JPH0326803A - Moist steam turbine stage - Google Patents

Abstract

PURPOSE:To effectively separate and remove moisture in steam by a method wherein a plurality of pre-separating stationary blades equipped with a moisture separating mechanism are provided over the center and the tip of a blade in the upstream along a stationary blade shaft of each stage. CONSTITUTION:In a steam turbine stage operating with moist-steam, pre- separating stationary blades 3, 6, 9 comprising a pointshaped circular front edge part and a streamlined rear edge part are provided in the upstream of stationary blades 1, 4, 7, 10. Almost all water drops are captured and separated by a plurality of sucking slits provided on the front edge part and the rear edge part of the pre-separating stationary blades 3, 6, 9. The water drops thus separated are led from inside the hollow-structured pre-separating stationary blades 3, 6, 9 via suction slots 20 to 22 to air bleeding chambers 23 to 35 to be discharged outside the turbine. With moisture distribution in the blade lengthwise direction of water drops scattering from moving blades 3, 5, 8 in the previous stage taken into consideration, the pre-separating stationary blades 3, 6, 9 are provided over the center and the tip of the blade. Therefore performance of separating water drops can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a paragraph of a nuclear turbine operated with wet steam;
The present invention also relates to improvements in the low-pressure stage structure of thermal power turbines.

[Conventional technology]

Due to the recent rise in the price of Oishi fuel, base load operation of nuclear turbines has become established. Furthermore, in thermal power turbines, the low-pressure final stage long blades tend to become increasingly longer in order to improve -ff performance. In such steam turbines that operate with wet steam, one of the factors that hinders the reliability of the turbine blades while improving the efficiency of the stage performance is the problem of moisture contained in the wet steam.

Effective measures for separating and removing moisture from wet steam have long been strongly sought after, and various ideas have been proposed. Among them, the representative idea was
There is a water droplet separation nozzle blade disclosed in Japanese Patent No. 27282. FIG. 2 and FIG. 3 show cross-sectional structural views of a turbine stage structure and a water droplet separation nozzle blade to which a conventional water droplet separation nozzle blade is applied.

Figure 2 shows stationary blades 1, 4, 7, 43, dynamic blades 2, 5, 8,
11. A water droplet separation nozzle blade having a suction slit 44 in the final stage stationary blade 43 of a low-pressure turbine stage, which is composed of diaphragm inner walls 12, 14, 1.6, 18 and diaphragm outer walls 13, 15, 17, 19, etc. The cross-sectional structure of the nozzle blade is as shown in FIG. Drilled suction slit 4
4 are connected to each other, and the suction slit 44 extends toward the outer circumferential side in the blade height direction. The water droplets contained in the wet steam are scattered by the ljJ blade 8 in the upstream stage of the separation stator blade 43, and a part of it is attached to and collected on the ventral surface 45 of the separation Ip blade 43, forming a water film on the blade surface. The liquid flows downward and is sucked into the stator vane holo part 47 through the suction slit 44. These water droplets are guided through a suction slot into a suction chamber 49 provided inside the diaphragm outer wall 19 disposed on the outer circumferential side of the separation stationary vane 43, and are further discharged to the outside of the turbine system from the outer circumferential suction slot 1-. be done.

Traditionally, water droplet separation nozzle blades with this structure or similar ones have been widely used in actual steam turbines that operate on wet steam, but the drawback of this 411-built water droplet separation nozzle blade is that the separation efficiency is not high enough to satisfy That's true. In the experience of the inventors, the separation efficiency depends on the level of humidity, and the separation efficiency at the humidity of an actual turbine is at most 0%.
It is as follows.

The main reason for this deterioration in separation performance is that in the case of ordinary steam turbines, the steam velocity in the nozzle is extremely high, so the velocity of the water film flowing down the blade surface increases, and the
It is conceivable that there is a limit to the flow of the water film that can be sucked at 4, and that as the humidity increases, the water film becomes thicker, causing a water splash phenomenon near the slit 44, and being carried away to the f flow side. .

On the other hand, as another means for separating and removing water droplets inside the wet steam stage, as described in Japanese Patent Publication No. 176602/1982, a large number of slits are provided on the inner surface of the outer wall of the diaphragm that holds the stationary vanes 43. Another invention has been proposed in which the water film adhering to the inner surface of the outer wall is separated and removed by introducing it into a slit. However, with this type of construction, it is difficult to separate and remove water droplets that collide with the rows of stator vanes and adhere to them, and is insufficient in terms of separation performance. [Problems to be Solved by the Invention] The above-mentioned conventional technology is capable of increasing the speed of the main steam flow and increasing the wetness in the row of water droplet separation stationary blades. Since no consideration was given to the influence of the immersion load, there was a problem in the separation performance of the two-water droplet separation stationary vane, that is, in achieving high efficiency.

An object of the present invention is to provide a stage structure that can effectively separate and remove moisture in the steam existing inside the low-pressure stage of an atomic turbine or thermal power turbine that operates on wet steam, and that can achieve highly efficient separation performance. It is about providing.

[Means to solve the problem]

In order to achieve the above object, the wet steam turbine stage structure of the present invention has a warhead-shaped circular leading edge and a flow path extending from the center of the vane upstream of the stator vane to the tip of the vane in the steam turbine stage operating with wet steam. The warhead-shaped leading edge has a water droplet capturing chamber with a conical opening and a leading edge suction slit with a circular cross section. , the streamlined trailing edge is part of the ventral and dorsal surfaces, or
Each of the three parts has suction slits, and these three types of suction slits are connected to a water droplet collection chamber with a hollow structure inside the front separation stator vane and a moisture separation mechanism that connects the entire blade height direction. It is characterized by the deployment of stationary separation vanes.

[Effect]

Normally, the flow conditions inside a steam turbine stage that operates with wet steam are as shown in Fig. 4: steam flow G shown by a chain line, water droplet flow shown by a solid line, and flow within a row of stator blades shown by hatching. It can be broadly divided into water film flow that adheres to the inner surface of the outer wall of the diaphragm.

Since the water droplets in the steam have a larger inertial force than the steam flow, most of the water droplets are blown away from the center of the blade toward the tip side by the centrifugal force of the front stage rotor blade. Therefore, as shown in Figure 5, the humidity at the inlet of the stationary blade ■0 is concentrated and distributed at a dimensionless height of 0.5 (blade center) to 1.0 (blade tip). . Therefore, in the present invention, the provision of the pre-separating stator vane from the center to the tip of the stator vane takes into full consideration the water droplet flow and humidity distribution, and provides an unprecedented separation effect from the viewpoint of water droplet capture performance. will be working.

Furthermore, the front separation stator vane is constructed by combining a warhead-shaped leading edge and a streamlined trailing edge, and a conical water droplet capturing chamber and a circular suction slit are provided at the leading edge, and the ventral surface of the streamlined trailing edge and The arrangement of multiple suction slits on the back allows these three types of suction slits to capture and separate most of the water droplets that fly from the front rotor blade outlet to the rear stage stator blade inlet. . In particular, the axis of the conical water droplet capture chamber provided in the warhead-shaped front part is made to match the angle at which the water droplets fly, taking into consideration the relative velocity vector of the water droplets shown in Figure 7. It acts as an effect to increase efficiency, and by causing minute water droplets that cannot be captured in the water droplet capture chamber to collide with the back and ventral surfaces of the trailing streamlined edge, the suction slits provided on the ventral and dorsal surfaces are An auxiliary separation effect can be exerted. Due to the provision of the pre-separation stator vane of the present invention, the water droplet capture and separation effect of the wet steam stage is more effective than before. [Example] Hereinafter, an example of the present invention will be described in detail using FIGS. 1, 6, 7, and 8. FIG. 1 shows an embodiment in which the present invention is applied to a typical structure of a multi-stage steam turbine stage operating on wet steam. The turbine stage is mainly composed of a pair of stator blades 1, rotor blades 2, diaphragm inner wall 12, and outer wall 13 from the upstream stage, and moves to the succeeding stage. First, an example of applying the invention will be described. The final stage includes the stator blade 10 and the stator blade 1 as in the conventional structure.
In addition to the diaphragm inner wall 18 holding 0, the 5 diaphragm outer wall 19, and the upper surface of the rotor blade, a plurality of pre-separation stator blades 9 are arranged in the circumferential direction at the axially upstream portion of the stator blade 10. The two-dimensional arrangement of the front separation stator vane 9, the final stage stator vane 10, and the front stage rotor blade 8 is as shown in FIG. The front stationary blade 9 is the fourth
The arrangement in the blade height direction is selected by fully considering the flow conditions and wetness distribution of the steam flow G, water droplet flow H, and water film flow 50 in the conventional wet steam stage shown in FIGS. . In other words, the submerged flow that flows into the stationary blade in the wet steam stage deviates from the steam flow G and is largely deflected in the radial direction due to the inertial force of the water droplets and the centrifugal force of the rotor blade in the previous stage, and is deflected greatly in the radial direction toward the blade tip side. The flow is like water droplets being pressed against the surface. Therefore, the humidity in the spanwise direction is as shown in Figure 5.
Humidity increases rapidly from the center of the wing to the tip of the wing.

This increase in wetness results in a decrease in performance in the blade tip region and the occurrence of 20 motion in the rotor blade.

Therefore, in the present invention, the pre-separating stationary vane 9 is arranged from the center of the blade where water droplets are concentrated to the tip of the blade, and the pre-separating stationary vane 9 is arranged to move the water droplets concentrated at the tip of the blade to the pre-separating stationary vane 9. 9 to capture and separate them. The water droplets separated by the front separation stationary vane 9 are guided to the oil chamber 25 through suction slots 1 and 22 formed in the outer wall 19 of the diaphragm, and are discharged to the outside of the turbine. Furthermore, in a turbine such as a nuclear power turbine that operates in a wet steam region in all stages, the pre-separation stator vane of the present invention is also applied to the stages upstream of the final stage in FIG. They are arranged like separation vanes 6 and 3. Next, the specific structure of the front separation stationary vane 9 will be explained using the embodiment shown in FIGS. 7 and 8.

FIG. 7 shows the two-dimensional cross-sectional structure of the front separation stator vane 9, so the front separation i1119a, 9b consists of the warhead-shaped leading edges 41a, 4lb, the streamlined trailing edge 60a connected thereto,
60b. Warhead-shaped leading edge 41a, 4lb
The water droplet collision part forms conical water droplet capture chambers 33a, 33b, and the entrance part of the water droplet capture chambers 33a, 33b is made up of 11 parts of the water droplet opening so as to easily capture the colliding water droplets. leading edge suction slit 1, 34a, 34b connected to this
A conical channel is formed by gradually narrowing the channel until reaching . The water droplet capturing chambers 33a and 33b are connected to water a collecting chambers 42a and 42b, each of which has a hollow structure inside the stator blade, through leading edge suction slits 34a and 34b, respectively.
Further, the angle θ formed between the axis 52 of the water droplet capturing chamber 33 and the tangential direction reference line 53 of the stationary blade is arranged so as to match the direction of the velocity vector of the inflowing water, which is also shown in FIG. That is, the relative velocity 29 of the water droplets flowing into the preseparation stator vane 9 is:
It is smaller than the relative velocity 26 of steam flowing out, and the velocity in the circumferential direction is almost the same as that of steam 27 and water droplets 3, so the velocity of water droplets actually flowing into the pre-separation stationary vane is The direction of the absolute velocity 30 is different from the steam velocity vector,
It has an angle O with respect to the tangential direction. By taking into consideration the flow characteristics of water droplets, the lui! ! It is important to select the direction of the l-line 52 in order to ensure sufficient capture performance for inflowing water droplets. As described above, by providing the water droplet capture chamber 9, most of the relatively large particle sizes among the inflowing water droplets are captured and separated by the water droplet capture chamber 9. Regarding this capture performance, A supplementary explanation will be provided using Figures 9 and 10. In general, the collision effectiveness rate η of a water droplet of diameter a colliding with a spherical object 54 of diameter D is a dimensionless parameter s 1 expressed by a quintic equation.
・It depends on the number of squares.

Stokes number Stx=ρz−d”U/9 prDwhere, ρ: Density of water droplets, μg: Viscosity coefficient of steam, U:
This Stokes number SLκ, which is the approach velocity of steam,
As shown in FIG. 10, the relationship between the collision efficiency η and the collision efficiency η is such that the collision efficiency rapidly increases as the number of squares increases. Operating conditions of actual steam turbine (SLK-t~1
In the region 0), the collision efficiency η is 40% to 90%.

Therefore, if the pre-separation stator vane 9 of the present invention is applied to an actual turbine, the stator vane with slits shown in the conventional example (see Fig. 2)
It is possible to obtain a significantly higher water droplet capture efficiency with a ratio of κ to κ.

- The ventral surface of the streamlined trailing edge of the front M stationary blade 9a, and
The suction slits h38a and 39a installed on the back are located on the ventral surface 3.
They are provided near the inflection point of the warhead 6a and at the sudden change part of the back surface 37a (near the joint with the warhead-shaped leading edge 41a). It functions to separate and remove the water film flows 35a and 40a adhering to the periphery and guide them to the water droplet collection chamber 42a. As described above, the capture performance of the warhead-shaped leading edge portion 41a decreases as the Stokes number decreases (water droplet diameter decreases).

Therefore, the suction slits 38a and 39a on the ventral and rear surfaces of the front separation stator vane 9a serve to assist the water droplet capture i33b of the warhead-shaped leading edge 11a and the separation action of the front air suction slit 34. 1-1 will also be received. In addition, the blade shape formed by the trailing edge end and the back surface of the streamlined trailing edge portion 60a is made to substantially match the turbine axis, and the trailing stationary blade 10
It goes without saying that the angle of attack should be set to almost zero to minimize steam flow loss.

In addition, the water droplet capture chamber 33 on the leading edge, the front air suction slit 34, and the suction slits 38 and 39 on the ventral surface and the back surface of the trailing edge blade are shown in FIG. As shown, it is arranged in the shape of a long and narrow slit over the entire height of the blade, and is connected to the water droplet collection chamber inside the blade.

In the present invention, the size of the inlet opening of the water droplet capture chamber 33 of the preseparator 19 is selected so that the Stokes number, which is a dimensionless parameter representing the water droplet collision performance described above, is 1 to 10. It is desirable to ensure sufficient water droplet capture performance.

〔Effect of the invention〕

Since the present invention is constructed in this manner, the following effects can be expected.

(1) In a steam turbine stage that operates with wet steam,
By deploying multiple pre-separated stator vanes from the center in the blade height direction upstream to the tip of each stage stator blade, we have taken into consideration the blade lengthwise wetness distribution of water droplets scattered from the rotor blade in the previous stage. It can achieve separation effect and contribute to improvement of separation performance.

(2) The front separation stator vane has a warhead-shaped front edge, and is equipped with a water droplet capture chamber equipped with a conical opening and a circular suction slit at the inlet part, and by optimizing its mounting angle. , most of the water droplets that collide with the leading edge are captured and separated, contributing to a marked improvement in the separation effect compared to the conventional stator vane structure with slits.

(3) In addition, the front separation stator vane has suction slits on the belly and back sides of the streamlined trailing edge, which assists the separation action in the water droplet capture chamber at the leading edge and improves the overall separation effect. can be increased.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing a wet steam turbine stage structure according to an embodiment of the present invention, FIG. 2 is a longitudinal sectional view showing a conventional wet steam turbine structure, and FIG. 3 is a longitudinal sectional view showing a conventional wet steam turbine structure. 4 and 5 are cross-sectional views of the stationary blades, and are explanatory diagrams of steam and water droplet flow conditions in the wet steam turbine stage. FIG. 6 is a sectional view taken along the Vl-■ arrow in FIG. 1. , FIG. 8 is a perspective view of the front separation stationary vane of the present invention, and FIGS. 9 and 10 are diagrams showing the collision characteristics and efficiency of water droplets. FIG. 9... Front separation stator blade, 10... Stator blade, 1 piece... Moving blade, 33... Water droplet capture chamber, 34... Leading edge suction slit, 38... Ventral suction slit, 39... Rear suction slit, Z port 3rd (2) younger brother ω 50 -゛ hood, Rl 2: to 3Lf, 6th eye'' 7 figure leather 5 ■

Claims (1)

[Claims] 1. In a low-pressure stage of a steam turbine that operates on wet steam, a moisture separation mechanism is provided at an axially upstream portion of the stator blades of each stage composed of a plurality of stator blades and a plurality of rotor blades. A plurality of front separation stator vanes are arranged, and the front separation stator vanes are arranged in the height direction from the center in the blade height direction to the tip where water droplets scattered from the rotor blades of the upstream stage are concentrated. , a wet steam turbine stage characterized in that moisture within the stage is separated and removed by the pre-separation stationary vane and led out of the turbine system. 2. In claim 1, the front separation stator vane is composed of a warhead-shaped circular leading edge and a streamlined trailing edge whose wall thickness gradually decreases toward the trailing edge, and the circular leading edge is It has a water droplet capture chamber with a conical cross section opening toward the upstream side and a leading edge suction slit with a circular cross section, and the water droplet capture chamber and the leading edge suction slit are hollowly bored inside the front separation stationary vane. A ventral suction slit and a back suction slit are connected to the collected water droplet collection chamber, and a ventral suction slit and a back suction slit are provided on a portion or multiple portions of the ventral surface and the dorsal surface of the streamlined trailing edge, and all of the three types of suction slits are A wet steam turbine stage characterized by being equipped with a moisture separation mechanism extending over the entire height of the stationary blades. 3. In claim 1 or 2, the angle between the central axis and the tangential direction of the opening of the water droplet capturing chamber of the leading edge of the front separation stationary vane provided in the front separation stationary vane is set to the water droplets scattered from the moving blade of the upstream stage. The relative velocity of the vane is made to match the angle made with the tangential direction, and the blade shape formed by the streamlined trailing edge end and the back surface of the front separation stator vane is made to match the turbine axis. Steam turbine paragraph.