JPS59126003A - Cooling structure of steam turbine - Google Patents

Abstract

PURPOSE:To enhance the cooling efficiency while suppressing the energy loss by a method wherein through holes, which are open to a space surrounded by a nozzle diaphragm inner ring and a rotor disc, are provided on the nozzle diaphragm inner ring in order to led a part of cooling steam to said space therethrough. CONSTITUTION:Cooling steam is led to the gap between a turbine rotor 26 and the labyrinth packing 24 implanted onto a nozzle diaphragm inner ring 23, which connectingly supports stator blades 22, in order to cool the turbine rotor 26 and a rotor disc 27. In this case, through holes 32, which are open to a space 33 surrounded by said inner ring 23 and the rotor disc 27, are provided on the inner ring 23. Due to the structure as mentioned above, a part of cooling steam supplied from a steam supply pipe 31 is directly led to the space 33 through the through holes 32, resulting in positively cooling a moving blade mortised part 29. At this time, because the steam to cool the moving blade mortised part 29 does not pass through the labyrinth packing 24 and consequently is able to keep its temperature enough low, the enhanced cooling effect is resulted.

Description

[Detailed description of the invention] [Technical field of invention] The present invention relates to a cooling structure for a steam turbine, and particularly relates to a cooling structure for a steam turbine.

[Technical background of the invention and its problems]

In general, in an axial flow turbine, the inner and outer ends of a large number of stator blades 1, which are arranged as shown in FIG. A one-stage turbine stage is formed by a stationary part that is integrally fixed to the outer ring 3 and a rotating part that is made up of rotor blades 7 that are embedded in a rotor disk 6 that is integrated with or fitted into the turbine rotor 5. Ru. An axial flow turbine is constructed by combining one or more of these turbine stages in the axial direction.

By the way, in steam turbines, in order to increase the power generation efficiency of the turbine, the steam pressure and temperature at the turbine inlet are increased. However, as the temperature of the steam flowing into the steam turbine increases, many expensive materials with excellent heat resistance must be used as turbine constituent materials, which raises the problem of increased manufacturing costs. For this reason, it is common practice to use inexpensive conventional materials while cooling the hot parts of the steam turbine. In particular, the turbine rotors in the high-pressure stage and reheat stage section of a steam turbine are exposed to high temperatures and therefore need to be cooled.

For this reason, conventionally, a cooling steam pipe 8 is attached to a stationary part of a steam turbine, and the cooling steam supplied from this steam pipe 8 is guided to the turbine rotor 5, and then passed through the gap between the labyrinth packing 9 and the turbine rotor 5. It is guided to a space [0] surrounded by the nozzle diaphragm inner ring 2 and the rotor disk 6, and cools the turbine rotor 5. On the other hand, a part of the cooling steam guided to the space [0 passes through the gap [2] between the rotor disk 6 and the implanted part 11 of the turbine dynamic sense 7, and cools the rotor disk 6 and the rotor blade implant s11. In this way, the remaining cooling steam is blown out to the main steam flow side while cooling the outer surface of the rotor blade embedded part 11. When the cooling steam blows up in the space 10, it receives velocity energy from the rotor disk 6 in the rotational direction.

Conversely, this results in a loss for the steam turbine by the amount of energy given to the cooling steam.

Next, FIG. 3 shows the relationship between the blow-up flow rate of cooling steam and the energy loss of the turbine. As can be understood from FIG. 3, the upflow flow rate and energy loss are almost proportional, and when the flow rate of cooling steam is increased to enhance the cooling effect, the energy loss of the turbine due to upflow increases. Moreover, since the cooling steam has a structure in which the turbine rotor 5 is cooled, the rotor disk 6 is cooled, and the rotor blade embedded part 11 is further cooled, in this cooling structure, the rotor blade embedded part 11 is cooled. There were problems such as high steam temperature and reduced cooling effect.

[Purpose of the invention]

The present invention takes the above-mentioned points into consideration, and aims to provide a cooling structure for a steam turbine that is capable of increasing the cooling efficiency of the turbine rotor and rotor disk, and reliably reducing the energy loss of the turbine due to cooling steam. purpose.

[Summary of the invention]

In order to achieve the above-mentioned object, in the cooling structure for a steam turbine according to the present invention, the entire cooling steam is guided through the gap between the turbine rotor and the labyrinth packing installed in the inner ring of the nozzle diaphragm that supports the stationary blades, and the turbine In a cooling structure for a steam turbine configured to cool a rotor and a rotor disk, the inner ring of the nozzle diaphragm is provided with one or more piercing holes that open into a space surrounded by the inner ring and the rotor disk, and the through holes A portion of the cooling steam is guided into the space through the space.

[Embodiments of the invention]

A preferred embodiment of a steam turbine cooling structure according to the present invention will be described with reference to the accompanying drawings.

4 and 5 show a cooling structure for a steam turbine according to the present invention, and the reference numerals in the figures indicate a nozzle diaphragm that is fixed in a turbine casing (not shown) of the steam turbine and constitutes a stationary part. show. This nozzle diaphragm is formed from a nozzle diaphragm outer ring 21, a stationary blade (nozzle part) 22, and a nozzle diaphragm inner ring B,
The stator vanes n are integrally fixed to the nozzle diaphragm outer ring 21 and its inner ring. Inside the nozzle diaphragm, a sealing packing is installed in the circumferential direction, and its packing action seals out steam.

On the other hand, a rotating part faces the stationary part to form a turbine stage, and an axial flow turbine is formed by rigidly combining one or more of these turbine stages in the axial direction of the turbine rotor. The rotating part 5 is composed of a turbine rotor, a rotor disk γ which is integrally fixed to the turbine rotor by being integrated with the turbine rotor or by being fitted into the turbine rotor, and a large number of rotor blade passages installed in the rotor disk. A gap having the same structure as a conventional turbine stage is formed in the embedded part 4 of the rotor disk nail of the turbine rotor blade.

Further, a steam supply pipe 31 for supplying cooling steam is attached to the nozzle diaphragm, and a plurality of through holes 32 are formed at appropriate intervals in the circumferential direction inside the diaphragm. Each through hole 32 is connected to the nozzle diaphragm inner ring 23.
It penetrates the turbine rotor in the axial direction and opens into the space 33 at a position slightly radially inward from the rotor blade installation section.

This space is formed between the nozzle diaphragm inner ring n and the rotor disk n.

Therefore, if the total cross-sectional area of each through hole 31 is A1, then A1
= n-' ((12--(1) n: number of through holes d: diameter of the through hole, and if the cross-sectional area of the gap between the labyrinth packing 24 and the turbine rotor 26 is A2, then A2= π・
(D+(!l)・C1...(2) However, D:
Turbine rotor diameter cl: expressed by the width of the gap. The ratio of the flow rate of cooling steam passing through each through hole 32 to the flow rate of steam passing through the gap M from the labyrinth packing is approximately proportional to the area ratio A1/A2. 6th
The figure shows the relationship between % AlA2 and the temperature of the turbine rotor 26 and the temperature of the turbine rotor blade embedded portion 4.

As the area ratio AlA2 increases, the flow rate passing through each through hole 32 increases, and therefore the temperature in the rotor blade implantation area decreases. Regarding the temperature of the turbine rotor, when the area ratio AlA2 increases, the amount of cooling steam passing through the labyrinth packing 24 decreases, so the temperature rises, but this temperature rises rapidly when the area ratio AL4z exceeds 1.5. , the area ratio A 2''; -2,0 reaches the limit temperature allowed by the turbine material.

In addition, it is known that the energy loss of the turbine that occurs when cooling steam blows up in the space surrounded by the inner ring of the nozzle diaphragm and the rotor disk is proportional to the blow-up flow rate, as shown in Figure 3. , when this is replaced by the cross-sectional area ratio 4A2 and the energy loss, it is expressed as shown in FIG. From this Figure 7, the area ratio AL/A
It can be seen that when 2 becomes smaller than 0.5, the energy loss of the turbine increases rapidly. Therefore, the area ratio A
By setting the I/42 diameter to 0.5, the energy loss of the turbine caused by cooling can be reduced.

Next, the operation of the present invention will be explained.

A part of the cooling steam supplied from the steam supply pipe 31 cools the turbine rotor 26 while passing through the gap part of the labyrinth packing M, as in the conventional case, and is formed by the inner ring of the nozzle diaphragm and the rotor disk n. You will be guided to the space where you will be treated. The remaining cooling steam is guided directly into the space 33 through each through hole 32 and actively cools the rotor blade implantation section. At this time, since the steam that cools the rotor blade embedded section does not pass through the labyrinth packing, the cooling steam temperature can be kept at a sufficiently low temperature and the cooling effect of the rotor blade embedded section can be enhanced. can.

〔Effect of the invention〕

As described above, in the steam turbine cooling structure according to the present invention, the nozzle diaphragm inner ring is provided with one or more through holes that open into the space surrounded by the inner ring and the rotor disk, and the through holes Since a part of the cooling steam is guided into the space through the through hole, the rotor blade installation part of the rotating part and the rotor disk can be actively and effectively cooled by the cooling steam passing through the through hole. Since the turbine rotor can be cooled in the same way as before,
The entire turbine rotor, rotor disk, and rotor blade installation group can be effectively cooled substantially uniformly.

In addition, a part of the cooling steam is guided through the through hole into the space surrounded by the nozzle diaphragm inner ring and rotor disk without passing through the labyrinth packing, so it is possible to reduce the blowing up steam in the space through the labyrinth packing. , the energy loss of the turbine can be reliably reduced.

[Brief explanation of drawings]

Figure 1 is a sectional view showing the cooling structure of a conventional steam turbine;
Fig. 2 is a diagram taken along the line ■-■ in Fig. 1, Fig. 3 is a graph showing the relationship between the energy loss of the steam turbine and the upflow flow rate of cooling steam, and Fig. 4 is the cooling of the steam turbine according to the present invention. A diagram showing an example of the structure, FIG. 5 is a diagram taken along the line ■-■ in FIG. A temperature curve graph showing the ratio A2 of the area A2 of the part and the temperature change of the turbine rotor and the rotor blade implantation part,
FIG. 7 is a graph showing the relationship between the area ratio At/A2 and the energy loss of the steam turbine. Add: Nozzle diaphragm, 21: Nozzle diaphragm outer ring, n: Stationary blade, n: Nozzle diaphragm inner ring, debris: Labyrinth seal, 5: Rotating part, A: Turbine rotor , n... rotor disk,
Domestic: Turbine moving blade, Fourth: Moving blade installation part, Addition...
Gap, 31... Steam supply pipe, 32... Through hole, 33
···space.帛 l Figure No. 2 Honyaku Kuroki OO Shakyo Tan 5th Volume 43 2/ Condolences, 5 animals No. 6 Figure '4FA2 No. 7 A'/A2

Claims (1)

[Claims] 1. A steam turbine that cools the turbine rotor and rotor disk by guiding cooling steam through the gap between the turbine rotor and the labyrinth packing installed in the inner ring of the nozzle diaphragm that supports the stationary blades. In the cooling structure, the inner ring of the nozzle diaphragm is provided with one or more through holes that open into a space surrounded by the inner ring and the rotor disk, and a part of the cooling steam is guided into the space through the through hole. A steam turbine cooling structure characterized by: A cooling structure for a steam turbine according to item 1. 3. The ratio of the total cross-sectional area A1 of the through-hole formed in the nozzle diaphragm inner ring to the cross-sectional area A2 of the labyrinth packing and turbine rotor gap is 0.5≦AL/A2≦2.
．． The steam according to claim 1 in the range 0°
Turbine cooling structure. 4. The steam turbine cooling structure according to claim 1, wherein the through hole formed in the nozzle diaphragm inner ring is located radially from the implanted portion of the turbine rotor blade.