JP2009041377A - Reheat type steam turbine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a preferable reheat type steam turbine minimizing a thermal deformation of a casing along with temperature fluctuations of reheated steam, thereby preventing a contact between a labyrinth packing and a rotor. <P>SOLUTION: In a reheat type steam turbine 1, a high pressure turbine 4 and an intermediate pressure turbine 5 are arranged on the same shaft center within a casing 3 formed in series, and reheated steam is supplied from an inflowing pipe 5A to the intermediate pressure turbine 5. The reheated steam supplied to the intermediate pressure turbine 5 was made to come into contact with an inner wall of an intermediate pressure turbine casing 5C after passing a nozzle 7a of at least one stage. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a reheat-type steam turbine in which a high-pressure turbine and an intermediate-pressure turbine are integrally provided and reheat steam is supplied to the intermediate-pressure turbine.

  5 (a) and 5 (b) show a conventional reheat steam turbine 1 'in which a high-pressure turbine and an intermediate-pressure turbine are integrally provided. The rotor 2 is disposed in the passenger compartment 3, a high-pressure turbine 4 is configured on the right side in the figure, and an intermediate-pressure turbine 5 is configured on the left side in the figure. A casing 4C of the high-pressure turbine portion and a casing 5C of the intermediate-pressure turbine portion are formed in series. The high-pressure turbine casing 4C is provided with an inflow pipe 4A and an exhaust pipe 4B for main steam. The casing 5C is provided with an inflow pipe 5A for reheated steam that is supplied after being reheated after leaving the high-pressure turbine casing 4B, and an exhaust pipe 5B. As is clear from the structure of the intermediate pressure turbine casing 5C shown in FIG. 5B, the reheat steam flows directly into the intermediate pressure turbine casing 5C from the inflow pipe 5A.

  The reheat steam turbine is generally a steam turbine, so that it can operate stably for a long period of time, has the advantages of high reliability and low operation repair costs, and is a reheat type. Therefore, it has an advantage that the thermal efficiency is high and the fuel consumption is improved.

A high-medium pressure integrated reheat steam turbine having the same structure as that shown in FIG. 5 is described in Patent Documents 1 and 2 below.
Japanese Patent Laid-Open No. 11-93607 JP 2001-82107 A

  In the reheat steam turbine, the temperature of the reheat steam supplied to the intermediate pressure turbine generally varies according to a load variation or the like. When the temperature of the reheat steam fluctuates, the temperature of the passenger compartment fluctuates in the intermediate pressure turbine, causing the passenger compartment to undergo thermal deformation. In a steam turbine, the labyrinth packing is arranged with a very small gap for each part of the rotor to prevent steam leakage. This tends to cause problems such as vibration and steam leakage.

  Therefore, even when the temperature of the reheat steam fluctuates, it is desirable that the temperature fluctuation or thermal deformation of the passenger compartment is small. However, as in the example of FIG. When flowing directly into the inside of the pressure turbine casing, the casing is likely to cause a large temperature fluctuation due to the influence of reheat steam. In addition, although the thermal deformation of a vehicle compartment is taken up also in patent document 2, the said literature 2 does not solve the problem resulting from the temperature fluctuation of reheated steam.

  The invention according to the claims is to provide a preferable reheat steam turbine capable of reducing the thermal deformation of the passenger compartment accompanying the temperature fluctuation of the reheat steam and thereby preventing the contact between the labyrinth packing and the rotor.

The invention according to the claim relates to a reheat-type steam turbine in which a high-pressure turbine and an intermediate-pressure turbine are arranged on the same axial center line in a series of vehicle interiors, and reheat steam is supplied to the intermediate-pressure turbine. The reheat steam supplied to the turbine is made to come into contact with the inner wall of the passenger compartment (the intermediate pressure turbine compartment) after passing through at least one stage nozzle (and therefore also through one stage rotary blade). It is characterized by.
Each time steam passes through the nozzles and rotary blades of each stage in the steam turbine, the temperature and pressure of the steam decrease. For this reason, if the reheated steam is brought into contact with the inner wall of the passenger compartment after passing through at least one stage nozzle as described above, even if the temperature fluctuation occurs in the reheated steam, it is in contact with the inner wall of the passenger compartment. When the steam is used, the temperature fluctuation range is small, and the temperature fluctuation of the passenger compartment, and hence the thermal deformation of the passenger compartment, can be reduced.
A long casing having a series of high-pressure turbines and medium-pressure turbines is likely to cause large thermal deformation even with relatively small temperature fluctuations. Therefore, if the thermal deformation of the casing is suppressed by the above, the effect is extremely large. . Also, if the turbine operates smoothly due to such effects, the above-described advantages of the reheat steam turbine are maximized.

It is preferable to form an independent steam chamber separated from the vehicle compartment (chamber of the intermediate pressure turbine) through the partition wall and the first stage nozzle in the inflow pipe of the reheat steam to the intermediate pressure turbine. For example, as shown in FIG. 1B, the partition wall 6a and the first stage nozzle 7a are provided to form the independent steam chamber 6.
When the independent steam chamber is provided in this way, as described above, the reheated steam supplied to the intermediate pressure turbine is brought into contact with the inner wall of the vehicle compartment through the nozzle of at least one stage. Then, as described above, even when the temperature variation occurs in the reheat steam, the temperature variation of the passenger compartment and the thermal deformation of the passenger compartment can be reduced.

A vehicle compartment holding means that restrains the displacement of the vehicle compartment in a specific direction (for example, the length of the vehicle compartment) near both ends of the vehicle compartment (near both ends along the axis of the turbine axis) and the middle part. It is further preferable to provide a holding means such as the key 8a shown in FIG. 3 that allows displacement in the direction and restrains displacement in the width direction of the passenger compartment.
When temperature fluctuations occur in the reheated steam, the passenger compartment will fluctuate even slightly, resulting in thermal deformation. It is effectively suppressed and inconveniences such as the labyrinth packing coming into contact with the rotor are avoided.
Conventionally, the vehicle compartment holding means has been provided in the vicinity of both ends of the vehicle compartment, but has not been provided in the middle portion. However, since the reheat steam is supplied to the intermediate pressure turbine at the middle part of the compartment, the deformation of the compartment due to the temperature change of the reheat steam is in the middle part. Likely to happen. Therefore, providing the vehicle compartment holding means in the middle part as well as near both ends of the vehicle compartment is extremely effective in preventing deformation of the vehicle compartment and avoiding contact between the labyrinth packing and the rotor. is there.

It is also preferable that the main steam inlet pipe supplied to the high-pressure turbine has a path symmetrical with respect to a vertical plane including the axis of the passenger compartment. An inflow pipe 4A shown in FIG. 3 is an example of such an inflow pipe.
Conventionally, the main steam inlet pipe supplies main steam to the passenger compartment from either the left or right direction of the passenger compartment, that is, from only one side that is not symmetric with respect to the vertical plane including the axial center of the passenger compartment. It was. However, since the main steam is also at a temperature higher than or equal to that of reheated steam, the temperature of the passenger compartment will be on the left and right (both sides across the plane above) if only one of them is supplied to the passenger compartment. It can be considered that the thermal deformation of the passenger compartment is increased due to the unevenness.
If the main steam inflow pipe has a symmetrical path as described above, the temperature of the passenger compartment becomes equal to the left and right, unlike the above, and therefore thermal deformation is effectively suppressed.
For the same reason, it is preferable that the reheat steam inflow pipe has a symmetrical path with respect to a vertical plane including the axis of the passenger compartment.

When the casing is configured by joining upper and lower portions using bolts, at least in a medium-pressure turbine, a heat conduction promoting material (thermal conductivity) is provided between the bolt and the bolt hole of the casing. High solids, granules or liquids (for example, copper plates or copper powders) are preferably added.
In the intermediate pressure turbine, as described above, the temperature fluctuation of the passenger compartment occurs based on the temperature fluctuation of the reheated steam. However, the temperature fluctuation is abrupt, and the temperature fluctuation of the joining bolt as described above is When the temperature is delayed by a considerable amount or more from the temperature fluctuation, the joining of the passenger compartment by the bolt may be loosened due to the difference in thermal expansion amount.
In this respect, if a heat conduction promoting material is inserted between the bolt and the bolt hole in the passenger compartment, the temperature fluctuation of the bolt is prevented from being greatly delayed from the temperature fluctuation of the passenger compartment. Is prevented from loosening.

The reheat steam turbine according to the invention is mounted on an LNG (Liquefied Natural Gas) carrier ship, and a boiler for generating reheat steam to the intermediate pressure turbine and main steam to the high pressure turbine is installed in the LNG tank of the carrier ship. If the evaporative gas is the main fuel, it is particularly advantageous in terms of fuel consumption.
The LNG tank in the LNG carrier has a heat insulating structure and keeps the LNG at a sufficiently low temperature. However, since the LNG evaporates little by little inside, it is necessary to extract the evaporated gas (boil-off gas). The extracted evaporative gas can be released into the atmosphere, but if it is used as a fuel, it is highly advantageous in terms of fuel consumption of the carrier ship. This evaporative gas is difficult to maintain stable combustion when used as a fuel for diesel engines, etc., while it is easy to use as fuel for boilers and can be co-fired with heavy oil for output adjustment etc. It is. Therefore, when the reheat steam turbine is mounted on an LNG carrier, if the main steam and reheat steam are generated by the boiler using the evaporated gas in the LNG tank as the main fuel, the combustion in the boiler is stabilized. This makes it possible to effectively improve the fuel efficiency required for navigation.

  The invention according to the claims is such that the reheat steam supplied to the intermediate pressure turbine is brought into contact with the inner wall of the passenger compartment through the nozzle of at least one stage. Even when this occurs, temperature fluctuations in the passenger compartment and thermal deformation of the passenger compartment can be reduced. For this purpose, it is preferable to form an independent steam chamber separated from the vehicle compartment via a partition wall and a first stage nozzle in the inflow pipe of the reheated steam to the intermediate pressure turbine.

If vehicle compartment holding means for restricting the displacement of the vehicle compartment in a specific direction is provided near both ends and in the middle of the vehicle compartment, thermal deformation of the vehicle compartment is further effectively suppressed.
If the main steam inflow pipe supplied to the high-pressure turbine has a symmetrical path with respect to a vertical plane including the axis of the passenger compartment, the temperature distribution of the passenger compartment becomes symmetric and the thermal deformation is reduced. Further effectively suppressed.

If a heat conduction promoting material is inserted between the bolt for joining the upper and lower parts of the passenger compartment and the bolt hole of the passenger compartment, the joint of the passenger compartment by the bolt is prevented from becoming loose.
If the reheat steam turbine of the invention is mounted on an LNG carrier and the steam for the turbine is generated in a boiler that uses the evaporated gas in the LNG tank as the main fuel, it is particularly advantageous with respect to the fuel consumption for navigation.

  One form regarding implementation of invention is shown in FIGS. FIG. 1A is an overall longitudinal sectional view showing a reheat-type steam turbine 1, and FIG. 1B is a detailed view of a portion b in FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1B, FIG. 3A is a detailed view of a portion III in FIG. 1A, and FIGS. 3B and 3C are the same as FIG. It is the front view and bottom view of the part to show. FIG. 4 is a system diagram showing the flow of fuel, steam and the like in the LNG carrier together with the steam turbine 1.

  As shown in FIG. 1A, in the reheat steam turbine 1, a high-pressure turbine 4 and an intermediate-pressure turbine 5 are arranged on the same axis line in a casing 3 in which a rotor 2 is arranged. The casing 3 is formed with a series of a high-pressure turbine casing 4C and an intermediate-pressure turbine casing 5C. The high-pressure turbine casing 4C is provided with a main steam inlet pipe 4A and an exhaust pipe 4B. In the pressure turbine casing 5C, an inflow pipe 5A for reheat steam that is supplied after being reheated after leaving the high pressure turbine casing 4B is formed at the upper part in the middle in the longitudinal direction, and the exhaust pipe 5B is It is formed below the end portion on the side away from the high-pressure turbine 4.

  The casing 3 is mounted on a base plate 8, and the rotor 2 is rotatably supported in the casing 3 via bearings 2A and 2B. That is, first, the rotor 2 is supported by a thrust bearing 2A that receives a radial load and a thrust load at the right end in the drawing at the tip of the high-pressure turbine 4, and the left end in the drawing at the tip of the intermediate pressure turbine 5. The portion is disposed in the passenger compartment 3 while being supported by a plain bearing 2B that receives only a radial load. The casing 3 restrains displacement in the axial direction and in the left and right direction (left and right direction across a vertical plane including the axis of the casing) at one location near the outside of the thrust bearing 2A. And is attached to the base plate 8 via a key and a key groove (not shown) that allow displacement in the vertical (vertical) direction, and at one location near the outside of the flat bearing 2B, It is attached to the base plate 8 via a key and a key groove (not shown) so as to constrain the displacement and allow displacement in the axial direction or the like.

  In the illustrated reheat-type steam turbine 1, the temperature of the reheat steam supplied from the inflow pipe 5A to the intermediate pressure turbine 5 is within a short time within a range of about 370 ° C. to 540 ° C. according to the fluctuation of the turbine load. fluctuate. Also in this turbine 1, since the labyrinth packing (not shown) is arranged at a position very close to each part of the rotor 2 as described above, the deformation of the passenger compartment due to the temperature variation of the reheat steam should be made as small as possible. Is desired. From such a viewpoint, in order to minimize the thermal deformation of the passenger compartment 3, the reheat steam turbine 1 newly adopts the following configuration.

First, the portion from the inflow pipe 5A to the intermediate pressure turbine casing 5C is configured as shown in FIG. 1 (b) and FIG. That is, the independent steam chamber 6 separated from the vehicle compartment 5C by the partition wall 6a and the first stage nozzle 7a is provided in the portion immediately before reaching the intermediate pressure turbine vehicle compartment 5C in the reheat steam inflow pipe 5A. However, as shown in FIG. 2, the independent compartment 3 is formed only in the upper half of the compartment 3 because the compartment 3 is integrated by joining the upper and lower portions with flanges 3Ca. In the lower half of the vehicle compartment 3, the inflow pipe 5 </ b> A and the independent steam chamber 6 are not communicated and the first stage nozzle 7 a does not exist.
With the above configuration, the reheat steam supplied from the inflow pipe 5A to the casing 5C flows into the intermediate pressure turbine casing 5C after passing through the first stage nozzle 7a and the rotary blade 7b adjacent thereto. It will come into contact with the inner wall. Since the temperature and pressure of the reheat steam are considerably reduced if the first stage nozzle 7a and the rotary blade 7b are passed through, the temperature fluctuation of the reheat steam contacting the vehicle compartment 5C is caused by the inflow pipe 5A or the like. This is considerably smaller than the temperature variation of the reheated steam inside the independent steam chamber 6. If the temperature fluctuation of the reheat steam is reduced in this way, the temperature change generated in the passenger compartment 5C is also reduced, and therefore, the thermal deformation of the passenger compartment 5C is suppressed. In addition, in FIG.1 (b), each of code | symbols 7c * 7d is the 2nd stage nozzle attached to the intermediate pressure turbine casing 5C, and the rotary blade adjacent to it.

  Between the casing 3 and the base plate 8 in the reheat-type steam turbine 1, keys and key grooves are arranged at two locations near both ends as described above. A vehicle compartment holding means including a key 8a and a key groove 5Ca is added to the middle portion in the longitudinal direction as shown in FIGS. In the illustrated example, a key groove 5Ca is provided on a part (a nozzle valve that opens and closes for long-term output adjustment) 4Aa of the casing 3 following the main steam inflow pipe 4A in the high-pressure turbine casing 4C through a bracket. On the other hand, a key 8a is provided in a part connected to the base plate 8 integrally. The key 8a and the key groove 5Ca extend in parallel with the axial center line of the casing 3 and allow the casing 3 to be displaced in the axial direction, and in the left-right direction (FIG. 3C). Displacement in the vertical direction) is not allowed. The middle part in the longitudinal direction of the vehicle compartment 3 provided with the vehicle compartment holding means is close to the place where the main steam flows in through the inflow pipe 4A and the reheated steam flows in through the inflow pipe 5A. If the displacement of the vehicle compartment 3 in the left-right direction is constrained, contact between the rotor 2 and the labyrinth packing can be effectively prevented.

  Further, in this example, as shown in FIG. 3, the main steam inflow pipe 4 </ b> A to the high-pressure turbine 4 is formed in the lower part of the passenger compartment 3 in a symmetrical shape. That is, the inflow pipe 4 </ b> A is formed as having a symmetrical path with respect to a vertical plane including the axis of the passenger compartment 3. Since the temperature of the main steam is as high as about 560 ° C., it is possible to minimize the thermal deformation of the passenger compartment 3 by making it symmetrical in this way.

  By the way, as previously described with reference to FIG. 2, the passenger compartment 3 is integrated by joining the upper half and the lower half with a flange 3Ca. That is, the flange 3Ca is joined by passing the bolt 3Cc through the insertion holes 3Cb provided at a plurality of locations and tightening with the nuts. When the temperature of the flange 3Ca is lowered together with the passenger compartment 3 along with the temperature fluctuation of the reheat steam, it is considered that the above-described joining by the bolt 3Cc or the like becomes loose if the temperature of the bolt 3Cc remains high. Therefore, in this turbine 1, a copper plate (heat conduction promoting material) is packed between the insertion hole 3Cb and the bolt 3Cc so that the heat moves quickly between the flange 3Ca and the bolt 3Cc. The bolt 3Cc and the copper plate are in contact with each other, and the copper plate and the flange 3Ca (the inner surface of the insertion hole 3Cb) are preferably in contact with each other. As a result, the temperature difference between the flange 3Ca and the bolt 3Cc is prevented from increasing, and the above-described joining is avoided.

  FIG. 4 is a system diagram illustrating the flow of fuel, steam, and the like in the LNG carrier equipped with the reheat steam turbine 1 as described above. Steam is supplied from the two boilers 12 a and 12 b to the reheat steam turbine 1, and first, main steam is sent to the high-pressure turbine 4 through the supply path 14. The main steam that has rotated the high-pressure turbine 4 is returned to the boilers 12a and 12b through the recovery path 15, reheated, and supplied as reheated steam (represented by a thick line. As described above, the reheated steam The medium pressure turbine 5 is supplied with a larger temperature fluctuation. The steam that has rotated the intermediate-pressure turbine 5 is guided by the path 17 to rotate the low-pressure turbine 20, returned to water by the condenser 21, and sent again from the path 23 to the boilers 12 a and 12 b by the pump 22. On the other hand, the outputs of the reheat steam turbine 1 including the high-pressure / medium-pressure turbines 4 and 5 described above and the low-pressure turbine 20 arranged separately are transmitted via a speed reducer 26 to a stern propeller 27 and a generator. It is set as the driving force to 28.

  As fuel for the boilers 12a and 12b, boil-off gas (natural vaporization gas) in the LNG tank 10 mounted on the carrier is mainly used. The boil-off gas is pressurized (and heated) by the low-pressure compressor 11 and then sent to the boilers 12a and 12b. A heavy oil supply path 13 is also connected to the boilers 12a and 12b. When only the boil-off gas is insufficient, heavy oil is supplied from the path 13 and mixed with the boil-off gas.

Table 1 below shows a comparison between a conventional non-reheat steam turbine (Conventional Plant) and the above-described reheat steam turbine (Kawasaki Reheat Plant). That is, in Table 1, in an LNG carrier having a tank capacity of 177,000 m ³ , the case of using a non-reheat steam turbine as the propulsion source and the case of using the reheat steam turbine 1 of the above type are shown. The specifications and fuel consumption are compared. It can be seen that the fuel consumption is reduced from 184 ton / day to 160 ton / day, resulting in a fuel efficiency improvement of 13% or more.

1 shows a reheat steam turbine 1 according to an embodiment of the invention, in which FIG. 1 (a) is an overall longitudinal sectional view of the turbine 1, and FIG. 1 (b) is a detailed view of part b in FIG. 1 (a). It is II-II sectional drawing in FIG.1 (b). FIG. 3A is a detailed view of part III in FIG. 3 (b) and 3 (c) are a front view and a bottom view of the portion shown in FIG. 3 (a). It is a systematic diagram which shows the flow of fuel, steam, etc. in an LNG carrier ship with the steam turbine 1. FIG. FIG. 5 (a) is an overall longitudinal sectional view showing a conventional reheat steam turbine 1 ′ integrally provided with a high / medium pressure turbine, and FIG. 5 (b) is a detailed view of a portion b in FIG. 5 (a). It is.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Reheat type steam turbine 2 Rotor 3 Casing 4 High pressure turbine 4A Main steam inflow pipe 4C High pressure turbine casing 5 Medium pressure turbine 5A Reheat steam inflow pipe 5C Medium pressure turbine casing 5Ca Key groove (chamber holding means )
6 Independent steam chamber 6a Partition wall 7a First stage nozzle 8 Base plate 8a Key (vehicle compartment holding means)
10 LNG tank 12a / 12b boiler

Claims (6)

A reheat-type steam turbine in which a high-pressure turbine and an intermediate-pressure turbine are arranged on the same axial center line in a series of vehicle interiors, and reheat steam is supplied to the intermediate-pressure turbine,
A reheat-type steam turbine is configured such that reheat steam supplied to an intermediate-pressure turbine is in contact with an inner wall of a passenger compartment through at least one stage of nozzles.   2. The reheat according to claim 1, wherein an independent steam chamber separated from the vehicle compartment is formed in the inflow pipe of the reheat steam to the intermediate pressure turbine through the partition wall and the first stage nozzle. Steam turbine.   The reheat according to claim 1 or 2, wherein a compartment holding means for restraining the displacement of the compartment in a specific direction is provided in the vicinity of both end portions and the middle portion of the compartment. Steam turbine.   The inflow pipe of the main steam supplied to the high-pressure turbine has a path formed symmetrically with respect to a vertical plane including the axial center of the passenger compartment. Reheat steam turbine.   The casing is configured by joining upper and lower portions using bolts, and at least in the intermediate-pressure turbine, a heat conduction promoting material is inserted between the bolt and the bolt hole of the casing. The reheat-type steam turbine according to any one of claims 1 to 4, wherein On the LNG carrier,
The boiler for generating the reheat steam to the medium pressure turbine and the main steam to the high pressure turbine is mainly composed of evaporated gas in the LNG tank in the carrier ship. The reheat steam turbine described in any one of 5 above.