JPH0734808A - Steam turbine - Google Patents

Abstract

PURPOSE:To prevent the turbine rotor from being bent due to the creep by reducing the temperature rise on the surface of the turbine rotor, and prevent the surface of the space to be formed by the nozzle box and the turbine rotor from being ground by solid particles. CONSTITUTION:First steam bypass holes 15a, 15b communicating a space 21 to be formed between a double discharge type nozzle box 5 and an inner wheel chamber 4 with steam chambers 20a, 20b after the governing stage are pierced in the pair of right and left high pressure blade rings 13a, 13b respectively. Second steam bypass holes 12a, 12b which are inclined in the same direction are pierced in the projecting part where the rotor blades of the governing stage are implanted of a turbine rotor 8. The steam condition after the right and left governing stage is set so that the steam pressure after the governing stage on the side where the radius of the bypass holes 12a, 12b is large may be lower than that on the side where the radius of the bypass holes is small.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a steam turbine, and more particularly to a steam turbine having a double-flow nozzle box.

[0002]

2. Description of the Related Art As the capacity of a steam turbine increases, the amount of steam used increases and the force acting on the inside of the turbine also increases. In particular, the stress acting on the high-pressure portion is remarkable, and a double-flow nozzle box as shown in FIG. 6 has been conventionally used for the purpose of reducing this stress.

That is, in the first conventional example shown in FIG. 6, a high-temperature, high-pressure steam flow 1 passes through a steam inlet pipe 3 supported by an outer casing 2 of a steam turbine, and then is supported by an inner casing 4. It is guided to the double-flow nozzle box 5 which is formed.

To the left and right of this double-flow nozzle box 5,
The nozzle blocks 6a and 6b are fixed,
The steam flow 1a accelerated by these nozzle blocks 6a and 6b is guided to the left and right speed control stage moving blades 7a and 7b, and the reaction thereof causes the turbine rotor 8 to rotate. Steam flow 1b that passes through speed control blades 7a and 7b and is reduced in temperature and pressure
Are further guided to the high-pressure blade groups 9a and 9b.

The speed control blades 7a, 7b are a pair of left and right convex portions 1 integrally formed on the outer peripheral portion of the turbine rotor 8.
It is implanted in 0a and 10b respectively.

Further, in the second conventional example shown in FIG. 7 to FIG. 9, a pair of right and left speed control stage rotor blade projecting projections 10a and 10b of the turbine rotor 8 in the steam turbine are arranged in the radial direction along the rotor axial direction. Steam bypass hole 1 inclined in the same direction
2a and 12b are provided respectively.

In this second conventional example, one of the speed control stage moving blades 7
A part of the steam 1b that has passed through a and reduced in temperature and pressure is
The cooling steam flow 1d is introduced into the space 11 from the one steam bypass hole 12a by the centrifugal force of the turbine rotor 8. The cooling steam flow 1d cools the surfaces of the turbine rotor 8 and the double-flow nozzle box 5 that form the space 11, and then the other steam bypass hole 12b.
Is discharged by the centrifugal force of the turbine rotor 8 and joins with the steam flow 1b that has passed through the other speed control blade 7b.

In this way, the temperature
Part of the steam whose pressure has been reduced is introduced into and exhausted from the space formed by the turbine rotor and the double-flow nozzle box through the steam bypass hole, the surface of the turbine rotor facing the space is cooled, and The solid particles contained in are no longer retained in the space.

[0009]

By the way, the above-mentioned 2
The two conventional examples had the following problems.

In the first conventional example shown in FIG. 6, in the space 11 formed by the double-flow nozzle box 5 and the turbine rotor 8, before the temperature and pressure are reduced by the speed control blades 7a and 7b. High temperature, high pressure steam 1c leaks from the left and right,
Form a stagnation of steam. Therefore, the surface temperature of the turbine rotor 8 facing the space 11 rises, and the turbine rotor 8 may bend due to creep after a long time operation.

Further, the solid particles mixed in the space 11 together with the leaking steam flow 1c from the left and right are not discharged from the space 11 but stay in this space, so that the double flow nozzle box 5 forming the space 11 and the turbine. The surfaces of the rotor 8 and the rotor 8 were sometimes scraped off by solid particles, resulting in a decrease in strength.

Next, in the second conventional example shown in FIGS. 7 to 9, as shown in FIG. 9, when the steam bypass hole 12a is bored, the jig is on the opposite side to the speed-control stage blade-implanting convex. In some cases, it may interfere with the portion 10b, making it impossible to punch.

Therefore, an object of the present invention is to prevent the turbine rotor from bending due to creep by reducing the temperature rise on the surface of the turbine rotor, and to prevent each surface forming the space 11 from being scraped by solid particles. To prevent. It is also an object to prevent the boring jig from interfering with the rotor protrusion when the above-mentioned steam bypass hole 12a is bored, so that the construction cannot be performed.

[0014]

The present invention was devised to solve the above-mentioned problems, and in a steam turbine having a double-flow nozzle box, a seal is provided between the nozzle box and the high-pressure blade ring. A first steam bypass hole, which is installed and connects the space formed between the nozzle box and the inner casing with the steam chamber after the speed-control stage, is formed in each of the pair of left and right high-pressure blade rings, and the turbine is provided. A second steam bypass hole that is inclined in the same direction is formed in each of the pair of right and left speed control blade implanting convex portions of the rotor, and the steam conditions after the left and right speed control steps are as follows. The steam turbine is characterized in that the steam pressure after the speed control stage on the side with a large radius is set to be lower than the steam pressure after the speed control stage on the side with a small radius.

The second steam bypass hole may be formed so as to be inclined in the radial direction from the axis and also in the circumferential direction.

[0016]

According to the above-described means, first, a part of the steam having the temperature and pressure reduced by passing through the speed control blades is transferred to the space formed by the turbine rotor and the double-flow nozzle box by the steam bypass hole. Is reliably introduced and exhausted through the space, the surface of the turbine rotor facing the space is cooled, and solid particles contained in the steam are not accumulated in the space.

Further, a part of the steam that has passed through the speed control blade is reliably introduced into the space between the nozzle box and the inner casing through the first steam bypass hole in the high pressure blade ring and is exhausted. Therefore, the outer surface of the nozzle box and the inner surface of the inner passenger compartment are cooled.

Further, a second steam bypass hole is bored in the convex portion of the speed-regulating blade impregnation so as to be inclined in the circumferential direction from the axial center, so that the convex portion of the speed-regulating blade impregnation on the opposite side is formed. Since the relative distance between the second steam bypass hole and the second steam bypass hole becomes large, the height difference becomes large. Can be drilled without interfering with.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the first invention will be described in detail below with reference to FIGS. In FIG. 2, the same parts as those shown in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted.

According to the present embodiment, however, the pair of left and right speed control stage blade impregnating projections 10a and 10b of the turbine rotor 8 of the steam turbine are inclined in the same direction along the rotor axial direction. Steam bypass holes 12a and 12b are formed.

Further, first steam bypass holes 15a and 15b are also formed in the left and right high pressure blade rings 13a and 13b, respectively.

Further, the speed control stage 7 slightly changes the blade shape on the left and right to make a slight difference in the steam pressure after the speed control stage. In the embodiment of FIGS. 1 and 2, the steam bypass hole 12a having a small diameter is used.
To the right steam chamber 2 on the side where the large-diameter steam bypass hole 12b is formed.
Set slightly higher than 0b.

Therefore, a part of the steam 1b, which has passed through one of the speed-control blades 7a and whose temperature and pressure have been reduced, is used as a cooling steam flow 1d from one steam bypass hole 12a to centrifugally separate the turbine rotor 8. By force and slight pressure difference,
It is introduced into the space 11. And this cooling steam flow 1d
Cools the surfaces of the turbine rotor 8 and the double-flow nozzle box 5 that form the space 11, and then is discharged from the steam bypass hole 12b of the other side by the centrifugal force of the turbine rotor 8 and a slight pressure difference, and Speed blade 7b
Joins with the steam flow 1b that has passed through.

On the other hand, part of the steam 1b after the speed control stage is introduced into the space 21 between the nozzle box 5 and the inner casing 4 from the steam chamber 20a through the steam bypass hole 15a due to a slight pressure difference. To be done. Further, the cooling steam 1e cools the inner surface of the inner casing and the outer surface of the nozzle box, and then passes through the steam bypass hole 15b due to a slight pressure difference, thereby passing through the steam chamber 20.
It is discharged to b and merges with the flow of the steam 1b which has passed through the other speed control blade 7b.

Next, an embodiment of the second invention will be described in detail with reference to FIGS. In the present invention, the steam bypass hole 120 formed in the protruding portion 10 for controlling the speed-adjusting blade is
It is also inclined in the circumferential direction with respect to the axis. This tilt angle θ
₂ is determined by the clearance between the speed-controlling stage blade-implanting convex portions 10a and 10b and the state of interference with the drilling jig of the steam bypass hole 120. An outline arrow 100 in the drawing indicates the approach direction of the punch jig.

By the way, the degree of spread of the distance to the opposite speed control stage blade implantation by the inclination angle θ ₂ is 1 / cos θ _2, which is shown in Table 1 below.

[0027]

[Table 1]

As described above, according to the first aspect of the invention, in the steam turbine provided with the double-flow nozzle box, the surface of the turbine rotor facing the double-flow nozzle box controls the temperature by the speed control blades. Since it is cooled by the reduced steam, it is possible to prevent the turbine rotor from bending due to creep after long-term operation.

Further, the solid particles contained in the steam do not stay in the space formed by the double-flow nozzle box and the turbine rotor, so that each surface of the double-flow nozzle box and the turbine rotor is formed by the solid particles. Erosion is eliminated, which can prevent a decrease in strength.

Further, since a small amount of cooling steam flows through the inner surface of the inside of the inner vehicle, the temperature of this portion is prevented from increasing due to the leak of high temperature main steam (in the case of FIG. 2), and a small heat transfer is performed. The temperature difference between the inside and the outside of the inner casing is small, and therefore troubles such as deformation of the casing can be prevented.

On the other hand, the nozzle box is heated to a high temperature because the high temperature main steam flows on its inner surface. Therefore, by filling the outer surface with cooling steam, the temperature of the nozzle box can be lowered and the creep strength can be improved.

Next, according to the second aspect of the present invention, when the second steam bypass hole is drilled, the drill jig interferes with the rotor convex portion and can be implemented.

By setting the inclination θ ₂ of the second steam bypass hole in the circumferential direction in the direction in which the steam easily flows in by the rotation of the rotor, the introduction efficiency of the cooling steam can be improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a main part of a steam turbine rotor according to a first embodiment of the first invention.

FIG. 2 is a sectional view of a main part of a steam turbine rotor showing a second embodiment of the first invention.

FIG. 3 is a perspective view of an essential part showing an embodiment according to the second invention.

FIG. 4 is a plan view of FIG.

5 is a cross-sectional view of FIG.

FIG. 6 is a cross-sectional view showing a main part of a steam turbine according to a first conventional example.

FIG. 7 is a cross-sectional view showing a main part of a steam turbine according to a second conventional example.

FIG. 8 is a plan view of a main part of a steam turbine rotor according to a second conventional example.

9 is a diagram showing a cross section of FIG. 8 for explaining the problem of the second conventional example.

[Explanation of symbols]

1 Steam Flow 1d Cooling Steam Flow 5 Double Flow Nozzle Box 7a, 7b Speed Control Blade 8 Turbine Rotors 10a, 10b Speed Control Blade Implant Convex 11 Space 12a, 12b, 120a, 120b Second Steam Bypass Hole 13a, 13b High-pressure blade ring 15a, 15b First steam bypass hole 16 Seal 20a Left steam chamber 20b Right steam chamber 21 Space

Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display area F01D 25/24 KG

Claims (2)

[Claims] 1. A steam turbine having a double-flow nozzle box, wherein a seal is installed between the nozzle box and the high-pressure blade ring, and a space formed between the nozzle box and the inner casing and a speed control stage. A first steam bypass hole that communicates with the subsequent steam chamber is formed in each of the pair of left and right high-pressure blade rings, and the pair of left and right speed-regulating stage rotor blade projection convex portions of the turbine rotor are inclined in the same direction. Two steam bypass holes are bored, and the steam conditions after the left and right speed control stages are as follows, after the speed control step on the side where the radius of the second steam bypass hole is large and the steam pressure on the side where the radius is small. A steam turbine characterized by being set to be lower than the steam pressure. 2. The steam turbine according to claim 1, wherein the second steam bypass hole is formed so as to be tilted in a radial direction from a shaft center and also in a circumferential direction.