CA1222903A - Pump volute communicating slot for stability - Google Patents
Pump volute communicating slot for stabilityInfo
- Publication number
- CA1222903A CA1222903A CA000444836A CA444836A CA1222903A CA 1222903 A CA1222903 A CA 1222903A CA 000444836 A CA000444836 A CA 000444836A CA 444836 A CA444836 A CA 444836A CA 1222903 A CA1222903 A CA 1222903A
- Authority
- CA
- Canada
- Prior art keywords
- point
- vaneless space
- slot
- centrifugal pump
- inlet
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04D—NON-POSITIVE-DISPLACEMENT PUMPS
- F04D29/00—Details, component parts, or accessories
- F04D29/40—Casings; Connections of working fluid
- F04D29/42—Casings; Connections of working fluid for radial or helico-centrifugal pumps
- F04D29/44—Fluid-guiding means, e.g. diffusers
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04D—NON-POSITIVE-DISPLACEMENT PUMPS
- F04D29/00—Details, component parts, or accessories
- F04D29/40—Casings; Connections of working fluid
- F04D29/42—Casings; Connections of working fluid for radial or helico-centrifugal pumps
- F04D29/426—Casings; Connections of working fluid for radial or helico-centrifugal pumps especially adapted for liquid pumps
- F04D29/428—Discharge tongues
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Structures Of Non-Positive Displacement Pumps (AREA)
Abstract
ABSTRACT
A centrifugal pump having a discharge chamber, a vaneless space, a volute diffuser having an inlet communicating with the vaneless space and an outlet communicating with the discharge chamber. A slot connects the volute diffuser at a point at a selected distance from the inlet to the vaneless space at a point at a selected distance from the inlet.
A centrifugal pump having a discharge chamber, a vaneless space, a volute diffuser having an inlet communicating with the vaneless space and an outlet communicating with the discharge chamber. A slot connects the volute diffuser at a point at a selected distance from the inlet to the vaneless space at a point at a selected distance from the inlet.
Description
This invention relates to centrifugal pumps, particularly centrifugal pumps having volute type diffusers.
In a centrifugal pump having a diffuser the diffuser rèceives relatively high velocity flow from the impeller and connects with the discharge. The volute increases in cross-sectional area to reduce the flow velocity and cause a corresponding increase in the static pressure head at the volute discharge.
Pumps of this type normally encounter significant problems when the pump discharge is throttled to reduce the flow to relatively low levels. At a certain low flow level the head ceases to rise as flow drops. This condition is undesirable because it results in unstable pump operation and decreased efficiency and creates flow problems when several pumps are operated in parallel.
With this invention a pump is provided that stabilizes the head/flow performance characteristic at low flows to decrease or eliminate the usual unstable characteristic. The advantages and objects of this inven-tion will be apparent from the following description.
According to a broad aspect of the present inven-tion there is provided a centrifugal pump having a discharge chamber, a vaneless space, a volute diffuser having an inlet communicating with the vaneless space and an outlet communicating with the discharge chamber. Means is provided for connecting the volute diffuser at a point at a selected distance from the inlet to the vaneless space at a point at a selected distance from the inlet, Figure 1 is a simplified cross-sectional end view of the impeller and vaneless space of a centrifugal pump according to this invention;
Figure 2 is a cross-sectional side view of the pump portion shown in Figure l;
FIGURE 3 is a curve showing pump head/flow characteristics under certain operating conditions.
Referring to Figures 1 and 2, a pump housing section 10 of a pumP (shown in part) creates a dis-charging portion by forming a pump discharge chamber 12 between a housing wall 11 and a diffuser body 13 and creates a vaneless space 15 surrounding an impeller 14 _ (shown in phantom). `
The discharging section also comprises a volute -diffuser 16 that connects between vaneless space 15 at a diffuser inlet 17 having a cutwater 21 and discharge -chamber 12 at an outlet 18. As known in the art, the ~-diffuser is arranged to discharge pump fluid as the -impeller rotates in a clockwise direction (as shown) to pump fluid that is received into the vaneless space from a pump inlet 20 that receives fluid. ~
A means for connecting volute diffuser 16 to -vaneless space 15 comprises a slot 30 in diffuser body --13 that communicates at one end at a selected point in 15 a volute diffuser 16 and at the other end to a selected --point in vaneless space 15. The slot is positioned at a selected distance from inlet 17 and cutwater 21 on -the diffuser side and at a selected distance from the -`
inlet or cutwater on the vaneless space side.
In the operation of the pump, fluid is received -`
through inl~t 20 and driven by impeller 14 into dif- -`
fuser inlet 17 and out through outlet 18 into discharge :
chamber 12. During low flow operation if slot 30 is `-not present the head instead of increasing tends in -~
25 many situations to decrease. In Figure 3 a dotted -curve N shows a typical example of how at low flows the -`
head may drop as flow decreases creating an unstable --condition. `
With slot 30 present communicating between the -diffuser and the vaneless space. The head/flow re-lationship as shown in curve S in Figure 3 can be obtained for any pump of this type by selecting the size, shape and orientation of the slot.
While some empirical evaluation of the type and ---~ . ...
_3_ lZ2Zgo~
arrangement of the slot is necessary for each particu-lar pump configuration and installation, these can be readily established. The primary factor to be con-sidered in e~alulation and correction is that increased stability results at low delivery flows because the pressure in the volute diffuser would normally be higher at a point A in the diffuser channel than at a point B in the vaneless space. Slot 30 allows flow from point A to point B, selected to be the point at which maximum head occursr which stabilizes the head toward zero flow as shown in curve S.
Also as the pump operates at higher delivery flows the pressure differential between points A and B
on each side of the slot diminishes as the flow in-creases and equalizes at about the best efficiencylevel of the pump. This equalization of pressure be-tween points A and B substantially eliminates the flow between points A and B through the slots so that the head/flow characteristic is relatively unaffected at the operating flow rates.
When the flow is increased beyond the point of maximum efficiency, the pressure at point B tends to exceed that at point A and flow occurs from point B to A. To diminish this the orientation of the slot and the size is selected to limit the amount of this flow so that the increase in flow at the higher flow rates, as shown in Figure 3, is not significant. This limitation while not essential is helpful in limiting the maximum driving motor size required for the pump.
.
. .
In a centrifugal pump having a diffuser the diffuser rèceives relatively high velocity flow from the impeller and connects with the discharge. The volute increases in cross-sectional area to reduce the flow velocity and cause a corresponding increase in the static pressure head at the volute discharge.
Pumps of this type normally encounter significant problems when the pump discharge is throttled to reduce the flow to relatively low levels. At a certain low flow level the head ceases to rise as flow drops. This condition is undesirable because it results in unstable pump operation and decreased efficiency and creates flow problems when several pumps are operated in parallel.
With this invention a pump is provided that stabilizes the head/flow performance characteristic at low flows to decrease or eliminate the usual unstable characteristic. The advantages and objects of this inven-tion will be apparent from the following description.
According to a broad aspect of the present inven-tion there is provided a centrifugal pump having a discharge chamber, a vaneless space, a volute diffuser having an inlet communicating with the vaneless space and an outlet communicating with the discharge chamber. Means is provided for connecting the volute diffuser at a point at a selected distance from the inlet to the vaneless space at a point at a selected distance from the inlet, Figure 1 is a simplified cross-sectional end view of the impeller and vaneless space of a centrifugal pump according to this invention;
Figure 2 is a cross-sectional side view of the pump portion shown in Figure l;
FIGURE 3 is a curve showing pump head/flow characteristics under certain operating conditions.
Referring to Figures 1 and 2, a pump housing section 10 of a pumP (shown in part) creates a dis-charging portion by forming a pump discharge chamber 12 between a housing wall 11 and a diffuser body 13 and creates a vaneless space 15 surrounding an impeller 14 _ (shown in phantom). `
The discharging section also comprises a volute -diffuser 16 that connects between vaneless space 15 at a diffuser inlet 17 having a cutwater 21 and discharge -chamber 12 at an outlet 18. As known in the art, the ~-diffuser is arranged to discharge pump fluid as the -impeller rotates in a clockwise direction (as shown) to pump fluid that is received into the vaneless space from a pump inlet 20 that receives fluid. ~
A means for connecting volute diffuser 16 to -vaneless space 15 comprises a slot 30 in diffuser body --13 that communicates at one end at a selected point in 15 a volute diffuser 16 and at the other end to a selected --point in vaneless space 15. The slot is positioned at a selected distance from inlet 17 and cutwater 21 on -the diffuser side and at a selected distance from the -`
inlet or cutwater on the vaneless space side.
In the operation of the pump, fluid is received -`
through inl~t 20 and driven by impeller 14 into dif- -`
fuser inlet 17 and out through outlet 18 into discharge :
chamber 12. During low flow operation if slot 30 is `-not present the head instead of increasing tends in -~
25 many situations to decrease. In Figure 3 a dotted -curve N shows a typical example of how at low flows the -`
head may drop as flow decreases creating an unstable --condition. `
With slot 30 present communicating between the -diffuser and the vaneless space. The head/flow re-lationship as shown in curve S in Figure 3 can be obtained for any pump of this type by selecting the size, shape and orientation of the slot.
While some empirical evaluation of the type and ---~ . ...
_3_ lZ2Zgo~
arrangement of the slot is necessary for each particu-lar pump configuration and installation, these can be readily established. The primary factor to be con-sidered in e~alulation and correction is that increased stability results at low delivery flows because the pressure in the volute diffuser would normally be higher at a point A in the diffuser channel than at a point B in the vaneless space. Slot 30 allows flow from point A to point B, selected to be the point at which maximum head occursr which stabilizes the head toward zero flow as shown in curve S.
Also as the pump operates at higher delivery flows the pressure differential between points A and B
on each side of the slot diminishes as the flow in-creases and equalizes at about the best efficiencylevel of the pump. This equalization of pressure be-tween points A and B substantially eliminates the flow between points A and B through the slots so that the head/flow characteristic is relatively unaffected at the operating flow rates.
When the flow is increased beyond the point of maximum efficiency, the pressure at point B tends to exceed that at point A and flow occurs from point B to A. To diminish this the orientation of the slot and the size is selected to limit the amount of this flow so that the increase in flow at the higher flow rates, as shown in Figure 3, is not significant. This limitation while not essential is helpful in limiting the maximum driving motor size required for the pump.
.
. .
Claims (7)
1. A centrifugal pump having a discharge chamber, a vaneless space, a volute diffuser having an inlet com-municating with the vaneless space and an outlet com-municating with the discharge chamber, and a means for connecting the volute diffuser at a point at a selected distance from the inlet to the vaneless space at a point at a selected distance from the inlet.
2. A centrifugal pump according to claim 1 wherein the means for connecting comprises a slot with the connec-ting point in the vaneless space selected to be the point in the vaneless space that maximum head occurs at low delivery flows.
3. A centrifugal pump according to claim 2 wherein the means for connecting comprises a slot having selected size, shape, and orientation.
4. In a centrifugal pump having a vaneless space, a discharge chamber outward of the vaneless space, and a volute diffuser communicating between the vaneless space and the discharge chamber;
a means for connecting the vaneless space to the volute diffuser between a selected point in the volute diffuser and a point in the vaneless space selected to be at the point at which maximum head occurs at low delivery flows.
a means for connecting the vaneless space to the volute diffuser between a selected point in the volute diffuser and a point in the vaneless space selected to be at the point at which maximum head occurs at low delivery flows.
5. A centrifugal pump according to claim 4 wherein the means for connecting comprises a slot.
6. A centrifugal pump according to claim 4 wherein the means for connecting comprises a slot having a selec-ted size.
7. A centrifugal pump according to claim 4 wherein the means for connecting comprises a slot having a selec-ted size, shape, and orientation.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US48518983A | 1983-04-15 | 1983-04-15 | |
| US485,189 | 1983-04-15 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1222903A true CA1222903A (en) | 1987-06-16 |
Family
ID=23927243
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000444836A Expired CA1222903A (en) | 1983-04-15 | 1984-01-06 | Pump volute communicating slot for stability |
Country Status (5)
| Country | Link |
|---|---|
| JP (1) | JPS59200100A (en) |
| CA (1) | CA1222903A (en) |
| DE (1) | DE3414105A1 (en) |
| FR (1) | FR2544402A1 (en) |
| GB (1) | GB2138504A (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5971023A (en) * | 1997-02-12 | 1999-10-26 | Medtronic, Inc. | Junction for shear sensitive biological fluid paths |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE259984C (en) * | ||||
| GB609971A (en) * | 1945-03-31 | 1948-10-08 | British Thomson Houston Co Ltd | Improvements in and relating to centrifugal compressors |
| US2764944A (en) * | 1954-02-03 | 1956-10-02 | Lucas Industries Ltd | Centrifugal pumps |
| US3120813A (en) * | 1960-04-28 | 1964-02-11 | Bell Aircraft Corp | Centrifugal pump |
| US3957392A (en) * | 1974-11-01 | 1976-05-18 | Caterpillar Tractor Co. | Self-aligning vanes for a turbomachine |
| JPS55151198A (en) * | 1979-05-11 | 1980-11-25 | Matsushita Electric Ind Co Ltd | Electric fan |
-
1984
- 1984-01-06 CA CA000444836A patent/CA1222903A/en not_active Expired
- 1984-01-27 JP JP1222984A patent/JPS59200100A/en active Pending
- 1984-02-24 GB GB8404857A patent/GB2138504A/en not_active Withdrawn
- 1984-04-13 FR FR8405935A patent/FR2544402A1/en active Pending
- 1984-04-13 DE DE19843414105 patent/DE3414105A1/en not_active Ceased
Also Published As
| Publication number | Publication date |
|---|---|
| GB2138504A (en) | 1984-10-24 |
| GB8404857D0 (en) | 1984-03-28 |
| JPS59200100A (en) | 1984-11-13 |
| DE3414105A1 (en) | 1984-10-18 |
| FR2544402A1 (en) | 1984-10-19 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |