JPH0953595A - Aluminum-alloy-made two-layer structural impeller for centrifugal compressor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a centrifugal compressor having low manufacturing cost and good responsiveness, even when the compression ratio is high, or when the gas temperature on the suction side is high. SOLUTION: The center part 1a along the rotor shaft 2 of a centrifugal compressor is formed by an age-precipitation reinforced type heat-resisting aluminum alloy, and a projected part 1b that has been connected to the center part 1a and projected toward the gas inlet 6 is formed by an aluminum-iron quenched solidified alloy, so that the compression ratio of the centrifugal compressor is increased and its performance can be enhanced. In that case, the manufacture of the impeller by means of aluminum alloy that is lightweight and has a good workability can be enabled, and a centrifugal compressor of good responsiveness can be obtained at low cost.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy two-layer structure impeller for a centrifugal compressor used as an engine supercharger or the like.

[0002]

2. Description of the Related Art In the conventional centrifugal compressor whose structure is shown in FIG. 3, the impeller 01 has a relatively low compression ratio and the maximum temperature (compressed air outlet) temperature rises up to about 160.degree. The single-stage type is made of heat-resistant aluminum alloy that is manufactured by normal melting / forging, and has high performance and a high compression ratio, or the gas temperature on the suction side is high and the highest part (compressed air). Outlet) temperature is 2
If the temperature exceeds 00 ° C, it was made of cast steel or titanium alloy.

Regarding the above heat-resistant aluminum alloy, from the viewpoint of heat resistance strength, Al-C, which has the best heat resistance at present, is used.
The u-Mg type JIS-A2618 alloy was often used.

In a conventional supercharger for a large diesel engine, since the compression ratio is relatively low at 3.5 or less, the above-mentioned impeller 01 is a single-stage air suction type made of heat-resistant aluminum alloy. Centrifugal compressors were used.

However, in recent years, in response to higher performance on the engine side, a higher compression ratio on the supercharger side has been demanded, and a centrifugal compressor having a compression ratio of more than 4.0 is also required. Became. In this case, the temperature of the air at the outlet of the impeller 01 becomes 200 ° C. or higher.

The heat-resistant aluminum alloy, which is the material of the impeller 01, is a type of alloy whose strength is secured by aging heat treatment (190 ° C. × 10 to 20 hours), and is heated for a long time in a temperature range exceeding this temperature. And the strength decreases. Therefore, when the impeller 01 is made of aluminum alloy, it is difficult to secure a high pressure ratio, and the impeller 01 of the centrifugal compressor used as a supercharger of a large diesel engine is made of cast steel or titanium alloy. Tends to move in the direction.

[0007]

In the conventional centrifugal compressor, as described above, in the case of an air suction type single-stage compressor whose compression ratio is relatively low and the maximum temperature rises only up to about 160 ° C. , The impeller was made of heat-resistant aluminum alloy.

This heat-resistant aluminum alloy has an aging heat treatment (19
This is an alloy of the type that secures strength by (0 ° C x 10 to 20 hours), and strength decreases when heated for a long time in a temperature range exceeding this temperature, so in the case of a compressor with a high compression ratio or on the suction side. In the case of a compressor whose gas temperature is high and the maximum temperature exceeds 200 ° C., its impeller was made of cast steel or titanium alloy and its strength was secured.

However, when these materials are used, since the impeller itself has a very complicated shape, the manufacturing and processing cost is significantly higher than that of the impeller made of aluminum alloy, and the impeller is made of aluminum alloy. In comparison, cast steel or titanium alloy has a large material density, and thus has a problem such as poor response as a centrifugal compressor. The present invention seeks to solve the above problems.

[0010]

According to a first aspect of the present invention, there is provided an aluminum alloy two-layer structure impeller for a centrifugal compressor, which is formed along a rotor shaft of the centrifugal compressor and communicates with a gas inlet. The central part of the car is made of a normal aging precipitation strengthening heat-resistant aluminum alloy that is made by a melting / forging process, and is connected to the central part and protrudes toward the gas outlet so as to communicate with the gas outlet. Is made of an aluminum-iron non-heat treatment type high strength heat resistant alloy produced by a rapid solidification method.

In the above, in the vicinity of the central portion of the impeller, the temperature rise during the operation of the centrifugal compressor is small, but the stress generated by the centrifugal force is the largest. On the other hand, in the protruding portion of the impeller, the stress generated by the centrifugal force is relatively small, but the temperature rise is large.

The heat-resistant aluminum alloy of age precipitation strengthening type has a sharp decrease in strength when the temperature rises above a certain temperature, or it has ductility at low temperatures, and the stress generated by the centrifugal force of the impeller, which is a high-speed rotating body, increases. It is a material that can withstand. On the other hand, the aluminum-iron rapidly solidified alloy does not have a sharp decrease in strength even in a high temperature state, but does not have ductility in a low temperature region, and is a material that is easily brittle fracture when the generated stress is large.
Complex processing is a difficult material.

Therefore, in the present invention, the central portion, which is low in temperature but has high stress generated by centrifugal force, is formed by using an age precipitation strengthening type heat-resistant aluminum alloy, and the generated stress is low and the temperature rise is large. Is formed by using an aluminum-iron-based rapidly solidified alloy, and these are combined to form an impeller.

Therefore, when the compression ratio of the centrifugal compressor is increased to improve its performance, it is possible to manufacture an impeller made of an aluminum alloy that is lightweight and has good workability, and a low-cost and highly responsive centrifugal compressor can be manufactured. It becomes possible to obtain.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION An aluminum alloy two-layer structure impeller for a centrifugal compressor according to an embodiment of the present invention will be described with reference to FIG. The centrifugal compressor according to the present embodiment,
It is used as a supercharger for large diesel engines.

In this embodiment shown in FIG. 1, an impeller 1 through which a rotor shaft 2 penetrates, and casings 3 and 4 surrounding the impeller 1.
In a centrifugal compressor equipped with, the central portion 1a of the impeller 1 which is formed in a rectangular shape whose cross section is parallel to the rotor shaft 2 and communicates with the gas inlet 5 is a normal aging precipitation produced by a melting / forging process. Al, a reinforced heat-resistant aluminum alloy
-The protrusion 1b of the impeller 1 which is made of Cu-Mg based JIS-A2618 alloy and which is connected to the central portion 1a and protrudes toward the gas outlet 6 is an aluminum manufactured by the rapid solidification method-
It is made of iron-based non-heat treatment type high strength heat resistant alloy.

In the above, since the temperature at the position of about 2/3 in the radial direction from the central axis of the impeller 1 during the operation of the centrifugal compressor is about 150 ° C., the central portion 1 of the impeller 1 is
Regarding a, Al-Cu used in the conventional impeller
-Mg based JIS-A2618 alloy can be used.

On the other hand, the temperature of the air at the gas outlet 6 of the impeller 1 rises according to the pressure ratio of the centrifugal compressor, and the pressure ratio is about 4.0 even when air at room temperature is sucked. When it reaches a certain level, the temperature of the air at the impeller outlet 6 reaches 200 ° C. or higher.

The Al-Cu-Mg system JIS-A26
18 alloy has an aging temperature of about 180 to 190 ° C.,
When heated at a temperature of 180 ° C. or higher for a long time (100 hr or higher), the strength is reduced. Therefore, the above alloy cannot be used for the protruding portion 1b of the impeller 1 in the centrifugal compressor aiming at a compression ratio of 4.0 or more and a total operating time of 100,000 hours or more.

On the other hand, the aluminum-iron non-heat treatment type high strength heat resistant alloy produced by the rapid solidification method is different from the age precipitation strengthening type alloy in that it is not an alloy which secures strength by heat treatment. Even in the temperature range exceeding ° C, there is no sudden decrease in strength, and the heat resistance is greatly improved compared to JIS-A2618 alloy, which is a heat-resistant aluminum alloy.

FIG. 2 shows a comparison of the temperature dependence of the tensile strength of the JIS-A2618 alloy and the aluminum-iron based alloy produced by the rapid solidification method. The JIS-A2618 alloy rapidly changes from 150 ° C. The strength of aluminum-iron alloy does not decrease sharply up to 250 ° C, but the strength of JIS-A2618 alloy at 180 ° C and the strength of aluminum-iron rapidly solidified alloy at 250 ° C are equal. Is.

As described above, the rapidly solidified aluminum-iron alloy is excellent in heat resistance, but has no ductility in the temperature range of 100 ° C. or less, and the elongation at break at room temperature is 3% or less. . The impeller 1 is a high-speed rotating body, and the temperature in the vicinity of the rotor shaft 2 is 100 ° C. or less, but the stress generated by the centrifugal force is the largest, and when a material having no ductility is used, brittle fracture occurs at the time of starting and stopping. There is a risk of one-time destruction by. Further, the aluminum-iron non-heat treatment type high strength heat resistant alloy produced by the rapid solidification method is difficult to produce and the material cost is high.

Therefore, in the present embodiment, taking these factors into consideration, the central portion 1a of the impeller 1 at which the temperature is 150 ° C. or less and the stress generated by the centrifugal force is high is ductile to some extent, and it has been practically used so far. Aluminum-iron manufactured by a heat-resistant rapid solidification method is used for the protruding portion 1b of the impeller 1 which uses a proven heat-resistant aluminum alloy of aging precipitation strengthening type, but the temperature exceeds 150 ° C, but the stress generated is low. It was decided to apply a non-heat treatment type high strength heat resistant alloy.

Regarding the joining of the central portion 1a and the protruding portion 1b of the impeller 1, the respective materials are roughly processed into a required shape, then diffusion-bonded by hot pressing (450 ° C. × 2 hours), and then precision Final finishing was performed by a processing machine to obtain a predetermined impeller. The processed impeller 1 is attached to a rotation tester on a table and rotated up to a predetermined operating speed, and it is confirmed that there is no particular abnormality such as vibration.

The above-mentioned joining may be mechanical joining (screw type / fitting type), shrink fit, diffusion joining, or the like. However, since the impeller 1 is a high-speed rotating body, from the viewpoint of preventing its destruction. From the viewpoint, it is considered that continuous bonding by diffusion bonding is more suitable.

When the two-layer structure impeller made of aluminum alloy obtained as described above is applied to a centrifugal compressor and this centrifugal compressor is used as a supercharger for a large diesel engine, the pressure ratio is about the current level. It is possible to raise from about 3.5 (maximum temperature; 170 ° C) to about 5.0 (maximum temperature;
It was possible to obtain a supercharger that can meet a wide range of demands for improved engine performance, is relatively inexpensive, and has excellent responsiveness as a centrifugal compressor. .

[0027]

EFFECT OF THE INVENTION Aluminum alloy for centrifugal compressor of the present invention 2
The layered impeller has a central portion along the rotor shaft of a centrifugal compressor formed of an age precipitation strengthening type heat-resistant aluminum alloy, and a protruding portion that is connected to the central portion and protrudes toward a gas outlet is made of aluminum-iron. Since it is made of a system rapidly solidified alloy, it is possible to manufacture an impeller made of an aluminum alloy that is lightweight and has good workability when increasing the compression ratio of a centrifugal compressor to improve its performance, and at a low price. It is possible to obtain a responsive centrifugal compressor.

[Brief description of drawings]

FIG. 1 shows a centrifugal compressor 2 according to an embodiment of the present invention.
It is explanatory drawing of a layer structure impeller.

FIG. 2 is a comparison diagram of temperature dependence of tensile strength of a JIS-A2618 alloy according to the above embodiment and an aluminum-iron based alloy produced by a rapid solidification method.

FIG. 3 is an explanatory diagram of a conventional centrifugal compressor.

[Explanation of symbols]

 1 Impeller 1a Central part 1b Projection part 2 Rotor shaft 3,4 Casing 5 Gas inlet 6 Gas outlet

Claims (1)

[Claims] 1. A center portion of an impeller formed along a rotor shaft of a centrifugal compressor and communicating with a gas inlet is made of a normal aging precipitation strengthening heat-resistant aluminum alloy produced by a melting / forging process. The protrusion of the impeller that is connected to the portion and projects toward the gas outlet and communicates with the gas outlet is made of an aluminum-iron non-heat-treatment type high-strength heat-resistant alloy manufactured by a rapid solidification method. Aluminum alloy two-layer structure impeller for centrifugal compressors.