JPH0454203A - Turbine rotor blade and turbine cascade - Google Patents

Abstract

PURPOSE:To reduce the profile loss at a rotor blade by forming the rotor blade so that the angle of the inlet part of the rotor blade is continuously reduced from the root part to the center part of the rotor blade and is then continuously increased from the center part to the tip end part of the rotor blade so as to adjust the angle of the inlet part thereof to the relative angle of working fluid discharged from static vanes having an inclined angle. CONSTITUTION:A turbine rotor blade is formed in a shape so as to have a root cross-section R-R, a center cross-section P-P and a tip end cross-section T-T. As for the center cross-section, the angle of the inlet part of the blade is set to beta'1P which is smaller than the angle beta1P of a center part of a conventional rotor blade which is shown by the chain line, in order to adjust the inlet part angle to the relative outlet angle of working fluid discharged from static vanes, and as for the root and tip end cross-sections, the angles of the inlet part are set to beta1R and beta1P, which are equal to those of the conventional rotor blade. Further, the angle xsi1 of the inlet part of the rotor blade is continuously and smoothly reduced from the root part to the center part of the rotor blade and is then continuously and smoothly increased from the center part to the tip end part thereof.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a turbine rotor blade of an axial flow turbine, and in particular, to reducing energy loss occurring in the turbine rotor blade and improving turbine performance. The present invention relates to turbine rotor blades obtained.

(Conventional technology) In recent years, the operating economics of five power plants have been improved.

Improving turbine performance has become an important issue in order to improve power generation efficiency.

In general, an axial flow turbine consists of a stator blade 3 fixed by a stator blade outer ring 1 and a stator blade inner ring 2, and a rotating shaft 4, as shown in FIG.
A stage is formed by the rotor blades 5 fixed to the rotor blades 5, and the stage is constructed by combining one stage or a plurality of stages in the axial direction.

In order to improve turbine performance, it is important to reduce internal energy loss as much as possible in the turbine stage configured as described above. Internal energy losses in the turbine stage include airfoil loss, secondary flow loss, leakage loss, etc. occurring within the static and rotor blades. Conventionally, an effective measure to improve stage performance has been to reduce secondary flow loss in stator vanes, especially when the aspect ratio is small and the stator vane height is low. The mechanism of secondary flow loss generation will be explained with reference to FIG. FIG. 5 is a perspective view of the stator vane 3 shown in FIG. 4, observed from the exit of the stator vane 3. The working fluid flows through the adjacent stationary blades 3a.
, 3b when flowing through the interblade flow path.

It flows in an arc shape in the flow path. At this time, the stationary blade 3a
A centrifugal force is generated from the back surface 6 toward the ventral surface 7, and this centrifugal force and static pressure are in balance, so the static pressure on the ventral surface 7 is high, while on the back surface 6, the flow velocity of the working fluid is high, so the static pressure is low. Therefore, a pressure gradient is generated in the flow path from the ventral surface 7 side to the back surface 6 side. This pressure gradient is the same in the slow flow layer, that is, the boundary layer, formed on the peripheral wall surfaces of the stator blade outer ring 1 and the stator blade inner shaft 2.

However, near the boundary layer, the flow velocity is low and the centrifugal force acting is also small, so the flow from the ventral surface 7 side to the back surface 6 side cannot resist the pressure gradient from the ventral surface 7 side to the back surface 6 side, that is, the secondary flow 8 occurs. Then, this secondary flow 8 collides with the back surface 6 side of the stator blade 3a and is rolled up.
Secondary flow vortices 9a and 9b are generated at both joint ends on the inner shaft 2 side and the outer shaft 1 side, respectively. In this way, the energy held by the working fluid is partially dissipated to form secondary flow vortices 9a and 9b, resulting in secondary flow loss.

By the way, a general rotor blade design method will be explained with reference to FIGS. 6 and 7. FIG. 6 is a cross-sectional view taken along the line A-A shown in FIG. 4, and FIG.
It is a superimposed view of a cross section and a T-T cross section.

As a design method for rotor blades, when the ratio of the rotor blade root diameter to the rotor blade tip diameter (boss ratio) is relatively small, the airfoil shape is designed on the average diameter of the rotor blade, and the blade is shaped in the radial direction. The rows are stacked to form moving blades. However, as the boss ratio increases, a three-dimensional design takes into account the flow velocity and radial distribution of the flow angle of the working fluid. In the three-dimensional design method, first, a two-dimensional airfoil is designed with several arbitrary radial cross sections, and a three-dimensional airfoil is formed by stacking these pieces in the radial direction. Considering the two-dimensional cross-sectional shape shown in FIG. 6, the working fluid flowing out from the stationary blade 3 has an angle of α degree and a flow velocity C. Furthermore, since the rotor blade 4 is rotating at the circumferential speed U together with the rotation axis, the working fluid flowing out from the stationary blade 3 flows into the rotor blade 4 at a relative inflow angle β. The airfoil shape on the two-dimensional cross section is designed to match the above-mentioned relative inflow angle β. If this is designed at each arbitrary radius cross section, as shown in Fig. 7, the relative inflow angle β1R is from the R-R cross section, which is the rotor blade root cross section, to the rotor blade tip cross section T-T cross section. Since it increases continuously from β to T, the rotor blade shape becomes a corresponding airfoil shape. A three-dimensional shape is formed by stacking these airfoils successively in the radial direction.

Japanese Patent Laid-Open No. 1-106903 discloses an example in which turbine performance is improved by combining a stator vane that reduces the secondary flow loss of the stator vane described above and a three-dimensionally designed rotor blade. FIG. 8 is a cross-sectional view of a stationary blade of a conventional example, viewed from the downstream side in the axial direction. According to this, the axes at both joint ends of the stator blade 3 are formed on a straight line, and the joint ends are formed so that the axis line is inclined toward the ventral surface of the stator blade 3 with respect to a reference line passing through the turbine rotation center. In addition to being joined, the stator blade 3 is configured such that its axis at the intermediate portion is curved in the ventral direction. By configuring the stator blade 3 in this way, the streamlines observed from the meridian plane are deviated in the radial direction near the stator blade outer ring 1 and the stator blade inner axis 2, as shown in FIG. The deviation of this streamline is the stator blade outer ring 1 and the stator blade inner ring 2.
This means that the nearby working fluid is pressed against the flow wall surface.

Therefore, the development of boundary layers on both wall surfaces is suppressed, and the generation of secondary flow vortices is prevented.6 According to the above patent publication, the axis and reference line at both joint ends of the stationary blade 3 shown in FIG. This shows that the turbine stage efficiency changes depending on the inclination angle θ. that's the first
Shown in Figure 0. In this figure, the vertical axis shows the efficiency ratio (ηb/ηa) of the turbine stage with the stator blade axis facing the reference line (θ=O), and the horizontal axis shows the inclination angle between the axis and the reference line at both joint ends of the stator blade. θ is taken. As shown in FIG. 10, there is an optimum angle θ1 of inclination angle θ at which the turbine stage efficiency is maximized, and the turbine stage efficiency is directed.

(Problems to be Solved by the Invention) In order to understand the characteristics of a single stator vane, it is common practice to measure the total pressure loss through experiments. FIG. 11 shows the total pressure loss of the stator vane when the inclination angle θ of the stator vane is changed in a conventional example.

According to this, compared to the inclination angle θ□ at which the turbine stage efficiency is the highest, the total pressure loss is smaller at the inclination angle θ2, which is larger. In other words, the performance of the stator vane alone is shown to be better as the inclination angle is larger. Nevertheless, as shown in FIG. 10, when looking at the turbine stage efficiency ratio, the stage performance is poor when the stator blade inclination angle is θ2.

The reason why the performance of a single stator vane differs from the stage performance when a stator vane and rotor blade are combined will be explained with reference to FIGS. 12 and 13. FIG. 12 is a diagram showing the difference in the relative inflow and outflow angles between the moving blade and the stationary blade, with the vertical axis representing the blade height and the horizontal axis representing the relative inflow angle β.

According to this, the rotor blade inlet angle β according to the conventional three-dimensional design
1 and the inclination angle θ2, the relative flow height angle β2 of the working fluid flowing out from the stationary blade has a large difference near the center of the blade height. This angular difference has a large effect on the airfoil loss in the rotor blade. Regardless of whether the blade is a stator vane or a rotor blade, it is generally known that airfoil shape loss increases if the actual working fluid inflow angle differs from the designed intake port angle. In particular, since the moving blade has a pointed tip, this is a significant increase compared to the stationary blade. FIG. 13 shows the increase in airfoil loss of the rotor blade due to the above-mentioned difference in inlet angle. The airfoil loss internal loss when there is no difference in the relative outflow angle of the stator blade and rotor blade and the rotor blade inlet angle is shown by the dotted chain line as ``airfoil loss of the rotor blade by conventional three-dimensional design.'' . However, when the stator blade inclination angle θ2 is used, the airfoil loss of the rotor blade increases significantly around the center of the blade height, as shown by the solid line.

In the figure, the area indicated by diagonal lines is the increased loss in the entire rotor blade. Therefore, although the stator blade having the inclination angle θ2 has excellent performance as a single stator blade, there is a problem in that the airfoil loss in the rotor blade increases and the stage performance deteriorates.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a turbine rotor blade that can reduce airfoil loss in the rotor blade and improve turbine performance.

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a rotor blade with an inlet angle of the rotor blade, which is adjusted to the relative outflow angle of the working fluid of the stator blade having an inclination angle θ, from the base portion of the rotor blade. It is characterized by being formed so that it decreases continuously toward the center of the rotor blade, and continuously increases from the center of the rotor blade to the tip of the rotor blade.

(Function) According to the turbine rotor blade having the above configuration, the rotor blade inlet angle is continuously adjusted from the root portion of the rotor blade to the center portion of the rotor blade in accordance with the working fluid relative flow height angle of the stator blade having the inclination angle θ. By decreasing the angle and continuously increasing it from the central part of the rotor blade to the tip of the rotor blade, it becomes possible to match the inlet angle of the rotor blade to the relative outflow angle of the working fluid of the stationary blade having an inclination angle θ. As a result, the airfoil loss in the rotor blade, which has conventionally occurred due to the difference between the relative outflow angle of the working fluid and the rotor blade inlet angle, is reduced.

As described above, according to the present invention, airfoil loss in the rotor blades is reduced and turbine performance can be significantly improved.

(Embodiment) Next, an embodiment of the present invention will be described with reference to the accompanying drawings FIGS. 1 to 3.

The turbine rotor blade according to the present invention has a rotor blade 4 root section (R-R cross section) similar to the conventional turbine stage shown in FIG.
The description will be given using a cross section at the center of the rotor blade 4 (PP cross section) and a cross section at the tip of the rotor blade 4 (T-T cross section). FIG. 1 is a diagram in which various surfaces of the turbine rotor blade of the present invention are superimposed. In the turbine rotor blade according to this embodiment, the rotor blade inlet angle of the rotor blade center cross section (P-P cross section) is adjusted according to the relative outflow angle of the working fluid flowing out from the stator blade, as shown by the broken line in the figure. The rotor blade center angle β
βxP is decreased from 1P, and the rotor blade root cross section (R-
The rotor blade inlet angle βIRI β□P is the same as the conventional rotor blade inlet angle (R cross section) and rotor blade tip cross section.

FIG. 2 shows the rotor blade inlet angle distribution in the blade height direction according to the present invention. The rotor blade inlet angle β according to the present invention is shown by a solid line, and the rotor blade inlet angle β according to the conventional three-dimensional design is shown by a dashed line. According to the present invention, the rotor blade inlet angle β: decreases continuously and smoothly from the root of the rotor blade toward the center of the rotor blade, and decreases continuously and smoothly from the center of the rotor blade toward the tip of the rotor blade. , has a structure that increases smoothly.

In the turbine rotor blade according to this embodiment, the relative flow angle of the working fluid flowing out from the stator blade matches the turbine rotor blade inlet angle, and the rotor blade is caused by the difference between the relative flow angle of the working fluid and the rotor blade inlet angle. The increase in airfoil loss can be eliminated.

In a turbine stage that eliminates this increase in loss in rotor blades, as shown in Figure 3, when using θ2, which is superior to a single stationary blade, the stage efficiency can be significantly improved compared to conventional stages. .

〔Effect of the invention〕

As explained above, by using the rotor blade according to the present invention, the one-stage efficiency can be significantly improved and the turbine performance can be improved.

[Brief explanation of drawings]

Fig. 1 is a superimposed cross-sectional view of a turbine showing an embodiment of a turbine rotor blade according to the present invention, Fig. 2 is an inflow angle distribution diagram of a rotor blade according to the present invention, and Fig. 3 is a diagram showing an inflow angle distribution diagram of a rotor blade according to the present invention. An efficiency graph comparing the stage and conventional stage, Fig. 4 is a top view of a conventional turbine stage passage, Fig. 5 is a perspective view showing the structure of a conventional turbine stationary blade, Fig. 6 is a sectional view of the stationary and rotor blades, Fig. 7 is a cross-sectional view of a conventional rotor blade, Fig. 8 is a sectional view of a conventional stator blade viewed from the outlet side, Fig. 9 is a sectional view showing working fluid streamlines in a conventional stage, and Fig. 10 is a conventional example. 11 is a graph showing the relationship between the inclination angle θ and the total pressure loss of the stator blade. FIG. FIG. 13 is a graph showing the relationship between airfoil loss and blade height in a conventional rotor blade. ■...Stator blade outer shaft, 2...Stator blade inner ring 3...
Stationary blade 4... Rotating shaft 5... Moving blade
6. Stator blade dorsal side 7... Stator blade ventral side 8
...Secondary flow 9a, b...Secondary flow vortex agent Patent attorney Nori Ken Yu Chika Go to Figure 1-b, 14 Ryoho θCtLe3. ) Figure W-Jump ζ A1! Yano

Claims (2)

[Claims] (1) In the turbine rotor blades that make up the axial turbine stage, the rotor blade inlet angle is continuously decreased from the rotor blade root portion to the rotor blade center portion, and continuously decreased from the rotor blade center portion to the rotor blade tip portion. A turbine rotor blade characterized in that it is formed so as to increase in size. (2) A plurality of stator vanes arranged in the circumferential direction with a predetermined inclination angle with respect to the radial direction, and a plurality of stator vanes arranged in the circumferential direction downstream of the stator vanes with an inclination angle that matches the relative outflow angle from these stator vanes. A turbine stage of an axial flow turbine having rotor blades.