JP2010038099A - Nozzle box for steam turbine, and steam turbine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nozzle box for a steam turbine capable of leading steam to a first-stage nozzle by reducing a pressure loss when the steam flows between reinforcing ribs, and to provide a steam turbine with the nozzle box for the steam turbine. <P>SOLUTION: The nozzle box 10 is configured such that the steam introduced from a steam inlet pipe 220 and led to flow into a circumferentially enlarging steam flow passage 20 is led to the first-stage nozzle 213a through the reinforcing ribs 30, 35. The reinforcing rib 35 of the reinforcing ribs 30, 35 arranged upstream of the first-stage nozzle 213a is arranged according to a steam flow direction at an angle different from the reinforcing rib 30. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a steam turbine nozzle box installed in a steam turbine and a steam turbine including the steam turbine nozzle box.

  BACKGROUND ART An axial flow rotary machine such as a steam turbine used in a thermal power plant or the like includes a cascade composed of a combination of a plurality of stages of nozzles with stationary flow paths through which a working fluid passes and rotating rotor blades. ing. In the case of a steam turbine, it is generally classified into a high-pressure part, an intermediate-pressure part, and a low-pressure part based on the conditions of steam as a working fluid. In each blade row, in order to improve work efficiency by the working fluid, the flow path between the blade rows needs to be designed in a shape that allows the working fluid to flow smoothly.

Conventionally, in order to effectively use energy resources and reduce CO ₂ emissions, it is important to improve the efficiency of power generation equipment. In order to improve the efficiency of the steam turbine, for example, it is possible to effectively convert the given energy into mechanical work. One countermeasure is to reduce various internal losses.

  Internal losses in steam turbines include profile loss due to blade shape, secondary loss due to secondary flow, leakage loss due to leakage of working fluid outside the cascade, and drains specific to the final blade group. There are losses in the steam turbine cascade, such as due to wet loss. Further, there are a steam valve, a passage portion for introducing steam to a certain blade row, a loss in a passage portion from a certain blade row to the next blade row, an exhaust loss in the low-pressure final stage, and the like.

  In order to reduce the pressure loss of the passage portion connecting the blade rows, the technology for guiding the steam to the blade rows as uniformly as possible is disclosed. For example, a steam turbine including a guide for controlling the flow of steam in order to guide steam as uniformly as possible to the cascade is disclosed (for example, see Patent Documents 1-3).

  Here, the configuration of the conventional nozzle box will be described. FIG. 8 is a view of a cross section perpendicular to the turbine rotor of the conventional nozzle box 300 as viewed from the first stage nozzle 303 side. FIG. 9 is a view showing a cross section taken along the line AA of FIG. In addition, although the turbine rotor is penetrated in the center, illustration of the turbine rotor is omitted here.

  As shown in FIG. 8, the nozzle box 300 is divided into two upper and lower spaces, and steam 301 from a boiler (not shown) is introduced into each space by two steam inlet pipes 302. As shown in FIG. 9, the steam 301 introduced into the nozzle box 300 passes through the reinforcing ribs 304 provided for holding the structure of the nozzle box 300 and is guided to the first stage nozzle 303. The passage section is connected to the entire circumference downstream of the first stage nozzle 303, and the steam 301 that has passed through the first stage nozzle 303 is guided to a first stage rotor blade (not shown).

  FIG. 10 is a view schematically showing the flow of the steam 301 when the steam 301 introduced from the steam inlet pipe 302 into the space of the nozzle box 300 flows between the reinforcing ribs 304. As shown in FIG. 10, all the reinforcing ribs 304 are configured in the same shape, and are disposed at equal intervals in the circumferential direction in a certain direction. Further, the reinforcing rib 304 is formed in a shape in which the center line 305 is a straight line, and is installed so that the center line 305 is parallel to the turbine rotor shaft. Here, α shown in FIG. 10 is an inflow angle of the steam 301 between the reinforcing ribs 304. This inflow angle α is equal to the direction parallel to the extension of the center line 305 at the most upstream end of the reinforcing rib 304 (hereinafter referred to as the front edge 304a) in the steam inflow portion between the reinforcing ribs 304 and the steam 301. This is the angle formed by the flow direction, that is, the streamline direction.

  As shown in FIG. 10, the larger the inflow angle α, the more easily the vortex 306 is generated in a part of the flow of the steam 301 flowing between the reinforcing ribs 304, and the pressure loss is more likely to occur. In addition, the steam 301 flowing between the reinforcing ribs 304 in this way flows into the first stage nozzle 303 installed on the downstream side of the reinforcing ribs 304 in a turbulent state.

  Here, FIG. 11 is a view showing the inflow angle α at the circumferential angle indicating the circumferential position of the reinforcing rib 304. FIG. 8 shows a position corresponding to this circumferential angle. The inflow angle α shown in FIG. 11 is obtained by three-dimensional thermal fluid analysis in a steady state using CFD (Computational Fluid Dynamics). In the inflow angle α shown on the vertical axis in FIG. 11, for example, when the inflow angle α is 0 degree, the flow direction of the steam 301 is parallel to the extending direction of the center line 305 at the front edge 304 a of the reinforcing rib 304. It becomes. In this case, the steam 301 flows between the reinforcing ribs 304 in parallel to the center line 305 of the reinforcing ribs 304 and is guided to the first stage nozzle 303.

  As shown in FIG. 11, the inflow angle α varies greatly in the circumferential direction angle. Further, when the inflow angle α is large, the vortex 306 is generated as described above, a pressure loss is generated, and the efficiency of the steam turbine is lowered.

  FIG. 12 is a view when a cross section perpendicular to the turbine rotor of the conventional nozzle box 300 having a configuration in which the steam 301 is introduced into the nozzle box 300 by two steam inlet pipes 302 is viewed from the first stage nozzle 303 side. . FIG. 13 is a diagram showing the inflow angle α at the circumferential angle indicating the circumferential position of the reinforcing rib 304 in the shape of the nozzle box 300 shown in FIG. 12. The shape of the reinforcing rib 304 is the same as that shown in FIG. Similarly to the inflow angle α shown in FIG. 11, the inflow angle α shown in FIG. 13 is obtained by a three-dimensional thermal fluid analysis in a steady state using CFD (Computational Fluid Dynamics). is there.

As shown in FIG. 13, also in this nozzle box 300, the inflow angle α varies greatly in the circumferential direction angle. Further, at a position having a large inflow angle α, the vortex 306 is generated as described above, a pressure loss is generated, and the efficiency of the steam turbine is lowered.
JP-A-8-260903 JP-A-8-49501 JP 2003-193809 A

  As described above, in the conventional nozzle box 300, a region where the steam 301 flows in has a large inflow angle α between the reinforcing ribs 304. As a result, there is a problem that pressure loss occurs and the efficiency of the steam turbine decreases.

  Accordingly, the present invention has been made to solve the above problems, and a nozzle box for a steam turbine capable of reducing the pressure loss when the steam flows between the reinforcing ribs and guiding the steam to the first stage nozzle. And it aims at providing the steam turbine provided with this nozzle box for steam turbines.

  In order to achieve the above object, according to one aspect of the present invention, steam introduced from a steam inlet pipe and flowing into a steam flow path extending in the circumferential direction is guided to the first stage nozzle through the reinforcing ribs. A steam turbine nozzle box, wherein at least one of the reinforcing ribs installed upstream of the first stage nozzle is installed at an angle different from that of the other reinforcing ribs. A nozzle box for a steam turbine is provided.

  Moreover, according to one aspect of the present invention, there is provided a nozzle box configured to guide the steam introduced from the steam inlet pipe and flowing into the steam flow path extending in the circumferential direction to the first stage nozzle through the reinforcing ribs. A steam turbine is provided, wherein the nozzle box is the nozzle box for a steam turbine described above.

  According to the steam turbine nozzle box of the present invention and the steam turbine provided with the steam turbine nozzle box, it is possible to reduce the pressure loss when the steam flows between the reinforcing ribs and guide the steam to the first stage nozzle. .

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

  FIG. 1 is a view showing a cross section of an upper half casing portion of a steam turbine 200 including a nozzle box 10 according to the present invention.

  As shown in FIG. 1, the steam turbine 200 includes, for example, a double-structure casing that includes an inner casing 210 and an outer casing 211 provided outside the inner casing 210. Further, a turbine rotor 212 is provided through the inner casing 210. A nozzle 213 is disposed on the inner surface of the inner casing 210, and a moving blade 214 is implanted in the turbine rotor 212. Further, the steam turbine 200 is provided with a steam inlet pipe 220 penetrating the outer casing 211 and the inner casing 210, and an end of the steam inlet pipe 220 is a nozzle that guides steam toward the moving blade 214 side. The box 10 is connected in communication. The nozzle box 10 includes a steam flow path 20 in which steam introduced from the steam inlet pipe 220 spreads in the circumferential direction. The nozzle box 10 includes reinforcing ribs 30 and 35 that guide the steam introduced into the steam flow path 20 to the first stage nozzle 213a.

  The steam that has flowed into the nozzle box 10 through the steam inlet pipe 220 spreads into the steam flow path 20, passes between the reinforcing ribs 30 and 35, and is guided to the first stage nozzle 213 a toward the first stage rotor blade 214 a. Is ejected. The jetted steam passes through the steam path between the nozzle 213 and the moving blade 214 in each stage, and rotates the turbine rotor 212. Further, most of the steam that has performed expansion work is exhausted, and flows into a boiler (not shown) through, for example, a low-temperature reheat pipe (not shown). Further, a part of the steam that has performed the expansion work is led between the inner casing 210 and the outer casing 211 as the cooling steam, and is exhausted from the ground portion or the exhaust path through which most of the steam that has performed the expansion work is exhausted. The

  Note that the configuration of the steam turbine 200 is not limited to the above-described configuration, and may be any steam turbine having a configuration in which steam flows into the nozzle box 10 via the steam inlet pipe 220.

  Next, the nozzle box 10 according to the present invention will be described.

(Nozzle box of the first embodiment)
FIG. 2 is a diagram schematically showing the installation configuration of the reinforcing ribs 30 and 35 and the first stage nozzle 213a in the nozzle box 10 according to the first embodiment of the present invention. FIG. 2 shows a circumferential cross-sectional development schematic diagram in which the circumferential cross-section (circumferential cross-section) of the reinforcing ribs 30 and 35 and the first stage nozzle 213a is developed on a plane, and the vertical direction in FIG. It is a circumferential direction (circumferential direction), and the left-right direction is the turbine rotor axial direction.

  As shown in FIG. 2, the reinforcing ribs 30 and 35 and the first stage nozzle 213 a are arranged at a predetermined interval in the circumferential direction corresponding to the steam flow path 20 of the nozzle box 10. The reinforcing ribs 30 and 35 are arranged at a predetermined interval from the first stage nozzle 213a on the upstream side of the first stage nozzle 213a, that is, on the steam flow path 20 side of the first stage nozzle 213a.

  Further, the steam introduced from the steam inlet pipe 220 and spreading into the steam flow path 20 becomes a passage formed between the reinforcing ribs 30 and 35 depending on the circumferential angle of the steam flow path 20 as shown in FIG. The inflow angle is different. For example, there is a flow that flows in parallel to the turbine rotor shaft, such as steam Sa, and a flow that flows in a direction shifted by a predetermined angle with respect to the turbine rotor shaft direction, such as steam Sb.

  Therefore, in the reinforcing ribs 30 and 35 in the nozzle box 10 according to the first embodiment of the present invention, the flow direction of the steam at the steam inflow portion between the reinforcing ribs is expressed by CFD (Computational Fluid Dynamics). The three-dimensional thermal fluid analysis in the steady state is performed, and the angle at which the reinforcing ribs 30 and 35 are installed is set based on the obtained result. For example, in the case of the flow direction of the steam Sa, the reinforcing rib 30 whose center line 31 is a straight line is installed so that the center line 31 of the circumferential section and the turbine rotor shaft are parallel to each other.

  On the other hand, for example, in the case of the flow direction of the steam Sb, the extending direction of the center line 36 in the circumferential cross section at the most upstream end (hereinafter referred to as the front edge 35a) of the reinforcing rib 35 is the flow direction of the steam Sb. The front edge 35a side of the reinforcing rib 35 is inclined so as to be parallel to the front surface. In this case, the center line 36 of the circumferential cross section of the reinforcing rib 35 is a curve. The flow direction of the steam Sb that determines the inclination of the reinforcing rib 35 on the front edge 35a side is, for example, each steam flow flowing through the steam inflow portion between the reinforcing ribs, that is, the portion formed by the front edge 35a of the reinforcing rib 35. It is possible to set an average of streamline directions. At this time, as shown in FIG. 2, a direction parallel to the extension of the center line 36 of the circumferential cross section at the front edge 35a of the reinforcing rib 35 configured to be parallel to the flow direction of the steam Sb, The angle β formed by the streamline direction of each steam flow flowing through the steam inflow portion between the reinforcing ribs varies depending on the shape of the front edge 30a, but is preferably ± 5 degrees or less. In other words, the angle β formed is a direction parallel to the extension line of the center line 36 of the circumferential cross section of the reinforcing rib 35 whose inclination on the front edge 35a side is determined as described above, and each flow between the reinforcing ribs. The range of the angle of deviation from the streamline direction of the steam flow is shown. The reason why the formed angle β is in this range is that the loss tends to increase when the formed angle β exceeds 5 degrees.

  Further, end portions on the most downstream side of the reinforcing ribs 30 and 35 (hereinafter referred to as rear edges 30b and 35b) are extensions of the center lines 31 and 36 in the circumferential direction of the rear edges 30b and 35b of the reinforcing ribs 30 and 35. It is preferable that the direction and the extending direction of the center line 231 of the circumferential cross section at the front edge 230 of the first stage nozzle 213a are parallel to each other. Further, the rear edges 30b and 35b of the reinforcing ribs 30 and 35 are configured to be positioned at a predetermined interval on the upstream side between the first stage nozzles 213a.

  Next, the flow of the steam that has flowed into the steam channel 20 will be described.

  Since a part of the steam (steam Sa) spreading in the steam flow path 20 flows in parallel to the turbine rotor shaft, it flows between the reinforcing ribs 30 parallel to the center line 31 of the reinforcing ribs 30 in the circumferential cross section. It flows into the stage nozzle 213a.

  On the other hand, the steam Sb flowing in a direction shifted by a predetermined angle with respect to the axial direction of the turbine rotor among the steam spreading in the steam flow path 20 corresponds to the flowing direction as described above in the circumferential cross section. It flows between the reinforcing ribs 35 that are inclined and flows into the first stage nozzle 213a.

  Here, the nozzle shown in FIG. 8 and FIG. 9 described above, which is divided into two upper and lower spaces and has a structure provided with two steam inlet pipes for introducing steam from a boiler (not shown) into each space. In the configuration in which the reinforcing ribs 30 and 35 and the first-stage nozzle 213a according to the first embodiment of the present invention described above are installed in a nozzle box having the same configuration as the box, the circumferential angle indicating the circumferential position of the reinforcing rib The inflow angle α was analyzed. FIG. 3 is a view showing the inflow angle α at the circumferential angle indicating the circumferential position of the reinforcing ribs 30 and 35. The inflow angle α is a direction parallel to the extension lines of the center lines 31 and 36 of the circumferential cross section at the front edges 30a and 35a of the reinforcing ribs 30 and 35 in the steam inflow portion between the reinforcing ribs 30 and 35. It is an angle formed by the flow direction of steam in the circumferential section, that is, the streamline direction in the circumferential section. 3 also shows an inflow angle α (see FIG. 11) at a circumferential angle indicating the circumferential position of the reinforcing rib when the above-described conventional nozzle box is used for comparison. Further, the inflow angle α shown in FIG. 3 is obtained by a three-dimensional thermal fluid analysis in a steady state using CFD (Computational Fluid Dynamics), similarly to the analysis shown in FIG.

  As shown in FIG. 3, it was found that the inflow angle α in the nozzle box according to the present invention has a smaller variation with respect to the circumferential direction angle than the inflow angle α in the nozzle box having the conventional configuration. Thereby, the occurrence of turbulence such as vortices at the front edge 35a of the reinforcing rib 35 is suppressed, and the pressure loss can be suppressed.

  As described above, according to the nozzle box 10 of the first embodiment, the front edge 35a side of the reinforcing rib 35 is inclined to correspond to the flow direction of the steam flowing between the reinforcing ribs. Flow separation and vortex generation at the leading edge 35a can be suppressed. Thereby, the steam can be smoothly guided to the first stage nozzle 213a, the pressure loss between the reinforcing ribs can be suppressed, and the efficiency of the steam turbine can be improved.

  In addition, the structure of the nozzle box 10 of 1st Embodiment is not restricted to an above-described structure. FIG. 4 is a diagram schematically illustrating another installation configuration of the reinforcing ribs 30 and 35 in the nozzle box 10 according to the first embodiment of the present invention. FIG. 5 is a view schematically showing another configuration of the reinforcing ribs 30 and 35 and the first stage nozzle 213a in the nozzle box 10 of the first embodiment according to the present invention. FIG. 6 is a view schematically showing still another installation configuration of the reinforcing ribs 30 and 35 in the nozzle box 10 of the first embodiment according to the present invention. 4 to 6 also show a circumferential cross-sectional development schematic diagram in which the circumferential cross-sections of the reinforcing ribs 30 and 35 and the first stage nozzle 213a in the nozzle box 10 are developed on a plane, similarly to FIG.

  The reinforcing ribs 30 and 35 shown in FIG. 2 are installed such that the rear edges 30b and 35b of the reinforcing ribs 30 and 35 are located at a predetermined interval on the upstream side between the first stage nozzles 213a. The configuration is not limited to this. For example, as shown in FIG. 4, the same number of reinforcing ribs 30 and 35 as the first stage nozzle 213a are disposed, and the rear edges 30b and 35b of the reinforcing ribs 30 and 35 are opposed to the front edge 230 of the first stage nozzle 213a. You may install so that it may become.

  By installing the reinforcing ribs 30 and 35 in this way, the rear edges 30b and 35b of the reinforcing ribs 30 and 35 and the front edge 230 of the first stage nozzle 213a face each other. Disturbances that occur immediately downstream of 30b and 35b are suppressed, and pressure loss can be reduced. Further, since the steam can be guided to the first stage nozzle 213a in a state in which the turbulence is suppressed, the pressure loss can be reduced also in the first stage nozzle 213a.

  Further, as shown in FIG. 5, the same number of reinforcing ribs 30 and 35 as the first stage nozzle 213a are arranged, and the rear edges 30b and 35b of the reinforcing ribs 30 and 35 are opposed to the front edge 230 of the first stage nozzle 213a. In addition, the distance between the rear edges 30b and 35b of the reinforcing ribs 30 and 35 and the front edge 230 of the first stage nozzle 213a may be set to be as small as possible. Also, the shape of the rear edges 30b, 35b of the reinforcing ribs 30, 35 and the front edge 230 of the first stage nozzle 213a, specifically, the shape of the surface of the rear edges 30b, 35b of the opposing reinforcing ribs 30, 35 and the first shape. The shape of the surface of the front edge 230 of the first-stage nozzle 213a may be the same, and a flow path through which steam can flow from the reinforcing ribs 30 and 35 toward the first-stage nozzle 213a without any step may be configured.

  By configuring the reinforcing ribs 30 and 35 and the first stage nozzle 213a in this manner, the steam flowing out from the rear edges 30b and 35b of the reinforcing ribs 30 and 35 smoothly flows into the first stage nozzle 213a. Therefore, the turbulence generated immediately downstream of the rear edges 30b and 35b of the reinforcing ribs 30 and 35 is suppressed, and the occurrence of turbulence when steam flows from the reinforcing ribs 30 and 35 to the first stage nozzle 213a is suppressed. The pressure loss can be reduced. Further, since the steam can be guided to the first stage nozzle 213a in a state in which the turbulence is suppressed, the pressure loss can be reduced also in the first stage nozzle 213a.

  Further, as shown in FIG. 6, in the configuration of the reinforcing ribs 30 and 35 shown in FIG. 4, for example, the reinforcing ribs 30 and 35 are arranged in the same number as the first stage nozzle 213 a without providing the same number of reinforcing ribs 30 and 35. It may be configured by thinning out every other. In this case as well, the rear edges 30b and 35b of the reinforcing ribs 30 and 35 are opposed to the front edge 230 of the first stage nozzle 213a, similarly to the configuration of the reinforcing ribs 30 and 35 shown in FIG. It is installed to become.

  By installing the reinforcing ribs 30 and 35 in this way, the rear edges 30b and 35b of the reinforcing ribs 30 and 35 and the front edge 230 of the first stage nozzle 213a face each other. Disturbances that occur immediately downstream of 30b and 35b are suppressed, and pressure loss can be reduced. Further, since the steam can be guided to the first stage nozzle 213a in a state in which the turbulence is suppressed, the pressure loss can be reduced also in the first stage nozzle 213a. Furthermore, by reducing the number of the reinforcing ribs 30 and 35, the cross-sectional area of the flow path between the reinforcing ribs can be increased, and the pressure loss when steam flows between the reinforcing ribs can be reduced.

(Nozzle box of the second embodiment)
FIG. 7 is a diagram schematically showing the installation configuration of the reinforcing ribs 30 and 35 and the first stage nozzle 213a in the nozzle box 10 according to the second embodiment of the present invention. 7 also shows a circumferential cross-sectional development schematic diagram in which the circumferential cross-sections of the reinforcing ribs 30 and 35 and the first stage nozzle 213a in the nozzle box 10 are developed on a plane, as in FIG. Moreover, the same code | symbol is attached | subjected to the component same as the structure of the nozzle box 10 of 1st Embodiment, and the overlapping description is abbreviate | omitted or simplified.

  Here, only the shape of the reinforcing rib 35 having a configuration in which the front edge 35a side is inclined so that the extending direction of the center line 36 in the circumferential section of the front edge 35a is parallel to the flow direction of the steam is the first described above. Therefore, the configuration of the reinforcing rib 35 will be mainly described.

  The steam that has spread to the steam flow path 20 of the nozzle box 10 has an inflow angle distribution with respect to the circumferential direction angle of the reinforcing rib, and in other words, the height direction of the reinforcing rib, that is, the radial direction of the reinforcing rib (that is, FIG. May also have an inflow angle distribution with respect to the front and back direction of the paper. The reinforcing rib 35 of the second embodiment has a configuration that can be applied even when the inflow angle distribution of steam is provided in the height direction of the reinforcing rib.

  In the reinforcing rib 35 shown in FIG. 7, the steam flow in the root portion 35 c that is the inner diameter side of the reinforcing rib 35 flows in parallel to the turbine rotor shaft, and in the tip portion 35 d that is the outer diameter side of the reinforcing rib 35. The steam flow is assumed to flow in a direction shifted by a predetermined angle with respect to the axial direction of the turbine rotor.

  Specifically, the shape of the root portion 35c of the reinforcing rib 35 has the same shape as that of the reinforcing rib 30, and the center line 36a in the circumferential cross section of the root portion 35c is a straight line, and the center line 36a and the turbine rotor shaft And become parallel. On the other hand, the leading edge 35a is gradually inclined from the root portion 35c in the height direction, that is, in the radial direction (outward direction) so as to be parallel to the steam flow direction, and the reinforcing rib 35 is formed in the circumferential section of the tip portion 35d. The extending direction of the center line 36b at the front edge 35a of the reinforcing rib 35 is configured to be parallel to the flow direction of the steam Sb. The center line 36b of the reinforcing rib 35 in the circumferential cross section at the tip 35d is a curve.

  Since the steam flowing between the reinforcing ribs having such a configuration flows in parallel to the turbine rotor shaft in the vicinity of the root portion 35c of the reinforcing rib 35, the steam flows between the reinforcing ribs in parallel to the center line 36a. It flows into 213a. On the other hand, in the vicinity of the front end portion 35d of the reinforcing rib 35, the steam Sb flowing in a direction deviated by a predetermined angle with respect to the turbine rotor axial direction is formed into a reinforcing rib that is configured so that the front edge 35a side is inclined corresponding to the flowing direction. And flows into the first stage nozzle 213a.

  By installing the reinforcing ribs 30 and 35 in this manner, even if the steam spreading in the steam flow path 20 of the nozzle box 10 has an inflow angle distribution in the height direction of the reinforcing ribs, that is, in the radial direction, the reinforcement is performed. Corresponding to the flow direction of the steam flowing between the ribs, the front edge 35a side of the reinforcing rib 35 is tilted to prevent flow separation and vortex generation at the front edge 35a. Thus, the steam can be smoothly guided to the first stage nozzle 213a, the pressure loss between the reinforcing ribs can be suppressed, and the efficiency of the steam turbine can be improved.

  Here, an example of the configuration in which the tip end side is inclined in the reinforcing rib 35 is shown, but depending on the inflow angle distribution of the steam flowing into the reinforcing rib 35, the root side may be inclined. In other words, the shape of the front edge 35a of the reinforcing rib 35 is appropriately set based on the distribution angle distribution of steam. Further, here, an example (see FIG. 2) in which the rear edges 30b and 35b of the reinforcing ribs 30 and 35 are disposed at a predetermined interval on the upstream side between the first stage nozzles 213a has been described. However, the structure which concerns on 2nd Embodiment is applicable also to the structure of the reinforcement ribs 30 and 35 shown by FIGS. 4-6, for example.

  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.

The figure which showed the cross section in the upper half casing part of the steam turbine provided with the nozzle box which concerns on this invention. The figure which showed typically the installation structure of the reinforcement rib in the nozzle box of 1st Embodiment which concerns on this invention, and a 1st step | paragraph nozzle. The figure which showed inflow angle (alpha) in the circumferential direction angle which shows the position of the circumferential direction of a reinforcement rib. The figure which showed typically the other installation structure of the reinforcement rib in the nozzle box of 1st Embodiment which concerns on this invention. The figure which showed typically the other structure of the reinforcement rib in the nozzle box of 1st Embodiment which concerns on this invention, and a 1st step | paragraph nozzle. The figure which showed typically the further installation structure of the reinforcement rib in the nozzle box of 1st Embodiment which concerns on this invention. The figure which showed typically the installation structure of the reinforcement rib in the nozzle box of the 2nd Embodiment which concerns on this invention, and a 1st step | paragraph nozzle. The figure when the cross section perpendicular | vertical to the turbine rotor of the conventional nozzle box is seen from the 1st stage nozzle side. The figure which shows the AA cross section of FIG. The figure which showed typically the flow of the vapor | steam when the vapor | steam introduce | transduced into the space of the nozzle box from the vapor | steam inlet pipe flows in between reinforcement ribs. The figure which showed inflow angle (alpha) in the circumferential direction angle which shows the position of the circumferential direction of a reinforcement rib. The figure when the cross section perpendicular | vertical to the turbine rotor of the conventional nozzle box provided with the structure which introduce | transduces a steam into a nozzle box by two steam inlet pipes is seen from the 1st stage nozzle side. The figure which showed the inflow angle (alpha) in the circumferential direction angle | corner which shows the position of the circumferential direction of a reinforcement rib in the shape of the nozzle box shown by FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Nozzle box, 20 ... Steam flow path, 30, 35 ... Reinforcement rib, 30a, 35a, 230 ... Front edge, 30b, 35b ... Rear edge, 31, 36, 231 ... Center line, 200 ... Steam turbine, 210 ... Inner casing, 211 ... outer casing, 212 ... turbine rotor, 213 ... nozzle, 213a ... first stage nozzle, 214 ... moving blade, 214a ... first stage moving blade, 220 ... steam inlet pipe, Sa, Sb ... steam.

Claims (6)

A steam turbine nozzle box configured to guide steam introduced from a steam inlet pipe and flowing into a steam flow path extending in a circumferential direction to a first stage nozzle between reinforcing ribs;
The steam turbine nozzle box, wherein at least one of the reinforcing ribs installed upstream of the first stage nozzle is installed at an angle different from that of the other reinforcing ribs.   2. The nozzle box for a steam turbine according to claim 1, wherein, in the at least one reinforcing rib, an angle with respect to a turbine rotor axial direction of a circumferential cross section of a front edge portion into which steam flows is different in a radial direction.   The nozzle box for a steam turbine according to claim 1 or 2, wherein an installation angle of the reinforcing rib is set based on a flow direction of steam flowing between the reinforcing ribs.   4. The steam turbine nozzle box according to claim 1, wherein the number of the reinforcing ribs to be installed is the same as the number of the first stage nozzles. 5.   5. The reinforcing rib is installed such that a rear edge portion where steam flows out of at least one of the reinforcing ribs is located at a position facing a front edge of the first stage nozzle. The nozzle box for steam turbines of any one of these. A steam turbine including a nozzle box configured to guide steam introduced from a steam inlet pipe and flowing into a steam flow path extending in a circumferential direction to the first stage nozzle through the reinforcing ribs;
The steam turbine according to any one of claims 1 to 5, wherein the nozzle box is a nozzle box for a steam turbine.

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