JP3176190B2 - Ceramic turbine rotor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a large-sized radial type ceramic turbine rotor used for a gas turbine engine or the like.

[0002]

2. Description of the Related Art In recent years, ultra-precision rotating bodies in various industrial machinery and rotating bodies used in a high-temperature atmosphere have low thermal expansion, excellent mechanical strength, excellent heat resistance and wear resistance, and low specific gravity. Utilizing the characteristics of ceramics that can realize a lighter product, oxide-based ceramic sintered bodies such as alumina (Al ₂ O ₃ ) and zirconia (ZrO ₂ ), silicon nitride (Si ₃ N ₄ ), and sialon Alternatively, a silicon nitride sintered body excellent in high-temperature strength and heat resistance is used for a rotating body using a non-oxide ceramic sintered body such as silicon carbide (SiC), especially for a ceramic rotor used in a high-temperature atmosphere. Various studies have been made and proposed.

Generally, in order to achieve higher thermal efficiency, a ceramic rotor made of a silicon nitride sintered body of this type is operated by increasing the number of revolutions by introducing a combustion gas at a much higher temperature and pressure than before. For example, a ceramic rotor represented by a turbine rotor of a gas turbine engine, a turbo rotor of a turbocharger, or the like rotates at a high speed of several tens of thousands to several hundred thousand rotations per minute.

[0004] Therefore, the higher the number of revolutions of the ceramic rotor, the greater the generated centrifugal force. Therefore, the stress generated in the ceramic rotor itself also increases, and the rotor itself breaks. Although it has been put to practical use in small ceramic rotors, such as a turbo rotor with a maximum diameter of 150 mm or less formed by a plurality of blades provided on the outer periphery of the disk, the large ceramic turbine rotor, etc. However, it has not been applied due to the problem that the risk of breaking due to a large stress such as that described above is extremely high.

However, recently, it has been considered to apply various ceramics to various parts such as a large gas turbine engine and the like. However, the solid large-sized product is liable to contain minute defects in the molding stage of the manufacturing process, and in the subsequent degreasing process and firing process of the molded product, the defects have internal defects such as large cracks. Tended to grow.

[0006] As a result, the centrifugal force generated in the ceramic turbine rotor rotating at high speed in a high-temperature atmosphere acts on the internal defect, and the danger that the ceramic turbine rotor itself is broken cannot be completely avoided. Easy-to-use large ceramic turbine rotors without defects, and various characteristics such as engine transient response that can be obtained with small ceramic rotors even with large and heavy ceramic turbine rotors It was desired to satisfy the same function as.

In order to meet such a demand, as shown in FIG. 3, it is necessary to provide a bottomed hole 12 in a disk 11 of a radial type ceramic turbine rotor 10.
No. 104301 has been proposed.

[0008]

However, in the ceramic turbine rotor 10, an opening 13 is provided on the fluid outlet side, and the sectional area of the opening 13 is made smaller than the sectional area of the bottom 14 of the bottomed hole 12. The annular part 15 at the open end is cut to correct the balance as a rotating body. Even if a small ceramic rotor is not so problematic, the large ceramic turbine rotor as described above is not used. In addition to the problem that thermal shock resistance is inferior, the moment of inertia increases due to the increase in weight, and the problem that the transient response of the engine deteriorates, the stress generated by the high-temperature and high-speed rotation applied to the balance correction portion cannot be ignored, Slight unbalance as a high-speed rotating body due to destruction from the disk and residue such as carbon in the combustion gas adhering and accumulating inside the opening Even if now the ceramic turbine rotor to rotate eccentrically, touching the inner wall of the turbine housing turbine rotor itself there is a risk of such damage.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems, and an object of the present invention is to provide a large-sized radial having a maximum outer diameter exceeding 150 mm formed by a trajectory drawn by rotating the wing around the center of rotation. Even with a type ceramic turbine rotor, internal defects do not occur, withstand high centrifugal force, reduce thermal stress during high-temperature high-speed rotation, and even out to prevent damage to the turbine rotor itself. An object of the present invention is to provide a ceramic turbine rotor having improved responsiveness.

[0010]

The ceramic turbine rotor of the present invention is formed by forming a radial radial turbine rotor made of ceramic having a plurality of blades on the outer periphery of a disk in a locus drawn by the rotation of the blades around the center of rotation. The nose portion and the back face portion have at least a convex portion connected to the rotation axis on the end surface of the disk portion having a substantially frustoconical shape having a thickness of 0.05 to 0.1 times the maximum outer diameter. The ceramic member forming the back face portion is joined and integrated, whereby the inside of the disk portion has a hollow shape without an opening.

[0011]

A disc having a plurality of blades on its outer periphery and a back face portion connected to at least a rotating shaft among a nose portion and a back face portion of a ceramic turbine rotor are formed as separate ceramic members. Since the inside of the disk is hollow with no opening by joining and integrating with the end of the cylindrical disk, thermal stress generated during high-temperature high-speed rotation is reduced and averaged, and the moment of inertia is reduced. The manufacturing process is also simplified very efficiently.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a ceramic turbine rotor of the present invention will be described in detail based on embodiments. FIG. 1 is a sectional view in which the ceramic turbine rotor of the present invention is applied to a large radial type turbine rotor.

In FIG. 1, reference numeral 1 denotes a cylindrical disk 2 having a predetermined thickness 5 made of a silicon nitride sintered body and having a nose portion 6 integrally formed and opened to the bag face portion side. A plurality of blades 3 made of the silicon nitride-based sintered body are provided on the outer periphery of the disk, and a back face portion 7 made of a silicon nitride-based sintered body having a projection 9 connected to a rotating shaft is joined to an end surface of the disk 2. This is a radial type ceramic turbine rotor integrated with a hollow portion 8 having no opening in the disk 2.

The molded body of the disk 2 having a plurality of blades 3 constituting the ceramic turbine rotor 1 can be molded by a molding method such as a slurry casting method or an injection molding method, and the back face portion 7 and the like are well known. Any of the above molding methods can be used, but a powder pressure molding method such as a CIP molding method is suitable.

The method of joining the silicon nitride sintered body forming the back face portion 7 to the end face of the disk 2 is based on the silicon nitride sintered material of the disk 2 and the back face portion 7 constituting the ceramic turbine rotor 1. Any of the well-known joining methods such as a method using a ceramic raw material having the same composition as that of the sintered body, metal silicon, or the like, and a diffusion joining method may be used.

In evaluating the ceramic turbine rotor of the present invention, first, alumina (Al ₂ O ₃ ), yttria (Y ₂ O ₃ ), and rare earth elements are used as sintering aids in silicon nitride (Si ₃ N ₄ ) raw material powder. An oxide or the like was added, and an organic solvent such as methanol and a dispersant were placed in a pot together with a ball made of a silicon nitride sintered body, and mixed and stirred with a rotary mill for 12 hours to form a slurry.

Then, after degassing the slurry in a vacuum,
The maximum outer diameter of the trajectory drawn by the plurality of blades provided on the outer periphery rotating around the rotation center, that is, the forming die of the radial type turbine rotor in which the dimension twice the maximum distance from the rotation center to the blade tip is set variously The slurry was poured, the silicon nitride-based raw material powder in the slurry was deposited on the mold wall surface of the disk portion, the retention time was changed, and the undeposited slurry was poured out to change the thickness of the disk,
A silicon nitride-based molded body integrated with a nose was molded.

The obtained silicon nitride-based molded body is dried and degreased, and then fired in a nitrogen gas atmosphere at a temperature of 1750 ° C. for 2 hours. And a substantially frustoconical cylindrical disk with openings at both ends.

The thickness of the blade is desirably small from the viewpoint of the centrifugal force, but from the viewpoint of strength, it is most preferably about 5 to 10 mm near the root of the blade.

On the other hand, a sintering aid similar to the above is added to the silicon nitride raw material powder, and an organic solvent such as methanol and a dispersant are placed in a pot together with a silicon nitride-based sintered body ball, and the resulting mixture is mixed with a rotary mill to form a powder. After mixing and stirring for a time, the back face portion was subjected to CIP molding using a molding raw material obtained by drying and granulating the mixture, and after cutting the molded body, degreased and baked in the same manner as the disk portion. The ceramic member of the back face part was obtained by grinding so as to fit to the joint part.

The minimum thickness of the nose portion and the back face portion is desirably equal to or greater than the thickness of the disk portion.

Next, using a three-dimensional coordinate measuring machine, the disk sintered body having a plurality of blades after the grinding process is used, and the plurality of blades are rotated around a rotation center to obtain a maximum outer diameter of a locus, that is, The dimension twice the maximum distance from the center of rotation to the tip of each blade and the thickness of the disk were measured to calculate the ratio of the thickness to the maximum outer diameter.

Thereafter, using the slurry used for molding the disk, the slurry is applied to the joint of the disk sintered body with the back face, and the sintered body of the back face is pressed and brought into close contact. After drying and degreasing, the resultant was heated again to the sintering temperature and fired to be joined and integrated to produce a ceramic turbine rotor for evaluation.

Using the ceramic turbine rotor for evaluation thus obtained, a non-destructive inspection for the presence or absence of internal defects is performed by X-ray transmission imaging and ultrasonic flaw detection.
At room temperature, a high-speed rotation test was performed at a maximum rotation speed of 40,000 rotations per minute to check for damage to the ceramic turbine rotor.

On the other hand, using a part of the disk sintered body, a bending test piece was cut out from the disk sintered body,
The four-point bending strength at room temperature and at a high temperature of 1350 ° C. was measured according to the S standard.
At ℃, it was confirmed that it was 430 Mpa or more.

Further, an oxidation resistance test was carried out using a test piece cut out from the disk sintered body under the condition that the test piece was kept in the atmosphere at 1400 ° C. for 24 hours. It was confirmed to be extremely small, ² or less.

After maintaining the temperature at 1300 ° C. using the ceramic turbine rotor for evaluation,
A thermal shock test was performed by blowing air at a rate of 100 m / s and rapidly cooling by blowing at 100 m / s, and the presence or absence of cracks was confirmed by a fluorescent penetrant inspection method.

[0028]

[Table 1]

In the above embodiment, the nose portion is integrally formed at the same time as the disk. However, as shown in FIG. 2, both the nose portion 6 and the back face portion 7 are separate ceramic members, and It has been confirmed that a similar effect can be obtained even with a ceramic turbine rotor bonded and integrated to both end surfaces of the two.

[0030]

As described above in detail, the ceramic turbine rotor of the present invention has a disk having a plurality of blades on the outer periphery, and has a maximum outer diameter formed by a locus drawn by rotating the blades around the center of rotation. Since it has a thickness of 0.05 to 0.1 times, and a ceramic member forming at least the back face portion is joined and integrated at least between the nose portion and the back face portion to form a hollow portion without an opening portion. Even with a large radial ceramic turbine rotor having a maximum outer diameter of more than 150 mm, there is no internal defect serving as a fracture source,
A ceramic turbine rotor that withstands high centrifugal force, reduces thermal stress during high-temperature high-speed rotation, and averages the damage to prevent damage to the turbine rotor itself, thereby improving the transient response of a gas turbine engine or the like.

[Brief description of the drawings]

FIG. 1 is a sectional view in which a ceramic turbine rotor according to the present invention is applied to a large radial type turbine rotor.

FIG. 2 is a sectional view showing another embodiment in which the ceramic turbine rotor according to the present invention is applied to a large radial type turbine rotor.

FIG. 3 is a cross-sectional view of a conventional radial turbine rotor made of ceramic.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ceramic turbine rotor 2 Disk 3 Blade 4 Maximum outer diameter 5 Thickness 6 Nose part 7 Back face part 8 Hollow part

Claims (1)

(57) [Claims] 1. A ceramic radial turbine rotor having a plurality of blades on the outer periphery of a disk, wherein the disk has a maximum outer diameter of 0.05 to 0 formed by a locus drawn by rotation of the blades around a rotation center. Among the back face portions having a thickness of one time and having a convex portion connected to the nose portion and the rotation axis , at least a ceramic member constituting the back face portion is integrally joined to the end face of the disk to form an opening.
Ceramic turbine rotor characterized by comprising form without hollow portion.