JPS63117104A - Moisture separating device for steam turbine - Google Patents

Abstract

PURPOSE:To aim at improvement in the drain trapping rate of the device in the caption by forming a groove, which has greater width than that of a suction slit, at the surface side end portion of the suction slit provided on the surface of a stationary blade. CONSTITUTION:On the surface of a stationary blade 2, a section slit 6 is provided to be intercommunicated with the low-pressure side of a condenser and the like through a cavity 7. At the surface side end portion of the suction slit 6, there is formed a through-groove 5, which has greater width than that of the suction slit 6 and runs in the same direction as the suction slit 6 does. Drain in a steam passage is trapped into the groove with greater width, thereby the drain trapping rate being enhanced.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Field of Application) The present invention relates to a moisture separator for a steam turbine, and particularly to a moisture separator for a steam turbine, which is capable of efficiently discharging condensate from a steam flow path. The present invention relates to a moisture separator for a steam turbine that can prevent the outflow of water.

(Prior art) In most stages of nuclear power turbines and geothermal turbines, and in the low-pressure section of thermal power turbines, a portion of steam, which is the working fluid, condenses and becomes drain, draining the inner and outer walls of the steam flow path and the rotor blades. flowing over the surface. Generally, this inner circumferential wall is made up of the inner ring surface of the stator vane, and the outer circumferential wall is made up of the casing wall, and the drain flowing on the surfaces of these inner circumferential walls etc. corrodes the downstream rotor blades and reduces the efficiency of the stage. It is the cause of this.

Therefore, in order to separate and remove such condensate from the main stream of steam, a moisture separator as shown in FIGS. 5 and 6 has been proposed.

In FIG. 5, stator blades 2 are fixedly joined by welding, casting, etc. between the outer circumferential wall 1 of the steam flow path 13 and the stator blade inner ring 11 constituting the inner circumferential wall of the flow path.

Further, rotor 3 is attached with rotor blades 4 .

In the stage upstream from the final stage rotor blade and where a part of the steam is condensed, suction slits 20 and 21 are opened on the surface near the outer peripheral wall 1 and the outside of the stationary blade 2, where drain is particularly concentrated. . FIG. 6 is a cross-sectional view taken along the line Vl-VT in FIG.
is connected to. The suction slit 20 in the outer circumferential wall communicates directly with the outer circumferential wall cavity 8a, while the suction slit 21 in the stator vane communicates via the stator vane cavity 7 with the outer circumferential wall cavity 8b. In addition,
Both of the outer circumferential wall cavities 8a and 8b are formed within the outer circumferential wall 1.

In addition, the outer peripheral wall cavities ga and 3b have drain outlets 12a and 1
2b communicates with a lower pressure location such as a condenser (not shown), so that the outer peripheral wall cavities 8a, 8b are at a lower pressure than the inside of the flow path. Therefore, the drain attempting to cross the suction slit 20.21 is sucked in by the suction slit 20.21 and is further discharged to the outside through the drain outlets 12a, 12b.

(Problems to be Solved by the Invention) The moisture separator proposed above has already been actually employed in the low-pressure stage of a steam turbine, and experience shows that it is effective to some extent in preventing erosion of the rotor blade tips.

However, it is insufficient to prevent corrosion when the final stage uses long blades of 26 inches or more, when the rotor speed is high, or when the humidity of the steam is high. The problem with moisture separators is that they are not sufficiently effective in improving stage efficiency.

In order to clarify the problems with such conventional moisture separators, experiments were conducted using a model turbine, and the following findings were made.

In other words, condensate flows near the outer peripheral wall 1 and the outer surface of the stationary blade 2 as expected when the steam is highly humid, but they often flow in streaks rather than in a film. The suction slit 20.
The opening 21 always sucks in mainstream steam. The steam sucked in in this way is cooled and condensed at the drain outlets 12a, 12b, etc., so although the apparent amount of drain removed is large, the result is that even the steam that does effective work flows out.

In such a case, it may be considered to reduce the width of the suction slits 20, 21 in order to prevent steam from flowing out. However, if the width of the suction slit 20.21 is made small, the thickness of the striped drain flow is large, so that most of the drain flow passes through the suction slit 20.21.

The present invention has been made in consideration of these points,
It is an object of the present invention to provide a moisture separator for a steam turbine that can efficiently separate and discharge condensate from steam and prevent the steam from flowing out.

[Structure of the invention]

(Means for Solving the Problems) The present invention provides at least one surface of the inner peripheral wall surface of the steam flow path, the outer peripheral wall surface of the steam flow path, or the stator vane surface, which communicates with a low pressure side of a condenser or the like. A moisture separator for a steam turbine that includes a suction slit to suck in condensate in a steam flow path and separate the steam from the condensate, the suction slit having a width larger than the suction slit width at a surface side end thereof, and It is characterized in that a groove is formed that continues in the same direction as the suction slit, and the drain is stored in this groove.

(Function) Since the drain in the steam flow path is captured in the groove having a width larger than the suction slit and stored in this groove, the rate of capturing the drain can be increased compared to the conventional device.

Moreover, since the drain stored in the groove covers the opening of the suction slit, the steam in the flow path will not be released from the suction slit to the outside.

(Example) Next, embodiments of the present invention will be described with reference to the drawings.

1 to 3 are diagrams showing an embodiment of a moisture separator for a steam turbine according to the present invention. Note that the same members as those in the conventional device are given the same reference numerals and detailed explanations will be omitted.

As shown in FIG. 1, the outer circumferential wall 1 of the steam flow path 13 is provided with a circumferentially continuous groove 9 for capturing outer circumferential wall drain. Further, on the downstream side of the bottom of the groove 9 with respect to the steam flow, a suction slit 10 in the outer circumferential wall narrower than the groove 9 is provided.
The grooves 8 and 9 are continuously provided in the same direction as the grooves 1 and 2, and communicate the outer circumferential wall cavity 8a formed in the outer circumferential wall 1 with the drain capturing groove 9.

The outer circumferential wall cavity 8a is provided with a drain discharge row 2a that communicates with a condenser (not shown) or the like having a lower pressure than the outer circumferential wall cavity 8a.

On the other hand, the surface of the stator blade 2 is coated in the radial direction (
A continuous stator blade drain capture groove 5 is provided in the longitudinal direction) perpendicular to the steam flow direction F.

A stator blade suction slit 6 narrower than the groove 5 is provided continuously in the same direction as the groove 5 on the downstream side of the steam flow F at the bottom of the full 5, and a stator blade cavity formed inside the stator blade 2 is provided. 7 and 5 for drain capture are connected.

The stator vane cavity 7 communicates with an outer circumferential wall cavity 8b formed in the outer circumferential wall 1, and the outer circumferential wall cavity 8b has a drain discharge row that communicates with a condenser (not shown) or the like having a lower pressure than the outer circumferential wall cavity 8b. 2b is provided.

Note that the grooves 5 and 9 described above have a sufficient depth compared to the suction slits 6.10 formed in each groove, and the depth of the suction slit 6.10 is the minimum required depth. It's deep.

Next, the operation of this embodiment having such a configuration will be explained.

When wet steam flows in the steam flow path 13, the condensate generated on the upstream side of the steam flow path 13 is shaken off by the moving blades 4 and collides with the flow path outer peripheral wall 1, and most of it is on the wall surface of the outer peripheral wall 1. Flows axially along to the next paragraph. By using a borescope or a fiberscope, it has been observed that the drain flowing on the wall surface of the outer peripheral wall 1 flows in the form of streaks, just like raindrops traveling through a glass window.

The drain flowing in the axial direction along the wall surface of the outer circumferential wall 1 falls into the outer circumferential wall drain capturing groove 9 provided in the circumferential direction perpendicular to the drain flow direction and is captured. The drain captured in the drain capture groove 9 flows downstream and fills the groove 9 in the circumferential direction due to the differential pressure between the outer circumferential wall cavity 8a and the steam flow path 13 and the surface tension of the water. completely cover the opening of the suction slit 10 that is exposed to the Area ratio of groove 9 and slit 10 and outer peripheral wall cavity 8a and steam flow path 1
By appropriately setting the pressure difference between the groove 9 and the inside of the slit 3, it is possible to maintain a state in which the groove 9 does not overflow and the suction slit 10 is not exposed to the steam.

If the steam pressure and humidity are distributed in the circumferential direction of the outer peripheral wall 1, the widths of the drain capture grooves 9 and the suction slits 10 should be adjusted in accordance with these pressures and humidity. It is also possible to have a distribution in the direction. The depth of the suction slit 10, which causes a large fluid resistance when suctioning the drain, can be made sufficiently small by increasing the depth of the groove 9.

The drain sucked in from the suction slit 10 flows into the outer peripheral wall cavity 8.
It temporarily accumulates in the drain a, and is then sucked into a lower pressure condenser or the like through the drain outlet 12a. In this way, most of the drain flowing on the surface of the outer peripheral wall 1 can be separated and discharged at this stage.

On the other hand, the mainstream steam is quiet from the upstream side! 2, changes its flow direction while expanding, flows into the rotor blade 4 located downstream, rotates the rotor 144, and converts thermal energy into mechanical energy that rotates the rotor 3. When steam expands within the stationary blade 2, new drainage is generated. In addition, the mainstream steam flowing into the stator blade 2 already contains minute condensate, and most of these old and new condensates cannot completely ride the steam flow, collide with the surface of the stator blade 2, and stick to it. do,
Thereafter, as shown in FIG. 2, it flows in roughly the same direction as the steam flow F as if being swept away by the steam.

S In this case as well, the drain often flows in streaks. The liquid then falls into a groove 5 for trapping the drain on the stator blade 2, which is provided perpendicularly to the drain flow direction, and is captured. As shown in FIG. 3, the steam flow F flows downstream without change, but the drain 14 captured in the groove 5 is caused by the difference in pressure between the outer wall cavity 8b and the steam passage 13 and the surface of the water. Due to the tension, the groove 5 expands in the radial direction (longitudinal direction), and the groove 5 is filled, and the opening of the suction slit 6 of the stationary blade is completely filled with the drain 1.
Covered by 4. In this case as well, by appropriately setting the area ratio of the groove 5 and the suction slit 6 and the size of the pressure difference between the outer peripheral wall cavity 8b and the flow path 13, it is possible to
It is possible to maintain a state in which the groove 5 does not overflow and the suction slit 6 is not exposed to the steam. Although it is possible to calculate the static pressure distribution on the surface of the stationary blade 2 in advance and process the grooves 5 and suction slits 6 on the isobaric line, the distribution of the drain flowing on the surface is not the same. When the drain is distributed in the longitudinal direction, the widths of the grooves 5 and suction slits 6 are distributed in the longitudinal direction, so that the water level of the drain in the grooves 5 can be kept constant in the longitudinal direction.

Also, in the case of static g2, by increasing the depth of the groove 5, the depth of the suction slit 6, which becomes a large resistance to the drain flow Fd, can be made sufficiently small.

As shown in FIG. 3, the drain 14 sucked in from the suction slit 6 is temporarily stored in the stationary vane cavity 7, and is sucked into the outer peripheral wall cavity 8b communicating therewith, and then drained from the drain outlet 12b at a lower pressure. It gets sucked into things like water vessels. In this way, most of the moisture in the steam flowing through the station 5A2 is separated and discharged, so that only steam flows into the downstream station X4.

As explained above, according to this embodiment, since the continuous groove 9 having a width larger than the suction slit 10 is formed on the surface of the outer peripheral wall 1 in a direction perpendicular to the drain flow direction, this groove 9 allows the drain to drain. can be captured and stored efficiently. In this case, the opening of the suction slit 10 is completely covered by the drain, so that no steam is released from the suction slit 10 to the outside.

Moreover, since the continuous groove 5 having a width larger than the suction slit 6 is formed in the direction perpendicular to the drain flow direction on the surface of the stator blade 2, the drain can be efficiently captured and stored by the groove 5.

In this case, the opening of the suction slit 6 is completely covered by the drain, so that no steam is released from the suction slit 6 to the outside.

Furthermore, the suction slit 6.10 is formed downstream of the grooves 5, 9 in the drain flow direction. Therefore, as shown in FIG. 3, for example, the drain 14 collides with the downstream wall of the groove 5 and is stored therein, so that it is easily sucked into the suction slit 6.

Next, another embodiment of the moisture separator for a steam turbine according to the present invention will be described with reference to FIG.

In FIG. 4, the seat m2 is formed by bending separate sheet metals for the dorsal side and the ventral side, then welding the edges of the dorsal side and the ventral side together, and polishing the welded parts. In this case, before welding and joining, the stator blade 2 is machined with a groove 5 for trapping the stator blade drain, and a groove sealing plate 15 is welded and attached to the inner surface of the stator blade 2 to open the suction slit 1.
Form 6. Furthermore, as in the first embodiment, the stator vane cavity 7 is communicated with a low-pressure location such as a condenser through the outer circumferential wall cavity and the drain outlet.

According to this embodiment, the depth of the suction slit 16 of the stator vane drain can be made zero, so that the suction resistance can be lowered and the suction performance from the suction slit 16 can be improved.

Further, since the suction slit 16 can be formed by welding without using expensive electrical discharge machining, manufacturing costs can be reduced. Furthermore, by using a sheet metal with good corrosion resistance for the groove sealing plate 15, it is possible to prevent the bottom of the groove 5 from being eroded during operation. Therefore, it is possible to prevent the suction slit 16 from becoming wide and causing not only drain but also steam to flow out.

Although an example is shown in which the groove sealing plate 15 is attached to the stationary blade 2, a suction slit having a zero depth may be formed by attaching the groove sealing plate to the outer peripheral wall 1.

Further, in the above embodiment, an example was shown in which the stator blade drain capture groove 5 was provided near the outer periphery of the ventral side of the stator blade 2, but the stator blade 2
It may be provided over the entire area from the inner periphery to the outer periphery, or may be provided on the back side of the station W2. By providing the groove 5 on the back side of the stationary blade 2, the drain removal efficiency can be increased. Furthermore, although an example was shown in which the suction slit 6.10 was continuously formed to have approximately the same length as the grooves 5 and 9, the suction slit 6.10
10 may be formed briefly and intermittently.

Further, although an example is shown in which the grooves 9 and slits 10 are formed in the outer circumferential wall 1, the grooves and slits may be formed in the inner circumferential wall constituted by the stator blade inner ring 11. In this case, the drain on the surface of the inner circumferential wall of the channel can be efficiently removed.

Furthermore, the formation direction of the drain trapping grooves 5 and 9 can be freely determined with respect to the drain flow direction Fd. can be determined.

[Effects of the Invention] According to the present invention, since the drain in the steam flow path is captured in the groove having a width larger than the suction slit, the drain capture rate can be increased compared to conventional devices. In addition, since the drain stored in the groove covers the opening of the suction slit,
The steam that does useful work in the flow path will not be released from the suction slit to the outside, and energy loss in the steam turbine can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing an embodiment of the moisture separator according to the present invention, FIG. 2 is a cross-sectional view taken along the line ■-■ in FIG. 1, and FIG. FIG. 4 is an enlarged view of part A showing the slits, FIG. 4 is a cross-sectional view showing grooves and suction slits in another embodiment of the steam turbine moisture separator according to the present invention, and FIG. 5 is a conventional steam turbine moisture separator. FIG. 6 is a sectional view showing the separation device, and FIG. 6 is a sectional view taken along the line Vl-VI in FIG. DESCRIPTION OF SYMBOLS 1... Outer peripheral wall, 2... Stationary blade, 3... Rotor, 4...
... Moving blade, 5... Groove, 6... Suction slit, 7...
・Stator blade cavity, 8a, 8b...Outer peripheral wall cavity, 9...Groove, 10...Suction slit, 11...Stator blade inner ring, 12
a, 12b... drain outlet, 13... steam flow path,
15... Groove sealing plate, 16... Suction slit, F
...Steam flow, Fd...Drain flow. Applicant's agent Sato - Yumani 5

Claims (1)

[Scope of Claims] 1. A suction slit communicating with the low pressure side of a condenser or the like is provided on at least one surface of the inner peripheral wall surface of the steam flow path, the outer peripheral wall surface of the steam flow path, or the surface of the stationary blade, so that the steam In a moisture separator for a steam turbine that sucks condensate in a flow path and separates steam and condensate, the suction slit has a width larger than the suction slit width at the surface side end thereof and continues in the same direction as the suction slit. A moisture separator for a steam turbine, characterized in that a groove is formed and drain is stored in the groove. 2. The moisture separator for a steam turbine according to claim 1, wherein the continuous groove is formed substantially perpendicular to the drain flow direction. 3. Claim 1, characterized in that the suction slit is arranged on the downstream side of the continuous groove in the drain flow direction.
A moisture separator for a steam turbine according to paragraph 1.