JP6311640B2 - Air bearings for rotating shafts with axial heat drop - Google Patents

Description

  The present invention relates to an air bearing using air as a lubricant, and more particularly to an air bearing for a rotary shaft having a heat drop in the axial direction.

  A structure in which a rotary shaft directly connecting a compressor and a turbine in a gas turbine is supported by an air bearing using air as a lubricant at an intermediate portion thereof is described in Patent Document 1 below. In the embodiments shown in FIGS. 4, 5, 6, and 7 of this patent document, air is flowed from one end close to the turbine toward the other end close to the compressor. In this example, air is flowed from one end closer to the compressor to the other end closer to the turbine. However, in each of the examples, details of the air flow path in the air bearing are not mentioned. Also not shown.

JP 2004-245193 A

  When a rotary shaft that directly connects a compressor and a turbine in a gas turbine is supported by a bearing at an intermediate portion thereof, the rotary shaft supports the compressor from one end portion that supports the turbine during operation after the gas turbine is warmed up. A fairly large heat drop is exhibited in the axial direction over the other end, so that the clearance between the rotating shaft and the bearing sleeve in the bearing is possible over the entire operating range starting from the cold start of the gas turbine. Therefore, in order to stabilize and improve the bearing performance, it is necessary to cool the side near the turbine of the bearing more strongly than the side near the compressor during the operation of the gas turbine.

  The present invention pays attention to the above-mentioned matters, and an air bearing that supports a rotating shaft directly connecting a compressor and a turbine in a gas turbine at an intermediate portion thereof is provided in the entire operation region starting from the cold start of the gas turbine. It is an object of the present invention to provide a structure in which the clearance between the rotating shaft and the bearing sleeve in the bearing portion is made as steady as possible.

  In order to solve the above problems, the present invention provides an air bearing that supports a rotating shaft that directly connects a compressor and a turbine in a gas turbine at an intermediate portion thereof, and a bearing sleeve that receives the rotating shaft from the surroundings, A plurality of air flow paths having a cylindrical housing that supports the bearing sleeve from the periphery via a plurality of radial ribs, and an annular space between the bearing sleeve and the cylindrical housing is partitioned by the plurality of radial ribs. Is extended from one end close to the compressor to the other end close to the turbine, and the radial ribs are reduced in thickness from the one end toward the other end. This is a proposal.

  As described above, the air bearing that supports the rotary shaft directly connecting the compressor and turbine in the gas turbine at the intermediate portion thereof has a bearing sleeve that receives the rotary shaft from the periphery, and a plurality of radial ribs from the periphery of the bearing sleeve. A plurality of air flow paths that are formed by partitioning an annular space between the bearing sleeve and the cylindrical housing with the plurality of radial ribs. If the radial rib extends to the other end closer to the turbine and the thickness of the radial rib is reduced from the one end toward the other end, the radial rib is exposed to the air flow path between the plurality of radial ribs. As the area of the wall surface of the bearing sleeve increases from the one end toward the other end, the bearing sleeve is cooled more strongly from the one end toward the other end. And the radial ribs are cooled more strongly by the air flow flowing through the air flow path from the one end toward the other end by reducing the thickness from the one end toward the other end. As a result, even if the amount of heat received by the bearing sleeve from the rotating shaft increases from one end of the bearing sleeve closer to the compressor to the other end closer to the turbine, the heat is applied to the bearing sleeve by the heat. The difference between the two ends of the resulting thermal deformation is suppressed.

It is the schematic which shows the point which supports the rotating shaft which directly connects the compressor and turbine in a gas turbine with the air bearing by this invention in the intermediate part. It is a figure which shows the structure of the air bearing shown in FIG. 1 with the longitudinal cross-section (A) which passes along an axis line, one end surface (B), and cut surface SS (C).

  FIG. 1 is a gas turbine in which the main parts related to the present invention are schematically shown. In FIG. 1, 1 is a compressor, 2 is a turbine, both are directly connected by a rotating shaft 3, and the rotating shaft is in an intermediate portion thereof. Are supported by the air bearing 4.

  The air bearing 4 has a structure in which a longitudinal section passing through the axis thereof is shown in FIG. 2A and an end surface close to the turbine 2 is shown in FIG. And a cylindrical housing 14 that supports the bearing sleeve from the periphery via a plurality of radial ribs 12, and a plurality of annular spaces between the bearing sleeve 10 and the cylindrical housing 14 are provided. A plurality of air flow paths 16 partitioned by the radial ribs 12 extend from one end 4c on the side close to the compressor to the other end 4t on the side close to the turbine. In the illustrated embodiment, eight radial ribs 12 are provided, and each radial rib is directed from one end 4c closer to the compressor to the other end 4t closer to the turbine, as shown in FIG. 2C. The thickness is reduced.

  Cooling air is introduced into the air flow path 16 from the one end 4c side and discharged from the other end 4t side by an appropriate cooling air circulation means not shown in the drawing. In this case, the area of the wall surface of the bearing sleeve 10 exposed to the air flow path 16 is reduced by reducing the thickness of the radial ribs 12 from the one end 4c near the compressor toward the other end 4t near the turbine. Is increased from the one end 4c toward the other end 4t, so that the bearing sleeve 10 is cooled more strongly from the one end 4c toward the other end 4t by the cooling air flowing into the air flow path 16. Further, since the thickness of the radial rib 12 is reduced from the one end 4c toward the other end 4t, the cooling effect exerted on the radial rib 12 by the air flow flowing through the air flow path 16 is directed from the one end 4c toward the other end 4t. Accordingly, the radial rib 12 is cooled more strongly by the air flow flowing through the air flow path 16 as it goes from the one end 4c to the other end 4t. Due to the change in the cooling effect from the two ends 4c toward the other end 4t, the amount of heat received by the bearing sleeve 10 from the rotating shaft 3 during the operation after the gas turbine is warmed up is close to the compressor 4 of the bearing sleeve. Even if it increases toward the other end 4t closer to the turbine, the difference between both ends of the thermal deformation generated in the bearing sleeve 10 by the heat is suppressed.

  It will be apparent to those skilled in the art that various modifications can be made to the embodiments described above within the scope of the present invention.

  DESCRIPTION OF SYMBOLS 1 ... Compressor, 2 ... Turbine, 3 ... Rotary shaft, 4 ... Air bearing, 4c ... One end of an air bearing, 4t ... The other end of an air bearing, 10 ... Bearing sleeve, 12 ... Radial rib, 14 ... Cylindrical housing, 16 ... Air flow path

Claims (1)

  An air bearing that supports a rotating shaft directly connecting the compressor and the turbine in the gas turbine at an intermediate portion thereof, a bearing sleeve that receives the rotating shaft from the periphery, and the bearing sleeve from the periphery through a plurality of radial ribs A plurality of air flow paths, each having an annular space between the bearing sleeve and the cylindrical housing divided by the plurality of radial ribs, from one end close to the compressor to the turbine. An air bearing characterized in that it extends to the other end on the near side, and the radial ribs are reduced in thickness from the one end toward the other end.

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