JP3276011B2 - Centrifugal pump impeller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a centrifugal pump impeller.

[0002]

2. Description of the Related Art In the design of a conventional centrifugal pump, a theoretical formula is derived from the theory of infinity of the number of blades, and the pump generating head is determined. Therefore, the greater the number of blades, the better. However, if the number of blades is large, the friction loss increases, and the loss increases due to the influence of the blade thickness, so that a certain number of blades gives the best efficiency. .

[0003] As an empirical empirical formula taking these factors into account,
Friday formula Or the Stepanov formula (Where, Z: the number of blades generating the highest efficiency D ₁ : impeller inlet diameter D ₂ : impeller outlet diameter β ₁ : blade inlet angle β ₂ : blade outlet angle) And Z is 5-9
Since the calculation is performed between the degrees, the number of blades of the conventionally designed impeller is the most frequently used number of blades.

On the other hand, at the blade entrance where the geometrical size is restricted, it is better to reduce the number of blades in view of the relationship between the blade entrance area and the number of blades. When the number of blades is increased, the substantial blade entrance area of the impeller having the same meridian cross section is reduced, the resistance at the blade entrance is increased, the loss is increased, and the efficiency is reduced. Along with this, the suction capacity of the pump naturally deteriorates. If you reduce the number of blades,
Since the generated head is reduced, in order to prevent this, the rotation speed of the impeller should be increased to increase the number of blades passing when the impeller rotates on the fixed side of the pump casing. This cannot be done because the speed cannot be increased at the design blade entrance. Therefore, the number of blades as described above is adopted.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a centrifugal impeller having a smaller number of blades than the conventional one and capable of rotating at a high speed and with a small resistance, which provides a higher efficiency than a conventionally designed centrifugal pump. It is to provide a pump impeller.

[0006]

In order to achieve the above object, an impeller of a centrifugal pump according to the present invention has a concave shape in a meridional plane of a shroud connected to a boss fitted to a rotary shaft of a pump impeller. The boss shroud where the blade inlet edge is attached is formed in a cylindrical shape almost parallel to the rotation axis, and the blade inlet edge is smoothly continuous from this inlet side boss shroud surface, and is greatly extended to the blade eyeball. And a casing-side blade inlet edge extending substantially perpendicular to the rotation axis, and a circle having a convex shape on the upstream side between the blade inlet edge attached to the cylindrical boss shroud and the casing-side blade inlet edge. An arc-shaped smooth curve connects them to form a blade inlet edge.The blade inlet angle is approximately 0 ° at the boss shroud-side inlet edge and approximately the angle calculated by the conventional design at the casing-side inlet edge. Blade having a blade entrance angle between the boss shroud side and the casing side, the blade entrance angle between the boss shroud side and the casing side being smoothly changed, and formed by a smooth curved surface from the blade-shaped blade entrance to the blade exit end. A centrifugal pump having a pump specific speed of 100 to 600 (m ³ / min · m ·
(rpm), the number of blades is three, and an arbitrary number of partial blades are provided between these three blades on the outer periphery of the impeller.

[0007]

The basic structure of the impeller of the centrifugal pump of the present invention is the same as the structure of the impeller described in the specification and the drawings of Japanese Patent Application No. 3-98941 (JP-A-4-365998). In other words, the blade inlet angle used for the impeller of the centrifugal pump of the present invention is set in the blade inlet diameter in the same manner as the blade inlet angle using the conventional design method, but is substantially 0 ° on the boss diameter side. Is set. With such a blade entrance angle, water cannot flow into the blade at all near the boss at the blade entrance according to the conventional design theory, resulting in deterioration of pump characteristics and cavitation characteristics. However, in fact, the opposite is true, the boss-side blade entrance edge is greatly extended to the blade eyeball portion, and the casing-side entrance edge is formed substantially at right angles to the rotation axis, so that the space between the boss-side blade entrance edge and the casing-side blade entrance edge is formed. By forming it with a smooth arc-shaped curve that forms a convex shape upstream, a wide flow path area at the blade inlet is secured, and the flow near the boss or shroud root can be efficiently led into the blade. As a result, the flow at the blade inlet becomes uniform, and an impeller acting on the entire blade (from the boss to the tip) can be obtained, whereby cavitation characteristics and pump characteristics can be improved. By combining this inlet-shaped blade with a shroud having an arc-shaped rotating surface with a concave meridian shape, the shroud can smoothly change the water flow flowing in from the axial direction in the radial direction. The best pump characteristics are obtained by minimizing the in-vehicle loss.
By adopting the above-mentioned blade inlet shape, the blade inlet passage area is secured, and uniform inflow to the blade inlet can be realized, so that the blade inlet meridian flow velocity can be increased from that of the conventional design. By adopting such a blade inlet shape, the rotation speed of the impeller can be increased and a high-speed pump can be obtained. As a result, the number of blades passing when the impeller rotates as viewed from the fixed side of the pump casing is 1,500 rpm × 5 sheets = 7,500
Per minute, but the number of revolutions of the impeller of the present invention is 8,000.
Assuming rpm, 8,000 rpm x 3 sheets = 24,0
This is 00 sheets / minute, which is equivalent to 16 blades at 1,500 rpm. Therefore, as the number of rotations is increased, the theory of the infinite number of blades is approached, and the efficiency is improved. In addition, as described later, an impeller having blades of the above-described shape has a specific speed of 100 to
As a result of an experiment in which the number of blades was changed within a range of 1,000 (m ³ /min·m·r.p.m), it was found that the best efficiency was obtained when the number of blades was three.

[0008] In particular, an arbitrary number of partial blades are provided between the three blades of the impeller of the above-mentioned patent application, which is the basic configuration of the impeller of the present invention, at the outer peripheral end of the impeller, and The specific speed is 100 to 600 (m ³ /min·m·r.p.
By setting the value in the range of m), a high head is obtained as described later, and as a result, the efficiency of the centrifugal pump having a relatively low specific speed is further greatly improved.

[0009]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a centrifugal pump according to an embodiment of the present invention.

FIG. 1 shows a longitudinal section of a centrifugal pump having an impeller according to the present invention. This centrifugal pump has a pump housing 12 having a volute casing 11, which is mounted on a base frame 13. This base frame 13 has a rotating shaft 1
4 is rotatably supported by bearings 15, 16;
A pulley 17 is fixed to an outer end of the rotating shaft 14, and an impeller 20 according to the present invention is fixed to an inner end of the rotating shaft 14 protruding to the center of the volute casing 11 of the pump housing 12. A mechanical seal 18 is mounted adjacent to the impeller. The front end face of the pump housing 12 has a suction port 19 for guiding the flow of water flowing into the blade inlet 21 of the impeller 20.
Is attached to the front casing 22.

The basic structure of the impeller 20 of the centrifugal pump according to the present invention is disclosed in Japanese Patent Application No. 3-98941 (Japanese Patent Application Laid-Open No. 4-365).
No. 998) and the configuration of the impeller described in the drawings. The impeller of the invention of this patent application is shown in FIGS. 2 to 8 and briefly described briefly below. Can be understood with reference to the specification and the drawings of this patent application, and thus are omitted here.

FIG. 2 shows the basic configuration of the impeller of the present invention.
FIG. 3 is a front view showing the shape of the impeller viewed from the rotation axis direction of the impeller of the above-mentioned patent application, and FIG. 3 shows a meridian section passing through the center of rotation of the impeller. FIGS. 5, 6, and 7 are cross-sectional views of the impeller of FIG. 2 taken along meridians B, C, and D from the blade inlet to the blade outlet. Note that the shape of the blade as viewed from the arrows A and E of the blade in FIG. 2 is indicated by the solid line in FIG. 3A and the solid line in E, respectively. As shown in FIGS. 2 to 7, the blade inlet angle used for the impeller of the above-mentioned patent application, which is the basic configuration of the impeller 20 of the centrifugal pump of the present invention, is based on the conventional design method for the blade inlet diameter. It is set in the same manner as the blade entrance angle, but is set to be substantially 0 ° on the boss diameter side. With such a blade entrance angle, water cannot flow into the blade at all near the boss at the blade entrance according to the conventional design theory, resulting in deterioration of pump characteristics and cavitation characteristics. However, in fact, the opposite is true, that is, the boss-side blade entrance edge 26a is greatly extended to the blade eyeball portion, and the casing-side entrance edge 26b is formed substantially perpendicular to the rotation axis, so that the boss-side blade entrance edge 26a and the casing-side blade entrance edge are formed. By forming the blade inlet edge 26 with a circular arc-shaped smooth curve so that the space between the blades 26b is convex toward the upstream, a large flow passage area at the blade inlet is ensured, and the flow near the root 24a of the boss or shroud 24 is increased. So that it can be efficiently guided into the blade. As a result, the impeller 20, which is a basic configuration of the present invention, has a uniform flow at the blade entrance, and is an impeller that acts on the entire blade (from the boss to the tip), thereby improving cavitation characteristics and pump characteristics. Can be. By combining this inlet-shaped blade with the shroud 24 having an arc-shaped rotating surface with a concave meridian shape, the shroud 24 can smoothly change the flow of water flowing in from the axial direction in the radial direction. In addition, the loss in the impeller 20 is minimized to obtain the best pump characteristics. By adopting the above-mentioned blade inlet shape, the blade inlet passage area is secured, and uniform inflow to the blade inlet can be realized, so that the blade inlet meridian flow velocity can be increased from that of the conventional design. By adopting the blade inlet shape as described above, the rotation speed of the impeller can be increased and a high-speed pump can be obtained.

In the impeller 20 having the blades 25 having such a shape, the specific speed is 100 to 1,000 (m ³ / min).
(M.r.p.m.) using a pump having the blade-shaped impeller 20 at approximately three types of specific speeds.
As a result of conducting an experiment while changing the number of the blades from 2 to 5 as shown in FIG. 8, it was found that the characteristic exhibiting the best efficiency was obtained when the number of the blades 25 was 3, as shown in FIG. Therefore, in the impeller 20 of the present invention, the number of the blades 25 is three. Further, from the results shown in FIG. 8, the pump specific speed, which is the pump design value, is set to 1 as the most appropriate specific speed.
It is set in the range of 00 to 600 (m ³ /min·m·r.p.m).

Further, the impeller 20 of the present invention is an impeller having three blades 25 as its basic configuration, and partial blades are provided between the blades 25. Hereinafter, the details will be described. FIG. 9 is a front view showing the impeller of the present invention provided with the partial blades, as viewed from the rotation axis direction. In addition,
In FIG. 9, the impeller 20 of the example shown in FIGS.
The same components as those described above are denoted by reference numerals obtained by adding 100 to the reference numerals. As shown in FIG. 9, in the impeller 120 of the present invention, the aforementioned impeller 2 shown in FIGS.
5, three blades 125 are arranged in the circumferential direction. Between these three blades 125, an arbitrary number (in the illustrated example, adjacent blades 125) (One sheet; three sheets in total).

FIG. 10 is a view showing a meridian section passing through the center of rotation of the impeller 120 shown in FIG. 9, and FIGS.
5 are from the blade inlet (blade inlet edge 126) of the impeller 120 shown in FIG.
FIG. 10 is a cross-sectional view of the cross-sectional shape of the single blade 125 and the partial blade 131 cut along meridians F, B, G, C, and D in FIG. 9, respectively.

The blade shape of the partial blade 131 is also formed on the outer peripheral edge side in the same manner as the blade-shaped outer peripheral side portion of the three blades 125. That is, FIG. 1 along the meridian F
1 and the cross section of the partial blade 131 shown in FIG.
15 along a meridian D which substantially corresponds to the position of the meridian F of FIG.
Are formed in substantially the same shape as the cross section of the blade 125 shown in FIG. Therefore, the blade shape of the partial blade 131 is the same as that of the specification and drawings of the above-mentioned patent application (the blade 1 of the present invention).
25 (equivalent to No. 25), and a detailed description thereof will be omitted.

In general, in the case of an impeller having a small specific speed, the number of blades of the blade 125 is too small to obtain a lift because the number of blades is three. However, as in the present invention, the shape of the inlet blade of the blade 125 and the outer periphery of the impeller 120 are different. By increasing the speed by combining with the partial blades 131 provided at the end, the above-mentioned theory of the infinite number of blades is approached. From the curve shown by the solid line in the case of only three blades 125 in FIG. Wings 125 and 3
The head shown in the dotted line in the case where the partial blades 131 are combined can significantly improve the head, and a high head can be obtained, thereby greatly improving the efficiency of the low specific speed pump.

[0018]

As described above, according to the centrifugal pump impeller of the present invention, the above-mentioned Japanese Patent Application No. 3-98941 is applied.
No. (JP-A-4-365998) and three blades having the same configuration as the configuration of the blade described in the specification and the drawings.
An arbitrary number of partial blades arranged between them are combined, and the pump specific speed 10
A higher head can be obtained by setting the range to a low range of about 0 to 600 (m ³ /min·m·rp.m).

Therefore, since such a high head is obtained, the efficiency of the low specific speed pump can be further greatly improved.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a centrifugal pump having an impeller according to the present invention.

FIG. 2 shows a basic configuration of the impeller of the present invention incorporated in FIG. 1 and disclosed in Japanese Patent Application No. 3-98941 (Japanese Patent Application Laid-Open No. 4-365).
998) is a front view of a blade impeller described in the specification and the drawings.

FIG. 3 is a longitudinal sectional view passing through a center axis of the impeller shown in FIG. 2;

FIG. 4 is a perspective view of the impeller shown in FIG.

FIG. 5 is a meridian section of the blade shown in FIG. 2 cut along a line B;

FIG. 6 is a meridian section of the blade shown in FIG. 2 cut along a line C;

FIG. 7 is a meridian section of the blade shown in FIG.

FIG. 8 is a graph showing a result of an experiment performed by changing the number of blades of the impeller shown in FIG.

9 shows an example of the impeller according to the present invention, and has partial blades arranged between the respective blades of the impeller shown in FIG. 2.
It is a front view of the impeller which combined three blades and three partial blades.

FIG. 10 is a vertical cross-sectional view passing through a center axis of the impeller shown in FIG.

FIG. 11 is a meridian section of the blade shown in FIG. 9 cut along a line F;

FIG. 12 is a meridian section of the blade shown in FIG. 9 cut along a line B;

13 is a meridian section of the blade shown in FIG. 9 cut along a line G. FIG.

FIG. 14 is a meridian section of the blade shown in FIG. 9 cut along a line C;

FIG. 15 is a meridian section of the blade shown in FIG. 9 cut along a line D;

FIG. 16: Japanese Patent Application No. 3-98941 (Japanese Patent Application Laid-Open No. 4-365)
998) and the three-bladed impeller of the present invention and the three-bladed impeller of the present invention.
It is a graph which shows the result of the comparative experiment with the impeller which combined the sheet | seat partial blade.

[Explanation of symbols]

 14 Rotary shaft 20, 120 Impeller 24, 124 Shroud 24a, 124a Boss shroud 26, 126 Blade inlet edge 26a, 126a Boss shroud blade inlet edge 26b, 126b Casing blade inlet edge 27, 127 … Vane outlet 131… Partial wing

Claims (1)

(57) [Claims] 1. A meridional surface of a shroud connected to a boss fitted to a rotating shaft of a pump impeller is a concave arc-shaped rotating surface, and a boss shroud at a blade inlet edge is a cylinder substantially parallel to the rotating shaft. The blade inlet edge is smoothly continuous from the inlet side boss shroud surface, is greatly extended to the eyeball portion, and the blade inlet edge on the casing side extends substantially at right angles to the rotation axis. A blade inlet edge is formed by connecting the blade inlet edge attached to the V-shaped boss shroud and the casing-side blade inlet edge by an arc-shaped smooth curve that forms a convex shape on the upstream side. At the side entrance edge, it is set to almost 0 °, and at the casing side entrance edge, the angle is calculated almost by the conventional design, and the blade entrance angle between the boss shroud side and the casing side is smoothly changed. Having a blade inlet shape, met impeller of a centrifugal pump having a vane which is formed by connecting in a smooth curved surface from the blade inlet to the blade outlet edge of the vane shape
The pump specific speed, which is the pump design value, is 100 to 600.
(M ³ /min.m.r.p.m.)
And the three blades around the impeller
An impeller for a centrifugal pump , wherein an arbitrary number of partial blades are provided therebetween .