JP2005098203A - Turbine blade and its flow loss reduction method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively reduce flow loss by reducing secondary flow or the like. <P>SOLUTION: In this turbine blades 1 and 2 arranged to respective stages, bypass passages 4 and 5 respectively passing through from sides 1c and 2c to back sides 1d and 2d while being close to a support wall surface 3 and a support wall surface not shown are arranged near a maximum thickness part. Accordingly, a part of a working fluid is bypassed from the belly sides 1c and 2c to the back sides 1d and 2d near the maximum thickness part of the respective turbine blades 1 and 2, at a position close to the support wall surface 3 and the support wall surface not shown, and pressure differences between the belly side 1c and the back side 1d and between the side 2c and the back side 2d of the respective turbine blades 1 and 2 near the support wall surface 3 and the support wall surface not shown are reduced, to decrease the secondary flow 8 thereby reducing the flow loss. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a turbine blade provided in each stage of a turbine and a flow loss reducing method thereof.

  Factors that increase the pressure loss of the working fluid in the turbine include, for example, flow loss such as secondary flow loss, separation loss, or mixing loss, and the designed turbine performance may not be exhibited due to these factors. For example, taking secondary flow loss as an example, the secondary flow is a flow having a component in the vertical plane direction with respect to the main flow. Generally, between turbine blades, if a stationary blade, a stationary blade inner ring, a stationary blade outer ring, If it is a blade, it grows as a large vortex toward the trailing edge due to the influence of the boundary layer near the supporting wall surface supporting the turbine blade, such as the outer periphery of the turbine wheel. As a result, when a secondary flow occurs, a part of the energy held by the working fluid is consumed to form a vortex, which causes an increase in pressure loss.

  As a technique for reducing this type of flow loss, conventionally, for the purpose of preventing an increase in secondary flow loss, the front edge portion of the turbine stationary blade and the vicinity of the rear rear edge portion are arranged in the vicinity of the inner ring or outer ring of the stationary blade. Some have been bypassed (see, for example, Patent Document 1), and others have slits on the tip side and the back of the root portion with respect to a hollow stationary blade (see, for example, Patent Document 2).

JP-A-1-163404

JP-A-2-196107

  In general, in a turbine blade, the ventral side with a depressed center is a pressure surface, and the back side with the center swollen is a suction surface. The working fluid turning between the turbine blades balances the centrifugal force and the pressure gradient on the ventral and back sides of the turbine blade during turning. However, in the boundary layer of the end wall (support wall surface) that limits the blade height, the working fluid is decelerated due to wall surface loss, and therefore the centrifugal force is reduced. As a result, the balance between the pressure gradients on the ventral side and the back side of the turbine blade is lost, and a flow from the positive pressure abdominal side to the back side of the adjacent turbine blade, that is, a secondary flow is generated, and a vortex is generated. Therefore, a part of the energy held by the working fluid is consumed to form a secondary flow vortex and is lost.

  However, in the technique described in Patent Document 1, since the working fluid is bypassed from the front edge portion to the back side rear edge portion, the pressure difference between the ventral side and the back side is the largest in the vicinity of the maximum thickness portion of the wing. Therefore, the pressure difference between the ventral side and the back side of the turbine blade is not effectively reduced. In the technique described in Patent Document 2, the ventral and dorsal slits are provided at the tip and root of the blade, respectively, and the introduced working fluid flows from the tip to the root in the blade length direction. The pressure difference between the ventral side and the dorsal side in the vicinity of the tip portion or the root portion is still not reduced.

  An object of the present invention is to provide a turbine blade and a method for reducing the flow loss that can reduce a secondary flow or the like and effectively reduce a flow loss.

  (1) In order to achieve the above object, according to the present invention, in the turbine blade provided in each stage of the turbine, a bypass flow path penetrating from the ventral side to the back side near the support wall surface in the vicinity of the maximum thickness portion. Was established.

  As described above, in general, in the turbine blade, the abdomen side is the pressure surface and the back side is the suction surface, and the pressure difference becomes maximum near the maximum thickness portion of the profile (blade). In the vicinity of the support wall surface where the main flow of the working fluid is decelerated due to the wall loss, a secondary flow is likely to occur due to the pressure difference between the ventral side and the back side. Therefore, in order to reduce the secondary flow loss, the back side and the ventral side of the tip part (Tip) or the root part (Root) in the vicinity of the supporting wall (end face wall) that limits the height of the blades. The secondary flow can be reduced by reducing the pressure difference.

  Therefore, in the present invention, a bypass channel for bypassing the working fluid from the abdominal side to the back side is provided close to the support wall surface in the vicinity of the maximum thickness portion where the pressure difference between the abdominal side and the back side is maximized. . Thereby, the pressure difference between the ventral side and the back side of the turbine blade can be effectively reduced. Moreover, energy can be given to the boundary layer on the back side surface by bypassing the working fluid from the ventral side. Therefore, by setting the diameter of the bypass flow path so that the required amount of working fluid is bypassed in consideration of the pressure difference between the ventral side and the back side of the blade required to obtain the rotational power of the turbine rotor at the design stage. Since the pressure difference in the vicinity of the support wall on the ventral side and the back side of the turbine blade can be optimized, the secondary flow can be reduced, and the flow loss can be effectively reduced.

  (2) In the above (1), preferably, the bypass flow path is provided slightly closer to the rear edge than the maximum thickness portion.

  (3) In the above (1) or (2), preferably, an ejection hole that branches off from the bypass flow path and penetrates in the vicinity of the back side rear edge portion is provided.

  Due to wall loss at the blade side, the energy of the working fluid decreases toward the trailing edge. Therefore, at the back side rear edge, the kinetic energy of the working fluid becomes insufficient with respect to the pressure increase in the boundary layer, and thus the back flow of the working fluid may occur. Separation, which is one of the flow losses, means that the working fluid along the back side moves away from the back side surface due to the back flow of the working fluid, which also contributes to an increase in pressure loss.

  Therefore, in the present invention, a part of the working fluid flowing through the bypass channel is branched by the ejection holes, and the working fluid is ejected from the ejection holes communicated in the vicinity of the back side rear edge near the separation point. The ejected working fluid is merged with the working fluid flowing along the back side surface. Thereby, since the working fluid with reduced kinetic energy flowing in the vicinity of the back side rear edge can be urged, the occurrence of separation can be suppressed and the flow loss can be effectively reduced.

  In addition, at the blade outlet (turbine blade trailing edge), the working fluid along the turbine blade abdomen and the working fluid along the turbine blade back merge together in the wake of the turbine blade. If the difference in pressure and flow velocity is large, the mixing loss increases, turbulence is promoted, and this also contributes to an increase in pressure loss. On the other hand, according to the present invention, by partially bypassing the working fluid from the ventral side in the vicinity of the back side rear edge portion by the ejection hole, the working fluid along the ventral side and the back side joining to the working fluid are aligned The pressure difference from the working fluid can be reduced, and energy can be given to the working fluid along the back side that joins the working fluid from the ventral side. Therefore, the mixing loss can be reduced, and the effect of reducing the flow loss can also be expected.

  (4) In the above (3), preferably, a plurality of the ejection holes are discretely arranged in the blade length direction.

  As described above, the separation loss is caused by the negative pressure state at the back side rear edge, and the mixing loss is caused by the pressure difference between the ventral side and the back side. However, it may occur at various points in the wing length direction. Therefore, by disposing a plurality of ejection holes in the blade length direction in a discrete manner, it is possible to suppress separation and mixing loss at various locations in the blade length direction, and to more effectively reduce flow loss.

  (5) In the above (3) or (4), more preferably, the ejection hole is provided so that the ejected working fluid joins the working fluid along the back side at a gentle inclination angle.

  (6) In order to achieve the above object, the present invention also provides a method for reducing the flow loss of turbine blades provided at each stage of the turbine, in the vicinity of the maximum wall thickness portion of the turbine blades at a position close to the support wall surface. The secondary flow is reduced by bypassing a part of the working fluid from the side to the back side and reducing the pressure difference between the ventral side and the back side of the turbine blade near the support wall surface.

  (7) In order to achieve the above object, the present invention also provides a method for reducing a flow loss of a turbine blade provided in each stage of a turbine, wherein a working fluid taken from a ventral side of the turbine blade is supplied to the back of the turbine blade. The occurrence of delamination is suppressed by ejecting the entire working fluid in the blade length direction to the vicinity of the side rear edge, and merging and energizing the ejected working fluid along the working fluid along the back side of the turbine blade. .

  (8) In order to achieve the above object, the present invention also provides a method for reducing a flow loss of a turbine blade provided in each stage of a turbine, wherein working fluid taken from the ventral side of the turbine blade is supplied to the back of the turbine blade. Mixing loss is reduced by jetting almost entirely in the blade length direction to the vicinity of the side rear edge, and reducing the pressure difference when the working fluid along the back side and the working fluid along the ventral side merge. .

  According to the present invention, as described above, the flow loss can be effectively reduced by reducing the secondary flow and the like. Therefore, it is possible to improve turbine efficiency and contribute to, for example, high output and miniaturization of gas turbine equipment and the like.

Hereinafter, embodiments of a turbine blade and a flow loss reducing method of the present invention will be described with reference to the drawings.
FIG. 1 is a perspective view illustrating an external configuration of an embodiment of a turbine blade of the present invention.
In FIG. 1, turbine blades 1 and 2 have root portions 1 a and 2 a supported by a support wall 3. The turbine blades 1 and 2 may be turbine stationary blades or turbine rotor blades, but in the present embodiment, the case of turbine stationary blades is taken as an example, and the root portions 1a and 2a are respectively stationary blades. It is assumed that the tip (Tip) portions 1b and 2b are fixed to the inner ring, that is, the support wall surface 3, to the stationary blade outer ring (not shown). If the turbine blades 1 and 2 are moving blades, the support wall surface 3 is, for example, an outer peripheral portion of the turbine wheel or a diaphragm attached to the turbine wheel. Further, in the present embodiment, only the turbine blades 1 and 2 are shown, but actually, in the respective stages of the turbine, more similar ones are arranged in a row in the circumferential direction of the return flow path. Yes.

2 is a cross-sectional view of an embodiment of the turbine blade of the present invention shown in FIG. 1. In FIG. 2, the same parts as those in FIG.
As shown in FIGS. 1 and 2, in the present embodiment, the turbine blades 1 and 2 include a dorsal side surface (back surface) 1 d, in which the center swells from a vent side surface (abdominal surface) 1 c, 2 c with a depressed center. Bypass channels 4 and 5 pass through 2d. These bypass passages 4 and 5 may penetrate the vicinity of the profile maximum thickness portion of the turbine blades 1 and 2, respectively, but in the present embodiment, as shown in FIG. A portion closer to the rear edges 1e and 2e than the portion is penetrated. Further, as shown in FIG. 1, the bypass flow paths 4 and 5 are substantially parallel to the stationary blade inner ring and the stationary blade outer ring in the vicinity of the stationary blade inner ring (support wall surface 3) and the stationary blade outer ring (not shown). The flow path diameter is set in consideration of the required bypass amount of the working fluid.

  Inside the turbine blades 1 and 2, branch passages 6 that connect the bypass passages 4 and 5 in the blade length direction are provided, respectively. From this branch flow path 6, an ejection hole 7 penetrating to the surface portion in the vicinity of the rear edge portions of the rear surfaces 1 d and 2 d is further branched. A plurality of the ejection holes 7 are arranged discretely in the blade length direction, and are arranged substantially evenly over the entire length of the blade. Further, in the present embodiment, the case where the ejection holes 7 are provided substantially parallel and linearly to the support wall surface 3 is illustrated. However, the present invention is not limited to this and may be slightly inclined, for example, the back surface 1d, It is good also as a flow path bent along 2d. However, it is desirable that the angle between the back surfaces 1d and 2d be as small as possible so that the working fluid that spouts joins the working fluid flowing along the back surfaces 1d and 2d with a gentle inclination angle. Moreover, the flow path diameter and the number of installation of the ejection hole 7 are set in consideration of the required amount of the working fluid to be ejected.

FIG. 3 is a graph showing the correlation between the axial distance and the pressure in the boundary layer on the ventral side and the back side of the turbine blade.
As shown in FIG. 3, when the turbine blades 1 and 2 having the above-described configuration are arranged in the flow of the working fluid, the ventral sides 1c and 2c become positive pressure surfaces, the back sides 1d and 2d become negative pressure surfaces, and the pressure difference is It becomes the maximum near the maximum thickness part of the turbine blades 1 and 2. In the vicinity of the support wall surface (static blade inner ring) 3 and the stationary blade outer ring (not shown) where the main flow of the working fluid is decelerated due to the wall loss, two pressures are caused by the pressure difference between the ventral side 1c, 2c and the back side 1d, 2d. The next flow 8 is likely to occur. Therefore, in order to reduce the secondary flow loss, the end portions 1b and 2b or the root portions 1a and 2a in the vicinity of the end walls (the supporting wall surface 3 and the stationary blade outer ring) that limit the blade height are located in the vicinity thereof. The secondary flow 8 can be reduced by reducing the pressure difference between the dorsal side and the ventral side.

  Therefore, in the present embodiment, as described above, the bypass flow that bypasses the working fluid from the ventral side to the dorsal side near the maximum thickness portion where the pressure difference between the ventral sides 1c and 2c and the dorsal side 1d and 2d is maximum. The roads 4 and 5 are provided close to the supporting wall surface (the supporting wall surface 3 and the stationary blade outer ring). Accordingly, as illustrated by arrows in FIG. 3, the working fluid on the abdominal side 1c, 2c having a high pressure is bypassed to the back side 1d, 2d having a low pressure, so that the abdominal sides 1c, 2c of the turbine blades 1, 2 are bypassed. In addition, the pressure difference between the back sides 1d and 2d can be effectively reduced. Moreover, energy can be given to the boundary layer of the back side surfaces 1d and 2d by bypassing the working fluid from the ventral sides 1c and 2c. Therefore, a required amount of working fluid is bypassed in consideration of the pressure difference between the ventral sides 1c and 2c and the back sides 1d and 2d of the turbine blades 1 and 2 required to obtain the rotational power of the turbine rotor at the design stage. By setting the flow path diameters of the bypass flow paths 4 and 5, the pressure difference in the vicinity of the support wall surfaces of the abdominal sides 1c and 2c and the back sides 1d and 2d of the turbine blades 1 and 2 can be optimized. The flow 8 can be reduced, and thus the flow loss can be effectively reduced.

  Moreover, the energy of the working fluid which flows through the boundary layer falls toward the trailing edges 1e and 2e due to the wall surface loss on the side surfaces of the turbine blades 1 and 2, that is, the abdominal surfaces 1c and 2c and the back surfaces 1d and 2d. Therefore, in the vicinity of the rear edge portions 1e and 2e of the back sides 1d and 2d, the kinetic energy of the working fluid becomes insufficient with respect to the pressure increase in the boundary layer, so that the working fluid may flow backward. Separation 9, which is one of the flow losses, means that the working fluid along the back side moves away from the back side surface due to the back flow of the working fluid, which also contributes to an increase in pressure loss.

  Therefore, in the present embodiment, the ejection hole 7 is provided. A part of the working fluid flowing through the bypass flow paths 4 and 5 flows into the branch flow path 6 branched from the bypass flow paths 4 and 5, further flows into the respective ejection holes 7 and flows through the ejection holes 7. It ejects in the vicinity of the rear edges 1e and 2e of the back sides 1d and 2d close to the separation point. As a result, the ejected working fluid is merged with the working fluid flowing along the back side surfaces 1d and 2d, and the working fluid with reduced kinetic energy flowing in the vicinity of the rear edges 1e and 2e of the back sides 1d and 2d is energized. Therefore, the generation of the separation 9 can be suppressed, and the flow loss can be effectively reduced.

  Further, at the outlets (rear edges 1e and 2e) of the turbine blades 1 and 2, as shown in FIG. 1, the working fluid 10 along the ventral sides 1c and 2c of the turbine blades 1 and 2 and the back side 1d, The working fluid 11 along 2d merges in the wake of the turbine blades 1 and 2, but if the difference in pressure and flow velocity between the working fluids 10 and 11 is large, the mixing loss increases and the pressure loss increases. It contributes.

  On the other hand, according to the present embodiment, by partially bypassing the working fluid 10 from the ventral side 1c, 2c in the vicinity of the rear edge portions 1e, 2e of the dorsal side 1d, 2d by the ejection hole 7, the ventral side The pressure difference at the time of merging between the working fluid 10 along 1c and 2c and the working fluid 11 along the back sides 1d and 2d that merges with the working fluid 10 is reduced, and the back that merges with the working fluid 10 from the ventral sides 1c and 2c. Energy can be applied to the working fluid 11 along the sides 1d, 2d. Therefore, the mixing loss can be reduced, and the effect of reducing the flow loss can also be expected.

  Further, unlike the secondary flow 8, the separation 9 and the mixing of the working fluids 10 and 11 may occur not only in the vicinity of the supporting wall surface but also in various parts in the blade length direction. Therefore, as shown in FIG. 1, by disposing a plurality of ejection holes 7 in the blade length direction, it is possible to suppress separation 9 and mixing loss at various locations in the blade length direction, and more effectively reduce the flow loss. Can be reduced.

  Further, as shown in FIG. 2, the ejection hole 7 has a small angle between the back surface 1d and 2d so that the ejected working fluid joins the working fluid along the back side at a gentle inclination angle. Since it is provided, consideration is given so as not to give different direction components to the working fluid 11 flowing along the back sides 1d and 2d. This also contributes to reduction of peeling 9 and mixing loss.

  As described above, according to the present embodiment, the flow loss can be effectively reduced by reducing the secondary flow 8, the separation 9, and the mixing loss. Therefore, it is possible to improve turbine efficiency and contribute to, for example, high output and miniaturization of gas turbine equipment and the like.

  In the above description, the bypass passages 4 and 5 are provided on both sides of the root portions 1a and 2a and the tip portions 1b and 2b of the turbine blades 1 and 2, but as described above, for example, the end walls have the root portions 1a and 2a. In the case where only the side is provided, the bypass flow path 5 on the tip end portions 1b, 2b side can be omitted. In this case, the same effect is obtained. Moreover, although embodiment which has the bypass flow paths 4 and 5 and the ejection hole 7 was demonstrated, the bypass flow paths 4 and 5 are mainly used for reduction of the secondary flow 8, and the ejection hole 7 is mainly used for separation 9 and operation. This is effective in reducing the mixing loss of the fluids 10 and 11, and even if they are provided independently, the corresponding effects can be obtained.

  Further, in the above, the example in which the bypass flow paths 4 and 5 are provided on the rear edges 1e and 2e side slightly from the maximum thickness portion of the turbine blades 1 and 2 is described, but the present invention is not necessarily limited thereto. The bypass flow paths 4 and 5 may be provided in the vicinity of the maximum thickness portion where the pressure difference between the most ventral sides 1c and 2c and the back sides 1d and 2d becomes large. Further, even if the shape of the flow path is not necessarily linear, the design can be changed as appropriate, for example, by bending the flow path in consideration of the flow of the working fluid. Furthermore, although the example which provided the bypass flow paths 4 and 5 slightly spaced apart from end walls (support wall surface 3 etc.) and substantially parallel to an end wall was shown, it is not restricted to this, For example, root part 1a, 2a or A bypass flow path that is notched (that is, provided with a groove) between the end walls facing the end walls of the front end portions 1b and 2b so as to penetrate from the ventral sides 1c and 2c to the dorsal sides 1d and 2d. It may be formed. In these cases, the same effect as described above can be obtained.

  Further, in the above, an example in which the plurality of ejection holes 7 are arranged substantially evenly in the blade length direction is illustrated, but the present invention is not limited to this, and the pitch between the ejection holes 7 may be changed as necessary. In addition, although a plurality of ejection holes 7 are provided, for example, when one is sufficient in the design stage depending on the blade length, it is not always necessary to provide a plurality. Furthermore, although the cylindrical ejection hole 7 is illustrated, the present invention is not limited to this. For example, if the opening area is taken into consideration in consideration of the ejection amount of the working fluid, a band-shaped flow path having a width in the blade length direction may be used. good. In these cases, the same effect as described above can be obtained.

It is a perspective view showing the external appearance structure of one Embodiment of the turbine blade of this invention. It is sectional drawing of one Embodiment of the turbine blade of this invention shown in FIG. It is a graph showing the correlation between the axial direction distance and the pressure in the boundary layer on the ventral side and the back side of the turbine blade.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Turbine blade 1c Abdominal side 1d Back side 1e Rear edge 2 Turbine blade 2c Abdominal side 2d Back side 2e Rear edge 3 Support wall surface 4 Bypass flow path 5 Bypass flow path 7 Ejection hole

Claims (8)

In turbine blades provided at each stage of the turbine,
A turbine blade, characterized in that a bypass flow path is provided in the vicinity of a maximum wall thickness portion, penetrating from the ventral side to the back side in the vicinity of the support wall surface.   The turbine blade according to claim 1, wherein the bypass flow path is provided slightly closer to the rear edge than the maximum thickness portion.   3. The turbine blade according to claim 1, wherein an ejection hole that branches from the bypass flow path and penetrates in the vicinity of a back side rear edge portion is provided.   The turbine blade according to claim 3, wherein a plurality of the ejection holes are discretely arranged in the blade length direction.   5. The turbine blade according to claim 3, wherein the ejection hole is provided such that the ejected working fluid joins the working fluid along the back side at a gentle inclination angle. 6. In the method for reducing the flow loss of turbine blades provided in each stage of the turbine,
A portion of the working fluid is bypassed from the ventral side near the maximum wall thickness of the turbine blade to the back side at a position close to the support wall surface, and the pressure difference between the ventral side and the back side of the turbine blade near the support wall surface is reduced. A method for reducing a flow loss of a turbine blade, wherein the secondary flow is reduced by reducing the secondary flow. In the method for reducing the flow loss of turbine blades provided in each stage of the turbine,
The working fluid taken in from the ventral side of the turbine blade is ejected almost entirely in the blade length direction toward the vicinity of the back side rear edge of the turbine blade, and the ejected working fluid is run along the back side of the turbine blade. A method for reducing flow loss of a turbine blade, characterized in that generation of separation is suppressed by joining and energizing the working fluid. In the method for reducing the flow loss of turbine blades provided in each stage of the turbine,
The working fluid taken in from the ventral side of the turbine blade is ejected almost entirely in the blade length direction toward the vicinity of the back side rear edge of the turbine blade, and the working fluid along the back side and the working fluid along the ventral side A method for reducing a flow loss of a turbine blade, characterized by reducing a mixing loss by reducing a pressure difference at the time of merging with the turbine blade.

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