JP2017020400A - Centrifugal Pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a centrifugal pump that comprises a wear ring that can reduce a leakage flow from the discharge side to the suction side and is less likely to generate vibration.SOLUTION: A centrifugal pump according to the present invention comprises: a rotating shaft 11; an impeller 1 fixed to the rotating shaft 11; a casing 3 housing the impeller 1; and a wear ring 5 arranged between the impeller 1 and the casing 3. The wear ring 5 comprises: a rotation side ring 5a surrounding a liquid inlet 1a of the impeller 1; and a fixed side ring 5b including an inner peripheral surface opposed to an outer peripheral surface of the rotation side ring 5a. The outer peripheral surface of the rotation side ring 5a and the inner peripheral surface of the fixed side ring 5b consist of smooth surfaces made of a water-repellent material.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a centrifugal pump for transferring a liquid.

  A centrifugal pump is known as a pump for transferring a liquid (for example, water). Centrifugal pumps are roughly classified into a diffuser pump in which a diffuser is provided on the radially outer side of the impeller and a spiral pump in which a volute chamber is provided on the radially outer side of the impeller. In the vortex pump, the liquid discharged from the impeller directly flows into the volute chamber. In the diffuser pump, the liquid discharged from the impeller passes through the diffuser, and the velocity energy of the liquid is converted into pressure energy.

  In these centrifugal pumps, as shown in FIG. 6, a gap is provided between the casing 103 that houses the impeller 101 and the impeller 101 so that the rotating impeller 101 does not contact the casing 103. It has been. The liquid discharged from the impeller 101 has a pressure Ph that is higher than the liquid pressure PL at the liquid inlet 101 a of the impeller 101. Therefore, due to the difference between the pressure Ph and the pressure PL, a part of the liquid discharged from the impeller 101 leaks through the gap between the impeller 101 and the casing 103 and flows into the suction side of the impeller 101. It becomes a flow (refer to the dashed-dotted arrow shown in FIG. 6).

  Such a leakage flow from the discharge side to the suction side reduces pump efficiency. Therefore, a wear ring 105 for reducing leakage flow is provided at the suction side end of the impeller 101. The wear ring 105 is a fixed side ring having a rotation side ring 105a fixed to the suction side end of the shroud 116 of the impeller 101, and an inner peripheral surface facing the outer peripheral surface of the rotation side ring 105a with a slight gap. 105b. The stationary side ring 105 b is fixed to the wall surface of the casing 103. The rotation side ring 105a and the fixed side ring 105b function as a non-contact annular seal that restricts the leakage flow.

  Specific examples of the annular seal include a smooth surface seal in which the outer peripheral surface of the rotating side ring and the inner peripheral surface of the fixed side ring are smooth surfaces, and one or both of the outer peripheral surface of the rotating side ring and the inner peripheral surface of the fixed side ring. And a labyrinth seal provided with a plurality of grooves extending in the circumferential direction, and a honeycomb seal provided with honeycomb-like irregularities on one or both of the outer peripheral surface of the rotating side ring and the inner peripheral surface of the stationary side ring.

  The smooth surface seal is superior in that vibration is unlikely to occur when liquid flows between the rotating side ring and the fixed side ring, but the clearance between the rotating side ring and the fixed side ring is below a certain limit. However, there is a limit to reducing the leakage flow. The labyrinth seal and the honeycomb seal can reduce the leakage flow as compared with the smooth surface seal, but have a problem that the manufacturing cost is high and vibration is likely to occur compared to the smooth surface seal.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a centrifugal pump having a wear ring that can reduce the leakage flow from the discharge side to the suction side and is less likely to generate vibration. And

  One aspect of the present invention for solving the above-described problems is a rotating shaft, an impeller fixed to the rotating shaft, a casing that houses the impeller, and an impeller disposed between the impeller and the casing. A wear ring, and the wear ring includes a rotation side ring surrounding a liquid inlet of the impeller, and a fixed side ring having an inner peripheral surface facing an outer peripheral surface of the rotation side ring, The centrifugal pump is characterized in that the outer peripheral surface of the rotating side ring and the inner peripheral surface of the stationary side ring are constituted by smooth surfaces made of a water repellent material.

  In a preferred aspect of the present invention, the main component of the water repellent material is a fluororesin.

  According to the present invention, due to the water repellent material constituting the outer peripheral surface of the rotating side ring and the inner peripheral surface of the stationary side ring, the leakage flow flowing through the gap between the rotating side ring and the stationary side ring Repulsive force that hinders the progress of the work. As a result, liquid leakage is reduced. The outer peripheral surface of the rotating side ring and the inner peripheral surface of the stationary side ring are composed of smooth surfaces without grooves and honeycombs, so that vibration is less likely to occur from the wear ring compared to labyrinth seals and honeycomb seals. .

Fig.1 (a) is a schematic sectional drawing which shows the centrifugal pump which is an example of a centrifugal pump, FIG.1 (b) is a schematic sectional drawing which shows the diffuser pump which is another example of a centrifugal pump. It is a fragmentary sectional view of the centrifugal pump shown in Drawing 1 (a) and Drawing 1 (b). It is an expanded sectional view of the wear ring shown in FIG. It is a schematic sectional drawing which shows a part of multistage diffuser pump. It is a cross-sectional perspective view along the AA line of FIG. It is a schematic diagram for demonstrating a leak flow.

  Embodiments of the present invention will be described below with reference to the drawings. 1 to 5, the same or corresponding components are denoted by the same reference numerals, and redundant description is omitted. Moreover, the structure shown by each embodiment is applicable also to other embodiment, as long as it does not contradict each other.

  Fig.1 (a) is a schematic sectional drawing which shows the centrifugal pump which is an example of a centrifugal pump, FIG.1 (b) is a schematic sectional drawing which shows the diffuser pump which is another example of a centrifugal pump. As shown in FIG. 1A, the centrifugal pump has an impeller 1 fixed to the rotary shaft 11 and a casing 3 that houses the impeller 1. The rotating shaft 11 is rotated by a driving source (for example, a motor) (not shown), and the impeller 1 rotates integrally with the rotating shaft 11 in the casing 3.

  A volute chamber 7 is formed inside the casing 3. The volute chamber 7 has a shape surrounding the periphery of the impeller 1. The casing 3 is formed with a cylindrical pump suction port 2 (refer to a dotted line in FIG. 1A) extending in the axial direction of the rotary shaft 11. Further, a pump discharge port 4 is formed in the casing 3.

  When the impeller 1 is rotated, the liquid flows from the pump suction port 2 into the impeller 1. Angular kinetic energy is imparted to the liquid by the rotation of the impeller 1, and further, the velocity energy is converted into pressure energy as the liquid passes through the volute chamber 7, which promotes an increase in the static pressure of the liquid. The pressurized liquid is discharged from the pump discharge port 4.

  As shown in FIG. 1B, the diffuser pump has a diffuser 9 that surrounds the impeller 1. Since the configuration other than the diffuser 9 in the diffuser pump shown in FIG. 1B is the same as the configuration of the centrifugal pump shown in FIG.

  The diffuser 9 has a plurality of diffuser blades 9a, and a diffuser flow path 9b through which the liquid discharged from the impeller 1 passes is formed between adjacent diffuser blades 9a. The cross-sectional area of the diffuser channel 9b is formed so as to increase from the inlet toward the outlet, and the velocity energy of the liquid is converted into pressure energy when the liquid passes through the diffuser channel 9b.

  FIG. 2 is a partial cross-sectional view of the centrifugal pump shown in FIGS. 1 (a) and 1 (b). In FIG. 2, only the upper half of the impeller 1 is shown. As shown in FIG. 2, the impeller 1 includes a disk-shaped hub 14, a plurality of blades 15 standing from the hub 14, and a shroud 16 that covers the front surface of the blade 15. The wings 15 are arranged at equal intervals along the circumferential direction of the hub 14. The front end of the shroud 16 has a cylindrical shape, and the liquid inlet 1 a of the impeller 1 is formed by the front end of the shroud 16.

  A wear ring 5 is provided between the impeller 1 and the casing 3. The wear ring 5 functions as a non-contact annular seal for reducing a leakage flow in which a part of the liquid discharged from the impeller 1 flows into the suction side of the impeller 1.

  The wear ring 5 includes a rotation side ring 5a surrounding the liquid inlet 1a of the impeller 1 and a fixed side ring 5b having an inner peripheral surface facing the outer peripheral surface of the rotation side ring 5a with a slight gap. . The rotation side ring 5 a has a cylindrical shape and is fixed to the suction side end of the shroud 16 of the impeller 1. The stationary side ring 5 b has a cylindrical shape and is fixed to the wall surface of the casing 3. The outer peripheral surface of the rotation side ring 5a and the inner peripheral surface of the fixed side ring 5b are constituted by smooth surfaces. That is, no grooves or honeycombs are formed on the outer peripheral surface of the rotation side ring 5a and the inner peripheral surface of the fixed side ring 5b.

  Although the rotation side ring 5a of this embodiment is comprised from the member different from the impeller 1, you may form the rotation side ring 5a integrally with the impeller 1. FIG. That is, the rotation side ring 5 a may be configured by a part of the shroud 16.

  FIG. 3 is an enlarged cross-sectional view of the wear ring 5 shown in FIG. In FIG. 3, the clearance between the rotation side ring 5a and the fixed side ring 5b is exaggerated for convenience of explanation. The clearance between the rotation side ring 5a and the stationary side ring 5b is about the same as a general smooth surface seal.

  The outer peripheral surface of the rotation side ring 5a and the inner peripheral surface of the fixed side ring 5b are smooth surfaces formed from a water repellent material. In the embodiment shown in FIG. 3, the outer peripheral surface of the rotation-side ring 5a, which is a smooth surface, is composed of a film 20 made of a water-repellent material. Similarly, the inner peripheral surface of the fixed side ring 5b which is a smooth surface is composed of a film 21 made of a water repellent material.

  The films 20 and 21 are made of a water-repellent material applied to the rotation side ring 5a and the stationary side ring 5b. The water repellent material may be applied only once to the rotating side ring 5a and the stationary side ring 5b to form the films 20 and 21 made of a single water repellent material, or a plurality of water repellent materials may be applied and dried. Repeatedly, the films 20 and 21 on which the water-repellent material is laminated may be formed. As another embodiment, the films 20 and 21 may be cylindrical sheets made of a water-repellent material attached to the rotating side ring 5a and the fixed side ring 5b. As still another embodiment, the entire rotation side ring 5a and fixed side ring 5b may be formed from a water repellent material.

  The main component of the water repellent material constituting the outer peripheral surface of the rotation side ring 5a and the inner peripheral surface of the stationary side ring 5b is, for example, silicon oxide, aluminum oxide, zirconium oxide, fluororesin, or a mixture thereof. In particular, a water-repellent material containing a fluororesin as a main component exhibits high water repellency and is extremely chemically stable. Therefore, a water-repellent material containing a fluororesin as a main component is preferably used.

  The liquid flowing between the outer peripheral surface of the rotating side ring 5a and the inner peripheral surface of the fixed side ring 5b is repelled from the outer peripheral surface of the rotating side ring 5a and the inner peripheral surface of the fixed side ring 5b. That is, repulsive force acts on the liquid from the films 20 and 21 made of the water repellent material. Since the repulsive force prevents the liquid from proceeding, the leakage flow passing through the wear ring 5 is reduced, and as a result, the pump efficiency is improved. Since the outer peripheral surface of the rotation side ring 5a and the inner peripheral surface of the fixed side ring 5b are composed of smooth surfaces without grooves and honeycombs, the vibration characteristics of the wear ring 5 are compared with labyrinth seals and honeycomb seals. It is good.

  FIG. 4 is a schematic cross-sectional view showing a part of a multistage diffuser pump having a plurality of impellers 1. In FIG. 4, the upper half of the two impellers 1 fixed to the rotating shaft 11 is shown. As shown in FIG. 4, the multistage diffuser pump has a plurality of impellers 1 fixed to the rotating shaft 11 and a casing 3 that houses the impellers 1 of each stage. A diffuser 9 is provided so as to surround each stage of the impeller 1. The rotating shaft 11 is rotated by a driving source (for example, a motor) (not shown), and the impeller 1 rotates integrally with the rotating shaft 11 in the casing 3. A guide vane 17 is disposed in the return flow path 25 that guides the liquid discharged from the impeller 1 and passed through the diffuser 9 to the next-stage impeller 1. The guide vane 17 guides the liquid flowing through the return channel 25 to the liquid inlet 1a of the next stage impeller 1.

  FIG. 5 is a cross-sectional perspective view taken along line AA of FIG. In FIG. 5, in order to clearly show the diffuser 9, the illustration of the impeller 1 and the rotating shaft 11 is omitted except for the liquid inlet 1 a of the impeller 1 arranged in the next stage. Further, in FIG. 5, illustration of the guide vanes 17 arranged in the return flow path 25 is also omitted. The diffuser 9 has a plurality of diffuser blades 9a, and a diffuser flow path 9b through which the liquid discharged from the impeller 1 passes is formed between adjacent diffuser blades 9a. The cross-sectional area of the diffuser channel 9b is formed so as to increase from the inlet toward the outlet, and the velocity energy of the liquid is converted into pressure energy when the liquid passes through the diffuser channel 9b. The liquid passing through the diffuser flow path 9b flows along the arrow shown in FIG. 5 and is guided to the liquid inlet 1a of the impeller 1 at the next stage.

  The wear ring 5 described with reference to FIG. 3 is provided between the impeller 1 of each stage and the casing 3. Similarly, in the present embodiment, since the liquid leakage from the discharge side to the suction side is reduced, the pump efficiency of the entire multistage diffuser pump can be improved.

  The embodiment described above is described for the purpose of enabling the person having ordinary knowledge in the technical field to which the present invention belongs to implement the present invention. Various modifications of the above embodiment can be naturally made by those skilled in the art, and the technical idea of the present invention can be applied to other embodiments. Accordingly, the present invention is not limited to the described embodiments, but is to be construed in the widest scope according to the technical idea defined by the claims.

DESCRIPTION OF SYMBOLS 1 Impeller 2 Pump suction port 3 Casing 4 Pump discharge port 5 Wear ring 5a Rotation side ring 5b Fixed side ring 9 Diffuser 9a Diffuser blade 9b Diffuser flow path 11 Rotating shaft 14 Hub 15 Blade 16 Shroud 17 Guide blade 20 Membrane 25 Return flow path

Claims (2)

A rotation axis;
An impeller fixed to the rotating shaft;
A casing for housing the impeller,
A wear ring disposed between the impeller and the casing,
The wear ring includes a rotation side ring surrounding a liquid inlet of the impeller, and a fixed side ring having an inner peripheral surface facing an outer peripheral surface of the rotation side ring,
The centrifugal pump characterized in that the outer peripheral surface of the rotating side ring and the inner peripheral surface of the stationary side ring are constituted by smooth surfaces made of a water repellent material.   The centrifugal pump according to claim 1, wherein a main component of the water repellent material is a fluororesin.

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