JP2001090506A - Stationary blade and stream turbine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce degradation of turbine performance caused by a humid loss and erosion of a moving blade tip positioned in the downstream, by effectively capturing drain generated in stream by a stationary blade to discharge the drain. SOLUTION: This steam turbine is provided with the stationary blade 1 formed inside an enlarged flow passage through which steam passes, an outer ring 3 for fixing a tip of the stationary blade 1, an inner ring 4 for fixing a root end of the stationary blade 1, a moving blade 2 arranged in a down stream of the stationary blade 1, of which the root end is fixed to a rotary shaft, drain discharge grooves 7, 8 formed in a surface of a root part of the stationary blade 1 to be extend along a substantially blade-longitudinal direction of the blade 1, and drain collectors 9, 10 formed inside the inner ring 4 to be communicated with the grooves 7, 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stationary blade arranged in a steam passage of a steam turbine and a steam turbine provided with the stationary blade.

[0002]

2. Description of the Related Art In a large-capacity steam turbine, since a volume change of a fluid is large with respect to a pressure change in a low-pressure section, a steam flow path generally becomes a rapid expansion flow path. The turbine stage provided in such an enlarged flow path must be composed of stationary blades and moving blades that match the flow path, but steam (expanding fluid) passing through these blades becomes a three-dimensional flow, It becomes a very complicated flow. Furthermore, in the latter half of the low-pressure paragraph, drain is generated in the steam that expands through the stationary vanes serving as nozzles, and the wet loss due to this drain accounts for about 30% of the total internal loss in each paragraph. This is a major cause of efficiency reduction. In addition, the drain scattered from the trailing edge of the stationary blade toward the downstream side causes erosion of the tip portion of the rotor blade. From the above, reducing the wet loss is a major factor in improving turbine efficiency.

[0003] Various studies have been made on improving the flow state of the inflation fluid in the above-described annular expansion channel and removing drain generated inside the expansion channel.

As described in Japanese Patent Application Laid-Open No. 7-19004, the improvement of the flow condition of the expanding fluid in the enlarged flow passage is performed by removing the tip of the vane 1 in the annular enlarged flow passage. The blade is inclined or curved in the rotation direction (+ side) with respect to the radial line, and the axial distance between the stationary blade and the moving blade in the axial direction of the turbine is larger on the outer side than on the radially inner side. Some are arranged so as to be inclined or curved.

As for the removal of the drain generated inside the enlarged flow passage, a slit is provided on the vane blade surface and the inside of the hollow vane is removed as described in JP-A-6-173607. A device that removes drain to the outside of the flow path via a passage, or as described in JP-A-6-123202, JP-A-8-61006, a junction between a stationary blade and a flow path outer peripheral wall or There is one in which a drain guide groove and a drain capture hole are formed on the outer peripheral wall between the stationary blades.

[0006]

SUMMARY OF THE INVENTION It has been found that the above stage device and drain removal device have a certain effect in improving the efficiency in the low pressure stage of the steam turbine and preventing erosion at the blade tip. ing.

However, with respect to the paragraph device described in Japanese Patent Application Laid-Open No. 7-19004, the three-dimensional flow of steam is optimized even in the enlarged flow passage, the fluid loss is reduced, and the turbine efficiency is improved. However, it is not considered to reduce the wet loss due to the generation of the drain and the erosion of the rotor blade located on the downstream side.

In addition, a drain removal device provided with a drain removal slit on the surface of the stationary blade, a drain guide groove or a drain capture hole is formed on the joint between the stationary blade and the outer peripheral wall of the flow passage or on the outer peripheral wall between the stationary blades. With regard to the drain removal device installed, only removal of drain flowing on the surface of the stationary vane blade and on the outer peripheral wall is considered. The drain removal method including the steam flow on the inner circumferential side of the road, the structure in which a drain recovery groove, a slit, and the like are provided at the base portion of the stationary blade, and the like are not considered.

According to the present invention, the drain generated in the steam is efficiently captured by the stationary vanes, and the drain is eliminated, whereby
It is an object of the present invention to provide a stationary blade and a steam turbine that can reduce turbine performance deterioration due to wet loss and erosion of a moving blade tip located downstream.

[0010]

In order to achieve the above object, a vane according to the present invention is provided with a groove extending substantially in a blade length direction on a surface of a root portion thereof. Preferably, the groove is formed on at least one of the front edge on the convex side or the rear edge on the concave side.

Alternatively, in order to achieve the above object, a steam turbine according to the present invention comprises: a stationary blade formed in an enlarged flow passage through which steam passes; an outer ring for fixing a tip of the stationary blade; An inner ring that fixes the root end of the stationary blade, a moving blade that is disposed downstream of the stationary blade and whose root end is fixed to the rotating shaft, and a substantially blade-length direction of the stationary blade that is formed on the surface of the root portion of the stationary blade. And a space formed in the inner race and communicating with the groove. And preferably, the groove is
It is formed so as to be inclined toward the downstream side of the flow of the steam as it goes from the tip side to the root side of the vane.

Alternatively, in order to achieve the above object, a steam turbine according to the present invention comprises a casing having an enlarged flow passage through which an expansion fluid passes, and a fixedly held wall of the enlarged flow passage.
A stationary blade arranged to extend in the radial direction, and a moving blade arranged downstream of the stationary blade and rotating together with the rotating shaft, wherein the stationary blade is arranged so as to be inclined in the rotating direction of the rotating shaft. The axial distance between the stationary blade and the moving blade is formed to be larger on the outer side than on the radially inner side, and a drain capture device is provided on a downstream outer peripheral wall of the stationary blade, and A drain trapping groove is provided on the inlet abdominal wing surface and the outlet dorsal wing surface at the part and the tip part, and a drain collection chamber communicating with the drain trapping groove is provided on the outer peripheral portion and the inner peripheral portion of the stationary blade. .

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on embodiments shown in the drawings. FIG. 13 shows a main part of the present invention.

The steam turbine is mainly formed of a turbine casing 20 and a rotating body 21. The rotating body 21 has a turbine shaft 22 and a root end fixed to the turbine shaft 22, and rotates together with the turbine shaft 22. And a moving blade 2.

The stationary blade 1 is disposed upstream of the moving blade 2 in the flow direction of steam, and is supported by the casing 20. The stationary blade 1 and the moving blade 2 are arranged in an enlarged flow passage 23 formed between the casing 20 and the turbine shaft 22.

In this configuration, the steam supplied to the inside of the casing 20 flows while expanding through the enlarged flow passage 23 from the center to the both ends in the figure, and is moved by the steam ejected through the stationary blade 1 by the steam. 2 is operated to rotate the rotating body 21.

FIG. 1 shows the details of the upper half part of the paragraph device composed of the stationary blade 1 and the moving blade 2. In this paragraph, there are an outer ring 3 held by the casing 20 and having an inclination angle θ on the inner wall surface, and an inner ring 4 holding the stationary blade 1.
The outer race 3 and the inner race 4 form an enlarged flow passage 23. A drain capture device 5 is formed immediately before the leading edge of the bucket 2 on the outer peripheral wall surface of the enlarged flow passage 23.

The stationary blade 1 arranged in the enlarged flow passage
Are radially arranged around the turbine shaft 22. The stationary blade 1 is provided with an outer race 3 forming an enlarged flow passage.
And the inner ring 4 at both ends thereof. That is, the outer ring 3 fixes the tip of the stationary blade 1, and the inner ring 4 fixes the root end of the stationary blade 1. A trailing edge 1a is disposed at an angle ε inclined upstream of the radial upright line r in the axial direction.
Further, a drain discharge groove 7 is formed on the wing surface of the stationary blade 1 on the outer peripheral side and the inner peripheral wall side on the abdomen side (concave side) of the leading edge of the stationary blade, and on the back side (convex side) of the trailing edge of the stationary blade. In the same manner, the drain discharge groove 8 is formed in the same manner. The trailing edge 1a of the stationary blade 1 refers to the downstream end of the steam flow in the stationary blade 1,
The leading edge of the stationary blade 1 refers to the upstream end of the steam flow in the stationary blade 1.

A moving blade 2 is planted on the rotating disk 6 on the downstream side of the stationary blade 1. An axial direction between a leading edge 2 a of the moving blade 2 and a trailing edge 1 a of the stationary blade 1 is set. The distance δ is arranged so that the distance gradually increases from the root side to the tip side, that is, from the radially inner side to the outer side (δt> δr).

Further, the stationary blade 1 is also arranged inclined in the circumferential direction. FIG. 2 is a view of the steam flow viewed from the downstream side in order to clarify the inclined state.
In the center of the blade length, the trailing edge 1a is arranged at an angle φ in the rotation direction (arrow 31) of the axis with respect to the radial upright line r.

As described above, the stationary blade 1 is held by the outer ring 3 and the inner ring 4 while being inclined in the circumferential direction and the axial direction. This inclination angle φ is equal to that of the outer ring 3 in a general steam turbine. Although it depends on the divergence angle θ, it is preferable to form it so that φ = 5 ° to 20 ° at the center of the blade length, and ε is set to ε = 3 ° to 10 ° and about 1/2 of the circumferential inclination angle. Then, a good flow can be obtained.

A drain catching device 5 is formed on the outer peripheral wall of the enlarged flow passage immediately before the leading edge of the moving blade 2. A drain discharge groove 7 is formed on the front edge abdominal side, and a drain discharge groove 8 is formed on the rear side of the stationary blade rear edge. Both the drain discharge groove 7 and the drain discharge groove 8 are formed substantially in the blade length direction of the stationary blade 1. A drain collection device 9 is provided at a fixed portion between the stationary blade 1 and the inner ring 4 on the inner peripheral side of the drain discharge groove 7, and a drain supplementary device is provided at a fixed portion between the stationary blade 1 and the outer ring 3 on the outer peripheral side of the drain discharge groove 8. And a drain passage communicating with the drain collection chambers 11 and 12 formed in a ring shape on the outer circumference and the inner circumference side of the flow path. The drain captured in the drain discharge grooves 7 and 8 is guided to the drain collection chambers 11 and 12 through this passage.

Further, as shown in FIG. 3, the drain collected in the drain collection chamber 12 on the inner peripheral side of the flow path is one of the lowermost vanes 1 radially arranged around the turbine axis. The liquid is collected in the drain collection chamber 11 on the outer peripheral side of the flow passage through the drain passage 13 formed inside. In this case, when the drain passage is provided in the stationary blade 1 located at the lowermost portion, the effect of gravity can be obtained in addition to the differential pressure, so that a high drain discharge effect can be obtained.
This drain passage is as shown in FIG. 15 in a sectional view of the stationary blade, but a plurality of drain passages 13 may be provided or at least one having a sectional area sufficient to obtain the effect.

These drain catchers are in direct or indirect communication with a low-pressure part such as a condenser (not shown) having a lower pressure than the opening surface, and drains on the enlarged flow passage downstream of the stationary blade 1. The drain flowing on the root and the tip side on the blade surface is sucked by the drain capturing device and discharged to the outside of the flow path. As a specific example of the drain discharge method to the outside of the flow path, as shown in FIG. 3, the drain capture device 5 and the outer-side drain collection chamber 11 are connected to each other. There is a method of discharging the drain to the condenser by providing a drain discharge hole 14 communicating with the condenser. In addition, there is a method of separately discharging the drain from the drain capturing device 5 and the outer peripheral side drain collection chamber 11 to the condenser. In any case, since the condenser side has a lower pressure than the drain capture device 5 and the drain collection chamber 11, the drain is discharged from the respective pressure differences to the condenser through the drain discharge holes 14. Will be discharged.

FIG. 4 is a cross-sectional view taken along the line CC in FIGS. 1 and 3 as viewed from the downstream side in the flow direction. As shown in FIG. 4, the ring-shaped inner drain collection chamber 11 is supplemented. The collected drain is guided to the outer peripheral side drain collection chamber 12 through the drain passage 13 provided in the lowermost stationary blade, and is discharged from the drain discharge hole 14 to the condenser.

A drain discharge device is formed not only as shown in FIG. 1 but also as shown in FIG. 11, a groove is formed on the entire outer peripheral wall on the downstream side of the stationary blade 1, and a drain discharge hole is formed in the groove. A plurality of grooves and a drain discharge hole may be formed in the outer peripheral wall on the downstream side of the stationary blade 1 as shown in FIG. Further, as shown in FIG. 14, the drain discharge groove 7 is formed in the outer periphery and the inner peripheral wall of the stationary blade in the front side of the leading edge of the stationary blade, and the drain discharge groove 8 is formed in the outer periphery of the stationary blade and in the rear side of the rear edge in the inner peripheral wall. Has been established.

Here, FIG. 9 shows the flow state of the fluid in the conventional stationary blade structure shown in FIG. 8 by streamlines. In this case, the state is located at the tip end side (upper side in the figure) of the stationary blade 1. A low flow rate portion (A1 portion) is generated and the flow does not follow the spread shape of the outer ring 3, and a sharp three-dimensional flow is generated at the tip of the bucket. A vortex may be generated in such a portion, and it becomes difficult to efficiently attach the drain in the steam to the outer peripheral wall surface.

FIG. 10 shows, by streamlines, the flow state of the fluid in the stationary blade structure in which the stationary blades are arranged inclined in the circumferential direction and the axial direction. In this case, the fluid flows toward the outer peripheral wall. , The axial distance (gap) between the stationary blade and the moving blade is increased, and the effect of the centrifugal force caused by the swirling flow flowing out of the stationary blade smoothly changes the inward flow to the outward flow along the enlarged wall. As a result, it is possible to suppress the generation of the rapid three-dimensional flow at the tip of the bucket as described above.

On the other hand, FIG. 5 shows the distribution of the wetness in the steam in the blade length direction. It can be seen from FIG. 5 that the drain is concentrated from the center to the tip of the blade. Therefore, if the drain that flows out can be attached to the outer peripheral wall over a wider area radially inward from the tip of the stationary blade 1 as a starting point, a larger amount of drain in the steam can be removed, and the turbine stage Efficiency can be improved.

In the flow field as described above, the behavior of water droplets, which are wet components in the steam flow, will be described as follows. In FIG. 6 (a), the stationary blade 1 'of FIG. 1 is viewed from the radially outer circumferential side perpendicular to the turbine axis, and the stationary blade 1' is shown. It flows out in the axial direction by an angle α from the circumferential direction in the turbine axial direction.
Therefore, at the exit of the stationary blade, there is a state in which there is a circumferential speed component (swirl component) much larger than the speed component in the turbine axial direction. The water droplet is subjected to the action of the centrifugal force due to this swirling component. As a result, the trajectory of the water droplet is not concentric (32) shown in FIG. It becomes a trajectory like
It will adhere to the outer peripheral wall. This is shown in relation to the distance δ between the stationary blade outlet end and the rotor blade inlet end. In FIG. 6, water droplets flowing out from the point b of the stationary blade length L are formed between the stationary blade outlet end and the rotor blade inlet end. It will adhere to the outer peripheral wall at the position of the distance δ.
As is clear from this, the water droplet in the range B on the tip side from the point b adheres to the outer peripheral wall before moving the distance δ.
FIG. 7 shows the relationship between the water droplets adhering to the outer peripheral wall and the range B in the vane blade length direction. As is clear from this figure, as the distance δ between the stationary blade outlet end and the rotor blade inlet end is larger, the range B from the tip becomes wider, and many parts of the blade length direction wetness distribution shown in FIG. It can be captured by attaching to the outer peripheral wall.

Therefore, if the trailing edge 1a of the stationary blade 1 is inclined toward the upstream side in the axial direction at an angle ε, the drain flowing out from the trailing edge 1a of the stationary blade is different from the conventional stationary blade which is not inclined. As a result, the water flows out from the upstream side, so that a wider range of drain can be attached to the outer peripheral wall from the blade tip toward the blade root. Furthermore, if the stationary blade is arranged in such a shape, the area of the outer peripheral wall to which the drain adheres on the downstream side from the trailing edge 1a of the stationary blade can be increased, and a larger amount of drain can be eliminated. Becomes possible. Since these drains adhere and flow on the outer peripheral wall,
The drain can be efficiently removed by installing the drain discharge device immediately before the blade leading edge 2a on the outer peripheral wall.

The drain generated on the inner peripheral side of the center of the flow path does not adhere to the outer peripheral wall and is carried over to the next paragraph, but moves to the outer peripheral side by the above-described effect. On the other hand, the drain generated in the vicinity of the inner peripheral wall does not move much to the outer peripheral side of the flow path due to the shape of the streamline in FIG. 9 and the small distance between the exit end of the stationary blade and the entrance end of the moving blade. From the above, the drain that is generated on the inner peripheral side of the flow path and cannot be discharged even by the paragraph apparatus having the above-described structure and flows into the next paragraph moves from the central part of the flow path to the outer peripheral side. Things near the peripheral wall will flow in without moving much.

However, the drain which cannot be discharged as described above and flows into the next paragraph is removed by forming a drain discharge groove 7 on the outer peripheral and inner peripheral wall sides of the tip portion of the stationary blade 1 which is the entrance of the paragraph. be able to. This drain discharge groove 7
Is because the drain in the steam flowing out of the trailing edge of the rotor blade in the previous paragraph is relatively concentrated on the ventral side of the leading edge of the stator blade in the next paragraph,
By piercing on the ventral side of the stationary blade, the discharge effect can be enhanced. In addition, since the drain discharge groove 7 or the drain discharge groove 8 is formed on the surface of the stationary blade, the structure of the stationary blade is simpler and the manufacturing process is simpler than in the case where the interior of the stationary blade is hollow and steam is sucked from the surface. Is easy.

Similarly, by forming a drain discharge groove 8 also at the trailing edge of the stationary blade, the drain generated in the steam passing through the stationary blade 1 while expanding and discharging on the stationary blade surface can be discharged. Can be. At the trailing edge of the stationary blade, the drain is concentrated on the back side of the stationary blade. Therefore, it is better to form the drain discharge groove 8 on the back side in this portion. And on the inner peripheral wall side.

According to the present embodiment, the stationary blades disposed in the enlarged flow passage of the low-pressure part of the steam turbine in which the drain is generated in the steam are arranged to be inclined in the rotating direction, and the shafts of the stationary blades and the moving blades are arranged. The direction distance is formed so as to increase from the root to the tip, and a drain discharge device is provided immediately before the leading edge of the rotor blade on the outer peripheral wall to optimize the three-dimensional flow in this enlarged flow passage. Thus, the amount of drain adhering to the outer peripheral wall on the downstream side of the stationary blade can be increased. In addition, a drain discharge groove is provided on the ventral side where drain is likely to concentrate at the leading edge of the vane, which corresponds to the entrance of the paragraph. By providing the groove, the drain discharge effect can be enhanced. Furthermore, erosion of the blade tip by water droplets can also be reduced, which leads to a reduction in wet loss generated inside the turbine, and a highly efficient steam turbine stage device can be obtained.

Further, it is preferable that the shape of the drain discharge groove 7 is inclined downstream as it goes from the tip side (outer peripheral side) to the root side (inner peripheral side) of the stationary blade. This allows
The drain on the surface of the stationary blade can be efficiently guided to the drain collection device by utilizing the flow of steam. Further, since the flow of steam is easily disturbed in the vicinity of the inner peripheral wall, the shape of the drain discharge groove 7 becomes deeper from the tip side (outer peripheral side) to the root side (inner peripheral side) of the stationary blade. It is preferable to reduce the size or the size of the uneven portion. Thus, it is possible to suppress an increase in turbulence of the steam flow near the inner peripheral wall due to the formation of the drain discharge groove 7.

In the above description, when the stationary blade 1 is inclined, it has been described that the stationary blade 1 is inclined linearly both in the circumferential direction and in the axial direction. However, the inclination is not always required. Either the circumferential direction or the axial direction may be curvedly inclined, and the other one may be linearly inclined, or both the circumferential direction and the axial direction may be curvedly inclined. In the paragraph apparatus described above, it is clear that the amount of improvement in paragraph efficiency due to the reduction in wet loss is improved by about 1% on average as compared with the conventional paragraph apparatus.

[0038]

According to the present invention, the drain formed in the steam is efficiently captured by the stationary blade by the groove formed at the root portion of the stationary blade, and the drain is removed. This has the effect of reducing erosion at the blade tip located downstream.

[Brief description of the drawings]

FIG. 1 is a vertical sectional side view of a paragraph device of a steam turbine of the present invention.

FIG. 2 is a front view of a stationary blade according to the present invention.

FIG. 3 is a vertical sectional side view of a stationary blade located at the lowermost part of the steam turbine of the present invention.

FIG. 4 is a sectional view taken along the line CC in FIGS. 1 and 3;

FIG. 5 is a characteristic diagram showing a wetness distribution in a blade length direction at a stator blade outlet portion of the steam turbine of the present invention.

FIG. 6 is a front view of the stage device of the steam turbine of the present invention viewed from the downstream side and a projected view of a stationary blade cascade.

FIG. 7 is a characteristic diagram showing a relationship between a distance between a trailing edge of a stationary blade and a leading edge of a moving blade and a drain adhesion range from the tip of the stationary blade.

FIG. 8 is a vertical side view of a conventional steam turbine paragraph device.

FIG. 9 is a vertical sectional side view showing a flow state of a working fluid in a conventional steam turbine stage device.

FIG. 10 is a vertical sectional side view showing a flow state of a working fluid in the paragraph device of the steam turbine of the present invention.

FIG. 11 is a cross-sectional side view of another drain discharge device of the steam turbine of the present invention.

FIG. 12 is a cross-sectional side view of another drain discharge device of the steam turbine of the present invention.

FIG. 13 is a vertical sectional side view of the steam turbine of the present invention.

FIG. 14 is a sectional view showing a drain discharge groove of the stationary blade of the present invention.

FIG. 15 is a sectional view of a lowermost stationary blade of the steam turbine of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Static blade, 2 ... Moving blade, 3 ... Outer ring, 4 ... Inner ring, 5 ... Drain capture device, 6 ... Rotating disk, 7, 8 ... Drain discharge groove,
9, 10 drain collecting device, 11, 12 drain collecting chamber, 13 drain passage, 14 drain discharge hole, 20 casing, 21 rotating body, 22 turbine shaft, 23 expanding flow passage, φ ... Slope angle in the circumferential direction, ε ... Slope angle in the axial direction.

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Yoshiaki Yamazaki 7-2-1, Omika-cho, Hitachi City, Ibaraki Prefecture F-term in Hitachi, Ltd. Electric Power and Electrical Development Laboratory 3G002 GA08 GA09 GA16 GA17 GA04 GB05 GB05

Claims (5)

[Claims] 1. A stationary blade arranged in a steam flow path of a steam turbine, wherein a groove extending substantially in a blade length direction is provided on a root surface of the stationary blade. 2. The vane according to claim 1, wherein the groove is formed on at least one of a leading edge on a concave surface and a trailing edge on a convex surface. 3. A stationary blade formed in an enlarged flow passage through which steam passes, an outer ring for fixing a tip of the stationary blade, an inner ring for fixing a root end of the stationary blade, and a downstream side of the stationary blade. A steam turbine having a rotor blade whose root end is fixed to a rotating shaft, the groove being formed on the root surface of the stator blade and extending substantially in the blade length direction of the stator blade; And a space formed to communicate with the groove. 4. The steam according to claim 3, wherein the groove is formed so as to be inclined toward the downstream side of the flow of the steam as going from the tip side to the root side of the stationary blade. Turbine. 5. A casing having an enlarged flow passage through which an inflation fluid passes, a stationary blade fixed and held on a wall of the enlarged flow passage and arranged in a radial direction, and a downstream side of the stationary blade. And a moving blade that rotates together with the rotating shaft, wherein the stationary blade is disposed so as to be inclined in the rotation direction of the rotating shaft, and the axial distance between the stationary blade and the moving blade is set in the radial direction. A drain capturing device provided on the outer peripheral wall on the downstream side of the stationary blade, the drain capturing device being formed so as to be larger on the outer side than on the inner side; A drain capture groove provided on the side wing surface,
A steam turbine, comprising: a drain collection chamber provided on an outer peripheral portion and an inner peripheral portion of the stationary blade and communicating with the drain capturing groove.