JPH10141003A - Nozzle flow straightening device for axial flow turbine stage - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nozzle flow straightening device to smoothly guide working fluid at an axial flow turbine nozzle part to a turbine stage without the occurrence of an unstable flow and an eddy current. SOLUTION: This nozzle flow straightening device of an axial flow turbine stage is constituted such that a nozzle outer ring flow passage wall inlet part 11 is inclined, the portion, ranging from the inlet part of a nozzle 13 to the outlet part thereof, of the nozzle outer ring flow passage wall 11 is formed in a curved surface state, and a throttle flow passage 56 comprises a nozzle outer peripheral wall 50 formed such that the portion, ranging from the inlet part of a nozzle 13 to the outlet part thereof, of a nozzle outer ring flow passage wall 11 is formed in a curve state and the height of the nozzle 13 is decreased; and a nozzle inner peripheral wall 54 formed such that a portion ranging from a nozzle inner ring central part to a nozzle inlet part is formed in a curve state having a recessed part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an axial flow turbine such as a thermal power turbine, and more particularly, to a working fluid supplied from the outside of a vehicle compartment or from an upstream stage to a turbine stage. The present invention relates to a nozzle straightening device for an axial flow turbine stage, which reduces the unstable flow in the circumferential direction of the turbine and improves the turbine efficiency.

[0002]

2. Description of the Related Art In general, in an axial flow type rotary machine, in a flow path of a working fluid, a working fluid is ejected from a stationary nozzle toward a rotor, and the rotor rotates. In the case of a turbine, a working fluid is expanded from a high pressure upstream to a low pressure downstream by a nozzle, and heat energy is converted into velocity energy. On the other hand, the blades are rotated by the velocity energy from the nozzle, and the energy is taken out as power. Further, in the case of a steam turbine, the vehicle compartment is classified into a high-pressure chamber, a medium-pressure chamber, and a low-pressure chamber according to the material, size, manufacturing method, and the like according to the condition of the fluid. The cabin is communicated with the steam pipe, and the working fluid passing from the entrance of each cabin through the paragraph entrance needs to flow smoothly and be converted into effective energy in the paragraph.

FIG. 10 is a cross-sectional view showing the shape and paragraphs of an inlet flow path having a double-flow nozzle conventionally employed in an axial flow turbine. 10 (a) is a longitudinal sectional view of the axial turbine, and FIG. 10 (b) is a sectional view of A in FIG. 10 (a).
FIG. 10 (c) is an enlarged vertical sectional view of a portion B in FIG. 10 (a).

As shown in FIG. 10, in a turbine stage, an inner casing 2 is provided radially inside the outer casing 1 of the turbine, and a throttle duct 9 is provided from the outer casing 1 side to the inner casing 2 side. Have been. The working fluid is supplied to the inner casing 2 via the throttle duct 9, is divided into two at the entrance of the inner casing 2, and is guided in the inner casing 2 in the circumferential direction. Further, FIG.
As shown in (c), a nozzle outer ring 3 is provided on the radially inner side of the inner casing 2, and on the radial inner side of the nozzle outer ring 3,
A nozzle inner ring 4 is provided. The nozzle 5 is formed between the nozzle outer ring 3 and the nozzle inner ring 4.

[0005] On the other hand, a rotor 6 is rotatably provided at the center of the inner casing 2.
A wheel 7 is provided, and a blade 8 is provided at a tip of the wheel 7. Thereby, the working fluid supplied from the throttle duct 9 is jetted to the blade 8 via the nozzle 5, and as a result, the wheel 7 and the rotor 6 rotate.

By the way, the working fluid is supplied into the inner casing 2 through a throttle duct 9, but in an axial turbine having a double-flow nozzle as shown in FIG. 10, it is supplied through a throttle duct. The working fluid flows as shown by an arrow a in FIG. 10 (b), divides as shown by an arrow b above the inner casing 2, and circulates in the inner casing 2 in the circumferential direction.
As shown by an arrow c in FIG.

[0007]

In the conventional flow path structure shown in FIG. 10, the fluid flows into the nozzle 5 because the fluid is not always uniformly distributed in the flow path in the inner casing 2 around the entire circumference. In this case, the flow becomes uneven and unstable. Also,
On the outer peripheral wall of the nozzle inlet, the fluid suddenly changes its flow direction and is guided to the nozzle, so that a separation flow occurs.
The cause will be described with reference to FIG.

FIG. 11 is a view directly above (θ = in FIG. 10B).
90 ° position. Hereinafter, the angle display is based on FIG. ) Shows the flow path, and the fluid supplied from the throttle duct changes the direction of the flow rapidly and directly enters the flow path of the nozzle 5.
As shown by arrow d, large peeling is likely to occur. Such an unstable separation flow may adversely affect the downstream blade 8.

FIG. 12 shows a circumferential flow rate distribution (FIG. 12 (a)) of a nozzle flow path and a loss (FIG. 12 (b)) at each part in the circumferential direction in the conventional technique. The flow distribution is
Directly above (θ = 90 °) and directly below (θ = 270) the average flow rate
(°), the flow rate greatly fluctuates, so that a non-uniform steady flow is generated in each part in the circumferential direction. As a result, the turbine efficiency is remarkably reduced due to loss due to fluctuation, loss due to a large incident angle at the nozzle inlet, loss occurring at a flow rate larger or smaller than the design flow rate, and separation loss occurring at the outer peripheral wall of the nozzle.

In order to prevent such a non-uniform circumferential flow generated in the flow path upstream of the nozzle and a separation flow generated in the outer peripheral wall, various rectifying means are employed. As one example, as shown in FIG. 13, a diversion protrusion 10 is conventionally provided on the inner wall side of the nozzle upstream portion, and a throttle duct (not shown) is provided.
There is a method of diverting the fluid supplied from the diverter 10 by the diverter 10 and guiding the fluid to the nozzle 5 smoothly. In such a paragraph configuration, the fluid supplied from the throttle duct (not shown) is smoothly guided to the nozzle 5, but since the fluid from the throttle duct (not shown) flows directly into the nozzle, the nozzle inlet Separation is likely to occur at the flow portion along the outer peripheral wall of the portion (arrow f in the figure). As a result, the performance of the turbine is adversely affected. In addition, the occurrence of the separation of the flow on the outer peripheral wall portion of the working fluid before the nozzle flows into the nozzle is not necessarily limited to the axial turbine stage having the double-flow nozzle, and the working fluid largely changes the flow direction as described above. This is a problem common to the paragraph of the axial flow turbine of the type flowing into the nozzle.
Therefore, there is a need for an improvement measure for reducing the loss due to the uneven flow.

The present invention has been made in view of such circumstances, and an object of the present invention is to guide fluid supplied from the outside of a vehicle compartment smoothly into a turbine stage, and to provide a fluid in a circumferential direction of a nozzle inlet portion. It is an object of the present invention to provide an axial turbine with reduced unstable flow and improved turbine stage efficiency.

[0012]

According to a first aspect of the present invention, there is provided a nozzle rectifying device for an axial flow turbine stage, in which the inlet of a nozzle outer ring flow path wall is inclined and the nozzle outer rectifier is provided with a nozzle outer rectifier. Reduced nozzle height at the outlet of the annular channel wall, formed a curved surface from the inlet to the outlet of the channel wall to form a nozzle outer peripheral wall, and a curved surface having a concave recess from the center of the nozzle inner ring to the nozzle inlet A throttle channel is formed by the inner peripheral wall of the nozzle and the outer peripheral wall of the nozzle.

As described above, since the flow straightening means is provided from the throttle duct to the first stage nozzle, the flow rate of the working fluid flowing into each nozzle arranged over the entire circumference in the circumferential direction is made uniform, and the working fluid is flown. Flowed smoothly. As a result, a non-uniform flow such as a vortex flow is prevented, a loss in the nozzle flow path due to the flow is reduced, and turbine stage efficiency is improved.

According to a second aspect of the present invention, there is provided a nozzle straightening device for an axial flow turbine stage, wherein an intermediate portion from a central portion of a nozzle inner ring to a nozzle inlet where a fluid divides a diameter of a nozzle inner ring into a concave shape is formed. The nozzle inner ring diameter has a minimum value at the center of the concave curve portion.

By forming a concave curved surface from the central portion of the inner ring of the nozzle to the inlet portion of the nozzle, the flow direction of the working fluid from the throttle duct can be smoothly changed, and unnecessary vortices and irregularities immediately after the nozzle outlet are obtained. Uniform flow is reduced, resulting in lower losses in the nozzle flow path and improved turbine stage efficiency.

According to a third aspect of the present invention, there is provided a nozzle straightening device for an axial turbine stage, wherein the nozzle height is increased by increasing the diameter of the nozzle inner ring from the center of the nozzle inner ring where the fluid is divided to the nozzle inlet. The diameter of the nozzle inner ring has a minimum value at the center of the inner ring.

As described above, the diameter of the inner ring of the nozzle is changed in a curved shape from the central portion to the nozzle inlet portion to reduce the height of the nozzle, so that the working fluid flowing from the throttle duct toward the nozzle flows into the nozzle smoothly. As a result, unnecessary eddy currents and non-uniform flows immediately after and immediately after the passage of the nozzle are reduced, resulting in a reduced loss in the nozzle flow path and improved turbine stage efficiency.

According to a fourth aspect of the present invention, there is provided a nozzle straightening device for an axial turbine stage, wherein the diameter of the inner ring of the nozzle is gradually reduced from the center of the inner ring of the nozzle provided with a projection for dividing the fluid into the inlet of the nozzle. It is characterized by having made it.

As described above, by disposing the diversion protrusion at the center of the inner ring of the nozzle, the diversion of the working fluid supplied from the throttle duct to the nozzle is performed smoothly, and the non-uniform flow and the non-uniform flow at the time of passing through the nozzle. Uniformity is reduced, resulting in lower losses in the nozzle flow path and improved turbine stage efficiency.

According to a fifth aspect of the present invention, there is provided a nozzle straightening device for an axial turbine stage, wherein a single-flow type nozzle in which a working fluid flows from just above or immediately below an upstream portion of the nozzle and turns in the rotor axial direction. In the nozzle of the axial turbine stage having, while inclining the nozzle outer ring flow path wall inlet portion,
Nozzle height is reduced by forming a curved surface from the nozzle inlet to outlet of the nozzle outer ring flow path wall to form a nozzle outer peripheral wall, and the nozzle inner peripheral wall and the nozzle outer periphery formed into a curved surface up to the nozzle inlet of the nozzle inner ring A throttle channel is constituted by the wall.

As described above, the nozzle outer ring portion near the nozzle inlet is inclined at a certain angle, is formed into a curved surface so as to reduce the nozzle height from the nozzle inlet to the outlet, and the inner diameter of the nozzle inner ring is adjusted to the nozzle inlet. Due to the curved increase toward the portion, the supplied working fluid can smoothly change its flow in the direction of the nozzle. In addition, unnecessary vortex generation and non-uniform flow during and immediately after the passage of the nozzle are reduced, resulting in reduced loss in the nozzle flow path and improved turbine stage efficiency.

According to a sixth aspect of the present invention, there is provided a nozzle rectifying device for an axial flow turbine stage, wherein the working fluid passes through a part of the turbine blade and a part of the entire circumference of the nozzle portion. In addition to inclining the inlet of the ring channel wall and forming a curved surface from the nozzle inlet to the outlet of the nozzle outer ring channel wall, the nozzle height is reduced to form the outer peripheral wall of the nozzle, and the nozzle from the front stage turbine blade of the nozzle inner ring to the nozzle It is characterized in that a portion reaching the inlet portion is formed into a concave curved surface to form a nozzle inner ring wall, and a throttle flow path is formed by the nozzle outer peripheral wall and the nozzle inner peripheral wall.

As described above, the nozzle outer ring near the nozzle inlet is inclined at a certain angle, the nozzle outer ring is formed in a curved surface so as to reduce the nozzle height from the nozzle inlet to the outlet, and the nozzle inner ring is formed. By forming the part from the previous stage turbine blade to the nozzle inlet part in a concave curved shape,
The working fluid supplied from the pre-stage turbine smoothly flows into the nozzle, and unnecessary vortex flow and uneven flow immediately after and immediately after passing through the nozzle are reduced, resulting in reduced loss in the nozzle flow path and reduced turbine stage efficiency. Be improved.

According to a seventh aspect of the present invention, there is provided a nozzle rectifier for an axial turbine stage, wherein a working fluid in a stage passage portion through which the working fluid passes and a working fluid supplied from outside the turbine are mixed. At the same time, the nozzle outer ring channel wall inlet portion is inclined, and the nozzle outer ring channel wall is formed from the nozzle inlet portion to the outlet portion in a curved shape to reduce the nozzle height to form the nozzle outer peripheral wall, and the nozzle inner ring diameter to It is characterized in that a portion from the vicinity of the pre-stage turbine blade to a portion from the nozzle inlet to the nozzle inlet portion is formed in a curved surface to be increased to form a nozzle inner ring wall, and a throttle flow path is formed by the nozzle outer peripheral wall and the nozzle inner peripheral wall.

As described above, the outer ring portion of the nozzle near the nozzle inlet portion is inclined at a certain angle, is formed into a curved surface so as to reduce the nozzle height from the nozzle inlet portion to the outlet portion, and the nozzle inner ring portion is formed at the nozzle inlet portion. By forming a curved surface up to the part, the supplied working fluid can smoothly change its flow in the direction of the nozzle. In addition, the generation of unnecessary vortices and the non-uniform flow during and immediately after the passage of the nozzle are reduced, resulting in a reduced loss in the nozzle flow path, and the turbine stage efficiency is improved.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a nozzle straightening device for an axial turbine stage according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a longitudinal sectional view of a paragraph passage portion of the axial turbine according to the first embodiment. A nozzle outer ring 11 is provided radially inside the inner casing 2, and a nozzle inner ring 12 is provided radially inside the nozzle outer ring 11.
Further, a nozzle 13 is formed between the nozzle outer ring 11 and the nozzle inner ring 12. On the other hand, a rotor 6 is rotatably provided at the center of the inner casing 2, and a wheel 7 is provided on a radially outer side of the rotor 6, and a blade 8 is provided at a tip of the wheel 7. I have. The working fluid supplied from the throttle duct (not shown) is jetted to the blade 8 via the nozzle 13, and as a result, the wheel 7 and the rotor 6 rotate.

In the present embodiment, the flow path wall surface 52 of the nozzle outer ring 11 on the upstream side of the nozzle 13 is inclined, and the nozzle inlet to outlet is formed into a curved surface to form a nozzle outer peripheral wall 50. The nozzle height is reduced to narrow the flow path in the nozzle 13. The flow path wall surface 52 of the nozzle inner ring 12 is also formed into a concave curved shape so as to reduce the flow path in the nozzle 13 from the center of the nozzle inner ring toward the inlet of the nozzle 13 to form a nozzle inner peripheral wall 54.

FIG. 2 shows the details of the shape of the throttle channel 56 in the nozzle 13 in an enlarged manner. The channel wall surface 52 of the nozzle outer ring 11 is inclined (θt in the figure) to prevent peeling, and the height of the nozzle is reduced to a curved surface from the inlet to the outlet. That is, the nozzle entrance height in the figure is reduced from L1 to the exit height L2. In addition, nozzle inner ring 1
2 is inclined toward the nozzle entrance (θ in the drawing).
r) to form a concave diaphragm chamber 58 (S in the figure).

With this configuration, as shown by arrows in FIG. 1, the working fluid (arrow j) supplied from the throttle duct is upstream of the nozzle 13 as shown by arrows k and l. The flow is restricted, and the flow is smoothly guided to the nozzle flow path. Therefore, the flow rate of the working fluid flowing into each of the nozzles 13 disposed over the entire circumference in the circumferential direction is made uniform, and the working fluid flows smoothly, thereby preventing a non-uniform flow such as a vortex flow. Furthermore, as shown by the arrow m, by reducing the height of the nozzles 13, secondary flow vortices generated at the outer peripheral portion of each nozzle 13 can be eliminated, and nozzle performance can be improved.

Next, the effects of the present embodiment will be described with reference to FIG. FIG. 3 is a diagram showing a comparison between a case having the nozzle rectifying device of the present embodiment and a case of the related art. FIG. 3A shows the circumferential flow rate distribution at the nozzle inflow portion. Conventionally, the flow rate is directly above (θ = 90 °) and directly below (θ = 27 °).
(0 °), a large flow rate change occurred, and a large loss as shown in FIG. The large change in the flow rate in this paragraph also had an adverse effect on the next and subsequent stages downstream. On the other hand, in the present embodiment, a nozzle rectifying device having a throttle flow path 56 structure is provided by the nozzle outer peripheral wall 50 and the nozzle inner peripheral wall 54 of the nozzle outer ring 11 and the nozzle inner ring 12, respectively.
As shown in (a) and (b), the flow rate in the circumferential direction becomes uniform, and the loss is reduced. FIG. 3 (c) shows that since the uneven flow distribution, eddy current, and the like at the first stage can be eliminated, the efficiency of the downstream and subsequent stages is increased with stable flow. As described above, the efficiency of each paragraph is greatly improved, and a great improvement effect can be obtained.

Next, a nozzle straightening device for an axial turbine stage according to a second embodiment of the present invention will be described with reference to FIG. In FIG. 4, the flow path wall surface 62 of the nozzle outer ring 11 on the upstream side of the nozzle 13 is inclined to form a nozzle outer peripheral wall 60,
Further, a configuration is adopted in which the height from the nozzle is reduced by forming a curved surface from the nozzle inlet portion to the outlet portion, and the flow path in the nozzle 13 is narrowed. Further, the flow path wall surface 6 of the nozzle inner ring 14
No. 2 is formed into a nozzle inner ring wall 64 from the center of the inner ring of the nozzle to the inlet of the nozzle so as to reduce the flow path in the nozzle 13. FIG. 5 shows the throttle channel 6 in the nozzle 13.
6 shows the details of the shape in an enlarged manner. Nozzle outer ring 11
Flow path wall surface 62 is inclined to prevent peeling (θt in the figure)
In addition, the height of the nozzle is reduced in a curved shape from the inlet to the outlet. That is, the nozzle entrance height in the figure is reduced from L1 to the exit height L2. The flow path wall surface 62 of the nozzle inner ring 14 is inclined (θr in the drawing) toward the nozzle inlet to provide a concave throttle chamber 68 (S in the drawing).

With this configuration, as shown by arrows in FIG. 4, the working fluid (arrow j) supplied from the throttle duct is upstream of the nozzle 13 as shown by arrows k and l. The flow is restricted, and the flow is smoothly guided to the nozzle flow path. Therefore, the flow rate of the working fluid flowing into each of the nozzles 13 disposed over the entire circumference in the circumferential direction is made uniform, and the working fluid flows smoothly, thereby preventing a non-uniform flow such as a vortex flow. Further, as shown by the arrow m, by reducing the nozzle height, it is possible to eliminate secondary flow vortices generated at the outer peripheral portion of each nozzle 13 and improve nozzle performance. With such a configuration, the same effects as in the first embodiment can be obtained, and the turbine efficiency can be improved.

Next, a description will be given of an axial flow turbine stage nozzle rectifier according to a third embodiment with reference to FIG. As shown in FIG. 6, a conventional diversion projection 10 is
In order to eliminate the vortex flow generated by the separation generated on the flow path wall 72 in the upstream part of the nozzle, the nozzle outlet is formed into a curved surface shape, and the nozzle outer peripheral wall 70 is used to narrow the flow path. 76. That is, the flow path height at the nozzle in the figure is reduced from L1 to L2.

With this configuration, the flow (arrow k) accompanied by the separation shown in FIG.
The flow is rectified by the nozzle outer peripheral wall 70 (arrow m), and uneven flow such as eddy current is prevented.

Next, a nozzle rectifier for an axial turbine according to a fourth embodiment will be described with reference to FIG. In the above-described first to third embodiments, the working fluid is supplied from directly above, and the fluid is divided into two in the upstream portion of the nozzle and flows into the opposed nozzle. In the embodiment, as shown in FIG. 7, the present invention relates to a single-flow nozzle rectifying device used for the first stage of reheating of a steam turbine or the like. In the conventional shape, as described above, it is easy for the uneven flow in the circumferential direction and the separation flow to occur on the flow path wall surface in the upstream portion of the nozzle. In the present embodiment, in order to prevent the separation flow of the flow path wall surface 82 of the nozzle outer ring 18 on the upstream side of the nozzle 20, the nozzle outer peripheral wall 80 is inclined (θt in the figure) to form a nozzle outer peripheral wall 80,
Further, the nozzle outlet portion is formed into a curved surface shape to form the throttle flow path 86
And That is, the height of the flow path in the nozzle in the figure is L1
To L2. In addition, the flow path wall surface 8 of the nozzle inner ring 19
No. 2 is inclined (θr in the figure) toward the nozzle inlet to form a nozzle inner peripheral wall 84, and a throttle chamber 88 (S in the figure) is formed in front of it.

With this configuration, the nozzle outer peripheral wall 80 flows (arrows n and q) as indicated by arrows in the figure.
And the flow (arrow p) of the nozzle inner peripheral wall 84 is rectified in the throttle flow path 86 of the nozzle, and uneven flow such as eddy current can be prevented.

Next, referring to FIG. 8, a description will be given of a nozzle rectifier for an axial turbine according to a fifth embodiment. In the above-described first to fourth embodiments, the fluid is supplied from directly above or directly below the nozzle, and the direction of the flow is turned and guided to the nozzle portion. However, in the fifth embodiment, As shown in FIG. 8, the present invention relates to a single-flow nozzle rectifying device used in a high pressure section two stages downstream of a partial feeding stage in which a working fluid such as a turbine high pressure section first stage passes through a part of the entire nozzle circumference. . As described above, downstream of the partial feeding stage, the flow passes through a discontinuous flow path and is uneven in the circumferential direction. In this embodiment, the flow path wall surface 92 of the nozzle outer ring 27 on the upstream side of the nozzle 29 is inclined (θt in the drawing) to prevent the separation flow, and the nozzle outlet is formed in a curved surface shape. And narrow the flow path. That is, the height of the flow path in the nozzle 29 in the figure is reduced from L1 to L2 to form the throttle flow path 96. In addition, the flow path wall surface 92 of the nozzle inner ring 28 is inclined (θr in the figure) toward the nozzle inlet portion to form a nozzle inner peripheral wall 94, and a throttle chamber 98 (S in the figure) is provided in front of the wall 94.

With this configuration, the flow of the nozzle outer peripheral wall 90 (arrows u,
w) and the flow (arrow v) of the nozzle inner peripheral wall 94 are rectified by the throttle portion 96 of the nozzle and guided smoothly. As a result, non-uniform flows such as eddies are prevented.

Next, referring to FIG. 9, a description will be given of an axial flow turbine nozzle rectifier according to a sixth embodiment. In the sixth embodiment, as shown in FIG. 9, the present invention relates to a single-flow nozzle rectifier of a mixed pressure turbine stage employed in a geothermal turbine or the like. In the conventional rectifier, as described above, it is easy for the uneven flow in the circumferential direction and the peeling to occur on the outer peripheral wall upstream of the nozzle.

In this embodiment, in order to prevent separation flow on the flow path wall surface 102 of the nozzle outer ring 36 on the upstream side of the nozzle 38, the flow path is inclined (θt in the drawing), and the nozzle outlet is formed in a curved surface shape. The nozzle outer peripheral wall 100 is used, and its flow path is referred to as a throttle flow path 106. That is, the nozzle 38 in FIG.
Is reduced from L1 to L2. Further, the flow path wall surface 102 of the nozzle inner ring 37 is inclined (θr in the figure) toward the nozzle inlet in a curved shape to form a nozzle inner peripheral wall 104,
The nozzle is formed so as to narrow the inlet portion.

With this configuration, the flow of the nozzle outer peripheral wall 100 (arrows k,
m) and the flow of the nozzle inner peripheral wall 104 (arrow 1) are rectified in the throttle flow path 106 of the nozzle and are smoothly guided. as a result,
Non-uniform flows such as eddies are prevented. It is needless to say that the present invention is not limited to the above-described embodiment, and various modifications are possible.

[0042]

As described above, in the present invention, since the throttle structure, that is, the rectifying device is provided on the outer peripheral wall of the nozzle upstream portion and the nozzle outlet portion, each nozzle disposed over the entire circumference in the circumferential direction is provided. The working fluid flowing in is made uniform,
The working fluid flows smoothly. As a result, the loss in the flow path between the nozzle and the blade due to this is reduced, and the turbine efficiency is improved.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a double-flow nozzle in an axial turbine stage according to a first embodiment of the present invention.

FIG. 2 is an enlarged detailed view of a nozzle unit in FIG.

FIG. 3 is a graph showing a comparison of a paragraph flow rate, a loss, and an efficiency in a case where the nozzle rectifier according to the first embodiment of the present invention is provided and a case where the conventional rectifier is not provided.

FIG. 4 is a cross-sectional view of a double-flow nozzle in an axial turbine stage according to a second embodiment of the present invention.

FIG. 5 is an enlarged detailed view of a nozzle unit in FIG. 4;

FIG. 6 is a cross-sectional view of a double-flow nozzle in an axial turbine stage according to a third embodiment of the present invention.

FIG. 7 is a cross-sectional view of a single-flow nozzle in an axial turbine stage according to a fourth embodiment of the present invention.

FIG. 8 is a sectional view of a nozzle in a partial feeding stage in an axial flow turbine according to a fifth embodiment of the present invention.

FIG. 9 is a sectional view of a nozzle in a mixed-pressure turbine stage of an axial-flow turbine according to a sixth embodiment of the present invention.

FIG. 10 is a cross-sectional view showing a shape and a paragraph of an inlet passage having a double-flow nozzle in a conventional axial flow turbine.

FIG. 11 is an enlarged detailed view of a nozzle unit in FIG. 10;

12 is a distribution diagram in the angular direction of the paragraph flow rate and the loss in FIG.

FIG. 13 is a longitudinal sectional view of an improved double-flow nozzle in a conventional axial turbine stage.

[Explanation of symbols]

1 outer casing 2, 17, 24, 26, 35 inner casing 3, 11, 15, 18, 27, 36 nozzle outer ring 4, 12, 14, 16, 19, 28, 37 …… Nozzle inner ring, 5,13,20,29,38… Nozzle, 6,21,30,39… Rotor, 7,22,3
1,40 ... wheel, 8,23,32,33,41
… Blade, 9… throttle duct, 10… diversion projection, 25… packing head, 34… steam pipe, 5
0, 60, 70, 80, 90, 100 ... Nozzle outer peripheral wall, 52, 62, 72, 82, 92, 102 ... Flow path wall surface, 54, 64, 84, 94, 104 ... Nozzle inner peripheral wall, 56 , 66, 76, 86, 96, 106 ... throttle channel 58, 68, 88, 98 ... throttle chamber S
Restriction chamber depth, L1 ... Nozzle inlet height, L2 ...
Outlet height, a, b, c, d, f ... Flow of working fluid in a conventional nozzle, j, k, l, m, n, p,
q, u, v, w... the flow of the working fluid in the nozzle straightening device of the present invention, θt... the inclination angle of the nozzle outer peripheral wall, θr
…… Inclination angle of the inner peripheral wall of the nozzle

Claims (7)

[Claims] In a nozzle of an axial turbine stage disposed in a flow path formed by a nozzle outer ring and a nozzle inner ring, a flow path wall inlet of the nozzle outer ring is inclined,
By forming a curved surface from the nozzle inlet to the outlet of the flow path wall of the nozzle outer ring, the nozzle height is reduced to form a nozzle outer peripheral wall, and has a concave depression from the center of the nozzle inner ring to the nozzle inlet. A nozzle straightening device for an axial flow turbine stage, wherein a throttle flow path is formed by a nozzle inner peripheral wall formed into a curved surface and the nozzle outer peripheral wall. 2. The nozzle according to claim 1, wherein the working fluid is a double-flow type nozzle that divides the working fluid in the rotor axial direction into two parts, and has a concave portion at a middle portion from a center portion of the nozzle inner ring where the fluid divides a nozzle inner ring diameter to a nozzle inlet portion. The nozzle straightening device for an axial turbine stage according to claim 1, wherein the nozzle inner race has a minimum value at the center of the concave curved surface portion. 3. The nozzle is constituted by a double-flow type nozzle in which a working fluid is divided into two in the axial direction of the rotor, and a diameter of the inner ring of the nozzle is increased in a curved shape from a central portion of the inner ring of the nozzle where the fluid is divided to a nozzle inlet. 2. The nozzle straightening device for an axial turbine stage according to claim 1, wherein the nozzle height is reduced so that the inner diameter of the nozzle has a minimum value at the center of the inner ring. 4. The nozzle is constituted by a double-flow type nozzle in which a working fluid is divided in a direction opposite to the rotor axial direction and divided into two parts, and the inner ring of the nozzle is gently formed from a central part of the inner ring of the nozzle in which a projection for dividing the fluid is formed to a nozzle inlet part. The nozzle straightening device for an axial turbine stage according to claim 1, wherein the diameter is reduced in a curved shape. 5. In a nozzle of an axial turbine stage having a single flow type nozzle in which a working fluid flows in from just above or immediately below a nozzle upstream portion and turns in the rotor axial direction, a flow path wall inlet of a nozzle outer ring is provided. The nozzle height was reduced by forming a curved surface from the nozzle inlet portion to the outlet portion of the flow path wall of the nozzle outer ring, and the nozzle outer ring was formed into a curved shape up to the nozzle inlet portion of the nozzle inner ring. A nozzle straightening device for an axial turbine stage, wherein a throttle flow path is formed by a nozzle inner peripheral wall and the nozzle outer peripheral wall. 6. A nozzle straightening device for an axial flow turbine stage, which is disposed in a flow path formed by a nozzle outer ring and a nozzle inner ring, and in which a working fluid passes through a part of a rotor blade of a turbine shaft and a part of the entire circumference of a nozzle portion. A nozzle outer peripheral wall is formed by reducing the nozzle height by forming a curved surface from the nozzle inlet to the outlet of the flow path wall of the nozzle outer ring while inclining the flow path wall inlet of the nozzle outer ring. A shaft formed by forming a portion from the vicinity of the front stage turbine blade portion of the inner ring to the nozzle inlet portion into a concave curved surface to form a nozzle inner ring wall, and forming a throttle flow path by the nozzle outer peripheral wall and the nozzle inner peripheral wall; Nozzle rectifier for flow turbine stage. 7. An axial turbine stage disposed in a flow path formed by a nozzle outer ring and a nozzle inner ring, wherein a working fluid in a stage passage portion through which the working fluid passes and a working fluid supplied from outside the turbine are mixed. In the nozzle rectifying device, the nozzle height of the nozzle outer ring is reduced by inclining the flow path wall inlet portion of the nozzle outer ring and forming a curved surface from the nozzle inlet portion to the outlet portion of the flow path wall of the nozzle outer ring. The outer peripheral wall is formed by increasing the diameter of the inner ring of the nozzle from the vicinity of the pre-stage turbine blade to the nozzle inlet portion in a curved shape, and this is used as the inner wall of the nozzle, and the narrowed flow is formed between the outer peripheral wall of the nozzle and the inner peripheral wall of the nozzle. A nozzle rectifying device for an axial turbine stage, wherein a passage is formed.