Fluid bearing and turbo machine

Abstract

To provide a fluid bearing which can suppress a self-excited vibration in a super high speed rotation.SOLUTION: A fluid bearing 3 according to one embodiment includes a housing 4. The housing 4 includes: an inner peripheral surface 41 that faces an outer peripheral surface of a rotational shaft; a plurality of recesses 5 formed so as to be aligned in a circumferential direction on the inner peripheral surface 41; a plurality of supply paths 6 that open on outer diameter-side wall surfaces of the recesses 5; and an orifice or a capillary diaphragm that is provided on the supply path 6. The supply path 6 is inclined in a direction opposite to a rotational direction of the rotational shaft toward a radial inner side of the rotational shaft. A plurality of holes 7 are provided on each of a pair of axial land parts 42 positioned on both sides of the recess 5 in an axial direction of the rotational shaft on the inner peripheral surface 41 of the housing 4. Each of the holes 7 is inclined in a direction away from a recess region 44 between the pair of axial land parts 42 toward a radial inner side of the rotational shaft.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] 2. Description of the Related Art 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 through which a rotating shaft passes.

[0003] Specifically, in the fluid dynamic bearing of Patent Document 1, the housing includes an inner circumferential surface facing the outer circumferential surface of the rotating shaft, a plurality of recesses formed in a line in the circumferential direction on the inner circumferential surface, a supply passage opening into an 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 circumferential 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 toward the inside of the radial direction 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 provided in the recess and the narrow gap, so that the occurrence of self-excited vibration during high-speed rotation can be suppressed. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] U.S. Pat. No. 5,433,528 Summary of the Invention [Problem to be solved by the invention]

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

[0007] Therefore, an object of the present disclosure is to provide a fluid bearing capable of suppressing the occurrence of self-excited vibration during ultra-high speed rotation, and a turbomachine including the fluid bearing. [Means for solving the problem]

[0008] From one aspect, the present disclosure provides a fluid bearing that uses a fluid which 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 in a line in the circumferential direction on the inner circumferential surface, a plurality of supply passages each opening into an outer diameter side wall surface 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, 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 being provided therein, 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 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, the turbomachine comprising a rotating shaft and the above-mentioned fluid bearing which supports the rotating shaft, and in which the supplied fluid or the pressurized fluid is guided to a supply passage of the fluid bearing. Effect of the Invention

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

[0011] [Figure 1] 1A and 1B are schematic diagrams of a centrifugal turbomachine including a fluid dynamic bearing according to one embodiment. [Diagram 2] FIG. 2 is a perspective view of the fluid bearing. [Diagram 3] FIG. 3 is a cross-sectional view taken along line III-III in FIG. [Figure 4] FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Fig. 2 shows a fluid dynamic bearing 3 according to one embodiment, and Figs. 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 a rotating shaft 2 of a 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] The turbine 1A shown in Fig. 1A is a multi-stage turbine including a first turbine mechanism 11 and a second turbine mechanism 12, but the hydrodynamic bearing 3 may be used in a single-stage turbine. Similarly, the pump 1B shown in Fig. 1B is a multi-stage pump including a first pump mechanism 13 and a second pump mechanism 14, but the hydrodynamic bearing 3 may be used in a single-stage pump.

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

[0017] A branch passage 1d branches off from the inlet passage 1a, and the branch passage 1d 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 passage 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, in more detail, 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 the branch path 1h is connected to the fluid bearing 3. That is, the high-pressure fluid pressurized by the second pump mechanism 14 is supplied through the branch path 1h to the fluid bearing 3. 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 through which the rotating shaft 2 passes. 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 formed on the inner circumferential surface 41 and aligned in the circumferential direction.

[0021] The recesses 5 are desirably provided at equal pitches. 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 like the inner peripheral surface 41, but the cross-sectional shape of the outer peripheral surface of the housing 4 may be rectangular.

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

[0024] As shown in Fig. 3, the housing 4 is provided with the same number of supply passages 6 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 guided to all of the supply passages 6 through the branch passages 1d or 1h described above. Each supply passage 6 is provided with an orifice or capillary restrictor 61.

[0025] Each supply passage 6 is inclined toward the radial inside 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 provided in each of the above-mentioned axial land portions 42 on the inner peripheral surface 41 of the housing 4. In this embodiment, each of the axial land portions 42 has three first hole rows formed in the axial direction, in which the first holes 7 are aligned in the circumferential direction at an equal pitch narrower than that 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 the circumferential direction between adjacent first hole rows may be shifted by half a pitch. Furthermore, the pitch of the first holes 7 in the circumferential direction does not necessarily have to be narrower than that of the recesses 5, and may be equal to or wider than that of the recesses 5. Furthermore, when the lengths of a pair of axial land portions 42 are different from each other, the numbers of first hole rows in both axial land portions 42 may be different.

[0028] 4, each first hole 7 is inclined toward the radial inside of the rotating shaft 2 in a direction away from the recessed region 44. The inclination angle of each first hole 7 with respect to the 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 toward the rotation direction of the rotating shaft 2 toward the radially inner side 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-mentioned circumferential land portions 43 on the inner peripheral surface 41 of the housing 4. In this 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 toward the radially inner side 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, not less than 30 degrees and not more than 60 degrees.

[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 described above, in the fluid bearing 3 of this embodiment, the fluid leaking out through the narrow gap between the rotating shaft 2 and the axial land portion 42 flows as if it is attracted to the side surface of the inclined first hole 7 due to the Coanda effect. Therefore, the first hole 7 provided in the axial land portion 42 is more likely to provide resistance than if it were 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 the turbomachine 1 using the fluid bearing 3, the occurrence of self-excited vibration at ultra-high speed rotation is suppressed, so stable operation at ultra-high speed rotation can be achieved. In other words, the stability against vibration of the rotating shaft 2 at ultra-high speed rotation is significantly improved, so it is possible to suppress vibration problems in the turbomachine 1. Since ultra-high speed rotation is required in turbomachines for liquid hydrogen or two-phase gas-liquid hydrogen, the present disclosure is particularly useful when the fluid is liquid hydrogen or two-phase gas-liquid hydrogen.

[0035] <Modification> The present disclosure is not limited to the above-described embodiments, 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, similarly to the above embodiment, if the turbomachine is a turbine, high-pressure fluid supplied to the turbine may be guided to the supply passage 6 of the fluid bearing 3, and if the turbomachine is a pump, high-pressure fluid pressurized by the pump may be guided to the supply passage 6 of the fluid bearing 3. Alternatively, the fluid bearing 3 may be used in machines other than turbomachines.

[0037] 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 toward the radially inner side 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 a higher rotation speed compared to the case where 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 a first aspect, the present disclosure provides a fluid bearing using a fluid which is a liquid or a gas-liquid multiphase flow, comprising: a housing including an inner circumferential surface facing an outer circumferential surface of a rotating shaft; a plurality of recesses formed in a line in the circumferential direction on the inner circumferential surface; a plurality of supply passages each opening into an outer diameter side wall surface of the plurality of recesses; and an orifice or capillary restrictor provided in each of the plurality of supply passages, wherein the supply passages are inclined toward the radially inner side of the rotating shaft in a direction opposite to the rotation direction of the rotating shaft, and a plurality of holes are provided in each of a pair of axial land portions located on both sides of the plurality of recesses in the axial direction of the rotating shaft on the inner circumferential surface of the housing, and each of the plurality of holes is 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] According to the above configuration, the fluid leaking through the narrow gap between the rotating shaft and the axial land portion flows as if it is drawn to the side of the inclined hole due to the Coanda effect. Therefore, the hole provided in the axial land portion is more likely to provide resistance than when it is not inclined, the amount of fluid leakage can be reduced, and the swirling strength of the flow in the narrow gap can be weakened. This makes it possible to suppress the occurrence of self-excited vibration during ultra-high speed rotation.

[0041] As 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 land portions between the plurality of recesses on the inner peripheral surface of the housing, and the plurality of second holes may be inclined toward the radially inner side of the rotating shaft in the rotation direction of the rotating shaft. With this configuration, the occurrence of self-excited vibration can be suppressed up to a higher rotation speed than when the second holes are not inclined.

[0042] As a third aspect, the present disclosure provides, from another aspect, 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 of the first or second aspect which supports the rotating shaft, and in which 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, so that 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. Since a turbomachine for liquid hydrogen or gas-liquid two-phase hydrogen is required to rotate at an extremely high speed, the present disclosure is particularly useful in the case where the fluid is liquid hydrogen or gas-liquid two-phase hydrogen. [Explanation of symbols]

[0045] 1. Turbomachinery 1A Turbine 1B Pump 2 Rotation Axis 3. Fluid bearings 4. Housing 41 Inner surface 42 Axial land 43 Circumferential land 44 Recess area 5 Recess 6 Supply route 61 Orifice or capillary restriction 7 First Hole 8. 2nd Hole

Claims

1. A fluid bearing using a fluid that is a liquid or a gas-liquid multiphase flow, 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 so as to be aligned in a circumferential direction, a plurality of supply passages each opening into an outer diameter side wall surface of the plurality of recesses, and an orifice or capillary restrictor provided in each of the plurality of supply passages, the supply passage is inclined toward a radially inner side of the rotating shaft in a direction opposite to a rotation direction of the rotating shaft, A hydrodynamic bearing, wherein a pair of axial land portions on the inner surface of the housing, located on either side of the multiple recesses in the axial direction of the rotating shaft, each have a multiple hole formed therein, and each of the multiple holes is inclined radially inward of the rotating shaft, away from a recess region between the pair of axial land portions in which the multiple recesses are located.

2. the hole is a first hole, 2. The fluid bearing as described in claim 1, wherein 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 rotational direction 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, A rotation axis; and a fluid dynamic bearing according to claim 1 or 2 that supports the rotating shaft. 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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