JP2014077397A - Steam turbine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steam turbine capable of effectively preventing corrosion and degradation of efficiency of a moving blade due to water droplets.SOLUTION: A steam turbine includes: moving blades 80 rotating a rotary shaft by steam pressure; a plurality of stationary blades 60 disposed at intervals in the circumferential direction of the rotary shaft at a radial outer side of the rotary shaft and forming steam flow to the moving blades 80; and an outer shroud 50 defining flow channels P of the steam together with the stationary blades 60. First ejection holes 91 for ejecting a gas, are formed on a surface 51 facing the flow channels P, of the outer shroud 50.

Description

  The present invention relates to a steam turbine.

  A steam turbine is a prime mover that converts the thermal energy of steam into kinetic energy and converts it into mechanical work. When high-pressure steam is introduced at a location lower than the steam, the steam expands due to a decrease in pressure. At that time, the heat energy of the steam is converted into kinetic energy, and a high temperature steam flow is obtained. Then, steam flowing at a high speed is supplied to the moving blade, and the rotating shaft supporting the moving blade is rotated together with the moving blade. By transmitting the rotational force to a generator or the like, the kinetic energy of the steam is converted into mechanical work.

  Steam expands and works in the steam turbine with changes in state such as pressure and temperature drops. For example, superheated steam is ejected from a boiler to a steam turbine, and the degree of superheat decreases as the pressure expands, resulting in a dry saturated state. Such dry and saturated steam is further expanded to become wet steam containing moisture.

  In the region of wet steam, moisture tends to aggregate on the surface of the stationary blade, and the moisture aggregated on the surface of the stationary blade becomes a water vein and circulates downstream by being blown by the steam flow. When the water vein reaches the trailing edge of the stationary blade, it scatters and becomes water droplets. Thus, the water droplets scattered from the stationary blade collide with the moving blade installed on the downstream side of the stationary blade by the steam flow, and may cause erosion (erosion phenomenon) of the moving blade.

  As described above, when water droplets scattered from the stationary blade collide with the moving blade on the downstream side, a force opposite to the rotating direction of the rotating shaft acts on the moving blade, and a braking action that suppresses the rotation occurs. . Generally, it is said that when the moisture in the steam increases by 1%, the internal efficiency of the steam turbine decreases by 1 to 1.2%.

  For example, those disclosed in Patent Documents 1 to 5 are known as techniques for removing the water veins on the blade surface caused by the condensation of moisture in the wet steam.

In the techniques disclosed in Patent Documents 1 to 3, a plurality of injection holes are provided in the whole or a part of the suction surface on the back side and the pressure surface on the abdomen side of the blade, and introduced into the blade inner space from the discharge hole. The water vein is scattered by ejecting steam.
In the technique disclosed in Patent Document 4, steam is introduced into the blade inner space to heat the blade, and steam is ejected from the ejection holes to reduce the wetness around the blade.
Further, in the technique disclosed in Patent Document 5, the trailing edge of the wing is formed into a substantially serrated shape, so that water droplets that are scattered are made finer, a part of the water vein is sucked from the slit on the wing surface, and discharged outside. It is said.

Japanese Patent Laid-Open No. 7-034804 Japanese Utility Model Publication No. 61-151004 Japanese Patent No. 4101358 JP 2001-501700 A JP-A 63-195302

  By the way, in the region of wet steam, moisture easily aggregates not only on the surfaces of the stationary blades but also on the surface of the shroud that connects the stationary blades to each other in the circumferential direction of the rotating shaft, and the moisture aggregated on the surface of the shroud A water vein is produced by circulating according to the flow. In addition, moisture condensed by the blades may adhere to the outer shroud due to centrifugal force, resulting in a water vein in the shroud.

  When such a water vein scatters as a water droplet at the trailing edge of the shroud and collides with the moving blade, erosion and efficiency reduction are caused as described above. However, although the above-described conventional technique can remove moisture adhering to the blade to some extent, it does not have an effect on moisture on the surface of the shroud. Therefore, there has been a problem that the blades are eroded by the water droplets scattered from the trailing edge of the shroud and the efficiency of the steam turbine is reduced.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a steam turbine capable of more effectively avoiding erosion of a moving blade and a decrease in efficiency due to water droplets.

In order to solve the above problems, the present invention proposes the following means.
That is, the steam turbine according to the present invention is provided with a plurality of rotor blades that rotate the rotating shaft by the fluid pressure of the steam, and radially outside the rotating shaft, spaced apart from each other in the circumferential direction of the rotating shaft, A stationary blade that forms a flow of the steam to the moving blade, and a shroud that connects the stationary blades adjacent to each other in the circumferential direction and defines a flow path of the steam together with the stationary blade, the shroud A first ejection hole for ejecting a gas is formed on the surface facing the flow path.

  According to the steam turbine having such characteristics, the water flowing on the surface of the shroud can be refined by ejecting gas from the surface of the shroud.

  In addition, it is preferable that the said gas is higher temperature than the vapor | steam which distribute | circulates the said flow path. By ejecting such a gas from the surface of the shroud, the water flowing on the surface of the shroud can be refined and the water can be evaporated.

  Further, in the steam turbine according to the present invention, the shroud is an outer shroud that connects the stationary blades to each other at an end portion on the radially outer side of the rotating shaft of the stationary blades, and the first ejection hole is the outer shroud. Preferably, the shroud is formed on the surface facing the flow path.

  Here, in the steam flowing through the steam turbine, a secondary flow toward the radially outer side of the rotating shaft is generated by the centrifugal force of the steam turbine. Therefore, moisture generated by condensation of wet steam is likely to be generated on the surface of the outer shroud that connects the stationary blades at the radially outer ends. On the other hand, in the steam turbine according to the present invention, since the first ejection holes are formed on the surface of the outer shroud, the moisture on the surface of the outer shroud can be refined, and moisture can be efficiently removed from within the steam turbine. It can be removed.

  Furthermore, the steam turbine which concerns on this invention WHEREIN: It is preferable that said 1st ejection hole has comprised the slit shape extended in the circumferential direction so that the said adjacent stationary blades may be covered.

  This ensures that water flowing through the outer shroud will pass through the slit. Therefore, the moisture can be surely miniaturized.

  Moreover, the steam turbine which concerns on this invention WHEREIN: It is preferable that the 2nd ejection hole which ejects the said gas is formed in the surface of the suction surface of the said stationary blade.

  As a result, not only the moisture on the surface of the shroud but also the moisture attached to the surface of the suction surface on the back side of the stationary blade can be refined. Therefore, it is possible to more reliably prevent water droplets from colliding with the moving blade.

  Further, in the steam turbine according to the present invention, a first flow path is formed in the shroud to flow the gas and guide the gas to the first ejection hole, and the gas flows in the stationary blade. Preferably, a second flow path is formed that is connected to the first flow path and guides the gas to the second ejection hole.

  According to the steam turbine having such a feature, the first flow path and the second flow path that lead the gas to the first ejection hole and the second ejection hole are connected, so that the first flow path and the second flow path are connected to each other. A gas supply source for supplying gas can be shared.

  According to the steam turbine of the present invention, the moisture on the surface of the shroud can be refined, so that water droplets based on the moisture are prevented from colliding with the moving blade, and the erosion of the moving blade and the reduction in efficiency are more effective. Can be avoided.

It is a longitudinal section showing a schematic structure of a steam turbine concerning a first embodiment of the present invention. It is a longitudinal section showing the important section of the steam turbine concerning a first embodiment of the present invention. It is AA sectional drawing of FIG. It is a schematic diagram which shows the cross section orthogonal to the axis line of the rotating shaft in the stationary blade of the steam turbine which concerns on 1st embodiment of this invention. It is a longitudinal cross-sectional view which shows the principal part of the steam turbine which concerns on 2nd embodiment of this invention. It is BB sectional drawing of FIG. It is a schematic diagram which shows the cross section orthogonal to the axis line of the rotating shaft in the stationary blade of the steam turbine which concerns on 2nd embodiment of this invention.

Hereinafter, an embodiment of a steam turbine of the present invention will be described in detail with reference to FIGS.
As shown in FIG. 1, the turbine 1 according to the present embodiment is rotatably provided inside a casing 10, a regulating valve 20 that adjusts the amount and pressure of steam S flowing into the casing 10, and the casing 10. , A rotating shaft 30 that transmits power to a machine such as a generator (not shown), a bearing portion 40 that supports the rotating shaft 30, an outer shroud 50 fixed to the inner surface of the casing 10, and the outer shroud 50 A stationary vane 60 held, an inner shroud 70 fixed to the stationary vane 60, and a moving blade 80 provided on the rotary shaft 30 on the downstream side of the stationary vane 60 are provided.

The casing 10 is configured to form a space inside thereof, and hermetically seals the inside space.
A plurality of regulating valves 20 are attached to the inside of the casing 10, and each includes a regulating valve chamber 21 into which steam S flows from a boiler (not shown), a valve body 22, a valve seat 23, and a steam chamber 24. Yes. In this regulating valve 20, the steam passage is opened by separating the valve body 22 from the valve seat 23, and the steam S flows into the internal space of the casing 10 through the steam chamber 24.

The rotating shaft 30 includes a shaft main body 31 and a plurality of disks 32 provided so as to project annularly from the outer periphery of the shaft main body 31 outward in the radial direction. The rotating shaft 30 transmits rotational energy to a machine such as a generator (not shown).
The bearing portion 40 includes a journal bearing device 41 and a thrust bearing device 42, and supports the rotary shaft 30 inserted into the casing 10 so as to be rotatable outside the casing 10.

The outer shroud 50 is fixed to the inner wall surface of the casing 10 and has a ring shape with the axis of the rotating shaft 30 as the center, as shown in FIGS. 1 and 2. A plurality (six in this embodiment) of outer shrouds 50 are provided at intervals in the axial direction.
In the present embodiment, the radially inner surface 51 of the outer shroud 50 is inclined toward the radially outer side toward the downstream side, and a moving blade, which will be described later, is disposed on an extension line on the downstream side of the inclination. The tip of 80 (end part on the outside in the radial direction) is located.

  As shown in FIGS. 1 and 2, the stationary blade 60 has a base end portion that is a radially outer end portion attached to the outer shroud 50, and extends radially inward from the outer shroud 50. It has a wing shape. The stationary blade 60 is formed so that the dimension in the axial direction becomes smaller toward the inner side in the radial direction. Note that the surface facing the one side in the circumferential direction of this stationary blade 60 (the front side in FIG. 2 and the lower side in FIG. 3) is a negative pressure surface 61 having a convex curved surface, and the other side in the circumferential direction (see FIG. 2 is a positive pressure surface 62 having a concave curved surface.

  A plurality of stationary blades 60 are provided at intervals in the circumferential direction of the rotating shaft 30 and the outer shroud 50, that is, a plurality of stationary blades 60 are arranged radially. Thus, the base end portions of the stationary blades 60 arranged in the circumferential direction are connected by the outer shroud 50.

  A plurality of stationary blades 60 arranged in the circumferential direction in this manner constitute a group of annular stationary blades that radiate so as to surround the rotating shaft 30 from the outer circumferential side. The annular stationary blade group is fixed to each of the plurality of outer shrouds 50, and is provided in the same number (six in this embodiment) as the outer shrouds 50 apart from each other in the axial direction.

As shown in FIGS. 1 and 2, the inner shroud 70 is an annular member centering on the axis similar to the outer shroud 50, and is the tip of the stationary blade 60 in the extending direction from the outer shroud 50, that is, The stationary blade 60 is fixed to the radially inner end. That is, the inner shroud 70 connects the tips, which are the radially inner ends of the stationary blades 60 arranged in the circumferential direction, in the circumferential direction.
The rotating shaft 30 is inserted inside the inner shroud 70, and a gap is formed between the inner shroud 70 and the rotating shaft 30. As a result, the rotating shaft 30 rotates about the axis without being interfered by the inner shroud 70.

  Here, between the adjacent stationary blades 60, the flow path P through which the steam S flows is defined by the stationary blades 60, the surface 51 of the outer shroud 50, and the surface 71 of the inner shroud 70. Is formed. Thereby, the surface 51 of the outer shroud 50 and the surface of the inner shroud 70 are surfaces facing the flow path P.

  As shown in FIGS. 1 and 2, the moving blade 80 has a base end attached to the outer peripheral portion of the disk 32 of the rotating shaft 30 and extends outward from the disk 32 in the radial direction. The rotor blade 8032 is formed so that the dimension in the axial direction of the rotary shaft 30 becomes smaller toward the outside in the radial direction. Further, a plurality of moving blades 80 are attached to the outer peripheral portion of the disk 32 at intervals in the circumferential direction of the rotating shaft 30, that is, a plurality of moving blades 80 are arranged radially. Thus, the moving blade 80 constitutes an annular moving blade group so as to surround the rotating shaft 30.

  This annular blade group is provided downstream of each annular stator group so as to form a pair with the annular stator group, that is, the same number (six in this embodiment) as the annular stator groups are arranged. Has been. That is, the steam turbine 1 of the present embodiment is a six-stage steam turbine 1 in which six stages including an annular stationary blade group and an annular moving blade group are arranged.

Here, the steam turbine 1 of the present embodiment includes a moisture removal structure for removing the moisture W in the flow path P.
As shown in FIGS. 2 to 4, the moisture removing structure includes a first ejection hole 91 formed so as to open on the surface 51 of the outer shroud 50, a first flow path 93 formed inside the outer shroud 50, The second flow path 94 formed inside the blade 60, the third flow path 95 formed inside the inner shroud 70, and the gas supply source 100 that supplies the gas G to the third flow path 95. ing.

  The first ejection hole 91 is formed on the surface 51 of the outer shroud 50, that is, the surface facing the flow path P facing radially inward. The first ejection holes 91 are formed in a slit shape extending in the circumferential direction so as to extend over the base ends of the adjacent stationary blades 60. That is, both ends in the extending direction of the first ejection holes 91 are in contact with the stationary blades 60 located on both sides in the circumferential direction of the first ejection holes 91. More specifically, the first ejection hole 91 extends across the negative pressure surface 61 of one stationary blade and the positive pressure surface 62 of the other stationary blade 60 among the adjacent stationary blades 60.

  The first flow path 93 is a hole formed so as to extend in the circumferential direction inside the outer shroud 50, and is connected to the first ejection hole 91. As a result, the first flow path 93 is in communication with the flow path P through the first ejection holes 91.

  The second flow path 94 is a hole formed so as to extend the stationary blade 60 in the extending direction of the stationary blade 60, that is, in the radial direction, and has a radially outer end. The portion is connected to a first flow path 93 formed in the outer shroud 50. Thereby, the first flow path 93 and the second flow path 94 are in communication with each other.

  The third flow path 95 is a hole formed so as to extend in the circumferential direction inside the inner shroud 70. The third flow path 95 is connected to the radially inner end of the second flow path 94 formed in the stationary blade 60 at the connection point between the inner shroud 70 and the stationary blade 60. As a result, the second flow path 94 and the third flow path 95 are in communication with each other, that is, the first flow path 93 and the third flow path 95 are in communication with each other via the second flow path 94. ing.

  The gas supply source 100 has a role of supplying the gas G to the third flow path 95 as shown in FIG. Further, the gas G supplied from the gas supply source 100 is injected into the flow path P so as to be ejected from the first ejection hole 91 via the third flow path 95, the second flow path 94 and the first flow path 93. The pressure is higher than that of the steam S.

As the gas G supplied from the gas supply source 100, steam, air, nitrogen, other inert gas G, or the like can be used.
When steam is employed as the gas G, a boiler or other steam generator can be used as the gas G supply source. Further, the gas supply source 100 may be configured to supply steam from a steam flow channel upstream of the flow channel P that ejects the gas G in the steam turbine 1. Further, when steam is used as the gas G, the gas G is preferably at a higher temperature than the steam flowing through the flow path P. More specifically, the gas G is preferably heated steam having a temperature higher than the saturation temperature at the pressure of the steam S in the flow path P.

  On the other hand, when air, nitrogen or other inert gas G is used as the gas G, a configuration in which the gas G is ejected from a tank sealed at high pressure and supplied to the third flow path 95 is adopted. can do. In addition, you may supply the gas G to the 3rd flow path 95 as a high voltage | pressure state with an air blower.

Next, the operation of the steam turbine 1 of the present embodiment will be described.
The steam turbine 1 operates by introducing steam S from the boiler into the casing 10 via the regulating valve 20. That is, the steam S flowing into the casing 10 passes through the flow path P between the stationary blades 60 in each stage and is supplied to the moving blades 80. When the fluid pressure of the steam S acts on the moving blade 80, the rotating shaft 30 rotates with the rotation of the moving blade 80. As a result, the machine connected to the rotating shaft 30 is driven.

  Here, when the steam S flowing through each stage becomes wet steam during the operation of the steam turbine 1, the moisture W is condensed on the surfaces of the stationary blade 60 and the moving blade 80, and the moisture W is scattered to the outer shroud 50. Adheres. Further, the wet steam may be directly condensed on the outer shroud 50 and the water W may adhere. When water veins along the flow of the steam S are generated on the surface 51 of the outer shroud 50 by such moisture W, water droplets scatter from the rear edge of the surface 51 of the outer shroud 50, and the water droplets are downstream of the moving blades. Colliding with 80 may cause erosion of the rotor blade 80 and a decrease in efficiency.

On the other hand, in the steam turbine 1 of this embodiment, scattering of water droplets is avoided by ejecting the gas G from the first ejection holes 91.
That is, during the operation of the steam turbine 1, the gas G from the gas supply source 100 described above is supplied to the third flow path 95 in the inner shroud 70 as shown in FIG. 4. The gas G in the third flow path 95 flows from the first ejection hole 91 toward the radially inner side through the second flow path 94 in the stationary blade 60 and the first flow path 93 in the outer shroud 50. It is ejected into the road P. At this time, since the first ejection holes 91 extend across the adjacent stationary blades 60, the water W flowing through the surface 51 of the outer shroud 50 toward the downstream side is always the gas G from the first ejection holes 91. Will come into contact.

  Thereby, the water W flowing through the surface 51 of the outer shroud 50 can be refined. That is, the moisture W on the surface 51 of the outer shroud 50 is dispersed according to the flow of the gas G by being exposed to the gas G from the first ejection hole 91 in the middle of the path. Thereby, it is possible to avoid the water W from being collected in a region downstream of the first ejection hole 91 on the surface 51 of the outer shroud 50 and forming a water vein. Therefore, it is possible to prevent the collected water W from being scattered as water droplets from the rear edge of the outer shroud 50, and it is possible to suppress the erosion of the moving blade 80 and the decrease in efficiency due to the water droplets.

  Furthermore, in the case where the gas G having a higher temperature than the steam S flowing through the flow path P facing the first ejection hole 91 is used as the gas G, in addition to the refinement of the water W due to the ejection of the gas G, The evaporation of moisture W can be promoted by heat. As a result, it is possible to further prevent the moisture W from being collected and distributed downstream of the first ejection holes 91.

  Moreover, in this embodiment, since the 1st ejection hole 91 was formed in the surface 51 of the outer shroud 50 in which especially the water | moisture content W tends to gather, the water | moisture content W can be efficiently removed from the inside of the steam turbine 1. FIG.

Next, a second embodiment of the present invention will be described with reference to FIGS. In the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.
The steam turbine 1 according to the second embodiment is different from the first embodiment in that a second ejection hole 92 is formed in the suction surface 61 of the stationary blade 60.

That is, in the second embodiment, as shown in FIGS. 5 to 7, the negative pressure surface 61 on the back side of the stationary blade 60 extends radially inward from the radially outer end of the negative pressure surface 61. A second ejection hole 92 having a slit shape is formed.
The second ejection hole 92 is connected to a second flow path 94 formed in the stationary blade 60, whereby the second flow path 94 is connected to the flow path P of the steam S via the second ejection hole 92. It is in a communication state.

When the dimension of the stationary blade 60 in the axial direction is the blade width of the stationary blade 60, the second ejection hole 92 is formed in the range of 50% to 70% of the blade width from the leading edge of the stationary blade 60. It is preferable.
Further, when the radial dimension of the stationary blade 60 is the blade height of the stationary blade 60, the second ejection hole 92 is within 50% to 70% of the blade height from the radially outer end of the stationary blade 60. It is preferable to form in the range.

According to the steam turbine 1 of the second embodiment as described above, in addition to the ejection of the gas G from the first ejection hole 91 formed in the surface 51 of the outer shroud 50, it is formed on the negative pressure surface 61 of the stationary blade 60. The gas G can be ejected from the second ejection hole 92 toward the flow path P.
As a result, not only the water W but also the water W adhering to the suction surface 61 of the stationary blade 60 can be removed from the surface 51 of the outer shroud 50.
Here, the moisture W on the surface of the stationary blade 60 is 50% or more and 70% or less of the blade width from the front edge portion of the stationary blade 60 on the suction surface 61 of the stationary blade 60 and the radially outer side of the stationary blade 60. It tends to adhere to the range of 50% to 70% of the blade height from the end of the blade. In the present embodiment, since the second ejection holes 92 are formed in the range on the surface of the stationary blade 60, the water W can be efficiently removed.

  Further, the first flow path 93 and the second flow path 94 that guide the gas G to the first ejection hole 91 and the second ejection hole 92 are connected to each other, so that the first flow path 93 and the second flow path 94 are filled with gas. The gas supply source 100 for supplying G can be shared. Thereby, simplification of the supply path of gas G can be aimed at, and the enlargement and complication of an installation can be avoided.

The embodiment of the present invention has been described above, but the present invention is not limited to this, and can be appropriately changed without departing from the technical idea of the present invention.
For example, in the embodiment, the first ejection hole 91 is formed on the surface 51 of the outer shroud 50 out of the outer shroud 50 and the inner shroud 70. It may be formed. By ejecting the gas G from the surface 71 of the inner shroud 70 radially inward, the water W on the surface 71 of the inner shroud 70 can be effectively removed.
Further, in addition to forming the first ejection holes 91 on the surface 51 of the outer shroud 50, ejection holes for ejecting the gas G may be formed on the surface 71 of the inner shroud 70.

  Furthermore, in the embodiment, the first ejection hole 91 and the second ejection hole 92 are both slit-shaped, but the present invention is not limited to this, and may be, for example, a circular or polygonal hole. Further, a plurality of first ejection holes 91 and a plurality of second ejection holes 92 may be formed.

  In the embodiment, the gas supply source 100 supplies the gas G to the third flow path 95, but the gas G may be supplied to the first flow path 93 inside the outer shroud 50. In this case, in the second embodiment, the gas G flows from the first flow path 93 to the second flow path 94, and the gas G is ejected from the second ejection holes 92 to the flow path P.

DESCRIPTION OF SYMBOLS 1 Steam turbine 10 Casing 20 Adjusting valve 21 Adjusting valve chamber 22 Valve body 23 Valve seat 24 Steam chamber 30 Rotating shaft 31 Axis main body 32 Disc 40 Bearing part 41 Journal bearing device 42 Thrust bearing device 50 Outer shroud 51 Surface 60 Stator blade 61 Negative Pressure surface 62 Pressure surface 70 Inner shroud 71 Surface 80 Moving blade 91 First ejection hole 92 Second ejection hole 93 First flow path 94 Second flow path 95 Third flow path 100 Gas supply source P Flow path S Steam G Gas W Water

Claims (6)

A rotor blade that rotates a rotating shaft by the fluid pressure of steam;
A plurality of vanes that are spaced apart from each other in the circumferential direction of the rotating shaft on the radially outer side of the rotating shaft, and forming a flow of the steam to the moving blade;
Connecting the stationary blades adjacent to each other in the circumferential direction, and a shroud that defines the flow path of the steam together with the stationary blades,
A steam turbine, wherein a first ejection hole for ejecting gas is formed on a surface of the shroud facing the flow path.   The steam turbine according to claim 1, wherein the gas has a temperature higher than that of the steam flowing through the flow path. The shroud is an outer shroud that connects the stationary blades with each other at the radially outer end of the rotating shaft of the stationary blades,
The steam turbine according to claim 1, wherein the first ejection hole is formed on a surface of the outer shroud facing the flow path.   The steam turbine according to any one of claims 1 to 3, wherein the first ejection hole has a slit shape extending in a circumferential direction so as to extend over the adjacent stationary blades.   The steam turbine according to any one of claims 1 to 4, wherein a second ejection hole for ejecting the gas is formed on the suction surface of the stationary blade. A first flow path is formed in the shroud for flowing the gas and guiding the gas to the first ejection hole.
6. The second flow path is formed in the stationary blade, wherein the gas flows and is connected to the first flow path and guides the gas to the second ejection hole. The described steam turbine.

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