JPS6332463Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a labyrinth seal device for preventing fluid leakage along the rotating shaft of a turbine, and particularly to a labyrinth seal device that reduces the excitation force applied to the rotating shaft.

Generally, a labyrinth seal device is provided in a turbine to prevent fluid leakage between the inside and outside of a casing or between a high pressure section and a low pressure section.

Figure 1 is a longitudinal cross-sectional view of a turbine. In the turbine, high-pressure fluid (steam, gas, water, etc.) is supplied through an inlet pipe 1, and a part of the pressure of the high-pressure fluid is converted into velocity through a nozzle 2. , act on the rotor blade 3.

Thereby, the disk 4 and rotating shaft 5 are rotated, and power is obtained. The fluid that has done work is discharged from an outlet pipe 6, and the rotating shaft 5 is supported by a radial bearing 7 and a thrust bearing 8.

The high pressure section 10 between the inside and outside of the casing 9 (parts A and B) and inside the casing 9
In order to prevent fluid from leaking along the rotating shaft 5 between the rotary shaft 5 and the low pressure section 11 (section C), there is a gap between the circumferential surface of the rotating shaft 5 and the inner circumferential surface of the casing 9 adjacent thereto. , a labyrinth seal consisting of multiple seal fins is provided.

These labyrinth seals have a simple structure and good performance in stopping leaks, so they are very often used in turbines, which are high-speed rotating machines such as those mentioned above.

However, as turbines have recently become more powerful and more compact, a problem has arisen in that vibrations are generated in the rotating shaft due to fluid action caused by labyrinth seals. Research is currently being conducted around the world on the fluid behavior of this seal, and it has not been discovered to date that the force that promotes vibration due to the seal is caused by pressure pulsations within the pocket between the seal fins. There is.

That is, as shown in FIG. 2 (an enlarged view of part C in FIG. 1), pressure pulsations (ΔP) within the pocket 20 (width L, diameter D) surrounded by the inlet fin 18 and the outlet fin 19 cause An excitation force F expressed by the following equation is then applied to the rotating shaft 4.

F=ΔP・L・D…(a) In Fig. 2, the symbol 16 is the shroud,
Reference numeral 17 indicates a seal ceiling, and reference numeral 21 indicates a tenon for attaching the shroud 16 to the rotor blade 3 by caulking.

In view of the above-mentioned circumstances, the present invention has been developed by reducing the pocket width between the seal fins.
It is an object of the present invention to provide a labyrinth seal device for a turbine that reduces the excitation force applied to the rotating shaft and improves the vibration stability of the turbine.

Therefore, the labyrinth seal device for a turbine of the present invention is a labyrinth seal device consisting of a plurality of seal fins implanted in a casing in order to prevent fluid leakage between the tip of a rotor blade of a turbine and a casing. Two seal fins are provided at a narrow interval so as to face only one end of the rotor blade tip, and the length of the seal fin on the high pressure side of the two seal fins is made longer than the length of the low pressure seal fin. The present invention is characterized in that a step corresponding to the length of the two seal fins is formed on the circumferential surface of the rotor blade tip facing the two seal fins.

A labyrinth seal device for a turbine as an embodiment of the present invention will be explained below with reference to the drawings. FIG. 3 shows the above device used between the tip of a rotor blade of a turbine and a casing corresponding to FIG. 2. The longitudinal sectional view shown in FIG. 4 is a schematic diagram showing the flow of leaked fluid, and the same reference numerals as in FIGS. 1 and 2 indicate the same parts.

In order to prevent fluid from leaking from the high pressure section 10 to the low pressure section 11 along the rotation axis of the turbine, two seal fins (inlet seal fin 18, outlet seal fin 19) are attached to the seal ceiling 17 of the casing with a narrow interval L'. It is implanted.

Further, this position corresponds to one end of the shroud as the tip of the rotor blade.

The dimensions of the seal fins are such that the seal fin 18 on the high pressure side (inlet side) is longer than the seal fin 19 on the low pressure side (outlet side).

Therefore, a step h is formed in the shroud 16 as the tip of the rotor blade to correspond to the size of the seal fin.

With the above-described configuration, the width L' of the pocket 20 surrounded by the inlet seal fin 18 and the outlet seal fin 19 is much smaller than in the past, so that the pressure pulsations of the leaking fluid inside the pocket 20 cause pressure pulsations in the rotating shaft. The applied excitation force F [see equation (a)] is significantly reduced.

Since a step h is formed on the surface of the shroud 16 where the inlet seal fin 18 and the outlet seal fin 19, which are provided close to each other, face each other, the leakage fluid flows as shown in FIG. As a result, leakage of fluid from the high-pressure side to the low-pressure side is prevented, and even if the inlet seal fin 18 and the outlet seal fin 19 are provided close to each other, their sealing action will not deteriorate.

Furthermore, in this embodiment, as shown in FIG. 3, the distance between the low-pressure side of the seal ceiling 17 and the shroud 16 is increased, thereby achieving the effect of further reducing the excitation force F.

Note that in this embodiment, the inlet seal fin 18,
Although the outlet seal fin 19 is provided close to the high pressure side (seal inlet section 22) of the seal ceiling 17, substantially the same operation and effect can be obtained even if the outlet seal fin 19 is provided close to the low pressure side (seal outlet section 23) of the seal ceiling 17. can get.

As described in detail above, according to the labyrinth seal device for a turbine of the present invention, a plurality of seal fins installed in the casing in order to prevent fluid leakage between the tip of the rotor blade of the turbine and the casing. In the labyrinth seal device,
Two seal fins are provided at a narrow interval so as to face only one end of the rotor blade tip, and the length of the seal fin on the high pressure side of the two seal fins is longer than the length of the low pressure measuring seal fin, It has an extremely simple structure in which a step corresponding to the length of the two seal fins is formed on the circumferential surface of the rotor blade tip facing these two seal fins. It becomes possible to significantly reduce the applied excitation force, which has the advantage of significantly improving the vibration stability of the turbine.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view showing a turbine and an example of how the labyrinth seal device is used in the turbine, FIG. 2 is an enlarged view of section C in FIG. 1, and FIGS. 3 and 4 are C sections of the turbine shown in FIG. This figure shows a labyrinth seal device for a turbine as an embodiment of the present invention used in the
The figure is a schematic diagram showing the flow of leakage fluid. 3... Moving blade, 4... Disc, 10... High pressure section, 1
1...Low pressure section, 16...Shroud, 17...Seal ceiling, 18...Inlet seal fin, 19...
Outlet seal fin, 20...Pocket, 21...
Tenon, 22... Seal inlet section, 23... Seal outlet section.

Claims (1)

[Scope of utility model registration request] In a labyrinth seal device consisting of a plurality of seal fins embedded in a casing in order to prevent fluid leakage between the tip of the rotor blade and the casing of a turbine, a labyrinth seal device that faces only one end of the tip of the rotor blade Two seal fins are provided at a narrow interval so that the seal fin on the high pressure side of the two seal fins is longer than the length of the low pressure seal fin, and the circumference of the rotor blade tip facing these two seal fins is A labyrinth seal device for a turbine, characterized in that a step corresponding to the length of the two seal fins is formed on the surface.