RU2534646C1 - Centrifugal compressor impeller - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: in centrifugal compressor impeller containing main disc with integral milled blades on it and integral milled from blades rivets; cover disc with holes for rivets by means which the cover disc is secured on the bearing discs; on internal surface of the cover disc the shoulders are made, as per contour the shoulders completely coincide with the appropriate contours of the blades and create grooves between them, in groves the blades are fixed, at that the middle lines of the shoulders are symmetrical to middle lines of blade contours of the bearing disc.

EFFECT: improvement of strength characteristics of the impeller, significant increasing of its service life.

10 dwg

Description

The present invention relates to the field of compressor engineering, in particular to the design of impellers, and can be used in the manufacture of centrifugal compressors or their impellers.

The impeller of a centrifugal compressor is known, including a bearing (main disk), integral with the blades, and a cover disk connected by rivets that pass through the body of the bearing disk, blades and cover disk (N. Yastrebova, A. Kondakov. I., Lubenets V.D., Vinogradov A.N. Technology of compressor engineering.M., Mechanical Engineering, 1987, p. 223, fig. 138 a, b, c; p. 226, table 6).

The known impeller is characterized by low strength characteristics due to the presence of significant critical stresses in the cover disk and shear and tensile stresses arising in the body of the rivets during operation of the impeller.

The closest in technical essence and the achieved result to the claimed invention is the impeller of a centrifugal compressor, in which the main disk is made with blades integrally milled on it and rivets completely milled from the body of the blades, and the cover disc is made with rivet holes, with which the cover disc is fixed to mostly drive. The cover disk is made conical, and the rivets are made in the form of cylindrical pins with fillets (Patent UA 66369, F04D 17/08, 29/28, according to application No. u 201110982 of 09/13/2011).

During the operation of this impeller, in each of its parts, a centrifugal force distributed in volume arises, acting in the radial direction. In this case, the stress-strain state caused by the action of centrifugal forces is proportional to the square of the peripheral speed of the wheel, and the centrifugal force is greater, the farther the point of its application is removed from the axis of rotation.

Moreover, taking into account the conical design of the casing disk, a normal component of the centrifugal force arises, as a function of the peripheral speed and cone angle Fcn = f (ω; α), which creates bending stresses, while increasing the internal static stresses of the casing disk in the zone of contact with the blade.

These stresses reach their maximum values on the inner surface of the hole of the cover disk at the interface with peripheral rivets. The decrease in structural fatigue strength in these sections is due to the high level of stresses and the presence of a stress concentrator - holes near the outer contour.

According to statistics (G. Rayer, Dynamics and Strength of Centrifugal Compressor Machines. Ed. Mashinostroenie, Leningrad 1968, p. 108), during the operation of impellers of a similar design, all defects are generated on the inner surface of the cover disk at the edge of the peripheral holes.

Another significant drawback of the above design are shear and tensile stresses arising in the body of the rivets. These stresses are similar to the stresses occurring in the cover disk and these stresses are greater the further the rivets are removed from the axis of rotation. In absolute terms, stresses arising in rivets are close to the yield strength of the material of these rivets, which leads to their plastic deformation (contouring) and, as a consequence, to breakage.

The known impeller 2, as well as the previous one, is characterized by low strength characteristics, which determine the insufficiently long service life of the impellers.

The basis of the invention is the task of improving the design of the impeller of a centrifugal compressor, in which by changing the form of execution of the elements of the impeller, as well as changes in connection with this form of the relationship of structural elements with each other, it is possible to achieve the maximum reduction of bending stresses in the cover disk that occur in the field centrifugal forces, as well as reducing the shear and tensile stress in rivets in order to improve strength and increase service life impeller.

The problem is solved in that in the impeller of a centrifugal compressor in which the main disk is made with rivets completely machined on it and rivets completely cut from the body of the blades, and the cover disc is made with rivet holes, with which the cover disc is fixed to the carrier disk, according to the invention protrusions are made on the inner surface of the casing disk, along the contours completely coinciding with the corresponding contours of the blades and forming grooves between themselves, in which blade members, and the middle lines of the protrusions are mirrored to the middle lines of the contours of the blades of the main disk.

The implementation of the inner surface of the casing disk with protrusions ensures the creation in this impeller of a kind of stiffening ribs that significantly compensate for the bending stresses in the casing disk arising from the action of the normal component of the centrifugal force, and, as a result, unload the peripheral holes in the casing disk, and allow reduce voltage data. Given the fact that each blade along its entire length is pinched into the corresponding groove located between the protrusions on the cover disk, it perceives shear and tensile stresses that were previously perceived by rivets, while the shear stress will be so many times less the transverse area of the blades is greater than the total cross-sectional area of the rivets.

The specific advantage of the proposed design is to increase the strength characteristics of the impeller, a significant increase in the resource of its work by increasing the stiffness of the cover disk and a significant reduction in critical stresses in it; unloading rivets by transmitting shear stresses and stretching to the blades.

The technical result of the proposed design is an increase in the strength characteristics of the impeller, a significant increase in the resource of its work.

The proposed impeller design includes the following elements:

- main drive;

- cover disk;

moreover, the main disk is made with completely milled blades on it and rivets milled and formed from the body of the blades;

- the inner surface of the casing disk is made with protrusions along the contours completely coinciding with the corresponding contours of the blades and forming between themselves grooves in which the blades are pinched, and the middle lines of the protrusions are mirrored to the middle lines of the contours of the blades of the main disk. The cover disk is made with holes for rivets, with which it is mounted on a carrier disk. The form of the rivets is formed under the protrusions located on the inner surface of the cover disk.

The proposed design of the impeller is illustrated in the drawing.

Figure 1 - A fragment of the impeller, a longitudinal section;

Figure 2 - Top view of Figure 1;

Figure 3 is a section along aa in figure 2;

Figure 4 - The main disk;

Figure 5 - Top view of Figure 4, a fragment;

Figure 6 is a section along BB in Figure 5;

7 - Covering disk;

Fig. 8 is a bottom view of Fig. 7, a fragment;

Fig.9 is a section along DD in Fig.8;

Figure 10 - Section along EE in Figure 8.

In the drawings, Figures 1-10 show:

main disk 1; cover disk 2; shoulder blades 3; rivets 4; protrusions 5; grooves 6; holes 7.

The drawings 3, 7, 9 show that the protrusions 5, made on the inner surface of the cover disk 2, along the contours completely coincide with the corresponding contours of the blades 3 and form between them grooves 6, in which the blades are pinched, and the middle lines of the protrusions 5 are mirrored the middle lines of the contours of the blades 3 of the main disk 1.

In the drawings Fig. 3, 6 shows a form of execution of rivets 4 under the protrusions 5 located on the inner surface of the cover disk 2.

In the process of assembling the impeller, the cover disk 2 is mounted on the main disk 1 so that the rivets 4 extend into the holes 7 of the cover disk 2, while the blades 3 are pinched in the grooves 6. The protruding ends of the rivets 4 are riveted to form a locking head.

The impeller operates as follows.

When the impeller rotates, the blades 3 act on the pumped gas, as a result of which the kinetic energy of the gas is incremented, followed by the transition of gas into diffusers, in which the kinetic energy is converted to potential, that is, the pressure is incremented.

During the operation of the impeller, bending stresses in the cover disk 2, arising from the action of the normal component of the centrifugal force, which increases the internal static stresses of the cover disk in the area of contact with the blades 3, are compensated by the so-called stiffeners formed by the protrusions 5, and, as a result, unload peripheral holes 7 in the cover disk 2, and can significantly reduce these voltages. Since each blade 3 along its entire length is pinched into a corresponding groove 6 located between the protrusions 5 on the cover disk 2, it perceives shear stresses and tensile stresses on themselves, which were previously perceived by rivets. In this case, the shear stress decreases many times less, how many times the transverse area of the blades is greater than the total cross-sectional area of the rivets.

Claims (1)

The impeller of a centrifugal compressor, in which the main disk is made with rivets completely milled on it and rivets completely milled from the body of the blades, and the cover disk is made with rivet holes, with which the cover disk is fixed to the main disk, characterized in that on the inner surface of the cover disk protrusions are made, along the contours completely coinciding with the corresponding contours of the blades and forming between themselves grooves in which the blades are pinched, and the middle lines of the protrusions of the mirrors They are the middle lines of the contours of the blades of the main disk.

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