JPH1077801A - Low aspect patio cascade - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low aspect ratio cascade remarkably improving the performance of a steam and a gas turbine by reducing both a cascade loss of a secondary low loss area itself due to a vortex generated by the secondary flow of a blade tip part in a three dimensional blade profile and a mutually interfering additional cascade loss incurring through movement of the secondary flow loss area simultaneously. SOLUTION: The front edge side of a three dimensional blade profile 02 is inclined at a bow angle θ+ being an angle at which the tangential line of a blade back 03 is inclined rather to the blade back side than the normal direction N of a blade end wall and a positive bow angle θ+ at which the tangential line of the blade back 03 of the rear edge side is inclined to the blade belly 04 side and forms a curve wherein a bow angle is monotonously and smoothly changed from a front edge toward a rear edge. This constitution suppresses movement in the direction of a blade height of a secondary flow loss area at a blade front edge part, reduces incurring of an additional cascade loss, suppresses development of a vortex at a blade rear edge part, reduces the strength of a secondary flow loss, and reduces incurring of a cascade loss due to a loss area itself.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a loss caused by a secondary flow loss region itself, which is used in a steam turbine, a gas turbine, or the like, and is generated near a tip of a three-dimensional airfoil constituting a cascade. The present invention relates to a low-aspect-ratio cascade in which the additional losses caused by the interference of the secondary flow loss areas can be reduced, and the performance can be greatly improved.

[0002]

2. Description of the Related Art A three-dimensional airfoil root forming a cascade, or a loss generated in a loss region itself formed by the development of a vortex generated by a secondary flow generated at a blade tip near a blade tip. ,
In the low aspect ratio cascade where a large cascade loss occurs due to the additional loss caused by the loss area generated at the tip of both wings moving in the blade height direction and interfering with each other, it occurs in the loss area itself It is important to improve both performance to reduce cascade losses and to reduce both cascade losses caused by additional losses.

[0003] That is, a three-dimensional airfoil having a low aspect ratio, in which the ratio of (wing height) ² to the blade area is reduced, is provided around the rotating disk at equal pitches to form a moving blade. Or between the outer and inner rings at equal pitch,
In a low aspect ratio cascade forming a stator vane, for example, a low aspect ratio cascade forming a moving blade, a three-dimensional airfoil blade back face, a disk on which a three-dimensional airfoil blade root is to be implanted, and its blade tip face each other. A vortex is formed by a secondary flow in a corner formed by a working fluid passage wall (hereinafter, the disk and the passage wall are collectively referred to as a wing tip wall), and a loss generated by the wing tip wall is formed. A concentrated loss region is formed, and the loss region itself generates a cascade loss.

Further, the height direction of the back surface of the three-dimensional airfoil is
In low-aspect-ratio cascades (hereinafter referred to as parallel cascades) that are the same as the normal direction of the blade tip wall, the loss regions generated on both blade tip walls move in the blade height direction and interfere with each other. By doing so, a large cascade loss occurs at the center in the blade height direction due to the additional loss. Therefore, it is necessary to effectively reduce both of these cascade losses to improve the performance of a low aspect ratio cascade.

For this reason, in a conventional low aspect ratio cascade, two-dimensional airfoils are piled up in the height direction in such a manner that they are inclined in the circumferential direction with respect to the normal direction of the blade tip wall and are sequentially stacked in the height direction. In addition, a three-dimensional airfoil having a concave or convex surface and having a shape that smoothly changes in the height direction and the axial direction is provided, and the blades are arranged around the airfoil to reduce the cascade loss.

That is, as shown in FIGS. 3 and 4, which are one example, the three-dimensional airfoil 02 provided between the wing tip walls 05, 05 The direction of the tangent drawn in the height direction to the wing back surface 03 at the wing tip portion is such that the positive bow angle θ ₊ inclined from the wing back surface 03 side to the wing abdominal surface 04 side
The formation of the low aspect ratio cascade 01 has been carried out.

The low aspect ratio cascade 01 having such a positive bow angle θ ₊ is hereinafter referred to as a forward bow cascade 011.

In such a forward bow cascade 011, the corner formed by the wing tip wall 05 and the wing back surface 03 has an obtuse angle, the formation of a strong vortex is suppressed, and the loss in the loss region itself due to the secondary flow Can be reduced.

On the other hand, in the low aspect ratio cascade 01, as shown in FIGS. 6 and 7, a tangent drawn in the height direction to the blade back surface 03 at the blade tip portion with respect to the normal direction of the blade tip wall 05. Is formed into a negative bow angle θ ₋ inclined from the wing abdominal surface 04 side to the wing back surface 03 side to form a three-dimensional airfoil 02.

[0010] Such negative bow angle theta _- the low aspect wing column 01 was hereinafter be referred to as an inverse bow cascade 012.

In the reverse bow cascade 012 shown in FIGS. 6 and 7, as described above, the vicinity of the wing tip wall 05 with respect to the normal direction N of the wing tip wall 05, The inclination is inclined from the wing abdominal surface 04 side to the wing back surface 03 side, and the corner shape formed by the wing tip wall 05 and the wing back surface 03 is an acute angle. The formed loss region is less likely to move toward the blade height center. Therefore, in the reverse bow cascade 012, the low aspect ratio cascade 01 in which the secondary flow loss areas from both the blade end walls 05, 05 interfere with each other to generate a large cascade loss.
In this case, the vortex, that is, the secondary flow loss area, can be prevented from moving toward the center of the blade height and interfered with the vortex, thereby reducing the additional loss due to the interference.

As shown in FIGS. 4 and 7, a three-dimensional airfoil 02
The wings in the height direction shape is the same in the axial direction, a positive bow angle theta ₊ the bow angle is set, a negative bow angle theta _- although the difference is, in the axial direction, the bow angle theta ₊ , Θ _- are fixed, the conventional forward bow cascade 011 and reverse bow cascade 012,
Due to the above-described effects, the cascade loss shown in FIG. 2 is obtained as compared with the cascade loss of the parallel cascade in which the bow angles θ ₊ and θ ₋ are not provided.

That is, in the forward bow cascade 011, as described above, the corner shape becomes obtuse and the formation of a strong vortex is suppressed, and the loss due to the loss region itself due to the secondary flow is reduced. In the inter-blade flow path between the three-dimensional airfoils, static pressure is applied from the blade back surface 03 of the adjacent three-dimensional airfoil 02 toward the blade abdominal surface 04 of the three-dimensional airfoil 02 as shown in FIG. Is formed, and this pressure field generates a pressure gradient at the blade back surface 03 where the static pressure increases toward the blade tip. As a result, in the forward bow cascade 011, the formation of strong vortices is suppressed, and the strength of the vortices is reduced. However, the loss region due to the secondary flow near the both wing end walls 05, 05 moves toward the center of the wing height. It becomes easier to move, interferes with each other, and causes an additional loss. At the center of the blade height, as shown in FIG. 2, a blade cascade loss larger than that of the parallel cascade 013 is generated. Becomes

On the other hand, in the reverse bow cascade 012, as described above, the vortex from the vicinity of both the wing end walls 05 is caused by the effect of the acute corner formed by the wing end wall 05 and the wing back surface 03, so that the wing height direction, To reduce the movement,
The additional cascade loss occurring near the center of the blade height, which reduces the interference between the secondary flow loss regions and increases due to the interference, is shown in FIG.
As shown in (1), there is an effect of reducing the loss as compared with the case of the parallel cascade 013, but there is no effect of reducing the loss itself caused in the loss region itself caused by the secondary flow.

Therefore, like the conventional forward bow cascade 011 and reverse bow cascade 012, a low aspect ratio in which the bow angles θ ₊ and θ ₋ are constant in the axial direction from the leading edge to the trailing edge of the blade. In the specific cascade 01, the loss is reduced by the secondary flow loss region itself,
At the same time, it is difficult to simultaneously prevent an increase in additional loss due to mutual interference in the secondary flow loss region. For this reason, the performance of the low aspect ratio cascade 01 has not been significantly improved so far. It is.

[0016]

SUMMARY OF THE INVENTION In view of the above-mentioned situation, the present invention has been developed in consideration of the loss caused by the secondary flow loss region itself at the tip of a three-dimensional airfoil and the loss at the two ends of a three-dimensional airfoil at both ends. It is an object of the present invention to provide a low aspect ratio cascade that can reduce both an additional loss caused by the following flow loss areas moving and interfering with each other, thereby achieving a significant performance improvement. And

[0017]

For this reason, the low aspect ratio cascade of the present invention has the following means. Two-dimensional airfoils with reduced thickness in the wing height direction are piled up sequentially inclining in the circumferential direction with respect to the normal direction of the wing tip wall, forming a concave or convex surface in the height direction of the wing surface, The three-dimensional airfoil formed by changing smoothly in the height direction and the axial direction is (1)
At the leading edge of the wing, the tangent in the height direction of the wing tip on the back side of the wing with respect to the normal direction of the wing tip wall is set to a negative bow angle inclined from the flank side to the back side of the wing. Then, the tangent in the wing tip height direction with respect to the tangential direction of the wing tip wall is set to a positive bow angle inclined from the wing back side to the wing abdomen side. In the axial direction toward the edge, a curved surface that is monotonously and smoothly changed is formed. (3) Near the leading edge of the blade, the shape in the blade height direction on the back surface of the blade is concave, and near the trailing edge, the blade is A low aspect ratio cascade provided in the circumferential direction was provided between the blade end walls with a convex shape in the blade height direction on the back side and arranged at equal pitches.

The two-dimensional airfoil is not limited to one having the same shape in the height direction and sequentially stacked. The low aspect ratio cascade of the present invention is also applicable to turbine blades and stationary blades.

In the low aspect ratio cascade according to the present invention, the three-dimensional airfoil according to the above-mentioned means (1) to (3) is arranged between the blade tip walls, so that the blade tip wall is formed. In the corner formed by the blade and the back of the blade, the inter-blade flow path formed by the back of the blade of the adjacent three-dimensional blade and the blade abdominal surface of the three-dimensional blade,
There is a vortex due to secondary flow from the upstream side, and as it flows downstream, this vortex moves toward the center of the wing height while developing greatly, but it has been set at the leading edge of the wing with a negative bow angle Therefore, in the area of the leading edge of the blade row of the low aspect ratio cascade, the secondary flow loss area, which has not yet developed so much, is used in this corner part by utilizing the sharp corner shape formed by the blade back face and the tip wall. It is possible to reduce the cascade and the movement in the height direction of the blade, to prevent interference with each other on the downstream side, thereby generating additional loss, and to reduce the cascade loss in the center in the height direction of the blade. it can.

In the region of the wing trailing edge, the wing trailing edge has a positive bow angle, so that the obtuse angle formed at the corner between the wing rear surface and the wing tip wall can be used. The formation of a strong vortex can be suppressed to prevent the secondary flow loss region itself from developing, and the cascade loss due to the loss region itself can be reduced.

Thus, in the low aspect ratio cascade of the present invention, both the loss generated in the secondary flow loss region itself and the additional loss generated by mutual interference in the secondary flow loss region are simultaneously reduced. Cascade loss can be reduced, and performance can be greatly improved.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a low aspect ratio cascade according to the present invention will be described below with reference to the drawings. FIG. 1 shows a low aspect ratio cascade 1 as a first embodiment of the present invention.
FIG. 3 shows an axial bow angle distribution provided on a three-dimensional airfoil. As shown in the figure, the axial distribution is such that the bow angle is a negative bow angle θ _{− in} the wing leading edge half and a positive bow angle θ _{+ in the} trailing edge half, from the wing leading edge to the wing trailing edge. By providing the cascade, as shown in FIG. 2, the cascade loss can be reduced.

That is, a low aspect ratio cascade is formed.
A three-dimensional airfoil is a two-dimensional airfoil with a small thickness in the height direction
To the wing tip wall in the circumferential direction with respect to the normal direction.
Concave or convex in the height direction of the
Surface, smooth in both blade height and blade axis directions
It was formed by changing. Also, at the leading edge of the wing,
The wing at the wing tip on the back side of the wing with respect to the normal direction of the end wall
As shown in FIGS. 6 and 7, the tangential direction in the height direction is
Negative bow, inclined from the plane 04 to the wing back 03
Angle θ_-At the wing trailing edge, the tangential direction of the wing tip wall
Tangent to the blade height direction at the blade tip on the back side of the blade
As shown in FIG. 3 and FIG. 4, the direction is
Positive bow angle θ inclined to surface 04 ₊Maximum value of
Has been. Furthermore, the axial direction from the leading edge to the trailing edge
Has the largest negative bow angle θ at the leading edge of the wing._-From the wing trailing edge to the maximum
Positive bow θ of₊The bow angle changes monotonically and smoothly
It is a curved surface. Therefore, the height of the wing back surface 04
Shape is convex at the leading edge of the wing and concave at the trailing edge of the wing.
Will be implemented.

At the corner between the blade end wall 05 and the blade back surface 03 of the low aspect ratio cascade around which such a three-dimensional airfoil is provided, the adjacent three-dimensional blade-shaped airfoil back surface 03,
In the inter-blade channel formed by the three-dimensional airfoil abdominal surface 04, there is a vortex due to a secondary flow from a considerably upstream side. And the secondary flow loss region where the loss generated by the wing tip wall 05 concentrates moves toward the center of the wing height, but since the bow angle at the leading edge of the wing is negative, the wing In the area of the leading edge, the sharply formed corner formed by the wing rear surface 03 and the wing tip wall 05 prevents the secondary flow loss area, which has not yet greatly developed, from being hardly stopped at this corner, and toward the blade height direction. Of the blades can be prevented from interfering with each other on the downstream side, and additional losses can be prevented, and the cascade loss at the center in the blade height direction can be reduced.

Since the bow angle is made positive at the trailing edge of the blade, the formation of a strong vortex is suppressed by the obtuse angle formed at the corner between the blade back surface 03 and the blade end wall 05. 2
The development of the secondary flow loss region itself can be prevented, and the cascade loss due to the secondary flow loss region itself can be reduced.

As described above, in the low aspect ratio cascade of the present embodiment, both the loss caused by the secondary flow loss region itself and the additional loss generated by mutual interference between the secondary flow loss regions are simultaneously reduced. The cascade loss can be reduced, and the performance can be greatly improved.

[0027]

As described above, according to the low aspect ratio cascade of the present invention, the loss occurring in the secondary flow loss region itself and the blade height from the blade tip wall can be achieved by the structure shown in the claims. Both additional losses, which are caused by mutual interference of the secondary flow loss regions moving in the vertical direction, can be reduced, and a significant performance improvement can be achieved.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an axial distribution of a bow angle showing a first embodiment of the present invention,

FIG. 2 shows the cascade loss distribution in the blade height direction in the embodiment shown in FIG. 1, and the blade cascade loss distribution in the blade height direction in the conventional reverse bow cascade, forward bow cascade, and parallel cascade. Figure,

FIG. 3 is a three-dimensional view of a conventional forward bow cascade,

FIG. 4 is a wing height profile of the forward bow cascade shown in FIG. 3,

FIG. 5 is a schematic diagram of a static pressure distribution in a cross section of a flow path between blades of a forward bow cascade shown in FIG.

FIG. 6 is a three-dimensional view of a conventional reverse bow cascade,

FIG. 7 is a blade height direction shape diagram of the inverted bow cascade shown in FIG. 6;

[Explanation of symbols]

1,01 Low aspect ratio cascade 011 Forward bow cascade 012 Reverse bow cascade 013 Parallel cascade 02 Three-dimensional airfoil 03 Back of wing 04 Wing abdominal surface 05 Wing tip wall θ ₊ positive bow angle θ _- negative bow angle N wing End wall normal

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[Procedure amendment]

[Submission date] December 16, 1996

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0002

[Correction method] Change

[Correction contents]

[0002]

2. Description of the Related Art A three-dimensional airfoil root forming a cascade, or a loss generated in a loss region itself formed by the development of a vortex generated by a secondary flow generated at a blade tip near a blade tip. ,
In the low aspect ratio cascade where a large cascade loss occurs due to the additional loss caused by the loss area generated at the tip of both wings moving in the blade height direction and interfering with each other, it occurs in the loss area itself while reducing the blade row loss, it is important performance improvements reduce both blade cascade loss caused by additional losses.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0011

[Correction method] Change

[Correction contents]

In the reverse bow cascade 012 shown in FIGS. 6 and 7, as described above, the vicinity of the wing tip wall 05 with respect to the normal direction N of the wing tip wall 05, The inclination is inclined from the wing abdominal surface 04 side to the wing back surface 03 side, and the corner shape formed by the wing tip wall 05 and the wing back surface 03 is an acute angle. The formed loss region is less likely to move toward the blade height center. Therefore, in the reverse bow cascade 012, the low aspect ratio cascade 01 in which the secondary flow loss areas from both the blade end walls 05, 05 interfere with each other to generate a large cascade loss.
When used, the vortex, i.e. the secondary flow loss region is able to suppress the interference by moving the blade height the center direction, the effect of suppressing the increase of the additional losses due to interference.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction contents]

[0014] On the other hand the reverse bow blade row 012, as described above, the effect of acute corners shape formed by the tip wall 05 and the blade suction surface 03, vortices from both wings end wall 05 near the wing in the height center direction The movement is suppressed, and the movement
The additional cascade loss occurring near the center of the blade height, which reduces the interference between the secondary flow loss regions and increases due to the interference, is shown in FIG.
As shown in (1), there is an effect of reducing the loss as compared with the case of the parallel cascade 013, but there is no effect of reducing the loss itself caused in the loss region itself caused by the secondary flow.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0015

[Correction method] Change

[Correction contents]

Therefore, like the conventional forward bow cascade 011 and reverse bow cascade 012, a low aspect ratio in which the bow angles θ ₊ and θ ₋ are constant in the axial direction from the leading edge to the trailing edge of the blade. in the fly front row 01, to reduce by that loss to the secondary flow loss region itself,
At the same time, it is difficult to simultaneously prevent an increase in additional loss due to mutual interference in the secondary flow loss region. For this reason, the performance of the low aspect ratio cascade 01 has not been significantly improved so far. It is.

[Procedure amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0019

[Correction method] Change

[Correction contents]

In the low aspect ratio cascade according to the present invention, the three-dimensional airfoil according to the above-mentioned means (1) to (3) is arranged between the blade tip walls, so that the blade tip wall is formed. In the corner formed by the blade and the back of the blade, the inter-blade flow path formed by the back of the blade of the adjacent three-dimensional blade and the blade abdominal surface of the three-dimensional blade,
There is a vortex due to secondary flow from the upstream side, and as it flows downstream, this vortex moves toward the center of the wing height while developing greatly, but it has been set at the leading edge of the wing with a negative bow angle Therefore, in the area of the leading edge of the blade of the low aspect ratio cascade, the secondary flow loss area, which has not yet developed much, is used in this corner part by utilizing the acute corner shape formed by the blade back face and the tip wall. stemmed, suppress the movement of the blade height direction
And braking and more in the downstream side interfere with each other to prevent additional loss occurs, it is possible to reduce the blade cascade loss of the blade height direction central portion.

[Procedure amendment 6]

[Document name to be amended] Statement

[Correction target item name] 0024

[Correction method] Change

[Correction contents]

[0024] was provided around such a three-dimensional airfoil, the inter-blade passage low aspect wing column, the corner portion formed by the tip wall 05 and the blade suction surface 03, secondary flow from the upstream side Nari or As the vortex exists and flows downstream, the vortex moves toward the center of the wing height while developing greatly, and the loss caused by the wing tip wall 05 concentrates. Direction, but the bow angle at the leading edge of the wing is negative, so that in the region of the leading edge of the wing, the sharp angle formed by the wing back surface 03 and the wing tip wall 05 is still too small. The secondary flow loss area, which has not developed significantly, is stopped at this corner, and movement in the blade height direction is prevented.
It is possible to suppress the interference with each other on the downstream side to prevent the additional loss from occurring, thereby reducing the cascade loss at the center in the blade height direction.

Claims (1)

[Claims] 1. A two-dimensional airfoil is used for a steam turbine or a gas turbine, and is successively piled up while being inclined in a circumferential direction with respect to a normal direction of a blade tip wall, and has a concave or convex shape in a height direction of a blade surface. In a low aspect ratio cascade provided in a three-dimensional airfoil shape having a convex shape and smoothly changing in a height direction and an axial direction, a normal direction of the blade tip wall and the 3
The bow angle formed by the tangent in the height direction of the wing tip of the back of the three-dimensional airfoil has a negative angle at the leading edge of the blade, in which the tangent is inclined from the abdominal surface of the three-dimensional airfoil toward the back of the blade. In the trailing edge of the blade, the tangent line is inclined from the rear side of the blade toward the front side of the blade, and is formed in a curved surface that is monotonically and smoothly changed in the axial direction. A low aspect ratio cascade characterized in that the shape of the direction is concave near the leading edge of the wing and convex near the trailing edge of the wing.