CN114857035A

CN114857035A - Sealing structure for centrifugal pump

Info

Publication number: CN114857035A
Application number: CN202110171359.5A
Authority: CN
Inventors: 蔡卓; 朱楠; 朱青松
Original assignee: Zhejiang Kaiborui Auto Parts Co ltd
Current assignee: Zhejiang Kaiborui Auto Parts Co ltd
Priority date: 2021-02-04
Filing date: 2021-02-04
Publication date: 2022-08-05
Anticipated expiration: 2041-02-04
Also published as: CN114857035B

Abstract

A seal structure for a centrifugal pump, the centrifugal pump comprising: motor element, pump shaft and pump body subassembly. The pump body assembly includes a pump sleeve and a plurality of impeller stage sets. The impeller stage group includes a support housing, a inducer housing, and an impeller. The impeller includes a hub, a tapered wall, a blade, and an impeller seat. The sealing structure comprises a dynamic sealing structure and a water throwing groove sealing structure. The dynamic seal structure includes an outer static seal ring. The outer static seal ring includes a radial contact portion and an axial contact portion. The radial contact portion defines a first space with a cylindrical base portion of an impeller seat of an impeller of a centrifugal pump, and the axial contact portion defines a second space with the cylindrical base portion. The width of the first space in the radial direction is smaller than the width of the second space in the axial direction. The water throwing groove sealing structure comprises a plurality of water throwing grooves arranged along the circumferential direction of the flow guide shell.

Description

Sealing structure for centrifugal pump

Technical Field

The present invention relates to a sealing structure for a centrifugal pump, and more particularly to a sealing structure for a high-speed, high-lift multistage centrifugal pump for a deep well.

Background

A deep well centrifugal pump generally includes a motor assembly and a pump body assembly containing an impeller driven to rotate by a pump shaft. The pump shaft rotating speed of the traditional centrifugal pump is about 3000rpm generally, and if the lift of water output by the centrifugal pump reaches 300m, the height of the centrifugal pump can reach 3m generally, so that the deep well pump is large in size and heavy.

Centrifugal pumps for deep wells are mostly used for agricultural irrigation, and the use environment is usually in the underground at different depths of 100m-500 m. In the application of severe natural environment such as high mountain, the operation is very inconvenient. In particular, the personnel are manually lifted to the top of the hill, which may take several hours or even a day, for the handling of the centrifugal pump alone, and it is very difficult to install the centrifugal pump, which is bulky and heavy, at the bottom of the shaft with a depth of several hundred meters and for possible subsequent maintenance. This limits the application of centrifugal pumps to a large extent. In the process of improving the pump, in order to increase the lift of the centrifugal pump, a measure of enlarging the diameter of the impeller is generally adopted, which further increases the volume and weight of the pump, and aggravates the above inconvenience of the pump.

In such cases, the seal configuration in the centrifugal pump may consume a large amount of work and generate vibrations, thereby reducing the overall efficiency of the centrifugal pump.

Disclosure of Invention

It is an object of the present application to provide a hydro slinger seal arrangement for a centrifugal pump that reduces water flow leakage while reducing frictional resistance and vibration of the impeller stage set.

To this end, the present application proposes a sealing structure for a centrifugal pump, the centrifugal pump comprising: 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 stage sets housed within the pump sleeve, the impeller stage sets comprising: a support housing and a guide housing attached together in an axial direction to define an impeller cavity, and an impeller accommodated in the impeller cavity and driven by a pump shaft to rotate synchronously therewith, wherein the impeller includes: a hub portion defining a central bore engaged with the pump shaft, and a tapered wall extending radially outward and axially upward from the hub portion, a vane extending spirally from a lower surface of the tapered wall, and an impeller seat attached to an outer periphery of the vane, the impeller seat defining an outer support end surface at a lower end thereof, characterized in that the seal structure includes a dynamic seal structure including an outer static seal ring including a radial contact portion parallel to the axial direction and an axial contact portion perpendicular to the axial direction, wherein the radial contact portion defines a first space with a cylindrical base portion of the impeller seat of the impeller of the centrifugal pump, and the axial contact portion defines a second space with the cylindrical base portion, wherein the first space has a width in the radial direction that is smaller than a width of the second space in the axial direction, and a water slinger seal structure including a plurality of water slingers provided at a lower end of the impeller seat radially outward of the outer support end surface, wherein, a plurality of water slingers are arranged along the circumference of the diversion shell.

According to an alternative embodiment, each water slinger of the plurality of water slingers comprises two sides arranged at an angle, the angle between the two sides being between 50 ° and 70 °.

According to an alternative embodiment, the guide casing of the impeller stage set comprises a central portion having a central bore allowing the pump shaft to extend therethrough, a peripheral portion axially engaged with the support casing and guide vanes extending helically between the central portion and the peripheral portion, the central portion, the peripheral portion and the guide vanes defining the guide passage of the impeller stage set.

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 surface perpendicular to the axial direction, the central support end surface is defined by the hub of the impeller or a central movable sealing ring embedded at the lower end of the hub, the flow guiding housing comprises a central abutting end surface in constant abutting contact with the central support end surface, and the flow guiding channel is in fluid communication with the centrifugal channel.

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

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

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

According to an alternative embodiment, a first axial end of the hub portion in an axial direction away from the motor assembly extends beyond the support housing and terminates in a central abutment end face within the support housing at a second axial end opposite the first axial end.

According to an alternative embodiment, the impeller seat defines an annular gap with the support housing.

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

The utility model provides a get rid of water groove seal structure for centrifugal pump, under the running state of centrifugal pump, because the effect of the centrifugal force of upflow water and impeller, no longer contact between the cylindric basal portion of the impeller seat of outside static sealing ring and the impeller of centrifugal pump, but form the gap, reduced the friction consumption of impeller. At the same time, under the effect of centrifugal force, the water in the second space is thrown out, so that an internal water pressure opposing the external water pressure is formed, so that the impeller can reduce the radial force generated by the water. In addition, the water pressure balance also enables the sealing between the impeller and the guide shell to be always realized, and the sealing failure caused by the high-speed rotation of the impeller can be avoided. Under the high-speed running state of the centrifugal pump, the water is thrown out by the water throwing grooves to form kinetic energy which is opposed to external water pressure so as to reduce water flow leakage, and meanwhile, the impeller is enabled to reach a dynamic floating state under the high-speed running state of the centrifugal pump so as to reduce friction resistance and vibration of the impeller stage group.

Drawings

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

FIG. 1 is a longitudinal section of an exemplary centrifugal pump of the present application;

FIG. 2 illustrates a longitudinal cross-sectional view of an impeller stage set of the centrifugal pump of FIG. 1;

FIG. 3 illustrates a perspective view of an impeller of the impeller stage set of FIG. 2; and

fig. 4 shows an enlarged perspective view of a portion a of the impeller of fig. 3.

Detailed Description

The centrifugal pump of the present application is described in detail below with reference to the accompanying drawings. Throughout the drawings, parts that are structurally or functionally the same or similar have the same reference numerals.

Fig. 1 is a longitudinal section of an exemplary centrifugal pump of the present application. Generally, a 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. An auxiliary system, such as a cooling system, that provides auxiliary functions for the operation of the motor is also provided within the motor housing. The pump block assembly 20 includes a pump sleeve 22 and a plurality of impeller stage sets 200 housed within the pump sleeve 22. The output shaft of the motor drives the impeller 70 of each impeller stage set 200 in the centrifugal pump to rotate via the pump shaft 11 of the centrifugal pump. In the illustrated embodiment, the pump shaft 11 is a six-tooth pump shaft.

In the present application, for 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 normally placed vertically during use, so the axial direction is also referred to as the vertical direction, the direction/end in the axial direction towards the motor assembly is referred to as the lower/lower end, the opposite direction/end is referred to as the upper/upper end. In a plane perpendicular to the axial direction, a direction from the pump sleeve 22 toward the central axis of the pump shaft 11 is referred to as radially inward, and conversely, a direction from the central axis of the pump shaft 11 toward the pump sleeve 22 is referred to as radially outward, with reference to the central axis of the pump shaft 11 defining the axial direction.

Referring back to fig. 1, the pump body assembly 20 includes, in order in an axial direction, from bottom to top, a water intake section 30, an impeller section 50 composed of a plurality of impeller stage sets, and a water outlet section 40, the structures of which are described in detail below.

In the water inlet section 30, water inlet holes 32 distributed in the circumferential direction are provided on the pump sleeve 22, and in the water inlet section 30, a cone housing 34 is provided inside the pump sleeve 22. The cone housing 34 is configured as an inverted cone that opens toward the motor assembly, including a central bore that allows the pump shaft 11 to pass through. A pump shaft connection portion that connects the pump shaft 11 to an output shaft of the motor assembly and supports the pump shaft 11 is disposed within a space 33 formed by an inner surface 37 of the cone housing 34 facing the motor assembly. An opposite outer surface 39 of cone housing 34 and pump sleeve 22 define a water space 35 in fluid communication with inlet opening 32 for receiving water entering through inlet opening 32 from outside the centrifugal pump. According to the present application, the water inlet 32 includes a plurality of water inlet groups spaced apart in the circumferential direction of the pump sleeve 22, each water inlet group including a plurality of water inlet holes densely distributed.

The following describes a plurality of impeller stage sets 200 included with the impeller section 50 mounted within the pump sleeve 22. The impeller section 50 of the illustrated centrifugal pump comprises 4 impeller stage sets 200, although the number of impeller stage sets of the centrifugal pump is not limited to 4, but may vary according to actual requirements.

The impeller stage set 200 in the impeller section 50 includes a stationary support housing 60 and a flow directing housing 250. In the axial direction, the inducer housing 250 is closer to the motor assembly and the water intake section 30 than the support housing 60, that is, the inducer housing 250 is located below the support housing 60 during use of the centrifugal pump in the vertical configuration. The support and

guide housings

60, 250 in an impeller stage set 200 engage each other in the axial direction, are attached together, together defining an impeller cavity running through in the axial direction, and the guide housing 250 of the last impeller stage set 200 and the support housing 60 of the next impeller stage set 200 in two impeller stage sets 200 arranged adjacent to each other in the vertical direction are attached together. The impeller stage set 200 also includes an impeller 70 located within the impeller cavity, the impeller 70 being engaged with the pump shaft 11 and driven for synchronous rotation by the pump shaft 11. In the field of centrifugal pumps, the impeller 70 and the pump shaft 11 are typically joined together by means of a splined engagement, the pump shaft 11 comprising six key teeth 111 evenly distributed in the circumferential direction.

Fig. 2 shows a longitudinal sectional view of the impeller stage assembly of the centrifugal pump of fig. 1. The impeller 70 includes a cylindrical hub portion 72 and a tapered wall 74 extending radially outward and axially upward from the hub portion 72, e.g., near an upper end thereof (opposite to the direction of extension of the cone housing 34, and thus also referred to as a "forward tapered wall"), a vane 76 extending spirally from a lower surface 79 of the tapered wall 74, and an impeller seat 78 fixedly attached to an outer periphery of the vane 76. The hub 72, conical wall 74, vanes 76 and impeller seat 78 of the impeller 70 collectively define a centrifugal passage 75 that allows water to flow therethrough. The impeller seat 78 and the rest of the impeller 70 may be integrally formed or may be separately formed and later attached together by any suitable method, such as ultrasonic welding, in accordance with the principles of the present application. 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 portion 72 defines a central bore 71, and the central bore 71 is adapted to be splined to the pump shaft 11 such that the pump shaft 11 drives the impeller 70 such that the impeller 70 rotates synchronously with the pump shaft 11. The lower end of the hub 72 defines an axially downward, i.e. towards the central support end surface 73, and the impeller seat 78, in particular the cylindrical base 782 thereof, defines an outer support end surface 77. The outer support end surface 77 includes one radial end surface parallel to the axial direction and two axial end surfaces perpendicular to the axial direction.

The flow guide housing 250 of the impeller stage set 200 includes a central portion 252 having a central bore that allows the pump shaft 11 to extend therethrough, an outer peripheral portion 254, and vanes 256 extending radially between the central portion 252 and the outer peripheral portion 254. The flow guide passage 55 is defined by a central portion 252 and an outer peripheral portion 254 of the flow guide housing 250 and the adjacent outer static seal ring 98. The outer stationary 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. The radial contact portion 263 and the cylindrical base portion 782 define a first space 265 therebetween. 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 function as a pressure balance. Specifically, during operation of the centrifugal pump, water attempting to intrude into the guide passage 55 from outside the impeller 70 via the second space 266 and the first space 265 decreases in velocity after entering the second space 266 so as not to continue to enter the first space 265, i.e., the water is blocked in the second space 266. At the same time, the water in the second space 266 is thrown out by centrifugal force, thereby creating an internal water pressure that opposes the external water pressure, so that the impeller 70 can reduce the radial force generated by the water. In addition, the above-mentioned water pressure balance also enables a seal to be always present between the impeller 70 and the guide housing 250, and the seal is not lost due to the high-speed rotation of the impeller.

In the upward direction toward the impeller 70, the center portion 252 of the draft housing 250 defines a center abutment end surface 262, the center abutment end surface 262 being configured to be always in abutting contact with the center support end surface 73.

In the non-operational state of the centrifugal pump, the impeller 70 fits within an axial impeller cavity defined by the support housing 60 and the inducer housing 250. The central support end surface 73 is in abutting contact with the central abutment end surface 262 such that the guide housing 250 provides a support for the impeller 70.

In the operating state of the centrifugal pump, the impeller 70 rotates at a high speed along with the pump shaft 11 (not shown in fig. 2), and water is drawn in from the guide passage defined by the guide housing 250 by the centrifugal force generated by the rotation of the impeller 70, enters the centrifugal passage 75 of the impeller 70, and is then thrown into the guide passage 55 of the next impeller stage group 200.

An annular gap for allowing impurities, such as silt, in the water to settle downward is defined between the outer circumference of the impeller seat 78 of the impeller 70, specifically, the upper end outer circumference of the forward tapered wall 784 thereof, and the support housing 60. Silt in the water stream flowing in the centrifugal channel 75 passes through the annular gap and enters the impurity collection space defined by the support housing 60, the guide housing 250 and the impeller seat 78 of the impeller stage set 200.

In the high-speed operation state of the centrifugal pump, the center support end surface 73 and the center abutting end surface 262 are always in abutting contact. In addition to providing support to the impeller 70, this abutment also receives an 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. To reduce the effect of this friction on the power and efficiency of the centrifugal pump, any surface treatment of the end faces 73 and 262 may be applied. In one embodiment, an anti-friction coating may be applied to the end surfaces 73 and 262. In the illustrated embodiment, rather than simply applying an anti-friction coating to the surface, additional components made of anti-friction material are provided to the impeller 70 and the inducer housing 250, respectively, to provide the end surfaces 73 and 262. For example, in FIG. 2, a central dynamic seal ring 92 made of ceramic is embedded within the hub 72 to provide the friction face 73 and a central static seal ring 94 made of tungsten steel is embedded within the deflector housing 250 to provide the friction surface 262.

Fig. 3 shows a perspective view of an impeller of the impeller stage set of fig. 2. Fig. 4 shows an enlarged perspective view of a portion a of the impeller of fig. 3. As shown, the impeller seat 78 includes a plurality of water slingers 785 disposed radially outwardly of the outer support end surface 77 at the lower end thereof. A plurality of water slinger 785 are arranged circumferentially of the deflector housing 77. Each of the plurality of water slingers 785 comprises two sides arranged at an angle. The angle between the two sides is between 50 ° and 70 °. In the high speed operation of the centrifugal pump, the plurality of water slinger slots 785 fling water out to create kinetic energy that opposes external water pressure to reduce water leakage, while allowing the impeller to reach a dynamically floating state in the high speed operation of the centrifugal pump to reduce frictional resistance and vibration of the impeller stage assembly 200.

It will be appreciated by those skilled in the art that the abutting end faces 73 and 262 may be provided in any suitable manner for improved pump efficiency and reduced frictional losses, and are in no way limited to the provision of additional features made from the impeller and water inlet block themselves, or from the application of anti-friction coatings to the impeller and water inlet block, or from embedded special materials, as described above, and that the materials of the anti-friction coatings or embedded additional features applied are not limited to those mentioned above.

The hub portion 72 of the impeller 70 of each impeller stage set 200 is designed to extend beyond the support housing 60 of that impeller stage set 200 at a first axial end in the axial direction away from the motor assembly, and to extend into the flow directing housing 60 at a second axial end opposite the first axial end and terminate in a central abutment end surface 73.

The center support end surface 73 is in constant abutting contact with the center abutting end surface 262. In the operating state of the centrifugal pump, the axial force received by the impeller 70 is transmitted to the guide housing 250 via the abutment of the end faces 73 and 262, and then to the pump sleeve 22. In this way, the axial forces experienced by the impellers 70 in all of the impeller stage sets are each transferred to the pump sleeve 22 so that no overlap of axial forces occurs between the vertically arranged impeller assemblies.

During centrifugal pump operation, water enters the water outlet section 40 after passing through the water inlet section 30 and the plurality of impeller stage sets 200. The water outlet section 40 includes an uppermost guide housing 250 connected to the support housing 60 of the last impeller stage set 200, a one-way valve 300 mounted on the uppermost guide housing 250, and an outlet seat 310 (shown in fig. 1) connected to the pump sleeve 22 and defining an outlet aperture 312.

During 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 of the impeller stage sets to rotate in unison. Water enters the water space 35 of the intake section 30 from outside the centrifugal pump through the intake holes 32 in the pump sleeve 22 and then into the impeller stage set 200, under the suction created by the rotation of the impeller 70. In the impeller stage set 200, water flows through the flow guide channels defined by the flow guide housing 250 and the centrifugal channels 75 defined by the impeller 70 in sequence, into the next stage impeller stage set 200, and so on. After the water is "thrown" out of the centrifugal channels 75 of the last impeller stage set 200, it exits the centrifugal pump via the outlet port 310 defined by the outlet seat 310 by opening the one-way valve 300 via the flow directing channel of the uppermost flow directing housing 250.

As described above, axial forces experienced by the impellers 70 in each impeller stage set 200 are transmitted to the pump sleeve 22 via contact of the central support end face with the respective central abutment end face without being superimposed on the underlying adjacent impeller stage set 200, which would otherwise increase the axial forces experienced by the underlying impeller stage set 200. Such an arrangement reduces pump power losses as the impeller 70 rotates. On the other hand, the surface treatment of the abutting end face can further reduce the lost pump power and improve the working efficiency of the pump.

The centrifugal pump adopts a motor structure component with the output rotating speed of 12000 or higher and a pump body component structure schematically shown in the figure, and can obtain the water output lift of about 300m by only configuring 5 impeller stage groups. In this case, the centrifugal pump has a total height of only about 1 m. Even if the controller of the centrifugal pump is housed inside the centrifugal pump, the total height of the centrifugal pump is only about 1.5 m. Compare in traditional centrifugal pump for deep well, the height of pump has shortened half to two-thirds, and the height shortens and means the weight of centrifugal pump's weight alleviates greatly. The structure makes the application of the deep well centrifugal pump wider, simpler and easier.

Although the present application has been described above with reference to the embodiments shown in the drawings, 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 therefore contemplated that all such equivalent embodiments and examples are within the spirit and scope of the present application and are intended to be covered by the following non-limiting claims for all purposes.

Claims

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

a motor assembly for providing a rotational movement of the motor,

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

A pump body assembly (20),

wherein the pump body assembly includes a pump sleeve (22) and a plurality of impeller stage sets (200) housed within the pump sleeve, the impeller stage sets (200) including: a support housing (60) and a guide housing (250) attached together in an axial direction to define an impeller cavity, and an impeller (70) accommodated in the impeller cavity to be driven by the pump shaft to rotate synchronously therewith,

wherein the impeller (70) comprises: a hub portion (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 portion, a vane (76) extending helically from a lower surface of the tapered wall, and an impeller seat (78) attached to an outer periphery of the vane (76), the impeller seat (78) defining an outer support end surface (77) at a lower end thereof,

it is characterized in that the preparation method is characterized in that,

the sealing structure comprises a dynamic sealing structure and a water throwing groove sealing structure,

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

the water slinger sealing structure comprises a plurality of water slingers (785) arranged at the lower end of the impeller seat (78) and radially outside the outer support end surface (77), wherein the plurality of water slingers (785) are arranged along the circumferential direction of the guide shell (77).

2. The sealing structure of claim 1,

each of the plurality of water slingers (785) comprising two sides arranged at an angle,

the angle between the two sides is between 50 ° and 70 °.

3. The sealing structure according to claim 1 or 2,

the flow guide housing (250) of the impeller stage set (200) includes a central portion (252) having a central bore allowing a pump shaft to extend therethrough, a peripheral portion (254) axially engaged with the support housing (60), and a guide vane (256) extending helically between the central portion (252) and the peripheral portion (254), the central portion (252), the peripheral portion (254), and the guide vane (256) defining a flow guide channel (55) of the impeller stage set (200).

4. The sealing structure of claim 3,

the impeller seat (78), the tapered wall (74) and the blades (76) define a centrifugal passage (75), the hub portion (72) defines a central support end surface (73) perpendicular to the axial direction, the central support end surface (73) is defined by the hub portion (72) of the impeller (70) or a central movable sealing ring (92) embedded at the lower end of the hub portion (72),

the flow guiding housing (250) comprises a central abutting end surface (262) which is always in abutting contact with the central supporting end surface (73), and

the flow directing channel (55) is in fluid communication with the centrifugal channel (75).

5. The seal of claim 4, wherein the center acting seal ring (92) is constructed of tungsten steel.

6. The seal structure of claim 3, wherein the central portion (252) is a flow guide seat that is separately formed and attached to the peripheral portion.

7. The seal structure of claim 6, wherein the central abutment end face (262) is provided by the deflector seat or a central static seal ring (94) embedded within the deflector seat.

8. A sealing arrangement according to claim 1 or 2, wherein a first axial end of the hub portion (72) in an axial direction away from the motor assembly extends beyond the support housing (60), and terminates in the support housing (60) at the central abutment end face (73) at a second axial end opposite the first axial end.

9. The seal structure of claim 8, wherein the impeller seat (78) and the support housing (60) define an annular gap.

10. The seal structure of claim 9, wherein the support housing (60), the baffle housing (250), and the impeller seat (78) collectively define a contaminant collection space for receiving contaminants from the annular gap.