JPS641518Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a shaft sealing device for a turbo compressor.

In turbo compressors, especially multi-stage turbo compressors, the bearing of the rotating main shaft is placed in the axial suction passage in order to maintain high performance by simplifying the shape of the inlet passage and to reduce costs by simplifying the structure. There are things to do.

Specifically, as shown in FIG. 1, one end side of a rotating main shaft 2 equipped with an impeller 1 protrudes into a suction casing 3 that sucks the atmosphere, and is provided with a bearing 4 that supports the end of the rotating main shaft 2. A bearing box 5 is fixed to the suction casing 3 via ribs 6 and 7.

A labyrinth seal portion 8 is provided in the bearing box 5 following the bearing 4, and the bearing 4 is supplied with oil from the outside through an oil supply passage 9 provided in the rib 6. The used oil in the bearing 4 is collected into an oil tank (not shown) through an oil drain passage 10 provided in the rib 7.

Incidentally, the oil supplied through the oil supply passage 9 is at a pressure slightly higher than atmospheric pressure because it requires oil injection, and some of the oil passes through the labyrinth seal portion 8 and reaches the bearing box 5 and the impeller fixing ring. The suction fluid may leak into the suction fluid flow path 12 from the gap ε formed between the suction fluid and the suction fluid flow path 11.

However, depending on the fluid being handled, it is necessary to avoid oil from getting mixed into it. Therefore, in order to prevent oil from being mixed into the handled fluid, a space 13 that communicates with the atmosphere is usually provided in a part of the labyrinth in the longitudinal direction, and the oil is dissipated into the atmosphere from there.

However, since the fluid is accelerated in the suction fluid flow path 12 by the rotation of the impeller, the static pressure P ₁ in the flow path is lower than the atmospheric pressure by the dynamic pressure P ₂ (=1/2ρV ² ). becomes smaller. However, ρ is the density and V is the flow velocity. Therefore, there is a drawback that oil for bearing lubrication is sucked out from the gap ε into the fluid flow path 12, and the oil is mixed into the fluid to be handled.

The cause of this contamination into the handled fluid is the space 13.
This is because the internal static pressure P 1 cannot be made sufficiently large due to constraints imposed by the overall structure, and the internal static pressure P ₁ reaches the labyrinth seal portion 8 .

Therefore, the technical problem of the present invention is to increase the pressure in the gap ε that opens to the fluid flow path 12 and make it equal to the pressure in the space 13 (atmospheric pressure).

As a method for solving the above problem, there is a method of injecting pressurized gas into the space 13 from the outside, but in that case, extra auxiliary equipment is required and the product cost is high.

Therefore, in the present invention, the technical means taken to achieve the above-mentioned problem without providing extra auxiliary equipment as described above is a bearing that supports the end of the rotating main shaft on which the impeller of the turbo compressor is attached. A bearing box containing the oil is placed in the suction channel, and the bearing box is labyrinth-sealed to the suction channel, and a space communicating with the atmosphere is provided in a part of the longitudinal direction of the labyrinth seal to discharge leaked oil. In the shaft sealing device of a turbo compressor equipped with
A ring having an annular projection forming an annular gap extending in the suction direction along the outer periphery of the end of the bearing box and connected to the labyrinth seal is fixed to the rotating main shaft.

The above technical means works as follows. That is,
As shown in the principle diagram in FIG. 2, an annular projection connected to the labyrinth seal 8 is formed by a ring having an annular protrusion that extends along the outer peripheral portion of the end of the bearing box in the suction direction and forms an annular gap connected to the labyrinth seal. A gap ε' is formed. On the other hand, the flow in the suction channel 12 is an accelerated flow, and the thickness of the wall boundary is sufficiently smaller than the gap ε', and the pressure inside the gap ε' is the dynamic pressure generated by the collision of the fluid there. _P2
Static pressure P ₁ is added to the pressure, which becomes equal to atmospheric pressure. The pressure inside this gap ε′ is applied to the space 13 via the labyrinth seal portion 8. Therefore, the pressure inside the gap ε' becomes equal to the pressure in the space 13, and there is no longer any leakage into the suction channel through the gap ε', resulting in the special effect that no oil is mixed into the handled fluid. It is played.

Hereinafter, embodiments of the present invention will be described in detail based on the enlarged explanatory view of the main part of FIG. 3.

Reference numeral 15 denotes an end of the bearing box 5 of the rotating main shaft 2, and a labyrinth 16 is provided on its inner surface.
A part of the longitudinal direction of 6 has a space 1 that communicates with the atmosphere.
3 is provided.

Reference numeral 11 denotes a ring provided between the end 15 of the bearing box 5 and the impeller 1, and a threaded portion 17 on the inner circumferential surface of which is provided with the rotating main shaft 2 so as to fix the position of the impeller 1. A female thread for threading is cut and fixed to the rotating main shaft 2. An annular protrusion 14 extending in the suction direction is provided on the side surface of the ring 11 on the bearing box side, along the outer peripheral surface of the end 15 of the bearing box 5. An annular gap ε' is formed between this annular projection 14 and the outer peripheral surface of the end portion of the bearing box. This annular gap ε' communicates with the labyrinth 16 via between the ring 11 and the side surface of the end of the bearing box.

When the rotating main shaft 2 rotates, fluid flows into the fluid flow path 12 in the suction casing, a part of the fluid that flows collides with the annular gap ε′, and dynamic pressure P ₂ due to the flow velocity of the fluid flow acts, Leakage of oil from the gap ε' to the fluid flow path 12 via the labyrinth seal portion 8 can be prevented.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a conventional shaft sealing device for a turbo compressor, FIG. 2 is an explanatory diagram of the principle of the present invention, and FIG. 3 is an enlarged explanatory diagram of the main parts of an embodiment of the present invention. 1: Impeller, 2: Rotating main shaft, 3: Suction casing, 4: Bearing, 5: Bearing box, 8: Labyrinth seal section, 11: Fixed ring, 12: Fluid flow path, 1
4: Annular process.

Claims (1)

[Scope of utility model registration request] A bearing box that houses a bearing that supports the end of the rotating main shaft with the impeller of the turbo compressor attached is placed in the suction flow path, and the bearing box is labyrinth-sealed to the suction flow path. In the shaft sealing device of a turbo compressor, which has a space communicating with the atmosphere to discharge partially leaked oil, between the bearing box and the impeller, there is a A shaft sealing device for a turbo compressor, characterized in that a ring having an annular projection forming an annular gap opposite to the labyrinth seal is fixed to a rotating main shaft.