EP2921711B1 - Radial fan wheel and blower unit - Google Patents

Description

The invention relates to a radial fan wheel with a support disk, an annular nozzle and a plurality of radially aligned fan blades, the lower edges of which are at least partially connected to the circular support disk, the upper edges of which are at least partially connected to the annular nozzle, which is arranged concentrically and spaced apart from the support disk, the inner edges of which are arranged radially on the inside and the outer edges of which are arranged radially outward, the lower edges having a first curvature in a projection plane aligned parallel to the support disc and the upper edges having a second curvature deviating from the first curvature in the projection plane. The invention also relates to a fan arrangement.

The BE 563373 A discloses differently curved blades for backward curved centrifugal fan wheels, for example concave curved, convex curved and alternately concave and convex curved blades.

From the EP 0 112 932 A1 a centrifugal fan with backward curved, profiled blades is known, in which the blades have a cover plate-side blade inlet angle which is slightly smaller than a support plate-side blade inlet angle, this blade geometry being achieved by twisting or shearing the blade profile.

The JP 406307390 A discloses a blade geometry for a profiled blade which can be obtained by twisting a profiled blade of uniformly curved design.

The GB 723,706 A is designed for blade geometries that can be produced by twisting optionally plate-shaped or profiled blades, whereby the cross-sections of the blade on the cover disk and on the rotor disk are identical.

From the EP 0 486 691 A1 a blade for a radial fan wheel is known in which the upper edge and the lower edge of the blade have the same curvature and are designed to be rotated relative to one another.

The WO 2013/073469 A1 discloses a bucket in which the curvature of the upper edge is identical to the curvature of the lower edge, the upper edge being oriented in a twisted manner to the lower edge.

The US 2012/005656 A1 discloses a turbo fan having a main plate and a plurality of blades spaced about an axis of rotation of the main plate, at least one blade comprising: a first blade portion having a leading end and a trailing end; a second sheet section having a leading end and a trailing end (T2), and a third sheet section having a leading end and a trailing end, the third sheet section being disposed between the first sheet section and the second sheet section, the trailing end of the first sheet section continuing in the direction of rotation as the rear end of the second blade section (A2), the rear end of the third blade section between the rear end of the first blade section and the rear End of the second sheet section is arranged, and wherein the leading end of the third sheet section is arranged further towards a negative pressure side of the sheet than the leading end of the first sheet section and wherein the leading end of the first sheet section between the leading end of the second sheet section and the leading end of the third blade section is arranged.

From the FR 2 811 156 A1 a fan is known which has a first set of blades defining outwardly diverging ventilation channels and a second set of blades shorter than the first set of blades and mounted on the outer end of the channels formed between the first set of blades , having.

The US 6 499 954 B1 discloses a centrifugal impeller blade having a leading edge, a trailing edge, a leading surface, and a trailing surface, with at least one of the leading or trailing surfaces being at least partially defined by a radius extending from the leading edge to the trailing edge.

From the DE 203 03 443 U1 a radial fan wheel with a cover disk having an inlet opening and a bottom disk, which are connected to one another via a blade ring, is known. In this case, the blade ring comprises guide blades that are inclined from the inside to the outside against the running direction and aligned in the axial direction, the outer edges of which run parallel to the axis of rotation define a blade outlet diameter.

From the DE 10 2004 047 993 A1 an oven is known with an open muffle that can be closed by an oven door and with a blower chamber arranged on the muffle rear side, in which a hot air blower is located, the air flows through air outlet openings in a parallel to the muffle rear side arranged blower chamber wall in the direction of the oven door.

The object of the invention is to provide a radial fan wheel and a blower arrangement which, regardless of the direction of rotation, enable the radial fan wheel to have a high degree of efficiency and low noise generation.

According to a first aspect of the invention, this object is achieved for a radial fan wheel of the type mentioned at the beginning with the features of claim 1.

With the radial fan wheel known from the prior art, a high degree of efficiency for converting introduced kinetic energy into flow energy of the fluid to be conveyed can only be achieved in a single direction of rotation. In a second direction of rotation for the radial fan wheel, the efficiency for conveying the fluid is significantly poorer. This is related to the design of the guide vanes, which is inclined against the running direction and which is optimized for a rotation of the radial fan wheel in a predeterminable direction of rotation. In the oven known from the prior art, a holding air fan is provided which includes a fan wheel which also has backward-curved blades and thus also only has an advantageous degree of efficiency for converting the introduced rotational energy in one of two possible directions of rotation. Particularly when radial fan wheels are used in household appliances such as ovens or tumble dryers, in which air circulation is provided in the respective device, radial fan wheels are required which have an advantageous degree of efficiency in both directions of rotation. This requirement can be met with the radial fan wheel according to the invention be fulfilled, in which the fan blades are not only curved in a single spatial direction, but are curved in several spatial directions, in contrast to the prior art. With a suitable design of the curvatures of the fan blades, an advantageous degree of efficiency can be achieved in both directions of rotation of the radial fan wheel. For this purpose, the upper and lower edges of the fan blades have different curvatures when projected into a common projection plane aligned parallel to the support disk, the respective curvatures being selected in such a way that the desired advantageous efficiency is set for the radial fan wheel, regardless of the direction of rotation. The term “curvature” also encompasses circular arc segments, elliptical segments or preferably continuous sequences of curves. Furthermore, this also includes radii of curvature which include a multiple of the length of the upper edge or lower edge, so that the respective edge corresponds at least almost to a straight line. In this case, it is assumed that only one of the two edges has such a large radius of curvature, while the other edge has a curvature with a radius of curvature that is, for example, less than 10 times the length of the respective edge.

According to the invention it is provided that the first curvature and the second curvature are opposite to one another in the plane of projection. It can be provided that when the lower edge and the upper edge are projected into the projection plane, two lines of curvature are generated which touch at a single point, touch at two points at the end, intersect at one point, intersect at several points or at a distance from one another are arranged. In any case, the centers of curvature are the first curvature and the second curvature opposite sides of the lines of curvature resulting from the projection of the lower edges and upper edges into the projection plane. For example, the curvatures of the lower and upper edges are designed in such a way that two mutually concave or two mutually convex curvature lines lie opposite one another or lie one above the other in the aforementioned manner.

In an advantageous development of the invention it is provided that the inner edge and the outer edge are aligned skewed to one another. The inner edge and the outer edge are each designed as straight lines and do not have a common plane, so that they neither intersect nor are parallel to one another.

It is preferably provided that the inner edge and / or the outer edge are curved, in particular curved in opposite directions to one another, thereby a particularly advantageous adaptation of the fan blades to the fluid flows that result from the rotation of the radial fan wheel in the two opposite directions of rotation will.

In an advantageous development of the invention it is provided that a surface of the fan blade between the inner edge and the outer edge is designed as a torsion surface. In this context, a torsion surface is to be understood as a surface which results when torsional stresses are applied to an originally flat fan blade. Fan blades shaped in this way can be produced, for example, by twisting a strip-shaped blade material parallel to a longest edge in order to subsequently to divide the twisted area into short sections, which are then used as fan blades between the support disc and the ring nozzle.

It is preferably provided that a torsion axis of the fan blade is aligned in the radial direction. According to the manufacturing example given above, the axis that is aligned parallel to the longest edge of the original strip material and serves as the axis of rotation for the strip material would determine the torsion axis, which is then oriented in the radial direction in the radial fan wheel when the corresponding fan blades are used.

It is useful if the inner edges of the fan blades border an annular inflow surface and / or the outer edges of the fan blades border an annular outflow surface. The inflow surface is located inside the radial fan wheel and describes the area through which fluid enters flow channels, which are bordered by the fan blades, the support disc and the ring nozzle, regardless of the direction of rotation of the radial fan wheel, whereby the fluid is conveyed outward in the radial direction regardless of the direction of rotation should. As an example, it can be assumed that the inflow surface results from a rotation of one of the inner edges of the fan blades about an axis of rotational symmetry of the support disk and / or the annular nozzle. The rain-shaped outflow surface can be generated in the same way as the ring-shaped inflow surface by rotating an outer edge of a fan blade around the rotational symmetry axis of the support disk and / or the ring nozzle and denotes the surface through which the fluid conveyed by the radial fan wheel, regardless of the direction of rotation, emerges outward in the radial direction. It is advantageous if an even number of fan blades of the same shape is provided and if fan blades arranged next to one another have opposite curvatures of the upper edges. By selecting the number of fan blades as a whole multiple of two as well as the use of fan blades of the same shape, each of which has mutually opposite curvatures of the upper edges, an identical interaction between the fan blades and the fluid is achieved for both directions of rotation of the radial fan wheel, so that regardless of the selected Direction of rotation for the radial fan wheel the same efficiency can be achieved. As an example, it is provided that fan blades arranged next to one another are arranged mirror-symmetrically to a mirror plane comprising the axis of rotational symmetry for the support disk and / or the annular nozzle. Furthermore, it is preferably provided that the fan blades are arranged in the circumferential direction of the radial fan wheel with the same angular division, in order to ensure a homogeneous fluid flow.

It is preferably provided that the fan blades have a forward curved and a backward curved area. The terms curved forward and curved backward each refer to a given direction of rotation for the radial fan wheel. Accordingly, when a single fan blade is considered, a forward curved area in a first direction of rotation becomes a backward curved area in a second direction of rotation of the radial fan impeller. Due to the opposing arrangement of adjacent fan blades, regardless of the selected direction of rotation, the result is that the same number and arrangement of forward-curved and backward-curved areas of the individual fan blades are effective in promoting the fluid. This ensures the desired identity of the degrees of efficiency for the two different directions of rotation of the radial fan wheel.

It is preferably provided that the fan blades have a continuous transition between the forward-curved and the backward-curved area. This constant transition between the two areas of curvature ensures that the fluid can flow in a fluid-dynamically advantageous manner along the fan blades regardless of the direction of rotation of the radial fan wheel and that undesirable eddies are not created in an undesirable manner by edges or other transition shapes between the areas of curvature, which would lead to deterioration the efficiency.

In an advantageous further development of the invention it is provided that in a first group of the fan blades the forwardly curved area is assigned to the annular nozzle and the backwardly curved area is assigned to the support disk. Accordingly, in a second group of fan blades, the forwardly curved area of the support disk and the backwardly curved area of the annular nozzle are assigned. However, this consideration is only to be made for one direction of rotation; when considering the opposite direction of rotation, the arrangements of forward-curved areas and backward-curved areas are reversed accordingly, since this is a definition that depends on the respective direction of rotation.

In a further embodiment of the invention it is provided that the fan blades have a varying thickness in at least one spatial direction, in particular one in the radial direction material thickness decreasing towards the outside. With a varying thickness or material thickness, the fan blades can advantageously be adapted to the requirements of the fluid flow in the radial fan wheel. For example, it can be provided that the fan blades have a material thickness that decreases in the radial direction outward.

It is advantageous if the fan blades comprise at least one area with a predetermined thickness and at least one area with a double thickness. Such fan blades can be made, for example, from sheet metal which, in order to produce areas with double thickness, is reshaped in areas such that two sheet metal layers touch.

The object of the invention is achieved according to a second aspect with a fan arrangement as specified in claim 13. The fan arrangement has an electric drive motor, which comprises a drive shaft for providing a rotational movement, furthermore a radial fan wheel according to one of claims 1 to 12, which is fixed with the support disk in a rotationally fixed manner on the motor shaft and a control device which is designed to provide electrical drive energy the drive motor is set up so that a rotation of the radial fan wheel can be predetermined by a rotation axis determined by the drive shaft in a first and in a second direction of rotation. Such a blower arrangement can be used, for example, in a household appliance, in particular in an oven or a tumble dryer, in order to bring about an alternating fluid flow through the respective flow arm in a reversing operation for the radial fan wheel.

Figur 1

eine perspektivische Darstellung eines Radialventilatorrads mit einer Tragscheibe, einer Ringdüse und mehreren radial ausgerichteten Ventilatorschaufeln, die in gleicher Winkelteilung angeordnet sind,

Figur 2

eine vergrößerte Darstellung einer Ventilatorschaufel des Radialventilatorrads gemäß der Figur 1,

Figur 3

Krümmungsverläufe für die Oberkante und die Unterkante der Ventilatorschaufel gemäß der Figur 2,

Figur 4

eine Draufsicht auf eine zweite Ausführungsform eines Radialventilatorrads,

Figur 5

eine Detaildarstellung einer Ventilatorschaufel der zweiten Ausführungsform des Radialventilatorrads gemäß der Figur 4,

Figur 6

eine schematische Seitenansicht eines Radialventilatorrads zur Verdeutlichung der Anordnung von Tragscheibe, Ringdüse und Ventilatorschaufeln,

Figur 7

eine Draufsicht auf eine dritte Ausführungsform Ventilatorschaufel für eine nicht dargestellte dritte Ausführungsform eines Radialventilatorrads,

Figur 8

eine Draufsicht auf eine vierte Ausführungsform Ventilatorschaufel für eine nicht dargestellte vierte Ausführungsform eines Radialventilatorrads,

Figur 9

eine Draufsicht auf eine fünfte Ausführungsform Ventilatorschaufel für eine nicht dargestellte fünfte Ausführungsform eines Radialventilatorrads,

Figur 10

eine Draufsicht auf eine sechste Ausführungsform Ventilatorschaufel für eine nicht dargestellte sechste Ausführungsform eines Radialventilatorrads,

Figur 11

eine perspektivische Darstellung einer siebten Ausführungsform eines Radialventilatorrads, bei der aus Gründen der Übersichtlichkeit die Ringdüse nicht dargestellt ist und

Figur 12

eine Detaildarstellung einer Ventilatorschaufel der siebten Ausführungsform des Radialventilatorrads gemäß der Figur 11.

Advantageous embodiments of the invention are shown in the drawing. Here shows:

Figure 1

a perspective view of a radial fan wheel with a support disk, an annular nozzle and several radially aligned fan blades which are arranged at the same angular pitch,

Figure 2

an enlarged illustration of a fan blade of the radial fan wheel according to FIG Figure 1 ,

Figure 3

Curvature profiles for the upper edge and the lower edge of the fan blade according to Figure 2 ,

Figure 4

a plan view of a second embodiment of a radial fan wheel,

Figure 5

a detailed representation of a fan blade of the second embodiment of the radial fan wheel according to FIG Figure 4 ,

Figure 6

a schematic side view of a radial fan wheel to illustrate the arrangement of the support disc, ring nozzle and fan blades,

Figure 7

a top view of a third embodiment of a fan blade for a third embodiment of a radial fan wheel, not shown,

Figure 8

a plan view of a fourth embodiment fan blade for a fourth embodiment of a radial fan wheel, not shown,

Figure 9

a plan view of a fifth embodiment fan blade for a fifth embodiment of a radial fan wheel, not shown,

Figure 10

a plan view of a sixth embodiment fan blade for a sixth embodiment (not shown) of a radial fan wheel,

Figure 11

a perspective view of a seventh embodiment of a radial fan wheel, in which the ring nozzle is not shown for reasons of clarity and

Figure 12

a detailed representation of a fan blade of the seventh embodiment of the radial fan wheel according to FIG Figure 11 .

An Indian Figure 1 The radial fan wheel 1 shown is designed for attachment to a drive shaft of a motor (not shown), in particular an electric motor. By optionally rotating in one of two directions of rotation, the radial fan wheel 1 can convey a fluid flow, preferably a gas flow, in particular an air flow, with a fluid flow directed outward in the radial direction. The radial fan wheel 1 is designed in such a way that it can produce the fluid flow in the radial outward direction, regardless of the selected direction of rotation, with an always at least almost identical efficiency, in particular with identical efficiency.

The radial fan wheel 1 comprises an exemplary circular disk-shaped support disk 2, an annular nozzle 3 arranged concentrically and at a distance from the support disk 2, and a plurality of fan blades 4 arranged between the support disk 2 and the annular nozzle 3 are preferred the fan blades 4 are arranged at a constant angular pitch around an axis of rotational symmetry 5 of the support disk 2 and the annular nozzle 3. The axis of rotational symmetry 5 is that axis which is aligned concentrically to the drive shaft of the motor, not shown, in order to ensure an advantageous concentricity for the radial fan wheel 1.

Furthermore, it is provided as an example that each fan blades 4 arranged adjacent to one another are a mirror image of one in the Figure 1 mirror plane, not shown, are aligned, the mirror plane comprising the axis of rotational symmetry 5.

As from the Figures 1 and 2 can be seen, the fan blade 4 is, for example, a sheet whose thickness 6 is chosen to be considerably smaller than a length of its edges 7, 8, 9 and 10. Such a sheet can be produced, for example, by reshaping a piece of sheet metal. The edges 7, 8, 9 and 10 correspond to the arrangement of the FIGS Figure 2 Fan blade 4 shown in the radial fan wheel 1 according to FIG Figure 1 around an inner edge 7, an outer edge 8, an upper edge 9 and a lower edge 10. The lower edge 10 is preferably adapted to the geometry of the support disk 2 in such a way that the lower edge 10 corresponds to a line of contact with the support disk 2, so that, for example, contact between the support disk 2 and the fan blade 4 are present along the entire length of the lower edge 10. The top edge 9 is at least partially adapted to the geometry of the ring nozzle 3 in such a way that the top edge 9 at least partially corresponds to a line of contact with the ring nozzle 3 and thus there is contact between the ring nozzle 3 and the fan blade 4 along part of the length of the top edge 9.

According to the invention, the fan blade 4 is designed to be three-dimensionally curved, so that when the upper edge 9 and the lower edge 10 are projected onto a projection plane aligned parallel to the support slide, for example the plane of representation according to FIG Figure 3 , each result in curvatures as shown in the Figure 3 are shown schematically. The in Figure 2 fan blade 4 shown in FIG Figure 3 The recognizable curvature of the upper edge 9 is carried out with a radius of curvature opposite to the curvature of the lower edge 10. There are midpoints of the respective curvatures at which it is according to the embodiment of the fan blade 4 according to the Figures 1 and 2 is a continuous stringing together of several curved sections, exemplarily arranged in different surface areas, as symbolized by the two radius arrows 11 and 12.

Due to the mirror-symmetrical arrangement of adjacent fan blades 4 on the radial fan wheel 1, a first group of fan blades 4, which are provided with the reference symbol 4L, can be distinguished from a second group of fan blades 4, which are provided with the reference symbol 4R. Due to the three-dimensional curvature of the fan blades 4 with opposing curvatures of the upper edges 9 and the lower edges 10, the result for the fan blades 4L when the in FIG Figure 1 The following flow-influencing properties are shown in the clockwise direction of the radial fan wheel: In a flow area near the support disk 2, the fan blades 4L have a backward-curved profile, which makes a contribution to energy-efficient fluid conveyance. In contrast, the fan blades 4L have a forward-curved profile in a flow area near the ring nozzle 3, which contributes to accelerated conveyance of the fluid. The fan blades 4R, on the other hand, have a forward curved profile when rotating clockwise in the flow area near the support disk 2 and a backward curved profile in the flow area near the annular nozzle 3.

Thus, over the entire ring-shaped flow cross-section of the radial fan wheel 1, which is determined by the support disk 2, the ring nozzle 3 and the fan blades 4, there is an advantageous interaction between the forward-curved and backward-curved areas of the respective fan blades 4, so that the radial fan wheel 1 rotates in the Clockwise can be operated energy-efficiently and with a high delivery rate. In the same way, this also applies to a counterclockwise rotation of the radial fan wheel 1, in which the fan blades 4R then have a forward-curved profile in the flow area near the ring nozzle 3 and a backward-curved profile in the flow area near the support disk 2.

As from the Figure 2 can be seen, a steady transition between the curvature of the upper edge 9 and the curvature of the lower edge 10 is provided, which is to avoid that the fluid flow running radially outward through the annular flow cross-section is locally detached from the fan blades 4, which has disadvantages in the Energy efficiency and the delivery rate for the radial fan wheel 1 would be connected.

A second embodiment of a radial fan wheel 21 is shown in plan view in FIG Figure 4 shown and differs from the radial fan wheel 1 according to FIG Figure 1 in the design of the fan blade 24. In the Figure 4 is the ring nozzle 3 to illustrate the three-dimensional curvature of the fan blade 24 cut open, the fan blade 24 is in the Figure 5 shown enlarged again. The upper edge 29 and the lower edge 30 correspond to the fan blade 4 according to FIGS Figures 1 and 2 also formed with opposing curvatures in order to alternately form the forward-curved and backward-curved flow areas, depending on the direction of rotation, in the area of the support disk 2 or in the area of the annular nozzle 3. The display level corresponds to Figures 4 and 5 the projection plane for the upper edge 29 and the lower edge 30. The basic design of the fan blades 24 does not, however, differ from the design of the fan blades 4.

From the schematic side view of the in Figure 6 The radial fan wheel 31 shown here shows that the support disk 2 is designed to be flat and that the ring nozzle 3 is designed as a body of rotation with a profile 32 that is rotated about the axis of rotational symmetry 33. Furthermore, this schematic representation according to FIG Figure 6 it can be seen that the fan blades 34 are designed at least essentially as rectangular planar bodies. In an embodiment of a radial fan wheel, not shown, the support disk has a cup-shaped recess or other, preferably rotationally symmetrical, profiling that enables stiffening of the support disk or improved attachment of a coupling for non-rotatable coupling to the drive shaft of the motor.

The ones in the Figures 7 to 10 The fan blades 44, 54, 64 and 74 shown differ from the fan blades 4 and 24 in that the upper edges 49, 59, 69 and 79 and the lower edges 50, 60, 70 and 80 have different curvatures, these curvatures also being designed that when these fan blades 44, 54, 64 and 74 are arranged between a support disk 2 and an annular nozzle 3, each with an adjacent, mirror-image arrangement, the same flow properties and similar efficiencies can be achieved in both directions of rotation.

At the in Figure 11 The seventh embodiment of a radial fan wheel 81 shown, the upper edges 89 and the lower edges 90 of the fan blades 84 also have the curvatures already known from the fan blades 4, 24, 34, 44, 54, 64 and 74. In addition, the fan blades 84 have, by way of example, a tapering of their cross section in the radial direction towards the outside. By way of example, a continuous, that is to say kink-free, tapering of the fan blades 84 in the radial direction is provided over their entire cross section.

Such a geometry of the fan blades 84 can be achieved in particular by production in the primary molding process, in particular in the metal casting process, in the plastic injection molding process, in the laser sintering process, in particular using metal powders, plastic powders or mixtures thereof, by production in an ablation process, in particular by machining, or by production can be achieved in a forming process such as a forging process.

In an alternative embodiment, not shown, the fan blade is made from a sheet metal material with a predetermined thickness, which is beveled in some areas in such a way that the sheet metal material is twice as thick.

A production of the remaining components or all components of the radial fan wheel, in particular the support disc, the ring nozzle and possibly also the fan blade is usually done by cutting and reshaping bleached parts, which are then connected to one another in a form-fitting and / or material-fit manner. Alternatively, a primary forming process, in particular a metal casting process, a plastic injection molding process, a laser sintering process, in particular using metal powders, plastic powders or mixtures thereof, or an ablation process, in particular with machining, or a forming process can also be used to manufacture the components of the radial fan wheel or the entire radial fan wheel how to use forging. Mixed forms for the production of the radial fan wheel such as the production of the fan blades in a metal casting process and the production of the ring nozzle and the support disk in a sheet metal forming process and a subsequent material connection between the support disk, fan blades and ring nozzle, in particular by welding, can also be provided.

Claims (13)

1. Radial fan wheel with a support plate (2), a ring nozzle (3) and a plurality of radially oriented fan blades (4; 24; 34; 44; 54; 64; 74; 84); the fan blades (4; 24; 34; 44; 54; 64; 74; 84) having lower edges (10; 30; 50; 60; 70; 80; 90) which are connected at least partially to the circular shaped support plate (2) and having upper edges (9; 29; 49; 59; 69; 79; 89) which are connected at least partially to the ring nozzle (3) which is arranged concentrically and at a distance from the support plate (2), and having inner edges (7) which are arranged radially on the inside and having outer edges (8) which are arranged radially on the outside, wherein the lower edges (10; 49; 59; 69; 79; 89) have a first curvature in a projection plane aligned parallel to the support plate (2) and wherein the upper edges (9; 29; 49; 59; 69; 79; 89) have a second curvature in the projection plane which second curvature differs from the first curvature, characterised in that the first curvature and the second curvature are opposite one another in the projection plane.
2. Radial fan wheel according to claim 1, characterized in that the inner edge (7) and the outer edge (8) are skewed with respect to each other.
3. Radial fan wheel according to claim 1, characterized in that the inner edge (7) and/or the outer edge (8) are curved, in particular curved in opposite directions to each other.
4. Radial fan wheel according to one of claims 1 to 3, characterized in that a surface of the fan blade between the inner edge and the outer edge is designed as a torsion surface.
5. Radial fan wheel according to claim 4, characterized in that one torsion axis of the fan blade is oriented in radial direction.
6. Radial fan wheel according to one of the preceding claims, characterized in that the inner edges (7) of the fan blades (4; 24; 34; 44; 54; 64; 74; 84) border an annular inflow surface and/or that the outer edges (8) of the fan blades (4; 24; 34; 44; 54; 64; 74; 84) border an annular outflow surface.
7. Radial fan wheel according to one of the preceding claims, characterized in that an even number of fan blades (4; 24; 34; 44; 54; 64; 74; 84) of the same shape is provided and that adjacently arranged fan blades (4; 24; 34; 44; 54; 64; 74; 84) have opposite curvatures of the upper edges (9; 29; 49; 59; 69; 79; 89).
8. Radial fan wheel according to one of the preceding claims, characterized in that the fan blades (4; 24; 34; 44; 54; 64; 74; 84) have a forward curved and a backward curved portion.
9. Radial fan wheel according to any of the preceding claims, characterized in that the fan blades (4; 24; 34; 44; 54; 64; 74; 84) have a continuous transition between the forward curved and the backward curved portions.
10. Radial fan wheel according to claims 7 and 8 or according to claims 8 and 9 and 10, characterized in that in a first group of the fan blades (4; 24; 34; 44; 54; 64; 74; 84) the forwardly curved region is associated with the ring nozzle (3) and the backwardly curved region is associated with the support plate (2).
11. Radial fan wheel according to one of the preceding claims, characterized in that the fan blades (84) have a varying thickness in at least one spatial direction, in particular a material thickness which decreases in the radial direction outwards.
12. Radial fan wheel according to claim 11, characterized in that the fan blades (84) comprise at least one region with a predetermined thickness and at least one region with a double thickness.
13. A fan assembly comprising an electric drive motor including a drive shaft for providing rotational motion, a radial fan wheel (1; 21; 31); 81) according to one of the preceding claims, which is fixed with the support plate (2) in a rotationally fixed manner to the motor shaft, and with a control device which is set up to provide electrical drive energy to the drive motor in such a way that a rotation of the radial fan wheel (1; 21; 31; 81) about an axis of rotation determined by the drive shaft can be specified in a first and in a second direction of rotation.

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