JPH07145707A - Steam turbine - Google Patents

Abstract

PURPOSE:To decrease a metal cemperature or a rotor or tne like so as to introduce main steam of higher temperature by providing a guide means for introducing the main steam from a speed regulating stage nozzle toward a first nozzle without its leakage toward a steam chamber, and a cooling steam introducing means for introducing cooling steam into a steam chamber. CONSTITUTION:Main steam of high temperature and high pressure introduced from a main steam inlet pipe into a nozzle chamber 5 flows from a steam blow-out port 6 into a speed regulating stage nozzle 8 for the purpose of work, and then, passes through a guide passage 22, to be thus accelerated in a first stage nozzle 11a. Thereafter, the main steam is expanded in a first stage moving blade 9a, a second stage nozzle 11b and a second moving blade 9b in order for the purpose of work. The main steam is guided without any leakage by means of an expanding portion 20 and a flow guide 21 of a blade ring 10 while cooling steam to be introduced from a cooling steam inlet pipe 24 into a steam chamber 3 flows toward a clearance 23 through a pumping hole 28, thereby cooling a rotor 4, the moving blades 9a, 9b and the like. Consequently, it is possible to introduce the main steam of higher temperature so as to enhance heat efficiency of a steam turbine.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steam turbine,
In particular, the present invention relates to a steam turbine in which super high temperature and high pressure steam can be introduced by effectively cooling a rotor and a nozzle chamber in the vicinity of a main steam inlet portion, thereby improving thermal efficiency.

[0002]

2. Description of the Related Art First, a structure near a main steam inlet of a conventional steam turbine will be described with reference to FIG. In FIG. 5, the rotor 4 is located at the center of the steam chamber 3 surrounded by the outer casing 1 and the inner casing 2 of the steam turbine.
Through the main steam inlet pipe, not shown,
A nozzle chamber 5 into which high temperature, high pressure main steam from the boiler is introduced is provided. Steam outlet 6 of this nozzle chamber 5
Faces the speed control nozzle 8 provided on the speed control disk 7 of the rotor 4.

Further, the rotor 4 is provided with a plurality of stages of moving blades 9a, 9b, 9c ... Implanted in each disk portion, and is provided in the blade ring 10 for each moving blade 9a, 9b, 9c. The nozzles 11a, 11b, 11c ... Which are arranged face each other. The blade ring 10 is connected to the inner casing 2. A speed-control stage outlet chamber 12 is formed between the speed-control stage nozzle 8 and the first-stage nozzle 11a. A plurality of pumping holes 13 are circumferentially formed at the base of the speed disc 7. The pumping hole 13 is bored from the speed control stage outlet chamber 12 side toward the steam chamber 3 so as to face from the inner diameter side of the rotor 4 to the outer diameter side.

In the conventional steam turbine configured as described above, the nozzle chamber 5 is removed from a boiler (not shown) or the like.
The high-temperature, high-pressure main steam introduced into the first stage flows into the speed control stage nozzle 8 from the steam outlet 6 to perform work, and then is accelerated by the first stage nozzle 11a to work in the first stage rotor blade 9a. . The steam whose temperature and pressure have dropped due to work is further diverted to the second
The stage nozzle 11b and the second stage rotor blade 9b successively expand to perform work, and then fall to the pressure and temperature at which high-pressure exhaust is performed.

[0005]

By the way, in the conventional steam turbine described above, the speed-control stage outlet is formed between the speed-control stage nozzle 8 and the first-stage nozzle 11a so as to surround the rotor 4. Main steam collects in the chamber 12, and the steam fills the steam chamber 3 behind the speed control stage through the pumping hole 13. Therefore, the steam filling the steam chamber 3 is kept stagnate without flowing, and the inner casing 2, the nozzle chamber 5, the speed control disk 7 surrounding the steam chamber 3 and the rotor 4 near them are provided. Is exposed to high-temperature steam, and the heat thereof heats the rotor 4 to deteriorate the material. Therefore, the conditions of the main steam to be introduced are limited by the high temperature strength of materials such as the rotor of the turbine.

That is, in a conventional subcritical pressure turbine having an inlet temperature of main steam of 566 ° C. and an inlet pressure of 170 kg / cm ² , a rotor made of low alloy steel has been used for a long time, and , 12C for recent supercritical pressure turbine with inlet temperature of 600 ℃ and inlet pressure of 250kg / cm ^2.
R-type high-strength materials have been developed, and rotors using these materials can be manufactured to realize high-efficiency turbines. However, with the aim of further improving thermal efficiency,
Although the development of an ultra-supercritical turbine with an inlet temperature of 650 ° C and an inlet pressure of 350 kg / cm ² is planned, the prospect of developing a new material is not clear.

The present invention has been made in order to solve the problems of the prior art, and an object thereof is to realize the ultra-supercritical turbine by using existing materials.

[0008]

In order to solve the above problems, the steam turbine according to the present invention prevents main steam introduced into the nozzle chamber through the main steam inlet pipe from flowing to the steam chamber side. Guide means for guiding the speed control stage nozzle to the first stage nozzle side, cooling steam introduction means for introducing cooling steam from the outside into the steam chamber, and speed control stage of the rotor for the cooling steam introduced into the steam chamber. A speed control disc part and at least a cooling steam passage formed in the blade root part of the first stage moving blade so as to join the main steam after passing through the disk part and at least the blade root part of the first stage moving blade. To do.

[0009]

[Operation] According to the above means, the high-temperature main steam is separated from the steam chamber and the speed-control stage disk portion of the rotor, and cooling steam is introduced into these parts to cool it. Since the metal temperature is lowered to increase the creep strength and the thermal fatigue strength to allow the introduction of higher temperature main steam, the thermal efficiency and reliability of the steam turbine can be further improved.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the steam turbine according to the present invention will be described in detail below with reference to FIGS. 1 and 2, the same parts as those of FIG. 5 are designated by the same reference numerals, and the description thereof will be omitted.

FIG. 1 is a horizontal sectional view showing a partial structure near a main steam inlet of an embodiment of a steam turbine according to the present invention, and FIG. 2 is a partial vertical sectional view thereof. Figure 2
And a main steam inlet pipe 15 that introduces high-temperature, high-pressure steam from the boiler to the nozzle chamber 5 through the outer casing 1 and the inner casing 2.
However, this is the same as the conventional one, that is, the main steam inlet pipe 15 is integrally formed with the outer casing 1, and the inner casing 2 and the nozzle chamber 5 are provided with seal members 16 and 17, respectively. Are combined.

In the present invention, first, the high-temperature main steam introduced from the main steam inlet pipe 15 is guided to the section where the original work is performed, and is prevented from leaking to other sections as much as possible. That is, as shown in FIG. 1, the tip of the overhanging portion 20 of the blade ring 10 is extended to a position so as to cover the upper portion of the speed control stage nozzle 8, and further the first stage nozzle 11a is provided with the same. A flow guide 21 is provided at the end on the rotor 4 side, and the flow guide 21 is extended along the axial direction of the rotor 4 to a position where it reaches the speed control stage disk 7. Therefore, the speed control stage outlet chamber 12 is partitioned by the flow guide 21, and the overhanging portion 20 of the blade ring 10 and the flow guide 21 are separated.
A guide passage 22 that is surrounded by and that guides the main steam from the first-stage nozzle 11a toward the moving blade 9a and a space 23 that is surrounded by the flow guide 21 and the rotor 4 are formed.
The void 23 serves as a cooling steam chamber.

Next, in the present invention, a cooling steam inlet pipe 24 that penetrates the outer casing 1 and the inner casing 2 and reaches the steam chamber 3 is provided. The cooling steam inlet pipe 24 has a flange 25 fixed to the outer casing 1 with bolts 26, and is attached to the inner casing 2 so as to maintain airtightness with a seal member 27 interposed. A plurality of pumping holes 28, which replace the conventional pumping holes 13, are formed in the root of the speed control disk 7 in a circumferential shape. The pumping holes 28 are a plurality of through holes communicating from the steam chamber 3 side to the gap 23 side formed between the rotor 4 and the flow guide 21, and from the steam chamber 3 side to the gap 23 side,
The rotor 4 is formed to face from the inner diameter side to the outer diameter side to form a cooling steam passage. Further, the first stage rotor blade 9a and the second stage rotor blade 9a
A plurality of through holes 29a and 29b are also formed circumferentially in the disk portion of the stage moving blade 9b, and these through holes also form a cooling steam passage.

The steam turbine of the present invention is constructed as described above, and its operation will be described below.

The high-temperature, high-pressure main steam introduced into the nozzle chamber 5 through the main steam inlet pipe 15 flows from the steam outlet 6 into the speed control stage nozzle 8 to perform work, and then the overhanging portion 20 of the blade ring 10. And is guided to the first stage nozzle 11 a through a guide passage 22 surrounded by the flow guide 21. And
This steam flow is accelerated by the first stage nozzle 11a and works in the first stage moving blade 9a. The steam whose temperature and pressure have decreased due to work is further expanded in order by the second-stage nozzle 11b and the second-stage rotor blade 9b in the downstream to perform work, and then falls to the pressure and temperature for high-pressure exhaust. . In this case, the flow of the main steam is guided by the overhanging portion 20 of the blade ring 10 and the flow guide 21 toward the first stage nozzle 11a side, and the steam chamber 3
It is prevented from leaking to the side.

On the other hand, the cooling steam introduced into the steam chamber 3 through the cooling steam inlet pipe 24 has a pressure slightly higher than the pressure of the main steam flowing into the speed control nozzle 8, and the temperature is set to be significantly low. ing. Therefore, the cooling steam flows from the steam chamber 3 through the pumping hole 28 to the gap 23 side, and further from the gap 23 to the first-stage moving blade 9a and the second-stage moving blade 9.
through holes 29a, 29b formed in the disk portion of FIG.
Through the third stage moving blade 9c and the nozzle 11c, the main steam is joined and discharged.

That is, due to the flow of the cooling steam, the rotor surface of the rotor 4 and the nozzle chamber 5 located in the steam chamber 3 portion, the rotor surface in the gap 23, the speed control disk 7 and the first stage moving blade 9a are included. , 9b, etc. are cooled. These parts are the parts that are exposed to the highest temperature and pose a problem in terms of material strength. Effective cooling of this part means that in steam turbines made using the same materials as conventional materials, higher temperature steam is used. It enables operation under the conditions.

Now, FIG. 3 is an expansion diagram showing the state of steam in the vicinity of the main steam inlet of the steam turbine.
Conventionally used subcritical pressure turbine (inlet temperature =
At 566 ° C., inlet pressure = 170 kg / cm ² ), the steam temperature after the speed control stage is about 520 ° C., and rotors made of low alloy steel have been used for a long time. In addition, recent supercritical pressure turbines (inlet temperature = 600 ° C, inlet pressure = 2
At 50 kg / cm ² ), the steam temperature after the speed control stage is about 550 ° C, but a 12Cr high-strength material was developed, and it became possible to manufacture a rotor using this, so steam conditions were improved and The thermal efficiency has been improved by about 2% compared to the critical pressure turbine.

An ultra-supercritical pressure turbine (inlet temperature = 650 ° C., inlet pressure =) for further improving thermal efficiency
At 350 kg / cm ² ), the steam temperature after the speed control stage is 605 ° C.
It is expected that the temperature of the steam turbine in the conventional structure shown in FIG. 5 will be as shown in FIG. 6, and the temperature distribution near the steam inlet will be as shown in FIG. Since it is not possible to manufacture a rotor or the like that withstands the above, it is not possible to realize an ultra-supercritical turbine as it is.

Therefore, in the present invention, the cooling steam is introduced into the inner casing 2 through the cooling steam inlet pipe 24 separately from the main steam, and the cooling steam is exposed to a high temperature to cause a problem in material strength. For example, the temperature distribution near the main steam inlet can be reduced by cooling the parts to around 550 ° C, which is the steam temperature after the speed-control stage of the supercritical pressure turbine, and separating the part to be cooled from the main steam. As shown in Fig. 4, an ultra-supercritical pressure turbine can be realized.

[0021]

As described in detail above, according to the present invention,
Even if rotors made of existing materials are used, by effectively cooling them, the inlet temperature of the main steam is 650
It is possible to realize an ultra-supercritical turbine with the inlet pressure of 350 kg / cm ² at ℃. Therefore, conventional supercritical pressure turbine (inlet temperature = 600 ℃, inlet pressure = 250kg
/ Cm ² ), a further improvement in thermal efficiency of about 2% is achieved,
As a result, for example, in the case of a power plant of 1 million KW, the fuel cost is expected to be reduced by about 5 to 1 billion yen per year, which is an extremely large effect.

Even if the present invention is applied not only to the super-supercritical pressure turbine but also to the above-described subcritical pressure turbine and supercritical pressure turbine, the metal temperature of the rotor near the main steam inlet is lowered to increase the creep strength and the creep strength. It goes without saying that the thermal fatigue strength can be increased to further improve the reliability.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view showing the vicinity of a main steam inlet of an embodiment of a steam turbine according to the present invention.

FIG. 2 is a partial vertical cross-sectional view of the steam turbine shown in FIG. 1 near a steam inlet portion.

FIG. 3 is an expansion diagram showing the state of steam near the main steam inlet of the steam turbine.

FIG. 4 is a temperature distribution diagram showing a temperature distribution in the vicinity of a main steam inlet of the steam turbine of the present invention.

FIG. 5 is a transverse cross-sectional view partially showing the structure of a conventional steam turbine near the main steam inlet.

FIG. 6 is a temperature distribution diagram showing a temperature distribution in the vicinity of a main steam inlet of a conventional steam turbine.

[Explanation of symbols]

 1 Outer Cabin 2 Inner Cabin 3 Steam Chamber 4 Rotor 5 Nozzle Chamber 7 Speed Control Stage Disk 8 Speed Control Stage Nozzle 9a, 9b, 9c Moving Blade 10 Blade Ring 11a, 11b Nozzle 15 Main Steam Inlet Pipe 20 Blade Blade Overhang 21 Flow guide 22 Guide passage 23 Gap 24 Cooling steam inlet pipe 28 Pumping hole (cooling steam passage) 29a, 29b Through hole (cooling steam passage)

Claims (2)

[Claims] 1. A guide means for guiding the main steam introduced into the nozzle chamber through the main steam inlet pipe from the speed control stage nozzle to the first stage nozzle side so as not to flow to the steam chamber side, and to the steam chamber from the outside. Cooling steam introducing means for introducing the cooling steam, and the cooling steam introduced into the steam chamber are merged with the main steam after passing through the speed control disc portion of the rotor and at least the blade root portion of the first stage moving blade. As described above, the steam turbine is provided with the speed-control stage disk portion and the cooling steam passage formed in at least the blade root portion of the first-stage rotor blade. 2. The steam turbine according to claim 1, wherein the guide means is provided on a blade ring overhanging portion in which an end portion of the blade ring is extended to a speed control stage nozzle side and an inner peripheral side of the first stage nozzle. A steam turbine comprising a flow guide extending toward the stepped disc portion, wherein the cooling steam passage is a plurality of through holes leading to a gap formed between the rotor and the flow guide.