JP3075071B2 - Impeller for centrifugal compressor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-speed rotating impeller such as a centrifugal compressor.

[0002]

2. Description of the Related Art In a seawater desalination plant or the like, a steam compression system for removing impurities such as salts by vaporizing steam such as steam under reduced pressure may be installed. In this case, a centrifugal compressor is used for compressing the steam. For example, the technique described in Japanese Patent Application Laid-Open No. Sho 60-62539 uses a centrifugal compressor to extract water vapor from a vacuum vessel. Also, the magazine “Chemical Factory”, Vol. 25, No. 1, p. The technique described in 86 to 92 uses a "special compressor made of stainless steel flexible blades".

The specific volume of water vapor under reduced pressure is, for example, 4.
Was 206.3m ³ / kg at 6 Torr, will account for about 123 times the volume of the specific volume 1.673m ³ / kg at atmospheric pressure. Therefore, even if the mass flow rate is small, the air volume becomes considerably large. As a result, the diameter of the impeller of the centrifugal compressor increases, and the rotation speed also increases.
For example, mass flow rate 1000 kg / h, inlet pressure 4.2 t
orr, outlet pressure 7.5 torr, impeller specifications: air volume 3730 m ³ / min, impeller diameter 148
7 mm and the number of rotations is 4817 rpm. At this time, the peripheral speed of the impeller is 375 m / s.

[0004] Such a high-speed rotating impeller is required first and foremost to have high specific strength and toughness. The specific strength is
It is required to be high in order to prevent the blade from being broken by its own weight due to the centrifugal force caused by the high-speed rotation. Even if the specific strength is high enough,
If the toughness is low, the blade is susceptible to impact and the blade is easily broken. If a part of the blade is destroyed, the impeller rotating at a high speed will cause a collision of fragments in a moment, resulting in an accident that destroys all the blades.

[0005] There are various types of impellers, and generally known ones are an impeller in which a blade and a hub are integrally machined, an impeller in which the blade is welded to the hub, and a blade attached to the hub. And the like.

FIG . 4 is a detailed view showing the structure of a blade and a hub of an impeller in which a blade of the prior art is fitted to a mounting portion of a hub. In the figure, 1 is a blade, 2 is a hub, 8 is a hole,
Reference numeral 9 denotes a slit, 10 denotes a mounting portion, and 12 denotes a fitting portion. The blade 1 is cut out of a thick plate, and the blade 1
Is fitted to the mounting portion 10 of the hub 2,
It constitutes an impeller.

[0007]

First, it is difficult to reduce the weight of the blade of an impeller in which the blade and the hub are integrally machined. This is because it is necessary to compensate for the low toughness of the blade because the workability of the raw material before the impeller is cut is low, and the blade is thickened or ribbed. In this case, the material is generally forged,
Since the dimensions are large, it is inevitable that the working ratio is lower than that of a rolled material or the like.

[0008] As described above, the impeller which has been integrally machined has thicker blades, so that the hub portion becomes larger and it is difficult to reduce the weight. As a result, the compressor becomes inefficient because the bearing of the compressor becomes large, the mechanical loss during operation increases, and the capacity of the motor also increases. In addition, in order to perform integrated machining, forging and heat treatment of a large material are required, and a large machine tool is also required.
Processing and manufacturing are difficult. In addition, of course, the material yield is the worst.

Next, in the impeller in which the blades are welded to the hub, the toughness of the weld is low. Therefore, it is necessary to use a particularly high toughness weld metal or to manufacture with a special welding method and condition, and the manufacturing cost increases. However, even if such attention is paid to the welding operation, the structure of the heat-affected zone of the weld generally becomes coarse, so that the toughness particularly at the root of the blade often decreases.

Finally, in the impeller in which the blades are fitted to the mounting portion of the hub, a thick plate can be used as a material for shaving the blades. Therefore, since the degree of processing of the material is higher than that of a forged material, which is a material of the integrated machining, the blade can be made thinner, that is, lighter in weight. However, since the blades must be formed by shaving, the processing cost is still high,
The material yield is also poor.

In general, the central part of the plate thickness has a coarse grain size and low toughness, but the material formed on the blade by cutting is the material near the central part of the plate thickness, and the toughness of the blade may be reduced. Unavoidable. This can be dealt with by separately performing processing such as forging on the blade portion, but it is not realistic to forge the blade individually, which is costly.

Further, if the fitting of the blade (12 in FIG. 5) and the mounting portion of the hub (10) are loose, if the fitting is loose, the blade may shift or rattle during operation, and conversely, the fitting is tight. In addition, it is necessary to partially modify the mounting portion. Therefore, in these processings, high processing accuracy (for example, tolerance:-
0, + several tens of μm), which is also a factor that increases the processing cost.

The present invention solves these problems and provides an impeller that can be reduced in weight and that is easy to manufacture.

[0014]

SUMMARY OF THE INVENTION The present invention comprises a hub having a mounting portion consisting of a slit opened on the outer periphery and a hole provided in connection with the slit, and a blade fitted to the mounting portion. In the impeller, (a) the blades are substantially composed of a rod and a thin plate that is sandwiched between the rods and that is a folded portion, and the entire surface of which is folded over,
(B) An impeller for a centrifugal compressor, wherein a folded portion of the blade is fitted in the hole and a part of the folded thin plate is fitted in the slit.

[0015]

In general, a thin plate has a higher degree of processing than a forged product or a thick plate, and therefore has a fine structure and high toughness. Therefore, the blade can be made thinner by manufacturing the blade with a thin plate. The blades can be manufactured basically by cutting a thin plate according to the width and length of the blades, and then by bending and press forming.

When the folded portion of the blade is fitted into the hole of the hub, the rod sandwiched by the folded portion is deformed. Thereby, the difference in shape between the hole of the hub and the folded portion of the blade is absorbed. Further, if the dimensions of the slit of the hub are processed in accordance with the thickness of the folded portion of the thin plate, the blade is fixed to the hub by fitting the blade with the slit.

[0017]

FIG. 1 is a structural view showing the structure of an impeller as one embodiment of the present invention. In the figure, 1 is a blade, 2 is a hub, 3 is a rotating shaft, and 10 is a mounting portion. FIG.
FIG. 3 is a detailed view of the blade 1 and the mounting portion 10. In the figure,
5 is a thin plate, 6 is a bar, 7 is a joint portion, 11 is a folded portion,
Reference numeral 8 denotes a hole, and 9 denotes a slit. Other symbols are the same as those in FIG.

Here, a round bar is used as the bar 6. The thin plate 5 is folded at the folded portion 11 so as to be wound around the round bar 6. The mating surface of the thin plate 5 is
It is joined by. An example of manufacturing a blade will be described.
First, the thin plate is bent into a U-shape and the round bar 6 is sandwiched. Next, the thin plate is folded by press working,
Is press-formed so as to sandwich the round bar 6. Finally, the mating surfaces of the thin plates 5 are joined by welding or the like.

In this embodiment, the joining portion 7 is provided by welding (spot welding) around the mating surface of the thin plate 5, but may be seam welding. Further, the joining portion may be provided not only on the periphery but also on the entire surface. Further, an adhesive or the like may be used for bonding.

The most part of the blade (excluding the folded portion 11) has high toughness because it is used as it is without processing a thin plate. If the thin plate is cut in the longitudinal direction, the toughness is increased.

The slit 9 in the mounting portion of the hub is manufactured by cutting. If this dimension is set to be twice the thickness of the thin plate, the blade can be securely fixed to the hub by fitting the folded thin plate.

The machining accuracy of the hole 8 in the mounting portion of the hub may be somewhat lower. In particular, if the strength of the thin plate 5 of the blade is higher than the strength of the rod 6 sandwiched inside the folded portion 11, the cross section of the rod 6 is slightly deformed when the blade is fitted, so that the familiarity with the folded portion 11 is improved. Get better. At the same time, the thin plate at the folded portion of the blade is pressed uniformly against the side surface of the mounting portion of the hub, and the residual stress at the fitting portion is made uniform, so that the fitting portion of the blade is less likely to break.

During the operation of the impeller, a centrifugal pull-out force acts on the folded portion 11, and this force acts on the thin plate 5 as tension. Therefore, if the strength of the thin plate is high, the thin plate is not broken at the folded portion 11. Although the bending of the folded portion is performed by cold working, there is no problem as long as no crack occurs during the bending. If it is a normal metal sheet, it is bent by 1t (bending radius is equal to the sheet thickness)
The degree is possible, and it can be used as a material for the blade unless it is a thin plate having low ductility.

With respect to the pulling force due to the centrifugal force, in the prior art, for example, as described with reference to FIG. A shear stress is generated in the inside. Therefore, the strength of the fitting portion 12 of the blade 1 needs to be high, which makes processing of the fitting portion difficult. In the present invention, the pull-out force acts on the thin plate 5 of the blade 1 as tension, and exerts a force, ie, a compressive force, on the rod 6 sandwiched inside the folded portion 11 to reduce its cross-sectional area.

In general, when the stress of the material is the compressive stress, the breaking stress is higher than the shearing stress. In practice, the bar will not break if the bar is not a brittle material, ie if it has some ductility. Therefore, there is no particular problem if a normal metal bar is used as the bar. in this way,
In the present invention, if the strength of the thin plate 5 is high, it is possible to sufficiently counter the pulling force due to the centrifugal force. The rod 6 may be not a round bar but a polygon, and may be a hollow tube.

As described above, according to the present invention, by combining a thin plate having high strength and a ductile rod, it is possible to obtain a blade having high strength including the fitting portion and well fitting to the mounting portion. The material of the thin plate 5 is desirably a lightweight and strong material such as aluminum, titanium, or an alloy thereof. Needless to say, these are selected according to the use such as corrosion resistance.

FIG . 3 is a diagram showing another embodiment. Here, the thin plate 5 constituting the blade 1 is bent to increase the rigidity of the blade.

[0028]

As described above, since a thin plate having high toughness is used, the blade can be made thinner. As a result, the weight of the entire impeller can be reduced. Further, since the cutting of the blade is not required, the yield of the material is remarkably improved, and the production and processing are easy.

When the folded portion of the blade is fitted to the mounting portion of the hub, the rod sandwiched inside the folded portion is deformed to absorb the difference in shape, so that the machining accuracy of the mounting portion of the hub is particularly increased. It can be easily implemented without it.

[Brief description of the drawings]

FIG. 1 is a structural diagram showing the structure of one impeller of an embodiment.

FIG. 2 is a detailed view of a blade 1 and a mounting portion 10;

FIG. 3 is a diagram showing another embodiment.

FIG. 4 shows a blade 1 and a mounting portion 10 according to the prior art .
Detailed view of .

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Blade 2 Hub 5 Thin plate 6 Rod 8 Hole 9 Slit 10 Mounting part 11 Folding part

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Toshiaki Otsuka 1-2-1 Marunouchi, Chiyoda-ku, Tokyo Inside Nippon Kokan Co., Ltd. (56) References: Japanese Patent Publication No. 32-6801 (JP, B1) −1042 (JP, Y1) (58) Fields investigated (Int. Cl. ⁷ , DB name) F04D 29/30 F04D 17/10

Claims (1)

(57) [Claims] 1. An impeller provided with a hub having a mounting portion comprising a slit opened on the outer periphery and a hole provided in connection with the slit, and a blade fitted into the mounting portion, wherein: is substantially as therein folded portion sandwiched the rod inside the rod consists of a thin plate entirely has been folded together, (b) the folded portion is the hole in the blade, folded sheet metal A part of the impeller for a centrifugal compressor is fitted in each of the slits.