JPS6396453A - Bearing device in expansion turbine - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is applicable to helium gas, hydrogen gas, oxygen, nitrogen, LP
The present invention relates to a bearing device that rotatably supports a rotor in an expansion turbine for liquefaction of G, LNG, etc.

2. Description of the Related Art Conventional rotor bearing devices for small-sized expansion turbines include one shown in FIG. 5, for example.

This device includes a rotor 011 equipped with a turbine wheel 013 at one end and a compressor wheel 014 at the other end, a pair of left and right journal bearings 020.040 provided in a bearing housing 090, and a single thrust bearing 060. I try to support myself with this.

As the journal bearing 0201040, in order to suppress the whirl that becomes a problem during high-speed rotation, a dynamic pressure type bearing is used, which is equipped with tilting pads 022 that are separated from each other in the circumferential direction of the rotor 011, and a thrust bearing 06
0, a spiral group bearing with a large load capacity is used.

The gas pressure in the bearing housing 090 is equalized to the turbine inlet pressure and the compressor outlet pressure.
No special seal is provided in either case.

Problems to be Solved by the Invention In the conventional structure as described above, if the outer diameter of the rotor 011 is not very large, the generation of whirl can be sufficiently suppressed, but the turbine flow rate increases and the rotor There is a problem in that as the outer diameter of 011 increases, whirl tends to occur more easily. The reason is as follows.

Generally, in the case of gas bearings, the bearing radius clearance ratio is designed to have a value close to that which provides maximum bearing rigidity, regardless of the shaft diameter. Assuming that the bearing is operated under a constant bearing clearance ratio, the spring stiffness and damping rate of the bearing are proportional to the circumferential speed of the rotor.

On the other hand, the rotational speed at which rotor whirl occurs is inversely proportional to the bearing diameter to the 1.5th power.

In view of turbine performance, expansion turbines are designed so that the speed around the turbine outer circumference is constant, so once the turbine outer diameter is determined, the rotor rotational speed becomes a value that is inversely proportional to the turbine outer diameter. However, since the whirl-generating rotational speed of the rotor is inversely proportional to the 1.5th power of the shaft diameter as described above, it tends to become unstable as the shaft diameter increases.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, an object of the present invention is to provide a bearing device for an expansion turbine that can sufficiently suppress the occurrence of whirl even when the outer diameter of the rotor increases. .

Means for Solving the Problems In the bearing device for an expansion turbine of the present invention, a rotor having a turbine wheel at one end and a compressor wheel at the other end is connected to a journal bearing and a thrust bearing provided in a bearing housing. The journal bearing is configured with a plurality of arc-shaped bearing pads separated from each other in a circumferential direction centered on the axis of the rotor, and each bearing pad is supported by a pivot supported within a bearing housing. The inner end of the shaft is supported by a spherical bearing, and is provided with a static pressure gas supply means for supplying static pressure gas to the bearing surface of each bearing pad.

According to the bearing device for an expansion turbine of the present invention, by feeding static pressure gas to the bearing surface of each bearing pad, the static pressure caused by the static pressure gas is added to the mechanical dynamic pressure caused by each bearing pad with respect to the rotor. In addition, the bearing spring stiffness increases.

The centripetal force exerted on the rotor by the bearings can be varied widely by controlling the pressure of the gas supplied to the bearing surface of each bearing pad.

Therefore, by adjusting the bearing supply gas pressure to obtain a centripetal force greater than the tangential component of the bearing resultant force generated in the expansion turbine operating region, it is possible to stably rotate the rotor and prevent whirl from occurring. I can do it.

EXAMPLE Hereinafter, an example of the present invention will be described in detail with reference to FIGS. 1 to 4.

In FIG. 1, reference numeral 10 denotes a rotor assembly, which includes a rotor 11 having a thrust collar 12 in the form of an enlarged disk in the center, and a turbine blade wheel fixed to the right end of the rotor 11 in FIG. 1 with a fixing bolt 111. 13, and a compressor wheel 14 which is fixed to the left end of the rotor 11 in FIG. 1 with a fixing bolt 112.

The rotor 11 is supported by i pairs of left and right journal bearings 40.20 provided in a bearing housing 90 and a thrust bearing 60 provided in between. ) within
Further, the compressor wheels 14 are located in the brake compressor chamber (the path shown) on the left side of the bearing housing 90, respectively.

The turbine wheel 13 is attached to the right end of the rotor 11 via a cylindrical thin-walled cylinder portion 114 that forms a hollow portion to prevent cold heat from escaping from the turbine chamber.

As shown in FIGS. 1 and 2, the right journal bearing 20 includes three arc-shaped bearing pads 22 separated from each other in the circumferential direction centered on the axis of the rotor 11. As shown in FIGS.

Note that the left journal bearing 40 has the same structure as the right journal bearing 20, so in the following explanation, only the right journal bearing 20 will be described in detail, and the details of the left journal bearing 40 will be described in detail. Further explanations will be omitted.

Each bearing pad 22 is supported by a spherical bearing 24 at the inner end of a pivot shaft 23 oriented radially with respect to the central axis of the rotor 11 (in FIG.
Only the support structure for one bearing pad 22 is illustrated, and the support structures for other bearing pads 22 are omitted. ).

The pivot shaft 23 is screwed so as to pass through the pivot mounting screw 26, and the pivot mounting screw 26 is attached to the annular bearing support block 21 provided in the bearing housing 90 by loosening the lock nut 27. The shaft 23 is screwed onto the shaft 23 so that the amount of movement thereof can be adjusted.

The spherical bearing 24 includes a large-diameter hemisphere 231 formed at the inner end of the pivot shaft 23, a seat 241 having a spherical recess for receiving the hemisphere 231, and a seat 241 fixed to the bearing pad 22. It consists of a cap 25.

By supporting each bearing pad 22 with such a pivot shaft 23 and spherical bearing 24, each bearing pad 22 can rotate by a minute angle in any direction around the center of curvature of the hemisphere 231, and Pivot axis 23
This is to prevent it from falling off.

The thrust bearing 60 is connected to the thrust collar 12 of the rotor 11.
The main thrust bearing 61 and the anti-thrust bearing 7 sandwich the
1, and serves to position the rotor 11 in the axial direction and to receive the load in the thrust direction. In order to keep the bearing clearance at a constant value, an annular spacer 72 is provided between the main thrust bearing 61 and the anti-thrust bearing 71, and these three members are connected to a left and right pair fixed in the bearing housing 90. It is sandwiched between backup plates 62 and fixed with bolts 73.

The bearing surface of each bearing pad 22 in the journal bearing 20.40 and the main thrust shaft 61 in the thrust bearing 60
The static pressure gas supply means 100, which supplies static pressure gas to each bearing surface of the anti-thrust bearing 71, is composed of the following thread path.

The static pressure gas for bearing supply (hereinafter simply referred to as static pressure gas) passes through the upper wall of the bearing housing 90 in the vertical direction from a gas inlet 95 provided at the upper center of the bearing housing 90 and is supplied to the thrust bearing 60 . The outer periphery of the bearing support block 21 is passed through the air supply hole 28 that successively passes through the spacer 72, the anti-thrust bearing 71, the right backup plate 62, and a part of the bearing support block 21 on the journal bearing 20.40 side in the lateral direction. Three air supply chambers 3 formed in
3.34.35 is supplied to one air supply chamber 33.

From there, the static pressure gas sent to the air supply chamber 33 flows through an annular groove 30.3 formed on the outer peripheral surface of the bearing support block 21.
1 to the other air supply chambers 34, 35, respectively.

Each air supply chamber 33, 34, 35 has the aforementioned pivot shaft 23.
The outer ends of the respective air supply chambers 33, 34 .
The static pressure gas supplied to the bearing pads 35 passes through the center hole 232 drilled in the center of the pivot shaft 23 and the center hole 242 drilled in the center of the seat 241, and is formed in the center of each bearing pad 22. is supplied to the conductive hole 221.

As shown in FIG. 3, on the bearing surface of each bearing pad 22,
A narrow rectangular groove 122 is bored, and this groove 122
An orifice 121 that communicates with the conductive hole 221 is opened at the center of each side.

Therefore, the static pressure gas supplied to the conduction hole 221 is supplied into the groove 122 through the orifice 121, and from there between the bearing surface of each bearing pad 22 and the outer periphery of the rotor 11.

Further, in both backup plates 62 on the thrust bearing 60 side, the air supply hole 28 and the upward air supply hole 63 are branched, and this air supply hole 63 is connected to the opposing surfaces of each backup plate 62, the main thrust bearing 61, and the anti-thrust bearing 71. They communicate with annular grooves 64 and 65 formed in the respective grooves.

As shown in FIG. 4, a plurality of orifices 161 communicating with the annular groove 65 are opened in the bearing surface of the main thrust bearing 61 and the bearing surface of the anti-thrust bearing 71.

Therefore, the static pressure gas branched from the air supply hole 28 to the air supply hole 63 side passes through the annular groove 64, 65 and the orifice 161, and flows between the bearing surface of the main thrust bearing 61 and the thrust collar 12, and the anti-thrust bearing. 71 and the thrust collar 12, respectively.

Further, as shown in FIG. 4, a spiral group 162 is bored in the bearing surface of the main thrust bearing 61 (and the anti-thrust bearing 71).

Gas discharged from each bearing surface of the journal bearings 20.40 is collected into the brenum chamber 66, which is a space formed around the outer periphery of the thrust bearing 60, through an exhaust hole 29 formed in the bearing support block 21, and is It joins with the gas discharged from the bearing surface of the bearing 60, and from there passes through the exhaust pipe 96 connected to the central lower part of the bearing housing 9G.
drawn into the low pressure section of the process gas loop.

A process high pressure gas source is used as the bearing supply static pressure gas. Therefore, the pressure within the axial pressure housing 90 is
The pressure is almost the same as the turbine inlet gas pressure. In order to use it as a hydrostatic gas bearing type, the gas pressure inside the bearing housing 90 needs to be lower than the process gas pressure. Therefore, the cooled gas from the turbine flows into the bearing housing 90 and the gas generated End plate 8 at the right end of bearing housing 90 so that the flow rate is not reduced.
A labyrinth gas seal 81 is provided between the rotor 11 and the right end of the rotor 11.

For the same reason, a labyrinth gas seal 83 is also provided on the brake compressor side between the end plate 82 at the left end of the bearing housing 90 and the left end of the rotor 11.

In this way, gas seals 81 and 83 are installed at both ends of the rotor 11.
If the rotor 11 is lengthened in order to provide the rotor 11, the problem of vibration due to overhang will arise, but in this embodiment, by providing the thrust collar 12 in the center of the rotor 11, the influence of the overhang is alleviated as much as possible. I have to.

Since this embodiment has the above-mentioned structure, the present invention can produce the same effects as described above, and also have the same effects as described below as effects of the present invention. By supplying static pressure gas to the thrust bearing 60 side, static pressure is added to the dynamic pressure at the thrust bearing 60, and the bearing load increases.
It has the advantage of being resistant not only to loads including aerodynamic fluctuations applied to the turbine wheel and compressor wheel, but also to whirling due to the conical mode of the rotor 11.

[Brief explanation of the drawing]

FIG. 1 is a central longitudinal sectional front view of an embodiment of the present invention, FIG. 2 is a sectional view taken along the line ■-■ in FIG. 1, and FIG. 3 is a cross-sectional view taken along the line ■--
■Enlarged line view, Figure 4 is a side view of the main thrust bearing,
FIG. 5 is a longitudinal sectional front view showing an example of a bearing device in a conventional expansion turbine. 11. Rotor, 13. Turbine wheel, 14. Compressor wheel, 20.40. Journal bearing, 22.
・Bearing pad, 23... Pivot shaft, 24... Spherical bearing, 60... Thrust bearing, 90... Bearing housing, 9
5... Gas inlet, 96... Discharge pipe, 100 (1 other person) Figure 2

Claims (1)

[Claims] In a bearing device for an expansion turbine, a rotor having a turbine wheel at one end and a compressor wheel at the other end is supported by a journal bearing and a thrust bearing provided in a bearing housing. a plurality of arc-shaped bearing pads separated from each other in the circumferential direction around the axis of the bearing, each bearing pad being supported by a spherical bearing at an inner end of a pivot shaft supported within a bearing housing. A bearing device for an expansion turbine, further comprising a static pressure gas supply means for supplying static pressure gas to the bearing surface of each of the bearing pads.