JP5427799B2 - Tilting pad journal bearing device and turbomachine using the same - Google Patents

Description

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

  A tilting pad journal bearing device is used as a bearing device for supporting a rotating shaft of a high-speed rotating machine such as a steam turbine.

  As described in Patent Document 1, a tilting pad journal bearing device is generally arranged around a rotating shaft of a rotating machine, and a plurality of pads that support the rotating shaft, and a pivot disposed on the back surface of the pad. And a bearing housing that supports and accommodates the plurality of pads via a pivot.

  The elliptical journal bearing device is suitable for high load conditions such as a steam turbine, but has a problem of unstable vibration caused by a bearing such as an oil whip or an oil whirl. That is, since the bearing load decreases and the eccentric amount of the shaft decreases, the stability of the shaft / bearing system is impaired, and thus there is a high possibility that self-excited vibration will occur.

  On the other hand, the tilting pad journal bearing device is less likely to cause unstable vibration due to a bearing such as an oil whip or an oil whirl in a high-speed rotating machine than an elliptical journal bearing device or the like.

  By the way, in a turbo machine such as a steam turbine, there is a possibility that self-excited vibration (unstable vibration in which a natural frequency component diverges) is generated due to the vertical and horizontal coupled spring characteristics of the working fluid force. This unstable vibration in the steam turbine is called steam whirl.

JP 2004-301258 A

  The steam whirl described above is generated by coupling the vertical vibration and the horizontal vibration by the coupled spring characteristics of the working fluid. That is, it can be said that steam whirl is more likely to occur as the vertical natural frequency governed by the vertical support stiffness and the horizontal natural frequency governed by the horizontal support stiffness are closer. Accordingly, steam whirl can be prevented by increasing the anisotropy of the support rigidity in the vertical and horizontal directions.

  In the conventional tilting pad journal bearing device, for example, as disclosed in FIG. 1 of Patent Document 1, there is a case where a device for stably forming a lubricating oil film is formed by processing the surface of the pad. is there. However, in this prior art, since the upper pad is processed, the influence on the rigidity of the bearing is small, and it is not considered to prevent the steam whirl by increasing the anisotropy of the bearing rigidity. Furthermore, since the above prior art is a load bit pad type that supports the bearing load from the 45 ° right and left directions, the anisotropy of the bearing rigidity is considered to be extremely small.

  Accordingly, an object of the present invention is to provide a tilting pad journal bearing device that suppresses unstable vibration caused by the working fluid force of a turbomachine with a simple structure by increasing the anisotropy of bearing rigidity. .

In order to achieve the above object, a tilting pad journal bearing device according to the present invention includes a plurality of pads arranged around a rotating shaft and supporting the rotating shaft, and a bearing housing that accommodates the plurality of pads. A load direction pad located in the load direction of the rotation axis and a pad adjacent to both sides of the load direction pad in the circumferential direction, and a rotation axis of the pad adjacent to both sides of the load direction pad in the circumferential direction The pressure receiving surface that supports the pressure direction is provided with a step so that the area of the pressure receiving surface that supports the rotation axis of the load direction pad is larger than the area of the pressure receiving surface of the pad adjacent to both sides in the circumferential direction of the load direction pad. It is a feature.

  According to the present invention, it is possible to provide a tilting pad journal bearing device that suppresses unstable vibration caused by the working fluid force of a turbomachine with a simple structure by increasing the anisotropy of the bearing rigidity. .

1 is an axial cross-sectional view of a tilting pad journal bearing device according to a first embodiment of the present invention. It is AA sectional drawing shown in FIG. It is BB sectional drawing shown in FIG. It is a partial sectional view of an example of a steam turbine to which the present invention is applied. FIG. 6 is a cross-sectional view perpendicular to the axis of a tilting pad journal bearing device according to a second embodiment of the present invention.

  EMBODIMENT OF THE INVENTION Below, the form for implementing this invention is demonstrated using drawing.

  A first embodiment of the present invention will be described. FIG. 1 is a cross-sectional view perpendicular to the axis of the tilting pad journal bearing device 1 of the present invention, FIG. 2 is a cross-sectional view taken along line AA shown in FIG. 1, and FIG. 3 is a cross-sectional view taken along line BB shown in FIG. .

  As shown in FIG. 1, the tilting pad journal bearing device 1 of the present embodiment is arranged around a rotating shaft 2 and supports a plurality of pads 3 that support the rotating shaft 2 and the pads 3 on the inner peripheral surface. And a bearing housing 4 accommodated therein. The rotating shaft 2 is a rotating body of a turbo machine that is a high-speed rotating machine, for example, a rotor of a steam turbine. The load direction, which is the direction in which the load of the rotary shaft 2 acts, is the downward direction in the figure.

  A plurality of pads 3 are provided in the bearing housing 4 in the circumferential direction. White metal or the like is lined on the inner peripheral surface of the pad 3, and a pressure receiving surface 5 that supports the rotating shaft 2 is formed. Lubricating oil is supplied into the bearing housing 4 from an oil supply hole (not shown), and the supplied lubricating oil is passed through the pressure receiving surface 5 of the pad 3 to form an oil film. The rotating shaft 2 is supported on the pressure receiving surface 5 of the pad 3 through an oil film of lubricating oil while rotating at high speed.

  Note that the lubricating oil supplied from the oil supply hole passes through the side surface and the back surface of the pad 3 to cool the pad 3 and to be supplied uniformly between the pads 3. A seal (not shown) is provided at the axial end of the bearing housing 4, and the lubricating oil is held in the housing by the seal, and excess lubricating oil is discharged outside the bearing through the seal gap.

  Returning to the description of the pad 3. The tilting pad journal bearing device 1 of the present embodiment has a load direction pad 3a located in the load direction of the rotating shaft 2 (downward in FIG. 1) on the lower half side of the tilting pad journal bearing device. ing. The load direction pad 3 a is a pad that receives the load of the rotary shaft 2 among the plurality of pads 3 arranged in the bearing housing 4. The pressure-receiving surface 5 of the load direction pad 3a has no irregularities such as grooves and steps along the circumferential direction, and is formed flat.

  On the other hand, a step 6 is provided along the circumferential direction on the pressure receiving surface 5 of the pads 3b and 3c adjacent to both sides in the circumferential direction of the load direction pad 3a on the lower half side of the tilting pad journal bearing device. .

  As shown in FIG. 2, the pressure receiving surface 5 of the pad 3 b adjacent to the upstream side of the rotation axis 2 of the load direction pad 3 a has a uniform cross section along the circumferential direction at the center in the axial direction. A groove 7 is provided. By providing the groove 7 on the pressure receiving surface 5, a step is formed on the pressure receiving surface 5 so that the axial cross section of the pad 3b has a concave shape.

  Further, as shown in FIG. 3, in the pressure receiving surface 5 of the pad 3c adjacent to the downstream side in the rotation direction of the rotation axis of the load direction pad 3a, both axial end portions excluding the central portion in the axial direction are arranged in the circumferential direction. A step is formed on the pressure receiving surface 5 so that the axial cross section of the pad 3c has a convex shape.

  In the tilting pad journal bearing device 1 of this embodiment, a step is provided on the pressure receiving surfaces of the pad 3b and the pad 3c, and no step is formed on the pressure receiving surface of the load direction pad 3a. The area of the pressure receiving surface of the pad 3b adjacent to the pad 3c is different from the area of the pressure receiving surface of the pad 3c, and the area of the pressure receiving surface of the load direction pad 3a is larger than the area of the pressure receiving surface of the pad 3b adjacent to the pad 3c. It is comprised so that it may become.

  Next, the function and effect of this embodiment will be described.

  When a turbomachine is modeled by the mass of a rotating shaft, a bearing spring and a working fluid coupled spring, the equation of motion is expressed by the following equation.

  Here, X is the vertical displacement, Y is the horizontal displacement, M is the mass of the rotating shaft, Kx is the vertical bearing spring constant, Ky is the horizontal bearing spring constant, and K is the coupled spring constant of the working fluid. Yes, ... represents the second derivative of time. Such a stability condition of the vibration system is expressed by the following equation.

  That is, it is understood that the stability increases as the anisotropy | Kx−Ky | of the bearing spring constant increases.

  In the present embodiment, on the lower half portion side of the tilting pad journal bearing device 1, a load direction pad 3a positioned in the load direction of the rotary shaft 2 and pads 3b and 3c adjacent to both sides in the circumferential direction of the load direction pad 3a are provided. Further, as described above, the step 6 is provided on the pressure receiving surfaces 5 of the pads 3b and 3c adjacent to both sides in the circumferential direction of the load direction pad 3a, whereby the pressure receiving area of the pads 3b and 3c can be reduced. Therefore, the spring constant in the direction perpendicular to the load due to the pads 3b and 3c can be reduced. For this reason, the anisotropy | Kx−Ky | of the bearing spring constant can be increased, and unstable vibration caused by the working fluid force of the turbomachine can be prevented.

  Furthermore, in addition to preventing unstable vibration, the groove 7 is formed in the pad 3b adjacent to the upstream side in the rotational direction of the rotation axis of the load direction pad 3a so that the pad cross-section is concave. Lubricating oil can be effectively supplied to the load direction pad 3a.

  The lubricating oil supplied to the upper half of the housing flows in the rotational direction along the rotation of the rotary shaft 2 and flows into the lower half of the housing. In the present embodiment, since the groove 7 is formed in the pad 3b adjacent to the upstream side of the rotation direction of the rotation axis of the load direction pad 3a so that the pad cross-section is concave, the rotation axis rotation direction from the upper half side of the bearing housing 4 A portion of the lubricating oil that flows to the lower half along the groove is collected in the groove 7, and the collected lubricating oil flows down the groove 7 and flows into the load direction pad 3a. Can be cooled.

  Moreover, the lubricating oil which lubricated the load direction pad 3a flows into the pad 3c along the rotation direction of a rotating shaft. In this embodiment, since the pad 3c on the downstream side in the rotational direction adjacent to the load direction pad 3a is formed in a convex cross section, the lubricating oil generated by the lubrication of the load direction pad 3a is effectively removed outside the bearing by the pad 3c. can do.

  In addition, even if both the axial cross-sectional shapes of the pads 3b and 3c provided adjacent to the load direction pad 3a are formed in a circumferentially uniform convex shape or concave shape, the pressure receiving area of the pads 3b and 3c is reduced. Therefore, the area of the pressure receiving surface of the load direction pad 3a can be made larger than the areas of the pressure receiving surfaces of the adjacent pad 3b and pad 3c, and the spring constant in the direction perpendicular to the load caused by the pads 3b and 3c can be reduced. For this reason, the anisotropy | Kx−Ky | of the bearing spring constant can be increased, and unstable vibration caused by the working fluid force of the turbomachine can be prevented.

  Further, in the tilting pad bearing device of the present embodiment, the area of the pressure receiving surface of the load direction pad 3a can be maintained by reducing the area of the pressure receiving surface of the adjacent pads 3b and 3c, and the bearing spring constant is anisotropic. The property | Kx−Ky | can be increased, and the rigidity in the load direction can be maintained.

  Further, in this embodiment, it is only necessary to provide a groove on the pressure receiving surface of the pad, the structure is simple, and the manufacturability and cost are excellent.

  The tilting pad journal bearing device 1 of the present invention can be used in a turbo machine such as a steam turbine, a gas turbine, or a centrifugal compressor.

  FIG. 4 is a partial cross-sectional view of an example of a general steam turbine. The steam turbine 13 includes a rotor 8 that is a rotating shaft, a casing 9 that includes the rotor 8 and forms a flow path of steam that is a working fluid, a stationary blade 10 that is fixed inside the casing 9, and a rotor 8. A fixed moving blade 11 and a bearing device 12 for supporting the rotor 8 are provided. A plurality of stationary blades 10 are fixed in the turbine circumferential direction inside the casing 9 to form a stationary blade row. In addition, a plurality of moving blades 11 are fixed to the rotor 8 in the circumferential direction to form a moving blade row. The steam turbine 13 forms a paragraph with a stationary blade row and a moving blade row provided facing the downstream side in the working fluid flow direction of the stationary blade row, and a plurality of stages in which a plurality of stages are provided in the axial direction of the rotor 8. It has a paragraph structure.

  By applying the tilting pad journal bearing device 1 of the present invention to the bearing device 12 of the steam turbine, unstable vibration caused by the working fluid force of the steam turbine, that is, steam whirl can be suppressed.

  A second embodiment of the present invention will be described. FIG. 5 is a cross-sectional view perpendicular to the axis of the tilting pad journal bearing device 1 according to the second embodiment. The same structural parts as those of the first embodiment are denoted by the same reference numerals and description thereof is omitted.

  In the present embodiment, the circumferential length of the load direction pad 3a is made larger than the pads 3b and 3c adjacent to both sides in the circumferential direction of the load direction pad 3a. Thereby, the area of the pressure receiving surface 5 of the pads 3b and 3c provided adjacent to both sides in the circumferential direction of the load direction pad 3a is smaller than the area of the pressure receiving surface 5 of the load direction pad 3a. In this structure, since the force of the bearing oil film in the direction perpendicular to the load by the pads 3b and 3c adjacent to both sides in the circumferential direction of the load direction pad 3a is reduced, the bearing rigidity in the direction perpendicular to the load is lowered, and the bearing rigidity is anisotropic. Therefore, unstable vibration caused by the working fluid force of the turbomachine can be prevented.

DESCRIPTION OF SYMBOLS 1 Tilting pad journal bearing apparatus 2 Rotating shaft 3, 3b, 3c Pad 3a Load direction pad 4 Bearing housing 5 Pressure receiving surface 6 Step 7 Groove 8 Rotor 9 Casing 10 Stator blade 11 Rotor blade 12 Bearing device 13 Steam turbine

Claims (6)

A plurality of pads arranged around the rotation axis and supporting the rotation axis;
A tilting pad journal bearing device with a bearing housing to accommodate
A load direction pad located in the load direction of the rotating shaft, and adjacent to both sides of the load direction pad in the circumferential direction
And the pad provided next to,
Pressure receiving for supporting the rotating shaft of the pad adjacent to both sides of the load direction pad in the circumferential direction
A step is provided on the surface, and the area of the pressure receiving surface of the load direction pad is the circumference of the load direction pad.
Tilte characterized in that it is larger than the area of the pressure-receiving surface of the pad adjacent to both sides.
Ing pad journal bearing device. The tilting pad journal bearing device according to claim 1,
  An axial cross-sectional shape of the pad adjacent to the upstream side in the rotational direction of the rotation axis of the load direction pad.
Shaft of the pad formed in a concave shape and provided adjacent to the downstream side in the rotational direction of the rotational axis of the load direction pad
Tilting pad journal bearing characterized in that the direction cross-sectional shape is formed in a convex shape
apparatus. The tilting pad journal bearing device according to claim 1,
The axial cross-sectional shape of the pad adjacent to both sides of the load direction pad in the circumferential direction is set in the circumferential direction.
Tilting pad journal characterized by having a uniform convex or concave shape
Le bearing device. A rotating shaft, a casing containing the rotating shaft, a stationary blade supported by the casing,
A rotor blade fixed to the rotating shaft, a plurality of pads arranged around the rotating shaft, and the plurality of pads;
And a tilting pad jar for supporting the rotating shaft.
A turbomachine comprising a null bearing device,
The tilting pad journal bearing device includes a load positioned in a load direction of the rotating shaft.
A heavy direction pad, and the pad adjacent to both sides in the circumferential direction of the load direction pad,
Pressure receiving for supporting the rotating shaft of the pad adjacent to both sides of the load direction pad in the circumferential direction
A step is provided on the surface, and the area of the pressure receiving surface of the load direction pad is the circumference of the load direction pad.
A turbomachine characterized in that it is larger than the area of the pressure receiving surface of the pad adjacent to both sides.
Machine. The turbomachine according to claim 4,
An axial cross-sectional shape of the pad adjacent to the upstream side in the rotational direction of the rotation axis of the load direction pad.
Shaft of the pad formed in a concave shape and provided adjacent to the downstream side in the rotational direction of the rotational axis of the load direction pad
A turbomachine having a directional cross-sectional shape formed into a convex shape. The turbomachine according to claim 4,
The axial cross-sectional shape of the pad adjacent to both sides of the load direction pad in the circumferential direction is set in the circumferential direction.
A turbomachine that is formed in a uniform convex or concave shape.

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