Centrifugal pump having a radial impeller

Abstract

A centrifugal pump includes a radial impeller surrounded by a housing. The housing has a channel associated with a front side space between a cover of the impeller and the casing. Flow is led through the channel from a pressure region of the pump to a radial gap at a suction region of the pump. The flow in the channel reduces angular momentum and results in an increase in pressure in the front side space which acts of in the cover side of the impeller to offset axial force from a rear side of the impeller.

Claims

1. A centrifugal pump, comprising: a casing, the casing including an inlet-side wall extending radially between a pump inlet and a pump outlet; and a radial impeller surrounded by the casing, wherein the casing includes a channel configured to guide a flow from a front impeller side space, the channel being formed between the inlet-side wall of the casing and a casing part, the casing part being located between a cover side of the radial impeller and the inlet-side wall of the casing, the front impeller side space is located between the cover side of the impeller and the casing, the casing part includes an axial section aligned parallel to an impeller rotation axis connected to a radially outer end of the casing part, the axial section of the casing part is not in contact with the casing in a region of the casing facing radially inward toward the axial section, and a surface of the region of the casing facing radially inward toward the axial section of the casing part has the same radius from the impeller rotation axis as a region of the casing facing radially inward toward the radially-outer end of the impeller.

2. The centrifugal pump as claimed in claim 1, wherein the flow enters the channel from the front impeller side space through a radial gap between the axial section of the casing part and the region of the casing facing radially inward toward the axial section.

3. The centrifugal pump as claimed in claim 2, wherein the channel has a radial section extending in a radial direction.

4. The centrifugal pump as claimed in claim 3, wherein the impeller has a cover shroud at the cover side.

5. The centrifugal pump as claimed in claim 4, wherein at least a portion of the radial section of the channel is arranged parallel to the cover shroud.

6. The centrifugal pump as claimed in claim 4, wherein the radial gap is a sealing gap.

7. The centrifugal pump as claimed in claim 6, wherein the centrifugal pump has a split ring seal arrangement which includes the sealing gap.

8. The centrifugal pump as claimed in claim 7, wherein the channel guides the flow on the impeller side to a region adjacent to the split ring seal arrangement.

9. The centrifugal pump as claimed in claim 8, wherein the channel is delimited by a casing part having a generally L-shaped cross-sectional profile.

10. The centrifugal pump as claimed in claim 9, wherein the casing part is pot-shaped or bell-shaped.

11. The centrifugal pump as claimed in claim 10, wherein a flow region in the front impeller side space has a radial speed profile with an S-shaped curve.

12. The centrifugal pump as claimed in claim 1, wherein a flow region in the front impeller side space has a radial speed profile with an S-shaped curve.

13. The centrifugal pump as claimed in claim 11, wherein a flow region in the front impeller side space has a tangential speed profile that is largely constant.

14. The centrifugal pump as claimed in claim 12, wherein a flow region in the front impeller side space has a tangential speed profile that is largely constant.

15. The centrifugal pump as claimed in claim 1, wherein a flow region in the front impeller side space has a tangential speed profile that is largely constant.

16. The centrifugal pump as claimed in claim 1, wherein at least a portion of the channel has a ring-shaped cross-section.

17. The centrifugal pump as claimed in claim 8, wherein at least a portion of the channel has a ring-shaped cross-section.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a sectional illustration through a centrifugal pump in accordance with an embodiment of the present invention,

(2) FIG. 2 shows a schematic illustration of a channel of the FIG. 1 embodiment,

(3) FIG. 3 shows a curve of the radial speed profile of the FIG. 1 embodiment, and

(4) FIG. 4 shows an illustration of the curve of the tangential speed profile of the FIG. 1 embodiment.

DETAILED DESCRIPTION OF THE DRAWINGS

(5) FIG. 1 shows a centrifugal pump with an impeller 1. The impeller 1 is designed in the form of a closed radial impeller and has a rear shroud 2 and cover shroud 3. Vanes are arranged on the rear shroud 2. Passages for delivering the medium are formed between the rear shroud 2 and the cover shroud 3. The impeller 1 is driven by a shaft 4. The impeller 1 is surrounded by a casing 5 which may be of multi-piece design. The casing 5 has a suction mouth 6. The centrifugal pump has a split ring seal arrangement 7. The split ring seal arrangement 7 delimits the gap volume flow which flows from the pressure region of the centrifugal pump back into the suction region. The impeller 1 is designed in the form of a radial impeller. The fluid flows to the impeller 1 in an axial direction and is then diverted through 90° and then exits the impeller 1 in a radial direction.

(6) FIG. 2 shows a schematic illustration of the front impeller side space 8 which is formed between the cover shroud 3 of the impeller and a casing part 9. The casing part 9 forms, together with a further casing part 10, a channel 11 for guiding a flow from the front impeller side space 8 to a radial gap 12.

(7) The angular momentum flow entering the front impeller side space 8 from the impeller is, at the outer edge, guided not into the actual front impeller side space 8 but into the outer channel 11. The channel 11 is delimited by stationary walls of the casing parts 9, 10. Consequently, the circumferential speed is greatly reduced and the channel 11 acts as a swirl brake. The diversion of the angular momentum flow results in the rotational speed of the fluid in the actual impeller side space 8 being reduced. This leads to an increase in the pressure in the front impeller side space 8 and thereby to an increase in the axial pressure force on the cover shroud 3. A counterforce to the pressure force which acts on the rear shroud 2 is thereby formed. The gap volume flow enters a first section 14 of the channel 11 through a ring-shaped opening 13, which first section extends in an axial direction.

(8) The gap volume flow is then diverted in the channel 11 and enters a second section 15, which runs largely parallel to the cover shroud 3.

(9) Finally, the volume flow flowing through the channel 11 flows into a third section 16, which extends in a radial direction.

(10) The casing part 9 has an L-shaped cross-sectional profile in order to form both a section in an axial direction and a section in a radial direction or parallel to the cover shroud 3. The casing part 9 is of pot-shaped or bell-like design.

(11) FIG. 3 shows the curve of the dimensionless radial speed at a central section. In this context, “central section” means that the speed profile at the mid-height (in a radial direction) between the shaft and the outer (radial) casing is involved. That is to say, exactly at the center of the impeller side space shown. The radial speed is 0 directly on the cover shroud and then increases sharply in the immediate vicinity of the cover shroud to a value of almost 0.08. Subsequently, a flow region 17 is formed in which the radial speed decreases in the manner of an S-shaped curve to a value of approximately −0.06. In the direction of the fixed, stationary casing part 9, the radial speed then increases again until it reaches a value of 0 on the casing part itself.

(12) FIG. 3 shows that a radial flow profile which is almost of piston-like form is formed in the channel, wherein the radial speed is 0 on the fixed walls of the casing parts 9, 10 and then the radial speed increases sharply in an axial direction to a value of approximately −0.07 and then remains almost constant and then decreases again to a value of 0 in the direction of the next casing part 10.

(13) FIG. 4 shows the curve of the dimensionless tangential speed. This is 1 at the beginning on the cover shroud of the impeller and then decreases sharply to a value of approximately 0.4. The tangential speed then remains largely constant in a flow region 18 before it decreases to a value of 0 in the direction of the stationary casing part 9. Within the channel 11, a parabolic curve of the tangential speed is formed, wherein, at the fixed ends of the casing parts 9 and 10, the speed increases from a value of 0, reaches a maximum and then decreases again. The flow profile is of approximately symmetrical form.

(14) The magnitude of the tangential speed is decreased as a result of the friction on the stationary walls when the channel is flowed through. A reduction in the swirl occurs. In this context, “reduction in the swirl” is to be understood as meaning a reduction in the tangential speed on the stationary walls as a result of the friction. A flow with a circumferential speed component is referred to as “swirling”.

(15) The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.