JP2012255345A - Two-shaft steam turbine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a two-shaft steam turbine that can suppress a temperature rise of a high pressure turbine due to windage loss.SOLUTION: The two-shaft steam turbine is composed of a high pressure turbine 1, an intermediate pressure turbine 2, a low pressure turbine 3, and adopts an intermediate pressure starting method. A clutch 11 fastens and releases a shaft of the high pressure turbine 1 with/from a shaft of the intermediate turbine 2. The shaft of the intermediate pressure turbine 2 and a shaft of the low pressure turbine 3 are coupled by a coupling 4. In load-up during starting by the intermediate pressure, the clutch 11 is released, steam is supplied to the intermediate pressure turbine 2 and the intermediate turbine is started. After a rotation speed of the intermediate turbine 2 reaches a rated one, the clutch 11 is engaged.

Description

  The present invention relates to a steam turbine, and more particularly to a two-shaft steam turbine suitable for measures against windage loss in a two-shaft steam turbine.

  In the single-shaft combined cycle, in order to reduce the steam turbine windage loss at start-up, the number of revolutions that the low-pressure turbine is heated by the windage loss is predicted in advance, and the low-pressure steam having a low temperature flows into the low-pressure turbine at that revolution number to cool There is a known method (see, for example, Patent Document 1).

  Also, in fields other than steam turbines, a method of cooling by increasing heat transfer efficiency by providing irregularities in a generator and its containment vessel is known (see, for example, Patent Document 2).

  The ones described in Patent Documents 1 and 2 do not reduce heat due to windage loss, but have a structure in which heat is reduced by cooling.

JP-A-61-94846 JP 2004-357498 A

  In a thermal power plant, an intermediate pressure startup plant is employed in order to shorten the plant startup time or to employ an inexpensive material for boiler piping.

  In an intermediate pressure startup plant, at the time of startup, the steam that has passed through the superheated steam system passes through the high pressure turbine bypass valve, then passes through the reheat steam system of the boiler, and flows to the intermediate pressure turbine and the low pressure turbine. At this time, the low-pressure turbine bypass valve is also open, and the steam flows to the condenser bypassing the low-pressure turbine. The steam condenses and returns to the boiler again via the heater. This steam flow allows both the overheating and reheating system of the boiler to warm up, so that the boiler can be prevented from being blown and the startup time can be shortened.

  However, in the intermediate pressure starting method, the high-pressure turbine bypass valve and the low-pressure turbine bypass valve are closed and the main steam stop valve and the regulator valve are opened during the load increase transfer region. Further, since the check valve and the ventilation valve are closed in order to increase the internal pressure in the high pressure turbine, the high temperature and high pressure steam temporarily stagnate inside the high pressure turbine. At this time, due to the steam stagnating inside the high-pressure turbine, the inside of the turbine becomes high temperature and windage damage occurs. Special design and control methods must be taken into account because wind damage can heat up the high pressure turbine and cause the turbine components to become hot.

  An object of the present invention is to provide a two-shaft steam turbine that can suppress an increase in temperature of a high-pressure turbine due to windage.

  In order to achieve the above object, according to the present invention, the windage loss is proportional to the cube of the rotational speed. To do. Therefore, specifically, the following configuration is adopted.

(1) In order to achieve the above object, the present invention is an intermediate pressure start-up steam turbine having a high pressure turbine, an intermediate pressure turbine, and a low pressure turbine, the shaft of the high pressure turbine and the intermediate pressure turbine A clutch that can be engaged and disengaged with the other shaft, and a coupling that connects the shaft of the intermediate-pressure turbine and the shaft of the low-pressure turbine.
With this configuration, the temperature increase of the high-pressure turbine due to windage can be suppressed.

  (2) In the above (1), preferably, when the load increases during the start of the intermediate pressure, the clutch is released, steam is supplied to the intermediate pressure turbine to start the intermediate pressure turbine, and the intermediate pressure turbine The clutch is engaged after the rotational speed reaches the rated rotational speed.

  (3) In the above (1), preferably, when the load increases during the start of intermediate pressure, the clutch is released, steam is supplied to the intermediate pressure turbine to start the intermediate pressure turbine, When the transfer region is in a state of taking the state, the clutch is engaged after the rotational speeds of the intermediate-pressure turbine and the low-pressure turbine shaft coincide with the rotational speed of the high-pressure turbine.

  (4) In the above (3), preferably, at the time of the transfer region, from the state where the intermediate pressure turbine and the low pressure turbine have reached the rated rotational speed, the intermediate pressure and the low pressure turbine take a load below the rating. It is a thing.

  (5) In the above (3), preferably, the high-pressure turbine in the transfer region is rotated at a lower rotational speed than the intermediate-pressure turbine and the low-pressure turbine.

  (6) In the above (3), preferably, at the end of the transfer region, the rotational speed of the high-pressure turbine is increased to a rated rotational speed, and the high-pressure turbine and the intermediate-pressure and low-pressure turbines are connected by a clutch. Is.

According to the present invention, an increase in the temperature of the high-pressure turbine due to windage can be suppressed.

It is the schematic which shows the structure of the two-shaft steam turbine by one Embodiment of this invention. It is the schematic of the steam system of the plant using the twin-shaft steam turbine by one Embodiment of this invention.

Initially, the structure of the two-shaft steam turbine by one Embodiment of this invention is demonstrated using FIG.
FIG. 1 is a schematic diagram showing the configuration of a two-shaft steam turbine according to an embodiment of the present invention.

  The high-pressure turbine 1 has a configuration different from that of the intermediate-pressure turbine 2 and the low-pressure turbine 3. The high-pressure turbine 1 and the intermediate-pressure turbine 2 are fastened and released by the clutch 11. The intermediate pressure turbine 2 and the low pressure turbine 3 are connected by a coupling 4.

  The shaft of the high-pressure turbine 1 is rotatably supported by bearings 5 and 6. The shaft of the intermediate pressure turbine 2 is rotatably supported by bearings 7 and 8. The shaft of the low-pressure turbine 3 is rotatably supported by bearings 9 and 10.

  By engaging the clutch 11, the shafts of the high-pressure turbine 1, the intermediate-pressure turbine 2, and the low-pressure turbine 3 can be finally set as one shaft. The shaft of the low-pressure turbine 3 is connected to a generator.

Next, a steam system of a plant using a two-shaft steam turbine according to an embodiment of the present invention will be described with reference to FIG.
FIG. 2 is a schematic diagram of a steam system of a plant using a two-shaft steam turbine according to an embodiment of the present invention.

  The flow of steam in the plant adopting the intermediate pressure starting method will be described. At start-up, the steam flows to the intermediate pressure turbine 2 via the reheat steam control valve 22, and the steam emitted from the exhaust of the intermediate pressure turbine 2 flows to the low pressure turbine 3. The steam also passes through the low-pressure bypass valve 23 and flows to the condenser 15, returns to the water via the condenser 15 and the heater system 16, and is supplied again to the boiler 12. The steam that has passed through the boiler superheat system 18 passes through the high-pressure turbine bypass valve 19, passes through the boiler reheat steam system 17, and flows again into the intermediate pressure turbine 2 via the reheat steam control valve 22.

  Since the boiler is warmed by passing through both steam systems 17 and 18 of the boiler 12 by the intermediate pressure starting method, the starting time is shortened.

  Further, in the transfer region when the load increases, the high pressure turbine bypass valve 19 and the low pressure turbine bypass valve 23 are closed, and the main steam stop valve 20 and the main steam control valve 21 are opened. At this time, the ventilation valve 24 and the check valve 25 are temporarily closed to increase the internal pressure of the high-pressure turbine 1. As a result, the steam is stagnated inside the high-pressure turbine 1 and a windage loss occurs.

  In order to suppress the windage loss, as shown in FIG. 1, the high-pressure turbine 1, the intermediate-pressure turbine 2, and the low-pressure turbine 3 are configured on different axes. The low-pressure turbine 3 can be rotated at a different rotational speed. Steam necessary only for warm air flows to the high-pressure turbine 1 and can be warmed at a low rotational speed. When the shaft rotation speeds of the intermediate pressure turbine 2 and the low pressure turbine 3 reach the rated 3000 RPM or 3600 RPM, the load is started. After starting to take the load, the rotational speed of the high-pressure turbine 1 is increased, and when the rated rotational speed is reached, the clutch 11 connects the shafts of the high-pressure turbine 1, the intermediate-pressure turbine 2, and the low-pressure turbine 3. . A structure that connects shafts and finally raises to the rated load.

  Based on the rotational speed information Rm of the intermediate pressure turbine 2 and the rotational speed information Rh of the high-pressure turbine 1, the control device 100 controls the high-pressure turbine bypass valve 19, the main steam stop valve 20, the main steam control valve 21, and the reheat steam control. Control of opening / closing of the valve 22, the low pressure bypass valve 23, the ventilation valve 24, and the check valve 25 is controlled. Further, the control device 100 controls the engagement / release of the clutch 11.

  The clutch 11 employs a clutch structure that is generally used in a single-shaft combined cycle of a gas turbine or a steam turbine. An example of such a clutch is disclosed in, for example, Japanese Patent Application Laid-Open No. 2005-54583.

As described above, in the present embodiment, the intermediate pressure and low pressure turbines and the high pressure turbine are separated from each other, so that the high pressure turbine and the intermediate pressure and low pressure turbine shafts have different rotational speeds when the load increases during startup. By rotating, an increase in the temperature of the high-pressure turbine due to windage can be suppressed.

DESCRIPTION OF SYMBOLS 1 ... High pressure turbine 2 ... Medium pressure turbine 3 ... Low pressure turbine 4 ... Coupling 5, 6, 7, 8, 9, 10 ... Bearing 11 ... Clutch 12 ... Boiler 15 ... Condenser 16 ... Heater system 17 ... Boiler reheat Steam system 18 ... Boiler superheat system 19 ... High pressure turbine bypass valve 20 ... Main steam stop valve 21 ... Main steam control valve 22 ... Reheat steam control valve 23 ... Low pressure bypass valve 24 ... Ventilation valve 25 ... Check valve 100 ... Control apparatus

Claims (6)

An intermediate-pressure startup steam turbine having a high-pressure turbine, an intermediate-pressure turbine, and a low-pressure turbine,
A clutch capable of fastening and releasing the shaft of the high-pressure turbine and the shaft of the intermediate-pressure turbine;
A two-shaft steam turbine comprising: a coupling that connects a shaft of the intermediate pressure turbine and a shaft of the low pressure turbine. The two-shaft steam turbine according to claim 1, wherein
When the load rises during the start of intermediate pressure, release the clutch, supply steam to the intermediate pressure turbine to start the intermediate pressure turbine,
The two-shaft steam turbine characterized in that the clutch is engaged after the rotational speed of the intermediate pressure turbine reaches a rated rotational speed. The two-shaft steam turbine according to claim 1, wherein
When the load rises during the start of intermediate pressure, release the clutch, supply steam to the intermediate pressure turbine to start the intermediate pressure turbine,
The two-shaft characterized in that the clutch is engaged after the rotational speed of the intermediate-pressure turbine and the low-pressure turbine shaft coincides with the rotational speed of the high-pressure turbine at the time of the transfer region in which a load is taken after startup. Type steam turbine. The two-shaft steam turbine according to claim 3,
At the time of the transfer region, the intermediate pressure turbine and the low pressure turbine take a load less than a rating from the state in which the intermediate pressure turbine and the low pressure turbine have reached a rated rotational speed. The two-shaft steam turbine according to claim 3,
The two-shaft steam turbine, wherein the high-pressure turbine in the transfer region rotates at a lower rotational speed than the intermediate-pressure turbine and the low-pressure turbine. The two-shaft steam turbine according to claim 3,
At the end of the transfer region, the rotational speed of the high-pressure turbine is increased to a rated rotational speed, and the high-pressure turbine and the intermediate-pressure and low-pressure turbines are connected by a clutch.

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