JPH0777009A - Stator of axial flow turbomachine - Google Patents

Abstract

(57) [Abstract] [Purpose] The objective is to realize a low-loss vane in order to improve the performance of an axial-flow turbomachine. [Structure] A plurality of stator blades of an axial flow type turbomachine arranged in an annular flow path are configured so that an axial inclination angle δ is changed in a radial direction so as to be arcuate in a meridian plane. [Effect] By inclining the stationary blade in the axial direction, the blade surface from the bent portion of the stationary blade to the downstream side has a flow path shape that presses the flow in the side wall direction. As a result, it is possible to realize the inter-blade flow that suppresses the secondary flow vortices generated in the boundary layer that develops on the side wall and the inter-blade flow path. Moreover, the effect of suppressing the secondary flow vortices generated in the boundary layer that develops on the side wall and the inter-blade flow path occurs without significantly affecting the outflow angle.
As a result, it is possible to realize a vane of an axial flow turbomachine with low loss.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stationary blade of an axial flow turbomachine such as a steam turbine, a gas turbine and an axial compressor.

[0002]

2. Description of the Related Art As a conventional technique for improving the internal flow of a paragraph by changing the structure of the vane, for example, in order to reduce the loss due to the secondary flow vortex generated in the internal flow of the vane, the vane is There is an arched shape that is symmetric in the central portion in the span direction when viewed from the axial direction. For this, see ASME P
aper No.90-GT-55 report title "The In
fluence of Blade Lean on Turbine Losses ”. Further, a stator blade having an asymmetrical bow shape when viewed from the axial direction is disclosed in Japanese Patent Application No. 2-67115. These conventional techniques are effective in reducing the loss due to the secondary flow vortices, but since the outflow angle of the stationary blade deviates largely from the design value, there arises a problem that the incident angle to the moving blade becomes large. Therefore, in order to further improve the performance of the axial-flow turbomachine, a high-performance vane structure in which the outflow angle of the vane does not greatly deviate from the design value is required.

[0003]

Generally, in the inter-blade flow of an axial flow type turbomachine, a secondary flow vortex is generated as a three-dimensional flow phenomenon due to the viscosity of the fluid. In other words, when a boundary layer flow with a low flow velocity that develops on the side wall that supports the stationary blades and rotor blades and a main flow part with a low flow velocity that does not affect the flow velocity are deflected by the blades, the centrifugal force acting on the fluid causes a difference in radial direction. A flow is generated, which results in the formation of a pair of vortices in the inter-blade flow.
Since this secondary flow vortex causes loss, it is desirable to prevent it as much as possible. It is a well-known fact that this secondary flow vortex can be mitigated by, for example, suction of the sidewall boundary layer, but it is not realistic to apply it to an actual turbomachine because of its complicated structure. It is an object of the present invention to provide a vane structure for reducing a loss due to a secondary flow vortex generated in such an inter-blade flow and realizing a high performance turbomachine.

[0004]

The first object of the present invention is to change the axial inclination angle δ of a stationary blade of an axial flow type turbomachine in a radial direction so that the stationary blade has a bow shape protruding toward a blade leading edge in a meridian plane. It is characterized in that here,
The axial tilt angle δ is an angle formed by the blade leading edge tangent line at each radial position and a line passing through the leading edge perpendicular to the rotation axis.

The second aspect of the present invention is to provide an axial inclination angle δ of the above vane.
The radial distribution of is set so as not to be symmetric with respect to the central part of the blade span, and the arched shape of the stationary vanes is viewed in the meridian plane, and is not symmetrical with respect to the central part of the blade span. is there.

In the third aspect of the present invention, the maximum displacement amount is in the range of 0 <F / H <0.2, where H is the blade length, and F is the maximum displacement of the axial arch shape from the axial position of the blade root on the meridian plane. It is characterized by having an arched shape.

[0007]

[Function] If the radial distribution of the axial inclination angle δ of the stationary blade is distributed so as to have an arched shape protruding toward the leading edge of the blade, the flow is pressed toward the side wall and the inclination in the circumferential direction is reduced. Since it does not exist, it is possible to suppress the development of the sidewall boundary layer and to reduce the secondary flow vortices generated in the blade-to-blade flow without significantly changing the outflow angle. That is, focusing on the blade shape near the side wall, when the radial distribution of the axial inclination angle δ is distributed so as to have an arched shape protruding toward the blade leading edge direction, the blade surface downstream from the curved portion of the blade is Will incline toward the upstream side from the side wall to the central portion, and will form a flow path shape that presses against the flow in the side wall direction. This flow channel shape pushes the flow toward the side wall with almost no deflection of the outflow angle, so while suppressing the development of the side wall boundary layer while maintaining the outflow angle of the vane outflow part, it occurs in the inter-blade flow. It produces the action of reducing the secondary flow eddies. Further, as described above, since the deviation of the outflow angle of the stationary vane portion is small, the flow can be guided to the moving blade at the designed outflow angle, so the incident angle to the moving blade portion becomes small, and Does not lead to an increase in the angle of attack loss.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIG. FIG. 1 is a view of the vane of the present invention viewed from the meridian plane. As is apparent from FIG. 1, the radial distribution of the inclination angle δ in the axial direction is distributed so as to have an arched shape protruding in the direction of the blade leading edge 4. Here, the axial inclination angle δ is an angle formed by the tangent line of the blade leading edge at each radial position and a line passing through the leading edge perpendicular to the rotation axis as shown in FIG. In order to show the change of the flow path shape according to FIG. 1, FIG. 2 shows the blade surface inclination when the stationary blade is moved to the upstream side as it is separated from the side wall. As shown in FIG. 1, by making the radial distribution of the axial tilt angle δ into an arched shape that projects toward the blade leading edge direction, the blade surface from the bent portion of the stationary blade to the downstream side is The flow path shape is such that it is pressed in the side wall direction. As a result, it is possible to realize the inter-blade flow that suppresses the secondary flow vortices generated in the boundary layer that develops on the side wall and the inter-blade flow path. Moreover, the arcuate shape protruding toward the blade leading edge can suppress the development of the secondary flow vortices generated in the sidewall boundary layer and the blade-to-blade flow passage without significantly affecting the outflow angle. As a result, the flow loss distribution generated in the vanes is reduced as shown in FIG. In FIG. 3, a is a conventional vane which is not a bow-shaped vane, b is a vane of the present invention which is bow-shaped in the axial direction, and c is a known bow in the circumferential direction. This is the loss distribution in the blade length direction when it is shaped. As is clear from FIG. 3, the vane loss of the present invention is smaller than that of the conventional vane, and is comparable to the case of the arcuate shape in the circumferential direction. FIG. 4 is a view showing the distribution of the outflow angle of the stationary blade outflow portion in the blade length direction, where a is a conventional stationary blade having no arched shape, and b is a stationary blade of the present invention in the axial direction. In the case of the arched shape, c is the outflow angle distribution in the blade length direction when the arched shape is formed in the circumferential direction, which is a known technique. In the stationary blade having the arched shape only in the circumferential direction of c, the outflow angle distribution of the stationary blade of the conventional stationary blade having no arched shape is significantly different from that of the stationary blade of the present invention of b. The outflow angle distribution has a smaller deviation from the outflow angle distribution of the conventional vane than that in the arcuate shape in the circumferential direction of c. The flow loss can be reduced while keeping the angle almost the same as the outflow angle of a conventional vane.

In an actual inter-blade flow of an axial turbomachine,
The upper half flow and the lower half flow do not become symmetrical in the central part of the blade span direction. In addition, depending on the flow conditions in the upstream paragraph, a flow with a large loss may appear near the root, or conversely, a flow with a large loss may appear near the tip. An embodiment of the present invention for coping with such a flow will be shown below.

A second embodiment of the present invention is shown in FIG. The present embodiment is designed to deal with the case where the side wall boundary layer at the blade root portion and the secondary flow are large, and FIG. 5 shows the vane of the present invention viewed from the meridional plane, as in FIG. It is a figure. Figure 5
As shown in Fig. 5, when the sidewall boundary layer at the blade root and the secondary flow are large, the overall tilt-blade flow performance is improved by increasing the axial tilt angle in the blade root direction. be able to.

FIG. 6 shows a third embodiment of the present invention. This embodiment is designed to deal with the case where the side wall boundary layer at the tip of the blade and the secondary flow are large, and FIG. 6 shows the vane of the present invention when viewed from the meridional plane, as in FIG. It is a figure. Figure 6
As shown in Fig. 4, when the sidewall boundary layer at the blade tip and the secondary flow are large, the overall tilt-blade flow performance is improved by increasing the axial tilt angle in the blade tip direction. can do.

The embodiments of the present invention have been described above. However, when the invention is applied to a stationary blade of an actual axial flow type turbomachine, there is an appropriate limit to the size of the bow-shaped convex portion. Considering the stationary blade of the present invention as shown in FIG. 7, the blade length is H, and the maximum displacement of the axial bow shape from the axial position of the blade root on the meridian plane is F. FIG. 8 shows the relationship between F / H and loss.
If 0 <F / H <0.2, the flow loss can be reduced as compared with the case of the conventional blade with F = 0. From this result, the range in which the effects of the present invention are exhibited can be defined as 0 <F / H <0.2. If a value of F that exceeds the above range is used,
On the contrary, the flow loss increases as compared with the case of F = 0 since the three-dimensional flow path shape cannot perform the predetermined blade function.

The above-mentioned bow shape is generally composed of a curved line, but even if the bow shape is approximated by a plurality of straight line groups for the purpose of simplifying the manufacture, a curved line is formed. It is possible to generate the same function as in the case of configuration. An example thereof is shown in FIG. FIG. 9 shows a case where the bow shape is approximated by two straight lines.

[0014]

According to the present invention, the radial distribution of the inclination angle δ in the axial direction is distributed so as to have an arcuate shape protruding toward the leading edge of the blade, so that the flow is pressed against the side wall side and further flows out. It is possible to suppress the development of the sidewall boundary layer and reduce the secondary flow vortices generated in the inter-blade flow without significantly changing the angle.

[Brief description of drawings]

FIG. 1 is a view of a vane of the present invention viewed from a meridian plane.

FIG. 2 is a view showing a blade surface inclination when the stationary blade moves to the upstream side as it separates from the side wall.

FIG. 3 is a comparative diagram of a flow loss distribution generated in a stationary blade.

FIG. 4 is a comparison diagram of the vane outflow angle distribution.

FIG. 5 is a view of the vane of the present invention as viewed from the meridian plane.

FIG. 6 is a view of the vane of the present invention as seen from the meridian plane.

FIG. 7 is a dimensional explanatory view of the present invention.

FIG. 8 is a diagram showing a relationship between F / H and loss.

FIG. 9 is a diagram showing another embodiment of the present invention.

[Explanation of symbols]

1 ... Upper diaphragm, 2 ... Lower diaphragm, 3 ... Static vane, 4 ... Static vane leading edge, 5 ... Static vane trailing edge, 6 ... Flow direction, 7 ...
A vane on the side wall, 8 ... A vane at a position away from the side wall.

Claims (4)

[Claims] 1. A stator blade of an axial flow type turbomachine, wherein a plurality of stator blades are arranged in an annular flow path, wherein an axial inclination angle δ of the stator blade is changed in a radial direction so that a shape of the stator blade on a meridian plane is changed. Stator blade A stator blade for an axial-flow turbomachine characterized by having an arcuate shape that protrudes toward the leading edge direction. 2. In a stationary blade of an axial flow type turbomachine arranged in a plurality of annular passages, the radial distribution of the axial inclination angle δ of the stationary blade is not symmetrical with respect to the central portion of the blade span. The stator vane of an axial-flow turbomachine according to claim 1, wherein even if the arched shape of the vane is viewed from the meridional plane, the vane is not symmetrical with respect to the central portion of the blade span. 3. The maximum displacement amount according to claim 1, wherein the blade length is H, and the maximum displacement of the axial bow shape is F from the axial position of the blade root in the meridian plane, and the maximum displacement amount is 0 <F / H <0. A stator blade for an axial-flow turbomachine characterized in that 4. A stator blade for an axial-flow turbomachine according to claim 1, 2 or 3, wherein the arched stator blade shape is formed by approximating a plurality of straight line groups.