JPH03294603A - Water drop removing device for steam turbine nozzle - Google Patents

Abstract

PURPOSE:To improve suction ability for water drop on nozzles by drillingly providing suction openings of slitting on the surface of nozzles, and providing a cooling device to cool steam flowing in the nozzles through the suction openings. CONSTITUTION:Hollow chambers of nozzles 1a, 1b formed into hollow shapes are communicated into nozzle inner rings 5a, 5b and nozzle outer rings 6a, 6b. Slitlike suction opening holes (a) are formed on the surface of respective nozzles. A cooling pipe 15 is arranged in the upper half nozzle inner ring 12b and the lower half nozzle outer ring 6a. By cooling condensation of steam, pressure difference between the inside and the outside of the hollow chambers can be sufficiently insured. In this way, suction ability for water drop can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a water droplet removal device for a steam turbine nozzle operated in a humid region.

(Prior art) Generally, in a steam turbine operated in a humid region,
Relatively small water droplets generated and grown in the steam passage are formed on the blades (
The centrifugal force of the rotating rotor blades causes the water to be blown to the vicinity of the tip of the nozzle (static vane), and most of it travels along the nozzle surface and is blown off from the trailing edge of the nozzle as coarse water droplets. It is known that erosion occurs in a high-speed rotating blade when the blade collides with the blade.

Furthermore, the water droplets do not flow smoothly along the surface of the blade, but collide with the back side of the blade and act as a braking force, which may result in a decrease in the performance of the turbine.

In other words, when the wetness of the steam is low and the water droplet diameter is very small, most of the water droplet flow passes through the nozzle passage between the nozzles together with the steam flow, and even after passing through the nozzles, the droplet diameter remains small. Since it is relatively small, it has little effect on blade erosion, but if the humidity is high, the steam flow B will be diverted along the shape of the passage in the nozzle 1, as shown in Figure 6. On the other hand, the water droplets A, which have increased in diameter, cannot be deflected due to inertia, collide with the ventral surface 2 of the nozzle, and are collected there. The collected water droplets flow along the ventral surface 2 of the nozzle to the rear edge 3 of the nozzle, and the water accumulated on the trailing edge 3 is blown off from there as coarse water droplets, which collide with the blades and generate two lotions on the blades. .

If the humidity becomes even greater, as shown in FIG. 7, the steam flow B will flow along the axial direction as described above, or the water droplets A will flow so as to directly collide with the nostle back surface 4. . Such a change in the inflow direction of the water droplet flow A occurs because when the diameter of the water droplets becomes very large, the exit relative speeds of the water droplets and the steam at the front stage vane become significantly different. In other words, when the humidity is high and the diameter of water droplets in steam becomes large, as shown in Fig. 8, the relative speed W' of water droplets at the blade exit becomes smaller than the relative speed W of steam at the blade exit. are equal, the absolute velocity C' of the water droplet at the blade exit changes greatly with respect to the absolute velocity C of the steam at the blade exit, and as a result, the water droplet flow collides with the nozzle back surface 4 and is collected, as shown in FIG. be done. The water droplets collected on the nozzle back surface 4 are also blown off from the nozzle trailing edge 3 as coarse water droplets, collide with the blades, and erode them.

Further, the coarse water droplets blown off from the nozzle trailing edge 3 impede the rotation of the blades by colliding with them, causing a decline in the performance of the turbine.

FIG. 9 is a diagram showing a nozzle structure designed to prevent erosion caused by the coarse water droplets and deterioration of turbine performance, in which slit-shaped suction openings are formed on the ventral surface and the back surface of the nozzle 1 formed in a hollow shape. A is drilled. Further, each hollow nozzle 1 communicates with a hollow nozzle inner ring 5 and a nozzle outer ring 6, respectively.
A pipe leading to a low pressure part such as a condenser is connected to the pipe.

The water droplets that have passed along the ventral surface 2 of the nozzle are sucked into the cavity of the nozzle 1 through the suction opening a on the ventral side, and the water droplets that have transmitted the back surface 4 of the nozzle are sucked into the cavity of the nozzle 1 through the suction opening a on the dorsal side. The water is discharged to a low-pressure part such as a condenser, and water droplets transmitted to the surface of the nozzle 1 are removed.

FIG. 10 schematically shows the nozzle section, and the reference numeral 1. 5. 6 schematically shows the same part as in FIG. 9, viewed in a direction perpendicular to the axle, and clearly shows the hollow part and the water droplet discharge route.

By the way, as shown in FIG. 10, the nozzle part is divided into two halves, an upper half and a lower half, for easy assembly and disassembly. Each of the nozzles 1 has a cylindrical shape, and a large number of nozzles are installed around the circumference, and FIG. 10 shows two in the lower half and two in the upper half.

In addition, the parts located in both the upper and lower halves of the nozzle part in the figure are indicated by the suffix a for those located in the lower half.
, and the suffix b is added to those located in the upper half.

Therefore, first, water droplets sucked into the hollow chamber 7a in the nozzle from the suction opening a of the lower half nozzle 1a flow into the hollow chamber 9a of the nozzle outer ring 6a through the through hole 8a due to its gravity. The water droplets that have flowed into the hollow chamber 9a of the nozzle outer ring 6a are discharged to a low pressure section such as a condenser through an external discharge hole 10.

On the other hand, the water droplets sucked into the hollow chamber 7b in the nozzle from the suction opening a of the upper half nozzle 1b are drawn into the through hole 1.1 by gravity. b through the hollow chamber 12b of the nozzle inner ring 5b.
It flows into the lower half hollow chamber 12a of the nozzle inner ring through the inner ring connecting pipe 13 provided on the dividing surface of the upper and lower halves of the nozzle inner ring.
flows into. Then, it passes through the inner and outer ring connecting passage 14 provided in the lower half nozzle la, reaches the outer ring hollow chamber 9a, and is discharged to the low pressure section through the external discharge hole 10.

(Problem to be solved by the invention) However, in recent years, there has been a demand for economical operation of power generation plants that corresponds to fluctuations in power demand such as day and night, weekdays and holidays, and seasons. In place of the conventional constant pressure operation, variable pressure operation is now being adopted. Therefore, when performing variable pressure operation with a steam turbine in which the opening width of the suction hole formed in the nozzle is fixed as described above, there is a problem that water droplets may not be sucked in optimally depending on the load condition. be.

In other words, when slit-shaped suction holes are formed on the ventral and back surfaces of a hollow nozzle to collect water droplets adhering to the nozzle surface, water droplets and the vapor that is entrained and inhaled at the same time as the water droplets (hereinafter referred to as entrained vapor) ) is discharged to a condenser or the like through the path described above.

FIG. 11 is a diagram illustrating the forces in each element constituting the flow path of the water droplets and accompanying steam.
Hollow chamber 7a of the nozzle.

The pressure at 7b is higher than the pressure inside the condenser, etc., but due to the low pressure inside the condenser, a differential pressure is generated between the nozzle steam passage and the nozzle hollow chamber, and the water droplets on the nozzle surface and the accompanying It is possible to inhale steam.

In addition, since the flow path area of the path from the nozzle hollow chamber to the condenser etc. is set larger than the total opening area of the slit-shaped suction holes bored in each nozzle, the nozzle hollow chamber 7a , 7b is hardly affected by the pressure on the nozzle surface, and is determined by the pressure of the condenser etc. and the resistance of the pipe line from the nozzle outer ring 6 to the condenser etc. Since the pressure in the condenser and the like hardly changes depending on the load on the steam turbine, the pressure in the nozzle cavity is kept almost constant.

Therefore, if the pressure difference between the nozzle surface and the nozzle hollow chamber is ΔP, and the pressure inside the nozzle hollow chamber is Pout, the pressure in the Plnsln steam passage section is set as Pout.

ΔP=PouL −Pin −(1) However, as mentioned above, since the pressure Pin in the nozzle hollow chamber is kept almost constant, the pressure Pout in the nozzle steam passage
If is constant, the differential pressure ΔP between the nozzle surface and the nozzle hollow chamber
is kept constant from equation (1).

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

That is, FIG. 12 shows the steam conditions in the steam passage section of the nozzle, with enthalpy on the vertical axis and entropy on the horizontal axis, where points E1 and E2 represent the nozzle when the load on the turbine is changed. represents the steam conditions in the steam passage section. Assuming that the conditions at the current rated load are the steam conditions at point E1 shown in FIG. 12, when the load on the turbine decreases, the steam condition at the steam passage section of the nozzle becomes point E2. Then, the pressure p out in the nozzle steam passage decreases to P2.

Therefore, from equation (1), the differential pressure ΔP between the inside and outside of the nozzle hollow becomes small.

Therefore, only enough water droplets are sucked in, and some of the water droplets travel along the nozzle wall surface and reach the trailing edge without being sucked in through the suction opening a, and the water that collects at this trailing edge becomes coarse water droplets from there. The blade may be blown off and collide with the blade, causing blade erosion.

In addition, in the water droplet discharge structure as described above, there is a passage from the suction aperture a of the lower half nozzle 1a to the external discharge hole]0 provided in the lower half, and a passage from the suction aperture a of the upper half nozzle 1b. In the passage leading to the same external discharge hole 10, the latter has a more complicated passage and suffers more pressure loss, so the ability to suck water droplets into the nozzle in the lower half and the ability to suck water droplets into the nozzle in the lower half are different. Unlike this, the upper half tends to have a poor ability to absorb water droplets. Therefore, some of the water droplets attached to the nozzle on the upper surface may not be sucked into the nozzle, but may be shaken off from the trailing edge of the nozzle and collide with the blades, causing problems such as causing erosion and reducing performance. .

In view of the above, an object of the present invention is to provide a steam turbine nozzle water droplet removing device that has approximately equal water droplet suction capacity of the upper and lower nozzles and has a suction capacity that corresponds to the turbine load. .

[Structure of the invention]

(Means for Solving the Problems) The present invention forms a hollow chamber inside a nozzle that communicates with a nozzle inner ring and a nozzle outer ring, and provides a slit-shaped suction opening on the nozzle surface. The present invention is characterized in that a cooling device is provided in at least one of the nozzle outer ring and the nozzle hollow chamber to cool the steam that has flowed into the nozzle through the suction opening.

(Function) The accompanying steam that flows into the nozzle hollow chamber along with water droplets from the slit-shaped suction opening bored on the nozzle surface is cooled and condensed by the cooling device. Therefore, the pressure inside the nozzle hollow chamber decreases, the pressure difference between the inside and outside of the nozzle hollow increases, and sufficient water droplets are sucked in, causing erosion due to the collision of water droplets with the blades and deterioration of turbine performance. 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, making the difference in pipe resistance negligible, and the ability to suck water droplets into the nozzle is equalized in both the upper and lower halves. It is also possible to do this.

(Example) Hereinafter, an example of the present invention will be described with reference to FIGS. 1 to 4. Note that the same parts in the figure as in FIG. 10 are given the same numbers, and detailed explanation thereof will be omitted.

In FIG. 1, nozzles la and lb are formed in a hollow shape.
The hollow chambers are formed by the nozzle inner rings 5a, 5b and the nozzle outer ring 6a.
, 6b, and is completely the same as the conventional one in that slit-shaped suction holes a are formed on the surface of each nozzle.

By the way, in this embodiment, cooling pipes 5 are disposed within the upper half nozzle inner ring 12b and the lower half nozzle outer ring 6a.

That is, the cooling pipe] 5 enters the hollow chamber 9a of the lower half nozzle outer ring 6a from the lower half outside of the nozzle part, rises from there into the hollow chamber 9b of the upper half nozzle outer ring 6b, and further crosses the steam passage section. It is inserted into the hollow chamber 12b of the upper nozzle inner ring 5b.

The cooling pipe that has made a half-circle inside 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 exits to the outside of the turbine. The cooling pipe 15 is provided with fins (not shown), and a cooling medium such as cooling water flows through the cooling pipe 15.

Therefore, the water droplets and accompanying steam sucked through the suction opening a of the nozzle 1b in the upper half are transferred to the hollow chamber 7b inside the nozzle 1b.
The vapor then enters the hollow chamber 12b of the inner ring 5b of the upper half nozzle, where the accompanying vapor exchanges heat with the cooling medium flowing in the cooling pipe 15 and is immediately condensed 1 2 . Then, the condensed water and water droplets fall under the hollow chamber 12b of the inner ring 5b of the upper half nozzle due to gravity, pass through the inner ring communication pipe 13, go from the hollow chamber 12a of the lower half nozzle inner ring, and pass through the inner and outer ring connecting path 14 to the lower half. Hollow chamber 9a of nozzle outer ring 6a
The water enters the water, joins with the water in the lower half, and is discharged from the external discharge hole 10 to the outside of the turbine via a drain trap valve (not shown) that normally shuts off the space between the nozzle outer ring and the condenser, etc., and discharges only the accumulated water droplets. be done.

In addition, water droplets and accompanying steam sucked from the suction opening a of the nozzle 1a in the lower half pass through the hollow chamber 7a of the nozzle 1a and enter the hollow chamber 9a of the lower half nozzle outer ring 6a, where they enter the hollow chamber 9a of the lower half nozzle outer ring 6a. Similarly, the accompanying steam 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.

In this way, the hollow chambers 7a of the nozzles la and lb together with water droplets
, 7b is condensed in the upper half nozzle inner ring 5b and the lower half nozzle outer ring 6a, so the hollow chamber 12b of the upper half nozzle inner ring 5b and the hollow chamber 9a of the lower half nozzle outer ring 6a are both in a vacuum. The pressure is maintained close to . Therefore, the hollow chambers 7a, 7 of each nozzle communicating with these
Inside b is also the hollow chamber 12b of the nozzle inner ring and nozzle outer ring.
.

The pressure is maintained at a low pressure close to 9a, and the differential pressure between the inside and outside of the nozzle increases (FIG. 11), and water droplets adhering 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 forcedly cooled, there is no pressure difference between the upper and lower halves, and the influence of conduit resistance unlike in the past is completely eliminated.
There is no difference in water droplet suction ability between the upper part and the lower part.

Furthermore, since condensed accompanying steam significantly reduces its volume, the inner ring connecting pipe 13 and the outer ring connecting path 14 only need to have an area sufficient to allow water to pass through, and this mechanism can be adopted even for small diameter nozzles. It is possible, and the degree of freedom in design increases.

In the above embodiment, one cooling pipe is inserted into the upper and lower parts, but separate upper and lower cooling pipes may be used.

FIG. 2 is a diagram 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 extending in the circumferential direction penetrate the inside of the nozzle 1a. They are communicated by pipe 15b1. In addition, the cooling pipe 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 is also a cooling pipe that penetrates the inside of the nozzle 1a]5
Contacted by a1.

Therefore, the accompanying steam that has flowed into the hollow chamber 7b through the suction opening a of the nozzle 1b in the upper half touches the cooling pipe 15b1 and is immediately condensed. Nozzle inner ring hollow chamber 12a1 inner and outer ring connection passage 14
The water enters the lower half nozzle outer ring hollow chamber 9a, joins with the water in the lower half, and is discharged from the external discharge hole 10.

In addition, the accompanying steam that is sucked in through the suction opening a of the nozzle la in the lower half is also cooled by the cooling pipe 15a1 in the same way as in the upper part and becomes water, and the vapor is turned into water in the lower half nozzle outer ring hollow chamber 9a.
It passes through and is discharged from the external discharge hole 10.

In this way, the hollow chamber of each nozzle is maintained at a pressure close to vacuum, and the water droplet suction capacity is uniform regardless of the nozzle position.

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

Further, FIG. 3 shows still another embodiment of the present invention, in which a spray pipe 6 is provided in place of the cooling pipe 15. That is, a spray pipe 16b extends circumferentially within the hollow chamber 12b of the upper half nozzle inner ring 5b, and a spray pipe 16a extends circumferentially within the hollow chamber 9a of the lower half nozzle outer ring 6a.

Thus, the accompanying steam sucked into each nozzle 1a, 1b is cooled and condensed by the cooling medium ejected from the spray pipes 16a, 16b, respectively, and the same effects as in the above embodiments are achieved.

FIG. 4 is a diagram showing still another embodiment of the present invention. 6 be.

In this embodiment, a steam passage force gauge 18 and a humidity gauge 19 are provided in the nozzle steam passage, and a nozzle internal pressure gauge 20 is provided in the hollow chamber 7 of the nozzle 1. Further, an adjustment valve 21 for adjusting the flow rate of cooling water is provided at the artificial part of the cooling pipe 15, and a controller 22 for operating the adjustment valve 2 is provided for the adjustment valve 2. The steam passage force meter 18, hygrometer 19, nozzle internal pressure δ120, and controller 22 are each electrically connected to a computing unit 23.

Therefore, the steam passage humidity Pout, the steam passage humidity, and the nozzle internal pressure P measured by the steam passage dynamometer 18, the humidity gauge 19, and the nozzle internal pressure 120 are calculated.
The in signal is sent to the arithmetic unit 23. and arithmetic unit 23
First, it is determined whether the humidity of the steam passage section is zero or not.

Therefore, if the turbine is operated under steam conditions such as point E2 shown in FIG. 5, and the steam passage humidity is zero, there is no need to suck in water droplets, so the controller 22 causes the regulating valve 21 to be fully closed. A signal is sent. As a result, the differential pressure ΔP between the inside and outside of the nozzle hollow chamber becomes zero, and the accompanying steam is prevented from being sucked into the nozzle.

On the other hand, if the steam passage humidity is not zero, the pressure difference ΔP between the inside and outside of the nozzle hollow chamber is calculated by equation (1) based on the signals from the steam passage force meter 18 and the nozzle internal pressure gauge 20. If the differential pressure ΔP is small, the nozzle hollow chamber 7
In order to lower the pressure Pin and increase the pressure difference ΔP between the inside and outside of the nozzle hollow, a signal is sent to the controller 22 to increase the opening degree of the regulating valve 21, and the opening degree of the regulating valve 21 is increased.

Therefore, the amount of cooling medium fed to the cooling pipe 15 is increased, and cooling and condensation of the accompanying steam is promoted.

〔Effect of the invention〕

As explained 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 hole is formed on the nozzle surface, and at least one of the inside of the nozzle inner ring, the nozzle outer ring, and the nozzle hollow chamber is cooled to cool the steam that has flowed into the nozzle through the above-mentioned suction hole. Since the device is provided, a sufficient differential pressure between the interior and exterior of the nozzle hollow space can be ensured by cooling and condensing the steam, and the water droplet suction ability can be improved. Furthermore, the suction capacities in the upper and lower halves of the nozzle part can be made equal to each other, and it is possible to prevent blade erosion and deterioration of turbine performance due to scattering of water droplets flowing on the nozzle surface. Furthermore, the amount of suction can be adjusted depending on the humidity level, thereby preventing a large amount of associated steam from being sucked in, and improving the performance of the turbine.

[Brief explanation of 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 other embodiments of the present invention, and FIG.
The figure is an explanatory diagram of changes in the wet area due to changes in steam conditions in the steam passage of the nozzle, Figures 6 and 7 are diagrams showing the generation of coarse water droplets in a conventional nozzle, and Figure 8 is a diagram showing the velocity of the front and rear blade exits. Figure 9 is a partial longitudinal side view showing a conventional steam turbine water droplet removal device, Figure 10 is a schematic configuration diagram of a conventional water droplet removal device, and Figure 11 is a slit-shaped suction opening on the nozzle surface. A diagram showing the pressure in the path where water droplets and associated steam sucked through the holes are discharged to the condenser,
FIG. 12 is a diagram showing steam conditions in the nozzle steam passage section. 1, la, lb... nozzle, 5... nozzle inner ring, 5
a... Lower nozzle inner ring, 5b... Upper half nozzle inner ring,
6... Nozzle outer ring, 6a... Lower nozzle outer ring, 6b
...Upper half nozzle outer ring, 7.7a, 7b...Nozzle hollow chamber, 9a...Lower half nozzle outer ring hollow chamber, 9b...
Hollow chamber of upper half nozzle outer ring, 10...external discharge hole, 1.
2a... Hollow chamber in the inner ring of the lower half nozzle, 12b... Hollow chamber in the inner ring of the upper half nozzle, 13... Inner ring communication pipe, 14.
... Inner and outer ring connecting pipes, 15, 15a, 15b - ... Cooling pipe, 16a. 16b...Spray pipe, 21...Adjustment valve, a...
Suction hole. 1 0 Figure 10 Entropy Prediction 2 Figure

Claims (1)

[Claims] A hollow chamber communicating with the nozzle inner ring and the nozzle outer ring is formed inside the nozzle, and a slit-shaped suction opening is formed on the nozzle surface, and at least one of the nozzle inner ring, nozzle outer ring, and nozzle hollow chamber is formed. A water droplet removing device for a steam turbine nozzle, characterized in that a cooling device is provided to cool the steam flowing into the nozzle through the suction opening.