JP2009221972A - Steam turbine and air extraction operating method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve turbine performance and thermal efficiency by improving air extracting structure. <P>SOLUTION: This steam turbine includes a casing 12, a turbine nozzle 1 provided inside the casing 12, and a turbine blade 5 arranged on a downstream side of the turbine nozzle, and the turbine nozzle 1 and the turbine blade 5 form multi-stage type turbine stages 11. An air extraction mechanism 25 for extracting air from working fluid is provided in each outlet of each turbine stage 11. The air extraction mechanism 25 has an extraction hole 22a opened in the inner peripheral surface 12b of the casing 12 and an extraction tube 22 communicated with the extraction hole 22a. The quantity of extraction air from the air extraction mechanism 25 is reduced in order from an upstream side turbine stage 11 to its downstream side. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a steam turbine and a bleed operation method thereof, and more particularly to a steam turbine and a bleed operation method thereof that can appropriately bleed air from each turbine stage outlet to improve thermal efficiency.

  In recent years, suppression of global warming has been strongly desired, and even in a power plant equipped with a steam turbine, it is necessary to reduce fuel consumption for power generation by suppressing power generation efficiency and to suppress carbon dioxide emission. Therefore, power generation efficiency by improving the performance of the turbine cascade of the steam turbine and improving the heat balance of the power plant is an important issue.

  Although the steam turbine has a plurality of turbine stages including a turbine nozzle and a turbine rotor blade stage, it is necessary to improve the loss of the turbine stage in order to improve the turbine performance. There are various turbine stage losses, including profile loss due to the blade shape of the nozzle blades and turbine blades, secondary flow loss due to fluid force flowing between the blade rows, and working fluid. It can be divided into external leakage loss caused by passing through the outside of the blade row without passing between the blade rows, that is, leaking.

  In particular, in the external leakage loss, in addition to the decrease in turbine output due to leakage of working fluid from between the blade rows to the outside, the leaked working fluid merges with the working fluid that has passed between the blade rows in the downstream stage. The resulting loss increases. Each of the main flow and the leakage flow rate of the working fluid is greatly different in the flow vector direction, and when combined, the flow becomes a complicated flow, causing cascade loss in the downstream paragraph and reducing the turbine performance.

  A configuration of a turbine stage of a general steam turbine is shown in FIG. Each turbine stage 11 includes a turbine nozzle 1 and a turbine rotor blade stage 5, and the turbine nozzle 1 is formed between a diaphragm outer ring 17, a diaphragm inner ring 16, a diaphragm outer ring 17, and a diaphragm inner ring 16. And nozzle blades 1a arranged in the circumferential direction. The turbine nozzle constitutes a stationary part of the steam turbine together with the casing 12. A labyrinth packing 18 is provided between the diaphragm inner ring 16 and the rotor 13 in the circumferential direction in order to reduce leakage of the working fluid.

  On the downstream side of the turbine nozzle 1 formed in this way, turbine blade stages 5 are arranged facing the turbine nozzles 1. The turbine rotor blade stage 5 includes a plurality of turbine rotor blades 5 a that are implanted in a row at predetermined intervals in the circumferential direction on the outer periphery of a rotor disk 21 provided on a rotor (turbine shaft) 13. Yes. The turbine rotor blade stage 5 has a shroud 20 at the outer peripheral end thereof that bundles and fixes a plurality of tip portions of the turbine rotor blades 5a provided in the circumferential direction. A tip packing 4 for reducing leakage of working fluid between the shroud 20 and the casing 12 is attached to the inner surface of the casing 12 which is a stationary portion surrounding the rotor blade stage 5 on the outer peripheral side of the shroud 20. Yes.

  On the other hand, the thermal cycle of a steam turbine plant generally consists of a reheat-regeneration cycle. FIG. 9 shows a schematic layout of a reheat-regeneration cycle of the steam turbine plant.

  As shown in FIG. 9, high-temperature and high-pressure steam is generated in the boiler 31, and the energy of the generated steam is recovered as power by working in the high-pressure turbine 32. The steam that has finished work is heated (reheated) again by the boiler 31 and sent to the intermediate pressure turbine 33 to perform work. The steam then works in the low pressure turbine 34 to generate more power. The generator 45 is rotated by the generated power to generate power. The steam that has finished the work in the low-pressure turbine 34 is led to the condenser 35 to condense, and becomes water to form a condensate pump 38, a condensate heat exchanger 39, a ground steam condenser 40, and a low-pressure feed water heater. 41, deaerator 42 and booster pump 43, and then fed to boiler 31 by feed water pump 36. The feed water from the feed water pump 36 is heated by the high-pressure feed water heater 37 in the middle of being sent to the boiler 31, whereby fuel consumption in the boiler 31 can be saved.

  The heat source of the high-pressure feed water heater 37 is composed of steam obtained by extracting a part of steam in the steam turbines 32 and 33 during reversible adiabatic expansion to the outside of the steam turbine. The steam extracted outside during expansion in this way is referred to as extraction, but in the feed water heaters 37 and 41, the latent heat held by the extraction is regenerated by supplying water to the boiler 31. In particular, the thermal efficiency of the reheat-regeneration cycle is influenced by the initial pressure / initial temperature and exhaust pressure of the high-pressure turbine 32 and the intermediate-pressure turbine 33 of the steam turbine, and in the high-pressure turbine 32 and the intermediate-pressure turbine 33 of the steam turbine. It is also related to the amount of bleed air taken out from the middle of the reversible thermal expansion. By extracting most of the high-temperature steam from the high-pressure turbine 32 and the intermediate-pressure turbine 33 and supplying it to the high-pressure feed water heater 37 to heat the feed water, the fuel consumed in the boiler can be saved. However, if the amount of extraction is increased, the steam flow rate in the high-pressure turbine 32 and the intermediate-pressure turbine 33 is reduced, and the outputs of the high-pressure turbine 32 and the intermediate-pressure turbine 33 may be reduced, leading to a decrease in thermal efficiency. For this reason, in order to improve the thermal efficiency of the steam turbine plant, it is important to optimize the extraction amount and extraction method in the high-pressure turbine 32 and the intermediate-pressure turbine 33.

  As described above, in the conventional steam turbine, the working fluid extracted from the high-pressure turbine 32 and the intermediate-pressure turbine 33 and the working fluid that has passed through the high-pressure turbine 32 and the intermediate-pressure turbine 33 merge. There is a problem in that the fluid becomes a complicated flow, and the loss between the cascades of the steam turbines 32 and 33 is increased to lower the turbine efficiency. Furthermore, as shown in FIG. 10, generally in a steam turbine, the bleed pipe 22 is installed at one place in the circumferential direction of the outlet of the turbine stage 11 to locally take out the working fluid. For this reason, in the turbine stage which bleeds, there existed a problem which the distribution of flow volume was formed in the circumferential direction and the performance fell in the downstream stage.

  The present invention has been made in consideration of such points, and by improving the bleed structure of the steam turbine, the steam turbine capable of improving turbine performance and thermal cycle by reducing loss and its bleed operation. It aims to provide a method.

  The present invention provides a casing in which a turbine shaft is disposed, and a stationary portion that is provided inside the casing and forms the stationary portion together with the casing, and an annular flow between the diaphragm outer ring, the diaphragm inner ring, and the diaphragm outer ring and the diaphragm inner ring. A turbine nozzle having a plurality of nozzle blades arranged in the circumferential direction of the path, and a plurality of turbine blades arranged in the circumferential direction of the turbine shaft at a position downstream of the turbine nozzle, and a turbine together with the turbine nozzle A turbine blade stage that forms a paragraph, and the turbine stage is arranged in the casing with a plurality of stages from the upstream side to the downstream side along the turbine axis, and at least of the plurality of turbine stages An extraction mechanism is provided at each stationary part of the two turbine stage outlet parts to The working fluid extracted from each of the extraction mechanisms is merged and supplied to the outside, and the plurality of extraction mechanisms have a higher extraction flow rate at the upstream side than at the downstream side. It is comprised so that it may become. The steam turbine characterized by the above-mentioned.

  The present invention is the steam turbine characterized in that at least one of the plurality of extraction mechanisms has a plurality of extraction holes opened on the inner surface of the stationary portion.

  The present invention is the steam turbine characterized in that the bleed hole opening in the inner surface of the stationary part is formed so that the working fluid to be bleed flows in with a velocity component in the axial direction of the turbine shaft.

  In the present invention, the bleed mechanism including a plurality of bleed holes opened on the inner surface of the stationary part is a steam turbine further having a bleed pipe communicating with each bleed hole.

  The present invention is a steam turbine characterized in that the working fluid extracted by each extraction mechanism is combined and supplied to the outside.

  The present invention is a steam turbine characterized in that at least a bleed mechanism other than the most downstream is provided with a throttle mechanism.

  According to the present invention, at least one of the turbine rotor blade stages has a shroud portion on the outer periphery, and an inner peripheral end portion of the shroud is positioned upstream of an outer peripheral end portion of the shroud at the outlet portion of the turbine rotor blade stage. The steam turbine is characterized in that an inner peripheral end portion and the shroud outer peripheral end portion are connected by an inclined surface inclined in a radial direction.

  The present invention includes a plurality of turbine stages configured by a pair of a turbine nozzle and a turbine rotor blade stage, and the working fluid is supplied from an upstream side to a downstream side in a working fluid passage in which the plurality of turbine stages are arranged in series. A steam turbine bleed operation method for rotating the turbine rotor blade stage by passing a flow, wherein a part of the working fluid is bleed from the working fluid flowing out from one turbine stage of the plurality of turbine stages. And extracting a working fluid having a flow rate smaller than that of the working fluid extracted in the one turbine stage from the working fluid flowing out from another turbine stage downstream of the one turbine stage. It is the extraction operation method of the steam turbine characterized by these.

  The present invention is a steam turbine bleed operation method characterized in that the working fluid extracted in one turbine stage is decompressed and joined with the working fluid extracted in the other turbine stage.

  According to the present invention, it is possible to appropriately perform extraction in the steam turbine, and it is possible to improve thermal efficiency.

DESCRIPTION OF EXEMPLARY EMBODIMENTS First Embodiment Hereinafter, an embodiment of the invention will be described with reference to the drawings. 1 to 4 are views showing a first embodiment of a steam turbine according to the present invention.

  The steam turbine according to the present embodiment is a steam turbine particularly suitable for a high-pressure turbine or an intermediate-pressure turbine in a steam turbine plant.

  As shown in FIG. 1, the steam turbine is provided in a casing 12, a rotor (turbine shaft) 13 rotatably provided in the casing 12, a plurality of turbine nozzles 1 provided in the casing 12, and the rotor 13. A plurality of turbine rotor blade stages 5.

  Of these, the turbine nozzle 11 and the turbine rotor blade stage 5 constitute a turbine stage 11. A plurality of stages of turbine stages 11 are arranged in the casing 12 along the rotor 13 from the upstream side to the downstream side. The working fluid introduced into the steam turbine flows from the upstream side to the downstream side as a working fluid flow path in the turbine stage, and the turbine rotor blade stage 5 and the rotor 13 are rotated in the meantime.

  Each turbine nozzle 1 has a diaphragm outer ring 17, a diaphragm inner ring 16, and a number of nozzle blades 1 a arranged in the circumferential direction between the diaphragm outer ring 17 and the diaphragm inner ring 16. The diaphragm outer ring 17 of the turbine nozzle 1 is fixedly provided inside the casing 12 and constitutes a stationary part of the steam turbine together with the casing 12.

  Further, the turbine rotor blade stage 5 has a plurality of turbine blades 5 a arranged in a row at predetermined intervals in the circumferential direction on the outer periphery of the rotor disk 21 provided in the rotor 13. Further, a shroud 20 is provided at the outer peripheral end of the turbine rotor blade stage 5 for bundling and fixing a plurality of tip portions of the turbine rotor blades 5a provided in the circumferential direction. The rotor 13 and the turbine rotor blade stage 5 are disposed on the inner side (inner peripheral side) of the stationary part such as the casing 12 and the turbine nozzle 1 to constitute a rotating part of the steam turbine.

  The diaphragm inner ring 16 is provided with a labyrinth packing 18 in the circumferential direction so that the working fluid does not leak from between the diaphragm inner ring 16 which is a stationary part and the rotor 13 which is a rotating part. Further, the tip packing 4 is attached to the inner peripheral surface 17 b of the diaphragm outer ring 17 so that the working fluid does not leak from the gap 26 between the diaphragm outer ring 17 which is a stationary part and the shroud 20 of the turbine rotor blade stage 5.

  Incidentally, bleed holes 22 a are formed in the vicinity of the outlet of each turbine stage 11 on the inner surface of the stationary part such as the inner peripheral surface 12 b of the casing 12 and the inner peripheral surface 17 b of the diaphragm outer ring 17. Each bleed hole 22 a bleeds the working fluid flowing inside the casing 12 and the diaphragm outer ring 17 and takes it out, and each bleed hole 22 a communicates with the bleed pipe 22. These extraction holes 22 a and extraction pipes 22 constitute an extraction mechanism 25 that performs extraction at the outlet of each turbine stage 11.

  Here, in the present embodiment, the bleed holes 22a are opened on the inner peripheral surface 12b of the casing 12 and the inner peripheral surface 17b of the diaphragm outer ring 17, that is, on the cylindrical surface with respect to the axis of the rotor 13 in the stationary part. It extends in the radial direction (radial direction), that is, the direction orthogonal to the axis of the rotor 13.

  In this embodiment, the bleeder mechanism 25 is provided in the vicinity of the outlet of each turbine stage 11, but the bleeder mechanism 25 does not need to be provided in the vicinity of the outlets of all the turbine stages 11, and some turbine stages 11 may not be provided in the vicinity of the outlet.

  A merging pipe 24 is connected to a bleed pipe 22 of a bleed mechanism 25 provided at the outlet of each turbine stage 11, and steam extracted from the plurality of bleed holes 22 a merges in the merging pipe 24. The junction pipe 24 may be provided in the casing 12 as described later, but may be provided in the casing 12, that is, outside the steam turbine. The working fluid extracted by the extraction mechanism 25 in each turbine stage and combined in the merging pipe 24 is supplied to a feed water heater 37 provided outside the steam turbine. The working fluid extracted by the extraction mechanism 25 and supplied to the feed water heater 37 exchanges heat between the feed water sent from the feed water pump 36 and the feed water heater 37 to heat the feed water. The feed water heated by the feed water heater is then sent to the boiler 31.

  The junction pipe 24 to which the extraction pipe 22 of the extraction mechanism 25 is connected may be provided inside the casing 12 as shown in FIG. In this case, it is preferable that the merging pipe 24 has a larger diameter than the working fluid channel in the extraction mechanism 25. In this manner, the working fluid extracted by the extraction mechanism 25 and joined by the large diameter joining pipe 24 can be taken out of the casing 12.

  As described above, in the steam turbine according to the present embodiment, the bleeder mechanism 25 is provided at the outlets of the plurality of turbine stages 11, and the bleeder pipes 22 received by these bleeder mechanisms 25 are joined pipes 24. However, since the working fluids flowing through the turbine stages 11 have different pressures, if the extraction pipes 22 are simply joined together at the joining pipes 24, depending on the pressure difference, depending on circumstances. May cause backflow.

  For this reason, in the present embodiment, each extraction pipe 22 of the extraction mechanism 25 is provided with a throttle mechanism 22b for adjusting the pressure. In the steam turbine shown in FIG. 1, the pressure adjusting throttle mechanism 22b is attached to all the extraction pipes 22, but the pressure is not necessarily reduced for the extraction mechanism 25 provided in the most downstream turbine stage 11. Therefore, the pressure adjusting throttle mechanism 22b can be omitted. In the present embodiment shown in FIG. 1, an orifice is employed as the throttle mechanism 22b. However, the throttle mechanism 22b may be a throttle valve or a throttle channel.

  In the present embodiment, the flow rate of the working fluid extracted by each extraction mechanism 25 is further configured to decrease from the upstream turbine stage 11 toward the downstream turbine stage 11. That is, in the present embodiment, the bleed flow rate at the bleed mechanism 25 provided at the outlet portion of the upstream turbine stage 11 is the bleed air at the bleed mechanism 25 provided at the outlet portion of the downstream turbine stage 11. It is comprised so that it may exceed the flow volume.

  Here, the extraction flow rate in each extraction mechanism 25 can be set by, for example, the flow path cross-sectional area of the portion (narrowest portion) where the flow cross-sectional area of the working fluid flow path of the extraction mechanism 25 is the smallest. Therefore, in order to increase the extraction flow rate of each extraction mechanism 25 toward the upstream side and decrease toward the downstream side, for example, the flow path cross-sectional area such as the pipe diameter of the narrowest part in the upstream extraction mechanism 25 is set. What is necessary is just to take larger and to take small the flow-path cross-sectional area of the pipe diameter narrowest part in the extraction mechanism 25 of the downstream. In particular, in the present embodiment, each bleeder mechanism 25 is provided with an orifice as the squeeze mechanism 22b. Therefore, the orifice cross-sectional area is the smallest among the working fluid channels of each bleeder mechanism 25. If it is set to be a portion (narrowest portion), the flow rate of the working fluid extracted by each extraction mechanism 25 is set by setting the orifice diameter so that the upstream extraction mechanism 25 becomes larger. It is possible to realize a configuration that decreases from the upstream turbine stage 11 toward the downstream turbine stage 11. That is, when the orifice portion is the narrowest portion of the working fluid flow path of each extraction mechanism 25, the orifice which is the pressure adjusting throttle mechanism 22b also has a flow rate adjusting function.

  Here, in determining the narrowest part of the working fluid flow path of the bleed mechanism 25, for the part where the working fluid flow paths are arranged in parallel, the sum of the cross-sectional areas of the parts arranged in parallel is calculated. Treated as channel cross-sectional area.

  Incidentally, the flow rate of the working fluid extracted by the extraction mechanism 25 (extraction flow rate) differs depending on the temperature, pressure, and the like of the working fluid in addition to the cross-sectional area of the narrowest portion of the working fluid flow path.

  In the above-described example, the diameter (cross-sectional area) of the orifice serving as the throttle mechanism 22b is gradually decreased from the upstream bleed mechanism 25 toward the downstream bleed mechanism 25 to thereby reduce the turbine from the upstream turbine stage 11 to the downstream turbine. Although the bleed flow rate is configured to decrease toward the paragraph 11, it is not limited to this. That is, as described above, the bleed flow rate differs depending on the steam condition (temperature / pressure) in addition to the flow path cross-sectional area. For example, the pressure of the working fluid gradually increases from the upstream turbine stage 11 toward the downstream turbine stage 11. When the temperature of the extraction mechanism 25 decreases, even if the cross-sectional area of the working fluid flow path of the extraction mechanism 25 is substantially the same or gradually increases from the upstream side to the downstream side, the extraction flow rate from each extraction mechanism 25 is increased upstream. It is possible to have a structure that decreases from the turbine stage 11 on the side toward the turbine stage 11 on the downstream side.

  Therefore, in the present embodiment, based on the pressure and temperature in each turbine stage 11 in addition to the flow path cross-sectional area of the portion (narrowest portion) where the flow cross-sectional area of the working fluid flow path of the extraction mechanism 25 is the smallest. Thus, by setting the bleed flow rate by the bleed mechanism 25 in each turbine stage 11, the flow rate of the working fluid bleed by each bleed mechanism 25 moves from the upstream turbine stage 11 toward the downstream turbine stage 11. A configuration that decreases can be realized.

  Next, the operation of the present embodiment having such a configuration will be described.

  In FIG. 1, the working fluid flowing into the casing 12 flows into the turbine blade stage 5 from the turbine nozzle 1 of each turbine stage 11, and rotates the turbine blade stage 5 and the rotor 13 which are rotating parts of the steam turbine. Let During this time, the working fluid in the casing 12 is extracted through the extraction pipe 22 from the extraction holes 22 a provided at the outlet of each turbine stage 11. At this time, the amount of extraction from the extraction pipe 22 decreases from the upstream turbine stage 11 toward the downstream turbine stage 11 as described above.

  FIG. 3 is a graph showing the axial position of the steam turbine and the extraction flow rate at that position. In determining the bleed flow rate by the bleed mechanism 25 at the outlet of each turbine stage 11, in the present embodiment, the position from the upstream side to the downstream side depends on the axial position from the inlet portion of the steam turbine as shown by the broken line in FIG. An extraction flow rate characteristic that decreases toward the side is given in advance as an optimum characteristic. At the time of designing the steam turbine, when the axial position of the outlet portion of each turbine stage 11 in the steam turbine is determined, each position is plotted on the extraction flow rate characteristic as shown in FIG. In this way, the extraction flow rate can be determined from the extraction flow characteristic.

  Note that the extraction flow rate characteristic curve indicated by a broken line in FIG. 3 can be appropriately determined by performing a heat balance simulation of the entire steam turbine plant. In FIG. 3, the horizontal axis is the axial position from the inlet of the steam turbine. However, the bleed flow characteristic curve can be given as a function of the static pressure in the working fluid flow path of the steam turbine. .

  FIG. 4 shows the temperature distribution of the working fluid in the blade height direction of the turbine rotor blade at the outlet of the turbine rotor blade 5a in the present embodiment.

  The turbine rotor blade stage 5 converts the thermal energy of the working fluid flowing into the plurality of turbine blades 5a provided into power. For this reason, the working fluid temperature at the outlet of the turbine rotor blade stage 5 is lower than the inlet temperature of the turbine stage 11 by performing work as the driving power of the turbine.

  On the other hand, a gap 26 of the tip packing 4 is formed between the shroud 20 at the outer peripheral end of the turbine rotor blade stage 5 and the inner surface 17b of the diaphragm outer ring 17 which is a stationary part. Since the working fluid that has passed through the gap 26 of the tip packing 4 does not perform work, it flows into the turbine rotor blade 5 outlet in the state of the turbine stage 11 inlet temperature, and the temperature of the high blade length portion increases as shown in FIG. To do.

  When bleed is not performed at the turbine rotor blade 5 outlet, the leaked fluid that has flowed out of the turbine nozzle 1 and leaked into the gap 26 between the tip packing 4 and the shroud 20 passes through the gap 26 and again passes through the passage of the turbine stage 11. And the main flow of the working fluid that has flowed between the turbine rotor blades 5a, which are passage portions of the turbine stage 11, is joined. However, since the direction of the flow of the leaked fluid to be merged with the main flow at this time is the central axis direction of the rotor 13, that is, the inner side in the radial direction, it is between the turbine rotor blades 5 a that are the passage portions of the turbine stage 11. The direction of the main flow of the working fluid that has flowed (substantially in the axial direction) is greatly different. For this reason, when this leaked fluid joins the main flow, the main flow of the working fluid is disturbed, thereby reducing the turbine cascade performance in the subsequent turbine stage 11.

  On the other hand, according to the present embodiment, the bleed mechanism 25 is provided at the outlet of the turbine rotor blade 5 of the plurality of turbine stages 11, and the bleed air is extracted from the bleed holes 22 a provided in the bleed mechanism 25. It is possible to reduce the flow rate of the leaked fluid from 26, suppress the leaked fluid from flowing into the main flow of the working fluid of the turbine stage 11, and improve the cascade performance.

  In particular, the cross-sectional area of the gap 26 between the shroud 20 portion and the inner surface 12b of the casing 12 relative to the throat area of the turbine blade 5a (ratio of the throat area and the blade tip portion gap cross-sectional area) is the blade of the turbine blade 5a. The upstream turbine stage with a short length and a small radius becomes larger. For this reason, in the present embodiment, an effect is obtained by increasing the extraction flow rate in the upstream turbine stage 11 and reducing the extraction flow rate in the downstream turbine stage 11 as compared with the extraction flow rate in the upstream turbine stage 11. In particular, the turbine performance can be improved. Further, since the leakage flow rate that has passed through the gap 26 is not working, the leakage flow rate is higher than the fluid temperature that has passed through the turbine rotor blade stage 5. By using such a high-temperature fluid as extraction air in the feed water heater 37, the feed water can be effectively heated. Thus, by effectively extracting the leaked fluid that has passed through the gap 26, fuel consumption in the boiler 31 can be further saved, and the thermal efficiency of the steam turbine plant can be improved.

  Further, as shown in FIG. 2, if the working fluid extracted in each turbine stage 11 is joined inside the casing 12 by the large diameter joining pipe 24 and then taken out of the casing 12, each turbine Heat dissipation from the extraction pipe 22 taken out from the outlet portion of the paragraph 11 can be suppressed. Thereby, since the temperature fall of extraction can be decreased and it can supply to the feed water heater 37, a steam turbine planton thermal efficiency can further be improved. Further, at this time, the bleeder pipe 22 of the bleeder mechanism 25 having a high bleeder pressure is provided with a throttle mechanism 22b to reduce the pressure, so that the pressure after merging can be kept constant and the operation can be stably performed.

Second Embodiment Next, a second embodiment of the present invention will be described with reference to FIGS. The second embodiment shown in FIGS. 5 to 6 is different from the first embodiment shown in FIGS. 1 to 4 only in the configuration of the extraction mechanism 25 provided for each turbine stage 11. It is almost the same. In the second embodiment shown in FIG. 5 to FIG. 6, the same parts as those in the first embodiment shown in FIG. 1 to FIG.

  FIG. 5A is an enlarged view showing the extraction mechanism in a meridional section of the steam turbine, and FIG. 5B is a sectional view taken along line B of FIG. 5A. As shown in FIGS. 5 (a) and 5 (b), an extraction mechanism 25 is provided for each outlet of each turbine stage 11, and one end of the extraction hole 22a of each extraction mechanism 25 has an inner peripheral surface 17b of the diaphragm outer ring 17, That is, a plurality of openings are provided at intervals in the circumferential direction on the inner peripheral surface of the stationary portion of the steam turbine. That is, in the present embodiment, a plurality of bleed holes 22a of the bleed mechanism 25 are provided at regular intervals over the entire circumference in the circumferential direction of the stationary portion (casing 12 or diaphragm outer ring 17) surrounding each turbine stage 11. Is provided. The bleed holes 22 a of the bleed mechanisms 25 extend in the radial direction (radial direction), that is, in the direction perpendicular to the axis of the rotor 13 from the opening provided on the inner peripheral surface of the stationary part. The diaphragm outer ring 17 is provided with a communication pipe 9 extending all around the inner peripheral surface 17b of the diaphragm outer ring 17, and the other end of the extraction hole 22a of the extraction mechanism 25 is connected to the communication pipe 9. It is formed to open. The bleeder tube 22 of the bleeder mechanism 25 is connected to the outer side of the communication tube 9, and the bleeder tube 22 is provided with a restrictor mechanism 22b as in the first embodiment.

  In such a configuration of the present embodiment, the working fluid extracted by the plurality of extraction holes 22 a provided in the inner peripheral surface 17 b of the diaphragm outer ring 17 is entirely perimeter along the inner peripheral surface 17 b of the diaphragm outer ring 17. Then, the refrigerant flows into the communication pipe 9 extending to the pipe and gathers, and is sent from the communication pipe 9 to the feed water heater 37 via the extraction pipe 22 and the junction pipe 24 shown in FIG.

  Leakage fluid, which is a working fluid that passes through the gap 26 between the shroud 20 at the tip of the turbine rotor blade 5 and the inner peripheral surface 17b of the diaphragm outer ring 17, is generated all around the inner peripheral surface 17b of the diaphragm outer ring 17. That is, as in the present embodiment, by providing the bleed holes 22a of the bleed mechanism 25 on the entire circumference of the inner peripheral surface of the stationary part, the working fluid is extracted from the entire circumference, and the inner peripheral surface 17b of the diaphragm outer ring 17 It is possible to prevent the leaked fluid that has passed through the gap 26 between the first and second fluids from joining the main flow of the working fluid that passes through the blade rows of the turbine stage 11 in the entire circumference. Thereby, it can prevent that the main flow changes locally and a non-uniform flow distribution in the circumferential direction is generated, and can suppress the reduction in blade row performance after the extraction stage.

  5 (a) and 5 (b), the extraction holes 22 are provided as radial holes opened on the inner peripheral surface of the steam turbine stationary portion. However, the present invention is not limited to this, and the extraction holes 22 are rotors in the meridional section. It is also possible to provide parallel to the shaft 3. Such an example will be described as a modification with reference to FIG.

  FIG. 6 is an enlarged view showing the extraction mechanism in a meridional section of the steam turbine, and FIG. 6B is a sectional view taken along the line B in FIG. Also in this modified example, a plurality of stationary portions (casing 12 or diaphragm outer ring 17) surrounding each turbine stage 11 are provided at regular intervals over the entire circumference in the circumferential direction. Inside, a communication pipe 9 extending along the entire inner peripheral surface 17 b of the diaphragm outer ring 17 is provided, and an extraction hole 22 a of the extraction mechanism 25 is formed to open to the communication pipe 9. Further, an extraction pipe 22 of an extraction mechanism 25 is connected to the outer side of the communication pipe 9, and an extraction mechanism 22 b is provided in the extraction pipe 22. And in this modification, as shown to Fig.6 (a) (b), the opening part of each extraction hole 22a is on the side wall 17a of the diaphragm outer ring | wheel 17 arrange | positioned downstream of the shroud 20 of the turbine rotor blade stage 5. As shown in FIG. It is provided to be located. In this case, the side wall 17a of the diaphragm outer ring 17 is a surface orthogonal to the rotor 13, and therefore each extraction hole 22a whose one end is opened is formed in parallel with the axis of the rotor 13 in the meridional section. The working fluid extracted by the air flows with a velocity component in the axial direction of the rotor shaft 3. Since the leakage fluid, which is the working fluid that passes through the gap 26 between the shroud 20 and the inner peripheral surface 17b of the diaphragm outer ring 17, flows with the velocity component in the axial direction of the rotor 13, this configuration makes it possible to The flow direction of the leaking fluid and the direction of extraction of the working fluid from the extraction hole 22a can be made the same, and the pressure loss due to extraction can be reduced.

  In other words, in the present embodiment, a plurality of bleed holes 22a are provided on the inner surface of a stationary part such as the casing 12 or the diaphragm outer ring 17 and are provided in a plurality over the entire circumference in the circumferential direction with respect to the axis of the rotor 13. Each bleed hole 22a itself may be arranged in the radial direction (radial direction) or in the axial direction. In particular, as shown in FIG. 6, when each extraction hole 22 a is formed parallel to the axis of the rotor 13 in the meridional section of the steam turbine, the extraction hole 22 a is circumferentially aligned with the rotational direction of the turbine rotor blade stage 5. It is also possible to adopt a configuration in which the leaked fluid is extracted more smoothly by being inclined to the position.

  The bleeder mechanism 25 according to the present embodiment as shown in FIGS. 5A and 5B and FIGS. 6A and 6B is the first embodiment shown in FIGS. It may be provided in all of the turbine stages 11, or may be provided in at least one of the turbine stages 11.

Third Embodiment Next, a third embodiment of the present invention will be described with reference to FIGS. The third embodiment shown in FIGS. 7 and 8 differs only in the configuration of the shroud 20 provided at the outer peripheral end of each turbine blade stage 5, and the others are the first shown in FIGS. 1 to 4. This is substantially the same as the embodiment.

  In the third embodiment shown in FIGS. 7 and 8, the same parts as those in the first embodiment shown in FIGS.

  As shown in FIGS. 7 and 8, the shroud 20 at the outer peripheral portion of the five-stage turbine rotor blade has the longitudinal length of the inner shroud portion shorter at the outlet than the longitudinal length of the outer shroud portion. Thus, an inclined portion 20a inclined in the radial direction is formed. That is, in the present embodiment, the shroud 20 has the shroud inner peripheral end located upstream of the shroud outer peripheral end at the rotor blade stage outlet, and the shroud inner peripheral end and the shroud outer peripheral end. Are connected by an inclined portion 20a which is an inclined surface inclined in the radial direction.

  FIG. 8 is a graph showing the relationship between blade height and local energy loss in each turbine blade 5a. Generally, at the outlet of the turbine rotor blade 5, energy loss increases at a portion where the blade length is high as shown in FIG. As a result, a fluid with a large energy loss flows to the downstream stage, which causes further energy loss and lowers the efficiency of the turbine.

  Therefore, as in the present embodiment, the outlet side of the shroud 20 located on the outer peripheral portion of the turbine blade stage 5 is the inclined portion 20a that is an inclined surface inclined in the radial direction. The working fluid with a large energy loss generated in the vicinity of the inner peripheral surface 12b of the casing 12 (part where the blade length is high) can be smoothly guided to the extraction hole 22a side by the inclined portion 20a and extracted. Thereby, since it is not necessary to deliver the fluid with a large energy loss to the downstream turbine stage 11, the loss reduction in the downstream turbine stage 11 can be suppressed. In addition, since the temperature of the fluid flowing through the high blade length portion with such a large energy loss is higher than the mainstream temperature of the working fluid, the water supply can be effectively heated by using this for extraction, An improvement in the thermal efficiency of the steam turbine plant can also be expected.

  In addition, about the structure of the shroud part 20 of the turbine rotor blade stage 5 which concerns on this Embodiment, you may make it provide in all the turbine paragraphs 11 of 1st Embodiment shown in FIG. 1 thru | or FIG. Alternatively, it may be provided in at least one of the turbine stages 11. It is also possible to combine with the second embodiment of FIG. 5 or FIG. 6 as appropriate.

FIG. 1 is a cross-sectional view showing a steam turbine according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view showing a steam turbine according to a modification of the first embodiment of the present invention. FIG. 3 is a diagram for explaining the operation of the steam turbine according to the first embodiment of the present invention. FIG. 4 is a supplementary diagram for explaining the operation of the steam turbine according to the first embodiment of the present invention. FIGS. 5A and 5B are views showing a steam turbine according to a second embodiment of the present invention. FIGS. 6A and 6B are views showing a steam turbine according to a modification of the second embodiment of the present invention. FIG. 7 is a sectional view showing a steam turbine according to a third embodiment of the present invention. FIG. 8 is a diagram for explaining the operation of the steam turbine according to the third embodiment of the present invention. The layout which shows the outline of a steam turbine plant. Sectional drawing which shows the conventional steam turbine.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Turbine nozzle 1a Nozzle blade 5 Turbine rotor blade 4 Tip packing 9 Communication pipe 11 Turbine stage 12 Casing 12a Side wall 12b Inner peripheral surface 13 Rotor 16 Diaphragm inner ring 17 Diaphragm outer ring 18 Labyrinth packing 20 Shroud 21 Rotor disk 22 Extraction pipe 22a Extraction hole 22b Throttle mechanism 24 Merge pipe 25 Bleed mechanism 26 Gap

Claims (9)

A casing in which the turbine shaft is disposed;
It is provided inside the casing and forms a stationary part together with the casing, and includes a diaphragm outer ring, a diaphragm inner ring, and a plurality of nozzle blades arranged in a circumferential direction of an annular flow path between the diaphragm outer ring and the diaphragm inner ring. A turbine nozzle,
A plurality of turbine rotor blades arranged in the circumferential direction of the turbine shaft at a position downstream of the turbine nozzle, comprising a turbine rotor blade stage that forms a turbine stage together with the turbine nozzle;
The turbine stage has a plurality of stages arranged from the upstream side to the downstream side along the turbine axis in the casing, and at each of the stationary parts of at least two turbine stage outlets among the plurality of turbine stages. A bleed mechanism is provided to bleed the working fluid at the turbine stage outlet, and the working fluid bleed from each bleed mechanism is merged and supplied to the outside; and
The plurality of extraction mechanisms are configured such that the upstream side has a higher extraction flow rate than the downstream side.   2. The steam turbine according to claim 1, wherein at least one of the plurality of extraction mechanisms has a plurality of extraction holes opened on an inner surface of the stationary portion.   The steam turbine according to claim 2, wherein the bleed hole opened to the inner surface of the stationary part is formed so that the working fluid to be bleed flows in with a velocity component in an axial direction of the turbine shaft.   4. The steam turbine according to claim 2, wherein the extraction mechanism including a plurality of extraction holes opened on the inner surface of the stationary part further includes an extraction pipe communicating with each extraction hole. 5.   The steam turbine according to any one of claims 1 to 4, wherein the working fluid extracted by each extraction mechanism is configured to be combined and supplied to the outside.   The steam turbine according to claim 5, wherein at least a bleed mechanism other than the most downstream side is provided with a throttle mechanism.   At least one of the turbine rotor blade stages has a shroud portion on the outer periphery, and the shroud inner peripheral end portion is located upstream of the shroud outer peripheral end portion at the turbine rotor blade stage outlet portion, and the shroud inner peripheral end portion The steam turbine according to any one of claims 1 to 6, wherein the shroud outer peripheral end is connected by an inclined surface inclined in the radial direction. A plurality of turbine stages composed of a pair of turbine nozzles and turbine blade stages are provided, and the working fluid is caused to flow from the upstream side to the downstream side through a working fluid passage in which the plurality of turbine stages are arranged in series. A steam turbine bleed operation method for rotating the turbine rotor blade stage by:
Extracting a part of the working fluid from the working fluid flowing out from one turbine stage of the plurality of turbine stages;
And a step of extracting a working fluid having a flow rate smaller than that of the working fluid extracted in the one turbine stage from a working fluid flowing out from another turbine stage downstream of the one turbine stage. A steam turbine bleed operation method.   The steam turbine bleed operation method according to claim 8, wherein the working fluid extracted in one turbine stage is decompressed and joined with the working fluid extracted in the other turbine stage.

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