JP2012052491A - Turbine stage, and steam turbine using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve turbine stage efficiency by reduction in a sidewall loss in a turbine stage and optimization of the blade height directional flow rate distribution of a working fluid of passing through between turbine blades.SOLUTION: This turbine stage is provided by forming an inter-blade flow passage 20 for flowing the working fluid between the adjacent turbine blades 10. A recessed part 21 recessed toward the inside of a sidewall is arranged in a position on the downstream side in the working fluid flow direction more than an inlet part of the inter-blade flow passage 20 and on the upstream side in the working fluid flow direction more than a throat of becoming minimum in a distance between the mutual adjacent turbine blades, on the sidewall for constituting a wall surface on the radial direction side of the inter-blade flow passage 20, and is characterized in that the recessed part 21 has a bottom part of a rectangular cross-sectional shape having a bottom surface having an equal radial distance from the turbine axis along an equal value line of connecting a blade pressure surface 18 and a blade suction side 19, between the mutually opposed blade pressure surface 18 and blade negative pressure surface 19, for constituting the wall surface on the peripheral directional side of the inter-blade flow passage 20, and the recessed part 21 has continuously the bottom part toward the throat part side from the inlet part side of the inter-blade flow passage 20.

Description

  The present invention relates to the structure of a turbine stage of an axial flow turbine, particularly a steam turbine.

  In the axial turbine, various technologies for improving performance are adopted, and high efficiency is realized. In order to improve the performance of the turbine, it is indispensable to reduce each loss such as pressure, paragraph, exhaust, and machine inside the turbine.

Especially, the side wall loss which is one of the paragraph losses is a loss common to each paragraph of the turbine.
One method for reducing this side wall loss is to suppress the secondary flow caused by the pressure difference between the turbine blades.

  To suppress the secondary flow, improve the flow of the working fluid between the blades by providing irregularities on the surfaces of the inner peripheral side wall and outer peripheral side wall installed at the tip and root of the turbine blade, A method for reducing the side wall loss is known. As an example, a method described in Japanese Patent Application Laid-Open No. 2009-209745 (Patent Document 1) has been proposed.

JP 2009-209745 A

  By the way, in addition to the reduction of the side wall loss, the stage performance can be further improved by optimizing the blade height direction flow distribution of the working fluid passing between the turbine blades.

  However, in the technique of Patent Document 1, no consideration is given to the optimization of the flow rate distribution of the working fluid in the blade height direction.

  Therefore, the present invention provides a turbine stage structure that can achieve improvement in paragraph efficiency by optimizing the blade height direction flow rate distribution of the working fluid passing between the turbine blades in an axial flow turbine such as a steam turbine. The purpose is to do.

  In order to achieve the above object, in the present invention, a plurality of turbine blades are provided in the circumferential direction between the outer peripheral side wall and the inner peripheral side wall that are used in the axial flow turbine and extend in the circumferential direction. In the turbine stage where the inter-blade flow path where the working fluid flows between the blades, when the straight line connecting the leading edges of the adjacent blades of the turbine blade is defined as the inlet of the inter-blade flow path, At least one side wall of the outer peripheral side and the inner peripheral side constituting the wall surface on the radial direction side of the flow path, and adjacent to the downstream side in the working fluid flow direction of the inter-blade flow path from the inlet of the inter-blade flow path A concave portion that is recessed toward the inner side of the side wall is provided at a position upstream of the throat portion where the distance between the matching turbine blades is the minimum in the working fluid flow direction, and the concave portion constitutes a wall surface on the circumferential direction side of the flow path between the blades. Opposed blade pressure surfaces of adjacent turbine blades A bottom portion having a rectangular cross-sectional shape with a bottom surface having an equal radial distance from the turbine central axis along an imaginary straight line connecting the blade pressure surface and the blade suction surface between the blade suction surface and the recess; The bottom part of the rectangular cross-sectional shape was continuously provided from the inlet part side of the inter-blade channel toward the throat part side.

  ADVANTAGE OF THE INVENTION According to this invention, optimization of the blade | wing height direction flow rate distribution of the working fluid which passes between turbine blades is possible, and, thereby, improvement of a paragraph efficiency can be achieved.

1 is a cross-sectional view illustrating a main part structure of a turbine stage of an axial flow turbine according to Embodiment 1. FIG. It is explanatory drawing explaining the shape of the side wall of the turbine stage which concerns on Example 1 seen from the turbine radial direction. It is sectional drawing showing the AA 'cross section shown in FIG. FIG. 3 is a meridional cross-sectional view of the inter-blade channel shown in FIG. 2 as viewed from the blade suction surface side and the blade pressure surface side in the circumferential direction. It is the graph which showed the relationship between the dimensionless length of a recessed part, and dimensionless depth. 4 is a graph showing a blade outlet flow rate distribution in the blade height direction of the turbine blade according to the first embodiment. 3 is a graph showing a loss distribution in the blade height direction of the turbine blade according to the first embodiment. It is the perspective view which showed the flow path between blades of a general turbine stage. It is the figure which looked at the cascade structure shown in FIG. 8 from the turbine radial direction. It is explanatory drawing explaining the side wall shape of the turbine stage which concerns on Example 2 seen from the turbine radial direction. It is sectional drawing showing the BB 'cross section described in FIG. It is a graph showing the blade | wing exit flow volume distribution of the blade height direction of the turbine stage which concerns on Example 2. FIG. It is a graph showing the loss distribution of the blade height direction of the turbine stage which concerns on Example 2. FIG.

  Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings as appropriate.

  Hereinafter, the structure of the turbine stage of the axial flow turbine according to the first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a cross-sectional view illustrating a main structure of a turbine stage of an axial turbine according to a first embodiment. FIG. 2 is a diagram illustrating the shape of the side wall of the turbine stage according to the first embodiment viewed from the radial direction of the turbine. FIG. 3 is a cross-sectional view showing the AA ′ cross section shown in FIG. 2. FIG. 4 is a meridional cross-sectional view of the inter-blade channel shown in FIG. 2 as viewed from the circumferential blade suction surface side and the blade pressure surface side. FIG. 5 is a graph showing the relationship between the dimensionless length and dimensionless depth of the recess shown in FIG. FIG. 6 is a graph showing the blade outlet flow distribution in the blade height direction of the turbine blade according to the first embodiment. FIG. 7 is a graph showing a loss distribution in the blade height direction of the turbine blade according to the first embodiment. FIG. 8 is a perspective view showing a flow path between blades of a general turbine stage. FIG. 9 is a view of the blade row structure shown in FIG. 8 as viewed from the turbine radial direction.

  A main structure of a turbine stage of an axial flow turbine to which the present invention is applied will be described with reference to FIG. In FIG. 1, 1 is a diaphragm outer ring, 2 is a diaphragm inner ring, 3 is a stationary blade, 4 is a turbine rotor, 5 is a moving blade, and 6 is a shroud. The turbine stage of the axial turbine according to the present embodiment includes a plurality of stationary blades 3 fixed in the circumferential direction of the turbine between a diaphragm outer ring 1 and a diaphragm inner ring 2, and a working fluid main flow 7 of the stationary blade 3 (hereinafter referred to as main flow). And a plurality of blades 5 fixed to the turbine rotor 4 in the circumferential direction so as to face the downstream side in the flow direction (hereinafter simply referred to as the downstream side). A shroud 6 for fixing adjacent blades is provided at the tip of the blade 5 in the turbine radial direction outer peripheral side. The axial turbine is configured by providing the above-described turbine stages in a plurality of stages in the axial direction.

  The main flow 7 passes from the front edge 8 of the stationary blade 3 through the inter-blade channel formed between the stationary blades adjacent in the circumferential direction, and flows out from the trailing edge 9 of the stationary blade. The main flow 7 flowing out from the trailing edge 9 of the stationary blade flows into the inter-blade channel formed between the downstream moving blades. The axial flow turbine causes the main flow 7 flowing out from the stationary blade 3 to collide with the moving blade 5 on the downstream side, thereby rotating the turbine rotor 4 and using a generator (not shown) connected to the end of the turbine rotor 4. It generates electricity by converting rotational energy into electrical energy.

  Here, as a comparative example for explaining the characterizing portion of the present embodiment, a flow path between blades in a turbine stage in a general axial turbine will be described with reference to FIGS.

  FIG. 8 is a perspective view showing a flow path between blades of a general turbine stage. In FIG. 8, 10 is a turbine blade, 11 is an outer peripheral side wall, 12 is an inner peripheral side wall, and 20 is a flow path between blades. The turbine blade 10 is a stationary blade or a moving blade. The outer peripheral side wall 11 corresponds to a diaphragm outer ring when the turbine blade 10 is a stationary blade, and corresponds to a shroud when the turbine blade 10 is a moving blade. The inner peripheral side wall 12 corresponds to a diaphragm inner ring when the turbine blade 10 is a stationary blade, and corresponds to a platform portion of the moving blade when the turbine blade 10 is a moving blade.

  Each of the outer peripheral side wall 11 and the inner peripheral side wall 12 is a member that extends in the circumferential direction around the turbine central axis. In FIG. 2 is the same). A plurality of turbine blades 10 are provided in the circumferential direction between the outer peripheral side wall 11 and the inner peripheral side wall 12, the blade tip 15 is fixed to the outer peripheral side wall 11, and the blade root portion 16 is disposed inside. It is fixed to the peripheral side wall 12. By providing a plurality of turbine blades 10 in the circumferential direction between the outer peripheral side wall 11 and the inner peripheral side wall 12, a turbine blade row is formed, and a blade through which a working fluid passes between adjacent turbine blades 10. An interchannel 20 is formed. The main stream flows from the front edge portion (hereinafter referred to as blade front edge portion) 13 side of the turbine blade 10 and moves toward the rear edge portion (hereinafter referred to as blade rear edge portion) 14 of the turbine blade 10. The interflow path 20 flows down.

  The turbine cascade structure shown in FIG. 8 will be described with reference to FIG. FIG. 9 is a view of the turbine cascade as viewed from the turbine radial direction. The surface of the turbine blade 10 formed on the blade belly side is referred to as a blade pressure surface 18 (hereinafter referred to as a pressure surface), and the surface formed on the blade back side is referred to as a blade suction surface 19 (hereinafter referred to as a suction surface). Describe). A wall surface on the turbine circumferential direction side of the inter-blade channel 20 is constituted by a pressure surface 18 and a negative pressure surface 19 of the adjacent turbine blades 10 facing each other. Further, as shown in FIG. 8, the wall surface on the turbine radial direction side of the inter-blade channel 20 includes an outer peripheral side wall 11 and an inner peripheral side wall 12.

  As shown in FIG. 8 and FIG. 9, the turbine blade 10 is arranged in the circumferential direction using the interval t (pitch length) between adjacent blades in the turbine circumferential direction, which is determined from the number of blades installed in the turbine blade row. Installed at regular intervals. A line that minimizes the distance between adjacent turbine blades 10 is referred to as a throat s, and an intersection between the throat s and the contour curve of the suction surface 19 of the turbine blade 10 is referred to as a throat point 17. The main flow 7 passes through the blade leading edge portion 13, flows down the blade flow path 20, is throttled to the throat s that has the minimum flow width, and is accelerated after passing through the throat s. Pass through the edge 14.

  In the conventional turbine stage, when the main flow 7 flows in from the blade leading edge portion 13 and flows down the inter-blade channel 20, a pressure gradient is generated in the inter-blade channel, and from the pressure surface 18 of the turbine blade 10, the turbine A flow toward the suction surface 19 of the blade 10 is generated. This is a so-called secondary flow. Due to the generation of the secondary flow, a secondary flow loss occurs and a side wall loss occurs. Further, due to the velocity boundary layer developed from the side wall and the influence of the secondary flow, a flow vortex (not shown) generated from the blade leading edge develops between the blades to cause a loss. The side wall loss is a loss including the influence of the secondary flow and the flow path vortex.

  Returning to the description of the present embodiment. FIG. 2 shows the shape of the inner peripheral side wall 12 of this embodiment viewed from the turbine radial direction. A plurality of turbine blades 10 are provided in the circumferential direction, and an inter-blade channel is formed between the negative pressure surface 19 and the pressure surface 18 of the adjacent turbine blades 10 facing each other. The main stream flows into the inter-blade channel from the blade leading edge 13 and flows down to the blade trailing edge 14 while accelerating.

  In the present embodiment, in all the inter-blade channels formed in the turbine blade row, the inter-blade channel side wall surfaces of the inner peripheral side wall 12 and the outer peripheral side wall 11 constituting the wall surface in the turbine radial direction of the inter-blade channel. 22 is provided with a recess 21 that is recessed toward the inside of the side wall.

  The shape of the recess 21 will be described below. Hereinafter, the most upstream point in the axial direction of the turbine blade 10 is defined as the tip of the blade leading edge, and a straight line (L) connecting the tips of the blade leading edges 13 of the adjacent turbine blades 10 is defined as the flow path between the blades. The description will be given by defining it as an entrance.

  In FIG. 2, reference numeral 24 denotes a contour curve of the pressure surface 18 at the connection portion (blade root portion) between the turbine blade 10 and the side wall. Reference numeral 25 denotes a contour curve of the suction surface 19 at the connection portion (blade root portion) between the turbine blade 10 and the side wall. The point X is a point at an arbitrary position on the contour curve 24 of the pressure surface 18, and the length (X1) of the contour curve 24 from the tip of the blade leading edge 13 to the point X of the contour curve 24 is represented by the contour curve. A value obtained by dividing the length (α1) of the contour curve 24 from the tip of the blade leading edge 13 to the tip of the blade trailing edge 14 is a dimensionless length (X1 /) in the contour curve 24 on the pressure surface 18 side. α1). The dimensionless length (X1 / α1) is a value representing the relative position of the point X between the blade leading edge 13 and the blade trailing edge 14 of the contour curve 24, and is represented by the following equation (1). It is a value that takes the range.

0.0 ≦ X1 / α1 ≦ 1.0 (1)
Next, the point Y is a point at an arbitrary position on the contour curve 25 of the suction surface 19, and the length (Y1) of the contour curve 25 from the tip of the blade leading edge portion 13 to the point Y of the contour curve 25 is determined. The value obtained by dividing the contour curve 25 by the length (β1) of the contour curve 25 from the tip of the blade leading edge 13 to the throat point 17 is the dimensionless length (Y1 / β1) in the contour curve 25 on the suction surface 19 side. ). The dimensionless length (Y1 / β1) is a value representing the relative position of the point Y between the blade leading edge 13 and the throat point 17 of the contour curve 25, and is a range represented by the following equation (2). It is a value that takes

0.0 ≦ Y1 / β1 ≦ 1.0 (2)
In FIG. 2, the straight lines with numerical values from 0 to 4 are on the contour curves 24 and 25 where the dimensionless length (X1 / α1) and the dimensionless length (Y1 / β1) are equal. These are virtual straight lines that connect positions, and these virtual straight lines are defined as isolines.

  The concave portion 21 of the present embodiment is provided on the downstream side of the inlet portion of the inter-blade channel 20 on the side wall and on the upstream side of the throat s. Further, the recess 21 is characterized in that it has a bottom portion having a bottom surface having an equal radial distance from the turbine central axis along an isoline between the pressure surface 18 and the suction surface 19.

  FIG. 3 is a cross-sectional view taken along the line AA ′ shown in FIG. 2, and is a cross-sectional view of the bottom of the recess 21 along the isoline with the numerical value 3. As shown in FIG. 3, the bottom of the recess 21 has a bottom surface (inner peripheral side wall 12) having the same radial distance from the turbine central axis along the isoline, and this bottom surface (inner peripheral side wall). 12) and a rectangular cross section formed by the pressure surface 18 and the negative pressure surface 19 at both ends thereof.

  In FIG. 2, only nine isolines are drawn for convenience of explanation. The numerical value from 0 to 4 attached to each isoline represents the degree of the depth of the recess 21 at that position, and the larger the value, the deeper the recess 21 is.

  In the present embodiment, the shape of the concave portion 21 is formed so as to continuously have a bottom of a rectangular cross-sectional shape in conformity with the isoline from the inlet portion (L) side of the inter-blade channel toward the throat s side. It is characterized by being. That is, in FIG. 2, for convenience of explanation, only nine isolines are shown, but in reality, each dimensionless length corresponds to a dimensionless length in the range of 0.0 to 1.0. An isoline is drawn, and a rectangular cross-sectional shape is formed along the isoline. Therefore, the recess 21 is formed so as to continuously have a bottom having a rectangular cross-sectional shape in conformity with the isoline from the inlet side of the inter-blade channel 20 toward the throat s side.

  FIG. 4 is a meridional cross-sectional view of the inter-blade channel of this embodiment as viewed from the turbine circumferential direction. (A) is the figure which looked at the turbine blade 10 from the pressure surface 18 side, (b) is the figure which looked at the negative pressure surface 19 side from the pressure surface 18 side of the turbine blade 10. FIG. The conventional side wall described in FIG. 8 is indicated by a broken line, and the side wall of the present embodiment is indicated by a solid line. As shown in FIG. 4A, the bottom of the concave portion 21 of the present embodiment protrudes from the blade leading edge 13 toward the blade trailing edge 14 toward the blade inner side on the pressure surface 18 side. On the other hand, as shown in FIG. 4B, on the suction surface 19 side, the concave portion 21 on the side wall is recessed from the blade leading edge 13 toward the throat point 17 toward the inner side of the side wall. The downstream side is formed at the same height in the turbine radial direction as the inter-blade channel side wall surface 22 of the side wall. In the present embodiment, the concave portion 21 having the same shape as the concave portion 21 of the inner peripheral side wall 12 is also formed in the outer peripheral side wall 11.

  FIG. 5 shows a graph showing the relationship between the dimensionless length and the dimensionless depth of the recess 21 according to the present embodiment. The horizontal axis indicates the dimensionless length, and the vertical axis indicates the dimensionless depth. Here, the side wall surface 22 between the blades in the side wall is defined as a reference surface, and the turbine radial direction distance (λ) from the reference surface to the bottom surface of the recess 21 at the isoline position where the dimensionless length is an arbitrary value. The value obtained by dividing the maximum distance δ in the radial direction from the reference surface to the bottom surface of the recess is defined as the dimensionless depth (λ / δ). A dimensionless length at which the dimensionless depth (λ / δ) is 1.0 is defined as a maximum dimensionless depth position. In FIG. 5, when the numerical value is negative, it indicates that it is recessed on the side wall side, and when the numerical value is positive, it indicates that it protrudes toward the inter-blade channel side.

  In the present embodiment, as shown in FIG. 5, a graph showing the distribution of values of each dimensionless depth (λ / δ) within the range of dimensionless length of 0.0 to 1.0 is maximum. It consists of a curve with one inflection point at the dimension depth position. Further, it is desirable that the maximum dimensionless depth position is only one point between the dimensionless lengths of 0.5 or more and 0.9 or less, as will be described later.

  Next, the function and effect of this embodiment will be described.

  FIG. 6 is a graph showing the blade outlet flow distribution in the blade height direction of the turbine stage according to the present embodiment obtained by analysis. The vertical axis represents the turbine blade height position, and the horizontal axis represents the blade outlet flow rate at the turbine blade outlet. A blade outlet flow rate of a turbine stage having a conventional non-concave side wall is indicated by a dotted line, and a blade outlet flow rate of the turbine stage of the present embodiment is indicated by a solid line. According to the analysis result, it can be seen that in this embodiment, a larger flow rate is distributed to the blade center than in the conventional case. This is due to the change in the dimensionless depth from the maximum dimensionless depth position shown in FIG. 5 to the dimensionless length 1.0, that is, the concave portion 21 is provided, and gradually from the maximum depth position toward the downstream side. This is based on the contraction effect in which the working fluid that has passed between the blades is distributed in a large amount at the center in the blade height direction.

  In order to make the flow distribution effect of the working fluid in the blade height direction effective, the velocity vector of the working fluid passing through the inter-blade channel must be perpendicular to the throat s when passing through the throat portion. Is desirable. According to the configuration of this embodiment, the bottom of the concave portion 21 is arranged along the flow path between the blades, and the cross section passes through the flow path between the blades by making a rectangular cross-sectional shape according to the isoline. Since the velocity vector to be applied acts in a direction near the throat line at the throat portion s, the effect of distributing the flow rate more effectively in the blade height direction can be obtained.

  Distributing a large flow rate at the blade center portion is equivalent to increasing the axial flow velocity of the working fluid at the blade height. That is, the increase in the axial flow velocity leads to a reduction in blade load at the blade center, and the paragraph efficiency of the turbine blade is improved.

  In addition, as shown in FIG. 5, by setting the maximum dimensionless depth position at one place, it is possible to suppress an increase in the surface area of the side wall due to the provision of the concave surface, and as a result, friction loss caused by the concave portion Can also be suppressed.

  FIG. 7 is a graph showing a loss distribution in the blade height direction of the turbine stage according to the first embodiment. The vertical axis represents the turbine blade height position, and the horizontal axis represents the turbine blade loss. The loss distribution graph of the turbine stage which has the conventional non-concave side wall is shown with a dotted line, and the loss distribution graph of the turbine stage which concerns on a present Example is shown with a continuous line. According to the present embodiment, the turbine blade loss at the blade central portion is reduced by the effect of distributing the flow rate of the working fluid to the blade central portion in the vicinity of the blade central portion. It can also be seen that the turbine blade loss is reduced in the vicinity of the blade tip and the blade root compared to the conventional one. This is because the flow distribution of this embodiment reduces the flow rate of the working fluid to the blade tip and the blade root near the blade tip where the side wall loss is large. This is because the interference with the fluid can be suppressed, and as a result, the side wall loss is reduced.

  Therefore, according to the configuration of the present embodiment, it is possible to optimize the blade height direction flow rate distribution of the working fluid passing between the turbine blades and reduce the side wall loss in the turbine stage. According to the analysis results, the efficiency of the turbine blade is improved by about 0.2% as compared with the conventional efficiency.

  Note that the contraction effect according to the present embodiment needs to effectively flow into the throat portion, and considering this point, the dimensionless length position having the maximum depth is between 0.5 and 0.9. It is desirable to exist.

  In consideration of the fact that the turbine blade takes out work from the working fluid, the recess 21 is provided on the downstream side where the working fluid flows from the position where the leading edges of the adjacent turbine blades are connected, and on the upstream side from the throat length between the turbine blades. It is more effective.

  Although this embodiment has been described as an example when applied to a turbine stage of an axial flow turbine, it is not limited to this. The effect can also be obtained by applying it to one or both of the stationary blades and moving blades of an axial flow turbine blade, or even if a concave sidewall is applied only to the turbine outer peripheral wall or only to the turbine inner peripheral wall. The same effect as the invention can be obtained. In addition, the present embodiment can be applied to either a steam turbine or a gas turbine.

  Next, a second embodiment of the present invention will be described with reference to FIGS. FIG. 10 is a view showing the shape of the inner peripheral side wall 12 of the turbine stage according to the present embodiment as viewed from the turbine radial direction. 11 is a cross-sectional view taken along the line BB ′ shown in FIG. FIG. 12 is a graph showing the blade outlet flow rate distribution in the blade height direction of the turbine stage according to the present embodiment. FIG. 13 is a graph showing the loss distribution in the blade height direction of the turbine stage according to the present embodiment.

  This embodiment is different from the first embodiment in the shape of the bottom of the recess 21. In this embodiment, as shown in FIG. 10, the isoline extends in parallel with the inlet portion (L) of the inter-blade flow path, and the bottom of the recess 21 of this embodiment is along this isoline. And has a rectangular cross-sectional shape with a bottom surface having an equal radial distance from the turbine central axis. Other elements are the same as those in the first embodiment, and a description thereof will be omitted. In addition, the same code | symbol is attached | subjected to the component same as Example 1. FIG.

  In FIG. 10, 24 represents the contour curve of the pressure surface 18 at the connection between the turbine blade 10 and the side wall. Reference numeral 25 denotes a contour curve of the suction surface 19 at the connection portion between the turbine blade 10 and the side wall. A point where a straight line m that passes through the throat point 17 of the suction surface 19 of the turbine blade 10 and is parallel to the straight line L that is the inlet of the inter-blade passage intersects the contour curve 24 of the pressure surface 28 of the adjacent turbine blade 10. Is defined as an intersection Z.

  Point X is a point at an arbitrary position on the contour curve 24 of the pressure surface 18, and the turbine axial distance (X 2) from the tip of the blade leading edge of the contour curve 24 of the pressure surface 18 to the point X is expressed as the pressure surface. The value divided by the axial distance (α2) from the tip of the blade leading edge of the 18 contour curve 24 to the intersection Z is defined as the axial dimensionless length (X2 / α2). The axial dimensionless length (X2 / α2) is a value that represents the relative axial position of the point X between the blade leading edge 13 and the blade trailing edge 14 of the contour curve 24. ) Is a value that takes the range represented by the formula.

0.0 ≦ X2 / α2 ≦ 1.0 (3)
Next, the point Y is a point at an arbitrary position on the contour curve 25 of the blade suction surface 19, and the turbine axial distance (Y 2) from the tip of the blade leading edge of the contour curve 25 of the suction surface 19 to the point Y is expressed as follows. The value obtained by dividing the contour curve 25 of the suction surface 19 by the axial distance (β2) from the tip of the blade leading edge to the throat point 17 is defined as the axial dimensionless length (Y2 / β2). The axial dimensionless length (Y2 / β2) is a value that represents the relative axial position of the point Y between the blade leading edge 13 and the throat point 17 of the contour curve 25. The following equation (4) It is a value that takes the range represented by.

0.0 ≦ Y2 / β2 ≦ 1.0 (4)
In FIG. 10, the straight lines with numerical values from 0 to 4 are the dimensionless axial length (X2 / α2) in the contour curve 24 on the pressure surface 18 side and the contour curve 25 on the suction surface 19 side. This is a straight line connecting positions where the axial dimensionless length (Y2 / β2) is equal, and this straight line is defined as an isoline. As in the first embodiment, the numerical values from 0 to 4 attached to the respective isolines represent the degree of the depth of the concave portion 21 at the position, and the larger the numerical value, the deeper the recess of the concave portion 21 is. Means.

  Similar to the first embodiment, the concave portion 21 of the present embodiment is provided on the downstream side of the inlet portion of the inter-blade channel 20 on the side wall and on the upstream side of the throat s. The concave portion 21 of the present embodiment is characterized in that it has a bottom portion having a bottom surface having an equal radial distance from the turbine central axis along an isoline between the pressure surface 18 and the suction surface 19. FIG. 11 is a cross-sectional view taken along line BB ′ shown in FIG. 10, and is a cross-sectional view of the bottom of the recess 21 along the isoline. As shown in FIG. 11, the bottom of the recess 21 includes a bottom surface (inner peripheral side wall 12) having the same radial distance from the turbine central axis along the isoline, and has a rectangular cross-sectional shape. The concave portion 21 continuously has a bottom portion having a rectangular cross-sectional shape from the inlet portion (L) side of the inter-blade channel toward the throat s side.

  Considering that the turbine blade takes out work from the working fluid, the recess 21 is provided on the downstream side where the working fluid flows from the position where the leading edges of the adjacent turbine blades are connected, and on the upstream side from the throat length between the turbine blades. It is more effective.

  Here, the velocity vector passing through the inter-blade channel in the present embodiment will be described with reference to FIG. As described above, since the throat s acts in a direction near to the throat line, the flow rate is more effectively distributed in the blade height direction. In the case of the present embodiment, the position where the side wall shape is changed is up to the throat point 17 and the point Z, and the velocity vector passes in the direction near the straight line m connecting the throat point 17 and the point Z, and the contraction effect is at this position. It is possible to obtain the effect of distributing a large amount of working fluid to the blade central part. Here, between the blades surrounded by the point Z on the contour curve 24, the trailing edge 14 of the turbine blade, and the throat point 17, the blade shape of the contour curves 24 and 25 has the flow distribution due to the above-described contraction effect. Affected, it passes with a velocity vector in a direction close to perpendicular to the straight line connecting the trailing edge 14 of the turbine blade and the throat point 17.

  As described above, also in the present embodiment, it is possible to obtain an effect of distributing a large flow rate to the blade central portion. Here, when the present embodiment is compared with the first embodiment, the concave surface shape is not changed to the throat position in the present embodiment. For this reason, the effect of distributing a large amount of working fluid to the blade central portion due to the contraction effect is greater in the above-described first embodiment.

  In the case of the present embodiment, as in the case of the first embodiment, a graph showing the distribution of values of each dimensionless depth (λ / δ) within the range where the axial dimensionless length is 0.0 to 1.0. It consists of a curve with one inflection point at the maximum dimensionless depth position. Since the inflection point exists at a position close to the throat portion, a larger contraction effect can be obtained. As an example, the dimensionless length position having the maximum depth is preferably present between the dimensionless length in the axial direction of 0.4 or more and 0.6 or less. In the present embodiment as well as the first embodiment, the flow rate of the working fluid is largely distributed to the blade central portion by the contraction effect in the blade height direction using the concave side wall shape, and the turbine blade loss in the blade central portion is reduced. The efficiency of the turbine blade is improved.

  FIG. 12 is a diagram showing the turbine blade height position on the vertical axis and the blade outlet flow rate in the blade height direction at the turbine blade outlet portion on the horizontal axis. A blade outlet flow rate which is a conventional non-concave side wall is indicated by a dotted line, and a blade outlet flow rate to which the concave side wall according to the second embodiment is applied is indicated by a solid line. As in the first embodiment, a large amount of flow is distributed to the blade center.

  FIG. 13 is a diagram illustrating the turbine blade height position on the vertical axis and the turbine blade loss on the horizontal axis. A conventional non-concave side wall is indicated by a dotted line, and a concave side wall to which Example 2 is applied is indicated by a solid line. As in the case of the first embodiment, the flow rate of the working fluid is largely distributed to the blade central portion by the contraction effect in the blade height direction using the concave sidewall shape, and the turbine blade loss at the blade central portion is reduced. As a result, the efficiency of the turbine blade is improved.

  As described above, according to the present invention, it is possible to provide an axial-flow turbine blade with improved paragraph efficiency as compared with the conventional axial-flow turbine blade.

  Although this embodiment has been described as an example when applied to a turbine stage of an axial flow turbine, it is not limited to this. The effect can also be obtained by applying it to one or both of the stationary blades and moving blades of an axial flow turbine blade, or even if a concave sidewall is applied only to the turbine outer peripheral wall or only to the turbine inner peripheral wall. The same effect as the invention can be obtained. In addition, the present embodiment can be applied to either a steam turbine or a gas turbine.

DESCRIPTION OF SYMBOLS 1 Diaphragm outer ring 2 Diaphragm inner ring 3 Stator blade 5 Rotor blade 6 Shroud 10 Turbine blade 11 Outer peripheral side wall 12 Inner peripheral side wall 17 Throat point 18 Pressure surface 19 Negative pressure surface 20 Interblade channel 21 Recess 22 Interblade channel side wall 24 25 Contour curve s Throat t Pitch length

Claims (6)

A blade used in an axial turbine and provided with a plurality of turbine blades in the circumferential direction between the outer peripheral side wall and the inner peripheral side wall extending in the circumferential direction, and the working fluid flows between the adjacent turbine blades A turbine stage in which an inter-channel is formed,
When a straight line connecting the blade leading edge tips of the adjacent turbine blades is defined as the inlet portion of the inter-blade channel,
The side wall of at least one of the outer peripheral side and the inner peripheral side constituting the wall surface on the radial direction side of the inter-blade channel is adjacent to the downstream side in the working fluid flow direction from the inlet portion of the inter-blade channel. Provide a recess recessed toward the inside of the side wall at a position upstream of the throat where the distance between the turbine blades is the minimum in the working fluid flow direction,
The concave portion constitutes a wall surface on the circumferential side of the inter-blade channel, and between the blade pressure surface and the blade suction surface facing each other of the adjacent turbine blades, the blade pressure surface and the blade suction surface A bottom of a rectangular cross-sectional shape with a bottom surface having an equal radial distance from the turbine central axis along a virtual straight line connecting
The said recessed part has the bottom part of the said rectangular cross-sectional shape continuously toward the said throat part side from the entrance part side of the said flow path between blades, The turbine stage characterized by the above-mentioned. The turbine stage according to claim 1,
The contour curve length (X1) from the tip of the blade leading edge to the arbitrary position of the blade pressure surface contour curve is defined as the contour from the blade leading edge tip to the blade trailing edge tip of the blade pressure surface contour curve. Define the value divided by the curve length (α1) as the dimensionless length (X1 / α1),
The contour curve length (Y1) from the tip of the blade leading edge of the blade suction surface side to an arbitrary position is defined as the contour curve length from the tip of the blade leading edge of the blade suction surface to the throat point. The value divided by (β1) is defined as the dimensionless length (Y1 / β1),
When a straight line connecting the dimensionless length (X1 / α1) on the blade pressure surface side of the equal value and the dimensionless length (Y1 / β1) of the suction surface is defined as an isoline,
The imaginary straight line is the isoline, the turbine paragraph. The turbine stage according to claim 2,
The side wall surface between the blades of the side wall having the recess as a reference plane,
The radial distance (λ) from the reference surface to the bottom surface of the recess at the isoline position where the dimensionless length is an arbitrary value is the maximum radial distance from the reference surface to the bottom surface of the recess ( The value divided by δ) is the dimensionless depth (λ / δ),
When the dimensionless length where the dimensionless depth (λ / δ) is 1.0 is defined as the maximum dimensionless depth position,
A graph showing the distribution of values of each dimensionless depth (λ / δ) in the range of dimensionless length 0.0 or more and 1.0 or less shows one inflection point at the maximum dimensionless depth position. Composed of curves
The turbine paragraph, wherein the maximum dimensionless depth position has only one point within a range of dimensionless length of 0.5 or more and 0.9 or less. The turbine stage according to claim 1,
An intersection (Z) is defined as an intersection of a straight line passing through a throat point on the contour curve of the blade suction surface and parallel to the inlet portion of the inter-blade channel and the contour curve of the blade pressure surface;
The turbine axial distance (X2) from the blade leading edge tip of the blade pressure surface contour curve to an arbitrary position is represented by the turbine from the blade leading edge tip of the blade pressure surface contour curve to the intersection (Z). The value divided by the axial distance (α2) is defined as the axial dimensionless length (X2 / α2),
Turbine axial distance (Y2) from the front edge of the blade suction surface contour curve to an arbitrary position, and the turbine axial distance from the front edge of the blade suction surface contour curve to the throat point ( Define the value divided by β2) as the axial dimensionless length (Y2 / β2),
When a straight line connecting the axial dimensionless length (X2 / α2) on the blade pressure surface side of the equivalent value and the axial dimensionless length (Y2 / β2) of the suction surface is defined as an isoline,
The imaginary straight line is the isoline, the turbine paragraph. The turbine stage according to claim 4,
The side wall surface between the blades of the side wall having the recess as a reference plane,
The radial distance (λ) from the reference surface to the bottom surface of the recess at the isoline position where the axial dimensionless length is an arbitrary value is the maximum radial distance from the reference surface to the bottom surface of the recess. The value divided by the value (δ) is the dimensionless depth (λ / δ),
When an axial dimensionless length where the dimensionless depth (λ / δ) is 1.0 is defined as the maximum dimensionless depth position,
A graph showing the distribution of values of each dimensionless depth (λ / δ) in the axial dimensionless length range of 0.0 or more and 1.0 or less is one inflection at the maximum dimensionless depth position. A turbine paragraph, comprising a curve having points, wherein the maximum dimensionless depth position is only one point within a range of an axial dimensionless length of 0.4 or more and 0.6 or less.   A steam turbine comprising the turbine stage according to any one of claims 1 to 5.

Images