WO2022166205A1 - Sealing structure for centrifugal pump - Google Patents

Abstract

A sealing structure for a centrifugal pump. The centrifugal pump comprises: a motor assembly, a pump shaft (11) and a pump body assembly (20). The pump body assembly (20) comprises a pump sleeve (22) and a plurality of impeller stage groups (200). Each impeller stage group (200) comprises a support housing (60), a flow guide housing (250) and an impeller (70). The impeller (70) comprises a hub portion (72), a conical wall (74), vanes (76), and an impeller base (78). The sealing structure comprises a dynamic sealing structure and a water-throwing groove sealing structure. The dynamic sealing structure comprises an external static sealing ring (98). The external static sealing ring (98) comprises a radial contact portion (263) and an axial contact portion (264). A first space (265) is defined between the radial contact portion (263) and a cylindrical base portion (782) of the impeller base (78) of the impeller (70) of the centrifugal pump, and a second space (266) is defined between the axial contact portion (264) and the cylindrical base portion (782). The width of the first space (265) in a radial direction is smaller than the width of the second space (266) in an axial direction. The water-throwing groove sealing structure comprises a plurality of water-throwing grooves (785) arranged in the circumference of the flow guide housing (250).

Description

Seal structure for centrifugal pump

This application claims priority to the following Chinese patent applications, the entire contents of which are incorporated herein by reference.

serial number	application date	Application Number	name
1	2021-02-04	202110171359.5	Seal structure for centrifugal pump
2	2021-02-04	202120354468.6	Seal structure for centrifugal pump

technical field

The present application relates to the technical field of centrifugal pumps, and in particular, to a sealing structure for centrifugal pumps.

Background technique

The centrifugal pump for deep well generally includes a motor assembly and a pump body assembly including an impeller driven to rotate by a pump shaft. The pump shaft speed of the traditional centrifugal pump is generally around 3000rpm. If the head of the water output by the centrifugal pump reaches 300m, the height of the centrifugal pump may reach 3m. Therefore, this kind of deep well pump is large and heavy.

Centrifugal pumps for deep wells are mostly used for agricultural irrigation, and the operating environment is usually at a depth ranging from 100m to 500m underground. In applications with harsh natural environments such as mountains, it is very inconvenient to operate. In particular, for the handling of centrifugal pumps alone, workers need to manually lift to the top of the mountain, which may take several hours, or even a day, to install the huge and cumbersome centrifugal pump to the bottom of the well hundreds of meters deep and the subsequent Possible repairs are very difficult. This largely limits the application of centrifugal pumps. In the improvement process of the pump, in order to increase the lift of the centrifugal pump, the method of increasing the diameter of the impeller is usually adopted, which further increases the volume and weight of the pump, and aggravates the above-mentioned inconvenience of the pump.

Under such circumstances, the sealing structure in the centrifugal pump consumes a large amount of work and generates vibrations, thereby reducing the overall efficiency of the centrifugal pump.

SUMMARY OF THE INVENTION

The purpose of the present application is to provide a water slinging groove sealing structure for a centrifugal pump, which reduces the leakage of water flow, and at the same time reduces the frictional resistance and the vibration of the impeller stage group.

To this end, the present application proposes a sealing structure for a centrifugal pump, the centrifugal pump includes: a motor assembly providing rotational motion, a pump shaft driven by an output shaft of the motor assembly, and a pump body assembly, wherein the pump body assembly includes A pump sleeve and a plurality of impeller stages housed within the pump sleeve, the impeller stages including: a support housing and a flow guide housing attached together in an axial direction to define an impeller cavity, and a housing The impeller is driven in the impeller cavity to rotate synchronously with the pump shaft, wherein the impeller includes: a hub portion defining a central bore for engagement with the pump shaft, and a conical extending radially outward and axially upward from the hub portion a wall, a blade extending helically from the lower surface of the tapered wall, and an impeller seat attached to the outer periphery of the blade, the impeller seat defining an outer support end face at its lower end, characterized in that the sealing structure includes a dynamic sealing structure and a slinger The water tank seal structure, the dynamic seal structure includes an outer static seal ring, and the outer static seal ring includes a radial contact portion parallel to the axial direction and an axial contact portion perpendicular to the axial direction, wherein the radial contact portion is connected with the centrifugal pump. A first space is defined between the cylindrical bases of the impeller seat of the impeller, and a second space is defined between the axial contact portion and the cylindrical base, wherein the width of the first space in the radial direction is smaller than that of the second space in the axial direction The water rejection groove sealing structure includes a plurality of water rejection grooves arranged on the radially outer side of the outer support end face at the lower end of the impeller seat, wherein the plurality of water rejection grooves are arranged along the circumferential direction of the guide casing.

According to an alternative embodiment, each of the plurality of water slinging troughs includes two sides arranged at an angle, and the included angle between the two sides is between 50° and 70°.

According to an alternative embodiment, the guide casing of the impeller stage comprises a central portion having a central bore allowing the pump shaft to extend through, a peripheral portion axially engaging the support casing and helical between the central portion and the peripheral portion A guide vane extending in a shape, the central portion, the peripheral portion and the guide vane define a guide channel of the impeller stage group.

According to an alternative embodiment, the impeller seat, the conical wall and the blades define a centrifugal channel, the hub defines a central support end face perpendicular to the axial direction, the central support end face passes through the hub portion of the impeller or is embedded in the center of the lower end of the hub portion The dynamic seal ring defines that the guide housing includes a central abutment end surface that is in constant abutment contact with the center support end surface, and the guide channel is in fluid communication with the centrifugal channel.

According to an alternative embodiment, the central dynamic sealing ring is constructed of tungsten steel.

According to an alternative embodiment, the central portion is a flow guide seat formed separately and attached to the peripheral portion.

According to an alternative embodiment, the central abutment end face is provided by a flow guide seat or a central static sealing ring embedded in the flow guide seat.

According to an alternative embodiment, the hub extends beyond the support housing at a first axial end in an axial direction away from the electric machine assembly and terminates within the support housing at a second axial end opposite the first axial end The center abuts the end face.

According to an alternative embodiment, the impeller seat and the support housing define an annular gap.

According to an optional embodiment, the support housing, the guide housing and the impeller seat together define a foreign matter collection space for receiving foreign matter from the annular gap.

The sealing structure of the water rejection groove of the present application for centrifugal pump, in the operating state of the centrifugal pump, due to the action of the upward flowing water and the centrifugal force of the impeller, the outer static seal ring and the cylindrical base of the impeller seat of the impeller of the centrifugal pump are formed. There is no longer contact between them, but a gap is formed, which reduces the frictional power consumption of the impeller. At the same time, under the action of centrifugal force, the water in the second space is thrown out, thereby forming an internal water pressure that opposes the external water pressure, so that the impeller can reduce the radial force generated by the water. In addition, the above-mentioned water pressure balance also ensures that there is always a seal between the impeller and the guide casing, and the seal will not fail due to the high-speed rotation of the impeller. In the high-speed operation of the centrifugal pump, the water is thrown out by a plurality of water-throwing tanks to form kinetic energy, which is opposed to the external water pressure to reduce the leakage of water flow. Low frictional resistance and vibration of impeller stages.

Description of drawings

The foregoing and other features, advantages and benefits of the present application will be described in detail below in conjunction with exemplary embodiments of the present application with reference to the accompanying drawings. It should be understood that the drawings are not to scale, and are merely used to illustrate the principles of the application and are not intended to limit the application to the embodiments illustrated.

1 is a longitudinal cross-sectional view of an exemplary centrifugal pump of the present application;

Figure 2 shows a longitudinal cross-sectional view of the impeller stages of the centrifugal pump of Figure 1;

FIG. 3 shows a perspective view of the impeller of the impeller stage of FIG. 2; and

FIG. 4 shows an enlarged perspective view of part A of the impeller of FIG. 3 .

Detailed ways

The centrifugal pump of the present application will be described in detail below with reference to the accompanying drawings. Parts that are structurally or functionally identical or similar have the same reference numerals throughout the drawings.

1 is a longitudinal cross-sectional view of an exemplary centrifugal pump of the present application. Generally, the centrifugal pump includes a motor assembly and a pump body assembly 20 . The motor assembly includes a motor housing and a motor, such as an electric motor, accommodated in the motor housing and capable of outputting a high rotational speed. Auxiliary systems that provide auxiliary functions for the operation of the motor, such as cooling systems, are also located within the motor housing. The pump body assembly 20 includes a pump sleeve 22 and a plurality of impeller stages 200 housed within the pump sleeve 22 . The output shaft of the motor drives the impeller 70 of each impeller stage group 200 in the centrifugal pump to rotate through the pump shaft 11 of the centrifugal pump. In the illustrated embodiment, the pump shaft 11 adopts a six-tooth pump shaft.

In the present application, for the convenience of description, the direction in which the pump shaft 11 extends is defined as an axial direction, and the circumferential direction extends around the axial direction. The centrifugal pump of the present application is usually placed vertically during use, so the axial direction is also referred to as the vertical direction, the direction/end toward the motor assembly in the axial direction is referred to as the lower/lower end, and the opposite direction/end Called the upper/upper end. In a plane perpendicular to the axial direction, with reference to the central axis of the pump shaft 11 defining the axial direction, the direction from the pump sleeve 22 toward the central axis of the pump shaft 11 is referred to as radially inward, and on the contrary, from The direction of the central axis of the pump shaft 11 toward the pump sleeve 22 is referred to as radially outward.

Referring back to FIG. 1 , in the axial direction, from bottom to top, the pump body assembly 20 sequentially includes a water inlet section 30 , an impeller section 50 composed of a plurality of impeller stages, and a water outlet section 40 , each of which will be described in detail below. Structure.

In the water inlet section 30 , the pump sleeve 22 is provided with water inlet holes 32 distributed in the circumferential direction, and, in the water inlet section 30 , a conical housing 34 is arranged in the pump sleeve 22 . The cone housing 34 is configured as an inverted cone open towards the motor assembly, including a central hole allowing the pump shaft 11 to pass through. The pump shaft connection that connects the pump shaft 11 to the output shaft of the motor assembly and supports the pump shaft 11 is provided in the space 33 formed by the inner surface 37 of the cone housing 34 facing the motor assembly. The opposite outer surface 39 of the cone housing 34 and the pump sleeve 22 define a water space 35 in fluid communication with the water inlet 32 for receiving water entering via the water inlet 32 from outside the centrifugal pump. According to the present application, the water inlet holes 32 include a plurality of water inlet hole groups that are spaced apart along the circumferential direction of the pump sleeve 22 , and each water inlet hole group includes a plurality of water inlet holes that are densely distributed.

The plurality of impeller stages 200 included in the impeller section 50 and mounted within the pump sleeve 22 are described below. The impeller section 50 of the illustrated centrifugal pump includes four impeller stages 200 . Of course, the number of impeller stages of the centrifugal pump is not limited to four, but can be changed according to actual needs.

The impeller stage 200 in the impeller section 50 includes a stationary support housing 60 and a flow guide housing 250 . In the axial direction, the guide housing 250 is closer to the motor assembly and the water inlet section 30 than the support housing 60, that is, during use of the centrifugal pump in a vertical configuration, the guide housing 250 Below the support housing 60 . The support housing 60 and the flow guide housing 250 in the impeller stage set 200 are axially engaged with each other, attached together, together defining an axially penetrating impeller cavity, and vertically adjacent The guide housing 250 of the upper impeller stage 200 of the two arranged impeller stages 200 is attached together with the support housing 60 of the next impeller stage 200 . The impeller stage 200 also includes an impeller 70 located in the impeller cavity, the impeller 70 is engaged with the pump shaft 11 and is driven by the pump shaft 11 to rotate synchronously. In the field of centrifugal pumps, the impeller 70 and the pump shaft 11 are usually joined together by spline engagement, and the pump shaft 11 includes six key teeth 111 evenly distributed along the circumferential direction.

FIG. 2 shows a longitudinal sectional view of the impeller stages of the centrifugal pump of FIG. 1 . The impeller 70 includes a cylindrical hub portion 72 and a conical wall 74 extending radially outward and axially upward from the hub portion 72, eg, near its upper end (opposite to the direction of extension of the conical housing 34, and thus also referred to as "" "forward tapered wall"), the vanes 76 extending helically from the lower surface 79 of the tapered wall 74, the impeller seat 78 being fixedly attached to the outer periphery of the vanes 76. The hub 72, tapered wall 74, vanes 76 and impeller seat 78 of the impeller 70 together define a centrifugal passage 75 through which water is allowed to flow. In accordance with the principles of the present application, the impeller seat 78 and other portions of the impeller 70 may be integrally formed, or may be formed separately and then attached together by any suitable method, such as ultrasonic welding. The impeller seat 78 of the impeller 70 includes a cylindrical base 782 and a forward tapered wall 784 extending obliquely radially outward and axially upward from an upper end of the cylindrical base 782 .

The hub 72 defines a central bore 71 adapted to spline engagement with the pump shaft 11 so that the pump shaft 11 drives the impeller 70 to rotate synchronously with the pump shaft 11 . The lower end of the hub portion 72 defines an axially downward, ie towards, central support end face 73 , and the impeller seat 78 , in particular its cylindrical base 782 , defines an outer support end face 77 . The outer support end face 77 includes one radial end face parallel to the axial direction and two axial end faces perpendicular to the axial direction.

The guide housing 250 of the impeller stage set 200 includes a central portion 252 having a central bore allowing the pump shaft 11 to extend therethrough, a peripheral portion 254 , and vanes 256 extending radially between the central portion 252 and the peripheral portion 254 . The flow guide passage 55 is defined by the central portion 252 and the peripheral portion 254 of the flow guide housing 250 and the adjacent outer static seal ring 98 . The outer static seal ring 98 includes a radial contact portion 263 parallel to the axial direction and an axial contact portion 264 perpendicular to the axial direction. A first space 265 is defined between the radial contact portion 263 and the cylindrical base portion 782 . A second space 266 is defined between the axial contact portion 264 and the cylindrical base portion 782 . The width of the first space 265 in the radial direction is smaller than the width of the second space 266 in the axial direction. The second space 266 may play a role of pressure equalization. Specifically, during the operation of the centrifugal pump, the water from the outside of the impeller 70 trying to intrude into the guide channel 55 via the second space 266 and the first space 265 decreases in speed after entering the second space 266, so that it will not continue to enter the first space 265 , that is, water is blocked in the second space 266 . At the same time, under the action of centrifugal force, the water in the second space 266 is thrown out, thereby forming an internal water pressure opposing the external water pressure, so that the impeller 70 can reduce the radial force generated by the water. In addition, the above-mentioned balance of water pressure also ensures that there is always a seal between the impeller 70 and the guide casing 250, and the seal will not fail due to the high-speed rotation of the impeller.

In the upward direction toward the impeller 70 , the center portion 252 of the guide housing 250 defines a center abutment end surface 262 that is configured to be in abutment contact with the center support end surface 73 at all times.

In the non-operating state of the centrifugal pump, the impeller 70 is assembled in the axial impeller cavity formed by the support housing 60 and the guide housing 250 . The central supporting end surface 73 is in abutting contact with the central abutting end surface 262 , so that the guide housing 250 provides support for the impeller 70 .

In the operating state of the centrifugal pump, the impeller 70 rotates at high speed with the pump shaft 11 (not shown in FIG. 2 ), and the centrifugal force generated by the rotation of the impeller 70 is sucked into the guide channel defined by the guide casing 250 and enters into The centrifugal channel 75 of the impeller 70 is then thrown into the guide channel 55 of the next impeller stage 200 .

The outer periphery of the impeller seat 78 of the impeller 70 , specifically the outer periphery of the upper end of the positive conical wall 784 thereof, and the support housing 60 define an annular gap allowing impurities in the water, such as sediment, to settle downward. The sediment in the water flow in the centrifugal channel 75 enters the impurity collection space jointly defined by the support casing 60 , the guide casing 250 and the impeller seat 78 of the impeller stage group 200 after passing through the annular gap.

In the high-speed operation state of the centrifugal pump, the center support end surface 73 and the center abutment end surface 262 are always kept in contact with each other. In addition to providing support to the impeller 70, this abutment also receives axial force from the impeller 70, and the transmission of the axial force causes friction between the two end faces 73 and 262 in contact with each other. In order to reduce the effect of this friction on the power and efficiency of the centrifugal pump, any surface treatment measures may be applied to the end faces 73 and 262 . In one embodiment, an anti-friction coating may be applied to the end faces 73 and 262 . In the illustrated embodiment, instead of simply applying an anti-friction coating to the surface, additional components made of anti-friction material are provided to the impeller 70 and the flow guide housing 250 to provide end faces 73 and 262, respectively. For example, in FIG. 2, a center dynamic seal ring 92 made of ceramic is embedded in the hub 72 to provide the friction end surface 73, and a center static seal ring 94 made of tungsten steel is embedded in the guide housing 250 to provide a friction surface 262.

FIG. 3 shows a perspective view of the impeller of the impeller stage of FIG. 2 . FIG. 4 shows an enlarged perspective view of part A of the impeller of FIG. 3 . As shown in the figure, the impeller seat 78 includes a plurality of water slinging grooves 785 provided at the lower end thereof on the radially outer side of the outer support end surface 77 . A plurality of water throwing grooves 785 are arranged along the circumferential direction of the guide casing 77 . Each of the plurality of slinger troughs 785 includes two sides arranged at an angle. The angle between the two sides is between 50° and 70°. Under the high-speed operation of the centrifugal pump, a plurality of water throwing grooves 785 throw out the water to form kinetic energy, which opposes the external water pressure, so as to reduce the leakage of the water flow, and at the same time, the impeller reaches a dynamic floating state under the high-speed operation of the centrifugal pump, so as to reduce the leakage of the water flow. Frictional drag and vibration of the impeller stage 200 are reduced.

It should be understood by those skilled in the art that in order to improve pump efficiency and reduce friction losses, the abutting end faces 73 and 262 may be provided in any suitable manner, and are by no means limited to the impeller and the water inlet seat itself as described above, or It is provided by applying anti-friction coating to the impeller and the water inlet seat, or by inserting additional parts made of special materials, etc., and the materials of the applied anti-friction coating or the embedded additional parts are not limited to the above-mentioned ones. and those.

The length of the hub 72 of the impeller 70 of each impeller stage 200 in the axial direction is designed to extend beyond the support housing 60 of the impeller stage 200 at the first axial end in the axial direction away from the motor assembly, It extends into the flow guide housing 60 at a second axial end opposite the first axial end and terminates in a central abutment end face 73 .

The center support end surface 73 is always in contact with the center abutment end surface 262 . In the operating state of the centrifugal pump, the axial force received by the impeller 70 is transmitted to the guide casing 250 via the abutment of the end faces 73 and 262, and then to the pump sleeve 22. In this way, the axial forces received by the impellers 70 in all the impeller stages are respectively transmitted to the pump sleeve 22, so that the superposition of the axial forces does not occur between the impeller assemblies arranged vertically.

During the operation of the centrifugal pump, the water enters the water outlet section 40 after passing through the water inlet section 30 and the plurality of impeller stages 200 . The water outlet section 40 includes an uppermost guide casing 250 connected to the support casing 60 of the last impeller stage 200 , a one-way valve 300 mounted on the uppermost guide casing 250 , and connected to the pump sleeve 22 The outlet seat 310 (shown in FIG. 1 ) is located thereon and defines a water outlet hole 312 .

During the operation of the centrifugal pump, the output shaft of the motor assembly drives the pump shaft 11 to rotate, and the pump shaft 11 drives the impellers 70 of all impeller stages to rotate synchronously. Under the action of suction generated by the rotation of the impeller 70 , the water enters the water space 35 of the water inlet section 30 from the outside of the centrifugal pump through the water inlet hole 32 on the pump sleeve 22 , and then enters the impeller stage group 200 . In the impeller stage 200, the water flows through the guide channel defined by the guide housing 250 and the centrifugal channel 75 defined by the impeller 70 in sequence, and enters the next stage of the impeller stage 200, and so on. After the water is "thrown" out of the centrifugal channel 75 of the last impeller stage 200 , through the guiding channel of the uppermost guiding housing 250 , the one-way valve 300 is opened, and the water exits the centrifugal pump through the water outlet 310 defined by the outlet seat 310 .

As described above, the axial forces borne by the impellers 70 in each impeller stage 200 are transferred to the pump sleeve 22 via the contact of the central support end face with the corresponding central abutment end face without being superimposed on adjacent adjacent faces below. On the impeller stage group 200, otherwise the axial force borne by the impeller stage group 200 below will increase. Such an arrangement reduces pump power losses as the impeller 70 rotates. On the other hand, the corresponding surface treatment of the abutting end surface can further reduce the lost pump power and improve the pump working efficiency.

The centrifugal pump of the present application adopts a motor structure assembly with an output speed of up to 12,000 or higher, and adopts the pump body assembly structure as schematically shown in the figure. It only needs to configure 5 impeller stages, and a water output of about 300m can be obtained. lift. At this time, the total height of the centrifugal pump is only about 1m. Even if the controller of the centrifugal pump is accommodated inside the centrifugal pump, the overall height of the centrifugal pump is only about 1.5 m. Compared with the traditional centrifugal pump for deep wells, the height of the pump is shortened by one-half to two-thirds, which means that the weight of the centrifugal pump is greatly reduced. Such a structure makes the application of the deep well centrifugal pump wider, simpler and easier.

Although the application has been described above with reference to the embodiments shown in the figures, it will be apparent to those of ordinary skill in the art that other embodiments and examples may perform similar functions and/or achieve similar results. It is hereby contemplated that all such equivalent embodiments and examples are within the spirit and scope of this application, and for all purposes are intended to be covered by the following non-limiting claims.

Claims (10)

1. A sealing structure for a centrifugal pump, the centrifugal pump comprising:

   Motor assemblies that provide rotary motion,

   the pump shaft (11) driven by the output shaft of the motor assembly, and

   pump body assembly (20),

   wherein the pump body assembly includes a pump sleeve (22) and a plurality of impeller stages (200) housed within the pump sleeve, the impeller stages (200) including: axially attached to A support casing (60) and a guide casing (250) that together define the impeller cavity, and an impeller (70) accommodated in the impeller cavity and driven by the pump shaft to rotate synchronously therewith,

   wherein the impeller (70) includes a hub (72) defining a central bore for engagement with the pump shaft, and a tapered wall (74) extending radially outward and axially upward from the hub, from the tapered a blade (76) extending helically on the lower surface of the wall, and an impeller seat (78) attached to the outer periphery of the blade (76), the impeller seat (78) defining at its lower end an outer support end face (77),

   It is characterized in that,

   The sealing structure includes a dynamic sealing structure and a water-throwing tank sealing structure,

   The dynamic sealing structure includes an outer static seal ring (98) including a radial contact portion (263) parallel to the axial direction and an axial contact portion (264) perpendicular to the axial direction ), wherein a first space (265) is defined between the radial contact portion (263) and the cylindrical base (782) of the impeller seat (78) of the impeller (70) of the centrifugal pump, the axial contact A second space (266) is defined between the portion (264) and the cylindrical base (782), wherein the width of the first space (265) in the radial direction is smaller than that of the second space (266) along the radial direction. width in the axial direction,

   The water rejection groove sealing structure includes a plurality of water rejection grooves (785) arranged on the radially outer side of the outer support end surface (77) at the lower end of the impeller seat (78), wherein the plurality of water rejection grooves (785) are arranged along the Circumferential arrangement of the guide housing (77).
2. The sealing structure according to claim 1, wherein,

   Each of the plurality of slinger grooves (785) includes two sides arranged at an angle,

   The included angle between the two sides is between 50° and 70°.
3. The sealing structure according to claim 1 or 2, characterized in that:

   The guide casing (250) of the impeller stage set (200) includes a central portion (252) having a central bore allowing the pump shaft to extend through, a peripheral portion (254) axially engaging the support casing (60) and guide vanes (256) extending helically between a central portion (252) and a peripheral portion (254), the central portion (252), the peripheral portion (254) and the guide vanes (256) defining The guide channel (55) of the impeller stage group (200).
4. The sealing structure according to claim 3, wherein,

   The impeller seat (78), conical wall (74) and vanes (76) define a centrifugal channel (75), and the hub (72) defines a central support end face (73) perpendicular to the axial direction, so The central support end surface (73) is defined by the hub portion (72) of the impeller (70) or the central dynamic seal ring (92) embedded in the lower end of the hub portion (72),

   The guide casing (250) includes a center abutment end surface (262) that is in constant contact with the center support end surface (73), and

   The guide channel (55) is in fluid communication with the centrifugal channel (75).
5. The sealing structure according to claim 4, wherein the central dynamic sealing ring (92) is made of tungsten steel.
6. The sealing structure of claim 3, wherein the central portion (252) is a flow guide seat formed separately and attached to the peripheral portion.
7. The sealing structure according to claim 6, wherein the central abutting end surface (262) is provided by the guide seat or a center static sealing ring (94) embedded in the guide seat.
8. The sealing structure according to claim 1 or 2, characterized in that the first axial end of the hub portion (72) in the axial direction away from the motor assembly extends beyond the support housing (60), A second axial end opposite the first axial end terminates within the support housing (60) at the central abutment end face (73).
9. The sealing structure according to claim 8, wherein the impeller seat (78) and the support housing (60) define an annular gap.
10. The sealing structure according to claim 9, characterized in that, the support casing (60), the guide casing (250) and the impeller seat (78) together define a space for collecting impurities for receiving Impurities from the annular gap.

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