Multi-stage pump with self-balancing axial forces

Abstract

This invention relates to a self-balancing multistage pump with axial force, solving the problems of high energy consumption, short lifespan, and poor operational stability caused by the large axial force generated by the equal outer diameter of the front and rear cover plates and a specific speed (ns>300) in existing technologies. The technical solution includes a pump body, an impeller string housed within the pump body, and several sets of impeller units within the impeller string. The key feature is that each impeller unit includes a guide shroud, an impeller housed in the guide cavity of the guide shroud, and the impeller comprising a front cover plate, a rear cover plate, and blades disposed between the front and rear cover plates. The outer diameter of the front cover plate is larger than that of the rear cover plate. The front cover plate mates with the bottom of the guide cavity and with the open portion of the guide cavity. Its effects are: by using an impeller with a front cover plate area larger than the rear cover plate area, and in conjunction with the guide shroud, self-balancing of the impeller axial force is achieved, making the pump operation more stable and reliable, significantly reducing power consumption, greatly improving social and economic benefits, and achieving the goal of energy conservation and emission reduction.

Description

Technical Field

[0001] This invention relates to a multistage pump, and more particularly to a multistage pump that self-balances axial force. Background Technology

[0002] Due to the limitations of hydraulic performance design, conventional multistage pumps typically use impellers with equal outer diameters for both the front and rear cover plates. Furthermore, there is currently no solution for matching the impeller with a guide vane within each stage of a multistage pump. In existing multistage pumps, the liquid is vertically thrown out of the impeller and into the pump body or guide vane by the centrifugal force of the impeller. The asymmetrical area ratio of the front and rear cover plates with the same outer diameter results in a significant axial force on the impeller. This is particularly problematic for multistage pumps, with up to 40 impellers, resulting in a very large cumulative axial force. This substantial axial force significantly reduces the lifespan of the motor and bearings, and also leads to poor pump operational stability. To balance the axial force, a dedicated motor is required, which increases the cost of the motor and contributes to the high cost of multistage pumps.

[0003] Of course, a small number of single-stage or multi-stage pumps also use a similar impeller structure with asymmetrical front and rear cover plates (i.e., the impeller outlet is obliquely cut). The specific speed ns>300 in the hydraulic parameters of these single-stage or multi-stage pumps. This type of impeller is also called a mixed-flow impeller or a diagonal-flow impeller. The purpose is twofold: first, to obtain a larger flow rate and a lower head; and second, to eliminate the impeller outlet backflow zone and control the secondary backflow of the liquid.

[0004] In summary, the shortcomings of existing technologies are as follows:

[0005] 1. From a structural performance perspective: It generates a large axial force, and balancing the axial force requires consuming the bearing load of the motor, which increases the energy consumption of the motor;

[0006] 2. From a hydraulic performance perspective: the flow direction is unstable, which easily leads to the formation of internal eddies and results in significant hydraulic losses, posing a bottleneck problem in the industry;

[0007] 3. In terms of overall performance: it can no longer meet the energy-saving requirements and is not conducive to responding to the call for carbon neutrality and carbon peaking.

[0008] However, the existing multistage pump products have a market share of over 25 billion yuan in municipal water supply and drainage, secondary water supply, industrial boosting, and seawater desalination. Under the national carbon neutrality and carbon peaking policy, there is a need for more suitable, reasonable, and improved multistage pump products. Summary of the Invention

[0009] The object of the present invention is to solve the above problems existing in the prior art and provide a multi-stage pump with self-balanced axial force. An impeller with a front cover plate area larger than the rear cover plate area is adopted, and at the same time, it is combined with a flow guide cover to achieve self-balancing of the axial force of the impeller, making the pump operate more stably and reliably, greatly reducing power consumption, greatly enhancing social and economic benefits, and achieving the purpose of energy conservation and emission reduction.

[0010] The above technical object of the present invention is mainly solved by the following technical solutions: A multi-stage pump with self-balanced axial force, including a pump body and an impeller string arranged in the pump body. The impeller string is composed of several groups of impeller units. The characteristic is that one group of the impeller units includes a flow guide cover and an impeller arranged in the flow guide cavity of the flow guide cover. The impeller includes a front cover plate, a rear cover plate, and blades arranged between the front cover plate and the rear cover plate. The outer diameter of the front cover plate is larger than the outer diameter of the rear cover plate. The front cover plate is matched with the bottom of the flow guide cavity, and the front cover plate is matched with the open part of the flow guide cavity.

[0011] By adopting an impeller with a front cover plate area larger than the rear cover plate area and at the same time combining it with a flow guide cover, self-balancing of the axial force of the impeller is achieved, making the pump operate more stably and reliably, greatly reducing the power consumption of the motor, greatly enhancing social and economic benefits, and achieving the purpose of energy conservation and emission reduction.

[0012] As a further improvement and supplement to the above technical solution, the present invention adopts the following technical measures:

[0013] Preferably, in order to better achieve self-balancing of the axial force caused by the cover plate force, the area ratio S of the front cover plate to the rear cover plate is: 0.95 ≤ S ≤ 1.

[0014] The outer diameter of the circumcircle of the blades is larger than the outer diameter of the rear cover plate, and the outer diameter of the circumcircle of the blades is smaller than the outer diameter of the front cover plate. The blades have an extension part at the periphery of the rear cover plate, and the front cover plate forms an overhanging part at the periphery of the extension part.

[0015] Under the combined action of the fluid, centrifugal force and thrust of the extension part of the blades and the overhanging part of the front cover plate, the liquid flow direction forms an inclined angle and smoothly enters the next-stage impeller unit along the streamline inner wall of the flow guide cover (mainly the flow guide part).

[0016] The specific speed ns of the impeller is: 80 < ns < 150. It is beneficial to improve the energy efficiency of the pump, and the hydraulic performance and structure are more stable, achieving the effect of energy conservation and consumption reduction, and all are accepted according to the highest energy efficiency index in the EU.

[0017] Preferably, the fairing includes a fairing housing, a stuffing box seat disposed on the back surface of the fairing housing, and a stuffing box cover mating with the stuffing box seat. An impeller stuffing box is provided at the stuffing box portion of the impeller. The impeller stuffing box is disposed in a stuffing box cavity formed between the stuffing box seat and the stuffing box cover. The diversion cavity is disposed in the fairing housing.

[0018] Preferably, the fairing housing includes an integrally formed diversion portion, a downward folding portion, a first horizontal folding portion, an upward folding portion, and a second horizontal folding portion. The diversion portion is in the shape of a flared drum. The inner cavity of the diversion portion is the diversion cavity. The upper edge of the downward folding portion mates with the inner edge of the diversion portion. The outer edge of the first horizontal folding portion mates with the lower edge of the downward folding portion. The lower edge of the upward folding portion mates with the inner edge of the first horizontal folding portion. The outer edge of the second horizontal folding portion mates with the upper edge of the upward folding portion. The inner edge of the second horizontal folding portion is in clearance fit with the outer wall of the impeller stuffing box.

[0019] Preferably, the cross section of the stuffing box cover is Z-shaped. The upper shoulder of the Z-shape presses on the upper end surface of the impeller stuffing box. The lower shoulder of the Z-shape presses on the first horizontal folding portion. The inclined arm of the Z-shape is buckled on the outside of the upward folding portion and forms an interference fit with the upward folding portion.

[0020] Preferably, the stuffing box cover is a rigid elastic deformation member, and the stuffing box seat is an inverted disk shape.

[0021] The beneficial effects of the present invention are as follows:

[0022] 1. Optimization of the product structure: An impeller with a front cover area larger than the rear cover area is adopted, and the ratio of the front and rear cover areas is controlled within the range of 0.95 - 1. At the same time, in cooperation with the fairing, self-balancing of the impeller axial force is achieved, making the pump operation more stable and reliable, and greatly reducing the power consumption of the motor. <..

[0023] 2. Optimization of the hydraulic structure: The specific speed ns of the adopted impeller is: 80 < ns < 150, improving the overall efficiency index of the pump and achieving the purpose of energy conservation and emission reduction.

[0024] 3. The blade has an extension portion at the periphery of the rear cover, and the front cover forms an overhanging portion outside the extension portion. Under the combined action of the extension portion of the blade and the overhanging portion of the front cover on the fluid, under the action of centrifugal force and thrust, the liquid flow direction forms an inclined angle and smoothly enters the next-stage impeller unit along the streamline inner wall of the fairing (mainly the diversion portion).

[0025] 4. A single pump can save 15,000 kWh of electricity per year. The procurement cost of the entire pump is much lower than the electricity cost saved in one year, and the pump has a long service life. With one purchase, it can be used for several years, greatly improving the social and economic benefits. Brief Description of the Drawings

[0026] Figure 1 This is a schematic cross-sectional view of the impeller and the guide vane in this invention.

[0027] Figure 2 This is a schematic diagram of one structure of the impeller in this invention.

[0028] Figure 3 yes Figure 1 A schematic diagram of the explosion structure.

[0029] Figure 4 hour Figure 3 A structural diagram from another perspective. Detailed Implementation

[0030] The technical solution of the present invention will be further described in detail below through embodiments and in conjunction with the accompanying drawings.

[0031] Example: Figure 1-4 As shown, a self-balancing axial force multistage pump includes a pump body and an impeller string disposed within the pump body. The impeller string consists of several sets of impeller units. Each set of impeller units includes a flow guide shroud 1 and an impeller 2 disposed in a flow guide cavity 11 of the flow guide shroud. The impeller includes a front cover plate 21, a rear cover plate 22, and blades 23 disposed between the front cover plate and the rear cover plate. The outer diameter of the front cover plate is larger than the outer diameter of the rear cover plate. The front cover plate mates with the bottom of the flow guide cavity and the front cover plate mates with the open portion of the flow guide cavity.

[0032] By using an impeller with a front cover area larger than the rear cover area, and in conjunction with a guide shroud, the axial force of the impeller is self-balanced, making the pump operation more stable and reliable, greatly reducing the power consumption of the motor, significantly improving social and economic benefits, and achieving the goal of energy conservation and emission reduction.

[0033] Preferably, in order to better achieve self-balance of the axial force caused by the cover plate force, the area ratio S of the front cover plate and the rear cover plate is: 0.95≤S≤1.

[0034] The outer diameter of the blade is larger than the outer diameter of the rear cover plate, and the outer diameter of the blade is smaller than the outer diameter of the front cover plate. The blade has an extension 23-1 around the rear cover plate, and the front cover plate forms an overhang 21-1 around the extension.

[0035] The combined action of the outer extension of the blade and the extended part of the front cover on the fluid, under the action of centrifugal force and thrust, the liquid flow direction forms an inclined angle and smoothly enters the next stage impeller unit along the streamlined inner wall of the guide shroud (mainly the guide part).

[0036] The specific speed ns of the impeller is: 80 < ns < 150. This is beneficial to improving the energy efficiency of the pump, making the hydraulic performance and structure more stable, achieving the effect of energy conservation and consumption reduction, and all are inspected according to the highest energy efficiency indicators in the EU.

[0037] Preferably, the guide cover 1 includes a guide cover shell 12, a seal ring seat 13 arranged on the back of the guide cover shell, and a seal ring cover 14 cooperating with the seal ring seat. A seal ring of the impeller is provided with an impeller seal ring 3. The impeller seal ring is arranged in a seal ring cavity formed by the cooperation of the seal ring seat and the seal ring cover. The guide cavity is arranged in the guide cover shell.

[0038] Preferably, the guide cover shell includes an integrally formed guide part 12-1, a downward folding part 12-2, a first horizontal folding part 12-3, an upward folding part 12-4, and a second horizontal folding part 12-5. The guide part is in the shape of a flared drum. The inner cavity of the guide part is the guide cavity. The upper edge of the downward folding part cooperates with the inner edge of the guide part. The outer edge of the first horizontal folding part cooperates with the lower edge of the downward folding part. The lower edge of the upward folding part cooperates with the inner edge of the first horizontal folding part. The outer edge of the second horizontal folding part cooperates with the upper edge of the upward folding part. The inner edge of the second horizontal folding part has a clearance fit with the outer wall of the impeller seal ring.

[0039] In this article, the direction towards the seal ring seat is downward, the direction towards the impeller is upward, the periphery of the impeller is the outer side, and the center direction of the impeller is the inner side.

[0040] Preferably, the cross-section of the seal ring cover 14 is in a Z shape. The upper shoulder 14-1 of the Z shape presses on the upper end face of the impeller seal ring. The lower shoulder 14-2 of the Z shape presses on the first horizontal folding part. The inclined arm 14-3 of the Z shape is buckled on the outer side of the upward folding part and forms an interference fit with the upward folding part.

[0041] Preferably, the seal ring cover is a rigid elastic deformation part, and the seal ring seat is in an inverted dish shape.

[0042] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. In the above embodiments, various changes and modifications can be made to the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A self-balancing axial force multistage pump, comprising a pump body, an impeller string disposed within the pump body, wherein the impeller string is composed of several sets of impeller units, characterized in that... A set of the impeller units includes a flow guide shroud, an impeller disposed in the flow guide cavity of the flow guide shroud, the impeller including a front cover plate, a rear cover plate and blades disposed between the front cover plate and the rear cover plate, the outer diameter of the front cover plate being larger than the outer diameter of the rear cover plate, the front cover plate engaging with the bottom of the flow guide cavity, and the front cover plate engaging with the open portion of the flow guide cavity; The outer diameter of the blade is larger than the outer diameter of the rear cover plate, the outer diameter of the blade is smaller than the outer diameter of the front cover plate, and the blade has an extension portion around the rear cover plate. The specific speed ns of the impeller is: 80 <ns<150; The flow guide includes a flow guide shell, an inlet ring seat disposed on the back of the flow guide shell, an inlet ring cover that cooperates with the inlet ring seat, an impeller inlet ring disposed on the inlet ring portion of the impeller, the impeller inlet ring being disposed in the inlet ring cavity in which the inlet ring seat and the inlet ring cover move, and the flow guide cavity being disposed in the flow guide shell; The flow guide cover includes an integral flow guide section, a lower fold section, a first horizontal fold section, an upper fold section, and a second horizontal fold section. The flow guide section is flared and drum-shaped. The inner cavity of the flow guide section is the flow guide cavity. The upper edge of the lower fold section mates with the inner edge of the flow guide section. The outer edge of the first horizontal fold section mates with the lower edge of the lower fold section. The lower edge of the upper fold section mates with the inner edge of the first horizontal fold section. The outer edge of the second horizontal fold section mates with the upper edge of the upper fold section. The inner edge of the second horizontal fold section has a clearance fit with the outer wall of the impeller inlet ring.

2. The multi-stage pump with self-balancing axial force according to claim 1, characterized in that... The area ratio S of the front cover plate and the rear cover plate is: 0.95≤S≤1.

3. The multi-stage pump with self-balancing axial force according to claim 1, characterized in that... The cross-section of the mouth ring cover is Z-shaped. The upper shoulder of the Z-shape presses against the upper end face of the impeller mouth ring, the lower shoulder of the Z-shape presses against the first horizontal fold, and the oblique arm of the Z-shape fastens against the outside of the upper fold and forms an interference fit with the upper fold.

4. The multi-stage pump with self-balancing axial force according to claim 3, characterized in that... The mouth ring cover is a rigid elastic deformation component, and the mouth ring seat is an inverted disc shape.

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