JPH0367001A - Turbine nozzle - Google Patents

Abstract

PURPOSE:To greatly improve the efficiency of a turbine by way of reducing the secondary flow loss of a nozzle by setting each nozzle so that it inclines against a standard radial line running through the center of the rotation of the turbine within the range of a specific angle in the direction of the intrados of the nozzle. CONSTITUTION:The inclination angle of each nozzle 14 against a standard radial line E, for example, the inclination angle theta of a nozzle rear edge 14a is set within the range of 3 deg.<=theta<=14 deg.. By inclining each nozzle 14 arranged at a circular flow passage 13, a flow passage 13a between nozzle blades formed between the nozzles 14, 14 comes to be an inclined curved pipe, and accordingly, a velocity vector G at the flow passage 13a between nozzle blades is directed to the side of the inner ring 11 of a nozzle diaphragm. In this way, the boundary layer generated adjacent to the inner peripheral wall surface of the inner ring 11 of the nozzle diaphragm is restricted in growth, and the secondary flow is lessened. Consequently, the scale of the secondary vortex caused by the secon dary flow is lessened and the loss of energy by the secondary flow is also reduced.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a turbine nozzle of an axial flow turbine used in a turbomachine, etc. This invention relates to a turbine nozzle that suppresses flow and reduces pressure loss due to secondary vortex flow.

(Prior Art) In recent years, improving turbine performance has become an important issue in order to improve the power generation efficiency of power plants.

In order to improve turbine performance, it is necessary to reduce internal losses in each turbine stage. Internal losses in a turbine stage include airfoil loss, secondary flow loss, leakage loss, etc., but especially in a turbine stage with a small aspect ratio (R height/blade code) and a low blade height, the secondary flow The proportion of energy loss caused by this is large, and reducing this loss is a major issue in improving turbine performance.

- The nozzle configuration of an in-shell axial turbine is shown in Figures 7 and 8.
As shown in the figure. An annular flow path 3 is formed between a nozzle diaphragm inner ring 1 and a nozzle diaphragm outer ring 2, and a plurality of nozzles 4 are fixedly installed in this annular flow path 3 at predetermined intervals. The turbine blades 5 are arranged in rows at predetermined intervals in the circumferential direction of the outer periphery of the rotor disk 6 .

A shroud 7 is provided at the outer peripheral end of the turbine blade 5 to fix the blade tip and to reduce leakage of working fluid.
is installed.

Next, in the turbine stage configuration of an axial flow turbine, the nozzle 4
The generation mechanism of the secondary flow will be explained below.

FIG. 7 is a perspective view of the turbine nozzle shown in FIG. 8, viewed from the nozzle outlet side.

Each nozzle l is provided along a reference radial line E passing through the rotation center of the turbine rotor, and is arranged perpendicularly to the outer circumferential wall surface of the nozzle diaphragm inner ring 1.

When a working fluid such as high-pressure steam flows through the nozzle inter-blade flow path 3a formed between adjacent nozzles 4.about.4, it is bent into an arc shape in this inter-blade flow path 3a. Therefore, due to the centrifugal force acting on the working fluid in the nozzle inter-blade flow path 3a, a pressure gradient is created in which the pressure on the nozzle vent surface F is higher than the pressure on the nozzle back surface B. On the other hand, nozzle diaphragm inner ring 1
A boundary layer with a slow flow rate grows near the wall surface due to the viscosity of the working fluid. According to the concept of boundary layer theory, the pressure gradient in the boundary layer is equivalent to the pressure gradient in the mainstream, so in order for the pressure gradient in the boundary layer to balance the centrifugal force acting on the working fluid, the flow velocity must be small. The curvature of the streamline must be reduced by that amount. Therefore, a flow from the nozzle vent surface F toward the nozzle back surface B, that is, a secondary flow 8 is generated.

This secondary flow 8 collides with the back surface B side of the nozzle 4 and rolls up to generate a secondary vortex (secondary vortex) 9.

As a result, the energy held by the working fluid is transferred to the secondary vortex 9
A part of it dissipates to form .

In addition to significantly reducing the nozzle performance in this way, this also causes energy loss in the working fluid flowing into the turbine blades (rotor blades) on the downstream side, thereby reducing the performance of the turbine stage.

(Problems to be Solved by the Invention) In conventional turbine nozzles, a large secondary vortex 9 is formed near the outer circumferential wall surface of the inner ring of the nozzle diaphragm, so a part of the energy held by the working fluid is dissipated, and the turbine In addition to significantly reducing the performance of the nozzle, it also greatly disturbs the working fluid flowing into the turbine blades (rotor blades) located downstream of the turbine nozzle, making it impossible to effectively transmit the energy held by the working fluid to the turbine blades. There was a problem that degraded the performance.

The present invention has been made in order to solve the above problems, and provides a turbine nozzle that can reduce energy loss due to secondary vortices generated near the wall surface of the turbine nozzle and improve turbine performance. With the goal.

[Structure of the invention]

(Means for Solving the Problems) In order to solve the problems of the prior art, the turbine nozzle according to the present invention forms an annular flow path between an inner ring of a nozzle diaphragm and an outer ring of the nozzle diaphragm, In a turbine nozzle in which a plurality of nozzles are arranged in a row at predetermined intervals in the circumferential direction, each of the nozzles is arranged at an angle of 3 to 14 degrees in the direction of the ventral surface of the nozzle with respect to a reference radial line passing through the rotation center of the turbine rotor. The nozzle diaphragm inner ring and the nozzle diaphragm outer ring are fixed to the nozzle diaphragm inner ring and the nozzle diaphragm outer ring with an inclination within a range of 100°.

Further, in order to solve the above-mentioned problems, the turbine nozzle of the present invention has a flow path between nozzle blades formed between each nozzle, in which the height of the flow path is gradually narrowed from the inlet side to the outlet side. The inner circumferential wall surface of the nozzle diaphragm outer ring is inclined or curved.

Furthermore, in order to solve the above-mentioned problems, a turbine nozzle according to the present invention forms an annular flow path between a nozzle diaphragm inner ring and a nozzle diaphragm outer ring, and a plurality of nozzles are arranged in the annular flow path at predetermined positions in the circumferential direction. In the turbine nozzles arranged in a row with an interval of , the inner peripheral wall surface of the nozzle diaphragm outer ring is inclined or curved within a range of 3 to 14 degrees with respect to the axial direction of the turbine rotor.

(Function) This turbine nozzle has nozzles arranged at intervals in the circumferential direction in the annular flow path between the inner ring of the nozzle diaphragm and the outer ring of the nozzle diaphragm, relative to a reference radial line passing through the rotation center of the turbine rotor. Then, toward the ventral surface of the nozzle,
Since the nozzle blades are tilted and fixed in the range of 3 degrees to 14 degrees, the flow path between the nozzle blades formed between the nozzles becomes an inclined curved pipe, and the velocity vector in the flow path between the nozzle blades is in the direction of the inner ring of the nozzle diaphragm. As a result, the growth of secondary vortices generated near the inner circumferential wall surface of the inner ring of the nozzle diaphragm is suppressed, so that the pressure loss of the secondary flow at the nozzle root portion is significantly reduced.

Furthermore, since the turbulence of the working fluid flowing into the turbine blades located downstream of the nozzle is reduced compared to the case of conventional turbine nozzles, the energy held by the working fluid can be efficiently transmitted to the turbine blades.

In addition, the nozzle is inclined at a predetermined angle in the direction of the ventral surface of the nozzle with respect to the reference radial line, and the inner periphery of the nozzle diaphragm outer ring is designed to narrow the flow path between the nozzle blades formed between each nozzle from the inlet side to the outlet side. When the wall surface is inclined or curved, the generation of secondary flow at the nozzle root can be more actively prevented, and pressure loss due to secondary vortices caused by the secondary flow can be effectively prevented.

Furthermore, even when the nozzles are arranged in the direction of the reference radial line, the inner circumferential wall surface of the nozzle diaphragm outer ring is adjusted so that the flow path between the nozzle blades formed between each nozzle is narrowed from the inlet side to the outlet side. 3 in the axial direction of the turbine rotor
Even if the nozzle is tilted or curved in the range of 14 degrees to 14 degrees, it is possible to suppress the generation of a secondary vortex due to the secondary flow generated in the nozzle root portion, and it is possible to reduce the pressure loss due to the secondary vortex.

According to the present invention, the secondary flow loss of the nozzle is reduced and energy is effectively transmitted to the turbine blades, so that the efficiency of the turbine can be significantly improved.

(Example) An example of a turbine nozzle according to the present invention will be described with reference to the accompanying drawings.

FIG. 1 and FIG. 2 show the nozzle configuration of an axial flow turbine used in a turbomachine or the like. The nozzle diaphragm 10 of the axial turbine is configured as a vane. This nozzle diaphragm 10 has an annular flow path 13 formed between a nozzle diaphragm inner ring 11 and a nozzle diaphragm outer ring 12, and a plurality of nozzles 14 arranged in a row at predetermined intervals in the circumferential direction in this annular flow path 13. will be permanently installed. The root portion and tip portion of each nozzle 14 are connected to the nozzle diaphragm inner ring 11.
and are respectively joined and fixed to the nozzle diaphragm inner ring 12. The blade cross-section of each nozzle 14 is shaped like a conventional nozzle and has a streamlined outer surface.

A plurality of turbine blades 15 are arranged on the downstream side facing each nozzle 14 . The turbine blades 15 constitute rotor blades of an axial flow turbine, and are implanted at predetermined intervals in the circumferential direction on the outer periphery of a rotor disk 16 that constitutes a turbine rotor. A shroud 17 that fixes the tip of the blade is attached to the outer peripheral end of the turbine blade 15.
7 to reduce leakage of working fluid.

Further, each nozzle 14 is fixed so as to be inclined in the direction of the nozzle ventral surface F with respect to a reference radial line E passing through the rotation center of the rotor disk 16. The inclination angle of each nozzle 14 with respect to the reference radial line E, for example, the inclination angle θ of the nozzle trailing edge 14a, is
As shown in FIG. 3, the angle is set within the range of 3°≦θ≦14°.

By inclining each nozzle 14 arranged in the annular flow path 13, the nozzle inter-blade flow path 13a formed between each nozzle 14.14 becomes an inclined curved pipe (curved flow path).
The velocity vector G in the nozzle inter-blade flow path 13a is directed toward the nozzle diaphragm inner ring 1 side. As a result, the growth of the boundary layer generated near the inner circumferential wall surface of the nozzle diaphragm inner ring 11 is suppressed, and the secondary flow is also reduced. As a result, a secondary vortex (secondary vortex) is generated due to the secondary flow.
The scale of the flow is reduced, and energy loss due to secondary flow is also reduced.

Furthermore, with reference to FIG. 4, the effect of reducing pressure loss, which is a measure of turbine nozzle performance, will be explained.

FIG. 4 is a graph showing a distribution curve A of total pressure loss at the outlet portion of the turbine nozzle shown in FIG. 1 in comparison with a conventional example. The conventional example indicated by a broken line B is a turbine nozzle shown in FIG. 7 in which the nozzle is not inclined with respect to a reference radial line E passing through the center of rotation. Comparing this example with the conventional example, it can be seen that the pressure loss near the root portion of the nozzle 14 is significantly reduced in this example than in the conventional example.

This is because, in the case of the turbine nozzle shown in this example, the secondary flow loss near the nozzle root portion is greatly reduced. The pressure loss near the nozzle tip is larger in this embodiment than in the conventional example. However, the amount of increase is minute compared to the amount of decrease near the nozzle root.

In FIG. 4, the pressure loss of the conventional turbine nozzle is larger near the nozzle root than near the nozzle tip for the following reason. In other words, in FIG. 9, which shows a conventional turbine nozzle observed from the nozzle outlet side, the flow Hr flowing out from the trailing edge near the root at a nearly right angle is easily separated by the inner wall surface of the nozzle root, which has curvature, and a secondary vortex is created. encourage the development of On the other hand, near the nozzle tip, the wall shape of the outer ring of the nozzle diaphragm acts in a direction to suppress the development of secondary vortices associated with the flow Ht flowing out from the trailing edge of the nozzle, so the pressure loss is smaller than near the nozzle root.

FIG. 5 defines the range of the inclination angle of the nozzle 14 in the present invention, for example, the inclination angle θ of the nozzle trailing edge line 14a. In FIG. 5, the horizontal axis is the angle (tilt angle) θ between the reference radial line E passing through the center of rotation and the nozzle trailing edge line on the inner ring 11 side of the nozzle diaphragm, and the vertical axis is the paragraph when the turbine nozzle of the present invention is used. The ratio between the efficiency η and the stage efficiency η when using a conventional turbine nozzle is shown. Fifth
As shown in the figure, the stage efficiency η is superior to the conventional stage efficiency η θ
The range is 3°≦θ≦14°. In this way, the tilt angle θ
The reason why there is a high efficiency range is that at θ<3°, the flow pattern is almost the same as that of a conventional turbine nozzle, and at θ>14°, the increase in pressure loss near the nozzle tip is greater than the flow pattern near the nozzle root. This is because the amount of pressure drop decrease is greater than the amount of pressure drop.

FIG. 6 shows another embodiment of the turbine nozzle according to the invention.

In this embodiment, the nozzle 1 of the nozzle diaphragm outer ring A
4 is inclined toward the ventral surface of the nozzle with respect to the reference radial line E. In addition, the nozzle diaphragm outer ring is arranged so that the height of the nozzle 14 decreases from the inlet side to the outlet side of the working fluid. The inner circumferential wall surface 12a of No. 12 is inclined. Due to this inclination of the inner circumferential wall surface 12a of the nozzle diaphragm outer ring 12, the interblade flow passage 13a formed between each nozzle 14 is narrowed on the nozzle diaphragm outer ring 12 side, reducing the pressure loss near the nozzle tip shown in FIG. can be reduced. This is the working fluid flow path 1 between the blades.
This is because by constricting 3a in the radial direction, growth of the boundary layer near the nozzle tip can be suppressed, secondary flow can be suppressed, and pressure loss due to secondary vortices can be reduced. In addition, in the embodiment shown in FIG. 6, a case is shown in which the inner circumferential wall surface of the nozzle diaphragm outer ring 12 changes linearly, but it does not necessarily have to be a straight line and may be curved into a smooth curve. You can also get the same effect.

Note that the range of the inclination angle θ in this case is also preferably within the range of 3°≦θ≦14° with respect to the axial direction of the turbine rotor.

Although FIG. 6 shows an example in which the nozzle 14 is inclined toward the ventral surface of the nozzle with respect to the reference radial line E, and the inner circumferential wall surface of the nozzle diaphragm outer ring 12 is inclined or curved, the nozzle diaphragm outer ring 12 The inner peripheral wall surface 12a may be simply sloped or curved. In this case, the nozzles 14 arranged in the annular flow path 13a between the nozzle diaphragm inner ring 11 and the nozzle diaphragm outer ring 12 may be installed along the reference radial line E, like conventional nozzles.

〔Effect of the invention〕

As explained above, in the turbine nozzle according to the present invention, each nozzle is attached at an angle of 3 to 14 degrees in the direction of the ventral surface of the nozzle with respect to the reference radial line E passing through the center of rotation. The inter-blade flow path formed between the blades is an inclined curved pipe, and the velocity vector in the inter-blade flow path is in the direction of the inner ring of the nozzle diaphragm. As a result, the growth of the secondary vortex generated near the wall surface of the inner ring of the nozzle diaphragm is suppressed, so that the pressure loss due to the secondary flow near the nozzle root portion is significantly reduced.

In addition, the nozzle is inclined at a predetermined angle in the direction of the ventral surface of the nozzle with respect to the reference radial line, and the inner periphery of the nozzle diaphragm outer ring is designed to narrow the flow path between the nozzle blades formed between each nozzle from the inlet side to the outlet side. When the wall surface is inclined or curved, the generation of secondary flow at the nozzle root can be more actively prevented, and pressure loss due to secondary vortices caused by the secondary flow can be effectively prevented.

Furthermore, even when the nozzles are arranged in the direction of the reference radial line, the inner circumferential wall surface of the nozzle diaphragm outer ring is adjusted so that the flow path between the nozzle blades formed between each nozzle is narrowed from the inlet side to the outlet side. Even if the tabin rotor is tilted or curved in the range of 3 to 14 degrees with respect to the axial direction, it is possible to suppress the generation of secondary vortices due to secondary flow generated at the nozzle root, and reduce pressure loss due to secondary vortices. It is possible to reduce the

In either case, the generation of secondary flows is suppressed and the growth of secondary vortices caused by secondary flows is suppressed, so the turbulence of the working fluid flowing into the turbine blades located downstream of the nozzle is reduced compared to conventional turbines. This is lower than in the case of a nozzle, so the energy held by the working fluid can be efficiently transmitted to the turbine blades. That is, according to the present invention, the secondary flow loss of the nozzle is reduced and energy is effectively transmitted to the turbine blades, so that the efficiency of the trickle turbine can be significantly improved.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an embodiment of a turbine nozzle according to the present invention, FIG. 2 is an explanatory diagram of a turbine stage equipped with the turbine nozzle, and FIG. 3 shows the turbine nozzle of FIG. 1 on the nozzle outlet side. Fig. 4 is a graph showing the pressure loss distribution of the turbine nozzle according to the present invention in comparison with the pressure loss distribution of a conventional turbine nozzle, and Fig. 5 is a graph showing the relationship between the nozzle inclination angle and the turbine stage efficiency ratio. A graph showing the relationship between
6 is a diagram showing another embodiment of the turbine nozzle according to the present invention, FIG. 7 is a diagram showing a conventional turbine nozzle, FIG. 8 is a diagram showing a turbine stage equipped with a conventional turbine nozzle, and FIG. The figure is a schematic diagram of a conventional turbine nozzle observed from the nozzle outlet side. 10, IOA... Nozzle diaphragm, 11... Nozzle diaphragm inner ring, 12... Nozzle diaphragm outer ring, 13... Annular flow path, 13a... Nozzle inter-blade flow path, 13... Nozzle, 14a ... Nozzle trailing edge, 15
...Turbine blade, 16...Turbine rotor, E.
・Reference radial line.

Claims (1)

[Claims] 1. An annular flow path is formed between the inner ring of the nozzle diaphragm and the outer ring of the nozzle diaphragm, and a plurality of nozzles are arranged in a row at predetermined intervals in the circumferential direction in this annular flow path. The turbine nozzle is characterized in that each of the nozzles is tilted at an angle of 3 to 14 degrees in the direction of the ventral surface of the nozzle with respect to a reference radial line passing through the center of rotation of the turbine rotor, and fixed to the inner ring of the nozzle diaphragm and the outer ring of the nozzle diaphragm. turbine nozzle. 2. The inner peripheral wall surface of the nozzle diaphragm outer ring is sloped or curved so that the flow path between the nozzle blades formed between each nozzle is gradually narrowed in height from the inlet side to the outlet side. The turbine nozzle according to claim 1. 3. In a turbine nozzle in which an annular flow path is formed between a nozzle diaphragm inner ring and a nozzle diaphragm outer ring, and a plurality of nozzles are arranged in a row at predetermined intervals in the circumferential direction, each of the above-mentioned The nozzle blade-to-nozzle flow path formed between the nozzles is such that the inner wall surface of the nozzle diaphragm outer ring is set at 3 degrees in the axial direction of the turbine rotor so that the height of the flow path is gradually narrowed from the inlet side to the outlet side. degree to 14
A turbine nozzle characterized by being inclined or curved in a range of degrees.