JPH06248903A - Waterdrop removing device for steam turbine - Google Patents

Abstract

PURPOSE:To provide a waterdrop removing device for a steam turbine, which is capable of sufficiently removing waterdrops running on the surface of a nozzle and the inner surface of a nozzle outer ring without causing perfamance drop of the turbine. CONSTITUTION:A hollow nozzle 1 is composed of a stationary member 1a and a movable member 1b, and a hollow, nozzle outer ring 6 is composed of a stationary member 6a and a movable member 6b. Further, a blade outlet guide ring 18 is fixed to the movable member 6b on the nozzle outer ring 6 side. The movable member 1b on the nozzle 1 side, the movable member 6b on the nozzle outer ring 6 side, and the blade outlet guide ring 18 are formed integrally to be driven through a driving rod 19 by a drive device 20 in the axis-direction R. The drive device 20 is driven-controlled by a control device 21. A humidity sensor 22 arranged in front of the nozzle 1 is connected to the control device 21, and the detected results of the humidity sensor 22 are inputted into the control device as electric signals.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water drop removing device for a steam turbine, and more particularly to a technique for improving the efficiency of water drop removal.

[0002]

2. Description of the Related Art In general, the vicinity of the final stage of a low pressure thermal turbine and most of the paragraphs of a nuclear turbine using saturated steam operate in wet steam containing a large amount of water droplets. Therefore, there have been problems such as erosion caused by water droplets colliding with the inlet edge of a moving blade having a high peripheral velocity, and reduction in blade efficiency due to wetness loss. Particularly in recent years, as the number of nuclear turbines with a high degree of wetness has increased, the overall capacity of steam turbines has also increased the size of the final stage rotor blades, and there is a strong demand for effective countermeasures to the above problems. It was

As a water drop removing device in a conventional steam turbine, for example, a device described in Japanese Patent Publication No. Sho 49-9522 is known. In this device, as shown in FIG.
As shown in (AA cross-sectional view in FIG. 8), slit-shaped water droplet suction ports 4 and 5 are formed in the abdominal surface 2 and the back surface 3 of the nozzle 1, respectively, and the inner surface 7 of the nozzle outer ring 6 is formed. Also, a slit-shaped water droplet suction port 8 is formed. Nozzle 1
And the nozzle outer ring 6 and the nozzle inner ring 9 that hold the nozzle 1 are all hollow, and the hollow portions 10, 11,
12 communicate with each other. Further, the hollow portion 11 on the nozzle outer ring 6 side communicates with a low pressure source such as a condenser (not shown), and suction is performed from the water droplet suction ports 4, 5, 8.

The water droplets transmitted along the ventral surface 2 of the nozzle 1 are sucked into the hollow portion 10 through the water droplet suction port 4, and the water droplets transmitted through the back surface 3 of the nozzle 1 through the water droplet suction port 5, respectively, and further on the nozzle outer ring side 6. It flows into the condenser from the hollow portion 12. Further, the water droplets that have propagated on the inner surface 7 of the nozzle outer ring 6 are sucked into the hollow portion 11 from the water droplet suction port 8 and also flow into the condenser. In this way, the water droplets traveling on the surfaces of the nozzle 1 and the nozzle outer ring 6 are removed, so that the generation of coarse water droplets on the trailing edge 13 of the nozzle 1 is reduced, and the erosion of the moving blade is reduced.

[0005]

Even if the above-mentioned conventional water drop removing device is adopted, the water drops cannot be actually sufficiently removed, and the erosion of the moving blade and the wet loss cannot be greatly reduced. It was The reason will be described in detail below.

FIG. 10 shows an expansion curve of a steam turbine in a general commercial thermal power plant. Point D in the figure
Indicates the steam state at the nozzle inlet in the preceding paragraph of the final stage (hereinafter referred to as L-1), similarly point E indicates the steam state at the nozzle outlet of L-1, and point F indicates the blade outlet of L-1. Point G shows the steam state at the nozzle exit of the final stage paragraph (hereinafter referred to as L-0), and point H shows the steam state at the rotor blade exit at L-0.

As can be seen from FIG. 10, the steam changes from dry steam to wet steam in the nozzle of L-1, and the wetness reaches about 10% at the moving blade outlet of L-0. However,
Even if the vapor reaches the theoretical wet region due to the expansion, it does not immediately start to condense and expands in a non-equilibrium state until the wetness reaches about 3 to 5%, and then water droplets are generated for the first time.
In this case, the diameter of the generated water droplets is about 0.1 to 1 μm, and the water droplets gradually grow as the steam expands. At this time, some water droplets collide with and adhere to the surfaces of the nozzle and the moving blade, but since the particle size is small, erosion of the moving blade hardly occurs at this stage.

However, in the L-1 rotor blade, centrifugal force,
The movement in the outer peripheral direction due to the Coriolis force and the steam force becomes dominant, and the water droplets adhere to the inner surface of the nozzle outer ring of L-0 and the outer peripheral portion of the nozzle blade surface. In FIG. 11, a vapor stream line in the L-0 paragraph J is indicated by a solid line L by a broken line K.
The water droplet streamline is shown in Fig. 1, but as can be seen from this figure, water droplets are generated in the rotor blade 14 of L-1 (indicated by I in the figure), and as shown by the water droplet streamline L, L- 0 (indicated by J in the figure)
The water film M is formed by adhering to the inner surface 7 of the nozzle outer ring 6 and the outer peripheral portion of the nozzle 1. The water film M reaches the trailing edge 13 of the nozzle L-0 while developing, is blown off by the steam force, is mixed in the steam, and is further sprayed in the form of water droplets.

The water droplet diameter formed at this time is 100 to 5
It reaches as much as 00 μm, which is much larger than naturally occurring water droplets. Then, this huge water droplet collides with the moving blade 15 of L-0 without being sufficiently accelerated by the steam force, and causes erosion of the moving blade 15.
FIG. 12 shows the degree of wetness in the nozzle of L-0. In this figure, the degree of wetness is rapidly increased in the outer peripheral portion of the nozzle 1, and water droplets are unevenly distributed in the outer peripheral portion of the nozzle 1. Understand well.

Most of the water droplets of the wet steam in the nozzle 1 are unevenly distributed on the outer peripheral portion of the nozzle 1 as described above, but the same can be said for the water film M. That is, the nozzle 1
Around the outer periphery of the nozzle and the inner surface 7 of the nozzle outer ring 6 have a diameter of 0.5 to
A large number of water droplets of about 1 μm are attached, and these water droplets are aggregated by flowing on the surface in the downstream direction by steam force, and develop into a water film M.

As shown in FIG. 13, when the behavior of the water film M propagating in the vicinity of the inner surface 7 of the nozzle outer ring 6 is seen from the outflow direction of the steam, the water film M1 propagating in the back surface 3 of the nozzle 1 (solid line in the figure). (Indicated by the arrow), the water film M2 hanging on the suction opening 5
Is sucked through the suction opening 5 and does not reach the nozzle trailing edge 13. However, the water film M3 that does not cover the suction opening 5 reaches the trailing edge 13 without being sucked, is blown off by the steam force and becomes a huge water droplet, and is mixed into the steam to cause erosion of the moving blade. . This also applies to the nozzle belly surface.

On the other hand, of the water film M4 (indicated by the broken line arrow in the figure) transmitted along the inner surface 7 of the outer ring 6 of the nozzle, the water film M5 which is applied to the suction opening 5 is sucked from the suction opening 5 and is drawn into the nozzle rear edge 1
It does not reach c. However, the water film M6 that does not reach the suction opening 5 is not sucked in and is pulled up to the back surface 3 of the nozzle 1 as it passes between the nozzles 1. I will explain this in a little more detail.

The pressure on the blade surface of the nozzle 1 is high on the ventral surface 2 and low on the back surface 3, as shown in FIG. Therefore, in the steam passage portion between the nozzles 1, a force from the abdominal surface 2 to the back surface 3 is generated. On the inner surface 7 of the nozzle outer ring 6, the flow velocity in the main steam flow direction is slow due to the viscosity of the steam, so that the above-described force from the belly surface 2 to the back surface 3 of the nozzle 1 has a great influence. Therefore, on the inner surface 7 of the nozzle outer ring 6, as shown in FIG. 15, a vortex flow O called a secondary flow is generated by the force N from the abdominal surface 2 of the nozzle 1 to the back surface 3.
As a result, in FIG. 13, of the water film M4 transmitted on the inner surface 7 of the nozzle outer ring 6, the water film M5 that does not reach the suction opening 8
After being pulled up to the back surface 3 of the nozzle 1 by the secondary flow and reaching the trailing edge 13, it is blown off from the nozzle trailing edge 13 and mixed in the steam, causing erosion of the moving blade.

Since the water film M behaves in this manner, it is necessary to remove the water films M1 and M4 from the surface of the nozzle 1 to the inner surface 7 of the nozzle outer ring 6 without leakage in order to reduce the erosion of the moving blade. is there. However, as shown in FIGS.
In the example shown in FIG. 3, the water films M2 and M5 that are hung on the suction openings 4 and 5 on the nozzle 1 side and the suction opening 8 on the nozzle outer ring 6 side are sucked, but the water films M that are not hung on the suction openings 4, 5, and 8.
3, M6 reach the trailing edge 13 of the nozzle 1 without being removed, and are blown off by the steam force to form huge water droplets, which are mixed in the steam and cause erosion of the moving blade.

Next, the second reason will be described.

As described above, slit-like suction openings 4, 5 and 8 are formed in the abdominal surface 2 and the back surface 3 of the hollow nozzle 1 and the inner surface 7 of the hollow nozzle outer ring 6, and the surface of the nozzle 1 and the nozzle outer ring 6 are formed. It is generally known that when sucking the water film M transmitted through the inner surface 7 of, the steam is also sucked together with the water film M. This entrained steam (hereinafter referred to as entrained steam) is originally capable of working as a working fluid, and if sucked through the suction openings 4, 5, 8 it will not work in the subsequent paragraphs. , Causes performance degradation.
Therefore, when the water film M is sucked through the suction openings 4, 5, 8 it is necessary to reduce the amount of associated steam as much as possible.

As shown in FIG. 16, the suction openings 4, 5,
If the width P of 8 is set appropriately, most of the water film M is sucked through the suction openings 4, 5, 8 while the vapor 16 that is the working fluid is hardly sucked. However, in recent years, there is a demand for economical power plant operation that responds to fluctuations in power demand due to day and night, weekday holidays, seasons, etc. In recent years, steam turbines that use variable pressure operation have been adopted instead of conventional constant pressure operation. Is increasing. Then, when the steam condition changes due to the variable pressure operation, the following problems occur.

FIG. 17 shows the steam conditions in the steam passage between the nozzles 1 with the enthalpy on the vertical axis and the entropy on the horizontal axis. The points E1, E2, and E3 change the turbine load. It shows the steam condition of the steam passage part when it is allowed. Here, the suction condition of the water film M shown in FIG. 16 is the steam condition at the point E1 shown in FIG. 17, and the wetness of the steam passage portion in this case is X1. Then, as the turbine load decreases, as shown in FIG. 17, the steam condition of the steam passage portion shifts to point E2, and the degree of wetness of the steam passage portion becomes X.
It becomes as small as 2. That is, the amount of the water film M is reduced. At this time, since the thickness of the water film M becomes small, a large gap is created between the suction opening 7 and the water film M, and as shown in FIG. 1
7 is sucked and the performance of the turbine deteriorates.

On the other hand, when the load on the turbine increases, as shown in FIG. 17, the steam condition of the steam passage portion of the nozzle shifts to point E3, and the wetness of the steam passage portion of the nozzle increases to X3. That is, the amount of the water film M increases. At this time, since no gap is created between the suction openings 4, 5, 8 and the water film M, the associated steam is not sucked in, as shown in FIG. However, since the water film M has a large thickness, a part of it reaches the nozzle trailing edge 13 without being sucked through the suction opening 2. The water film M collected at the trailing edge 13
From there, it is blown off as coarse water droplets and collides with the rotor blades, causing erosion, and also prevents the rotor blades from rotating and reduces turbine performance.

Therefore, an object of the present invention is to solve the problems of the above-mentioned prior art, and to sufficiently remove the water droplets transmitted on the nozzle surface and the inner surface of the nozzle outer ring without deteriorating the performance of the turbine. It is to provide a removal device.

[0021]

In order to achieve the above object, a water droplet removing apparatus for a steam turbine according to the present invention is a nozzle in which a hollow portion communicating with a hollow portion between a nozzle inner ring and a nozzle outer ring is formed. In the steam turbine having, each of the nozzle and the nozzle outer ring is divided into a fixed member and a moving member, and the moving member is relatively moved in the axial direction by a driving device, so that the nozzle is separated from the fixed member. It is characterized in that a continuous slit-shaped suction opening is formed over the outer ring of the nozzle.

[0022]

According to the present invention, since the suction opening is formed continuously from the nozzle to the outer ring of the nozzle, the water film from the surface of the nozzle to the inner surface of the outer ring of the nozzle can be removed without leakage. Further, by driving the moving member, the width of the suction opening is changed, and it is possible to prevent suction of the associated steam and suction leakage of the water film.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the water drop removing device according to the present invention will be described below with reference to the accompanying drawings. The same members as those of the conventional device described above are designated by the same reference numerals. As shown in FIG. 1, in this embodiment, the hollow nozzle 1 is composed of a stationary member 1a and a moving member 1b, and the hollow nozzle outer ring 6 is composed of a stationary member 6a and a moving member 6b. . The blade outlet guide ring 18 is fixed to the moving member 6b on the nozzle outer ring 6 side. The moving member 1b on the nozzle 1 side, the moving member 6b on the nozzle outer ring 6 side, and the blade outlet guide ring 18 are integrated, and are driven in the axial direction R by a drive device 20 via a drive rod 19 (movement). This is indicated by the one-dot chain line). The drive unit 20 is drive-controlled by the control unit 21. A wetness sensor 22 arranged in front of the nozzle 1 is connected to the control device 21, and the detection result of the wetness sensor 22 is input as an electric signal.

As shown in FIG. 2 (a sectional view taken along line BB in FIG. 1), a slit-like suction opening 4 on the abdominal surface 2 and the back surface 3 are formed by the gap between the stationary member 1a on the nozzle 1 side and the moving member 1b. And a slit-shaped suction opening 5 are formed. Further, due to the gap between the stationary member 6 a and the moving member 6 b on the nozzle outer ring 6 side, the slit-shaped suction opening 8 is also formed on the inner surface 7 of the nozzle outer ring 6.
Is configured. As described above, the moving member 1b on the nozzle 1 side and the moving member 6b on the nozzle outer ring 6 side are connected to the drive device 20.
Can move integrally in the axial direction R. When both the moving members 1b and 6b move in the axial direction R, the gaps between the two stationary members 1a and 6a change, so that the widths P1, P2 and P3 of the suction openings 4, 5 and 8 change.

As shown in FIG. 3, since the moving member 1b on the nozzle 1 side and the moving member 6b on the nozzle outer ring 6 side are integrated, the suction opening 5 on the rear surface 3 side and the suction member on the nozzle outer ring 6 side are sucked. It is continuous with the opening 8. Similarly, the suction opening 4 on the abdominal surface 2 side and the suction opening 8 on the nozzle outer ring 6 side are also continuous.

The operation of this embodiment will be described below. As shown in FIG. 4, in this embodiment, the water film M1 (shown by the solid arrow in the figure) transmitted to the back surface 3 is sucked from the suction opening 2b of the back surface 3 and transmitted to the inner surface 7 of the nozzle outer ring 6. The water film M4 (indicated by a dashed arrow in the figure) is sucked through the suction opening 8 on the nozzle outer ring 6 side. Further, as described above, since the suction openings 4, 5 on the abdominal surface 2 side and the back surface 3 side of the nozzle 1 and the suction opening 8 on the nozzle outer ring 6 side are continuous, any of the suction openings 4, 5, 8 can be used. There is no water film M that does not hang.

FIG. 5 shows the axial position S of the moving members 1b and 6b.
Is a control flowchart for determining the
At 1, the wetness sensor 22 measures the wetness X of the nozzle vapor passage portion. Next, in step S2, the control device 21
The axial position S of the moving members 1b and 6b is calculated and determined from the wetness X measured by. Finally in step S3,
An electric signal corresponding to the axial position S is sent to the drive device 20,
The moving members 1b and 6b are moved in the axial direction. It should be noted that this control is repeatedly performed at predetermined intervals, and the moving member 1
The positions of b and 6b are changed so that the widths of the suction openings 4, 5, and 8 are always the optimum values.

FIG. 6 shows an example of a calculation curve for determining the axial position S of the moving members 1b, 6b from the wetness X used in the control device 21, and FIG. 7 shows the moving members 1b, 6b.
It shows the relationship between the axial position S of b and the width P of the suction openings 4, 5, 8. As shown in these figures, if the wetness degree X is large, the axial position S of the moving members 1b and 6b is S.
Shifts rearward, and the width P of the suction openings 4, 5, 8 also increases. Therefore, even if the thickness of the water film M transmitted on the surface of the nozzle 1 or the inner surface 7 of the nozzle outer ring 6 increases in accordance with the degree of wetness X, the areas of the suction openings 4, 5, 8 are sufficient to suck the water film M. It is maintained at a proper value and prevents blade erosion. Further, since no gap is created between the suction openings 4, 5, 8 and the water film M, the produced steam is hardly sucked in, and deterioration of the turbine performance can be prevented.

[0029]

As is apparent from the above description, according to the present invention, a continuous slit-shaped suction opening is formed from the nozzle to the outer ring of the nozzle due to the gap between the stationary member and the moving member. The water film on the inner surface of the outer ring can be removed without leakage, and the erosion of the moving blade due to the collision of water droplets can be prevented. In addition, by driving the moving member, the width of the suction opening can be changed according to the thickness of the water film, etc. Wing erosion can be prevented.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing an embodiment of a water droplet removing device for a steam turbine according to the present invention.

FIG. 2 is a sectional view taken along line BB in FIG.

FIG. 3 is a perspective view showing the vicinity of the outer ring of the nozzle of the steam turbine of the embodiment.

FIG. 4 is a perspective view showing a suction state of a water film in the steam turbine of the embodiment.

FIG. 5 is a control flowchart of the driving device in the embodiment.

FIG. 6 is a graph showing a calculation curve for determining the axial position of the moving member.

FIG. 7 is a graph showing the relationship between the axial position of the moving member and the width of the suction opening.

FIG. 8 is a side view showing a nozzle of a conventional steam turbine.

9 is a cross-sectional view taken along the line AA in FIG.

FIG. 10 is a graph showing an expansion curve of a steam turbine.

FIG. 11 is an explanatory diagram showing vapor streamlines and water droplet streamlines before and after the final stage.

FIG. 12 is a graph showing the degree of wetness in the nozzle in the final paragraph.

FIG. 13 is a perspective view showing a suction state of a water film in a conventional steam turbine.

FIG. 14 is a graph showing a pressure on a blade surface of a nozzle.

FIG. 15 is a perspective view showing a secondary flow from the abdominal surface to the back surface of the nozzle 1.

FIG. 16 is an explanatory diagram showing a state in which a water film is sucked in through a suction opening.

FIG. 17 is a graph showing steam conditions in a steam passage between nozzles.

FIG. 18 is an explanatory diagram showing a state in which a water film and associated steam are sucked in through a suction opening.

FIG. 19 is an explanatory diagram showing a state in which a part of a water film flows on the nozzle surface without being sucked.

[Explanation of symbols]

 1 Nozzle 1a Nozzle-side fixed member 1b Nozzle-side moving member 2 Nozzle belly face 3 Nozzle back face 4 Suction opening 5 Suction opening 6 Nozzle outer ring 6a Nozzle outer ring side fixed member 6b Nozzle outer ring side moving member 7 Nozzle outer ring surface 8 Suction opening 9 Nozzle inner ring 10, 11, 12 Hollow part 15 Moving blade 19 Drive rod 20 Drive device 21 Control device 22 Wetness sensor M Water film P Width of suction opening

Claims (2)

[Claims] 1. A steam turbine having a nozzle in which a hollow portion communicating with a hollow portion of an inner ring of a nozzle and a hollow portion of an outer ring of the nozzle is formed, and the nozzle and the outer ring of the nozzle are divided into a fixed member and a moving member, respectively. Steam is characterized in that a continuous slit-like suction opening is formed between the fixed member and the moving member by moving the moving member in the axial direction relative to the fixed member. Turbine water drop removal device. 2. A wetness sensor for detecting the wetness of a vapor passage between the nozzles, and a controller for controlling the drive unit by determining the position of the moving member based on the detection result of the wetness sensor. The water droplet removing device for a steam turbine according to claim 1, further comprising: