Multistage radial turbine

Abstract

A multi-stage radial turbine (1) according to one embodiment includes a rotating shaft (2), a first impeller (3A) and a second impeller (3B) attached to the rotating shaft (2) in opposite directions, and a turbine body (4). The turbine body (4) includes a first introduction chamber (52) positioned around the first impeller (3A), a second introduction chamber (55) positioned around the second impeller (3B), and a plurality of inflow ports (41) arranged in the circumferential direction. A plurality of supply lines equipped with supply valves is connected to the respective inflow ports (41). Furthermore, the turbine body (4) includes an annular intermediate chamber (54) into which a working fluid decompressed by the first impeller (3A) flows, and a plurality of intermediate flow paths (7) that communicate the intermediate chamber (54) and the second introduction chamber (55) and are arranged in the circumferential direction centered on the axis of the rotating shaft (2).

Description

Title of Invention: MULTISTAGE RADIAL TURBINE Technical Field

[0001] The present disclosure relates to a multistage radial turbine. Background Art

[0002] Conventionally, multistage radial turbines that absorb power from a working fluid are known. For example, Patent Literature 1 discloses a multistage radial turbine in which a first bladed wheel and a second bladed wheel are mounted to a rotating shaft. Each of the first bladed wheel and the second bladed wheel includes a concave curved surface that guides a radial flow into an axial flow.

[0003] Specifically, in the multistage radial turbine of Patent Literature 1, an annular inlet passage is positioned around the first bladed wheel, and a working fluid is supplied radially inward from the inlet passage to the first bladed wheel. The working fluid whose pressure has been reduced by the first bladed wheel is led to the second bladed wheel via a connecting passage. The connecting passage converts the axial flow from the first bladed wheel into a radially outward flow, and then converts the radially outward flow into a radially inward flow to the second bladed wheel. Citation List Patent Literature

[0004] PTL 1: Japanese Laid-Open Patent Application Publication No. 2011-132877 Summary of Invention Technical Problem

[0005] In a multistage radial turbine, during rated operation in which a working fluid flows in at a design flow rate, the pressure ratio between an inlet pressure and an outlet pressure of the working fluid is at a design point, and the turbine efficiency is high. On the other hand, in a multistage radial turbine, part-load operation may be performed in a low flow rate range in which the flow rate of the working fluid is lower than the design flow rate. Also during the part-load operation, operation at a high pressure ratio close to the design point is desired. However, with a conventional structure, it is difficult to obtain high turbine efficiency by maintaining a sufficient pressure ratio during the part-load operation.

[0006] Further, in a multistage radial turbine, a back-to-back structure in which the facing direction of some bladed wheels is opposite to that of other bladed wheels may be adopted to reduce a thrust load exerted on the rotating shaft. Also in such a back-to-back structure, it is desired to obtain high turbine efficiency by maintaining a sufficient pressure ratio during partload operation.

[0007] In view of the above, an object of the present disclosure is to provide a multistage radial turbine that makes it possible to, in a back-to-back structure, obtain high turbine efficiency by maintaining a sufficient pressure ratio during part-load operation. Solution to Problem

[0008] The present disclosure provides a multistage radial turbine that absorbs power from a working fluid, the multistage radial turbine including: a rotating shaft; a first bladed wheel mounted to the rotating shaft; a turbine body including a first introduction chamber and inlets, the first introduction chamber being positioned around the first bladed wheel, the inlets communicating with the first introduction chamber and being located in a circumferential direction about a center axis of the rotating shaft; supply valves located on respective supply lines connected to the respective inlets; and a second bladed wheel facing in a direction opposite to a direction in which the first bladed wheel faces, the second bladed wheel being mounted to the rotating shaft, wherein the turbine body includes: a second introduction chamber positioned around the second bladed wheel; an annular intermediate chamber into which the working fluid whose pressure has been reduced by the first bladed wheel flows; and intermediate passages through which the intermediate chamber and the second introduction chamber communicate with each other, the intermediate passages being located in the circumferential direction about the center axis of the rotating shaft. Advantageous Effects of Invention

[0009] The present disclosure provides a multistage radial turbine that makes it possible to, in a back-to-back structure, obtain high turbine efficiency by maintaining a sufficient pressure ratio during part-load operation. Brief Description of Drawings

[0010] [FIG. 1] FIG. 1 is a sectional view of a multistage radial turbine according to one embodiment. [FIG. 2] FIG. 2 is a sectional view taken along line II-II of FIG. 1. [FIG. 3] FIG. 3 is a sectional view taken along line III-III of FIG. 1. [FIG. 4] FIG. 4 is a sectional view taken along line IV-IV of FIG. 1. [FIG. 5] FIG. 5 is a sectional view of a multistage radial turbine according to a variation, corresponding to FIG. 4. Description of Embodiments

[0011] FIG. 1 shows a multistage radial turbine 1 according to one embodiment. The multistage radial turbine 1 absorbs power from a working fluid. The absorbed power is utilized in, for example, a power generator, a blower, an oil pump, or an oil brake. The working fluid is not particularly limited to a specific type of fluid. For example, the working fluid may be cryogenic liquid hydrogen, LNG (Liquefied Natural Gas), liquid nitrogen, or liquid oxygen, or may be room-temperature oil.

[0012] Specifically, the multistage radial turbine 1 includes: a rotating shaft 2; and a first bladed wheel 3A and a second bladed wheel 3B, which are mounted to the rotating shaft 2. The multistage radial turbine 1 further includes a turbine body 4, which supports a rotor via a bearing in a rotatable manner. The rotor includes the rotating shaft 2, the first bladed wheel 3A, and the second bladed wheel 3B. As shown in FIG. 2, the multistage radial turbine 1 further includes supply lines 12 and supply valves 13. The supply lines 12 are branched off from a source line 11, which is the supply source of the working fluid. The supply valves 13 are located on the respective supply lines 12.

[0013] The rotating shaft 2 penetrates the first bladed wheel 3A and the second bladed wheel 3B. A lock nut 21, which serves to hold the first bladed wheel 3A and the second bladed wheel 3B, is fixed to the distal end of the rotating shaft 2. In the description below, for the sake of convenience of description, the axial direction of the rotating shaft 2 toward the distal end is referred to as upper, and the axial direction of the rotating shaft 2 toward the opposite side is referred to as lower. In the present embodiment, the first bladed wheel 3A is located at a lower position, and the second bladed wheel 3B is located at an upper position. Alternatively, the position of the first bladed wheel 3A and the position of the second bladed wheel 3B may be switched with each other.

[0014] The multistage radial turbine 1 adopts a back-to-back structure in which the first bladed wheel 3A and the second bladed wheel 3B are mounted to the rotating shaft 2 such that they face in opposite directions to each other. That is, the back surface of the first bladed wheel 3A and the back surface of the second bladed wheel 3B face each other.

[0015] Each of the first bladed wheel 3A and the second bladed wheel 3B includes: a hub including a concave curved surface that guides a radial flow into an axial flow; and blades protruding from the concave curved surface. Between the blades, there is a bent passage that is open in both radial and axial directions. In each bladed wheel, the side toward which the axial opening of the bent passage is open is the front side, and the side opposite thereto is the back side. That is, the aforementioned back surface of each bladed wheel is the surface facing the side opposite the axial opening of the bent passage.

[0016] The turbine body 4 includes: a housing 5 surrounding the first bladed wheel 3A and the second bladed wheel 3B; and a casing 6 accommodating the housing 5. The casing 6 includes: a cylindrical portion extending in the axial direction of the rotating shaft 2; and a closing portion that closes the upper opening of the cylindrical portion. The outer peripheral surface of the housing 5 is in contact with the cylindrical portion of the casing 6, and the upper end surface of the housing 5 is in contact with the closing portion of the casing 6.

[0017] The housing 5 includes, at positions corresponding to the first bladed wheel 3A and the second bladed wheel 3B, respectively, convex curved surfaces facing the concave curved surfaces of the respective bladed wheels. The housing 5 further includes an annular first introduction chamber 52 positioned around the first bladed wheel 3A and an annular second introduction chamber 55 positioned around the second bladed wheel 3B. The working fluid is supplied radially inward from the first introduction chamber 52 to the first bladed wheel 3A. Similarly, the working fluid is supplied radially inward from the second introduction chamber 55 to the second bladed wheel 3B.

[0018] In the present embodiment, each of the first introduction chamber 52 and the second introduction chamber 55 is a passage parallel to a radial direction extending from the center axis of the rotating shaft 2. The first introduction chamber 52 includes nozzle vanes 81 as shown in FIG. 2, and the second introduction chamber 55 includes nozzle vanes 82 as shown in FIG. 4.

[0019] The housing 5 further includes: an annular intermediate chamber 54 positioned around the front side of the first bladed wheel 3A; a curved passage 53, which is curved by 90 degrees from the front side of the first bladed wheel 3A and connects to the intermediate chamber 54; intermediate passages 7, through which the intermediate chamber 54 and the second introduction chamber 55 communicate with each other; and an outflow opening 56 positioned on the front side of the second bladed wheel 3B.

[0020] The working fluid whose pressure has been reduced by the first bladed wheel 3A flows into the intermediate chamber 54 through the curved passage 53. The working fluid that has flowed into the intermediate chamber 54 flows into the second introduction chamber 55 through the intermediate passages 7. The working fluid whose pressure has been reduced by the second bladed wheel 3B flows out through the outflow opening 56.

[0021] As shown in FIG. 3, the intermediate passages 7 are located at regular angular intervals in the circumferential direction about the center axis of the rotating shaft 2. However, the angular intervals between the intermediate passages 7 need not be completely equal. In the present embodiment, the number of intermediate passages 7 is ten. However, the number of intermediate passages 7 is suitably changeable. In the present embodiment, each intermediate passage 7 has a circular sectional shape. Alternatively, each intermediate passage 7 may have a square sectional shape or an elliptical sectional shape.

[0022] Each intermediate passage 7 includes: a radially extending portion 71, which extends radially outward from the intermediate chamber 54; an axially extending portion 72, which is bent in the axial direction of the rotating shaft 2 from the radially extending portion 71; and an introduction portion 73, which is bent perpendicularly from the axially extending portion 72 and connects to the second introduction chamber 55.

[0023] In the present embodiment, as shown in FIG. 4, the introduction portion 73 is inclined in the rotation direction of the second bladed wheel 3B relative to a radial direction extending from the center axis of the rotating shaft 2. That is, the inner end of the introduction portion 73 is positioned downstream of the outer end of the introduction portion 73 in the rotation direction of the second bladed wheel 3B. For example, the angle of the introduction portion 73 relative to the radial direction extending from the center axis of the rotating shaft 2 is 30 degrees or greater and 80 degrees or less. Alternatively, the introduction portion 73 may extend in the radial direction extending from the center axis of the rotating shaft 2.

[0024] The housing 5 includes introduction holes 51 extending radially outward from the first introduction chamber 52. As shown in FIG. 2, the introduction holes 51 are located at regular angular intervals in the circumferential direction about the center axis of the rotating shaft 2. However, the angular intervals between the introduction holes 51 need not be completely equal. In the present embodiment, the number of introduction holes 51 is equal to the number of intermediate passages 7, and in the axial direction of the rotating shaft 2, at a position where the first introduction chamber 52 is present, the introduction holes 51 and the intermediate passages 7 are located alternately in the circumferential direction about the center axis of the rotating shaft 2. Alternatively, the number of introduction holes 51 may be different from the number of intermediate passages 7.

[0025] Also, in the present embodiment, when viewed in the axial direction of the rotating shaft 2, the first introduction chamber 52 has a shape tapered toward each introduction hole 51. In other words, the first introduction chamber 52 includes an inner peripheral surface facing radially inward, the inner peripheral surface including, on both sides of each introduction hole 51, a pair of tapered surfaces such that a space between the tapered surfaces increases in accordance with an increase in the distance from the introduction hole 51.

[0026] The cylindrical portion of the casing 6 includes tubular portions 61, which are extensions of the respective introduction holes 51. The introduction holes 51 and the tubular portions 61 form inlets 41 of the turbine body 4. That is, the inlets 41 communicate with the first introduction chamber 52, and are located in the circumferential direction about the center axis of the rotating shaft 2.

[0027] As shown in FIG. 1, the closing portion of the casing 6 includes a tubular portion 62, which forms an outlet 42 of the turbine body 4 together with the outflow opening 56 of the housing 5.

[0028] As described above, in the multistage radial turbine 1 of the present embodiment, when all the supply valves 13 are opened during rated operation, the working fluid is supplied to the first bladed wheel 3A from the entire circumference of the first introduction chamber 52. On the other hand, when some of the supply valves 13 are closed during part-load operation, the working fluid is supplied to the first bladed wheel 3A from the first introduction chamber 52 in a state in which the working fluid has a circumferential pressure distribution and a circumferential flow velocity distribution. Moreover, since the intermediate passages 7 between the intermediate chamber 54 and the second introduction chamber 55 are located in the circumferential direction, the working fluid whose pressure has been reduced by the first bladed wheel 3A is supplied from the second introduction chamber 55 to the second bladed wheel 3B in a state in which the working fluid maintains the circumferential pressure distribution and the circumferential flow velocity distribution. Therefore, also during the part-load operation, high turbine efficiency can be obtained by maintaining a sufficient pressure ratio close to the design point. Furthermore, since the facing direction of the second bladed wheel 3B is opposite to that of the first bladed wheel 3A, this advantageous effect can be obtained in a back-to-back structure.

[0029] Also, in the present embodiment, in the axial direction of the rotating shaft 2, at a position where the first introduction chamber 52 is present, the introduction holes 51 and the intermediate passages 7 are located alternately in the circumferential direction about the center axis of the rotating shaft 2. Accordingly, the spaces between the inlets 41 of the turbine body 4 can be used to form the intermediate passages 7.

[0030] Further, in the present embodiment, the introduction portion 73 of each intermediate passage 7 is inclined in the rotation direction of the second bladed wheel 3B. Accordingly, a flow from the intermediate passage 7 becomes a flow along a swirling flow toward the second bladed wheel 3B, and as a result, a pressure loss is reduced. In particular, in the present embodiment, a blade angle at the inlet of each nozzle vane 82 and the angle of a flow into a nozzle between the nozzle vanes 82 are close to each other. This makes it possible to further increase the turbine efficiency. The advantageous effect that the turbine efficiency is further increased due to a reduction in pressure loss can be obtained even in a case where the nozzle vanes 82 are absent.

[0031] <Variations> The present disclosure is not limited to the above-described embodiment. Various modifications can be made without departing from the scope of the present disclosure.

[0032] For example, within the first introduction chamber 52, there may be partition plates that divide the first introduction chamber 52 into multiple cells located in the circumferential direction. Similarly, within the second introduction chamber 55, there may be partition plates that divide the second introduction chamber 55 into multiple cells located in the circumferential direction.

[0033] Further, for example, as in a multistage radial turbine 1A, which is a variation shown in FIG. 5, the nozzle vanes 82 may be eliminated from the second introduction chamber 55, and instead, the second introduction chamber 55 may be formed by the same number of introduction passages 55a as the number of intermediate passages 7, the introduction passages 55a each being inclined in the rotation direction of the second bladed wheel 3B. In FIG. 5, the introduction portion 73 of each intermediate passage 7 extends radially inward from the axially extending portion 72 of the intermediate passage 7, and obliquely connects to the corresponding introduction passage 55a.

[0034] In contrast, similarly to the above-described embodiment, the introduction portion 73 of each intermediate passage 7 may be inclined in the rotation direction of the second bladed wheel 3B, and the introduction portion 73 and the introduction passage 55a may form a continuous straight passage. According to this configuration, a flow from each intermediate passage 7 becomes a flow along a swirling flow toward the second bladed wheel 3B, and as a result, a pressure loss is reduced. This makes it possible to further increase the turbine efficiency.

[0035] <Summary> The present disclosure provides, as a first aspect, a multistage radial turbine that absorbs power from a working fluid, the multistage radial turbine including: a rotating shaft; a first bladed wheel mounted to the rotating shaft; a turbine body including a first introduction chamber and inlets, the first introduction chamber being positioned around the first bladed wheel, the inlets communicating with the first introduction chamber and being located in a circumferential direction about a center axis of the rotating shaft; supply valves located on respective supply lines connected to the respective inlets; and a second bladed wheel facing in a direction opposite to a direction in which the first bladed wheel faces, the second bladed wheel being mounted to the rotating shaft, wherein the turbine body includes: a second introduction chamber positioned around the second bladed wheel; an annular intermediate chamber into which the working fluid whose pressure has been reduced by the first bladed wheel flows; and intermediate passages through which the intermediate chamber and the second introduction chamber communicate with each other, the intermediate passages being located in the circumferential direction about the center axis of the rotating shaft.

[0036] According to the above configuration, when all the supply valves are opened during rated operation, the working fluid is supplied to the first bladed wheel from the entire circumference of the first introduction chamber. On the other hand, when some of the supply valves are closed during part-load operation, the working fluid is supplied to the first bladed wheel from the first introduction chamber in a state in which the working fluid has a circumferential pressure distribution and a circumferential flow velocity distribution. Moreover, since the intermediate passages between the intermediate chamber and the second introduction chamber are located in the circumferential direction, the working fluid whose pressure has been reduced by the first bladed wheel is supplied from the second introduction chamber to the second bladed wheel in a state in which the working fluid maintains the circumferential pressure distribution and the circumferential flow velocity distribution. Therefore, also during the part-load operation, high turbine efficiency can be obtained by maintaining a sufficient pressure ratio close to the design point. Furthermore, since the facing direction of the second bladed wheel is opposite to that of the first bladed wheel, this advantageous effect can be obtained in a back-to-back structure.

[0037] As a second aspect, in the first aspect, in an axial direction of the rotating shaft, at a position where the first introduction chamber is present, the inlets and the intermediate passages may be located alternately in the circumferential direction about the center axis of the rotating shaft. According to this configuration, the spaces between the inlets of the turbine body can be used to form the intermediate passages.

[0038] As a third aspect, in the first or second aspect, for example, each of the intermediate passages may include: a radially extending portion that extends radially outward from the intermediate chamber; an axially extending portion that is bent in an axial direction of the rotating shaft from the radially extending portion; and an introduction portion that is bent perpendicularly from the axially extending portion and connects to the second introduction chamber.

[0039] As a fourth aspect, in the third aspect, the introduction portion may be inclined in a rotation direction of the second bladed wheel relative to a radial direction extending from the center axis of the rotating shaft. According to this configuration, a flow from each intermediate passage becomes a flow along a swirling flow toward the second bladed wheel, and as a result, a pressure loss is reduced. This makes it possible to further increase the turbine efficiency.

[0040] As a fifth aspect, in any of the first to fourth aspects, for example, the working fluid may be liquid hydrogen.

Claims

1. A multistage radial turbine that absorbs power from a working fluid, the multistage radial turbine including:a rotating shaft;a first bladed wheel mounted to the rotating shaft;a turbine body including a first introduction chamber and inlets, the first introduction chamber being positioned around the first bladed wheel, the inlets communicating with the first introduction chamber and being located in a circumferential direction about a center axis of the rotating shaft;supply valves located on respective supply lines connected to the respective inlets; anda second bladed wheel facing in a direction opposite to a direction in which the first bladed wheel faces, the second bladed wheel being mounted to the rotating shaft, whereinthe turbine body includes:a second introduction chamber positioned around the second bladed wheel;an annular intermediate chamber into which the working fluid whose pressure has been reduced by the first bladed wheel flows; andintermediate passages through which the intermediate chamber and the second introduction chamber communicate with each other, the intermediate passages being located in the circumferential direction about the center axis of the rotating shaft.

2. The multistage radial turbine according to claim 1, whereinin an axial direction of the rotating shaft, at a position where the first introduction chamber is present, the inlets and the intermediate passages are located alternately in the circumferential direction about the center axis of the rotating shaft.

3. The multistage radial turbine according to claim 1 or 2, whereineach of the intermediate passages includes:a radially extending portion that extends radially outward from the intermediate chamber;an axially extending portion that is bent in an axial direction of the rotating shaft from the radially extending portion; andan introduction portion that is bent perpendicularly from the axially extending portion and connects to the second introduction chamber.

4. The multistage radial turbine according to claim 3, whereinthe introduction portion is inclined in a rotation direction of the second bladed wheel relative to a radial direction extending from the center axis of the rotating shaft.

5. The multistage radial turbine according to claim 1 or 2, whereinthe working fluid is liquid hydrogen.

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