade, numeral 40 designates a moving blade and cooling passages 41A, 41B, 41C, 41D, 41E, 41F and 41G are provided therein so that cooling air 43 is supplied into the cooling passages 41A, 41D and 41E, respectively. The cooling air 43 which has entered the cooling passage 41A is injected from a leading edge portion to effect a shower head cooling, same as mentioned above. The cooling air 43 which has entered the cooling passage 41D flows through the cooling passages 41C and 41B and the cooling air 43 which has entered the cooling passage 41E flows through the cooling passages 41F and 41G both to be injected from a blade surface to effect a film cooling. Also, the cooling air 43 which has so flown through the cooling passages 41F and 41G is injected through a trailing edge to effect a pin fin cooling. In each of the cooling passages 41A to 41G, in order to make the cooling air 43 convection-activated and enhance a heat transfer ability, there are provided a multiplicity of orthogonal turbulators 42, wherein the turbulators 42 are of same shapes arranged orthogonally with respect to each of the cooling passages, as shown in Fig. 8. As mentioned above, the prior art turbulators of gas turbine cooled blades are made in one kind either of oblique turbulators or of orthogonal turbulators and it is said generally that the oblique turbulators are more excellent in the heat transfer characteristics in case where the cooling passages have a square cross sectional shape. Also, of recent papers on the turbulators, one titled, "Heat transfer performance in triangular channels", Zhang et al., 1994, for example, shows a comparison example as shown in Fig. 5, with detailed description made therein being omitted here. In Fig. 5, cases (a) to (e) are examples where there are provided ribs in the triangular channels, respectively. Case (a) is an example where ribs 61, 62 and 63 are provided separately from each other to inner walls of the triangular channel respectively with angle α = 90°, α being an angle relative to air flow direction. Case (b) is an example where a rib 71 is provided along an entire circumference of the inner wall of the triangular channel likewise with the angle α = 90°. Case (c) is an example where the ribs 61, 62 and 63 are provided separately like the case (a) but obliquely with an angle β < 90°, β being an angle relative to air flow direction. Case (d) is an example where the rib 71 is provided along the entire circumference of the inner wall like the case (b) but obliquely with the angle β < 90° and Case (e) is an example where the ribs 61 and 62 are provided to two sides of the inner wall of the triangular channel obliquely with the angle β < 90°. In the mentioned cases (a) to (e), if they are to be shown in the order of good heat transfer coefficient, the order is (a), (b), (c), (d) and (e). Thus, as to the ribs provided to the inner wall of the triangular channel, the case where the ribs 61, 62 and 63 are provided separately to the inner wall with the angle α = 90°, as the case (a), is most excellent in the heat transfer coefficient. In the prior art turbulators of gas turbine cooled blade as mentioned above, the turbulators are made either in oblique ones or in orthogonal ones. On the other hand, there is needed a large amount of cooling air for cooling of the blades and moreover the cooling air which has been so used for the cooling of the blades is discharged into a gas passage. Hence, it is necessary that the turbulators are arranged in a cooling passage so as to give excellent heat transfer characteristics to thereby enhance a cooling efficiency of the cooling air. Leading edge of the blade is a portion which is most largely influenced by a high temperature combustion gas flow and while cooling of the leading edge portion is required to be done efficiently, it is the present situation that the turbulators provided in the cooling passage of the leading edge portion are only either oblique ones or orthogonal ones. As for the triangular cross sectional passage in which ribs are provided as mentioned above, it is known that the case where the three ribs 61, 62 and 63 are provided separately with the angle α = 90°, that is, orthogonally to air flow, as the case (a) in Fig. 5, is most excellent in terms of the heat transfer. A gas turbine cooled blade comprising turbulators with the features of the preamble portion of claim 1 is described in JP 62 085102 A. In this gas turbine cooled blade heat transfer accelerating fins are formed on the inner surface of a forward portion of a leading edge flow path within the blade and oblique turbulators are provided to the inner wall surface of a bulkhead which in turn is inserted into the inner space of the blade leading edge portion with a gap being formed between the bulkhead and the blade inner wall surface by means of fin-like projections. US-A-4 515 526 discloses a gas turbine cooled blade in which so-called "trip strips" and a vortex generator are arranged so as to be connected to each other from the blade leading edge portion to the rear portion thereof. JP 61 001804 A discloses that cooling fins provided to the inner wall surface of a blade leading edge and guide plates provided to the inner wall surface in the rear thereof are arranged apart from each other. The guide plates regulate the flow of air by separating it into two paths but do not serve to create air turbulence in the flow of air for the purpose of enhancing the heat transfer effect. US-A-4 786 233 discloses a gas turbine cooled blade where orthogonal ribs provided to the inner wall surface of the blade leading edge and obliquely arranged members referred to as "cylindrical penetrating members" are positioned in the rear thereof. These members have a blade-like or elliptic cross-sectional shape to guide the stream of cooling fluid and are arranged so as to extend in the blade inner space so as to connect both the side walls of the blade. It is the object of the present invention to provide a gas turbine cooled blade comprising turbulators which is improved so as to obtain a better heat transfer. In order to attain this object the present invention provides a gas turbine cooled blade with the features of claim 1. In the present invention, the rounded inner wall portion of the transverse cross sectional tip portion of the leading edge portion cooling passage is approximated by a triangle shape in which the orthogonal turbulators are excellent in the heat transfer characteristics. Hence, the orthogonal turbulators are arranged in this rounded inner wall portion. The smoothly curved inner wall portion in the rear of said rounded inner wall portion is approximated by a square shape in which the oblique turbulators are known to be excellent in the heat transfer characteristics. Hence, the oblique turbulators are arranged in this smoothly curved portion. By the present invention in which the turbulators are so arranged, the heat transfer characteristics of the leading edge portion cooling passage can be enhanced as compared with the prior art arrangement in which the turbulators either of orthogonal ones or of oblique ones only are provided. BRIEF DESCRIPTION OF THE DRAWINGS: Fig. 1 is a schematic arrangement view of turbulators of an example serving to explain certain aspects of the present invention, said turbulators being provided in a leading edge portion cooling passage of a gas turbine cooled blade, and shows a transverse cross section of the cooling passage on one hand and a longitudinal inner wall side face of same on the other hand, wherein Fig. 1(a) is a view in which a portion of the cooling passage is approximated by a triangular passage, Fig. 1(b) is a view in which another portion of the cooling passage is approximated by a square passage and Fig. 1(c) is a view in which said both portions are combined so as to form the leading edge portion cooling passage. Fig. 2 is a transverse cross sectional view of the gas turbine cooled blade provided with the turbulators of the example of Fig. 1. Fig. 3 is a transverse cross sectional view of a leading edge portion cooling passage provided with turbulators of a variation example of an embodiment of the invention. Fig. 4 is a view showing a longitudinal inner wall side face provided with turbulators of an embodiment of the invention. Fig. 5 is a view showing cases where ribs are provided in triangular channels, respectively, wherein cases (a), (b), (c), (d) and (e) show excellence in heat transfer characteristics in said order. Fig. 6 is a longitudinal cross sectional view of a prior art gas turbine moving blade and shows oblique turbulators provided therein. Fig. 7 is a transverse cross sectional view of the moving blade of Fig. 6. Fig. 8 is a longitudinal cross sectional view of another prior art gas turbine moving blade and shows orthogonal turbulators provided therein. DESCRIPTION OF THE PREFERRED EMBODIMENTS: Herebelow, embodiments according to the present invention will be described concretely with reference to figures. Fig. 1 shows a transverse cross section and a longitudinal inner wall side face of a leading edge portion cooling passage of a gas turbine cooled blade which is provided with turbulators of one example sewing to explain certain aspects of the present invention, wherein the leading edge portion cooling passage is sectioned into two parts so as to be approximated by a triangular passage and a square passage, respectively, and turbulators are arranged in the passages so as to obtain excellent heat transfer characteristics, respectively, which results in obtaining an excellent turbulator arrangement of a leading edge portion in combination of said two passages. Fig. 2 is a transverse cross sectional view of the gas turbine cooled blade provided with the turbulators of Fig. 1. Fig. 1(a) shows a rounded inner wall portion, with turbulators provided thereto, of a transverse cross section of the leading edge portion cooling passage which is approximated by a triangular passage, Fig. 1(b) shows a smoothly curved inner wall portion, with turbulators provided thereto, in the rear thereof of the leading edge portion cooling passage which is approximated by a square passage and Fig. 1(c) shows a transverse cross section of the leading edge portion cooling passage formed in combination of the cooling passages of Figs. 1(a) and (b). In Fig. 1(a), numeral 1 designates a triangular cooling passage and numerals 11, 12 designate orthogonal turbulators provided to both inner wall side faces of the triangular cooling passage 1. As described above in Fig. 5, it is known that ribs arranged orthogonally exhibit best heat transfer characteristics in a sharp triangle-shaped passage, hence the orthogonal turbulators 11, 12 are arranged in the triangular cooling passage 1, as shown in Fig. 1(a). In Fig. 1(b), numeral 2 designates a square cooling passage and numerals 13, 14 designate oblique turbulators provided to both inner wall side faces of the square cooling passage 2. In this square cooling passage, the oblique turbulators 13, 14 are arranged as is known generally. In Fig. 1(c) in which turbulators are arranged in a leading edge portion cooling passage in combination of arrangements of Figs. 1(a) and (b), numeral 21 designates orthogonal turbulators arranged to the rounded tip portion of the leading edge portion cooling passage 3 and numerals 22, 23 designate oblique turbulators arranged to both sides of the smoothly curved inner wall portion in the rear thereof. The orthogonal turbulators 21 correspond to those described in Fig. 1(a), that is, the orthogonal turbulators 11, 12 of Fig. 1(a) are extended in arcs to connect to each other so as to form the orthogonal turbulators 21 and the oblique turbulators 22, 23 correspond to the oblique turbulators 13, 14 of Fig. 1(b). As shown in Fig. 1(c), the orthogonal turbulators 21 and the oblique turbulators 22, 23 are arranged separately from each other and the oblique turbulators 22, 23 extend to a position of line L of terminal ends of the orthogonal turbulators 21 in a mid position of two turbulators of the orthogonal turbulators 21. By employing the cooling passage provided with such separated and complicated turbulators, convection is activated and heat transfer coefficient is enhanced greatly. The gas turbine cooled blade provided with the turbulators so arranged is shown in the cross sectional view of Fig. 2. Fig. 3 shows a variation example of the turbulators of Fig. 1(c), wherein the orthogonal turbulators 21 of Fig. 1(c) are divided at a central portion thereof into two portions with a gap d being maintained therebetween, thus orthogonal turbulators 24, 25 are formed there so that cooling air flows easily through the rounded tip portion of the leading edge portion cooling passage 3 and cooling of this portion is accelerated. Fig. 4 shows another variation example of the turbulators of Fig. 1(c) representing an embodiment of the present invention, wherein the oblique turbulators 22, 23 shown in Fig. 1(c) are extended so that terminal ends of the oblique turbulators 22', 23' come inside between each of the orthogonal turbulators 21 by a length t, thus oblique turbulators 22', 23' are formed there so that the cooling air passage is made more complicated as compared with that of Fig. 1(c), thereby the air flow is made turbulent to be activated and heat transfer effect thereof is enhanced. It is to be noted that the arrangements of the turbulators in the leading edge portion as described above with respect to Figs. 1 to 4 are not only for moving blades of gas turbine but naturally are applicable to stationary blades also. In the examples and embodiments described above, the orthogonal turbulators 21 or 24, 25 are provided to the rounded portion of the leading edge portion 3 of the gas turbine cooled blade and the oblique turbulators 22, 23 or 22', 23' are provided to the portion in the rear thereof, thereby the cooling performance thereof is enhanced by approximately 10% as compared with the prior art arrangement in which the oblique turbulators only are provided in the leading edge portion.

Claims: A gas turbine cooled blade comprising turbulators provided in a leading edge portion cooling passage (3), wherein orthogonal turbulators (21;24,25) are provided to a rounded inner wall portion of a transverse cross sectional tip portion of said leading edge portion cooling passage (3) and oblique turbulators (22',23') are provided to a smoothly curved inner wall portion in the rear thereof, wherein said orthogonal turbulators (21;24,25) are arranged so as to be apart from said oblique turbulators (22',23') so as to make no contact with each other, characterized in that said oblique turbulators (22',23') are extended so that terminal ends of said oblique turbulators (22',23') come inside between said orthogonal turbulators (21;24,25). The gas turbine cooled blade according to claim 1, characterized in that said orthogonal turbulators (24,25) provided to the rounded inner wall portion of the transverse cross sectional tip portion of said leading edge portion cooling passage (3) are divided at a central portion thereof so as to provide a gap (d) in said orthogonal turbulators (24,25).

Inventors: AOKI SUNAO, FUKUNO HIROKI, SUENAGA KIYOSHI, TOMITA YASUOKI, AOKI, SUNAO, FUKUNO, HIROKI, SUENAGA, KIYOSHI, TOMITA, YASUOKI, AOKI, Sunao, Takasago Mach. Works of Mitsubishi, FUKUNO, Hiroki, Takasago Mach. Works of Mitsubishi, SUENAGA, Kiyoshi, Takasago Res. Dev. Cen. Mitsub., TOMITA, Yasuoki, Takasago Mach. Works of Mitsubi.
Applicants: MITSUBISHI HEAVY IND LTD, MITSUBISHI HEAVY INDUSTRIES, LTD.
Application year: 1998
Main classification: F01D5
IPC codes: F02C7, F01D5