JPS60108501A - Disc structure for axial-flow machine - Google Patents

Abstract

PURPOSE:To aim at reducing thrust, by inserting a flexible sleeve made of resilient materials, in a balance hole formed in the end face of a disc. CONSTITUTION:A flexible sleeve 19 made of resilient materials is inserted in a balance hole 17 formed in the end face of a disc which carries a plurality of rotary blades, so that the flow passage area of the balance hole 17 is adjustable. Since the sleeve 18 is resilient, it extends and retracts in the axial or radial direction of the disc due to the pressure differential between pressures upstream and downstream of the disc to regulate the flow passage area. With this arrangement, thrust acting upon the disc 5 may be reduced.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a disk structure for an axial flow fluid machine, and in particular,
The present invention relates to a disk structure that can appropriately adjust the thrust acting on a steam turbine, gas turbine, or IJI compressor.

[Background of the invention]

BACKGROUND ART In recent years, power plants have been increasing in ultra-high temperature and high pressure in order to improve and improve plant thermal efficiency. For this reason, the various axial flow machines used in power generation plants are operated under harsh conditions from the standpoint of equipment reliability, and more reliable equipment than ever before is required. come. One of the issues is the issue of thrust due to ultra-high pressure. In other words, as the pressure becomes ultra-high, the stage pressure difference that acts on each stage of the -+llb flow machine increases, and as a result, the thrust that acts on the rotor disk that firmly holds the rotor blades in one rotation also increases significantly. On the other hand, the conventional structure results in an increase in the size and shaft length of the bearing.

Figure 1 shows the internal structure of the stages and disks of a typical axial flow machine. In general, the internal structure of the stage and disk of an axial flow machine includes upper diaphragms 4 and 10 that fixedly hold stationary blades 2 and 9, lower diaphragms 3 and 11, and fixedly hold rotary blades 1 and 8 on rotor 16. disc 5
and 12, shaft seal fins 7 and 15, tip seal fins 6 and 13, and the like. The disks 5 and 12 are each provided with a plurality of lance holes 14 to reduce the thrust that normally acts in the axial direction.
and 17 are arranged. The thrust acting on the paragraph and disk of this structure is as shown in Figure 2 (a)
It is classified into three types: packet thrust, Φ) wheel thrust, and (C) packet thrust. That is, the packet thrust) Fb is expressed by the following equation:
is the axial force acting on atlb,1.

In addition, wheel thrust F is a thrust that acts on the disc 5 due to the pressure difference between the pressure Pdf in the non-space formed by the disc 5 and the lower diaphragm 3 and the pressure pdr in the rear space of the disc 5, and is expressed by the following equation. .

Fv −f (Pdr−pdr ) dA On the other hand, Packins thrust is an axial force that acts on the stepped portion of the shaft 16.

Among these three types of thrust, packet thrust is 1
Normally, it can be arbitrarily determined and Vi-y <, paragraph ゛It is a property that can be determined according to the design method, so
The axial force acting on the rotating rotor blade 1 cannot be changed structurally. However, the front side pressure Pdf of the disc 5 caused by the wheel thrust acting on the disc 5 is determined by the amount of leakage from the shaft seal fin 7, the balance hole 17
It is said that it is difficult to evaluate the amount of leakage from the rotor (and the pressure on the upstream side of the rotor blade 1), which are complicated5.
The front pressure pdt of the disk 5 is determined by the operating conditions of the axial flow machine (
When the rotation speed, pressure difference, etc.) changes, it increases significantly,
Therefore, the wheel thrust will also change. Such a disk 5 is usually only provided with a balance hole 17 with a constant diameter, and changes in rotational speed,
The disk structure does not allow for changes in operating conditions such as changes in stage pressure difference.

Therefore, if the conventional structure is to cope with the above-mentioned ultra-high pressure, it is necessary to increase the size and shaft length of the bearing to cope with the excessive thrust.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a disk structure that allows for reduction and adjustment of thrust acting on a disk section of an axial flow machine.

＼ [Summary of the Invention] The feature of the present invention is that a sleeve made of a flexible elastic material is installed inside a balance hole bored in a disk that fixedly holds rotary blades of an axial fluid machine, and the balance is adjusted by expanding and contracting the sleeve. This makes it possible to control the channel area of the hole.

[Embodiments of the invention]

Hereinafter, details of embodiments of the present invention will be explained using the drawings.

FIG. 3 shows the structure of a disk portion of an axial fluid machine to which the present invention is applied. A plurality of balance holes 17 are arranged in the circumferential direction of the disk 5 that fixes and holds the rotating rotor blade 1 on the rotor, and a lower diaphragm 3 and the disk 5 that fixes and holds the stationary blade 2 disposed on the front side of the disk 5. The fluid that has flowed into the space (arrows 28a and 28b) is discharged to the rear space 29 of the disk 5. In this case, according to the present invention, a sleeve 1 made of a flexible elastic material is provided inside the balance hole 17.
Attach B. Because the sleeve 18Vi is an elastic material, it expands and contracts in the axial direction or radial direction due to the pressure difference between the front side pressure and the rear side pressure of the disk 5, and the opening area of the slit provided in the sleeve 18 changes to maintain balance. hall 17
The amount of fluid passing through is controlled. Therefore, from the mutual relationship between the flow rate passing through the balance hole 17 and the initial front pressure 2 of the disk 5, the disk front pressure and the flow rate converge to a certain constant value when the appropriate opening ratio is reached, and the converging disk front pressure will necessarily be kept lower than the initial pressure. Due to the above-mentioned balance of flow rate and pressure, the wheel thrust, which is the thrust acting on the disk 5, is reduced compared to the initial state, and the thrust can be controlled according to the initial pressure level. FIG. 4 shows a view taken along arrow l'V-IV in FIG.
A plurality of balance holes 17a are arranged in the circumferential direction.

17b, 17C, . . . are fitted with flexible elastic sleeves 18a, 18b, 18C, .

Next, the specific configuration, structure, and operation of the sleeve 18 made of a flexible elastic material will be explained using FIGS. 5 and 6. The sleeve 18 attached to the balance hole 17 bored in the disk 5 is composed of a circumferential sleeve 19 and an axial sleeve 20, as shown in FIG. The circumferential sleeve 19 and the axial sleeve 2o are joined at right angles near the entrance end of the balance hole 17, and the circumferential sleeve 1
The outer peripheral surface of the balance hole 9 and the inner peripheral surface of the balance hole 17 are tightly coupled. Further, the axial sleeve 20 is shown in FIG. 5(b).
As shown in FIG. 2, it is composed of a plurality of openings 24 and a plurality of closing parts 23, and the fluid 21 on the front side of the disk 5 passes through the opening 24 of the axial sleeve 20 (arrow 22) and exits from the balance hole 17. It is ejected to the rear side of the disk 5.

Under conditions where the fluid machine is not operated and no pressure is applied to the front surface of the disk 5, the opening area A1 of the axial sleeve 20 is
remains close to zero. However, when pressure is applied to the front surface of the disk 5, the axial sleeve 2o, which is made of a flexible elastic material,

As shown in FIG. 6, it extends in an arcuate manner toward the exit side of the balance hole 17. Therefore, as shown in FIG. 6(b), the opening 24 of the axial sleeve 2o is also gradually lowered, and the opening area A2 at this time becomes larger than the initial opening area A+. . The area expansion rate of the opening 24 of the axial sleeve 2o can be automatically changed in proportion to the pressure difference between the front pressure and the rear pressure of the disk 5. Therefore, the elastic material of the present invention has a
Mounting the disc 18 makes it possible to control the flow path area of the balance hole 17 in response to arbitrary operating conditions and pressure load conditions, making it possible to control and reduce the wheel thrust acting on the disc 5.

FIGS. 7 and 8 show a modified embodiment of the present invention. 7th
In the modification shown in the figure, a sleeve 25 made of a flexible elastic material and having a concave cross section is installed inside a plurality of balance holes 17 that are bored in the circumferential direction of the two disks 5. Under conditions where the pressure on the front surface of the disk 5 is almost zero, the opening area A3 of the sleeve 25 is also almost zero, but when pressure is applied to the front surface of the disk 5, the sleeve 25 becomes a flexible elastic material. As a result, the inner circumferential surface of the sleeve 25 is expanded in the radial direction, and the opening area also becomes wider than in the initial state. This aperture area expansion rate is.

The pressure increases in proportion to the pressure difference between the front pressure and the rear pressure of the disk 5. That is, the opening area can be controlled according to the load of the turbine, and the front pressure of the disk 5 and the flow rate passing through the balance ball 17 can be controlled similarly to the above embodiment, and the thrust acting on the disk 5 can be controlled. Force control can be achieved.

In addition, the flow rate passing through the balance hole 17 and the disk 5
When attempting to delicately control the front pressure of the balance ball 17, as shown in FIG. The structure is tapered in the axial direction to expand the area. Then, a rod portion 27 made of a flexible elastic material is attached to the rear side of the sleeve 26. disk 5
As pressure is applied to the front surface of the balance hole 17, the area formed by the space between the inner peripheral surface 28 of the tapered sleeve 26 and the rod portion 27 expands from A4 to A5, and the fluid passing through the balance hole 17 increases. The amount of pressure acting on the front surface of the disk 5 can be controlled.

〔Effect of the invention〕

According to the invention.

(1) It is possible to control and reduce the thrust acting on the disk portion of an axial flow machine, and it is possible to provide highly reliable equipment that can handle ultra-high pressures.

(2) The effect of reducing shaft thrust can prevent the thrust bearing from becoming larger and the shaft from becoming longer.

[Brief explanation of the drawing]

Figure 1 is a typical paragraph configuration diagram of an axial flow machine. Figure 2 is an explanatory diagram of the thrust acting on the paragraph. Figures 3 and 4 are disk configuration diagrams of a paragraph according to an embodiment of the present invention. FIG. 6 is a diagram showing details of the present invention. 7 and 8 are cross-sectional views of modified embodiments of the present invention. DESCRIPTION OF SYMBOLS 1... Rotating blade, 2... Stationary blade, 3.4... Diaphragm, 5... Disk, 16... Rotor shaft, 1
7... Balance hole, 18... Sleeve, 25.
··sleeve. No. S (0-)

Claims (1)

[Claims] 1. In a disk structure that fixes and holds a plurality of rotating rotor blades on a rotor, a balance hole bored in the end surface of the disk has a flexible structure that can adjust the flow path area of the balance hole. A disk structure for an axial flow machine characterized by inserting an elastic sleeve. 2. In claim 1. The elastic sleeve is made of a member that is flexible in the axial direction of the balance hole due to the pressure difference between the front and rear of the disk. A disk structure for an axial flow machine, wherein the member is disposed at an upstream end or a downstream end of the balance hole. 3. In claim 1, the elastic sleeve is constituted by a ball-flexible member before and after the disk, and the flow path area is made variable by expanding and contracting the flexible member in the radial direction. Disk structure of axial flow machine featuring.