CN114810609A

CN114810609A - Multi-stage vane pump with special flow guide structure and multi-stage partial flow pump

Info

Publication number: CN114810609A
Application number: CN202210406045.3A
Authority: CN
Inventors: 卢才美
Original assignee: Wenling Gaoshen Pump Technology Co ltd
Current assignee: Wenling Gaoshen Pump Technology Co ltd
Priority date: 2022-04-19
Filing date: 2022-04-19
Publication date: 2022-07-29
Also published as: CN118088493A

Abstract

The invention belongs to a multi-stage vane pump with a special flow guide structure and a multi-stage partial flow pump with a special flow guide structure in fluid machinery, solves the problems of large hydraulic loss, heavy weight, large occupied space and unsatisfactory flow guide performance of the flow guide structure of the conventional multi-stage pump, and solves the design and manufacturing problems of pumps with low specific speed. Is characterized in that: the pump cover and the guide vane or the pump body are provided with part guide seats corresponding to the outer sides of the impellers, one or more spiral guide surfaces are arranged on the guide seats or the various guide seat assemblies and in a space formed by the inner sides of the guide seats and the cylindrical surfaces or the conical surfaces on the outer sides of the impellers, and the multiple single-stage assemblies are assembled into various multi-stage pumps. The fluid is mainly guided in a tangential flow mode, the structure of the guide vane can be called a tangential guide vane, and the guide vane is a guide vane with a special guide mode after a radial guide vane, a flow passage type guide vane and a space guide vane of a multi-stage vane pump. The device is mainly used in the chemical industry, the petrochemical industry and the like which need high pressure and in the occasions which need small and exquisite structure and light weight.

Description

Multi-stage vane pump with special flow guide structure and multi-stage partial flow pump

Technical Field

The invention belongs to a multistage pump in fluid machinery, and relates to a guide vane type multistage vane pump and a multistage fractional flow pump.

Background

In the guide vane type multistage vane pump, especially in guide vane type multistage centrifugal pump, guide vane type multistage mixed flow pump, all be provided with radial formula guide vane, including the water conservancy diversion structure of positive guide vane, annular space bend, reverse guide vane, there are radial oversize, heavy scheduling problem, and the speed direction of its liquid need pass through from radial to axial, again through from axial to radial twice sharp turn transform, the runner of passing through the guide vane gets into the import department of next stage impeller. The large hydraulic loss of liquid turning, collision, local vortex and the like exists, and the ideal performance cannot be achieved.

In a multi-stage partial flow pump, such as the patent application of CN202110317417.0, the flow guiding performance is affected to some extent due to the absence of flow guiding structure.

The guide vane type multistage vane pump and the multistage partial flow pump are hereinafter referred to as multistage pumps, the radial guide vanes with front guide vanes and annular spaces removed and only reverse guide vanes reserved are hereinafter referred to as guide vanes, the arc diffusion chambers of the multistage partial flow pump are hereinafter referred to as diffusion chambers, and parts with the diffusion chambers are hereinafter referred to as pump bodies.

Disclosure of Invention

The purpose of the invention is: the single-stage component of the multistage pump with the special flow guide structure has the advantages of simple structure, easiness in manufacturing, improvement of flow guide performance and reduction of hydraulic loss, and the weight and the size of the multistage vane pump can be reduced.

Another object of the invention is: the multi-stage pump can be developed and provided with a plurality of multi-stage pump products with special flow guide structures by using a plurality of single-stage assemblies for assembly, and the problem that the multi-stage pump, particularly the multi-stage pump with low specific speed, is complex in design is solved.

The former object of the present invention can be achieved by the following technical solutions: the multistage vane pump of special water conservancy diversion structure and the multistage fractional flow pump of special water conservancy diversion structure, its single-stage subassembly includes: impeller and both sides part pump cover, stator or the pump body, characterized by: the pump cover and the guide vane or the pump body are provided with a single part guide seat corresponding to the outer side of the impeller blade or a guide seat assembly combined with the pump cover, the guide vane or the pump body, and one or more spiral guide surfaces are arranged on the guide seat or the guide seat assembly and in a space formed by the inner side of the guide seat or the guide seat assembly and a cylindrical surface or a conical surface formed by the outer side of the impeller blade.

According to the multi-stage pump, the guide seat assembly can further comprise the following structures: (1) the guide seat and the pump cover are cast into a whole; (2) the guide seat and the guide vane or the pump body are cast into a whole; (3) the guide base, the guide vane or the pump body and the next-stage pump cover are cast into a whole; (4) the guide base, the guide vane or the pump body, the next-stage pump cover and the next-stage guide base are cast into a whole; (5) the guide vane or pump body is cast with the next-stage pump cover and the next-stage guide seat into a whole.

According to the multistage pump, the terminal point surface of the spiral flow guide surface can be connected with the bottom of the guide vane of the multistage vane pump or the bottom of the diffusion chamber of the multistage partial flow pump in a connecting mode; or adopting a contact joint mode; or a double-bevel joint mode is adopted.

According to the multi-stage pump, the spiral flow guide surface can be formed by connecting positive spiral surfaces, oblique spiral surfaces or oblique spiral surfaces with curved generatrices with different lead lengths; or the spiral flow guide surface can be composed of long spiral surfaces or long and short spiral surfaces which are arranged in groups at intervals; or different combinations of the above structures; the inner end of the cross section of the spiral surface can also be provided with a chamfer or/and a casting fillet is arranged at the joint of the inner end of the cross section of the spiral surface and the outer wall of the flow guide seat or the flow guide seat assembly.

According to the multistage pump described above, the impeller type of the multistage vane pump may be closed or semi-open; the impeller type of the multi-stage partial flow pump can be open type, semi-open type or between the open type and the semi-open type; or a twisted blade surface is arranged at the excircle part of the blade.

According to the multistage pump, a boss can be arranged at the position, corresponding to the guide vane flow channel, of the bottom of the pump cover of the multistage pump or at the position of the flow channel of the diffusion chamber of a partial flow pump, or/and a flow guide conical surface can be arranged at the position, corresponding to the inlet of the impeller, of the bottom of the pump cover of the multistage pump; or/and an interstage seal may be provided at the guide vane or pump body inner circle.

According to the multistage pump, the throat part of the partial flow pump can be arranged in front of the diffusion chamber after the spiral flow guide surface terminal surface of the multistage partial flow pump.

The other purpose of the invention can be realized by the following technical scheme: the multi-stage vane pump with various special flow guide structures and the multi-stage partial flow pump with the special flow guide structures are assembled by using a plurality of single-stage assemblies of any one of the above parts and combining with other spare parts. According to the multi-stage pump described above, the suction port of the impeller and the relevant portions of the corresponding parts can be accessed to the motor or other power output end, constituting an inverted type multi-stage pump as opposed to a general multi-stage pump arrangement.

According to the multistage pump, each set of single-stage components can be fastened through a plurality of pull rods; or mechanically pressed and fastened in the pump cylinder; or one of the single-stage components is welded with the pump barrel or other pump bases into a whole after being pressed.

Compared with the prior art, the invention has the beneficial effects that:

compared with the existing guide vane type multistage vane pump, the guide vane type multistage vane pump is provided with the spiral guide vane, the positive guide vane and the annular space are removed, the hydraulic loss caused by two sharp turns of liquid flow is avoided, the radial and axial spaces occupied by the original positive guide vane are avoided, the radial space occupied by the original annular space can be reduced, and the weight is also reduced. Compared with a multi-stage partial flow pump, the multi-stage partial flow pump has the advantages that the spiral flow guide surface is added, the flow guide performance is improved or enhanced, the hydraulic loss is reduced, and the liquid can be guided to the diffusion chamber in all directions at every angle.

The guide vane has a structure which can be called a tangential guide vane, a circumferential guide vane or an axial guide vane, is a radial guide vane, a flow passage type guide vane of a multi-stage vane pump and is a new guide vane with a special guide structure behind a space guide vane, and has smooth guide and high efficiency. The pump is particularly suitable for multi-stage pumps with high speed, high pressure and small flow, because the impeller blades of the pumps are arranged at a large angle, the absolute speed of liquid flow is close to the peripheral speed, namely the tangential speed, and the pump needs a tangential flow guiding mode to guide the flow.

The invention can avoid the problems, can obtain products with different specifications only by adjusting the diameter of the impeller or/and the width of the spiral guide surface, can produce numerous products by selecting impellers with different types and sizes and the spiral guide surface designed by only using three simple parameters of a spiral angle, the width of the spiral guide surface and the area of a flow passage inlet, is equivalent to another large series of products of the current multistage pump, breaks through the development situation of the multistage pump which has not been developed for decades, and solves the problem that the design of the multistage pump, particularly the multistage pump with low specific speed is complicated.

At present, no multi-stage partial flow pump products are sold, the design and the manufacture of the products are realized in a simple mode, and the blank of multi-stage partial flow pumps or guide vane type multi-stage partial flow pumps in product classification is filled. Can become a unique variety in the world.

Compared with the prior multistage vane pump guide vane which has narrow and long flow passage and is difficult to cast, the invention has simple structure and easy manufacture.

The multistage pump of the present invention is also simple to assemble and can be assembled into various multistage pumps. The assembly and fastening can be realized by various methods, and the type arrangement is flexible, such as an inverted type structure, thereby improving the operation reliability and reducing the manufacturing cost.

The multistage pump of the invention meets the gas diversion characteristic due to simple structure, good heat dispersion, thin flow deflector and large variability of impeller type, and can also convey other fluids besides liquid, such as gas, gas-liquid mixture and the like.

Drawings

FIG. 1 is a schematic view of a multi-stage fractional flow pump with a special flow guide structure, in which a spiral flow guide surface is arranged in a combined member in which a flow guide seat and a pump cover are cast into a whole;

FIG. 2 is a schematic view of a multi-stage vane pump with a special flow guide structure, in which a spiral flow guide surface is arranged in a combined member in which a flow guide seat and a pump cover are cast into a whole;

FIG. 3 is a schematic view of a multi-stage pump having a spiral flow guide surface in an assembly of a flow guide base and a pump body that are integrally molded;

FIG. 4 is a schematic view of a multi-stage pump with a spiral flow guide surface in the assembly of the flow guide base with the pump body and the next stage pump cover cast as one piece;

FIG. 5 is a schematic view of a multi-stage pump with a spiral flow guide surface in an assembly of a flow guide with a pump body, a next stage pump cover and a next stage flow guide cast as one piece;

FIG. 6 is a schematic view of a multi-stage pump with a spiral flow guide surface in the assembly of the pump body with the next stage pump cover and the next stage flow guide seat cast as one piece;

FIG. 7 is a perspective view of a multi-stage pump with various spiral flow guide surfaces disposed in a flow guide seat;

FIG. 8 is a schematic diagram of a spiral flow guide surface and a throat part of a multi-stage partial flow pump with a special flow guide structure;

fig. 9 is a schematic diagram of an impeller provided with a twisted blade surface at the outer circle part of the blade.

Detailed Description

The following are specific embodiments of the present invention and are further described with reference to the drawings, but the present invention is not limited to these embodiments.

As shown in fig. 1, the multi-stage partial flow pump with a special flow guiding structure is provided, wherein an impeller 7 is a partial flow pump impeller, and is usually mainly composed of radial straight blades, a pump cover 10 and a pump body 4 are provided on two side parts, a part corresponding to the outer cylindrical surface of the blade of the impeller 7 is a flow guiding seat 8, and the flow guiding seat 8 and the pump cover 10 are cast into a flow guiding seat assembly.

As shown in fig. 2, the multi-stage vane pump with a special flow guide structure is provided, the impeller 17 is a centrifugal or mixed flow type impeller, the pump cover 20 and the guide vane 14 are arranged on two side parts of the impeller, the part corresponding to the outer cylindrical surface of the vane of the impeller 17 is a flow guide seat 18, and the flow guide seat 18 and the pump cover 20 are cast into an integrated flow guide seat assembly. If the blades of the mixed-flow impeller 17 are inclined, the outer conical surfaces of the blades are formed. The blades of the centrifugal or mixed flow impeller 17 and the partial flow pump impeller 7 can also be set in an inclined state, namely the diameter of one side of the blade on the rear cover plate is smaller than that of the other end of the blade, and the outer side of the blade forms a conical surface. The impeller 17 may be sealed by a seal flat surface 21 provided on the pump cover 20, or may be sealed by another impeller seal ring such as a cylindrical ring.

One or more

spiral guide surfaces

9 and 19 are arranged on the

guide bases

8 and 18 or the guide base assembly thereof and in the space with the cylindrical surface or the conical surface configuration formed by the inner sides of the guide bases and the outer sides of the blades of the

impellers

7 and 17, and the spiral guide surfaces are simply as follows: namely, a spiral guide surface is arranged outside the impeller. The liquid can be guided to the inlet 5 of the diffusion chamber of the partial flow pump of the current stage or the inlet 15 of the guide vane channel of the multi-stage pump, and then guided to the inlet of the next-stage impeller through the diffusion chamber or the guide vane channel, so that the flow guide of the current stage is finished. The structure of the diffusion chamber is described in CN202110317417.0 patent application. The thickness of the

spiral guide surfaces

9 and 19 is similar to that of the

guide seats

8 and 18.

As shown in fig. 3, the guide seat 8 and the pump body 4 or the guide seat 18 and the guide vane 14 are cast into a guide seat assembly 22, and one or more spiral guide surfaces 23 are arranged on the guide seat assembly 22 and in a space formed by a cylindrical surface or a conical surface formed by the inner side of the guide seat and the outer side of the blade of the impeller 7 or the impeller 17, and can be cast into a whole with the starting point of the arc-shaped diffusion chamber bottom 6 or the guide vane bottom 16 of the partial flow pump, and the spiral guide surfaces are called a connection mode, so that the bottom surface of the flow channel is in smooth transition, and the liquid flow loss is further reduced. Other descriptions of this figure are described in fig. 1 and fig. 2.

As shown in fig. 4, the flow guide assembly 22 may be integrally molded with the next-

stage pump cover

2, 12 to form a flow guide assembly 24, which reduces the number of parts, and each single-stage assembly has only two parts, namely the impeller 7 and the flow guide assembly 24, based on the structure shown in fig. 3.

As shown in fig. 5, on the basis of the structure shown in fig. 4, the flow guide seat assembly 24 can be cast with the next

flow guide seat

1, 11 into a flow guide seat assembly 26, and one or more spiral flow guide surfaces 25 are arranged thereon, which are equivalent to the spiral flow guide surfaces 9, so that the number of parts can be reduced, the concentricity between the front and rear spiral

flow guide surfaces

23, 25 can be improved, and the product quality can be improved.

Referring to fig. 6, the pump body 4 may be integrally cast with the next-stage pump cover 2 and the next-stage baffle seat 1, or the guide vane 14 may be integrally cast with the next-stage pump cover 12 and the next-stage baffle seat 11 to form a baffle seat assembly 27, as shown in fig. 1, and other descriptions are the same as above.

The bosses 3 or 13 are arranged at the bottom of each stage of pump covers 2, 10, 12, 20 corresponding to the inlet 5 of the diffusion chamber, the inlet 15 of the rest flow channels or guide vanes and the rest flow channels, the area of the flow channels of the diffusion chamber or guide vanes can be adjusted, the height of the bosses 3 or 13 can be changed on the rest flow channels, the diffusion degree of the flow channels can be adjusted, the requirements of products with similar specifications can be met, the generalization degree is improved, or/and the guide conical surfaces 28 are arranged at the central positions of the pump covers 2, 10, 12, 20 at the positions corresponding to the inlets of the

impellers

7, 17, the flow area and the liquid flow in front of the inlets of the

impellers

7, 17 can be enlarged and the smooth transition of the liquid flow can be realized, meanwhile, the liquid reflux at the inlet parts of partial flow pump impellers 7 can be reduced, or/and the interstage seals 29 are arranged at the central positions of the pump body 4 or guide vanes 14 and each guide base assembly, thereby reducing interstage leakage and further improving the volumetric efficiency, the interstage seal 29 may be a high performance stainless steel shell teflon seal, a cylindrical clearance seal, an oil seal, or the like.

Under the conditions of similar product specifications, performances and the like, the impeller 17 and the sealing surface 21 in fig. 2 can be used in the structures in fig. 3 to 6, and the pump body 4 and the assembly thereof are replaced by the guide vane 14 and the assembly thereof, or the speed reduction and the energy increase are carried out by directly utilizing a diffusion chamber of a partial flow pump without replacing, so that the speed can be converted into the pressure energy, and the pressure energy can smoothly enter the next-stage impeller.

As shown in fig. 7, one or more

spiral guide surfaces

9, 19, which are similar to the spiral reinforcing ribs on the inner wall of the cylinder, are arranged on the

guide bases

8, 18 and in the space formed by the cylindrical surface or the conical surface formed by the inner side 33 and the outer side of the impeller blade, and can be spiral guide surfaces formed by connecting

spiral surfaces

31, 32 with different lead lengths, and can be a regular spiral surface, an oblique spiral surface or an oblique spiral surface with a curved generatrix; one or more short helicoids 30 can be arranged between the plurality of

helicoids

9 and 19 to form long and short spaced groups of helicoids. The bus is a straight positive spiral surface, such as a tooth-shaped part of a square thread and a pedal of an annular stair, and the hydraulic performance of the oblique spiral surface with the bus being oblique line or curve is better. The helical surfaces are formed when a helical line and an axis on an outer cylindrical surface of the

impeller

7 or 17 blade outside which a gap is needed are added are wires, if the outer end of the

impeller

7 or 17 blade is in an inclined state, the helical line and the axis on the outer conical surface of the

impeller

7 or 17 blade outside which the gap is needed are formed when the wires are added, the lead of the helical line is equal to the lead of the helical flow guide surface, and the lead is determined when a product is designed. The cross section of the spiral surface, namely the position corresponding to the generatrix, the inner end of the spiral surface can be provided with a chamfer angle similar to a thinning guide vane, or/and the other end of the spiral surface is provided with a casting fillet similar to an oblique spiral surface with the generatrix being curved and the specific function thereof. Different combinations of the above-described patterns may also be utilized.

The terminal surfaces of the

spiral guide surfaces

9, 19 and 25 and the bottom 6 of the diffusion chamber of the multi-stage partial flow pump or the guide vane bottom 16 of the multi-stage vane pump can adopt a contact connection mode; or both the above-mentioned two are made into the inclined plane, carry on the joint mode of the double-inclined plane laminating; this forms one face of the flow channel. Because there is the deviation in manufacturing and installation, allow to have certain clearance, because of there is the inertia of motion in liquid, also can smoothly lead current.

The inner diameter of the spiral surface or the terminal point thereof is the same as or close to the inner diameter of the corresponding flow passage, and a required gap is kept between the inner diameter of the spiral surface or the terminal point and the outer diameter of the corresponding impeller; the spiral surface of the large pump can be manufactured separately and fastened by welding, embedding and other methods, and different materials can be used; the components can be made of metal or nonmetal.

The blades of the

impellers

7 and 17 and various spiral flow guide surfaces are in an intersected state in radial projection, liquid flowing out of the upper half parts of the blades conducts flow guide mainly in a tangential direction through the front surfaces of the spiral flow guide surfaces, and the liquid flowing out of the lower half parts of the blades enters the front surface of the next spiral flow guide surface in a flow form mainly in the tangential direction under the action of the tangential force of the rotation of the impellers in a space between the back surfaces of the spiral flow guide surfaces and the pump cover, so that all liquid in each angle and all directions flows down through the spiral flow guide surfaces to guide the liquid.

The vanes of the

impellers

7 and 17 are larger than the

spiral guide surfaces

9, 19, 23 and 25, each spiral guide surface is provided with a plurality of vanes, the liquid flowing out from the vanes is tangentially acted by the tangential force of the vanes in the previous period, the liquid is acted by the normal reaction force when contacting the inner sides 33 of the

guide seats

8 and 18, the two forces are synthesized to form a circumferential force, so that the liquid flows circumferentially, namely moves circumferentially, and all the liquid is guided down on the spiral guide surfaces in the guide seats or the assemblies thereof. Briefly: in the later stage, the liquid is made to move circularly under the action of the tangential force of the vanes and the counterforce of the wall surface. The resistance to these two flows of fluid is minimal. The flow guide mode can be called a tangential, circumferential or axial flow guide mode, is a special flow guide mode and a special flow guide structure, has much less loss than a radial guide vane, and improves the flow guide performance of the multistage pump.

The

flow guide seats

8 and 18 are simple in structure, convenient to design, easy to manufacture, excellent in performance and strong in universality, and are suitable for mass production.

As shown in fig. 8, the multi-stage fractional flow pump with a special flow guiding structure may be provided with a throat portion 34 of the fractional flow pump connected thereto after the end point of the spiral flow guiding surface 9, and then connected to the diffusion chamber inlet 5. This can improve the dimensional stability of the diffusion chamber inlet channel and also can improve the performance stability of the multi-stage pump. The above structure can also be applied to a multistage vane pump.

As shown in fig. 9, the impeller form of the multistage vane pump may be a closed impeller 17 or a semi-open type; the impeller type of the multi-stage partial flow pump can be an open type impeller 7, a semi-open type impeller or an impeller 7 between the open type impeller and the semi-open type impeller; or a twisted blade surface 36 is arranged at the excircle part of the blades of the

impellers

7 and 17.

The multi-stage components of the multi-stage pump can be formed by using the multiple sets of single-stage components, and various multi-stage pump products can be formed by using other spare parts. The multi-stage pump with similar performance specifications does not need to be changed too much and redesigned. Can meet various requirements of high pressure, high speed, light weight and small volume.

For the multi-stage pump, the suction ports of the

impellers

7 and 17 and the relevant parts of the corresponding parts, such as the guide conical surface 28 and the sealing plane 21 of the pump cover, can be close to the motor or other power output ends to form an inverted multi-stage pump which is opposite to the arrangement of the common multi-stage pump, such as an inverted deep-well pump. This can reduce the requirement of sealing performance between the multi-stage pump and the motor or other power, and can replace the high-pressure sealing device with the low-pressure sealing device, thereby improving the reliability of the multi-stage pump and reducing the cost.

For the multi-stage pump, the radial and axial directions of two adjacent parts can be positioned by the boss cylindrical surfaces of the outer walls and the end surfaces thereof, the circumferential positioning can be realized by adopting a contact joint mode or a joint mode of double-inclined-surface fitting through the bottom 6 of the diffusion chamber or the guide vane bottom 16 and the terminal surfaces of the spiral flow guide surfaces 9, 19 and 25, and the parts can be fastened by various mechanical methods, such as a plurality of pull rods; or threads, pins, etc. are pressed and fastened in the pump barrel 35; one of the pieces of the unit assembly in a maintenance-free product may be welded to the barrel 35 or other pump mount after compression.

The described embodiments of the present invention are merely illustrative of the spirit of the present invention and modifications, substitutions, variations, additions and the like may be made without departing from the principles of the invention without departing from the scope of the invention as defined in the accompanying claims.

Claims

1. The multistage vane pump of special water conservancy diversion structure and the multistage fractional flow pump of special water conservancy diversion structure, hereinafter be referred to as multistage pump for short, its single-stage subassembly includes: impeller and both sides part pump cover, stator or the pump body, characterized by: the guide seat assembly is arranged on the guide seat or guide seat assembly, and one or more spiral guide surfaces are arranged in a space formed by a cylindrical surface or a conical surface formed by the inner side of the guide seat or guide seat assembly and the outer side of the impeller blade.

2. The multistage pump of claim 1, wherein: the flow guide seat assembly can also comprise the following structures: (1) the guide seat and the pump cover are cast into a whole; (2) the guide seat and the guide vane or the pump body are cast into a whole; (3) the guide base, the guide vane or the pump body and the next-stage pump cover are cast into a whole; (4) the guide base, the guide vane or the pump body, the next-stage pump cover and the next-stage guide base are cast into a whole; (5) the guide vane or pump body is cast with the next-stage pump cover and the next-stage guide seat into a whole.

3. A multistage pump according to claim 1 or 2, wherein: the end point surface of the spiral flow guide surface can be connected with the bottom of a guide vane of the multi-stage vane pump or the bottom of an arc-shaped diffusion chamber of the multi-stage partial flow pump in a connecting mode; or adopting a contact joint mode; or a double-bevel joint mode is adopted.

4. The multistage pump of claim 3, wherein: the spiral flow guide surface can be formed by connecting positive spiral surfaces, oblique spiral surfaces or oblique spiral surfaces with curved generatrices in different lead lengths; or the spiral flow guide surface can be composed of long spiral surfaces or long and short spiral surfaces which are arranged in groups at intervals; or different combinations of the above structures; the inner end of the cross section of the spiral surface can also be provided with a chamfer or/and a casting fillet is arranged at the joint of the inner end of the cross section of the spiral surface and the outer wall of the flow guide seat or the flow guide seat assembly.

5. The multistage pump of claim 4, wherein: the impeller type of the multistage vane pump can be closed or semi-open; the impeller type of the multi-stage partial flow pump can be open type, semi-open type or between the open type and the semi-open type; or a twisted blade surface is arranged at the excircle part of the blade.

6. The multistage pump of claim 5, wherein: a boss or/and a flow guide conical surface can be arranged at the position, corresponding to the guide vane flow channel, of the bottom of the multi-stage pump cover or at the position, corresponding to the partial flow pump diffusion chamber flow channel; or/and an interstage seal may be provided at the guide vane or pump body inner circle.

7. The multistage pump of claim 6, wherein: the throat part of the partial flow pump can be arranged behind the spiral flow guide surface terminal surface of the multistage partial flow pump and in front of the arc-shaped diffusion chamber.

8. The multistage pump, characterized by: a single stage assembly comprising a plurality of sets of multi-stage pumps according to any one of claims 1 to 7.

9. The multistage pump of claim 8, wherein: the suction inlet of the impeller and the relevant parts of the impeller can be close to the motor or other power output ends, and an inverted multi-stage pump which is opposite to the general multi-stage pump arrangement is formed.

10. A multistage pump as claimed in claim 8 or 9, wherein: each set of single-stage components can be fastened through a plurality of pull rods; or mechanically pressed and fastened in the pump cylinder; or one of the single-stage components is welded with the pump barrel or other pump bases into a whole after being pressed.