JPS59165802A - Cooling apparatus for moving blade shroud of steam turbine - Google Patents

Abstract

PURPOSE:To prevent the reduction of material strength of the caulking part of a moving blade shroud, by forming, on the side surface of the outer ring of the nozzle diaphragm, each opened part of the passages which penetrate the outer ring of the nozzle diaphragm and opened towards the moving blade shroud. CONSTITUTION:Each opened part of the steam passages 10 and 11 which penetrate a casing 9 and a nozzle diaphragm outer ring of 4 respectively is formed on the side surface of the outer ring 4 of the nozzle diaphragm, and the cooled steam is jetted-out in the axial direction towards the side surface of a moving blade shroud 1. Since the both inner and outer surfaces of the shroud 1 are cooled, the thermal deformation due to the temperature difference between the inner and the outer surfaces is not generated, and the reduction of material strength at the caulking part where the shroud 1 is fixed at the top edge of the moving blade is prevented.

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention relates to a cooling structure for a steam turbine (two systems, particularly a rotor blade tip (-a shroud provided with a cooling device (two cooling devices)).
Two matters.

[Technical background of the invention and its problems]

General (= Increasing the steam temperature at the inlet of a steam turbine leads to higher efficiency of the steam turbine, but on the other hand, it has negative effects such as a decrease in material strength.

As shown in Figure 1 (2), a shroud 1 is provided at the tip of the steam turbine rotor blade for vibration damping and to prevent steam leakage at the end of the wlJ blade tip. The protrusion 2 is made to protrude, and the protrusion 2 is caulked (1 m1 is added to the protrusion 2).A large stress is generated in this caulked part because the shroud 1 receives centrifugal force. # The gap between the tip fin 3 and the tip fin 3 provided to prevent steam leakage at the true tip is designed to be narrow in order to prevent steam leakage and improve the efficiency of the steam turbine. Therefore, slight deformation of the shroud 1 contact with the tip fin 3 (two connections), causing unstable vibration of the turbine rotor and leading to a serious accident.In addition, the steam temperature becomes sieve temperature, causing the shroud caulked part to become hot. The material strength of the shroud 1 is reduced, and the centrifugal force that the shroud 1 is subjected to (the cooling part of the shroud crimped part may be deformed or destroyed, increasing the risk of a contact accident between the shroud 1 and the tip fin 3). There is a need to.

Conventionally, shroud cooling (for example, the cooling structure shown in Fig. 1 (2) has been considered. The nozzle plate 6 fixed by them, the nozzle passage section (2) which is accelerated by the rotor disk 7, the fixed rotor blade 8, Shroud 1 and (
It flows to the next stage through the rotor blade passage section which is composed of two parts.

Low-temperature steam for cooling the shroud section is blown out through the passage 10 of the casing 9 and the passage 11 of the nozzle diaphragm outer ring 4 into the shroud 1 (twice.
2 cooling structures (in 2, the outer surface of shroud 1 is cooled by low-temperature cooling steam (2), but the inner surface of shroud 1 (2 is cooled by high-temperature steam, so there is a temperature difference between the inner and outer surfaces of the shroud). As a result, the shroud 1 is deformed in the outer surface direction 42 and there is a risk of contact accident between the shroud 1 and the tip fin 3. Also, the root of the caulked part is exposed to high temperature steam (2). Therefore, there is little cooling, and there is a risk that the strength of the material in this area will decrease, leading to deformation and breakage.

[Purpose of the invention]

The present invention has been made in order to eliminate the drawbacks of the above-mentioned prior art (2).The present invention has been made in order to eliminate the disadvantages of the above-mentioned prior art. It is an object of the present invention to provide a cooling device for a rotor blade shroud that does not cause such a problem.

[Summary of the invention]

To achieve the above object, the present invention is characterized in that the opening of the steam path is provided on the side surface of the nozzle diaphragm outer ring, so that cooling steam is ejected in the axial direction (two directions) toward the side surface of the shroud.

[Embodiments of the invention]

A central flow example of the present invention will be described below with reference to FIGS. 2 and 3. Figure 2 (2, Nozzle plate 6
In order to make the length of the blade a little shorter than the blade length of the conventional technology, the inner diameter of the nozzle diaphragm outer ring was changed. Make it smaller. Casing 9
1 has a casing passage 1 for guiding external high-pressure discharged hot steam.
0 is provided, nozzle diaphragm outer ring 4t = provided nozzle diaphragm outer ring passage 11 (two connected. , This part (2) As shown in FIG. 3 (2) The fin 12 is provided at the same angle as the nozzle tip outflow angle α.

In the steam turbine rotor blade shroud cooling structure configured in this way, high-temperature steam generated during operation is accelerated at the nozzle passage (-) and flows into the rotor blade.At this time, the nozzle plate blade length is shorter than in the prior art, and the casing passage 1o and nozzle diaphragm outer ring passage 1
The high-pressure, low-temperature cooling steam that enters the tip of the rotor blade (2) through the shroud 1 (2) and the high-pressure, low-temperature cooling steam that enters the shroud (2) through the shroud 1 (2) prevents high-temperature steam from hitting the inner and outer surfaces of the rotor blade (2). The same flow as the fin 3 (- flows. In this way, the shroud l has a cooling gradient J steam flow not only on the outer surface but also on the inner surface.
Because it is cooled, there is no temperature difference between the inside and outside surfaces (there is no thermal deformation due to
g Decrease in material strength at the tip caulked portion can be prevented, and the reliability of the shroud can still be maintained. Nozzle diaphragm outer ring passage e4
The flow of cooling air flowing from No. 11 toward the tip of wing a is as follows:
It is covered with a fastening triangle shown in FIG. The cooling steam pressure and the spacing between each fin 120 must be determined so that the absolute outflow velocity C and the flow angle α are equal to the conventional technique. The speed is W, the relative inflow angle is β, which is the same as the conventional technology, and the fluid loss at the tip of the rotor blade can be kept low.The above explanation (
In the second step, the fins 12 are provided (in the second step, steam flow is realized at the outlet of the nozzle diaphragm outer ring passage section, but it is also possible to realize it with holes having an angle α instead of fins. By appropriately selecting the relative radial position of the passage outlet and the shroud and the meridional plane angle at the outlet, it is also possible to change the outer and inner surfaces of the shroud (=the ratio of flowing cooling steam).

〔Effect of the invention〕

As mentioned above (according to the present invention), the MJJ blade shracto is cooled not only on the outer surface but also on the inner and outer surfaces uniformly by a stone to keep the fluid loss low. It is also possible to provide a cooling device for rotor blade shrouds to realize a highly reliable steam turbine.

[Brief explanation of the drawing]

FIG. S1 is a sectional view showing a conventional steam turbine NIJg shroud cooling system, FIG. 2 is a sectional view showing an embodiment of the present invention, and FIG. 3 is a sectional view taken along the line A--A in FIG. DESCRIPTION OF SYMBOLS 1... Shroud, Nozzle diaphragm outer ring for 4, 6... Nozzle plate, 8-river moving blade, 9... Casing, 1o... Passage of casing, 11... Passage of nozzle diaphragm outer ring, 12・・・
·fin. Agent: Patent Attorney Noriyuki Chika (1 person) Figure 1 Figure 2

Claims (4)

[Claims] (1) Remove the casing and nozzle diaphragm 131
The steam passage FJ'6+= which penetrates the fihIx shroud and opens toward the nozzle diaphragm outer ring. A cooling device for a steam turbine rotor blade shroud, characterized in that the cooling steam is jetted in the axial direction toward the side surface of the shroud. (2) The inner diameter of the nozzle diaphragm outer ring was made smaller to shorten the nozzle plate blade length! ? ! A cooling device for a steam turbine rotor blade shroud according to claim 1, wherein the cooling device is defined as fe. (3) The opening of the cooling steam passage is shaped like an annular groove, a plurality of fins are provided in this groove, and the exit angle of the fins is made equal to the exit angle of the nozzle blade. A cooling device for a steam turbine rotor blade shroud according to scopes 1 and 2. (4) The opening of the cooling steam passage has a plurality of holes;
A cooling device for a steam turbine shroud according to claims 1 and 2, characterized in that the exit angle of the hole is equal to the exit angle of the nozzle blade.