JPH0527201U - Axial turbine - Google Patents

Abstract

(57) [Summary] [Structure] A moving blade used in combination with a stationary blade that is curved or linearly inclined in the circumferential direction has a discharge angle α closer to the root and tip than the discharge angle at the center. It is formed so as to gradually and continuously decrease toward both ends. That is, the outflow angle α is a predetermined height h ₁ from the root end.
And a twist is added so as to gradually decrease from the position h ₂ lower than the tip end to the tip end. [Effect] Since the radial flow in the moving blade can be suppressed and the flow at the outlet of the moving blade can be optimized, the efficiency of the turbine can be improved.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a paragraph structure of an axial turbine.

[0002]

[Prior Art]

 For example, in large-capacity steam turbines, improvement of efficiency is an important research issue, and in particular, the improvement of efficiency in the low-pressure stage is becoming more important as the capacity increases. However, the elucidation or improvement based on the three-dimensional flow of the steam flow in the low pressure stage of the steam turbine has not been sufficiently made.

FIG. 4 shows the meridional shape of the final stage of a low pressure turbine with a flare angle (the angle at which the stator vane diaphragm outer ring expands downstream to increase the flow passage area). A stationary blade 1 and a moving blade 2 are provided in a flow path of a working fluid, and the stationary blade 1 is held by a diaphragm outer ring 3 and a diaphragm inner ring 4 which form the flow path. The rotor blade 2 is attached to a disk 7 of a rotating rotor 5. When the flare angle of the stationary blade is large, the flow flowing into the rotor blade 2 has a radial velocity component, and the radial velocity component is accelerated by centrifugal force in the rotor blade, but the work done by the rotor blade is increased. Is independent of the radial velocity component, and the radial velocity component is lost as it is. Conventionally, as a countermeasure, when the flare angle of the low-pressure turbine is large, as described in JP-A-62-170707, a method of forming the stationary blade trailing edge 6 into various shapes in the rotating direction of the moving blade has been performed. It was For example, as shown in FIG. 5, the inclination angle in the circumferential direction is inclined toward the rotor blade rotation direction at the root of the stator blade, and the inclination angle is reduced toward the tip of the stator blade. Attempts have been made to tilt it in the opposite direction.

[0004]

[Problems to be solved by the device]

 The above-mentioned prior art is intended to improve the radial flow pattern in the paragraph having a large flare angle by the stationary blade shape, and no special consideration is given to the moving blade.

FIG. 6 shows the distribution of the axial flow velocity of the steam flowing out from the rotor blade 2 in the blade length direction. The flow is pressed toward the root and the tip side by the compound circumferential inclination angle of the stator blade in FIG. As a result, the axial flow velocity Va at the blade outlet is faster than the average value at the root and tip, and slower at the center. The axial flow velocity Va at the blade outlet is preferably a uniform flow in the radial direction in terms of performance. In particular, it is important to suppress radial flow at the root of the blade and separation flow at the root in extreme cases, but increasing the amount of steam flowing at the root of the blade is not a good performance measure. . This is because the root of the blade 2 has a large airfoil cord length, and since the turning angle of the flow is large, the airfoil loss is large, and the flow rate at this root is increased to increase the load ratio at the root. Doing this is not a good idea in terms of overall paragraph performance.

The phenomenon shown in FIG. 6 is due to the flow being pressed to the root side and the tip side by the circumferential inclination angle of the stationary blade. Furthermore, at the tip, the flow was biased toward the outer periphery due to the centrifugal force in the blade. This is because the rotor blade is designed so that the circumferential tilt angle of the conventional stator blade is not taken into consideration despite the fact that the flow is pressed to the end.

An object of the present invention is to provide a turbine stage structure that suppresses radial flow in the rotor blade and uniformizes the axial flow velocity at the outlet of the rotor blade to improve the stage performance.

[0008]

[Means for Solving the Problems]

 In order to achieve the above object, the present invention twists a blade in a direction in which the outlet angle of the moving blade end is suddenly reduced from a predetermined height toward the end, in combination with a stationary blade inclined in the circumferential direction. Characterized by an octopus.

[0009]

[Action]

 The present invention has an inclination angle in the circumferential direction of the stationary blade to press the flow at the root of the stationary blade toward the root of the moving blade to suppress the outward radial flow of the moving blade and Since the minimum flow passage width (throat width) between adjacent blades is continuously and sharply narrowed in the section, it is possible to reduce the amount of steam flowing out from the root portion of the blade and to reduce the axial flow velocity.

In addition, the inclination angle of the stationary blade in the circumferential direction is reduced toward the tip portion of the stationary blade, and sometimes the tip portion of the stationary blade is tilted in the direction opposite to the rotating direction of the moving blade to operate the stationary blade tip portion. This facilitates the flow of fluid, suppresses the outward radial flow at the blade tip, and continuously and suddenly narrows the minimum flow channel width (throat width) with the adjacent blade at the blade tip. It is possible to reduce the amount of steam flowing out from the blade tip and reduce the axial flow velocity.

This makes it possible to make the outflow angle of the steam flowing out from the root portion and the tip portion of the moving blade proper and to eliminate the nonuniformity of the amount of steam flowing between the root portion and the tip portion.

[0012]

【Example】

FIG. 1 shows a rotor blade row when the present invention is applied. The rotor blade 2 changes substantially linearly between the tip end position 9 of the rotor blade trailing edge 8 and the root position 10. The blade shape is twisted so that the throat width decreases from the position of the tip 9 of the moving blade toward the tip, and the throat width is twisted so that the width of the throat decreases from the position of the root 10 toward the root. It is twisted. FIG. 2 shows the distribution of the geometrical outflow angle α of the rotor blade according to the present invention in the blade length direction in comparison with the distribution according to the conventional method. Due to the twisting of the blade, the geometrical outflow angle α continuously decreases suddenly from the position h ₂ from the tip compared to the conventional blade compared to the conventional blade. The position of h ₂ is near the radial position of the intersection 12 between the inlet end 11 of the stationary blade 1 and the diaphragm outer ring wall shown in FIG. On the other hand, the geometrical outflow angle α continuously decreases sharply from the conventional blade toward the end from the position h ₁ from the root. Further, the position of h ₁ is set to a dimensionless blade height h / H = about 0.1 to 0.3. On the contrary, the geometrical outflow angle α is slightly larger in the central portion of the blade length than in the conventional blade.

FIG. 3 shows the axial flow velocity distribution of the steam flowing out from the rotor blade when the paragraph structure of the present invention is applied. Compared with FIG. 6, the axial flow velocity at the root portion and the tip portion is shown. There is almost no increase in and the axial velocity is uniform.

The embodiment of the present invention is the case where the inclination of the trailing edge 6 of the stationary blade shown in FIG. 5 changes in a curve. In the case of the stationary blade shown in FIG. 7 in which the inclination of the trailing edge of the stationary blade changes linearly, the axial velocity distribution at the blade outlet may be large only at the root portion as shown in FIG. In this case, the geometric outflow angle α may be reduced only on the root side as shown in FIG.

[0015]

[Effect of the device]

 According to the present invention, the radial outward flow is suppressed in the moving blades of the turbine stage where the flow passage area expands to the downstream side, and the outflow angle of the fluid flowing out from the moving blades near the inner and outer wall surfaces is controlled appropriately. To reduce the flow rate near the inner and outer wall surfaces, where the airfoil loss is relatively large, and to increase the flow rate in the center of the blade, where the loss is relatively small. The efficiency of the axial flow turbine can be improved because it can be converted to.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a rotor blade row according to an embodiment of the present invention.

FIG. 2 is a distribution diagram of geometrical outflow angles of moving blades.

FIG. 3 is an axial flow velocity distribution diagram at the blade outlet when the paragraph structure of the present invention is applied.

FIG. 4 is a meridional section view of a low pressure turbine stage.

FIG. 5 is an explanatory view of a trailing edge shape of a stationary blade.

FIG. 6 is an axial flow velocity distribution diagram at the rotor blade outlet when a conventional paragraph structure is applied.

FIG. 7 is a trailing edge shape diagram of a stationary blade.

FIG. 8 is an axial flow velocity distribution diagram at the rotor blade outlet when another conventional paragraph structure is applied.

FIG. 9 is a distribution diagram of a geometrical outflow angle of a moving blade according to another embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Stationary blade, 2 ... Moving blade, 3 ... Diaphragm outer ring, 4 ... Diaphragm inner ring, 6 ... Stationary blade trailing edge, 7 ... Disc, 8 ... Moving blade trailing edge.

Claims (2)

[Scope of utility model registration request] 1. An axial flow turbine stage comprising a group of stationary blades and a group of moving blades, wherein a trailing edge of the stationary blade or an airfoil center of gravity line is inclined in a rotor circumferential direction, and a predetermined blade of the moving blade is provided. An axial flow turbine characterized by being twisted so that the outflow angle continuously decreases sharply from the height position toward the end. 2. The axial turbine according to claim 1, wherein the outflow angle is continuously reduced only from the predetermined height position toward the root-side end.