JP5135296B2 - Turbine cascade, turbine stage using the same, axial turbine - Google Patents

Description

  The present invention relates to a turbine cascade, a turbine stage using the turbine cascade, and an axial flow turbine, and more particularly to a turbine cascade having a reduced secondary loss, and a turbine stage and an axial turbine using the turbine cascade.

  FIG. 11 is a meridional sectional view schematically showing a turbine stage in a section (meridional section) including a central axis of a rotor as an example of a conventional axial turbine. The turbine stage of the axial turbine 21 includes a plurality of stationary blade rows 25 in which a plurality of stationary blades 24 are disposed in the circumferential direction between a diaphragm outer ring 22 and a diaphragm inner ring 23, and a turbine shaft (rotor) 26. A single blade 27 is implanted in the circumferential direction, and is composed of a blade row 28 provided on the downstream side of the stationary blade row 25. The axial flow turbine 21 configured by including a plurality of such turbine stages in the axial direction is accelerated when the working fluid passes between the blades of the stationary blade row 25 and then flows into the moving blade row 28. Work is performed by converting the retained velocity energy into rotating mechanical energy.

  The stationary blade row 25 and the moving blade row 28 become a resistance against the working fluid, and the working fluid is disturbed to generate a loss. Examples of such loss include blade loss (profile loss) and secondary loss generated in the vicinity of both end portions (root portion and tip portion) in the blade height direction.

  FIGS. 12 and 13 show loss distributions in the blade height direction of the stationary blade 24 and the moving blade 27 (that is, in the radial direction with respect to the central axis of the turbine shaft (rotor) 26), respectively. In both cases, along with the blade losses 24a and 27a, secondary losses 24b and 27b are generated near both ends in the blade height direction. In particular, with respect to the moving blade 27, as shown in FIG. 13, the secondary loss 27b generated in the root portion (the turbine shaft 26 side, that is, the inner diameter side end portion) is caused by the centrifugal force accompanying rotation to the central portion side in the blade height direction. The performance is degraded.

  FIG. 14 shows a state in which the working fluid passes through the turbine blade 32 as the stationary blade 24 or the moving blade 27. FIG. 14 schematically shows a blade cross section in the circumferential direction with respect to the central axis of the turbine shaft (rotor) 26. With respect to the working fluid passing between the blades of the turbine blades 32, the slow flow 33 passing near the abdominal surface 32a of one turbine blade 32 (upper side in the figure) and the other turbine blade 32 (lower side in the figure). It is roughly divided into a fast flow 34 passing near the back surface 32b. The slow flow 33 and the fast flow 34 increase the static pressure in the vicinity of the abdominal surface 32 a of one turbine blade 32 compared to the static pressure in the vicinity of the back surface 32 b of the other turbine blade 32. Thereby, a pressure gradient is generated between the blades of the turbine blade 32 in a direction normal to the main flow.

  On the other hand, since the main flow is turned by the turbine blades 32, the centrifugal force Fr in the direction opposite to the force Fp due to the pressure gradient described above is acting on the main flow. However, in the boundary layer near both sides in the blade height direction (radial direction with respect to the central axis of the turbine shaft (rotor) 26), that is, in the vicinity of the bottom surface that connects the adjacent turbine blades 32, the friction of the working fluid is caused by friction with the bottom surface. The flow velocity is slower than the main flow. For this reason, the centrifugal force Fr received by the working fluid is reduced in the vicinity of both sides in the blade height direction, and the force Fp due to the pressure gradient is relatively increased, so that a flow in the normal direction to the main flow is generated.

  This flow is called a secondary flow, and vortices are generated near both sides of the turbine blade 32 in the blade height direction, and a large secondary loss 24b is generated near both sides of the blade height direction as shown in FIGS. , 27b. The secondary losses 24b and 27b increase as the vortex grows.

  As a method of suppressing such secondary losses 24b and 27b, for example, the value of the ratio S / T between the throat length S and the annular pitch T of the turbine blade 32 as shown in FIG. Although not shown, the trailing edge of the turbine blade 32 is curved so as to protrude to the most fluid outflow side (abdominal surface side) at the center in the blade height direction. There is known a method of making the maximum at the center in the height direction (see, for example, Patent Documents 1 and 2).

  In addition, a method is known in which the blade pressure surface of the turbine blade 32 is curved so as to protrude in the circumferential direction, and the ratio between the circumferential pitch and the circumferential protrusion amount is constant regardless of the number and height. (For example, see Patent Document 3). Further, a method is known in which a protrusion shape having a top portion between a front end edge and a rear end edge is provided on an end wall surface in the blade height direction of the turbine blade 32 (see, for example, Patent Documents 4 and 5).

JP-A-6-272504 JP-A-8-109803 JP-A-10-131707 Japanese Patent No. 3626899 JP-A-8-109803

  As an environmental load reduction measure such as energy saving, it is recognized that the efficiency of an axial turbine is effective. Since the performance of the turbine cascade greatly affects the performance of the axial turbine, reducing the loss in the turbine cascade and making it highly efficient is effective in increasing the efficiency of the axial turbine. In particular, the secondary loss accounts for a large proportion of the losses in the turbine cascade, and reducing this is effective for increasing the efficiency of the turbine cascade.

  As described above, although various methods have been studied for reducing the secondary loss, it cannot always be sufficiently reduced. The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a turbine cascade having a reduced secondary loss, a turbine stage using the turbine cascade, and an axial turbine.

  The turbine blade row of the present invention comprises a plurality of turbine blades arranged in the circumferential direction in an annular flow path of an axial flow turbine, and is provided on the bottom surface between the blades between the turbine blades on the belly surface of the turbine blades. And a convex portion that is convex in the height direction of the turbine blade, and connects the convex portion and the abdominal surface of the turbine blade, and a substantially horizontal step portion that is lower in height than the convex portion. It has the protruding part which consists of.

The raised portion has a height of the convex portion Ha, a width La, a height of the stepped portion Hb, a width Lb, a height of the turbine blade H, and a distance between the back surfaces of the turbine blade L. When
0 <Hb / H <Ha / H ≦ 0.35 and
0 <(La + Lb) /L≦0.75
It is preferable to satisfy the relationship.

  The raised portion is a convex shape that is continuously provided from the front edge portion to the rear edge portion of the turbine blade and has the highest height at a substantially central portion between the front edge portion and the rear edge portion. It is preferable to have.

  According to the present invention, it is possible to suppress the secondary flow between the turbine blades and reduce the secondary loss.

The typical meridional sectional view showing the turbine cascade of the present invention, the turbine stage, and the axial flow turbine. The typical external appearance perspective view which shows a protruding part. The typical circumferential direction sectional view showing a protruding part. The typical top view which shows a protruding part. The external view which shows an example of the turbine cascade which can apply this invention. Explanatory drawing explaining throat length S and annular pitch T. FIG. The distribution map which shows the suitable distribution state of S / T. Explanatory drawing explaining the turbine blade in which a rear end edge inclines in the circumferential direction. Explanatory drawing explaining the turbine blade in which a rear end edge inclines in an axial flow direction. Explanatory drawing explaining the turbine blade from which a rear-end edge becomes convex shape in an axial flow direction. Sectional drawing which shows the turbine stage of the conventional axial flow turbine. The distribution diagram which shows the loss distribution of the moving blade in the conventional axial flow turbine. The distribution diagram which shows the loss distribution of the stationary blade in the conventional axial flow turbine. Explanatory drawing explaining the generation | occurrence | production factor of the loss in the blade | wing of the conventional axial flow turbine. Explanatory drawing explaining the throat length S and the annular pitch T in the conventional axial flow turbine.

The present invention will be described below with reference to the drawings.
FIG. 1 is a cross-sectional view schematically showing an example of an axial flow turbine having a turbine stage constituted by the turbine blade rows of the present invention. FIG. 1 is a schematic diagram showing a turbine stage in a meridian cross section (a cross section including a central axis of a turbine shaft (rotor)). The turbine stage of the axial flow turbine 1 includes a stationary blade row 5 in which a plurality of stationary blades 4 are arranged in the circumferential direction between a diaphragm outer ring 2 and a diaphragm inner ring 3, and a downstream side of the stationary blade row 5. Provided on the outer periphery of the turbine shaft (rotor) 6, and a plurality of blades 7 are implanted in the circumferential direction. A shroud 9 for fixing the moving blade 7 and suppressing leakage of the working fluid is provided at the tip of the moving blade 7. The axial-flow turbine 1 has a configuration in which a plurality of turbine stages in which the stationary blade row 5 and the moving blade row 8 are paired are provided in the axial direction.

  Here, each of the stationary blade row 5 and the moving blade row 8 is the turbine blade row of the present invention, and the stationary blade 4 in the stationary blade row 5 or the moving blade 7 in the moving blade row 8 is the turbine blade in the present invention. It will be. Hereinafter, the stationary blade row 5 and the moving blade row 8 will be collectively referred to as a turbine blade row 11, and the stationary blade 4 and the moving blade 7 will be collectively referred to as a turbine blade 12.

  The turbine blade row 11 of the present invention is characterized by having a raised portion 14 on the bottom surface 13 between the blades 12 adjacent to each other in the circumferential direction of the turbine shaft (rotor) 6. 1, each of the turbine blade rows 11 shown in FIG. 1 has a bottom surface 13 between the blades on the turbine shaft 6 side, that is, the outer peripheral surface of the diaphragm inner ring 3 for the stationary blade row 5, and the turbine shaft 6 for the moving blade row 8. The example which provided the protruding part 14 in each outer peripheral surface is shown.

  The raised portion 14 is not necessarily provided on the bottom surface 13 between the blades on the turbine shaft 6 side, and the bottom surface 13 between the blades on the opposite side of the turbine shaft 6, that is, the stationary blade row 5, is provided inside the diaphragm outer ring 2. The circumferential surface and the moving blade row 8 may be provided on the inner circumferential surface of the shroud 9, respectively.

  FIG. 2 is an external perspective view schematically showing such a raised portion 14. FIG. 3 is a view schematically showing a circumferential cross section of the raised portion 14 shown in FIG. 2 with respect to the turbine shaft (rotor) 6. 2 and 3, the turbine blades 12 adjacent to each other in the circumferential direction are illustrated for the sake of explanation.

  The raised portion 14 shown in FIG. 2 is, for example, in the stationary blade row 5 shown in FIG. 1 and is provided on the outer peripheral surface of the diaphragm inner ring 3 as the inter-blade bottom surface 13. The raised portion 14 is formed at a portion that becomes the inter-blade bottom surface 13 between the turbine blades 12 along the abdominal surface 12 a of the turbine blade 12. As shown in FIG. 3, the raised portion 14 has a blade height direction (radial direction with respect to the turbine shaft (rotor) 6) in a cross section in the inter-blade direction (circumferential direction with respect to the turbine shaft (rotor) 6) between the turbine blades 12. ) And a convex portion 14a that is convex, and the convex portion 14a and the abdominal surface 12a of the turbine blade are connected to each other, and the height in the blade height direction (hereinafter simply referred to as height) is lower than the convex portion 14a. And a step portion 14b (cylindrical surface shape with respect to the turbine shaft (rotor) 6). The heights of the convex portions 14a and the stepped portions 14b gradually increase from the front edge of the turbine blade 12 into which the working fluid flows into the vicinity of the center along the abdominal surface 12a (that is, the direction in which the working fluid flows). In addition, it is provided so as to gradually become lower in the flow direction of the working fluid (rear edge direction along the abdominal surface 12a) from the vicinity of the center to the rear edge portion of the turbine blade 12.

  In the present invention, the secondary flow can be suppressed by providing such a raised portion 14. That is, by providing a step 14b having a predetermined height adjacent to the abdominal surface 12a of the turbine blade 12, the working fluid that flows in from the front edge of the turbine blade 12 and flows in the vicinity of the abdominal surface 12a has a height of the step 14b. As the pressure increases, the static pressure in this portion decreases. Thereby, the pressure difference with the static pressure of back surface 12b vicinity of the other adjacent turbine blade 12 can be made small, and a secondary flow can be weakened. Further, by accelerating the fluid flowing in the vicinity of the abdominal surface 12a of the turbine blade 12 in this way, the boundary layer formed on the inter-blade bottom surface 13 in the vicinity of the abdominal surface 12a can be thinned and the secondary flow vortex can be weakened. .

  Furthermore, by providing the convex part 14a higher than the step part 14b on the central part side in the inter-blade direction (circumferential direction) with respect to the step part 14b, as the height of the convex part 14a increases in the flow direction, The working fluid that has flowed in from the upstream side is further accelerated in the vicinity of the convex portion 14a, and the static pressure is further lowered than that of the stepped portion 14b. As a result, it is possible to induce a flow in the direction opposite to the general secondary flow from the vicinity of the convex portion 14a toward the stepped portion 14b and the abdominal surface 12a of the turbine blade 12, and in the vicinity of the abdominal surface 12a of the turbine blade 12. The secondary flow vortex that is formed can be further weakened.

  Thus, according to the present invention, the secondary flow and the secondary flow vortex are reduced by providing the raised portion 14 having a specific shape having the convex portion 14a and the stepped portion 14b at a specific position of the turbine blade row 11. Thus, the secondary loss can be reduced and the performance can be improved.

  Such a raised portion 14 may be formed integrally with the turbine blade 12, for example, or formed separately from the turbine blade 12 and arranged and fixed so as to be in close contact with the abdominal surface 12 a of the turbine blade 12. It may be what was done.

For example, in the cross section in the blade-to-blade direction (circumferential direction of the turbine shaft (rotor) 6) as shown in FIG. When the width is Lb, the height of the turbine blade 12 is H, and the distance between the back surfaces in the circumferential direction (interblade direction) of the bottom surface 13 between the blades of the turbine blade 12 is L,
0 <Hb / H <Ha / H ≦ 0.35 and
0 <(La + Lb) /L≦0.75
It is preferable to satisfy the relationship.

  Here, with respect to the raised portion 14, it is preferable that the above relationship is satisfied with respect to the cross section in the inter-blade direction in the direction extending along the abdominal surface 12 a of the turbine blade 12, but at least the direction along the abdominal surface 12 a (that is, the working fluid It is only necessary to satisfy the above relationship with respect to the cross section in the inter-blade direction (circumferential direction) at the portion where the height Ha of the convex portion 14a is maximum in the vicinity of the center of the flow direction.

  Note that the height Ha of the convex portion 14a is the height from the bottom surface 13 between the blades, and the width La is a portion having the same height as the bottom surface 13 between the blades from the portion where the inclination starts substantially on the step portion 14b side. It is the distance to. Here, the position of the bottom surface 13 between the blades can be defined as a radial distance from the center of the turbine shaft (rotor) 6 at the wall surface end portion of the rear surface 12 b of the turbine blade 12. Further, the height Hb of the stepped portion 14b is also the height from the bottom surface 13 between the blades, and the width Lb is a distance from the abdominal surface 12a of the turbine blade 12 to the portion where the inclination of the convex portion 14a starts substantially. It is.

  Further, the height H of the turbine blade 12 is a radial distance from one of the illustrated blade bottom surfaces 13 (for example, the root side) to the other blade blade bottom surface 13 (for example, the tip side) (not illustrated) facing the blade blade 12. The distance L between the rear surfaces of the turbine blades 12 is a circumferential direction (inter-blade direction) distance from the rear surface 12b of the turbine blade 12 to the rear surface 12b of the turbine blade 12 adjacent in the circumferential direction on the bottom surface 13 between the blades.

  By satisfy | filling the above-mentioned relationship with the protruding part 14, the working fluid which flows through the protruding part 14, ie, the convex part 14a and step 14b vicinity, can be accelerated, and a secondary flow can be suppressed. Thereby, a secondary loss is reduced and it can be made excellent in performance.

  That is, when Hb / H is 0 (zero), the stepped portion 14b is not formed, and the fluid flowing in the vicinity of the abdominal surface 12a of the turbine blade 12 cannot be accelerated. Further, when Ha / H is equal to or less than Hb / H, the state is substantially the same as when only the stepped portion 14b is formed, and a flow in the direction opposite to the general secondary flow described above is induced. I can't. Moreover, when Ha / H exceeds 0.35, the convex part 14a will be too high, and there exists a possibility that the loss based on the convex part 14a may become large on the contrary.

  On the other hand, when (La + Lb) / L is 0 (zero), the raised portion 14 is not substantially formed, and the fluid flowing in the vicinity of the abdominal surface 12a of the turbine blade 12 is accelerated. A flow in the direction opposite to the next flow cannot be induced. When (La + Lb) / L exceeds 0.75, the range in which the raised portion 14 is formed is too wide, so that the fluid flowing in the vicinity of the abdominal surface 12a of the turbine blade 12 cannot be efficiently accelerated. Moreover, there is a possibility that a flow in the direction opposite to that of a general secondary flow cannot be efficiently induced.

  4 is a plan view of the turbine blade 12 and the raised portion 14 shown in FIG. 2 when viewed from the blade height direction (outward in the radial direction with respect to the turbine shaft (rotor) 6). As shown in FIG. 4, the raised portion 14 is preferably provided continuously from the front end edge 12 c to the rear end edge 12 d of the turbine blade 12. In addition, as shown in FIG. 2, the height is highest at the substantially central portion in the direction along the abdominal surface 12a of the turbine blade 12, that is, at the substantially central portion between the front end edge 12c and the rear end edge 12d of the turbine blade 12. It is preferable that the height is raised. At this time, it is preferable that the front end edge 12 c side and the rear end edge 12 d side of the raised portion 14 have the same height as the inter-blade bottom surface 13.

  In this way, the raised portion 14 is provided in substantially the entire direction along the abdominal surface 12a of the turbine blade 12 (the flow direction of the working fluid), and has the highest height at a substantially central portion in the direction along the abdominal surface 12a of the turbine blade 12. By adopting a convex shape that becomes higher, it is possible to efficiently reduce the secondary loss while suppressing the loss due to the raised portion 14 itself. The raised portion 14 does not necessarily have to be provided from the front end edge 12c to the rear end edge 12d of the turbine blade 12, but at least a distance of 1 along the abdominal surface 12a from the front end edge 12c to the rear end edge 12d. / 2 or more is preferable, and it is preferable to be provided in a range of 2/3 or more.

  As described above, the turbine blade row 11 of the present invention has been described by way of an example. As already described, such a turbine blade row 11 may be any one of the stationary blade row 5 and the moving blade row 8 as shown in FIG. There may be. Further, the inter-blade bottom surface 13 on which the raised portion 14 is provided may be any inter-blade bottom surface 13 on both sides (the root side and the tip side) of the turbine blade row 11 in the blade height direction. 5 may be either the inner peripheral surface (tip side) of the diaphragm outer ring 2 or the outer peripheral surface (root side) of the diaphragm inner ring 3, and in the case of the blade row 8, the outer peripheral surface of the turbine shaft 6. Either the (root side) or the inner peripheral surface (tip side) of the shroud 9 may be used. At this time, the raised portion 14 may be provided only on one of the bottom surfaces 13 between the blades facing each other in the blade height direction, or may be provided on both the bottom surfaces 13 between the blades facing each other.

  Further, for the turbine stage and axial turbine 1 having such a turbine blade row 11, only one of the stationary blade row 5 or the moving blade row 8 may be formed of such a turbine blade row 11. Both may be composed of such turbine blade rows 11. At this time, the inter-blade bottom surface 13 on which the raised portion 14 is provided may be different between the stationary blade row 5 and the moving blade row 8.

  The turbine blade row 11 of the present invention can be used by being appropriately applied to a known turbine blade row. In this way, in addition to the original effect of the known turbine cascade to be applied, the effect of the turbine cascade 11 of the present invention, that is, the suppression of the secondary flow by the ridge 14, the secondary by these The effect of reducing loss can be obtained together.

  As shown in FIG. 5, for example, as shown in FIG. 5, the turbine blade row 11 to which the present invention is applied has a cross section of a turbine blade 12 that has a most protruding point at a substantially central portion in the blade height direction (radial direction with respect to the turbine shaft (rotor) 6). One that is curved on the circumferential fluid outflow side (abdominal surface 12a side) so as to exist.

  Further, in such a structure, as shown in FIG. 6, the shortest distance between the rear end edge 12d of the turbine blade 12 and the rear surface 12b of the turbine blade 12 adjacent thereto in the circumferential section with respect to the turbine shaft (rotor) 6 is throated. When the length is S and the circumferential distance between the rear end edges 12d is an annular pitch T, the ratio S / T is maximized at a substantially central portion in the height direction as shown in FIG.

  By providing the raised portions 14 in these turbine blade rows 11, in addition to the effect of making the shape and ratio S / T of the turbine blades 12 predetermined, the secondary flow and the secondary flow vortex by the raised portions 14 are reduced. Thus, the effect of reducing the secondary loss can be obtained together.

  Further, as an applicable turbine blade row 11, for example, as shown in FIG. 8, in the circumferential direction so as to gradually leave the rear edge 12 d of the turbine blade 12 with respect to a radial line 15 extending radially from the turbine shaft 6. An inclined one is mentioned. For such a thing, in addition to the effect that the rear end edge 12d of the turbine blade 12 is inclined in the circumferential direction by providing the raised portion 14, the secondary flow and the secondary flow vortex by the raised portion 14 are reduced. Thus, the effect of reducing the secondary loss can be obtained together.

  Furthermore, as another applicable turbine blade row 11, for example, as shown in FIG. 9, the rear end edge 12 d of the turbine blade 12 is gradually inclined in the axial flow direction from one end to the other end in the blade height direction. In addition, for example, as shown in FIG. 10, the rear end edge 12d of the turbine blade 12 may be convex in the axial direction at a substantially central portion in the blade height direction. 9 and 10 illustrate the stationary blade row 5 as the turbine blade row 11. Also in these cases, by providing the raised portion 14, in addition to the effect that the rear end edge 12d of the turbine blade 12 has a predetermined shape, the secondary flow is suppressed by the raised portion 14, and the secondary loss is thereby reduced. Such effects can also be obtained.

  Although not shown, as another applicable turbine blade row 11, the chord length in the blade cross section of the turbine blade 12 is maximized on one end side in the blade height direction of the turbine blade 12, and the other What is minimized on the end side of the. For such a thing, in addition to the effect of providing the chord length of the turbine blade by providing the raised portion 14, the secondary flow is suppressed by the raised portion 14 and the secondary loss is thereby reduced. The effect can also be obtained.

  DESCRIPTION OF SYMBOLS 1 ... Axial turbine, 2 ... Diaphragm outer ring, 3 ... Diaphragm inner ring, 4 ... Stator blade, 5 ... Stator blade row, 6 ... Turbine shaft, 7 ... Rotor blade, 8 ... Rotor blade row, 9 ... Shroud, 11 ... Turbine Blade row (stator blade row, moving blade row), 12 ... turbine blade (stator blade, moving blade), 12a ... abdominal surface, 12b ... back surface, 12c ... front edge, 12d ... rear edge, 13 ... interblade bottom surface, 14 ... Bump, 14a ... Convex, 14b ... Step

Claims (5)

A turbine blade row composed of a plurality of turbine blades arranged circumferentially in an annular flow path of an axial flow turbine,
Formed along the belly surface of the turbine blades on the bottom surface between the blades between the turbine blades, and connecting the convex portion convex in the height direction of the turbine blades, the convex portion and the belly surface of the turbine blades, A turbine cascade having a raised portion formed of a substantially horizontal step portion having a height lower than that of a convex portion. The raised portion has a height of the convex portion Ha, a width La, a height of the stepped portion Hb, a width Lb, a height of the turbine blade H, and a distance between the back surfaces of the turbine blade L. When
0 <Hb / H <Ha / H ≦ 0.35 and
0 <(La + Lb) /L≦0.75
The turbine blade row according to claim 1, wherein:   The raised portion is a convex shape that is continuously provided from the front edge portion to the rear edge portion of the turbine blade and has the highest height at a substantially central portion between the front edge portion and the rear edge portion. The turbine cascade according to claim 1, wherein the turbine cascade is provided. A stationary blade row composed of a plurality of stationary blades disposed in the circumferential direction in the annular flow path of the axial flow turbine, and a plurality of sheets disposed downstream of the stationary blade row and disposed in the circumferential direction of the turbine shaft. A turbine stage having a moving blade row composed of moving blades,
4. A turbine stage, wherein at least one turbine blade row selected from the stationary blade row and the moving blade row comprises the turbine blade row according to any one of claims 1 to 3. A stationary blade row composed of a plurality of stationary blades arranged in the circumferential direction in the annular flow path of the axial flow turbine, and a plurality of blades arranged downstream of the stationary blade row and implanted in the circumferential direction of the turbine shaft An axial flow turbine having a moving blade row composed of a plurality of moving blades,
The axial flow turbine, wherein at least one turbine blade row selected from the stationary blade row and the moving blade row comprises the turbine blade row according to any one of claims 1 to 3.

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