JPH08121107A - Steam turbine nozzle - Google Patents

Abstract

PURPOSE: To prevent drain flowing in the outer circumferential wall surface of a turbine nozzle from flowing into the back side of a nozzle blade by secondary flow inside a nozzle cascade, reduce erosion of a moving blade and thereby impede deterioration of turbine performance. CONSTITUTION: With regard to a steam turbine nozzle having the outer circumferential side end part of a nozzle blade 3 stuck fast to the outer circumferential wall and the inner circumfernential side end part stuck fast to the inner wall, the outer circumferential wall 11 and a part 11 of the inner circumferential wall 10 are integrally formed with the nozzle blade 3 and a slit shaped opening 13 for discharging drain is provided on a part of the outer circumferential wall 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steam turbine nozzle, and more particularly to a steam turbine nozzle designed to prevent erosion and deterioration of performance of a moving blade caused by a drain in steam colliding with a tip of the moving blade. Regarding

[0002]

2. Description of the Related Art Generally, in most paragraphs of nuclear turbines and geothermal turbines, and in low-pressure paragraphs of thermal power turbines, a part of steam, which is a working fluid, is condensed to form a drain, which is gathered on the outer peripheral side by centrifugal force. It flows mainly on the outer peripheral side of the nozzle blade surface and on the inner peripheral surface of the nozzle outer ring, which collides with the downstream rotor blade and causes the erosion of the tip portion of this rotor blade and reduces the efficiency of the paragraph. .

Therefore, there has been proposed a steam turbine nozzle in which the above-mentioned drain is separated and removed from the steam passage portion.

FIG. 10 is a sectional partial view of a conventional steam turbine nozzle portion provided with the above drain separation device. A rotor 1 is provided with rotor blades 2 in a plurality of stages, and the rotor blades 2 are moved in each stage. Nozzle blades 3 are arranged upstream of the row of blades 2.

The above-mentioned nozzle vanes 3 are arranged between a nozzle outer ring 5 which constitutes the outer peripheral wall 4 of the steam passage of the turbine and a nozzle inner ring 6 which constitutes the inner peripheral wall of the flow passage, and both ends of the nozzle vanes 3 are the nozzle outer ring. 5 and the nozzle inner ring 6 are fixed by welding, casting, or the like.

By the way, in the paragraph where a part of steam is easily condensed, drain catchers 7 and 8 are opened on the inner peripheral wall surface of the nozzle outer ring 5 where the drain is particularly concentrated. The drain catchers 7 and 8 are directly or indirectly connected. In general, the drain catchers 7 and 8 are communicated with a low pressure portion such as a condenser having a lower pressure than the opening surface of the drain catchers 7 and 8.

Therefore, when the drain adheres to the inner surface of the nozzle outer ring 5 and flows along the inner surface and reaches the openings of the drain catchers 7, 8, the drain is sucked into the drain catchers 7, 8 by a low pressure. , Is discharged outside the steam flow path.

[0008]

The steam turbine nozzle configured as described above has already been adopted in the actual low pressure stage of a steam turbine, and has been empirically proven to be effective to some extent in preventing erosion of the tip of the moving blade. I know that.

However, for example, when a long blade of 26 inches or more is adopted, when the rotation speed of the rotor is high, and when the reheat steam temperature is low and the steam wetness is high, it is insufficient for preventing erosion. In addition, the steam turbine nozzle as described above does not always exhibit sufficient effect in reducing the loss caused by the collision of water droplets ejected from the trailing edge of the nozzle blade with a relatively large particle diameter on the moving blade. There's a problem.

That is, on the inner surface of the outer peripheral wall of the nozzle blade,
As the wetness increases, a large amount of drain flow concentrates. In this case, most of the drain flowing in from the outer peripheral wall of the upstream paragraph is removed by the drain catchers 7 and 8, but the water droplets in the steam having the circumferential velocity component are downstream from the drain catcher 7 due to the centrifugal force. Therefore, the drain collected by colliding with the outer peripheral wall cannot always be removed.

Further, there is also a drain in which a part of the drain that flows into the nozzle blade row and collects flows on the outer peripheral wall surface by a secondary flow caused by the pressure difference between the back side and the abdominal side of the nozzle blade. When most of this drain passes through the outer peripheral portion of the nozzle blade, it is drawn to the back side of the adjacent nozzle blade by the secondary flow, and becomes a flow on the back surface of the nozzle blade, and the nozzle blade trailing edge. There is also a possibility that it will flow out of the tank and collide with the rotor blades, causing erosion.

Separately from this, there is a drain flow on the surface of the nozzle blade, which is considered to be caused by the collision of water droplets in the steam main flow on the back side and the ventral side. This also causes the erosion of the moving blade. Has become.

In order to cope with such a problem, a method of providing a slit-shaped suction opening on the surface of the nozzle blade and discharging the drain has been experimentally confirmed to be effective, and has also been applied to an actual machine.

However, this is also effective mainly for the drain gathered by colliding with the outer peripheral wall downstream of the drain catcher and the drain in the steam main flow on the nozzle blade surface, but for the drain generated by other causes. It is known from actual experience that it is not effective enough.

In view of such a point, the present invention prevents the drain flowing on the outer peripheral wall surface from flowing into the back side of the nozzle blade by the secondary flow in the nozzle blade row, thereby reducing the erosion of the moving blade, and An object of the present invention is to obtain a steam turbine nozzle that does not deteriorate turbine performance.

[0016]

According to a first aspect of the present invention, there is provided a steam turbine nozzle having an outer peripheral end of a nozzle blade fixed to an outer peripheral wall and an inner peripheral end fixed to an inner peripheral wall. A part of the inner peripheral wall is formed integrally with the nozzle blade, and a slit-shaped opening for drain discharge is provided in a part of the outer peripheral wall.

According to a second aspect of the invention, the slit-shaped opening extends from the back side of the nozzle blade to the ventral side of the adjacent nozzle blade, and the front end of the slit-shaped opening extends from the front edge of the nozzle blade in the axial chord length of the nozzle blade. The position is 1/3 to 1/2 of C, and the rear end of the slit-shaped opening is at (1/3 to 1/2) C from the rear end edge of the nozzle blade adjacent to the nozzle blade. Is characterized by.

According to a third aspect of the present invention, the nozzle blade tip portion and a part of the outer peripheral wall provided with the slit-shaped opening and the nozzle blade root portion and a part of the inner peripheral wall are separately manufactured, and the nozzle blade tip portion is formed. It is characterized in that the nozzle blade root portion and the nozzle blade root portion are joined and integrated by welding.

In a fourth aspect of the invention, a part of the outer peripheral wall having a slit-shaped opening, a part of the inner peripheral wall, and the nozzle blade are separately manufactured, and the nozzle blade is formed on a part of the outer peripheral wall. The end of the nozzle blade is inserted into each of the tip end insertion opening and the nozzle blade root end insertion opening formed in a part of the inner peripheral wall, and is fixed by welding and integrated.

[0020]

When the drain on the outer peripheral wall flows toward the back side of the nozzle blade by the secondary flow in the flow passage of the nozzle blade row, it is discharged from the slit-shaped opening provided in a part of the outer peripheral wall. Therefore, the drain does not flow into the back surface of the nozzle blade, the amount of water droplets ejected from the trailing edge of the nozzle blade is reduced, and erosion of the moving blade can be reduced. further,
The outer peripheral wall, the inner peripheral wall, the nozzle blade, etc. are appropriately divided and manufactured,
By connecting them by welding, their manufacture can be easily and precisely processed.

[0021]

Embodiments of the present invention will be described below with reference to the accompanying drawings. In the figure, the same parts as those in FIG. 10 are designated by the same reference numerals, and detailed description thereof will be omitted.

As shown in FIG. 1, nozzle vanes 3 are arranged upstream of the moving vanes 2 planted on the outer periphery of the rotor 1. As shown in FIG. 2, the inner peripheral side wall 10 and the outer peripheral side wall 11 are integrally formed at the inner peripheral side end and the outer peripheral side end of each nozzle blade 3, respectively.

Each inner side wall 10 formed integrally with the nozzle blade 3 is formed so as to be connected in the circumferential direction to form an annular shape when disposed on the outer circumference of the nozzle inner ring 6. The inner ring 6 is joined and fixed to the outer periphery of the inner ring 6 by welding or the like to form the inner peripheral wall of the turbine nozzle. Further, each outer peripheral side wall 11 formed integrally with each nozzle blade 3 is also formed so as to be annularly connected to each other when the nozzle blades 3 are arranged in the circumferential direction. The outer peripheral side wall 11 is fixed to the inner peripheral surface of the nozzle outer ring 5 by welding or the like.

The nozzle outer ring 5 is, as shown in FIG.
It has a concave groove 5a extending in the circumferential direction and opening to the inner peripheral side, and the opening by the concave groove 5a is sealed by the outer peripheral side wall 11 arranged in the circumferential direction, and the outer periphery arranged in the above annular shape. The side sidewall 11 and the nozzle outer ring 5 constitute an outer peripheral wall 12 of the turbine nozzle.

As shown in FIG.
As shown in FIG. 3, when these are arranged in the circumferential direction, a slit-shaped opening 13 extending from the vicinity of the back side inlet of the nozzle blade 3 to the vicinity of the ventral side outlet of the adjacent nozzle blade is provided.

Then, in the flow path of the steam turbine in which the moist steam flows, the minute water droplets generated by the expansion of the steam collide with the nozzle blades 3 and the moving blades 2 and become large water droplets. The water droplets that have collided with the moving blades at the upstream stage of the nozzle blades 3 are swept by the moving blades, collide with the outer peripheral wall, and drain on the outer peripheral wall surface. Of these, most of the water that has collided on the upstream side of the drain catcher 8 is removed by the drain catcher 8, but the water that has collided on the downstream side of this flows through the outer peripheral portion of the nozzle blade 3.

On the other hand, the outer peripheral wall 1 in the flow path of the nozzle blade 3
On the surface of 2, there is a secondary flow due to the pressure difference between the nozzle blade ventral surface side and the nozzle blade back surface side, and the drain on the outer peripheral wall crosses the outer peripheral wall and is dragged by the secondary flow, Nozzle blade back side 3b of adjacent nozzle blades from blade side 3b
Flows to FIG. 4 shows the flow W of these drains.

As described above, the drain flowing along the outer peripheral wall surface, that is, the inner surface of the outer peripheral side wall 11 is sucked into the concave groove 5a of the nozzle outer ring 5 through the slit-shaped opening 13, and is returned through the drain discharge passage. It is led to a water container. Therefore, the drain flowing into the back surface of the nozzle blade is reduced, the amount of water droplets ejected from the trailing edge of the nozzle blade is reduced, and the erosion of the moving blade is reduced.

By the way, since a horseshoe-shaped vortex is generated around the front edge of the nozzle blade 3 as is well known, the drain does not flow into the ventilating surface of the nozzle blade at this portion. According to the model test, in order to effectively discharge the drain flowing into the outer peripheral wall surface of the nozzle blade and flowing to the nozzle blade back surface 3b by the secondary flow, the nozzle blade axial direction chord length C on the back surface side of the nozzle blade is On the line connecting the point 1/3 to 1/2 away from the nozzle leading edge, and the point upstream from the nozzle trailing edge on the ventral side of the nozzle blade by (1/3 to 1/2) C. Since the drain flows in a direction orthogonal to the line, it is effective to provide the slit-shaped opening 13 on the line.

Further, the nozzle blade 3 and both sidewalls 1
In the case of manufacturing a sidewall integrated nozzle blade in which 0 and 11 are integrally formed, a method of die forging or cutting out from a square material by machining is not realistic in view of economical efficiency, and should be manufactured by a precision casting method. Is preferred.

When a slit-shaped opening is formed on the outer peripheral wall 5 of the nozzle, the manufacturing method thereof becomes a problem. If the slit-shaped opening is machined in advance on the outer peripheral wall of the nozzle by electric discharge machining or laser processing, and the nozzle blade is joined to the outer peripheral wall by welding,
Since it is necessary to provide the slit-shaped opening close to the back surface of the nozzle blade and the ventral surface of the nozzle blade, the slit-shaped opening is blocked by welding, or the shape of the slit-shaped opening deviates from the optimum value due to thermal deformation, and drainage There is a possibility that the discharge effect will decrease sharply, and it will not be possible to sufficiently prevent erosion of the rotor blades.

On the other hand, in the present invention, the size and the position of the slit-shaped opening are also formed by forming the side wall having the slit-shaped opening 13 and the nozzle blade integrally by the precision casting method. The optimum shape is maintained, and the optimum drainage effect can be achieved.

By the way, in the manufacturing process by the precision casting method, if the sidewall-integrated nozzle blade does not enter the coating tank or the dewaxing device, as shown in FIG. In the state of being divided into two in the vicinity of the central portion in the direction, the outer peripheral side wall 11 and the nozzle blade tip portion 20a are integrated, and the inner peripheral side wall 10 and the nozzle blade root portion 20b are integrated separately. The nozzle blade tip portion 20a and the nozzle blade root portion 20b can be integrated by welding by manufacturing by precision casting.

FIG. 6 is a view showing another method of manufacturing the nozzle blade 3 portion according to the present invention, in which the outer peripheral side wall 11 is formed.
And an opening 11 having the same shape as the end of the nozzle blade 3 in the inner sidewall 10 and into which the end can be inserted.
a and 10a are formed, and as shown in FIGS. 7 and 8, the ends of the nozzle blades 3 are inserted into the openings 11a and 10a, and fixed on the surface opposite to the steam passage surface by fillet welding to form one body. Turn into.

When a nozzle blade and a side wall are integrally manufactured by precision casting, it is not possible to make the shape of the base portion of the side wall and the nozzle blade sharp due to the relationship with the molten metal. Has a curved portion of about 2R. Therefore, due to the influence of the curved portion, the drain easily flows to the nozzle blade rear surface side without resistance at the root portion.

On the other hand, in the case shown in FIGS. 6 to 8, in particular, as shown in FIG. 8, the angle formed between the base of the nozzle blade 3 and the side wall becomes sharp, and the dead water area 21 of the drain is formed in the portion. Due to the eddies formed and generated in the dead water region 21, the inflow of drain to the back side of the nozzle blade is reduced.

FIG. 9 shows still another embodiment of that shown in FIG. 6, in which the nozzle blade is divided into a nozzle blade tip portion 20a and a nozzle blade root portion 20b at the middle portion in the length direction. Fabrication and subsequent integration by welding can facilitate its manufacture.

[0038]

As described above, in the present invention, a part of the outer peripheral wall such as the outer peripheral side wall, a part of the inner peripheral wall such as the inner peripheral wall sidewall, and the nozzle blade are integrally formed, Since a slit-shaped opening for drain discharge is provided in a part of the outer peripheral wall, the outer peripheral wall of the portion of the outer peripheral wall of the steam passage that is sandwiched between the back surface side of the nozzle blade and the ventral surface side of the nozzle blade adjacent to this is set. The flowing drain is discharged from the slit-shaped opening and is prevented from flowing into the nozzle blade back side by the secondary flow, the amount of water droplets ejected from the nozzle blade trailing edge is reduced, and the blade erosion can be reduced. it can. Moreover, since a part of the outer peripheral wall having the slit opening and a part of the inner peripheral wall are integrally formed with the nozzle blade, the turbine nozzle can be simply welded to the outer peripheral wall and the inner peripheral wall. It is possible to maintain the size and position of the slit opening in an optimum shape, and it is possible to achieve an optimum drain discharge effect. Further, when a part of the outer peripheral wall and the nozzle blades are separately manufactured and integrated by welding, the manufacturing can be performed more easily.

[Brief description of drawings]

FIG. 1 is a partial vertical cross-sectional view of a steam turbine nozzle of the present invention.

FIG. 2 is a perspective view of a nozzle blade according to an embodiment of the present invention.

FIG. 3 is a sectional view taken along line AA of FIG. 1;

FIG. 4 is a diagram showing a flow of drain of a nozzle portion.

FIG. 5 is an exploded perspective view showing another embodiment of the nozzle blade in the present invention.

FIG. 6 is an exploded perspective view showing still another embodiment of the nozzle blade according to the present invention.

FIG. 7 is an enlarged side view of the tip portion of the nozzle blade shown in FIG.

FIG. 8 is a sectional view taken along the line BB of FIG. 7;

FIG. 9 is an exploded perspective view showing another embodiment of the nozzle blade in the present invention.

FIG. 10 is a cross-sectional view showing an example of a conventional moisture separator in a turbine.

[Explanation of symbols]

 1 Rotor 2 Blade 3 Nozzle 7,8 Drain catcher 10 Inner peripheral side wall 11 Outer peripheral side wall 13 Slit-shaped opening

Claims (5)

[Claims] 1. A steam turbine nozzle having an outer peripheral end of a nozzle blade fixed to an outer peripheral wall and an inner peripheral end fixed to an inner peripheral wall, wherein the outer peripheral wall and a part of the inner peripheral wall are integrally formed with the nozzle blade. And a slit-shaped opening for drain discharge is provided in a part of the outer peripheral wall,
Steam turbine nozzle. 2. The slit-shaped opening extends from the back surface side of the nozzle blade to the ventral surface side of the adjacent nozzle blade, and the front end of the slit-shaped opening extends from the front edge of the nozzle blade to the axial chord length C of the nozzle blade.
Of the slit-shaped opening at the position of 1/3 to 1/2 of the nozzle vane adjacent to the nozzle vane (1
The steam turbine nozzle according to claim 1, wherein the steam turbine nozzle is in a position of / 3 to 1/2) C. 3. A nozzle blade tip portion and a portion of an outer peripheral wall provided with a slit-shaped opening, and a nozzle blade root portion and a portion of an inner peripheral wall are separately manufactured, and the nozzle blade tip portion and the nozzle blade root portion are manufactured separately. The steam turbine nozzle according to claim 1, wherein and are integrated by welding. 4. A part of an outer peripheral wall having a slit-shaped opening, a part of an inner peripheral wall, and a nozzle blade are separately manufactured to insert a nozzle blade tip end portion formed in a part of the outer peripheral wall. The steam according to claim 1, characterized in that the ends of the nozzle blades are respectively inserted into the openings for inserting the nozzle blade root end portions formed in the openings and a part of the inner peripheral wall, and are fixed by welding and integrated. Turbine nozzle. 5. The steam turbine nozzle according to claim 4, wherein the root portion and the tip portion of the nozzle blade are separately manufactured and integrated by welding.