Liquid transfer pump

Abstract

A liquid transfer pump includes: a first housing defining a containment chamber; a second housing including a pump inlet and a pump outlet fluidly connecting by a pump chamber; an impeller assembly, including a centrifugal impeller and an axial flow impeller, at least partially disposed within the pump chamber, the impeller assembly including a hollow body portion, having a first end located adjacent to the pump inlet and a second end opposite the first end and located away from the pump inlet, the axial flow impeller being formed at the first end and the centrifugal impeller being formed at the second end of the hollow body portion; and a drive assembly, at least partially disposed within the containment chamber, configured to drive the impeller assembly. Adding the axial flow pump to the front of the centrifugal pump solves the airlock problem in the pump, improving its reliability.

Description

BACKGROUND OF THE INVENTION

[0001] This invention relates to the field of water pump technology and liquid transfer equipment, and more particularly to a liquid transfer pump.

[0002] A liquid transfer pump is a device that converts mechanical energy into liquid kinetic energy, and is widely used in agricultural irrigation, industrial production, urban water supply, sewage treatment, etc. Among various types of liquid transfer pumps, vertical submersible centrifugal pumps are widely used in various industrial fields due to their high efficiency, energy conservation, and small footprint. However, centrifugal pumps often encounter the problem of airlock during operation, where the pump cavity is filled with air. Due to the low density of air, the centrifugal force generated after the pump starts rotating is small, and the low pressure formed in the central area of ​​the impeller is insufficient to draw the liquid into the pump cavity, preventing the liquid transfer pump from pumping liquid normally.

[0003] Current technologies primarily address this issue by installing a priming pipe within the pump chamber, using the pipe to introduce liquid into the chamber and thereby expel air. Other approaches involve installing a nozzle inside the pump chamber to spray the liquid out, creating negative pressure and expelling air. While these methods can mitigate the airlock problem to some extent, they require additional priming pipes or nozzles, increasing the complexity and cost of the equipment. Furthermore, these methods only provide a temporary solution; if air re-enters the pump chamber, the pump will still fail to operate properly.

[0004] Therefore, there is an urgent need for a method and device that can solve the problem of airlock in centrifugal pumps without the need for additional water pipes or nozzles.SUMMARY OF THE INVENTION

[0005] To address the problems and shortcomings existing in the conventional technology, the objective of the present invention is to provide a method and device for solving the problem of airlock in centrifugal pumps without the need for additional water pipes or nozzles.

[0006] Based on this, according to one embodiment of the present invention, a liquid transfer pump is provided, which includes: a first housing defining a containment chamber; a second housing including a pump inlet, a pump outlet, and a pump chamber fluidly connecting the pump inlet and the pump outlet; an impeller assembly at least partially disposed within the pump chamber of the second housing, including a centrifugal impeller and an axial flow impeller, wherein the impeller assembly includes a hollow body portion, the hollow body portion including a first end located adjacent to the pump inlet and a second end opposite the first end and located away from the pump inlet, the axial flow impeller being formed at the first end of the hollow body portion, and the centrifugal impeller being formed at the second end of the hollow body portion; and a drive assembly, at least partially disposed within the containment chamber of the first housing, the drive assembly being configured to drive the impeller assembly.

[0007] In some embodiments, the drive assembly is configured to drive the axial flow impeller to rotate, thereby drawing liquid from the pump inlet into the pump chamber, and to drive the centrifugal impeller to rotate, thereby conveying the liquid drawn in by the axial flow impeller through the pump chamber to the pump outlet.

[0008] In some embodiments, the impeller assembly is integrally formed, and the axial flow impeller and the centrifugal impeller rotate coaxially.

[0009] In some embodiments, the second end of the hollow body includes a radially outwardly extending disc-shaped portion, the centrifugal impeller includes a plurality of centrifugal blades circumferentially spaced apart on the disc-shaped portion, and the axial flow impeller includes a plurality of axial flow blades circumferentially spaced apart on an inner wall of the first end.

[0010] In some embodiments, the drive assembly includes a brushless DC motor.

[0011] In some embodiments, the containment chamber of the first housing includes a first sub-chamber and a second sub-chamber, wherein a stator of the brushless DC motor is disposed in the first sub-chamber, and a rotor of the brushless DC motor is disposed in the second sub-chamber and coupled to the impeller assembly.

[0012] In some embodiments, the second housing includes an outwardly protruding portion adjacent to the axial flow impeller, wherein one or more through holes are formed on a side of the outwardly protruding portion to define the pump inlet.

[0013] In some embodiments, a top of the outward protruding portion is formed with a cylindrical body that is inserted into the hollow body portion from the first end.

[0014] In another aspect, the present invention provides a liquid transfer pump, which includes: a first housing defining a containment chamber; a second housing including a pump inlet, a pump outlet, and a pump chamber fluidly connecting the pump inlet and the pump outlet, wherein the second housing includes an outwardly extending nozzle which surrounds an opening that defines the pump inlet, wherein an edge of the nozzle defines a plurality of circumferentially distributed notches; an impeller assembly at least partially disposed within the pump chamber of the second housing, including a centrifugal impeller and an axial flow impeller arranged coaxially in series with the centrifugal impeller, wherein the axial flow impeller is disposed adjacent to the nozzle of the second housing; and a drive assembly, at least partially disposed within the containment chamber of the first housing, configured to drive the impeller assembly.

[0015] In some embodiments, the drive assembly is configured to drive the axial flow impeller to rotate, thereby drawing liquid from the pump inlet into the pump chamber, and to drive the centrifugal impeller to rotate, thereby conveying the liquid drawn in by the axial flow impeller through the pump chamber to the pump outlet.

[0016] In some embodiments, the drive assembly includes a drive shaft, wherein the centrifugal impeller and the axial impeller are sleeved onto the drive shaft.

[0017] In some embodiments, the drive assembly includes a brushless DC motor.

[0018] Compared with the conventional technology, embodiments of the present invention solve the airlock problem without adding extra water pipes or nozzles, and also improves the practicality and economy of the liquid transfer pump. By adding an axial flow pump at the front end of the centrifugal pump, the air inside the pump chamber and impeller is forcibly expelled at the start of the liquid transfer pump operation, preventing airlock in the centrifugal pump. This not only improves the reliability and stability of the liquid transfer pump, but also extends its service life and reduces maintenance costs. Secondly, the pump uses the same rotational speed to drive both the centrifugal pump and the axial flow pump, simplifying the equipment design and reducing the complexity and cost of the equipment.BRIEF DESCRIPTION OF DRAWINGS

[0019] The features, advantages and other aspects of the various embodiments of the present invention will become more apparent with reference to the following detailed description in conjunction with the accompanying drawings, in which several embodiments of the present invention are shown in an illustrative and non-limiting manner. In the accompanying drawings:

[0020] FIG. 1 is a cross-sectional view of a liquid transfer pump according to one embodiment of the present invention;

[0021] FIG. 2 is a schematic bottom view of a liquid transfer pump according to one embodiment of the present invention;

[0022] FIG. 3 is a schematic diagram of an integrated rotor and impeller according to one embodiment of the present invention;

[0023] FIG. 4 is a schematic diagram of a centrifugal impeller according to one embodiment of the present invention;

[0024] FIG. 5 is cross-sectional view from another and of an integrated rotor and impeller assembly according to one embodiment of the present invention;

[0025] FIG. 6 is a schematic bottom view of an integrated rotor and impeller assembly according to one embodiment of the present invention;

[0026] FIG. 7 is an exploded schematic diagram of a liquid transfer pump according to one embodiment of the present invention;

[0027] FIG. 8 is a cross-sectional view of a liquid transfer pump according to another embodiment of the present invention;

[0028] FIG. 9 is a schematic bottom view of a liquid transfer pump according to another embodiment of the present invention;

[0029] FIG. 10 is an exploded schematic diagram of a liquid transfer pump according to another embodiment of the present invention.DETAILED DESCRIPTION OF THE INVENTION

[0030] Embodiments of the present invention are described in detail below with reference to the drawings. In the specification and drawings, like features are designated by like reference symbols. The descriptions below should be taken as explanations of the overall inventive concept of the present invention and should not be construed as a limitation on the present invention.

[0031] In the descriptions below, terms such as “including” are intended to be open-ended and mean “including without limitation”, and can include other contents. “Based on” means “at least partly based on.”“An embodiment” means “at least one embodiment.”“Another embodiment” means “at least another embodiment,” etc.

[0032] Current technologies primarily address the problem of airlock in centrifugal pumps by installing a priming pipe or nozzle within the pump chamber to expel air, allowing the pump to operate normally. However, if air re-enters the pump chamber, the pump will still fail to function properly. Therefore, existing technologies not only increase the complexity and cost of liquid transfer pumps but also have significant limitations.

[0033] The liquid transfer pump according to various embodiments of the present invention can effectively solve the problem of airlock by incorporating an axial flow pump at the front end of the centrifugal pump. The self-priming capability of the axial flow pump generates negative pressure, thereby expelling air within the entire pump chamber. The liquid transfer pump according to various embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0034] FIG. 1 shows a cross-sectional view of a liquid transfer pump according to one embodiment of the present invention; FIG. 2 shows a schematic bottom view of the liquid transfer pump of the embodiment. Referring to FIGS. 1 and 2, the exemplary liquid transfer pump 10 includes a first housing 11, a second housing 12, an impeller assembly 13, and a drive assembly 16. The second housing 12 includes a pump inlet 121, a pump outlet 122, and a pump chamber 123 that fluidly connects the pump inlet 121 and the pump outlet 122.

[0035] The impeller assembly 13 is at least partially disposed within the pump chamber 123 of the second housing 12. The impeller assembly 13 includes a centrifugal impeller 14 and an axial impeller 15. The axial impeller 15 may be located adjacent to the pump inlet 121 of the second housing 12.

[0036] The structure of the impeller assembly 13 may take various forms. In one embodiment, the impeller assembly 13 may include a hollow body portion 131. The hollow body portion 131 may include a first end 132a located adjacent to the pump inlet 121 and a second end 132b opposite to the first end 132a and located away from the pump inlet 121. The axial flow impeller 15 may be formed at the first end 132a of the hollow body portion 131, and a centrifugal impeller 14 may be formed at the second end 132b of the hollow body portion 131. In one embodiment, the second end 132b of the hollow body portion 131 may be located adjacent to the pump outlet 122.

[0037] The drive assembly 16 is at least partially disposed within a containment chamber 111 of the first housing 11 to drive the impeller assembly 13. In one embodiment, the drive assembly 16 may drive the axial flow impeller 15 to rotate, drawing liquid from the pump inlet 121 into the pump chamber 123, and drive the centrifugal impeller 14 to rotate, conveying the liquid drawn in by the axial flow impeller 15 through the pump chamber 123 to the pump outlet 122. When the drive assembly 16 drives the axial flow impeller 15 to rotate, the axial flow impeller 15 draws liquid from outside the liquid transfer pump 10 into the pump inlet 121 through the axial force generated by its rotation. Because the axial flow impeller 15 generates a self-priming force when rotating, a negative pressure is formed at the pump inlet 121, helping the liquid to quickly fill the pump chamber 123, pushing any air originally present in the pump chamber 123 towards the pump outlet 122 and expelling it, ensuring that no air remains in the pump chamber 123. At the same time, the drive assembly 16 drives the centrifugal pump 14 to rotate. Under the rotation of the axial flow impeller 15, the pump chamber 123 is cleared of air and filled with liquid. The centrifugal force generated by the rotation of the centrifugal impeller 14 further pressurizes the liquid in the pump chamber 123 and propels the liquid towards the pump outlet 122, finally discharging the liquid from the pump outlet 122.

[0038] In one embodiment, the axial impeller 15 and the centrifugal impeller 14 may be arranged to rotate coaxially. Coaxial rotation ensures that the centrifugal impeller 14 and the axial impeller 15 rotate at the same speed, simplifying the equipment design and reducing the complexity and cost of the equipment.

[0039] In one embodiment, the impeller assembly 13 may be integrally formed. However, in other embodiments, the axial impeller 15 and the centrifugal impeller 14 in the impeller assembly 13 may be two separate components.

[0040] In one embodiment, the second housing 12 also includes an outwardly protruding portion 124 adjacent to the axial flow impeller 15. The side of the outwardly protruding portion 124 may be formed with a plurality of evenly distributed through holes 125 (e.g., four through holes), which define the pump inlet 121. It is understood that the number of through holes 125 is not limited to four, and may be set according to practical needs. A cylindrical body 126 is also formed on the top of the outwardly protruding portion 124, inserted from the first end 132a into the hollow body portion 131, so that the liquid entering the pump cavity 123 through the through holes 125 flows axially upward along the cylindrical body 126.

[0041] In one embodiment, the drive assembly 16 may be a brushless DC (direct current) motor. Brushless DC motors typically reduce wear due to the absence of carbon brushes, thereby improving motor efficiency and reliability, while also offering the advantage of low noise. However, in other embodiments, the drive assembly 16 may also be other types of motors or structures with driving capabilities.

[0042] In one embodiment, the containment chamber 111 defined by the first housing 11 may also include a first sub-chamber 111a and a second sub-chamber 111b. The stator 161 of the brushless DC motor may be disposed within the first sub-chamber 111a. The rotor 162 of the brushless DC motor may be disposed within the second sub-chamber 111b and coupled to the impeller assembly 13 to drive the centrifugal impeller 14 and the axial impeller 15 in the impeller assembly 13 to rotate.

[0043] The stator 161 may be made, for example, by stacking silicon steel sheets and winding coils around them. An electrical current is supplied through a motor driver (not shown) to activate the drive assembly 16 and generate a rotating magnetic field in the stator 161. The rotor162 may be made, for example, of a ring-shaped plastic casing enclosing a magnetic ring, or of other materials with good conductivity such as copper or aluminum. The rotor 162 is cut by the magnetic field lines generated by the stator 161, thereby generating current. These currents interact with the magnetic field generated by the stator 161, forming an electromagnetic torque that drives the rotor 162 to rotate continuously.

[0044] FIG. 3 shows a schematic diagram of an integrated rotor and impeller assembly according to one embodiment of the present invention; FIG. 4 shows a schematic diagram of a centrifugal impeller according to one embodiment of the present invention. Referring to FIGS. 3 and 4, the centrifugal impeller 14 is coupled to the rotor 162, forming an integrated structure of the rotor 162 and impeller assembly 13. In one embodiment, the second end 132b of the hollow body portion 131 of the impeller assembly 13 may also include a radially outwardly extending disc-shaped portion 133. The centrifugal impeller 14 may include a plurality of centrifugal blades 141, which are circumferentially spaced and arranged on the disc-shaped portion 133. The number of centrifugal blades 141 may be two or more, and they are arranged centrally symmetrically on the disc-shaped portion 133. The inner wall of the hollow portion 1621 of the rotor 162 may also include a bearing 18, which supports the rotation of the rotor 162 and can effectively reduce the friction generated during the rotation of the rotor 162, ensuring its rotational accuracy and reducing maintenance costs in subsequent use. The bearing 18 may be made of graphite material, or other materials with good self-lubricating properties, chemical stability, and high-temperature resistance.

[0045] FIG. 5 shows a cross-sectional view from another angle of the integrated rotor and impeller according to one embodiment of the present invention; FIG. 6 shows a bottom view of the integrated rotor and impeller according to one embodiment of the present invention. Referring to FIGS. 5 and 6, the axial flow impeller 15 includes a plurality of axial flow blades 151, which are circumferentially spaced and arranged on the inner wall of the first end 132a of the hollow body 131. The number of axial flow blades 151 may be two or more, and may be set according to practical needs. For example, when the head of the axial flow pump formed by the axial flow impeller 15 is not higher than two meters, the number of axial flow blades 151 may be two to four; when the head is higher than two meters, the number of axial flow blades 151 may be five to ten.

[0046] Centrifugal pumps formed by centrifugal impeller 14 typically have low flow rate and high head characteristics, while axial flow pumps formed by axial flow impeller 15 typically have high flow rate and low head characteristics. Therefore, when the centrifugal impeller 14 and the axial flow impeller 15 rotate coaxially, if the ratio of the height H of the axial flow blade 151 to the diameter D of the axial flow impeller 15 is set improperly, it will negatively affect the performance of the centrifugal pump. Possible negative effects include, for example, reduced pump head, reduced flow rate, increased noise, and increased power consumption of the entire liquid transfer pump system. Therefore, based on experimental data analysis, it was concluded that when the ratio of the height H of the axial flow blade 151 to the diameter D of the axial flow impeller 15 is within the range of 0.3 to 0.6, it can effectively solve the problem of airlock in the centrifugal pump and ensure that it does not negatively affect the liquid transfer pump.

[0047] FIG. 7 shows an exploded schematic diagram of a liquid transfer pump according to one embodiment of the present invention. Referring to FIG. 7, a pump shaft 17 is first inserted into the top groove 1261 of the cylindrical body 126 at the top of the outwardly protruding portion 124 of the second housing 12. The pump shaft 17 may be made of ceramic material, for example, or other materials with good corrosion resistance, wear resistance, and high hardness. Then, the pump shaft 17 is passed through the hollow body portion 131 of the impeller assembly 13 so that the impeller assembly 13 is sleeved on the pump shaft 17, and the cylindrical projection 126 is inserted into the hollow body portion 131. Because the rotor 162 and the impeller assembly 13 are integrated, the pump shaft 17 also passes through the hollow portion 1621 of the rotor 162 so that the rotor 162 is sleeved on the pump shaft 17. Finally, the first housing 11, which already contains the stator 161 (not shown), is sleeved onto the outside of the integrated rotor 162 and impeller assembly 13 and fixedly installed on the second housing 12. The first housing 11 and the second housing 12 may be assembled together in various suitable ways, such as screw connection, snap connection, or rigid connection. When the liquid transfer pump 10 is operating, both the rotor 162 and the impeller assembly 13 will rotate around the pump shaft 17 as their center.

[0048] FIG. 8 shows a cross-sectional view of a liquid transfer pump according to another embodiment of the present invention; FIG. 9 shows a bottom schematic view of a liquid transfer pump according the other embodiment of the present invention. Referring to FIGS. 8 and 9, the exemplary liquid transfer pump 20 includes a first housing 21, a second housing 22, an impeller assembly 23, and a drive assembly 26. The second housing 22 includes a pump inlet 221, a pump outlet 222, and a pump chamber 223 that fluidly connects the pump inlet 221 and the pump outlet 222. The second housing 22 may also include an outwardly extending nozzle 224, which surrounds an opening that defines the pump inlet 221.

[0049] The edge of the nozzle 224 has multiple circumferentially distributed notches 225 (for example, four grooves). It is understood that the number of notches 225 is not limited to four, and the number may be set according to practical needs. The notches 225 allow liquid to enter the pump chamber 223 from the pump inlet 221 and contact the impeller assembly 23 at the start of the liquid transfer pump 20 operation, allowing some of the air in the pump chamber 223 to be discharged from the notches 225.

[0050] The impeller assembly 23 is at least partially disposed within the pump chamber 223 of the second housing 22. The impeller assembly 23 includes a centrifugal impeller 24 and an axial impeller 25 arranged coaxially in series with the centrifugal impeller 24. The axial impeller 25 may be positioned adjacent to the nozzle 224 of the second housing 22.

[0051] In one embodiment, the axial flow impeller 25 may also include axial flow blades 251 and an axial flow hub 252, with the axial flow blades 251 arranged circumferentially spaced apart on the axial flow hub 252. The number of axial flow blades 251 may be two or more, and may be set according to practical needs.

[0052] The drive assembly 26 is at least partially disposed within the containment chamber 211 of the first housing 21 to drive the impeller assembly 23. In one embodiment, the drive assembly 26 can drive the axial flow impeller 25 to rotate, drawing liquid from the pump inlet 221 into the pump chamber 223, and drive the centrifugal impeller 24 to rotate, conveying the liquid drawn in by the axial flow impeller 25 through the pump chamber 223 to the pump outlet 222. When the drive assembly 26 drives the axial flow impeller 25 to rotate, the axial flow impeller 25 will draw liquid from outside the liquid transfer pump 20 into the pump inlet 221 through the axial force generated by its rotation. Because the axial flow impeller 25 generates a self-priming force when rotating, a negative pressure can be formed at the pump inlet 221, helping the liquid to quickly fill the pump chamber 223, so that the air originally present in the pump chamber 223 is pushed towards the pump outlet 222 by the liquid flow and discharged, ensuring that no air remains in the pump chamber 223. At the same time, the liquid flows axially upward along the outside of the axial flow hub 252 of the axial flow impeller 25 and enters the centrifugal impeller 24 through the opening 241 at the bottom of the centrifugal impeller 24. Under the rotation of the axial flow impeller 25, the pump chamber 223 is cleared of air and filled with liquid. The centrifugal force generated when the drive assembly 26 drives the centrifugal impeller 24 to rotate further pressurizes the liquid in the pump chamber 223 and pushes the liquid towards the pump outlet 222, and finally the liquid is discharged from the pump outlet 222.

[0053] In one embodiment, the drive assembly 26 may be a brushless DC motor. Brushless DC motors are typically preferred because the absence of carbon brushes reduces wear, thereby improving motor efficiency and reliability, while also offering the advantage of low noise. However, in other embodiments, the drive assembly 26 may also be other types of motors or structures with driving capabilities.

[0054] In one embodiment, the containment chamber 211 defined by the first housing 21 may also include a first sub-chamber 211a and a second sub-chamber 211b. The stator 261 of the brushless DC motor may be disposed within the first sub-chamber 211a. The rotor 262 of the brushless DC motor may be disposed within the second sub-chamber 211b.

[0055] In one embodiment, the drive assembly 26 may also include a drive shaft 263, which is fixedly connected to the rotor 262 through a first bearing 27. The drive shaft 263 may be made of ceramic material, for example, or other materials with good corrosion resistance, wear resistance, and high hardness. The top of the drive shaft 263 is fixed within the second sub-chamber 211b by a second bearing 28. Both the first bearing 27 and the second bearing 28 may be made of graphite material, for example, or other materials with good self-lubricating properties, chemical stability, and high temperature resistance. When the rotor 262 continuously rotates due to electromagnetic torque, it drives the drive shaft 263 to rotate, and further drives the impeller assembly 23, which is coaxially connected in series on the drive shaft 263, to rotate.

[0056] FIG. 10 shows an exploded schematic diagram of a liquid transfer pump according to another embodiment of the present invention. Referring to FIG. 10, the centrifugal impeller 24 is first sleeved onto the lower end of the drive shaft 263, which is fixedly connected to the rotor 262, through the central hollow portion 242 of the centrifugal impeller 24. Then, the axial flow impeller 25 is sleeved onto the lower end of the drive shaft 263 through the central hollow portion 253 of the axial flow hub 252. Both the centrifugal impeller 24 and the axial flow impeller 25 may be affixed to the drive shaft 263 using snap-fit ​​or other suitable fixing methods. Finally, the first housing 21, which accommodates the stator 261 (not shown), is sleeved onto the outside of the liquid transfer pump 20 and fixedly installed on the second housing 22. The first housing 21 and the second housing 22 may be assembled together in various suitable ways, such as screw connection, snap-fit ​​connection, or rigid connection. When the liquid transfer pump 20 is operating, the rotor 262 drives the centrifugal impeller 24 and the axial flow impeller 25 connected to the same drive shaft 263, causing the centrifugal impeller 24 and the axial flow impeller 25 to maintain the same rotational speed.

[0057] The pump according to embodiments of the present invention solves the problem of airlock without adding extra water pipes or nozzles, and also improves the practicality and economy of liquid transfer pumps. By adding an axial flow pump to the front end of the centrifugal pump, the air inside the pump chamber and impeller is forcibly expelled at the start of the liquid transfer pump operation, preventing airlock in the centrifugal pump. This not only improves the reliability and stability of the liquid transfer pump, but also extends its service life and reduces maintenance costs. Furthermore, the pump uses the same rotational speed to drive both the centrifugal pump and the axial flow pump, simplifying the equipment design and reducing its complexity and cost.

[0058] While various embodiments are described above, the present invention is not limited to these embodiments. For those skilled in the art, the embodiments of the present invention may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the embodiment of the present invention are within the scope of the present invention.

[0059] Although the embodiments of the present invention have been described, it should be understood that the present invention is not limited to the disclosed specific embodiments. The embodiments of the present invention are intended to cover various modifications and equivalent arrangements included in the spirit and scope of the appended claims. The scope of the appended claims should be given the broadest reasonable interpretation, and cover all such modifications and equivalent structures and functions.

Claims

1. A liquid transfer pump, comprising: a first housing defining a containment chamber; a second housing including a pump inlet, a pump outlet, and a pump chamber fluidly connecting the pump inlet and the pump outlet; an impeller assembly at least partially disposed within the pump chamber of the second housing, including a centrifugal impeller and an axial flow impeller,wherein the impeller assembly includes a hollow body portion, the hollow body portion including a first end located adjacent to the pump inlet and a second end opposite the first end and located away from the pump inlet, the axial flow impeller being formed at the first end of the hollow body portion, and the centrifugal impeller being formed at the second end of the hollow body portion; and a drive assembly, at least partially disposed within the containment chamber of the first housing, configured to drive the impeller assembly.

2. The liquid transfer pump of claim 1, wherein the drive assembly is configured to drive the axial flow impeller to rotate, thereby drawing liquid from the pump inlet into the pump chamber, and to drive the centrifugal impeller to rotate, thereby conveying the liquid drawn in by the axial flow impeller through the pump chamber to the pump outlet.

3. The liquid transfer pump of claim 2, wherein the impeller assembly is integrally formed, and the axial flow impeller and the centrifugal impeller rotate coaxially.

4. The liquid transfer pump of claim 1, wherein the second end of the hollow body includes a radially outwardly extending disc-shaped portion, the centrifugal impeller includes a plurality of centrifugal blades circumferentially spaced apart on the disc-shaped portion, and the axial flow impeller includes a plurality of axial flow blades circumferentially spaced apart on an inner wall of the first end.

5. The liquid transfer pump of claim 1, wherein the drive assembly includes a brushless DC motor.

6. The liquid transfer pump of claim 5, wherein the containment chamber of the first housing includes a first sub-chamber and a second sub-chamber, wherein a stator of the brushless DC motor is disposed in the first sub-chamber, and a rotor of the brushless DC motor is disposed in the second sub-chamber and coupled to the impeller assembly.

7. The liquid transfer pump of claim 1, wherein the second housing includes an outwardly protruding portion adjacent to the axial flow impeller, wherein one or more through holes are formed on a side of the outwardly protruding portion to define the pump inlet.

8. The liquid transfer pump of claim 7, wherein a top of the outward protruding portion is formed with a cylindrical body that is inserted into the hollow body portion from the first end.

9. A liquid transfer pump, comprising:a first housing defining a containment chamber; a second housing including a pump inlet, a pump outlet, and a pump chamber fluidly connecting the pump inlet and the pump outlet, wherein the second housing includes an outwardly extending nozzle which surrounds an opening that defines the pump inlet, wherein an edge of the nozzle defines a plurality of circumferentially distributed notches; an impeller assembly at least partially disposed within the pump chamber of the second housing, including a centrifugal impeller and an axial flow impeller arranged coaxially in series with the centrifugal impeller, wherein the axial flow impeller is disposed adjacent to the nozzle of the second housing; and a drive assembly, at least partially disposed within the containment chamber of the first housing, configured to drive the impeller assembly.

10. The liquid transfer pump of claim 9, wherein the drive assembly is configured to drive the axial flow impeller to rotate, thereby drawing liquid from the pump inlet into the pump chamber, and to drive the centrifugal impeller to rotate, thereby conveying the liquid drawn in by the axial flow impeller through the pump chamber to the pump outlet.

11. The liquid transfer pump of claim 9, wherein the drive assembly includes a drive shaft, wherein the centrifugal impeller and the axial impeller are sleeved onto the drive shaft.

12. The liquid transfer pump of claim 9, wherein the drive assembly includes a brushless DC motor.

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