JPH09125907A - Shroud structure for turbine moving blade - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a shroud structure ensuring high reliability during operation, and allowing easy fabrication by dividing a shroud into shroud units along a peripheral direction, sintering and jointing the outer monolithic ceramic layer and the inner abradable seal of the units to each other, and then directing the contact surface of each unit in a radial direction. SOLUTION: A shroud 5 with a porous ceramic abradable seal 6 easily abraded due to the contact of a turbine moving blade 1 with the inner surface thereof is provided around a shroud fixing ring. The shroud 5 is divided into a plurality of shroud units to be arranged in a peripheral direction, and the divided units 5 are kept in contact with each other. Furthermore, the contact surface of each unit 5 is radially directed. In this case, the shroud unit 5 is made of an outer monolithic layer of silicon nitride, and an inner abradable seal 6, and both layers are sintered and jointed to each other. Also, the shroud 5 is fixed with a shroud fixing ring 4 in a radial direction, and with a stationary blade fixing ring 7 and a ring 8 in an axial direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shroud structure of a turbine rotor blade for improving turbine efficiency by narrowing a space between a tip of a ceramic turbine rotor blade and a shroud provided on an inner surface of a turbine casing as much as possible. .

[0002]

2. Description of the Related Art In a turbine portion of a gas turbine, a plurality of turbine moving blades are planted at intervals in a circumferential direction on a turbine disk provided on a rotating shaft, and a slight clearance is provided from the tips of these turbine moving blades. With a cylindrical shroud
They are arranged in a turbine casing.

It is preferable that the gap between the tip of the turbine rotor blade and the inner peripheral surface of the shroud be as narrow as possible because the turbine efficiency decreases if the working gas leaks from the gap. However, if it is made too narrow, the rotor blades may be extended due to high-speed rotation of the turbine disk, and the tips thereof may contact the inner peripheral surface of the shroud, resulting in damage to the rotor blades. This is fatal when the rotor blade is made of ceramic. This is because the broken pieces that come into contact with the inner peripheral surface of the casing may sequentially damage the ceramic moving blades on the downstream side.

Therefore, the applicant of the present invention first provided an abradable seal made of a ceramic porous body on the inner peripheral surface of a turbine casing made of metal, without damaging the blade when the tip of the turbine blade contacts. , Has developed a blade that can scrape off only the abradable seal (Japanese Patent Application No. 5-158363).

However, when a ceramic abradable seal is laminated on a metal turbine casing, there is a large difference in thermal expansion between metal and ceramic. Therefore, the abradable seal is formed by repeating the thermal cycle of starting and stopping. Peeling / cracking may occur. As a measure against this,
An intermediate layer that absorbs the difference in thermal expansion may be provided between the turbine casing and the abradable seal, but it is not preferable because the structure becomes complicated and peeling from the intermediate layer portion is also considered.

Further, in the metal turbine casing,
Even if a refractory metal such as Inconel is used, it is possible to use ultra high temperature (1800 to 2000
In the (° C class) gas turbine, it is necessary to cool the turbine casing in order to protect it from the combustion gas having an extremely high temperature, and the temperature of the working gas is lowered by that much, and the thermal efficiency of the entire turbine is deteriorated.

In consideration of such circumstances, the applicant of the present invention further created a turbine casing structure in which a casing was made of ceramics, and an abradable seal made of a ceramic porous body was arranged on the inner surface of the casing, and filed a patent application (patent pending). Wishhei 6
─116855 (unpublished)).

According to the present invention, a cylindrical turbine casing, which is arranged so as to surround the radially outwardly arranged ceramic turbine blades, is formed of a ceramic dense body, and the turbine rotor blades are formed on the inner peripheral surface thereof. Is a turbine casing structure provided with an abradable seal made of a ceramic porous body, which wears when the tip of the ceramic body comes into contact, and the ceramic dense body and the ceramic porous body are shrink-fitted, cold-fitted, press-fitted (hereinafter burned It is integrated by sintering or called).

Since the abradable seal and the turbine casing are both made of ceramic, the difference in thermal expansion between the two is eliminated, and peeling and cracking of the abradable seal due to the thermal cycle of operation / stop of the turbine is prevented. To be done.

Further, since the turbine casing itself is a dense ceramic body, it is not necessary to cool the turbine casing even in an extremely high temperature (1800 to 2000 ° C class) gas turbine using a turbine turbine blade. , Thermal efficiency is improved.

[0011]

However, the turbine casing structure described above has the following problems. (1) With a fixing method such as shrinkage fitting, when residual stress remains in the abradable seal or shroud ring and is exposed to high-temperature combustion gas, the residual stress causes an accident such as damage. (2) With a fixing method such as shrink fitting, it is necessary to increase the thickness of the abradable seal in order to maintain the strength of the abradable seal with low strength. Must be sacrificed, resulting in a decrease in strength. (3) The assembling structure of the abradable seal may be a shrink fit method or a thermal spraying method. However, the thermal spraying method of ceramics is an unestablished technology, and the joining surface is not reliable. Also,
Unlike metal, shrink fit has a low linear expansion coefficient,
It is difficult to insert it accurately because it needs to be heated to around 00 degrees, and it is easy to cause stress concentration due to inclination and the like. (4) In the case of a fixing method such as shrinkage fitting, when the abradable seal is damaged, the interference is likely to open, and there is a high possibility of collision with the moving blade, in which case the ceramic parts are fatal. Take damage. (5) Since the casing is large, defects are likely to occur when integrally molded and sintered.

The present invention has been devised in view of the above problems of the prior art, and an object of the present invention is to provide a shroud structure for a ceramic turbine blade that has high reliability during operation and is easy to manufacture. To do.

[0013]

To achieve the above object, a shroud structure for a turbine rotor blade according to the present invention is provided on an inner surface of a metal turbine casing that surrounds radially arranged ceramic turbine rotor blades. An annular ceramic shroud fixing ring is arranged, and the shroud is arranged on the inner surface of the shroud fixing ring. The shroud has a ceramic porous body that wears when the tip of the turbine blade contacts the inner peripheral surface. A shroud structure of a turbine blade having an abradable seal made of a body, wherein the shrouds are circumferentially aligned, and are composed of a plurality of shroud units arranged in contact with each other,
Each abutting surface faces in a radial direction, and each shroud unit has an outer monolithic ceramic layer and an inner abradable seal joined by sintering.

Next, the operation of the present invention will be described. In the present invention, the shroud having the abradable seal is divided into a plurality of shroud units, and each unit has an outer abradable ceramic layer and an inner abradable seal that are joined by sintering to form an abradable seal. (1) Residual stress does not remain on the shroud ring or abradable seal because it is not shrink-fitted to the shroud ring. (2) Since the abradable seal itself is not required to have compressive strength, the abradable seal can be made thin. (3) Since they are joined by sintering, a strong joint surface can be obtained between the outer monolithic ceramic layer and the abradable seal. Therefore, the abradable seal does not fall off and collide with the moving blade.

Further, since the contact surface of each shroud unit is oriented in the radial direction, there is a wedge effect, and some units do not fall inward.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a shroud structure for a turbine blade of the present invention will be described below with reference to the drawings. Figure 1 shows a turbine with ceramic blades 1
It is a sectional side view of a part. FIG. 2 is a view taken along the line AA of FIG. 1, and shows a part of the moving blade removed. In these figures, reference numeral 1 denotes a ceramic turbine rotor blade, and by inserting a root portion 1a into a groove 2a formed in the outer periphery of a cobalt-based heat-resistant alloy turbine disk 2, Radially mounted.
Reference numeral 3 denotes a turbine casing made of a heat-resistant alloy, which is provided so as to surround the turbine moving blade. The casing 3 is provided with a cooling air passage (not shown) and is air-cooled.
Reference numeral 4 denotes a ring-shaped shroud fixing ring made of a silicon nitride monolithic ceramic, and fitted into the inner surface of the turbine casing 3.

A shroud 5 is arranged on the inner surface of the shroud fixing ring 4, and is made of a ceramic porous body that is easily worn when the tip of the turbine rotor blade 1 contacts the inner peripheral surface of the shroud 5. It has an abradable seal 6. The shroud 5 is divided into a plurality (eight in this embodiment) of shroud units 5a arranged side by side in the circumferential direction, the units 5a are in contact with each other, and the contact surfaces 5b are in the radial direction. .

Each shroud unit 5a is composed of an outer silicon nitride monolithic ceramic layer 5c and an inner abradable seal 6, which are joined by sintering. Reference numeral 7 is a stationary blade fixing ring made of monolithic ceramics, and 8 is a fixing ring fixed to the casing 3. The shroud 5 has a shroud fixing ring 4 in the radial direction and a stationary blade fixing ring 7 in the axial direction.
And are fixed by a ring 8, respectively. Reference numeral 9 is a nose control, 10 is a vane, and 11 is an arrow indicating the flow of high-temperature combustion gas.

The shroud unit 5a is integrally molded. That is, the monolithic ceramics layer 5c and the abradable seal 6 made of porous ceramics are separately molded by an isotropic static pressure press (CIP) molding method, a cast molding method or a uniaxial press die forming method, and they are superposed. With CIP, a pressure higher than the pressure at the time of molding is applied to integrate them. The integrated molded body is 500 ° C to 600 ° C
Degreasing is performed, and then firing and sintering are performed at a high temperature of 1500 ° to 2000 ° C.

The molding method is not limited to the above, and the material of the abradable seal 6 may be formed on the inner surface of the material of the previously molded monolithic ceramics layer 5c by casting or spraying, degreasing and sintering. .

Next, the operation of the present embodiment will be described. When the turbine is rotated by the combustion gas 11 of high temperature and high pressure, the turbine rotor blade 1 extends due to the thermal expansion of the metal disk and the action of centrifugal force, and the tip thereof contacts the abradable seal 6. The abradable seal 6 is worn by friction with the tip of the turbine rotor blade 1 and maintains the clearance with the turbine rotor blade 1 to a minimum. Therefore, the turbine rotor blade 1 and the shroud 5
Leakage of the combustion gas 11 between and becomes small, and the turbine efficiency can be improved.

In the present invention, the shroud 5 is divided into a plurality of pieces in the circumferential direction, and the abradable seal 6 on the inner surface is joined to the monolithic ceramics layer on the outer surface by sintering, so that the joint interface strength is dramatically improved. The abradable seal 6 does not fall off the interface, and the reliability is improved. Since the contact surface of each of the divided shroud units 5a faces the radial direction, there is a wedge effect, and there is no risk that some of the shroud units 5a will drop inward.

[0023]

As described above, the shroud structure of the turbine rotor blade of the present invention divides the shroud into a plurality of shroud units in the circumferential direction, and each unit is divided into an outer monolithic ceramic layer and an inner abradable seal. Are joined by sintering, and the contact surfaces of the units are oriented in the radial direction, so that the following effects can be obtained. (1) Since stress concentration and residual stress do not occur in the shroud, the reliability of the ceramic gas turbine is dramatically improved. (2) The abradable seal is separated at the interface with the shroud due to the release of the stress due to the local destruction of the abradable seal that occurs in the fixing method by the shrink fit method, and serious damage such as collision with the moving blade is not caused. , A monolithic ceramic layer and an abradable seal that are integrally formed do not have a strong interface. (3) Due to the divided structure, if uneven wear occurs, it can be dealt with by replacing the damaged unit. (4) Since the abradable seal can be manufactured as thin as about 1 mm, the thickness of the monolithic ceramics layer can be increased and the strength of the shroud is increased, so that the reliability of the gas turbine is dramatically improved. (5) When the abradable seal is made of a porous material, it has good heat insulating properties, so thermal stress is generated between the monolithic ceramics layer and the abradable seal. Since the gradient is small, the thermal stress can be small. (6) The division is also advantageous in that thermal stress generated in the circumferential direction is divided. (7) By adopting a divided structure, the selection of molding methods is widened, which is advantageous and easy to increase in size. (8) Since there is a wedge effect, there is no risk that some shroud units will fall inside.

[Brief description of the drawings]

FIG. 1 is a side sectional view of a shroud structure for a turbine blade of the present invention.

FIG. 2 is a view as viewed in the direction of arrows AA in FIG. 1;

[Explanation of symbols]

 1 Turbine blade 3 Turbine casing 4 Shroud fixing ring 5 Shroud 5a Shroud unit 5b Shroud unit contact surface 5c Monolithic ceramic layer 6 Abradable seal

Front page continued (72) Inventor Takeshi Sakita 3-1-15 Toyosu, Koto-ku, Tokyo Ishikawajima Harima Heavy Industries Ltd. Technical Research Institute (72) Inventor Shigenobu Asada 3-15-15 Toyosu, Koto-ku, Tokyo Ishikawajima Harima Heavy Industry Co., Ltd. Technical Research Center

Claims (1)

[Claims] 1. An annular ceramic shroud fixing ring is arranged on an inner surface of a metal turbine casing which is arranged so as to surround radially arranged ceramic turbine blades, and a shroud is formed on an inner surface of the shroud fixing ring. The shroud has a shroud structure of a turbine rotor blade having an abradable seal made of a ceramic porous body that is worn when the tip of the turbine rotor blade comes into contact with the inner peripheral surface of the shroud. , The shroud is arranged in the circumferential direction, and is composed of a plurality of shroud units arranged in contact with each other, each contact surface is directed in the radial direction, each shroud unit and the outer monolithic ceramic layer A shroud structure for a turbine blade, characterized in that the abradable seal on the inside is joined by sintering.