JPH05195989A - Impeller for centrifugal pump - Google Patents

Abstract

PURPOSE:To provide an impeller rotatable at high speed with little resistance as well as having a smaller number of blades than an existing one so as to provide a centrifugal pump with higher efficiency compared to a centrifugal pump of existing design. CONSTITUTION:A blade inlet edge 26 on the boss shroud 24a side is smoothly continued to the cylindrical boss shroud and projects largely to a blade eye part, and a blade inlet edge 26b is extended almost at a right angle to a rotary shaft. These blade inlet edges are connected by a circular smooth curve formed into protruding shape on the upper side to form a blade inlet edge, and a blade inlet angle is set to be almost 0 deg. at the boss shroud side inlet edge. In such an impeller, the pump specific speed, which is the pump design value, is to be in a range of 100-1,000, and the number of blades is to be three.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art In the design of a conventional centrifugal pump, a theoretical formula is derived from the theory of infinite number of blades to determine the pump head. Therefore, the larger the number of blades, the better. However, the larger the number of blades, the more the friction loss increases and the loss due to the influence of the blade thickness. Therefore, a certain number of blades gives the best efficiency. ..

As an empirical empirical formula that takes these into consideration,
Friday ceremony Or the Stepanov formula (Where Z is the number of blades that produce the highest efficiency, D _{1 is the} impeller inlet diameter, D _{2 is the} impeller outlet diameter, β _{1 is the} blade inlet angle, β _{2 is the} blade outlet angle), and so on. As Z is 5-9
The number of blades of the impeller of the conventional design is 5 to 9, which is the most adopted number of blades, since it is calculated within a period of time.

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

[0005]

SUMMARY OF THE INVENTION An object of the present invention is a centrifugal impeller that has a smaller number of blades than conventional ones and can rotate at a high speed and with a small resistance, and provides higher efficiency than a centrifugal pump of a conventional design. 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 is disclosed in Japanese Patent Application No. 3-98.
The blade shape of the impeller described in No. 941 is used. That is, the meridian surface shape of the shroud connected to the rotation shaft of the pump impeller is a concave arc-shaped rotation surface, and the boss shroud attached to the blade inlet edge is formed in a cylindrical shape substantially parallel to the rotation shaft. The blade inlet edge is smoothly continuous from this inlet-side boss shroud surface, and is greatly extended to the impeller eyeball portion. The blade inlet edge that is attached to the boss shroud and the casing-side blade inlet edge are connected by an arc-shaped smooth curve that is convex toward the upstream side to form the blade inlet edge. The inlet angle of this blade is the boss shroud side inlet The edge is set to about 0 °, the casing side inlet edge is set to an angle calculated by the conventional design, and the blade inlet angle between the boss shroud side and the casing side is changed smoothly. In a centrifugal pump impeller having a blade inlet having a shape and having blades formed by connecting the blade-shaped blade inlet to the blade outlet end with a smooth curved surface, the pump specific speed, which is the pump design value, is 100 to 1,000. (m ³ / min ・
The number of blades is 3 in the range of m.rpm).

The blade inlet angle used in the impeller of the centrifugal pump of the present invention is set in the same manner as the blade inlet angle using the conventional design method in the blade inlet diameter, but is almost 0 ° on the boss diameter side.
Is set to be With such a blade inlet angle, according to the conventional design theory, in the vicinity of the boss of the blade inlet, water cannot flow into the blade at all, resulting in deterioration of pump characteristics and cavitation characteristics.
However, in fact, it is completely the opposite, the boss side blade inlet edge is greatly extended to the blade eyeball portion, the casing side inlet edge is formed substantially at right angles to the rotation axis, and the boss side blade inlet edge and the casing side blade inlet edge are formed. By forming a convex arc-shaped smooth curve upstream, a wide flow area at the blade inlet can be secured, and the flow near the boss or shroud root can be cut off and guided efficiently into the blade. It becomes possible, the flow at the blade inlet becomes uniform, and the impeller can operate in the entire blade area (from the boss to the tip), and the cavitation characteristics and the pump characteristics can be improved. By combining this inlet-shaped blade with a shroud that forms an arcuate surface of revolution with a concave meridian surface,
With this shroud, the water flow flowing in from the axial direction can be smoothly changed in the radial direction, and the loss in the impeller is minimized to obtain the best pump characteristics. With the blade inlet shape as described above, the blade inlet passage area is secured and uniform inflow to the blade inlet can be realized, so the blade inlet meridian flow velocity can be increased more than that of the conventional design. With such a blade inlet shape, the rotational speed of the impeller can be increased to provide a high-speed pump. As a result, the number of blades that the impeller rotates when viewed from the stationary side of the pump casing is 1,500 rpm × 5 sheets = 7,500 sheets / minute for a typical centrifugal pump, but the number of rotations of the impeller of the present invention is At 8,000 rpm, 8,000 r.
pm × 3 = 24,000 / min, which is equivalent to 16 blades at 1,500 rpm, and the more the rotation speed is increased, the closer to the theory of infinite number of blades. Is improved. As will be described later, when the number of blades of the impeller having the above-mentioned shape of blades was changed in the range of 100 to 1,000, the best efficiency was obtained when the number of blades was three.

Further, in the impeller of claim 1, when the specific speed is in the range of 100 to 600 (m ³ / min · m · rpm),
The number of blades is set to 3 and these 3
If an arbitrary number of partial blades are provided between the blades, the efficiency of the low specific speed pump can be significantly improved as described later.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An impeller of a centrifugal pump according to the present invention will be described in detail below with reference to embodiments shown in the drawings.

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 with a volute casing 11, which is mounted on a base frame 13. This base frame 13 has a rotary shaft 1
4 is rotatably supported by bearings 15 and 16,
A pulley 17 is fixed to the outer end of the rotary shaft 14, and an impeller 20 according to the present invention is fixed to the inner end of the rotary shaft 14 protruding to the center of the volute casing 11 of the pump housing 12. A mechanical seal 18 is attached adjacent to this impeller. The front end surface 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.
The front casing 22 is attached.

As the blade shape of the impeller 20 of the centrifugal pump according to the present invention, the blade shape described in Japanese Patent Application No. 3-98941 is used. This blade shape will be described with reference to FIGS. 2 and 3.
FIG. 4 shows a perspective view thereof.

FIG. 2 is a front view showing the shape of the impeller as seen from the direction of the rotation axis, and FIG. 3 is a meridian section passing through the center of rotation of this impeller. 5, 6 and 7 are cross-sectional views taken along meridians B, C and D of each blade cross-sectional shape from the blade inlet to the blade outlet of the impeller of FIG. The shapes of the blades viewed from the arrows A and E of the blades in FIG. 2 are shown by the solid lines A and E in FIG. 3, respectively.

According to the present invention, in an impeller having blades of such a shape, the number of blades is 3 in the range of a pump specific speed of 100 to 1,000 (m ³ / min · m · rpm), which is a design value of the pump. And This is the case when an experiment was performed by changing the number of blades from 2 to 5 using a pump having the blade-shaped impeller at about 3 specific speeds within the range of 100 to 1,000. It is clear from the characteristic that the best efficiency is obtained when the number of blades is 3, as shown in FIG.

Next, in the centrifugal pump impeller having three blades of the above-mentioned shape, the specific speed thereof is 100 to 600 (m ³
In the range of low specific speed (/ min · m · rpm), as shown in FIG. 9, according to the present invention, an arbitrary number of partial blades 131 can be provided between the three blades 125 on the outer peripheral portion of the blade. Parts similar to the previous embodiment are provided with a reference numeral plus 100.

FIG. 9 is a front view showing the blade shape as seen from the direction of the rotation axis, and FIG. 10 shows a Meridian section passing through the center of rotation of this impeller. 11 to 15 are cross-sectional views obtained by cutting the cross-sectional shapes of the three blades and the partial blade from the blade inlet to the blade outlet of the impeller of FIG. 8 along meridians F, B, G, C, and D, respectively. is there.

Since the blade shape of the partial blade 131 is also the same as the blade shape of the three-blade 125, detailed description thereof will be omitted.

Generally, in the case of an impeller having a small specific speed, if the number of blades is 3 it is too small to obtain a lift, but as in the present invention, the shape of the inlet blade and the partial blade provided on the outer peripheral portion of the blade
By combining with 131 to increase the speed, the number of blades approaches infinity, and as shown in FIG. 16, the head can be significantly improved from the solid curve to the dotted curve, and a high head can be obtained. The efficiency of the specific speed pump can be greatly improved.

[0018]

As described above, according to the present invention, in the impeller having the above-mentioned blades, the number of blades is set to 3 within the range of the pump specific speed of 100 to 1,000 which is the pump design value. , The best efficiency is obtained.

In the impeller, the specific speed is
A high lift can be obtained by providing an arbitrary number of partial blades on the outer peripheral part of the impeller between the three blades in the low range of 100 to 600, and as a result, the efficiency of the low specific speed pump can be greatly improved. You can

[Brief description of drawings]

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

FIG. 2 is a front view of an embodiment of the three-blade impeller of the present invention incorporated into FIG.

FIG. 3 is a vertical cross-sectional view taken along the central axis of the impeller of FIG.

4 is a perspective view of the impeller of FIGS. 2 and 3. FIG.

5 is a Meridian cross section of the blade of FIG. 2 taken along line B. FIG.

6 is a Meridian cross section of the vane of FIG. 2 taken along line C. FIG.

7 is a Meridian cross section of the vane of FIG. 2 taken along line D. FIG.

FIG. 8 is a graph showing a result of an experiment in which the number of blades of the impeller is changed and the pump efficiency is shown.

FIG. 9 is a front view of a three-bladed impeller having partial blades according to the present invention.

FIG. 10 is a vertical cross-sectional view taken along the central axis of the impeller of FIG.

11 is a Meridian cross section of the vane of FIG. 9 taken along line F. FIG.

12 is a Meridian cross section of the vane of FIG. 9 taken along line B. FIG.

13 is a Meridian section taken along line G of the vane of FIG.

14 is a Meridian cross section of the vane of FIG. 9 taken along line C. FIG.

FIG. 15 is a Meridian cross section of the blade of FIG. 9 taken along line D.

FIG. 16 is a graph showing the results of a comparative experiment of a three-blade impeller of the present invention and a three-blade impeller having partial blades.

[Explanation of symbols]

 14 rotating shaft 20,120 impeller 24,124 shroud 24a, 124a boss shroud 26,126 blade inlet edge 26a, 126a boss shroud side blade inlet edge 26b, 126b casing side blade inlet edge 27, 127 blade outlet 131 partial blade

Claims (2)

[Claims] 1. A boss shroud to which a blade inlet edge is attached is a cylinder substantially parallel to a rotation axis, wherein a meridian surface shape of a shroud connected to a boss fitted to a rotation axis of a pump impeller has a concave arc-shaped rotation surface. The blade inlet edge is made smooth and continuous from this inlet side boss shroud surface, and it is extended to the blade eyeball portion so that the casing side blade inlet edge extends almost at right angles to the rotation axis. -Shaped boss shroud The blade inlet edge and the casing-side blade inlet edge are connected by an arc-shaped smooth curve that is convex toward the upstream side to form the blade inlet edge, and the inlet angle of this blade is the boss shroud. The side inlet edge is set to almost 0 °, the casing side inlet edge is set to an angle calculated by the conventional design, and the blade inlet angle between the boss shroud side and the casing side is smoothly changed. In a centrifugal pump impeller having a blade inlet having a shape, and having blades formed by connecting the blade-shaped blade inlet to the blade outlet end with a smooth curved surface, the pump specific speed which is the pump design value is 100 to 1 , 00
An impeller for a centrifugal pump, characterized in that the number of blades is three in the range of 0 (m ³ / min ・ m ・ rpm). 2. The impeller according to claim 1, wherein the specific speed is within a range of 100 to 600 (m ³ / min · m · rpm), the number of blades is three, and the peripheral portion of the impeller is An impeller of a centrifugal pump, characterized in that an arbitrary number of partial blades are provided between three blades.