JP6139362B2 - Steam turbine water drop remover - Google Patents

Description

  The present invention relates to a water droplet removal apparatus for removing water droplets generated in a steam turbine.

  In general, the vicinity of the low-pressure final stage of a thermal turbine and most paragraphs of a nuclear turbine operate in wet steam containing a large number of water droplets, and the problem of blade erosion due to the water droplets arises. With the increase in the length of the last stage rotor blades accompanying the increase in the capacity of thermal power and nuclear turbines, effective countermeasures against the above problems have been strongly demanded.

  A water droplet removing device in the paragraph of a conventional steam turbine will be described with reference to FIG. FIG. 7 is a longitudinal sectional view of a conventional water droplet removing device for a steam turbine. In the drawing, slit-shaped suction holes 2 a and 2 b are formed in the abdomen and rear surfaces of a hollow nozzle 1. These slit-like suction holes 2a and 2b drilled in the abdominal surface and the back surface are divided in the longitudinal direction and arranged in a staggered manner. The hollow nozzle 1 is communicated with other hollow nozzles arranged in the circumferential direction by a hollow nozzle inner ring 3 and a hollow nozzle outer ring 4, and the hollow portion 4 a of the nozzle outer ring 4 is a condenser. It communicates with the low pressure part.

  Water droplets transmitted through the nozzle vent surface are sucked into the nozzle inner space from the vent suction port 2a, and water droplets transmitted through the nozzle back surface through the nozzle outer ring and connected to the nozzle outer ring and condenser. It is discharged to the condenser through the pipe. In this way, the water droplets transmitted through the nozzle belly surface and the nozzle back surface are removed, so that coarse water droplets at the nozzle trailing edge are removed. Such a structure is disclosed in JP-A-4-255504.

  FIG. 8 shows the relationship between the turbine output, the differential pressure between the condenser and the hollow nozzle (hereinafter referred to as slit differential pressure), and the turbine output and the condenser vacuum degree. In a state where the turbine output is small, the vacuum generator connected to the condenser has started to be activated, and the vacuum degree of the condenser is poor. Therefore, the slit differential pressure is in a low state close to zero.

  On the other hand, when the turbine output is increased, the condenser vacuum is improved and the slit differential pressure is also increased. Thus, in a state where the turbine output is sufficiently large, the slit differential pressure is large, so that water droplets can be sucked into the hollow nozzle.

  Therefore, water drops are sufficiently removed during rated operation. However, since the slit differential pressure becomes small at low load and it becomes difficult for water droplets to be sucked into the hollow nozzle, the water droplets that have been guided to the nozzle trailing edge without being removed, and have been removed at the nozzle backing edge, are removed from the rotor blade. Colliding with the leading edge, the erosion of the moving blade proceeds. In this way, water droplets can be sufficiently removed at a load with a large turbine output, but water droplets cannot be sufficiently removed at a low turbine output, and this is one of the causes of erosion of moving blades. ing.

JP-A-4-255504

  As described above, from FIG. 8, during rated operation with a sufficiently large turbine output, the vacuum of the condenser is good and the slit differential pressure is also large. Therefore, water droplets can be removed sufficiently. However, when the turbine output is small and the load is low and the load is low, the vacuum degree of the condenser is poor and the slit differential pressure becomes small, so that water droplets cannot be removed sufficiently. As described above, in the conventional water droplet removal apparatus, the fact that the water droplets are not sufficiently removed at a low load is one of the causes of the erosion of the moving blades.

  The present invention has been made to solve the above-described problems of the prior art, and an object thereof is to provide a water droplet removal apparatus for a steam turbine that can sufficiently remove water droplets transmitted on the nozzle blade surface under a condition where the turbine output is small. It is in.

The present invention comprises a slit provided on the nozzle surface and a nozzle hollow portion communicating with the slit.
In the water drop removal device provided, a vacuum generator is provided in which the nozzle hollow part is connected by piping.
The pipe connected to the vacuum generator is branched, and the branched pipe is connected to the condenser.
If the turbine output is less than a predetermined value, the vacuum generator is driven and the turbine output
If the value is larger than the predetermined value, control is performed to stop the vacuum generator.
Achieve the purpose.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS.

(First embodiment)
The configuration of the steam turbine water droplet removal apparatus according to the present embodiment is shown in FIG. This figure shows a water droplet removing device for the final stage stationary blade, and slit-like suction holes 2a and 2b are formed on the belly surface and the back surface of the hollow nozzle 1, and the hollow nozzle 1 includes a hollow nozzle inner ring 3 and a hollow nozzle. The nozzle outer ring 4 communicates with other hollow nozzles disposed in the circumferential direction, and the hollow portion 4a of the nozzle outer ring 4 communicates with the vacuum generator by piping. Thus, the hollow nozzle in which the abdominal suction hole 2a and the back suction hole 2b are formed is connected to the vacuum generator by the pipe.
In the conventional steam turbine water droplet removal apparatus, the hollow nozzle having the suction holes 2a and 2b is connected to the condenser by piping. However, as shown in FIG. 8, the condenser vacuum is good and the slit differential pressure is large during rated operation with high output, whereas the condenser vacuum is poor and the slit differential is low during low load operation with low output. The pressure is reduced. As described above, in the structure of the conventional water droplet removing device, the water droplet removing ability depends on the vacuum degree of the condenser, and the slit differential pressure is small during low load operation. It was one of the causes of progressing erosion.

  Therefore, in the steam turbine water droplet removal apparatus according to the first embodiment, the hollow nozzle having the ventral side suction hole 2a and the back side suction hole 2b is not connected to the condenser but connected to the vacuum generator by piping. It is characterized by a direct connection structure. For this reason, the slit differential pressure can be increased by maintaining a constant pressure without being influenced by the condenser vacuum even during low-load operation. As a result, even when the turbine output is low and the load is low, the differential pressure of the slit increases, so that the water droplets that have traveled through the nozzle abdominal surface and the water droplets that have traveled through the nozzle back surface through the back side suction hole 2b. It is sucked into the internal space, passes through the nozzle outer ring, and is discharged to the vacuum generator through the pipe connected to the nozzle outer ring and the condenser. In this way, the water droplets transmitted through the nozzle abdominal surface and the nozzle back surface are removed, so that coarse water droplets at the nozzle trailing edge are removed, and erosion of the moving blade can be reduced.

(Second Embodiment)
The configuration of the steam turbine water droplet removal apparatus according to this embodiment is shown in FIG. This figure shows that the pipe connecting the hollow nozzle 1 and the vacuum generator 6 of the steam turbine water droplet removing apparatus of Embodiment 1 is branched, and the tip of the branched pipe is connected to the condenser 10. It is a feature. When the output during low load operation is small and the condenser vacuum is low, the slit differential pressure is small. For this reason, for example, when the slit differential pressure is a predetermined value or less (that is, the turbine output is a predetermined value or less), the slit differential pressure can be increased by operating the vacuum generator.

  On the other hand, when the turbine output increases and the pressure in the condenser 10 is low and a sufficient slit differential pressure can be secured, that is, when the slit differential pressure becomes larger than the predetermined value (the turbine output becomes larger than the predetermined value). Then, the vacuum generator 6 is stopped. As a result, the power of the vacuum generator 6 can be reduced, the economy is excellent, and a certain water droplet removing capability can be secured at any turbine output.

(Third embodiment)
The configuration of the steam turbine water droplet removal apparatus according to this embodiment is shown in FIG. In this figure, the pipe connected to the vacuum generator 6 of the steam turbine water droplet removing apparatus of the second embodiment is branched, and in the pipe connected from the branch to the low pressure part of the condenser 6, the pressure of the condenser is A valve 5 is provided as a means for adjusting a differential pressure between the vacuum generator and the condenser vacuum pressure according to a signal. In the example of FIG. 3, a pressure gauge 11 for detecting pressure is attached to the condenser 10, and the pipe connected to the low pressure portion of the condenser 10 is connected to the vacuum generator 6 by the signal of the pressure gauge 11. A valve 5 that adjusts the differential pressure with the condenser 10 is provided.

  In the absence of a valve, when the condenser pressure is very high at low load, a flow from the condenser to the vacuum generator occurs, and a sufficient slit differential pressure cannot be secured. However, by providing the valve 5 that can control the opening degree according to the degree of vacuum, the flow from the condenser to the vacuum pump during low load operation can be prevented, and a sufficient slit differential pressure can be secured. By predetermining the valve valve opening with respect to the degree of vacuum and appropriately controlling the valve based on this, the slit differential pressure can always be kept constant even when the condenser pressure is very high.

(Fourth embodiment)
The configuration of the steam turbine water droplet removal apparatus according to this embodiment is shown in FIG. This figure is provided with means 15 for controlling the pressure generated in the vacuum generator 6 by the output signal 13 of the turbine in the water droplet removing apparatus of the second and third embodiments, and is generated by the vacuum generator as the turbine output increases. A control method for increasing the pressure is provided.

  In the example of FIG. 4, the pressure generated in the vacuum generator is controlled by the turbine output signal. As a control method, as shown in FIG. 5, the pressure is increased as the turbine output increases. Thereby, when a vacuum generator is a vacuum pump, for example, a pressure can be changed according to a turbine output, and the pressure of a vacuum pump can be switched to operation, a stop, and partial load operation as needed.

  When the turbine output increases, the pressure in the condenser decreases, so that the slit differential pressure becomes excessive when the vacuum generator is operated at a constant pressure. Therefore, in this embodiment, the slit differential pressure can be made constant by changing the operation state of the vacuum generator and increasing the pressure according to the turbine output. Accordingly, since the slit differential pressure is not excessively large than necessary, it is possible to prevent excessive suction of the fluid, to suppress the decrease in efficiency, and to reduce erosion. Moreover, since the vacuum generator is operated in a necessary state, the power of the vacuum generator can be reduced, and the economy is excellent.

(Fifth embodiment)
The configuration of the steam turbine water droplet removal apparatus according to the present embodiment is shown in FIG. This figure shows a final stage stationary blade and a stationary blade in a stage upstream of the final stage stationary blade, with slit-like suction openings 2a and 2b formed therein, and a hollow portion 1 communicating with the nozzle inner ring 4 and the nozzle outer ring 4 is formed therein. In addition, the hollow portion 1 and the pipe 8 are communicated with each other, and the hollow portions 1 of the respective paragraphs are communicated with each other through a pipe and connected to a vacuum generator. Further, there may be a plurality of stationary blades in the upstream stage from the final stage stationary blade.

  The pipe connected to the hollow portion of each paragraph is provided with means 14 for adjusting the pipe differential pressure before and after joining with the pipe in the downstream paragraph, and means 12 for detecting the pipe pressure before joining. A means 16 for controlling the pipe differential pressure before and after merging is provided by the signal and the turbine output signal. In FIG. 6, the means for adjusting the pipe differential pressure is a valve 18 for adjusting the pipe differential pressure.

  In the operation state of the steam turbine, water droplets may be generated in an upstream stage other than the final stage. In particular, in a nuclear turbine, water droplets are generated on the upstream side of several stages other than the final stage even under rated operating conditions. For this reason, there is a problem that the erosion of the moving blade proceeds even outside the final paragraph. With the water droplet removal apparatus of this embodiment, it is possible to remove water droplets in the upstream paragraph as in the final paragraph. However, since the pressure in the upstream paragraph is higher than that in the final paragraph, the slit differential pressure in the upstream paragraph is larger than the slit differential pressure in the final paragraph. A mechanism for adjusting the pipe differential pressure is provided in order to prevent excessive fluid from being sucked in the upstream paragraph and reducing efficiency. Thereby, the slit differential pressure | voltage of an upstream paragraph can be adjusted and the progress of the erosion of a moving blade can be suppressed, preventing a decline in efficiency. Also, in the turbine operating state, predict how much water droplets are generated in the upstream paragraph, and the valve output from the turbine output indicating the turbine operating state and the piping pressure for adjusting the piping differential pressure An appropriate slit differential pressure can be maintained by the control. Accordingly, it is possible to always maintain an appropriate slit differential pressure in any operation state of the turbine, and to suppress the progress of the erosion of the rotor blade while preventing the efficiency from being lowered.

The figure which shows the 1st Embodiment of this invention The figure which shows the 2nd Embodiment of this invention The figure which shows the 3rd Embodiment of this invention The figure which shows the 4th Embodiment of this invention The figure which shows the control method of the 5th Embodiment of this invention. The figure which shows the 5th Embodiment of this invention A diagram showing a conventional water droplet removing device for a steam turbine Diagram showing turbine output and condenser vacuum, and relationship between turbine output and slit differential pressure

DESCRIPTION OF SYMBOLS 1 ... Nozzle 2 ... Suction opening 2a ... Suction opening 2b of a stomach surface ... Suction opening 3 of back side ... Nozzle inner ring 4 ... Nozzle outer ring 4a ... Hollow part of a nozzle outer ring

Claims (7)

A moving blade that is rotated by working steam and a nozzle that guides the working steam to the moving blade. A slit-like suction opening is formed in the blade surface of the nozzle, and a hollow portion that communicates with the opening is formed. In the steam turbine water droplet removal device,
Comprising a vacuum generator in which the hollow portion is connected by piping;
The pipe connected to the vacuum generator is branched, and the branched pipe is connected to the condenser.
If the turbine output is below a predetermined value, the vacuum generator is driven and the turbine output is
A water droplet removing apparatus for a steam turbine, wherein control is performed to stop the vacuum generator when the predetermined value is larger . The water droplet removing apparatus according to claim 1 , further comprising means for detecting the pressure of the condenser and means for adjusting a differential pressure between the vacuum generator and the condenser vacuum pressure based on a detection result of the detecting means. A water droplet removing device for a steam turbine, characterized in that: 3. The water droplet removing apparatus according to claim 1, further comprising means for controlling a pressure generated by the vacuum generator based on an output signal of the turbine. 4. The water droplet removing apparatus according to claim 3 , wherein control is performed to increase the pressure generated by the vacuum generator as the turbine output increases. 5. The water droplet removing apparatus according to claim 1, wherein a slit-like suction opening is formed in any of the nozzles upstream of the final stage nozzle, and a hollow portion communicating with the opening is formed. A steam turbine water droplet removal apparatus, wherein a hollow part of a final stage nozzle and a hollow part of a nozzle upstream of the final stage nozzle are connected to the vacuum generator by the pipe. In the water droplet removing apparatus according to claim 5 , for the pipe connected to the hollow portion of each paragraph,
A steam turbine water droplet removing apparatus comprising means for adjusting a pipe differential pressure before joining with a pipe in a downstream paragraph. 7. The water droplet removing apparatus for a steam turbine according to claim 6 , wherein the pipe differential pressure before and after merging is controlled by means for detecting the pressure of the pipe before merging with the downstream pipe, and the pressure signal and the turbine output signal. A water droplet removing device for a steam turbine, characterized by comprising a mechanism for performing the operation.

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