JP2927140B2 - Axial force balancing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an axial force balancing device for reducing axial force due to fluid pressure of a rotary machine such as a gas compressor.

[0002]

2. Description of the Related Art FIG. 5 shows a schematic configuration of a multistage gas compressor as an example of a rotary machine. In the compressor 1, a plurality of impellers 4, 4 are mounted on a rotating shaft 3 supported in a casing 2.
Are provided so that a predetermined fluid to be compressed (gas) can be compressed in multiple stages. That is, the fluid to be compressed is compressed by the first stage impeller 4 through a suction scroll (not shown), and then sent to the next stage impeller 4 through the return guide vane 5 to be compressed. After being compressed by the impeller 4 and compressed by the final impeller 4, it is discharged through the discharge scroll 6. By the way, a force corresponding to the fluid pressure difference between the suction side and the discharge side is applied to the impeller 4 of each stage, and the axial force F ₁ corresponding to the sum of the forces generated in each stage is applied to the rotating shaft 3 on the suction side. (Right side of the figure). For this reason, in the compressor 1 and the like as described above,
Axial force balancing device 7 for reducing the axial force F ₁ acting on the rotary shaft 3 is provided.

Conventionally, as shown in FIG. 4, an axial force balancing device 7 has a balance piston 8 formed coaxially on the outer periphery of a rotating shaft 3 and an end face 8 of the balance piston 8 on the impeller 4 side.
a is communicated with the discharge scroll 6, and the opposite end face 8b is communicated with a balance chamber (not shown) connected to the suction pipe. Therefore, the balance piston 8, the thrust force F ₂ acts due to the difference in the area of difference between the both end faces of the pressure acting on both end faces thereof, thereby the axial force F
₁ can be reduced. That is, by creating a force F ₂ to balance the above axial force F ₁ by changing both end faces 8a, the area of 8b of the balance piston 8 can be reduced in the thrust direction load of the rotary shaft 3.

[0004]

By the way, in the conventional axial force balancing device 7 described above, fluid leakage from the high pressure side (the impeller 4 side) of the balance piston 8 to the low pressure side (the balance chamber side) is prevented. To prevent this, a labyrinth seal 9 is provided between the outer periphery of the balance piston 8 and the casing 2. However, considering the vibration and thermal expansion of the rotating shaft 3, there is a limit to reducing the gap between the labyrinth seals 9, and therefore, the reduction of the amount of leakage and the reduction of the power loss have naturally been limited.

In particular, in the case of a low-capacity or high-pressure compressor, the ratio of the amount of leakage from the labyrinth seal 9 to the total amount of processing becomes large, resulting in a problem that the efficiency is extremely reduced. .

SUMMARY OF THE INVENTION It is an object of the present invention to provide an axial force balancing device capable of reducing fluid leakage from a high pressure side to a low pressure side of a balance piston, thereby improving efficiency.

[0007]

In order to achieve the above-mentioned object, the present invention provides a shaft which forms a balance piston on an outer periphery of a rotating shaft supported in a casing and applies a fluid pressure to an end face of the balance piston. In the force-balancing device, a space surrounding the end face is formed on the low-pressure side of the balance piston, and a mating ring provided on the rotating shaft and one end face of the ring provided on a stationary system are provided in the space. An end face type non-contact seal comprising a seal ring in contact with the end face is provided , and a balance diameter of the end face type non-contact seal is provided .
Is substantially matched with the diameter of the balance piston .

[0008]

DETAILED DESCRIPTION OF THE INVENTION The present invention consists of a space formed on the low-pressure side of the balance piston, a mating ring which is provided on the rotary shaft, the seal ring facing contact with one end surface of the mating ring is provided in the stationary system Provide an end face type non-contact seal ,
Adjust the balance diameter of the end face type non-contact seal
In Rukoto substantially coincide with the diameter of tons, closes the passage of the fluid leaked to the low pressure side (in the space) through the outer peripheral side of the balance piston, it can further prevent leakage to the downstream side, while,
The load in the thrust direction of the rotating shaft can be easily reduced.
I can .

[0009]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

In FIG. 1, reference numeral 2 denotes a casing of a multi-stage gas compressor, in which a rotating shaft 3 is rotatably supported. A plurality of impellers 4, 4,... (See FIG. 5) are mounted on the outer periphery of the rotating shaft 3 at intervals as in the prior art so that a predetermined gas (compressed fluid) can be compressed in multiple stages. . Therefore, the rotary shaft 3 is already predetermined axial force F ₁ as described is to act toward the suction side (right side in the figure). A balance piston 8 is provided on the outer periphery of the rotating shaft 3 and on the back side of the impeller 4 at the last stage. The balance piston 8 is for reducing the axial force F ₁ , and a high-pressure chamber 10 communicating with the discharge scroll 6 is formed on the impeller 4 side. The high-pressure chamber 10 is formed so as to surround one end face 8a of the balance piston 8, and applies the discharge pressure of the compressor 1 to the end face 8a. On the other hand, on the opposite side (low-pressure side) of the high-pressure chamber 10 of the balance piston 8, an accommodation space 11 for accommodating an end-face type non-contact seal 12 described later is formed. The accommodation space 11 is formed so as to surround the other end face 8 b of the balance piston 8 and communicates with a balance chamber (not shown) through a gap 17. The balance chamber (not shown) is connected to the suction side of the compressor 1 via a suction pipe, and is always maintained at a suction pressure (almost atmospheric pressure).

In the axial force balancing device of this embodiment,
In order to prevent leakage of gas from the high-pressure chamber 10 as much as possible, a labyrinth seal 9 is provided between the outer periphery of the balance piston 8 and the casing 2 and an end face non-contact is provided in the accommodation space 11. A seal 12 is provided.

The end face type non-contact seal 12 is for blocking gas leaked from the high-pressure chamber 10 through the labyrinth seal 9 into the space 11, and is coaxially mounted on the outer periphery of the rotary shaft 3 and is mounted on the rotary shaft 3. 3, and a sealing ring 14 provided on the stationary casing 2 and in contact with an end surface 13 a of the mating ring 13.

The mating ring 13 is mounted on the rotating shaft 3 via a holding bracket 15. Holding bracket 15
Is mounted adjacent to the end face 8b of the balance piston 8, and a mating ring 13 is mounted in an annular groove 15a formed on the holding metal 15 on the side opposite to the piston 8. A spiral groove 16 is formed on the sliding surface 13a (the surface in contact with the seal ring 14) of the mating ring 13, as shown in FIG. The spiral groove 16 is formed to be inclined rearward in the rotational direction from the outer peripheral edge of the sliding surface 13a toward the inner peripheral edge side and has a predetermined length. When the rotary shaft 3 rotates, the spiral groove 16 is formed in a pressure chamber 22 described later. Gas can be taken in.

On the other hand, the seal ring 14 is fitted coaxially with the mating ring 13 so as to be movable in the axial direction in an annular groove 2a formed at a position in front of the mating ring 13 of the casing 2. Here, the seal ring 14
Is almost the same as the outer diameter of the mating ring 13,
The inner diameter of the seal ring 14 is formed to be larger than the inner diameter of the mating ring 13, whereby the inner peripheral side of the end face of the mating ring 13 faces the balance chamber (not shown) through the gap 17. A compression coil spring 18 is provided on the back side of the seal ring 14 as urging means, and the seal ring 14 comes into surface contact with the mating ring 13 by the urging force of the coil spring 18. On the outer peripheral side of the seal ring 14, a rotation preventing member 19 is provided upright from the inner bottom of the annular groove 2a, and the rotation of the seal ring 14 is restrained by the rotation preventing member 19. Reference numeral 20 denotes a seat for the spring 18 attached to the back of the seal ring 14.
The receiving seat 20 is provided with an O-ring 21 for sealing the inner periphery of the seal ring 14.

In this embodiment, a seal ring 14 is fitted on the inner peripheral side of the annular groove 2a, and both rings 13 and
A pressure chamber 22 surrounding the outer periphery of the pressure chamber 14 is defined. The pressure chamber 22 communicates with the end of the labyrinth seal 9 on the low pressure side through the back side of the holding bracket 15, and is maintained at a predetermined pressure by gas leaking from the end of the labyrinth seal 9. In addition, pressure chamber 2
2 is a mating ring 13 and a seal ring 14
Of the labyrinth seal 9 so that opposing forces act on both rings 13 and 14. In other words, by making the inner diameter of the pressure chamber 22, that is, the balance diameter D coincide with the diameter of the labyrinth seal 9, the same pressure can be applied to the rings 13 and 14 in the same area in the pressure chamber 22. Ring 13,
14 can be offset.

Next, the attachment of the mating ring 13 to the rotating shaft 3 will be described.

As shown in FIG. 3, a holding member 15 for holding the mating ring 13 includes a boss portion 23a fitted to the rotating shaft 3 and a disk-shaped support portion 23b formed at one end of the boss portion 23a. An annular groove 15a is formed inside the support portion 23b (left side in the figure) coaxially with the rotating shaft 3. When the mating ring 13 is fitted in the annular groove 15a, the sleeve 25 and the bolt 24
Mounted by Note that the sleeve 25 is a bolt 26
As a result, it is fixed to the end face of the boss 23a. The attachment of the holding member 15 to the rotating shaft 3 is performed by fitting the holding member 15 to the rotating shaft 3 and then further fitting the sleeve 27 from the outside thereof. Here, in order to equalize the gap between the rotating shaft 3, the ring 13, and the boss portion 23a, a concave portion is formed at an appropriate position on the inner and outer periphery of the boss portion 23a, and a ring-shaped leaf spring is formed in the concave portion. 28 are interposed.

Next, the operation of the present embodiment will be described.

The gas sucked into the compressor 1 is compressed by the impellers 4, 4... Of each stage and then discharged out of the casing 2 through the discharge scroll 6 and introduced into the high-pressure chamber 10 from the discharge scroll 6. Is done. The gas introduced into the high pressure chamber 10 further leaks to the pressure chamber 22 through the labyrinth seal 9, but is blocked by the end face type non-contact seal 12, and does not leak downstream from the seal 12. . That is, when the mating ring 13 is rotated by the rotation of the rotating shaft 3, the gas in the pressure chamber 22 is taken into the spiral groove 16 (FIG. 2) formed on the sliding surface 13a of the mating ring 13 and the pressure is increased.
As a result, a so-called gas bearing is formed between the sliding surfaces 13a and 14a of the mating ring 13 and the seal ring 14, and the two rings 13 and 14 rotate relative to each other in a non-contact state. μm), there is almost no gas leakage.

Meanwhile, when the multi-stage gas compression in the impeller 4 of each stage, as described above, the rotary shaft 3 large axial force F ₁ toward the suction side occurs, the axial force F ₁ is balanced canceled by a force F ₂ acting on the piston 8. That is, the end surface 8a of the balance piston 8 on the impeller 4 side includes:
The pressure in the high-pressure chamber 10 (discharge pressure of the compressor 1) acts, and conversely, the suction pressure corresponding to the balance diameter D of the end face non-contact seal 12 is applied to the end face 8b on the balance chamber side.
Act through. For this reason, the axial thrust caused by the discharge pressure acting on the end face 8a and, conversely, the axial thrust caused by the suction pressure acting on the end face 8b act on the balance piston 8 as in the prior art. opposing force F ₂ in the axial force F ₁ is obtained.

As described above, according to the present embodiment, the accommodation space 11 surrounding the end face 8b is provided on the low pressure side of the balance piston 8.
And an end face type non-contact seal 1 for blocking gas leaked from the high pressure chamber 10 into the accommodation space 11.
2, the amount of gas leaking from the high-pressure chamber 10 can be reduced as much as possible, and the power loss can be significantly reduced. That is, although the mating ring 13 and the seal ring 14 rotate relative to each other in a non-contact manner with each other, the gap between them can be made extremely small as compared with the labyrinth seal 9, so that the pressure loss increases and the sealing performance is improved. Can be achieved. Actually, in the structure using only the conventional labyrinth seal 9, the power loss was about ten and several percent due to the low capacity type, but in the structure using the seal 12 of the present embodiment, the power loss was reduced. Can be easily reduced to about one hundredth of the conventional value.

Further, according to the present embodiment, the balance diameter D of the end face type non-contact seal 12 is made equal to the diameter of the labyrinth seal 9, so that the low pressure side end face 8b of the balance piston 8 is formed.
The conventional and can act the suction pressure in the same manner, the axial force F ₁ by a simple modification of the existing compressor 1 can create opposing force F _2, the thrust-direction load of the easy axis of rotation 3 Can be reduced.

Further, the mating ring 13 of the present embodiment
Since the seal ring 14 is detachable, various gas seals can be handled by selecting a material according to the type of gas to be compressed.

Further, by forming a gas bearing between the sliding surfaces 13a and 14a of the mating ring 13 and the seal ring 14, the rings 13 and 14 can be rotated in a non-contact state to suppress heat generation. Therefore, the compressor 1 is excellent in durability, hardly causes an accident and the like, and can obtain a highly reliable compressor 1.

In the above embodiment, the labyrinth seal 9 is provided between the balance piston 8 and the casing 2, but this is not always necessary. However, if the labyrinth seal 9 is provided, it is effective as a backup when the end face type non-contact seal 12 fails. Also,
In the above embodiment, an example in which the invention is applied to a multi-stage gas compressor has been described, but the invention may be applied to other rotating machines.

[0026]

In summary, according to the present invention, the following excellent effects are exhibited.

[0027] dramatically decreased the leakage of the flow body in the balance piston, can be reduced significantly reduced efficiency, be simply to reduce the axial force acting on the rotary shaft
I can .

[0028]

[Brief description of the drawings]

FIG. 1 is a sectional view showing a schematic configuration of an axial force balancing device of the present invention.

FIG. 2 is a partially enlarged view showing a sliding surface of a mating ring in an end face type non-contact seal.

FIG. 3 is a diagram for explaining a mounting structure of a mating ring in an end face type non-contact seal.

FIG. 4 is a sectional view showing a schematic configuration of a conventional axial force balancing device.

FIG. 5 is a sectional view showing a schematic configuration of a multi-stage gas compressor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Multi-stage gas compressor 2 Casing 3 Rotating shaft 8 Balance piston 10 High pressure chamber 11 Housing space 12 Non-contact seal of end face 13 Mating ring 14 Seal ring

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) F04D 29/00-29/16 F16J 15/447

Claims (1)

(57) [Claims] 1. An axial force balancing device in which a balance piston is formed on an outer periphery of a rotating shaft supported in a casing and a fluid pressure is applied to an end surface of the balance piston. Along with forming a surrounding space, an end face type non-contact seal including a mating ring provided on the rotating shaft and a seal ring provided on a stationary system and in contact with one end face of the ring is provided in the space , Balance diameter of the end face type non-contact seal
Is approximately equal to the diameter of the balance piston .