JP5106476B2 - Low pressure steam turbine - Google Patents

Description

  The present invention relates to a low-pressure steam turbine, and more particularly, to a low-pressure steam turbine that can suppress the influence of flashback from a feed water heater.

  In the steam turbine system of the power plant, the generated steam converts thermal energy into rotational energy while passing through the low-pressure turbine from the high-pressure turbine, and is sent to the water supply line again after being converted into water by the condenser. For example, several stages of low-pressure feed water heaters and high-pressure feed water heaters are provided in the feed water line. The feed water that passes through these low-pressure feed water heaters and high-pressure feed water heaters is heated by high-temperature steam extracted from the turbine passage portion of the steam turbine.

  Next, a configuration for extracting air in a conventional low-pressure turbine will be described. FIG. 8 is a view showing a part of a cross section of the steam passage along the axial direction of the turbine rotor 312 in the conventional low-pressure turbine 300. FIG. 9 is a view showing a cross section perpendicular to the axial direction of the turbine rotor 312 of the conventional low-pressure turbine 300. In FIG. 9, the configuration of the steam passage, that is, the configuration of the moving blade, the nozzle, the turbine rotor, and the like is omitted, and the passage through which the extracted steam in the casing 310 flows is mainly illustrated.

  As shown in FIG. 8, in the low-pressure turbine 300, a turbine rotor 312 in which a moving blade 311 is implanted in a casing 310 is penetrated. In addition, stationary blades 313 are arranged on the inner surface of the casing 310 so as to alternate with the moving blades 311 in the axial direction of the turbine rotor 312. The circumferential blade row composed of the stationary blades 313 and the circumferential blade row composed of the moving blades 311 located immediately downstream of the blade row form one paragraph. Further, the paragraph is formed in a plurality of stages in the axial direction of the turbine rotor 312 and constitutes a steam passage 314.

  Moreover, although not shown in figure, the vapor | steam which passed the last paragraph is guide | induced to the condenser with a high degree of vacuum through an exhaust passage. Therefore, the steam flowing through the steam passage 314 expands toward the exhaust passage side (exit side). Therefore, the cross-sectional area of the steam passage 314 is configured to gradually increase as it goes downstream.

  In addition, in order to extract a part of the steam flowing through the steam passage 314 between predetermined paragraphs, slit-like extraction ports 320 are provided in the circumferential side wall of the steam passage 314 in the circumferential direction. ing. Further, an extraction channel 321 is formed in the thickness of the casing 310 so as to communicate with the extraction port 320 over the circumferential direction. As shown in FIG. 9, a plurality of reinforcing ribs 322 necessary for dividing the casing 310 are provided in the circumferential direction in the extraction channel 321 to maintain the mechanical strength of the casing 310. Further, as shown in FIG. 9, an extraction pipe 323 for guiding the extracted steam to a feed water heater (not shown) is provided at the end of the extraction flow path 321.

  In the conventional low-pressure turbine 300 configured as described above, the pressure at the extraction port 320 is higher than the pressure in the feed water heater during normal operation, and therefore, the extraction port 320, the extraction channel 321, and the extraction pipe 323 are connected from the steam passage 314. Steam flows toward the feed water heater through the.

  On the other hand, when the flow rate of the steam flowing through the steam passage 314 decreases, such as when the load is cut off, the load in the paragraph is reduced, and the pressure of the extraction port 320 becomes a negative pressure close to that of the condenser. Therefore, the pressure of the extraction port 320 becomes lower than the pressure in the feed water heater, and the water in the feed water heater boils and evaporates. Then, the evaporated steam may flow backward from the extraction port 320 into the steam passage 314 through the extraction pipe 323. At that time, as described above, since the plurality of reinforcing ribs 322 are provided in the circumferential direction in the extraction flow path 321, the steam flowing back in the extraction flow path 321 has a distribution in the circumferential direction. In the state where the distribution is maintained, the gas flows back into the steam passage 314. That is, the flow rate of the steam that flows back into the steam passage 314 is nonuniform in the circumferential direction.

  The fact that the steam flowing back into the steam passage 314 has such a distribution may cause the fluid force acting on the moving blade 311 of the paragraph adjacent to the extraction port 320 to fluctuate.

  In order to respond to the steam reverse flow phenomenon at the low load of such a low-pressure steam turbine, when the load shutoff signal is input or when the pressure fluctuation of the extraction port is detected from the pressure fluctuation detector, the feed water heating A technique for rapidly reducing or emptying the drain in the vessel is disclosed (for example, see Patent Document 1). Further, a technique for reducing the temperature in the feed water heater has been disclosed in order to cope with the steam reverse flow phenomenon when the low-pressure steam turbine is under a low load (for example, see Patent Document 2). Further, a technique for adjusting the amount of steam supplied to the low-pressure steam turbine by a steam flow rate control valve so as to maintain a low rotational speed in order to cope with the steam reverse flow phenomenon at the time of low load of the low-pressure steam turbine is disclosed. (For example, refer to Patent Document 3).

JP 2008-101494 A JP 2008-75526 A JP 2008-75580 A

  In the conventional low-pressure steam turbine as described above, when the steam boiled and evaporated in the feed water heater flows back into the steam passage, the vibration stress of the moving blades arranged in the steam passage increases due to this transient back flow. There was something to do. In addition, since the reverse flow to the steam passage collides and mixes so as to be almost orthogonal to the main flow flowing in the steam passage, the main flow is greatly disturbed, a large number of vortices are generated, and the fluid force acting on the moving blade increases. There was a thing.

  Therefore, the present invention has been made to solve the above problem, and when the steam boiled and evaporated in the feed water heater flows back into the steam passage, the fluid force acting on the stationary blade and the moving blade varies. An object of the present invention is to provide a low-pressure steam turbine capable of suppressing the above.

In order to achieve the above object, according to one aspect of the present invention, there is provided a low-pressure steam turbine including a bleed pipe that guides bleed steam to a feed water heater provided outside. A turbine rotor in which a plurality of stages of moving blades are implanted, a plurality of stages of stationary blades disposed alternately with the moving blades in the axial direction of the turbine rotor, and the casing. A steam inlet pipe that introduces steam from the outside into a steam passage that has a plurality of stages composed of the stationary blade and the moving blade, and flows through the steam passage while performing expansion work, An exhaust passage that guides the steam that has passed through the rotor blade of the final stage from the inside of the casing to the outside, and is formed over the circumferential direction in the thickness of the casing that constitutes the outer peripheral wall portion of the steam passage; The steam flow path flows between predetermined paragraphs. An extraction port for extracting a part of the steam to be extracted, an extraction passage for guiding the extracted steam to the extraction pipe, and a circumferential direction within the wall thickness of the casing; And a guide member for guiding the backflowed steam from the extraction flow path to the cavity when the steam flows back from the feed water heater via the extraction pipe. A low pressure steam turbine is provided.

  According to another aspect of the present invention, there is provided a low-pressure steam turbine including an extraction pipe that guides extracted steam to a feed water heater provided outside. A turbine rotor in which stages of moving blades are implanted; a plurality of stages of stationary blades alternately disposed in the casing in the axial direction of the turbine rotor; and the stator blades passing through the casing A steam inlet pipe for introducing steam from the outside, a steam inlet pipe for introducing steam from the outside, and a flow of the steam passage while performing expansion work, An exhaust passage that guides the steam that has passed from the inside of the casing to the outside, and a wall thickness of the casing that constitutes a wall portion on the outer peripheral side of the steam passage. Extracting part of the steam flowing through the steam channel A bleed passage for guiding the evacuated steam to the bleed pipe, and a part of the bleed passage that extends circumferentially within the thickness of the casing and that is connected to the bleed port. A steam channel formed adjacently, and having a jet outlet capable of ejecting the steam that has flowed back into the steam channel in a predetermined direction when the steam flows back from the feed water heater through the extraction pipe; A low-pressure steam turbine is provided that includes a guide member for guiding the backflowed steam from the extraction flow path to the steam flow path.

  According to the low-pressure steam turbine of the present invention, fluctuations in fluid force acting on the stationary blades and the moving blades can be suppressed when the vapor that has boiled and evaporated in the feed water heater flows back into the steam passage.

It is a figure showing an example of a steam turbine system provided with a low-pressure steam turbine of a 1st embodiment. It is the figure which showed a part of cross section of the steam path in alignment with the axial direction of a turbine rotor in the low pressure steam turbine of 1st Embodiment. It is the figure which showed a part of cross section of the steam path along the axial direction of a turbine rotor in the low pressure steam turbine of 1st Embodiment provided with the cavity part of another structure. It is the figure which showed a part of cross section of the steam path along the axial direction of a turbine rotor in the low pressure steam turbine of 1st Embodiment in which the cavity part was provided over the inside of a stationary blade. It is the figure which showed a part of cross section of the steam path in alignment with the axial direction of a turbine rotor in the low pressure steam turbine of 2nd Embodiment. It is the figure which showed a part of cross section of the steam path in alignment with the axial direction of a turbine rotor in the low pressure steam turbine of 3rd Embodiment. It is the figure which showed a part of cross section of the steam path in alignment with the axial direction of a turbine rotor in the low pressure steam turbine of 3rd Embodiment. It is the figure which showed a part of cross section of the steam path along the axial direction of a turbine rotor in the conventional low pressure turbine. It is the figure which showed the cross section perpendicular | vertical to the axial direction of the turbine rotor of the conventional low pressure turbine.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a diagram illustrating an example of a steam turbine system 1 including a low-pressure steam turbine 12 according to a first embodiment. FIG. 2 is a diagram illustrating a part of a cross section of the steam passage 24 along the axial direction of the turbine rotor in the low-pressure steam turbine 12 according to the first embodiment.

  As shown in FIG. 1, the steam turbine system 1 includes a steam generator 10, a high-pressure steam turbine 11, a low-pressure steam turbine 12, a condenser 13, a condensate pump 14, a feed water heater 15, and a generator 17 as main parts. It is configured. In addition, the structure of this steam turbine system 1 is not restricted to this, For example, a steam turbine system provided with the some low pressure steam turbine 12 may be sufficient.

  Here, the steam generation unit 10 generates steam, for example, generates steam by heat generated in the core of the nuclear reactor. Specifically, the steam generator 10 means a nuclear reactor in a boiling water reactor (BWR), and a steam generator in a pressurized water reactor (PWR).

  As shown in FIG. 1, the high-temperature and high-pressure steam generated in the steam generator 10 is introduced into a high-pressure steam turbine 11, performs expansion work, passes through a moisture separator (not shown), and enters the low-pressure steam turbine 12. be introduced. Here, although not illustrated, for example, a steam flow rate adjusting valve for adjusting the steam flow rate is provided between the steam generation unit 10 and the high pressure steam turbine 11 or between the high pressure steam turbine 11 and the low pressure steam turbine 12. ing.

  In addition, although the system which introduce | transduces the steam from which the water droplet was removed through the moisture separator immediately to the low pressure steam turbine 12 is shown here, it is not restricted to this system. For example, steam that has passed through a moisture separator and from which water droplets have been removed is heated by a heater using, for example, part of the steam introduced into the high-pressure steam turbine 11 or steam extracted from the high-pressure steam turbine 11. A steam reheating method may be employed.

  The steam that has been expanded by the low-pressure steam turbine 12 is condensed by the condenser 13 to become water (feed water), and then sent to the feed water heater 15 by the condensate pump 14. Steam extracted from the low-pressure steam turbine 12 is introduced into the feed water heater 15 through the extraction pipe 16, and the feed water flowing through the feed water heater 15 is heated by the extracted steam. The feed water heated by the feed water heater 15 is guided to the steam generation unit 10, heated again to become high-temperature and high-pressure steam, and is introduced into the high-pressure steam turbine 11. Further, the generator 17 is rotated using the rotation of the turbine rotor of the low-pressure steam turbine 12 to generate electric power.

  Next, the low-pressure steam turbine 12 of the first embodiment will be described.

  As shown in FIG. 2, the low-pressure steam turbine 12 includes a casing 20, and a turbine rotor 22 in which a moving blade 21 is implanted is provided in the casing 20. In addition, stationary blades 23 are disposed on the inner surface of the casing 20 so as to alternate with the moving blades 21 in the axial direction of the turbine rotor 22. The circumferential blade row composed of the stationary blades 23 and the circumferential blade row composed of the moving blades 21 positioned immediately downstream of the blade row form one paragraph. Further, the paragraph is formed in a plurality of stages in the axial direction of the turbine rotor 22, and constitutes the steam passage 24. Further, the low-pressure steam turbine 12 includes an exhaust passage (not shown) that guides the steam that has passed through the steam passage 24 and passed through the final stage from the inside of the casing 20 to the outside.

  In the low-pressure steam turbine 12, the steam that has flowed into the steam passage 24 through a steam inlet pipe (not shown) passes between the stationary blades 23 and the moving blades 21 in each stage and rotates the turbine rotor 22. The steam that has passed through the steam passage 24 and passed through the final stage is guided to the condenser 13 having a high degree of vacuum through the exhaust passage. Therefore, the steam flowing through the steam passage 24 expands toward the exhaust passage side (exit side). Thus, the cross-sectional area of the steam passage 24 is configured to gradually increase as it goes downstream.

  In addition, in order to extract a part of the steam flowing through the steam passage 24 between the predetermined paragraphs, the inner wall of the casing 20, which is the outer peripheral side wall constituting the steam passage 24, is slit-shaped in the circumferential direction. A bleed port 30 is provided. In the wall thickness of the casing 20, an extraction flow path 31 is formed for flowing a part of the steam extracted through the extraction port 30 and flowing in the steam passage 24. Similar to the configuration shown in FIG. 9, the extraction channel 31 has a plurality of reinforcing ribs (not shown) required in the circumferential direction to maintain the mechanical strength of the casing 20 and to divide the casing 20. Is provided. In addition, the extraction pipe 16 for guiding the extracted steam to the feed water heater 15 is provided at the end of the extraction flow path 31 as in the configuration shown in FIG. 9.

  Further, a hollow portion 32 communicating with the extraction flow passage 31 is formed in the wall thickness of the casing 20 in the circumferential direction. The cavity 32 has a cavity with a predetermined volume in the circumferential direction, and is configured to be a closed space except for a portion communicating with the extraction channel 31. In FIG. 2, the cavity portion 32 is configured to be positioned on the downstream side of the extraction channel 31, but may be configured to be positioned on the upstream side of the extraction channel 31.

  For example, during normal operation of the low-pressure steam turbine 12, the pressure at the extraction port 30 is higher than the pressure in the feed water heater 15, so that the steam passage 24 goes to the feed water heater 15 through the extraction passage 31 and the extraction pipe 16. Steam flow occurs. That is, a part of the steam flowing through the steam passage 24 from the extraction port 30 is extracted and supplied to the feed water heater 15 via the extraction flow path 31 and the extraction pipe 16.

  On the other hand, in the low-pressure steam turbine 12, when the flow rate of the steam flowing through the steam passage 24 decreases, such as when the load is interrupted, the load in the paragraph is reduced, and the pressure of the extraction port 30 becomes a negative pressure close to the condenser 13. . Therefore, the pressure of the extraction port 30 becomes lower than the pressure in the feed water heater 15, and the water in the feed water heater 15 boils and evaporates. Then, the evaporated vapor flows backward through the extraction pipe 16 into the extraction flow path 31. In FIG. 2, the reverse flow of the steam is indicated by arrows.

  As described above, when the steam flows backward from the feed water heater 15 through the extraction pipe 16, the backward flow becomes a transient flow. Here, the transient flow refers to a flow in which the flow rate of the backflowing steam increases rapidly with time and reaches a peak, and then rapidly decreases. The cavity 32 has a steam which has flown back before flowing into the steam passage 24 so that this transient flow does not flow directly into the steam passage 24 from the extraction passage 31 via the extraction port 30. Is a space that once accommodates and uniformizes the flow.

  Further, in order to smoothly introduce the back-flowing steam from the extraction flow path 31 to the hollow portion 32 without directly flowing into the vapor passage 24 through the extraction port 30, the space between the extraction flow passage 31 and the hollow portion 32 is provided. It is preferable to provide the guide member 33 over the circumferential direction. The guide member 33 once squeezes a part of the extraction flow path 31 in which the backflowed steam flows so as to be substantially orthogonal to the axial direction of the turbine rotor 22, and guides the backflow steam that has passed through the throttle part 31 a to the cavity part 32. It is the member which forms the flow path for this. As shown in FIG. 2, the guide passage 34 formed by providing the guide member 33, which is a communication passage between the extraction passage 31 and the cavity 32, is connected to the casing 20 from the extraction port 30 in the extraction passage 31. It is comprised so that it may be substantially orthogonal with respect to the flow path 31b extended in the wall thickness. A part of the guide passage 34 is constituted by an extraction passage 31. Moreover, the guide member 33 is comprised by members, such as a ring shape which curves according to the curvature of the circumferential direction of the casing 20, for example. The material constituting the guide member 33 is not particularly limited, but as the material constituting the guide member 33, for example, a heat-resistant metal or ceramic having heat resistance can be used.

  Here, the flow of steam that has flowed back into the extraction channel 31 will be described.

  The flow of the steam that flows backward in the extraction flow path 31 and flows so as to be substantially orthogonal to the axial direction of the turbine rotor 22 is throttled by the throttle portion 31a. The backflowed steam that has passed through the throttle portion 31 a is bent in a direction substantially parallel to the axial direction of the turbine rotor 22 and guided to the guide passage 34. Most of the flow of the back-flowed steam guided to the guide passage 34 does not flow directly into the flow path 31b provided so as to be orthogonal to the guide passage 34, but flows along the guide passage 34 due to inertia, and the cavity 32 Flow into. The flow passage cross-sectional area of the guide passage 34 is configured to be larger than the flow passage cross-sectional area of the flow passage 31b.

  The back-flowed steam guided to the cavity 32 spreads in the cavity 32 and has a substantially uniform distribution in the circumferential direction, and the flow is time-averaged. Here, the time averaging means that the above-described transient flow, that is, a flow having a distribution in flow rate over time is changed to a flow in which the flow rate becomes substantially constant over time. Then, the steam whose flow is time-averaged flows into the steam passage 24 through the extraction port 30.

  According to the low-pressure steam turbine 12 of the first embodiment, when the steam flows backward from the feed water heater 15 via the extraction pipe 16, the flow flowing out to the steam passage 24 is time-averaged in the cavity portion 32 and maximized. The flow is greatly reduced. Therefore, the flow velocity of the back-flowing steam that collides with the stationary blade 23 or the moving blade 21 located in the vicinity of the bleed port 30 is reduced, and the fluctuation of the fluid force acting on the stationary blade 23 or the moving blade 21 can be suppressed.

  Note that the configuration of the cavity 32 is not limited to the above configuration. FIG. 3 is a view showing a part of a cross section of the steam passage 24 along the axial direction of the turbine rotor 22 in the low-pressure steam turbine 12 including the cavity 32 having another configuration. In addition, in FIG. 3, the flow of the vapor | steam which flows backward is shown by the arrow.

  As shown in FIG. 3, the guide member 33 temporarily throttles a part of the extraction flow path 31 through which the back-flowed steam flows so as to be substantially orthogonal to the axial direction of the turbine rotor 22, and introduces it into the cavity 32 described below. The reversely flowed steam is provided in the circumferential direction so as to form a flow path that leads from the extraction port 30 to a flow path 31b that extends into the thickness of the casing 20. Moreover, the cavity part 32 is provided over the circumferential direction in the direction (here, the direction substantially orthogonal to the axial direction of the turbine rotor 22) in which the backflowed steam that has passed through the throttle part 31a flows. That is, the entrance of the cavity portion 32 is opened so as to face the throttle portion 31a. Moreover, the front-end | tip part of the cavity part 32 of the direction through which the reverse flowed steam which passed the throttle part 31a flows is obstruct | occluded. The cavity 32 is formed adjacent to the flow path 31b so as to communicate with the flow path 31b.

  In the low-pressure steam turbine 12 having the cavity portion 32 with this configuration, the flow of the steam that flows backward in the extraction flow path 31 and flows so as to be substantially orthogonal to the axial direction of the turbine rotor 22 is throttled by the throttle portion 31a. The backflowed steam that has passed through the throttle portion 31 a advances straight due to inertia and flows into the cavity portion 32. The backflowed steam that has flowed into the cavity 32 spreads in the circumferential direction, and flows in a direction opposite to the direction in which it collides with the closed end of the cavity 32 and flows in as shown in FIG.

  Due to the flow flowing in the direction opposite to the flow direction, the flow rate of the backflowed steam passing through the throttle portion 31a is reduced. Accordingly, it is possible to prevent the transient flow from flowing into the flow path 31b while maintaining the change in flow rate, and flowing into the steam passage 24 from the extraction port 30. That is, the flow of the backflowed steam is time-averaged and flows into the steam passage 24 through the extraction port 30. Therefore, the flow velocity of the back-flowing steam that collides with the stationary blade 23 or the moving blade 21 located in the vicinity of the bleed port 30 is reduced, and the fluctuation of the fluid force acting on the stationary blade 23 or the moving blade 21 can be suppressed.

  The hollow portion 32 is not limited to being formed only within the thickness of the casing 20. FIG. 4 is a view showing a part of a cross section of the steam passage 24 along the axial direction of the turbine rotor 22 in the low-pressure steam turbine 12 in which the cavity portion 32 is provided over the inside of the stationary blade 23. In addition, in FIG. 4, the flow of the vapor | steam which flows backward is shown by the arrow.

  As shown in FIG. 4, the cavity 32 may be formed across the interior of the stationary blade 23 located on the downstream side where the extraction port 30 is formed. The stationary blade 23 in which the cavity portion 32 is formed is formed in at least one stationary blade 23 among the stationary blades 23 arranged in the circumferential direction, which constitutes the immediately downstream stage in which the extraction port 30 is formed. It only has to be. In order to make the backflowed steam have a substantially uniform distribution in the circumferential direction, for example, the cavity portions 32 are formed in every other or every two of the stationary blades 23 arranged in the circumferential direction of the paragraph. It is preferable to provide a stationary vane 23. Moreover, you may comprise all the stationary blades 23 arranged in the circumferential direction of the paragraph by the stationary blade 23 in which the cavity part 32 was formed.

  In the low-pressure steam turbine 12 having the cavity portion 32 with this configuration, the flow of the steam that flows backward in the extraction flow path 31 and flows so as to be substantially orthogonal to the axial direction of the turbine rotor 22 is throttled by the throttle portion 31a. The backflowed steam that has passed through the throttle portion 31 a is bent in a direction substantially parallel to the axial direction of the turbine rotor 22 and guided to the guide passage 34. Most of the flow of the back-flowed steam guided to the guide passage 34 does not flow directly into the flow path 31b provided so as to be orthogonal to the guide passage 34, but flows along the guide passage 34 due to inertia, and the cavity 32 Flow into. The flow passage cross-sectional area of the guide passage 34 is configured to be larger than the flow passage cross-sectional area of the flow passage 31b.

  The back-flowed steam guided to the cavity 32 spreads in the cavity 32 and has a substantially uniform distribution in the circumferential direction, and the flow is time-averaged. Then, the steam whose flow is time-averaged flows into the steam passage 24 through the extraction port 30.

  In this way, by forming the cavity 32 inside the stationary blade 23, when the steam flows backward from the feed water heater 15 through the extraction pipe 16, the flow flowing out to the steam passage 24 is time-averaged in the cavity 32. The maximum flow rate is greatly relaxed. Therefore, the flow velocity of the back-flowing steam that collides with the stationary blade 23 or the moving blade 21 located in the vicinity of the bleed port 30 is reduced, and the fluctuation of the fluid force acting on the stationary blade 23 or the moving blade 21 can be suppressed. Further, by forming the cavity portion 32 inside the stationary blade 23, even when there is no region for forming the cavity portion 32 having a predetermined volume within the thickness of the casing 20, the cavity portion 32 having the predetermined volume is used. Can be formed.

(Second Embodiment)
FIG. 5 is a diagram illustrating a part of a cross section of the steam passage 24 along the axial direction of the turbine rotor 22 in the low-pressure steam turbine 12 according to the second embodiment. In the following embodiments, the same parts as those in the configuration of the low-pressure steam turbine 12 of the first embodiment are denoted by the same reference numerals, and redundant description is omitted or simplified.

  The low-pressure steam turbine 12 according to the second embodiment differs from the low-pressure steam turbine 12 according to the first embodiment only in the configuration of the cavity, and therefore, the configuration of the cavity is particularly described here.

  In the low-pressure steam turbine 12 according to the second embodiment, as shown in FIG. 5, the cavity 40 extends in the downstream direction over the circumferential direction within the wall thickness of the casing 20 until reaching the exhaust passage (not shown). It is extended. Therefore, the cavity 40 is a space in which a portion communicating with the extraction channel 31 and a portion communicating with the exhaust passage are opened.

  Here, the cavity 40 has a pressure loss in the cavity 40 so that the steam extracted from the steam passage 24 does not flow to the exhaust passage through the cavity 40 during normal operation of the low-pressure steam turbine 12. It is comprised so that it may become larger than the pressure loss in the flow path from the opening | mouth 30 to the feed water heater 15. FIG. Specifically, the cavity 40 and the like are formed so that the channel cross-sectional area in the cavity 40 is smaller than the channel cross-sectional area in the channel from the extraction port 30 to the feed water heater 15.

  In the low-pressure steam turbine 12 of the second embodiment described above, for example, during normal operation of the low-pressure steam turbine 12, the pressure at the extraction port 30 is higher than the pressure in the feed water heater 15. Steam flows toward the feed water heater 15 through the passage 31 and the extraction pipe 16. That is, a part of the steam flowing through the steam passage 24 from the extraction port 30 is extracted and supplied to the feed water heater 15 via the extraction flow path 31 and the extraction pipe 16.

  On the other hand, in the low pressure steam turbine 12, when the flow rate of the steam flowing through the steam passage 24 decreases, such as when the load is interrupted, the pressure of the extraction port 30 becomes lower than the pressure in the feed water heater 15 as described above. The water in the heater 15 boils and evaporates. Then, the evaporated vapor flows backward through the extraction pipe 16 into the extraction flow path 31. In FIG. 4, the reverse flow of the steam is indicated by arrows.

  Next, the flow of steam that has flowed back into the extraction channel 31 will be described.

  The flow of the steam that flows backward in the extraction flow path 31 and flows so as to be substantially orthogonal to the axial direction of the turbine rotor 22 is throttled by the throttle portion 31a. The backflowed steam that has passed through the throttle portion 31 a is bent in a direction substantially parallel to the axial direction of the turbine rotor 22 and guided to the guide passage 34. Most of the flow of the back-flowed steam guided to the guide passage 34 does not flow directly into the flow path 31b provided so as to be orthogonal to the guide passage 34, but flows along the guide passage 34 due to inertia, and the cavity 40 Flow into. The flow passage cross-sectional area of the guide passage 34 is configured to be larger than the flow passage cross-sectional area of the flow passage 31b.

  The backflowed steam guided to the cavity 40 flows in the cavity 40 toward the exhaust passage because the pressure of the opening on the exhaust passage side of the cavity 40 is smaller than the pressure of the extraction port 30. It flows into the exhaust passage.

  According to the low pressure steam turbine 12 of the second embodiment, when the steam flows backward from the feed water heater 15 through the extraction pipe 16, most of the flow flowing out to the steam passage 24 is via the cavity 40. It flows into the exhaust passage. Therefore, it is possible to avoid the backflowed steam from colliding with the stationary blade 23 and the moving blade 21 located in the vicinity of the extraction port 30, and it is possible to prevent the fluctuation of the fluid force acting on the stationary blade 23 and the moving blade 21. .

(Third embodiment)
FIGS. 6 and 7 are views showing a part of a cross section of the steam passage along the axial direction of the turbine rotor 22 in the low pressure steam turbine 12 of the third embodiment.

  In the low pressure steam turbine 12 of the third embodiment, the low pressure steam turbine 12 of the first embodiment described above and the reverse flow steam flow path 51 through which the steam that has flowed back from the feed water heater 15 through the extraction pipe 16 passes. Since this is different, this point will be mainly described.

  As shown in FIGS. 6 and 7, in the low-pressure steam turbine 12 according to the third embodiment, a cascade composed of a stationary blade 23 and a cascade composed of a moving blade 21 located immediately downstream of the cascade. Among the paragraphs configured as above, slit-like extraction ports 30 are formed between predetermined paragraphs. The bleed port 30 is formed in the circumferential direction on the inner wall of the casing 20 serving as the outer peripheral side wall constituting the steam passage 24 in order to extract part of the steam flowing through the steam passage 24.

  Further, in the wall thickness of the casing 20, an extraction passage 31 is formed for flowing the steam extracted from the steam passage 24 through the extraction port 30. In addition, the extraction pipe 16 for guiding the extracted steam to the feed water heater 15 is provided at the end of the extraction flow path 31 as in the configuration shown in FIG. 9.

  Further, a flow extending in the wall thickness of the casing 20 from the bleed port 30 that forms a part of the bleed flow passage 31 in the circumferential direction on the inner wall of the casing 20 that forms the outer peripheral side wall constituting the steam passage 24. A reverse flow steam channel 51 having a discharge port 50 is formed adjacent to the channel 31b. The reverse flow steam channel 51 communicates with the extraction channel 31 (including the channel 31b). Further, the discharge port 50 is provided with an ejection guide 52 that can eject the backflowed steam in a predetermined direction over the circumferential direction. By providing the ejection guide 52, a slit-shaped ejection port 52 a is formed between the inner wall of the casing 20.

  Here, the ejection guide 52 shown in FIG. 6 has a configuration for ejecting the backflowed steam in the downstream direction along the outer peripheral side wall constituting the steam passage 24. Further, the ejection guide 52 shown in FIG. 7 has a configuration in which the backflowed steam is ejected in the rotational direction of the turbine rotor 22 along the outer peripheral side wall constituting the steam passage 24.

  In addition, the extraction flow path 31 temporarily throttles a part of the extraction flow path 31 in which the backflowed steam flows so as to be substantially orthogonal to the axial direction of the turbine rotor 22, and guides the backflowed steam to the backflow steam flow path 51. In addition, a guide member 33 is provided over the circumferential direction. As shown in FIGS. 6 and 7, the throttle portion 31 a is formed so that the outlet end surface of the throttle portion 31 a and the inlet end surface of the backflow steam channel 51 face each other.

  Next, the flow of steam in the extraction channel 31 and the reverse flow channel 51 will be described.

  During normal operation of the low-pressure steam turbine 12, the pressure at the extraction port 30 is higher than the pressure in the feed water heater 15, so a part of the steam flowing through the steam passage 24 is extracted through the extraction port 30, and the extraction channel 31. A steam flow toward the feed water heater 15 occurs through the extraction pipe 16 (including the flow path 31b). That is, a part of the steam flowing through the steam passage 24 from the extraction port 30 is extracted and supplied to the feed water heater 15 via the extraction flow path 31 and the extraction pipe 16.

  At this time, since the pressure at the discharge port 50 is higher than the pressure in the feed water heater 15 as in the case of the extraction port 30, a part of the steam flowing through the steam passage 24 is also extracted by the jet port 52a, and the reverse flow A steam flow toward the feed water heater 15 also occurs through the steam channel 51, the extraction channel 31, and the extraction pipe 16.

  On the other hand, in the low-pressure steam turbine 12, when the flow rate of the steam flowing through the steam passage 24 is reduced, such as when the load is interrupted, the load in the paragraph is reduced, and the pressure at the outlet 50 is a negative pressure close to the condenser 13. . Therefore, the pressure of the jet outlet 52a and the extraction port 30 becomes lower than the pressure in the feed water heater 15, and the water in the feed water heater 15 boils and evaporates. Then, the evaporated vapor flows backward through the extraction pipe 16 into the extraction flow path 31. In FIG. 6 and FIG. 7, the reverse flow of steam is indicated by arrows.

  The flow of the steam that flows backward in the extraction flow path 31 and flows so as to be substantially orthogonal to the axial direction of the turbine rotor 22 is throttled by the throttle portion 31a. Most of the backflowed steam that has passed through the throttle portion 31 a goes straight by inertia and flows into the backflow steam channel 51. At this time, as described above, the pressure of the extraction port 30 is a negative pressure close to that of the condenser 13 as in the case of the ejection port 52a. Therefore, the back-flowed steam may flow into the flow path 31b side, but most of the back-flowed steam induced by the guide member 33 flows into the back-flow steam flow path 51 due to inertia, so the flow path 31b side The flow rate flowing into the is very small.

  The backflowed steam that has flowed into the backflow steam channel 51 is jetted into the steam passage 24 in a predetermined direction by the jet outlet 52 a of the jet guide 52. In the low-pressure steam turbine 12 shown in FIG. 6, the backflowed steam is ejected in the downstream direction along the outer peripheral side wall constituting the steam passage 24 by the ejection port 52 a of the ejection guide 52. On the other hand, in the low-pressure steam turbine 12 shown in FIG. 7, the backflowed steam is ejected in the rotation direction of the turbine rotor 22 along the outer peripheral side wall constituting the steam passage 24 by the ejection port 52 a of the ejection guide 52. .

  Note that the jet outlet 52a of the jet guide 52 opens toward the downstream side or opens toward the rotation direction of the turbine rotor 22. Therefore, the main flow that flows through the steam passage 24 during extraction is performed during normal operation. However, it does not flow into the spout 52a by itself.

  As described above, according to the low-pressure steam turbine 12 of the third embodiment, when the steam flows backward from the feed water heater 15 through the extraction pipe 16, the flow flowing out to the steam passage 24 is caused to flow through the ejection guide 52. By providing, it can be ejected in the downstream direction along the outer peripheral side wall constituting the steam passage 24 or in the rotational direction of the turbine rotor 22 along the outer peripheral side wall constituting the steam passage 24. As a result, the backflowed steam can be ejected into the steam passage 24 without greatly disturbing the main flow flowing through the steam passage 24. Therefore, fluid force fluctuations acting on the stationary blade 23 and the moving blade 21 located in the vicinity of the extraction port 30 can be suppressed.

Although the present invention has been specifically described above with reference to the embodiments, the present invention is not limited to these embodiments, and various modifications can be made without departing from the scope of the invention.

  DESCRIPTION OF SYMBOLS 1 ... Steam turbine system, 10 ... Steam generation part, 11 ... High pressure steam turbine, 12 ... Low pressure steam turbine, 13 ... Condenser, 14 ... Condensate pump, 15 ... Feed water heater, 16 ... Extraction pipe, 17 ... Electric power generation 20 ... casing, 21 ... moving blade, 22 ... turbine rotor, 23 ... stationary blade, 24 ... steam passage, 30 ... extraction port, 31 ... extraction flow path, 31a ... throttle part, 31b ... flow path, 32, 40 DESCRIPTION OF SYMBOLS ... Hollow part, 33 ... Guide member, 34 ... Guide passage, 50 ... Discharge port, 51 ... Backflow steam flow path, 52 ... Jet guide, 52a ... Jet port.

Claims (5)

A low-pressure steam turbine provided with an extraction pipe for guiding extracted steam to a feed water heater provided outside;
A casing,
A turbine rotor penetrating into the casing and having a plurality of stages of blades implanted therein;
In the casing, a plurality of stages of stationary blades arranged alternately with the moving blades in the axial direction of the turbine rotor;
A steam inlet pipe that introduces steam from the outside into a steam flow path that has a plurality of paragraphs that pass through the casing and are configured of the stationary blade and the moving blade;
An exhaust passage that flows through the steam passage while performing expansion work and guides the steam that has passed through the rotor blade of the final stage from the inside of the casing;
Extraction for extracting a part of the steam that is formed in the wall thickness of the casing constituting the outer peripheral wall portion of the steam flow path and that flows through the steam flow path between predetermined paragraphs An extraction flow path having a mouth and guiding the extracted vapor to the extraction pipe;
A cavity formed in the wall thickness of the casing over the circumferential direction and communicating with the extraction flow path ;
A low pressure steam turbine, comprising: a guide member for guiding the backflowed steam from the extraction flow path to the cavity when the steam flows back from the feed water heater through the extraction pipe . The hollow portion is provided over at least one stationary blade located immediately downstream where the extraction port is formed, or is provided so as to communicate with the exhaust passage. The low-pressure steam turbine according to claim 1. The hollow portion is provided in a direction in which the backflowed steam is guided by the guide member;
The low-pressure steam turbine according to claim 1, wherein a part of the extraction flow path connected to the extraction port is formed adjacent to the cavity . A low-pressure steam turbine provided with an extraction pipe for guiding extracted steam to a feed water heater provided outside;
A casing,
A turbine rotor penetrating into the casing and having a plurality of stages of blades implanted therein;
In the casing, a plurality of stages of stationary blades arranged alternately with the moving blades in the axial direction of the turbine rotor;
A steam inlet pipe that introduces steam from the outside into a steam flow path that has a plurality of paragraphs that pass through the casing and are configured of the stationary blade and the moving blade;
An exhaust passage that flows through the steam passage while performing expansion work and guides the steam that has passed through the rotor blade of the final stage from the inside of the casing;
Extraction for extracting a part of the steam that is formed in the wall thickness of the casing constituting the outer peripheral wall portion of the steam flow path and that flows through the steam flow path between predetermined paragraphs An extraction flow path having a mouth and guiding the extracted vapor to the extraction pipe;
When the steam flows backward from the feed water heater through the bleed pipe, formed in the wall thickness of the casing in the circumferential direction and adjacent to a part of the bleed flow path connected to the bleed port, A steam channel having a spout capable of ejecting steam that has flowed back into the steam channel in a predetermined direction;
A guide member for guiding the backflowed steam from the extraction channel to the steam channel;
A low-pressure steam turbine comprising: The predetermined direction is a downstream direction along a wall portion on the outer peripheral side of the steam flow path, or a rotation direction of the turbine rotor along a wall section on the outer peripheral side of the steam flow path. The low-pressure steam turbine according to claim 4 .

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