Fluid bearing and turbomachine

Abstract

A fluid bearing (3) according to one embodiment includes a housing (4). The housing (4) includes: an inner peripheral surface (41) facing an outer peripheral surface of a rotating shaft; a plurality of recesses (5) formed in the inner peripheral surface (41) so as to be aligned in a circumferential direction; a plurality of supply passages (6), each opening in a radially outer side wall surface of each recess (5); and an orifice or a capillary restrictor provided in each of the supply passages (6). Each supply passage (6) is inclined in the opposite direction to the rotation direction of the rotating shaft and toward the inside in the radial direction of the rotating shaft. In the inner peripheral surface (41) of the housing (4), a plurality of holes (7) are provided in each of a pair of axial land portions (42) located on both sides of the recesses (5) in the axial direction of the rotating shaft. Each hole (7) is inclined in a direction away from a recessed region (44) between the pair of axial land portions (42) and toward the inside in the radial direction of the rotating shaft.

Description

Fluid bearings and turbomachinery

[0001] The present disclosure relates to a hydrodynamic bearing and a turbomachine including said hydrodynamic bearing.

[0002]

[0003] Conventionally, fluid bearings using a fluid that is a liquid or a gas-liquid multiphase flow have been known. For example, Patent Document 1 discloses a fluid bearing that includes a housing that is penetrated by a rotating shaft.

[0003] Specifically, in the fluid bearing of Patent Document 1, the housing includes an inner peripheral surface facing the outer peripheral surface of the rotating shaft, a plurality of recesses formed in a row in the circumferential direction on the inner peripheral surface, a supply passage opening into the outer diameter side wall surface of the recess, and an orifice provided in the supply passage. When fluid is supplied to the recess through the supply passage, the fluid leaks out through a narrow gap between the rotating shaft and the inner peripheral surface of the housing, while the rotating shaft is held in a non-contact state with the housing by the fluid in the recess and in the narrow gap.

[0004] The supply passage is inclined radially inward of the rotating shaft in the opposite direction to the rotation direction of the rotating shaft. With this configuration, a flow in the opposite direction to the rotation direction of the rotating shaft is imparted to the recess and the narrow gap, thereby suppressing the occurrence of self-excited vibration during high-speed rotation.

[0005] U.S. Pat. No. 5,433,528

[0006] As described above, while the fluid bearing of Patent Document 1 can suppress the occurrence of self-excited vibration at high speeds (e.g., 10,000 to 30,000 rpm), there is a demand for suppressing the occurrence of self-excited vibration at even faster, ultra-high speeds (e.g., 40,000 rpm or higher).

[0007] Therefore, an object of the present disclosure is to provide a fluid bearing that can suppress the occurrence of self-excited vibration during ultra-high speed rotation, and a turbomachine that includes the fluid bearing.

[0008] From one aspect, the present disclosure provides a fluid bearing that uses a fluid that is a liquid or a gas-liquid multiphase flow, the fluid bearing comprising a housing including an inner circumferential surface facing the outer circumferential surface of a rotating shaft, a plurality of recesses formed in a row in the circumferential direction on the inner circumferential surface, a plurality of supply passages that open into outer diameter side wall surfaces of the plurality of recesses, and orifices or capillary restrictors provided in each of the plurality of supply passages, the supply passages inclined toward the radially inner side of the rotating shaft in a direction opposite to the rotation direction of the rotating shaft, and a pair of axial land portions on the inner circumferential surface of the housing, located on both sides of the plurality of recesses in the axial direction of the rotating shaft, each of which has a plurality of holes, and each of the plurality of holes inclined toward the radially inner side of the rotating shaft in a direction away from a recess region in which the plurality of recesses are located between the pair of axial land portions,

[0009] From another aspect, the present disclosure provides a turbomachine that is a turbine driven by a supply of a fluid that is a liquid or a gas-liquid multiphase flow, or a pump that pressurizes the fluid, the turbomachine comprising a rotating shaft and the above-mentioned fluid bearing that supports the rotating shaft, and the supplied fluid or the pressurized fluid is guided to a supply path of the fluid bearing.

[0010] According to the present disclosure, there are provided a fluid bearing capable of suppressing the occurrence of self-excited vibrations during ultra-high speed rotation, and a turbomachine including the fluid bearing.

[0011] 1A and 1B are schematic diagrams of a centrifugal turbomachine including a fluid dynamic bearing according to one embodiment. A perspective view of the fluid dynamic bearing. A cross-sectional view taken along line III-III in FIG. 2. A cross-sectional view taken along line IV-IV in FIG. 3.

[0012] 2 shows a fluid dynamic bearing 3 according to one embodiment, and Figures 1A and 1B show a centrifugal turbomachine 1 including the fluid dynamic bearing 3. However, the fluid dynamic bearing 3 may also be used in an axial-flow turbomachine.

[0013] The fluid bearing 3 uses a fluid that is a liquid or a gas-liquid multiphase flow. In this embodiment, the fluid used in the fluid bearing 3 is also the working fluid of the turbomachine 1. The fluid is, for example, liquid hydrogen, liquid nitrogen, liquid oxygen, LNG (Liquefied Natural Gas), or the like.

[0014] The fluid bearing 3 rotatably supports the rotating shaft 2 of the turbomachine 1. The turbomachine 1 may be a turbine 1A that is driven by a supply of the fluid at high pressure, in other words, that recovers power from the high-pressure fluid, as shown in Fig. 1A, or a pump 1B that pressurizes the fluid, as shown in Fig. 1B.

[0015] 1A is a multi-stage turbine including a first turbine mechanism 11 and a second turbine mechanism 12, but the fluid bearing 3 may also be used in a single-stage turbine. Similarly, the pump 1B is a multi-stage pump including a first pump mechanism 13 and a second pump mechanism 14, but the fluid bearing 3 may also be used in a single-stage pump.

[0016] More specifically, regarding the turbine 1A, a high-pressure fluid is supplied to the first turbine mechanism 11 through an inlet passage 1a, the fluid at reduced pressure is guided from the first turbine mechanism 11 to the second turbine mechanism 12 through an intermediate passage 1b, and the fluid at further reduced pressure is discharged from the second turbine mechanism 12 through an outlet passage 1c.

[0017] A branch path 1d branches off from the inlet path 1a and is connected to the fluid bearing 3. In other words, the high-pressure fluid supplied to the first turbine mechanism 11 is also supplied to the fluid bearing 3 through the branch path 1d. In the turbine 1A, the rotating shaft 2 connects the impeller of the first turbine mechanism 11 and the impeller of the second turbine mechanism 12.

[0018] With regard to pump 1B, more specifically, fluid is supplied to first pump mechanism 13 through inlet path 1e, pressurized fluid is guided from first pump mechanism 13 to second pump mechanism 14 through intermediate path 1f, and further pressurized high-pressure fluid is discharged from second pump mechanism 14 through outlet path 1g.

[0019] A branch path 1h branches off from the outflow path 1g and is connected to the fluid bearing 3. In other words, high-pressure fluid pressurized by the second pump mechanism 14 is supplied to the fluid bearing 3 through the branch path 1h. In the pump 1B, the rotating shaft 2 connects the impeller of the first pump mechanism 13 and the impeller of the second pump mechanism 14, and is rotated by the electric motor 15.

[0020] 2, the fluid dynamic bearing 3 includes a housing 4 that is penetrated by the rotating shaft 2. The housing 4 includes an inner circumferential surface 41 that faces the outer circumferential surface of the rotating shaft 2, and a plurality of recesses 5 that are formed on the inner circumferential surface 41 and aligned in the circumferential direction.

[0021] The recesses 5 are preferably provided at equal intervals. In this embodiment, the number of recesses 5 is four as shown in Fig. 3, but the number of recesses 5 is not limited to this and can be changed as appropriate.

[0022] The diameter of the inner peripheral surface 41 of the housing 4 is slightly larger than the diameter of the rotating shaft 2, and a narrow gap is formed between the outer peripheral surface of the rotating shaft 2 and the inner peripheral surface 41 of the housing 4. In this embodiment, the cross-sectional shape of the outer peripheral surface of the housing 4 is circular, just like the inner peripheral surface 41, but the cross-sectional shape of the outer peripheral surface of the housing 4 may also be rectangular.

[0023] 2, the inner peripheral surface 41 includes a pair of axial lands 42 located on both sides of the recess 5 in the axial direction of the rotating shaft 2, and a plurality of circumferential lands 43 between the recesses 5. In other words, the region between the pair of axial lands is a recess region 44 in which the recesses 5 are present, and in the recess region 44, the circumferential lands 43 and the recesses 5 are arranged alternately in the circumferential direction.

[0024] As shown in Figure 3, the housing 4 is provided with supply passages 6, the same number as the recesses 5. Each supply passage 6 opens to the outer diameter side wall surface of the corresponding recess 5 and the outer circumferential surface of the housing 4. High-pressure fluid is introduced to all supply passages 6 through the branch passages 1d or 1h described above. Each supply passage 6 is provided with an orifice or capillary restriction 61.

[0025] Each supply passage 6 is inclined radially inward of the rotating shaft 2 in the opposite direction to the rotation direction of the rotating shaft 2. The inclination angle of each supply passage 6 with respect to the radial direction of the rotating shaft 2 at a position passing through the center of the opening of the supply passage 6 on the recess 5 side is, for example, not less than 10 degrees and not more than 80 degrees.

[0026] 2 , a plurality of first holes 7 are formed in each of the above-described axial land portions 42 on the inner peripheral surface 41 of the housing 4. In the present embodiment, each axial land portion 42 is formed with three first hole rows in the axial direction, in which the first holes 7 are aligned in the circumferential direction at equal pitches that are narrower than those of the recesses 5.

[0027] However, the method of providing the first holes 7 is not limited to this. For example, the number of first hole rows in each axial land portion 42 may be two or four or more, and the positions of the first holes 7 in adjacent first hole rows may be shifted by half a pitch in the circumferential direction. Furthermore, the circumferential pitch of the first holes 7 does not necessarily have to be narrower than the recesses 5, and may be equal to or wider than the recesses 5. Furthermore, when the lengths of a pair of axial lands 42 are different from each other, the number of first hole rows in both axial lands 42 may be different.

[0028] 4, each of the first holes 7 is inclined radially inward of the rotating shaft 2, in a direction away from the recess region 44. The inclination angle of each of the first holes 7 with respect to a direction perpendicular to the axial direction of the rotating shaft 2 is, for example, not less than 30 degrees and not more than 60 degrees.

[0029] When viewed from the axial direction of the rotating shaft 2, the extension direction of each first hole 7 may be the radial direction of the rotating shaft 2. Alternatively, each first hole 7 may be inclined radially inward of the rotating shaft 2 in the rotation direction of the rotating shaft 2. The diameter of each first hole 7 is, for example, 5% to 50% of the width of the recess 5 in the axial direction of the rotating shaft 2.

[0030] 3, a plurality of second holes 8 are provided in each of the above-described circumferential land portions 43 on the inner peripheral surface 41 of the housing 4. In the present embodiment, three second holes 8 are provided for one circumferential land portion 43, but the number of second holes 8 for one circumferential land portion 43 may be two or four or more.

[0031] Each second hole 8 is inclined radially inward of the rotating shaft 2 in the rotation direction of the rotating shaft 2. The inclination angle of the second hole 8 with respect to the radial direction of the rotating shaft 2 at a position passing through the center of the opening of each second hole 8 is, for example, 30 degrees or more and 60 degrees or less.

[0032] When viewed from the circumferential direction of the rotating shaft 2, the extension direction of each second hole 8 may be a direction perpendicular to the axial direction of the rotating shaft 2. Alternatively, each second hole 8 may be inclined in a direction approaching one of the axial land portions 42 toward the radially inner side of the rotating shaft 2. The diameter of each second hole 8 is, for example, 5% to 50% of the width of the recess 5 in the axial direction of the rotating shaft 2.

[0033] As explained above, in the hydrodynamic bearing 3 of this embodiment, fluid leaking through the narrow gap between the rotating shaft 2 and the axial land 42 flows as if drawn to the side of the inclined first hole 7 due to the Coanda effect. As a result, the first hole 7 provided in the axial land 42 is more likely to provide resistance than in a case where it is not inclined, making it possible to reduce the amount of fluid leakage and weaken the swirling strength of the flow in the narrow gap. This makes it possible to suppress the occurrence of self-excited vibration during ultra-high speed rotation.

[0034] Furthermore, in a turbomachine 1 using the fluid bearing 3, the occurrence of self-excited vibration at ultra-high speed rotation is suppressed, thereby enabling stable operation at ultra-high speed rotation. In other words, stability against vibration of the rotating shaft 2 at ultra-high speed rotation is significantly improved, making it possible to suppress vibration problems in the turbomachine 1. Because ultra-high speed rotation is required in turbomachines for liquid hydrogen or gas-liquid two-phase hydrogen, the present disclosure is particularly useful when the fluid is liquid hydrogen or gas-liquid two-phase hydrogen.

[0035] <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.

[0036] For example, when the fluid bearing 3 is used in an axial flow turbomachine, as in the above embodiment, if the turbomachine is a turbine, high-pressure fluid supplied to the turbine may be guided to the supply path 6 of the fluid bearing 3, or if the turbomachine is a pump, high-pressure fluid pressurized by the pump may be guided to the supply path 6 of the fluid bearing 3. Alternatively, the fluid bearing 3 may be used in machines other than turbomachines.

[0037] Furthermore, the extending direction of the second holes 8 provided in each circumferential land portion 43 may be the radial direction of the rotating shaft 2. However, if the second holes 8 are inclined radially inward of the rotating shaft 2 in the rotation direction of the rotating shaft 2 as in the above embodiment, the occurrence of self-excited vibration can be suppressed up to an even higher rotation speed compared to when the second holes 8 are not inclined.

[0038] Furthermore, the second holes 8 do not necessarily have to be provided in each circumferential land portion 43 .

[0039] <Summary> In one aspect, the present disclosure provides a fluid bearing that uses a fluid that is a liquid or a gas-liquid multiphase flow, the fluid bearing comprising: a housing including an inner circumferential surface facing an outer circumferential surface of a rotating shaft; a plurality of recesses formed on the inner circumferential surface and aligned circumferentially in the inner circumferential surface; a plurality of supply passages that open into outer diameter side wall surfaces of the plurality of recesses; and orifices or capillary restrictors provided in each of the plurality of supply passages, the supply passages inclined toward the radially inner side of the rotating shaft in a direction opposite to the rotation direction of the rotating shaft, and a pair of axial land portions on the inner circumferential surface of the housing, located on both sides of the plurality of recesses in the axial direction of the rotating shaft, each of which is provided with a plurality of holes, and each of the plurality of holes inclined toward the radially inner side of the rotating shaft in a direction away from a recess region in which the plurality of recesses are located between the pair of axial land portions,

[0040] With the above configuration, fluid leaking through the narrow gap between the rotating shaft and the axial land is drawn to the side of the inclined hole due to the Coanda effect. Therefore, the hole in the axial land is more likely to provide resistance than a non-inclined hole, reducing the amount of fluid leakage and weakening the swirling strength of the flow in the narrow gap. This makes it possible to suppress self-excited vibration during ultra-high speed rotation.

[0041] In a second aspect, in the first aspect, the hole may be a first hole, and a plurality of second holes may be provided in each of a plurality of circumferential lands between the plurality of recesses on the inner peripheral surface of the housing, and the plurality of second holes may be inclined radially inward in the rotation direction of the rotating shaft. With this configuration, the occurrence of self-excited vibration can be suppressed up to an even higher rotation speed than when the second holes are not inclined.

[0042] In a third aspect, from another aspect, the present disclosure provides a turbomachine that is a turbine driven by a supply of a fluid that is a liquid or a gas-liquid multiphase flow, or a pump that pressurizes the fluid, the turbomachine comprising a rotating shaft and a fluid bearing of the first or second aspect that supports the rotating shaft, and the supplied fluid or the pressurized fluid is guided to a supply passage of the fluid bearing.

[0043] According to the above configuration, the occurrence of self-excited vibration at ultra-high speed rotation is suppressed, and stable operation at ultra-high speed rotation can be achieved.

[0044] As a fourth aspect, in the third aspect, the fluid may be liquid hydrogen or gas-liquid two-phase hydrogen. Because a turbomachine for liquid hydrogen or gas-liquid two-phase hydrogen is required to rotate at extremely high speeds, the present disclosure is particularly useful when the fluid is liquid hydrogen or gas-liquid two-phase hydrogen.

Claims

1. A fluid bearing that uses a fluid which is a liquid or a gas-liquid multiphase flow, comprising a housing including an inner circumferential surface facing the outer circumferential surface of a rotating shaft, a plurality of recesses formed in a row in the circumferential direction on the inner circumferential surface, a plurality of supply passages each opening into the outer diameter side wall surfaces of the plurality of recesses, and orifices or capillary restrictors provided in each of the plurality of supply passages, wherein the supply passages are inclined toward the radially inward direction of the rotating shaft in a direction opposite to the rotation direction of the rotating shaft, and a pair of axial land portions on the inner circumferential surface of the housing, located on both sides of the plurality of recesses in the axial direction of the rotating shaft, each of the plurality of holes is provided, and each of the plurality of holes is inclined toward the radially inward direction of the rotating shaft in a direction away from the recess region in which the plurality of recesses are located between the pair of axial land portions.

2. A fluid bearing as described in claim 1, wherein the hole is a first hole, and a plurality of second holes are provided in each of a plurality of circumferential land portions between the plurality of recesses on the inner surface of the housing, and the plurality of second holes are inclined toward the radially inward direction of the rotating shaft in the direction of rotation of the rotating shaft.

3. A turbomachine which is a turbine driven by a supply of a fluid which is a liquid or a gas-liquid multiphase flow, or a pump which pressurizes the fluid, comprising: a rotating shaft; and a fluid bearing as described in claim 1 or 2 which supports the rotating shaft, wherein the supplied fluid or the pressurized fluid is guided to a supply passage of the fluid bearing.

4. The turbomachine according to claim 3, wherein the fluid is liquid hydrogen or two-phase hydrogen.

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