JPH1037703A - Turbine nozzle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a turbine nozzle wherein a nozzle vane is improved so that a main stream is more gathered at an intermediate part of the nozzle vane which is formed in a protruded bent line along a belly side, and the main stream positively and surely catches water drops which is generated in the midst of passing through the nozzle vane. SOLUTION: A nozzle vane 21 is arranged in a row in a circumferential direction in a ring-like flow channel 20 which is formed between a diaphragm outer ring 18 and a diaphragm outer ring 19. Both ends of each nozzle vane 21 are connected to the diaphragm outer ring 18 and the diaphragm inner ring 19. Besides, a vane height direction of the nozzle vane 21 is formed in a protruded bent surface CS toward the belly side, and an inclined flow wall 25 is formed at least on the side of a chip part 23 and the side of the root part 24.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a turbine nozzle, and more particularly to a turbine nozzle, which effectively suppresses a secondary flow loss caused by a secondary flow vortex generated in a flow path of a nozzle blade, thereby improving blade efficiency.
The present invention also relates to a turbine nozzle having improved reliability.

[0002]

2. Description of the Related Art In general, a turbine causes a high-temperature and high-pressure working fluid (hereinafter referred to as a main flow) to perform expansion work in a turbine stage in which a nozzle blade and a moving blade are combined, and converts thermal energy of the main flow into rotational energy. The conversion is performed, and one example is a configuration shown in FIG.

The turbine stage 1 includes a nozzle blade 6 arranged in a line along the circumferential direction of a turbine shaft 5 in an annular flow path 4 formed between a diaphragm outer ring 2 and a diaphragm inner ring 3, and a nozzle blade 6. The blades 7 are arranged opposite to each other on the downstream side, and are converted into velocity energy when the main flow 8 passes through the cascade of the nozzle blades 6. Energy (torque) is generated. In addition, the moving blade 7 has a tip (wing tip).
9 is provided with a band-shaped shroud 10 along the cascade.
To prevent leakage outside the cascade.

As described above, the conventional turbine is a so-called axial flow type in which the turbine stage 1 is formed by combining the nozzle blades 6 and the moving blades 7 and the turbine stage 1 is arranged in a plurality of stages along the turbine shaft 5. It has become.

[0005] The axial flow type turbine is suitable for a large output, and is designed to convert all the heat energy of the main flow 8 into rotational energy. When the velocity energy is obtained through the passage 6, various losses occur, and these losses decrease the efficiency of the nozzle blades, and cause all the heat energy of the main stream 8 to be unable to be converted into rotational energy. I have.

The losses that lower the turbine stage 1 include an airfoil loss, a leakage loss in which the main flow 8 leaks from a gap formed by the boundary layer in the annular flow path 4 between the rotating portion and the stationary portion, and a main flow 8 is an annular flow. When passing through the path 4, there is a secondary flow loss associated with a secondary flow flowing from the nozzle blade 6 to the adjacent nozzle blade 6 across the main flow 8. Especially in turbine nozzles with relatively low blade height and small aspect ratio, secondary flow loss is a bottleneck in improving nozzle blade efficiency.
Reducing the secondary flow loss is a factor that dramatically improves nozzle blade efficiency.

FIG. 6 is a view showing a mechanism of generating a secondary flow vortex which causes secondary flow loss.

Most of the main stream 8 having an arbitrary velocity distribution 11 flows in a direction along the shape of the blade, which is obstructed by the nozzle blade 6, but a part of the main stream 8 collides with the leading edge 12 of the nozzle blade 6. Then, the nozzle blade 6 is divided into a back side 14 and a ventral side 15 and flows as a vortex 13.

However, when the main flow 8 passes through the annular flow path 4, a pressure gradient is generated between the ventral side 15 and the back side 14 of the adjacent nozzle blade 6, with the ventral side 15 being high and the back side 14 being low. Therefore, a secondary flow from the ventral side 15 to the adjacent dorsal side 14 occurs. For this reason, among the vortices 13 generated by the collision at the leading edge 12 of the nozzle blade 6, the vortices 13 particularly toward the ventral side 15 are:
Since the direction of the swirl coincides with the direction of the secondary flow, it grows and develops greatly in the annular flow path 4 to become the secondary flow vortex 13a.
The secondary flow vortex 13a is one of the factors that degrade the performance of the turbine stage 1. The vortex 13 toward the back side 14
Is absorbed by the secondary flow vortex 13a when reaching the trailing edge 16.

Thus, in the conventional turbine nozzle,
Due to the generation and growth of the secondary flow vortex 13a, the streamline fluctuates while the main flow 8 passes through the nozzle blade 6, and a part of the energy is lost, thereby dramatically improving the nozzle blade efficiency. Was a factor that could not be done.

Recently, many turbine nozzles have been proposed to reduce the secondary flow loss caused by the secondary flow vortex 13a generated in the annular passage 4 of the nozzle blade 6.

For example, in the turbine nozzle shown in FIG. 7, a rear edge 16 of the nozzle blade 6 having both ends fixedly provided by the outer diaphragm ring 2 and the inner diaphragm ring 3 is formed in a protruding curved surface in the direction of the ventral side 15. The secondary flow vortex 13a generated around the wall surfaces of the diaphragm outer ring 2 and the diaphragm inner ring 3
(Japanese Patent Application Laid-Open No. 1-169090), or as shown in FIG.
A curved flow path 17 is formed at the connection end between the diaphragm outer ring 2 and the diaphragm inner ring 3 on the back side 14 of the nozzle blade 6, and the secondary flow vortex 1 is formed by utilizing the pressing force of the curved flow path 17.
There is one that reduces 3a (JP-A-56-118502).

[0013]

In the conventional turbine nozzle shown in FIG. 8, since the curved flow path 17 is formed at the connection end of the diaphragm inner ring 3 on the back side 14 of the nozzle blade 6, the turbulence of the main flow 8 is reduced. Although the flow line is relatively small and its streamline is also relatively uniform, the antinode of the nozzle blade 6 because the curved flow path 17 is stopped only at the root portion (blade root portion) of the back side 14 of the nozzle blade 6. The effect of the pressure (static pressure) from the side 15 to the back side 14 of the adjacent nozzle blade 6 is still high, and it cannot be expected to suppress the secondary flow vortex 13a accompanying the secondary flow as designed.

In the conventional turbine nozzle shown in FIG. 7, a secondary flow vortex 13a generated at the leading edge 12 of the nozzle blade 6 is formed.
Of the main flow 8 passing through the middle part of the nozzle blade 6 as shown in FIG. 9, while having an excellent advantage that the pressure can be suppressed by the pressing force from the raised curved surface of the ventral side 15 to the diaphragm outer ring 2 and the diaphragm inner ring 3. Is relatively low, the pressure loss is low, and the flow rate in the middle part where the nozzle performance is high is low, which is not preferable.

Conventionally, particularly in a low pressure part of a turbine, in order to cope with an increase in the specific volume of the main flow 8 and realize a smooth expansion of the main flow 8, as shown in FIG. The tip portion of the nozzle blade 6 is formed in the annular flow path 4 that expands.

In the expanding annular flow path 4, the main flow 8 enters a wet area during the expansion in the nozzle blade 6, and there is a problem that many water droplets are generated and erosion of the moving blade 7 on the downstream side. . In particular, since water droplets concentrate on the tip due to centrifugal force, erosion often occurs at the tip of the rotor blade.

In order to suppress the erosion problem of the rotor blade 7, the main flow 8
However, in the conventional turbine nozzle, as shown in FIG. 9, a relatively large amount of the main flow 8 flows in the root portion and the tip portion of the nozzle blade 6, so that the turbine blade 7 The erosion that occurs is increased, which may cause breakage or destruction.

The present invention has been made in view of such circumstances, and has been improved so that a large amount of the main flow also flows in the middle portion of the nozzle blade, and has a low pressure loss and a high nozzle performance in the middle portion of the nozzle blade. To provide a high-quality turbine nozzle that increases the flow rate and improves the nozzle blade efficiency, and suppresses erosion of the moving blade by actively capturing water droplets contained in the main flow while passing through the nozzle blade. With the goal.

[0019]

According to the present invention, a nozzle vane is provided in an annular flow path formed between an outer ring of a diaphragm and an inner ring of a diaphragm. The nozzle blades are arranged in a row in the circumferential direction, both ends of each nozzle blade are connected to a diaphragm outer ring and a diaphragm inner ring, respectively, and the blade height direction of the nozzle blade is formed on a convex curved surface toward the belly side, An inclined flow wall is formed on at least one of the tip side and the root side of the blade.

According to the present invention, in order to achieve the above object, the inclined line of the inclined flow wall is formed from one of the ventral side and the rear side of the nozzle blade. It is formed so as to face either the back side or the ventral side of the adjacent nozzle blade.

Furthermore, in order to achieve the above-mentioned object, the present invention provides an inclined flow wall provided with a suction port.

Further, in order to achieve the above-mentioned object, the present invention provides, as set forth in claim 4, an inlet provided on one of an outlet side of the nozzle blade and a back side of the nozzle blade. Things.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a turbine nozzle according to the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a partially cut-away schematic perspective view schematically showing a turbine nozzle according to the present invention.

The turbine nozzle according to the present embodiment includes a nozzle diaphragm outer ring 18 and a nozzle diaphragm inner ring 1
9 and the plurality of nozzle vanes 2
1 are arranged in a line at equal intervals at a distance in the circumferential direction. Both ends on the tip side (blade top) and the root side (blade root) of each nozzle blade 21 are connected to a nozzle diaphragm outer ring 18 and a nozzle diaphragm inner ring 19, respectively.

Each of the nozzle blades 21 is formed in a curved line CS that is convex toward the ventral side 22 from the connection end of each of the nozzle diaphragm outer ring 18 and the nozzle diaphragm inner ring 19. In addition, a flow wall 25 is formed on at least one of the tip portion 23 side and the root portion 24 side of each nozzle blade 21 along the nozzle diaphragm outer ring 18 and the nozzle diaphragm inner ring 19, respectively.

Each flow wall 25 is provided on the tip portion 23 side.
Ventral side 22 of one nozzle blade 21 of each nozzle blade 21
From the other nozzle blade 21 toward the back side 26 of the other nozzle blade 21, and is formed with a linear or curved slope line SL having a downward slope. Each of the blades 21 is formed with a linear or curved inclined line SL having a downward slope from the back side 26 of the blade 21 toward the ventral side 22 of one nozzle blade 21.

In the turbine nozzle according to the present embodiment, the main flow 27 flowing into the nozzle diaphragm outer ring 18 side
Presses the boundary layer of the wall surface by the vector in the direction of the normal of the inclined line SL while flowing along the flow wall 25, thereby effectively suppressing the secondary flow vortex. In addition, the flow rate of the main flow 27 near the flow wall 25 is concentrated at an intermediate portion of the nozzle blade 21 due to the above vector.

On the other hand, the wall boundary layer on the side of the nozzle diaphragm inner ring 19 is similarly pressed, and the secondary flow vortex is suppressed. At the same time, the flow of the main flow 27 is collected in the middle part of the nozzle blade 21, so that the secondary flow vortex 13 a And the pressure loss of the main flow 27 passing through the middle part of the nozzle blade 21 increases.

As described above, in the turbine nozzle according to this embodiment, the nozzle blade 21 has the convex curved line C facing the ventral side 22.
S, and the slope line SL is formed on the flow wall 25 provided on at least one of the nozzle diaphragm outer ring 18 and the nozzle diaphragm inner ring 19, and as shown in FIG. 3, the pressure loss characteristic B1 is shown in FIG. The pressure loss characteristic A2 of the conventional turbine nozzle can be maintained substantially equal to the pressure loss characteristic A1 of the conventional turbine nozzle. As shown in FIG. It can be collected much more than the flow characteristic A2.

Therefore, in the turbine nozzle according to the present embodiment, more main flow 27 is collected in the middle portion of the nozzle blade 21 having a low pressure loss, so that the blade efficiency of the blade 21 can be further improved as compared with the conventional case.

FIG. 2 is a partially cut-away schematic perspective view showing a first embodiment of the turbine nozzle according to the present invention. The same components as those of the first embodiment are denoted by the same reference numerals, and the description thereof will not be repeated.

The turbine nozzle according to the present embodiment has a nozzle diaphragm outer ring 18 and a nozzle diaphragm inner ring 1.
A suction port 29 is formed in the inclined flow wall 25 formed along 9 to remove water droplets contained in the main stream 27 before flowing to the bucket on the downstream side.

Conventionally, in a turbine, particularly in a turbine low-pressure stage, the main stream 27 is in a wet area, so that the main stream 27 contains many water droplets. There is a phenomenon in which the water droplets collide with the rotating blades rotating at a high speed and erode the blade surface.

The turbine nozzle according to the present embodiment has a flow wall 2 for actively catching water droplets of the main flow 27 generated while passing through the annular flow passage 20 formed between the nozzle blades 21.
5 is provided with a suction port 29. Each suction port 29
When the secondary flow vortex cannot be sufficiently suppressed only by the pressing force of the convex curved line CS toward the ventral side 22 of the nozzle blade 21;
If the secondary flow vortex can be sufficiently suppressed by drilling along the back side 26 of the nozzle blade 21 where relatively large amounts of water droplets are collected, or if the pressing force of the convex curved line CS can sufficiently suppress the water droplets, the water droplets inevitably collect. It is desirable to perforate the outlet side of the annular flow path 20.

As described above, in the turbine nozzle according to the present embodiment, the suction port 29 formed in the flow wall 25 is connected to the nozzle blade 21.
Is provided on one of the back side 26 and the outlet side of the annular flow path 20, so that water droplets separated from the main stream 27 can be reliably captured.

[0037]

As described above, in the turbine nozzle according to the present invention, the blade height direction of the nozzle blade is formed as a convex curved line facing the ventral side, and the tip side and the root of each nozzle blade are formed. Since at least one of the side portions has an inclined flow wall formed along the outer ring of the nozzle diaphragm and the inner ring of the nozzle diaphragm, the secondary flow vortex can be suppressed to reduce the pressure loss. You can gather more mainstream.

Therefore, in the turbine nozzle according to the present invention, since the main flow is collected in the middle portion of the nozzle blade having a low pressure loss, the blade efficiency of the nozzle blade can be further improved as compared with the conventional case.

Further, in the turbine nozzle according to the present invention,
A suction port is drilled in the inclined flow wall, and the suction port is drilled in one of the back side of the nozzle blade and the outlet side of the annular flow path, so that the main flow reliably removes water droplets generated during expansion work. It can be captured and erosion of the rotor blade can be prevented beforehand.

[Brief description of the drawings]

FIG. 1 shows an embodiment of a turbine nozzle according to the present invention.
FIG. 4 is a partially cutaway schematic perspective view observed from a trailing edge.

FIG. 2 shows a first embodiment of a turbine nozzle according to the present invention;
FIG. 4 is a partially cutaway schematic perspective view observed from a trailing edge.

FIG. 3 is a graph comparing pressure losses of a turbine nozzle according to the present invention and a conventional turbine nozzle.

FIG. 4 is a graph comparing the flow rate distribution per unit area between the turbine nozzle according to the present invention and the conventional turbine nozzle.

FIG. 5 is a schematic sectional side view showing a conventional turbine stage.

FIG. 6 is a schematic diagram showing a process of generation and growth of a secondary flow vortex.

FIG. 7 is a schematic perspective view of a conventional turbine nozzle observed from a trailing edge.

FIG. 8 is a schematic perspective view of another conventional turbine nozzle observed from a trailing edge.

FIG. 9 is a graph showing a flow rate distribution per unit area of the turbine nozzle shown in FIG. 7;

FIG. 10 is a schematic sectional side view showing a final stage of a turbine low-pressure section in a conventional turbine stage.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Turbine stage 2 Diaphragm outer ring 3 Diaphragm inner ring 4 Annular flow path 5 Turbine shaft 6 Nozzle blade 7 Moving blade 8 Main flow 9 Chip 10 Shroud 11 Boundary layer 12 Front edge 13 Vortex 13a Secondary flow vortex 14 Back side 15 Ventral side 16 Rear edge 17 Curved flow path 18 Nozzle diaphragm outer ring 19 Nozzle diaphragm inner ring 20 Annular flow path 21 Nozzle blade 22 Ventral side 23 Tip part 24 Root part 25 Flow wall 26 Back side 27 Main flow 28 Front edge 29 Suction port CS Curved line SL Slope

Claims (4)

[Claims] 1. A method according to claim 1, wherein nozzle vanes are arranged in a line in the circumferential direction in an annular flow passage formed between the diaphragm outer ring and the diaphragm inner ring, and both ends of each nozzle blade are connected to the diaphragm outer ring and the diaphragm inner ring, respectively. The blade height direction of the nozzle blade is formed in a convex curved surface toward the ventral side, and an inclined flow wall is formed on at least one of the tip portion side and the root portion side of the nozzle blade. Turbine nozzle. 2. The method according to claim 1, wherein the inclined line of the inclined flow wall is formed so as to extend from one of the ventral side and the dorsal side of the nozzle vane to one of the dorsal side and the ventral side of the adjacent nozzle vane. The turbine nozzle according to claim 1, wherein: 3. The turbine nozzle according to claim 1, wherein a suction port is provided in the inclined flow wall. 4. The turbine nozzle according to claim 3, wherein the suction port is provided on one of an outlet side of the nozzle blade and a back side of the nozzle blade.