JPH10311205A - Axial flow turbine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a fluid leakage quantity in a seal fin part by forming projecting fins in plural rows in the intermediate part of flat parts formed in the outer peripheral surface tip part of an integral cover arranged in a moving blade tip part, and specifying the dimension of a clearance or the like between a projecting fin tip part and a stationary part side fin tip part. SOLUTION: The inflow side end part and the outflow side end part of a working fluid are formed in flat parts 53a and 53b on the outer peripheral surface of an integral cover 52 arranged on the tip of the moving blade 51 of the stepped passage part of an axial flow turbine, and plural projecting fins 54 are formed in its intermediate part. Here, when respective outside diametrical dimensions of the flat part 53a, the projecting fins 54 and the flat part 53b are denoted by D1 to D3 and a radial directional clearance distance between the flat part 53a and a seal fin 58 tip part in a position opposed to this is denoted by C1 and a radial directional clearance distance between the projecting fins 54 and the seal fin 58 tip part in a position opposed to these is denoted by C2 , the respective parts are set so as to satisfy the relationship of [D1 <D3 <D2 and C2 =(0.5 to 1.0)×C1 ].

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 the like which prevents fluid from leaking from a gap between a rotating portion at the tip of a moving blade and a stationary portion such as a casing.

[0002]

2. Description of the Related Art In general, an axial turbine such as a steam or gas turbine comprises a stationary nozzle and a rotating blade. The nozzle expands a working fluid such as steam from a high pressure upstream to a low pressure downstream and converts thermal energy into velocity energy. The rotor blades are rotated by this velocity energy to become rotational energy, and the rotating energy turns a generator or the like to extract power.

[0003] As described above, in the axial flow turbine, the tip of the rotating blade and the stationary portion composed of a nozzle and the like are close to each other with an appropriate gap. Therefore, a part of the working fluid such as steam flowing from the nozzle to the rotor blade flows into the gap.
This flow does not contribute to the energy for rotating the turbine and causes a decrease in efficiency. Therefore, conventionally, in order to reduce this flow as much as possible, a fin-shaped member is provided on the moving blade or the stationary portion. As an example, FIG. 10 shows a leakage prevention device at the tip of a moving blade conventionally used in a steam turbine.

[0004] The turbine stage section 1 is mounted on a nozzle diaphragm 4 fixed by a casing 2 on a nozzle 5 forming a flow path section and on a wheel 6 at the center of the casing 2 and concentric with a rotatable rotor 3. It is provided with a moving blade 7 that is provided to form a passage, a shroud 9 fixed by a tenon 8 at the tip of the moving blade 7, and a seal fin 10 attached to the nozzle diaphragm 4. In such a turbine stage 1, the leakage fluid 1 passing through the blade tip 11
4 flows through the gap 13 between the shroud 9 and the seal fin 10. This leakage amount is 1 to 3% of the total flow rate in the paragraph section.
In this case, the energy conversion cannot be performed effectively, and the turbine efficiency is reduced, which greatly affects the performance.

There is a method of reducing the gap 13 between the shroud 9 and the seal fin 10 in order to reduce the amount of leakage. However, if the gap 13 is too small, mechanical contact between the shroud 9 and the seal fin 10 tends to occur, Gap 13
There is a limit to the value of.

For this reason, the structures shown in FIGS. 11 to 14 have conventionally been proposed in order to prevent leakage. In the example of FIG. 11, the number of teeth of the seal fins 10 is increased and the seal fins 10 are arranged continuously in the flow direction to enhance the sealing effect.

FIG. 12 shows a step 15 provided on the inflow side and the outflow side of the shroud 9. The step 15 attenuates the velocity energy of the leaked steam 14 flowing into the seal chamber 20, and the leaked steam 14 is sealed. This is a structure for preventing the air from flowing through the inside of the chamber 20. Further, as shown in FIG. 13, the conventional tenon 8 is abolished and the shroud 9 is integrally formed with the moving blade 7 to form an integral cover 17 as a method having a high sealing effect, and a concave groove 18 is formed at the center of the cover 17. In some cases, the sealing effect is enhanced by providing a plurality of the step portions 15 in FIG. 12 described above.

Further, as shown in FIG. 14, the specific volume of the turbine generally increases when the fluid expands from a high pressure to a low pressure. Therefore, in order to correspondingly increase the height of the nozzles and the moving blades in the paragraph passage from the high-pressure portion toward the low-pressure portion, the inclined portions 5a and 17a are formed in the nozzle 5 and the tip flow passage portion of the moving blade 7. The structure is adopted. In this case, since the conventional seal fin 16 shown in FIGS. 11 to 13 cannot be installed structurally, a flat surface 19 is provided on the outflow side of the shroud 9 and the seal fin 16 is provided.
Is partially installed.

[0009]

By the way, in the conventional leak preventing means, for example, in the case of FIG.
If the number of zeros is excessively increased or the gap 13 is increased, the velocity energy from the upstream is not sufficiently attenuated at the narrowed portion of the tip of the seal fin 10, and the residual energy causes the gap 13 between the seal fin 10 and the shroud 9. Phenomenon occurs, and the sealing effect is reduced.

On the other hand, in the case of FIG. 12, the above-mentioned disadvantage can be solved by providing the step portion 15. However, when the number of the seal fins 16 is large, the volume of the seal chamber 20 is reduced. The attenuation is reduced and its effect is reduced.

Further, in the case of FIG. 13, if the axial expansion due to thermal expansion of the turbine (rotor 3) is large, the contact between the concave groove 18 and the seal fin 16 is considered, and in the worst case, the seal fin 16 16 may not be installed. In the case of FIG. 14, since the nozzle 5 and the rotor blade 7 both have the inclined portions 5a and 17a, the seal fin 1
The number of 6 is reduced, and the sealing effect is low.

As described above, the conventional leak prevention device has various drawbacks, which causes a decrease in turbine efficiency.
SUMMARY OF THE INVENTION The present invention has been made in view of the above-described circumstances, and prevents an increase in the amount of fluid leakage due to a blow-through phenomenon of a seal fin portion. It is an object of the present invention to provide a leakage prevention device that can be applied to a stage, and to provide an axial flow turbine with improved stage efficiency of the turbine.

[0013]

In order to achieve this object, an axial flow turbine according to a first aspect of the present invention is an axial flow turbine comprising a stationary portion comprising a nozzle for discharging a working fluid and a rotating blade. A flat portion is formed on each of the working fluid inflow side and the outflow side of the rear end portion of the outer peripheral surface of the integral cover provided integrally with the front end portion of the rotor blade, and a plurality of rows of projection fins are provided in the middle portion thereof. The working fluid inflow side flat portion, the projection fin, and the working fluid outflow side flat portion have outer diameters of D1, D2, and D3, respectively, and are provided on the working fluid inflow side flat portion and a stationary portion opposed thereto. When the distance of the radial gap from the formed fin tip is C1 and the distance of the radial gap between the protruding fin tip and the fin tip provided on the stationary portion opposed thereto is C2, the following equation is used. Features that satisfy the conditions of To.

[0014]

D1 <D3 <D2 C2 = (0.5 to 1.0) × C1 As described above, the flat portions are provided on both sides of the protruding fins, and the seal fins are provided so as to face the protruding fins. The effect is improved, the leakage fluid is reduced, and the seal fins do not come into contact with the projecting fins even when the rotor is displaced in the axial direction due to thermal expansion of the turbine. Also, even if the projection fins and the seal fins come into contact with each other, slight damage is sufficient, so that the gap can be further reduced.

To achieve the above object, an axial flow turbine according to a second aspect of the present invention is an axial flow turbine comprising a stationary portion comprising a nozzle for discharging a working fluid and a rotating blade, wherein the tip of the blade is provided. A flat portion is formed on each of the working fluid inflow side at the front end portion of the outer peripheral surface of the integral cover provided integrally with the portion and the outflow side at the rear end portion, and a plurality of rows of projection fins are formed at an intermediate portion thereof. The outer diameter of each of the inflow side flat portion, the projection fin, and the working fluid outflow side flat portion is D1, D
2, D3, and the distance of the radial gap between the working fluid inflow side flat portion and the fin tip provided on the stationary portion opposed thereto is C1, and the distance between the projecting fin tip and the stationary portion opposed thereto is C1. When the distance of the radial gap from the provided fin tip is C2, the following condition is satisfied.

[0016]

D1 <D2 <D3 C2 = (0.5-1.0) × C1 Thereby, a flat portion is provided on both sides of the projecting fin, and a seal fin is provided opposite to the projecting fin. The seal fins do not contact the projection fins even when the rotor is displaced in the axial direction due to the thermal expansion of the turbine. Also, even if the projection fins and the seal fins come into contact with each other, slight damage is sufficient, so that the gap can be further reduced.

To achieve this object, an axial flow turbine according to a third aspect of the present invention is an axial flow turbine comprising a stationary portion comprising a nozzle for discharging a working fluid and a rotating moving blade. A plurality of flat portions and a concave groove formed lower than the adjacent flat portion are alternately provided between the working fluid inflow side at the front end portion and the outflow side at the rear end portion of the outer peripheral surface of the integral cover provided integrally with the portion. And the outer dimensions of the working fluid inflow side flat portion, the working fluid inflow side second flat portion, the working fluid outflow side first flat portion, and the working fluid outflow side flat portion are D1, D2, D3. When D4 is satisfied, the following condition is satisfied.

[0018]

D1 <D2 <D3 <D4 As a result, the velocity energy of the leaked fluid is attenuated in each concave groove portion, so that the leaked fluid does not pass through the gap between the seal fin and the integral cover, and the sealing effect is improved. .

In order to achieve this object, an axial flow turbine according to a fourth aspect of the present invention is an axial flow turbine comprising a stationary portion comprising a nozzle from which a working fluid flows out and a rotating blade, wherein the tip of the blade is provided. A plurality of flat portions are formed in a step-like manner between the working fluid inflow side at the tip of the outer peripheral surface of the integral cover provided integrally with the portion and the outflow side at the rear end. When the outer diameters of the flat portion and the working fluid outflow side flat portion are D1, D2, and D3, the following condition is satisfied.

[0020]

D1 <D2 <D3 As a result, the velocity energy of the leaked fluid is attenuated in the stepped portion, so that the leaked fluid does not pass through the gap between the seal fin and the integral cover, and the sealing effect is improved.

In order to achieve this object, an axial flow turbine according to a fifth aspect of the present invention is characterized in that an axial fin is formed at the upper end of the flat portion on the upstream side of the working fluid toward the upstream side. And

Accordingly, the velocity energy of the leaked fluid is attenuated at the fin portion inclined to the upstream side, so that the leakage fluid does not pass through the gap between the seal fin and the integral cover, and the sealing effect is improved.

In order to achieve this object, an axial flow turbine according to a sixth aspect of the present invention is an axial flow turbine comprising a stationary portion comprising a nozzle from which a working fluid flows out and a rotating blade, wherein the tip of the blade is provided. A plurality of flat portions and a plurality of protruding fins are alternately formed between the working fluid inflow side at the front end portion of the outer peripheral surface of the integral cover provided integrally with the portion and the outflow side at the rear end portion. The outer diameters of the fluid inflow side flat portion, the working fluid inflow side projection fin, the center flat portion, the working fluid outflow side projection fin, and the working fluid outflow side flat portion are D1, D
2, D3, D4, and D5, and the distance of the radial gap between the working fluid inflow side flat portion and the fin tip portion provided on the stationary portion opposed thereto is C1, and the working fluid outflow side projection fin tip portion is C1. When the distance of the radial gap between the fin tip provided on the stationary portion facing the fin and the fin is C2,
It satisfies the following condition.

[0024]

D1 <D2> D3 <D4> D5 C2 = (0.5-1.0) × C1 Accordingly, the velocity energy of the leaked fluid is attenuated at the protruding fin portion, and the leaked fluid is sandwiched between the protruding fins. Since the seal fins are also provided on the flat portions, the seal fins do not pass through the gaps, and the sealing effect is improved. Further, since the flat portions are provided on both sides of the projecting fins, the seal fins and the integral cover do not come into contact with each other even if the rotor blade moves in the axial direction due to thermal expansion of the turbine.

In order to achieve this object, an axial flow turbine according to a seventh aspect of the present invention is an axial flow turbine comprising a stationary portion comprising a nozzle from which a working fluid flows out and a rotating blade. A plurality of flat portions are formed stepwise between the working fluid inflow side at the tip of the outer peripheral surface of the integral cover provided integrally with the portion and the outflow side at the rear end. When the outer diameters of the flat portion and the working fluid outflow side flat portion are D1, D2, and D3, the following condition is satisfied.

[0026]

D1>D2> D3 As a result, the leakage fluid impinges on the seal fin several times while passing through the gap between the integral cover and the seal fin, so that the velocity energy is attenuated during that time, and the leakage fluid leaks. The amount is reduced and the sealing effect is improved.

In order to achieve this object, an axial flow turbine according to claim 8 of the present invention is an axial flow turbine comprising a stationary portion comprising a nozzle from which a working fluid flows out and a rotating blade. A flat portion is formed on each of the working fluid inflow side at the front end portion of the outer peripheral surface of the integral cover provided integrally with the portion and the outflow side at the rear end portion, and a plurality of rows of projection fins are formed at an intermediate portion thereof. The outer dimensions of the inflow side flat portion, the projection fins, and the working fluid outflow side flat portion are D1, D
2, D3, the outer diameter of the flat portion of the working fluid inflow side and the outer diameter of the protruding fin are D in order from the inflow side to the outflow side of the working fluid.
1, D2, D3, the distance of the radial gap between the flat portion and the fin tip provided on the stationary portion opposed thereto is C1, and the distance between the flat fin tip and the stationary portion opposed to the protruding fin tip is C1. When the distance of the radial gap from the fin tip is C2, the following condition is satisfied.

[0028]

D1 = D3 <D2 C2 = (0.5-1.0) × C1 This allows the fluid passing through the gap between the integral cover and the projection fin to hit the projection fin or the seal fin several times. The velocity energy is attenuated and cannot pass through the gap. Therefore, the amount of leaked fluid is reduced, and the sealing effect is improved. Further, since the flat portions are provided on both sides of the projecting fins, the seal fins do not come into contact with the integral cover even in the axial displacement of the moving blade due to thermal expansion of the turbine.

In order to achieve this object, an axial flow turbine according to a ninth aspect of the present invention is an axial flow turbine comprising a stationary portion comprising a nozzle from which a working fluid flows out and a rotating blade, wherein the tip of the blade is provided. A plurality of flat portions and a plurality of fins are alternately formed between the working fluid inflow side at the tip of the outer peripheral surface of the integral cover provided integrally with the portion and the outflow side at the rear end,
The outer diameters of the working fluid inflow side flat portion, the working fluid inflow side fin, the center flat portion, the working fluid outflow side fin, and the working fluid outflow side flat portion are D1, D2, D3, D4, and D5, respectively. The distance of the radial gap between the fluid inflow side flat portion and the fin tip provided on the stationary portion facing the fluid inflow portion is represented by C
1, wherein the distance of the radial gap between the tip end of the working fluid inflow side projecting fin and the tip end of the fin provided on the stationary portion opposed thereto is C2, and the following condition is satisfied. .

[0030]

D1 = D5 ≦ D3 <D2 = D4 C2 = (0.5-1.0) × C1 As a result, the leakage fluid passes through the gap between the integral cover and the seal fin several times. Since it hits the seal fin, the velocity energy is attenuated during that time, the amount of leakage is reduced, and the sealing effect is improved. Further, since the flat portions are provided on both sides of the projecting fins, the seal fins do not come into contact with the integral cover even in the axial displacement of the moving blade due to thermal expansion of the turbine.

[0031]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An axial turbine according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of a blade tip portion of a stage passage portion of the axial flow turbine according to the first embodiment. At the tip of the moving blade 51, an integral cover 52 formed integrally with the moving blade 51 is provided. On the outer peripheral surface, flat portions 53a and 53b are formed at an inflow end and an outflow end of the working fluid, and a plurality of projecting fins 54 are formed at an intermediate portion.

Here, the flat portion 53a, the projection fin 54,
The outer diameter of each flat portion 53b is D1, D2, D3, and the radial gap distance between the flat portion 53a and the tip of the seal fin 58 at a position facing the flat portion 53a is C1,
The radial gap distance between the projection fin 54 and the tip of the seal fin 58 at a position facing the projection fin 54 is represented by C2.
Then, a structure that satisfies the following condition is obtained.

[0033]

D1 <D3 <D2 C2 = (0.5 to 1.0) × C1 In this embodiment, the outer diameter of the flat portion 53a on the outer peripheral surface of the integral cover 52 at the tip of the wing and the outer diameter of the projection fin 54 are smaller. Because of the difference, after the fluid 57 flows out from the nozzle 55,
The leaking fluid 56 passing through the tip of the rotor blade 51 flows through the flat portion 53a on the inflow side and collides with the side surface of the downstream projection fin 54 (arrow a in the drawing). The leaked fluid that has reached the outflow side also collides with the seal fin 58 (arrow b in the drawing). As a result, the phenomenon that the leaked fluid flows from the inflow side flat portion 53a to the outflow side flat portion 53b through the protruding fins 54 is eliminated, and the flow resistance increases, so that the sealing effect can be further improved.

Further, since the seal fin 58 at the center is disposed so as to face the projecting fin 54 projecting from the integral cover 52, the sealing effect is higher than that of the conventional continuous fin. Further, even if the seal fin 58 and the projection fin 54 come into contact with each other due to some abnormal phenomenon during the rotation of the turbine, the contact portion becomes a point contact, so that damage is less than in the conventional seal fin, and the radial gap is further reduced. It is possible to further reduce the amount of leakage.

On the other hand, the projection fin 54 and the seal fin 58
By improving the leakage prevention means at the center of the integral cover 52, the length W1 of the center can be made shorter than before, and the length W2 and the flat portion 53b of the flat portion 53a are correspondingly reduced. Can be lengthened. Therefore, the difference in the amount of expansion and contraction due to the thermal expansion of the turbine shaft and the casing 2 can be absorbed by the lengths W2 and W3.
Contact with the four sides is avoided. That is, the present invention can be applied to a paragraph section in which the difference between the amount of expansion and contraction in the axial direction due to the thermal expansion of the turbine and the amount of expansion and contraction of the casing 2 is large.

With this configuration, the amount of leakage from the blade tip can be greatly reduced, and a significant improvement in the stage efficiency of the turbine can be obtained. Next, an axial turbine according to a second embodiment will be described with reference to FIG.

FIG. 2 is a sectional view of a blade tip portion of a stage passage portion of an axial flow turbine according to a second embodiment. Bucket 61
Integral cover 62 integral with rotor blade 61
Is provided. On the outer peripheral surface, flat portions 63a and 63b are formed at the inflow side end and the outflow side end, respectively, and a projection fin 64 is formed at the center between the flat portions 63a and 63b. The outer diameter of each of the flat portion 63a, the projection fin 64, and the flat portion 63b is D1, D2,
D3, the radial gap distance between the flat portion 63a and the tip of the seal fin 68 at a position facing the flat portion 63a is C1, the projection fin 64 and the tip of the seal fin 68 at a position facing the projection fin 64. Is defined as C2, the structure satisfies the following condition.

[0038]

D1 <D2 <D3 C2 = (0.5-1.0) × C1 In this embodiment, the outer diameters of the flat portions 63a and 63b on the outer peripheral surface of the integral cover 62 at the tip of the blade and the projection fins 64 Is different from the first embodiment, after the fluid 67 flows out of the nozzle 55 as in the first embodiment, the leakage fluid 66 passing through the blade tip flows through the flat portion 63a on the inflow side, and flows downstream. (See arrow c in the figure). Further, the leaked fluid that has reached the outflow side also collides with the side surface of the flat portion 63 provided at the outflow side end (arrow d in the figure).

As a result, the phenomenon that the leakage fluid flows from the inflow side flat portion 63a to the outflow side flat portion 63b through the protruding fins 64 is eliminated, and the flow resistance increases.
The sealing effect can be further improved. Further, since the seal fin 68 at the center is disposed so as to face the protruding fin 64 projecting from the integral cover 62, even when these fins come into contact with each other, point contact occurs and the rotor blade is greatly affected. Since it has no effect, the gap C2 can be made smaller than that of the conventional continuous fin, so that the sealing effect is improved.

The difference in the amount of expansion and contraction due to the thermal expansion between the turbine shaft and the casing 2 is determined by the inner diameter of the casing 2 and the moving blade 61.
Since the outer diameter of the distal end portion is increased toward the downstream side, the outer diameter can be absorbed.
To avoid contact with the side of the Therefore,
This is effective when the moving blade 61 largely moves downstream due to the difference in the axial expansion and contraction amount between the turbine and the casing 2 due to thermal expansion.

Next, an axial turbine according to a third embodiment will be described with reference to FIG. FIG. 3 is a sectional view of a blade tip portion of a stage passage portion of an axial flow turbine according to a third embodiment. At the tip of the moving blade 71, an integral cover 72 is provided integrally with the moving blade 71. The outer peripheral surface is provided with a plurality of flat portions 73 and concave grooves 75 alternately from the inflow side to the outflow side. The flat portion 73a, 73b,
When D1, D2, D3, and D4 are set in order from 73c and 73d, a structure that satisfies the condition of the following expression is obtained.

[0042]

D1 <D2 <D3 <D4 The seal fins 78 arranged at positions facing the flat portions 73a to 73d are respectively flat portions 73a to 73d.
Is set to have a uniform gap.

In this embodiment, the fluid 77 is
After flowing out, the leaked fluid 76 passing through the blade tip flows through the flat portion 73a at the inflow side end and collides with the side surface of the flat portion 73b immediately downstream (arrow f in the figure). Since the flat portions 73a, 73b, 73c, 73d are stepped, the leaked fluid repeats a similar movement. Due to the collision, the velocity energy of the leaked fluid is attenuated, so that the leaked fluid passing through the gap between the seal fin 78 and the flat portion 73 is reduced, and the sealing effect is improved.

The difference in the amount of expansion and contraction due to thermal expansion between the turbine shaft and the casing 2 is determined by comparing the inner diameter of the casing 2 with the moving blade 71.
Since the outer diameter of the tip portion can be absorbed by increasing the outer diameter toward the downstream side, it is effective when the moving blade 71 largely moves downstream due to a difference in the axial expansion and contraction amount of the turbine and the casing 2 due to thermal expansion. .

In FIG. 3, the flat portion 73 has been described as having four steps. However, the same effect can be obtained even with five or more steps. Next, a leakage prevention device for an axial turbine according to a fourth embodiment will be described with reference to FIG.

FIG. 4 is a sectional view of a blade tip portion of a stage passage portion of an axial flow turbine according to a fourth embodiment. Bucket 81
The integral cover 82 is integrated with the rotor blade 81 at the tip of
Is provided. A plurality of flat portions 83 are formed on the outer peripheral surface from the inflow side to the outflow side, and each is provided with a step-like step. When the outer diameter of the flat portion 83 is set to D1, D2, and D3 in order from the flat portions 83a, 83b, and 83c disposed on the inflow side, a structure that satisfies the following condition is obtained.

[0047]

D1 <D2 <D3 In the present embodiment, after the fluid 87 flows out of the nozzle 55, the leaking fluid 86 passing through the tip of the bucket flows through the flat portion 83a on the inflow side, and is immediately downstream of the flat portion 83a. It collides with the side surface of the flat part 83b (arrow g in the figure). Each flat portion 83a, 83b,
Since 83c has a step shape, the leaking fluid 86 repeats a similar movement. The collision causes the leaked fluid to attenuate the velocity energy possessed by the leaked fluid, so that the leaked fluid 86 passes through the gap between the seal fin 88 and the flat portion 83.
Is reduced and the sealing effect is improved.

The difference between the expansion and contraction due to the thermal expansion of the turbine shaft and the casing 2 is determined by the inner diameter of the casing 2 and the moving blade 81.
Since the outer diameter of the tip portion is increased by increasing the diameter toward the downstream side, it can be absorbed. Therefore, it is effective when the moving blade 81 moves largely to the downstream side due to the difference in the amount of expansion and contraction of the turbine and the casing 2 in the axial direction due to thermal expansion.

Next, a leakage prevention device for an axial turbine according to a fifth embodiment will be described with reference to FIG. FIG.
FIG. 13 is a sectional view of a blade tip portion of a paragraph passage portion of an axial flow turbine according to a fifth embodiment. At the tip of the moving blade 91, an integral cover 92 is provided integrally with the moving blade 91. In addition, a plurality of flat portions 93 are provided on the outer peripheral surface so as to provide a step-like step from the inflow side to the outflow side.
An axial fin 94 is formed at a corner of the upper surface of each flat portion 93 toward the upstream side of the leakage fluid.

A radial gap is formed between the seal fin 98 attached to the casing 2 and the flat portion 93, and a gap is also formed in the axial direction between the axial fin 94 and the seal fin 98 immediately upstream thereof. doing. Flat part 9
Flat portions 93a, 93 arranged on the inflow side with an outer diameter of 3
When D1, D2, and D3 are set in order from b and 93c, a structure that satisfies the condition of the following expression is obtained.

[0051]

D1 <D2 <D3 In the present embodiment, after the fluid 97 flows out of the nozzle 55, the leaking fluid 96 passing through the tip of the bucket flows through the flat portion 93a on the inflow side, and immediately downstream of the flat portion 93a. It collides with the side surface of the flat part 93b (arrow h in the figure). Further, since the flow is once restricted in the axial gap formed by the axial fins 94 and the seal fins 98, the leaked fluid attenuates the velocity energy possessed and increases the flow resistance.
The leakage fluid passing through the gap between the flat portion 93 and the flat portion 93 is reduced, and the sealing effect is improved.

The difference in the amount of expansion and contraction due to the thermal expansion between the turbine shaft and the casing 2 is determined by comparing the inner diameter of the casing 2 with the moving blade 91.
Since the outer diameters of the tip portions are increased as they go toward the downstream side, the absorption can be achieved. Therefore, it is effective when the moving blade 91 largely moves downstream due to the difference in the amount of expansion and contraction of the turbine and the casing 2 in the axial direction due to thermal expansion.

Next, an axial turbine according to a sixth embodiment will be described with reference to FIG. FIG. 6 is a sectional view of a blade tip portion of a stage passage portion of an axial flow turbine according to a sixth embodiment. At the tip of the bucket 101, an integral cover 102 is provided integrally with the bucket 101, and a plurality of flat portions 103 are provided on the outer peripheral surface from the inflow side to the outflow side.
And the projection fins 104a and 104b are formed alternately. Inflow side flat portion 103a and inflow side projection fin 10
4a, central flat portion 103b, outflow side projecting fin 104
b, the outer diameter of the outflow side flat portion 103c is set to D1, D2, D3, D4, D in order from the one arranged on the inflow side.
5, the inflow side flat portion 103a and the inflow side flat portion 10a.
The radial gap distance formed by the seal fin 108 and the tip end of the seal fin 108 disposed at a position opposed to 3a is C1, the outflow-side protrusion fin 104b and the seal fin 108 disposed at a position opposite to the outflow-side protrusion fin. Assuming that the radial gap distance formed between the front end portion and the tip portion is C2, the structure satisfies the following condition.

[0054]

D1 <D2> D3 <D4> D5 C2 = (0.5-1.0) × C1 In this embodiment, after the fluid 107 flows out of the nozzle 55,
Leakage fluid 106 passing through the tip of the bucket flows on the flat surface 103a at the inflow-side end, and collides with the side surface of the protruding fin 104a immediately downstream thereof (arrow j in the figure). Also, the leaked fluid that has reached the center collides with the side surface of the seal fin 108 provided near the center of the flat portion 103b (arrow k in the figure).

Due to the collision, the leaked fluid 106 attenuates the velocity energy possessed by the seal fin 10.
Leakage fluid passing through the gap between the nozzle 8 and the flat portion 103 is reduced, and the sealing effect is enhanced. Also, the projection fins 104a, 104
4b, the amount of leakage is smaller than in the prior art, so the length of the projection fins 104a, 104b in the axial direction (W4, W in the figure)
5) can be shortened, and the flat portions 103a, 103
The length of B, 103c (W6 to W9 in the figure) can be increased. Therefore, it is effective when the rotor blade 101 is largely displaced due to a difference in the axial expansion between the turbine shaft and the casing due to thermal expansion.

Next, an axial turbine according to a seventh embodiment will be described with reference to FIG. FIG. 7 is a sectional view of a blade tip portion of a stage passage portion of an axial flow turbine according to a seventh embodiment. At the tip of the moving blade 111, an integral cover 112 is provided integrally with the moving blade 111. And
A plurality of flat portions 113 are formed on the outer peripheral surface in a stepwise manner from the inflow side to the outflow side. Flat part 1
13 with the outer diameter dimension of the flat portion 1 arranged on the inflow side
D1, D2, D3 in order from 13a, 113b, 113c
Then, a structure that satisfies the following condition is adopted.

[0057]

D1>D2> D3 In this embodiment, after the fluid 117 flows out of the nozzle 55,
The leaking fluid 116 passing through the tip of the bucket flows through the flat portion 113a at the inflow side end, and collides with the side surface of the seal fin 118 located immediately downstream thereof (arrow m in the drawing). Further, it collides with the side surface of the seal fin 118 located downstream (arrow n in the figure). Due to these collisions, the velocity energy of the leaked fluid is attenuated, so that the leaked fluid passing through the gap between the seal fin 118 and the flat portion 113 is reduced, and the sealing effect is improved.

The difference in the amount of expansion and contraction due to the thermal expansion of the turbine shaft and the casing 2 is determined by the inner diameter of the casing 2 and the moving blades 11.
(1) Since the outer diameters of the tip portions are made smaller toward the downstream side, they can be absorbed. Therefore, it is effective when the moving blade 111 moves largely to the upstream side due to the difference in the axial expansion and contraction amount of the turbine and the casing 2 due to thermal expansion. .

Next, an axial turbine according to an eighth embodiment will be described with reference to FIG. FIG. 8 is a sectional view of a blade tip portion of a stage passage portion of an axial flow turbine according to an eighth embodiment. The basic structure is the same as that of the first embodiment. When the outer diameters of the working fluid inflow side flat portion 123a, the projection fins 124, and the working fluid outflow side flat portion 123b are D1, D2, and D3, the flat portion 123a and the flat portion 123a are disposed at positions facing each other. The radial gap distance formed between the tip of the sealed fin 128 and
1. Assuming that a radial gap distance formed between the protruding fin 124 and the distal end of the seal fin 128 disposed at a position facing the protruding fin 124 is C2, the structure satisfies the following condition.

[0060]

D1 = D3 <D2 C2 = (0.5-1.0) × C1 In this embodiment, after the fluid 127 flows out of the nozzle 55,
The leaking fluid 126 passing through the tip of the rotor blade 121 flows through the flat portion 123a at the inflow side end, and collides with the side surface of the projection fin 124 immediately downstream thereof (arrow u in the figure). Further, the leaked fluid 126 that has reached the outflow side also collides with the seal fin 128 (arrow p in the drawing). As a result, the phenomenon that the leaked fluid flows from the inflow side flat portion 123a to the outflow side flat portion 123b through the protruding fins 124 is eliminated, and the flow resistance increases, so that the sealing effect can be further improved.

Next, an axial turbine according to a ninth embodiment will be described with reference to FIG. FIG. 9 is a sectional view of a blade tip portion of a stage passage portion of an axial flow turbine according to a ninth embodiment. The basic structure is the same as that of the first embodiment. Working fluid inflow side flat surface 133a, working fluid inflow side projection fin 134a, central flat portion 133b, working fluid outflow side projection fin 134b, working fluid outflow side flat portion 1
33c is D1, D2, D3, D4, D
5, the radial gap distance formed by the working fluid inflow side flat portion 133a and the tip of the seal fin 138 disposed at a position facing the working fluid inflow side flat portion 133a is C1, the projection fin 134 portion is Assuming that the radial gap distance formed by the tip of the seal fin 138 disposed at a position facing the projection fin 134 is C2, the structure satisfies the following condition.

[0062]

D1 = D5 ≦ D3 <D2 = D4 C2 = (0.5-1.0) × C1 In this embodiment, after the fluid 137 flows out of the nozzle 55,
The leaking fluid 136 passing through the tip of the rotor blade flows on the flat surface 133a at the inflow end, and collides with the side surface of the protruding fin 134a immediately downstream thereof (arrow q in the figure). Further, the leakage fluid 136 that has reached the central flat portion 133b is also used for the seal fin 13 provided near the facing surface of the casing 2.
8 (arrow r in the figure). Due to this collision, the velocity energy of the leaked fluid is attenuated, so that the leaked fluid passing through the gap between the seal fin 138 and the flat portion 133 is reduced, and the sealing effect is improved. The present invention is, of course, not limited to the above-described embodiment,
Various modifications are possible.

[0063]

As described above, according to the present invention, a flat portion or a plurality of protruding fins are formed on the outer peripheral surface of the integral cover at the tip of the rotor blade, and the outer diameter of the outer peripheral surface is changed to allow the leakage fluid to flow. The diameter of the seal fins on the opposite side of the casing is changed in accordance with the change in the outer peripheral surface of the integral cover, reducing the blow-through phenomenon and the difference in the axial expansion of the turbine. The leakage prevention device applicable to a paragraph having a large diameter can greatly improve the paragraph efficiency of the turbine.

[Brief description of the drawings]

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

FIG. 2 is a sectional view of a section showing a main part of an axial flow turbine according to a second embodiment of the present invention.

FIG. 3 is a sectional view of a section showing a main part of an axial flow turbine according to a third embodiment of the present invention.

FIG. 4 is a sectional view of a paragraph showing a main part of an axial flow turbine according to a fourth embodiment of the present invention.

FIG. 5 is a sectional view of a paragraph showing a main part of an axial flow turbine according to a fifth embodiment of the present invention.

FIG. 6 is a sectional view of a paragraph showing a main part of an axial flow turbine according to a sixth embodiment of the present invention.

FIG. 7 is a sectional view of a section showing a main part of an axial flow turbine according to a seventh embodiment of the present invention.

FIG. 8 is a sectional view of a section showing a main part of an axial turbine according to an eighth embodiment of the present invention.

FIG. 9 is a sectional view of a paragraph showing a main part of an axial flow turbine according to a ninth embodiment of the present invention.

FIG. 10 is a sectional view showing a conventional example of an axial turbine stage section.

FIG. 11 is a sectional view of a stage portion of an axial flow turbine showing another conventional example.

FIG. 12 is a sectional view of a stage section of an axial flow turbine showing another conventional example using a step.

FIG. 13 is a sectional view of a stage section of an axial flow turbine showing a conventional example using an integral cover.

FIG. 14 is a cross-sectional view of a stage portion of an axial flow turbine showing a stage portion in which a blade tip is inclined.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Turbine stage part 2 ... Casing 3 ... Rotor 4 ... Nozzle diagram 5 ... Nozzle 5a ... Inclined part 6 ... Wheel 7 ... Moving blade 8 ... Tenon 9 ... Shroud 10 ... Seal fin 11 ... Blade top 12 ... Main fluid flow 13 ... Gap 14 ... Leaked fluid 15 ... Step 16 ... Seal fin 17 ... Integral cover 17a ... Inclined part 18 ... Concave groove 19 ... Flat part 20 ... Seal chamber 51,61,71,81,91,101,111,12
1,131 ... rotor blade 52,62,72,82,92,102,112,12
2, 132: Integral cover 75: Recessed groove 53a, 53b, 63a, 63b, 73, 73a, 73
b, 73c, 73d, 83, 83a, 83b, 83c,
93, 93a, 93b, 93c, 103, 103a, 1
03b, 103c, 113, 113a, 113b, 11
3c, 123, 123a, 123b, 133, 133
a, 133b, 133c ... flat portions 54, 64, 94, 104a, 104b, 124, 13
4a, 134b Projection fin 55 Nozzle 56, 66, 76, 86, 96, 106, 116, 12
6,136 ... Leaked fluid 57,67,77,87,97,107,117,12
7,137 ... Main fluid flow 58,68,78,88,98,108,118,12
8,138 ... Seal fins a, b, c, d, f, g, h, j, k, m, n, p,
q, r, u ... flow of leaked fluid

Claims (9)

[Claims] 1. An axial flow turbine comprising a stationary part comprising a nozzle for discharging a working fluid and a rotating blade.
A flat portion is formed on each of the working fluid inflow side and the outflow side of the rear end of the outer peripheral surface of the integral cover provided integrally with the tip of the rotor blade, and a plurality of rows of projecting fins are formed in the middle. The outer diameters of the working fluid inflow side flat portion, the projection fins, and the working fluid outflow side flat portion are D1, D2, and D3, and are provided on the working fluid inflow side flat portion and the stationary portion opposed thereto. The distance of the radial gap from the fin tip is C
1, and the distance of the radial gap between the tip of the protruding fin and the tip of the fin provided on the stationary portion opposed thereto is C
An axial flow turbine characterized by satisfying the following condition when 2. D1 <D3 <D2 C2 = (0.5-1.0) × C1 2. An axial flow turbine comprising a stationary part comprising a nozzle for discharging a working fluid and a rotating blade.
A flat portion is formed on each of the working fluid inflow side and the outflow side of the rear end of the outer peripheral surface of the integral cover provided integrally with the tip of the rotor blade, and a plurality of rows of projecting fins are formed in the middle. The outer diameters of the working fluid inflow side flat portion, the projection fins, and the working fluid outflow side flat portion are D1, D2, and D3, and are provided on the working fluid inflow side flat portion and the stationary portion opposed thereto. The distance of the radial gap from the fin tip is C
1, and the distance of the radial gap between the tip of the protruding fin and the tip of the fin provided on the stationary portion opposed thereto is C
An axial flow turbine characterized by satisfying the following condition when 2. D1 <D2 <D3 C2 = (0.5-1.0) × C1 3. An axial flow turbine comprising a stationary part comprising a nozzle for discharging a working fluid and a rotating blade.
A plurality of flat portions and a concave portion formed lower than a flat portion adjacent to a plurality of flat portions between the working fluid inflow side at the front end portion of the integral cover and the outflow side at the rear end portion of the integral cover integrally provided at the front end portion of the bucket. The working fluid inflow side flat portion, the working fluid inflow side second flat portion, the working fluid outflow side first flat portion, and the working fluid outflow side flat portion are formed alternately by D.
An axial turbine characterized by satisfying the following condition when 1, D2, D3, and D4 are satisfied. ## EQU3 ## D1 <D2 <D3 <D4 4. An axial flow turbine comprising a stationary portion comprising a nozzle for discharging a working fluid and a rotating blade.
A plurality of flat portions are formed in steps between the working fluid inflow side at the tip of the outer peripheral surface of the integral cover provided integrally with the tip of the rotor blade and the outflow side at the rear end. An axial flow turbine characterized by satisfying the following condition when the outer diameter of each of the flat portion, the intermediate flat portion, and the working fluid outflow side flat portion is D1, D2, and D3. ## EQU4 ## D1 <D2 <D3 5. The axial flow turbine according to claim 4, wherein an axial fin is formed at an upper end of the flat portion on the upstream side of the working fluid toward an upstream side. 6. An axial flow turbine comprising a stationary part comprising a nozzle for discharging a working fluid and a rotating blade.
A plurality of flat portions and a plurality of protruding fins are alternately formed between the working fluid inflow side at the front end of the integral cover and the outflow side at the rear end of the integral cover provided integrally with the tip of the bucket. The outer diameter of each of the working fluid inflow side flat portion, the working fluid inflow side projection fin, the center flat portion, the working fluid outflow side projection fin, and the working fluid outflow side flat portion is D1, D2, D3.
D4, D5, and the distance in the radial direction between the working fluid inflow side flat portion and the fin tip portion provided in the stationary portion opposed thereto is C1, and the working fluid outflow side projection fin tip portion faces the fin tip portion. An axial flow turbine characterized by satisfying a condition of the following expression, where C2 is a distance of a radial gap from a fin tip provided at a stationary portion to be provided. D1 <D2> D3 <D4> D5 C2 = (0.5-1.0) × C1 7. An axial flow turbine comprising a stationary part comprising a nozzle for discharging a working fluid and a rotating blade.
A plurality of flat portions are formed in steps between the working fluid inflow side at the tip of the outer peripheral surface of the integral cover provided integrally with the tip of the rotor blade and the outflow side at the rear end. An axial turbine characterized by satisfying the following condition when the outer diameter of each of the flat portion, the central flat portion, and the working fluid outflow side flat portion is D1, D2, and D3. D1>D2> D3 8. An axial flow turbine comprising a stationary part comprising a nozzle for discharging a working fluid and a rotating blade.
A flat portion is formed on each of the working fluid inflow side and the outflow side of the rear end of the outer peripheral surface of the integral cover provided integrally with the tip of the rotor blade, and a plurality of rows of projecting fins are formed in the middle. The outer dimensions of the working fluid inflow side flat portion, the projection fins, and the working fluid outflow side flat portion are D1, D2, and D3, and the outer diameters of the working fluid inflow side flat portion and the projection fins are the same as those of the working fluid. D1, D2, in order from the inflow side to the outflow side
D3, the distance of the radial gap between the flat portion and the fin tip provided in the stationary portion opposed thereto is C1,
An axial flow turbine characterized by satisfying the following equation, where C2 is a radial gap distance between the tip of the protruding fin and the tip of the fin provided in the stationary portion opposed thereto. D1 = D3 <D2 C2 = (0.5-1.0) × C1 9. An axial flow turbine comprising a stationary part comprising a nozzle for discharging a working fluid and a rotating blade.
A plurality of flat portions and a plurality of fins are alternately formed between a working fluid inflow side and a rear end outflow side of an outer peripheral surface front end portion of an integral cover provided integrally with a leading end portion of the rotor blade, Inflow side flat part, working fluid inflow side fin, central flat part,
The outer diameters of the working fluid outflow side fin and the working fluid outflow side flat portion are D1, D2, D3, D4, and D5, respectively, and the fin tips provided on the working fluid inflow side flat portion and the stationary portion opposed thereto. When the distance of the radial gap between the fin and the fin is provided as C1, and the distance of the radial gap between the tip of the working fluid inflow side protruding fin and the fin of the fin provided on the stationary portion opposed thereto is C2, An axial flow turbine characterized by satisfying the following conditions. D1 = D5 ≦ D3 <D2 = D4 C2 = (0.5 to 1.0) × C1