JPH06173607A - Corrosion preventive device for steam turbine blade - Google Patents

Abstract

PURPOSE:To prevent an energy loss and performance deterioration by forming a water droplet recovering hole on a blade surface of a nozzle, forming hollow chambers inside of the nozzle so as to be communicated with the water droplet recovering hole, and arranging a valve opening commanding unit to output a valve opening operation signal to increase or decrease valve opening of a steam blowdown valve according to a turbine load. CONSTITUTION:An Upstream side hollow chamber 13 and a downstream side hollow chamber 14 are formed inside of a nozzle 10. A water droplet recovering hole 11 is formed on a blade surface of the nozzle 10 so as to suck water droplet contained steam by communicating with the upstream side hollow chamber 13, and a steam injecting hole 23 is formed so as to inject steam obtained by removing water droplet from the water droplet contained steam by communicating with the downstream side hollow chamber 14. A drain separator 21 to obtain only steam by removing the water droplet from this water droplet contained steam, a steam blowdown valve 19 and a steam valve are arranged. A valve opening commanding unit 24 is arranged to increase or decrease valve opening of the steam blowdown valve 19 and the steam valve 22 according to a turbine load of a wattmeter 25. Thereby, an energy loss can be reduced, and deterioration of turbine performance can be minimized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a blade erosion preventive device for a steam turbine, which prevents blade erosion caused by water droplets in a turbine stage of a thermal power plant or the like.

[0002]

BACKGROUND OF THE INVENTION Generally, the working fluid of low pressure sections of thermal turbines and nuclear turbines is wet steam containing water droplets.
The velocity of water droplets in the steam is much smaller than that in mainstream steam. Therefore, the tip of the blade having a high peripheral speed is eroded by the collision of water droplets. Also, the rotational energy of the blades will be reduced due to the brake loss when the water droplets strike the blades. In order to overcome this problem, many blade erosion preventive devices have been proposed and put into practical use.

An example of a conventional blade erosion preventive device will be described with reference to FIGS.

FIG. 5 is a sectional view showing a conventional turbine stage structure. A nozzle diaphragm 2 fixed to the casing 1 is provided with a nozzle 3 that forms a passage, and a wheel 4 that rotates concentrically with the nozzle 3 and the casing 1.
Turbine blades are formed from the blades 5 attached to the blades and forming the passage portion. Wet steam containing water droplets expands from the nozzle 3 to the blades 5 as shown by the solid arrow in the drawing and flows downstream.

Large water droplets in the passage are blown off to the outer peripheral side by the centrifugal force of the blades 5 as indicated by the broken line arrows, and the water droplets scattered by the blades 5 are collected by the drain catcher 6 installed on the nozzle diaphragm 2. However, since the recovery rate is small, the residual water droplets easily flow into the tips of the nozzle 7 and the blade 8 in the downstream stage. Therefore, for the purpose of further removing the residual water droplets, the inside of the blade of the nozzle 7 is made hollow, and a plurality of recovery holes 7a and 7b are provided on the blade surface to suck the wet steam in the nozzle passage and at the same time collect the water droplets. The discharge holes 9a formed in the nozzle diaphragm 9 are discharged directly to the outside of the turbine stage.

That is, as shown in FIG. 6 and FIG. 7 which is a sectional view taken along the line AA of FIG.
It is sucked from 7b and discharged from the hollow portion 7c to the outside through the discharge hole 9a of the upper nozzle diaphragm 9 to remove residual water droplets.

[0007]

However, in the steam turbine blade erosion preventive device having the structure shown in FIG. 5, even when the turbine is operated at a low load, it is recovered even though the degree of wetness in the turbine stage is small. Since a large amount of moist steam is uniformly sucked from the holes 7a and 7b, there is a problem that turbine performance is deteriorated.

The above problem will be described with reference to FIG. 8 showing the flow of water droplets in the nozzle passage. The water droplets upstream of the nozzle 7 tend to adhere to the ventral and dorsal sides of the blade surface of the nozzle 7. The attached water droplets flow along the blade surface, and the nozzle 7
Water droplets larger than the trailing edge are scattered in the direction of the arrow Y in the figure.

Here, the absolute nozzle outlet velocity of steam C2,
Assuming that the blade peripheral speed is U, the relative speed W2 is the blade inlet relative speed of steam from the speed triangle. Similarly, assuming that the drain nozzle absolute velocity C2d of the water droplet Y and the blade peripheral velocity U are, the drain blade inlet relative velocity W2d of the water droplet Y with respect to the water droplet Y is in the chain line direction in the figure.

From this figure, the outflow speed C2d of the water droplet Y scattered from the outlet side of the nozzle 7 is smaller than the absolute nozzle outlet speed C2 of the steam, and the water droplet flowing into the blade 8 is the relative blade inlet speed W2d of the illustrated drain. Will flow in,
The relative velocity W2d at the blade inlet of the drain is equal to the peripheral velocity U of the blade, and the inflow direction is almost the rotational direction, so that a high-speed water droplet directly hits the inlet portion of the blade 8. Therefore, when the leading edge of the blade 8 is eroded, the rotational energy is also reduced due to the brake loss.

Therefore, an object of the present invention is to provide a blade erosion preventive device for a steam turbine, which prevents blade erosion when water droplets and steam are discharged to the outside of a paragraph and prevents deterioration of turbine performance.

[0012]

According to a first aspect of the present invention, there is provided a blade erosion preventive device for a steam turbine, which collects steam containing water droplets adhering to a blade surface of a nozzle into the nozzle to prevent erosion of turbine blades. While forming a water drop collection hole for sucking steam containing water drops on the blade surface of the nozzle, a hollow chamber for collecting the steam containing the sucked water drops is formed inside the nozzle so as to communicate with the water drop collecting hole. , A steam exhaust pipe communicating with the hollow chamber for exhausting the steam containing the collected water droplets outside the turbine stage via the steam exhaust valve, and opening the turbine load and the steam exhaust valve to prevent deterioration of turbine performance. And a valve opening degree commander that outputs a valve opening degree operation signal for increasing or decreasing the valve opening degree of the steam discharge valve according to the turbine load.

According to a second aspect of the present invention, there is provided a blade erosion preventive device for a steam turbine, wherein steam containing water droplets attached to a blade surface of the nozzle is collected in the nozzle to prevent erosion of turbine blades. While forming an upstream side hollow chamber and a downstream side hollow chamber, the blade surface of the nozzle is connected to the upstream side hollow chamber, to form a water droplet recovery hole for sucking vapor containing water droplets, the downstream side hollow chamber A drain separator and steam that form a steam injection hole for injecting steam from the steam containing water droplets into the turbine stage by communicating with the drain separator and removing only water vapor from the steam containing water droplets. A valve is provided and a steam pipe that connects the upstream hollow chamber and the downstream hollow chamber is provided, and the relationship between the turbine load and the valve opening of the steam valve is set in advance in order to prevent performance deterioration of the turbine. Depending on the turbine load, the steam valve It is obtained as provided with the valve opening command for outputting a valve opening degree command for increasing or decreasing the degree of opening.

[0014]

According to the first aspect of the present invention, the vapor containing the water droplets attached to the blade surface of the nozzle is sucked through the water droplet collecting hole, and the vapor containing the sucked water droplet is collected in the hollow chamber. The steam containing the collected water droplets is discharged outside the turbine stage through a steam discharge valve provided in the steam discharge pipe. In this case, the valve opening commander presets the relationship between the turbine load and the valve opening of the steam discharge valve so that the energy loss is small and the performance of the turbine is not deteriorated, and the steam discharge valve is set according to the turbine load. Increase or decrease the valve opening of. As a result, steam containing water droplets sucked from the blade surface of the nozzle is discharged to the outside of the turbine stage according to the turbine load, so there is little energy loss, and water droplets on the blades are minimized while minimizing the deterioration of turbine performance. Can be prevented from colliding.

According to the second aspect of the present invention, the vapor containing the water droplets adhering to the blade surface of the nozzle is sucked from the water droplet collecting hole, and the vapor containing the sucked water droplet is collected in the upstream hollow chamber. The steam including the collected water droplets is removed by a drain separator provided in the steam pipe to become only steam, which flows into the downstream hollow chamber via the steam valve and is injected from the steam injection hole. In this case, the valve opening commander presets the relationship between the valve opening of the steam valve and the turbine load so that the energy loss is small and the turbine performance is not degraded, and the valve of the steam valve is set according to the turbine load. Increase or decrease the opening. As a result, only the water droplets of the steam containing the water droplets sucked from the blade surface of the nozzle are discharged to the outside of the turbine stage according to the turbine load, so there is little energy loss and the deterioration of turbine performance is suppressed to a minimum. . Furthermore, the steam from which the water droplets have been removed is jetted at high speed from the steam injection holes, and the large water droplets that have accumulated on the blade surface of the nozzle are subdivided and removed, so that the water droplets can be prevented from colliding with the blades.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of a turbine stage equipped with a blade erosion preventive device for a steam turbine showing an embodiment of the present invention. The same reference numerals as those in FIG. 5 indicate the same or corresponding portions. In the drawing, the nozzle 10 has a hollow structure, and a partition plate 12 is disposed inside the hollow, an upstream hollow chamber 13 and a downstream hollow chamber 14 are formed, and a plurality of water droplet collection holes 11 are formed in the upstream hollow chamber 13. Has been done. The nozzle diaphragm outer ring 15 is formed with an upstream collection chamber 16 and a downstream collection chamber 17, which communicate with the upstream hollow chamber 13 and the downstream hollow chamber 14, respectively, and further, the upstream collection chamber 16 is a steam discharge pipe. 18 communicates with the outside through the discharge valve 19 and the steam discharge pipe 18 is branched and connected to the steam inflow pipe 20.
It communicates with the downstream collection chamber 17 through the drain separator 21 and the control valve 22, and communicates with the outside through the steam injection hole 23 formed in the downstream hollow chamber 14.

The valve opening commander 24 has a discharge valve 19 and a control valve 22 connected to the output side thereof, and an electric power meter 2 connected to the inlet side thereof.
5 is connected, the valve opening degree is calculated with respect to the load amount of the turbine, and the discharge valve 19 and the control valve 22 are opened / closed.

With the above construction, the water droplets adhering to the blade surface of the nozzle 10 are sucked together with the steam in the turbine stage from the water droplet recovery hole 11 and flow into the upstream hollow chamber 13 of the nozzle 10.
The water droplets and steam that have flowed into the upstream hollow chamber 13 are guided to the steam discharge pipe 18 through the upstream collection chamber 16, and are discharged to the outside of the turbine stage through the discharge valve 19.

Here, the degree of wetness (ratio of water contained in steam) in the turbine stage is determined by the turbine load (100%, 75% in the figure) as shown by the entropy enthalpy diagram in the turbine expansion line of FIG. , 50%, 30%), and at a rated load of 100%, the degree of wetness in each paragraph is large, and at about 10%, it is a steam that contains many water droplets. %, The wetness is about 3% to 4% and the water droplets are minute.

In the valve opening commander 24, the valve opening 19 of the discharge valve 19 with respect to the turbine load is changed from the relationship between the water drop and the steam with respect to the turbine load shown in FIG.
The relationship between a and the valve opening degree 22a of the control valve 22 is preset. The valve opening commander 24 determines the discharge valve 19 and the control valve 2 according to the turbine load from the power meter 25 based on the above relationship.
2 and are controlled respectively.

As a result, when the turbine load is about 40% to 100%, the discharge valve 19 changes from fully closed to fully open according to the turbine load, and water droplets are discharged to the outside according to the opening degree.

In this way, the valve opening of the discharge valve 19 is opened and closed according to the turbine load, and the optimum collection of water droplets is achieved, so that it is possible to prevent the intake of steam from the water droplet collection hole 11 at a low load more than necessary. At the same time contributing to the improvement of turbine efficiency,
Water droplets can be collected efficiently.

On the other hand, the turbine load is about 75% to 100
When it is%, the steam discharge pipe 18 is changed from fully closed to fully open according to the turbine load, and steam is flown into the downstream collection chamber 17 according to the turbine load. This steam is drain separator 2
1, the water droplets are removed, and the downstream collection chamber 17 moves to the downstream hollow chamber 1
Inflow to 4. Since the area around the nozzle outlet end is in a vacuum state, high-speed steam is injected to the outside from the steam injection hole 23 at the nozzle outlet end. At this time, the nozzle 10
The large water droplets that have adhered to the wing surface of and are accumulated are subdivided by the injection of high-speed steam. As a result, large water droplets on the blade surface of the nozzle 10 are removed, and erosion of the blade is prevented.

In this way, the nozzle is made hollow and two water drop collecting chambers are provided in the outer ring 15 of the nozzle diaphragm, and the flow rate control attached to the steam pipe for guiding the water drop and the steam sucked from the water drop collection hole on the nozzle blade surface to the outside of the paragraph. The valve controls the flow rate according to the turbine load to perform optimal water droplet collection that does not inhale steam more than necessary, and further improves the turbine performance by allowing steam outside the turbine stage to flow into the turbine stage again. Can be made.

FIG. 4 is a sectional view of a turbine stage showing a second embodiment of the present invention.

The difference from the first embodiment shown in FIG. 1 is that a drain separator 29 and a control valve 30 are provided in the middle of a steam pipe 28 connected from the upstream collection chamber 26 to the downstream collection chamber 27. .

With this structure, the water droplets and the steam sucked in the water droplet collecting hole 11 pass through the steam pipe 28 and pass through the drain separator 2
The water droplets are removed at 9, and then the flow rate is adjusted by the control valve 30 according to the turbine load, and high-speed injection is performed from the steam injection hole 23 at the outlet end of the nozzle 10. The same effects as those of the blade erosion prevention device shown in FIG. 1 can be obtained by the configuration shown in this embodiment.

[0029]

As described above, according to the first aspect of the present invention, the steam containing water droplets sucked from the blade surface of the nozzle according to the turbine load is generated so that the energy loss is small and the turbine performance is not deteriorated. Since it is discharged to the outside of the turbine stage, energy loss is small, and it is possible to prevent water droplets from colliding with the blades while suppressing the deterioration of turbine performance to a minimum.

According to the second aspect of the invention, only the water droplets of the steam including the water droplets sucked from the blade surface of the nozzle depending on the turbine load have a small energy loss and do not deteriorate the performance of the turbine. Since it is discharged outside the turbine stage, there is little energy loss, and the deterioration of turbine performance is suppressed to a minimum. Furthermore, since the steam is sprayed at high speed from the steam spray holes to remove large water droplets accumulated on the blade surface of the nozzle, it can be more effectively prevented.

[Brief description of drawings]

FIG. 1 is a sectional view of a turbine stage equipped with a blade erosion preventive device according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a method of calculating a wetness degree by an enthalpy entropy diagram according to a turbine load.

FIG. 3 is a valve opening diagram of each of a discharge valve and a control valve showing a valve opening with respect to a turbine load.

FIG. 4 is a sectional view of a turbine stage equipped with a blade erosion preventive device showing a second embodiment of the present invention.

FIG. 5 is a sectional view of a conventional turbine stage.

FIG. 6 is an explanatory view of a turbine paragraph showing the operation of FIG.

7 is a cross-sectional view taken along the line AA of FIG.

FIG. 8 is an explanatory diagram showing a flow pattern of water droplets and a velocity of water droplets on a conventional nozzle blade surface.

[Explanation of symbols]

 1 Casing 10 Nozzle 11 Water Droplet Recovery Hole 12 Partition Plate 13 Upstream Hollow Chamber 14 Downstream Hollow Chamber 15 Nozzle Diaphragm Outer Ring 16 Upstream Collection Chamber 17 Downstream Collection Chamber 18 Steam Discharge Pipe 19 Discharge Valve 20 Steam Inflow Pipe 21 Drain Separator 22 Control Valve 23 Steam injection hole 24 Valve opening commander

Claims (2)

[Claims] 1. A vane erosion preventive apparatus for a steam turbine, wherein steam containing water droplets adhering to a blade surface of a nozzle is collected inside the nozzle to prevent erosion of a blade of a turbine, wherein the water droplet is provided on a blade surface of the nozzle. While forming a water droplet recovery hole for sucking vapor containing, inside the nozzle,
A hollow chamber that communicates with the water droplet collection hole and collects the steam containing the sucked water droplets is formed, and communicates with the hollow chamber that discharges the steam containing the collected water drops through a steam discharge valve outside the turbine stage. To provide a steam discharge pipe to preset the relationship between the turbine load and the valve opening of the steam discharge valve in order to prevent deterioration of turbine performance, and to increase or decrease the valve opening of the steam discharge valve according to the turbine load. And a valve opening commander that outputs a valve opening operation signal of the blade opening prevention device for a steam turbine. 2. A vane erosion preventive device for a steam turbine, wherein vapor containing water droplets adhering to a blade surface of a nozzle is recovered in the nozzle to prevent erosion of turbine vanes, wherein the nozzle has an upstream hollow chamber. And a downstream hollow chamber, the blade surface of the nozzle communicates with the upstream hollow chamber to form a water droplet recovery hole for sucking vapor containing the water droplet, and the downstream hollow chamber. A drain separator that communicates with the water vapor and forms a steam injection hole for injecting steam from the steam containing the water droplets into the turbine stage, and removing the water drops from the steam containing the water droplets to leave only the steam. And a steam valve, and a steam pipe that connects the upstream hollow chamber and the downstream hollow chamber is provided, and in order to prevent deterioration of the performance of the turbine, the relationship between the turbine load and the valve opening of the steam valve is preset. Set and turbine negative Blade erosion prevention device of a steam turbine is characterized by providing a valve opening command for outputting a valve opening degree command for increasing or decreasing the valve opening of the steam valve in response to.