JPH0932506A - Wheel chamber cooling system of steam turbine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent overheat of a steam inlet wheel chamber and reduction in turbine output by arranging cooling steam pipe lines to introduce low temperature cooling steam expanded up to prescribed pressure higher than its inlet wheel chamber internal pressure and flow control valves to adjust a flow rate of its steam pipe lines, in the steam inlet wheel chamber. SOLUTION: A part of steam in a high pressure exhaust chamber 18 whose pressure is higher than pressure in a steam inlet wheel chamber 11 of medium pressure turbine and which is expanded up to a low temperature, is extracted, and is introduced to a first cooling steam pipe 1, and is sent to the steam inlet wheel chamber 11. A part of steam of a high pressure intermediate stage whose pressure is further higher than the high pressure exhaust chamber 18 and temperature is lower than the inside of the steam inlet wheel chamber 11 of the medium pressure turbine, is introduced to a second cooling steam pipe 2, and is sent to the steam inlet wheel chamber 11. Therefore, two kinds of cooling steam having different pressure and temperature can be sent and supplied to the steam inlet wheel chamber 11, and respective openings of flow regulating valves 31 and 32 interposed between the respective cooling steam pipe lines 1 and 2 are adjusted. Therefore, the inside of the steam inlet wheel chamber 11 can be always maintained at a proper temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steam turbine, and more particularly to a cooling device for cooling a turbine casing of a reheat type steam turbine having a thermal shield for heat shielding provided at a steam inlet.

[0002]

In a reheat type steam turbine in which steam after high-pressure exhaust is recirculated to a boiler, reheated in the boiler and guided to a medium-pressure stage turbine, a steam inlet portion of a medium-pressure turbine casing is used. Because of the high temperature, a thermal shield is installed at the steam inlet to reduce the heat load on the intermediate pressure turbine blade cascade.

A conventional example of a reheat type steam turbine equipped with such a thermal shield is shown in FIG. 2, 16 is a turbine rotor, 10 is an outer casing of the turbine, 17 is an inner casing, 20 is a high-pressure stage blade row, 30 is a medium-pressure stage blade row, 8 is a main steam inlet of the high-pressure turbine, and 19 is a high pressure. A high pressure exhaust port of the turbine, 9 is a reheat steam inlet of the medium pressure turbine, and 21 is a medium pressure exhaust port.

Reference numeral 5 denotes a heat shield thermal shield provided at the reheat steam inlet of the medium-pressure turbine, which is composed of an annular heat-resistant metal plate, and the reheat steam inlet of the turbine casing is provided by the same heat shield. It is partitioned into a steam inlet casing 11 communicating with the steam inlet 9 and a turbine inlet casing 7 communicating with the inlet of the intermediate pressure stage blade row 30.

Reference numeral 12 is a cooling steam hole formed in the outer casing 10. The low-temperature steam in the high-pressure exhaust chamber 18 is caused to flow into the steam inlet casing 11 through the cooling steam hole 12, and the low-temperature steam is discharged. The same part is cooled by.

The amount of cooling steam introduced into the cooling steam hole 12 is uniquely determined by the passage area of the steam hole 12 and the pressure loss from the high-pressure exhaust chamber 18 to the medium-pressure reheat steam inlet, and the flow rate is adjusted. I can't.

Therefore, if the amount of the cooling steam becomes excessive, the steam at the inlet of the intermediate pressure turbine becomes supercooled, the heat quantity of steam at the inlet of the intermediate pressure decreases, and the required output of the intermediate pressure turbine cannot be obtained. On the other hand, during low load operation, the reheat steam inlet of the high pressure exhaust chamber 18 and the intermediate pressure turbine (steam inlet chamber 1
Since the pressure difference with 1) becomes small, a sufficient amount of cooling steam cannot be obtained, the turbine casing becomes hot, and thermal stress becomes excessive, resulting in deformation of the casing, cracking, defective sealing of the sealing part, etc. It will cause trouble.

An object of the present invention is to make it possible to automatically control the flow rate of low-temperature cooling steam for cooling the steam inlet casing of the turbine casing and obtain the cooling steam adapted to the operating condition of the steam turbine, thereby obtaining the casing. This is to prevent the occurrence of problems such as overheating of the turbine and a reduction in turbine output.

[0009]

Means for Solving the Problems The present invention is to solve the above-mentioned problems, and the gist of the invention is to connect a steam inlet of a turbine casing to a steam inlet by a thermal shield for heat insulation. In the steam turbine, which is divided into a steam inlet casing and a turbine inlet casing communicating with the blade cascade inlet, the steam inlet casing is expanded to a predetermined pressure higher than the inlet casing pressure. A cooling device for a turbine casing is provided with a cooling steam pipe for introducing low-temperature cooling steam and a flow control valve for adjusting the flow rate of the steam pipe.

Since the present invention is configured as described above, during the operation of the steam turbine, the cooling steam having a higher pressure and a lower temperature than the steam inlet passenger compartment always smoothly flows through the cooling steam pipeline. It is introduced into the room and cools the steam entrance compartment separated from the turbine entrance compartment by a thermal shield.

At this time, since the flow rate of the steam in the cooling steam pipe is adjusted by the opening degree of the flow control valve, the cooling steam amount suitable for the operating condition is introduced into the steam inlet compartment and the steam inlet compartment is closed. Maintained at a suitable temperature.

In addition to the above means, a temperature detector for detecting the metal temperature of the turbine casing and a control device for adjusting the opening of the flow control valve based on a metal temperature detection signal from the temperature detector. The provision of and is also one of the means of the present invention.

According to such means, the opening degree of the flow control valve is automatically adjusted by the control device according to the metal temperature of the turbine casing, so that the turbine casing temperature is adjusted to a proper temperature more accurately than in the above case. This is maintained, and the occurrence of problems due to overcooling or overheating of turbine inlet steam is prevented.

Further, the cooling steam pipeline is composed of a plurality of low temperature steam collecting portions and a plurality of pipelines connecting the passenger compartment to the steam inlet, and each of these pipelines is provided with the flow control valve. What is obtained is also one means of the present invention.

According to such means, it is possible to change the sampling source of the cooling steam having different steam pressures by selectively opening / closing or adjusting the opening degree of the flow control valve, thereby supplying the cooling steam into the steam inlet compartment. And the steam temperature in the steam inlet compartment can be easily controlled.

[0016]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows the height of a reheat type steam turbine equipped with a thermal shield according to an embodiment of the present invention.
A cross-sectional view of a main part along the rotor axis of the intermediate pressure stage is shown.

In FIG. 1, 16 is a turbine rotor, 2
Reference numeral 0 denotes a high-pressure turbine blade row of a high-pressure turbine, 30 denotes a medium-pressure turbine blade row of a medium-pressure turbine, 10 denotes an outer casing of the turbine, 17 denotes an inner casing, 8 denotes a main steam inlet of the high-pressure turbine, and 19 denotes a high-pressure exhaust port. , 9 is a reheat steam inlet of the medium pressure turbine, and 21 is a medium pressure exhaust port.

Reference numeral 5 is a thermal shield for heat shield provided at the reheat steam inlet of the intermediate-pressure turbine, and is composed of an annular heat-resistant metal plate. With this thermal shield 5, the reheated steam inlet portion of the turbine compartment is reheated steam inlet 9
Is divided into an annular steam inlet casing 11 on the outer peripheral side that communicates with the turbine inlet casing 7 that communicates with the inlet of the intermediate pressure stage blade row 30, and both casings 11 and 7 are located at a plurality of positions in the circumferential direction. It will be communicated only through the provided communication path (not shown).

1 is the high-pressure exhaust chamber 18 and the steam inlet compartment 1
A first cooling steam pipe connecting 1 to the first cooling steam pipe 2 is a second cooling steam pipe connecting a steam passage of the high pressure intermediate stage 6 of the high pressure stage blade row 20 to the steam inlet casing 11, and the steam inlet casing 11 Has
Cooling steam of different pressure, that is, a part of the steam in the high-pressure exhaust chamber 18 via the first cooling steam pipe 1 is higher in pressure than the high-pressure exhaust chamber 18 via the second cooling steam pipe 2 in the high-pressure intermediate stage 6 Part of the steam will be introduced respectively.

Reference numerals 31 and 32 are flow rate control valves provided in the first cooling steam pipeline 1 and the second cooling steam pipeline 2, respectively, for adjusting the passage areas of these pipelines 1 and 2.

Reference numeral 15 is a control device which is connected to the flow rate control valves 31 and 32 and outputs a valve operation signal for adjusting the opening degree of the flow rate control valves 31 and 32.
The temperature of the turbine casing detected by the casing metal temperature detector 4, that is, the temperature T _E of the wall surface of the outer casing 10 facing the steam inlet casing 11 is input to 5.

During operation of the reheat type steam turbine equipped with the cooling device for the turbine casing configured as described above,
The reheated steam that performs expansion work in the high-pressure turbine, is recirculated to the boiler via the high-pressure exhaust chamber 18 and the high-pressure exhaust port 19, and is reheated in the boiler, is reheated from the reheated steam inlet 9 of the intermediate-pressure turbine to the steam inlet compartment. Introduced in 11.

The steam in the annular steam inlet casing 11 is cooled to a predetermined temperature by injecting cooling steam introduced from first and second cooling steam pipes 1 and 2 which will be described later, and then the thermal shield 5 and After entering the turbine inlet casing 7 through a communication path (not shown) formed between the casing and the outer casing 10, the static pressure is increased there, and then flows through the intermediate pressure stage blade row 30 to perform expansion work. And is discharged from the intermediate pressure exhaust port 21 to the outside of the turbine.

In this case, the thermal shield 5
It is possible to prevent damage to the inside of the turbine inlet casing 7 and the members facing the turbine casing due to thermal shock due to the steam flowing into the steam inlet casing 11.

In the first cooling steam pipe 1, a part of the steam in the high pressure exhaust chamber 18 which has been expanded to a temperature higher than the pressure in the steam inlet casing 11 of the intermediate pressure turbine and has been extracted to a low temperature is extracted. It is introduced and sent to the steam inlet casing 11 as cooling steam.

Further, in the second cooling pipe 1, a part of high-pressure intermediate-stage steam having a pressure higher than that of the high-pressure exhaust chamber 18 and having a temperature lower than that of the steam inlet casing 11 of the intermediate-pressure turbine is provided. Introduced and used as cooling steam in the steam inlet compartment 11
Sent to.

Therefore, two kinds of cooling steams having different pressures and temperatures can be fed to the steam inlet casing 11 of the intermediate pressure turbine, and the flow rate adjustments interposed in the cooling steam pipe lines 1 and 2 can be performed. By adjusting the opening degree of each of the valves 31 and 32, the sampling destination of the cooling steam to be fed into the steam inlet casing 11 can be selected, and thereby the temperature and pressure of the cooling steam can be controlled.

On the other hand, the turbine casing facing the steam inlet casing 11 detected by the casing metal temperature detector 4 (outer casing 1
The metal temperature T _E of the inner wall surface of 0) is input to the controller 15. The control device 15 receives the detection signal of the metal temperature T _E , calculates the openings of the flow control valves 31, 32,
The metal temperature T _E is within the allowable temperature range, that is, the steam inlet compartment 1
The openings of the flow rate control valves 31 and 32 are controlled so that the inside of 1 does not become supercooled and is set to a temperature range set so as not to be overheated.

As a result, the cooling steam into the steam inlet casing 11 is supplied so that the steam temperature in the steam inlet casing 11 is adapted to the constantly operating state and the metal temperature in the casing is within the optimum range. It will be maintained within the optimum range.

[0030]

According to the present invention, during the operation of the steam turbine, the cooling steam, which has a higher pressure and a lower temperature than the steam inlet passenger compartment, is introduced into the passenger compartment at the steam inlet through the cooling steam pipeline. The cooling steam can be smoothly introduced into the steam inlet compartment, and the flow rate of the steam in the cooling steam pipeline is adjusted by the opening of the flow control valve. It is possible to maintain a proper temperature inside the steam inlet passenger compartment at all times.

As a result, it is possible to suppress an increase in the temperature difference in the axial direction of the turbine due to a locally high temperature in the turbine casing, reduce the thermal stress due to this, and prevent overcooling of the steam inlet casing. It is also possible to prevent a decrease in output due to this.

According to the invention of claim 2, in addition to the above, the controller automatically adjusts the opening degree of the flow control valve according to the metal temperature of the turbine casing, and the turbine casing temperature is as described above. More accurately and maintained at the proper temperature,
It is possible to achieve the effect of preventing the occurrence of problems due to overcooling or overheating of turbine inlet steam.

Further, according to the third aspect of the present invention, by selectively opening / closing or adjusting the opening degree of the flow rate control valve, it becomes possible to change the sampling source of the cooling steam having different steam pressures / temperatures. Cooling steam is smoothly supplied to the steam inlet, and the effect of easily controlling the steam temperature in the steam inlet compartment is also superimposed.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of essential parts along a turbine rotor axis of a vehicle interior cooling device for a reheat type steam turbine according to an embodiment of the present invention.

FIG. 2 is a drawing corresponding to FIG. 1 showing high and medium pressure portions of a conventional reheat type steam turbine.

[Explanation of symbols]

 1 1st cooling steam pipe 2 2nd cooling steam pipe 4 Vehicle interior metal temperature detector 5 Thermal shield 6 High pressure intermediate stage 7 Turbine inlet vehicle compartment 9 Reheat steam inlet 10 Outer vehicle compartment 11 Steam inlet vehicle compartment 15 Controller 18 High pressure Exhaust chamber 20 High pressure stage blade row 30 Medium pressure stage blade row 31 Flow control valve 32 Flow control valve

Claims (3)

[Claims] 1. A steam inlet section of a turbine casing is divided into a steam inlet casing communicating with the steam inlet and a turbine inlet casing communicating with the blade row inlet by a thermal shield for heat insulation. In the steam turbine to be used, a cooling steam pipeline for guiding low-temperature cooling steam expanded to a predetermined pressure higher than the inlet cabin pressure to the steam inlet cabin, and a flow rate for adjusting the flow rate of the steam pipeline. A vehicle interior cooling device for a steam turbine, comprising: a control valve. 2. A temperature detector for detecting the metal temperature of the turbine casing, and a control device for adjusting the opening of the flow control valve based on a metal temperature detection signal from the temperature detector. A steam turbine casing cooling device according to claim 1. 3. The cooling steam pipeline is composed of a plurality of pipelines connecting a plurality of low-temperature steam collecting sections and the steam inlet compartment, and each of these pipelines is provided with the flow control valve. A vehicle interior cooling device for a steam turbine according to claim 1 or 2.