CN109209897B

CN109209897B - Axial force balancing mechanism of multistage centrifugal pump rotor

Info

Publication number: CN109209897B
Application number: CN201811311051.0A
Authority: CN
Inventors: 叶晓琰; 胡敬宁
Original assignee: Jiangsu University
Current assignee: Jiangsu University
Priority date: 2018-11-06
Filing date: 2018-11-06
Publication date: 2020-09-15
Anticipated expiration: 2038-11-06
Also published as: CN109209897A

Abstract

The invention aims to provide a multistage centrifugal pump rotor axial force balancing mechanism capable of reducing energy loss and having a simple structure, which comprises a first-stage impeller of a centrifugal pump and an inlet section of the centrifugal pump, wherein a first radial gap C1, a first axial gap C2 and a second axial gap C3 which are sequentially communicated are arranged between a front cover plate and the inlet section of the first-stage impeller, a liquid outlet of the first radial gap C1 is communicated with an inlet of the centrifugal pump, a second axial gap C3 is communicated with a liquid outlet of the first-stage impeller, the inlet section is provided with a high-pressure liquid flow introducing channel, high-pressure liquid flow is introduced into the introducing channel from a rear cover plate of a last-stage impeller of the centrifugal pump to form a backflow channel, and a throttling hole. The axial force from the front end to the rear end is generated by introducing the high-pressure liquid flow, and the axial force is balanced with the axial force from the rear end to the front end generated by the impeller under the influence of water power.

Description

Axial force balancing mechanism of multistage centrifugal pump rotor

Technical Field

The invention belongs to the field of design and manufacture of centrifugal pumps, and particularly relates to an axial force balancing mechanism of a rotor of a multistage centrifugal pump.

Background

When the centrifugal pump operates, the rotation of the impeller generates water pressure at the front cover plate and the rear cover plate, and the action area of the rear cover plate of the impeller under the action of water pressure is larger than that of the front cover plate due to the objective existence of the impeller suction inlet, so that the forces acting on the front cover plate and the rear cover plate cannot be balanced with each other, an axial force can be generated, and the direction of the axial force always points to the front cover plate from the rear cover plate of the impeller. For the multi-stage segmental centrifugal pump with impellers arranged in the same direction, each impeller generates axial forces with basically the same size and consistent directions, and the total force of the axial forces is very large (for example, in a seawater desalination device, the axial force generated by the impeller of the multi-stage centrifugal pump with the water production scale of 5000m 3/d-20000 m3/d is about 40 kN-100 kN). Therefore, the multi-stage centrifugal pump must have an axial force balancing mechanism, which generates an opposite axial force to balance the axial force generated by the impeller.

The traditional axial force balancing method is to balance the axial force of the impeller by adopting a balance disc and a balance drum (a special case that the balance drum does not generate balance force is that the balance disc is singly adopted for balancing). The operation of the balancing device is the process of reducing the flow having high pressure energy to a flow having low pressure energy, but this process results in a loss of energy, which is the volumetric loss described in the pump industry.

Disclosure of Invention

The invention aims to provide an axial force balancing mechanism of a multistage centrifugal pump rotor, which can reduce energy loss and has a simple structure.

In order to achieve the purpose, the invention adopts the technical scheme that: the utility model provides a multistage centrifugal pump rotor axial force balance mechanism, the induction zone of centrifugal pump and the first impeller of centrifugal pump, be provided with first radial clearance C1, first axial clearance C2 and second axial clearance C3 that communicate in proper order between the front shroud of first impeller and the induction zone, the liquid outlet of first radial clearance C1 communicates with the import of centrifugal pump, the liquid outlet of second axial clearance C3 communicates with the liquid outlet of first impeller, the induction zone is provided with high-pressure liquid flow inlet channel, high-pressure liquid flow introduces the inlet channel and constitutes the backward flow route from the back shroud department of centrifugal pump last stage impeller, be provided with the orifice in the inlet channel.

In the scheme, because the high-pressure liquid flow is introduced to generate an axial force from the front end to the rear end, the axial force is balanced with the axial force generated by the impeller under the influence of water power from the rear end to the front end, compared with a traditional multi-stage pump axial force balancing mechanism, the structure is simplified, the recovery of partial balanced liquid flow is realized, and the leakage loss is reduced.

Drawings

FIG. 1 is a schematic view of the overall structure of the present invention;

fig. 2 is a partially enlarged schematic view of fig. 1.

Detailed Description

As shown in fig. 1 and fig. 2, the multi-stage centrifugal pump rotor axial force balancing mechanism comprises a first-stage impeller 10 of the centrifugal pump and an inlet section 20 of the centrifugal pump, wherein a first radial gap C1, a first axial gap C2 and a second axial gap C3 which are sequentially communicated are arranged between a front cover plate of the first-stage impeller 10 and the inlet section 20, a liquid outlet of the first radial gap C1 is communicated with an inlet of the centrifugal pump, a liquid outlet of the second axial gap C3 is communicated with a liquid outlet of the first-stage impeller 10, the inlet section 20 is provided with a high-pressure liquid flow introducing channel 22, high-pressure liquid flow is introduced into the introducing channel 22 from a rear cover plate (not shown in the figure) of the centrifugal pump at a final stage to form a backflow channel, and the introducing.

The flow direction of the water flow at the inlet of the centrifugal pump shown in figure 1 is from right to left, and because the pressure area of the left rear cover plate of each stage of impeller of the centrifugal pump is larger than that of the right front cover plate, when the centrifugal pump runs, the impeller generates an axial force with unbalanced waterpower, and the direction is right. Suppose that the resultant of the axial forces generated by the impellers of each stage is F1, i.e., the rightward force applied to the entire rotor is F1. The invention takes the front cover plate of the first-stage impeller 10 of the centrifugal pump as a force-bearing part of the balance force, high-pressure liquid flow enters from the high-pressure liquid flow introducing channel 22, and the whole balance mechanism generates a larger balance force towards the left, and the acting force is assumed to be F2. When the centrifugal pump normally operates, F2 is equal to F1, so that the axial force balance of the rotor 30 can be ensured; because the operating condition of the centrifugal pump is changed frequently, both F2 and F1 are changed, at the moment, if F2 is larger than F1, the rotor moves leftwards, in the process, the first axial gap C2 and the second axial gap C3 are gradually enlarged, the first radial gap C1 is unchanged, the flow of the introduced high-pressure liquid flow is increased, and because the introduction channel 22 is provided with the throttle hole 21, the pressure difference between the front cover plate and the rear cover plate of the first-stage impeller 10 is reduced, and the F2 is also reduced; when F2 is smaller than F1, the rotor moves rightwards, in the process, the first axial clearance C2 and the second axial clearance C3 become smaller gradually, the first radial clearance C1 does not change, the flow rate of the introduced high-pressure liquid flow is reduced, and due to the fact that the throttle hole 21 is arranged in the introducing channel 22, the pressure difference between the front cover plate and the rear cover plate of the first-stage impeller 10 is increased, and F2 is increased; the axial force borne by the centrifugal pump rotor reaches dynamic balance by reciprocating in this way, so that the centrifugal pump rotor runs near a certain balance position. In the process, the flow of the balancing device passing through the first axial clearance C2 and the first radial clearance C1 replaces the leakage of the first-stage impeller, so that the leakage amount of the centrifugal pump can be reduced; the balance device liquid flow passing through the second axial gap C3 enters the outlet main flow of the primary impeller, and partial liquid energy recovery is realized.

Preferably, the inner wall of the inducer 20 is provided with a sleeve 40 arranged coaxially with the rotor 30, the inner wall of the sleeve 40 and the mouth ring 11 arranged on the front cover plate of the primary impeller 10 form the first radial gap C1, the end face of the sleeve 40 and the inner balance ring 12 arranged on the front cover plate of the primary impeller 10 form the first axial gap C2, and the end face of the inducer 20 and the outer balance ring 13 arranged on the front cover plate of the primary impeller 10 form the second axial gap C3.

Further, a chamber a is formed between the first and second axial clearances C2, C3, and the orifice 21 provided in the inducer 20 communicates the chamber a with the high-pressure liquid stream introduction passage 22.

The total flow Q of the introduced high-pressure liquid flow is divided into two paths: one liquid flow (flow Q1) enters the outlet of the first-stage impeller 10 along a variable second axial gap C3 and converges with the outlet main flow of the first-stage impeller of the pump; the other flow (flow Q2) enters the pump inlet along the variable first axial gap C2 and the constant first radial gap C1 and converges with the main pump inlet flow. Because the acting area of the rear cover plate of the first-stage impeller 10 is larger than that of the front cover plate, when the centrifugal pump operates, the impeller generates hydraulic unbalanced axial force, the direction of the axial force is from front to back, namely the whole rotor generates backward displacement due to backward acting force, so that the first axial gap C2 and the second axial gap C3 become larger, the flow Q1 entering the first-stage impeller through the second axial gap C3 is obviously increased, although the first axial gap C2 is increased, the first radial gap C1 is fixed and constant and plays a role of throttling all the time, so that the increase of Q2 is limited; the significant increase in Q1 and the slight increase in Q2 result in a significant increase in the total flow Q of the liquid stream, and the rotor will move forward as the pressure P1 in chamber a is greatly reduced by the provision of the orifice 21 in the inducer liquid stream inlet passage 22, with a consequent significant reduction in the counter balance force. Thus, the rotor 30 always has a certain balance position, and the axial force generated by the impeller is equal to the balance force, so that the automatic balance of the axial force is realized.

The invention completely cancels the traditional balance disc and balance drum, greatly simplifies the structure; part of the liquid flow enters the outlet of the first-stage impeller 10 through the second axial gap C3, so that the flow of the centrifugal pump is formed, and the energy recovery of part of the balance leakage liquid flow is realized; part of the flow enters the suction inlet of the centrifugal pump through the first radial clearance C1 and the first axial clearance C2, the part of the flow replaces the leakage flow at the traditional impeller opening ring, the volumetric efficiency of the primary impeller 10 is improved, the energy loss is reduced, and the leakage amount of the axial force balancing device with the traditional structure is fully and effectively utilized.

Claims

1. The utility model provides a multistage centrifugal pump rotor axial force balance mechanism which characterized in that: the centrifugal pump comprises a first-stage impeller (10) of the centrifugal pump and an inlet section (20) of the centrifugal pump, wherein a first radial gap C1, a first axial gap C2 and a second axial gap C3 which are sequentially communicated are arranged between a front cover plate of the first-stage impeller (10) and the inlet section (20), a liquid outlet of the first radial gap C1 is communicated with an inlet of the centrifugal pump, a liquid outlet of the second axial gap C3 is communicated with a liquid outlet of the first-stage impeller (10), the inlet section (20) is provided with a high-pressure liquid flow introducing channel (22), high-pressure liquid flow is introduced into the introducing channel (22) from a rear cover plate of a last-stage impeller of the centrifugal pump and forms a backflow passage, and a throttling hole (21) is arranged;

a sleeve (40) which is coaxial with the rotor (30) is arranged on the inner wall of the inlet section (20), a first radial gap C1 is formed between the inner wall of the sleeve (40) and a mouth ring (11) arranged on a front cover plate of the first-stage impeller (10), a first axial gap C2 is formed between the end face of the sleeve (40) and an inner balance ring (12) arranged on the front cover plate of the first-stage impeller (10), and a second axial gap C3 is formed between the end face of the inlet section (20) and an outer balance ring (13) arranged on the front cover plate of the first-stage impeller (10);

the chamber between the first and second axial clearances C2, C3 constitutes a chamber A, and an orifice (21) provided in the inlet section (20) communicates the chamber A with the high-pressure liquid flow introduction passage (22).