GAS TURBINE ENGINE

Abstract

Gas turbine engine (1) which features: a turbine (7); a bearing (19) designed in such a way as to keep a rotor of the turbine (7) rotatable; an exhaust gas diffuser (11) connected to a downstream end of the turbine (7), wherein the exhaust gas diffuser (11) has an inner tube (15) and an outer tube (13) such that the inner tube (15) and the outer tube (13) form an annular exhaust gas passage between them; a bearing chamber (23) which is formed radially inside the inner tube (15) and is designed to accommodate the bearing (19); a multitude of hollow struts extending over the exhaust passage and connecting the inner tube (15) and the outer tube (13); an oil inlet passage (33) which extends through one of the plurality of struts (21) and is designed to introduce oil (0l) to be supplied to the storage chamber (23); an oil drain passage (41) extending through one of the plurality of struts (21) and designed to drain the oil (0l) from an oil drain inlet (41a) open on a floor surface of the storage chamber (45); and an oil discharge passage (51) which is designed to discharge a portion of the oil (0l) that has passed through the oil inlet passage (33) in the direction of the oil drain inlet (41a), characterized by that the oil discharge passage (51) branches off radially within the strut (21) at a position in the oil inlet passage (33).

Description

CROSS-REFERENCE TO THE RELATED APPLICATION

[0001] This application claims priority under the Paris Convention to Japanese Patent Application No. 2017-119377, filed on June 19, 2017, the entire disclosure of which is hereby incorporated by reference into this application. BACKGROUND OF THE INVENTION (Field of the invention)

[0002] The present invention relates to a gas turbine engine, particularly to an oil drain structure of a gas turbine engine. (Description of the state of the art)

[0003] As a structure for exhaust gas discharge from a turbine in a gas turbine engine, a dual structure is generally used, consisting of sheet metal outer and inner tubes. The outer and inner tubes forming the exhaust gas diffuser are connected by struts extending in a radial direction (for example, Patent Document 1).

[0004] Such a gas turbine engine with the struts as mentioned above further includes oil passages (oil supply passage and oil drain passage) for a rotor support bearing located on an inner diameter side of the exhaust diffuser, the oil passages extending through the interior of the struts. Thus, the gas turbine engine as a whole can be made compact by effectively utilizing the space within the gas turbine engine. [Related document][Patent specification] [Patent Document 1] JP Laid-Open Publication No. 2015-00211 GB 1 531 705 A discloses a gas turbine design. US 10 082 041 B2 discloses a system for preventing oil leaks in gas turbines. CA 2 676 235 A1 discloses a drainage and cooling system for gas turbine bearings. OVERVIEW OF THE INVENTION

[0005] Since struts designed to pass through the exhaust diffuser cause exhaust gas pressure loss, it is preferable to make the struts as narrow as possible to improve the efficiency of the gas turbine engine. To this end, it is necessary to provide an oil supply passage and an oil drain passage extending through the struts with a small diameter. However, if the oil drain passage is simply designed with a small diameter, oil drainage from a bearing chamber will be impaired.

[0006] To solve the above problem, the present invention has an object to improve the discharge of oil from a bearing chamber in a gas turbine engine having a structure in which an oil supply passage and an oil discharge passage for a bearing pass through the interior of struts, so that the oil discharge passage can be made with a smaller diameter, thereby making the struts with a smaller diameter to improve the efficiency of the gas turbine engine.

[0007] To achieve the object, a gas turbine engine according to the present invention comprises: a turbine; a bearing configured to rotatably support a rotor of the turbine; an exhaust diffuser connected to a downstream end of the turbine, the exhaust diffuser having an inner tube and an outer tube such that the inner pipe and the outer pipe form an annular exhaust passage between them; a bearing chamber formed radially inside the inner tube and configured to receive the bearing; a plurality of hollow struts extending across the exhaust passage and connecting the inner tube and the outer tube; an oil introduction passage extending through one of the plurality of struts and configured to introduce oil to be supplied to the bearing chamber; an oil drain passage extending through one of the plurality of struts and configured to drain the oil from an oil drain inlet open on a bottom surface of the bearing chamber; and an oil discharge passage configured to discharge a portion of the oil that has passed through the oil introduction passage toward the oil drain inlet.

[0008] With this configuration, the oil discharge from the oil discharge passage into the oil discharge passage creates a discharge effect in the oil discharge inlet region of the oil discharge passage, improving oil discharge from the bearing chamber. This means that since the provision of the oil discharge passage makes it possible to design the oil discharge passage with a small diameter without impairing oil discharge, the struts can be made compact. Thus, pressure loss in the exhaust passage is suppressed, enhancing the efficiency of the gas turbine engine.

[0009] In one embodiment of the present invention, the oil discharge passage may be configured to discharge oil from an interior of the bearing chamber toward the oil discharge inlet. With this configuration, oil discharge is further enhanced because oil discharge from the oil discharge passage toward the oil discharge inlet is performed from a position closer to the oil discharge inlet.

[0010] In one embodiment of the present invention, the oil discharge passage may branch at a position in the oil introduction passage radially inward of the strut. With this configuration, since the oil discharge passage branches at a position radially inward of the strut, that is, a position closer to the bearing chamber, it is possible to improve oil discharge while preventing an increase in the complexity or size of the oil supply / discharge structure as a whole.

[0011] In one embodiment of the present invention, the gas turbine engine may include an upper oil supply passage branching from the oil introduction passage and configured to supply oil from above the rotor to the bearing chamber, and a lower oil supply passage branching from the oil introduction passage and configured to supply oil from below the rotor to the bearing chamber. With this configuration, arranging the oil supply passages above and below the rotor enables the uniform supply of oil in the circumferential direction to the bearing chamber. Furthermore, providing the oil supply passages and the oil discharge passage as separate passages enables uniform supply in the circumferential direction and improves oil drainage.

[0012] In one embodiment of the present invention, a rear end of the rotor may be located forward relative to an axial position of the oil introduction passage, and the oil discharge passage may extend along an axis of the oil introduction passage. This configuration enables a simplification of the structure from the oil introduction passage to the oil discharge passage.

[0013] In one embodiment of the present invention, the oil introduction passage, the oil discharge passage, and the oil drain passage may extend in a vertical direction and be arranged concentrically with each other. This configuration enables the utilization of gravity to effectively discharge oil from the oil introduction passage via the oil discharge passage to the oil drain passage, providing a higher discharge effect.

[0014] In one embodiment of the present invention, a rear end of the rotor may be located rearward relative to an axial position of the oil introduction passage, and the oil discharge passage may extend to bypass the rotor. This configuration enables the provision of an oil discharge passage for improving oil drainage in a gas turbine engine having a structure in which, in the prior art, the rear end of a rotor is located rearward relative to an axial position of an oil introduction passage, while minimizing modification of the known structure.

[0015] In one embodiment of the present invention, the rotor may include a rotor cover covering the rear end of the rotor, and at least a portion of the oil drainage passage may be formed in the rotor cover. This configuration enables the provision of an oil drainage passage by utilizing the rotor cover in the gas turbine engine having a structure including the rotor cover to improve oil drainage, while preventing an increase in the number of components.

[0016] In one embodiment of the present invention, the gas turbine engine may include an upper oil supply passage branched from the oil introduction passage and configured to supply oil from above the rotor to the bearing chamber, and a lower oil supply passage branched from the oil introduction passage and configured to supply oil from below the rotor to the bearing chamber, and the oil discharge passage may be provided branching from the lower oil supply passage. With this configuration, oil can be introduced into the oil discharge passage using the lower oil supply passage in the gas turbine engine having the lower gas supply passage to enhance oil discharge, while preventing an increase in the complexity or size of the oil supply / discharge structure as a whole.

[0017] In one embodiment of the present invention, the oil discharge passage may have a downstream end formed with an accelerating portion configured to accelerate the oil. Specifically, for example, the accelerating portion may have a shape with a diameter gradually decreasing from an upstream side toward a downstream side, or the accelerating portion may be configured such that the accelerating portion has a smaller channel cross-sectional area than that on an upstream side of the accelerating portion and has a longer channel perimeter in cross section than that on the upstream side of the accelerating portion. Such a configuration of the oil discharge passage makes it possible to achieve a higher discharge effect, thereby further improving oil discharge.

[0018] In one embodiment of the present invention, the oil drain passage may have an upstream end portion formed with a constricted portion. Such a configuration of the oil drain passage enables a higher discharge effect to be achieved, thereby further improving oil drainage.

[0019] The present invention encompasses any combination of at least two features disclosed in the claims and / or the description and / or the drawings. In particular, any combination of two or more of the appended claims must also be understood as falling within the scope of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention will be better understood from the following description of preferred embodiments thereof in conjunction with the accompanying drawings. However, the embodiments and the drawings are for the purpose of illustration and explanation only and are not to be construed as limiting the scope of the present invention in any way, which scope is defined by the appended claims. In the accompanying drawings, like reference numerals are used to designate like parts throughout the different views. Fig. 1 is a partially broken side view of a gas turbine engine according to a first embodiment of the present invention; Fig. 2 is an enlarged cross-sectional view of an area around an exhaust diffuser of the Fig. 1 shown gas turbine engine; Fig. 3 is a schematic cross-sectional view showing a variant of an oil discharge passage used in the Fig. 2 shown gas turbine engine; Fig. 4 is a schematic front view showing a further variant of the oil discharge passage in the Fig. 2 shown gas turbine engine; Fig. 5 is a schematic cross-sectional view of the oil discharge passage and the oil drain passage shown in Fig. 2 shown gas turbine engine; Fig. 6 is a schematic cross-sectional view showing a variant of an acceleration part of the Fig. 5 shown oil discharge passage; Fig. 7 is a schematic cross-sectional view showing a further variant of the acceleration part of the Fig. 5 shown oil discharge passage; Fig. 8 is a schematic cross-sectional view showing a variant of the oil discharge passage and the oil drain passage in the Fig. 2 shown gas turbine engine; Fig. 9 is an enlarged cross-sectional view of an area around an exhaust diffuser of a gas turbine engine according to a second embodiment of the present invention; Fig. 10 is an enlarged cross-sectional view of an area around an exhaust diffuser of a gas turbine engine according to a third embodiment of the present invention; and Fig. 11 is a schematic cross-sectional view showing a variant of the Fig. 10 shown gas turbine engine. DESCRIPTION OF THE EMBODIMENTS

[0021] Embodiments of the present invention will be described below with reference to the drawings, but the present invention should not be construed as being limited to these embodiments.

[0022] Fig. 1 is a partially cutaway side view of a gas turbine engine (hereinafter simply referred to as a "gas turbine") according to a first embodiment of the present invention. The gas turbine 1 is configured to compress air A using a compressor 3, introduce the air into a combustor 5, inject fuel F into the combustor 5 to combust the fuel with the compressed air A, and rotate a turbine 7 using high-temperature and high-pressure combustion gas G obtained thereby. The turbine 7 is configured to drive a load (not shown) such as a generator connected via a rotor 9. In the following description, a side of the compressor 3 in an axial direction of the gas turbine 1 is referred to as "front" or "forward," and a side of the turbine 7 is referred to as "rear" or "backward."Even when a term is used as "axis" or "axial," it refers to an axis C1 of the gas turbine. In essentially the same way, when terms are used as "radial direction" or "radial" and "circumferential direction" or "circumferential," these refer to a radial direction or a circumferential direction of the gas turbine and components arranged concentrically with the gas turbine, respectively.

[0023] In the turbine 7, an outlet is connected to an exhaust diffuser 11 configured to discharge exhaust gas EG from the turbine 7 to the outside. The exhaust diffuser 11 is formed by an outer pipe 13 and an inner pipe 15 arranged concentrically with each other. That is, the outer pipe 13 and the inner pipe 15 define an annular space between them, forming an exhaust passage 17 through which the exhaust gas EG passes. The outer pipe 13 and the inner pipe 15 are castings made, for example, of a metal material with excellent thermal resistance. Methods for manufacturing the outer pipe 13 and the inner pipe 15 are not limited to casting, and the outer pipe 13 and the inner pipe 15 may be made, for example, of a sheet material made of the aforementioned metal material. The rotor 9 is supported for radial rotation in the exhaust diffuser 11 by a bearing 19.

[0024] As in Fig. As shown in Figure 2, the outer tube 13 and the inner tube 15 are connected by struts 21. There are a plurality of struts 21 arranged in a circumferential direction of the exhaust diffuser 11. The struts 21 extend across the exhaust passage 17. In the illustrated example, the struts 21 extend in a radial direction of the exhaust diffuser 11. Alternatively, the struts 21 may extend inclined relative to the radial direction of the exhaust diffuser 11. Each strut 21 is formed as a hollow member.

[0025] A bearing chamber 23, which is configured to accommodate the bearing 19, is defined radially inside the inner tube 15 of the exhaust diffuser 11. The bearing chamber 23 is defined as a space in a bearing housing 25 having a bottomed, substantially cylindrical shape. In the illustrated example, the bearing housing 25 is formed by a bearing retainer 27 having a substantially cylindrical shape and a rear wall 29 having a disc shape. The bearing retainer 27 is fixed to an inner peripheral surface of the inner tube 15. The bearing 19 is fixed to an inner peripheral surface of the bearing retainer 27. That is, the bearing 19 is held by the inner tube 15 via the bearing retainer 27. The rear wall 29 is connected to a rear end of the bearing retainer 27 to close the rear part of the bearing chamber 23.The bearing chamber 23 has a front end with an annular sealing element 31 configured to slidably seal a gap between an outer peripheral surface of the rotor 9 and the bearing holder 27. The sealing element 31 is connected to a front end portion of the bearing holder 27.

[0026] Next, an oil supply structure and an oil discharge structure for oil OL to be supplied to the bearing chamber 23 will be described. An oil supply system for supplying oil to the bearing chamber 23 includes an oil introduction passage 33 configured to introduce the oil OL from outside a casing H of the gas turbine 1 into the bearing support 27, and an oil supply passage 35 branched from the oil introduction passage 33 and configured to supply the oil OL to the bearing chamber 23. The oil introduction passage 33 extends through one of the plurality of struts 21. In the following description, the strut 21 through which the oil introduction passage 33 passes may also be referred to as "oil introduction strut 21A" for convenience.

[0027] Specifically, the portion of the oil introduction passage 33 passing through one of the plurality of struts 21 is formed by a tubular oil introduction line 37. A portion of an outer peripheral wall of the bearing housing 25 located on an inner diameter side of the strut 21 is formed with an oil introduction recess 39, which is the most downstream portion of the oil introduction passage 33. The oil introduction recess 39 is formed to be recessed radially inward from the outer peripheral surface of the bearing retainer 27. The oil introduction recess 39 is connected to a downstream end portion (i.e., an inner diameter-side end portion) of the oil introduction line 37. Thus, the oil introduction recess 39 of the bearing retainer 27 forms the most downstream portion of the oil introduction passage 33.

[0028] An oil drain system for draining oil from the bearing chamber 23 includes an oil drain passage 41 configured to drain the oil OL in the bearing chamber 23 from the bearing chamber 23 to the outside of the casing H of the gas turbine 1. The oil drain passage 41 is formed by a tubular oil drain pipe 43. The oil drain passage 41 is provided such that its oil drain inlet 41a is open to a bottom surface 45 of the bearing chamber 23. Specifically, the bottom surface 45 of the bearing chamber 23 is formed on an inner peripheral portion in a lower region of the bearing housing 25. In the illustrated example, the bottom surface 45 is formed as a flat surface generally inclined downward from the bearing 19 side toward the oil drain passage 41 side (rearward in the illustrated example). However, the floor surface 45 does not necessarily have to be a flat surface.

[0029] In the present embodiment, since the oil is drained using gravity, no driving device such as a pump is provided for draining the oil. However, a driving device such as a pump may be provided for draining the oil in the oil drain system. The oil drain passage 41 extends to pass through one strut 21 of the plurality of struts 21. In the following description, the strut 21 through which the oil drain passage 41 passes may also be referred to as "oil drain strut 21B" for convenience.

[0030] In the present embodiment, an oil discharge passage 51 is provided between the oil supply system and the oil drain system. The oil discharge passage 51 is configured to discharge a portion of the oil OIL that has passed through the oil introduction passage 33 toward the oil drain inlet 41a. In the illustrated example, the oil discharge passage 51 is formed from a tubular discharge line 53. The oil discharge passage 51 branches off at a position in the oil introduction passage 33 radially inward of the oil drain stay 21A. In the present embodiment, the oil discharge passage 51 is arranged to discharge the oil OIL from inside the bearing chamber 23 toward the oil drain inlet 41a. That is, at least one discharge port 51a of the oil discharge passage 51 is arranged in the bearing chamber 23.

[0031] In the illustrated example, the rotor 9 is arranged such that its rear end is located forward relative to the position of the oil introduction passage 33 in the direction of the axis C1. The oil discharge passage 51 is provided so as to extend along the axis C2 of the oil introduction passage 33. The discharge port 51a, which is an opening at a downstream end of the oil discharge passage 51, is located below the rotor 9. Specifically, the discharge port 51a is located below a lowermost part B of a sliding surface of the seat member 31 and above the oil drain inlet 41a. The position (a position in the vertical direction) of the lowermost part B of the sliding surface of the seal member 31 is an upper limit position of an oil surface of the oil OL accumulated in the bearing chamber 23.

[0032] In the present embodiment, both the oil introduction passage 33 and the oil discharge passage 51 extend in the vertical direction. The discharge line 53 constituting the oil discharge passage 51 is provided so as to branch from the downstream end of the oil introduction recess 39 (that is, connected to the downstream end of the oil introduction recess 39), and the oil discharge passage 51 is arranged concentrically with the oil introduction passage 33. Such a configuration makes it possible to simplify the structure from the oil introduction passage 33 to the oil discharge passage 51. Furthermore, the oil drain line 43 also extends in the vertical direction and is arranged concentrically with the oil introduction passage 33 and the oil discharge passage 51. That is, the discharge port 51a of the oil discharge passage 51 and the oil drain inlet 41a of the oil drain passage 41 are arranged to share the axis C2.

[0033] In the rotor 9, the rear end thereof may be located rearward relative to the position of the oil introduction passage 33 in the direction of the axis C1. In this case, the oil discharge passage 51 may be provided to bypass the rotor 9 so that the discharge port 51a is located above the oil discharge inlet 41a. In this case, the Fig. 3, for example, the oil discharge passage 51 may be provided such that it bypasses the rotor 9 in the direction of the axis C1, ie, to extend further rearward relative to the rear end of the rotor 9. Alternatively, as shown in Fig. 4, the oil discharge passage 51 may be provided so as to bypass the rotor 9 in the radial direction. In the illustrated example, the oil discharge passage 51 bypasses the rotor 9 such that the oil discharge passage 51 is curved along the shape of the outer peripheral surface of the rotor 9 (in a C-shape). Note that the configuration of the oil discharge passage 51 bypassing the rotor 9 in the radial direction is not limited to this example.

[0034] As in Fig. 5, in the present embodiment, the downstream end portion of the oil discharge passage 51 is formed with an accelerating part 55 configured to accelerate the oil OL. The term "accelerating the oil" used here means that the structure of the accelerating part 55 itself causes the oil OL to be accelerated beyond the acceleration under the influence of gravity. In the illustrated example, the accelerating part 55 has a shape with a diameter gradually decreasing from an upstream side to a downstream side. However, the configuration of the accelerating part 55 is not limited to the example of Fig. 5, as long as the acceleration part is capable of accelerating the oil OL toward the discharge port 51a. For example, the acceleration part 55 may be formed such that the acceleration part has a smaller channel cross-sectional area than that of the upstream side of the acceleration part 55 and has a longer channel perimeter in cross section than that of the upstream side of the acceleration part 55. In particular, the acceleration part 55 may, for example, have a plurality of through holes as shown in Fig. 6, or a cross-section with a petal shape, as in Fig. 7 have shown.

[0035] Thus, the acceleration part 55 provided at the downstream end portion of the oil discharge passage 51 enables a high discharge effect to be produced in the region of the oil discharge inlet 41a of the oil discharge passage 41 to improve the discharge of oil from the bearing chamber.

[0036] As in Fig. As shown in FIG. 5, in the present embodiment, the oil drain passage 41 has an upstream end portion formed with a constriction portion 57. That is, the upstream end portion of the oil drain passage 41 has a channel cross-sectional area that gradually narrows from the oil drain inlet 41a toward the constriction portion 57 and widens from the constriction portion 57 toward a downstream side. Thus, the constriction portion 57 provided at the upstream end portion of the oil drain passage 41 enables a high discharge effect to be achieved to further improve oil discharge.

[0037] It should be noted that the acceleration part 55 does not necessarily have to be provided at the downstream end portion of the oil discharge passage 51. As shown in Fig. As shown in Figure 8, the downstream end portion of the oil discharge passage 51 may have the same shape and dimension as the remaining portion of the oil discharge passage 51. That is, the discharge port 51a of the oil discharge passage 51 may simply be formed as a hole or opening. Furthermore, the constriction portion 57 does not necessarily need to be provided at the upstream end portion of the oil discharge passage 41. Even if the acceleration portion 55 and the constriction portion 57 are omitted, the oil OL is discharged from the discharge port 51a toward the oil discharge inlet 41a of the oil discharge passage 41, thus creating a discharge effect in the region of the oil discharge inlet 41a of the oil discharge passage 41 to enhance the discharge of oil from the bearing chamber 23. Although Fig. 8 shows an example in which the acceleration part is not provided in the oil discharge passage 51 and the constriction part is not provided in the oil discharge passage 41, only one of the acceleration part and the constriction part may be omitted.

[0038] As described above, the discharge port 51a of the oil discharge passage 51 and the oil discharge inlet 41a of the oil discharge passage 41 may be provided to share the same axis C2, so that a high discharge effect can be achieved. However, as long as the oil discharge passage 51 is arranged to discharge the oil OL toward the oil discharge inlet 41a, it is not necessary to arrange the discharge port 51a of the oil discharge passage 51 to have the same axis as that of the oil discharge inlet 41a.

[0039] Furthermore, as with reference to Fig. 2, the discharge port 51a of the oil discharge passage 51 is preferably provided in the bearing chamber 23, more preferably below the rotor 9, and even more preferably below the lowermost part B of the sliding surface of the seal member 31, so that the discharge port 51a of the oil discharge passage 51 may be provided adjacent to the oil discharge inlet 41a but not in the oil discharge passage 41, thereby achieving a high discharge effect. However, the position of the discharge port 51a of the oil discharge passage 51 is not limited to these positions. For example, the discharge port 51a may be located above the bearing chamber 23 or below the bearing chamber 23, that is, below the oil discharge inlet 41a (in the oil discharge passage 41).

[0040] In the gas turbine 1 according to the first embodiment described above, the discharge of oil OL from the oil discharge passage 51 formed in Fig. 2, the oil discharge passage 41 produces a discharge effect in the region of the oil discharge inlet 41a of the oil discharge passage 41 to enhance the discharge of oil from the bearing chamber 23. That is, the provision of the oil discharge passage 51 allows the oil discharge passage 41 to be formed with a smaller diameter without impairing the discharge of oil, thereby making the struts 21 compact. Thus, the pressure loss in the exhaust passage 17 is suppressed to enhance the efficiency of the gas turbine 1.

[0041] Fig. 9 shows a gas turbine 1 according to a second embodiment of the present invention. This gas turbine 1 has common points with the first embodiment in that the gas turbine has basic features similar to those of the gas turbine 1, including the exhaust diffuser 11 and the struts 21, and the oil discharge passage 51. However, it differs from the first embodiment mainly in specific features of the oil supply system and the oil discharge system, including the oil discharge passage 51. Hereinafter, explanations will be given mainly with respect to differences from the first embodiment, and descriptions of common points will not be repeated.

[0042] Specifically, in the present embodiment, the rear end of the rotor 9 is located rearward relative to the position of the oil introduction line 37 in the direction of the axis C1, and the oil discharge passage 51 extends to bypass the rotor 9. Specifically, at least a part of the oil discharge passage 51 is formed in a rotor cover 61 that covers the rear end of the rotor 9. In the illustrated example, the rear wall 29 constituting the bearing housing 25 is used as the rotor cover 61. That is, in this example, the oil discharge passage 51 extends to bypass the rotor 9 in the direction of the axis C1.

[0043] In the illustrated example, the oil discharge passage 51 includes a branch part 51b branching rearward at the downstream end portion of the oil introduction passage 33; an intermediate part 51c extending downward from a rear end of the branch part 51b in the rear wall 29 of the bearing housing 25; a downstream part 51d extending forward from a downstream end (i.e., lower end) of the intermediate part 51c, that is, extending toward the bearing 19 side in the outer peripheral wall of the bearing housing 25; and a discharge part 51e extending downward from the downstream part and having a lowermost end formed with a discharge port 51a.

[0044] In this embodiment, the downstream end portion of the oil discharge passage 51 is similarly formed with an accelerating part 55 configured to accelerate the oil OL. Furthermore, the upstream end portion of the oil drain passage 41 is formed with a constricting part 57. However, as described in the first embodiment, the accelerating part 55 in the oil discharge passage 51 and / or the constricting part 57 in the oil drain passage 41 may be omitted in this embodiment as well.

[0045] In substantially the same manner as in the first embodiment, in the gas turbine 1 according to this embodiment, the discharge of oil OL from the oil discharge passage 51 into the oil discharge passage 41 causes a discharge effect in the region of the oil discharge inlet 41a of the oil discharge passage 41 to enhance the discharge of oil from the bearing chamber 23. Consequently, it is possible to form the oil discharge passage 41 with a smaller diameter and make the struts 21 compact to enhance the efficiency of the gas turbine 1. Furthermore, the gas turbine 1 according to this embodiment enables the provision of the oil discharge passage 51 in the gas turbine engine having a structure in which the rear end of the rotor 9 is located rearward relative to the axial position of the oil introduction passage 33 according to the prior art to enhance the discharge of oil, while minimizing change in the known structure.In particular, this configuration enables the provision of the oil discharge passage 51 by utilizing the rotor cover 61 in the gas turbine 1 having a structure including the rotor cover 61 to improve oil discharge, while suppressing an increase in the number of components.

[0046] Fig. 10 shows a gas turbine 1 according to a third embodiment of the present invention. This gas turbine 1 has common points with the first embodiment in that the gas turbine has basic features similar to those of the gas turbine 1, including the exhaust diffuser 11 and the struts 21, and the oil discharge passage 51. However, it differs from the first embodiment mainly in specific features of the oil supply system and the oil discharge system, including the oil discharge passage 51. Hereinafter, explanations will be given mainly with respect to differences from the first embodiment, and descriptions of common points will not be repeated.

[0047] Specifically, in the gas turbine 1 according to this embodiment, the oil supply system includes, in addition to the oil supply passage (main oil supply passage) 35, an upper oil supply passage 63 branched from the oil introduction passage 33 and configured to supply the oil OL from above the rotor 9 to the bearing chamber 23, and a lower oil supply passage 65 branched from the oil introduction passage 33 and configured to supply the oil OL from below the rotor 9 to the bearing chamber 23. Further, the oil discharge passage 51 is provided to branch from the lower oil supply passage 65.

[0048] The lower oil supply passage 65 branches off rearward at the downstream end of the oil introduction passage 33 and extends to bypass the rotor 9, and is configured to supply the oil OL to the bearing 19 from a position below the rotor 9 and inside the bearing housing 25. Specifically, the lower oil supply passage 65 includes a branch portion 65a branching off rearward at the downstream end portion of the oil introduction passage 33; an intermediate portion 65b extending downward from a rear end of the branch portion 65a in the rear wall 29 of the bearing housing 25; and a downstream portion 65c extending forward, that is, toward the bearing 19, from a downstream end (i.e., lower end) of the intermediate portion 65b in the outer peripheral wall of the bearing housing 25. The oil discharge passage 51 branches downward at a middle part of the downstream part 65c of the lower oil supply passage 65.In the illustrated example, the second upper oil supply passage 63 is provided so as to branch forward at a central part of the intermediate part.

[0049] In this embodiment, the downstream end portion of the oil discharge passage 51 is also formed with an accelerating part 55 configured to accelerate the oil OL. Furthermore, the upstream end portion of the oil drain passage 41 is formed with a constricting part 57. However, as described in the first embodiment, the accelerating part 55 in the oil discharge passage 51 and / or the constricting part 57 in the oil drain passage 41 may be omitted in this embodiment as well.

[0050] In substantially the same manner as in the first embodiment, in the gas turbine 1 according to this embodiment, the discharge of oil OL from the oil discharge passage 51 into the oil discharge passage 41 causes a discharge effect in the region of the oil discharge inlet 41a of the oil discharge passage 41 to enhance the discharge of oil from the bearing chamber 23. Consequently, it is possible to form the oil discharge passage 41 with a smaller diameter and make the struts 21 compact, thus enhancing the efficiency of the gas turbine 1. Furthermore, in this embodiment, the oil supply system of the gas turbine 1, which includes the upper oil supply passage 63 and the lower oil supply passage 65, enables the uniform supply of oil in the circumferential direction to the bearing 19.In addition, the oil discharge passage 51 provided so as to branch from the lower oil supply passage 65 enables the lower oil supply passage 65 to be used to introduce the oil OL into the oil discharge passage 51, so that the discharge of oil can be improved while preventing an increase in the complexity or size of the oil supply / discharge structure as a whole.

[0051] It should be noted that even if the oil supply system of the gas turbine 1 has the upper oil supply passage 63 and the lower oil supply passage 65, the oil discharge passage 51 may branch off from the oil introduction passage 33, as shown in Fig. 11 is shown as a variant of this embodiment. That is, in this example, the oil discharge passage 51 is provided as a separate passage that has no common part with both the upper oil supply passage 63 and the lower oil supply passage 65. In the illustrated example, the oil discharge passage 51 is formed to branch off from the oil introduction passage 33 and bypass the rotor 9 in the direction of the axis C1. However, the configuration of the oil discharge passage 51, which is provided as a separate passage from both the upper oil supply passage 63 and the lower oil supply passage 65, is not limited to this example. With this configuration, the respective oil supply passages 63, 65 provided at the top and bottom enable the uniform supply of oil in the circumferential direction to the bearing chamber 23.Furthermore, since the oil supply passages 63, 65 and the oil discharge passage 51 are provided as independent passages, it is possible to supply the oil uniformly in the circumferential direction and to improve the discharge of oil.

[0052] Furthermore, in the example of Fig. 11, the branching point (connection point) where the oil discharge passage 51 branches from the oil supply passage 33 is located upstream of the branching point where the upper oil supply passage 63 and the lower oil supply passage 65 branch from the oil introduction passage 33. This configuration enables more reliable, uniform supply of oil in the circumferential direction even when the oil discharge passage 51 is provided. However, the positional relationship between the branching points where the respective oil passages branch from the oil introduction passage 33 is not limited to this example.

[0053] It should be noted that while a plain bearing is used as the bearing 19 in the first and second embodiments, the bearing 19 may also be a rolling bearing. Although a rolling bearing is used as the bearing 19 in the third embodiment, the bearing 19 may also be a plain bearing. Similarly, while a single bearing 19 is used in these embodiments, a plurality of bearings may also be used. In such a case, all of the bearings 19 may be plain bearings or rolling bearings, or a combination of these bearings.

[0054] With reference to Fig.2 as a characteristic example, in any of the above-described embodiments, the oil introduction strut 21A and the oil discharge strut 21B are provided at opposite positions in the circumferential direction radially outside the bearing chamber 23. Specifically, the oil introduction strut 21 extends upward in the vertical direction, and the oil discharge strut 21B extends downward in the vertical direction. Such a configuration enables the utilization of gravity to effectively supply and discharge oil. However, the positions of the oil supply strut 21A and the oil discharge strut 21B are not limited to these examples. Specifically, for example, the struts 21 located downstream of the position of the bearing chamber 23 in the direction of the axis C1 in the exhaust diffuser 11 can be used as the oil supply strut and the oil discharge strut.Furthermore, the oil supply strut and the oil drain strut need not necessarily be provided as separate struts 21. For example, a single strut 21 extending downward in the vertical direction can be used as a common strut for supplying oil and draining oil.

[0055] The present invention has been fully described in conjunction with the preferred embodiments with reference to the drawings. However, various additions, modifications, or deletions may be made without departing from the scope of the invention. Therefore, such modifications are also within the scope of the invention.

Claims

[1] Gas turbine engine (1) comprising: a turbine (7); a bearing (19) configured to rotatably support a rotor of the turbine (7); an exhaust diffuser (11) connected to a downstream end of the turbine (7), the exhaust diffuser (11) comprising an inner tube (15) and an outer tube (13) such that the inner tube (15) and the outer tube (13) form an annular exhaust passage therebetween; a bearing chamber (23) formed radially inside the inner tube (15) and adapted to receive the bearing (19); a plurality of hollow struts extending across the exhaust passage and connecting the inner tube (15) and the outer tube (13); an oil introduction passage (33) extending through one of the plurality of struts (21) and configured to introduce oil (0l) to be supplied to the bearing chamber (23); an oil drain passage (41) extending through one of the plurality of struts (21) and configured to drain the oil (0l) from an oil drain inlet (41a) open on a bottom surface of the bearing chamber (45); and an oil discharge passage (51) designed to discharge part of the oil (0l) that has passed through the oil introduction passage (33) towards the oil discharge inlet (41a), characterized by , that the oil discharge passage (51) branches off at a position in the oil introduction passage (33) radially inside the strut (21). [2] Gas turbine engine (1) according to claim 1, wherein the oil discharge passage (51) is formed to discharge the oil (0l) from an interior of the bearing chamber (23) toward the oil discharge inlet (41a). [3] Gas turbine engine (1) according to claim 2, comprising: an upper oil supply passage (63) branching off from the oil introduction passage (33) and configured to supply the oil (0l) from above the rotor (9) to the bearing chamber (23); and a lower oil supply passage (65) branching off from the oil introduction passage (33) and configured to supply the oil (0l) from below the rotor (9) to the bearing chamber (23). [4] A gas turbine engine (1) according to claim 2 or 3, wherein a rear end of the rotor (9) is located forward relative to an axial position of the oil introduction passage (33), and the oil discharge passage (51) extends along an axis of the oil introduction passage (33). [5] Gas turbine engine (1) according to claim 4, wherein the oil introduction passage (33), the oil discharge passage (51) and the oil drain passage (41) extend in a vertical direction and are arranged concentrically with each other. [6] A gas turbine engine (1) according to claim 2 or claim 3, wherein a rear end of the rotor (9) is located rearward relative to an axial position of the oil introduction passage (33) and the oil discharge passage (51) extends to bypass the rotor (9). [7] Gas turbine engine (1) according to claim 6, wherein the rotor (9) has a rotor cover covering the rear end of the rotor, and at least a part of the oil discharge passage (51) is formed in the rotor cover [8] Gas turbine engine (1) according to claim 1 or 2, comprising: an upper oil supply passage (63) branching off from the oil introduction passage (33) and configured to supply the oil (0l) from above the rotor (9) to the bearing chamber (23); and a lower oil supply passage (65) branching off from the oil introduction passage (33) and configured to supply the oil (0l) from below the rotor (9) to the bearing chamber (23), wherein the oil discharge passage (51) is provided such that it branches off from the lower oil supply passage (65). [9] A gas turbine engine (1) according to any one of claims 1 to 8, wherein a downstream end of the oil discharge passage (51) is formed with an acceleration part configured to accelerate the oil (0l). [10] A gas turbine engine (1) according to claim 9, wherein the acceleration part has a shape with a diameter gradually decreasing from an upstream side toward a downstream side. [11] A gas turbine engine (1) according to claim 9, wherein the acceleration part is formed to have a smaller channel cross-sectional area than that on an upstream side of the acceleration part and to have a longer channel perimeter in cross section than that on the upstream side of the acceleration part. [12] A gas turbine engine (1) according to any one of claims 1 to 11, wherein an upstream end portion of the oil drain passage (41) is formed with a constriction part.

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