Method for operating a fan and fan

Abstract

A method serves to operate a fan, in particular an axial or diagonal fan, wherein the fan comprises an electric drive with at least one impeller associated with the drive, from which at least primary motor sensor parameters are acquired during operation and processed for the quantitative determination of the respective current operating state. A fan uses a corresponding method.

Description

The present invention relates firstly to a method for operating a fan, in particular an axial or diagonal fan, wherein the fan comprises an electric drive with at least one impeller associated with the electric motor. The current fluid dynamic operating state, particularly the flow rate, is continuously determined during operation. Continuously monitoring and knowing the current operating state of a fan offers numerous applications and advantages, such as implementing demand-based constant flow control, determining or estimating the icing status of a heat exchanger, identifying undesirable operating states like stalling, monitoring filter conditions, implementing intelligent fan control, and integrating an airflow meter, etc. In current technology, fans often consist of only one impeller with an associated drive. With suitable sensors, the current rotational speed and motor current, or other electrical motor parameters of the fan drive, can be monitored during operation with relatively little construction effort. However, it has been shown that the information provided by the rotational speed and electrical motor parameters of a fan with only one drive is often insufficient to allow for a clear and reasonably accurate quantitative assessment of the fan's current operating state, even when information on the fluid temperature and / or density is included. In particular, an aerodynamic operating condition, such as the current flow rate, cannot be quantitatively determined with sufficient accuracy.This problem is particularly prevalent with axial fans and backward curved radial fans. It is known in the prior art that the flow rate can be determined by adding further sensor data, for example using a vane anemometer according to EP 3 833 877 A. However, the use of an additional sensor regularly entails increased construction effort, which is particularly significant for large fans, as well as an increased susceptibility to failure. The object of the invention is to provide a method for operating a fan with reliable, continuous quantitative determination of the current operating state based exclusively or predominantly on sensor parameters detectable internally within the motor. A correspondingly functioning sensor will be specified. The underlying problem is solved by the features of dependent claims 1 and 13. According to the invention, it has been recognized that if the drive performance data of at least two different impellers of a fan, namely their respective rotational speed and shaft power, are evaluated separately, the air performance of the entire fan can in many cases be clearly and with high accuracy deduced from this information, in particular the current delivery volume flow and dependent quantities such as pressure increase, efficiency, axial thrust or sound power. If a fan uses at least two electric drives, i.e., two electric motors and / or a double electric motor, to which different impellers or impeller groups are assigned, the current flow rate or related quantities (in particular the pressure increase, the efficiency, the axial thrust or also the sound power) can be reliably and with high accuracy deduced from the current speeds and the current motor currents or motor powers, whereby the density, which characterizes the state of the conveyed fluid, can also be advantageously included in the process as a separately acquired input value. This applies in particular to fans with at least two impellers or at least two electric drives. The invention can easily be applied to other types of turbo-turbine machines. Advantageous embodiments of the claimed teaching can be found in the dependent claims, the reproduction of which is omitted here. There are now various ways to advantageously elaborate and further develop the teaching of the present invention. For this purpose, reference is made, on the one hand, to the claims subordinate to claim 1, concerning the method, and to the claims subordinate to claim 13, concerning the fan, 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. In the drawing, Fig.Figure 1 shows a fan according to the invention in a side view and in section along a plane through the axis, with a larger and a smaller impeller, wherein the main flow direction in the illustration runs approximately from left to right and the impellers are arranged in series (one behind the other in the flow direction). Figure 2 shows a further embodiment of a fan with a smaller impeller with looped blades, similar to the view according to Figure 1, wherein the smaller impeller, which is designed with looped blades, and its drive are supported by a support grid on an outer, downstream area of ​​the housing 2.Figure 3 shows a diagram in which the course of the motor current pairs for a variable delivery volume flow of the fan is shown for a measurement of a fan with two motors and each associated impeller for constant motor speeds, and Figure 4 shows another diagram of the same type as in Figure 3 for another fan in which one of the impellers has been replaced by another with a different geometric design compared to the embodiment according to Figure 3, again for constant speeds of the two impellers. Fig. 1 shows, in a side view and in section along a plane through the axis (axis of rotation), an embodiment of an axial fan 1 according to the invention, with two impellers 19A and 19B arranged one behind the other (in series) in the direction of flow. Each of the impellers 19A, 19B is attached to the rotor of a corresponding electric motor 34A or 34B, respectively. The two electric motors 34A and 34B can be operated at independent speeds, and in addition to the speeds, the electrical motor data (e.g., motor currents, winding voltages, or motor power) can be independently measured. For this purpose, corresponding sensors with sufficient accuracy are provided in the fan 1, advantageously directly in the motors 34A, 34B. The fan 1 is suitable for operation using a method in which the current aerodynamic operating state, in particular the current volumetric flow rate (or mass flow rate) of the fan 1, is continuously determined quantitatively during operation. For this purpose, the rotational speeds of the various motors 34A and 34B, as well as their respective electrical motor data such as motor current or motor power, are recorded as the main input parameters and processed by a device-specific evaluation algorithm to obtain a quantitative value for the current aerodynamic operating state, in particular the current volumetric flow rate. The aforementioned quantities (four in the exemplary embodiment: two rotational speeds and two electrical motor data points) are also referred to in this document as primary motor sensor data. For high accuracy, it can be advantageous to determine the actual current density of the conveyed medium as additional information or to process this data in the evaluation algorithm. This can be achieved with special sensors near the fan or as input from the air handling system. The use of temperature and / or humidity sensors and / or material composition sensors is particularly beneficial here. In the embodiment of the fan 1 according to Fig. 1, a larger impeller 19A and a smaller impeller 19B are provided with regard to their outer diameter. The smaller wheel 19B is advantageously a wheel with loop wings 22B, i.e. its wings 22B have the shape of a loop with two separate connection areas (foot areas) to the hub 21B and an outer connection area 38B of the wings 22B. A supporting, non-rotating guide device, which in particular has the supporting guide vanes 11, is advantageously arranged between the two running wheels 19A and 19B. 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, 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 and, in the view shown in Fig. 1, flows within the housing 2 approximately from left to right, first through the running section 29A, then through the diffuser section 10, before exiting the fan 1. As a result of the rotation of the two impellers 19A and 19B during operation, energy is transferred between the impellers 19A and 19B and the fluid, thus maintaining the flow. The guide assembly or guide housing 2, in the embodiment shown in Fig. 1, 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, running area 29A, and 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 thus provide the load-bearing connection between the hub ring 4 and the outer housing contour. 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 suitable upstream mounting provisions, or in the area of ​​the diffuser 10 with suitable downstream mounting provisions. On the downstream side and / or the inflow side of the guide housing 2, fastening provisions 25 for a protective grille are advantageously arranged in such a way that a suitable protective grille can be attached, advantageously 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. 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 sub-area of ​​the inner flow area 7. Therefore, it 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. To achieve good efficiency and acoustic performance, the smaller impeller 19B in the exemplary embodiment is advantageously designed with loop vanes 22B. These loop vanes 22B have no free radially outer ends that would need to run radially directly against a housing wall. Thus, the diameter can be made 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 predetermined diameters of the guide element, for example, the inner ring 5. 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 affecting the flow there, i.e., through power transfer. However, this can be achieved in radially inner regions with relatively low 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 head gap eddy noise, is relatively low. 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. 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. In the exemplary embodiment, the direction of rotation of the smaller, downstream impeller 19B with the guide vanes 22B is the same as the direction of rotation of the upstream, larger impeller 19A. 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, particularly without guide vanes between the wheels connected in series, an opposite direction of rotation of the wheels can also be advantageous. 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. The larger impeller 19A is essentially formed from a hub ring 31A and wings 22A attached to it, and is attached to a drive 34A by its hub ring 31A. In other embodiments, the larger impeller may additionally have a cover ring that connects the outer ends of its wings in the circumferential direction. The wheel 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. While the larger impeller 19A carries essentially the entire flow rate and is driven by power, the smaller impeller 19B carries only a partial flow rate and interacts with only a partial flow rate through power transmission. This is particularly evident in the smaller outer diameter of the smaller impeller 19B. With the rotational speeds of both impellers 19A and 19B kept constant, the motor data (motor operating states, e.g., motor input power or motor currents) of the associated drives 34A and 34B change as soon as the aerodynamic operating state of the fan 1 changes, i.e., in particular the volumetric flow rate, but also pressure build-up, efficiency, etc. In practice, this often occurs due to a change in the pressure resistance of a connected air handling system. Because one impeller has a significantly smaller diameter than the other and interacts only with a partial internal flow, the motor data of the different drives 34A and 34B change in a manner that is at least partially independent of each other. The information content of both electrical motor data sets is therefore "richer" than the information content of the sensor data (electrical motor data) of a single motor. The combined use of both electrical motor data sets thus enables a significantly improved assessment of the aerodynamic operating state of the entire fan 1, in particular its delivery volume flow rate. This is also related to the fact that the near-axis or near-hub flow of an axial fan is sometimes significantly more sensitive to changes in the operating point at a constant speed. Thus, the electrical motor data of motor 34B, assigned to the smaller impeller 19B, reacts much more sensitively to changes in the operating point, especially in an operating range where the motor data of motor 34A, assigned to the larger impeller 19A, reacts little or not at all to such changes. Therefore, the "additional" sensor signal significantly improves, or even enables, the accuracy of predicting the aerodynamic operating state of fan 1, or even makes such predictions possible in the first place. In the embodiment shown in Fig. 1, the flow during fan operation – 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 within the inlet nozzle 9, then through the cylindrical area 29A of the outer housing contour, which here also forms the area for the larger impeller 19A, and then through the area of ​​the outer diffuser wall 10. The flow splits into two flow areas approximately after passing through the larger impeller 19A: 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 downstream housing 2. 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 simultaneously 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. In this exemplary embodiment, 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, is additionally subjected to power transfer during rotation. Power transfer is possible in both directions; however, power transfer from the smaller impeller 19B to the flow passing through it is advantageous, as this transfer can be assigned to a flow area 8 of the smaller impeller 19B. The flow area 8 of the smaller impeller 19B is a portion of the flow from the inner flow area 7 that is assigned to a region near the axis. Advantageously, with regard to the imaginary cross-sectional area through which the flow passes, it only represents a proportion of about 35%-85% of the inner flow area 7, but in other embodiments it can also cover almost the entire flow area 7. The part of the flow that passes through the outer flow area 6 does not essentially pass through the smaller impeller 19B, so that, for example, no additional sound can be generated in this area by interaction with rotating blades. In any case, only a part 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 fraction of 20%-50%, and further advantageously 25% to 45%, of the total fan. 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 in the area of ​​the smaller impeller, the flow can be merged and then flows through the larger impeller. 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. 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. The wheel 19A according to the embodiment shown in Fig. 1 or its hub 31A is connected to the rotating part of the drive 34A by means of connecting devices 30A, advantageously screwed in place. 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. Figure 1 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. 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 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. 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. If the smaller of the wheels is arranged on the upstream side, it can advantageously be equipped with an aerodynamically designed hub cap. As drives 34A, 34B, continuously variable speed electric motors are advantageously used, as are permanent magnet EC motors, and further 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 advantageously 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. To operate fan 1 using the method in which the aerodynamic operating state of the fan is continuously and quantitatively recorded during operation, separate measurement of the rotational speeds of the different motors (34A, 34B) and their electrical motor parameters, e.g., their motor current, motor winding voltage, motor power, or similar, is necessary. Suitable sensors must be provided for the application of this method, advantageously integrated into the drives themselves. Depending on the embodiment, one or more electronic housings 13 can be formed in the area of ​​the drives 34A, 34B, in which the control electronics are housed. 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. The two rotational speeds are advantageously controlled using a special control method within the fan operating procedure. This method must ensure a required flow rate in some way, 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. The control method used to adjust the speed of the two impellers can be advantageously based on methods of artificial intelligence or "machine learning", but simpler, more deterministic control methods can also be very effective. 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. The fan 1 can also transmit its quantitatively measured aerodynamic operating state or information derived therefrom to the higher-level system. 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 2 (see also Fig. 2). This illustration clearly shows that, in the exemplary embodiment, 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 on the stator side. Within the connecting piece 28 there is ample space for control electronics or the like. 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, both from the user's perspective and from the stator side. In a particularly advantageous embodiment, such a “dual motor” can be prefabricated as a structural unit, in particular with a uniform control electronics, the sensors required for the method and the hardware and software infrastructure for implementing the operating procedure for the fan, in which the aerodynamic operating state of the fan, in particular the delivery volume flow, is continuously determined, as well as uniform connection interfaces. 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. The speed ratio of impellers 19A and 19B can also be controlled to ensure particularly high prediction accuracy or unambiguity of the aerodynamic operating state. It may be advantageous to adjust this speed ratio intermittently from time to time to periodically check or slightly recalibrate the quantitative evaluation of the aerodynamic operating state. 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. The speed ratio of the impellers 19A and 19B can also be regulated so that the long-throw behavior is optimized, i.e., that the outflow of the fan into a room connected on the downstream side, for example, has as deep an effect as possible, or that the conveyed air penetrates as deep as possible into the connected room. 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. Additionally, it must be possible to separately measure electrical motor sensor parameters, such as the motor current or similar parameters, for all drives in order to enable the application of the operating procedure. 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 is possible for some of the drives of a fan). In Fig. 2, a further embodiment of a fan 1 is shown in a planar side view and in section on a plane through the fan axis and through an outer connection area for the support grid, with a larger impeller 19A together with associated drive 34A and a smaller impeller 19B together with its drive 34B, wherein the smaller impeller 19B, as well as its drive 34B, is supported by a support unit on a radially outer area of ​​the housing 2. 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. 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. 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 19B does not extend as far outwards, and the nearest rotating part, the large impeller 19A, is considerably further away from the grid 46. 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. 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. 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. 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 running in pairs, at least approximately parallel or at an acute angle to each other, with a wire diameter of at least 5 mm. In other embodiments, it may also be advantageous to use an add-on diffuser or an extension of the outer diffuser wall of the diffuser 10 of the housing 2, so that the outer diffuser as a whole extends axially beyond the impeller 19B, the drive 34B and the supporting protective grid 46 in the outflow direction. The embodiment shown in Fig. 2 has commonalities and similarities, in particular, to the embodiment shown in Fig. 1, and the reference numerals are used consistently. Therefore, reference can be made to the figure description there for the corresponding features. In particular, the guide housing 2 and the impellers 19A and 19B with the drives 34A and 34B are very similar in design. By using the support grid 46 to connect the smaller impeller 19B to the outer housing 2, it is not necessary in the embodiment shown in Fig. 2 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. In the exemplary embodiment, each of the drives 34A, 34B has its own control electronics 13A or 13B. 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. 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. 2. In an embodiment with a supporting grid 46 for a smaller impeller 19B with its drive 34B, it is advantageous to route the connecting cables of the motor 34B on the supporting grid 46 or radially outwards along one of its support struts. In another embodiment with a supporting grid 46 (or a comparable, separate support unit attached to the outer housing 2, possibly also without a touch protection function) for a smaller impeller 19B with its drive 34B, it is advantageous to provide a central control unit for controlling the two drives (or the multiple drives) to which it is connected, preferably on the outside of the housing 2, so that the operating method, which uses sensor parameters of both drives 34A and 34B in conjunction to continuously determine the current aerodynamic operating state, in particular the current flow rate, can be implemented and applied. With a central control unit advantageously mounted externally on the housing, which is connected upstream of the drives 34A and 34B with their respective controllers, the speeds of the two or more impellers, especially in relation to each other, can also be regulated on the fan side. 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. In an embodiment with a central, in particular an externally mounted, control unit that can be assigned to the overall fan (which includes several drives), it is advantageous that only one input stage is needed for the electrical connection power. In an embodiment with a central, in particular externally mounted, control unit assignable to the overall fan (which comprises several drives) with only one input stage for the electrical connection power of the fan, this input stage can be provided with a power factor correction filter (PFC), so that only one power factor correction filter is needed for the fan with several drives. In another embodiment, the input stage and, if applicable, the power correction filter can be assigned to one of the motors, preferably the largest or most powerful one of the fan, and implemented in the area of ​​its control electronics, whereby supply lines must then be provided from this to the other motor(s) of the fan; preferably, in this case, the supply is in a DC circuit. In another embodiment, the operating procedure can be implemented on the control electronics of one of the motors 34A, 34B (master control). Appropriate communication links, either wired or wireless, between the motors 34A, 34B and their control electronics must be provided to exchange the necessary sensor information and control signals. Figure 3 shows a diagram illustrating the behavior of the motor current pairs (I1, I2) for a variable fan flow rate, as measured for a fan with two motors and their respective impellers, similar to the fan shown in Figure 1. The diagram depicts the fan's aerodynamic operating state, particularly the flow rate, as it changes along the experimentally recorded line shown in the diagram, while the motor speeds remain constant. This change can be caused, for example, by a change in the air resistance (throttling) of an aerodynamic system at constant speeds. In the diagram and example shown, the flow rate decreases steadily from a high initial value along the drawn curve, starting from the bottom left. Conversely, the static pressure increase, also a quantifiable quantity that describes the aerodynamic operating state, increases starting from the bottom left, but not monotonically increasing over the entire course of the curve, since there is a region (here in the region 7 A < I1 < 8 A) in which the static pressure increase decreases in phases in this direction of the curve. Each point on the curve can be uniquely assigned an aerodynamic operating state. For this to work, the method for evaluating the current operating state must be able to access appropriate calibration functions that assign the corresponding operating state, in particular the current mass flow rate or volumetric flow rate (at a given calibration density), to each position on the displayed curve (which results from the currently measured sensor values ​​of the two motor currents I1 and I2 of the two fan drives). The accuracy of predicting the flow rate can be improved by using currently recorded values ​​of the actual fluid density, for example determined with suitable sensors, in particular temperature and / or humidity and / or absolute pressure sensors. The curve shown in Fig. 3 and its associated calibration correspond exactly to one speed combination of the two drives. These curves and calibrations change depending on the actual speeds of the two drives. Therefore, the two speeds are first recorded in order to then obtain suitable calibration curves for the aerodynamic operating conditions, for example, using two-dimensional interpolation. The actual evaluation algorithm for the current aerodynamic operating state can be implemented in a variety of ways. For example, it is conceivable to use multidimensional interpolation methods or successively applied one-dimensional interpolation methods. The application of methods from the fields of artificial intelligence and machine learning is also quite feasible. Crucially, however, the use of the described sensor signals as input parameters is essential: namely, the rotational speeds of at least two independent drives and, for each motor, at least one electrical motor parameter, such as motor current or motor power. The diagram shown in Fig. 3 (also Fig. 4) is intended to illustrate, in particular, that the information content of these sensor parameters allows, at least to a large extent, an accurate and unambiguous evaluation of the current aerodynamic operating state of the fan. Each point on the curve according to Fig. 3 can be uniquely assigned an aerodynamic operating state once the point is known in the form of the electrical motor sensor parameters. Based on the curve shown in Fig. 3, which shows the continuously changing aerodynamic operating state of the fan, it can be determined that the same motor current I1 (or the same electrical motor rating of the first motor) occurs under several aerodynamic operating states, particularly under several different flow rates. For example, it is not possible to unambiguously determine an aerodynamic operating state for a motor current I1 of 7.5 A. Therefore, the information provided solely by the electrical motor rating (I1) of the first motor, at known speeds, is insufficient to determine the aerodynamic operating state. In addition to the first electrical motor rating, the use of a further electrical motor rating from at least a second drive (here I2) is necessary to unambiguously and accurately determine the current aerodynamic operating state, especially the current flow rate. In the diagram according to Fig. 3, the shape of the curve, particularly in the range between I1 = 7 A and I1 = 8 A, shows that in regions where the electrical motor parameter I1 of the first motor exhibits only a low rate of change along the curve, the electrical motor parameter I2 of the second motor exhibits a high rate of change. This is advantageous for achieving good accuracy in the quantitative evaluation of the aerodynamic operating condition based on the selected input parameters, namely the primary motor sensor parameters: the motor speed and the electrical motor parameter of each of at least two motors of the fan. In the diagram according to Fig. 3, it can be seen from the overall shape of the curve, particularly in the region I1 > 8 A, that in areas where the electrical motor parameter I2 of the second motor exhibits only a low rate of change along the curve, the electrical motor parameter I1 of the first motor exhibits a high rate of change. This is advantageous for achieving good accuracy in the quantitative evaluation of the aerodynamic operating condition based on the selected input parameters, namely the primary motor sensor parameters: the motor speed and the electrical motor parameter of each of at least two motors of the fan. Fig. 4 shows another diagram of the same type as in Fig. 3, for a different fan, in which one of the impellers has been replaced by another with a different geometric design compared to the embodiment according to Fig. 3, again for constant rotational speeds of the two impellers. The impeller replaced compared to the fan shown in Fig. 3 is the second one, which in both cases has a smaller outer diameter. In the fan shown in Fig. 4, this impeller has an even smaller outer diameter, so that the motor current I2, with the same motor and the same rotational speed, tends to be lower than in Fig. 3. The same principles described in Fig. 3 can be observed using Fig. 4. With known drive speeds (depending on the speed, the representation is shown in Fig. 3 or Fig. 4) and known electrical motor parameters (here I1 and I2), the operating point can be unambiguously determined, as each point on the curve corresponds to an operating point. It is also clear that the information I1 OR I2 alone does not always allow for a unique conclusion regarding the operating point, as there are areas of ambiguity under these circumstances. In the diagram shown in Fig. 4, there is, however, a single point where a clear assignment is not possible, resulting in ambiguity. This is the intersection of the curve with itself at approximately I1 = 8.3 A and I2 = 1.13 A. At precisely this point, a definitive determination of the aerodynamic operating state would not be possible. However, this point is identifiable by the evaluation method on the fan; that is, it is known in advance, and the evaluation algorithm can react to it appropriately. One way to solve this difficulty is for the second impeller, should such a critical point occur, to briefly modify its rotational speed "as a test," because at a different speed this intersection point would then be at a different aerodynamic operating condition or at a different throttling state of the aerodynamic system. Thus, with a different speed combination of the motors, one would again be in a clearly identifiable operating condition and could determine it precisely quantitatively. This means that, under certain circumstances, particularly when there are ambiguities due to the combination of values ​​of the electrical motor parameters, the fan may intermittently change one or more fan speeds to improve the evaluation of the current aerodynamic operating state. The two operating states at the intersection of the curve with itself in Fig. 4 must be evaluated very differently. The one corresponding to the ascending branch is a "regular" operating state in which there is no or only local flow separation. The other aerodynamic operating state, located on the branch with a negative slope (i.e., with decreasing I1 and increasing I2), involves a massive flow separation in which regular or efficient fan operation is no longer possible; in particular, the efficiency is very low and / or the noise and / or vibration levels are very high. However, this is already the case "before" this point in the curve, running from the bottom left to the top right of the diagram. A flow separation indicator would have to enter a warning state earlier, reporting a flow separation based on values ​​specific to the fan stored in the evaluation software. If one can assume that the aerodynamic operating state changes only steadily or gradually at constant speeds, the fan might not even reach the "unfavorable" operating state at the intersection point, since a warning would have been issued long before the fan traversed the curve, indicating that it was experiencing a stall and potentially switching to emergency mode or shutting down. Under such a scenario, no further specific measures regarding the critical intersection point of the curve with itself might be necessary, as the fan would at least "know" that it was operating in a stall zone. If the fan were to "run out" of the flow separation, it would automatically identify the operating state again, since it would then also run away from the intersection of the curve with itself. Advantageously, the evaluation algorithm for the current aerodynamic operating state over time sets a "flag" if critical operating ranges are identified and clears it as soon as non-critical operating ranges are identified. At the intersection of the curves with themselves, the "flag" then indicates on which branch of the curve the current aerodynamic operating state lies. This information ("stall zone or normal zone") can also be advantageously output to higher levels, such as the air handling system, a data network, or the user. 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. Finally, it should be expressly pointed out that the exemplary embodiments of the teaching described above serve only to discuss the claimed teaching, but do not limit it to these exemplary embodiments. Reference symbol list 1 fan 2 downstream housings, housings 3 strut wings 4 Hub ring of the support unit 5Intermediate ring of the guide unit or diffuser 6 outer flow area 7 inner flow area 8 Flow area of ​​the small impeller 9 Inlet nozzle 10 outer diffuser wall 11 inner guide element, guide vane 12. Egress edge of the intermediate ring 13 Electronic housing 13A Electronic housing of the first motor 34A 13B Electronic housing of the second motor 34B 19A wheel with larger diameter 19B impeller with smaller diameter 22A Blade of the larger impeller 19A 22B Wing of the smaller wheel 19B 23 inflow-side edge of the intermediate ring of the guide unit 25. Fastening device for grille on downstream side 28 Connecting piece of the motors 29A area for a larger impeller 19A, approximately cylindrical area of ​​an outer housing contour 30A30B Mounting device for motor 34A or 34Bam Impeller 19A or 19B 31A hub of the larger wheel 19A 31B hub of the smaller wheel 19B 34A Motor A of the larger impeller 19A 34B Motor B of the smaller wheel 19B 35 cable holders on the guide system 36 Cable penetration in the housing 37 Hubcap of a wheel 38A Winglets of the wings of the larger wheel A 38 Outer connecting area of ​​a loop wing 46 Load-bearing grid 53 cable connections on the stator or electronics housing of the motor QUOTES INCLUDED IN THE DESCRIPTION This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature EP 3 833 877 A

[0004]

Claims

Method for operating a fan, in particular an axial or diagonal fan, wherein the fan comprises an electric drive with at least one impeller associated with the drive, from which at least primary motor sensor parameters are detected during operation and processed to quantitatively determine the current operating state. Method according to claim 1, characterized in that the electric drive comprises at least two electric motors and at least two wheels associated with the electric motors. Method according to claim 1 and / or claim 2, characterized in that the electric drive comprises a double motor with two independent impellers, wherein the impellers can have independently controllable rotational speeds. Method according to one of claims 1 to 3, characterized in that the primary motor sensor parameters are the motor speed and an electrical motor parameter, in particular the motor current or motor power. Method according to one of claims 1 to 4, characterized in that, based on the motor sensor parameters, it is decided whether the fan operates in a favorable (first) or unfavorable (second) operating range and, depending on this, different quantitative methods are applied to determine the operating state. Method according to claim 5, characterized in that a more precise determination method is used in the favorable (first) operating range and a less precise determination method is used in the unfavorable (second) operating range, and wherein a warning signal can be issued and / or the fan can be switched off or enter emergency operation in the unfavorable (second) operating range. Method according to one of claims 1 to 6, characterized in that the determination of the operating state is based on an algorithm according to which the motor speeds are first processed successively and the operating state is then deduced from the electrical motor parameters. Method according to claim 7, characterized in that active temporary changes of one or more motor speeds are applied in the algorithm to increase the quality or accuracy of the operating state determination. Method according to claim 7 or 8, characterized in that the algorithm applies methods of artificial intelligence or machine learning. Method according to one of claims 1 to 9, characterized in that the properties of the conveyed medium, in particular its density, are used to determine the operating state, which is determined on the basis of further sensor data during operation of the fan, for example by using the conveyed medium temperature and / or the moisture content of the conveyed medium. Method according to one of claims 1 to 10, characterized in that the continuously quantitatively determined fluid dynamic operating state is transmitted into a data network and can be viewed by users, operators and / or the fan manufacturer in order to influence the fan or system control. Method according to one of claims 1 to 11, characterized in that the continuously quantitatively determined fluid dynamic operating state is used to identify undesirable operating states of the fan, such as flow separation, very high noise levels or very low efficiency values, and, if necessary, to transmit a warning signal to a higher-level system or a data network. Method according to one of claims 1 to 12, characterized in that the continuously quantitatively determined fluid dynamic operating state, in particular the delivery volume flow rate, is used to realize a control of the fan to a setpoint (target value) of the fluid dynamic operating state. Method according to one of claims 1 to 13, characterized in that the continuously quantitatively determined fluid-technical operating state or information derived therefrom is sent or transferred to a higher-level system, in particular also as an indicator for the state of the higher-level system, for example an icing state of a heat exchanger, the clogging state of a filter, an external wind load, a sound emission of the device, a long-range throwing characteristic or the like. A fan with two or more impellers and at least two motors or a double motor, which drives the impellers or, if applicable, impeller groups, which can be operated using a method according to one of claims 1 to 14, is advantageously operated. Fan according to claim 15, characterized in that at least two of the impellers of the fan, which are advantageously assigned to different motors, are arranged one behind the other (in series) in the main flow direction. Fan according to claim 15 or 16, characterized in that an impeller is attached to the rotor side of each of the motors of the fan. Fan according to one of claims 15 to 17, characterized in that geometrically different impellers are arranged in the fan, wherein at least one of the impellers has a significantly smaller outer diameter than another impeller of the same fan. Fan according to claim 18, characterized in that the maximum outer diameter of at least one of the impellers of the fan is smaller by at least 40%, advantageously at least 45%, than that of the impeller of the fan with the largest outer diameter. Fan according to one of claims 15 to 19 with preferably two impellers, characterized in that a rotationally fixed guide device, which may include guide vanes, is provided in the flow area between adjacent impellers and preferably supports the impellers together with the drive(s). Fan according to claim 20, characterized in that the guide device has 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 advantageously assigned to the inner, near-axis flow area or operates in this area. Fan according to one of claims 15 to 21, characterized in that the impellers preferably rotate in the same or opposite direction to each other. Fan according to one of claims 15 to 21, characterized in that, in the case of independent drives of the impellers, the rotational speeds of at least two of the impellers are independently adjustable or controllable. Fan according to one of claims 15 to 22, characterized in that the fan operation is optimized by adjusting the rotational speed of one or more impellers, preferably at least one impeller with a smaller diameter, preferably driven by an EC drive. Fan according to one of claims 15 to 23, characterized in that the rotational speeds of the impellers can be optimally adjusted or controlled with the aid 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, if applicable, at least one further target variable, for example, the overall efficiency. Fan according to one of claims 15 to 25, characterized in that all two or more impellers are attached directly or indirectly to the outer housing via a supporting guide unit with guide vanes. Fan according to one of claims 15 to 26, characterized in that one of the impellers, preferably an impeller with a smaller diameter, preferably with loop blades, is attached to the outer housing via a separate support structure, i.e. not the guide unit, preferably a support grid.

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