JP2723334B2 - Steam turbine nozzle water droplet removal equipment - Google Patents

Description

The present invention relates to a device for removing water droplets from a steam turbine nozzle operated in a wet area.

(Prior Art) Generally, in a steam turbine operated in a wet area, relatively small water droplets generated and grown in a steam passage portion are caused by centrifugal force of rotation of a blade (rotor blade) to form a tip portion of a nozzle (stationary blade). Flying to the vicinity, most of it travels along the nozzle surface and is blown off as coarse water droplets from the trailing edge of the nozzle, and the blown-off coarse water droplets collide with high-speed rotating blades, causing erosion on the blades It has been known. Further, the water droplets do not flow smoothly along the surface of the blade, but collide with the back side of the blade to act as a braking force, which may cause a decrease in turbine performance.

In other words, when the wettability of steam is small and the water droplet diameter is very small, most of the water droplet flows together with the steam flow through the curved nozzle passage, and even after passing through the nozzle, the water droplet diameter is relatively small. It has little effect on erosion, but when the wetness is high, the steam flow B diverges along its shape in the passage of the nozzle 1 while the wetness is high, as shown in FIG. The large water droplet A cannot turn due to inertial force, collides with the nozzle abdominal surface 2 and is collected there. The collected water droplets flow along the nozzle abdominal surface 2 and flow out to the rear edge 3 of the nozzle, and the water collected at the rear edge 3 is blown off as coarse water droplets therefrom, colliding with the blade and causing erosion on the blade.

When the wetness is further increased, as shown in FIG. 7, the vapor flow B flows in the axial direction in the same manner as described above, but the water droplet A flows so as to directly collide with the nozzle back surface 4. . Such a change in the inflow direction of the water droplet flow A occurs when the diameter of the water droplet becomes extremely large because the relative speeds of the outlet of the water droplet and the steam at the front stage blade differ greatly. That is, when the wetness is large and the diameter of water droplets in the steam is large, the eighth
As shown in the figure, the relative speed W 'of the blade outlet of the water droplet is smaller than the relative speed W of the blade outlet of the steam. Since the peripheral speed U is the same for both the water droplet and the steam, the absolute speed C' of the blade outlet of the water droplet is As shown in FIG. 7, the droplet flow collides with the nozzle back surface 4 and is collected, as shown in FIG. The water droplets collected on the back surface 4 of the nozzle also become coarse water droplets from the trailing edge 3 of the nozzle, are blown off, collide with the blades, and erode.

The coarse water droplets blown off from the nozzle trailing edge 3
The impact on the blades impedes the rotation of the blades, causing a reduction in turbine performance.

FIG. 9 is a view showing a nozzle structure for preventing the erosion and deterioration of the performance of the turbine due to the above-mentioned coarse water droplets, wherein a slit-shaped suction opening is formed on the ventral surface and the back surface of the hollow nozzle 1. a is drilled.
Each of the hollow nozzles 1 is communicated with a hollow nozzle inner ring 5 and a nozzle outer ring 6, respectively, and a pipe communicating with a low-pressure portion of the condenser is connected to the nozzle outer ring 6.

Thus, water droplets transmitted through the abdominal surface 2 of the nozzle are sucked into the cavity of the nozzle 1 from the suction opening a on the abdominal side, and water droplets transmitted through the back surface 4 of the nozzle are sucked into the cavity of the nozzle 1 from the suction hole a on the back side. It is discharged to low pressure parts such as condenser through 6,
Removal of water droplets transmitted to the surface of the nozzle 1 is performed.

FIG. 10 schematically shows the nozzle portion, and reference numerals 1, 5, and 6 in the figure schematically show the same parts as those in FIG. 9 and are seen in a direction perpendicular to the axle. It is a figure which shows the hollow part and the discharge path of a water droplet in an easy-to-understand manner.

By the way, as shown in FIG. 10, the nozzle portion is divided into two parts so as to be easily assembled and disassembled so as to be divided into an upper half and a lower half. Each of the nozzles 1 has an airfoil shape, and a large number of nozzles are installed all around the circumference. FIG. In the drawing, the suffix a is attached to the nozzle located at both the upper half and the lower half, and the suffix b is attached to the nozzle located at the upper half.

Therefore, first, the water droplet sucked into the hollow chamber 7a in the nozzle from the suction opening a of the lower nozzle 1a flows into the hollow chamber 9a of the nozzle outer ring 6a via the through hole 8a due to the gravity.
Then, water droplets flowing into the hollow chamber 9a of the nozzle outer ring 6a are discharged to a low-pressure portion such as a condenser through an external discharge hole 10.

On the other hand, the water droplet sucked into the hollow chamber 7b in the nozzle from the suction opening a of the upper half nozzle 1b,
It flows into the hollow chamber 12b of the nozzle inner ring 5b through 11b, and flows into the lower half hollow chamber 12a of the nozzle inner ring via the inner ring connecting pipe 13 provided on the upper and lower half divided surfaces of the nozzle inner ring. And
Through the inner / outer ring connecting path 14 provided in the lower half nozzle 1a, it reaches the outer ring hollow chamber 9a, and is discharged to the low pressure portion through the outer discharge hole 10.

(Problems to be Solved by the Invention) However, in recent years, it has been required to operate an economical power generation plant in accordance with fluctuations in power demand during the day, night, weekday holidays, seasons, and the like. Instead of the conventional low-pressure operation, a variable-pressure operation is adopted. Therefore, when performing a pressure-changing operation in a steam turbine in which the opening width of the suction opening formed in the nozzle as described above is fixed, there is a problem that optimal suction of water droplets is not performed depending on a load condition. is there.

That is, when a slit-shaped suction opening is formed on the abdominal surface and the back surface of a hollow nozzle to collect water droplets adhering to the nozzle surface, the water droplets and the vapor sucked together with the water droplets (hereinafter, the accompanying vapor) Is discharged to a condenser or the like through the above-described route.

FIG. 11 is a diagram for explaining the force in each element constituting the water droplet and the accompanying flow path, and illustrates the hollow chamber of the nozzle.
Due to the pipe resistance of the path from 7a, 7b to the condenser, etc., the pressure in the hollow chambers 7a, 7b of the nozzle becomes higher than the corresponding pressure in the condenser, etc., but due to the low pressure in the condenser, etc. Thus, a pressure difference is generated between the nozzle vapor passage portion and the nozzle hollow chamber, so that water droplets and accompanying vapor on the nozzle surface can be sucked.

Further, since the flow passage area of the path from the nozzle hollow chamber to the condenser or the like is set to be larger than the total opening area of the slit-shaped suction openings formed in each nozzle, the nozzle hollow chamber 7a , 7b are hardly affected by the pressure on the nozzle surface and are determined by the pressure of the condenser and the like and the pipe resistance of the path from the nozzle outer ring 6 to the condenser and the like. Since the pressure of the condenser or the like hardly changes depending on the load of the steam turbine, the pressure of the nozzle hollow chamber is kept almost constant.

Therefore, the pressure difference between the nozzle surface and the nozzle hollow chamber is ΔP
Assuming that the pressure in the nozzle hollow chamber is Pin and the pressure in the nozzle vapor passage is Pout, the following equation is established.

ΔP = Pout−Pin (1) However, as described above, the pressure Pin in the nozzle hollow chamber is kept almost constant, so that if the pressure Pout in the nozzle vapor passage is constant, the gap between the nozzle surface and the nozzle hollow chamber is kept constant. The differential pressure ΔP is kept constant according to the equation (1).

However, when the steam conditions change due to the variable pressure operation, the following problems occur.

That is, FIG. 12 shows enthalpy on the vertical axis and entropy on the horizontal axis, and shows the steam conditions of the steam passage portion of the nozzle, where points E1 and E2 change the turbine load when the nozzle load is changed. Represents the steam conditions of the steam passage.
If the condition at the time of the rated load is the steam condition at the point E1 shown in FIG. 12, when the load on the turbine is reduced, the steam condition of the steam passage portion of the nozzle becomes the point E2. Then, the pressure Pout in the nozzle vapor passage becomes small and becomes P2. Thus, the differential pressure ΔP between the inside and outside of the nozzle hollow chamber becomes smaller than the equation (1).

Therefore, a sufficient amount of water droplets are not sucked in, and some of the water droplets reach the trailing edge along the nozzle wall without being sucked from the suction opening a, and the water accumulated at the trailing edge becomes coarse water droplets therefrom. And may be blown off, collide with the blade and cause erosion of the blade.

Further, in the water droplet discharging structure as described above, the passage from the suction opening a of the lower half nozzle 1a to the external discharge hole 10 provided in the lower half is the same as the passage from the suction opening a of the upper half nozzle 1b. In the passage leading to the external discharge hole 10, since the latter has a more complicated passage and receives more pressure loss, the ability to suck water drops into the upper half nozzle and the ability to suck water drops into the lower half nozzle are reduced. However, the upper half tends to be inferior in the ability to suck water drops. Therefore, some of the water droplets attached to the nozzle in the upper half are not sucked into the nozzle and are shaken off from the trailing edge of the nozzle and collide with the blade, causing erosion,
There are problems such as a decrease in performance.

In view of the foregoing, it is an object of the present invention to obtain a steam turbine nozzle water droplet removing device that has substantially equalized water droplet suction capabilities of upper and lower nozzles and has a suction capability according to a turbine load. .

[Configuration of the invention]

(Means for Solving the Problems) According to the present invention, a hollow chamber communicating with a nozzle inner ring and a nozzle outer ring is formed inside a nozzle, and a slit-shaped suction opening is formed on the nozzle surface. A cooling device is provided in at least one of the outer ring of the nozzle and the hollow chamber of the nozzle, for cooling the steam flowing into the nozzle through the suction opening.

(Operation) The accompanying steam that flows into the nozzle hollow chamber together with water droplets from the slit-shaped suction opening formed in the nozzle surface is cooled and condensed by the cooling device. Therefore, the pressure inside the nozzle hollow chamber is reduced, the pressure difference between the outside and the inside of the nozzle hollow chamber is increased, sufficient water droplets are sucked, and erosion due to the collision of the water droplets with the blades and the performance of the turbine are reduced. Is prevented.

In addition, by installing a cooling device, the pressure in the nozzle inner ring hollow chamber and the nozzle outer ring hollow chamber can be made almost the same, the difference in pipe resistance can be ignored, and the suction capacity of water droplets into the nozzle is equalized in the upper and lower halves. It can also be made.

(Example) Hereinafter, an example of the present invention will be described with reference to FIGS. In the drawing, the same portions as those in FIG. 10 are denoted by the same reference numerals, and detailed description thereof will be omitted.

In FIG. 1, the hollow chambers of the nozzles 1a and 1b formed in a hollow shape are communicated with the nozzle inner rings 5a and 5b and the nozzle outer rings 6a and 6b, and a slit-shaped suction opening a is formed on each of the nozzle surfaces. It is exactly the same as the conventional one in that it is formed.

By the way, in the present embodiment, the cooling pipes 15 are arranged in the upper half nozzle inner ring 12b and the lower half nozzle outer ring 6a.

That is, the cooling pipe 15 enters the hollow chamber 9a of the lower half nozzle outer ring 6a from the lower half outside of the nozzle portion, rises into the hollow chamber 9b of the upper half nozzle outer ring 6b from there, and further traverses the passage portion. Are inserted into the hollow chamber 12b of the upper half nozzle inner ring 5b. Then, the cooling pipe, which has made a half circumference in the hollow chamber 12b of the upper half nozzle inner ring 5b, returns to the hollow chamber 9a of the lower half nozzle outer ring 6a through the same route and goes out of the turbine.
The cooling pipe 15 is provided with a fin (not shown),
A cooling medium such as cooling water is circulated in the cooling pipe 15.

Thus, the water droplets and the accompanying steam sucked from the suction opening a of the upper half nozzle 1b enter the hollow chamber 12b of the upper half nozzle inner ring 5b through the hollow chamber 7b in the nozzle 1b, where the accompanying steam is It exchanges heat with the cooling medium flowing in the cooling pipe 15 and is immediately condensed. Then, the condensed water and the water drops fall below the hollow chamber 12b of the upper half nozzle inner ring 5b due to gravity, pass through the inner ring connecting pipe 13, and from the lower half nozzle inner ring hollow chamber 12a through the inner / outer ring connecting path 14 to the lower half. Enter the hollow chamber 9a of the nozzle outer ring 6a,
The water merges with the water in the lower half, and is discharged from the turbine through a drain trap valve (not shown) that normally shuts off the outer ring of the nozzle and the upper part of the condenser and discharges only accumulated water droplets.

Further, water droplets and accompanying steam sucked from the suction opening a of the lower nozzle 1a enter the hollow chamber 9a of the lower half nozzle outer ring 6a through the hollow chamber 7a of the nozzle 1a, where the upper half is located. Similarly, the accompanying vapor is cooled and condensed by the cooling medium in the cooling pipe 15, and is discharged from the external discharge hole 10 together with water droplets.

As described above, the accompanying steam flowing into the hollow chambers 7a and 7b of the nozzles 1a and 1b together with the water droplets is condensed in the upper half nozzle inner ring 5b and the lower half nozzle outer ring 6a, so that the hollow chamber 12b of the upper half nozzle inner ring 5b and Both the hollow chambers 9a of the lower half nozzle outer ring 6a are maintained at a pressure close to a vacuum. Therefore, the hollow chambers 7a and 7b of the nozzles communicating with the nozzles are also kept at a low pressure close to the hollow chambers 12b and 9a of the nozzle inner ring and the nozzle outer ring, and the differential pressure between the hollow chamber and the nozzle inside increases. (Fig.), Water droplets attached to the nozzle surface are efficiently sucked into the nozzle.
Moreover, since both the nozzle inner ring hollow chamber and the nozzle outer ring hollow chamber are forcibly cooled, there is no pressure difference between the upper half and the lower half, and there is no influence of the conventional pipe resistance,
There is no difference between the upper and lower halves in the water suction capability.

In addition, the volume of condensed associated steam is significantly reduced, so that the inner ring connecting pipe 13 and the inner and outer ring connecting path 14 only need to secure enough area to allow water to pass, and this mechanism can be used for nozzles with small diameters This increases the degree of freedom in design.

In the above embodiment, one cooling pipe is inserted vertically and one cooling pipe is inserted. However, separate cooling pipes may be used.

FIG. 2 is a view showing another embodiment of the present invention, in which a cooling pipe is also inserted into the hollow chamber of each nozzle.

That is, cooling pipes 15b extending in the circumferential direction are provided in the hollow chamber 9b of the upper half nozzle outer ring 6b and the hollow chamber 12b of the upper half nozzle inner ring 5b, respectively, and the cooling pipes 15b in the inside and outside penetrate through the nozzle 1b. It is communicated by tube 15b1. Further, cooling pipes 15a provided in the hollow chamber 9a of the lower half nozzle outer ring 6a and the hollow chamber 12a of the lower half nozzle inner ring 5a are also connected by a cooling pipe 15a1 penetrating through the nozzle 1a.

Then, the hollow chamber is opened from the suction opening a of the upper half nozzle 1b.
The accompanying steam that has flowed into 7b touches the cooling pipe 15b1 and immediately condenses, passes through the upper half nozzle inner ring hollow chamber 12b, the inner ring connecting pipe 13, the lower half nozzle inner ring hollow chamber 12a, and the inner and outer ring connecting path 14 to form the lower half nozzle outer ring. The water enters the hollow chamber 9a, merges with the water in the lower half, and is discharged from the external discharge hole 10.

Also, the associated steam sucked from the suction opening a of the nozzle 1a in the lower half is cooled by the cooling pipe 15a1 to become water as in the upper half, and is discharged to the outside through the hollow outer chamber 9a of the lower nozzle outer ring. It is discharged from the hole 10.

In this way, the pressure in the hollow chamber of each nozzle is kept close to a vacuum, and the suction capability of water droplets becomes uniform regardless of the nozzle position.

In this case, the independent cooling pipes are provided in the upper half and the lower half. However, the cooling pipes in the upper half and the lower half may be connected to each other.

FIG. 3 is a view showing still another embodiment of the present invention, in which a spray pipe 16 is provided instead of the cooling pipe 15. That is, the spray pipe 16b extends in the circumferential direction in the hollow chamber 12b of the upper half nozzle inner ring 5b, and the spray pipe 16a extends in the hollow direction in the hollow chamber 9a of the lower half nozzle outer ring 6a.

Thus, the associated vapor sucked into each of the nozzles 1a and 1b is cooled and condensed by the cooling medium ejected from the spray pipes 16a and 16b, respectively, and has the same operation and effect as those of the above-described embodiments.

 FIG. 4 is a view showing still another embodiment of the present invention.

In the present embodiment, a steam passage section pressure gauge 18 and a wetness meter 19 are provided in the nozzle steam passage section.
Inside, a nozzle internal pressure gauge 20 is provided. An adjusting valve 21 for adjusting the flow rate of the cooling water is provided at the inlet of the cooling pipe 15, and the adjusting valve 21 is provided with a controller 22 for operating the adjusting valve. The steam passage pressure gauge 18, the wetness gauge 19, the nozzle internal pressure gauge 20 and the controller 22 are each electrically connected to a computing unit 23.

Thus, the steam passage section pressure gauge 18, the wetness meter 19, the steam passage section pressure Pout measured by the nozzle internal pressure gauge 20,
The signal of the steam path wetness and the signal of the nozzle internal thick path Pin are sent to the arithmetic unit 23. Then, the arithmetic unit 23 first determines whether or not the wetness of the steam passage is zero.

Therefore, if the turbine is operated under steam conditions such as point E2 shown in FIG. 5 and the wetness of the steam passage is zero, it is not necessary to suck in water droplets.
Is sent to fully close the. Thus, the pressure difference ΔP between the inside and the outside of the nozzle hollow chamber becomes zero, and the suction of the accompanying steam into the nozzle is prevented.

On the other hand, if the wetness of the steam passage is not zero, the pressure difference ΔP between the inside and outside of the nozzle hollow chamber is calculated by the equation (1) based on the signals of the steam passage pressure gauge 18 and the nozzle internal pressure gauge 20.
If the differential pressure ΔP is small, a signal for increasing the opening degree of the regulating valve 21 is sent to the controller 22 in order to reduce the pressure Pin of the nozzle hollow chamber 7 and increase the differential pressure ΔP outside and inside the nozzle hollow chamber, The opening of the regulating valve 21 is increased. Therefore, the amount of the cooling medium supplied to the cooling pipe 15 is increased, and the cooling and condensation of the accompanying steam is promoted.

〔The invention's effect〕

As described above, in the present invention, a hollow chamber communicating with the nozzle inner ring and the nozzle outer ring is formed inside the nozzle, a slit-shaped suction opening is formed in the nozzle surface, and the nozzle inner ring and the nozzle outer ring are formed. In addition, since at least one of the nozzle hollow chambers is provided with a cooling device for cooling the steam flowing into the nozzle through the suction opening, it is possible to sufficiently secure a differential pressure between the outside and the nozzle hollow chamber by cooling and condensing the steam. It is possible to improve the ability to suck water droplets. In addition, the suction capacity in the upper half and the lower half of the nozzle portion can be made equal to each other, so that erosion of the blades and deterioration of turbine performance due to scattering of water droplets flowing on the nozzle surface can be prevented. Furthermore, the amount of suction can be adjusted according to the degree of wetness, thereby preventing a large amount of accompanying steam from being sucked and improving the performance of the turbine.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a water droplet removing device of the present invention, FIGS. 2 to 4 are diagrams showing another embodiment of the present invention, and FIG.
FIGS. 6A and 6B are diagrams for explaining a change in a wet area due to a change in steam conditions in a steam passage portion of a nozzle, FIGS. 6A and 6B are diagrams showing generation of coarse water droplets in a conventional nozzle, and FIGS. FIG. 9 is a longitudinal sectional side view showing a conventional water droplet removing device of a steam turbine, FIG. 10 is a schematic configuration diagram of a conventional water droplet removing device, and FIG. 11 is a slit-shaped suction opening on a nozzle surface. FIG. 12 is a diagram showing a pressure in a path until water droplets and accompanying steam sucked from a hole are discharged to a condenser,
The figure shows the steam conditions in the nozzle steam passage. 1, 1a, 1b ... Nozzle, 5 ... Nozzle inner ring, 5a ... Lower half nozzle inner ring, 5b ... Upper nozzle inner ring, 6 ... Nozzle outer ring,
6a …… Lower nozzle outer ring, 6b …… Upper nozzle outer ring, 7,7a, 7
b… Nozzle hollow chamber, 9a …… Lower half nozzle outer ring hollow chamber, 9
b: Hollow chamber of upper half nozzle outer ring, 10: External discharge hole, 12a
…… Hollow chamber of inner ring of lower half nozzle, 12b …… Hollow chamber of inner ring of upper half nozzle, 13… Inner ring connecting pipe, 14… Inner / outer ring connecting pipe, 1
5,15a, 15b …… Cooling pipe, 16a, 16b …… Spray pipe, 21…
Adjusting valve, a ... Suction opening.

Claims (1)

(57) [Claims] 1. A hollow chamber communicating with a nozzle inner ring and a nozzle outer ring is formed inside a nozzle, and a slit-shaped suction opening is formed in the nozzle surface, and the nozzle inner ring, the nozzle outer ring, and the nozzle hollow chamber are formed. A device for removing water droplets from a steam turbine nozzle, wherein at least one of the cooling devices is provided for cooling steam flowing into the nozzle through the suction opening.