JPH09310602A - Axial flow turbine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an axial flow turbine which is improved in blade efficiency by optimumly aiming a flow rate balance of steam passing a step from a semi-diameter position of a nozzle root over an all area of a semi-diameter position of a nozzle chip. SOLUTION: Steps are formed in axial flow line along the axial direction. The step is composed of a nozzle 12 and a moving blade. Both ends of the nozzle 12 is fixed by a nozzle inner ring 15 and a nozzle outer ring 16. The nozzle outer ring 16 is extended axially to form a widened flow passage. In such an axial flow passage, a rear edge line 19 of the nozzle 12 is a straight line SL between the nozzle inner ring 15 and an intermediate position of the nozzle. The straight rear edge line 19 is inclined with respect to a reference line Xr passing a rotational center of a turbine shaft 14. The rear edge line 19 is a curved line CL between the intermediate position of the nozzle height and the nozzle outer ring 16.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an axial flow turbine, and more particularly, to a turbine section housed in an expansion passage.
The present invention relates to an axial flow turbine with improved blade efficiency of a nozzle.

[0002]

2. Description of the Related Art In recent years, a prime mover in a power plant, such as a steam turbine, is divided into a high pressure turbine, a medium pressure turbine, and a low pressure turbine for increasing the output.
The thermal energy of the steam supplied from the steam generator is used for expansion work in each turbine to obtain rotational power.When obtaining rotational power, how to increase expansion work in each paragraph of the turbine is power generation. It is an important issue for improving efficiency. In particular, the low-pressure turbine handles a large amount of steam with a relatively low pressure and temperature after expansion work in the high-pressure turbine and medium-pressure turbine, and the output per paragraph is higher than that of the high-pressure turbine and medium-pressure turbine despite the disadvantageous steam conditions. High in comparison.

As described above, the role of the low-pressure turbine in the steam turbine is high, and the improvement of the output per stage of the low-pressure turbine has an important meaning for improving the output of the entire turbine.

Conventionally, a low-pressure turbine is called an axial flow type and is provided with a plurality of paragraphs for expanding work of steam flowing along the axial direction of the turbine shaft. A part of the paragraph is shown in FIG. The configuration shown is employed.

The paragraph 1 is composed of a nozzle 2 and a moving blade 3, and is provided in a plurality of rows along the axial direction Xa of the turbine shaft 4.

Nozzle 2 and moving blade 3 which form one paragraph
Are arranged in an annular shape along the circumferential direction with respect to the turbine shaft 4, and the thermal energy of the steam passing between the annular rows is expanded into work by the nozzle 2 to change it into velocity energy. The turbine shaft 4 is rotated and the rotational force is obtained from the turbine shaft 4.

The nozzle 2 which gives velocity energy to the rotor blade 3 to rotate it is fixed at both ends with a ring-shaped nozzle inner ring 5 and nozzle outer ring 6, and its nozzle inner peripheral wall 7 to nozzle outer peripheral wall 8 are fixed.
The nozzle width (blade width) gradually widens toward the moving blade 3 side downstream, and the velocity energy of the steam ejected from the trailing edge line 9 becomes
The distribution is made uniform from the radial position Rr of the nozzle root portion (on the inner peripheral wall side of the nozzle) to the radial position Rt of the nozzle tip portion (on the outer peripheral wall side of the nozzle).

Further, the nozzle outer peripheral wall 8 at the nozzle tip portion radial position Rt is formed in an expanded flow path having a flare angle, and is accompanied by a decrease in steam pressure and temperature during expansion work of steam in the preceding paragraph. The expansion work of the nozzle 2 can be performed more in response to the increase in the specific vapor volume.

On the other hand, another embodiment in which the output per paragraph of the low pressure turbine is improved is shown in FIGS. 17 and 23.

In the example shown in FIG. 17, the blade shape of the nozzle 2 is the same as that shown in FIG. 11, while the trailing edge line 9 of the nozzle extending from the nozzle root portion radial position Rr to the nozzle tip portion radial position Rt is The radial line Xr (radial direction line) extending radially from the center point O of the axis 4 is intersected with the radial line Xr. Further, in the example shown in FIG. It is formed into a bay-shaped curve that is connected from Rr to the nozzle tip portion radial position Rt by an arc having a constant curvature.

In the former nozzle 2, the leading edge line 10 and the trailing edge line 9 are connected to the radial line Xr in order to prevent the steam flow from becoming a low flow rate region around the nozzle root radius position Rr. It is so-called forward tilt (counter-rotating direction of turbine shaft 4) or backward tilt (rotating direction of turbine shaft 4).

In the latter nozzle 2, the trailing edge line 9 is changed to the radial line in order to prevent the steam flow from becoming a low flow rate area around the nozzle root radius position Rr and the nozzle tip radius position Rt. It is a bay curve formed by connecting arcs to Xr.

As described above, the conventional low-pressure turbine extends the advantages of the nozzle 2 itself, complements the drawbacks, and improves the blade efficiency to improve the output around the paragraph.

However, in recent axial flow turbines,
It is required to reduce fuel energy consumption to raise power generation efficiency more than ever, and as part of this, improvement of output per paragraph, particularly improvement of nozzle blade efficiency is being sought. In order to improve the nozzle blade efficiency more than ever, it is necessary that the flow rate distribution of the steam ejected from the trailing edge of the nozzle be uniform over the entire area from the nozzle root radius position to the nozzle tip radius position. is there.

[0015]

In the conventional nozzle 2 shown in FIG. 11 and FIG. 12, both the leading edge line 10 and the trailing edge line 9 are substantially different from the radial line Xr extending radially from the center point of the turbine shaft 4. Since the blades are so-called straight blades (nozzles) in parallel positions, the periphery of the nozzle root portion radial position Rr extending from the center point O is a low flow rate region where boundary layer separation easily occurs, and in order to improve blade efficiency. It was one of the bottleneck.

The reason why the low flow area of steam around the nozzle root radial position Rr is considered to be as follows.

Generally, the straight blade type nozzle 2 is
As shown in FIG. 13, the steam outflow angle α ejected from the trailing edge line 9 is defined by the angle α around the nozzle root portion radial position Rr.
The angle αt is set to be small and the angle αt is set to be large around the nozzle tip portion radial position Rt. That is, the vane shape of the nozzle 2 changed the vapor outflow angle from the nozzle root radius position Rr to the nozzle tip radius position Rt.

The reason why the steam outflow angle α is larger at the nozzle tip radius position Rt than at the nozzle root radius position Rr is based on the following theory.

Usually, when a cylinder forms a flow path without expansion along the axial direction, the peripheral velocity component Vt of steam is a vortexless theory (free vortex) when the cylinder has a radius R and a constant C _1. Is given by

[0020]

## EQU2 ## R × Vt = C ₁ (1) From equation (1), the smaller the radius R of the cylinder is, the larger the circumferential component Vt of the steam becomes.

However, in order to increase the blade efficiency, the flow rate distribution of the steam ejected from the trailing edge line 9 of the nozzle 2 is made uniform from the nozzle root radius position Rr to the nozzle tip radius position Rt. Is desirable. In particular,
It is desirable that the axial flow velocity component Va of vapor (the velocity component in the radial direction) be constant. As shown by the velocity triangle in FIG. 14, this axial flow velocity component Va is a vector line when the velocity component Vt in the circumferential direction of the turbine shaft 4 and the outflow velocity V of the steam ejected from the nozzle 2 and its outflow angle α are used. From the figure, it is geometrically expressed by the following equation.

[0022]

## EQU3 ## Va = Vttan α (2) From the above equations (1) and (2), the following equation holds for the relation between the radius R of the cylinder and the outflow angle α of the vapor.

[0023]

Α = tan ⁻¹ (Va / C ₁ × R) (3) In the equation (3), (Va / C ₁ ) is changed from the nozzle root portion radial position Rr to the nozzle tip portion radial position Rt. Since it is constant over the range, the outflow angle α of the steam increases in proportion to the increase of the radius R of the cylinder. In FIG. 14, the Xa coordinate indicates the axial direction of the turbine shaft 4, and the coordinate Xc indicates the circumferential direction of the turbine shaft 4.

In this way, the straight blade-shaped nozzle 2
As shown in FIG. 13, the vapor outflow angle α is increased from the nozzle root portion radial position value Rr toward the nozzle tip portion radial position Rt to equalize the vapor outflow distribution amount.

However, in the straight blade type nozzle 2, as described above, the vapor outflow angle α is increased from the nozzle root portion radial position Rr toward the nozzle tip portion radial position Rt so that the vapor outflow distribution amount is uniform. However, as shown in FIG. 15, the steam flow line S is relatively biased relatively to the nozzle outer peripheral wall 8 on the nozzle tip part radial position Rt side, and the nozzle on the nozzle root part radial position Rr side, as shown in FIG. The area around the inner wall 7 was in the low flow rate region. The reason for the low flow rate area around the inner peripheral wall 7 of the nozzle is that when the streamline S of the steam passes through the moving blade 3, it is pushed toward the nozzle outer ring 6 side by centrifugal force, and this pressing force is applied only to the moving blade 3. It is considered that the flow line S passing through the nozzle 2 is also affected without stopping. Further, the nozzle outer peripheral wall 8 on the nozzle tip radius position Rt side copes with the specific volume of vapor increased by the expansion work in the preceding paragraph, and extends from the nozzle root radius position Rr to the entire nozzle tip radius position Rt. It is formed in the expansion channel with a flare angle so as to perform equal expansion work, but due to the large specific volume of steam, it cannot follow the expansion channel due to the influence of gravity. A slight turbulence was generated in the steam flow line S, and the flow of steam was slightly deteriorated, though not so much as on the nozzle inner peripheral wall 7 side.

The flow rate distribution based on the streamline S of the steam passing through the nozzle 2 is shown in FIG.
The steam flow rate on the nozzle inner peripheral wall 7 side of r is extremely low, and the steam flow rate on the nozzle outer peripheral wall 8 side of the nozzle tip radius position Rt is slightly reduced. In FIG. 16, the coordinate R is the radial distance of the nozzle 2 (radial line Xr direction distance), and the coordinate Q is
Indicate the flow rate of steam passing through the nozzle 2.

In this way, the straight blade-shaped nozzle 2
However, since the steam flow rate passing through the entire area from the nozzle root portion radial position Rr to the nozzle tip portion radial position Rt is not uniform, boundary layer separation is likely to occur from the low flow rate region, and the blade efficiency cannot be increased. Was becoming.

Further, the nozzle 2 shown in FIGS.
Is a nozzle root portion radial position Rr of the trailing edge line 9 formed straight from the nozzle inner peripheral wall 7, an arbitrary radial position R ₀ ,
Inclination angle β at each position of the nozzle tip portion radial position Rt
Each of r, β ₀ , and β _tl is a so-called backward tilting blade (nozzle) in which all of them are plus angles with respect to a reference line (hereinafter referred to as a radial line Xr). The vicinity of the outer peripheral wall 8 is a low flow rate region where boundary layer separation easily occurs, which is a drawback in improving blade efficiency. The inclination angles βr, β ₀ , β _tl are set such that the rotation direction of the turbine shaft 4 is positive and the counter rotation direction thereof is negative.

It is considered that the reason why the low flow area of the steam is present around the nozzle inner peripheral wall 7 side of the nozzle tip radial position Rt is as follows.

When the trailing edge line 9 of the nozzle 2 intersects with the radial line Xr and is inclined toward the plus side (the rotational direction side of the turbine shaft 4), the outflow angle α of the steam ejected from the trailing edge line 9
Is the nozzle root radius position Rr as shown in FIG.
The angle αr is small around the nozzle tip portion and the angle αt is large around the nozzle tip portion radial position Rt.
It is the same as the steam outflow angle distribution diagram shown in 3. The steam outflow angle distribution diagrams are the same because the blade element shape itself is the same even when the trailing edge line 9 of the nozzle 2 is intersected with the radial line Xr, and the main axis of inertia of the blade element (blade element) This is because the center of the cross section of) has not changed.

On the other hand, the inclination angle β of the trailing edge line 9 of the nozzle 2 with respect to the radial line Xr is, as shown in FIG. 19, at each of the nozzle root portion radial position Rr, the arbitrary radius position R ₀ , and the nozzle tip portion radial position Rt. If you look at each point position,

## EQU5 ## The relational expression is βr> β ₀ > β _tl > 0 (4). This relational expression can be inevitably obtained from geometrical calculation, and when the relation of the above expression is plotted, the inclination angle distribution diagram of the trailing edge line 9 shown in FIG. 20 is obtained.

In this way, when the trailing edge line 9 of the nozzle 2 is set to the inclination angles βr, β ₀ , β _tl which satisfy the above relationship with respect to the radial positions Rr, R ₀ , Rt, FIG. As shown in
Of the streamlines S passing through the paragraph 1, the streamlines S on the nozzle inner peripheral wall 7 side at the nozzle root radius position Rr of the nozzle 2 are made uniform, but on the nozzle outer peripheral wall 8 side at the nozzle tip radius position Rt. There is no streamline S, which is a so-called low flow rate region. When the flow rate distribution of steam based on the streamline S is graphed, as shown in FIG. 22, the nozzle inner peripheral wall 7 side at the nozzle root radius position Rr has a higher steam flow rate than the nozzle tip radius. The number of nozzles on the outer peripheral wall 8 side of the position Rt is extremely small.

Considering this cause in detail, the trailing edge line 9 of the nozzle 2 has radial positions Rr, R as shown in FIG.
_Since the radial lines Xr, Xr, ... At ₀ , Rt are inclined to the plus side (the rotation direction of the turbine shaft 4), the steam ejected from the trailing edge line 9 is in the nozzle at the nozzle root radius position Rr. It is considered that a pressing force (vector) is generated toward the peripheral wall 7 side, and this pressing force resists the centrifugal force of the moving blade 3.

As described above, in a so-called backward tilting blade in which the trailing edge line 9 of the nozzle 2 is inclined to the plus side with respect to the radial line Xr, a low flow rate region on the nozzle inner peripheral wall 7 side at the nozzle root radius position Rr is provided. Even if the problem is solved, there still remains a problem of the low flow rate region on the nozzle outer peripheral wall 8 side at the nozzle tip portion radial position Rt, which causes the blade efficiency not to be improved.

Further, the trailing edge line 9 of the bay-shaped curved nozzle 2 shown in FIGS. 23 and 24 is the radial position R of the nozzle root portion.
the base point r, under a constant curvature, the curve C ₁ toward the arbitrary radial position R _0, also under the constant curvature from any radial position R _0, the curve C ₂ toward the nozzle tip portion radial position Rt Each of them is drawn, and the inclination angle βr with respect to the radial lines Xr, Xr
Is a plus angle (rotational direction of the turbine shaft 4) and the inclination angle β _tl is a minus angle (counter-rotational direction of the turbine shaft 4). That is, when the inclination angle β ₀ with respect to the radial line Xr at the arbitrary radial position R ₀ is set to zero, the inclination angle with respect to the radial line Xr at the nozzle root portion radial position Rr is βr> 0, and the radial angle at the nozzle tip portion radial position Rt is set. The inclination angle with respect to the line Xr is β _tc <0
It was made.

[0036] The nozzle 2 of the inclined angle .beta.r, bay-shaped curve having a beta _tc, the inclination angle .beta.r shown in FIG. 19, Comparing the wing defeated with a beta _tl, also be seen from FIG. 25 As described above, the inclination angle β at each of the radial positions Rr, R ₀ , Rt
The absolute values of r, R _tl , and β _tc are smaller in the bay-shaped curve nozzle. 25, the coordinate R indicates the radial direction / distance of the radial line Xr radially extending from the center point O of the turbine shaft 4, and the coordinate β indicates the inclination angle value with respect to the radial line Xr.

The inclination angle of the nozzle 2 of the bay-shaped curve .beta.r, both beta _tc, the inclination angle .beta.r the defeated wing, the absolute value than beta _tl is small, the steam nozzle route ejected from the edge line 9 after the nozzle 2 It is considered that the pressing force toward the nozzle inner peripheral wall 7 side at the part radius position Rr is weak, and the pressing force toward the nozzle outer peripheral wall 8 side at the nozzle tip part radius position Rt of steam is relatively high.

When the streamline S of the steam passing through the paragraph 1 is plotted under such consideration, as shown in FIG. 26, the number is small on the nozzle root portion radial position Rr side, and the nozzle tip portion radius is also small. It is dense on the position Rt side. Also, when the flow rate distribution of steam is graphed based on the streamline S in FIG. 26, as shown in FIG. 27, the flow rate is low on the nozzle root part radius position Rr side, and the nozzle tip part radius is The flow rate Q is high on the position Rt side. It is considered that the high flow rate Q is caused by the influence of the centrifugal force of the moving blade 3 in addition to the pressing force.

As described above, even with the nozzle 2 having the trailing edge line 9 formed in a bay curve, the flow of steam is poor on the nozzle root radius position Rr side and the nozzle tip radius position Rt side. As a result, there is a deviation in the flow rate balance, which is the reason why the blade efficiency cannot be improved.

The present invention has been made in consideration of the above circumstances, and optimizes the flow rate balance in which steam passing through a paragraph uniformly flows from the radial position of the nozzle root portion to the radial position of the nozzle tip portion. It is an object of the present invention to provide an axial flow turbine with improved blade efficiency.

[0041]

In order to achieve the above object, an axial flow turbine according to the present invention has, as described in claim 1, a paragraph in an axial flow row along the axial direction, and the paragraph is a nozzle. And a moving blade, wherein both ends of the nozzle are fixed to the inner ring of the nozzle and the outer ring of the nozzle, and the outer ring of the nozzle is axially extended to form an expanded flow path. Is formed linearly from the nozzle inner ring to the nozzle height intermediate position, and the linear trailing edge line is inclined with respect to a reference line passing through the center of rotation of the turbine shaft, while at the nozzle height intermediate position. The trailing edge line of the nozzle is formed in a bay curve up to the outer ring of the nozzle.

In order to achieve the above-mentioned object, the axial flow turbine according to the present invention has a trailing edge line of a nozzle inclined linearly with respect to a reference line passing through the center of rotation of the turbine shaft. Is on the rotational direction side of the turbine shaft.

In the axial flow turbine according to the present invention, in order to achieve the above object, as described in claim 3, the trailing edge line of the nozzle formed in a bay-shaped curve from the intermediate position of the nozzle height to the outer ring of the nozzle is The turbine shaft is on the side opposite to the rotation direction.

In the axial flow turbine according to the present invention, in order to achieve the above object, as described in claim 4, the curvature R of the trailing edge line of the nozzle formed in the bay curve is from the rotation center of the turbine shaft. The distance Rr is from the inner peripheral wall of the nozzle inner ring to the distance Rr from the center of rotation of the turbine shaft to the outer peripheral wall of the nozzle outer ring.
When t,

(Equation 6) It is characterized by satisfying the relational expression of.

In order to achieve the above-mentioned object, the axial turbine according to the present invention is formed in a straight line by inclining from the inner ring of the nozzle to the intermediate position of the nozzle height, as described in claim 5. The position where the inclination angle of the trailing edge line of the nozzle formed in a bay curve from the intermediate position to the outer ring of the nozzle with respect to the reference line passing through the central rotation of the turbine shaft to zero is set between the intermediate position of the nozzle height and the outer ring of the nozzle. It is characterized by being set to.

[0046]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of an axial flow turbine according to the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a schematic sectional view showing a part of a paragraph of the axial flow turbine according to the present invention.

The paragraph 11 is composed of a nozzle 12 and a moving blade 13, and a plurality of them are provided in an axial flow row along the axial direction Xa of the turbine shaft 14.

The nozzle 12 has both ends fixed by a ring-shaped nozzle inner ring 15 and a nozzle outer ring 16, and the nozzle outer ring 16 is engaged and held by a casing (not shown).
Further, the nozzle 2 has a nozzle inner peripheral wall 17 of the nozzle inner ring 15.
To the outer diameter direction of the nozzle outer peripheral wall 18 of the nozzle outer ring 16 (outward in the nozzle longitudinal direction), the nozzle width (blade width) is gradually expanded, and the velocity energy of the steam ejected from the trailing edge line 19 is
It is designed to have a uniform distribution in the radial direction from the nozzle root portion (nozzle inner peripheral wall side) radial position Rr to the nozzle tip portion (nozzle outer peripheral wall side) radial position Rt.

Further, the nozzle outer peripheral wall 18 at the nozzle tip portion radial position Rt is extended along the axial direction Xa,
When the expansion work of the flare angle is provided, the expansion work of the nozzle 12 is performed more in response to the increase of the specific volume of the steam due to the decrease of the steam pressure / temperature during the expansion work of the steam in the preceding paragraph. I am trying to make it possible.

On the other hand, the moving blade 13 is planted in the turbine shaft 14 and is rotated by the velocity energy of the steam ejected from the nozzle 12, and the rotational power (torque) for driving a generator (not shown) is generated from the rotational force. It has gained.

FIG. 2 shows the nozzle 1 as seen from the line AA of FIG.
It is a schematic perspective view of 2.

The nozzle 12 is a ring-shaped nozzle inner peripheral wall 1
7 and the nozzle outer peripheral wall 18 are annularly arranged to form a steam passage 20, and when the heat energy of the steam flowing from the front edge line 21 is expanded in the steam passage 20, it is converted into velocity energy. Velocity energy from trailing edge line 19 to blade 1
It is supposed to be given to 3.

The trailing edge line 19 of the nozzle 12 is, as shown in FIG. 3, a reference line (hereinafter, referred to as a radial line) passing through the rotation center O of the turbine shaft 14 with respect to the inner peripheral wall of the nozzle. A straight line SL extending radially from the nozzle root portion radial position Rr of 17 and inclined in the rotation direction of the turbine shaft 14 (circumferential direction of the nozzle inner peripheral wall 17) and from the middle to the nozzle tip portion radial position Rt of the nozzle outer peripheral wall 18. It is divided into a bay curve CL formed in the counter-rotational direction of the turbine shaft 14.

The shape of the trailing edge line 19 of the nozzle 12 will be specifically described. As shown in FIG. 4, the straight line SL has an inclination angle βr with respect to the radial line Xr passing through the rotation center O of the turbine shaft 14. Nozzle P. C. D. It is radially extended to a radial position R _PCD (abbreviation of pitch circle of diamond, which refers to an intermediate position of a region where steam passes through the nozzle 12).

On the other hand, the bay curve CL has a curvature R,
Nozzle P. C. Connect to straight line SL at D radial position R _PCD ,
At the radial position R ₀ passing through the rotation center O of the turbine shaft 14, the inclination angle is set to zero with respect to the radial line Xr, and the nozzle tip portion is extended to the radial position Rt. In addition, the nozzle P.
C. D. The inclination angle of the bay-shaped curve CL at the radial position R _PCD is the radial line Xr passing through the rotation center O of the turbine shaft 14.
On the other hand, β _PCD and the nozzle tip radius position R
The inclination angle of the bay curve CL at t is βt with respect to the radial line Xr.

The curvature R of the bay curve CL is as follows at the nozzle root radius position Rr and the nozzle tip radius position Rt:
It is set by satisfying the relation range of the following formula.

[0058]

(Equation 7)

In the range of this relational expression, the pressing action force of the steam ejected from the bay curve CL is slightly saved in consideration of the influence of the centrifugal force of the moving blade 13, and the nozzle tip radius position Rt is set.
These are the experimental results calculated by repeating trial and error in order to avoid a high flow rate on the side.

The above relational expression is the most preferable range of application for avoiding a high flow rate on the nozzle tip portion radial position Rt side due to the pressing force of steam.

FIG. 5 shows the inclination angle value of the straight line SL of the trailing edge line 19 of the nozzle 12 and the bay curve CL with respect to the radial line Xr passing through the rotation center O of the turbine shaft 14 at the coordinate β.
And the radial distance value extending radially through the rotation center O of the turbine shaft 14 at the coordinate R. Further, FIG. 6 shows the outflow angle of steam corresponding to the inclination angle change values of the straight line SL and the bay-shaped curve CL shown in FIG. The coordinate α indicates the steam outflow angle change value corresponding to the inclination angle change value of the straight line SL and the bay-shaped curve CL in FIG.

In FIGS. 5 and 6, the straight line SL
The inclination angle β of the nozzle P. C. D. The steam outlet angle α decreases from the radial position R _PCD to the nozzle P.D.
C. D. From these data, the pressing action force of the steam ejected along the straight line SL of the trailing edge line 19 increases from the radial position R _PCD to the nozzle P. C. D. The direction is changing as it goes to the radial position R _PCD side. Therefore, since the pressing force of the steam ejected from the straight line SL of the trailing edge line 19 is also acting on the nozzle root radius position Rr side, the steam flows to the nozzle root radius position Rr, and the low pressure around the nozzle root radius position Rr. The flow range can be avoided.

On the other hand, the bay curve CL is, as shown in FIGS. C. D. The inclination angle β sharply decreases from the radial position R _PCD to the nozzle tip radial position Rt, while the inclination angle β of the nozzle tip radial position Rt increases.
The absolute value of t is the inclination angle βr of the nozzle root radius position Rr.
And the change value of the outflow angle α of the steam corresponding to the change value of the inclination angle β. C. D. A peak value is taken at a zero tilt angle value with respect to the radial line Xr at the nozzle radial position R ₀ within the range from the radial position R _PCD to the nozzle tip radial position Rt, and thereafter, the outflow angle αt decreases at the nozzle tip radial position Rt. There is.

As can be understood from the above data, the pressing force of the steam ejected from the bay curve CL is maximum at the nozzle radial position R ₀ . The reason why the pressing action force is maximized at the nozzle radial position R ₀ is to avoid that the nozzle tip portion radial position Rt side becomes the high flow rate region due to the influence of the centrifugal force of the moving blade 13.

FIG. 7 shows the change value of the inclination angle β of the straight line SL and the bay-shaped curve CL shown in FIGS. 5 and 6, and the outflow angle α of the steam.
FIG. 8 is a plot of the streamline S of the steam passing through the paragraph 11 based on the change value of
The distribution of the vapor flow rate Q from the nozzle root portion radial position Rr to the nozzle tip portion radial position Rt is created based on the above equation.

As can be understood from FIG. 7 and FIG. 8, when the steam jets from the trailing edge line 19 of the nozzle 12, the vapor moves from the nozzle root portion radial position Rr to the nozzle tip portion radial position Rt.
Is uniform over the entire area.

As described above, in the axial flow turbine according to the present invention, the trailing edge line 19 of the nozzle 12 is divided into an inclined straight line and a bay curve, and a pressing force is applied to the nozzle root radius position Rr. Therefore, it is possible to avoid the low flow rate region on the nozzle root portion radial position Rr side. Further, since the pressing force applied to the nozzle tip portion radial position Rt is saved, it is possible to avoid the high flow rate region on the nozzle tip portion radial position Rt side.

9 and 10 are schematic views showing a first embodiment of an axial flow turbine according to the present invention. In addition,
The same components as those in FIGS. 2 and 3 are designated by the same reference numerals.

In this embodiment, as shown in FIG.
Although the trailing edge line 2 of 2 is divided into a straight line SL and a bay-shaped curve CL, it is basically in line with the embodiment shown in FIGS. 2 and 3, but the bay-shaped curve CL has different shapes. There is.

As shown in FIG. 10, the bay-shaped curve CL has an inclination angle βr with respect to the radial line Xr passing through the rotation center O of the turbine shaft 14, and the radial position Rr of the nozzle root portion is provided.
To the nozzle P. C. D. It is connected to a straight line SL that extends radially toward the radial position R _PCD, and the curvature thereof is a deformed oval curvature. The curvature of the deformed oval is set so that the inclination angle with respect to the radial line Xr is _zero at the nozzle radial position R ₀ and the high flow rate region can be avoided at the nozzle tip radial position Rt.

As described above, in the present embodiment, the trailing edge line 19 of the nozzle 12 is prevented from being in the low flow rate region on the nozzle root part radial position Rr side, and the nozzle tip part radial position Rt is also set.
Since it is divided into a straight line SL and a bay-shaped curve CL for preventing the side from becoming a high flow rate region, as in the embodiment shown in FIGS. 2 and 3, jetting is performed from the trailing edge line 19 of the nozzle 12. The steam flow distribution can be made uniform.

[0072]

As described above, in the axial turbine according to the present invention, the trailing edge line of the nozzle is the nozzle P. C. D is formed in an inclined straight line over the radial position, and the nozzle P. C. D. Since the bay-shaped curve is formed from the radial position to the nozzle tip portion radial position, steam can be flowed at an appropriate flow rate on both the nozzle root portion radial position side and the nozzle tip portion radial position side.

Further, in the axial flow turbine according to the present invention, the curvature of the bay curve is (Rt-Rr) / 2 <R <10 (Rt-
Rr), the nozzle P. C. D.
A uniform vapor flow rate can be flowed from the radial position side to the nozzle tip portion radial position side.

Further, in the axial flow turbine according to the present invention, the peak value of the pressing action force of the steam ejected from the bay curve is determined by the nozzle P. C. D. Since it is set within the range from the radial position to the radial position of the nozzle tip portion, steam can be made to flow toward the radial position of the nozzle tip portion at an appropriate flow rate even if it is affected by the centrifugal force of the moving blade.

Therefore, in the axial turbine according to the present invention, the flow rate distribution of the steam ejected from the trailing edge line of the nozzle can be made uniform from the radial position of the nozzle root portion to the radial position of the nozzle tip portion, and the blade efficiency is improved. It is possible to realize a high nozzle and to improve the blade efficiency of the axial flow turbine, so that the power generation efficiency can be dramatically improved.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing a part of a paragraph of an axial flow turbine according to the present invention.

FIG. 2 is a schematic perspective view of a nozzle as viewed in the direction of arrows AA in FIG.

FIG. 3 is a schematic cross-sectional view seen from the trailing edge side of a nozzle of an axial flow turbine according to the present invention.

FIG. 4 is a schematic view showing the shape of a nozzle according to the present invention.

FIG. 5 is a distribution diagram showing a tilt angle of a trailing edge line of a nozzle with respect to a reference line (radial line) passing through a rotation center of a turbine shaft.

FIG. 6 is a distribution diagram showing an outflow angle of steam ejected from a trailing edge line of a nozzle.

FIG. 7 is a diagram showing streamlines of steam passing through a paragraph.

FIG. 8 is a distribution diagram showing the flow rate of steam ejected from the trailing edge line of the nozzle.

FIG. 9 is a schematic cross-sectional view showing the first embodiment of the axial flow turbine according to the present invention, as seen from the trailing edge line side of the nozzle.

FIG. 10 is a schematic diagram showing the shape of the nozzle in the first embodiment according to the present invention.

FIG. 11 is a schematic cross-sectional view showing a part of a paragraph of a conventional axial flow turbine.

FIG. 12 is a schematic cross-sectional view of the nozzle as viewed in the direction of arrow BB in FIG.

13 is a distribution diagram showing the inclination angle of the trailing edge line of the nozzle with respect to a reference line (radial line) passing through the center of rotation of the turbine shaft in FIG.

FIG. 14 is a diagram showing a velocity triangle of steam ejected from a nozzle.

FIG. 15 shows a streamline of steam passing through a paragraph according to FIGS. 13 and 14.

FIG. 16 is a distribution diagram showing the flow rate of steam based on FIG.

FIG. 17 is a schematic cross-sectional view seen from the trailing edge side of a nozzle of an axial flow turbine showing another conventional example.

FIG. 18 is a distribution diagram showing an outflow angle of steam ejected from the nozzle in FIG.

19 is a schematic diagram showing the shape of the nozzle in FIG.

20 is a distribution diagram showing the inclination angle of the trailing edge line of the nozzle with respect to a reference line (radial line) passing through the center of rotation of the turbine shaft in FIG.

FIG. 21 shows a streamline of steam passing through a paragraph according to FIGS. 18 and 20.

FIG. 22 is a distribution diagram showing the flow rate of steam based on FIG. 21.

FIG. 23 is a schematic cross-sectional view as seen from the trailing edge side of a nozzle of an axial flow turbine showing still another example of the related art.

24 is a schematic diagram showing the shape of the nozzle in FIG.

FIG. 25 is a tilt angle distribution diagram comparing the tilt angle of the falling blade and the tilt angle of the nozzle having the bay curve.

FIG. 26 is a diagram showing the flow rate of steam passing through a paragraph based on FIG. 25.

27 is a distribution diagram showing the flow rate of steam based on FIG. 26. FIG.

[Explanation of symbols]

 1 paragraph 2 nozzle 3 moving blade 4 turbine shaft 5 nozzle inner ring 6 nozzle outer ring 7 nozzle inner peripheral wall 8 nozzle outer peripheral wall 9 trailing edge line 10 leading edge line 11 paragraph 12 nozzle 13 moving blade 14 turbine shaft 15 nozzle inner ring 16 nozzle outer ring 17 nozzle Inner peripheral wall 18 Nozzle outer peripheral wall 19 Trailing edge line 20 Steam passage 21 Leading edge line SL Straight line CL Bay curve

Claims (5)

[Claims] 1. An axial flow row is provided with a paragraph along an axial direction, the paragraph is constituted by a nozzle and a moving blade, and both ends of the nozzle are fixed by a nozzle inner ring and a nozzle outer ring, and the nozzle outer ring is axially arranged. In the axial flow turbine extended to form an expanded flow path, the trailing edge line of the nozzle is linearly formed from the inner ring of the nozzle to the intermediate position of the nozzle height, and the linear trailing edge line is the turbine. The axial flow turbine, wherein the nozzle trailing edge line at an intermediate position of the nozzle height is formed into a bay-shaped curve up to the nozzle outer ring while being inclined with respect to a reference line passing through a rotation center of the shaft. 2. The axial flow according to claim 1, wherein a trailing edge line of the nozzle, which is linearly inclined with respect to a reference line passing through a rotation center of the turbine shaft, is on a rotation direction side of the turbine shaft. Turbine. 3. An axial flow turbine according to claim 1, wherein a trailing edge line of the nozzle, which is formed in a bay-shaped curve from the intermediate position of the nozzle height to the outer ring of the nozzle, is on the side opposite to the rotation direction of the turbine shaft. . 4. The curvature R of the trailing edge line of the nozzle formed in a bay curve is the distance Rr from the center of rotation of the turbine shaft to the inner peripheral wall of the nozzle inner ring, and from the center of rotation of the turbine shaft to the outer peripheral wall of the nozzle outer ring. Is a distance Rt, The axial flow turbine according to claim 1 or 3, wherein the relational expression is satisfied. 5. The center of the turbine shaft of the trailing edge line of the nozzle, which is formed in a straight line by inclining from the inner ring of the nozzle to the intermediate position of the nozzle height, and is formed in a bay-shaped curve from the intermediate position of the nozzle height to the outer ring of the nozzle. The axial turbine according to claim 1, wherein a position where an inclination angle with respect to a reference line passing through rotation is zero is set between the nozzle height intermediate position and the nozzle outer ring.