JPS6350607A - Device for labyrinth sealing - Google Patents

Abstract

PURPOSE:To prevent the occurrence of a turning stream by installing plates which partition a chamber circumferencially within the most upstream-side chamber formed by seal fins, and slits through which the chamber is connected to the upstream. CONSTITUTION:Plates 17 which partition circumferencially the most upstream- side chamber 16 out of chambers 16 formed by seal fins 14, are installed within said most upstream-side chamber 16. The plates 17 are fitted in such that an angle beta is formed with a steam stream, in relation to the rotational direction U of a rotor. Each of partitioned chambers 16 is provided with a slit 18 so as to be connected to the upstream side. accordingly, the steam in a stagnation range or an excess flow range runs downstream, thereby preventing the occurrence of a turning stream within the chamber.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Field of Application) The present invention is a method suitable for suppressing rotor instability caused by a swirling flow of steam generated around a rotor of a steam turbine. This invention relates to a labyrinth seal device.

(Prior art) As shown in Figure 6, a steam turbine, which occupies a representative position in the axial flow turbo region, is constructed by arranging a large number of stages consisting of moving blades and stationary blades in the axial direction of the rotor. Ru.

That is, in the figure, the reference numeral 1 indicates a rotor which is a central element of a rotating body of a steam turbine.
is rotatably supported at both ends by bearings 2, and a large number of rotor blades 3 are provided via a disk 4 along the axial direction of the rotor 1 located between the bearings 2. are connected by a shroud 5 in the circumferential direction.

On the other hand, reference numeral 6 denotes a casing that surrounds the rotating body and confines high-temperature, high-pressure steam therein, and a large number of stationary blades extend from the inner surface of the casing 6 toward the rotor 1. 7 is provided via a nozzle diaphragm 8, forming a pair with the rotor blades 3 to form independent stages one by one, and converting the thermal energy of the steam into mechanical energy and extracting it as power. .

Furthermore, in order for this energy conversion to be carried out efficiently, it is necessary to prevent high pressure steam from rising between each stage and leaking to the lower pressure side. For this purpose, the gap between the stationary body and the rotating body is sealed using a suitable seal, but in many cases, a seal with a labyrinth structure is used, that is, a seal ring 9 is lined with a large number of sealing fins 10, and a maze-like continuous chamber 11 is formed. The configuration is used. In addition, as shown in FIG. 5, this sealing device is provided in each stage, and in the part where the rotor 1 penetrates the casing 6, that is, in the ground part.

(Problems to be Solved by the Invention) In recent years, there have been attempts to push the limits of efficiency of such steam turbines by roughly increasing the temperature and pressure mentioned above. In such cases, the sealing gap between the rotating body and the stationary body is usually made narrower in order to reduce the amount of leaked steam, and the narrower the gap, the more problems arise. That is, a typical problem is a phenomenon called steam whirl caused by a swirling flow of steam around the rotor 1. When this phenomenon occurs, the rotating body centered on the rotor 1 swings around greatly due to the imaging cycle specific to the system of the rotating body, resulting in loss of stability as a machine.

This steam whirl phenomenon will be explained in more detail below. That is, in general, the rotor 1 is affected by the oil film force of the lubricating oil supplied to the bearing 2 and the casing 6 when it is stationary, such as during assembly, and when it is operating (subdivided into low-speed rotation and high-speed rotation). Due to thermal influences, the center of rotation relative to the stationary body is not constant, and even in the sealing device, the center O of the rotor 1 is eccentric to the center O of the seal fin 10, as shown in FIG. It rotates out of alignment.

In this case, the pressure distribution in the circumferential direction within the chamber 11 formed between adjacent seal fins 10 has a symmetrical pressure distribution with the maximum value in the eccentric direction, and by integrating this pressure distribution, each The force generated in the chamber 11, that is, the force acting on the rotor 1 is calculated.If this acting force P is applied to the rotor 1 from a direction opposite to the eccentric direction, the eccentricity me of the rotor 1 is reduced. move as you do.

However, if the flow of steam flowing into the sealing device is deflected by the influence of the stationary blades 6 or the rotational force of the rotor 1, and flows into the swirling flow W in the same direction as the rotation of the rotor 1, the flow of steam flowing into the sealing device is caused to flow into the chamber 11 as shown in FIG. The location of maximum pressure within the seal changes rotationally upstream relative to the minimum clearance point of the seal. Therefore, the acting force on the rotor 1 includes an acting force P in the above-mentioned deflection direction and an acting force Q in the perpendicular direction. When this acting force Q matches the rotational direction of the rotor 1]
It is the power that causes unstable 1-stroke movement as a shin-kyoku force. As described above, the acting force generated within the sealing device greatly influences the direction of the swirling flow W of the steam together with the operating conditions such as the pressure difference between the sealing portions.

As a method of dealing with such an unstable phenomenon of the rotor 1, for example, Japanese Patent Application Laid-Open No. 58-222902 discloses a method in which vanes are oriented in the opposite direction to the rotational direction of the rotor 1.
As seen in Japanese Patent No. 8-38666, a method is known in which a partition plate is provided in the sealing device to prevent the swirling flow W from occurring.

However, the method disclosed in Japanese Patent Application Laid-Open No. 58-222902 has the disadvantage that the effective sealing area is reduced by providing a vane in addition to the sealing device.Furthermore, in the labyrinth sealing device, the gap between the seal fin 10 and the rotor 1 is reduced. There is a problem that the flowing steam does not expand within the chamber 11, and the vanes and partition plates cannot act on the steam in the stagnation region or the overflow region to prevent the generation of swirling flow. Sufficient improvement effect has not been obtained.

Therefore, an object of the present invention is to provide an improved labyrinth seal device that can effectively prevent the generation of swirling flow by touching the steam in the stagnation region or overflow region of the flow in the chamber. .

[Structure of the Invention] (Means for Solving the Problems) The labyrinth seal device according to the present invention includes a plurality of plates that partition the inside of the chamber in the circumferential direction in the chamber of the first stage when viewed in the direction of steam flow. In addition, each of the partitioned chambers is characterized by having slits or through holes for communicating with the upstream side of the steam flow.

(Operation) The above technical means operates as follows. That is, as shown in FIG. 7, if the rotor 1 rotates eccentrically by an eccentric amount e within the sealing device, and the steam flow flowing therein has a swirling component in the same direction as the rotational direction of the rotor 1. , a necessary acting force is generated on the rotor 1 depending on the steam power. This acting force acts as an acting force Q in a perpendicular direction to the minimum clearance point formed between the rotor 1 and the seal fin 10, causing the rotor 1 to vibrate in the same direction as the rotational direction of the rotor 1. It is known that the magnitude of this acting force Q is also affected by the eccentricity le of the rotor 1, and has a value expressed by the following equation.

Q=mu+−e・・・・・・・・・(1) Here, e=
The amount of eccentricity of the rotor = rigidity coefficient and + = C-3! nα B---------(2>Here, α1 = rotor axis and inflow angle of steam C = proportionality constant i = number of seal stages, that is, it is necessary to effectively rectify the flow of steam. .

However, a part of the chamber to which a plate for rectifying the steam flow can be attached has a stagnation area for the steam flow or is filled with persulfuric acid, and the rectification effect is low. Therefore, in the present invention,
A plate is provided to divide the inside of the chamber, and a slit is cut in the seal fin on the upstream side to create a flow of steam along the plate. Furthermore, since the flow in the previous stage of the seal determines the flow in the next stage, it is sufficient to rectify the flow of steam to the first stage or the next stage of the seal.

At the seal stage where this slit is cut, the amount of steam flowing in increases and the pressure rises, but this does not affect the seal fins on the downstream side and the seals in the next stage, and only the direction of steam inflow can be changed. is.

Incidentally, by setting the mounting angle of the plate at an angle at which the steam flow is opposed to the rotation direction, it can be made to act as a force to suppress the excitation force on the rotor.

That is, in equation (2) of the previous 5=, by setting α<Q, Q<0, and the force that was conventionally applied as an excitation force acts as a force that suppresses imaging.

However, the value of αl changes depending on the number of plates and the width of the slit, but for the plate installation angle β, α1 = CO - B (3) Here, Co
= proportionality constant However, O<Co<1.

(Example) An example of the present invention will be described below with reference to FIGS. 1, 2, and 3.

In FIG. 1, a grooved portion 12 and a raised portion 13 are formed in a stepped manner on the surface of the rotor 1, and a seal fin 14 is attached to a stationary body toward the grooved portion 12 and the raised portion 13. For example, a sealing device is formed by extending the packing rings 15 supported on the inner surface of the nozzle diaphragm 8 to form chambers 16 that are connected in a maze-like manner. In the present invention, for this sealing device, a plurality of plates 17 are provided inside the chamber 16 of the first stage, dividing the inside of the chamber in the circumferential direction as shown in FIG. The mounting force of the plate 17 is set at an angle β opposite to the steam flow with respect to the rotational direction U of the rotor 1, as shown in FIG. In determining this angle β, it is necessary to take into consideration the steam pressure, the rotation speed of the rotor 1, the shape of the seal, etc., and although it cannot be set as a constant value, it is determined within the range of 0 to 60 degrees.

Furthermore, a slit 18 is provided that allows each of the divided chambers 16 to communicate with the upstream side of the steam flow. This slit 18 is connected to the seal fin 14 on the upstream side of the plate 17.
952G is generated near the position where it is in contact with.

Note that the reference numeral 19 in FIG. 1 indicates a spring.

In the above configuration, the above flow is deflected by an angle α with respect to the axis of the rotor 1, but flows through the slit 18 into the chamber 1.
6, where it is reversed by a plate 17 and rectified into a flow along the plate 17. This steam then flows through the gap between the rotor 1 and the sealing fin 14 to the next chamber 16, where it merges with the main stream of steam passing through the sealing device and roughly flows toward the subsequent chamber 16. It flows. Figure 4 shows a diagram simulating the flow of steam described above.

That is, by appropriately setting the width of the slit 18 and the number of plates 17 in consideration of the usage conditions, the second
By giving the angle α1 of the flow into the seals in the subsequent stages so as to be opposite to the rotational direction of the rotor 1, it is possible to change the pressure distribution within the seal device. Therefore, the force acting on the rotor 1 does not act as an excitation force but as a force for suppressing vibration, thereby preventing the occurrence of the steam whirl phenomenon.

On the other hand, FIG. 5 shows an embodiment suitable for providing a sufficient rectifying effect and preventing an increase in the amount of steam leakage when the swirling flow is larger than in the above embodiment.

That is, here, the plates 17 are provided at two locations: the chamber 16 of the first stage and the next stage.

In addition, a through hole 1 is provided in each upstream seal fin 10.
9 is worn.

In this embodiment, the rectification effect is more reliable than in the above embodiments, and it becomes a more effective means for preventing the steam whirl phenomenon.

The slits 18 and through-holes 19 in each of the above embodiments are considered disadvantageous in terms of the sealing function because they increase the gap area, but in the final stage of the seal or the stage immediately before it, which affects the leakage characteristics of the sealing device. By suppressing unstable vibrations, the overall gap between the rotor 1 and the seal fin 14 can be made narrower than before, which more than makes up for the disadvantages.

[Effects of the Invention] As explained above, the present invention provides a plurality of plates that partition the inside of the chamber in the circumferential direction in the first stage chamber as viewed in the direction of steam inflow, and also Since each is provided with a slit or a through hole that communicates with the upstream side of the steam flow, the present invention has the advantage that the unstable phenomenon of the rotor caused by the swirling flow of steam can be eliminated. It has a great effect.

[Brief explanation of drawings]

1, 2, and 3 are a sectional view, a front view, and a developed view showing one embodiment of the labyrinth seal device according to the present invention, FIG. 4 is an explanatory view showing the flow state of steam, and FIG. 5 6 is a developed view showing another embodiment of the present invention, FIG. 6 is a sectional view showing the main parts of a conventional steam turbine, and FIGS. 7 and 8 explain the unstable phenomenon of the rotor caused by swirling flow. This is a diagram for 1...Rotor 12...Concave section 13...Convex section 14...Seal fin 15・・・・・・Patsukin Ring 16・・・・・・
...Chamber 17...Plate 18...Slit 19...Through hole Representative Patent attorney Noriyuki Chika Yudo Hirofumi Mitsumata Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (2)

[Claims] (1) Concave portions and convex portions are arranged alternately in the axial direction of the rotor, and seal fins are installed from a packing ring supported on the inner surface of the stationary body toward these concave portions and convex portions. In a labyrinth seal device in which a chamber is formed between extending seal fins, a plurality of plates are provided in the chamber of the first stage as viewed in the direction in which steam flows, dividing the inside of the chamber in the circumferential direction; A labyrinth seal device characterized in that each of the partitioned chambers is provided with a slit or a through hole that communicates with the upstream side of the steam flow. (2) The labyrinth seal device according to claim 1, wherein the plate is inclined in a direction opposite to the steam flow with respect to the rotational direction of the rotor.