EP3140548B1 - Impeller for regenerative pump - Google Patents

Description

The invention relates to an impeller according to the features of the preamble of claim 1.

An impeller of the type in question is, for example, from DE 10 2005 008 388 A1 known.

Next is the prior art on the US2003/118438 A1 , the U.S. 5,407,318 A , the U.S. 2005/226715 A1 and the U.S. 2003/026686 A1 to refer.

The U.S. 5,407,318 A discloses blades that end freely on the outside, the edge of which is clearly set back to a maximum radial dimension of the blade walls.

Based on the prior art mentioned in accordance with US2003/118438 A1 , the invention is concerned with the task of further developing an impeller of the type mentioned in an advantageous manner, in particular with regard to improved efficiency.

This object is achieved with the subject matter of claim 1, whereby it is based on the fact that the largest offset dimension corresponds to 0.1 times or more the difference between the second and the first radius dimension and that the closing edge essentially follows a radius line and that a radius of the Final edge is removed from a circle center in a circumferential direction following vane chamber is located.

Impellers of this type are widely used in side channel compressors and side channel vacuum pumps, which enable a wide range of industrial applications, for example in printing, packaging, electronics, environmental and medical technology, etc. These turbomachines have at least one annular working space with a substantially circular cross section, in which an impeller with blading, ie blades and blade chambers located between them, is rotatably accommodated in the circumferential direction of the impeller. The unfilled cross-section of the working space, possibly bordering the blading on both sides of the impeller, forms a side channel in each case, which is interrupted on the circumference by the so-called interrupter. An inlet for a fluid to be compressed (e.g. gas or liquid) is located behind the interrupter in the direction of rotation or rotation of the impeller, while an outlet is located in front of the interrupter in the direction of rotation. Due to the rotation of the impeller, the fluid flows through the inlet into the side channel and is carried along by the blades of the impeller. In the flow spaces, the fluid is pushed outwards due to the centrifugal force and is compressed there. The inflowing fluid pushes the compressed fluid out of the blades into the side channel, where it is directed radially inward and reenters the impeller blading. The fluid flows from the side channel at the front of the impeller through a radially inner chamber inlet area into the flow space bordered by the vane chambers and, after flowing through the vane chamber, returns to the side channel through a radially outer chamber outlet area. This so-called circulation is repeated several times so that the fluid can be compressed in several stages up to the outlet.

The largest misalignment preferably corresponds to 0.1 to 0.6 times, if necessary also more, the difference between the first and second radius dimension. The largest offset dimension can also correspond to approximately one third of the difference between the first and second radius dimensions.

The radius of the terminal edge is taken from a circle center, which is based on a distance to the geometric axis of rotation of the impeller between the first and second radius dimension. The center of the circle lies within a blade chamber, and also in a blade chamber following in the circumferential direction of the blade wall having the terminal edge. The center of the circle can thus lie in the upstream vane chamber viewed in the direction of rotation of the impeller. More preferably, the center of the circle lies on or adjacent to a radius line of the geometric axis of rotation of the impeller, which radius line runs centrally between the first and the second radius dimension.

The terminal edge of a blade wall preferably also extends radially outwards essentially in the direction of the impeller-impeller axis of rotation. Accordingly, a radially outer edge results, which extends essentially perpendicularly to the terminal edge of the blade wall. The marginal edge can, for example, run perpendicularly to the closing edge in a range of +/−5°. Furthermore, this radially outer edge determines the extent of the larger radius of the impeller, at least in the case of a design that is open radially on the outside, in which the blade chambers open radially on the outside. In this case, the blades end freely radially outwards.

The blade wall merges radially on the outside into a peripheral end wall. The blade chamber that is formed is limited and preferred with respect to a cross section by the chamber floor and the inner and outer boundary wall or blade walls that follow one another in the direction of rotation open only in the area of an area given by the terminal edges of the blade walls. An outer edge of the radially outer end wall defines the second radius dimension.

The imaginary connecting line between the entry point of the closing edge in the inner boundary wall and the radially outer end can run in relation to the top view in such a way that it is parallel to a radial emanating from the geometric impeller axis of rotation. In particular, when a radial passing through the inner inlet point or the radially outer end of the boundary wall is viewed with reference to the top view, the connecting line can enclose an acute angle of, for example, 0.05 to 15° with the radial. It is preferred that the connecting line extends in the direction of the geometric axis of rotation of the impeller at a distance from the geometric axis of rotation of the impeller.

The vertical distance of the connecting line from the geometric axis of rotation of the impeller is given by the length of a perpendicular to the connecting line, which perpendicular intersects the geometric axis of rotation of the impeller. The vertical spacing may be in the range of -40% to 40% of the outer radius. In a restricted view, the distance can be in the range of -40% to +40% of the radius difference between the inner and outer radius.

The radially outer end of the terminating wall can be either "leading" in relation to the entry point into the inner boundary wall or "lagging behind". Viewed radially outwards from the inlet point mentioned, the radially outer end of the closing wall can be designed to lead in the direction of rotation and also to lag behind in the direction of rotation for a given direction of rotation.

The radially outer end of the terminating edge can enclose an acute angle of up to 90° with the connecting line or with a radial line going through the radially outer end (starting from the axis of rotation). An acute angle of 50 to 75°, for example 70°, is preferred. The acute angle refers to an inflow section of the terminal edge into the outer wall. The radially outer end of the terminating edge preferably runs tangentially into a circular line connecting the radially outer ends of all terminating edges, or, as more preferably, into the radially outer terminating wall, so that the acute angle described above is between a through the intersection of the terminating edge and a there given idealized, i.e. averaged line of the tangent to the end wall and the connecting line.

If the end wall runs straight in the inlet section, the acute angle refers to the angle between the straight line that brings about the straight run and the connecting line.

With reference to the floor plan, the terminating edge can be composed at least partially of straight sections. A straight section can be provided, but also a plurality of straight sections arranged one behind the other, for example two, three, four or even ten straight sections. These straight sections extend over the shortest distance between a respective straight section start and a straight section end. Such a straight section can then continue into a curved section. An area between two straight sections can be formed by a curved area.

Referring to the plan, two or more adjacent straight sections are angled relative to each other (notwithstanding any curved section therebetween). Preference is given here obtuse angles greater than 90° up to 179°, such as 150 or 160°.

The terminating edge can also run continuously curved between the inner and outer radius. An uninterrupted curvature between the inner and outer radius is preferred here, which curvature is composed of several, for example two, three, four or ten curved sections arranged one behind the other. One or more curved sections can be curved in a circle and follow a radius accordingly. In the case of several or all curved sections following a radius, these can have different radii, it also being possible for a plurality of curved sections to have the same radii in the case of a plurality of curved sections.

Preferably, the terminating edge essentially follows a radius line, so that over the extension length of the terminating edge a constant radius is set, possibly having a deviation of, for example, +/-5% of the relevant radius dimension.

In an embodiment of the terminating edge along a radius line, the radius of the terminating edge is preferably removed from a circle center which, based on a distance from the geometric impeller axis of rotation, lies between the first and the second radius dimension. The center of the circle preferably lies within a blade chamber, moreover preferably in a blade chamber following the blade wall having the terminal edge in the circumferential direction. The center of the circle can thus lie in the upstream vane chamber viewed in the direction of rotation of the impeller. More preferably, the center of the circle lies on or adjacent to a radius line of the geometric axis of rotation of the impeller, which radius line runs centrally between the first and the second radius dimension.

In the case of a terminating edge that is curved—in the top view mentioned—as well as in the case of a terminating edge that is at least partially composed of straight sections, the end sections of the terminating edge that face the first and second radius dimensions can be curved.

The radius of these end sections of the terminating edge, which preferably run tangentially into the radially inner boundary wall and optionally into the radially outer terminating wall and more preferably run in the shape of a segment of a circle, can be selected to be smaller or larger than a radius dimension, for example a terminating edge following a radius line. The radius of the outer end regions of the terminating edge preferably corresponds to 0.5 to 0.9 times the radius of the terminating edge between the end regions.

Starting from the terminal edge, the blade wall can increase in wall thickness in the direction of the geometric impeller axis of rotation or in the direction of a chamber base. Thus, the wall thickness of the blade wall near or at the transition to the chamber base can correspond to 2 to 4 times, more preferably 3 times, the wall thickness in the area of the terminal edge.

The increase in wall thickness can be different in relation to the circumferential direction. In relation to a cross section through the blade wall, in the circumferential direction of the impeller, radially between the inner inlet point and the outer end of the blade wall, for example the middle between the first radius dimension and the second radius dimension, the blade wall edges can have a parallel to the geometric impeller axis of rotation enclose different acute angles. In relation to the straight line described above, the angle of a blade wall edge can be 1 to 10°, while the angle of the opposite blade wall edge to the straight line is 11 to 30°.

The acute angle of the blade wall edge against the direction of rotation is preferably larger than the acute angle of the blade wall edge in the direction of rotation. There can be a ratio between these different angles of 1:3 to 1:10.

Viewed in the direction of rotation, the blade wall can be convex. Correspondingly, the blade wall, which is curved in plan, opens in the direction of rotation.

The chamber floor can run circularly or elliptically in a cross-section in the connecting line or parallel thereto. In the case of a circular course, preference is given to a circular shape with a radius that remains constant in cross section over the length of the chamber floor. A curvature with different radii can also be provided over the extension length.

In any case, the chamber floor can extend radially inwards, for example following a circular or elliptical line, up to an upper edge of the inner end wall.

In a cross-section in the connecting line or parallel thereto, a configuration of the vane chamber in the shape of a semicircular disc can result.

The greatest depth of the chamber floor preferably corresponds to 0.25 to 0.75 times the radius difference between the inner and outer radius. In one embodiment, the depth corresponds to half the radius difference. In this case, the depth is measured starting from a (possibly greatest) height of the terminating edge in the direction of the axis of rotation.

Due to the preferred curvature of the blades, which are aligned at least approximately radially overall, the radial speed is increased in addition to the peripheral speed during operation compared to the known solutions during pressure build-up. The pressure build-up is improved. In addition, the proposed solution offers the possibility of an impeller that is closed radially on the outside, with which a two-stage operation can be implemented with only one impeller.

The ranges or value ranges or multiple ranges specified above and below also include all intermediate values with regard to the disclosure, in particular in steps of 1/10 of the respective dimension, ie possibly also dimensionless. For example, the specification 0.1 to 0.5 times also includes the disclosure of 0.11 to 0.5 times, 0.1 to 0.49 times, 0.12 to 0.5 times , 0.12 to 0.9 fold, 0.12 to 0.48 fold, 0.1 to 0.48 fold etc., the revelation of 15 to 40% also the revelation of 15:1 to 40%, 15 to 39.9%, 15.1 to 39.9%, 15.2 to 40%, 15.2 to 39.9%, 15.2 to 39.8%, 15 to 39.8 % etc., the revelation from 60° to 89° also the revelation from 60.1° to 89°, 60° to 88.9°, 60.2° to 89°, 60.2° to 88.9°, 60.2° to 88.8°, 60° to 88.8° etc. This disclosure can on the one hand be used to delimit a specified range limit from below and/or above, but alternatively or additionally to disclose one or more singular values from a respectively specified serve area.

Fig. 1

ein Laufrad in Draufsicht;

Fig. 2

den Schnitt gemäß der Linie II-II in Figur 1;

Fig. 3

die Unteransicht des Laufrades;

Fig. 4

die Herausvergrößerung des Bereiches IV in Figur 1, eine erste Ausführungsform einer Schaufelwand betreffend;

Fig. 5

eine der Figur 4 entsprechende Darstellung, eine alternative Ausführungsform der Schaufelwand betreffend;

Fig. 6

den Schnitt gemäß der Linie VI-VI in Figur 3;

Fig. 7

den Schnitt gemäß der Linie VII-VII in Figur 6;

Fig. 8

eine Schnittdarstellung gemäß Figur 7, jedoch eine weitere Ausführungsform der Schaufelwand betreffend;

Fig. 9

eine der Figur 6 entsprechende Darstellung bezüglich einer weiteren Ausführungsform;

Fig. 10

eine weitere, der Figur 6 entsprechende Darstellung in einer weiteren Ausführungsform (keine Ausführungsform gemäß der Erfindung).

The invention is explained below with reference to the attached drawing, which, however, only represents exemplary embodiments. A part that is only explained in relation to one of the exemplary embodiments and is not (precisely) replaced by another part in a further exemplary embodiment due to the special feature highlighted there, is thus also described as a possible existing part for this further exemplary embodiment. On the drawing shows:

1

an impeller in plan view;

2

the cut according to the line II-II in figure 1 ;

3

the bottom view of the impeller;

4

the enlargement of area IV in figure 1 , relating to a first embodiment of a blade wall;

figure 5

one of the figure 4 Corresponding representation relating to an alternative embodiment of the blade wall;

6

the cut according to the line VI-VI in figure 3 ;

7

the cut according to the line VII-VII in figure 6 ;

8

a sectional view according to figure 7 , but relating to a further embodiment of the blade wall;

9

one of the figure 6 corresponding representation with respect to a further embodiment;

10

another, the figure 6 corresponding representation in a further embodiment (not an embodiment according to the invention).

Shown and described is initially with reference to figure 1 an impeller 1 for a side channel machine, such as a side channel compressor or a side channel vacuum pump.

The impeller 1 has a central hub 2 with a through hole 3, which is used to fasten the impeller 1 to a drive shaft, not shown, of a side channel machine.

Distributed evenly in the circumferential direction, the impeller 1 has a reference to a figure 2 blade chambers 4 open towards the upper opening level E. Viewed in the circumferential direction, these are bordered laterally by blade walls 6 forming blades 5.

The blades 5 as well as the blade chambers 4 are formed in a radially outer area of the impeller 1 . Preferably and in the exemplary embodiment, the blades 5 form the radially outer boundary of the impeller 1, possibly with the exception of an end wall, as explained below.

The particular in the Figures 1 to 9 illustrated embodiments relate to an impeller 1 for forming a two-stage side channel machine. Correspondingly, blades 5 for forming blade chambers 4 are formed on both sides of the center plane with respect to a center plane which runs parallel to the opening plane E and which perpendicularly intersects the geometric impeller axis of rotation x.

The blade chambers 4 are delimited radially on the inside by an inner, circumferential delimiting wall 7. With reference to a cross section, this ends with the formation of a delimiting wall edge 8 in the opening plane E.

An end wall 10 is formed circumferentially along the peripheral edge 9, preferably also forming it. This also extends, for example, according to figure 6 up to the opening plane E, forming an end wall edge 11 running in the opening plane E.

The inner boundary wall 7 runs along a first, inner radius dimension r ₁ . This radius dimension r ₁ preferably relates to a radial inner edge of the boundary wall 7 and corresponds in the exemplary embodiments shown preferably two-thirds of a radius dimension r ₂ of a radially outer edge of the end wall 10.

The blade walls 6 extend between the radially inner boundary wall 7 and the radially outer end wall 10 and each run convexly viewed in the direction of rotation d (seen from a preceding blade wall to the following blade wall in the direction of rotation).

Thirty to forty-five blades 5, for example, can be provided evenly distributed over the circumference, for example thirty-five blades 5.

Each blade wall 6 has an exposed upper end edge 12 extending in the plane E of the opening. This terminating edge 12 runs radially inwards into the inner boundary wall, in particular in the boundary wall edge 8, and ends radially on the outside in the peripheral edge 9, in particular in the terminating wall edge 11 of the terminating wall 10.

An imaginary connecting line V can be drawn between the radially inner entry point of the blade wall 6 into the boundary wall 7 and the radially outer end of the blade wall 6, for example the end of the blade wall 6 running into the end wall 10 (cf figure 4 ).

In this case, the connecting line V runs in the opening plane E or in a plane parallel thereto.

In particular, the terminal edge 12 of each blade wall 6 runs perpendicularly to the connecting line V with a different offset dimension a. The largest offset dimension a is preferably obtained in the middle between the radially inner one Boundary wall 7 and the radially outer end wall 10 or the peripheral edge 9.

In the illustrated exemplary embodiments, the offset dimension a corresponds to approximately one third of the difference dimension c between the second radius dimension r ₂ and the first radius dimension r ₁ .

The blade walls 6 according to the invention are formed in such a way that their terminal edges 12 essentially follow a radius line. The radius r ₃ - based on the inner edge of the terminal edge facing the center of the radius - is plotted from a circle center P, which lies in an upstream blade chamber 4 in the direction of rotation d or in the blade wall 6 separating the upstream blade chamber 4 from the described blade chamber 4.

Continue with reference in particular to those in a floor plan pursuant figure 4 the edge of the terminating edge 12 facing the circle center P, the ends of the terminating edge 12 preferably run tangentially into the facing boundary wall 7 or terminating wall 10. For this purpose, the end sections of the terminating edge 12 can be provided with a radius that is different than the radius r ₃ , in particular with a smaller one in comparison Radius whose center is in the vane chamber 4 delimited by the vane wall 6 described.

The circle center P of the radius r ₃ can lie on the radius line r ₄ bisecting the blade chamber 4 in the radial direction between the boundary wall 7 and the end wall 10 .

In one embodiment, the center point P of the circle is in the radial direction to the geometric axis of rotation x of the impeller by a dimension z in relation to the radius line r ₄ offset radially outwards. The dimension z corresponds to about one tenth to one fifth of the difference dimension c.

The blade wall 6, in particular the terminal edge 12, can also be composed at least partially of straight sections 13, which are shown in plan according to FIG figure 5 each take different acute angles to a radial. The straight sections 13 are arranged overall in such a way that, viewed in the direction of rotation d of the impeller 1, the result is a convex course.

At each end, a terminating edge 12 designed in this way can run tangentially into the boundary wall 7 and into the peripheral edge 9 or into the terminating wall 10 with a radius line.

The radially outer end of the terminating edge 12, possibly a tangent T passing through the point of intersection of the terminating edge 12 and the terminating wall 10, can preferably enclose an acute angle α of about 70° with the connecting line V (cf figure 4 ). The radially outer end of the terminating edge 12 is given by a curved edge line of the terminating edge 12 in the case of a planar configuration of the terminating edge 12 , as is preferred and also given for the exemplary embodiments.

The connecting line V extends in the direction of the geometric axis of rotation of the impeller x at a distance b (see, for example, Figure 1) from the geometric axis of rotation of the impeller x, which vertical distance b corresponds to about one twentieth to one fifteenth of the outer radius r2.

The chamber floor resulting between two vane walls 6 arranged one behind the other, viewed in the direction of rotation d, and the inner boundary wall 7 and, in one embodiment, also the radially outer end wall 10 14 runs in a cross section in which the impeller axis of rotation x is represented as a line, in the form of a segment of a circle (cf figure 6 ). The center of the circle describing the chamber floor 14 preferably lies within the opening plane E.

In particular, the circular line describing the chamber floor 14 runs radially on the inside as far as the boundary edge 8.

In one embodiment of the invention with blade chambers 4 closed radially on the outside, as shown in FIGS Figures 1 to 9 this circular line preferably also runs radially outwards up to the closing edge 11 extending in the opening plane E.

Alternatively, the chamber floor 14 as shown in figure 9 also be in the form of a half rectangle with rounded corners 15. The chamber floor 14 is preferably designed to run parallel to the opening plane E. From the areas of the rounded corners 15 facing away from the chamber floor 14, wall sections extend into the opening plane E, which wall sections run parallel to the impeller axis of rotation x or enclose an acute angle thereto.

The greatest depth u of a vane chamber 4 viewed in the direction of the impeller axis of rotation x—removed starting from the opening plane E—can correspond to 0.5 times the difference c between the second radius r ₂ and the first radius r ₁ .

With reference to a cross-section through a blade wall 6 as shown in FIG figure 7 It can be seen that the blade wall 6 increases in wall thickness w starting from the opening plane E and thus starting from the closing edge 12 in the direction of the chamber floor 14 .

A wall thickness w is specified in the transition to the chamber floor 14 which corresponds to approximately 3 times the wall thickness w in the area of the closing edge 12 .

With reference to a straight line running parallel to the impeller axis of rotation x and running parallel to the impeller axis of rotation x, the blade wall edges 16 enclose the same acute angles to the straight line, particularly in the area of the radius line r ₄ .

An alternative embodiment is shown figure 8 .

In relation to a cross section through the blade wall 6 between the inner inlet point and the outer end, for example the middle between the first radius r ₁ and the second radius r ₂ , the blade wall edges 16 enclose different acute angles with the straight line. The blade wall edge 16 pointing counter to the direction of rotation d encloses an acute angle β ₁ of, for example, 15 to 30°, in particular approximately 20°, to the straight line, while the other blade wall edge 16 in the direction of rotation d encloses an acute angle β ₂ to the straight line of, for example, 2 to 5° includes.

According to the illustration in figure 10 (Not shown according to the invention), the vane chambers 4 can also be designed to be open radially outwards. The blade wall 6, which ends freely radially on the outside, extends radially on the outside in the direction of the impeller axis of rotation d and determines the size of the second radius size r ₂ . <b>List of reference characters:</b> 1 Wheel a angle 2 hub beta ₁ angle 3 through hole β ₂ angle 4 shovel chamber a offset dimension 5 shovel b Distance 6 blade wall c difference measure 7 boundary wall i.e direction of rotation 8th boundary wall edge r ₁ radius measure 9 perimeter edge r ₂ radius measure 10 end wall r ₃ radius 11 end wall edge r ₄ radius line 12 finishing edge and depth 13 straight section w Wall thickness 14 chamber floor x impeller axis of rotation 15 Corner e.g measure 16 blade wall edge E opening level P circle center T tangent V connecting line

Claims (15)

1. Impeller (1) for a side channel machine, such as a side channel compressor or a side channel vacuum pump, having blades (5) which are distributed in the circumferential direction, each formed by a blade wall (6) forming, in a plan view of the impeller (1), open blade chambers (4), in which plan view a geometric impeller axis of rotation (x) is depicted in a punctiform manner, wherein a blade wall (6) begins in the plan view at a first radius dimension (r₁) relative to the geometric impeller axis of rotation (x), which first radius dimension (r₁) corresponds to half or more of a second radius dimension (r₂), which second radius dimension (r₂) defines a peripheral edge (9) of the impeller (1) and wherein the first radius dimension (r₁) defines a radially inner boundary wall (7) of the blade chamber (4), wherein further a blade wall (6) has an exposed upper end edge (12) which correspondingly runs radially inwardly into the inner boundary wall (7) and in plan view ends radially outwardly in the peripheral edge (9), wherein an imaginary connecting line (V) can be drawn between a point of entry of the end edge (12) into the inner boundary wall (7) and a radially outer end of the end edge (12) and the end edge (12) extends perpendicularly to the connecting line (V) with a different offset dimension (a), a maximum offset dimension (a) being given, the blade wall (6) merging radially on the outside into a circumferential end wall (10) and an outer edge of the end wall (10) determining the second radius dimension (r₂), characterised in that the largest offset dimension (a) corresponds to 0.1 times or more the difference between the second radius dimension (r₂) and the first radius dimension (r₁) and in that the end edge (12) substantially follows a radius line and in that a radius (r₃) of the end edge (12) is removed from a circle center point (P) which lies in a blade chamber (4) following in the circumferential direction.
2. Impeller according to claim 1, characterised in that the largest offset dimension (a) corresponds to 0.1 to 0.6 times the difference (c) of the second (r₂) and the first radius dimension (r₁).
3. Impeller according to one of the preceding claims, characterised in that the end edge (12) extends radially outwards in the direction of the impeller axis of rotation (x).
4. Impeller according to one of the preceding claims, characterised in that the connecting line (V) runs in extension in the direction of the geometric impeller rotation axis (x) with a distance dimension (b) perpendicular to the geometric impeller rotation axis (x).
5. Impeller according to claim 4, characterised in that the perpendicular distance dimension (b) of the connecting line (V) to the geometric impeller axis of rotation (x) is formed in the range of -40% to +40% of the radius dimension (r₂).
6. Impeller according to one of the preceding claims, characterised in that the radially outer end of the end edge (12), optionally a tangent (T) passing through the point of intersection of the end edge (12) and the end wall (10), encloses an acute angle (α) of up to 90° with the connecting line (V).
7. Impeller according to one of the preceding claims, characterised in that the end edge (12) is at least partially composed of straight sections (13).
8. Impeller according to one of the claims 1 to 6, characterised in that the end edge (12) runs continuously curved between the first (r₁) and the second radius dimension (r₂).
9. Impeller according to one of the preceding claims, characterised in that the blade wall (6), starting from the end edge (12), increases in the direction of the geometric impeller axis of rotation (x) with respect to a wall thickness (w).
10. Impeller according to claim 9, characterised in that the increase in wall thickness (w) is different with respect to the circumferential direction.
11. Impeller according to one of the claims 9 or 10, characterised in that, with respect to a cross-section through the blade wall (6) between the inner runin point and the outer end, for example in a centre between the first radius dimension (r₁) and the second radius dimension (r₂), blade wall edges (16) enclose different acute angles (β₁, β₂) with a straight line running parallel to the geometric impeller rotation axis (x).
12. Impeller according to claim 11, characterised in that an acute angle (β₁) of the blade wall edge (16) against the direction of rotation (d) is greater than an acute angle (β₂) of the blade wall edge (16) in the direction of rotation.
13. Impeller according to one of the preceding claims, characterised in that a blade wall (6) is convex in the direction of rotation (d).
14. Impeller according to one of the preceding claims, characterised in that a chamber bottom (14) of a blade chamber (4) extends in a cross-section in the connecting line (V) or parallel thereto in a circular or elliptical shape, wherein in any case radially inwardly the circular or elliptical line extends into an upper edge of the inner end wall (10).
15. An impeller according to any one of the preceding claims, characterised in that a greatest depth (u) of a chamber bottom (14) corresponds to 0.25 to 0.75 times the radius difference (c).

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