JPH04266666A - Sealing device - Google Patents

Abstract

PURPOSE:To prevent the leak of a gas in a machine to the atmospheric side while regularly holding the non-contact between a floating ring and a rotating shaft regardless of the rotating speed of the rotating shaft. CONSTITUTION:A floating ring 15 provided around a rotating shaft 11 with a minute clearance circumferentially has a plurality of narrow holes 16 opened toward the surface of the rotating shaft 11, and a buffer gas having a higher pressure than the gas pressure in a rotating machine is injected toward the surface of the rotating shaft 11 through the narrow holes 16.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mechanical seal device used for sealing gas inside a rotating machine such as a gas turbine or a gas compressor.

0002

2. Description of the Related Art FIG. 3 is a sectional view showing a conventional sealing device. In this figure, 1 is a rotating shaft of a gas turbine or the like, and a seal casing 2 is provided on the outer periphery of the shaft. The seal casing 2 includes a fixed seal plate 3, a pair of seal ring casings 4, and a floating ring 5 held by the seal ring casing 4.
and both seal ring casing 4 and floating ring 5
A buffer gas supply ring 6 located between the two is built-in. These are integrated with the seal casing 2 by a seal ring casing mounting plate 7 and are attached to the main casing 8. The floating ring 5 is provided with a small gap around the rotating shaft 1 and is prevented from rotating, and the inner circumferential surface of the seal casing 2 and the outer circumferential surface of the seal ring casing 4 are An O-ring 9 is inserted into the contact portion to perform a sealing action.

Here, the space a on the left side of the seal ring casing mounting plate 7 in FIG. 3 is inside a machine such as a gas turbine, and the space b on the right side of the seal casing 2 is on the atmosphere side. Further, a space c of the buffer gas supply ring 6 located between both the seal ring casings 4 and the floating ring 5 is a buffer gas flow path to which a buffer gas as a sealing fluid is supplied. In this buffer gas flow path c,
Buffer gas supply hole 1 provided in seal casing 2
0, a high-pressure buffer gas such as nitrogen gas is supplied, and after lubricating and cooling the sealing part, it passes through the small gap between the floating ring 5 and the rotating shaft 1 to the inside of the machine and to the atmosphere, respectively. leak. Note that since the space a inside the machine, such as a gas turbine, is filled with high-temperature, high-pressure gas, the buffer gas is supplied at a pressure higher than the pressure inside the machine. In this way, in-flight gas is prevented from leaking into the atmosphere.

Next, the function of the floating ring 5 will be explained. The inner diameter of the floating ring 5 is formed to be slightly larger than the outer diameter of the rotating shaft 1, so that the floating ring 5 and the rotating shaft 1
A small gap is formed between the two. Therefore, when the rotating shaft 1 rotates at high speed, the dynamic pressure fluid lubrication effect of the buffer gas acts on the minute gap between the floating ring 5 and the rotating shaft 1, causing the floating ring 5 to float from the rotating shaft 1 and separating them. can be kept in contact and the floating ring 5 will function as a hydrodynamically lubricated gas bearing. The floating ring 5 vibrates in the radial direction while maintaining non-contact with the rotating shaft 1 in response to the radial vibration of the rotating shaft 1.

[0005]

[Problem to be Solved by the Invention] Since the radial clearance of the floating ring 5 is small as described above, the floating ring 5 has the characteristic that it consumes less buffer gas than a labyrinth seal having a large clearance, but it has the following drawbacks. There is.

At the time of starting and stopping, since the rotational speed of the rotating shaft 1 is zero or small, the dynamic pressure fluid lubrication effect acting between the floating ring 5 and the rotating shaft 1 is small. will be in direct contact with. Therefore, there are problems in that frictional heat is generated and wear occurs.

[0007] Furthermore, even when the rotating shaft 1 is in steady rotation,
Since the viscosity of gas is smaller than that of liquid, the dynamic pressure fluid lubrication effect is small, and therefore the floating ability of the floating ring 5 is not very large. Therefore, when the vibration of the rotating shaft 1 is large, the friction between the floating ring 5 and the seal plate 3, or the friction between the floating ring 5 and the seal ring casing 4 is large, the floating ring 5 comes into direct contact with the rotating shaft 1. As a result,
There was a problem that damage such as seizure was likely to occur.

The present invention was made with the aim of solving such problems, and provides a structure that increases the levitation force of the floating ring and maintains the floating ring and the rotating shaft without contact at all times. It is something.

[0009]

[Means for Solving the Problems] According to the present invention, a floating ring is provided around the rotating shaft of a rotating machine with a slight gap between the inner circumferential surface of the floating ring and the outer circumferential surface of the rotating shaft. In a sealing device that supplies buffer gas at a pressure higher than the in-machine gas pressure of a rotating machine to the gap between the two, the floating ring is provided with a plurality of pores opening toward the surface of the rotating shaft in the circumferential direction, The structure is such that buffer gas is ejected from these pores toward the surface of the rotating shaft.

0010

[Operation] According to the above means, by blowing out the buffer gas from the pores of the floating ring toward the surface of the rotating shaft, a hydrostatic fluid lubrication effect works between the floating ring and the rotating shaft. The floating ring is floated from the rotating shaft. Due to this hydrostatic fluid lubrication effect, a minute gap is formed between the floating ring and the rotating shaft to prevent direct contact between the two even when stopped or at low speeds. When the rotating shaft reaches a steady rotation speed, dynamic pressure fluid lubrication works in addition to static pressure fluid lubrication, which further increases the floating force of the floating ring and prevents contact between the floating ring and the rotating shaft. make it stronger.

[0011]

[Example] An example of the sealing device according to the present invention will be described below.
This will be explained in detail with reference to FIGS. 1 and 2. Furthermore, Figure 1
In FIG. 2, the same parts are designated by the same reference numerals.

FIG. 1 shows an embodiment of the sealing device of the present invention. In this figure, 11 is a rotating shaft of a gas turbine, etc., and a seal casing 1 is attached to the outer circumference of the rotating shaft.
2 is provided. The seal casing 12 includes a fixed seal plate 13 and a seal ring casing 1.
4 is attached, and a floating ring 15 is held. These are integrated with the seal casing 12 by a seal ring casing mounting plate 17 and are attached to the main body casing 18.

The floating ring 15 is a ring located around the rotating shaft 11 having a U-shaped cross section, and its inner diameter is slightly larger than the outer diameter of the rotating shaft 11. A minute gap is formed between the rotary shaft 11 and the rotary shaft 11. The floating ring 15 is provided with a plurality of pores 16 in the circumferential direction that open toward the surface of the rotating shaft 11. Although not shown in the drawings, the floating ring 15 is prevented from rotating, and one surface of the floating ring 15 is elastically prevented from rotating with respect to the seal plate 13 and the other surface thereof with respect to the seal ring casing 14 by an O-ring 19. is widely supported. In addition, the seal casing 12
An O-ring 20 is inserted into the contact portion between the inner circumferential surface of the seal ring casing 14 and the outer circumferential surface of the seal ring casing 14 so as to perform a sealing action.

Here, the space a on the left side of the seal ring casing mounting plate 17 in FIG. 1 is inside the machine such as a gas turbine, and the space b on the right side of the seal casing 12 is on the atmosphere side. Further, the U-shaped space c of the floating ring 15 is a buffer gas flow path into which a buffer gas as a sealing fluid is introduced. High-pressure buffer gas is supplied to this buffer gas flow path c from a buffer gas supply hole 21 provided in the seal casing 12 via the seal ring casing 14. Then, the buffer gas is supplied to the floating ring 15 and the rotating shaft 1 from the pores 16 provided in the floating ring 15 so as to open toward the surface of the rotating shaft 11.
1, and further leaks into the inside of the machine and the atmosphere through this small gap. In addition,
Since a space a inside a machine such as a gas turbine is filled with high-temperature, high-pressure gas, the buffer gas is supplied at a pressure higher than the pressure inside the machine. Therefore, the cabin gas will not leak into the atmosphere.

Next, the operation of the present invention will be explained. The buffer gas introduced into the U-shaped space c of the floating ring 15 is ejected from the pores 16 provided in the floating ring 15 into the minute gap between the floating ring 15 and the rotating shaft 11. At this time, in areas with small gaps in the circumferential direction, pores 1
The gas pressure at the point where the gas exits from the pore 16 becomes high, and conversely, the gas pressure at the point where the microscopic gap is large becomes low at the point where the gas exits from the pore 16. As a result of such circumferential gas pressure distribution,
The floating ring 15 can be floated concentrically with respect to the rotating shaft 11, and this is called the hydrostatic fluid lubrication effect of the buffer gas.

[0016] Such a hydrostatic fluid lubrication effect is applied to the rotating shaft 1.
It works regardless of the number of rotations. Therefore, the floating ring 1
5 can be floated to prevent direct contact with the rotating shaft 11. When the rotating shaft 11 rotates at high speed, hydrodynamic lubrication acts on the minute gap between the floating ring 15 and the rotating shaft 11 due to the wedge effect caused by the rotation of the rotating shaft 11, and this adds to the hydrostatic lubrication. Floating ring 15
The floating force of the floating ring 15 and the rotating shaft 11 becomes even larger.
This will strengthen the prevention of contact with

Note that the gas pressure in the minute gap between the floating ring 15 and the rotating shaft 11 is lower than the pressure of the introduced buffer gas, so the gas pressure in the minute gap is higher than the in-machine gas pressure. Therefore, it is necessary to set the buffer gas pressure to be introduced in advance. This can prevent in-flight gas from leaking to the outside. Gas leakage from the gap on the side surface of the floating ring 15 is prevented by an O-ring 19. Instead of the O-ring 19, gas leakage can also be prevented by supporting both sides of the outer periphery of the floating ring 15 with piston rings 22, as shown in FIG. Further, the pore 16 may be an orifice.

[0018]

[Effects of the Invention] As detailed above, according to the present invention,
Even in a low rotational speed range where the rotational speed of the rotating shaft 11 does not reach the steady rotational speed, such as when starting or stopping a turbine or the like, or during low-speed rotation, the floating ring 15 is floated by the hydrostatic fluid lubrication effect, and the rotating shaft 11 You can avoid direct contact with
Abrasion and seizure can be prevented. When the rotating shaft 11 reaches a steady rotation speed, dynamic pressure fluid lubrication works in addition to the static pressure fluid lubrication action, so the floating ring 15
The floating force of the floating ring 15 can be further increased, and the floating ring 15 can also follow the radial vibration of the rotating shaft 11 to prevent contact with the rotating shaft 11, thereby further improving reliability.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of a sealing device according to the present invention.

FIG. 2 is a sectional view showing a modification of the sealing device according to the present invention.

FIG. 3 is a sectional view showing a conventional sealing device.

[Explanation of symbols]

11 Rotation axis 15 Floating ring 16 Pore 21 Buffer gas supply hole

Claims (1)

[Claims] Claim 1: A floating ring is provided around the rotating shaft of a rotating machine with a minute gap, and the in-machine gas of the rotating machine is supplied to the gap between the inner circumferential surface of the floating ring and the outer circumferential surface of the rotating shaft. In a sealing device configured to supply buffer gas at a pressure higher than the pressure, the floating ring is provided with a plurality of pores opening toward the surface of the rotating shaft in the circumferential direction, and the buffer gas is supplied from the pores. A sealing device configured to emit water toward the surface of the rotating shaft.