JP2013147999A - Steam turbine and blade for steam turbine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steam turbine and a blade of the steam turbine that can favorably collect water generated in the steam turbine, and prevent reduction in turbine efficiency.SOLUTION: A steam turbine includes: a turbine rotor shaft 3; a plurality of blades 2 provided on the turbine rotor shaft 3 and rotated by a steam flow; tip covers 20 attached to tip ends of the respective blades 2 and connected to and in contact with one another; at least one water drip fin 30 provided along a circumferential direction at the tip cover 20, and outwardly extending in a radial direction of each of the blades 2; and a diaphragm outer ring 40 disposed at an outer circumferential side from each of the blades 2, and having a drain catcher 43 opposed to a tip end part of the water drip fin 30. The tip cover 20 has a leading edge formed at a downstream side in an axial direction from a leading edge of the blade 2 or at a position in the axial direction corresponding to the leading edge of the blade 2 in the axial direction.

Description

  Embodiments described herein relate generally to a steam turbine and a moving blade of a steam turbine.

  In the turbine low pressure part of a nuclear turbine, a geothermal turbine, or a thermal turbine, the temperature of turbine drive steam becomes comparatively low. A part of the turbine-driven steam is condensed during the expansion work and becomes moisture and flows to the inner and outer peripheral walls of the steam passage and the turbine blade.

  Moisture flowing through the inner and outer peripheral walls of the steam passage and the turbine blades eventually grows into water droplets having a relatively large particle size. The water droplets erode the leading edge of the turbine blade, cause a collision resistance against the rotation of the turbine blade, and reduce the blade efficiency of the turbine blade.

  Thus, the presence of moisture in the turbine adversely affects turbine efficiency and reliability. On the other hand, conventionally, a steam turbine having a structure for removing attached moisture is known. Specifically, this steam turbine has a seal fin provided at the tip of the turbine rotor blade and a space provided for the purpose of capturing moisture at the tip of the seal fin. Moisture flowing through the steam turbine is scattered in the outer peripheral direction by centrifugal force when it hits the seal fin, and is captured in the space.

Japanese Patent Laid-Open No. 2005-2917

  In the conventional steam turbine, moisture in the steam turbine is captured by a seal fin provided at the tip of the turbine rotor blade. However, since the conventional steam turbine uses seal fins for the purpose of preventing steam leakage, it cannot be said that water is sufficiently collected. Specifically, the flow of steam in the steam turbine and centrifugal force act, and even if seal fins are used, moisture cannot be suitably guided to the space.

  As a result, the conventional steam turbine has a problem that it cannot suppress erosion due to drain generated in the steam turbine and a decrease in rotational resistance of the turbine rotor blade.

  The present invention has been made in view of such circumstances, and provides a steam turbine and a steam turbine rotor blade that can suitably recover moisture generated in the steam turbine and prevent a decrease in turbine efficiency. For the purpose.

  In order to solve the above-described problems, a steam turbine according to an embodiment of the present invention includes a turbine rotor shaft, a plurality of blades provided on the turbine rotor shaft and rotated by a steam flow, and tips of the blades. A tip cover attached to and connected to each other, at least one draining fin provided along the circumferential direction of the tip cover and extending radially outward of each of the blades, and on the outer peripheral side of each of the blades And a diaphragm outer ring having a drain catcher disposed opposite to the tip of the draining fin. The tip cover has a leading edge formed at an axial position downstream of the leading edge of the moving blade in the axial direction or at an axial position that coincides with the leading edge of the moving blade in the axial direction.

The block diagram which shows one Embodiment of the steam turbine which concerns on this invention. The top view which shows the moving blade of the steam turbine of FIG. 1 from an outer peripheral side. The block diagram for demonstrating the positional relationship of the axial direction of a draining fin and the opening part of a drain catcher. Explanatory drawing of the flow of the steam in a steam turbine. The block diagram which shows the steam turbine as a 1st modification in which the water droplet guide groove was formed. The top view which shows the moving blade of the steam turbine of FIG. 5 from an outer peripheral side. The block diagram which shows the steam turbine as a 2nd modification provided with two or more draining fins. The top view which shows the moving blade of the steam turbine of FIG. 7 from an outer peripheral side. The block diagram which shows the steam turbine as a 3rd modification by which the draining fin was intermittently arrange | positioned.

  An embodiment of a steam turbine and a moving blade of a steam turbine according to the present invention will be described with reference to the accompanying drawings. The steam turbine and the rotor blade of the steam turbine in the present embodiment are applied to, for example, a low pressure portion of the turbine.

  FIG. 1 is a configuration diagram showing an embodiment of a steam turbine according to the present invention.

  FIG. 2 is a plan view showing the rotor blade 2 of the steam turbine 1 of FIG. 1 from the outer peripheral side.

  In FIG. 1 and FIG. 2, the steam flows from left to right. In the moving blade 2, the left side is assumed to be the front and the right side is assumed to be the rear. Since the flow direction of steam in the steam turbine 1 coincides with the direction of the turbine rotor shaft 3, the flow direction of steam is defined as the axial direction.

  As shown in FIG. 1, the steam turbine 1 mainly includes a turbine rotor shaft 3, a moving blade 2, and a stationary blade 4.

  The moving blades 2 are arranged opposite to the downstream side of the stationary blades 4 and form blade rows in the circumferential direction of the turbine rotor shaft 3. The moving blade 2 has a tip cover 20 formed integrally with the moving blade 2 at the tip of the blade.

  As shown in FIG. 2, the tip cover (cover) 20 is formed by a back cover 21 extending in the back circumferential direction of the moving blade 2 and a vent cover 22 extending in the ventral circumferential direction of the moving blade 2. Is done. Adjacent covers 20 are in contact with each other. The axial direction position of the cover front edge 25 of the ventral cover 22 coincides with the blade effective portion front edge 12 in the axial direction rearward side (axially downstream side) or the blade effective portion front edge 12 in the axial direction. To do. When the cover 20 is untwisted (torsional moment generated in the direction opposite to the twist of the blade) due to the centrifugal force of the moving blade 2, the back cover 21 and the ventral cover 22 of the adjacent moving blades 2 are in contact with each other. Contact at surface 23. Thereby, the steam turbine 1 obtains the vibration damping effect of the entire circumference of the moving blade 2.

  The cover 20 has chip draining fins 30 formed integrally with the cover 20 on the cover outer peripheral surface 27. The tip draining fins (draining fins) 30 are fins that extend outward in the radial direction of the rotor blade 2 along the front edge 25 of the cover, and are provided annularly over the entire circumference of the cover 20. The draining fin 30 may be provided on the rear side of the cover front edge 25.

  As shown in FIG. 1, the outer diameter φB at the tip position of the draining fin 30 is smaller than the maximum outer diameter φA of the cover 20. The cover 20 has a front-declining slope, and has an outer diameter such that the cover rear edge 26 side is large and the cover front edge 25 side is small. The length of the draining fin 30 in the radial direction is larger than that of the cover rear edge 26. The outer diameter φB is determined so as not to increase.

  The stationary blade 4 is provided between a nozzle diaphragm outer ring 40 and a nozzle diaphragm inner ring 45 located on the radially inner side of the nozzle diaphragm outer ring 40. The nozzle diaphragm outer ring (diaphragm outer ring) 40 includes a nozzle strip 60 and a drain catcher 43.

  The nozzle strip 60 is provided in the diaphragm outer ring 40 facing the rear side of the moving blade 2. The nozzle strip 60 functions as a flow path resistance in the space between the cover 20 and the diaphragm outer ring 40, and reduces the tip-side leakage steam flow rate.

  The drain catcher 43 is a space for collecting water droplets peeled off from the draining fins 30. The drain catcher 43 has an opening 46 at an axial position facing the tip of the draining fin 30.

  Here, FIG. 3 is a configuration diagram for explaining the axial positional relationship between the draining fin 30 and the opening 46 of the drain catcher 43.

  In general, the maximum difference in the axial direction of the low-pressure turbine is about 20 mm. In the draining fin 30, the dimension of the opening 46 of the drain catcher 43 (the axial position of the draining fin 30 with respect to the opening 46) is determined in consideration of this difference in elongation.

  Specifically, as shown in FIG. 3, even when the maximum elongation difference occurs in the front-rear direction in the draining fin 30 (turbine rotor shaft 3) during steady operation, the maximum elongation difference at the tip of the draining fin 30 is The drain catcher 43 is configured to be within the axial width of the opening 46.

  The opening inlet side 47 of the drain catcher 43 has a trumpet shape in a cross-sectional view, and the axial position of the opening inlet side 47 is changed from the front axial position X1 to the rear axial position X2 (position X1 in FIG. 3). , X2 is the position where the trumpet-shaped opening begins to shrink. The tips of the draining fins 30 are designed to be within the axial range of the opening inlet side 47 when stopped and during steady operation where a maximum difference in elongation can occur.

  Next, the operation of the steam turbine 1 and the moving blade 2 will be described.

  FIG. 4 is an explanatory diagram of steam flow in the steam turbine 1.

  During operation of the steam turbine 1, part of the driving steam is condensed and becomes a liquid film L and adheres to the stationary blade 4. When the liquid film L reaches the stationary blade trailing edge 5 of the stationary blade 4, it becomes a water droplet D and scatters from the stationary blade trailing edge 5 as indicated by an arrow A in the figure. At this time, the energy of the steam is used for accelerating the water droplets D and consumes the energy of the steam.

  The water droplets D cannot catch the steam flow due to inertia and collide with and adhere to the leading edge 12 of the blade effective portion of the rotating moving blade 2. The collision of the water droplet D becomes a braking force against the rotation of the moving blade 2 and decreases the turbine efficiency. Further, the collision of the water droplet D becomes a factor that causes the erosion of the leading edge 12 of the blade effective portion of the moving blade 2 by the impact.

  As shown in FIG. 1, the water droplet D moves the blade surface of the moving blade 2 radially outward by centrifugal force, and reaches the radial tip of the blade effective portion side surface 11. Of the water droplets D that have reached the radial tip of the blade effective portion side surface 11, the water droplet D that exists in front of the cover end surface 24 of the cover leading edge 25 is at the boundary between the blade effective portion side surface 11 and the blade effective portion outer peripheral surface 13. Transfers to the blade effective part outer peripheral surface 13 by surface tension.

  The water droplet D on the blade effective portion outer peripheral surface 13 moves backward by the steam force and reaches the draining fin 30. The water droplet D that has reached the draining fin 30 moves to the tip of the draining fin 30 by centrifugal force, is blown off from the tip to the outer peripheral side of the rotor blade 2, and is collected by the drain catcher 43.

  It is also known that the distribution of the amount of water adhering to the stationary blade 4 (diaphragm outer ring 40) is larger on the outer peripheral side, and that a large amount of water is also present on the inner peripheral wall surface 42 of the diaphragm outer ring 40. Further, the water droplet D scattered from the stationary blade 4 is deflected to the outer peripheral side by a centrifugal force due to its own circumferential speed component. Therefore, a part of the water droplet D splashed from the stationary blade 4 and the inner peripheral wall surface 42 directly adheres to the cover end surface 24 of the cover front edge 25, the cover outer peripheral surface 27 or the fin end surface 31 in front of the chip draining fin 30 and is described above. It is collected by the drain catcher 43 as shown.

  The steam turbine 1 and the moving blade 2 in the present embodiment can effectively remove and collect the water droplets D attached to the moving blade 2. Thereby, the steam turbine 1 and the moving blade 2 can prevent erosion due to the water droplets D. Moreover, the steam turbine 1 and the moving blade 2 can suppress the rotational resistance of the moving blade 2 due to the water droplets D and prevent the turbine efficiency from being lowered.

  In particular, the moving blade 2 is attached to the blade effective portion side surface 11 because a cover having a cover leading edge 25 that is rearward of the blade effective portion leading edge 12 of the moving blade 2 or coincides with the blade effective portion leading edge 12 is provided. In addition, the water droplets D that have reached the blade effective portion outer peripheral surface 13 can be efficiently removed.

  Further, since the draining fin 30 is provided not for sealing the leaked steam but for collecting the water droplet D in the drain catcher 43, the outer diameter φB at the tip position of the draining fin 30 is set to the maximum of the chip cover 20. It can be made smaller than the outer diameter φA. For this reason, it is possible to avoid the risk that the tip of the draining fin 30 interferes with the inner peripheral surface of the diaphragm outer ring 40 or the nozzle strip 60 during assembly and operation of the steam turbine 1.

  In addition, you may comprise the steam turbine 1 and the moving blade 2 in this embodiment like the modification demonstrated below.

  FIG. 5 is a configuration diagram showing a steam turbine 1 as a first modified example in which the water droplet guide groove 15 is formed.

  FIG. 6 is a plan view showing the moving blade 2 of the steam turbine 1 of FIG. 5 from the outer peripheral side.

  The rotor blade 2 has one or more water droplet guide grooves 15 (two in FIG. 5 and FIG. 6) on the front side (blade effective portion front edge 12 side) of the cover front edge 25 on the blade back side surface 14. The water droplet guide groove 15 extends in the radial direction of the moving blade 2, and one end reaches the tip of the moving blade 2.

  The moving blade 2 moves the water droplet D to the blade effective portion outer peripheral surface 13 by the water droplet guide groove 15 when the water droplet D attached to the blade back side surface 14 moves in the outer peripheral direction of the moving blade 2. Thereby, the steam turbine 1 and the moving blade 2 can more reliably remove the moisture adhering to the blade back side surface 14.

  FIG. 7 is a configuration diagram showing a steam turbine 1 as a second modified example in which a plurality of draining fins 30 are provided.

  FIG. 8 is a plan view showing the rotor blade 2 of the steam turbine 1 of FIG. 7 from the outer peripheral side.

  The cover 20 has a plurality of draining fins 30 (two in FIGS. 7 and 8) arranged in the axial direction. By providing a plurality of draining fins 30, the water droplets D that have reached the cover outer peripheral surface 27 can be reliably collected by the drain catcher 43.

  FIG. 9 is a configuration diagram showing the steam turbine 1 as a third modified example in which the draining fins 30 are intermittently arranged.

  The draining fins 30 extend radially outward of the moving blade 2 along the cover front edge 25 and are provided intermittently in the circumferential direction of the cover 20. The draining fin 30 is provided for the purpose of mainly removing moisture from the outer peripheral surface 13 of the blade effective portion. For this reason, when the trajectory of the water droplet D from the blade effective portion outer peripheral surface 13 is appropriately predicted, the draining fins 30 can be intermittently arranged so as to coincide with the trajectory of the water droplet D.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  For example, the outer diameter φB at the tip position of the draining fin 30 may be larger than the maximum outer diameter φA of the cover 20. In this case, the distance between the opening inlet side 47 (see FIG. 3) of the drain catcher 43 and the tip of the draining fin 30 is reduced, which is effective in that the water droplet D can be reliably guided to the drain catcher 43.

  Further, instead of the nozzle strip 60 of the diaphragm outer ring 40, a chip seal fin provided in an annular shape over the entire periphery may be provided integrally with the cover outer peripheral surface 27 of the chip cover 20.

DESCRIPTION OF SYMBOLS 1 Steam turbine 2 Moving blade 3 Turbine rotor shaft 4 Stator blade 15 Water drop guide groove 20 Tip cover (cover)
21 Back side cover 22 Abdominal side cover 30 Tip draining fin 40 Nozzle diaphragm outer ring (diaphragm outer ring)
43 Drain catcher 45 Nozzle diaphragm inner ring 46 Opening

Claims (7)

A turbine rotor shaft;
A plurality of rotor blades provided on the turbine rotor shaft and rotated by a steam flow;
A tip cover attached to the tip of each of the blades and connected to each other;
At least one draining fin provided along the circumferential direction on the tip cover and extending radially outward of each of the blades;
A diaphragm outer ring disposed on the outer peripheral side of each of the moving blades and having a drain catcher facing the tip of the draining fin;
The steam turbine according to claim 1, wherein the tip cover has a leading edge formed at an axial position downstream of the leading edge of the moving blade in the axial direction or at an axial position that coincides with the leading edge of the moving blade in the axial direction.   The steam turbine according to claim 1, wherein the draining fin is provided along a front edge of the tip cover.   The steam turbine according to claim 1 or 2, wherein a tip position of the draining fin has an outer diameter smaller than a maximum outer diameter of the tip cover.   The steam turbine according to claim 1, wherein a plurality of the draining fins are provided on the tip cover along a circumferential direction.   Each of the moving blades has a water droplet guide groove extending in a radial direction of the moving blade and upstream of a front edge of the tip cover on a back side surface and having one end portion reaching the tip of the moving blade. The steam turbine of any one of 1-4.   The drain catcher has an opening where the maximum elongation difference is within the axial width of the opening even when a maximum elongation difference occurs in the axial position of the tip of the draining fin during steady operation. The steam turbine as described in any one of 1-5. A rotor blade rotated by a steam flow;
A tip cover attached to and connected to the tip of the rotor blade; and
The tip cover is provided along the circumferential direction, and includes at least one draining fin extending outward in the radial direction of each blade.
The tip cover has a leading edge formed at an axial position downstream of the leading edge of the moving blade in the axial direction or at an axial position that coincides with the leading edge of the moving blade in the axial direction. Wings.

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