JPH06212902A - Turbine moving blade - Google Patents

Abstract

PURPOSE:To restrict the growth of secondary eddy so as to improve the turbine performance by setting the tilt angles of the center lines of blade element sections within specified range, and setting the heights of the center lines of the blade element sections to specified dimensions. CONSTITUTION:With the center line 4 of blade element sections for connecting together the central points of respective blade elements from the bottom part to the top part of a moving blade 1, the portion from the bottom part to the blade-intermediate part is formed to be curved in the direction of the belly side 6 of the blade. And the portion from the blade-intermediate part to the blade-top part is shifted in the direction of the back side 7 of the blade, and the blade-intermediate part is formed to be curved in the belly side 6. When the tilt angle of the center line 4 of the blade element section at the blade bottom part relative to a reference line 5 is alphar, and the tilt angle of the blade element section at the blade top part to the reference line 5 is alphat, both angles alphar, alphat are set in the range of 2 deg. to 22 deg.. Further, the heights 1r, 1t of the center lines 4 of the blade element sections at the bottom and top parts of the moving blade 1 are set in the range of 0 to 35% relative to the total blade height (h). Thus, the growth of secondary eddy is restricted, the flow of working stream becomes smooth, in the blade-intermediate part and thus the turbine performance can be tremendously improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a turbine rotor blade applied to, for example, a super-large-sized axial flow turbine, and more particularly, to a boundary formed in a passage wall of inter-blade passages implanted in a row in a turbine rotor. The present invention relates to a turbine rotor blade that suppresses the development of a layer to prevent the generation of a secondary flow, further reduces the loss due to a secondary vortex generated by the disturbance of the secondary flow, and seeks a dramatic improvement in turbine performance.

[0002]

2. Description of the Related Art In recent years, power plants are required to dramatically improve turbine performance in order to save fuel such as oil and natural gas that produce working steam. Turbine paragraph loss is a factor that affects the performance. There is an improvement.

Turbine paragraph loss includes various types of loss such as airfoil loss, leakage loss, and outflow loss. In particular, loss due to a secondary flow generated in a flow path formed between blades through which working steam passes. Occupies a large proportion, and the loss due to this secondary flow is directly linked to the blade element shape of the turbine blade. For this reason, improvement of the blade element shape is indispensable to make the turbine performance leap. However, in the turbine rotor blade applied to the conventional super-large axial flow turbine, the blade having the blade element shown in FIG. 7 is used.

Reference numeral 1 indicates a moving blade, and a blade element cross-section center line 4 of this moving blade 1 (a line connecting the centers of the pieces when the moving blade is finely cut transversely) is linear from the top to the bottom. It has been formed. The bottom portion of the rotor blade 1 is integrally formed with the implant portion 2 and is molded as shown in the figure. The top portion of the rotor blade 1 is fitted with the shroud 3 and is caulked and fixed by the tenon 3a. ing. The turbine rotor blades having such a configuration are arranged in a row along the circumferential direction of the turbine rotor and form a part of a turbine stage.

Next, a mechanism for generating a secondary flow in the moving blade 1 forming a part of the above-mentioned turbine stage will be described with reference to FIG. 8 is a perspective view of the flow path formed between the moving blades shown in FIG. 7 as observed from the working steam outlet side.

[0006] When the working steam flows through the flow paths of the adjacent moving blades 1 and 1, the working steam is bent in an arc shape in the flow paths and flows. In this case, if a boundary layer develops at the entrance of the rotor blades 1 and 1,
The boundary layer collides with the leading edge of the rotor blade and a vortex is generated. This vortex is divided into left and right, and the vortex on the ventral side goes to the back side of the adjacent wing due to the pressing force according to the pressure gradient generated between the wings. The boundary layer formed on the wall surface between the blades moves from the ventral side to the dorsal side as indicated by the arrow due to the pressing force corresponding to the pressure gradient.

The secondary flow caused by such turbulence eventually grows into a passage portex or a counter vortex, pulls up the boundary layer on the back side and rolls up, forming a large vortex to block the passage. This is a factor that significantly reduces turbine performance.

The above-described secondary flow generating mechanism is one in which the adjacent blades are regarded as one block, and such a secondary flow occurs in the entire area of the turbine rotor arranged in rows in the circumferential direction. There is.

[0009]

By the way, considering the secondary flow generation for a moment, the flow passage formed between the blades has a finite width, and the blade element cross-section center of the blade is Due to the straight line from the top to the bottom, the flow path formed between the blades is rectangular when viewed from the blade outlet side, which is why there is no part for eddy energy dissipation or absorption. it seems to do.

Therefore, the present invention has been made to solve the problems of the prior art. By slightly improving the blade element cross-sectional shape, the present invention produces a flow path formed between rotor blades. The purpose is to announce the turbine blades that reduce the loss due to the secondary flow and improve the turbine performance.

[0011]

SUMMARY OF THE INVENTION According to the present invention, there is provided a rotor blade having a bottom portion integrally formed with an implant portion and having a shroud mounted on the top portion thereof.
In turbine rotor blades arranged in a row in the circumferential direction of the turbine rotor, the blade element cross-section center line that connects the center points of the blade elements from the bottom to the top of the rotor blade is With respect to the reference line extending radially from the center of rotation, the blade is formed in a straight line by inclining from the bottom and top of the blade toward the ventral side of the blade, and the blade element cross-section center line in the middle of the blade is A reference extending radially from the turbine rotor rotation center point of the blade element cross-section center line, which is formed in a curved shape in the ventral direction, while the height of the blade is h, and is straightened by inclining the bottom and top of the blade. The inclination angle to the line is α _r ,
Let α _t be the height of the blade element cross-section center lines that are inclined and straight at the bottom and top of the blade, and let _{r t} and l _t be 2 ° ≦ α _r and α _t ≦ 22 ° 0 ≦ The structure satisfies the relational expressions l _r and l _t ≤0.35.

[0012]

According to the turbine rotor blade having the above-described structure, the blade element cross-section center line connecting the center points of the blade elements from the blade bottom portion to the blade top is determined from the rotation center point of the turbine rotor in which the blade is planted. The working steam flowing into the vicinity of the blade bottom and the tip of the blade was straightened because it was tilted in the direction from the blade bottom and the tip of the blade toward the ventral side of the blade with respect to the radially extending reference line. The pressing force is applied by the surrounding wall. Therefore, the development of the boundary layer on both peripheral walls is effectively suppressed,
Furthermore, the secondary flow suppresses the growth of secondary vortices generated on the back side of the rotor blade.

Further, since the blade element cross-section center line in the middle portion of the moving blade is formed to be bent in the ventral direction, the working steam flowing into the portion smoothly changes, and no large disturbance occurs.

Therefore, in the turbine blade according to the present invention, the development of the boundary layer is suppressed and the growth of the secondary vortex accompanying the secondary flow is suppressed, but the flow of the working steam is not disturbed. Therefore, turbine performance can be significantly improved.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of a turbine rotor blade according to the present invention will be described with reference to the accompanying drawings FIGS.

FIG. 1 is a perspective view showing the structure of a turbine rotor blade according to the present invention, showing an example observed from the rotor blade outlet side. Further, FIG. 2 shows the shape of the blade element of the moving blade, and is a conceptual view seen from the outlet side of the moving blade. The same components as those of the conventional example shown in FIG. 7 are designated by the same reference numerals.

In the turbine rotor blade according to this embodiment, the implant portion 2 integrally formed on the blade bottom portion and the tenon 3 on the top portion thereof.
and a shroud 3 which is crimped and fixed by a. Each of the moving blades 1 is planted in the circumferential direction of the turbine rotor via the implanting portion 2, and the whole thereof is arranged in rows to form a group of annular blades.

Each moving blade 1 is, as shown in FIG.
The blade elements are stacked from the blade bottom toward the blade top, and the blade element cross-section center line 4 connecting the center points of the blade elements extends from the blade bottom to the blade intermediate portion in the direction of the ventral side 6 and the blade. The blade intermediate portion is formed to bend in the ventral side 6 by moving in the direction of the back side 7 from the intermediate portion toward the blade top. In addition, the center line of the blade cross section at the blade bottom / top 4
Is formed in a straight line by inclining with respect to the reference line 5 extending radially from the center of rotation of the turbine rotor, and the inclination angle of the blade element cross-section center line 4 at the blade bottom with respect to the reference line 5 is α _r , If the inclination angle of the center line of the blade element at the top with respect to the normal line 5 is α _t, both angles α _r and α _t are 2 °.
It is set in the range of ~ 22 °.

The height of the straight line of the blade element cross-section center line 4 at the blade bottom portion and the straight line of the blade element cross-section center line 4 at the blade tip portion projected on the reference line 5 is l _r ,
When l _t, against Ryotaka l _r, l _t wing Height h 0~3
It is set within the range of 5%.

In the turbine rotor blade according to this embodiment, since the center line 4 of the blade element cross section at the blade bottom / top is inclined toward the ventral side 6, the working steam flowing from the blade bottom / top is inclined by this inclination. Receive pressing force. Therefore, the wing bottom
It is possible to suppress the development of the boundary layer on the peripheral wall of the top portion, and also to suppress the secondary vortices that develop in the flow path formed between the adjacent wings.

Further, the blade element cross-section center line 4 at the blade intermediate portion 4
Bends in the direction of the ventral side 6, this bend smoothes the flow of the working steam, and no large disturbance occurs. As described above, in the turbine rotor blade according to the present invention, the loss in the flow path formed between the blades is reduced, and the turbine performance can be significantly improved.

Next, the size comparison of the Mach number distribution acting on the conventional moving blade and the moving blade according to the present invention will be described with reference to FIGS. 3 and 4. In FIG. 3, the abscissa represents the lengths of both the dorsal and ventral blade surfaces from the leading edge to the trailing edge of the blade element cross section, and the ordinate represents the Mach number at the blade top. Further, in FIG. 4, the horizontal axis represents the lengths of both the dorsal and ventral blade surfaces from the leading edge to the trailing edge of the blade element cross section, and the vertical axis represents the Mach number at the blade bottom. 3 and 4, the broken line indicates the Mach number acting on each blade surface length of the conventional blade, and the solid line indicates the Mach number acting on each blade surface length of the present invention. Show.

In FIGS. 3 and 4, the Mach number distribution acting on each blade surface length of the moving blade is the maximum of the difference between the dorsal side and the ventral side Mach number when the conventional example and this example are compared. The values of this embodiment are smaller in both the wing top (see FIG. 3) and the wing bottom (see FIG. 4) than in the conventional example, and the deceleration change of the Mach number at the trailing edge of the back side is also in this embodiment. Is smaller.

Here, there is a close causal relationship between the loss due to the secondary flow and the Mach number. That is, the smaller the loss due to the secondary flow, the smaller the pressure difference between the back side and the ventral side, that is, the Mach number difference. This relationship means that the smaller the Mach number difference between the dorsal side and the ventral side, the less the flow from the ventral side to the dorsal side, and such suppression of the flow suppresses the growth of the secondary flow vortex. If the deceleration change of the Mach number is small at the back edge of the back side, the development of the boundary layer is suppressed.

Accordingly, the turbine rotor blade according to this embodiment has a smaller Mach number difference between the back side and the ventral side than the conventional example, and the deceleration change of the Mach number at the rear end of the back side is also small. It can be said that it is superior to the wing performance.

In this embodiment, the difference in the Mach number distribution acting on the dorsal side and the ventral side at the blade bottom / top will be described, and the difference in the Mach number distribution acting on the dorsal side and the ventral side at the blade intermediate portion will be described. Although not described, the difference in the Mach number distribution in the blade middle portion of this embodiment is actually larger than that in the conventional example. However, since the blade element cross-section centerline 4 in the middle of the blade in this embodiment is curved in the direction toward the ventral side 6, even if the difference in the Mach number distribution increases in that portion, the loss due to the secondary flow. Has a small effect on turbine blade performance. Further, it will be explained that the turbine rotor blade according to the present invention has a good effect on the efficiency of the turbine stage.

5 and 6 are graphs showing that the turbine stage efficiency is improved. That is, FIG.
Is the turbine stage efficiency when the inclination angles α _r and α _t are set to 2 ° to 22 ° with respect to the reference line 5 extending radially from the center of rotation of the turbine rotor of the blade cross section centerline 4 at the blade bottom / top. Is a graph shown, where the vertical axis represents the paragraph efficiency η _i according to this embodiment with respect to the paragraph efficiency η ₀ of the conventional turbine rotor blade.
Shows the ratio (η _i / η ₀ ).

As can be easily understood from this figure, if the inclination angles α _r and α _t are selected within the range of 2 ° to 22 °, the turbine stage efficiency ratio η _i / η ₀ exceeds 1, which is a conventional value. It turns out that it is more effective than the example.

The inclination angles α _r and α _t are selected in the range of 2 ° to 22 ° in order to improve the turbine stage effect ratio (η _i / η ₀ ). When it is increased, while the loss at the blade outlet is reduced, the flow rate of the working steam at the relevant portion is increased, and the flow rate at the blade middle portion, which is originally excellent in performance, is reduced, and the overall turbine stage efficiency is: Rather, the decrease is one of the reasons. Further, in the case of a moving blade, the inclination angle cannot be increased because it is restricted in strength.

FIG. 6 shows a height l _r projected onto a reference line 5 extending radially from the rotation center points of the turbine rotors on both straight lines when the blade element cross-section center line 4 at the blade bottom apex is a straight line.
4 is a graph showing the effect of l _t on turbine stage efficiency, where the horizontal axis represents the inclination straight line ratio (l _r / h,
l _t / h), and the vertical axis represents the turbine stage efficiency η _i according to this embodiment with respect to the turbine stage efficiency η ₀ according to the conventional example.
The ratio (η _i / η ₀ ) is shown.

As can be seen in this figure, l _r / h, l
_It can be seen that when _t / h is within the range of 0.35, η _i / η ₀ exceeds 1, and the turbine stage efficiency is improved.

By the way, when l _r / h and l _t / h exceed 0.35, the straight line of the blade element cross-section center line 4 at the apex of the blade bottom becomes too long, and it becomes impossible to obtain the curvature which gives the middle portion of the blade a bend. The shape of the wing element is as if it were a V-shape. Therefore, the turbine rotor blade causes an unexpected loss due to its shape change. Therefore, the range of l _r / h and l _t / h within 0.35 is a preferable application example.

The inclination angle α _{r at} the bottom of the blade,
It is not necessary for both α _t or the blade height ratios l _r / h and l _t / h to have the same value, and different values may be selected by looking at the blade passing flow rate distribution characteristics of the working steam.

[0034]

As described above, according to the turbine rotor blade of the present invention, the blade blade cross-section center line connecting the center points of the blade blades from the blade bottom to the blade tip is planted. While forming a straight line by inclining in a direction from the blade bottom apex toward the ventral side of the blade with respect to a reference line radially extending from the rotation center of the turbine rotor, Since it is formed in a curved shape in the ventral direction of the blade, a pressing force is applied from the peripheral wall at the top of the blade bottom to the working steam, and the growth of secondary vortices accompanying the development of the boundary layer is suppressed. The smooth steam flow results in a dramatic improvement in turbine performance.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of a turbine rotor blade according to the present invention.

FIG. 2 is a conceptual diagram of a blade element shape observed from an outlet side of a turbine rotor blade according to the present invention.

FIG. 3 is a wing surface Mach number distribution at the wing top,
The graph which compares and shows the Example concerning this invention, and a prior art example.

FIG. 4 is a wing surface Mach number distribution at the wing bottom,
The graph which compares and shows the Example concerning this invention, and a prior art example.

FIG. 5 is a graph showing the relationship between the inclination angle of the blade element cross-section center line and the turbine stage efficiency ratio.

FIG. 6 is a graph showing the relationship between the height of an inclined straight line of the blade element cross-section center line and the turbine stage efficiency ratio.

FIG. 7 is a perspective view showing an example of a conventional turbine rotor blade.

FIG. 8 is a diagram illustrating a secondary flow generation mechanism.

[Explanation of symbols]

1 Moving Blade 2 Implanted Part 3 Shroud 4 Blade Cross Section Centerline 5 Reference Line Radially Extending from Rotation Center Point of Turbine Rotor 6 Ventral Side 7 Dorsal Side

Claims (1)

[Claims] 1. A turbine rotor blade in which a bottom portion is integrally formed with an implant portion and shrouds are attached to the top portion of the turbine rotor blades arranged in a row in a circumferential direction of a turbine rotor, from the bottom portion to the top portion of the rotor blade. The blade element cross-section center line that connects the center points of the blade elements is located from the bottom and top of the blade to the ventral side of the blade with respect to the reference line that extends radially from the center of rotation of the turbine rotor that implants the blade. Inclining in the direction to form a straight line,
The center line of the blade element cross section in the middle part of the blade is curved in the ventral direction, while the height of the blade is h, and the blade element cross section center is inclined and straight at the bottom and top of the blade. The inclination angles of the line with respect to the reference line extending radially from the turbine rotor rotation center point are α _r and α _t, and the height of the blade element cross-section center line which is inclined and straight at the bottom and top of the blade is l _r , L _t , satisfying the relational expressions of 2 ° ≦ α _r and α _t ≦ 22 ° 0 ≦ l _r and l _t ≦ 0.35.