Impeller, fan with at least one impeller, and method for controlling the fan

Abstract

An impeller for a fluid machine, preferably for a turbomachine, in particular for a fan, wherein the impeller comprises a hub with blades attached thereto, is characterized in that the blades form loops. A fan comprises at least one such impeller. Furthermore, a method for controlling such a fan is provided.

Description

[0001] IRON, FAN WITH AT LEAST ONE IRON AND METHOD FOR REGULATING THE FAN

[0002] The present invention relates to an impeller for a turbomachine, preferably for a turbomachine, in particular for a fan, wherein the impeller has a hub with blades attached thereto. The invention further relates to a fan with a corresponding impeller and a method for controlling such a fan.

[0003] Impellers are used in turbomachinery to transmit power from a rotating shaft to a fluid or vice versa. Impellers are particularly common in fans, where the fluid is typically gaseous, usually air. More generally, impellers can also be used in other turbomachinery. Impellers, especially for fans, are well-known in the art.

[0004] A turbomachine or fan can have one, two, or more impellers connected in series in the direction of flow. With two or more impellers, it is referred to as a multi-stage turbomachine or fan. Impellers often generate unwanted noise during operation, which is significantly amplified by turbulence flowing towards the impeller and / or spatial and / or temporal inhomogeneities (flow irregularities). This noise is amplified in addition to the noise generated by the impeller's other sound sources.

[0005] Particularly in multi-stage fans or turbomachinery, impellers located downstream of other impellers generate additional inflow noise superimposed on their own noise, caused by inhomogeneous or turbulent inflow. This is especially true for impellers connected in series, particularly those located downstream and operating in the turbulent and / or spatially and / or temporally inhomogeneous wake of one or more upstream impellers. Generally, in turbulent or inhomogeneous inflows, but especially in turbomachinery with two or more impellers, noise generation, particularly inflow noise, should be reduced by designing novel impellers.

[0006] For the state of the art, reference is made, for example, to EP 3 289 224 A1. This discloses impellers optimized for inflow noise, which have corrugated fan blades. However, further reductions in inflow noise, particularly for downstream impellers, are necessary for two-stage or multi-stage turbomachines or fans in order to achieve low overall noise emissions.

[0007] The present invention is based on the objective of designing and further developing the generic impeller in such a way that it exhibits further reduced sound emissions. A corresponding fan will be specified. Furthermore, a method for controlling a preferably multi-stage fan will be specified.

[0008] The aforementioned problem concerning the impeller is solved by the features of claim 1, according to which the impeller is equipped with loop-shaped wings. For the sake of simplicity, these are hereinafter referred to as loop wings.

[0009] These loop wings can be connected to a hub at two foot areas offset from each other in the circumferential and / or axial direction, with the two foot areas being connected to each other radially further outwards via an outer connecting area.

[0010] This design of the impeller, or rather its loop vanes, is advantageous for low noise generation, as the loop vanes have no external free ends that would significantly contribute to noise. The impeller can operate highly efficiently without a direct external enclosure because the loop vanes have no external free ends.

[0011] The total surface area of ​​the impeller according to the invention, with its looped blades, is also considerably smaller than that of a comparable impeller with a rotating cover ring that connects the outer blade ends of conventional blades to avoid exposed outer blade ends. A low total surface area of ​​an impeller at a given rotational speed and flow rate is particularly advantageous for low inflow noise.

[0012] The impeller according to the invention, with its looped blades, which can advantageously be operated without a housing wall directly or almost directly adjacent to it radially, makes it possible or simplifies the design of the impeller in a multi-stage fan, in particular an axial or diagonal fan, with a smaller diameter than other impellers of the fan or than the main housing wall that directly surrounds another, larger impeller. In particular, it makes it possible to operate the impeller only in a partial flow area, which is advantageously located close to the axis, without the need for an intermediate housing wall associated with the smaller impeller, which would entail significant disadvantages in terms of acoustics, manufacturing effort, and efficiency.

[0013] Thus, the impeller according to the invention makes it possible to form a particularly quiet fan which has at least one such impeller.

[0014] In particular, it makes it possible to form low-noise and efficient multi-stage fans, wherein at least one impeller is an impeller according to the invention.

[0015] In particular, it makes it possible to form low-noise and efficient multi-stage fans, wherein at least one impeller is an impeller according to the invention and has a significantly smaller diameter than another impeller of the fan and advantageously operates only in a partial flow range of the total flow through the fan.

[0016] In an advantageous embodiment, the two base regions of a loop wing, namely one leading and one trailing in the direction of rotation, correspond to two sub-wings of the loop wing, whose radially inner ends they form, and constitute the connection areas of the loop wing to the hub. The sub-wings of a loop wing are then connected to each other at their radially outer end regions via the connection region to form the loop wing. Advantageously, 2-5 essentially identical loop wings, distributed essentially uniformly around the circumference and comprising 4-10 sub-wings, are formed on the impeller or its hub. Furthermore, advantageously, the entire loop wing is a largely kink-free, i.e., tangent-continuous, structure, at least along a path from a base point on one sub-wing, through this sub-wing, the connection region, and the second sub-wing, to a base point on its base region.For this purpose, transition areas between the partial wings and the connecting area are advantageously designed.

[0017] In a further advantageous embodiment, at least one, and preferably both, of the partial wings of a loop wing are designed, at least in a radial area, in section on a cylinder, similarly to the cross-section of an airfoil profile with an inflow edge area, an outflow edge area, a suction side and a pressure side, with a ratio of the maximum thickness to the chord length > 6 and advantageously an angle of attack of the chord to the circumferential direction between 15° and 50° and further advantageously different inflow and outflow angles of a difference of at least 8°.

[0018] The impeller advantageously has a three-dimensional, multiply curved contour and is advantageously manufactured using a casting process, or further advantageously, by plastic injection molding. Fiber-reinforced thermoplastic materials are preferably used because they are readily available at low cost, have a comparatively low density, contribute to a lightweight design, and can ensure sufficient dimensional stability. In an advantageous design, the impeller geometry has no or only negligible undercuts in the demolding direction (preferably parallel to the axial direction) and is manufactured as a single, integral component.

[0019] The present invention further relates to a fan with at least one impeller. Preferably, the fan has two or more impellers.

[0020] Fans of the generic type, particularly those with two or more impellers arranged one behind the other in the direction of airflow, are known from DE 102021 213480 A1 and from practical experience. They are problematic in operation with regard to noise emissions, which are particularly high. Furthermore, the efficiency of such fans decreases rapidly beyond the "design point" (i.e., beyond the point of maximum efficiency) with increasing or decreasing throttle, since usually only a single control variable is available: the fan speed. This is typically suitable for setting a required air flow rate but does not serve for further optimization of the fan operation.

[0021] The noise emission of multi-stage, and especially two-stage, fans in series arrangement is particularly high because a downstream impeller is subjected to the turbulence and / or spatial and temporal flow inhomogeneities of at least one upstream impeller. This can lead to a significantly increased noise generation in impellers located downstream of other impellers. This is especially pronounced in radially extended areas of the downstream impeller, because high relative velocities or rotational velocities of the local impeller or blade contours occur here as a result of the rotational movement.

[0022] With conventional single-impeller fans, vibration-critical rotational speeds can only be reduced or even eliminated by deviating from the required airflow, either upwards or downwards. The so-called long-throw characteristic cannot be influenced independently of the airflow during operation. Similarly, the uniformity of the airflow to a downstream machine, such as a heat exchanger or the like, cannot be influenced independently of the fan's airflow. A further objective of the invention, with regard to the fan, is to overcome these disadvantages of conventional single-impeller fans.

[0023] The underlying problem concerning a fan is solved by the features of claim 10. According to this claim, the fan comprises at least one impeller according to the invention. The fan can also comprise two impellers arranged one behind the other in the direction of flow. The two impellers can have a common drive or separate drives, which are typically electric drives.

[0024] The use of two impellers can fundamentally increase the efficiency and pressure increase of the fan. In an advantageous embodiment, the two impellers can be operated at independently selectable speeds. This allows the speed ratio of the two impellers to be dynamically selected at all times, so that in addition to the air flow rate, another target parameter is optimized, for example, the efficiency, the sound power, the throw distance, or the flow rate through a heat exchanger connected on the downstream side.

[0025] In particularly advantageous embodiments, a smaller impeller has a maximum outer diameter that is at least 40% smaller, and even more advantageously at least 45% smaller, than the largest impeller of the fan. Such an embodiment exhibits particularly low sound power, especially compared to conventional fans with two or more impellers. Furthermore, the power consumption of the smaller impeller is more than 50% lower, and advantageously more than 75% lower, than that of the larger impeller, which allows for the use of a significantly smaller and less expensive drive for the smaller impeller.

[0026] In a particularly preferred embodiment, one of the running wheels, preferably one with a smaller outer diameter, is designed with loop-shaped wings which are connected to a hub at two circumferentially offset foot areas, wherein the two foot areas are connected to each other radially further outwards via an outer connecting area.

[0027] At least one rotationally fixed guide device can be provided between the two or more impellers. This guide device can include guide vanes. The guide device is arranged in the flow area between two impellers and preferably has a load-bearing function with respect to the drive(s). Advantageously, a guide device comprises an outer, off-axis flow area and an inner, near-axis flow area, the flow areas preferably being separated from each other by an intermediate ring. It is further advantageous if a smaller impeller is assigned to the inner, near-axis flow area.

[0028] Furthermore, it is conceivable that the wheels rotate in the same or opposite directions; the same direction of rotation has proven to be advantageous, especially with regard to low noise generation.

[0029] In embodiments with a guide device and intermediate ring, it is advantageous that a smaller impeller also has a significantly smaller outer diameter than the intermediate ring of the guide device. The ratio between the largest outer diameter of the smaller impeller and the smallest outer diameter of the intermediate ring is then advantageously less than 80%, and particularly advantageously less than 75%.

[0030] In an advantageous embodiment, which in particular allows existing fans with an impeller and guide vane to be retrofitted with the second, smaller impeller, the second impeller with its drive is attached to the outer housing of the fan as a fully functional electromechanical unit. In a further advantageous embodiment, a supporting grille is used for this purpose, which, in the assembled state, also serves as a protective grille.

[0031] In an advantageous embodiment with fans featuring a guide vane with an intermediate ring, the second, smaller impeller with its drive is attached to the intermediate ring of the guide vane as a fully functional electromechanical unit. In a further advantageous embodiment, a supporting grid is used for this purpose, which, in the assembled state, also serves as a protective grille. With regard to the method, the underlying problem is solved by the features of claim 11.

[0032] By adjusting / changing the rotational speeds of the impellers, the fan operation is optimized, particularly with regard to maximizing the overall efficiency and / or minimizing the overall noise emission and / or minimizing the vibration values.

[0033] By providing independent drives for the impellers, the speeds of the fan impellers can be set or controlled independently of each other.

[0034] It is also conceivable that the rotational speeds of the fan's impellers are coordinated and preferably adjustable depending on the operating point.

[0035] By adjusting the speed of one of the impellers, preferably the second impeller with an EC drive, the fan operation can be optimized.

[0036] It is advantageous if the rotational speeds of the impellers can be adjusted or controlled using a special controller, particularly by using methods of artificial intelligence, machine learning and / or conventional control algorithms with regard to the desired air performance and possibly with regard to at least one other target variable, for example the overall efficiency.

[0037] Further parameters to be optimized include vibration levels, axial thrust, efficiency, acoustics, psychoacoustic aspects, throw behavior, flow pattern in relation to a heat exchanger or the like, etc. Thus, the fan according to the invention forms a platform for the realization of an intelligent fan. Although such a fan is inherently a turbo-turbine machine, the invention can be applied to other turbo-turbine machines. In embodiments with a smaller impeller and a separate EC motor, for example, in an embodiment with a retrofit kit option or as an optionally available variant with two impellers, it is advantageous if the fan has a separate control unit that handles the speed control of the two individual motors. Such a control unit can, for example, be mounted externally on the fan housing and electrically connected to the motors accordingly.

[0038] It should be noted at this point that it is not absolutely necessary for the fan according to the invention to include an impeller with loop-shaped blades.

[0039] With regard to the fan according to the invention, it is conceivable that it is equipped with two or more impellers arranged one behind the other in the direction of flow, each with a common drive or with its own drive. It is advantageous that the maximum outer diameter of at least one impeller is at least 40%, preferably at least 45%, smaller than that of the fan's largest impeller in terms of outer diameter.

[0040] If at least two impellers are provided, a rotationally fixed guide device, preferably supporting the impellers and drive(s), may be provided in the flow area between adjacent impellers and may include guide vanes.

[0041] The guide device can have an outer, off-axis flow area and an inner, near-axis flow area, wherein the flow areas are preferably separated from each other by an intermediate ring, and wherein the smaller impeller is assigned to the inner, near-axis flow area or operates in this area.

[0042] The wheels preferably rotate in the same or opposite directions to each other. With independent drives for the wheels, the rotational speeds of at least two of the wheels can be adjusted or controlled independently.

[0043] The rotational speeds of two independently speed-controlled impellers are matched to each other and can be advantageously controlled depending on the operating point.

[0044] By adjusting the rotational speed of one or more impellers, preferably at least one with a smaller diameter, the fan operation is optimized. An EC drive is preferably used.

[0045] The rotational speeds of the impellers can be optimally adjusted or controlled with the help of a special controller, in particular using methods of artificial intelligence, machine learning and / or conventional control algorithms with regard to the desired air performance and possibly at least one other target variable, for example the overall efficiency.

[0046] All two or more impellers are attached directly or indirectly to the outer housing via a supporting guide vane system.

[0047] One of the impellers, preferably an impeller with a smaller diameter and preferably with loop wings, is attached to the housing via a separate support structure, i.e., not via the guide device, preferably by means of a support grid.

[0048] With regard to the fan, it should be noted that it can comprise at least one impeller according to the invention, namely with loop-shaped blades.

[0049] For a method of controlling a fan, it is essential that a requested power or air flow rate of the fan is ensured while maximizing the overall efficiency and / or minimizing the overall noise emission and / or minimizing the overall vibration values ​​and / or the vibration values ​​by adjusting or controlling the speeds of the impellers for this purpose, preferably using a control unit assigned to or integrated into the fan.

[0050] There are now various ways to advantageously develop and further refine the teaching of the present invention. For this purpose, reference should be made, on the one hand, to claims 2-9, which are subordinate to claim 1 and relate to the impeller, and on the other hand, to the following explanation of preferred embodiments of the invention with reference to the drawing. In conjunction with the explanation of the preferred embodiments of the invention with reference to the drawing, generally preferred embodiments and further developments of the teaching are also explained. The drawing shows

[0051] Fig. 1 shows a perspective view from the downstream side of an embodiment of an impeller according to the invention with loop vanes applied to the rotor of a drive motor.

[0052] Fig. 2 shows the impeller with the motor as shown in Fig. 1 in an axial top view from the downstream side.

[0053] Fig. 3 shows a plan view from the side and a section in a plane through the fan axis of the impeller with the motor according to Figs. 1 and 2, where the motor is not shown in section.

[0054] Fig. 4a shows a schematic representation of a section through a partial wing of a loop wing with largely constant thickness in a developed cylindrical section, with characteristic dimensions shown.

[0055] Fig. 4b shows a schematic representation of a section through a partial wing of a looped impeller with variable thickness, similar to a section through a profiled airfoil with characteristic dimensions shown in a developed cylindrical section. Fig. 5 shows an embodiment of a fan according to the invention, viewed from the downstream side, with a larger and a smaller impeller, wherein the smaller impeller is an impeller according to the invention with looped blades.

[0056] Fig. 6 shows the fan from Fig. 5 in a plan view axially from the outflow side.

[0057] Fig. 7 shows a side view and a section in a plane through the axis of the fan according to Figs. 5 and 6, wherein in fan operation the flow flows essentially from left to right, the motor not shown in section,

[0058] Fig. 8 in a side view and in section on a plane through the axis, similar to the view according to Fig. 7, shows another embodiment of a fan with a smaller impeller with looped blades, wherein an outer diffuser on the outer housing projects axially beyond the smaller impeller in the outflow direction, wherein the motor is not shown in section.

[0059] Fig. 9 shows a perspective view of the fan as seen from the outflow side, according to Fig. 8.

[0060] Fig. 10, in perspective view from the downstream side, shows an embodiment similar to that shown in Figs. 5-7, wherein the hub of the smaller impeller with loop wings has a smaller diameter than the hub ring of the support unit.

[0061] Fig. 11 shows the fan according to Fig. 10 in a planar, axially parallel view seen from the outflow side.

[0062] Fig. 12 shows the fan according to Figs. 10 and 11 in a planar side view and in section along a plane through the fan axis, with the motor not shown in section. Fig. 13 shows a further embodiment of a fan in a perspective view from the downstream side, wherein a smaller impeller, designed with looped blades, and its drive are supported by a support grid on an outer, downstream area of ​​the housing 2.

[0063] Fig. 14 shows the fan according to Fig. 13 in a planar side view and in section on a plane through the fan axis and through an outer attachment area for the support grid, with the motor not shown in section.

[0064] Figure 1 shows an embodiment of an impeller 19B with blades 22B, designed as loop blades 22B, in a perspective view from the downstream side. The impeller 19B is attached to the rotor of an associated motor 34B. This attachment is provided by fastening features 30B, such as bores, in a central area of ​​the hub 31B of the impeller 19B. Advantageously, the impeller 19B is fastened to the motor 34B with screws. The loop blades 22B are attached to the outer surface of the hub 31B.

[0065] In the embodiment shown in Fig. 1, the impeller 19B is advantageously manufactured as a single, integral piece using a casting process, preferably plastic injection molding. The hub 31B with the mounting devices 30B for attaching the impeller 19B to a motor 34B, as well as the vanes 22B formed on the hub 31B, are thus part of a single cast workpiece, the impeller 19B. This eliminates the need for a complex connection of the vanes 22B to the hub; and allows for considerable design freedom with regard to the shape, particularly of the vanes 22B.

[0066] It is conceivable to implement different motor connections in the casting tool of the otherwise identical impeller with identical vanes 22B by means of interchangeable inserts in the casting tool, i.e., for example, differently designed connection provisions 30B for connecting different motors adapted to the respective requirements.

[0067] In the exemplary embodiment, four loop-shaped wings 22B are provided on the hub 31B of the impeller 19B. In other embodiments, this number can vary, particularly advantageously from two to six.

[0068] Each of the loop wings 22B is connected to the hub 31B at two foot regions 41B and 42B. The two foot regions 41B and 42B are offset from each other and do not intersect, i.e., there is a gap between them. In particular, the foot regions 41B and 42B of a loop wing 22B are offset from each other circumferentially, but may also have a certain offset from each other axially.

[0069] The impeller 19B with the loop wings 22B has a designated direction of rotation 32B, in the exemplary embodiment and in the illustration according to Fig. 1 approximately counterclockwise. With regard to the designated direction of rotation or the actual direction of rotation in operation, one of the foot sections of a loop wing 22B is a leading foot section 41B, and the other is a trailing foot section 42B, which, viewed in the direction of rotation 32B, lead or trail the other.

[0070] The foot areas 41 B, 42B of a loop wing 22B are physically connected to each other on the one hand via the hub 31 B of the wheel 19B, but also on the other hand via the loop wing 22B itself, so that a closed physical contour is created without freestanding ends of the wing, especially viewed in the radial direction.

[0071] Extending radially outwards from the base areas 41B and 42B, the partial blades 39B and 40B, respectively, adjoin the latter and are accordingly also referred to as the leading partial blade 39B and the trailing partial blade 40B. The partial blades 39B and 40B are advantageously designed, particularly as seen in a section of a cylindrical shell 33 coaxial with the fan axis, similarly to a known fan blade and, in this respect, similarly to an airfoil, either profiled with variable thickness or unprofiled with a largely constant thickness (see Fig. 2, Fig. 3).

[0072] 4a, Fig 4b).

[0073] The two partial wings, the leading 39B and the trailing 40B, of a loop wing 22B are radially connected to each other via connecting areas 38B. Thus, the loop wings 22B have no open radially outer ends.

[0074] Due to the external connection of the two partial wings 39B and 40B, the loop wing 22B has a particularly stable design, and can therefore be manufactured with thinner thicknesses or from cheaper materials than comparable impellers with wings with open, unattached outer end areas.

[0075] The transition areas 14 and 15 lie between the leading 39B and the trailing partial wing 40B and the connecting area 38B. These transition areas are advantageously designed to be rather rounded or curved or tangent-continuous, in particular without a kink or the like in their course between partial wing 39B or 40B and the connecting area 38B.

[0076] In other embodiments, one or both transition areas 14 or 15 may optionally have a kink or an edge in their course between partial wing 39B or 40B and the connection area 38B, so that the partial wing 39B or 40B may transition directly into the connection area 38B without rounding or the like.

[0077] In other embodiments, the two partial wings 39B, 40B can be designed in such a way that they transition directly into each other, advantageously in a tangentially continuous manner.

[0078] The loop vanes 22B have inflow edges 27B on the upstream side and outflow edges 26B on the downstream side. These are thin areas that can be idealized as linear features, for example, along their center line. They extend from the leading base 41B of a loop vane 22B to the trailing base 42B. In an advantageous design of a loop vane 22B without a kink, particularly without a kink at the transition areas 14 and 15 between the leading sub-vane 39B or the trailing sub-vane 40B and the connecting area 38B, the inflow and outflow edges 27B and 26B, respectively, describe curved, approximately horseshoe-shaped lines, advantageously without kinks.

[0079] In an advantageous design of a loop wing 22B without a kink, in particular without a kink at the transition areas 14 and 15 between the leading partial wing 39B or the trailing partial wing 40B and the connecting area 38B, the pressure side 45 (see also Figs. 4a, 4b) of the leading partial wing 39B, the outer surfaces of the transition areas 14 and 15 and the connecting area 38B, as well as the suction side 44 of the trailing partial wing 40B, form a curved, bent, and at least largely tangent-continuous outer surface of the loop wing 22B, which extends from the leading base area 41B to the trailing base area 42B. Such a design is particularly advantageous for low noise generation, high efficiency, and high strength.

[0080] In an advantageous design of a loop wing 22B without a kink, in particular without a kink at the transition areas 14 and 15 between the leading partial wing 39B or the trailing partial wing 40B and the connecting area 38B, the suction side 44 (see also Figs. 4a, 4b) of the leading partial wing 39B, the radially inner surfaces of the transition areas 14 and 15 and the connecting area 38B, as well as the pressure side 45 of the trailing partial wing 40B, form a curved, bent, and at least largely tangent-continuous inner surface of the loop wing 22B, which extends from the leading base area 41B to the trailing base area 42B. Such a design is particularly advantageous for low noise generation, high efficiency, and high strength.

[0081] In Fig. 2, the impeller 19B with the loop vanes 22B is shown in a planar, axially parallel view from the downstream side. For further description, reference is made to Fig. 1. In Fig. 2, a cylindrical section 33 is shown at an exemplary radius, intersecting the two partial vanes of a loop vane 22B, a leading partial vane 39B and a trailing partial vane 40B. Exemplary sectional views of advantageous designs of the partial vanes 39B and 40B in the developed cylindrical section on a cylindrical shell 33 are shown in Figs. 4a and 4b and are described with reference to them.

[0082] If the impeller 19B is considered as a one-piece, integrally manufactured casting, the advantageous design of the embodiment can be readily understood using the axially parallel view shown in Fig. 2. With respect to an opening direction of a casting tool parallel to the axis, i.e., towards or away from the viewer, the impeller 19B exhibits no undercut or only a negligible undercut. No partial wing 39B, 40B of the impeller 19B, viewed in axial projection, obscures any area of ​​another partial wing 39B, 40B, or a connection area 38B, or a transition area 14, 15, so that the casting tool can open freely away from the component contour in both directions. This enables a simple design of a casting tool, which can therefore be manufactured cost-effectively and has a simple and efficient operation in the production of impellers 19B.

[0083] The connection areas 38B of the loop vanes 22B have an approximately cylindrical contour of nearly constant, comparatively small thickness, e.g. < 5 mm, in areas between the associated transition areas 14 and 15, which is advantageous for high efficiency and low noise generation of a fan with the impeller 19B.

[0084] In the exemplary embodiment, mounting openings 24 are provided in an inner area of ​​the hub 31 B, which facilitate or enable the mounting of the impeller 19B on a fan.

[0085] Fig. 3 shows the impeller 19B with the loop vanes 22B and the motor 34B, to which the impeller 19B is attached, in a planar section along a plane through the fan axis, in a side plano view. For clarity, the motor 34B is not shown in section. This allows it to be easily identified in the illustration.

[0086] The impeller 19B is connected to the rotor of the motor 34B by means of fastening devices 30B in an internal area of ​​the hub 31B. When a fan is operating, the impeller 19B rotates, driven by the motor 34B or its rotor.

[0087] The motor 34B may also be a generator or a motor that can be operated as a generator.

[0088] On the stator side, the motor must be firmly connected to a supporting structure of the fan.

[0089] In cross-section, the connection area 38B of the loop wings 22B has, at least in some areas, an approximately axially parallel course in the exemplary embodiment. This is particularly advantageous. In other embodiments, courses that deviate slightly from the axially parallel course are also conceivable.

[0090] Figures 4a and 4b schematically illustrate possible sections of a cylindrical shell 33 (see Figure 2) coaxial with the fan axis of a partial blade 39B or 40B of a loop blade 22B, with some characteristic dimensions shown.

[0091] Fig. 4a shows a partial wing 39B, 40B with a largely constant wing thickness.

[0092] In Fig. 4b, however, a partial wing 39B, 40B with variable wing thickness is shown in a design similar to that of a section through a profiled airfoil with an area of ​​maximum thickness and a thin trailing edge 26B.

[0093] The sections of the leading partial wing 39B and a trailing partial wing 40B of a loop wing 22B are advantageously similar or identical in design, but may differ to a moderate degree, particularly with regard to the dimensions.

[0094] In the case of a partial blade 39B or 40B, the dimensions shown in Figs. 4a and 4b can advantageously change depending on the radius of the cylindrical section, so that the partial blades 39B and / or 40B are ideally adapted to the prevailing flow conditions at each radial position. This results in three-dimensionally shaped, often three-dimensionally curved partial blades 39B and / or 40B or loop blades 22B.

[0095] The design of a partial wing 39B, 40B, as seen in a section shown (Fig. 4a, 4b), is characterized in particular by its chord s of length s. The chord has an angle β relative to the circumferential direction 43, which is advantageously in a range between 15° and 50°.

[0096] The wing section 39B, 40B has a camber, meaning that in cross-section it does not run straight, but curved over the chord s. Therefore, the inflow angle β1 between the circumferential direction 43 and the tangential extension of the wing section centerline at the leading edge 27B of the loop wing 22B has a different value than the outflow angle β2 between the circumferential direction 43 and the tangential extension of the wing section centerline at the trailing edge 27B of the loop wing 22B, in order to enable low-loss flow deflection during operation. Advantageously, β2 is greater than β1, preferably by at least 10°.

[0097] The advantageously curved design creates a convex side of a partial wing 39B, 40B, the suction side 44, as well as a concave side of a partial wing 39B, 40B, the pressure side 45.

[0098] The two partial wings, namely the leading partial wing 39B and the trailing partial wing 40B of a loop wing 22B, can be designed to be largely identical at a certain cutting radius.

[0099] The two blade sections, namely the leading blade section 39B and the trailing blade section 40B of a loop blade 22B, can also be designed to differ moderately from each other at a specific cutting radius in order to be optimally adapted to the flow conditions. The deviation of the two blade sections 39B and 40B of a loop blade 22B from each other can be between 1° and 5° in the chord angle β as well as in the inflow and outflow edge angles β1 and β2, and they can differ from each other in the length of the chord s by 0%–10%.

[0100] The exemplary wing section 39B or 40B in Fig. 4a has, in cross-section, a largely constant thickness d from the leading edge 27B to the trailing edge 26B. Nevertheless, the area at the leading edge 27B, in particular, is rounded, and not sharp-edged. This is advantageous for high efficiency and / or low noise generation.

[0101] The exemplary wing section 39B or 40B in Fig. 4a has, in cross-section, a largely constant thickness from the leading edge 27B to the trailing edge 26B. However, the area at the trailing edge 26B, in particular, is locally tapered and thin. This is advantageous for high efficiency and / or low noise generation.

[0102] The exemplary wing section 39B or 40B in Fig. 4b has a variable thickness in cross-section from the leading edge 27B to the trailing edge 26B. Advantageously, in cross-section, it is shaped similarly to an airfoil profile, with a point or region of maximum thickness d between the leading edge 27B and the trailing edge 26B. The leading edge 27B is rounded, and the wing section 39B, 40B tapers towards the trailing edge 26B. This is advantageous for high efficiency and / or low noise generation.

[0103] Fig. 5 shows, in a perspective view from the downstream side, an embodiment of a fan 1 of axial design according to the invention, with a larger impeller 19A and a smaller impeller 19B. The smaller impeller 19B is an impeller with loop vanes 22B. A supporting, non-rotating guide element, which in particular comprises the supporting guide vanes 11, is arranged between the two impellers 19A and 19B.

[0104] The guide vanes are integrated as a single unit into a downstream guide housing 2, which, in addition to the supporting downstream guide vanes 11, also includes the outer housing contour with the sections inlet nozzle 9 (see also Fig. 7), running section 29A for the larger impeller A, and a diffuser section 10. During fan operation, fluid is drawn into the fan 1 through the inlet nozzle 9, flows within the housing 2 first through the running section 29A of the larger impeller 19A, then through the diffuser section 10, before exiting the fan 1 obliquely to the left and towards the viewer, as shown in Fig. 5. Due to the rotation of the two impellers 19A and 19B during operation, energy is transferred between the impellers 19A, 19B and the fluid, thus maintaining the flow.

[0105] The guide assembly, or guide housing 2, is designed with an intermediate ring 5 integrally manufactured with the guide housing 2, as well as outer strut wings 3, which are also integrally manufactured with the guide housing 2. The guide wings 11 are designed as inner guide wings, extending radially, or in the span direction, from a hub ring 4, which is also integrally manufactured with the intermediate ring 5, only as far as the intermediate ring 5. The intermediate ring 5 extends circumferentially and is located between the radially inner hub ring 4 and the outer housing contour, formed by the inlet nozzle 9, the running area 29A of the larger impeller 19A, and the diffuser 10. The strut wings 3 extend between the intermediate ring 5 and the outer housing contour. Together, the strut wings 3, the intermediate ring 5, and the guide wings 11 provide the load-bearing connection between the hub ring 4 and the outer housing contour.

[0106] The two impellers 19A and 19B with their respective drives 34A and 34B are attached directly or indirectly to the hub ring 4. The guide housing 2, and thus the entire fan 1, can be attached to a higher-level air handling system, typically in the area of ​​the outer housing contour, for example in the area of ​​the inlet nozzle 9 with the inflow-side mounting provisions 20 or in the area of ​​the diffuser 10 with the outflow-side mounting provisions 21.

[0107] On the downstream side of the guide housing 2, fastening provisions 25 for a protective grille are advantageously arranged so that a suitable protective grille can be attached in such a way that it does not protrude axially beyond the guide housing 2, namely by screwing the protective grille axially into the guide housing 2.

[0108] The intermediate ring 5 separates a radially inner flow area 7 from a radially outer flow area 6, both of which lie within the outer housing contour defined by the inlet nozzle 9, the running area 29A of the large impeller 19A, and the diffuser wall 10. In effect, the total flow rate passing through the fan 1 and also through the area of ​​the large impeller 19A with its blades 22A is divided between the inner flow area 7 and the outer flow area 6. However, the smaller impeller 19B with its loop blades 22B only covers approximately an area 8 in the radial or span direction, which is advantageously only a portion of the inner flow area 7 (see also Fig. 7), and therefore has a significantly smaller diameter than the larger impeller 19A, for example, a diameter less than 65% of the diameter of the larger impeller 19A.

[0109] To achieve good efficiency and acoustic performance, the smaller impeller 19B is designed with loop vanes 22B. These loop vanes 22B have no free radial outer ends that would need to run directly against a housing wall. This allows the diameter to be sufficiently small to achieve low noise levels, yet large enough to ensure high efficiency. In particular, the diameter of the impeller 19B with the loop vanes can be freely selected, independent of any predetermined diameters of the guide element, such as the inner ring 5.

[0110] While the large impeller 19A carries essentially the entire flow rate and is subjected to power, the smaller impeller 19B carries only a partial flow rate and interacts with only a partial flow rate through power transfer. This is particularly evident in the smaller outer diameter of the smaller impeller 19B. In a radially inner region of the fan 1, the efficiency and pressure stability of the entire fan 1 can be significantly influenced by modifying the flow there, i.e., by power transfer. However, this can be achieved in radially inner regions with only minimal noise generation; that is, for the smaller impeller 19B with its blades 22B, the noise generation, for example, due to rotor-stator interaction and / or rotor-rotor interaction and / or turbulence-rotor interaction, is relatively low.

[0111] With regard to noise generation, the inflow noise plays a particularly significant role in the case of the impeller (19B) connected in series downstream of another impeller (19A) in the flow path. This refers to the inflow noise that arises at the downstream impeller 19B as a result of turbulence and spatial and temporal flow irregularities encountered there, caused primarily by the upstream impeller 19A, but also, for example, by the upstream guide vane. Due to the design of impeller 19B with its smaller diameter and, in particular, with the loop vanes 22B, this inflow noise can be minimized, thereby also minimizing the overall noise of the fan 1.

[0112] The non-rotating guide vanes 11 arranged between the two impellers 19A and 19B can provide intermediate straightening (swirl reduction) of the flow, which can be advantageous, with the guide vanes 11 also having a supporting function.

[0113] In the exemplary embodiment, the direction of rotation 32B of the smaller, downstream impeller 19B with the guide vanes 22B is the same as the direction of rotation 32A of the upstream, larger impeller 32A. This has proven particularly advantageous with regard to low noise generation. For impellers connected in series with the same direction of rotation, an intermediate guide wheel with downstream guide vanes 11 is particularly advantageous. In other embodiments, especially without guide vanes between the impellers connected in series, an opposite direction of rotation of the impellers can also be advantageous.

[0114] In other embodiments, it is also conceivable that no intermediate ring is incorporated in the guide housing and that the guide vanes extend continuously from a hub ring to an outer housing contour. For such an embodiment, an impeller with loop vanes is particularly suitable as a downstream, smaller impeller to achieve high efficiency and low noise levels.

[0115] The larger impeller 19A is essentially formed from a hub ring 31A (Fig. 7) and wings 22A attached to it, and is attached to a drive 34A by its hub ring 31A.

[0116] In other embodiments, the larger impeller can additionally have a cover ring that connects the outer ends of its blades in the circumferential direction.

[0117] The impeller 19B is essentially formed from a hub ring 31B and loop wings 22B attached to it, and is attached to a drive 34B by its hub ring 31B. A detailed description of the construction of an impeller 19B with loop wings 22B can be found in the exemplary embodiment shown in Fig.

[0118] 1-4 along with the corresponding description can be taken from this document.

[0119] Fig. 6 shows, in a plan axial top view from the downstream side, the fan 1 with two impellers 19A, 19B of different diameters as shown in Fig. 5. In addition to the descriptions for Fig. 5, the identical directions of rotation 32A of the larger impeller 19A and 32B of the smaller impeller 19B can be clearly seen.

[0120] As can also be seen in Fig. 6, the outer strut wings 3 are angled sharply in the axial direction relative to the trailing edges 26A of the wings 22A of the larger impeller 19A, for example at an angle > 45° to the trailing edges 26A of the impeller 19A in the projection onto the view according to Fig. 5. This is particularly advantageous for low rotational noise generation in the radially outer region with high rotational speeds.

[0121] In the radially inner region, a relatively large number of inner guide vanes 11 oppose the vanes 22B of the smaller impeller 19B. The rotational tone is therefore of a higher frequency there, which is often advantageous, and less intense.

[0122] The trailing edges 26A of the wings 22A of the large impeller 19A are serrated to minimize trailing edge noise.

[0123] The trailing edges 26B of the blades 22B of the smaller impeller 19B are not serrated, since the smaller impeller 19B, due to its small diameter, emits only a negligible amount of trailing edge noise compared to the total noise of the fan 1 during operation. In other embodiments, it is also conceivable to design the trailing edges of a smaller impeller or its blades to be serrated.

[0124] Mounting openings 24 are provided on the hub 31B of the smaller impeller 19B. These facilitate the installation of the motor 34A (not visible here) with its support unit integrated into the guide housing 2. For fans with two impellers of different diameters, it can be advantageous to have such or similar mounting openings in one of the impellers, typically in the hub area. These openings can also be closed after the fan has been installed, for example, to prevent noise during operation.

[0125] Figure 7 shows a side view and a section in a plane through the axis of the fan 1 according to Figures 6 and 7 with two impellers 19A and 19B of different diameters. During fan operation, the flow – in this view – flows essentially from left to right through the fan 1 or its housing 2 within the outer housing contour, first through the area inside the inlet nozzle 9, then through the cylindrical area 29A of the outer housing contour, which here also forms the running area for the larger impeller 19A, and then through the area of ​​the outer diffuser wall 10. Approximately after passing through the larger impeller 19A, the flow divides into two flow areas: an inner flow area 7 and an outer flow area 6, which are separated from each other by a wall, namely the intermediate wall 5 of the guide housing 2.

[0126] The wall separating the inner flow area 7 and the outer flow area 6 is a non-rotating partition integrated as a single unit into the entire guide housing 2, which also forms the intermediate ring 5 of the guide housing 2 and the guide device integrated therein with the guide vanes 11. After passing through the larger impeller 19A, the flow flows over the upstream edge 23 of the intermediate ring 5 and is there divided into the two flow areas, the inner flow area 7 and the outer flow area 6.

[0127] Essentially, only the portion of the flow passing through the inner flow area 7 subsequently flows, either wholly or partially, through the smaller impeller 19B in the flow path and, as a result of its rotation, is additionally subjected to power transfer. Power transfer is possible in both directions; however, power transfer from the smaller impeller 19B to its flow, which can be assigned to a flow area 8 of the smaller impeller 19B, is advantageous. The flow area 8 of the smaller impeller 19B is a portion of the flow from the inner flow area 7 that is located near the axis. Advantageously, with regard to the hypothetical cross-sectional area through which the flow passes, this portion comprises only about 35%–85% of the inner flow area 7, but in other embodiments, it can also cover almost the entire inner flow area 7.

[0128] The portion of the flow passing through the outer flow area 6 does not essentially pass through the smaller impeller 19B, so that, for example, no additional noise can be generated in this area through interaction with rotating blades. In any case, only a portion of the total flow through the fan 1 passes through the smaller impeller 19B in its associated flow area 8, which advantageously has a flow-through cross-sectional area of ​​20%–50%, and more advantageously 25%–45%, of the total fan area.

[0129] It is also conceivable that a smaller impeller is arranged upstream of the larger impeller in the direction of flow. In such embodiments, the division of the total fan flow into at least two flow zones, in particular the flow zone assigned to the smaller impeller, is designed upstream of the larger impeller, so that after passing through the several flow zones, the flow can be merged and flows through the larger impeller.

[0130] A smaller impeller with loop blades is also ideally suited for a fan in which the flow path first passes through the smaller impeller and then the larger impeller, especially because the design with the loop blades eliminates the need for a stationary partition radially directly outside the smaller impeller.

[0131] The large impeller can also have a circumferential cover ring connecting the outer blade tips. In such cases, this outer cover ring can help define the outer housing contour, which in this case should more accurately be described as the outer flow contour.

[0132] The wheel 19A according to the embodiment shown in Fig. 7 or its hub 31A is connected to the rotating part of the drive 34A by means of connecting devices 30A, advantageously screwed in place.

[0133] The wheel 19B or its hub 31B is connected to the rotating part of the drive 34B by means of connecting devices 30B, advantageously screwed in place.

[0134] Figure 7 clearly shows the respective drives, preferably electric drives, 34A and 34B of the large impeller 19A and the small impeller 19B, respectively. The impellers 19A and 19B, or rather their hubs 31A and 31B, are connected to the rotating interfaces of the drives 34A and 34B, respectively, so that the drives 31A and 31B hold the impellers 19A and 19B and drive them in the direction of rotation, whereby power is transmitted between the drives and the impellers.

[0135] The larger impeller 19A typically features a larger drive 34A with higher power and torque than the smaller impeller 19B, which requires only a smaller drive 34B with lower power and torque. Since the less powerful drive 34B requires only a small fraction (< 50%) of the manufacturing effort of the larger drive 34A, expressed in terms of cost or CO2 equivalent, the manufacturing effort for the entire fan 1 is only slightly higher than for a comparable state-of-the-art system without the smaller impeller and drive. Despite this only slightly increased manufacturing effort, the power density, efficiency, application range, and adaptability can be significantly improved compared to the state-of-the-art fan.

[0136] The impeller arranged first on the upstream side in the direction of flow, here the larger impeller 19A, is equipped in the area of ​​its hub 31A or its upstream side with an aerodynamically favorable, curved hub cover 37 that rotates during operation.

[0137] If the smaller of the wheels is arranged on the upstream side, it can advantageously be equipped with an aerodynamically designed hub cap.

[0138] The drives 34A and 34B are advantageously continuously variable speed electric motors, and further advantageously permanent magnet EC motors, and even more advantageously external rotor motors. The motors, including their respective control electronics, can be manufactured completely independently of one another, or a common control electronics unit can be used. In any case, the control electronics unit(s) is / are arranged close to the motor, for example, in the area of ​​a support unit, as in the illustrated embodiment, within the hub ring 4 of the supporting guide unit of the guide housing 2. Depending on the embodiment, one or more electronic housings 13 can be provided in the area of ​​the drives 34A and 34B, in which the control electronics unit(s) are housed.

[0139] It is particularly advantageous if the rotational speeds of the two impellers 19A and 19B, or their drives 34A and 34B, can be set completely independently of each other. This allows the speed ratio of the two impellers to be optimally adjusted as required.

[0140] The two rotational speeds are controlled in a particularly advantageous way by a special controller. This controller must ensure a required flow rate in some form, but also has an additional degree of freedom (because two rotational speeds are available as control variables) to, for example, maximize efficiency, minimize power consumption, minimize noise, minimize vibration, optimize long-range performance, or optimize the flow through a heat exchanger near the fan. In particular, vibration can also be minimized, thereby automatically preventing critical rotational speeds of either impeller.

[0141] Advantageously, the controller used to adjust the speed of the two impellers can be based on methods of artificial intelligence or "machine learning", but simpler, more deterministic control methods can also be very effective.

[0142] The drives 34A and 34B, or the control electronics, must be electrically and / or electronically connected to the higher-level system; in particular for the transmission of electrical power via power cables, but possibly also via control cables. Various devices can be provided for this purpose, for example, cable connections 53 on the control electronics and / or cable penetrations, openings, or the like on the hub housing in the area of ​​the hub 4 of the suspension and / or cable holders 35 on guide elements or support struts and / or cable penetrations 36 in the area of ​​the outer housing (see also Fig. 9). It is also conceivable to have fan designs with two or more impellers arranged in series, at least one of which has a significantly smaller diameter than another, in which the rotational speeds of the two impellers are coupled, i.e., equal.The advantage of such a design is that only one drive and no gearbox is necessary.

[0143] Figure 8 shows a further embodiment of a fan 1 with two impellers 19A and 19B of different diameters in a side view and in a section along a plane through the axis, similar to the view in Figure 7. In contrast to the otherwise similarly constructed fan shown in Figures 5 to 7, the radially outer flow boundary after the diffuser area 10 integrated into the housing 2 has an additional extension 16 of the diffuser wall. This extension 16 connects seamlessly to the integrated diffuser wall 10 at its inner contour. Such a diffuser-like extension of the radially outer flow boundary of the fan 1, within which the flow cross-section continuously widens, can be advantageous for achieving particularly high efficiency values.

[0144] The outer flow boundary, in the form of the diffuser wall extension 16, completely extends beyond the smaller impeller 19B when viewed axially towards the outflow direction, which is on the right in the illustration. This provides further advantages in addition to the high efficiency. For example, a flat protective grille can now be designed at the downstream end of the diffuser attachment 16 to prevent accidental contact with the smaller impeller 19B or its drive 34B. This also makes it easier to stack several fans 1 on top of each other for transport.

[0145] In an embodiment with an extension 16 of the nozzle wall, it is also conceivable to attach a supporting contact protection grid to the axially outflow-side end of the extension 16, to which the smaller impeller (19B) with its drive (34B) is attached. Alternatively, an axially long external diffuser extending over the smaller impeller 19B or its drive 34B can also be integrally manufactured with the housing 2.

[0146] In the case of non-integral manufacturing of an add-on diffuser 16, it can be made of sheet metal, solid plastic or foamed plastic or the like.

[0147] In advantageous embodiments, it is conceivable to retrofit the smaller impeller 19B, particularly with its drive 34B, to an existing prior art fan in order to achieve, for example, higher efficiency, lower specific sound power, higher air flow, greater operational flexibility, or other functional optimizations. It is particularly advantageous to use an impeller with loop blades as the smaller impeller 19B.

[0148] Fig. 9 shows a perspective view from the downstream side of the embodiment of the fan 1 with two impellers 19A, 19B of different sizes as shown in Fig. 8. In this illustration, the outer contour of the diffuser 16 implemented in the exemplary embodiment is clearly visible. At the outlet, the diffuser has a non-circular, more square, and thus approximate square cross-section. This allows for a compact arrangement of several fans 1 side by side, for example, on an air handling unit. Downstream heat exchangers, which are more angular in shape, can be subjected to more homogeneous flow through such a design.

[0149] Fig. 10 shows, in a perspective view from the downstream side, another embodiment of a fan 1 similar to that shown in Figs. 5-7, wherein the hub 31B of the smaller impeller 19B with the loop vanes 22B has a smaller diameter than the hub ring 4 of the guide housing 2. This can be advantageous for efficiency and / or low noise emissions and / or good long-range performance and / or good transfer to a downstream heat exchanger, since the open flow cross-section and, if applicable, the flow area swept by the loop vanes 22B in the region of the smaller impeller 19B is further increased inwards towards the axis in the flow path after the guide device with the guide vanes 11. A smaller diameter hub 30B of the smaller impeller 19B, compared to the hub 4 of the guide housing, has further advantages. For example, the mass of the impeller 19B can be easily reduced.

[0150] A smaller diameter hub 30B of the smaller impeller 19B, compared to the hub 4 of the guide housing, offers further advantages. This creates a radial gap between the hub 4 of the guide unit and the hub 30B of the smaller impeller 19B, through which fluid, particularly air, can flow unhindered axially opposite to the main flow direction into the interior of the hub 4 of the guide housing. There, this fluid can be advantageously used for cooling the drive(s) or their control electronics.

[0151] Fig. 11 shows the fan 1 according to Fig. 10 in a planar view in the axial direction, seen from the downstream side. The radial gap between the hub 31B of the smaller impeller 19B with the loop vanes 22B and the hub ring 4 of the guide housing 2 is clearly visible in this view. Through this gap, fluid or air can enter unhindered into a region radially within the hub ring 4, where it can, in particular, improve the cooling of one or more drives.

[0152] Fig. 12 shows the fan 1 according to Figs. 10 and 11 in a planar side view and in a section along a plane through the fan axis, with the motors 34A and 34B not shown in section. The smaller outer diameter of the hub 31B of the smaller impeller 19B with the guide vanes 22B is clearly visible in comparison to the diameter of the hub ring 4, which connects to the radially inner ends of the guide vanes 11 of the guide housing 2.

[0153] In the exemplary embodiment, the hub 31 B even projects slightly axially into the axial area of ​​the hub ring 4.

[0154] This illustration clearly shows that, in the exemplary embodiment, as well as in the exemplary embodiments according to Figs. 5-9, the drive 34B is rigidly connected to the drive 34A on the stator side. A connecting piece 28 serves this purpose. Thus, both drives 34A and 34B are held together on the fan 1 on the stator side.

[0155] Within the connecting piece 18 there is ample installation space for control electronics of the drives or the like.

[0156] The two drives 34A and 34B, together with the connecting piece 28, can also be considered a single unit, thus forming a "dual motor" with two rotors or rotating interfaces, which advantageously have independently controllable speeds. Such a dual motor requires only one mechanical interface on the stator side and can also be electrically powered via a single connection cable. From the outside, it can be viewed as a single unit from both the user's and the stator's perspectives.

[0157] In a particularly advantageous embodiment, such a “dual motor” can be prefabricated as a structural unit, in particular with a uniform control electronics and uniform connection interfaces.

[0158] The speed ratio of the impellers 19A and 19B can also be regulated so that the flow through the pressure-side connected heat exchangers is as homogeneous as possible.

[0159] As a result of the effect of the smaller impeller 19B of the fan 1, the heat exchangers opposite the central area of ​​the fan 1, which are connected on the pressure side, are subjected to a significantly more homogeneous flow. Backflow in these areas is avoided in a simple manner.

[0160] The speed ratio of impellers 19A and 19B can also be controlled to optimize the long-range throw, i.e., to ensure that the fan's outflow into a downstream connected space, for example, extends as far as possible into the room, or that the conveyed air penetrates as deeply as possible into the connected space. In a particularly advantageous embodiment, the drive can also be designed as a "dual drive," i.e., a drive with common components such as a common drive and / or electronics housing, but with two different drive speeds, whereby the two impellers can be connected to different rotors and driven at fundamentally independent rotational speeds.

[0161] In other advantageous embodiments that require less manufacturing effort, the rotational speeds of the two impellers can be coupled, for example in a fixed ratio. This can be achieved with gearboxes, e.g., gear drives or magnetic drives.

[0162] In other advantageous embodiments, which involve less manufacturing effort, the rotational speeds of the two impellers can be the same, advantageously with the same direction of rotation. Then the impellers can be mechanically mounted on the same shaft or shaft.

[0163] Depending on the design and operating condition, the smaller impeller can also transfer power to its electric drive, which in that case becomes a generator (reversal of the power flow direction).

[0164] In Fig. 13, a further embodiment of a fan 1 is shown in a perspective view from the downstream side, wherein a smaller impeller 19B, which is designed with loop vanes 22B (see Fig. 14), and its drive 34B are supported by a support unit on a radially outer area of ​​the housing 2.

[0165] The support unit in the exemplary embodiment is advantageously a supporting protective grid 46, which is attached to the downstream housing 2 at its downstream mounting provisions 25 for a grid, preferably screwed in place.

[0166] In the exemplary embodiment, the supporting protective grid 46 advantageously fulfills the function of a protective barrier against accidental contact with parts rotating during operation, such as in particular the impellers 19A and 19B and, if applicable, the rotating parts of the motors 34A and 34B.

[0167] The supporting protective grid 46 is advantageous in that the spacing between adjacent grid elements or wires is optimally adapted locally to the minimum distances to rotating parts. Thus, the spacing between adjacent wires can be larger in radially outer areas because the small impeller 34B does not extend as far outwards and the nearest rotating part, the large impeller 19A, is considerably further away from the grid. In radially inner areas of the supporting protective grid 46, the spacing between adjacent grid elements or wires must be smaller because the distance to the smaller, rotating impeller 19B can be considerably less.

[0168] The supporting grid 46 is shaped to be sufficiently stable in order to securely hold the motor 34B with the smaller impeller 19B attached to it on the housing 2 of the fan 1 and to minimize vibration during fan operation.

[0169] The supporting protective grille 46 carries the load-bearing function for the smaller impeller 19B with its drive 34B and simultaneously provides a safety barrier. Since safety barriers are frequently necessary on the downstream side of the fan 1, this functional integration is particularly advantageous.

[0170] In order to support the impeller 19B with its drive 34B, the support struts of the support grid 46, which extend predominantly radially and at whose radially outer end the support grid 46 is attached to the housing 2, are dimensioned with sufficient stability, for example with a wire diameter of at least 6 mm. Advantageously, these are wire struts that run at least approximately parallel or at an acute angle to each other and have a wire diameter of at least 5 mm.

[0171] In other embodiments, it may also be advantageous to use an add-on diffuser or an extension of the outer diffuser wall (16) similar to the embodiment according to Fig. 8 and Fig. 9, if implemented, and to attach a supporting grid, in particular for a smaller impeller with its drive, at the downstream end of the add-on diffuser.

[0172] The embodiment shown in Figures 13 and 14 exhibits commonalities and similarities, in particular, to the embodiment shown in Figures 5 to 7, and the reference numerals are used consistently. Therefore, reference can be made to the figure descriptions therein for the corresponding features. In particular, the guide housing 2 and the impellers 19A and 19B with the drives 34A and 34B are designed very similarly.

[0173] Fig. 14 shows the fan according to Fig. 13 in a planar side view and in section along a plane through the fan axis and through an outer connection area for the support grid 46. By using the support grid 46 to connect the smaller impeller 19B to the outer housing 2, it is not necessary to connect the two drives 34A and 34B internally or to use a dual drive. The two drives 34A and 34B are therefore not directly coupled statically, but only via the outer housing.

[0174] Such an embodiment is ideally suited for implementing a retrofit solution, in which the support grid 46 with the attached second motor 34B and the impeller 19B can be subsequently provided or attached to a finished, possibly already in operation fan with the guide unit (2) with guide device with guide vanes (11), the impeller 19A and the motor 34A.

[0175] It is also conceivable to offer, optionally, a fan with only one impeller or, as required, a fan with two or more impellers, using many identical components, particularly in an embodiment similar to the embodiment shown in Fig. 14.

[0176] In an embodiment with a supporting grid 46 for a smaller impeller 19B with its drive 34B, it is advantageous to route the connection cables of the motor 34B along the supporting grid 46 or radially outwards along one of its support struts. In an embodiment with a supporting grid 46 for a smaller impeller 19B with its drive 34B, it is advantageous to provide a control unit for intelligent control of the two drives (or multiple drives) on the outside of the housing 2, so that the speed control of the two or more impellers, especially in relation to each other, can be carried out by the fan. An interface between the control unit and the higher-level system then serves to control higher-level operating parameters such as the air flow rate or the speed of the larger impeller.

[0177] Regarding further advantageous embodiments of the teaching according to the invention, reference is made to the general part of the description and to the attached claims in order to avoid repetition.

[0178] Finally, it should be expressly pointed out that the exemplary embodiments of the invention described above serve only to illustrate the claimed teaching and do not limit it to these exemplary embodiments.

[0179]

[0180]

Claims

Claims 1. Impeller for a turbomachine, preferably for a turbomachine, in particular for a fan, wherein the impeller has a hub with blades attached to it, characterized by the fact that the wings are loop-shaped.

2. Wheel according to claim 1, characterized in that the wings are each attached to the hub at two foot areas offset from each other in the circumferential direction and / or axial direction, wherein a radially outer connection of the two foot areas may exist, which has an outer connection area extending in the circumferential direction.

3. Wheel according to claim 1 or 2, characterized in that all foot areas of all wings are distributed approximately uniformly over the circumference, wherein, if necessary, the circumferential distance of the two foot areas of a wing may be slightly smaller or larger than the circumferential distance of directly adjacent foot areas of adjacent wings, wherein this difference, measured at an angle, is not greater than 5°.

4. Impeller according to one of claims 1 to 3, characterized in that one foot region of a wing is the radially inner end of a leading partial wing of the wing in the direction of rotation and the other foot region of the same wing is the radially inner end of a trailing partial wing of the wing in the direction of rotation, wherein the two partial wings are connected to each other at their radially outer region via the connection region, wherein advantageously 2-5 substantially identical and substantially uniformly distributed wings comprising 4-10 partial wings can be formed on the impeller or its hub.

5. Impeller according to claim 4, characterized in that at least one, and advantageously both, transitions between the two partial wings of a loop wing and the connection area are rounded, largely without kinks or the like, so that the loop wing advantageously has a contour or surfaces that run continuously and advantageously tangentially from one foot area to the other.

6. Impeller according to claim 4 or 5, characterized in that at least one, advantageously both, of the partial vanes of a loop vane is designed, at least in a radial area, in section on a cylinder, similarly to the cross-section of an airfoil profile with an inflow edge area, an outflow edge area, a suction side and a pressure side, with a ratio of the maximum thickness to the chord length > 6 and, advantageously, an angle of attack of the chord to the circumferential direction between 15° and 50° and further advantageously different inflow and outflow angles of a difference of at least 8°.

7. Impeller according to claim 6, characterized in that the two partial vanes, viewed in section, are designed to be identical or similar to each other at least over the inner 50% of their radial extent, with maximum differences in angles such as inflow angle, outflow angle and / or angle of attack of a maximum of 5° and / or maximum differences in chord length of a maximum of 10%.

8. Impeller according to one of claims 6 or 7, characterized in that a loop vane has an outer, continuous and advantageously tangentially continuous surface comprising the pressure side of the leading partial vane, the suction side of the trailing partial vane, and the outer surfaces of the connection area and optionally the transition areas, as well as an inner, continuous and advantageously tangentially continuous surface comprising the suction side of the leading partial vane, the pressure side of the trailing partial vane, and optionally the inner surfaces of the connection area and optionally the transition areas.

9. Impeller according to one of claims 1 to 8, characterized in that it is manufactured in one piece in a casting process, advantageously in plastic injection molding with a fiber-reinforced thermoplastic material, and that it advantageously has an undercut-free surface with respect to tool opening directions parallel to the axis of rotation.

10. Fan, in particular with at least one impeller according to one of claims 1 to 9, advantageously with at least 2 impellers.

11. Method for controlling a fan according to claim 10, characterized in that a requested power or air performance of the fan is ensured while maximizing the overall efficiency and / or minimizing the overall noise emission and / or minimizing the overall vibration values ​​and / or the vibration values ​​by adjusting or regulating the rotational speeds of the impellers for this purpose, preferably using a control unit or regulating unit assigned to or integrated into the fan.

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