JPH0259341B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a shaft seal device, and in particular uses a viscoseal to handle chemically active fluids such as potassium vapor and extremely low temperatures (for example, around -273°C). ) or high-temperature (for example, 600°C or higher) fluid.

[Conventional technology]

Conventionally, shaft sealing devices for vertical sodium pumps have been put into practical use to seal high-temperature fluids such as molten metal, but the permissible fluid temperature of these devices is 600°C or less; With regard to molten metal seals at higher temperatures, there are only a few examples under limited conditions in special fields such as space engineering, and until now it has been thought that stable operation over a long period of time at the general industrial level is impossible.

[Problem that the invention seeks to solve]

The main purpose of the shaft sealing device of the present invention is to seal such high-temperature fluids, cryogenic fluids, and chemically active fluids.

[Means for solving problems]

In order to achieve this object, the shaft sealing device of the present invention seals the gap between the housing of various rotating equipment such as a turbine and the rotating shaft inserted into the shaft hole of the housing. A pair of visco seals are disposed that face each other in the axial direction and generate pump pressures in opposite directions toward the opposing chambers, and a sealing fluid is supplied from a liquid tank to the opposing chambers, and a sealing fluid is supplied to the opposing chambers from the outside of the visco seals. The shielding chambers formed in the above-mentioned pair of viscoseals are made to communicate with each other and a shielding fluid is supplied thereto, a sealing device is disposed outside the shielding chamber, and the clearance of the outer viscoseal of the pair of viscoseals is set to the inner viscoseal. The configuration is such that the clearance is narrower than the seal clearance.

The shaft sealing device of the present invention having the above configuration exhibits excellent sealing performance as described below due to the combined effects of the visco seal, the sealing fluid, the shielding fluid, and the sealing device such as the mechanical seal. It becomes like this.

〔Example〕

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

In FIG. 1, reference numeral 1 indicates the rotation axis, and
are first to third housings each having a shaft hole through which the rotating shaft 1 is inserted; It works to prevent steam (hereinafter simply referred to as steam) from leaking to the right in the figure.

A pair of visco seals 6 and 7 are provided on the inner wall surface of the shaft hole of the second housing 3, symmetrically with respect to an annular opposing chamber 5 provided at the center in the axial direction, and oriented in opposite directions. When the rotating shaft 1 rotates in a certain direction, the inside visco seal 6 on the left side in the figure moves from the first housing 2 to the opposing chamber 5, and the outer visco seal 7 on the right side in the figure moves towards the third housing 4. Pump pressure is generated from the pump to the opposing chamber 5, respectively. The inner periphery of the shaft hole of the third housing 4 is provided with an air supply pipe 9, an exhaust pipe 10, an oil supply pipe 12, and an oil drain pipe 13, which communicate with an external pump (not shown), respectively, from left to right in the figure. First and second shielding chambers 8 and 11 having an annular shape are provided, and the first shielding chamber 8 and the outer second shielding chamber 11 communicate with each other with the outer visco seal 7; Mechanical seals 14 and 15 as sealing devices are interposed to separate the air from the atmosphere. Reference numeral 16 denotes a liquid tank that provides a constant water head h to the opposing chamber 5 between the pair of Visco seals 6 and 7, and communicates with the air pipe 9 of the first shielded chamber 8 through a path 17. . In the outer visco seal 7, the rotating shaft 1 inserted therein is partially formed with a large diameter, or the inner side of the visco seal 7 is narrowed, so that the clearance around the inner circumference of the visco seal 7 is smaller than that of the inner visco seal 7. The clearance is narrower than the clearance around the inner circumference of the seal 6.

When sealing potassium steam in a potassium turbine using the shaft sealing device with the above configuration, the steam to be sealed is sealed with a substance that is the same as the steam and liquefies when it is cooled, that is, liquid potassium. Argon gas, which is an inert gas, is supplied as a fluid (sealant, 18) into the liquid tank 16 from an external tank to the first shielding chamber 8, and a mechanical seal is supplied from the external tank to the second shielding chamber 11. Supply oil that does not react with potassium to lubricate. Mechanical seal 14 inside the machine
Use a bellows type made of a material that does not react with potassium. Outer mechanical seal 1
A generator and the like driven by the turbine are connected to the right side of 5.

Now, the rotating shaft 1 is rotated at a predetermined rotational speed, and the height h of the liquid potassium 18 in the liquid tank 16 is
The pressure in the shielded chamber 8 is maintained constant, and the pressure in the shielded chamber 8 is adjusted so that the pressure of potassium vapor in the first housing 2 and the pressure of argon gas in the first shielded chamber 8 have a constant pressure difference. Adjust. This adjustment is
This is done by discharging a part of the argon gas fed into the shielded chamber 8 from the external tank via the air supply pipe 9 to the outside from the exhaust pipe 10, and both pipes 9 and 10 are equipped with pressure regulating valves ( (not shown) is provided. The adjusted pressure is also applied to the liquid level in the liquid tank 16 via the path 17.

As described above, when the rotating shaft 1 rotates, the pump pressure acts on the left and right visco seals 6 and 7 to pressurize the opposing chamber 5. Therefore, in the visco seal 6 on the left side of the figure, the water head h of the liquid tank 16 is
A gas-liquid interface 19 is created such that the sum of the pump pressure of the Visco seal 6 and the potassium vapor pressure is balanced by the sum of the pump pressure of the visco seal 6 and the potassium vapor pressure. Also, in the visco seal 7 on the right side of the figure, there is another air-liquid interface 20 so that the water head h and the pump pressure of the visco seal 7 are balanced.
Can be done. The former left gas-liquid interface 19 moves in the axial direction depending on the magnitude of the pressure difference between potassium vapor pressure and argon gas, but the latter right gas-liquid interface 20 remains at a fixed position regardless of the argon gas pressure.

The above-mentioned shaft seal device has a pair of front and rear visco seals arranged on the side close to potassium vapor, which is the fluid to be sealed, and liquid potassium of the same type as the potassium vapor is retained in the visco seals to directly release the potassium vapor. Argon gas or mechanical seals 14, 15 are used to seal and supply the liquid potassium to the outside.
This multilayered structure provides a complete shaft sealing function.

If a so-called gas injection occurs at the gas-liquid interface 20 on the outside (right side) where liquid potassium and argon gas are in contact, the performance of the Visco seal 7 itself will deteriorate, and in order to cope with this, the seal length must be increased, etc. However, by narrowing the clearance of the visco seal 7 to such an extent that it becomes a laminar flow region, the gas-liquid interface 20 can be stabilized without entrainment of gas. That is, to describe the clearance C of this Visco seal 7 with reference to Figs. 5 and 6, the Reynolds number Rec and critical Reynolds number (Recrit) are Rec = πDNC/60ν where D: axis length (m) N: rotation Number (rpm) ν: Kinematic viscosity coefficient of sealing fluid (liquid potassium) (m ² /s) Recrit=41.1 [D/2/(1-γ)C+βγC] ^1/2 where γ=b/a+b β=h+c/ C abh: Expressed as shown in the figure, and since it is laminar flow when Rec<Recrit, the clearance C is set accordingly. Second
The figure shows an example. Furthermore, clearance C
If it is made smaller, it will be difficult to incorporate and adjust the visco seal 7, but in order to obtain the same maximum cut-off pressure (ΔPmax) as in the case of turbulent flow, the seal length L can be shortened, so there is no problem, and the device can be made more compact. It becomes possible to aim for.

ΔPmax=6μUL/C ² Λ μ: Viscosity coefficient of sealing fluid (liquid potassium) (Kg
^s /m ² ) L: Seal length (m) Λ: Seal coefficient U: Circumferential speed (m/s) On the other hand, a turbulent flow type with a large clearance is used for the inner (left side) visco seal 6. In this case, there is no problem with assembly even if the seal length is a little long. Air-liquid interface 1 formed within the visco seal 6
In step 9, potassium vapor and liquid potassium come into contact, and since both are essentially the same, gas injection does not occur.

Although the pressure within the first housing 2 may fluctuate depending on the operating status of the turbine, this pressure fluctuation can be absorbed by controlling the argon gas pressure. This control uses differential pressure gauges, pressure regulators, pressure regulating valves, etc. On the other hand, when the pressure fluctuation is small and no control is required, the first shielding chamber 8 is evacuated to prevent gas from flowing toward the first housing 2 side.

Further, as a means to further shorten the seal length, the visco seal 6 is shortened to cause liquid potassium, which is a sealing fluid, to overflow into the first housing (2. turbine chamber). This embodiment is shown in FIG. 2, where 21 is an overflow sealing fluid and 22 is a sealing fluid feed pipe. Due to the overflow, the shutoff performance of the visco seal 6 is improved as shown in FIG. 3, and the heat transmitted to the rotating shaft 1 within the first housing is effectively cooled down as shown in FIG. 4.

〔Effect of the invention〕

The shaft sealing device of the present invention has the configuration as described above, and has extremely good sealing performance.Since the non-contact type Visco seal is in direct contact with the fluid to be sealed, it is highly sensitive to the temperature, pressure, and type of the fluid to be sealed. It can be used regardless of the situation, and can operate stably under such various conditions.
It also has a long life and can follow pressure and temperature fluctuations. In addition, because the clearance of the outer visco seal is narrower than the clearance of the inner visco seal, the shielding fluid does not get caught up in the sealing fluid, there is no need to add a mechanism (circulation path, etc.) to prevent this entanglement, and the seal Since the length can be shortened, the entire device can be made compact.

[Brief explanation of the drawing]

Figures 1 and 2 are cross-sectional views of a shaft sealing device according to an embodiment of the present invention, Figure 3 is a graph showing the performance test results of the Visco seal, and Figure 4 shows the temperature distribution expected for the Visco seal. FIG. 5 is a graph showing the characteristics of Visco Seal, and FIG. 6 is a sectional view showing the basic structure of Visco Seal. 1... Rotating shaft, 2, 3, 4... Housing, 5
...Opposite room, 6,7...Visco seal, 8,11
...shielded room, 9 ... air pipe, 10 ... exhaust pipe, 1
2... Oil feed pipe, 13... Oil drain pipe, 14, 15...
Mechanical seal, 16...Liquid tank, 17...Route, 18...Sealing fluid, 19, 20...Air-liquid interface, 21...Overflow sealing fluid, 22...Sealing fluid supply pipe.

Claims (1)

[Claims] 1. In a shaft sealing device that seals a gap between a housing of various rotating equipment such as a turbine and a rotating shaft inserted into a shaft hole of the housing, a shaft sealing device that faces in the axial direction via an annular opposing chamber around the shaft and toward the opposing chamber A pair of visco seals that generate pump pressures in opposite directions are arranged, sealing fluid is supplied from a liquid tank to the opposing chambers, and the opposing chambers and a shielding chamber formed outside the pair of visco seals are communicated with each other. a sealing device is arranged outside the shielding chamber, and the clearance of the outer visco seal of the pair of visco seals is narrower than the clearance of the inner visco seal. A shaft sealing device characterized by: