Bearing device with squeeze film damper and centrifugal compressor

Abstract

To make it possible to early detect abnormalities in a bearing device with a squeeze film damper, and make it possible to determine their causes.SOLUTION: A bearing device 1 with a squeeze film damper comprises a main bearing 2 supporting a rotating shaft 4, a bearing housing 7 constituting an outer peripheral part of the main bearing 2, a housing 9 provided on an outer peripheral side of the bearing housing 7, a squeeze film damper part 3 provided in a gap between the bearing housing 7 and the housing 9, a relative displacement measurement sensor 15 for measuring a relative displacement 17 of the rotating shaft 4, an absolute displacement measurement sensor 16 for measuring an absolute displacement 18 of the rotating shaft 4, and an abnormality detection part 31. The abnormality detection part 31 calculates a correlation between the relative displacement 17 and the absolute displacement 18, analyzes a change in the correlation, and detects abnormalities of the main bearing 2 and the squeeze film damper part 3.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a bearing device with a squeeze film damper that supports a rotating shaft and a centrifugal compressor. [Background technology]

[0002] To support the rotating shaft of a high-speed rotating machine, a fluid dynamic bearing is often used, which forms a lubricating oil film in the gap between the rotating shaft and the bearing and supports the rotating shaft using the pressure of that oil film. Patent Document 1 describes a bearing device with a squeeze film damper that integrates a fluid dynamic bearing and a squeeze film damper to enable even higher speeds. A bearing device with a squeeze film damper is a bearing device with excellent vibration stability, in which a squeeze film damper is formed on the outer surface of the main bearing that supports the rotating shaft. Patent Document 1 describes that the main bearing is a tilting pad journal bearing, which is elastically supported by an S-shaped spring member and has a fluid film damper on the outer surface of the main bearing. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-100434 Summary of the Invention [Problem to be solved by the invention]

[0004] In high-speed rotating machinery supported by fluid dynamic bearings, one or more vibration meters are installed in immovable locations (such as the bearing case or pedestal) to monitor the vibration of the rotating shaft. If the measured vibration amplitude exceeds a preset threshold, an alert is issued or the machine is automatically stopped. However, this monitoring method has several issues. First, it is difficult to identify the cause of abnormal vibration, which means that countermeasures take time. Furthermore, it is unable to detect early on vibrations caused by insufficient lubrication due to an increase in lubricant sludge that accumulates on the surface of the fluid dynamic bearing, clogged piping, or an abnormality in the oil supply pump. Furthermore, in the case of bearing systems with squeeze film dampers, it is difficult to early on detect abnormalities caused by damage to the elastic springs that support the main bearings.

[0005] The object of the present invention is to enable the early detection of at least one of the following abnormalities in a bearing device with a squeeze film damper: an increase in lubricating oil sludge, insufficient oil supply, and damage to the springs supporting the main bearings, and to enable the identification of their causes. [Means for solving the problem]

[0006] In order to solve the above problems, one of the representative squeeze film bearing devices of the present invention is as follows: A bearing device with a squeeze film damper includes: a main bearing that supports a rotating shaft; a bearing housing that forms part of the main bearing and configures an outer periphery of the main bearing; a housing that is provided on the outer periphery of the bearing housing with a gap between it and the bearing housing; and a squeeze film damper portion that is provided in the gap between the bearing housing and the housing, a relative displacement measuring sensor that measures a relative displacement of the rotating shaft as viewed from the main bearing, an absolute displacement measuring sensor that measures an absolute displacement of the rotating shaft as viewed from the housing, and an abnormality detection unit, The abnormality detection unit calculates the correlation between the relative displacement measured by the relative displacement measurement sensor and the absolute displacement measured by the absolute displacement measurement sensor, analyzes changes in the correlation, and detects an abnormality in at least one of the main bearing or the squeeze film damper unit. [Effects of the Invention]

[0007] According to the present invention, abnormalities occurring in the main bearing can be detected early to prevent accidents before they occur. In addition, the time required to identify the cause of abnormal vibration can be reduced, contributing to loss cost reduction.

[0008] Problems, configurations, and effects other than those described above will become apparent from the following description of the embodiments. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a longitudinal cross-sectional view of a squeeze film damper-equipped bearing device according to an embodiment of the present invention, as viewed from the axial direction. [Figure 2] 1 is a cross-sectional view of a squeeze film damper-equipped bearing device according to one embodiment of the present invention. [Figure 3] 4 is a flowchart showing a diagnostic flow for a squeeze film damper-equipped bearing device according to one embodiment of the present invention. [Figure 4] 1 is a mass-spring-damping model of a bearing assembly with a squeeze film damper according to one embodiment of the present invention. [Figure 5] FIG. 1 is an explanatory diagram showing an example of the effect of a squeeze film damper-equipped bearing device according to an embodiment of the present invention. [Figure 6] 10A and 10B are explanatory diagrams showing another example of the effect of the squeeze film damper-equipped bearing device according to one embodiment of the present invention. [Figure 7] 1 is a cross-sectional view showing an embodiment of a centrifugal compressor equipped with a squeeze film damper-equipped bearing device according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] A squeeze film damper-equipped bearing device 1 according to the present invention will be described with reference to FIGS.

[0011] First, the configuration of a squeeze film damper-equipped bearing device 1 will be described with reference to FIGS.

[0012] Fig. 1 is a longitudinal cross-sectional view of a bearing device with a squeeze film damper 1 according to one embodiment of the present invention, as viewed from the axial direction. Fig. 2 is a transverse cross-sectional view of a bearing device with a squeeze film damper 1 according to one embodiment of the present invention. In the following explanation, the "bearing device with a squeeze film damper" will be referred to simply as the "bearing device."

[0013] As shown in Fig. 1, lubricating oil is piped from an oil tank (not shown) through a pump, sent to the bearing device 1, and distributed to the main bearing 2 and squeeze film damper section 3. The main bearing 2 is located radially inward (inner diameter side) from the dashed line in Fig. 2.

[0014] The main bearing 2 is a tilting pad journal bearing that supports the rotating shaft 4. The tilting pad journal bearing that constitutes the main bearing 2 is composed of pads 5, a pivot 6 (see Figure 2), and a bearing housing 7. In this embodiment, the pad arrangement of the main bearing 2 is of the load-between-pad (hereinafter referred to as LBP) type, with two pads 5 arranged directly below the rotating shaft 4 in the direction of its own weight. Although Figure 1 shows four pads 5, this is not necessarily the case. Lubricating oil is supplied to the main bearing 2 and flows into the gap between the pads 5 and the rotating shaft 4, forming a main bearing oil film 8.

[0015] A housing 9 is located on the outer periphery of the bearing housing 7 of the main bearing 2, and multiple squeeze film damper units 3 are disposed in the gap between the bearing housing 7 and the housing 9. Although four squeeze film damper units 3a to 3d are shown in FIG. 1, the number of squeeze film damper units 3 does not necessarily have to be four. A squeeze film is formed by the lubricating oil supplied to the squeeze film damper units 3. Each squeeze film damper unit 3a to 3d is provided with one or more elastic bodies 11 for repelling radial forces. Although four elastic bodies 11 are shown in FIG. 1, the number of elastic bodies 11 does not necessarily have to be four. The elastic bodies 11 may be metal springs or leaf springs, for example. The main bearing 2 is movably supported by the squeeze film damper units 3. The squeeze film damper units 3 are housed in a bearing case 12, and the bearing case 12 is fixed to the ground via a pedestal 13.

[0016] As shown in FIG. 2 , a side plate 14 that moves together with the movable main bearing 2 is installed at the axial end of the main bearing 2. A relative displacement measurement sensor 15 is provided on the side plate 14 to measure the relative displacement of the rotating shaft 4 as viewed from the movable main bearing 2. The relative displacement measurement sensor 15 may be, for example, an eddy current displacement sensor, but is not limited to this. Furthermore, an absolute displacement measurement sensor 16 is provided on the stationary housing 9 of the squeeze film damper section 3 to measure the absolute displacement of the rotating shaft 4 as viewed from the housing 9. The absolute displacement measurement sensor 16 may be, for example, an eddy current displacement sensor, but is not limited to this. The relative displacement measurement sensor 15 and the absolute relative measurement sensor 16 are each arranged in two locations, and are paired with each other. This improves the measurement accuracy of the relative displacement 17 and the absolute displacement 18.

[0017] As shown in Figure 1, the squeeze film damper-equipped bearing device 1 includes an abnormality detection unit 31, which is connected to the relative displacement measurement sensor 15 and the absolute displacement measurement sensor 16 via a signal line 33. The abnormality detection unit 31 is configured with a CPU and other components, and performs abnormality diagnosis using past correlation analysis data and the like stored in a storage device 30.

[0018] A diagnostic flow for the bearing device with a squeeze film damper 1 using the relative displacement measuring sensor 15 and the absolute displacement measuring sensor 16 will be described with reference to Fig. 3. Fig. 3 is a flowchart showing the diagnostic flow for the bearing device with a squeeze film damper 1 according to one embodiment of the present invention.

[0019] The abnormality detection unit 31 (see FIG. 1) receives (S1) relative displacement 17 (see FIG. 4) measured by relative displacement measurement sensor 15, absolute displacement 18 (see FIG. 4) measured by absolute displacement measurement sensor 16, and operation information such as rotational speed. At a predetermined rotational speed (preferably the rated operating speed of the rotating machine) suitable for damage detection (S2), the abnormality detection unit 31 calculates (S3) the correlation between relative displacement 17 and absolute displacement 18, and monitors changes in this correlation (S4) to detect abnormalities in the main bearing 2 and squeeze film damper unit 3. The calculation of the correlation also includes information on the temperature and amount of lubricating oil supplied to the main bearing 2 and squeeze film damper unit 3, eliminating the effect of these parameters on the correlation of displacement and improving detection accuracy.

[0020] That is, the abnormality detection unit 31 calculates the correlation between the relative displacement 17 measured by the relative displacement measurement sensor 15 and the absolute displacement 18 measured by the absolute displacement measurement sensor 16, analyzes changes in the correlation, and detects an abnormality in at least one of the main bearing 2 or the squeeze film damper unit 3.

[0021] Next, the effects of this embodiment will be described with reference to FIGS. 4 to 6 in addition to FIG. FIG. 4 is a mass-spring-damping model of a squeeze film damper bearing device 1 according to one embodiment of the present invention. FIG. 5 is an explanatory diagram showing an example of the effect of a squeeze film damper bearing device according to one embodiment of the present invention. FIG. 6 is an explanatory diagram showing another example of the effect of a squeeze film damper bearing device according to one embodiment of the present invention. Note that FIG. 4 shows the behavior when supporting a rotating shaft 4.

[0022] As shown in Fig. 4, the mass M of the rotating shaft 4 is supported by the oil film spring Kmain and oil film damping Cmain of the main bearing lubricating oil film 8. The mass m of the main bearing 2 is supported by the spring Ksf of the elastic body 11 and the damping Csf of the squeeze film 10. The figure also shows a relative displacement 17 measured by a relative displacement measuring sensor 15 and an absolute displacement 18 measured by an absolute displacement measuring sensor 16.

[0023] First, we will use Figures 3 and 5 to explain the displacement that occurs when lubricant sludge buildup or insufficient oil supply occurs in the main bearing 2. As shown in Figure 5, when lubricant sludge buildup or insufficient oil supply occurs in the main bearing 2, the area where the main bearing lubricant film 8 forms becomes smaller, resulting in a thinner main bearing lubricant film 8. As the oil film 8 becomes thinner, the oil film spring Kmain increases. In this case, as shown by the dashed line in Figure 5, the displacement between the rotating shaft 4 and the main bearing 2 becomes smaller, and the rotating shaft 4 and the main bearing 2 move in phase. As a result, when absolute displacement 18 and relative displacement 17 are compared, absolute displacement 18 >> relative displacement 17, and both displacements are in phase. Therefore, as shown in Figure 3, by measuring and analyzing both relative displacement 17 and absolute displacement 18 and monitoring changes in their relationship, it becomes possible to quickly detect an increase in lubricant sludge buildup or insufficient oil supply in the main bearing 2 (S41) and issue an alert. Specifically, as shown in FIG. 3, when the absolute displacement 18 and the relative displacement 17 are in phase and the absolute displacement 18 is sufficiently larger than the relative displacement 17, an alert is issued.

[0024] Next, detection of damage to the elastic body 11 will be described with reference to FIGS. When the elastic body 11 is subjected to repeated loads due to the vibration of the rotating shaft 4, tiny cracks may develop within the elastic body 11 due to fatigue. Once a crack develops, further repeated loads may propagate the crack and ultimately lead to fracture. As a crack develops in the elastic body 11, the spring force Ksf of the elastic body 11 changes. When Ksf changes, the absolute displacement 18 remains unchanged, but the relative displacement 17 increases. Therefore, as shown in FIG. 3, by understanding the normal relationship between the relative displacement 17 and the absolute displacement 18 and comparing and monitoring the relationship between the relative displacement 17 and the absolute displacement 18 with the normal state (past correlation analysis data), early detection of damage to the elastic body 11 becomes possible (S42) and issuing an alert. Specifically, as shown in FIG. 3, an alert is issued when the absolute displacement 17 remains unchanged and the relative displacement 18 increases compared to the normal state. For this reason, the squeeze film damper-equipped bearing device 1 includes a storage device 30 that stores past correlation analysis data.

[0025] As described above, by applying this embodiment, it is possible to detect an abnormality early and identify its cause, thereby shortening the period for taking measures and reducing loss costs.

[0026] Specifically, the squeeze film damper-equipped bearing device 1 of this embodiment can prevent accidents by detecting abnormalities caused by an increase in sludge or insufficient oil supply in the main bearing 2, as well as signs of damage to the elastic body 11 that movably supports the main bearing 2. It also reduces the time required to identify the cause of abnormal vibration, contributing to reduced loss costs.

[0027] A centrifugal compressor 29 to which the above-described bearing device with a squeeze film damper 1 is applied will be described with reference to Fig. 7. Fig. 7 is a cross-sectional view showing an embodiment of a centrifugal compressor 29 equipped with a bearing device with a squeeze film damper 1 according to an embodiment of the present invention.

[0028] The centrifugal compressor 29 includes a casing 19 formed into a cylindrical shape or the like and serving as a stationary part (stator), a rotating shaft 4 rotatably mounted within the casing 19 and supported by a squeeze film damper-equipped bearing device 1 and a thrust bearing 20, and a multi-stage (five-stage in FIG. 7 ) impeller 21 attached to the rotating shaft 4. The rotating shaft 4 and the impeller 21 form a rotor (rotating body) 22. Note that, in this embodiment, a single-shaft multi-stage centrifugal compressor in which multiple impellers 21 are provided on a single rotating shaft 4 will be described as an example, but the present invention can also be applied to a single-stage centrifugal compressor in which only one impeller 21 is provided.

[0029] The casing 19 is provided with an intake passage 23 that introduces gas, which is the working fluid, into the first-stage impeller 21, a diffuser 24 that converts the kinetic energy of the gas emitted from each stage of the impeller 21 into pressure energy, a return passage 25 that introduces the compressed gas from the diffuser 24 into the next-stage impeller 21, and a discharge passage 26 that discharges the gas emitted from the final-stage impeller 21 out of the casing 19.

[0030] The rotating shaft 4 of the rotor 22 is rotatably supported via squeeze film damper bearings 1 provided at the suction side (left side in FIG. 7) end and the discharge side (right side in FIG. 7) end of the casing 19. A thrust bearing 20 that receives a thrust load is provided at the suction side end of the rotating shaft 4, and a balance piston 27 that offsets the thrust load is provided at the discharge side of the multi-stage impellers 21 on the rotating shaft 4.

[0031] A driving machine such as a motor (not shown) is connected to the discharge side end of the rotating shaft 4, and this driving machine rotates and drives the rotor 22. As the rotor 22 rotates, gas is sucked into the suction passage 23, compressed sequentially by the multiple stages of impellers 21, and finally discharged from the discharge passage 26.

[0032] An impeller nozzle labyrinth seal (not shown) is provided in the gap between the nozzle of each stage impeller 21 and the casing 19, which prevents gas emitted from the impeller 21 from passing through the gap and returning to the inlet side of the impeller 21. An intermediate stage labyrinth seal (not shown) is provided in the gap between the rotor 22 and the casing 19 between the front stage impeller 21 and the rear stage impeller 21, which prevents gas in the return flow path 25 from passing through the gap and returning to the outlet side of the front stage impeller 21. A balance piston part labyrinth seal 28 is provided in the gap between the balance piston 27 of the rotor 22 and the casing 19, which prevents high-pressure gas emitted from the final stage impeller 21 from leaking to the low-pressure part.

[0033] Since the centrifugal compressor 29 rotates at high speed, if an abnormality occurs in the rotating shaft or bearing, vibration increases, and in the worst case, there is a risk of the device breaking down. In this embodiment, as described above, it is possible to detect such abnormalities early and identify their causes, thereby improving the reliability of the centrifugal compressor 29 and shortening the time required to take measures when an abnormality occurs. As a result, it is possible to reduce loss costs.

[0034] The above-described embodiment of the present invention has the following features. (1) A bearing device 1 with a squeeze film damper includes a main bearing 2 that supports a rotating shaft 4, a bearing housing 7 that forms part of the main bearing 2 and configures the outer periphery of the main bearing 2, a housing 9 that is provided on the outer periphery of the bearing housing 7 with a gap between it and the housing 9, and a squeeze film damper portion 3 that is provided in the gap between the bearing housing 7 and the housing 9, The apparatus includes a relative displacement measurement sensor (15) that measures the relative displacement of the rotating shaft (4) viewed from the main bearing (2), an absolute displacement measurement sensor (16) that measures the absolute displacement of the rotating shaft (4) viewed from the housing (9), and an abnormality detection unit (31), The abnormality detection unit 31 calculates the correlation between the relative displacement 17 measured by the relative displacement measurement sensor 15 and the absolute displacement 18 measured by the absolute displacement measurement sensor 16, analyzes changes in the correlation, and detects an abnormality in at least one of the main bearing 2 or the squeeze film damper unit 3.

[0035] (2) The relative displacement measuring sensor 15 and the absolute displacement measuring sensor 16 are eddy current displacement meters.

[0036] (3) The relative displacement measuring sensor 15 and the absolute displacement measuring sensor 16 are each disposed at two locations.

[0037] (4) The rotation speed when calculating the correlation is a predetermined rotation speed.

[0038] (5) The predetermined rotational speed for calculating the correlation is the rated operating speed of the target rotating machine.

[0039] (6) The abnormality detection unit 31 calculates the correlation including information on the temperature of the lubricating oil and the amount of oil supplied.

[0040] (7) A centrifugal compressor 29 including a casing 19, a rotary shaft 4 rotatably provided inside the casing 19 and supported by a squeeze film damper-equipped bearing device and a thrust bearing 20, and a multi-stage impeller 21 attached to the rotary shaft 4, As the bearing device with a squeeze film damper, the above-described bearing device with a squeeze film damper 1 is mounted.

[0041] The present invention is not limited to the above-described embodiments, but includes various modifications. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the configurations. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations. [Explanation of symbols]

[0042] 1...bearing device with squeeze film damper, 2...main bearing, 3...squeeze film damper portion, 4...rotating shaft, 5...pad, 6...pivot, 7...bearing housing, 8...main bearing oil film, 9...housing, 10...squeeze film, 11...elastic body, 12...bearing case, 13...pedestal, 14...side plate, 15...sensor for measuring relative displacement, 16...sensor for measuring absolute displacement, 17...relative displacement, 18...absolute displacement, 19...casing, 20...thrust bearing, 21...impeller, 22...rotor, 23...suction passage, 24...diffuser, 25...return passage, 26...discharge passage, 27...balance piston, 28...seal, 29...centrifugal compressor, 30...past correlation data.

Claims

1. A bearing device with a squeeze film damper includes: a main bearing that supports a rotating shaft; a bearing housing that forms part of the main bearing and configures an outer periphery of the main bearing; a housing that is provided on the outer periphery of the bearing housing with a gap between it and the bearing housing; and a squeeze film damper portion that is provided in the gap between the bearing housing and the housing, a relative displacement measuring sensor that measures a relative displacement of the rotating shaft seen from the main bearing, an absolute displacement measuring sensor that measures an absolute displacement of the rotating shaft seen from the housing, and an abnormality detection unit, the abnormality detection unit calculates a correlation between the relative displacement measured by the relative displacement measurement sensor and the absolute displacement measured by the absolute displacement measurement sensor, analyzes a change in the correlation, and detects an abnormality in at least one of the main bearing or the squeeze film damper unit.

2. 2. The squeeze film damper-equipped bearing device according to claim 1, 10. A bearing device with a squeeze film damper, wherein the relative displacement measuring sensor and the absolute displacement measuring sensor are eddy current displacement meters.

3. 2. The squeeze film damper-equipped bearing device according to claim 1, a bearing device with a squeeze film damper, wherein the relative displacement measuring sensor and the absolute displacement measuring sensor are each disposed at two locations;

4. 2. The squeeze film damper-equipped bearing device according to claim 1, A squeeze film damper-equipped bearing device, wherein the rotational speed when calculating the correlation is a predetermined rotational speed.

5. 5. The squeeze film damper-equipped bearing device according to claim 4, 10. A bearing device with a squeeze film damper, wherein the predetermined rotational speed for calculating the correlation is the rated operating speed of the target rotary machine.

6. 2. The squeeze film damper-equipped bearing device according to claim 1, The bearing device with a squeeze film damper is characterized in that the abnormality detection unit calculates the correlation by taking into account information on the temperature and amount of lubricating oil supplied.

7. A centrifugal compressor comprising: a casing; a rotary shaft rotatably provided inside the casing and supported by a squeeze film damper-equipped bearing device and a thrust bearing; and a multi-stage impeller attached to the rotary shaft, 7. A centrifugal compressor comprising the squeeze film damper bearing device according to claim 1, as the squeeze film damper bearing device.

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