JPS62228602A - Rotation body for heat engine - Google Patents

Abstract

PURPOSE:To prevent the occurrence of getting chipped by arranging for a heat engine such as a gas turbine and the like the ceramic fiber of the tip portions of the fin part of a rotation body along the fin-face and toward the direction of the tip-edges as well. CONSTITUTION:The hub portion 12 and the shaft portion 11 of a rotation body 1 are formed out of ceramic sintered body containing no ceramic fiber. And the fin part 13 is formed out of ceramic sintered body containing ceramic fiber. The ceramic fiber 3 of the tip portions 131 of the fin part 13 is arranged along the fin-face and toward the direction of the tip-edges as well. By this, the occurrence of getting chipped at the fin-tip portions by coming into collision with a foreign matter may be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a rotating body for a heat engine, such as a turbine wheel of a gas turbine or a turbocharger, which is provided with fins and used in a heat engine.

[Prior art]

In recent years, heat-directing engines such as gas turbines and turbochargers have been manufactured using high-temperature, high-strength ceramic materials such as silicon nitride and silicon carbide for the purpose of improving thermal efficiency by increasing the operating temperature and replacing rare resources. Attempts have been made to use a rotating body (turbine wheel).

Conventionally, turbine wheels have been manufactured by casting heat-resistant alloys such as nickel and chromium, but metals do not have sufficient heat resistance and there is a limit to the operating temperature of the heat engine. For this reason,
Ceramic turbine wheels have come to be manufactured using ceramic materials such as silicon nitride and silicon carbide, which have high strength and excellent heat resistance, by molding methods such as injection molding and cast molding.

Ceramic turbine wheels are manufactured by first adding an appropriate organic substance or water to a ceramic powder raw material to give it fluidity, and then molding it into a desired shape.

Next, additives such as organic substances and moisture are removed from the obtained molded body by heating, and the molded body is fired to obtain a dense baked viscous product.

[Problem that the invention seeks to solve]

A turbine wheel rotates at high speed to generate output using high-temperature combustion gas burned in a combustor or combustion chamber.2For example, in a turbocharger, the maximum circumferential speed of the outermost circumference of the turbine wheel reaches approximately 600 m/sec. .

The combustion gas contains fine particles such as various types of dust, metal oxide fragments, and particulates contained in the intake air, and these particles collide with the turbine wheel, which is rotating at high speed.

At this time, in a metal turbine wheel with excellent impact resistance, even if particles collided with it, only a dent occurred in the outer circumferential portion where the circumferential speed was highest, and no performance problems occurred. However, the ceramic turbine wheel has a problem in that, because of its B hazard, when fine particles collide with the tips of the fins on the outer periphery of the turbine wheel, chips occur, which reduces the performance of the turbine wheel.

In addition, as a countermeasure against this, 2, for example, the patent application filed in 1983 by the present applicant.
As in No. 132779, an extra portion is provided at the outer peripheral tip of the fin molding portion of the cavity in a mold for molding a rotating body for a heat engine equipped with fins.

A molded body is obtained by filling the cavity with a ceramic material containing ceramic fibers, the molded body is degreased and fired to form a sintered body, and after the molded body is molded or made into a sintered body, the surplus of the fin tip is removed. by removing the part.

An attempt was made to improve the strength of the ceramic material at the fin tips, which is prone to chipping due to collisions with foreign objects, by oriented the ceramic fibers at the tips of the fins on the outer periphery of the rotating body along the fin surface and in the direction of the tip edges. ing.

That is, this means provides a ceramic rotor for a heat engine in which the tip of the fins on the outer periphery of the rotor is strengthened and will not be chipped even when collided with fine particles.

However, ceramic fibers are expensive.

Since this ceramic fiber is used throughout the rotating body, it is difficult to manufacture a single rotating body at low cost.

On the other hand, the strength of the ceramic material itself is at a level that can sufficiently withstand the stress applied to the rotating body due to nine rotations, except for impact resistance against foreign objects and the like.

Therefore, in order to manufacture an inexpensive ceramic rotating body, it is desired to strengthen only the fin tips, which are prone to chipping due to collision with foreign objects, with oriented ceramic fibers.

The present invention has been made in view of the above circumstances.

To provide a rotating body for a heat engine at a low cost, in which the tip of the fins on the outer periphery of the rotating body is reinforced with ceramic/vri fiber so that chipping does not occur even if fine particles such as metal oxides collide with the fin part of the rotating body. , the purpose of this is to solve the conventional problems.

[Means for solving problems]

The rotating body for a heat engine of the present invention has a fin portion made of a sintered body of a ceramic material containing ceramic fibers, and an integrated hub portion and shaft portion made of a sintered body of a ceramic material that does not contain ceramic fibers. The rotating body of the present invention is characterized by:

As shown in FIG. 1, a fin portion 13 containing ceramic fibers
The ceramic fibers 3 of the tip portion 131 are oriented in a direction parallel to the fin surface and toward the tip edge.

The rotating body fin portion of the present invention in which such orientation is imparted to the ceramic fibers 3 uses a mold in which an extra portion 22 is extended at the tip of the fin molding portion 21, as shown in FIG. The ceramic material mixed with fibers is filled and molded, the molded body is degreased and fired to form a sintered body, and the surplus manufactured parts are removed after molding or sintering to obtain the desired rotating body fin part. .

On the other hand, as shown in FIG. 3, the hub portion 12 and shaft portion 11 that do not contain ceramic fibers are formed by injection molding or slip casting, or by processing after molding or after molding and first firing. able to make.

The rotating body for a heat engine of the present invention has a fin portion 13 containing ceramic fibers and an integral hub portion 12 not containing ceramic fibers.
and shaft portion 11 are molded separately, then combined and bonded, and then fired. The hub portion 12 and the shaft portion 11 are connected to each other by forming a hub integral with the degreased body of the fin portion 13, which is molded by adjusting the density of the degreased body or molded body in advance so that the firing shrinkage rate approximates that of the hub portion 12 and the shaft portion 11. This is done by combining the portion 12 and the degreased body or molded body of the shaft portion 11 and applying hydrostatic pressure to the combination.

In addition, the degreased body of the fin part 13 which is molded with the density adjusted in the same manner, or the ceramic material that forms the fin part 13 or the integral part of the hub part 12 and the fitting part with the degreased body or molded body of the shaft part 11, This can also be done by filling and then assembling a slip made of a ceramic material of the same quality as the ceramic material forming the hub portion 12 and shaft portion 11 of.

In addition, in the rotor for a heat engine of the present invention, the fin portion 13, the integrated hub portion 12, and the shaft portion 11 are molded and fired separately to form a sintered body, and then the two are combined using a powder pressure transmission medium. It can also be manufactured by bonding the two together by hot pressing or hot isostatic pressing (HIP).

Further, in the rotating body for a heat engine of the present invention, the fin portion 13 and the integral hub portion 12 and shaft portion 11 are separately molded, and only the integral hub portion 12 and shaft portion 11 are fired in advance to form a sintered body. Thereafter, the integral sintered body of the hub part 12 and shaft part 11 is arranged so as to be inserted into the degreased body of the fin part 13, and is integrally fired.

Due to the shrinkage effect of the fin portion 13 as the sintering progresses.

It can also be manufactured by combining the two together.

FIG. 4 shows another example of the integration of two rotating bodies of the present invention, and the shape of the hub part 12 and shaft part 11, which are integral with the fin part 13, is such that they can be firmly integrated. For example, any shape or method may be used.

On the other hand, examples of the ceramic material forming the fin portion of the rotor for a heat engine include silicon carbide and silicon nitride.

Alumina, zirconia, sialon, etc. may be used.

Silicon carbide is also used as a ceramic fiber.

Any one or a plurality of fibers such as silicon nitride, alumina, graphite, and boron nitride may be used.

The ceramic fiber used in the present invention is a fibrous ceramic body, and may be polycrystalline or amorphous.

Any single crystal called a whisker may be used, and preferably one having a diameter of 0.3 to 50 μm and a length of about 5 to 1000 μm. If the fiber is thinner or shorter than this, the effect of reinforcing the fiber will be small; if it is thicker than this, the strength will decrease, and if it is longer than this, the fiber will break and be crushed during kneading and molding of the material.

The appropriate ceramic fiber content in the material is about 6 to 70% by weight. If the amount is smaller than this, the effect of reinforcing the fibers will be small, and if it is too large, the strength will actually decrease.

In addition, as the ceramic material forming the integral hub portion and shaft portion that do not contain the ceramic fibers, silicon carbide, silicon carbide,
Silicon nitride, alumina, zirconia.

Sialon etc. may be used.

Note that if the ceramic fiber content in the fin portion is small and the desired effect cannot be obtained by adding ceramic fiber, the desired effect may be obtained by further applying hot isostatic pressing (HIP) treatment. can.

[Effect]

The tip of the fin of a rotating body for a heat engine has the highest circumferential speed, and is easily chipped by collisions with foreign objects in the gas. In many cases, the chipping occurs at the tip of the fin that protrudes toward the outer diameter in a direction substantially perpendicular to the protruding direction, that is, in the Y direction shown in FIG. 5. However, since the ceramic fibers are oriented in the protruding direction, that is, in the X direction perpendicular to the chipping direction, chipping is prevented.

Furthermore, when the fin portion of the rotating body is molded by injection molding or cast molding, the ceramic fibers 3 in the ceramic material flowing through the fin molding portion 21 of the cavity as shown in FIGS. 6(A) and 6(B) The direction of least resistance, that is, the direction along the flow direction.

The fibers at the tip are oriented approximately perpendicular to the flow direction.

Therefore, in the present invention, as shown in FIG. 2, an extra portion 22 is provided at the tip of the fin forming portion 21 of the cavity.

After molding, the excess portion of the product is removed as shown in FIGS. 7 and 8, so that the fibers at the tip of the fin are oriented in the direction toward the tip. Therefore, chipping of the tips of the two fins due to the collision of particles during the operation of the single rotating body is prevented.

Furthermore, by including ceramic fibers only in the fin portions, the amount of expensive ceramic fibers that are packed into the rotating body for a heat engine can be reduced, and the single rotating body can be manufactured at low cost. Furthermore, by separately molding the fin part, the hub part, and the shaft part, which are integrated into the fin part, the degreasing time required to thermally decompose and remove the organic matter added to the ceramic raw material can be reduced. Compared to when molding is done, the time required is significantly shorter and the rotating body can be manufactured with higher productivity. This makes it possible to manufacture three large rotating bodies at low cost and with good productivity, which is beyond practical use.

〔Example〕

(Example 1) Silicon carbide fibers with an average particle size of 0.6 μm in diameter and 10 to 20 μm in length, and 5% by weight of Ittria and 5% by weight of magnesia-alumina spinel as sintering aids were added.
A ceramic raw material was prepared by mixing 8 μm silicon nitride powder at a ratio of 30% and 70%, respectively. 23 parts by weight of a thermoplastic resin and a plasticizer were added to 100 parts by weight of this ceramic raw material, and the mixture was heated and kneaded in a kneader and pulverized to produce pellets for injection molding.

FIG. 6 shows a mold for injection molding the fin portion of the rotating body of the present invention, and this mold 2 has an extra portion 22 formed at the tip of the fin molding portion 21 of the cavity. Then, the above-mentioned pellet is injection molded into the mold 2 from the direction of the arrow, and as shown in FIGS. 9 and 10, a plurality of fins 13 are formed.
A molded body 1'' of a fin portion of a rotating body was obtained.

Next, this molded body 1' was placed in a degreasing furnace, and the organic matter added to the ceramic raw material was removed by thermal decomposition.

The time required for this degreasing was 90 hours. On the other hand, by using silicon nitride powder with an average particle size of 0.8 μm obtained by removing silicon carbide fibers from the raw materials, and adding the same raw materials as those for the fin portion, an integrated hub portion 12 and shaft portion 11 as shown in FIG. It was hydrostatically pressed into the shape of .

Next, this molded body was placed in a degreasing furnace, and a small amount of organic matter added to the ceramic raw material was removed by thermal decomposition.

The thus obtained fin part molded body 1'' and the integrated hub part and shaft part molded body were combined, bonded by hydrostatic pressure using 3t/(Jll), and baked to be integrated to obtain a sintered body of one rotating body. Ta.

Next, the surplus portion 14 at the tip of the fin of this sintered body was removed by grinding, and the outer diameter of the sintered body was 601 m as shown in FIGS. A ceramic rotating body 1 was obtained.

FIGS. 6(A) and 6(B) show the flow of ceramic raw materials including ceramic fibers during injection molding. As shown in FIG. 6(A), when the ceramic raw material flows through the fin forming part 21 of the cavity of the mold 2, the ceramic fibers 3 are oriented in the flow direction so as to have less resistance. However, at the tip in the flow direction of the raw material, the ceramic fibers 3 are oriented perpendicular to the flow direction, and when a mold with a cavity shaped to match the intended product is used, as shown in Figure 6 (B), the fin tip The ceramic fibers in the fin are oriented in the thickness direction of the fin.

On the other hand, in the present invention, as shown in FIG.
8), the ceramic fibers 3 at the tip of the fin are oriented in the above flow direction, that is, parallel to the fin surface and toward the tip.

Turbine wheel 1 of the present invention obtained as described above
was attached to a turbocharger and rotated at a speed of 120,000 rpm using combustion gas from the engine. At this time, the circumferential speed of the outermost circumference of the rotating body (the tip of the fin) is approximately 380 m/sec.
It became. In this state, in order to measure the impact resistance, 5 pieces of iron oxide weighing approximately 100 mg each weighing 10 to 20 mg each.
It was mixed into the exhaust gas in batches.

After the rotation test, collision marks of iron oxide pieces were seen at the tip of the rotating body 1, but no chipping occurred at all.

In addition, when the tip was cut and observed with a scanning electron microscope, ceramic fibers were found in the tip as shown in Figures 1 and 7.
As shown in FIG. 8, it was confirmed that they were oriented in the same direction.

(Example 2) The mixing ratio of silicon carbide fiber and silicon nitride powder was 1
A ceramic fiber-containing rotating body was sintered using the same method and conditions as in Example 1, except that the content was 0% by weight and 90% by weight. Furthermore, this sintered body was subjected to HIP treatment to produce a rotating body.

The rotating body thus obtained was subjected to a rotation test in the same manner as in Example 1, and no chipping occurred at the fin tip.

(Comparative Example 1) A mold with a cavity having the same shape as the product and no surplus part was used, and the fin part, hub part, and shaft part were manufactured separately under the same conditions as in Example 1 of the present invention. When a ceramic fiber-containing rotating body was tested under the same conditions as above, small chips were observed in several fins along with iron oxide impact marks at the tips of the fins.

(Comparative Example 2) Using a mold in which the fin part, the hub part, and the shaft part are integrally formed, and an extra part is formed at the tip of the fin molding part, the integral part is made in the same manner as in Example 1. A rotating body containing silicon carbide fibers was manufactured. As in Example 1, no chipping occurred in the rotation test, but since it was integral, it took a long degreasing time of 150 hours to thermally decompose and remove the organic matter from the molded body.

(Comparative Example 3) A fin portion, a hub portion, and a shaft portion were created separately under the same raw material conditions as in Example 2, and a ceramic fiber-containing turbine wheel without HIP treatment was manufactured. When this was subjected to a rotation test, a minute chip was observed in one fin at the tip of the fin.

As explained above, in the present invention, the fin portion of the rotating body for a heat engine is constructed from a fiber-reinforced ceramic sintered body.

In addition, by orienting the fibers at the tips of the fins, it is possible to prevent the fins from chipping during one operation.

In addition, when molding the fin portion of a single rotating body, by using a mold having an extra portion at the tip of the fin molding portion of the cavity, the fin portion of the rotating body with oriented fibers at the tip of the fin can be formed at low cost and with high productivity. can be manufactured.

Note that the shape of the excess portion of the mold cavity is not particularly limited, and any shape may be used as long as the ceramic material can further flow beyond the portion that is to become the fin tip.

Furthermore, the present invention is not limited to the radial type rotating body of the embodiment,
Needless to say, the same effect can be obtained even when used in an axial rotating body.

[Brief explanation of drawings]

Figures 1 to 11 show a rotating body for a heat engine according to the present invention and its main parts, with Figure 1 being a partially cutaway side view, and Figure 2 showing a mold for injection molding the fin portion of the rotating body. FIG. 3 is a side view of the hub portion and shaft portion; FIG. 4 is a partially cutaway side view showing the integral connection of the hub portion, shaft portion, and fin portion; FIG. 5 is a front view; Figure 6 (A), (B)
is a diagram showing the direction of fibers in the ceramic material during injection molding of the fin portion of the rotating body, FIGS. 7 and 8 are diagrams showing the fiber orientation in section A of FIGS. 9 and 10, respectively, and FIG. FIG. 3 is a perspective view of a main part of a fin portion.

Claims (1)

[Claims] A rotating body for a heat engine equipped with fins, consisting of a fin part made of a ceramic sintered body containing ceramic fibers, and an integrated hub part and shaft part made of a ceramic sintered body not containing ceramic fibers, A rotating body for a heat engine, characterized in that ceramic fibers at the tip of the fin portion of the body are oriented along the fin surface and in the direction of the tip edge.