JPH0861005A - Nozzle of mixed flow turbine - Google Patents

Abstract

PURPOSE: To eliminate the cause of loss by preventing generation of deformation and, ununiformity of flow, differences in flowing angles, mismatching. etc., in a nozzle vane provided between a scroll type pass passage and an impeller. CONSTITUTION: (1) A blade angle α1 K on the leading edge of a nozzle vane 10B is monotonously increased in the direction of a rotary shaft from a hub side toward a shroud side. (2) A distance r2 from the center line of the rotary shaft of the trailing edge of the nozzle vane is monotonously reduced in the rotary shaft direction from the hub side toward the shroud side. (3) In the nozzle vane, an angle defined by the following expression, α2 O/ P (Z)=sin<-1> [O(Z)/P(Z)], is monotonously increased in the rotary shaft direction from the hub side toward the shroud side. Z is a coordinate defined in the rotary shaft direction from the hub side toward the shroud side, O (Z) is a throat width in Z and P (Z) is a nozzle exit pitch in Z.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nozzle of a mixed flow turbine used in various turbines such as a gas turbine expansion turbine and a steam turbine.

[0002]

2. Description of the Related Art FIG. 3 is a vertical cross-sectional view showing the structure of a nozzle vaneless type among conventional types of mixed flow turbines. In the figure, 1 is a turbine casing, 2 is a scroll type gas passage formed in a spiral shape by the casing, 6 is a back plate, 5 is a rotating shaft orthogonal to the turbine casing, and 3 is an impeller fixed to the rotating shaft. The moving blade 10 is a nozzle portion surrounded by the hub side wall surface 13, the shroud side wall surface 14, and the imaginary lines 15 and 16. This is an annular space. In addition, 31 is a leading edge of a moving blade, and 8 is an impeller exit.

FIG. 4 is a vertical sectional view showing the structure of a nozzle vane type in the conventional mixed flow turbine types. The difference from the nozzle vaneless type shown in FIG. 3 is that a plurality of nozzle vanes 1 arranged and fixed at predetermined intervals in the annular nozzle space of FIG.
0A is provided. In addition, 11 is a front edge of the nozzle vane 10A, and 12 is a rear edge thereof.

In both types, the high-pressure gas sent into the scroll-type gas passage 2 is expanded and accelerated by the nozzle 10 and enters the moving blade 3 to give its kinetic energy to the impeller, and its rotational force is the rotating shaft 5. Is transmitted from the outside.

[0005]

FIG. 5 shows the characteristics of a conventional mixed flow turbine. The characteristics of the mixed flow turbine according to the present invention, which will be described later, are also shown in this drawing, but in the following description, the description will be made with reference to the portion relating to the above-mentioned conventional technique in the drawing. [I] Problems with nozzle vaneless type (see FIGS. 3 and 5) (a) Flow path wall length on the shroud side where the flow path wall length from the scroll gas passage 2 to the impeller outlet 8 is shorter Since the flow rate is larger than that on the longer hub side (see FIG. 5 (d)), the inlet flow angle α _1f (see FIG. 5 (a)) at the nozzle inlet virtual plane 15 is larger on the shroud side and smaller on the hub side, and the flow is not flowing It is uniform. (B) Exit flow angle α at the nozzle exit virtual surface 16
_{In 2f} , the distortion of the flow is further increased due to the difference in the wall surface length.
(See FIG. 5B.) (C) Since the angular momentum C _u r is a free vortex flow, the central part is constant, but a boundary layer develops in the vicinity of both wall surfaces.
Distorted at both ends as shown in (c).

As described above, the loss due to the strain of the flow until it flows into the moving blade 3 is large, the nonuniformity of the flow at the leading edge 31 of the moving blade increases the loss, and the turbine efficiency is lowered. [Ii] Problems of nozzle vane type (see FIGS. 4 and 5) In order to solve the problems of the nozzle vaneless type, the nozzle vane 10A shown in FIG. 4 is mounted. As a conventional nozzle vane, a two-dimensional nozzle with a constant blade profile in the rotation axis direction is used for ease of manufacture, but a new problem cannot be solved until the nozzle vaneless type problem can be sufficiently solved. The points are derived.
(A) Gas flow angle α _{1f at the} leading edge 11 of the nozzle vane
Is the same as the case of the nozzle vaneless type shown by the alternate long and short dash line in FIG. 5A, but the blade angle α _{1K at the} leading edge 11 of the nozzle vane is constant in the rotation axis direction as shown by the broken line in the figure. , The flow angle α _{1f at the} leading edge 11 of the nozzle vane
And the blade angle α _1K disagree with each other, resulting in a loss. (B) Since the nozzle vane 10A is formed to have a constant blade profile in the rotation axis direction, the outlet O / P angle α _{2O / P} of the nozzle vane 10A is constant as shown in FIG. Although the flow rate G passing through is smaller than that of the vaneless type, the shroud side is larger and the outlet flow angle α _2f is larger on the shroud side as shown in the figure, and there is a loss due to this discrepancy. (C) When the angular momentum C _ur is examined, it also has a part that is proportional to the flow rate G, and as a result, it becomes larger on the shroud side, so a mixed flow turbine blade of the shape normally used for superchargers. In the case of No. 3, in such a C _u r distribution, the blade angle at the blade leading edge 31 and the inflow angle are mismatched and a large loss occurs.

The present invention aims to solve the above-mentioned drawbacks of the prior art and to provide a mixed flow turbine nozzle that does not cause flow distortion, non-uniformity, flow angle misalignment, mismatching and the like.

[0008]

DISCLOSURE OF THE INVENTION The present invention has solved the above problems, and a nozzle vane provided between a scroll type gas passage and an impeller satisfies the following condition. It relates to a turbine nozzle. (1) The blade angle α _{1K at the} leading edge of the nozzle vane increases monotonically from the hub side to the shroud side in the rotation axis direction. (2) The distance r _{2 of the} trailing edge of the nozzle vane from the center line of the rotation axis decreases monotonically from the hub side toward the shroud side in the rotation axis direction. (3) In the nozzle vane, the angle α _{2O / P} (Z) = sin ^-1 [O (Z) / P (Z)] defined by the following equation is monotonous from the hub side to the shroud side in the rotation axis direction. To increase. Here, Z is a coordinate defined from the hub side to the shroud side in the rotation axis direction, O (Z) is the throat width in Z, and P (Z) is the nozzle outlet pitch in Z.

[0009]

The condition (1) reduces the loss at the nozzle inlet. The condition (2) compensates for the decrease in the flow rate on the hub side and makes the flow rate distribution at the rotor blade inlet uniform. According to the condition (3), the outflow angle on the hub side becomes small and the circumferential component of the absolute flow velocity becomes large, so that the performance is improved.

[0010]

1 is a longitudinal sectional view of a mixed flow turbine according to an embodiment of the present invention. In the figure, 10B is the nozzle vane of this embodiment, 11 is its leading edge, and 12 is its trailing edge. ZZ is the rotation axis center line.

FIG. 2 is a cross-sectional view of the nozzle vane of the above embodiment, in which the portion drawn with a thick line is X- at the center of the vane.
The X section and the hatched portion show the YY section close to the hub side wall surface of the vane. In these figures, r _Z1 is the distance from the center of the rotary axis (Z-Z) of the blade cord in the XX section, and r _Z2 is the center of the rotary axis (Z-Z) of the trailing edge in the YY section. Is the distance. In the nozzle vane 10B, the blade cord length L _Z , the inlet angle α _Z , and the outlet O / P angle α _{2O / P} increase from the hub side wall surface 13 toward the shroud side wall surface 14, and the blade trailing edge 1
The distance from the center of rotation axis (Z-Z) of 2 becomes small. The configuration other than the above is the same as the conventional technique.

This nozzle vane is designed by the following means (design policy). (1) The blade angle α _1K of the nozzle leading edge 11 monotonically increases in the Z direction from the nozzle hub wall surface 13 toward the nozzle shroud wall surface 14 (FIG. 5 (a)).
Design the nozzle airfoil 15 in. (2) Design the shape of the nozzle trailing edge 12 so that the radial position r ₂ (Z) of the nozzle trailing edge 12 at the axial coordinate Z monotonically decreases in the Z direction from the nozzle hub wall surface 13 toward the nozzle shroud wall surface 14. To do. (3) The nozzle O / P angle α ₂ O / P defined by the following equation is from the nozzle hub wall surface 13 to the nozzle shroud wall surface 14 in the Z direction.
The nozzle airfoil 15 in the vicinity of the nozzle trailing edge 12 is designed so as to increase monotonously (FIG. 5 (b)). Here, α ₂ O _{/ P} (Z) = sin ^-1 [O (Z) / P (Z)] O (Z): throat width at Z, P (Z): nozzle outlet pitch at Z.

The action and effect of the nozzle vane designed and manufactured by the above means are as follows. Regarding the means of the above (1), the nozzle inlet blade angle α _1Z
As shown in FIG. _6A , the loss at the nozzle inlet is reduced by increasing the height in the blade height direction (from the hub side to the shroud side) in accordance with the flow angle α _1f . In the means of the above item (3), the nozzle outlet O / P angle α ₂ O _{/ P} is approximately the nozzle outlet angle α _2f.
As shown in FIG. 6, by making the nozzle O / P angle on the hub side smaller than that on the shroud side, the outlet angle α _2f on the hub side is made smaller and the circumferential component C _u of the absolute flow velocity is made larger. Aim to improve performance. However, if α _{2 O / P} is reduced while keeping the same radius (distance from the center of the rotating shaft) of the nozzle outlet on the hub side, the flow rate on the hub side decreases as shown in Fig. 7 and the above item (3) In some cases, the expected effect may not be obtained. Further, the flow rate distribution in the blade height direction at the blade inlet becomes large, the flow in the blade also deteriorates, and the turbine efficiency rather decreases. Therefore, by making the nozzle outlet radius on the hub side larger than that on the shroud side by means of the above item (2), the decrease in the flow rate on the hub side due to the decrease in α _{2 O / P} is compensated, and the flow rate distribution at the blade inlet is distributed. To correct.

[0014]

Since the nozzle vane of the mixed flow turbine of the present invention satisfies the following conditions, there is no flow distortion, non-uniformity, difference in flow angle, mismatching, etc., and loss can be reduced. . (1) The blade angle α _{1K at the} leading edge of the nozzle vane increases monotonically from the hub side to the shroud side in the rotation axis direction. (2) The distance r _{2 of the} trailing edge of the nozzle vane from the center line of the rotation axis decreases monotonically from the hub side toward the shroud side in the rotation axis direction. (3) In the nozzle vane, the angle α _{2O / P} (Z) = sin ^-1 [O (Z) / P (Z)] defined by the following equation is monotonous from the hub side to the shroud side in the rotation axis direction. To increase. Here, Z is a coordinate defined from the hub side to the shroud side in the rotation axis direction, O (Z) is the throat width in Z, and P (Z) is the nozzle outlet pitch in Z.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a mixed flow turbine according to an embodiment of the present invention.

FIG. 2 is a sectional view of the nozzle vane of the above embodiment.

FIG. 3 is a vertical cross-sectional view of a conventional nozzle vaneless type mixed flow turbine.

FIG. 4 is a vertical cross-sectional view of a conventional nozzle vane type mixed flow turbine.

FIG. 5 is a characteristic diagram of a mixed flow turbine according to the related art and the present invention.

FIG. 6 is an explanatory view of a velocity triangle at the nozzle outlet.

FIG. 7 is an explanatory view of a velocity triangle at the nozzle outlet.

[Explanation of symbols]

 1 Turbine casing 2 Scroll type gas passage 3 Rotating blade 5 Rotating shaft 6 Back plate 8 Impeller outlet 10 Nozzle 10A Nozzle vane (conventional) 10B Nozzle vane (Example) 11 Nozzle front edge 12 Nozzle rear edge 13 Hub side wall surface 14 Shroud side wall surface

Claims (1)

[Claims] 1. A nozzle for a mixed flow turbine, characterized in that a nozzle vane provided between the scroll type gas passage and the impeller satisfies the following conditions. (1) The blade angle α _{1K at the} leading edge of the nozzle vane increases monotonically from the hub side to the shroud side in the rotation axis direction. (2) The distance r _{2 of the} trailing edge of the nozzle vane from the center line of the rotation axis decreases monotonically from the hub side toward the shroud side in the rotation axis direction. (3) In the nozzle vane, the angle α _{2O / P} (Z) = sin ^-1 [O (Z) / P (Z)] defined by the following equation is monotonous from the hub side to the shroud side in the rotation axis direction. To increase. Here, Z is a coordinate defined from the hub side to the shroud side in the rotation axis direction, O (Z) is the throat width in Z, and P (Z) is the nozzle outlet pitch in Z.