EP3303845B1 - Self-priming pump assembly - Google Patents

Description

TECHNICAL AREA

The invention relates to a self-priming pump aggregation, which is a series connection of a working as a rotary positive displacement liquid ring pump and a normal suction centrifugal pump, according to the preamble of claim 1. The invention relates in this context, in particular the liquid-carrying return line, the annular channel of the centrifugal pump with the interior of the positive displacement pump connects, wherein the return line opens out on the annular channel side via the first connection opening, which is arranged in the laterally extending to the impeller plane lateral boundary surface of the annular channel.

STATE OF THE ART

A self-priming pump aggregation of the generic type is from the DE 10 2007 032 228 A1 and from the nachangemeldeten WO 2009/007075 A1 known. In this known pump aggregation necessary for the suction of a liquid evacuation of the suction-side portion of the normal-suction centrifugal pump is accomplished by the centrifugal pump upstream rotary displacement pump. The rotating positive displacement pump embodied as a so-called liquid ring pump is, with sufficient liquid charge in its housing, capable of delivering gas and thus can evacuate an upstream process arrangement and suck and convey liquid or a two-phase flow consisting of liquid and gas. As soon as liquid is sucked in and enters the positive displacement pump and thus into the downstream centrifugal pump, the centrifugal pump essentially takes over the delivery of the liquid or possibly within limits of the two-phase flow in accordance with its delivery characteristic influenced by the flow losses in the upstream positive displacement pump.

The positive displacement pump requires a permanent readiness for operation before evacuation, which may become necessary, of the process arrangement connected on the suction side always the mentioned sufficient liquid template, so that the feed chamber formed by its screw conveyor can ensure the necessary gas transport if necessary. In addition to the supply via the suction line of the pump aggregation, this liquid feed is additionally fed and maintained by a return line for fluid which establishes a connection between a pressure-side interior of the centrifugal pump arranged downstream of the impeller, as seen in the flow direction (a first connection point or first connection opening). and on the other hand the interior of the housing or the suction nozzle of the positive displacement pump or the suction line connected to the latter (a second connection point or second connection opening).

Since the liquid feed of the positive displacement pump to be fed via the return line, it is desirable and advantageous if this return line is primarily applied with liquid. However, the fluid delivery in the return line is necessarily an image of what is available at the first connection point or first connection opening of the return line on the pressure-side interior to each fluid. Depending on the respective process conditions, the pump aggregation and thus also the centrifugal pump in the area of the vorg. pressure-side interior of exclusively liquid up to exclusively gas each two-phase flow, formed of liquid and gas in each given proportions, promoted, so that the known return line is also inevitably acted upon by this respective two-phase flow.

From the vorg. The prior art is known to connect the return line to the annular channel, which is an integral part of the pressure-side interior, and the relevant first connection opening at a radially or approximately radially oriented lateral boundary surface, which is part of the rear housing part and the annular channel in the axial direction in shape an annular surface frontally limited to provide. In this annular channel, which may be formed as a spiral annular channel or as a vane-less annular space with a constant passage cross-section, the flow is delayed, resulting in a part of the kinetic energy the flow leaving the impeller is converted to static pressure so that the static pressure in the annular duct increases overall. The static pressure is, in sufficient height compared to the static pressure in the positive displacement pump, needed for fluid transport in the return line. The arrangement of the first connection opening on the above-described radial or approximately radially oriented lateral boundary surface makes use of the fact that preferably at least not too critical two-phase flow, liquid is in this area and can be "harvested" there, since gas components in axial Direction seen, rearmost, frontal wall area of the annular channel or shovel-free annulus avoid if possible.

It is also known from the aforementioned prior art to position the first port opening with respect to the discharge port of the centrifugal pump, that an assembly plane passing through a radial direction vector, on the one hand by the center of the first port and on the other hand by the axis of rotation of the Pump aggregation runs, is penetrated by the longitudinal axis of the pressure nozzle vertically. In this case, because this is suitable for production, a longitudinal axis of the first connection opening or the return line is preferably arranged centrally or approximately centrally relative to the radial extension region of the lateral boundary surface.

Nevertheless, the improved harvesting of fluid in the region of the connection opening, in particular in its inflow and outflow region, remains a still existing goal. In addition, it has been found that due to the gas admixtures inevitably harvested with the two-phase flow in the inlet region and the immediately adjoining pipe region of the return line additional flow losses occur, which in conjunction with the homogenization effect in the return line disadvantageous to the feed of the positive displacement pump and thus ultimately on the Intake capacity of the entire pump aggregation effect.

Out EP 1 191 228 A2 a self-priming centrifugal pump is known in which a control valve in the return line is arranged to improve the flow to and in the return line. Out GB 1 292 194 A For example, a separate air separation chamber is known to reduce turbulence during the self-priming phase. Out EP 0 936 356 A1 For example, a self-priming centrifugal pump is known in which a reduction in fluid velocity is to be achieved by means of a diffuser provided with a return channel and associated deflector.

It is an object of the present invention to develop a self-priming pump aggregation of the generic type such that the fluidic Conditions for the flow of fluids to and in the return line can be improved.

SUMMARY OF THE INVENTION

The object is achieved by a self-priming pump aggregation with the features of claim 1. Advantageous embodiments of the device according to the invention are described in the subclaims.

The invention proceeds in a manner known per se from a self-priming pump aggregation, which constitutes a series connection of a liquid-ring pump operating as a rotating positive-displacement pump and a normal-suction centrifugal pump. The centrifugal pump has a rotatably mounted shaft with an impeller in a housing provided with an inlet opening and a pressure port. The housing consists preferably, seen in the flow direction, of a front and a rear housing part, and it forms, in addition to the impeller receiving area, an annular channel, the area of the impeller radially outside either in the impeller level and / or in at least one encloses axially adjacent area. The inlet opening is arranged coaxially on the front housing part, wherein an interior bounded by a housing jacket of the displacement pump is connected via the inlet opening to a suction-side interior of the centrifugal pump. In the housing shell, a screw conveyor is arranged, which is fastened on the shaft passing through the impeller and in the housing shell. A fluid-carrying return line is provided, which connects the annular channel with the interior, wherein the return line opens out on the annular channel side via a first connection opening, which is arranged in a lateral boundary surface of the annular channel extending laterally relative to the impeller plane.

The basic inventive idea is that the first connection opening has a bulge which encloses a sectoral axis along a longitudinal axis of the first connection opening. The latter is one-sided and the center of Pump aggregation oriented towards, and it constantly widens the first port to the annular channel out directly or indirectly. At its end facing the annular channel, the bulge with a transition surface in the lateral boundary surface or in an adjoining the latter inner peripheral wall of the annular channel is continuous.

The feature of "steady" extension or "steady" transition should be understood in terms of the known types of mathematical continuity. This means that the composition of a transition curve according to the invention, which presents itself as such in a selected cross-section of an associated transition surface, is made of small pieces or curve segments. For this composition then there is the requirement that the curves should be continuous within the individual segments and that continuity conditions should apply in the connection points. As a result, bumpless entry of the flow into the first connection opening and thus also into the return line is ensured as a result.

These features do not predictably lead to a reduced speed in the inlet region to the first connection opening in cooperation with the peripheral speed in the annular channel on the one hand and a first secondary flow forming in the annular channel as a result of the curved flow and an opposing second secondary flow. This reduction of the speed results from a recirculation flow in the inlet region to the first connection opening, whereby quasi a Totwasserbereich forms there. The recirculation flow is displaced radially into the bulge and the dead water region resulting from this flow effect, a first flow region, is positioned marginally in the annular channel. As a result, the inflow conditions in the inlet region to the first port are thereby improved. The reduction of the speed in the inlet region also leads there to an increase in the static pressure, which increases compared to solutions according to the prior art, the flow in the return line causing pressure difference and reduces the suction time of the pump aggregation.

Furthermore, the measure according to the invention leads to a reduction of the flow vortices in the return line. This reduced turbulence, which can be detected especially in the pipe section of the return line directly adjoining the inlet region, reduces the flow losses and the homogenization effect in the return line (mixing, division and distribution of the gas admixtures into the liquid), whereby the suction time is further reduced and the supply of the Positive displacement pump is further improved.

In the context of a preferred embodiment of the housing of the centrifugal pump, the features essential to the invention come into their own in a special way. This embodiment provides that the front housing part has the outer peripheral wall of the annular channel forming, circular, substantially cylindrically extending outer annular channel housing wall and the latter emerging from the discharge nozzle, which is connected tangentially to the outer annular channel housing wall. The rear housing part has the inner circumferential wall of the annular channel forming inner annular channel housing wall, which preferably runs parallel to the outer annular channel housing wall. In this case, the annular channel is formed in an axially adjacent region of the impeller plane, which, viewed in the flow direction, lies behind the impeller and exclusively outside the region covered by the impeller. The lateral boundary surface is part of the rear housing part, which is preferably aligned radially and the annular channel bounded in the axial direction as the rear, frontal wall region.

In all the above-defined embodiments of the housing of the centrifugal pump, the inflow conditions to and the inlet conditions in the first port and thus in the return line further improved and the recirculation flow is amplified and sustainably generated when, as provided, the first port to the annular channel initially expanded in the form of a countersink. In this embodiment, the bulge according to the invention engages in the axial direction into the countersink or through the countersink, resulting in a continuous cross-sectional widening of the described area towards the annular channel. If the bulge engages only in the countersink, then only the countersink extends to the annular channel out. If it passes through the countersink, then, as viewed in the direction of flow through the return line, the first connection opening widens toward the annular channel. The countersink can be completely or even partially covered in the radial direction of the bulge. The countersink may be, for example, conical, conical, conical in the broadest sense or tulip-shaped. It is preferably formed axially symmetrical and coaxial with the longitudinal axis of the first connection opening, which significantly simplifies their cutting shaping.

A further improvement of the inflow conditions to and the inlet conditions in the first connection opening and thus in the return line turns when, as another proposal provides, the longitudinal axis of the first connection opening is eccentrically offset from the radial extension region of the lateral boundary surface and offset radially inwards , This measure makes a further contribution to the reinforcement and sustainable generation of the recirculation flow already described above. It is in the context of the above-defined radial offset of the longitudinal axis also advantageous if it is spaced apart from the annular channel radially inner side bounding inner peripheral wall to a half inner diameter of the return line. Thereby engage the bulge and / or the countersink, when the latter is provided with a suitable inclination against the longitudinal axis, in the inner annular channel housing wall, whereby the recirculation flow and thus the inflow conditions and the inlet conditions in the first port and thus in the return line are positively influenced in terms of flow.

A preferred embodiment of the invention provides that the longitudinal axis of the first connection opening is perpendicular to and at the point of contact of the tangent to the lateral boundary surface. This embodiment then creates particularly simple geometric conditions with regard to the connection of the return line to the annular channel when the lateral boundary surface of the annular channel is radially aligned.

If there is a radially aligned lateral boundary surface, then a further proposal provides that an axis of symmetry of the bulge forms an angle with the longitudinal axis of the first connection opening perpendicular to the lateral boundary surface, the axial extension direction of the bulge being oriented radially inward. This refinement further improves the inflow conditions for and the inlet conditions into the first connection opening and thus into the return line, because it counteracts a contraction of the flow in the region of the first connection opening by additional expansion of the first connection opening. In addition, thereby the steady transition from the bulge in the adjacent inner peripheral wall of the annular channel is realized virtually without additional shaping measure.

The positive effects described above in connection with a radially directed lateral boundary surface are further enhanced when, as also suggested, a valley bottom, seen towards the center of the pump aggregation, recedes radially inwardly behind the inner peripheral wall and when the bulge with the transition surface steadily merges into the inner peripheral wall.

The above-described measures for the design of the bulge, the countersink and the radial arrangement of the first connection opening are on the one hand per se by cutting shaping relatively easy to produce and on the other hand, they are particularly effective in terms of flow, when the inner and outer peripheral wall of the annular channel parallel or approximately parallel to each other run and the annular channel at its end remote from the impeller level end is bounded by a radially oriented lateral boundary surface.

A further embodiment provides that the longitudinal axis of the first connection opening, viewed in the direction of flow through the return line, is oriented radially inwards towards the center of the pump aggregation. This embodiment is applicable to any geometric shape of the annular channel, even on parallel circumferential walls in conjunction with a radially oriented lateral Limiting surface. It improves in each case the bumpless entry of the flow in the return line, because the described inclination of the longitudinal axis causes a similar fluidic effect as the above-described inclination of the symmetry axis of the bulge.

An advantageous embodiment provides that the first connection opening, seen in a cross-sectional plane perpendicular to the rotation axis of the pump aggregation, is positioned with respect to the discharge nozzle in such a way that a first arrangement plane passing through a radial directional vector, on the one hand through the center of the first connection opening and on the other hand passes through the axis of rotation of the pump aggregate, is penetrated perpendicularly by the longitudinal axis of the pressure port.

Another advantageous embodiment proposes that, in the manner defined above, the first connection opening is positioned in relation to the pressure connection such that a second arrangement plane passing through a radial directional vector passes through the center of the first connection opening on the one hand and through an axial one on the other Symmetryeachse the housing shell extends, is penetrated perpendicularly by the longitudinal axis of the pressure port.

The respectively defined position of the first connection opening means that a point in the annular channel is selected immediately before entry of the flow in the discharge nozzle of the centrifugal pump, at which the maximum possible static pressure within the housing of the centrifugal pump is present. It is understood that the first connection opening can also be arranged between the first and the second arrangement level or in a narrow sectoral area in each case, viewed in the circumferential direction, adjacent to these arrangement areas, without leaving the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Figur 1

in perspektivischer Darstellung die selbstansaugende Pumpenaggregation gemäß der Erfindung;

Figur 2

einen Meridianschnitt durch die Pumpenaggregation gemäß Figur 1 entsprechend einem dort mit A-A gekennzeichneten Schnittverlauf;

Figur 3

einen Querschnitt durch die Zentrifugalpumpe der Pumpenaggregation gemäß Figur 1 entsprechend einem Schnittverlauf, der gegenüber einem in Figur 2 mit B-B gekennzeichneten Schnittverlauf axial so weit vorverlegt ist, dass das hintere Gehäuseteil nicht geschnitten ist, wobei das vor der Schnittebene angeordnete Laufrad zusätzlich in Ansicht dargestellt ist;

Figur 4

in halb Schnitt und halb Ansicht eine in Figur 2 mit "X" gekennzeichnete Einzelheit im Bereich des Ringkanals und eines Teils der sich anschließenden Rückführleitung;

Figur 5

eine Seitenansicht der Anordnung gemäß Figur 4 ;

Figur 6

eine vergrößerte Darstellung der in Figur 2 mit "X" gekennzeichneten Einzelheit, wobei die Darstellung auf den Meridianschnitt durch den Ringkanal und einen Teil der sich anschließenden Rückführleitung beschränkt ist,

Figur 7

eine vergrößerte Darstellung der Anordnung gemäß Figur 6 zur Verdeutlichung strömungstechnischer Vorgänge im dargestellten Bereich und

Figur 7a

die Strömungsverhältnisse im Bereich der durch die Umfangsgeschwindigkeit im Ringkanal quer angeströmten ersten Anschlussöffnung.

A preferred embodiment of the self-priming pump aggregation according to the invention is shown in the drawing and will be described below. Show it

FIG. 1

in perspective view of the self-priming pump aggregation according to the invention;

FIG. 2

a meridian section through the pump aggregation according to FIG. 1 according to a section marked there with AA ;

FIG. 3

a cross section through the centrifugal pump of the pump aggregation according to FIG. 1 according to a cutting process, which is opposite to a FIG. 2 with BB marked cutting path is axially advanced so far that the rear housing part is not cut, wherein the arranged in front of the cutting plane impeller is also shown in view;

FIG. 4

in half cut and half view one in FIG. 2 with "X" marked detail in the region of the annular channel and a part of the subsequent return line;

FIG. 5

a side view of the arrangement according to FIG. 4 ;

FIG. 6

an enlarged view of in FIG. 2 with "X" marked detail, wherein the representation is limited to the meridian section through the annular channel and a part of the subsequent return line,

FIG. 7

an enlarged view of the arrangement according to FIG. 6 to clarify fluidic processes in the area shown and

Figure 7a

the flow conditions in the area of the first connection opening through which the peripheral speed flows in the annular channel.

DETAILED DESCRIPTION

A self-priming pump aggregation 1 ( FIGS. 1 to 3 ) is from a normal suction centrifugal pump (centrifugal pump) 2 and one of these, seen in the flow direction, upstream rotary positive displacement pump 20, which is designed in the embodiment as a so-called. Liquid ring pump is formed. The displacement pump 20 is on the housing side of a housing shell 20.1 ( Figures 2 . 1 ) and a housing cover 20.2 with a centrally arranged on the latter suction nozzle 20.2a limited, wherein the housing shell 20.1 is fixedly connected at its end remote from the housing cover 20.2 end with a front housing part 2.1 of the centrifugal pump 2.

An axial axis of symmetry a _{2 of} the housing shell 20.1 is opposite a rotational axis a _{1 of} the pump aggregation 1 (see FIGS. 1 and 3 ), based on the drawing position of the pump aggregation 1, which also corresponds to the usual installation position, offset by a vertical eccentricity e down. As a result, located in the positive displacement pump 20 screw conveyor 21, which is arranged on a shaft extension 8b of an impeller 4 of the centrifugal pump 2 bearing shaft 8 to this vertical eccentricity e within the housing shell 20.1 moved upwards. The shaft extension 8b adjoins a hub 8a of the shaft 8, wherein on the hub 8a, the impeller 4 is fixed, and it engages through the front housing part 2.1 and in the housing shell 20.1 a. An inner space 20.3 bounded on the inside by the housing jacket 20.1, the housing cover 20.2 and the front housing part 2.1 is provided via an inlet opening 2.1b (2.1b ₎ arranged concentrically in the front housing part 2.1 and thus concentrically with the axis of rotation a1. FIG. 2 ) With a suction-side interior 2.1c of the centrifugal pump 2 fluidly connected.

The structure of the centrifugal pump 2 is for example from the DE 103 14 425 B4 known. A consisting of the front 2.1 and a rear housing part 2.2 housing 2.1 / 2.2 of the centrifugal pump 2 is mounted on a mounting flange 7 on a flying motor 6 ( FIGS. 1 and 2 ). At the front housing part 2.1, the inlet opening 2.1b is centrally formed and at its periphery and there tangentially opening out a discharge nozzle 5 is connected, which ends via a conical extension 5a in a connecting piece 5b.

From the in FIG. 1 with AA marked cutting curve results in accordance with the meridian section FIG. 2 , The front and the rear housing part 2.1, 2.2 are adapted to the impeller 4 in their radial extension region, each with a narrow annular gap. On the annular circumferential impeller outlet cross-section is followed by a blade-less annular space 3a on the outside, which is limited in the radial direction initially on both sides of the front and the rear housing part 2.1, 2.2 a piece and then outside bounded by an unnamed transition surface of the front housing part 2.1. This transition surface is then continued in an outer annular channel housing wall 2.1 a, wherein this at least on the inside, for example, has the shape of a cylinder jacket, ie a constant radius of curvature, an outer radius, has ( FIG. 3 ). The rear housing part 2.2 is formed in the region of the impeller 4 as a preferably radially extending disk. In the outer region of this disk, a mainly axially oriented, from the impeller 4 in the axial direction onward, the axis of rotation a ₁ enclosing inner ring channel housing wall 2.2a connects, the local radius of curvature (variable local inner radius; FIG. 3 ) is variable to realize, for example, a spiral course over the circumference.

The outer and inner annular channel housing wall 2.1a, 2.2a thus form between them an annular channel 3 *, which can be designed as a spiral annular channel 3 ** in the case of a continuously changing passage cross section (variable local radius of curvature). Nevertheless, with the arrangement shown, an annular channel 3 * with a passage cross section which is constant over the circumference can also be realized. The (spiral) annular channel (3 **) 3 * joins laterally to the blade-less annular space 3a; together they form a pressure-side interior 3 of the centrifugal pump second

FIG. 3 shows by way of example how the spiral annular channel 3 **, seen over the circumference, steadily widened. Starting at the farthest point of penetration of the pressure port 5 with the front housing part 2.1, seen in a direction of rotation n of the centrifugal pump 2, the passage cross section of the spiral annular channel 3 ** increases steadily from a minimum cross-section to a point where in FIG. 3 the horizontal center line intersecting with the axis of rotation a _{1 forms} a vertical with the longitudinal axis of the pressure port 5. Up to this point, the inner annular channel housing wall 2.2a is continuously curved. This is followed, preferably, by a non-designated planar wall region which, in the region of the spiral-shaped annular channel 3 **, ensures a passage cross-section which corresponds at least to the passage cross-section of the pressure nozzle 5. Instead of the flat wall region, the inner annular channel housing wall 2.2a may also be formed in a different form, for example continuously curved.

The outer axial boundary of the (spiral) annular channel (3 **) 3 * is realized via a laterally to the inner annular channel housing wall 2.2a, from the axis of rotation a ₁ in the radial direction, in a lateral to the impeller plane extending lateral boundary surface 2.2b, which is part of the rear housing part 2.2 ( FIG. 2 ). The lateral boundary surface 2.2b is preferably oriented radially and bounds the annular channel 3 *, 3 ** in the axial direction as the rearmost, frontal wall region.

The lateral boundary surface 2.2b preferably continues radially outward over the outermost radial extent of the outer annular channel housing wall 2.1a ( FIG. FIG. 2 ). The outer annular channel housing wall 2.1a is adjoined by an unspecified, radially oriented annular surface which corresponds to the lateral boundary surface 2.2b and is detachably connected thereto, which on the outside comprises the lateral boundary surface 2.2b. The two radially oriented aforementioned surfaces are sealed against each other on the annular channel side (housing seal 28; FIG. 6 ), and they have a plurality of distributed through their circumference, mutually corresponding through holes through which the front and the rear housing part 2.1, 2.2 are preferably screwed together.

A return line 9 ( Figures 2 . 1 . 3 ) is connected on the centrifugal pump side via a first connection opening 9a to the annular channel 3 * or the spiral annular channel 3 **. A preferred arrangement point for the first connection opening 9a is the radially oriented lateral boundary surface 2.2b, which is part of the rear housing part 2.2 and the annular channel 3 *, 3 ** frontally limited in the radial direction, ie the annular channel 3 *, 3 ** flows there into the first connection opening 9a.

Best results are achieved if the first connection point 9a is positioned with respect to the discharge nozzle 5 in such a way that a first arrangement plane E (see FIG FIG. 3 ), which passes through a radial direction vector which extends on the one hand through the center of the first connection opening 9a and on the other hand through the axis of rotation a _{1 of} the pump aggregation 1, is penetrated perpendicularly by the longitudinal axis of the pressure port 5. Comparable results are ensured if, instead of the first arrangement plane E, a second arrangement plane E1 is selected which is offset parallel to the first arrangement plane E by the vertical eccentricity e. In this case, the first connection opening 9a is positioned with respect to the discharge nozzle 5 such that the second arrangement plane E1, which passes through a radial direction vector, on the one hand by the center of the first connection opening 9a and on the other hand by an axial axis of symmetry a _{2 of} the housing shell 20.1, is penetrated perpendicularly by the longitudinal axis of the pressure port 5. It is understood that the first connection opening 9a can also be arranged between the first and the second arrangement plane E, E1 or in a narrow sectoral area, viewed in the circumferential direction of the centrifugal pump 2, next to these arrangement planes E, E1, without departing from the invention becomes.

The return line 9 communicates via a second connection opening 9b with the inner space 20.3, the second connection opening 9b being able to be arranged on the housing jacket 20.1 or on the housing cover 20.2 or on the suction nozzle 20.2a or on a suction line 24.

For ease of assembly, the return line 9 between the two connection openings 9 a, 9 b is preferably divided and the ends are connected to one another with a screw 26. For the purpose of the fluid-tight shut-off of the return line 9, a shut-off valve 22 is arranged in this, which is remotely controllable in a preferred embodiment. The remotely controllable shut-off valve 22 is connected via a control line 27 to a signal transmitter 23 which is arranged, for example, in the discharge nozzle 5 or in a pressure line 25 and generates a control signal from a physical variable characterizing the liquid conveyance in the pump aggregation 1 ( Figures 2 . 3 ).

A preferred embodiment of the housing 2.1 / 2.2 and the annular channel 3 *, 3 ** of the centrifugal pump 2 show the Figures 2 and 4 to 7 . The front housing part 2.1 ( FIGS. 6 . 2 ) has an outer peripheral wall 29 of the annular channel 3 *, 3 ** forming, circular, substantially cylindrically extending outer annular channel housing wall 2.1a and the latter emerging from the discharge nozzle 5, which is connected tangentially to the outer annular channel housing wall 2.1a is. The rear housing part 2.2 has the inner circumferential wall 30 of the annular channel 3 *, 3 ** forming inner annular channel housing wall 2.2a, which preferably runs parallel to the outer annular channel housing wall 2.1a. In this case, the annular channel 3 *, 3 ** is preferably formed in an axially adjacent region of the impeller plane, which, seen in the flow direction, is behind the impeller 4 and exclusively completely outside the region covered by the impeller 4. The lateral boundary surface 2.2b is part of the rear housing part 2.2); it is preferably radially aligned and bounds the annular channel 3 *, 3 ** in the axial direction as the rear, frontal wall region.

The features of the invention characterizing and advantageously ausgestaltenden features are exemplified in the above-defined preferred embodiment of the housing 2.1 / 2.2 and the annular channel 3 *, 3 ** represented ( FIGS. 4 to 7 ) and explained in their mode of action. The ring channel 3 *, 3 ** has in the illustrated meridian plane ( FIG. 6 ) a local ring channel width s, the center of which is defined by a respective half local ring channel width s / 2 shown. A longitudinal axis a _{3 of} the first connection opening 9a is a radial offset Δr eccentrically offset to the lateral extent of the lateral boundary surface 2.2b and radially offset inwardly, the latter being within the annular channel 3 *, 3 ** as the end wall 31.

This arrangement leads unpredictably in cooperation with a peripheral speed c _u in the annular channel 3 *, 3 ** (see Figures 3 and 5 ) on the one hand and a first secondary flow S1 forming there as a result of the curved flow and an opposing second secondary flow S2 (FIG. FIG. 7 On the other hand, at a reduced speed in a first flow area B1. The first flow region B1, seen in the direction of flow through the ring line 9, precedes the inlet region to the first connection opening 9a and radially displaces the bulge 33 designed and positioned according to the invention. It forms in the first flow area B1, marginally in the annular channel 3 *, 3 **, quasi a dead water zone. This dead water zone results from a recirculation flow R, as in Figure 7a which finds its cause and its generation in the bulge 33 and which significantly improves the inflow conditions in the inlet region to the first connection opening 9a. The described reduction of the speed also leads there to an increase in the static pressure, which increases compared to solutions according to the prior art, the flow in the return line 9 causing pressure difference and reduces the suction time of the pump aggregation 1.

On the one hand, the bulge according to the invention leads to a reduction in the number of flow vortices and, on the other hand, to a reduction in their intensity in the return line 9. This reduced turbulence, particularly in a tube region of the return line 9 directly adjoining the inlet region to the first connection opening 9a, has an in FIG. 7 B2, the flow losses and the Homogenisierungseffekt (mixing, distribution and distribution of Gasbeimengungen into the liquid) in the return line 9, which further reduces the suction time of the pump aggregation 1 and the supply of the positive displacement pump 20 with less gas laden Fluid further improved becomes. As a result of the features according to the invention, the second flow region B2 is noticeably slimmer and less narrowing in cross-section than without these features.

An advantageous embodiment provides that the first connection opening 9a is widened towards the annular channel 3 *, 3 ** initially in the form of a countersink 32 ( FIG. 6 ). In this case, the bulge 33 engages in the axial direction either only in the countersink 32 or through it completely into the first connection opening 9a or the inner diameter of the return line 9 therethrough. If the bulge 33 engages axially only in the countersink 32, then only the countersink 32 widens toward the annular channel 3 *, 3 **. If it passes through the countersink 32, then, as seen in the direction of flow through the return line 9, the first connection opening 9a or the inner diameter of the return line 9 widens toward the annular channel 3 *, 3 **. The countersink 32 can be completely or even partially covered in the radial direction by the bulge 33. This countersink 32 may be conical, conical or conical or tulip-shaped, wherein the transition to the inner tube of the return line 9 is preferably rounded, ie preferably convexly curved, designed to avoid or at least reduce a constriction of the pipe flow.

A preferably cutting shaping of the countersink 32 is simplified if the latter is formed axially symmetrical and coaxial to the longitudinal axis a ₃ . In this case, the annular channel-side end portion of the inner tube of the return line can serve, for example, as a guide for the cutting shaping tool.

A further improvement of the inflow conditions to and the inlet conditions in the first port opening 9a and thus in the return line 9 adjusts ( FIG. 6 ), When the longitudinal axis a _{3 of} the first connection opening 9a is arranged eccentrically offset from the radial extension region of the lateral boundary surface 2.2b and radially inwardly. The radial offset of the longitudinal axis a ₃ ( FIGS. 7 , 7a ) enhances the formation of the recirculation flow R and also ensures its sustainable generation.

It is in connection with the above-defined radial offset of the longitudinal axis a ₃ further advantageous if it is spaced apart from the annular channel 3 *, 3 ** radially inner side bounding inner peripheral wall 30 to a half inner diameter of the return line 9. Thereby engage the bulge 33 and / or the countersink 32, when the latter is provided with a suitable inclination against the longitudinal axis a ₃ , in the inner annular channel housing wall 2.2a, whereby the recirculation flow R and thus the inflow conditions and the inlet conditions in the Bulge 33, the countersink 32, the first port 9a and thus in the return line 9 fluidically positively influenced.

With regard to the direction of the outlet of the return line 9 from the annular channel 3 *, 3 **, the invention provides two alternative variants. The first variant is characterized in that the longitudinal axis a _{3 is} perpendicular to and at the point of contact of the tangent to the lateral boundary surface 2.2b. In the second variant, the longitudinal axis a ₃ , viewed in the direction of flow of the return line 9, is oriented radially inwards toward the center of the pump aggregation 1.

The choice of the two variants mentioned is also dependent on the course of the lateral boundary surface 2.2b. The centrifugal pump technique knows annular channels with circular, oval, elliptical, trapezoidal radially outwardly expanding, rectangular or square passage cross-section. In accordance with an extension profile of the lateral boundary surface 2.2b, resulting from the above cross-sectional shape, to which the return line 9 is connected according to the invention, the result is whether the flow can enter the first connection opening 9a to the return line 9 more or less smoothly. Bump-free entry can be brought about by changing the angle of inclination between the longitudinal axis a ₃ and the direction of the lateral boundary surface 2.2b. For example, if the lateral boundary surface 2.2b is radial aligned, then by applying the second variant (orientation of the longitudinal axis a ₃ radially inwardly), the degree of deflection of the entering into the return line 9 flow in the region of the first connection opening 9a can be reduced. If, for example, the annular channel 3 *, 3 ** is circular and the first connection opening 9a is located, for example, in the middle region of the first quadrant of the circular cross section of the annular channel 3 *, 3 **, then the first variant (longitudinal axis a ₃ is perpendicular to and at the point of contact of the tangent to the lateral boundary surface 2.2b) are applied, because then the longitudinal axis a ₃ , seen in the direction of flow of the return line 9, is already aligned per se radially inward.

If the embodiment of the annular channel 3 *, 3 ** provides a radially oriented lateral boundary surface 2.2b, then a further improvement of the inflow conditions for and the inlet conditions into the first connection opening 9a results from a proposal which provides that an axis of symmetry a ₄ of FIG Bump 33 forms an angle w with the perpendicular to the lateral boundary surface 2.2b longitudinal axis a ₃ , wherein the axial extension direction of the bulge 33 is oriented radially inwardly.

According to another proposal, the above embodiment can be aerodynamically further optimized in that a low point of the bulge 33, viewed in the direction of the center of the pump aggregation 1, recedes radially inwards behind the inner peripheral wall 30 and that the bulge 33 with the transition surface 34 in steadily the inner peripheral wall 30 passes.

The embodiments of the pump aggregation 1 described above include the bulge 33 and / or the countersink 32 and / or the radial offset of the first connection opening 9a in accordance with the claims. Any meaningful combination of these inventive features, starting in each case from the realization of the bulge 33, is executable and each provides a solution that has advantages over the acknowledged relevant prior art. For example, the bulge 33 can directly follow the first connection opening 9a, the latter being offset radially or centered in the annular channel 3 *, 3 ** can be arranged. The annular channel 3 *, 3 ** itself can be realized in relation to the area covered by the impeller 4 in the most different axial positions, which are applied in the claims and also indicated in the above description. The annular channel 3 *, 3 ** is designed either as a vane-free annular space 3 * with a passage cross section which is constant over the circumference or as a spiral annular channel 3 ** with a continuously changing passage cross section. The cross-sectional shape of the annular channel 3 *, 3 ** may be circular, oval, elliptical, trapezoidal and radially outwardly enlarging, rectangular or square.

REFERENCE LIST OF ABBREVIATIONS USED

1

self-priming pump aggregation

2

(normal suction) centrifugal pump (centrifugal pump)

2.1 / 2.2

casing

2.1

front housing part

2.1a

outer ring channel housing wall

2.1b

inlet port

2.1c

suction-side interior

2.2

rear housing part

2.2a

inner ring channel housing wall

2.2b

lateral boundary surface

3

pressure-side interior

3 *

annular channel

3 **

spiral annular channel

3a

Bladeless annulus

4

Wheel

5

pressure port

5a

conical extension

5b

spigot

6

engine

7

mounting flange

8th

wave

8a

hub

8b

Shaft extension

9

(liquid-carrying) return line

9a

first connection opening

9b

second connection opening

20

rotating positive displacement pump (liquid ring pump)

20.1

housing jacket

20.2

housing cover

20.2a

suction

20.3

inner space

21

Auger

22

shut-off valve

23

signaler

24

suction

25

pressure line

26

screw

27

control line

28

housing seal

29

outer peripheral wall

30

inner peripheral wall

31

bulkhead

32

Countersink (cone-shaped, tulip-shaped)

33

bulge

34

Transition surface

a ₁

Rotary axis of the pump aggregation 1

a ₂

Axial axis of symmetry of the housing shell 20.1

a ₃

Longitudinal axis of the first connection opening 9a

a ₄

Symmetry axis of the bulge 33

c _u

Peripheral speed in the ring channel 3 *, 3 **

e

(vertical) eccentricity

n

direction of rotation

s

local ring channel width

s / 2

half local ring channel width

w

angle of attack

B1

first flow area

B2

second flow area

e

first arrangement level

E1

second arrangement level

R

recirculation

S1

first secondary flow

S2

second secondary flow

Claims (12)

1. Self-priming pump unit (1) which constitutes a series connection of a liquid ring pump operating as a rotating positive displacement pump (20) and a normally priming centrifugal pump (2), the centrifugal pump (2) being arranged in a housing (2.1/2.2) which is provided with an inlet opening (2.1b) and pressure connection piece (5), the housing (2.1/2.2) having a rotatably mounted shaft (8) with an impeller (4), the housing (2.1/2.2), viewed in the direction of flow, comprising a front housing part (2.1) and a rear housing part (2.2) and forms an annular channel (3*; 3**) which surrounds the region of the impeller (4) radially on the outside, either in the impeller plane and/or in at least one axially adjacent region, the inlet opening (2.1b) being arranged coaxially on the front housing part (2.1), an internal space (20.3) bounded by a housing casing (20.1) of the positive-displacement pump (20) is connected to an interior space (2.1c) on the suction side of the centrifugal pump (2) via the inlet opening (2.1b) and a screw conveyor (21) is arranged in the housing casing (20.1), which screw conveyor (21) is fastened on the shaft (8) which engages through the impeller (4) and into the housing casing (20.1), a liquid-conducting return line (9) being provided, which connects the annular channel (3*; 3**) to the interior (20.3), the return line (9) terminating on the annular channel side via a first connecting opening (9a) which is arranged in a lateral boundary surface (2.2b) of the annular channel (3*; 3**) running laterally to the impeller plane,
   characterized by in that the first connecting opening (9a) has a bulge (33) which sectorally encloses a longitudinal axis (a3) of the first connecting opening (9a), in that the bulge (33) is oriented on one side and towards the centre of the pump unit (1), in that the bulge (33) continuously extends the first connecting opening (9a) towards the annular channel (3*; 3**) directly or indirectly, and in that the bulge (33), at its end section facing the annular channel (3*; 3**), has a transition surface (34) which continuously extends into the lateral boundary surface (2.2b) or into an inner circumferential wall (30) of the annular channel (3*; 3**) adjoining the latter.
2. Self-priming pump unit (1) according to claim 1, characterised in that, the front housing part (2.1) has the circular, substantially cylindrically extending outer ring channel housing wall (2.1a) forming an outer circumferential wall (29) of the ring channel (3*;3**) from which the pressure connection piece (5) leads to, which is connected tangentially to the outer ring channel housing wall (2.1a), in that the rear housing part (2.2) has the inner ring channel housing wall (2.2a) which forms the inner circumferential wall (30) of the ring channel (3*;3**) and runs parallel to the outer ring channel housing wall (2.1a), in that the ring channel (3*;3**) is formed in a region which is axially adjacent to the impeller plane and which, viewed in the flow direction, lies behind the impeller (4) and exclusively outside the region encompassed by the impeller (4), and in that the lateral boundary surface (2.2b) is part of the rear housing part (2.2) which is radially aligned and encloses the ring channel (3*;3**) in the axial direction as the rearmost wall region on the end face.
3. Self-priming pump unit according to claim 1 or 2, characterized in that the first connecting opening (9a) is initially widened towards the annular channel (3*; 3**) in the form of a countersink (32), and in that the bulge (33) engages in the countersink (32) in the axial direction or through the countersink (32) and in the process continuously widens the countersink (32) towards the annular channel (3*; 3**).
4. Self-priming pump unit according to claim 3, characterized in that the countersink (32) is axially symmetrical and coaxial with the longitudinal axis (a3).
5. Self-priming pump aggregation according to one of the preceding claims, characterized in that the longitudinal axis (a3) is arranged eccentrically to the radial extent region of the lateral boundary surface (2.2b) and offset radially inwards.
6. Self-priming pump unit according to claim 5, characterized in that the longitudinal axis (a3) is spaced apart from the inner circumferential wall (30) delimiting the annular channel (3*; 3**) radially on the inside by half an inner diameter of the return line (9).
7. Self-priming pump uniting according to one of the preceding claims, characterized in that the longitudinal axis (a3) is perpendicular to and at the point of contact of the tangent to the lateral boundary surface (2.2b).
8. Self-priming pump unit (1) according to claim 7 and having a radially aligned lateral boundary surface (2.2b), characterized in that an axis of symmetry (a4) of the bulge (33) forms an angle (w) with the longitudinal axis (a3) which in turn is perpendicular to the lateral boundary surface (2.2b), the axial direction of extension of the bulge (33) being oriented radially inwards.
9. Self-priming pump unit (1) according to claim 8, characterized in that a low point of the bulge (33), viewed in the direction towards the centre of the pump unit (1), recedes radially inwards behind the inner circumferential wall (30), and in that the bulge (33) with the transition surface (34) merges continuously into the inner circumferential wall (30).
10. Self-priming pump unit according to one of claims 1 to 6, characterized in that the longitudinal axis (a3), viewed in the throughflow direction of the return line (9), is oriented radially inwards towards the centre of the pump aggregation (1).
11. Self-priming pump unit according to one of the preceding claims, characterized in that the first connecting opening (9a) is positioned with respect to the pressure connecting piece (5) in such a way that a first plane of arrangement (E) which passes through a radial direction vector, the radial direction vector spanning from the centre of the connecting opening (9a) through an axis of rotation (a1) of the pump assembly (1), is perpendicularly penetrated by the longitudinal axis of the pressure connecting piece (5).
12. Self-priming pump unit according to one of the preceding claims 1 to 10, characterized in that the first connection opening (9a) is positioned with respect to the pressure connecting piece (5) in such a way that a second arrangement plane (E1) which passes through a radial direction vector the radial direction vector spanning from the centre of the connecting opening (9a) through an axial axis of symmetry (a2) of the housing casing (20.1) and on the other hand is penetrated by the longitudinal axis of the pressure connecting piece (5).

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