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

Multi-stage radial turbine

[0001] The present disclosure relates to a multi-stage radial turbine.

[0002] Multi-stage radial turbines that absorb power from a working fluid have been known for some time. For example, Patent Document 1 discloses a multi-stage radial turbine having a first impeller and a second impeller attached to a rotating shaft. Each of the first impeller and the second impeller has a concave curved surface that guides a radial flow into an axial flow.

[0003] Specifically, in the multi-stage radial turbine of Patent Document 1, an annular inlet passage is located around a first impeller, and a working fluid is supplied radially inward from the inlet passage to the first impeller. The working fluid decompressed by the first impeller is guided to the second impeller via a connecting passage. The connecting passage converts the axial flow from the first impeller into a radially outward flow, and then converts it into a radially inward flow to the second impeller.

[0004] JP 2011-132877 A

[0005] In a multi-stage radial turbine, during rated operation with the working fluid flowing in at the design flow rate, the pressure ratio between the inlet and outlet of the working fluid is the design point, and turbine efficiency is high. However, multi-stage radial turbines are sometimes operated at partial loads in a low flow rate range where the flow rate of the working fluid is less than the design flow rate. Even during partial load operation, it is desirable to operate at a high pressure ratio close to the design point. However, with conventional structures, it is difficult to maintain a sufficient pressure ratio and achieve high turbine efficiency during partial load operation.

[0006] In addition, multi-stage radial turbines sometimes use a back-to-back structure in which some impellers are oriented in the opposite direction to the other impellers to reduce the thrust load acting on the rotating shaft. Even with this back-to-back structure, it is desirable to maintain a sufficient pressure ratio and achieve high turbine efficiency during partial load operation.

[0007] Therefore, an object of the present disclosure is to provide a multi-stage radial turbine that can maintain a sufficient pressure ratio and obtain high turbine efficiency during partial load operation in a back-to-back structure.

[0008] The present disclosure provides a multi-stage radial turbine that absorbs power from a working fluid, comprising: a rotating shaft; a first impeller attached to the rotating shaft; a turbine body including a first introduction chamber located around the first impeller and including a plurality of inlets that are lined up in a circumferential direction around the axis of the rotating shaft and communicate with the first introduction chamber; a plurality of supply valves provided on a plurality of supply lines connected to the plurality of inlets, respectively; and a second impeller attached to the rotating shaft in a direction opposite to that of the first impeller, wherein the turbine body includes a second introduction chamber located around the second impeller; an annular intermediate chamber into which working fluid decompressed by the first impeller flows; and a plurality of intermediate flow passages that are lined up in the circumferential direction around the axis of the rotating shaft and communicate between the intermediate chamber and the second introduction chamber.

[0009] According to the present disclosure, a multi-stage radial turbine is provided that can maintain a sufficient pressure ratio and obtain high turbine efficiency during partial load operation in a back-to-back configuration.

[0010] Fig. 1 is a cross-sectional view of a multi-stage radial turbine according to an embodiment. Fig. 2 is a cross-sectional view taken along line II-II in Fig. 1. Fig. 3 is a cross-sectional view taken along line III-III in Fig. 1. Fig. 4 is a cross-sectional view of a modified multi-stage radial turbine, corresponding to Fig. 4.

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

[0012] Specifically, the multi-stage radial turbine 1 includes a rotating shaft 2, and a first impeller 3A and a second impeller 3B attached to the rotating shaft 2. The multi-stage radial turbine 1 also includes a turbine body 4 that rotatably supports, via bearings, a rotor formed by the rotating shaft 2, the first impeller 3A, and the second impeller 3B. Furthermore, as shown in Fig. 2 , the multi-stage radial turbine 1 includes a plurality of supply lines 12 branching off from a source line 11 that is a supply source of the working fluid, and a plurality of supply valves 13 provided on each of the supply lines 12.

[0013] The rotating shaft 2 passes through the first impeller 3A and the second impeller 3B. A lock nut 21 for holding the first impeller 3A and the second impeller 3B is fixed to the tip of the rotating shaft 2. For ease of explanation, the direction toward the tip of the axial direction of the rotating shaft 2 will be referred to as "upward," and the direction opposite to the tip will be referred to as "downward." In this embodiment, the first impeller 3A is located downward and the second impeller 3B is located upward, but the positions of the first impeller 3A and the second impeller 3B may be interchanged.

[0014] The multi-stage radial turbine 1 employs a back-to-back structure, with the first impeller 3A and the second impeller 3B attached to the rotary shaft 2 in opposite directions. That is, the back surface of the first impeller 3A and the back surface of the second impeller 3B face each other.

[0015] Each of the first impeller 3A and the second impeller 3B includes a hub with a concave curved surface that guides radial flow into axial flow, and a plurality of blades protruding from the concave curved surface. Curved flow passages that open in the radial and axial directions are formed between the blades. In each impeller, the front side is the side where the axial openings of the curved flow passages open, and the back side is the side opposite the side where the axial openings of the curved flow passages open. In other words, the back side of the impeller described above is the side facing away from the axial openings of the curved flow passages.

[0016] The turbine body 4 includes a housing 5 that surrounds the first impeller 3A and the second impeller 3B, and a casing 6 that houses the housing 5. The casing 6 includes a cylindrical portion that extends in the axial direction of the rotating shaft 2 and a closing portion that closes an upper opening of the cylindrical portion. The outer peripheral surface of the housing 5 abuts against the cylindrical portion of the casing 6, and the upper end face of the housing 5 abuts against the closing portion of the casing 6.

[0017] The housing 5 has convex curved surfaces at positions corresponding to the first impeller 3A and the second impeller 3B, which face the concave curved surfaces of the impellers. The housing 5 also includes an annular first introduction chamber 52 located around the first impeller 3A and an annular second introduction chamber 55 located around the second impeller 3B. The working fluid is supplied radially inward from the first introduction chamber 52 to the first impeller 3A, and is supplied radially inward from the second introduction chamber 55 to the second impeller 3B.

[0018] In this embodiment, the first introduction chamber 52 and the second introduction chamber 55 are each flow passages parallel to the radial direction centered on the axis of the rotary shaft 2. The first introduction chamber 52 is provided with a plurality of nozzle vanes 81 as shown in Fig. 2, and the second introduction chamber 55 is provided with a plurality of nozzle vanes 82 as shown in Fig. 4.

[0019] Furthermore, the housing 5 includes an annular intermediate chamber 54 located around the front side of the first impeller 3A, a curved flow path 53 that curves 90 degrees from the front side of the first impeller 3A and leads to the intermediate chamber 54, a plurality of intermediate flow paths 7 that connect the intermediate chamber 54 and the second introduction chamber 55, and an outlet opening 56 located on the front side of the second impeller 3B.

[0020] The working fluid decompressed by the first impeller 3A flows into the intermediate chamber 54 through the curved flow path 53. The working fluid that has flowed into the intermediate chamber 54 flows into the second inlet chamber 55 through the intermediate flow path 7. The working fluid decompressed by the second impeller 3B flows out through the outlet opening 56.

[0021] As shown in Fig. 3, the intermediate flow passages 7 are arranged at equal angular intervals in the circumferential direction around the axis of the rotating shaft 2. However, the angular intervals at which the intermediate flow passages 7 are arranged do not have to be completely equal. In this embodiment, there are 10 intermediate flow passages 7, but the number of intermediate flow passages 7 can be changed as appropriate. In this embodiment, the cross-sectional shape of each intermediate flow passage 7 is circular, but the cross-sectional shape of each intermediate flow passage 7 may be square or elliptical.

[0022] Each intermediate flow path 7 includes a radially extending portion 71 extending radially outward from the intermediate chamber 54, an axially extending portion 72 bending from the radially extending portion 71 in the axial direction of the rotating shaft 2, and an introduction portion 73 bending vertically from the axially extending portion 72 and connecting to the second introduction chamber 55.

[0023] 4 , the introduction portion 73 is inclined toward the rotation direction of the second impeller 3B with respect to the radial direction centered on the axial center of the rotating shaft 2. In other words, the inner end of the introduction portion 73 is located downstream of the outer end of the introduction portion 73 in the rotation direction of the second impeller 3B. For example, the angle of the introduction portion 73 with respect to the radial direction centered on the axial center of the rotating shaft 2 is equal to or greater than 30 degrees and equal to or less than 80 degrees. However, the introduction portion 73 may extend in the radial direction centered on the axial center of the rotating shaft 2.

[0024] The housing 5 includes a plurality of introduction holes 51 extending radially outward from the first introduction chamber 52. As shown in FIG. 2 , the introduction holes 51 are arranged at equal angular intervals in the circumferential direction around the axis of the rotating shaft 2. However, the angular intervals at which the introduction holes 51 are arranged do not have to be completely equal. In this embodiment, the number of introduction holes 51 is equal to the number of intermediate flow paths 7, and at positions in the axial direction of the rotating shaft 2 where the first introduction chambers 52 are present, the introduction holes 51 and the intermediate flow paths 7 are arranged alternately in the circumferential direction around the axis of the rotating shaft 2. However, the number of introduction holes 51 may be different from the number of intermediate flow paths 7.

[0025] In this embodiment, when viewed from the axial direction of the rotating shaft 2, the first introduction chamber 52 has a shape that tapers toward each introduction hole 51. In other words, the inner circumferential surface of the first introduction chamber 52 that faces radially inward has a pair of tapered surfaces on both sides of each introduction hole 51 that become more spaced apart as they move away from the introduction hole 51.

[0026] The cylindrical portion of the casing 6 is provided with a plurality of tubular portions 61 that extend the introduction hole 51. The introduction hole 51 and the tubular portions 61 form the inlet 41 of the turbine body 4. In other words, the inlet 41 communicates with the first introduction chamber 52 and is aligned in the circumferential direction around the axis of the rotating shaft 2.

[0027] As shown in FIG. 1, the closed portion of the casing 6 is provided with a tubular portion 62 which, together with the outlet opening 56 of the housing 5, constitutes the outlet port 42 of the turbine body 4.

[0028] As described above, in the multi-stage radial turbine 1 of this embodiment, when all supply valves 13 are opened during rated operation, the working fluid is supplied to the first impeller 3A from the entire circumference of the first introduction chamber 52. On the other hand, when operating at partial load, when some of the supply valves 13 are closed, the working fluid is supplied from the first introduction chamber 52 to the first impeller 3A with a circumferential distribution of pressure and flow velocity. Furthermore, because the intermediate flow passages 7 between the intermediate chamber 54 and the second introduction chamber 55 are aligned circumferentially, the working fluid decompressed by the first impeller 3A is supplied from the second introduction chamber 55 to the second impeller 3B while maintaining the circumferential distribution of pressure and flow velocity. Therefore, even during partial load operation, a sufficient pressure ratio close to the design point can be maintained, thereby achieving high turbine efficiency. Furthermore, because the second impeller 3B is oriented in the opposite direction to the first impeller 3A, the effect of a back-to-back structure can be achieved.

[0029] Furthermore, in this embodiment, at the position in the axial direction of the rotating shaft 2 where the first introduction chamber 52 is located, the introduction holes 51 and the intermediate flow passages 7 are arranged alternately in the circumferential direction centered on the axis of the rotating shaft 2, so that the intermediate flow passages 7 can be formed by utilizing the space between the inlets 41 in the turbine body 4.

[0030] Furthermore, in this embodiment, the inlet portions 73 of each intermediate passage 7 are inclined in the rotation direction of the second impeller 3B, so that the flow from the intermediate passage 7 flows along a swirling flow toward the second impeller 3B, thereby reducing pressure loss. In particular, in this embodiment, the blade angle at the inlet of the nozzle vane 82 and the angle of the flow entering the nozzle between the nozzle vanes 82 become closer. This makes it possible to further improve turbine efficiency. Note that the effect of further improving turbine efficiency due to reduced pressure loss can be obtained even if the nozzle vanes 82 are not used.

[0031] <Modifications> The present disclosure is not limited to the above-described embodiment, and various modifications are possible without departing from the gist of the present disclosure.

[0032] For example, a plurality of partition plates may be provided in the first introduction chamber 52 so as to divide the first introduction chamber 52 into a plurality of cells arranged in the circumferential direction. Similarly, a plurality of partition plates may be provided in the second introduction chamber 55 so as to divide the second introduction chamber 55 into a plurality of cells arranged in the circumferential direction.

[0033] 5, instead of omitting the nozzle vanes 82 in the second introduction chamber 55, the second introduction chamber 55 may be configured with introduction passages 55a inclined in the rotation direction of the second impeller 3B and the same number as the number of intermediate passages 7. In FIG. 5, the introduction portion 73 of each intermediate passage 7 extends radially inward from the axial extension portion 72 and is connected obliquely to the corresponding introduction passage 55a.

[0034] Alternatively, as in the above embodiment, the inlet portion 73 of each intermediate passage 7 may be inclined in the rotation direction of the second impeller 3B, and a straight passage may be formed in which the inlet portion 73 and the inlet passage 55a are continuous. With this configuration, the flow from the intermediate passage 7 follows a swirling flow toward the second impeller 3B, thereby reducing pressure loss. This can further improve turbine efficiency.

[0035] <Summary> In a first aspect, the present disclosure provides a multi-stage radial turbine that absorbs power from a working fluid, the multi-stage radial turbine comprising: a rotating shaft; a first impeller attached to the rotating shaft; a turbine body including a first introduction chamber located around the first impeller and including a plurality of inlets that are aligned in a circumferential direction about an axis of the rotating shaft and communicate with the first introduction chamber; a plurality of supply valves provided on a plurality of supply lines connected to the plurality of inlets, respectively; and a second impeller attached to the rotating shaft in a direction opposite to that of the first impeller, wherein the turbine body includes a second introduction chamber located around the second impeller; an annular intermediate chamber into which the working fluid decompressed by the first impeller flows; and a plurality of intermediate flow passages that are aligned in the circumferential direction about the axis of the rotating shaft and communicate between the intermediate chamber and the second introduction chamber.

[0036] According to the above configuration, when all supply valves are opened during rated operation, the working fluid is supplied to the first impeller from the entire circumference of the first introduction chamber. On the other hand, when some of the supply valves are closed during partial load operation, the working fluid is supplied from the first introduction chamber to the first impeller with a circumferential distribution of pressure and flow velocity. Furthermore, because the intermediate passages between the intermediate chamber and the second introduction chamber are aligned in the circumferential direction, the working fluid decompressed by the first impeller is supplied from the second introduction chamber to the second impeller while maintaining the circumferential distribution of pressure and flow velocity. Therefore, even during partial load operation, a sufficient pressure ratio close to the design point can be maintained, thereby achieving high turbine efficiency. Furthermore, because the second impeller is oriented in the opposite direction to the first impeller, the effects of a back-to-back structure can be achieved.

[0037] As a second aspect, in the first aspect, the plurality of inlets and the plurality of intermediate flow passages may be arranged alternately in a circumferential direction around an axis of the rotating shaft at a position in the axial direction of the rotating shaft where the first introduction chamber is located. With this configuration, it is possible to form the intermediate flow passages by utilizing the spaces between the inlets in the turbine body.

[0038] As a third aspect, in the first or second aspect, for example, each of the plurality of intermediate flow paths may include a radially extending portion extending radially outward from the intermediate chamber, an axially extending portion bending from the radially extending portion in the axial direction of the rotation shaft, and an introduction portion bending vertically from the axially extending portion and connecting to the second introduction chamber.

[0039] As a fourth aspect, in the third aspect, the introduction section may be inclined in the rotation direction of the second impeller with respect to the radial direction about the axis of the rotating shaft. With this configuration, the flow from the intermediate flow passage becomes a swirling flow toward the second impeller, thereby reducing pressure loss. This can further improve turbine efficiency.

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

Claims

1. A multi-stage radial turbine that absorbs power from a working fluid, comprising: a rotating shaft; a first impeller attached to the rotating shaft; a turbine body including a first introduction chamber located around the first impeller and including a plurality of inlets that communicate with the first introduction chamber and are arranged in a circumferential direction around the axis of the rotating shaft; a plurality of supply valves provided on a plurality of supply lines connected to the plurality of inlets; and a second impeller attached to the rotating shaft in an opposite direction to the first impeller, wherein the turbine body includes a second introduction chamber located around the second impeller, an annular intermediate chamber into which working fluid decompressed by the first impeller flows, and a plurality of intermediate flow passages that are arranged in a circumferential direction around the axis of the rotating shaft and that communicate between the intermediate chamber and the second introduction chamber.

2. A multi-stage radial turbine as described in claim 1, wherein at a position in the axial direction of the rotating shaft where the first introduction chamber is located, the plurality of inlets and the plurality of intermediate flow passages are arranged alternately in the circumferential direction around the axis of the rotating shaft.

3. A multi-stage radial turbine as described in claim 1 or 2, wherein each of the plurality of intermediate flow paths includes a radially extending portion extending radially outward from the intermediate chamber, an axially extending portion bending from the radially extending portion in the axial direction of the rotating shaft, and an introduction portion bending perpendicularly from the axially extending portion to connect to the second introduction chamber.

4. A multi-stage radial turbine according to claim 3, wherein the introduction section is inclined in the direction of rotation of the second impeller with respect to a radial direction centered on the axis of the rotary shaft.

5. A multi-stage radial turbine according to claim 1 or 2, wherein the working fluid is liquid hydrogen.

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