JPH0791961B2 - Steam turbine vane - Google Patents

Description

The present invention relates to a stationary blade of a steam turbine, and more particularly, to blade erosion caused by the fact that the drain in the steam collides with the tip of the moving blade. The present invention relates to a vane of a steam turbine suitable for preventing deterioration in performance.

(Prior Art) In most paragraphs of nuclear power turbines and geothermal turbines, or in the low pressure section of thermal power turbines, a part of steam, which is a working fluid, condenses into drain, which flows on the surface of the stationary blade.
It is known that these drains erode the blades located downstream and reduce turbine efficiency.

The drain generated on the surface of the stationary blade grows, aggregates, flows to the trailing edge, and scatters from there, impinges on the moving blade without being able to follow the velocity of the main steam flow. The collision speed is faster toward the tip of the wing, and drains are often generated near the outer circumference of the wing. Therefore, the tip of the rotor blade is intensively eroded. Further, the collision of the drain with the moving blade acts as a brake on the rotation of the moving blade, which causes a decrease in turbine efficiency.

In order to improve such a problem, conventionally, FIGS.
A steam turbine having a moisture separator as shown in the figure has been proposed.

In FIG. 8, about 50 to 100 stationary blades 3 are radially fixed by welding or casting between the outer peripheral wall 1 of the flow path and the inner race 2 of the stationary blade. A drain catching groove 4 is formed on the downstream side of the ventral side surface 3a of the vane 3 as shown in FIG. 9, and the drain catching groove 4 extends in the longitudinal direction from the flow path outer peripheral wall 1 side to near the flow path center. Has been done. Further, the drain capturing groove 4 communicates with a drain recovery chamber 5 provided in the outer peripheral wall 1 of the flow path via a communication hole 6. Drain suction slits 8 are provided in the outer peripheral wall 1 of the flow passage on the upstream side and the downstream side of the vane 3, and are connected to the drain recovery chamber 5. The drain recovery chamber 5 is connected to a low pressure condenser (not shown) or the like. Also, the stationary wings 3
A vane 10 embedded in the wheel 9 is disposed downstream of the.

The mainstream steam flows into the stationary vane 3 from the left side in FIG. 8, where it is accelerated while changing the direction of the flow and then flows into the moving blade 10 to rotate it. In a steam turbine stage in which moist steam having a low temperature and a low pressure is flowing, a part of the steam is condensed on the stationary blades 3 and the outer peripheral wall 1 of the flow path to generate a drain. The drain flowing on the ventral side of the stationary blade 3 is captured by the drain capturing groove 4, sucked into the drain recovery chamber 5 through the communication hole 6, and discharged outside the flow path. The drain on the outer peripheral wall 1 of the flow path is discharged to the outside of the flow path through the drain suction slit 8.

(Problems to be Solved by the Invention) A drain flow is present on the dorsal side surface of the stationary blade 3 similarly to the ventral side surface, and the amount thereof is 20% to 120% of the drainage flowing on the ventral side surface.
There are also many drains that attach and grow near the downstream side of the dorsal surface. Looking at the radial distribution of the drain, most of the drain is concentrated from the central part of the flow channel to the outside, and especially, it is concentrated more than 75% of the flow channel height to the outside. Even in the outer peripheral wall 1 of the flow path, a large amount of drain flows in the form of a film. When the drain trapping groove 4 is provided on the surface of the vane 3 in the longitudinal direction as described above, the drain is trapped here, the velocity of the drain in the main flow direction disappears, and then the static pressure gradient along the groove lowers the pressure. It has been observed to be swept away.

In other words, in the above-mentioned conventional technique, not only the drain flowing on the dorsal surface of the vane is not captured, but also the drain captured by the drain capturing groove 4 on the ventral side reaches the communication hole 6 due to the static pressure gradient as a resistance. It is limited to a part, and the rest is likely to leak again. Further, the communication hole 6 is filled with a large amount of drain flowing through the outer peripheral wall 1 and the drain capturing groove 4
There is also the possibility that the drain will flow back. Although it is possible to increase the size of the communication hole 6 in order to prevent such a phenomenon, the steam that performs effective work is also discharged, which leads to a decrease in turbine efficiency.

Therefore, the present invention solves the above-mentioned drawbacks in drain discharge of the conventional steam turbine stationary blade, prevents corrosion of the moving blade due to drain generated on the surface of the stationary blade, and improves turbine efficiency. That is the purpose.

[Structure of Invention]

(Means for Solving Problems) In order to achieve the above object, the present invention has a vane in which an outer peripheral side end is supported by a flow channel outer peripheral wall and an inner peripheral side end is supported by a stationary vane inner ring. However, a drain trap groove extending in the longitudinal direction from the position spaced from the flow passage outer peripheral wall toward the stator vane inner ring side is formed on at least one surface of the back surface or ventral surface of the stator blade. It is what

(Operation) According to the present invention, the drain flowing on the surface of the vane is caught by the drain trapping groove, and the drain is prevented by the static pressure gradient in the groove that the static pressure on the outer peripheral wall side is higher than the static pressure on the inner ring side. It is flown to the inner ring side and is guided to a radial position where the peripheral speed of the moving blades located downstream of the stationary blade becomes sufficiently small, and the drain flows out to the surface of the stationary blade again near the disappearance of the groove, and from the trailing edge. Scatter. Here, unlike the vicinity of the tip of the moving blade, its peripheral speed is small, so that the collision speed of the drain against the moving blade is small, the moving blade is not eroded, and the turbine efficiency is not lowered by the braking action. Further, since the drain steam is not discharged from the flow path to the outside, the loss of steam is reduced.

(Embodiment) An embodiment of a stationary blade of a steam turbine according to the present invention will be described below with reference to FIGS. 1 to 3. The same parts as those in FIG. 8 are designated by the same reference numerals and the description thereof will be omitted.

In FIG. 1, a drain capturing groove 4 is formed along the longitudinal direction of the vane 3 near the rear edges of the dorsal and ventral sides of the vane 3. The groove 4 has a shape that does not open to the flow path outer peripheral wall 1 side, and in this embodiment, the distance D between the outer peripheral side end of the groove 4 and the flow path outer peripheral wall 1 is separated by about 3 mm or more. . On the other hand, the inner peripheral side end of the groove 4 is formed so as to be closer to the inner ring 2 side than 75% of the height of the stationary blade with respect to the outer peripheral surface of the stationary blade inner ring 2.

The groove 4 on the back side of the vane 3 is formed near the trailing edge so as to be substantially parallel to the trailing edge, and the groove 4 on the ventral side of the vane 3 has an outer peripheral end on the front side of the profile and an inner periphery. The side end portion is formed so as to approach the trailing edge side of the profile.

Next, the operation of the vane of the steam turbine in the present invention will be described.

In a steam turbine in which wet steam flows, when the steam flows between the stationary blades 3, the moisture in the steam cannot follow the speed change in the flow direction and collides with the surface of the stationary blades 3, or Drain occurs on the surface of the stationary blade 3 due to condensation while flowing along the surface.

The profile surface static pressure distributions in the III-III cross section and the IV-IV cross section (see FIG. 1) of the stationary blade 3 have a relationship as shown in FIG. 3, and the III-III cross section on the outer circumference side is the inner circumference. The pressure is higher than the IV-IV cross section on the side. Therefore, when the drain capturing groove 4 is formed, a pressure difference is generated along the groove 4 that is high on the outer peripheral side and low on the inner peripheral side on both the back and ventral sides. In FIG. 3, this pressure difference is indicated by ΔP ₁ and ΔP ₂ on the ventral side and the dorsal side, respectively. However, on the back side, a sufficient pressure difference is generated only by making the groove 4 parallel to the trailing edge, but on the ventral side, as is clear from FIG. The pressure difference is increased by forming the end portion on the inner peripheral side closer to the edge and closer to the trailing edge of the profile.

The drain on the surface of the vane 3 is caught in the drain trapping groove 4 while flowing on the surface of the vane, flows toward the inner peripheral side due to the static pressure gradient in the groove 4, and flows out again near the portion where the groove 4 disappears. It is made to flow to the trailing edge of the stationary blade 3. The drain route during this time is the first
It is designated by the symbol Fd in the figure. The drain that has reached the trailing edge is scattered from there and collides with the moving blade 7, but since the drain capturing groove 4 is sufficiently long and the radius at which the drain collides is sufficiently small, the collision velocity of the drain is Small enough.

On the other hand, it has been found through experiments that the amount of drain flowing in the form of a film on the outer peripheral wall 1 of the flow channel is large.
There is a distance D of 3 mm or more between the drain capturing groove 4 and the flow passage outer peripheral wall 1, the drain on the outer peripheral wall 1 does not flow into the groove 4, and the drain on the outer peripheral wall 1 is downstream of the stationary blade 3. Is efficiently sucked into the drain suction slit 8.

Normally, 75% from the tip for the final stage blade up to about 26 inches
In the range up to the height, the collision speed with the drain is large and the erosion is severe. In this embodiment, at least this area is protected by forming the drain trap groove 4.

As described above, by guiding the drain generated on the surface of the stationary blade 3 to the inner peripheral side portion where the collision velocity when colliding with the moving blade is sufficiently small, the erosion of the moving blade can be significantly reduced, and the reliability can be improved. And the cost of repairing the turbine can be reduced. Further, since the collision loss on the moving blade is small, the paragraph efficiency of the turbine is improved. In this embodiment,
Since the drain and steam do not flow out of the flow path, there is no steam loss.

Further, in the final stage stationary blade, the steam velocity flowing out of the stationary blade increases toward the inner peripheral side, so guiding the drain to the inner peripheral side before flowing it out further reduces the size of the drain particles scattered from the trailing edge of the stationary blade. Therefore, the effect of further reducing the erosion of the moving blade can be obtained.

According to the present invention, since the structure is simple in that the grooves are provided on the surface of the vane 3, not only can the cost of the turbine using wet steam as a working fluid be reduced, but it can also be easily applied to existing equipment. Prevention of blade erosion and performance improvement can be realized at low cost.

Next, another embodiment of the present invention will be described with reference to FIGS. Note that FIG. 5 is a VV cross-sectional view of the stationary blade 3 shown in FIG.

In FIG. 4, a plurality of drain capturing grooves 4 are formed on both the back and ventral sides of the stationary blade 3. The outer peripheral side ends of all the grooves 4 are separated from the outer peripheral wall 1 of the flow path by a distance D in the same manner as in FIG. 1, and the lengths of the grooves 4 become shorter toward the downstream side, and The radial positions of the inner peripheral side end portions of all the grooves 4 including the ventral side are different.

With this configuration, it is possible to reliably capture the drain that could not be captured by the single groove 4 and the drain that is newly generated downstream of the first groove 4, and to control the radial position where the drain flows out. It is possible to prevent the drain from colliding with the rotor blades even if it is dispersed at low speed.

Another embodiment will be described with reference to FIGS. 6 and 7. 7 is a sectional view of the vane of FIG. 6 taken along line VI-VI.

The vane 3 has a hollow structure and has a cavity 11 inside, and a drain suction slit 10 that communicates the outside and the cavity 11 is provided near the back front edge and the ventral rear edge where the surface pressures are almost equal. Are formed. The slit 10 is formed along the longitudinal direction of the vane 3 and orthogonal to the flow, and is divided into three so as not to reduce the strength of the vane 3 (see FIG. 6). A drain recovery chamber 5 communicating with the cavity 11 is provided inside the outer peripheral wall 1 of the flow path, and the recovery chamber 5 is connected to a lower pressure part such as a condenser. Further, a drain capturing groove 4 is formed on the back side surface near the trailing edge of the stationary blade 3 in parallel with the trailing edge.

In the steam turbine stationary blade configured as described above, the drain flowing on the surface of the blade is sucked into the cavity 11 through the drain suction slit 10, passes through the drain recovery chamber 5, and is discharged to the low pressure portion. By the way, since the stationary blade drain suction slit 10 on the back side is formed near the leading edge, even if all the drains are sucked in here, the drains are generated by condensation in the downstream thereof. This drain is caught by the drain catching groove 4 near the rear edge of the back side, and the drain is guided to a position where the radial position is sufficiently small. In the present embodiment, since the suction of drain and the movement of drain by the groove 4 are used together, it is particularly effective for a turbine stage where the degree of wetness is high and there is a large amount of drain, which cannot be prevented by the conventional hollow stationary blade having only the suction slit. It is possible to effectively prevent erosion due to the drain generated on the downstream side.

〔The invention's effect〕

As is apparent from the above description, according to the present invention, the drain on the surface of the stationary blade is eroded by the drain through the drain capturing groove formed on at least one of the back surface and the ventral surface of the stationary blade. Since it is guided to a position in the radial direction that does not give the effect, it is possible to prevent erosion of the moving blade and improve the efficiency of the turbine stage.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a vertical sectional view of a steam turbine final stage showing an embodiment of the present invention, FIG. 2 is a sectional view taken along line II-II of FIG. 1, and FIG. Profile surface static pressure distribution diagram of the vane in III-III cross section and IV-IV cross section, FIG. 4 is a vertical cross sectional view of a steam turbine final stage vane showing another embodiment, and FIG. 5 is VV of FIG.
Sectional drawing, FIG. 6 is a longitudinal sectional view of a final stage of a steam turbine showing another embodiment, FIG. 7 is a sectional view of a VII-VII section of FIG. 6, and FIG. 8 is a longitudinal sectional view of a conventional steam turbine final stage. , Fig. 9 shows 8
FIG. 9 is a sectional view taken along line IX-IX in the figure. 1 ... Outer wall of flow passage, 2 ... Inner ring of vane, 3 ... Vane, 4 ...
… Drain catching groove, 5 …… Drain recovery cavity, 6 …… Communication hole, 7 …… Movement blade, 8 …… Drain suction slit, 10 …… Static vane drain suction slit, 11 …… Static vane cavity, Fd …… Drain flow.

 ─────────────────────────────────────────────────── --- Continuation of the front page (56) Reference JP-A-61-108806 (JP, A) JP-A-58-176404 (JP, A) JP-A-57-44706 (JP, A) JP-A-63- 183205 (JP, A) Actual Open Sho 53-132506 (JP, U) Actual Open Sho 51-141702 (JP, U) Actual Open Sho 60-73801 (JP, U) Japanese Patent Sho 49-9522 (JP, B1) Actual Public Sho 52-27282 (JP, Y1) Actual Public Sho 51-20322 (JP, Y1)

Claims (6)

[Claims] 1. A stator blade having an outer peripheral side end supported by a flow passage outer peripheral wall and an inner peripheral side end supported by a stationary vane inner ring, and at least one of a back side surface and a ventral side surface of the stationary blade. A stationary blade of a steam turbine, characterized in that a drain trap groove extending in the longitudinal direction is formed from a position spaced from the outer peripheral wall of the flow path toward the inner ring side of the stationary blade. 2. The above-mentioned groove is such that an outer peripheral side end of the groove is separated from the outer peripheral wall of the flow path by at least 3 mm or more, and an inner peripheral side end of the groove is a stator vane height based on an outer peripheral surface of the stationary vane inner ring. The stator blade of the steam turbine according to claim 1, wherein the stator blade is formed so as to reach a position of 75% or less of the height. 3. The vane of a steam turbine according to claim 1, wherein the groove is formed near the trailing edge of the back side surface and substantially parallel to the trailing edge. 4. The groove is formed such that an outer peripheral side end of the groove is located closer to a profile front edge and an inner peripheral side end of the groove is located closer to a profile rear edge, and the groove is formed from the outer peripheral side end to the inner peripheral side. The static blade of the steam turbine according to claim 1, wherein the static pressure in the groove is lowered toward the side end portion. 5. The two or more grooves are formed in parallel on the same plane of the back surface or ventral surface of the stationary blade, and the length of the groove is shorter as the groove is closer to the trailing edge. A stationary blade of a steam turbine according to claim 1, characterized in that. 6. The stator vane is formed in a hollow structure, and along the longitudinal direction of the steam stator vane along the profile leading edge side in the back side and the profile trailing edge side in the ventral side where the steam pressure becomes the same, and in the steam flow. A slit-shaped drain suction port that is orthogonal to each other is formed, and the groove is formed near the rear edge of the back side surface substantially parallel to the rear edge.
The stationary blade of the steam turbine according to the item.