CN113464445A

CN113464445A - Modularized integrated low-noise centrifugal pump and design method thereof

Info

Publication number: CN113464445A
Application number: CN202110805975.1A
Authority: CN
Inventors: 武鹏; 吴大转; 施培丽; 李娟红
Original assignee: Zhejiang University ZJU
Current assignee: Zhejiang University ZJU
Priority date: 2021-07-16
Filing date: 2021-07-16
Publication date: 2021-10-01
Anticipated expiration: 2041-07-16
Also published as: CN113464445B

Abstract

The invention discloses a modularized integrated low-noise centrifugal pump and a design method thereof, wherein the modularized integrated low-noise centrifugal pump comprises a pump body, a pump shaft, an impeller and a driving motor, wherein the impeller is an even-level impeller and is positioned between a pair of rolling bearings at two ends of the pump shaft, and the surface of the even-level impeller is symmetrically arranged on the pump shaft in a surface-to-surface mode, so that the axial force is balanced and the axial movement of a rotor is reduced; the driving motor is a flat motor, a rotor cantilever of the driving motor is arranged at the end part of the pump shaft, and the driving motor is coaxial with the impeller and shares the same pair of rolling bearings with the impeller. According to the centrifugal pump disclosed by the invention, the motor does not need to be supported by an additional bearing, the rigidity of the pump rotor can be effectively improved, the centering problem of the double shafts is avoided, the whole operation is more stable and reliable, the vibration noise of the pump is effectively reduced, and the impeller stage number can be increased in a modularized manner, so that the pump lift of the pump is improved.

Description

Modularized integrated low-noise centrifugal pump and design method thereof

Technical Field

The invention relates to the field of fluid machinery, in particular to a modular integrated low-noise centrifugal pump and a design method thereof.

Background

The existing conventional motor-driven centrifugal pump adopts an alternating current asynchronous motor or a permanent magnet synchronous motor, the length-diameter ratio of the motor is large, and a motor rotor is coaxial with a pump rotor or is connected with the pump rotor through a coupler.

When the conventional coaxial design is adopted, the pump rotor does not have an independent bearing and shares a bearing with the motor, the impeller is of a cantilever structure, flow excitation in the pump acts on the impeller rotor, if the impeller is more in stages, the longer pump shaft cantilever structure aggravates vibration response generated by impeller fluid excitation, and great difficulty is brought to vibration reduction and noise reduction of the pump.

If the split shaft design of coupling joint is adopted, although the problem of vibration aggravation caused by the cantilever of the impeller rotor can be avoided, the requirement on the alignment of the motor shaft and the pump shaft is higher for reducing the vibration noise of the pump, and the difficulty of pump assembly is increased.

In addition, the motor shell and the pump shell of the conventional centrifugal pump and the motor rotor and the pump rotor are independently designed and are integrally installed and debugged after being respectively processed and assembled. In the situation with higher requirements for vibration reduction and noise reduction, the application and implementation of the whole vibration reduction and noise reduction measures are lacked because the rotor system and the structure cannot be integrally designed and analyzed.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a modularized integrated low-noise centrifugal pump and a design method thereof, wherein a motor and a pump rotor system are integrally designed, the impellers adopt even-level impellers which are arranged face to face, the motor adopts a high-energy-density flat motor such as a disc motor, bearings are arranged on two sides of an impeller rotor, and a flat motor cantilever is arranged at one end or two ends of the pump rotor, so that additional bearing support is not needed, the rigidity of the pump rotor can be effectively improved, the centering problem of double shafts is avoided, the whole operation is more stable and reliable, and the vibration noise of the pump is effectively reduced. The motor and the pump body shell are integrally analyzed and designed, so that the structural rigidity of the pump is integrally improved, and the pump is also beneficial to vibration reduction and noise reduction of the pump.

The specific technical scheme of the invention is as follows:

a modular integrated low-noise centrifugal pump comprises a pump body, a pump shaft, an impeller and a driving motor;

the impeller is an even-level impeller and is positioned between a pair of rolling bearings at two ends of the pump shaft;

starting from the design target of vibration reduction and noise reduction, the even-level impeller surface is symmetrically arranged on the pump shaft in a surface-to-surface mode, so that the axial force is balanced, the axial load of a bearing is reduced, and the axial movement of a rotor is reduced;

the driving motor is a flat motor, a rotor cantilever of the driving motor is installed at the end part of the pump shaft, and the driving motor is coaxial with the impeller and shares the same pair of rolling bearings with the impeller.

Furthermore, the number of the driving motors is two, and the rotors of the driving motors are respectively arranged at two ends of the pump shaft in a cantilever mode, so that the asymmetry of a single cantilever motor is improved.

Further, the centrifugal pump also comprises a middle opening ring positioned in the middle of the rotating shaft and an impeller opening ring matched with the inlet of each stage of impeller.

Further, the centrifugal pump further comprises a guide vane located at the impeller outlet.

The centrifugal pump further comprises a volute, an upper mechanical seal and a lower mechanical seal, wherein the volute is positioned between the last-stage impeller and the upper pump cover, and the upper mechanical seal and the lower mechanical seal are respectively positioned between the impellers at two ends of the pump shaft and the rolling bearing and are used for sealing a medium conveyed by the centrifugal pump; the centrifugal pump is also provided with an upper pump cover and a lower pump cover at the upper end and the lower end. Due to the design, the motor and the pump head share the shell and the upper and lower pump covers, and the structural integrity is good.

Further, the water inlet and the water outlet of the pump body are both located on the side face of the pump body.

A design method of a modular integrated low-noise centrifugal pump comprises the following steps:

(1) determining a designed rotating speed and a designed stage number through preliminary hydraulic design based on a given rated flow and a given lift, and further estimating the shaft power of the pump;

(2) performing optimization design on a hydraulic component, and performing electromagnetic design on a motor synchronously based on the obtained rotating speed and shaft power;

(3) obtaining the fluid excitation characteristic frequency and the electromagnetic excitation characteristic frequency of the hydraulic component through theoretical and numerical calculation analysis, and using the fluid excitation characteristic frequency and the electromagnetic excitation characteristic frequency as input conditions of subsequent integrated pump shell and shafting design;

(4) by means of structural modal analysis, the motor and the pump body shell are integrally analyzed and designed, so that the structural rigidity of the pump body shell is integrally improved;

(5) by means of rotor dynamics analysis, shaft system design of an impeller rotor and a motor rotor system is carried out, and the rigidity of the rotor system is integrally considered to be improved;

(6) drawing a drawing to finish the design.

The invention has the following beneficial effects:

(1) the motor adopts a flat motor, the bearings are arranged on two sides of the impeller rotor, the flat motor cantilever is arranged at one end of the pump rotor, additional bearing support is not needed, the rigidity of the pump rotor can be effectively improved, the problem of double-shaft centering is avoided, the whole operation is more stable and reliable, and the vibration noise of the pump is effectively reduced.

(2) The centrifugal pump adopts the impellers with even number of stages, and compared with a single-stage impeller, the centrifugal pump can effectively increase the bearing span and improve the rigidity of the cantilever arrangement of the motor; the arrangement of the impellers of even number stages can effectively balance the axial force and reduce the axial load of the bearing, thereby reducing the self vibration noise of the bearing; the impellers are arranged in an even number of stages in a face-to-face mode, axial forces of the impellers on two sides point to the inner side, the impeller rotor is always in a compression state when the pump operates, axial movement of the impeller rotor can be reduced, and vibration reduction and noise reduction are facilitated.

(3) The impeller structures arranged face to face in even number stages can conveniently increase the impeller stages without generating great influence on the pump structure, and can increase the impeller stages in a modularization mode, so that the pump lift is improved, and the structure is compact.

(4) The traditional structure often splits pump and motor, carries out the motor after the pump design is accomplished and selects the type, and such mode has more not enough to the application occasion that the vibration noise required much. The invention starts from the idea of integrating the pump and the motor, and can integrally consider the vibration and noise reduction measures of the pump by synchronously designing the rotors and the shells of the pump and the motor in an integrated manner. The integrated structure of the invention not only integrates the pump shaft and the motor shaft, but also integrates the pump body. Because the pump shell and the motor shell are of an integral structure, the structural rigidity can be integrally considered during structural design, and vibration and noise reduction of the pump structure is facilitated.

Drawings

Fig. 1 is a schematic structural view of a two-stage integrated centrifugal pump of embodiment 1;

FIG. 2 is a schematic view of a rotor system of a two-stage integrated centrifugal pump;

FIG. 3 is a schematic structural view of a four-stage integrated centrifugal pump;

FIG. 4 is a schematic view of a two-stage, two-motor integrated centrifugal pump;

FIG. 5 is a schematic view of a two-stage, two-motor integrated centrifugal pump rotor system;

FIG. 6 is a schematic view of a two-stage double-motor bearing external integrated centrifugal pump;

FIG. 7 is a schematic view of a two-stage dual-motor bearing external integrated centrifugal pump rotor system;

fig. 8 is a flow chart of the design of the modular integrated low noise centrifugal pump of the present invention.

In the figure, 1-first-stage impeller, 2-pump shaft, 3-first-stage guide vane, 4-pump body, 5-pump inlet, 6-secondary impeller, 7-volute, 8-motor, 9-upper pump cover, 10-upper bearing, 11-upper bearing seat, 12-upper mechanical seal, 13-pump outlet, 14-middle port ring, 15-lower mechanical seal, 16-lower pump cover, 17-lower bearing, 18-lower bearing seat, 19-lower bearing end cover, 20-first-stage port ring, 21-secondary port ring, 22-third-stage impeller, 23-fourth-stage impeller, 24-third-stage guide vane, 25-fourth-stage guide vane, 26-lower motor and 27-lower motor cover.

Detailed Description

The present invention will be described in detail below with reference to the accompanying drawings and preferred embodiments, and the objects and effects of the present invention will become more apparent, it being understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

As one embodiment, as shown in fig. 1, the centrifugal pump is a two-stage integrated centrifugal pump, and the centrifugal pump includes a first-stage impeller 1, a pump shaft 2, a first-stage guide vane 3, a pump body 4, a pump inlet 5, a second-stage impeller 6, a volute 7, an upper drive motor 8, an upper pump cover 9, an upper bearing 10, an upper bearing seat 11, an upper mechanical seal 12, a pump outlet 13, a middle port ring 14, a lower mechanical seal 15, a lower pump cover 16, a lower bearing 17, a lower bearing seat 18, a lower bearing end cover 19, a first-stage impeller port ring 20, and a second-stage impeller port ring 21.

The primary impeller 1 and the secondary impeller 6 are symmetrically arranged at two ends of the pump shaft 2 in a face-to-face manner, and the primary guide vane 3 is arranged at the outlet of the primary impeller 1 and is positioned between the lower pump cover 16 and the pump body 4. The volute 7 is positioned between the secondary impeller 6 and the upper pump cover 9, fluid is sucked from the pump inlet 5, is guided to the secondary impeller 6 to do work through the first-stage guide vane 3 after doing work through the first-stage impeller 1, and finally flows out of the pump outlet 13 after being diffused through the volute 7. The upper driving motor 8 may be a disk motor or other flat motor, and its rotor is mounted on the top end of the pump shaft 2, as shown in fig. 2, and the electronic rotor shares the same pair of rolling bearings with the primary impeller 1 and the secondary impeller 6. The pair of rolling bearings includes an upper bearing 10 and a lower bearing 17, which are respectively installed in an upper bearing housing 11 and a lower bearing housing 18. The upper mechanical seal 12 and the lower mechanical seal 15 are respectively positioned between the secondary impeller 6 and the primary impeller 1 at two ends of the pump shaft 2 and the corresponding rolling bearings and are used for sealing the medium conveyed by the centrifugal pump. The upper end and the lower end of the pump are respectively provided with an upper pump cover 9 and a lower bearing cover 19. Due to the design, the motor and the pump head share the shell and the upper and lower pump covers, and the structural integrity is good.

The multistage centrifugal pump rotor structure has a significant effect on pump vibration, and in the rotor system shown in fig. 2, the primary components that determine the rotor stiffness are the primary impeller eye 20, the secondary impeller eye 21, and the intermediate eye 14. The middle port ring 14 is sleeved at the middle part of the pump shaft 2, the primary impeller port ring 20 and the secondary impeller port ring 21 are respectively sleeved at the inlets of the primary impeller 1 and the secondary impeller 6, liquid films with certain thicknesses exist in the primary impeller port ring 20, the secondary impeller port ring 21 and the middle port ring 14, certain pressure difference exists between the two sides, and reasonable and sufficient design calculation is needed for the gap and the length between the liquid films so as to improve the rigidity of liquid film support and reduce the pump vibration noise caused by a rotor system.

As another embodiment, because the motor and the impeller in the centrifugal pump structure of the invention adopt a coaxial design, increasing the impeller stage number has little influence on the pump body structure, a modular design can be realized, and different lift requirements can be matched, as shown in fig. 3, pump lift multiplication can be realized only by increasing the three-stage impeller 22, the four-stage impeller 23, the three-stage guide vane 24 and the four-stage guide vane 25, and each stage of impeller and guide vane has certain universality.

As another embodiment, in order to improve the asymmetry of the top cantilever motor and reduce the mass and moment of inertia of the rotor of a single motor, the motor in the first embodiment may be designed as a dual motor drive, as shown in fig. 4, in which an upper driving motor 8 and a lower driving motor 26 are disposed at the upper and lower sides of the pump, respectively. The double-motor structure can improve the symmetry of the integrated pump and is beneficial to the vibration reduction design of the rotor. Fig. 5 is a schematic view of the structure of the lower rotor. When the centrifugal pump is designed to be driven by two motors, the centrifugal pump can remove the lower bearing cover 19 and add the lower motor cover 27, and the lower motor cover 27 is symmetrical to the upper part and plays a role in supporting and sealing the lower driving motor 26.

As another embodiment, in order to increase the rigidity of the rotor, a bearing may be disposed at the outermost end of the shaft system, as shown in FIG. 6, an upper bearing 10 and a lower bearing 17 are respectively disposed outside an upper driving motor 8 and a lower driving motor 26 of the pump, and FIG. 7 is a schematic view of the structure of the lower rotor. The above design places the rotor parts of the motor and the pump between the bearings, which is more beneficial to improving the rigidity of the rotor and reducing the vibration.

In addition, the pump inlet 5 and the pump outlet 13 of the centrifugal pump of the invention are both arranged in a side-in side-out mode, so that the volume of the pump is not increased even under the condition of a multi-stage pump, and the effect of compact structure is achieved.

The pump and the motor are designed integrally, the design process is different from that of the traditional centrifugal pump, as shown in fig. 8, the design process of the modular integrated low-noise centrifugal pump is described as follows:

based on the given rated flow and the given lift, the designed rotating speed and the number of stages are determined through preliminary hydraulic design, and further the shaft power of the pump is estimated. And then, carrying out the optimal design of the hydraulic component, and synchronously carrying out the electromagnetic design of the motor based on the obtained rotating speed and shaft power parameters. And obtaining the fluid excitation characteristic frequency and the electromagnetic excitation characteristic frequency of the hydraulic component through theoretical and numerical calculation analysis, and using the fluid excitation characteristic frequency and the electromagnetic excitation characteristic frequency as input conditions of subsequent integrated pump shell and shafting design. In order to realize low-vibration design, when the structure of the integrated pump shell is designed, the integrated analysis design of the motor and the pump shell is developed by means of structural modal analysis, so that the structural rigidity of the integrated pump shell is integrally improved, vibration and noise reduction of the pump are facilitated, and meanwhile, by means of rotor dynamics analysis, the shafting design of an impeller rotor and a motor rotor system is developed, the rigidity of the rotor system is integrally improved, and the vibration excitation of the rotor is reduced. And finally, drawing an integrated pump engineering drawing to complete the design.

It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and although the invention has been described in detail with reference to the foregoing examples, it will be apparent to those skilled in the art that various changes in the form and details of the embodiments may be made and equivalents may be substituted for elements thereof. All modifications, equivalents and the like which come within the spirit and principle of the invention are intended to be included within the scope of the invention.

Claims

1. A modular integrated low-noise centrifugal pump is characterized by comprising a pump body (4), a pump shaft (2), an impeller and a driving motor (8);

the impeller is an even-numbered impeller and is positioned between a pair of rolling bearings at two ends of the pump shaft (2);

the impeller faces of the even-numbered stages are symmetrically arranged on the pump shaft (2) in a surface-to-surface mode, so that the axial force is balanced, and the axial movement of a rotor is reduced;

the driving motor is a flat motor, a rotor cantilever of the driving motor is installed at the end part of the pump shaft (2), and the driving motor is coaxial with the impeller and shares the same pair of rolling bearings with the impeller.

2. The modular integrated low noise centrifugal pump according to claim 1, wherein said driving motors are two, and rotors of said driving motors are respectively cantilever-mounted at both ends of said pump shaft (2), thereby improving asymmetry of a single cantilever motor.

3. The modular one-piece low noise centrifugal pump of claim 1, further comprising a center ring (14) in the middle of the shaft and an impeller ring fitted to the inlet of each stage of impeller.

4. The modular integrated low noise centrifugal pump of claim 1, further comprising a vane at said impeller outlet.

5. The modular integrated low-noise centrifugal pump according to claim 1, further comprising a volute (7), an upper mechanical seal (12) and a lower mechanical seal (15), the volute (7) being located between the last impeller and the upper pump cover (9), the upper mechanical seal (12) and the lower mechanical seal (15) being respectively located between the impellers and the rolling bearings at both ends of the pump shaft (2) for sealing of the centrifugal pump delivery medium; the centrifugal pump is also provided with an upper pump cover (9) and a lower pump cover (16) at the upper end and the lower end.

6. The modular one-piece low noise centrifugal pump of claim 1, wherein the water inlet and water outlet of the pump body are both located on a side of the pump body.

7. A method of designing a modular one-piece low noise centrifugal pump as defined in claim 1, comprising the steps of:

(1) based on the given rated flow and the given lift, the designed rotating speed and the number of stages are determined through preliminary hydraulic design, and further the shaft power of the pump is estimated.

(6) drawing a drawing to finish the design.