Method for the quantitative determination of an actual operating state-dependent variable of a fan, in particular of a pressure change or pressure increase, and fan

Abstract

The invention relates to a method for quantitatively determining an actual operating-state-dependent variable, for example the pressure increase of a fan, wherein, an actual operating-state-dependent variable is determined via its rotational speed using known volume or mass flows of the fan.

Description

[0001] The invention relates to a method for the quantitative determination of current operating-state-dependent quantities of a fan during operation, such as the pressure change, in particular the pressure increase, and to a fan in which a quantitative determination of at least one current operating-state-dependent quantity, such as the pressure change, in particular the pressure increase, is carried out during operation.

[0002] Knowledge of current, operating-condition-dependent variables can be of numerous benefits. For example, the fan can be controlled or regulated based on one or more of these variables. Similarly, a higher-level system in which the fan is installed and operated can also be controlled or regulated based on one or more of these variables. Furthermore, these variables can be recorded or integrated over time and used in a variety of other ways.

[0003] For example, when operating fans, knowing the current pressure increase is desirable. This knowledge can be used to advantage. Users can then monitor and check the current condition of an air handling system, such as the icing status of a heat exchanger, the degree of filter clogging, critical damper positions, or current wind loads.

[0004] Knowing the pressure increase allows monitoring of the pressure reserve of a fan that is prone to failure, for example. It is possible to determine whether a fan is operating within a permissible range, including whether a so-called drum rotor is operating at excessively low pressures.

[0005] It is already known from practical experience to determine the pressure increase using differential pressure sensors. This is complex and usually cannot be done directly at the fan. In most cases, extensive piping or electrical wiring is required.

[0006] Another disadvantage of determining differential pressure using pressure sensors is the dependence of the measured differential pressure on the position of the pressure sensors and the associated problem of where and how such pressure sensors can be placed or attached.

[0007] It is also known from the prior art to determine the volume flow rate via the shaft moment in backward-curved radial impellers, via differential pressure measurements at the inlet nozzle, or via vane anemometers or thermal anemometers.

[0008] As explained above, it is possible to determine the pressure change or pressure increase of a fan using pressure sensors, in particular also speed monitoring or torque monitoring of a fan, in order to indirectly detect the clogging of filters or icing.

[0009] Determining the current sound emissions of a fan can, for example, be used to regulate a fan in such a way that a certain prescribed limit for sound emissions is not exceeded.

[0010] Determining the current drive torque of a fan can be used to control a fan in such a way that a certain limit drive torque is not exceeded, for example to avoid overloading the drive motor.

[0011] Determining the current efficiency of a fan can be used to control a system with one or more fans in such a way as to achieve the highest possible efficiency.

[0012] For an example of the prior art in printed form, reference is made to DE 10 2013 204 137 A1. This document discloses a method for determining the operating state of a cooker hood fan. It is defined as a function of the speed and power consumption of the electric motor. However, measuring the air volume flow rate via the motor torque is not possible with backward-curved fans.

[0013] From EP 1 039 139 A1 it is known to generate a target speed signal based on an actual speed, a current motor current or supply current, blower-specific data such as wheel diameter, density of the conveyed medium, blower coefficients and motor coefficients as well as a blower target characteristic curve.

[0014] From EP 2799789 A1, a method for automatically adjusting the operation of a fan is known. Here, an operating point of the fan is calculated based on a current speed value and a power value and used to determine a new speed value of the fan.

[0015] Publication EP 2 505 848 A1 deals with a method for determining a standstill of a fan when the fan is controlled by a frequency converter.

[0016] The present invention is based on the objective of providing a method for the quantitative determination of current operating-state-dependent parameters of a fan during operation, for example, the pressure change or pressure increase, whereby the current operating-state-dependent parameter, for example, the pressure change or pressure increase, of the fan can be determined with sufficiently good accuracy without the use of complex sensors such as pressure sensors, and without limitation to specific fans. The aforementioned objective is achieved by the features of claim 1 and, with regard to a fan, by the features of dependent claim 11, according to which, given a known volume or mass flow rate of the fan, current operating-state-dependent parameters, such as pressure change or pressure increase, are quantitatively determined via its rotational speed.According to the invention, for a known volume flow rate or mass flow rate and known rotational speed, an operating-condition-dependent quantity is calculated by calculating at least one characteristic curve for the current rotational speed from a stored calibration characteristic curve, determining the intersection point of a calculated characteristic curve for the current rotational speed with a line of the constant, currently determined volume flow rate or mass flow rate, and determining or reading off a current operating-condition-dependent quantity at the intersection point.

[0017] Regarding the determination of the current pressure increase, the invention is based on the fundamental idea / realization that the fan "infallibly" measures the pressure change or pressure increase occurring at it, since it has to provide the necessary power to overcome, for example, the pressure increase.

[0018] Advantageously, the user or a higher-level system can read out the determined current operating-state-dependent variable, such as the pressure change or pressure increase, and use it to control the fan or the entire air handling system. It is also conceivable to use the current operating-state-dependent variable or its temporal profile to define a time for maintenance, cleaning, or de-icing of the air handling system or one or more components of such a system.

[0019] In one embodiment of the invention, the fan can determine and output the back pressure acting upon it during a pressure increase without the aid of pressure sensors. This back pressure is determined at the fan, i.e., at the "source" where the pressure increase arises or is generated, regardless of the cause. Compared to the use of external pressure sensors, measurement errors and vulnerabilities related to the sensors are eliminated. This applies particularly to dependencies of the measurement results on the selected position of the respective pressure sensors and the current flow conditions at or around the pressure sensors. This includes, for example, flow separation and eddies that can occur under certain operating conditions. Failure probabilities of the pressure sensors, as well as of the wiring or data transmission between the pressure sensors and the electronics, are eliminated.

[0020] The invention is based on determining the air volume flow rate or air mass flow rate of the fan using a high-accuracy method, advantageously based on an analysis of a flow velocity field. Subsequently, the current operating-condition-dependent parameter of the fan, for example the fan pressure rise, is determined by taking into account the current rotational speed, optionally measured or estimated information about the current density, and a characteristic curve stored on the fan.

[0021] For a fan that can be controlled to a constant volume flow or mass flow rate, determining the air volume flow or mass flow rate via a sensor is unnecessary, as the preset volume flow or mass flow rate can be used directly. However, a fan with such constant volume flow or mass flow control capability typically still incorporates a sensor for direct or indirect determination of the volume or mass flow rate.

[0022] In contrast to the prior art, the determination of the current operating-condition-dependent quantity, such as the pressure change, especially the pressure increase, of a fan is carried out without complex sensors such as pressure sensors, sound sensors, or torque sensors, and is performed close to the fan. However, a preliminary determination of the current air volume flow with the highest possible accuracy is required. Only one sensor is needed for the direct or indirect determination of the air volume flow or the air mass flow.

[0023] Given a known volume or mass flow rate of the fan, the current operating-condition-dependent parameter, such as pressure increase, noise emission, drive torque, drive power, efficiency, vibration, or axial thrust, is determined via the rotational speed. The influence of the current air density, ambient temperature, or humidity can be taken into account. According to the invention, the volume flow rate is determined in advance with high accuracy using a vane anemometer. To determine the current operating-condition-dependent parameter, for example, the pressure increase or pressure change, it is necessary that at least one calibration curve is stored on the fan for each operating-condition-dependent parameter of interest.A calibration characteristic curve essentially represents a functional relationship between the volume flow rate or mass flow rate and a suitable operating-condition-dependent parameter for a specific rotational speed or rotational speed profile and a specific density (for example, pressure increase Δp as a function of the volume flow rate V at a specific constant rotational speed and density). The use of an equivalent characteristic curve is conceivable; for example, if the air volume flow rate or air mass flow rate is already known, a conversion between static pressure increase and total pressure increase can be performed.

[0024] The fan can control itself using the calculated current operating-condition-dependent variable. For example, speed control is possible as a function of a currently determined pressure increase.

[0025] It is also conceivable that the pressure increase or another current operating condition-dependent variable can be read by a user or a higher-level system, so that the user or the higher-level system can control or otherwise influence the fan speed or the air handling system based on this information.

[0026] The current operating-condition-dependent value and its temporal progression can also be saved and / or transmitted to the user or the fan manufacturer to enable further optimization. This can be helpful in the initial selection of the fan or in the design and technical optimization of the fan.

[0027] The pressure increase / pressure change Δp can generally be understood, depending on requirements, as a static pressure increase (total-to-static), a total pressure increase (total-to-total), or another application-specific definition of pressure increase. It is only necessary to determine the calibration characteristic curve usable for determining the desired pressure increase and to save it to the fan.

[0028] In general, the method can be used to determine a current operating-condition-dependent quantity, provided the speed dependence of the target quantity is known at least approximately. For example, it is conceivable to determine the pressure increase (approximately proportional to n^2), the drive torque (approximately proportional to n^[4..6]), the sound emission (approximately proportional to n^[4..6]), the axial thrust (approximately proportional to n^2), or vibration parameters (the dependence on n would have to be determined specifically for the fan in this case). Derived operating-condition-dependent parameters can also be determined, such as the drive power using the speed and drive torque, or the efficiency using the air volume flow, a pressure increase, and the drive power. In each case, corresponding calibration curves must be determined and stored on the fan.

[0029] 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 and, on the other hand, to the following explanation of preferred embodiments of the method according to the invention or of a fan using this method 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 Fig. 1 shows a diagram in which, for a fan at a specific fluid density, two characteristic curves of a pressure increase Δp are shown as a function of a flow rate V for two different constant rotational speeds. Fig. 2 shows a diagram in which, for a fan at a specific fluid density, four curves of a pressure increase Δp are shown as a function of a rotational speed n for four different flow rates. Fig. 3 shows, in a perspective view and in section at a plane through the axis of rotation of the impeller, an embodiment of a fan, wherein the determination of a current operating-condition-dependent quantity is carried out with the aid of a fluid flow rate V precisely determined by means of a vane anemometer.

[0030] In Fig. 1The diagram shows two characteristic curves of the pressure increase Δp of an exemplary fan as a function of its conveying air volume flow rate V for two different, constant rotational speeds n. These characteristic curves are merely examples. They were determined based on experimental measurements of a specific fan and may vary quantitatively and in shape depending on the fan. Generally, a characteristic curve of a pressure increase Δp is defined as a functional relationship between a volume flow rate V or a mass flow rate ṁ and a pressure increase Δp, which is often specified at a constant rotational speed, but can also be specified for a defined variable rotational speed profile. Given a known conveying volume flow rate V or mass flow rate ṁ, and provided the current rotational speed matches the rotational speed on which the characteristic curve is based, the pressure increase Δp can be determined from the characteristic curve.It can be seen that the pressure increase Δp depends quantitatively on the flow rate V, and is therefore a variable dependent on the operating conditions.

[0031] Accordingly, characteristic curves for other operating-condition-dependent parameters can be determined and stored for specific speeds or speed profiles. These other operating-condition-dependent parameters can then also be determined using the corresponding characteristic curve, given a known flow rate or mass flow rate.

[0032] In Fig. 1Two characteristic curves are shown, each at a constant rotational speed n, as well as a curve for a constant volume flow rate V. Generally, to determine the fan pressure increase Δp, it is sufficient to determine only one characteristic curve for a specific rotational speed. The other can be obtained by conversion, as in this example. This conversion uses the similarity laws for a fixed fan geometry, according to which V̇ ~ n and Δp - n ≤ 2. If a characteristic curve for a rotational speed n is available, the pressure increase Δp can be determined as follows, given a known volume flow rate V and a known rotational speed n: 1. Calculation of the characteristic curve (e.g., in the form of Δp(V̇)) for the current rotational speed n from the stored calibration characteristic curve (example: calibration characteristic curve for n_calibration=1800 rpm, current rotational speed n=2200 rpm), 2. Determination of the intersection point of the calculated characteristic curve for the current rotational speed n with the line of the constant, currently determined volume flow rate V, 3. Reading of the current pressure increase Δp at the intersection point.

[0033] Additionally, the influence of density can be taken into account, whereby the pressure increase is proportional to the density. For this, the ratio of the current density to the density corresponding to the calibration characteristic curve must be determined or estimated.

[0034] Accordingly, other operating-condition-dependent parameters, particularly the flow rate or mass flow rate and the current rotational speed, can also be determined. Only a calibration curve needs to be stored that enables the calculation of the desired target value. It should be noted that different target parameters have different dependencies on the rotational speed n, which must be taken into account in the respective form.

[0035] In practice, a pressure increase or other operating-condition-dependent parameter of the fan can be influenced by the fan's installation environment. Advantageously, a correction factor or function can be considered when determining the pressure increase or other operating-condition-dependent parameter, depending on the installation situation. Alternatively, the calibration characteristic curve can be determined in the installation situation or a configuration that models the installation situation, stored on the fan, and used to determine the operating-condition-dependent parameter. To achieve the most accurate determination of a current operating-condition-dependent parameter, the current volumetric flow rate V or the current mass flow rate ṁ must be determined with the highest possible accuracy. This is particularly important in areas where the characteristic curves are represented according to... Fig. 1If the flow rate is steep, even small errors in determining the volumetric flow rate V or the mass flow rate ṁ can lead to relatively large errors in the calculated operating-condition-dependent quantity. An accuracy of no more than 5% deviation from the actual value for determining the volumetric / mass flow rate is advantageous; for particularly high accuracy requirements, a deviation of no more than 2% from the actual value of the current volumetric / mass flow rate is acceptable. It has been shown that such high accuracy requirements for determining the volumetric / mass flow rate are met particularly well with methods based on an analysis of the flow velocity field at a suitable location within the fan area. According to the invention, such methods are based on...

[0036] Method based on the rotational speed measurement of a vane anemometer.

[0037] It has also been shown that a time-averaged measurement of the specific volume flow rate V or mass flow rate m and / or the specific operating-condition-dependent quantity over a few seconds, for example >=10 s, is advantageous.

[0038] In Fig. 2 For a specific example fan, the pressure increase Δp is shown as a function of the rotational speed n for several example constant volume flow rates V. Such a representation can be derived solely from a known calibration characteristic, similar to that in Fig. 1 described, and derived from a known rotational speed dependence of the target variable, here Δp. It is easy to see that for a known volume flow rate V and a known rotational speed n, the pressure increase Δp can be uniquely determined. Here too, the correction of the pressure increase with the density is analogous to Fig. 1 , to carry out.

[0039] The procedure for determining the pressure increase Δp works accordingly if the mass flow rate m is used instead of the volume flow rate V, except that the effect of the medium density is then already included in the mass flow rate m. In this case, the mass flow rate ṁ is determined using a known method instead of the volume flow rate V. A density correction for the pressure increase Δp is no longer necessary. A calibration curve may be stored on the fan, describing a functional relationship between the mass flow rate ṁ and the volume flow rate V, for example, at constant rotational speed. The methods for determining the mass flow rate are essentially similar to those for determining the volume flow rate. For example, the mass flow rate ṁ can be determined using a vane anemometer; however, in addition to the anemometer rotational speed, the current medium density must also be determined or estimated and incorporated into the mass flow rate calculation.

[0040] Representations similar to those shown above can also be used for target variables other than a pressure increase Δp that depend on the operating condition. Fig. 2 Establish the parameters. It is important to consider that the speed dependence varies depending on the target variable. Speed ​​dependencies can often be derived from general fan laws; for example, pressure increase, drive torque, or axial thrust are approximately proportional to the square of the speed. The air volume flow rate or air mass flow rate should always be considered linearly proportional to the speed. Sound power levels or sound pressure levels are proportional to the fourth to sixth power of the speed. Furthermore, target variables can be derived from two or more parameters. For target variables where the speed dependence cannot be derived from general (fan) laws, speed dependencies can also be estimated based on experiments or simulations.

[0041] Fig. 3 Figure 1 shows a perspective view and a section in a plane through the axis of rotation of the impeller 3 of an embodiment of a fan 1, wherein the determination of the current operating-condition-dependent quantity is carried out with the aid of a conveying medium volume flow rate V precisely determined by means of a volume flow measuring wheel 2. The volume flow measuring wheel 2 is, in particular, constructed from a hub 7 and vanes 6 attached thereto. The volume flow measuring wheel 2 and its mounting on an inlet-side structure, here an inlet grille 26, are clearly visible in the illustration. An axle 13 for mounting the volume flow measuring wheel 2 is attached to the central area 30 of the inlet grille 26 via a receiving area 31.

[0042] The volumetric flow meter 2 is mounted on the shaft 13 by means of bearings; in the exemplary embodiment, two bearings (not shown) are provided. The bearings are inserted into the volumetric flow meter 2 in designated receptacles 20 within the hub 7. This allows the volumetric flow meter 2 to rotate freely with respect to the inlet grid 26 and independently of the rotor 11 of the motor 4, which drives the impeller 3 of the fan 1. The current flow rate V of the conveyed medium can be determined with good accuracy by measuring the rotational speed of the volumetric flow meter 2.

[0043] The impeller 3 of the fan 1 is attached to the rotor 11 of the motor 4 by a mounting device 15, which is designed as a sheet metal disc cast into the impeller 3 and pressed onto the rotor 11. Measuring and evaluating the rotational speed nAne of the volumetric flow measuring wheel 2 enables a precise determination of the conveyed medium volumetric flow rate V, with or without taking the impeller rotational speed n into account.

[0044] If the conveying medium volume flow rate V is determined, advantageously with the aid of electronics integrated in the stator 12 of the motor 4, the current operating-state-dependent quantity, for example a pressure increase Δp, is calculated in the exemplary embodiment based on this, as shown by Fig. 1 and Fig. 2The rotational speed n of the impeller 3, which is composed in particular of a cover ring 8, a hub ring 10, and impeller blades 9 extending between them, and thus the rotational speed n of the motor 4, consisting in particular of a stator 12 and a rotor 11, must be known. It can be easily determined within the motor 4. Temperature or humidity sensors can be used to determine the current density of the conveyed medium. Alternatively, the density can simply be estimated or transmitted to the motor 4 via an interface from a higher-level system.

[0045] Advantageously, motor 4 also features an interface for transferring at least one current operating-state-dependent variable to a higher-level system. Furthermore, it is advantageous that a time-dependent profile of one or more operating-state-dependent variables can be stored on motor 4 at a suitable temporal resolution and read out as needed.

[0046] For the sake of completeness, it should also be mentioned that in Fig. 3 Not all components of the fan 1 are shown. In particular, for the sake of clarity, a motor mount that connects the stator 11 of the motor 4 to the nozzle plate 29, for example, is not shown. The fan 1 may include numerous other components not shown. Reference symbol list

[0047] 1 Fan 2 Flow sensor wheel 3 Fan impeller 4 Motor 5 Inlet nozzle 6 Blade of a flow sensor wheel 7 Hub of a flow sensor wheel 8 Cover ring of an impeller 9 Blade of an impeller 10 Hub ring of an impeller 11 Rotor of a motor 12 Stator of a motor 13 Shaft for supporting the flow sensor wheel 15 Mounting device for the impeller on the motor 20 Bearing receptacle in the flow sensor wheel 26 Inlet grille 29 Nozzle plate 30 Central area of ​​the inlet grille 31 Shaft receptacle in the inlet grille

Claims

1. A method for the quantitative determination of a current operating state-dependent variable of a fan, for example a pressure increase or pressure change, wherein, at a known volume flow rate or mass flow rate of the fan, a current operating state-dependent variable is ascertained from its rotational speed, wherein, at a known volume flow rate or mass flow rate and a known rotational speed, an operating state-dependent variable is calculated as follows: calculating at least one characteristic curve for the current rotational speed from a stored calibration characteristic curve, determining the intersection point of a calculated characteristic curve for the current rotational speed with a line of the constant, currently determined volume flow rate or mass flow rate, ascertaining or reading a current operating state-dependent variable at the intersection point, wherein a calibration characteristic curve for a certain rotational speed or a certain rotational speed progression and, where applicable, a certain air density is stored on the fan, wherein the calibration characteristic curve describes a functional relationship between the volume flow rate or mass flow rate and an operating state-dependent variable, wherein the volume flow rate or mass flow rate is ascertained in advance using an impeller anemometer.

2. The method according to claim 1, characterized in that the influence of the current air density is taken into account, wherein, for example, the pressure increase is proportional to the air density.

3. The method according to claim 2, characterized in that the current air density is measured or is calculated or estimated.

4. The method according to claim 3, characterized in that in order to take the air density into account, the ratio of the current air density to the air density corresponding to the stored calibration characteristic curve is determined or estimated.

5. The method according to any of claims 1 to 4, characterized in that a correction factor or a correction function is used to determine the operating state-dependent variable, which correction factor or correction function takes into account the installation situation and / or the surroundings of the fan.

6. The method according to claim 5, characterized in that the calibration characteristic curve is used to determine the operating state-dependent variable, which calibration characteristic curve is obtained in the installation situation or in a configuration modeling or simulating the installation situation and is stored on the fan.

7. The method according to any of claims 1 to 6, characterized in that one or more ascertained operating state-dependent variables are used for regulating or self-controlling the fan.

8. The method according to claim 7, characterized in that the self-control comprises controlling the rotational speed as a function of one or more operating state-dependent variables.

9. The method according to any of claims 1 to 8, characterized in that one or more operating state-dependent variables can be read out by a user or a higher-level system, such that the user or the higher-level system can control or influence the rotational fan speed or the ventilation system on the basis of the one or more operating state-dependent variables.

10. The method according to any of claims 1 to 9, characterized in that one or more operating state-dependent variables and / or the progression over time of one or more operating state-dependent variables are stored and / or forwarded to the user or the fan manufacturer to carry out optimizations, for example of the operation, the selection of the specific fan, and / or the design or the construction of the fan.

11. A fan comprising a quantitative determination of one or more operating state-dependent variables, wherein, at a known volume flow rate or mass flow rate of the fan, at least one current operating state-dependent variable can be ascertained from its rotational speed, for applying a method according to any of claims 1 to 10.

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