JP2753367B2 - Full shroud impeller - Google Patents

Description

The present invention relates to a method of manufacturing a centrifugal compressor, for example, a single-shaft multi-stage centrifugal compressor, an expansion turbine, for example, a full-shoulder impeller suitable for use in an expansion turbine for a liquefied helium refrigerator. About.

[Conventional technology]

In the conventional full shroud, the blade is divided into an upper half portion and a lower half portion, and there is no particular limitation. The divided members are formed by diffusion bonding. In addition, shaving the blades from both the side plate side and the core plate side is
There is also a problem in accuracy and cost, and there is an example of a so-called T-shaped joint in which blades are cut out from either side plate or core plate (15th Turbomachinory Symposium, November 1986 (15th Turbo Machinery Symposium)) .

[Problems to be solved by the invention]

In the prior art, no consideration was given to an appropriate division position, and there was a problem in strength reliability. An object of the present invention is to provide a full shroud impeller with improved strength reliability of a diffusion joint.

[Means for solving the problem]

In order to achieve the above object, the blade dividing position is divided at a position where centrifugal stress is close to 0 on both the back side and the belly side of the impeller outlet blade, and diffusion bonding is performed. In other words, from the results of stress analysis by the finite element method (FEM) and experiments, 40% of the blade height in the height direction of the blade from the inner surface of the core plate
It became clear that it would be better to split at a location corresponding to the range of ~ 60%.

[Action]

When the centrifugal stress acting on the impeller is calculated and analyzed using the finite element method while the impeller is operating (rotating), it is found that a large tensile and compressive centrifugal stress is applied to the impeller blade. Further, it can be seen that there are stress distributions on the side plate side and the core plate side of the blade portion and on the dorsal side and the ventral side of the blade, and there are places where the maximum value and the minimum value are present. Therefore, in order to fabricate a full shroud impeller by splitting the blades and diffusion bonding,
It suffices to divide at a place where the centrifugal stress is small. Therefore, as a result of various analysis by calculation and stress measurement by experiment, it was found that the centrifugal stress acting on the back side and the abdomen side of the blade part at the impeller outlet side is larger than other parts. Therefore, if the centrifugal stress acting on the dorsal side and the ventral side of the wing portion is a value close to 0, the divided portion is defined as
It becomes an impeller with high strength reliability. On the other hand, when splitting and joining at the location showing the maximum stress, from the point of strength reliability,
Quite a disadvantage. In consideration of the above, the division position was examined, and as a result, 40% of the blade height in the height direction from the inner surface of the core plate
It was concluded that there would be no problem in strength if it was divided at a point within the range of ~ 60%.

〔Example〕

In FIG. 1, a metal member in which the upper half 1 of each blade is integrally formed with the side plate portion 2 and a metal member in which the lower half 3 of each blade is integrally formed with the core plate portion 4 are separately manufactured. A full shroud impeller 5 in which the upper half 1 of the blade and the lower half 3 of the blade are abutted and diffusion bonded is shown. 400m impeller diameter
m, the number of the blades 13, the width of the blades 3 3 mm, and the angle of 18 ° between the side plate inner surface 7 and the core plate inner surface 8,
Is 5.5 mm away from the inner surface of the core plate. The blade height at the impeller outlet side is 10 mm.

Fig. 2 shows the impeller outlet when rotating at 14000rpm.
10 shows centrifugal stress distribution in ten blades. The stress has a maximum value and a minimum value on both the blade back side 11 and the blade ventral side 12. The stress value is 0 at a position about 5.5 mm from the core plate side of the blade height. Therefore, here, as shown in the same figure, it suffices to divide, that is, join at a position 5.5 mm away from the inner surface of the core plate. However, since there are other restrictions in practical use, it may be divided within a range of 4 to 6 mm from the inner surface of the core plate portion, and there is no problem in strength. The diffusion bonding impeller manufactured in this way was subjected to an overspeed test (rotation speed 14000 rpm,
At a peripheral speed of 293 m / s), the residual elongation of the core / side plate outer diameter after the test was 0.025% or less, which was a satisfactory result. Further, no abnormalities were found in the joints in the magnetic flaw inspection after the experiment.

If the shape and dimensions of the impeller change, the location to be divided also changes. For example, 550mm in diameter, 13 blades, 3mm blade width,
For the impeller with inlet blade height of 16mm, outlet blade height of 6mm and (side plate angle of 4 °), the locations where the centrifugal stress acting on the back and ventral sides of the outlet blade are close to 0 are determined by experiments and calculations. According to the analysis based on the above, dividing the portion at a distance of 3 mm from the core plate side results in a diffusion bonding impeller with high reliability.

〔The invention's effect〕

According to the present invention, strength reliability can be improved. For example, in the experimental example, in the impeller where the splitting part is set to the place where the maximum stress acts, the centrifugal stress of up to 500MPa during operation (during rotation) is applied to the back side of the blade and 500M to the ventral side.
It will be subjected to compressive stress of Pa. On the other hand, in the present invention, only the centrifugal stress of 50 MPa or less acts on the joint.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a full-shroud diffusion bonding impeller according to an example of the present invention, and FIG. 2 is a characteristic diagram of a centrifugal stress distribution acting on an outlet blade during rotation of the impeller obtained by calculation. DESCRIPTION OF SYMBOLS 1 ... Upper half of a blade, 2 ... Side plate part, 3 ... Lower half of a blade, 4
… Core plate part, 5… Furshroud impeller, 6… Blade, 7
... inner surface of side plate portion, 8 ... inner surface of core plate portion, 9 ... split portion, 10 ... impeller outlet portion, 11 ... blade back side, 12 ... blade ventral side.

Claims (1)

(57) [Claims] 1. A full shroud impeller in which blades having different heights on a fluid inlet side and a fluid outlet side are formed between a core plate and a side plate, wherein the blade is provided on the blade integrally formed on the side plate. The butting surface of the half part and the lower half part of the blade integrally formed on the core plate are formed by diffusion bonding, and the butting surface is a straight line perpendicular to the rotation axis of the full shroud impeller. A full shroud impeller, wherein a height from the core plate to the butting surface is within a range of 40% to 60% of a height of the blade on the fluid outlet side.