EP0599204A1 - Submersible pump assembly - Google Patents

Abstract

The submersible-pump (submerged-pump) assembly (unit) essentially consists of an electric motor (1) and a centrifugal pump driven thereby, which are arranged coaxially in a common casing (2). It has an inlet port (15) and an outlet port constructed as a discharge nozzle (16). Concentrically with the impeller (10) there runs a casing wall (21) which surrounds the impeller and has a fillet (18) which forms a stagnation zone for the discharge-side flow. Adjoining in or near this stagnation zone there is a duct (17), for example in the form of a pipe, which runs to the discharge nozzle (16). <IMAGE>

Description

The invention relates to a submersible pump unit with a free passage for balls up to diameter d, consisting essentially of an electric motor and a centrifugal pump driven by it, which are arranged axially, with an inlet opening and an outlet opening designed as a pressure port.

Such units are used for example in the field of wastewater technology. They are used not only to convey pure or contaminated liquids, but also to transport solids carried in the liquid. Such units are therefore designed so that solid parts can be conveyed up to the size of a ball that fits through the inlet opening. They are therefore often e.g. used in the construction or food industry.

In order to allow the passage of large solid parts, it is known to design the impeller as a single-bladed, ducted or free-flow impeller. The inlet opening is usually located on the underside of the pump directly below the impeller. The outlet opening in the form of the pressure port is usually arranged radially to the impeller. Such a pump is known for example from US Pat. No. 4,454,993 or US Pat. No. 4,697,746. However, these pumps are a shredder assigned in the conveying direction in front of the impeller, which is to shred the solid parts before entering the area of the pump impeller.

Submersible pump units with a concentric housing are also known, from which the fluid is radially discharged and then directed in a bend in the direction parallel to the axis.

All these known submersible pump units have in common a comparatively poor efficiency, since large losses occur within the pump housing during the conversion of kinetic to potential energy. Another disadvantage of this type of construction is that due to the radially led out pressure connection, the pump assembly is relatively bulky, which is particularly disadvantageous when it is used in narrow shafts, pipes or the like.

On the basis of the prior art described in the introduction, the object of the invention is to create a submersible pump unit which has a better efficiency, in particular with a large free delivery cross section, and which can be made slimmer in comparison to the known submersible pump units.

This object is achieved according to the invention in that the approximately concentric pump housing with an inner diameter D is formed as a molded part, the housing wall of which has a bulge which forms a stagnation zone for the pressure-side flow, in which the fluid is deflected in a substantially axially parallel direction and is led through a channel to the pressure port.

In the present invention, a significantly better efficiency is achieved compared to known designs, since the Conversion of kinetic into potential energy takes place with less loss. The deflection of the flow in the area of the stowage zone in the direction parallel to the axis while simultaneously reducing the speed to the pressure port level ensures low-loss energy conversion in the pressure area of the unit.

bis zur Wand des konzentrischen Gehäuses hin ab. Diese Umfangskomponente an der Gehäusewand liegt bei den meisten der bekannten Pumpen im Bereich der zwei- bis fünffachen Stutzengeschwindigkeit des jeweiligen Aggregats. Durch die Verformung der konzentrischen Wand zu einer Stauzone mit einem in diesem Bereich anschließenden, zum Druckstutzen führenden Kanal kann ein Teil der im drallbehafteten Förderstrom vorhandenen kinetischen Energie in potentielle Energie umgesetzt werden. Gleichzeitig wird eine Umlenkung der Strömung in eine etwa achsparallele Richtung, also in der Regel vertikale Richtung vorgenommen, wodurch sich der Aggregatdurchmesser erheblich verringern läßt, weil der Querschnitt des Kanals auch einen Teil der zwischen dein Laufrad und dem konzentrischen Gehäuse liegenden Fläche überdecken darf. Die Lage des Mittelpunktes M, von dem aus der Kreisbogenteil für die Ausbuchtung zu ziehen ist (vorzugsweise mit dem Radius $\text{r = d/2}$

), sollte so gewählt werden, daß der Abstand vom Kreisbogen des konzentrischen Gehäuses (Durchmesser D) nicht größer als d/4 ist. Der Übergang von der Stauzone zum konzentrischen Gehäuse sollte abgerundet, und zwar mit einem Übergangsradius r_ü ausgeführt sein.The circumferential component of the flow c _u leaving the impeller is based on the area set

${\text{r · c}}_{\text{u}}\text{= const.}$

down to the wall of the concentric housing. With most of the known pumps, this peripheral component on the housing wall is in the range of two to five times the nozzle speed of the respective unit. Due to the deformation of the concentric wall to form a storage zone with a channel in this area that leads to the pressure port, part of the kinetic energy present in the swirling flow can be converted into potential energy. At the same time, the flow is deflected in an approximately axially parallel direction, that is to say generally in the vertical direction, as a result of which the aggregate diameter can be considerably reduced because the cross section of the channel may also cover part of the area between the impeller and the concentric housing. The location of the center point M, from which the circular arc part for the bulge is to be drawn (preferably with the radius $\text{r = d / 2}$

), should be chosen so that the distance from the circular arc of the concentric housing (diameter D) is not greater than d / 4. The transition from the storage zone to the concentric housing should be rounded, with a transition radius r _ü .

Experiments have shown that the additional pressure head build-up by the solution according to the invention - in which the center M of the bulge lies on the diameter D of the concentric housing and the radius of this bulge corresponds to half the ball diameter, the base of the bulge being part of a spherical surface - compared with a submersible pump unit with the same delivery rate and the same free delivery passage according to the state of the art in the order of 6 to 10% of the pump head. This percentage is roughly equivalent to improving pump efficiency.

In addition to the increase in efficiency due to the improved fluid flow inside the unit, there is the advantage that the unit can be built in a slimmer form, which increases the area of application and reduces the material expenditure.

The size of the unit, especially the motor, can be reduced if adequate cooling can always be guaranteed. This is particularly effective when the liquid is used as a cooling liquid. A simple solution is to provide openings at the beginning and end of the duct that lies within the unit housing and runs between the accumulation zone and the pressure port. Through the openings at different pressure levels, a partial flow for motor cooling is passed through the annular space between the unit housing and the encapsulated stator.

In order to achieve a comparatively good efficiency with the largest possible free passage, the unit is advantageously equipped with a single-bladed, ducted or free-flow impeller, the wall surrounding the impeller then expediently being part of a shell-shaped housing part which belongs to the unit housing and forms, for example, the lower housing part. Such a shell-shaped housing part can be formed inexpensively from cold-formed steel sheet, which also has the advantage that the roughness of the surface is very low, which in turn benefits the improvement in efficiency.

The bulge forming the storage zone in the housing wall is advantageously designed such that the cross section of this bulge follows an arc in the storage area, the diameter of this circle corresponding to that of the inlet opening and that of the channel and the pressure port. This largely ensures that everything that can enter the unit through the inlet opening is also conveyed out again, in particular does not become lodged within the unit.

bewegen.In order to achieve the best possible conversion of kinetic to potential energy, the bulge which forms the storage zone is advantageously arranged in the housing wall in such a way that, viewed in the direction of flow, it connects approximately tangentially to the concentric part of the housing wall. The transition radius from the storage zone to the concentric part of the housing has also proven to be influential. This transition radius r _ü should be between the limits

${\text{d / 8 ≦ r}}_{\text{ü}}\text{≦ d / 4}$

move.

In particular, if the conveying liquid carries solid particles, an increased abrasive load will be found in the area of the storage zone. It is therefore expedient either to form this part of the wall from correspondingly wear-resistant material or to cover it with wear-resistant material.

Figur 1

in stark vereinfachter Darstellung ein Tauchpumpenaggregat im Längsschnitt,

Figur 2

eine Draufsicht auf das untere Gehäuseteil des Aggregates,

Figur 3

einen Schnitt längs der Schnittlinie III-III in Figur 2 und

Figur 4

eine perspektivische Darstellung der Pumpengehäusewand im Bereich des Laufrades und der Stauzone sowie die Anordnung des die Stauzone mit dem Druckstutzen verbindenden Rohres innerhalb des Gehäuses.

The invention is explained below with reference to an embodiment shown in the drawing. Show it:

Figure 1

in a greatly simplified representation, a submersible pump unit in longitudinal section,

Figure 2

a plan view of the lower housing part of the unit,

Figure 3

a section along the section line III-III in Figure 2 and

Figure 4

a perspective view of the pump housing wall in the area of the impeller and the accumulation zone and the arrangement of the tube connecting the accumulation zone with the pressure port within the housing.

FIG. 1 shows a submersible pump unit which has an encapsulated motor 1 which is seated within the essentially cylindrical unit housing 2. The electrical supply line 3 of the motor 1 is led out of the motor housing 4 and the unit housing 2 upwards. The motor housing 4 sits slightly eccentrically within the unit housing 2, an annular space 5 being formed in this area between the outer circumference of the motor housing 4 and the inside of the unit housing 2. This annular space is closed at the top by the end wall 6 of the unit housing and at the bottom by an annular end wall 7, which forms part of the actual pump housing.

The shaft 8 of the motor 1 is led out of the motor housing 4 downwards and sealed against it in this area. The lower free shaft end protrudes into the pump chamber 9 and carries there an impeller 10 in the form of a free-flow impeller. The impeller is closed at the top by a disk-shaped impeller part 11, which is arranged perpendicular to the shaft 8 and carries impeller blades 12.

The pump chamber 9 is delimited at the top by the lower end of the motor housing 4 and the end wall 7. The lateral and lower boundary is formed by a molded part 13, which is approximately bowl-shaped, consists of cold-formed sheet metal and is firmly connected to the other unit housing 2, in particular the foot 14.

The foot 14 is flush with the cylindrical outer contour of the other unit housing 2 and (not shown) has sufficiently large recesses for the free passage of the medium. The molded part 13 has a circular recess 15 in the area under the impeller 10, that is, in the extension of the shaft 8, which forms the inlet opening of the pump.

The outlet opening of the unit is formed by a pressure port 16 arranged on the upper end face, which is connected to the pump chamber 9 via a pipe 17 arranged in the annular space 5 of the unit housing 2, approximately parallel to the longitudinal axis of the unit and the shaft 8. The tube 17 opens into the end wall 7, specifically in the area above a bulge 18 forming a storage zone in the molded part 13. The tube 17 connects to the pump chamber 9 approximately at the level of the disk-shaped impeller part 11.

Shortly above its connection to the pump chamber 9, but above the end wall 7, that is to say in the area of the annular chamber 5, the tube 17 has recesses 19 in the form of circular openings. Corresponding recesses 20 are close the upper end, that is, close to the pressure connection 16 in the pipe 17. These recesses 19 and 20 are at different pressure levels during operation of the pump, so that in addition to the main flow flowing through the pipe 17, a secondary flow flowing out of the pipe 17 via the recesses 19 and re-entering via the recesses 20 adjusts the annular space 5 flows through and thus cools the engine 1. This cooling flow can be adjusted by appropriate dimensioning of the recesses 19 and 20 and other suitable fluidic measures within the annulus 5 according to the cooling requirements.

The molded part 13 is shown in detail with reference to FIGS. 2 to 4. In the area of the actual pump chamber, it has an approximately concentric housing wall 21, which merges tangentially into the corresponding wall part of the bulge 18 in the area 22. The area 22 is in plan view (FIG. 2) both tangential to the concentric housing wall part 21 and to that of the bulge 18 which is eccentrically aligned with the pipe 17. The housing wall 21 merges upwards with a small radius into a horizontal part 23 with which it is connected to the rest of the unit housing 2. This horizontal part 23 is followed, as can be seen in FIG. 3 and FIG. 4, by a collar-shaped part 24.

At the bottom, the housing wall 21 merges with a large radius into a likewise horizontal, but inwardly running wall part 25, which limits the pump chamber 9 in this area at the bottom. In the area below the impeller 10, the horizontal wall part 25 runs downward like a shell toward the recess 15, this shell-shaped part is designated by 26. The radius r with which the housing wall 21 merges into the wall part 25 corresponds to the radius r of the bulge 18, which in this area has a spherical surface follows. The radius r is half the diameter d of the inlet opening 15, the tube 17. This diameter d also corresponds approximately to the distance between the impeller and the underlying housing parts of the molded part 13. In this way, a free passage of the order of one Ball with the aforementioned diameter d guaranteed by the entire pump unit.

While the housing wall 21 merges tangentially into the bulge 18 in the flow direction, which is identified by the arrow 27 in FIG. 4, a projection 28 is formed in the opposite direction, where the tangents of the housing wall parts 21 of the concentric part and the bulge 18 intersect.

The geometric relationships of the molded part 13 have already been explained in the introduction, they are shown in detail in FIG. 2. The ball diameter of the largest ball is indicated with d, which can be conveyed through the unit with the flow. D denotes the diameter of the concentric part of the pump housing, that is to say in the concentric region of the housing wall 21. The bulge 18, which follows a spherical surface with the radius r, is arranged such that the center M of this sphere lies on an arc of a diameter B arranged concentrically with the pump impeller 10. This diameter B can be freely selected in the range between B _max and B _min , B _{max being} determined by the diameter D of the concentric housing part 21 plus a quarter of the ball diameter d and B _min by the aforementioned diameter D minus a sixth of the ball diameter d, the following relationship applies:

${\text{B}}_{\text{Max}}{\text{= D + d / 4 ≧ B ≧ D - d / 6 = B}}_{\text{min}}$

The transition radius r _ü already mentioned at the beginning is one sixth of the ball diameter in the embodiment shown, but it can be between an eighth and a quarter of the ball diameter d

${\text{d / 4 ≧ r}}_{\text{ü}}\text{≧ d / 8.}$

It goes without saying that the ball diameter d not only determines the design of the molded part 13, but in the same way the diameter of the recess 15, that of the tube 17 and that of the adjoining pressure connector 16.

When the pump is operating, the unit is partially or completely immersed in the liquid to be pumped. The pumped medium enters the pump chamber 9 through the inlet opening 15 and is set in motion by the impeller 10, namely in the radial and tangential directions. It is then guided through the housing wall 21 and directed over the area 22 to the bulge 18. A storage zone now forms here, the conveying liquid is deflected upwards, where it enters the pipe 17 and finally exits at the pressure connection 16. The partial flow for cooling that is formed has already been described above.

Reference list

1

- Engine

2nd

- Unit housing

3rd

- Management

4th

- motor housing

5

- annulus

6

- front wall

7

- annular end wall

8th

- Wave

9

- pump room

10th

- Wheel

11

- impeller part (disc)

12th

- impeller blade

13

- molded part

14

- Foot

15

- recess (inlet opening)

16

- discharge nozzle

17th

- Pipe

18th

- bulge

19th

- recess at the bottom

20th

- Recess at the top

21

- housing wall

22

- Area

23

- horizontal part

24th

- collar-shaped part

25th

- wall part (horizontal)

26

- bowl-shaped part

27

- flow direction

28

- Head Start

r _ü

- transition radius

r

- Radius of the bulge 18

M

- Geometric center of the bulge 18

D

- Diameter of the concentric pump housing in the area 21

B

- Circular arc with the center point M.

B _max

- maximum diameter B

B _min

- minimum diameter B

d

- ball diameter

Claims (8)

Submersible pump unit with free passage for balls up to diameter d, consisting essentially of an electric motor (1) and a centrifugal pump driven by it, which are arranged axially with an inlet opening (15) and an outlet opening designed as a pressure port (16), characterized in that the approximately concentric pump housing with an inner diameter D is formed as a molded part (13), the housing wall (21) of which has a bulge (18) which forms a stagnation zone for the pressure-side flow, in which the fluid is deflected in an essentially axially parallel direction and through a channel (17) to the pressure port (16) is guided. Submersible pump unit according to Claim 1, characterized in that a circle can be written into the bulge (18), the radius r of which lies between one and two thirds of the ball diameter d, preferably corresponds to half the ball diameter d, and that the center M of this circle is concentric on one to the pump axis is a circular arc whose diameter B lies in the range between D - d / 6 and D + d / 4. Submersible pump unit according to claim 1 or 2, characterized in that the base of the bulge (18) is part of a spherical surface. Submersible pump unit according to one of the preceding claims, characterized in that the channel (17) located within the housing (2) has at least two openings (19, 20) located at different pressure levels in order to divert part of the delivery liquid as a cooling flow for the motor (1). to branch off. Submersible pump unit according to one of the preceding claims, characterized in that the pump has a single-bladed, ducted or free-flow impeller (10) and that the wall (21) surrounding the impeller (10) is part of a shell-shaped housing part (13). Submersible pump unit according to one of the preceding claims, characterized in that the shell-shaped housing part (13) consists of cold-formed sheet steel. Submersible pump unit according to one of the preceding claims, characterized in that the housing wall (21) in the region (22) leading to the accumulation zone (viewed in flow direction 27) extends approximately tangentially to its concentric part and to the bulge (18) and from the bulge ( 18) rounded with a transition radius r _ü into the concentric housing wall part, the transition radius r _{ü being} between an eighth and a quarter of the ball diameter d. Submersible pump unit according to one of the preceding claims, characterized in that the housing wall is covered with wear-resistant material at least in the area of the storage zone.

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