JPH094409A - Axial flow steam turbine - Google Patents

Abstract

PURPOSE: To equalize flow velocity distribution in a circumferential direction by forming a recession on an outer peripheral surface of a diaphragm inner ring to which an opening of a steam inlet piping is opposed, which recession has maximum depth at its portion opposed to the opening of the steam inlet piping, while the depth being decreased gradually in an axial direction. CONSTITUTION: Steam flow is introduced from a steam inlet piping 11 into a daughnut-like inlet steam chamber 12 formed by an inner casing. A recession 16 and a projection 17 are formed on a center portion of a diaphragm inner ring 13 against which steam strikes on the side of the steam inlet piping 11. Even flow is thus obtained in diameter and circumferential directions. Namely, the steam shows even flow when it enters a nozzle blade 15, as a whole. The recession 16 of the diaphragm inner ring 13 promotes shifting of the steam in a circumferential direction. A flow passage area of the steam formed on inner and outer rings 13, 14 of the diaphragm including the recession 16 is gradually decreased in a circumferential direction. The shifted steam is thus pushed out while obtaining even flow velocity distribution in a circumferential direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of an axial flow steam turbine, and more particularly to an axial flow steam turbine of a type in which steam is introduced in a radial direction with respect to a rotating shaft and divided into two axial directions. is there.

[0002]

2. Description of the Related Art An axial flow steam turbine of this type that has been generally adopted in the past has a turbine casing portion provided with a steam inlet pipe that penetrates the casing in a radial direction and supplies steam to a steam chamber. It is usual that the steam flow path formed by the inner ring of the diaphragm and the outer ring of the diaphragm is divided into left and right axial directions to drive the blades.

In the steam turbine having the steam inlet pipe thus formed, the flow rate distribution in the blade is unbalanced between the side with the steam inlet pipe and the side without the steam inlet pipe, that is, the flow velocity in the circumferential direction. A non-uniform distribution of the flow and a difference in pressure loss between the outer peripheral side and the inner peripheral side of the steam passage in the axial direction, that is, a non-uniform flow of the flow velocity distribution in the radial direction are likely to occur.

This non-uniform flow of the flow velocity distribution in the radial direction naturally causes a pressure loss for each paragraph, resulting in a reduction in the efficiency of the axial flow steam turbine. Generally, in order to reduce the unevenness of the flow velocity distribution in the circumferential and radial directions, the distance from when the flow turns in the axial direction, that is, the axial distance from the center of the steam inlet pipe to the first nozzle blade Or a guide collar is provided on the outer periphery of the inner ring of the diaphragm so that the steam supplied from the radial direction can be easily redirected to the axial direction to make the radial flow velocity distribution in the axial flow path uniform. ing.

Incidentally, as for those related to this, Japanese Patent Laid-Open No. 57-93607 and Japanese Utility Model Laid-Open No. 57-10780.
No. 3, etc. are mentioned.

[0006]

As described above, in the steam turbine in which the guide flange is provided on the outer peripheral portion of the diaphragm inner ring and the supply steam is guided by the guide flange, the steam turbine is provided with a certain degree of axial flow path. It is possible to make the radial flow velocity distribution uniform, but at the bend, deflection occurs due to the relationship between the vapor flow velocity and centrifugal force,
After all, it is difficult to make the flow velocity distribution uniform in the radial direction, and it is not possible to sufficiently reduce the pressure loss for each paragraph.

Further, in the case where the above-mentioned axial distance from the steam inlet pipe to the nozzle blade is long, if the distance is sufficient, it is possible to obtain a uniform flow velocity distribution. In the case of the steam turbine, the length of the rotary shaft of the steam turbine is extended, so that there is a dislike of causing vibration of the rotary shaft and increasing the size of the turbine.

The present invention has been made in view of this, and an object of the present invention is to extend the length of the rotating shaft without extending the axial distance from the steam inlet pipe to the nozzle blade. It is an object of the present invention to provide an axial steam turbine of this kind capable of sufficiently uniforming the radial velocity distribution. Further, the present invention is to provide an axial flow steam turbine of this type that can make the flow velocity distribution in the radial direction uniform and also make the flow velocity distribution in the circumferential direction uniform.

[0009]

That is, the present invention relates to a steam inlet pipe that penetrates a turbine casing and supplies steam, an inner casing that is arranged in the casing and forms an inlet steam chamber, and the inner casing. In an axial-flow steam turbine including a diaphragm inner ring and a diaphragm outer ring that form a steam flow path that separates from the steam chamber in the left and right directions of the axial flow, and nozzle vanes provided between the diaphragm outer ring and the diaphragm inner ring. , On the outer peripheral surface of the diaphragm inner ring where the opening of the steam inlet pipe is opposed,
A portion facing the opening of the steam inlet pipe is deepest, and a concave groove formed so as to become gradually shallower as it goes away from the opening of the steam inlet pipe is provided to achieve the intended purpose. It was done like this.

Further, on the outer peripheral surface of the diaphragm inner ring, a collar extending in the circumferential direction and projecting outward from the outer peripheral surface of the diaphragm inner ring is provided, and on both sides in the axial direction of the collar portion,
A portion facing the opening of the steam inlet pipe is deepest, and a groove is provided which becomes shallower as it goes away from the opening of the steam inlet pipe.

[0011]

In other words, in the axial-flow steam turbine thus formed, the portion of the diaphragm inner ring facing the opening of the steam inlet pipe has a portion facing the opening of the steam inlet pipe. Since there is a groove that is deepest and gradually shallows away from the opening of the steam inlet pipe, the steam introduced from the steam inlet pipe by this groove is the steam in the circumferential direction. The wraparound is promoted, and as the flow area decreases in the circumferential direction, the steam that wraps around is extruded into the axial flow, thereby making the flow velocity distribution distributed in the circumferential direction uniform,
Therefore, the steam flow velocity distribution in the radial direction can be made sufficiently uniform without extending the length of the rotating shaft, that is, without extending the axial distance from the steam inlet pipe to the nozzle blade.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the illustrated embodiments. FIG. 1 is a cross-sectional view showing the structure around the steam inlet of the axial flow steam turbine. The steam that drives the turbine is introduced from a steam inlet pipe 11 that extends perpendicularly to the rotating shaft 19 in a radial direction, and has a donut shape formed by an inner casing provided circumferentially with respect to the rotating shaft 19. It is guided to the inlet steam chamber 12. Then, while circling around the inlet steam chamber 12, after that, it collides with the inner ring 13 of the diaphragm and splits into the left and right directions of the axial flow.
In contrast, the gas flows through the nozzle blades 15 and the blades 20 of the turbine that are provided in the circumferential direction. The moving steam causes the moving blades 20 to operate, that is, the rotating blades 20 to operate the axial-flow steam turbine.

The inner diaphragm 13 and the outer diaphragm 14 having the nozzle blades 15 are fixed to the casing, and the moving blades 20 are fixed to the rotary shaft 19.

2 and 3 are enlarged views showing the vicinity of the steam inlet portion. The structure of the steam inlet portion of the axial steam turbine is a donut shape formed by the steam inlet pipe 11 and the inner casing. It is composed of an inlet steam chamber 12, a diaphragm inner ring 13, a diaphragm outer ring 14, and nozzle vanes 15. In particular, the central portion of the diaphragm inner ring 13 on the side where the steam inlet pipe 11 is located, that is, the outer peripheral surface of the diaphragm inner ring 13 that faces the opening of the steam inlet pipe faces the opening of the steam inlet pipe. The deepest part is provided with a concave groove formed so that it gradually becomes shallower as it moves away from the opening of the steam inlet pipe,
Further, a flange portion that extends in the circumferential direction and protrudes outward, that is, a convex portion 17 is provided at the central portion in the axial direction of the concave groove.

In this configuration, the steam flow is the steam flow line 1
As shown by the arrow 8, the inner ring 1 of the diaphragm is guided from the steam inlet pipe 11 and enters the donut-shaped steam chamber 12 of the inlet formed by the inner casing to collide with steam.
By providing the concave groove 16 and the convex portion 17 in the central portion on the side where the steam inlet pipe 11 of 3 is located, the flow is uniform in the radial direction and the circumferential direction, that is, when the steam enters the nozzle blades 15, the entire It becomes a uniform flow.

Concave groove 16 provided on the inner ring 13 of the diaphragm
Is a flow passage that promotes the wraparound of the steam introduced from the steam inlet pipe 11 in the circumferential direction and that wraps around in the circumferential direction formed by the diaphragm inner ring 13 and the diaphragm outer ring 14 including the concave groove 16 thereof. By changing the area in the circumferential direction so that the flow path area gradually decreases, the circling steam is pushed out to the axial flow,
The flow velocity distribution distributed in the circumferential direction is made uniform.

At this time, one in which the flow passage area is changed in the diaphragm inner ring 13 so that the action of the circulated steam being pushed out into the axial flow occurs after the steam flow turns from the radial direction to the axial direction. Is effective.

Convex portion 17 provided on the inner ring 13 of the diaphragm
Has the effect of promoting split flow in two directions of the axial flow, and at the same time, even on the side with the steam inlet pipe, the groove provided in the inner ring of the diaphragm restricts the flow below the nozzle blades and The convex portion promotes the flow above the nozzle blades to make the flow velocity distribution distributed in the radial direction uniform.

FIG. 4 is a comparison of this embodiment and the conventional one from the viewpoint of the flow of steam. In the conventional one, the steam introduced from the radial direction perpendicular to the rotation axis is directed to the left and right of the axial flow. However, since the streamline is from one direction, there is a difference in velocity between the inside and outside where the flow is changed, as in a normal curved pipe. As a result, the inhomogeneous state of the flow velocity distribution is not sufficiently resolved in the radial direction at the entrance of the first nozzle blade.

On the other hand, in the case of the present invention, since there are recesses as shown by the streamlines, the streamlines entering the axial direction can be formed in two upper and lower directions, which results in the radial direction at the entrance of the first nozzle blade. The distribution of the flow velocity can be made uniform.

FIG. 5 shows changes in the circumferential direction of the recess provided in the inner ring of the diaphragm. The vertical axis represents the difference between R1 and R2 in FIG. 4, and the horizontal axis represents the circumference of the rotary shaft. The direction angle is shown. By changing the circumferential flow passage area formed by the diaphragm inner ring including the recess and the diaphragm outer ring in the circumferential direction so that the flow passage area is gradually reduced, the steam that has circulated in the circumferential direction By being pushed out by the flow, the distribution of the flow velocity distributed in the circumferential direction is made uniform.

FIG. 6 shows the flow velocity distribution in the circumferential direction and the radial direction when this embodiment is applied. Two of the broken lines are those in which the concave groove 16 and the convex portion 17 are not provided in the diaphragm inner ring 13, and the two of which are solid lines are the concave groove 16
This is the case where the convex portion 17 is provided. The line marked with ◯ is the side with the steam inlet pipe 11, and the line marked with x is the side without the steam inlet pipe 11. The slope between the broken line and the solid line is steeper when the solid line is larger. This means that the flow velocity distribution, which is distributed in the radial direction when the concave groove 16 and the convex portion 17 are provided in the diaphragm inner ring 13, is made uniform. It is shown that.

Further, regarding the positions of ○ and ×, two lines closer to the solid line than the broken line are closer to each other. This means that when the inner groove 13 of the diaphragm is provided with the concave groove 16 and the convex portion 17, it is in the circumferential direction. It is shown that the flow velocity distribution distributed in the is uniformed. That is, FIG. 6 shows that the flow can be made uniform both in the circumferential direction and the radial direction.

FIG. 7 shows another embodiment, which is different from the one shown in FIG.
The shape of 6 is different. That is, in FIG. 3, the convex portion 17 is provided in the central portion of the diaphragm inner ring 13 and the concave grooves 16 are provided on both sides thereof, whereas in FIG. 7, only the concave groove 16 is provided in the central portion of the diaphragm inner ring 13. None, a guide portion 25 for guiding a part of the inflowing steam in the axial direction is provided between the groove and the steam inlet pipe opening. Even when formed in this way, there is almost the same effect, that is, there is an effect of making the flow in the circumferential and radial directions uniform.

FIG. 8 shows that the outer peripheral surface of the diaphragm inner ring facing the opening of the steam inlet pipe is deepest at the portion facing the opening of the steam inlet pipe, and is surrounded by the opening of the steam inlet pipe. Only the recessed groove 16 is formed so that it becomes shallower as it is separated in the axial and axial directions. Even when formed in this manner, substantially the same effect can be obtained although the uniformity is somewhat inferior to that of the above-mentioned embodiment.

[0026]

As described above, according to the present invention, the outer peripheral surface of the diaphragm inner ring has the deepest portion facing the opening of the steam inlet pipe, and is separated from the opening of the steam inlet pipe. Since the concave groove is formed so as to become gradually shallower, the steam introduced from the steam inlet pipe is promoted in the wraparound of the steam in the circumferential direction,
In addition, since the circulated steam is extruded into the axial flow, the flow velocity distribution distributed in the circumferential direction is made uniform, and therefore the length of the rotating shaft is not extended, that is, from the steam inlet pipe to the nozzle blade. It is possible to obtain an axial-flow steam turbine of this kind in which the steam flow velocity distribution is made uniform, without extending the axial distance of.

[Brief description of drawings]

FIG. 1 is a vertical side view showing an embodiment of an axial steam turbine of the present invention.

FIG. 2 is a vertical sectional front view of a steam inlet of an axial steam turbine according to an embodiment of the present invention.

3 is a sectional view taken along the line AA of FIG.

FIG. 4 is a flow velocity distribution diagram showing a flow of steam at a steam inlet portion of an axial steam turbine.

FIG. 5 is a diagram showing a circumferentially changing state of a recess provided in the diaphragm.

FIG. 6 is a diagram showing a flow velocity distribution in a circumferential direction and a radial direction.

FIG. 7 is a vertical cross-sectional side view of a steam inlet portion showing another embodiment of the axial steam turbine of the present invention.

FIG. 8 is a vertical sectional side view of a steam inlet of the axial flow steam turbine according to still another embodiment of the present invention.

[Explanation of symbols]

11 ... Steam inlet piping, 12 ... Inlet steam chamber formed by inner casing, 13 ... Diaphragm inner ring, 1
4 ... Diaphragm outer ring, 15 ... Nozzle blade, 16 ...
Grooves on inner ring of diaphragm, 17 ... Projections on inner ring of diaphragm, 18 ... Streamline of steam, 19 ... Rotating shaft, 20 ...
Moving blade.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Michiaki Tominaga 3-1, 1-1 Sachimachi, Hitachi City, Ibaraki Prefecture Hitachi Ltd. Hitachi Factory

Claims (12)

[Claims] 1. A steam inlet pipe that penetrates a turbine casing and supplies steam, and is arranged in the casing.
An inner casing that forms an inlet steam chamber, a diaphragm inner ring and a diaphragm outer ring that form a steam flow path that separates from the steam chamber of the inner casing in the left and right directions of the axial flow, and are provided between the diaphragm outer ring and the diaphragm inner ring. In an axial-flow steam turbine provided with a nozzle vane, the outer peripheral surface of the diaphragm inner ring facing the opening of the steam inlet pipe is deepest in the part facing the opening of the steam inlet pipe. The axial-flow steam turbine is characterized in that a concave groove is formed so as to become gradually shallower as it goes away from the opening of the steam inlet pipe in the axial direction. 2. A steam inlet pipe that penetrates a turbine casing and supplies steam, and is arranged in the casing.
An inner casing that forms an inlet steam chamber, a diaphragm inner ring and a diaphragm outer ring that form a steam flow path that separates from the steam chamber of the inner casing in the left and right directions of the axial flow, and are provided between the diaphragm outer ring and the diaphragm inner ring. In an axial-flow steam turbine provided with a nozzle vane, the outer peripheral surface of the diaphragm inner ring facing the opening of the steam inlet pipe is deepest in the part facing the opening of the steam inlet pipe. , The portion that is formed so as to become gradually shallower as it moves away from the opening of the steam inlet pipe in the axial direction, and that faces the opening of the steam inlet pipe is the widest, and extends in the circumferential direction from the opening of the steam inlet pipe. An axial-flow steam turbine, which is provided with a concave groove formed so as to become gradually narrower as the distance increases. 3. A steam inlet pipe for penetrating a turbine casing to supply steam, and arranged in the casing,
An inner casing that forms an inlet steam chamber, a diaphragm inner ring and a diaphragm outer ring that form a steam flow path that separates from the steam chamber of the inner casing in the left and right directions of the axial flow, and are provided between the diaphragm outer ring and the diaphragm inner ring. In an axial-flow steam turbine provided with a nozzle vane, the outer peripheral surface of the diaphragm inner ring facing the opening of the steam inlet pipe is deepest in the part facing the opening of the steam inlet pipe. , The area of the steam inlet pipe gradually decreases as it moves away from the opening of the steam inlet pipe in the axial direction, and the area gradually decreases in the circumferential direction from a portion facing the opening of the steam inlet pipe. An axial-flow steam turbine, which is provided with a groove formed as described above. 4. The depth of the groove is formed such that the portion facing the opening of the steam inlet pipe has the deepest depth and becomes gradually shallower as it goes away from the opening of the steam inlet pipe in the circumferential direction. The axial steam turbine according to claim 3. 5. The axial steam turbine according to claim 1, wherein the bottom of the groove is formed as a curved surface that is curved in the axial direction. 6. A steam inlet pipe that penetrates a turbine casing and supplies steam, and is arranged in the casing.
An inner casing that forms an inlet steam chamber, a diaphragm inner ring and a diaphragm outer ring that form a steam flow path that separates from the steam chamber of the inner casing in the left and right directions of the axial flow, and are provided between the diaphragm outer ring and the diaphragm inner ring. In an axial-flow steam turbine provided with a nozzle vane, the outer peripheral surface of the diaphragm inner ring facing the opening of the steam inlet pipe is deepest in the part facing the opening of the steam inlet pipe. , A concave groove is formed so that it gradually becomes shallower as it goes away from the opening of the steam inlet pipe, and a flange portion that extends in the circumferential direction and projects outward is provided at the axial central portion of the concave groove. An axial-flow steam turbine characterized by the above. 7. A steam inlet pipe for penetrating a turbine casing and supplying steam, and arranged in the casing,
An inner casing that forms an inlet steam chamber, a diaphragm inner ring and a diaphragm outer ring that form a steam flow path that separates from the steam chamber of the inner casing in the left and right directions of the axial flow, and are provided between the diaphragm outer ring and the diaphragm inner ring. In the axial flow steam turbine provided with the nozzle vane provided, a flange extending outward in the circumferential direction and protruding outward from the outer peripheral surface of the diaphragm inner ring is provided on the outer peripheral surface of the diaphragm inner ring, and the shaft of the flange portion is provided. Axial flow steam characterized in that a groove facing the opening of the steam inlet pipe is deepest on both sides in the direction, and the groove gradually becomes shallower as it goes away from the opening of the steam inlet pipe in the circumferential direction. Turbine. 8. The axial steam turbine according to claim 7, wherein a circumferential length of the flange portion is formed to be substantially equal to a circumferential length of the concave groove. 9. The axial steam turbine according to claim 7, wherein the bottom of the groove is formed in a curved surface that is curved in the axial direction. 10. The depth of the portion of the groove facing the pipe opening is about ½ of the distance between the diaphragm inner and outer rings.
The axial flow steam turbine according to claim 7, 8 or 9, wherein the axial flow steam turbine is formed. 11. A steam inlet pipe which penetrates a turbine casing and supplies steam, an inner casing which is arranged in the casing and forms an inlet steam chamber, and two left and right axial flows from the steam chamber of the inner casing. In an axial flow steam turbine comprising a diaphragm inner ring and a diaphragm outer ring that form a steam flow path that separates in a direction, and a nozzle blade provided between the diaphragm outer ring and the diaphragm inner ring, the opening of the steam inlet pipe is On the outer peripheral surface of the diaphragm inner ring facing each other, the portion facing the opening of the steam inlet pipe is deepest, and gradually becomes shallower as it goes away from the opening of the steam inlet pipe in the circumferential direction and the axial direction. In addition to providing the recessed groove, a flange portion that extends in the circumferential direction and protrudes in the radial direction is provided in the axial center portion of the recessed groove. Axial flow steam turbine, wherein the door. 12. A steam inlet pipe that penetrates a turbine casing to supply steam, an inner casing that is arranged in the casing and forms an inlet steam chamber, and two left and right axial flows from the steam chamber of the inner casing. In an axial flow steam turbine comprising a diaphragm inner ring and a diaphragm outer ring that form a steam flow path that separates in a direction, and a nozzle blade provided between the diaphragm outer ring and the diaphragm inner ring, the opening of the steam inlet pipe is On the outer peripheral surface of the diaphragm inner ring facing each other, the portion facing the opening of the steam inlet pipe is deepest, and gradually becomes shallower as it goes away from the opening of the steam inlet pipe in the circumferential direction and the axial direction. And a guide part for guiding a part of the inflowing steam in the axial direction between the groove and the steam inlet pipe opening. Axial flow steam turbine, characterized in that the so that.