JPH10238303A - Axial flow turbine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an axial flow turbine to suppress a secondary flow vortex occurring accompanying to a secondary flow between the blade trains of moving blades and improve efficiency of a blade. SOLUTION: An axial flow turbine is constituted such that a blade element section central line I to linearly connecting the blade element section central point of the root part 26b of a moving blade 23, with the blade element section central point of a tip part 26a, and the blade element section central point of a tip part 26a, is inclined based on a rotation center reference line R passing through the center of a turbine axis 24, and the inclination is arranged to the wake flow side of the turbine axis 24. Further, the inclination angle α of the blade element section central line I of the moving blade 23 with a rotation center reference line R passing through the center 0 of the turbine axis 24 is set in the range of 0<α<=15 deg..

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an axial turbine, and more particularly to an axial turbine in which secondary flow vortices growing in a cascade are suppressed to improve blade efficiency.

[0002]

2. Description of the Related Art Generally, an axial flow turbine, for example, a steam turbine or a gas turbine is provided with a number of stages 1 along a flow of a working fluid (hereinafter referred to as a main flow F) as shown in FIG. In the first paragraph, a nozzle (stationary blade) 2 and a moving blade 3 are combined.

[0003] The nozzles 2 are supported by a diaphragm outer ring 4 and a diaphragm inner ring 5, and are arranged in an annular row in the circumferential direction with respect to the turbine shaft 6, and the moving blades 3 are attached to the nozzles 2 arranged in the annular row. Correspondingly, the implantation part 7 of the turbine shaft 6
It is planted in.

[0004] Further, the rotor blade 3 is provided with a shroud 8 and a seal fin 9 at its tip (wing apex), and the vibration generated during operation is suppressed by the shroud 8.
The passage of the main stream F is prevented by the seal fins 9.

In the axial flow turbine having such a configuration, the main flow F flowing into the nozzle 2 increases velocity energy by expansion, gives the velocity energy to the rotor blades 3 and rotates the rotor, and utilizes the rotational force. A rotation torque is generated from the turbine shaft 6.

In order to generate more rotational torque from the limited energy of the mainstream, it is important how effectively the mainstream F passing between the cascades flows. However,
A limited curved flow path is formed between the cascades, and the behavior of the main flow F flowing therethrough is also complicated. For this reason, in the conventional axial turbine, the flow of the main flow F has a loss, and this loss has become one of the factors that cannot improve the blade efficiency.

[0007]

One of the obstacles to the improvement of the blade efficiency is a secondary flow vortex accompanying the generation of the secondary flow of the main flow F.

When the main flow F passes through a flow path formed between the cascades, the secondary flow effectively flows along the blade shape at an intermediate portion of the blade height, but the tip portion (wing top) and the route Part (wing root part) means flowing in a direction intersecting with the main flow F flowing through the middle part. The crossflow of this mainstream F is
This is due to the pressure on the ventral side of one wing being higher than the pressure on the dorsal side of the other adjacent wing.

When the main flow F generates a secondary flow, it is accompanied by a vortex. The vortex is generated and grows as shown in FIG. That is, when the main flows Fa and Fb accompanied by the inlet boundary layers 10a and 10b flow into the flow paths 12a and 12b formed by the blades 11a, 11b and 11c, the leading edges 13a and 1b.
The vortices 14a and 14b are generated by colliding with 3b.

The vortices 14a and 14b are formed in a ventral horseshoe vortex 15
a, 15b and the dorsal horseshoe vortex 16a, 16b, 16c. Dorsal horseshoe vortex 16a, 16b, 1
6c are negative pressure wings 11a, 11
While flowing along the dorsal sides 17a, 17b, 17c of b, 11c, they flow to the trailing edges 18a, 18b, 18c while gradually growing by involving the boundary layer of the flow paths 12a, 12b.

On the other hand, the ventral horseshoe vortex 15a, 15b is formed on the ventral side 19 of the wings 11a, 11b, 11c under positive pressure.
a, 19b, 19c, adjacent wing 11 under negative pressure
Due to the pressure difference between the back sides 17b and 17c of the b and 11c, the adjacent blades 11b and 11c together with the secondary flows 20a and 20b.
When flowing toward the back sides 17b and 17c of the
a, 12b, which grows greatly, involving the boundary layer, and turns into the channel vortices 21a, 21b, and eventually the dorsal horseshoe vortex 16a, 1
Merge with 6b and 16c.

Thus, the wings 11a of the mainstream Fa, Fb,
The vortices 14a, 14b generated by the collision of the front edges 11a, 13b of the 11b are divided into ventral horseshoe vortices 15a, 15b and dorsal horseshoe vortices 16a, 16b, 16c, respectively, and the ventral horseshoe vortex 15a , 15b grow large and become channel vortices 21a, 21b, and dorsal horseshoe vortices 16a, 1b.
The large growth of 6b, 16c while flowing along the dorsal side 17a, 17b, 17c is collectively called secondary flow vortex.

The secondary flow vortex disturbs the streamlines of the main flows Fa and Fb passing near the wall surface 22 of the flow paths 12a and 12b,
This is a major cause of lowering the blade efficiency of the blades 11a, 11b, 11c. For this reason, how to suppress the secondary flow vortex has been a problem to dramatically improve the blade efficiency as compared with the conventional one.

As a technique in which the suppression of the secondary flow vortex is applied to a nozzle, for example, the document “The Effect of Nozzle Le”
an on Turbrine Efficiency ”(ASME paper PWR. Vol.1
3) and Japanese Patent No. 2038293, and have obtained good results in actual application.

However, with respect to the moving blade 2, the nozzle 2
Similarly to the above, despite the occurrence of secondary flow vortices accompanying the secondary flow of the main flow F, little progress has been seen in its development. Since the rotor blade 3 rotates by the velocity energy given from the nozzle 2 and only transmits its rotational force to the turbine shaft 6, the development and emphasis are placed on its strength and vibration countermeasures, and the emphasis is on improving blade efficiency. It is considered not.

However, today, research is being conducted to improve the thermal efficiency of a power plant. Improving the blade efficiency of the rotor blade 3 is also important in dramatically improving the overall stage efficiency of the axial turbine. is there.

The present invention has been made under such background art, and suppresses a secondary flow vortex generated due to a secondary flow generated between the blade rows of the moving blades, thereby improving blade efficiency. It is an object of the present invention to provide an intended axial turbine.

Another object of the present invention is to provide an axial turbine in which the blade efficiency of the nozzle is further improved as well as the blade efficiency of the moving blade.

[0019]

SUMMARY OF THE INVENTION In order to achieve the above object, an axial flow turbine according to the present invention, as described in claim 1, includes a stage in which a nozzle and a moving blade are combined in the axial direction of the turbine shaft. Axial turbines arranged in multiple stages along
The blade element cross-section center line connecting the blade element cross-section center point of the root portion of the rotor blade and the blade element cross-section center point of the tip portion in a straight line is inclined with respect to a rotation center reference line passing through the center of the turbine shaft,
Further, it is configured such that its inclination is directed to the downstream side of the turbine shaft.

In order to achieve the above object, in the axial flow turbine according to the present invention, the blade element cross-sectional center line is inclined with respect to a rotation center reference line passing through the center of the turbine shaft. When the inclination angle α is 0 <α ≦ 15 °
Is set in the range.

In order to achieve the above object, in the axial flow turbine according to the present invention, a plurality of stages each including a combination of a nozzle and a moving blade are arranged along the axial direction of the turbine shaft. In the axial flow turbine, the blade element cross-section center line of the rotor blade is a straight line inclined from the blade element cross-section center point of the root portion with respect to the rotation center reference line passing through the center of the turbine shaft, and the blade portion of the tip portion. This is a combination of a straight line inclined from the elementary cross-section center point and a convex curved line toward the upstream side of the turbine shaft at the intermediate portion.

In order to achieve the above object, in the axial flow turbine according to the present invention, as set forth in claim 4, the blade element cross-section center line is a straight line inclined from the blade element cross-section center point of the root portion. When the inclination angle with respect to the rotation center reference line passing through the center of the turbine shaft is βr, and the inclination angle with respect to the rotation center reference line passing through the center of the turbine shaft of a straight line inclined from the blade element sectional center of the tip portion is βt. , Each inclination angle β
r and βt are set in a range of 0 ° <βr, βt ≦ 20 °.

In order to achieve the above object, the axial flow turbine according to the present invention has a stage in which nozzles and moving blades are combined are arranged in a plurality of stages along the axial direction of the turbine shaft. In an axial flow turbine, when viewed from the meridian plane, the blade element cross-section center line of the rotor blade is a straight line inclined from the blade element cross-section center point of its root with respect to a rotation center reference line passing through the center of the turbine shaft. And a straight line inclined from the center point of the blade element cross section of the tip portion and a convex curved line directed to the upstream side of the turbine shaft in combination with the intermediate portion, while observing from the transverse direction of the turbine shaft. Then, with respect to the rotation center reference line passing through the center of the turbine shaft, a straight line inclined from the blade element cross-sectional center point of the root portion and a straight line inclined from the blade element cross-sectional center point of the tip portion, Above the blade of the bucket It is obtained by constituting a convex arc line toward the combination.

In order to achieve the above object, in the axial flow turbine according to the present invention, the center line of the blade element cross section is, when observed from a direction transverse to the turbine axis, the blade of the root portion. The inclination angle relative to the rotation center reference line passing through the center of the turbine axis of the straight line inclined from the elementary section center point is δr
Where δt is the inclination angle of a straight line inclined from the blade element cross-section center point of the tip portion with respect to the rotation center reference line passing through the center of the turbine axis, each inclination angle δr, δt is defined as 0 <δ
r, δt ≦ 20 °.

In order to achieve the above object, in the axial flow turbine according to the present invention, a plurality of stages in which nozzles and moving blades are combined are arranged along the axial direction of the turbine shaft. In the axial flow turbine, a blade element cross-section center line that linearly connects the blade element cross-section center point of the root portion of the rotor blade and the blade element cross-section center point of its tip portion is defined as a rotation center reference passing through the center of the turbine shaft. And the nozzle is tilted in the same direction as the blade element cross-sectional center line of the blade so that the nozzle is upstream of the blade. It is arranged in.

In order to achieve the above object, in the axial flow turbine according to the present invention, a stage in which a nozzle and a moving blade are combined is arranged in a plurality of stages along the axial direction of the turbine shaft. In the axial flow turbine, the blade element cross-section center line of the rotor blade is a straight line inclined from the blade element cross-section center point of the root portion with respect to the rotation center reference line passing through the center of the turbine shaft, and the blade portion of the tip portion. A straight line inclined from the center point of the elemental section and a convex curved line facing the upstream side of the turbine shaft at the intermediate portion are combined, and the nozzle has the same shape as the blade element section center line of the rotor blade. And arranged upstream of the rotor blade.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an axial turbine according to the present invention will be described below with reference to the drawings.

FIG. 1 shows a first embodiment of an axial flow turbine according to the present invention.
It is a schematic diagram showing an embodiment. FIG. 1 shows a moving blade constituting a part of the paragraph in the axial flow turbine.

The moving blades 23 according to the present embodiment are implanted in an implant 25 of a turbine shaft 24 and are arranged in an annular row along the circumferential direction of the turbine shaft 24.

The rotor blade 23 has a blade element section center line (inertial principal axis) I connecting the blade element section center point A of the tip section 26a and the blade element section center point B of the root section 26b with a center O of the turbine shaft 24. Is tilted at an angle α with respect to a rotation center reference line R passing through. That is, with respect to the flow of the main flow F, the blade element cross-sectional center line I is formed so as to be inclined toward the downstream side of the turbine shaft 24.

The center line I of the blade element cross section of the rotor blade 23 is defined with respect to a rotation center reference line R passing through the center O of the turbine shaft 24.
The inclination angle α is set in a range of 0 <α ≦ 15 °.

The moving blade 23 according to the present embodiment sets the inclination angle α of the blade element sectional center line I within a range of 0 <α ≦ 15 ° with respect to a rotation center reference line R passing through the center O of the turbine shaft 24. When set, as shown in FIG. 2, the inlet passage cascade line Ti of the tip portion 26a is inclined toward the downstream side of the turbine shaft 24 with respect to the inlet passage cascade line Ri of the root portion 26b. 1
As shown in a vector V shown in FIG. 5, a pressing force is generated against the flow of the main flow F against the tip portion 26a.

Therefore, in the present embodiment, the tip 2
Since the main flow F generates a pressing force of the vector V with respect to 6a, the dorsal horseshoe vortices 16a and 16b and the channel vortices 21a and 21b shown in FIG. 15 can be suppressed.

Further, the effect of reducing the pressure difference between the ventral side and the dorsal side will be described with reference to FIG.

FIG. 3 shows a pressure gradient (secondary flow 20a) generated from the ventral side 19a to the dorsal side 17b shown in FIG.
Is a graph showing a comparison with a conventional example. As compared with the conventional pressure gradient shown in FIG. 15, the abdominal static pressure distribution has almost the same value, but the dorsal static pressure distribution is higher in the present embodiment than in the conventional art. The pressure difference between the ventral side and the dorsal side is significantly reduced in the present embodiment and is reduced. The effect of reducing the pressure difference is that the center line I of the blade element cross section of the rotor blade 23 is tilted to the downstream side of the flow of the main flow F as compared with the related art.
It is considered that the pressing force of the vector V is generated at the tip portion 26a with respect to the flow of the main flow F, and the load sharing of the main flow of the tip portion 26a is reduced by the pressing force as compared with the related art.

As described above, when the pressure difference between the ventral side and the back side becomes small, as shown in FIG. 16, the secondary flow 28 becomes strong due to the large pressure difference, and the back side generated at the front edge 27 is formed. In the present embodiment, as shown in FIG. 4, since the confluence vortex 29 of the horseshoe type vortex and the flow path vortex grows greatly on the back side 30 of the other adjacent moving blade 23, the pressure difference is small. The next flow 28 is also weakened, and the confluence vortex 29 is relatively small. For this reason, the turbulence of the streamline of the main stream F is reduced, and the blade efficiency can be improved as compared with the conventional case.

Next, the ratio (η _i / η ₀ ) of the blade efficiencies η _i when the inclination angle α of the blade element section center line I of the rotor blade 23 is changed in the range of 0 ° <α ≦ 15 °. Is shown.

FIG. 5 shows that the blade efficiency ratio exceeds 1.0 when the inclination angle α is in the range of 0 ° to 15 °, and that the blade efficiency is superior to the conventional one.

Further, the pressure loss of the moving blade 23 will be described with reference to FIG. FIG. 6 is a graph showing the pressure loss distribution along the blade height direction at the blade outlet in comparison with the related art. Compared with the pressure loss of the conventional moving blade, the pressure loss distribution A according to the present embodiment is almost similar to the middle portion of the moving blade and the root portion 26b, but the fluctuation is significantly reduced at the tip portion 26a. I have. Normally, since the pressure loss of the rotor blade is affected by the secondary flow, its root portion 2
6b and the tip portion 26a are larger,
In the present embodiment, the blade element cross-sectional center line I of the blade 23 is inclined toward the downstream side of the flow of the main flow F so that the blade 2
Since the inclined pressing force V is generated from 3, the pressure loss of the tip portion 26a is reduced as shown in FIG.

FIG. 7 shows a second embodiment of the axial turbine according to the present invention.
It is a schematic diagram showing an embodiment. The same parts as those in the first embodiment are denoted by the same reference numerals.

The moving blade 23 according to the present embodiment, when observing the blade element cross-sectional center line I in the meridian plane, has the blade element cross-sectional center point A of the tip part 26a and the blade element cross-sectional center point B of the root part 26b. In each case, a straight line I having an inclination angle βt, βr with respect to a rotation center reference line R passing through the center O of the turbine shaft 24.
_1, the I _2, in which the intermediate portion toward the front edge 27 and the convex curved line I _3, and the serially connected and constitute a curved line I ₃ the respective straight lines I _1, I ₂ is there.

The straight lines I ₁ and I ₂ of the blade element section center line I respectively set the inclination angles βt and βr with respect to the rotation center reference line R in the range of 0 ° <βt, βr ≦ 20 °. Is done.

The moving blade 23 according to this embodiment has the inclination angles βt, βr of the straight lines I ₁ , I ₂ with respect to the rotation center reference line R passing through the center O of each turbine shaft 24 among the blade element cross-sectional center lines I. Is set in the range of 0 ° <βt, βr ≦ 20 °, the pushing of the vectors V ₁ and V ₂ to the tip part 26a and the root part 26b with respect to the flow of the main flow F, respectively, as in the first embodiment. Pressure develops.

Therefore, in the present embodiment, the tip 2
6a and the root portion 26b respectively have a vector V ₁ ,
Since the pressing force of the V ₂ occurs, it is possible to reduce the pressure gradient between the back side of the blade to suppress secondary flows next to one blade ventral and other, along with this two Generation of the next flow vortex can also be suppressed relatively low as compared with the related art.

Next, among the blade element cross-sectional center lines I of the rotor blades 23, the inclination angles βt and βr of the straight lines I ₁ and I ₂ were changed in the range of 0 ° <βt, βr ≦ 20 °. The degree of influence on the blade efficiency ηi in this case will be described. FIG. 8 is a graph showing the relationship between the inclination angles βt and βr and the blade efficiency ηi when the straight lines I ₁ and I ₂ are taken out of the blade element cross-sectional center line I of the rotor blade 23. The ratio (η _i / η ₀ ) of the blade efficiency η _i in the present embodiment to the blade efficiency η ₀ of FIG.

FIG. 8 shows that the inclination angles βt and βr are 0 ° to 2 °.
The blade efficiency ratio exceeds 1.0 in the range of 0 °, and it is recognized that the blade efficiency is superior to the conventional one.

As shown in FIG. 6, when the pressure loss of the rotor blade 23 is compared with that of the prior art, in the pressure loss distribution B according to the present embodiment, the fluctuation is also reduced in the tip portion 26a and the root portion 26b. . This means that the vectors V ₁ and V ₁ directed to the tip part 26a and the root part 26b,
Probably because of the influence of the pressing force of ₂ .

FIG. 9 shows a third embodiment of the axial flow turbine according to the present invention.
It is a schematic diagram showing an embodiment. The same components as those of the first embodiment are denoted by the same reference numerals. Also, in the drawing,
The left diagram and the right diagram correspond to the positional relationship of the components, the left diagram is the rotor blade 23 observed from the meridian plane as in the second embodiment, and the right diagram is the transverse direction of the turbine shaft 24. 4 shows the moving blade 23 observed from FIG.

As shown in the right figure, the moving blade 23 according to the present embodiment is configured such that the blade element cross-sectional center line I is defined by the blade element cross-sectional center point A of the tip part 26a and the blade element cross-sectional center point B of the root part 26b. In each case, a straight line I ₁ , at an inclination angle δt, δr with respect to a rotation center reference line R passing through the center O of the turbine shaft 24,
To I _2, the middle portion toward the ventral side 31 and the convex curved line I _3, is obtained by the serially connected and constitute a curved line I ₃ the respective straight lines I _1, I _2.

The straight lines I ₁ and I ₂ of the blade element section center line I respectively set the inclination angles δt and δr with respect to the rotation center reference line R in the range of 0 ° <δt, δr ≦ 20 °. Is done.

The moving blade 23 according to the present embodiment has a straight line I among the blade element sectional center lines I observed from the meridional plane shown in the left diagram.
₁ and I ₂ are directed toward the leading edge 27 and the straight lines I ₁ and I ₂ observed from the transverse direction of the turbine shaft 24 shown in the right figure are directed toward the ventral side 31 by combining them. , The vector V toward the tip 26a and the root 26b.
₁ and V ₂ are generated, and the vector V is applied from the ventral side 31 toward the tip 26a and the root 26b.
_3, the pressing force of the V ₄ occurs, the secondary flow and the secondary flow vortices these pressing force is synergistic can be significantly suppressed than the prior art.

In the present embodiment, of the blade element section center lines I observed from the transverse direction of the turbine shaft 24, a straight line I
_The inclination angles δt, δr of ₁ and I ₂ with respect to the rotation center reference line R passing through the center O of the turbine shaft 24 are defined as 0 ° <δt, δr
When it is set in the range of ≦ 20 °, as shown in FIG. 10, the blade efficiency ratio of the blade efficiency η _i to the conventional blade efficiency η ₀ (η _i /
η ₀ ) can be improved.

As shown in FIG. 6, when the pressure loss of the rotor blades 23 is compared with the conventional one, in the pressure loss distribution C according to the present embodiment, the fluctuation is significantly reduced even at the tip portion 26a and the root portion 26b. I have. This is the tip 2
The pressing force of the vector V _1, V ₂ toward the 6a and the root portion 26b and, due to the influence of synergy between the pressing force of the vector V _3, V ₄ toward the ventral 31 direction to the tip portion 26a and the root portion 26b it is conceivable that.

FIG. 11 is a schematic view showing a fourth embodiment of the axial turbine according to the present invention. The same parts as those of the first embodiment are denoted by the same reference numerals.

In this embodiment, the blade element cross-sectional center line I of the rotor blade 23 is inclined to the downstream side of the turbine shaft 24 by an inclination angle α with respect to a rotation center reference line passing through the center O of the turbine shaft 24. Accordingly, the rear edge 35 of the nozzle 34 supported by the diaphragm outer ring 32 and the diaphragm inner ring 33 is inclined linearly from the tip 26a toward the root 26b toward the downstream side of the turbine shaft 24. is there.

Generally, in the stage 36 of the axial flow turbine in which the nozzle 34 and the blade 23 are combined, the trailing edge 35 of the nozzle 34
A wake with a non-uniform velocity distribution due to the thickness of the wake occurs. For this reason, the rotor blade 23 arranged on the downstream side of the nozzle 34 generates an additional loss due to the generation of the downstream side. This loss is classified into mixing loss and unsteady flow loss.

This mixing loss is caused by the mixing of the main flow F and the velocity loss due to the thickness of the trailing edge 35, as shown in FIG. 12, and as shown in FIG. As the mixture becomes larger, the mixing of the two proceeds, so that the loss increases.

The unsteady flow loss is caused by the moving blade 2 of the main flow F.
3 is generated because the inflow angle and the inflow speed to the nozzle 3 periodically fluctuate due to the wake from the trailing edge 35 of the nozzle 34. As the distance between the nozzle 34 and the blade 23 increases, the magnitude of the fluctuations increases. Being mitigated reduces its losses.

Therefore, as shown in FIG. 12, the gap between the nozzle 34 and the rotor blade 23 has an appropriate value that minimizes the total loss which is the sum of the mixing loss and the unsteady flow loss.

When designing paragraph 36 of an axial turbine,
Conventionally, the gap between the trailing edge 35 of the nozzle 34 and the blade 23 is such that the blade element cross-sectional center line I of the blade 23 passes through the center of each blade toward the blade height direction. An appropriate value has been set so as to match the center line I of the elementary section.

However, if the conventional proper gap value is adopted as it is, in the present embodiment, the gap between the trailing edge 35 of the nozzle 34 and the moving blade 23, particularly the gap of the tip portion, becomes too large. For this reason, in the present embodiment, as shown in FIG.
The nozzle 3 is adjusted to match the center line I of the blade element cross section of the rotor blade 23.
The leading edge 37 and the trailing edge 35 are inclined toward the downstream side of the turbine shaft 24.

Therefore, in the present embodiment, the leading edge 3 of the nozzle 34 is
The gap value between the trailing edge 35 of the nozzle 34 and the moving blade 23 is shown in FIG. 12 because the trailing edge 7 and the trailing edge 35 are inclined toward the downstream side of the turbine shaft 24 from the tip portion 26a to the root portion 26b. It can be kept at an appropriate value, and the conventional total loss can be kept low.

FIG. 13 is a schematic view showing a fifth embodiment of the axial turbine according to the present invention. The same parts as those of the first embodiment are denoted by the same reference numerals.

In this embodiment, when the blade element section center line I of the rotor blade 23 is observed on the meridian plane, the blade element section center point A of the tip section 26a and the blade element section center point B of the root section 26b are respectively determined. At a rotation center reference line R passing through the center O of the turbine shaft 24, the straight lines I ₁ ,
Along with the configuration of continuous connection to each of I ₂ , the shapes of the leading edge 37 and the trailing edge 35 of the nozzle 34 are also changed to the blades of the rotor blade 23 in which the straight lines I ₁ , I ₂ and the curved line I ₃ are combined. This is in accordance with the shape of the elementary sectional center line I.

In the present embodiment, the shapes of the leading edge 37 and the trailing edge 35 of the nozzle 34 are adjusted to the shape of the blade element cross-sectional center line I of the moving blade 23. Can be set to an appropriate value shown in FIG.

Therefore, in this embodiment, the nozzle 34
Since the gap between the trailing edge 35 and the rotor blade 23 is set to an appropriate value, the total loss shown in FIG. 12 can be reduced.

[0067]

As described above, in the axial flow turbine according to the present invention, the center line of the blade element section of the moving blade is set to the rotation center reference line passing through the center of the turbine shaft from the tip portion to the root portion. On the other hand, it is configured linearly in the direction toward the wake side of the main flow, and generates a pressing force toward each of the tip part and the root part, so the generation of secondary flow and secondary flow vortex can be suppressed. Thus, the blade efficiency can be greatly improved as compared with the conventional case.

Further, in the axial flow turbine according to the present invention, the center line of the blade element cross section of the rotor blade is formed into a straight line which is inclined with respect to the rotation center reference line at the tip portion and the root portion, and the upstream portion of the main flow at the intermediate portion. Each of the straight lines and the curved lines is continuously connected to generate a pressing force toward each of the tip portion and the root portion of the moving blade, so that a more secondary shape is obtained. Generation of flow and secondary flow vortices can be suppressed. At that time, when observed from the transverse direction of the turbine axis, the blade element cross-sectional center line of the rotor blade is, as described above, a straight line inclined with respect to the rotation center reference line at the tip part and the root part, and the intermediate part thereof Each of the straight lines and the curved lines was continuously connected to generate a pressing force from the ventral side toward each of the tip portion and the root portion. The secondary and secondary flow vortices can be reliably suppressed.

In the axial flow turbine according to the present invention, the shape of the nozzle is formed so as to conform to the center line of the blade element cross section of the moving blade, and the gap between the nozzle and the moving blade is set to an appropriate value.
The combined loss of the mixing loss and the unsteady flow loss can be reduced, and an axial turbine with high blade efficiency can be realized.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a first embodiment of an axial turbine according to the present invention.

FIG. 2 is a schematic plan development view of the blade according to the first embodiment observed from a tip portion.

FIG. 3 is a graph comparing pressure distributions generated on the ventral and dorsal sides of the rotor blade according to the first embodiment with those of the related art.

FIG. 4 is a view for explaining the behavior of the secondary flow of the rotor blade according to the first embodiment.

FIG. 5 is a diagram showing the blade element cross-sectional center line of the rotor blade according to the first embodiment;
9 is a graph showing a relationship between an inclination angle and a blade efficiency ratio when inclined with respect to a rotation center reference line passing through the center of a turbine shaft.

FIG. 6 is a graph showing distribution of pressure loss of a moving blade in the first embodiment, the second embodiment, and the third embodiment in comparison with a conventional case.

FIG. 7 is a schematic view showing a second embodiment of the axial flow turbine according to the present invention.

FIG. 8 shows a blade element cross-sectional center line of the rotor blade according to the second embodiment,
The root portion and the tip portion are inclined with respect to the rotation center reference line passing through the center of the turbine shaft to make a straight line, and the intermediate portion is formed into a convex curved line toward the upstream side of the main flow, and the straight line and the curved line are formed. 7 is a graph showing the relationship between the inclination angle of the straight line and the blade efficiency ratio when.

FIG. 9 is a schematic view showing a third embodiment of the axial turbine according to the present invention.

FIG. 10 is a diagram illustrating the blade according to the second embodiment viewed from a direction transverse to the turbine axis. The blade element cross-sectional center line is defined with respect to a rotation center reference line passing through the center of the turbine shaft at the root portion and the tip portion. A graph showing the relationship between the angle of inclination of the straight line and the blade efficiency ratio when these straight lines and curved lines are combined by forming the intermediate portion into a curved line convex toward the ventral side by inclining it into a straight line. .

FIG. 11 is a schematic view showing a fourth embodiment of the axial flow turbine according to the present invention.

FIG. 12 is a view for explaining a loss generated due to a gap between a nozzle and a rotor blade.

FIG. 13 is a schematic view showing a fifth embodiment of the axial flow turbine according to the present invention.

FIG. 14 is a schematic view showing an embodiment of a conventional axial flow turbine.

FIG. 15 is a diagram illustrating generation and behavior of a secondary flow and a secondary flow vortex.

FIG. 16 is a view for explaining the behavior of a secondary flow of a conventional moving blade.

[Explanation of symbols]

 1 Paragraph 2 Nozzle (Static Blade) 3 Moving Blade 4 Diaphragm Outer Ring 5 Diaphragm Inner Ring 6 Turbine Shaft 7 Implanted Section 8 Shroud 9 Seal Fin 10a, 10b Inlet Boundary Layer 11a, 11b, 11c Blade 12a, 12b Channel 13a, 13b Front Edge 14a, 14b Vortex 15a, 15b Ventral horseshoe vortex 16a, 16b, 16c Dorsal horseshoe vortex 17a, 17b, 17c Dorsal 18a, 18b, 18c Trailing edge 19a, 19b, 19c Ventral 20a, 20b Secondary flow 21a, 21b Flow path vortex 22 Wall surface 23 Rotor blade 24 Turbine shaft 25 Implantation part 26a Tip part 26b Root part 27 Front edge 28 Secondary flow 29 Merging vortex 30 Back side 31 Abdominal side 32 Diaphragm outer ring 33 Diaphragm inner ring 34 Nozzle 35 Rear Edge 36 Paragraph 37 Front edge

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Mitsuko Toi 1-1-1 Shibaura, Minato-ku, Tokyo Inside Toshiba Corporation Head Office

Claims (8)

[Claims] 1. An axial flow turbine in which a stage in which a nozzle and a moving blade are combined is arranged in a plurality of stages along an axial direction of a turbine shaft, a blade element cross-sectional center point of a root portion of the moving blade and a blade element cross section of a tip portion. The center line of the wing element section connecting the center point in a straight line,
An axial flow turbine, wherein the turbine is inclined with respect to a rotation center reference line passing through the center of the turbine shaft, and the inclination is directed to the downstream side of the turbine shaft. 2. When the blade element sectional center line is inclined with respect to a rotation center reference line passing through the center of the turbine shaft, the inclination angle α is set in a range of 0 <α ≦ 15 °. The axial flow turbine according to claim 1. 3. An axial flow turbine in which a stage in which a nozzle and a moving blade are combined is arranged in a plurality of stages along an axial direction of a turbine shaft, wherein a center line of a blade element cross section of the moving blade is a rotation center passing through the center of the turbine shaft. With respect to the reference line, a straight line inclined from the center point of the blade element cross section of the root part, a straight line inclined from the center point of the blade element cross section of the tip part, and a convex part in which the middle part faces the upstream side of the turbine shaft. An axial flow turbine comprising a combination of a curved line and a curved line. 4. The blade element cross-section center line is defined as βr, the inclination angle of a straight line inclined from the blade element cross-section center point of the root portion with respect to a rotation center reference line passing through the center of the turbine axis. Assuming that an inclination angle of a straight line inclined from the center point with respect to a rotation center reference line passing through the center of the turbine shaft is βt, each inclination angle βr, βt is 0 ° <βr, βt ≦
The axial turbine according to claim 3, wherein the axial flow turbine is set within a range of 20 °. 5. In an axial flow turbine in which a stage in which a nozzle and a moving blade are combined is arranged in a plurality of stages along an axial direction of a turbine shaft, when a blade element cross-sectional center line of the moving blade is observed from a meridian plane, With respect to the rotation center reference line passing through the center of the shaft, a straight line inclined from the blade element cross-section center point of the root part, a straight line inclined from the blade element cross-section center point of the tip part, and the intermediate part are the turbine shaft. And a convex curved line directed toward the upstream side of the turbine shaft, and when viewed from a direction transverse to the turbine shaft, a blade element cross section of the root portion with respect to a rotation center reference line passing through the center of the turbine shaft. A straight line inclined from the center point, a straight line inclined from the center point of the blade element cross section of the tip portion, and a middle curved portion formed by combining a convex curved line facing the ventral side of the rotor blade. And axial flow turbine. 6. The blade element cross-section center line, when observed from the transverse direction of the turbine axis, represents an angle of inclination with respect to a rotation center reference line passing through the center of the turbine axis of a straight line inclined from the blade element cross-section center point of the root portion. Let δr denote the angle of inclination of a straight line inclined from the blade element cross-section center point of the tip portion with respect to the rotation center reference line passing through the center of the turbine axis. 6. The axial flow turbine according to claim 5, wherein the angle is set in a range of 20 [deg.]. 7. An axial flow turbine in which a plurality of stages each including a nozzle and a moving blade are arranged along an axial direction of a turbine shaft, wherein a blade element cross-sectional center point of a root portion of the moving blade and a blade element of a tip portion thereof are provided. The blade element cross-section center line connecting the cross-section center point in a straight line is inclined with respect to the rotation center reference line passing through the center of the turbine shaft, and the inclination is directed to the downstream side of the turbine shaft. An axial flow turbine, wherein the nozzle is arranged in the same direction as the center line of the blade element cross section of the rotor blade and arranged upstream of the rotor blade. 8. In an axial flow turbine in which a stage in which a nozzle and a moving blade are combined is arranged in a plurality of stages along an axial direction of a turbine shaft, a center line of a blade element cross section of the moving blade is a rotation center passing through the center of the turbine shaft. With respect to the reference line, a straight line inclined from the center point of the blade element cross section of the root part, a straight line inclined from the center point of the blade element cross section of the tip part, and a convex part in which the middle part faces the upstream side of the turbine shaft. Wherein the nozzle is formed in the same shape as the center line of the blade element cross section of the moving blade, and is arranged upstream of the moving blade.