JP5463211B2 - Tilting pad type journal bearing device and steam turbine using the same - Google Patents

Description

  The present invention relates to a tilting pad type journal bearing device.

  In bearings used in steam turbines, tilting pad bearings are used when the average surface pressure (the load applied to the bearing divided by the projected area of the bearing) is relatively low. This is because, compared to other types of bearings (round bearings, elliptical bearings, etc.), the force in the direction of rotating the rotating shaft caused by the oil film pressure is small and unstable vibrations caused by the bearings are less likely to occur. It is.

  However, when a force in the direction of swinging the rotating shaft is generated in another part such as a seal, there is a problem that unstable vibration is likely to occur particularly when the average surface pressure is small. This is because when the vertical rigidity and the horizontal rigidity due to the oil film of the bearing are isotropic (uniform), it is impossible to cancel the force that swings the rotating shaft.

  As an improvement measure, the difference (bearing spring anisotropy) between the rigidity in the vertical direction and the rigidity in the horizontal direction due to the oil film of the bearing may be increased. In Patent Document 1, in order to give anisotropy to the rigidity of the oil film itself, the dimensions of the curvature radius, thickness, width, and arc angle of the pad inner surface are changed individually or in combination.

  The rigidity of the bearing is influenced not only by the characteristics of the oil film formed between the rotating shaft and the pad, but also by the rigidity of the support member of the bearing. Therefore, in Patent Document 2, the bearings are attached by the first and second elastic support devices, and the rigidity of these support devices is different so that the rigidity of the bearing can be made anisotropic.

Japanese Patent Laid-Open No. 60-60320 JP 61-248915 A

  However, in the method described in Patent Document 1, in order to examine the influence of each dimension specification on bearing rigidity, it is necessary to obtain the characteristics of the oil film according to the specification by numerical analysis.

  Moreover, in the method described in patent document 2, it is necessary to attach two types of support apparatuses, and a structure is complicated.

  An object of the present invention is to provide a tilting pad type journal bearing device that can reduce unstable vibration of a rotating shaft with a simple structure.

The present invention relates to a tilting pad type journal bearing device comprising a plurality of pads for supporting a rotating shaft, a pivot fixed to the back surface of the plurality of pads, and a housing for supporting the plurality of pads via the pivot. The rigidity of the pivot fixed to at least one pad installed in the load direction of the rotating shaft is larger than the rigidity of the pivot fixed to the other pad, and the surface in contact with the housing of the pivot fixed to each pad is The radius of curvature of the spherical surface of the pivot that is a spherical surface and is fixed to the at least one pad installed in the load direction of the rotating shaft is larger than the radius of curvature of the spherical surface of the pivot fixed to the other pad. It is characterized by that.

  According to the tilting pad type journal bearing device of the present invention, the unstable vibration of the rotating shaft is reduced by a simple structure which gives the bearing rigidity anisotropy by changing the rigidity of the pivot which is a member supporting the bearing pad. it can.

It is sectional drawing which shows the tilting pad type journal bearing apparatus which concerns on the Example of this invention. 1 is an overall schematic diagram of a steam turbine according to an embodiment of the present invention. It is explanatory drawing explaining the anisotropy and stability of bearing rigidity. It is explanatory drawing explaining the oil film spring and pivot spring of a bearing.

  Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings as appropriate. In addition, the same code | symbol is attached | subjected to the equivalent component through each drawing.

  An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a sectional view showing an example of a tilting pad type journal bearing device according to this embodiment. FIG. 2 is an overall schematic view showing an example of a steam turbine according to an embodiment of the present invention. FIG. 3 is a diagram for explaining the anisotropy and stability of bearing rigidity. FIG. 4 is a view for explaining the oil film spring and the pivot spring of the bearing.

  In FIG. 1, 1a and 1b are pads, 2 is a rotating shaft, 3 is a housing, and 5a and 5b are pivots.

  As shown in FIG. 1, pads 1 a and 1 b are disposed around the rotation shaft 2. The pad 1a is a pad installed in the load direction of the rotating shaft 2 indicated by W, and mainly supports the load of the rotating shaft 2. Pivots 5 a and 5 b are fixed to the back surfaces of the pads 1 a and 1 b, respectively, and these pivots are in contact with the inner surface of the housing 3. Therefore, the pads 1a and 1b are supported by the housing via the pivots 5a and 5b, respectively.

Since the surface in contact with the housing 3 of the pivot 5a is a spherical surface that is spherically processed with _a radius of curvature ra, the pad 1a can swing while the pivot 5a is in contact with the housing 3. Incidentally, the spherical machining of the housing surface in contact likewise curvature radius r _b of the pivot 5b is a spherical surface that has been subjected, and has a r _a> r _b.

  Lubricating oil is present in a space surrounded by the pad 1 and the rotating shaft 2 by supplying the lubricating oil from an oil supply port (not shown). When the rotating shaft 2 rotates, an oil film is formed between the respective pads 1 and the rotating shaft 2 by lubricating oil. Since the rotating shaft 2 is lifted by the pressure generated in the oil film, the rotating shaft 2 can rotate without directly contacting the pad 1. The pressure generated in the oil film is the largest in the pad 1a installed in the load direction shown as W in FIG. 1, and the pressure in the other pads 1b is smaller than that. Since these oil films have spring and damping characteristics, they affect the vibration of the rotating shaft 2.

  In the rotating shaft 2 of the steam turbine as shown in FIG. 2, a vibration that causes the rotating shaft 2 to swing is generated by a fluid force generated in a seal (not shown) installed in each stage of the turbine stage of the turbine 6. Cheap.

FIG. 3 explains the influence of the sealing fluid force and the bearing spring anisotropy on the stability of the shaft vibration. When the seal fluid force is taken on the vertical axis and the bearing spring anisotropy is taken on the horizontal axis, the boundary between the stability and instability of the shaft vibration becomes an upward curve as shown by a solid line in the figure. The sealing fluid force is determined by the shape of the sealing portion. For example, when a bearing having a bearing fluid anisotropy of d ₁ is attached when the seal fluid force is k ₁ , the shaft becomes unstable and vibrations occur. On the other hand, when a bearing whose spring anisotropy is d ₂ is attached, the shaft is stabilized and no vibration occurs. Thus, if the sealing fluid force is the same, the stability is improved by attaching a bearing having a large anisotropy.

  By the way, in FIG. 2, the spring characteristics of the bearing 4 that supports the rotary shaft 2 are affected not only by the characteristics of the oil film but also by the characteristics of the pivot. As shown in FIG. 4, the oil film spring 11 and the pivot spring 12 are connected in series via the pad 1. Since the mass of the pad 1 is very small compared with the mass of the rotating shaft 2 and can be almost ignored, it may be considered that these springs are simply connected in series. In other words, the spring characteristics of the bearing 4 can be adjusted by adjusting the pivot spring 12.

The adjustment of the pivot spring 12 can be adjusted by the radius of curvature of spherical processing applied to the contact portion with the housing. The larger the radius of curvature, the smaller the deformation and the greater the spring stiffness.

In the embodiment of the present invention, because the curvature radius r _a of the pivot 5a is fixed to the pad 1a supporting become main load, it is larger than the radius of curvature r _b of the other pad 1b, to load The bearing spring stiffness in the load direction can be increased compared to the bearing spring stiffness in the vertical direction. As a result, according to the present embodiment, a bearing having high spring rigidity anisotropy can be realized, and a steam turbine that is stable against vibration can be realized.

Therefore, according to the tilting pad type journal bearing of this embodiment, the curvature radius r _a of the pivot 5a is fixed to the pad 1a supporting become main load, greater than the radius of curvature r _b of the other pad 1b With this simple structure, unstable vibration of the rotating shaft can be reduced. Further, as described in FIG. 4, the bearing spring rigidity can be calculated on the assumption that the oil film spring and the pivot spring are in series. According to the structure of this embodiment, it is only necessary to change the characteristic value of the pivot spring according to the radius of curvature. Compared to calculating the oil film characteristic value by numerical analysis, the calculation of the pivot spring characteristic value by mathematical formula is simpler, so the calculation of the characteristic is also simpler than other methods that change the oil film characteristic to change the bearing spring characteristic. is there.

  In addition, this invention is not limited to an above-described Example, For example, the pad 1a installed in a load direction is not limited to one piece. The above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Further, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

1a, 1b Pad 2 Rotating shaft 3 Housing 4 Bearing 5 Pivot 6 Turbine 11, 12 Spring

Claims (2)

A steam turbine comprising a rotating shaft, a tilting pad type journal bearing device that supports the rotating shaft, a turbine attached to the rotating shaft, and a seal provided in a stage portion of the turbine,
The bearing device includes:
A plurality of pads for supporting the rotating shaft;
A pivot fixed to each back surface of the plurality of pads;
A housing that supports the plurality of pads via the pivot;
Wherein among the plurality of pads, the pivot of the rigid fixed to at least one of said pads disposed in the load direction of the rotating shaft, much larger than the said pivot rigid fixed to the other of the pad ,
The surface of the pivot that is fixed to the plurality of pads is in contact with the housing is a spherical surface,
Of the plurality of pads, the radius of curvature of the spherical surface of the pivot fixed to at least one of the pads installed in the load direction of the rotating shaft is the other of the pivots fixed to the other pad. A steam turbine characterized by being larger than a radius of curvature of a spherical surface. A plurality of pads that support the rotation axis;
A pivot fixed to each back surface of the plurality of pads;
A tilting pad type journal bearing device comprising a housing for supporting the plurality of pads via the pivot,
Said at least one rigid fixed said pivot to said pad disposed in the load direction of the rotating shaft, much larger than the rigidity of the pivot fixed to the other of said pad,
The surface of the pivot that is fixed to the pad and in contact with the housing is a spherical surface,
The radius of curvature of the spherical surface of the pivot fixed to at least one of the pads installed in the load direction of the rotating shaft is larger than the radius of curvature of the spherical surface of the pivot fixed to another pad. Tilting pad type journal bearing device.

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