JPS5970815A - Gland labyrinth sealing of steam turbine - Google Patents

Abstract

PURPOSE:To simplify operations of disassembly and replacement by incorporating an upper-and-lower divided construction to a sleeve mounted on the rotor side, by furnishing a flange at each end, and by consolidating the sleeve with a right-and-left divided ring screwed fast to the flange surfaces by bolts. CONSTITUTION:An upper-and-lower divided sleeve is composed of upper half 6a and lower half 6b, each being equipped with a flange 6c with bolt holes. There are rings 8 to be coupled with the flanges 6c, each being in divided construction into left and right halves. The horizontal division surfaces of the sleeve are equipped with a slope eta so as to reside a compression stress at the its center during assembly. A pin 9 is to fix the relative movement of the rotor with sleeve as well as to fix movement in the axial direction. Processing to make sleeve for labyrinth sealing rougher is made after fixation to the rotor, and thereafter disassembly may once be made for putting each dimension in recordings, which shall serve as dimensions for processing a replacing sleeve. This divided construction ensures simple operation of disassembly and replacement.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a grand labyrinth seal for a steam turbine, and particularly to a structure for preventing aging of a rotor-side labyrinth seal.

[Technical background of the invention and its problems]

Conventionally, a labyrinth seal structure has been adopted for the grand section where the rotor of a steam turbine passes through a single chamber. The grand labyrinth of the low-pressure casing connected to the nitrogen gas is designed to prevent air from inside the turbine building from entering the casing.

As is well known, the principle of the labyrinth is that a number of fins are provided with a narrow gap between the stationary part and the rotating body, and the pressure drop due to the expansion and speed of the fluid flowing at the tip of the fins. This is a non-welding seal that limits the amount of leakage by repeatedly evacuating and decelerating the pressure in the 161 expansion chamber between the fins.

In order to prevent the effectiveness of the seal from being impaired due to so-called blow-through, where part of the velocity of the fluid passing through one fin tip is carried over to the other fin tip, the rotor has a labyrinth seal structure with unevenness. .

The grand labyrinth seal structure described above will be explained with reference to FIG. i1 In the figure, 1 is the on-board gland part of the steam turbine,
2 is a rotor, and 3 is a packing ring. Fins 4a and 4b are implanted in the packing ring. The packing ring is divided into four or more parts on the circumference, and each packing ring is pressed toward the rotor by a leaf spring 5 on the back side.

A is inside the turbine, on the high-pressure steam side, and an opening is outside the turbine, on the air side. In order to prevent high-pressure steam from leaking to the outside port of the turbine, two pockets are provided in the middle of the first part, one in the middle and one in the second part. The cap is connected to a line (not shown) that drains any steam that has escaped through the labyrinth. The second pocket is connected to the ground steam condenser line (not shown), but since this line is kept at a pressure lower than atmospheric pressure, the steam with the pressure of the convex part is further transferred to the second part. It flows in, but at the same time, the air from the mouth is also sucked in. In this way, the gland prevents steam from leaking from the turbine casing. In the case of a low-pressure gland, A is a high vacuum, but steam at a constant pressure of about Q, 3 atr is sealed in a pocket C.

FIG. 2 is an enlarged view of the fin section. After passing through the long fins 4a, the leaked steam collides with the convex portion 2b of the rotor, and simultaneously expands in the expansion chamber between the next fin and the velocity energy is converted into thermal energy. The short fins 4b similarly perform a labyrinth effect.

The fins are made of a soft material such as nickel silver or phosphor bronze, and have sharp tips so that the rotor does not generate excessive heat when it comes into contact with the rotor.

The purpose of the leaf spring 5 is to further prevent heat generation due to wear by bending the leaf spring when the fins and the rotor come into contact with each other.

Now, the purpose of the labyrinth is to limit the amount of steam leaking, but especially in the case of the rotor uneven part, which is designed to prevent leakage, if there is excessive moisture in the steam, the convex part will be caused by drain erosion. Thickness decreases and labyrinth function declines. In this case, the fin side is made of Cr-Mo@%, which has good corrosion resistance, and we are taking all possible precautions by having a spare packing ring to prevent fin wear over time.

On the other hand, drain erosion of the protrusions on the rotor side has conventionally been dealt with by shrink-fitting and fixing a sleeve with irregularities formed on the outer periphery of the grand labyrinth portion. FIG. 3 shows the shrink-fit sleeve structure, in which the ground labyrinth sleeve 6 is shrink-fit to the rotor 2. 7 is a shrink fit type shaft joint.

This conventional shrink-fit type ground labyrinth sleeve has the following problems. The sleeve 6 is a machined body with a certain shrinkage fit, is thermally expanded by force, is inserted from the end of the rotor in the direction of the person in FIG. 3, and is fixed to the rotor 2. On the other hand, since the diameter of the gland part is smaller than the outer diameter of the shaft joint, the shaft joint cannot be made into a fabricated type, so it must necessarily be made into a shrink-fit type. This is the sleeve protrusion 2 after aging.
When the sleeve has to be replaced due to excessive erosion in point (b), the shaft joint must also be tempered, resulting in major remodeling work. For the heat-out process, first separate the shaft coupling 7 and pull it out from the rotor 2, pull it out with full heat, and shrink-fit a new sleeve. Since center alignment between shaft joint 7 and rotor 2 is extremely important, it is necessary to precisely measure runout on the end face and outer circumference of the shaft joint after re-shrink fitting, and perform correction processing.

In order to avoid these problems, it is easy to think of a two-part sleeve, but if the sleeve is divided into two parts, there will be technical difficulties in fixing the half-cylinders to each other in the rotational centrifugal field of the turbine. accompany.

That is, if the flange is provided horizontally as shown in Figure 4(C),
There are protrusions at two places on the circumference, and it is difficult to obtain a narrow radial clearance for a non-contact seal.
), (b), in which welding is performed by creating a groove along the parting line of the sleeve after fitting it to the rotor, is difficult to apply to turbine rotating bodies due to the reliability of welding, and cannot be overcome. Even if it were, it would be difficult to fit the new sleeve and re-weld the f& parts that have deteriorated over time.

[Purpose of the invention]

In view of the above points, the present invention is a grand labyrinth that has a structure that is easy and reliable to attach to the rotor and is easy to replace after deterioration over time in a steam turbine that uses steam with high humidity. The object of the present invention is to provide a sealing device.

[Summary of the invention]

In order to achieve the above object, the present invention divides the sleeve added to the rotor side into upper and lower parts, provides flanges on both I4i parts, and bolts the left and right halves of the ring to the flange surface to integrate the sleeve. It is characterized by this.

(Embodiment of the Invention) Hereinafter, the assembly of the present invention will be explained with reference to Fig. 5. In Fig. 5, 62 is the upper half of the sleeve divided into upper and lower halves, 6b is the lower half, and the axis of the sleeve is attached to each end. It has a flange 6C with bolt holes in the direction.

Flange 6 of 86-1' sleeve 6a, 5b in agS drawing
It is a ring that is connected via a cK reamer bolt, and has a structure that is divided into left and right halves. 9 is the rotating sleeve 6a
, 5b is a bottle for suppressing relative movement with the rotor 2.

During turbine operation: sleeves 6a and 6b are separated by centrifugal force
The ring 8, which is divided into two parts on the left and right, restrains the two parts from separating. If the overall length of the sleeve is long, this constraint will be less near the center of the sleeve in the i1 direction, so a horizontal dividing plane K11 oblique θ shown in FIG. 6 is provided depending on the diameter and length of the sleeve and the rotation of the turbine. Maximum compressive stress should remain in the center of the sleeve during assembly. The bin 9 is a gap-free bin (
Remabin) represents. Similarly, the fixing bolts 1o between the sleeves 6a, 6b and the left and right halves of the ring 8 are made one-sided, and the depth of the bolt heads is set at 1 to prevent the bolt heads from being eroded by moisture and becoming difficult to disassemble. A counterbore will be provided on the side, and the bolts will be hexagon socket head bolts. This assembled state is shown in FIG. The roughening of the labyrinth seal sleeve is performed after the sleeve is fixed to the rotor. After this, you can disassemble it once and accurately measure the dimensions of each part and keep a record to use them as dimensions for machining replacement sleeves after aging, or you can create and deliver a set of spare sleeves from Todoroki, such as bearing 6 and packing. You may.

By not providing the flanges of the sleeves 6a and 6b, but by providing them in the middle as shown in FIG. 8, it is possible to prevent the sleeves from blistering due to centrifugal force and to have a baffle effect for leaking steam. Similarly, the fin shape of the labyrinth seal is also limited to the shape described in the present invention. Furthermore, the restraining ring 8 of the upper and lower halves of the IJ-pro a, 5b is not fixed with a reamer bolt, but is shaped into a circumferential headband as required, and is fixed by welding or the like, as a modification of the present invention. It is regarded. FIG. 9 shows a typical example of this, in which a sleeve divided into upper and lower halves is surrounded by a headband 11 divided into left and right halves, and welded together at 12.

〔Effect of the invention〕

According to the present invention, it is possible to employ a labyrinth that prevents air vents with a high sealing function in the gland part of a turbine that uses steam with high humidity, such as a light water reactor type nuclear power turbine or a geothermal turbine, and at the same time, it is possible to use a labyrinth that prevents a blowout with a high sealing function. Since it is assembled in two parts instead of having a structure, it can be easily disassembled and replaced on site.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing a general Guerand Labyrinth/School device, Fig. 2 is a partially enlarged sectional view of Fig. 1, Fig. 3 is a sectional view showing a conventional shrink-fit sleeve, Fig. 4(a),
(b), (C1 is a front view and side view showing a two-part sleeve, Figures 5 (a), (b), (C) and; Figure 16 is a front view and side view showing an embodiment of the present invention. 7 is a partially enlarged cross-sectional view of FIG. 5(a), and FIGS. 8 and 9 are cross-sectional views showing other different embodiments of the present invention.
and Figure 1. 2...Rotor, 6...S I+-F, 6C
...Flange, 8...Ring. (7317) 1st Patent Attorney Kensuke Norichika (and 1 other person)
Figure 1 Figure 2 Figure 4 Figure 5 ty

Claims (1)

[Claims] In a grand labyrinth sealing device for a steam turbine, in which a sleeve having an axially uneven surface on its outer periphery is fixed to the rotor to form the rotor side, the sleeve is divided into upper and lower halves, flanges are provided at both ends, and the flange surface A grand labyrinth sealing device for a steam turbine, which is characterized by an integral sleeve formed by bolting a ring divided into left and right halves.