FAN WHEEL, FAN AND SYSTEM WITH AT LEAST ONE FAN

Description

[0001] The invention relates to a fan wheel, a fan and a system with at least one fan.

[0002] Fan wheels generally include radial fan wheels, diagonal fan wheels, axial fan wheels, but also guide wheels or post-guide wheels (stators) of fans.

[0003] Providing fans with low noise emissions while achieving certain required air performance (volume flow and pressure increase) is of fundamental interest to fan manufacturers. In particular, noise emissions should be low, even for fans integrated into a system. In such systems, airflow disturbances are often present at the fan inlet. Such airflow disturbances cause high noise levels (tonal noise) in conventional fans, particularly at discrete frequencies that are integer multiples of the blade repetition frequency. If a fan consists of several impellers, for example, a stator and a rotor, the downstream impeller experiences airflow disturbances caused by the upstream impeller. This leads to loud, particularly tonal, noise.Furthermore, for manufacturing and / or economic reasons, it is advantageous to have fan blades made of sheet metal (unprofiled fan blades). However, fans with such blades tend to have increased noise emissions across a broad range (broadband noise). Furthermore, the blunt trailing edge of fan blades, which can be present in both unprofiled and profiled fan blades, is a source of noise (trailing edge noise).

[0004] EP 2 418 388 A2 per se discloses an axial fan which, due to a special design of the fan impeller in the radially outer region of the fan blades, has particularly low noise emissions in the broadband frequency range caused by leakage flow at the tip gap. This special design is achieved in particular by the fact that locally in the radially outer region, the shape of the fan blades, seen in the span direction, is characterized by a significant deviation from the span direction in the remaining region of the fan blades. However, such a design of the fan impeller cannot, or only inadequately, reduce the tonal noise caused by inflow disturbances. Likewise, such a design cannot, or only inadequately, reduce broadband noise in unprofiled blades and trailing edge noise.

[0005] From US 2013 / 0164488 A1, a profiled fan blade is known which, through a special wavy design of its leading edge in a fan, can reduce the tonal noise caused by inflow disturbances.

[0006] WO 2014 / 026246 A1 shows the design of a blade, for example, for a fan. The fan does not have a cover ring.

[0007] The situation is similar with EP 2 230 407 A1. This document also describes a fan, but without a cover ring.

[0008] DE 31 37 544 A1 discloses a fan with an impeller in which the blades are serrated but not corrugated. DE 31 37 544 A1 does not disclose any corrugation of the blades.

[0009] EP 0 955 469 A2 and JP S56 143594 U show a fan without a cover ring.

[0010] US 2003 / 012656 A1 shows a fan impeller for a fan with at least two undulating fan blades. The fan comprises a hub ring and a cover ring, with the fan blades extending between the hub ring and the cover ring and being attached to both the hub ring and the cover ring. The fan blades are at an angle of 75° to 105°, preferably approximately 90°, to both the hub ring and the cover ring.

[0011] EP 2 426 362 A2 shows a radial and a diagonal fan with comparable features to those of the aforementioned document.

[0012] It is important to note that none of the prior art documents deals with a detailed description of the waviness of the fan blades.

[0013] The present invention is based on the object of designing a fan impeller such that it has lower noise emissions compared to the prior art. At the same time, it should be simple in design and manufacture. A corresponding fan and a system including a fan are to be specified.

[0014] According to the invention, the above object is achieved by the features of claim 1. According to this, the fan wheel according to the invention is characterized by a hub ring and a cover ring, wherein the fan blades extend between the hub ring and the cover ring and are fastened to both the hub ring and the cover ring in such a way that the fan blades are at an angle of 75° to 105°, preferably of approximately 90°, to the hub ring and the cover ring. The waviness extends across the entire fan blade surface in order to effect a more extensive noise reduction. In concrete terms, the waviness can preferably extend with the same or variable amplitude from the inner blade end to the outer blade end and from the blade leading edge to the blade trailing edge, wherein these two edges are also wavy.

[0015] The ripple is approximately sinusoidal, with amplitudes ranging from 3 mm to 50 mm. The amplitudes represent between 0.5% and 5% of the maximum fan diameter, with angular dimensions ranging from 0.3° to 3°.

[0016] A fan blade is advantageously designed by corrugation in the area of ​​its inner and / or outer end at the transition to a hub ring and shroud. The corrugation design ensures that a fan blade is at an angle of 75° to 105°, preferably approximately 90°, to the hub ring and shroud, whereas a non-corrugated reference blade would be at a much more acute or blunt angle to the hub ring or shroud. This is advantageous for manufacturing, strength, aerodynamics, and aeroacoustics.

[0017] From a manufacturing and cost perspective, it is particularly advantageous if the fan blade is made of a single layer of sheet metal (metal or plastic). The corrugated design of a sheet metal fan blade can achieve advantages in the fan's aerodynamics and aeroacoustics, similar to those achieved with fan blades with cross-sections similar to those of an airfoil, which are much more complex and expensive to produce.

[0018] Fan blades with cross-sections similar to those of an airfoil profile can also advantageously be designed with a wavy shape, whereby in the context of such a design, a casting technology (plastic or metal) of fan blades or the complete fan wheel is suitable.

[0019] The fan impeller can be a radial / diagonal / axial fan impeller or a guide vane or post-guide vane.

[0020] A correspondingly equipped fan comprises at least one fan impeller according to the above statements. It is also conceivable for the fan to have at least one additional, per se known fan impeller according to the prior art. Combining a fan impeller according to the invention with a conventional fan impeller can be advantageous, although a compromise regarding noise emissions must be accepted.

[0021] With regard to a system equipped with a corresponding fan, it should be noted that this is a system with at least one fan of the aforementioned type, i.e., using at least one fan impeller according to the invention. Air conditioning units or precision air conditioning units, compact air conditioning units, electronic cooling modules, generator ventilation systems for industrial and residential buildings, heat pumps, etc. are mentioned merely as examples. It is essential for a system according to the invention that at least one fan according to the invention with at least one fan impeller according to the invention is used.

[0022] There are now various possibilities for advantageously embodying and developing the teachings 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 the undulating design of the fan impeller of preferred embodiments of the invention with reference to the drawings. In In conjunction with the explanation of the preferred embodiments of the invention with reference to the drawings, generally preferred embodiments and further developments of the teaching are also explained. In show the figures Fig. 1 to 3 schematic representations to explain the wavy design of the fan wheel, specifically Fig. 1a a schematic representation of a section through a radial fan wheel to explain the definition of iso-span areas, Fig. 1b a schematic representation of a section through a diagonal fan wheel to explain the definition of iso-span areas, Fig. 1c a schematic representation of a section through an axial fan wheel to explain the definition of iso-span areas, Fig. 2a a schematic representation of a section of an iso-span area with an unprofiled fan blade, Fig. 2b a schematic representation of a section of an iso-span area with a profiled fan blade, Fig. 3 a representation of function curves to explain the definition of the waviness of a function curve in the span direction, Fig.4a a perspective view of an axial fan wheel with wavy fan blades, the inner and outer ends of which have a special design, Fig. 4b fan blade of the axial fan wheel according to . Fig. 4a , viewed in axial direction and in a plane section, Fig. 5a a perspective view of a radial fan wheel in sheet metal construction with unprofiled, wavy fan blades, where the blade surfaces are not wavy, Fig. 5b the radial fan wheel according to Fig. 5a , viewed in radial direction and in a plane section, Fig. 6a a perspective view of a radial fan wheel in sheet metal construction with unprofiled, wavy fan blades, whereby the blade surfaces are wavy, Fig. 6b the radial fan wheel according to Fig. 6a , viewed in radial direction, Fig. 6c the radial fan wheel after Fig. 6a , viewed in radial direction and in a plane section, Fig. 7a a perspective view of a guide wheel (stator) with profiled, wavy fan blades, where the blade surfaces are wavy near the leading edge of the blade, and Fig. 7b fan blade of the guide wheel according to Fig. 7a , viewed in radial direction and in a plane section,

[0023] Based on the Figuren 1a , 1b and 1c The definition of iso-span surfaces of a fan impeller will be explained, which subsequently forms the basis for the definition of the waviness of a fan impeller blade. Iso-span surfaces are surfaces of revolution of certain curves, hereinafter referred to as iso-span curves, which lie in a meridional plane around the corresponding fan impeller axis. Sections of such iso-span surfaces with fan blades will then be considered in particular.

[0024] Figur 1a shows a schematic representation of a fan wheel 2 of radial design in a plane through the fan wheel axis 1, which corresponds to the axis of rotation. Such a plane is generally referred to as a meridional plane. The fan wheel axis 1 is always aligned horizontally in the selected representation. The exemplary radial fan wheel essentially consists of a hub ring 4, a cover ring 5 and fan blades which extend between the hub ring 4 and the cover ring 5. In the exemplary embodiment, the hub ring 4 and the cover ring 5 are rotating bodies with respect to the fan wheel axis 1. They are shown in a dotted section through the viewing plane, with only half of the hub ring 4 and the cover ring 5 being shown above the fan wheel axis 1. The fan blades are shown in the form of their meridional fan blade surface 3a.The meridional fan blade surface 3a corresponds to the totality of all points of the meridional section plane above the fan wheel axis 1, which lie within a fan blade at least in one arbitrary rotational position of the fan wheel 2 around the fan wheel axis 1.

[0025] The meridional fan blade surface 3a has four edges 6, 7, 8 and 9. The inflow-side edge 6 and the downstream edge 7 represent the boundary of the fan blade surface 3a in the flow direction. The inner edge 8, which corresponds to the inner, hub ring-side end of the blades, and the outer edge 9, which corresponds to the outer, shroud-side end of the blades, represent the boundaries in the span direction.

[0026] Using the inner edge 8 and the outer edge 9, the innermost and outermost iso-span curves 10 and 11 are defined at the normalized span coordinates s=0.0 and s=1.0, respectively. First, the edges 8 and 9 themselves are used as segments of the corresponding iso-span curves 10 and 11. In order for the entire meridional fan blade surface 3a to lie within the general quadrilateral spanned by the two iso-span curves 10 and 11 and the two straight lines 12 and 13, which each connect the two upstream and downstream end points of the same iso-span curves 10 and 11, sufficiently long straight extensions are attached, if necessary, to the upstream and / or downstream end points of the two edges 8 and / or 9, which extensions are then also part of the corresponding iso-span curves 10, 11.The straight line 12 is referred to as the upstream isomeridional position curve, where the origin for the meridional longitude m is defined. The straight line 13 is referred to as the downstream isomeridional position curve, where the meridional longitude m takes as its value the length of the corresponding iso-span curve from the straight line 12 to the straight line 13. The value of the meridional longitude m at a point between the lines 12 and 13 corresponds to the length of the corresponding iso-span curves from the straight line 12 to the point under consideration.

[0027] Iso-span curves between the innermost and outermost iso-span curves 10 and 11 are defined at each normalized span coordinate s between 0.0 and 1.0 by a linear combination of the innermost and outermost iso-span curves, whereby the linear combination is always carried out for equal values ​​of the meridional coordinate m. Fig. 1a An example 14 of an iso-span curve at s=0.7 is shown.

[0028] Fig. 1b shows a schematic representation of a fan wheel 2 of diagonal design in a meridional plane. The iso-span curves can be calculated analogously to the explanations for Fig. 1a In contrast to, for example, Fig. 1a In this case, an extension of the edges 8, 9 at their downstream end is necessary, while in the example according to Fig. 1a An extension of the edges 8,9 at their upstream end is necessary. Depending on the impeller geometry, it may be that no extension is necessary, or an extension may be necessary at both ends.

[0029] Further shows Fig. 1c A schematic representation of an axial fan wheel 2 in a meridional plane. A cover ring is not present in this example, and the fan blade 3 has an outer, free end. Here, too, the iso-span curves can be used in a manner equivalent to the explanations for Fig. 1a or 1b The iso-span surfaces, which are always defined as surfaces of rotation of the iso-span curves around the fan wheel axis 1, are cylindrical surface areas in the example shown, which is a typical case for axial fan wheels.

[0030] There are also fan impeller geometries, particularly for fan blades 3 with free outer ends, where the division of the edge of a meridional fan blade surface 3a into boundaries 6, 7, 8, 9 is not unambiguous. In particular, for some geometries, an inner boundary 8 and / or an outer boundary 9 cannot be clearly assigned. In such cases, the division of the entire boundary of the meridional fan blade surface into finite-length boundaries 6, 7, 8, 9 must be performed intuitively, in the sense of the terms "upstream" and "downstream" for boundaries 6 and 7, respectively, as well as "inside in the span direction" and "outside in the span direction" for boundaries 8 and 9, respectively. The definition of the iso-span curves is not unambiguous, i.e., there can be several valid definitions for a fan impeller geometry within the meaning of the described invention.A wing is wavy within the meaning of the invention if the following definition of waviness applies to a valid definition of the iso-span curves.

[0031] In the same way, iso-span curves and iso-span areas can also be defined for stators (e.g., guide vanes or vanes).

[0032] In the Figuren 2a and 2b Sections 16 of fan blades 3 with iso-span areas at any standardized span coordinates s between 0.0 and 1.0 are shown as examples and schematically. Such sections generally do not lie on a plane. To achieve the schematic representation in a plane, a conformal (angle-conform) mapping is used, i.e., the angles shown in the Figuren 2a and 2bhave the same magnitude as in the 3-dimensional section of the iso-span surfaces with a wing. All lengths indicated in the sections represent the actual lengths on the 3-dimensional section surface. They are distorted by the mapping onto the plane.

[0033] In Figur 2a The section 16 of an unprofiled blade 3 with an iso-span area is shown schematically. In the section, the 2-dimensional coordinate system 15 with the coordinate axes Θ and m is drawn at the origin (zero point). Θ is a length coordinate in the circumferential direction of the fan wheel 2, and m is the already explained meridional coordinate. The origin (zero point) with respect to Θ lies for each span coordinate s at the same angular position (the same meridional plane) in the fan wheel-fixed coordinate system. The origin (zero point) with respect to m lies, as in Fig. 1a-1c described in the upstream isomeridional position curve 12.

[0034] The wing section 16 is primarily characterized by its imaginary centerline 17. Superimposed on this centerline is a wing thickness d. For unprofiled blades 3, the thickness d is essentially constant across the meridional extent of the blade. For such fan blades 3, the thickness d is generally also essentially constant for all span coordinates s. This makes it possible to manufacture the fan blade 3 cost-effectively from metal or plastic sheet. Near the leading edge 18 of the blade, the thickness d in the example deviates from the constant thickness because the sheet metal blade is rounded there, which can have acoustic advantages. Near the trailing edge 19 of the blade, the thickness profile tapers, which can be achieved, for example, by post-processing a sheet of constant thickness to reduce trailing edge noise. Nevertheless, such a blade is referred to as an unprofiled sheet metal blade.

[0035] The center point 20 of the center line 17, which lies at half the meridional extension of the center line 17 measured from the blade leading edge 18, has the coordinates mc and Θ c . These coordinates characterize the displacement of the section in the meridional direction and in the circumferential direction, respectively. The section 16 has an extension I in the direction of the meridional coordinate m. At the blade leading edge 18, the center line 17 forms an angle β1 with the circumferential direction. At the blade trailing edge 19, the center line 17 forms an angle β2 with the circumferential direction. The angles β1 and β2 are decisive for the aerodynamic and aeroacoustic properties of a fan impeller 2. The mean of the two angles is a measure of the stagger angle of the blade section 16, and the difference between the two angles is a measure of the relative camber of the blade section 16.The extension of the wing section 16 in the circumferential direction depends significantly on its extension I in the meridional direction and the stagger angle, i.e. approximately the mean value of β1 and β2.

[0036] In Figur 2b The section 16 of a profiled wing 3 with an iso-span area is shown schematically. The explanations for Fig. 2a However, the thickness distribution is not constant. Rather, the thickness is a function of the meridional position m. In the exemplary embodiment, a thickness distribution is present which is similar to that of an airfoil profile. There is a maximum thickness d max at the blade section 16. Such thickness distributions are characteristic of profiled fan blades 3. Profiled fan blades 3 are advantageous for the efficiency and acoustics of a fan. However, the production of such fan blades 3 is more complex than with unprofiled blades, particularly when made from sheet metal. With profiled blades, the thickness distribution and the maximum thickness d max can also depend on the span coordinate s.

[0037] The wing cuts 16 in the Figuren 2a and 2bencompass the entire area of ​​the wing 3 from a wing leading edge 18 to a wing trailing edge 19 without interruption. Depending on the fan geometry and the definition of the innermost and outermost iso-span curves, it may happen, particularly for standardized span coordinates s in the area of ​​the innermost and / or outermost iso-span curves, that a wing 3 is only partially intersected, i.e., sections 16 do not include the entire area from a wing leading edge 18 to a wing trailing edge 19 without interruption. Such sections 16 are defined as irrelevant for the definition of the waviness, and the range of the considered standardized span coordinates s is restricted for the definition of the waviness in such a way that such incomplete sections do not occur.

[0038] For those after the Figuren 2a and 2bdefined geometric sizes of a section 16 of a fan blade 3 with an iso-span area, the course for any fan blade 3 can be considered as a function of the standardized span coordinate s.

[0039] Based on Figur 3 It is explained when such a function curve is defined as wavy. Figur 3 shows a function curve 21 of any desired value, which can be, for example, β1, β2, I, mc , Θ c , β1-β2, d max , the thickness d at a specific position m* in the meridional direction or another value of a wing section, depending on the normalized span coordinate s. Obviously, the function curve of 21 is wavy. The function curve 22, which is also shown, tends to be similar to the function curve 21, but is not wavy. It was derived by filtering the function curve 21. The filter used is the approximation of 21 by a 3rd degree polynomial using the method of least squares in the relevant interval from s=0.0 to s=1.0.

[0040] Furthermore, the difference 23 between function curve 21 and the filtered function curve 22 is shown. With the help of the difference function 23, suitable definitions of waviness can be specified. In particular, the difference function 23 has several extrema in the relevant interval from s=0.0 to s=1.0, preferably more than 4 extremes. The difference function 23 has several zero crossings in this interval, preferably more than 3. The difference function also has several inflection points, preferably more than 3. Each of the above criteria leads to the conclusion that the function curve 21 is wavy. This example also shows that if you want to start from a non-wavy curve of a function and arrive at a wavy curve, you can additively superimpose the non-wavy function with a suitable wavy function similar to the difference function 23.

[0041] Based on Figur 3 The wavelength λ and the amplitude A of a wave function are defined. The wavelength λ is defined as the difference of the normalized span coordinate s between a zero crossing and the next but one zero crossing of the difference function 23. λ is a dimensionless wavelength that is to be viewed in relation to the normalized span coordinate s, which runs from 0.0 to 1.0 for the entire fan blade. Therefore, the number of waves across the span of a fan blade is approximately 1.0 / λ.

[0042] Furthermore, a dimensioned wavelength Λ is introduced, which has the unit of length and which, in particular, has the geometric distance between two successive wave crests, measured in the span direction, as its value. The amplitude A corresponds to the magnitude of the function value of an extremum of the difference function 23. λ, Λ and A are not constants, but can vary within a certain range over the course of the difference function 23 or, as seen across a fan blade. In examples that do not correspond to the invention, it is possible that the difference function does not necessarily have a course similar to a sine function. Deviating from the invention, it can also have jagged, step-shaped, sawtooth-shaped, comb-shaped, tongue-shaped or other courses, as long as the previously described definition of waviness is met.

[0043] In general, a fan blade 3 is said to be wavy in the span direction if the course of at least one of the functions β1, β2, I, mc , Θ c , β1-β2, d max , β1+β2 or d(m*) is wavy according to the definitions given.

[0044] Fig. 4a shows a perspective view of an axial-type fan wheel 2, seen obliquely from the rear. The fan blades 3 are wavy. The waviness of these fan blades 3 was achieved by superimposing the length coordinate Θ c in the circumferential direction of a non-wavy reference blade with a sinusoidal waviness of amplitude 10 mm. Advantageous amplitudes for wavinesses of length sizes are 3 mm to 20 mm. Relative to the fan blade 3, this leads to waviness of the sickle and the V-position. The waviness of the fan blades 3 is clearly visible in the exemplary embodiment by the pronounced waviness of the blade leading edge 18 and the blade trailing edge 19. With this type of waviness, the amplitude superimposed on the length coordinate Θ c can also be found in approximately the same size in the waviness of the blade leading edge 18 and the blade trailing edge 19.

[0045] In Fig. 4b , which shows a fan blade 3 of the same fan wheel 2 in a sectional view, it can be seen that the waviness continues through the entire fan blade 3. The entire surface of the fan blade is wavy. Approximately 4 1 / 4 wavelengths extend over the entire span of the fan blades 3. Advantageously, approximately 3 - 12 wavelengths extend over the entire span of the fan blades 3. In Fig. 4b The coordinate direction of the standardized span s, which lies in the section plane, is shown. Furthermore, the dimensioned wavelength Λ in the span direction is shown at one point in the section. In the exemplary embodiment, this wavelength is approximately 3 cm with a maximum fan wheel diameter of 630 mm. According to the invention, such wavelengths are between 3 mm and 50 mm, or between 0.5% and 5% of the maximum fan wheel diameter.

[0046] The waviness of the blade leading edge 18 leads to a reduction in particular of the tonal noise which is caused by inflow disturbances to a fan wheel 2 during operation. The waviness of the sickle in the example of the Figuren 4a and 4bFrom an aerodynamic perspective, this causes a waviness in the lift coefficient. This waviness induces longitudinal vortices, which stabilize the suction-side flow around the blade and thereby reduce flow separation and the associated noise generation. The waviness of the blade trailing edge 19 mitigates noise generation mechanisms caused by local separation regions or by the blunt trailing edge geometry. The waviness of the blade surface scatters generated and reflected noise from the blade more effectively, which leads to advantages in the noise behavior of the fan. By simply superimposing a waviness on the length coordinate Θ c in the circumferential direction, the acoustic behavior of a fan can be improved at several causal mechanisms.

[0047] Particularly advantageous designs of the waviness can also Figuren 4a and 4bFirstly, the outermost region 26 of the axial fan blade 3 is very specifically designed with the help of the corrugation. In this region, the fan blade 3 ends with a high, negative sickle and V-position. The outermost blade cuts are locally shifted significantly against the direction of rotation. Such a design has a massive effect on reducing broadband noise, which is often a significant source of noise in an axial fan due to the flow over the head gap. In this respect, the exemplary design also takes on the aeroacoustic function of a winglet. One could also say that the winglet and corrugation have been perfectly and seamlessly integrated with one single design measure.

[0048] A very specific design has also been carried out in the innermost area 25 of the fan blade 3. As shown in Fig. 4b As can be seen, the fan blade 3 locally impacts the hub ring 4 at an approximately right angle. This brings decisive advantages in joining processes between the hub ring 4 and the fan blade 3, particularly during welding. Such a design is also particularly advantageous for the plastic injection molding manufacturing process in the integral production of a fan wheel 2. Furthermore, the notch stresses at the blade root are minimized by such a design. The impact of the fan blades 3 on the hub ring 4 and the cover ring 5 at an angle of 75° to 115°, preferably 90°, is achieved by the waviness. The non-waviness reference blade, which has comparable aerodynamic properties (efficiency and air performance), would impact the hub ring 4 and the cover ring 5 at a considerably more acute angle.

[0049] Fig. 5a shows a perspective view of a radial fan wheel 2, viewed from the front. The fan blades 3 are wavy. The waviness of these fan blades 3 is expressed in particular by a waviness of the quantities mc (position of the blade section in the direction of the meridional coordinate) and Θ c (position of the blade section in the direction of the circumferential length coordinate). The extension I of the sections in the meridional direction is not wavy. Other quantities can also have a less pronounced waviness. The waviness is found in the course of the blade leading edge 18 and the blade trailing edge 19. This reduces leading edge noise due to inflow disturbances as well as trailing edge noise. In the example, approximately 7.5 wavelengths are present across the entire span.The dimensioned wavelength Λ tends to be larger in the area of ​​the wing leading edge 18 than at the wing trailing edge 19, which is due to the fact that the wing leading edge 18 is significantly longer than the wing trailing edge 19 over the entire span.

[0050] Out of Fig. 5b , which is the subject of Fig. 5a in a radial section, it becomes clear that the waviness in this non-inventive example is selected such that the surface of the fan blades 3 is not wavy when viewed in section. In particular, the waviness of mc and Θ c and other variables is selected in such a way that this surface, viewed in section, is not wavy.

[0051] This leads to a slight reduction in the acoustic benefits due to the waviness, but has manufacturing advantages. The fan wheel 2 in this example is a fan wheel with unprofiled fan blades 3. The thicknesses d of the fan blades 3 are, as shown in the planar section 24 of a fan blade 3 in Fig. 5b As can be seen, the waveform is essentially constant. Such a fan impeller is advantageously made of sheet metal (metal or plastic). The production of fan blades 3 from sheet metal is considerably simpler and more cost-effective if the surface of the fan blades 3 is not wavy in cross-section, since the deformation energy required for stamping or deep-drawing the sheet metal blades is considerably lower in this case. The waviness of the leading and trailing edges, which alone provides significant acoustic advantages, can be realized in manufacturing processes, for example, by trimming or punching.

[0052] Fig. 6a shows a perspective view of a radial fan wheel 2, viewed diagonally from the front. The fan blades 3 are wavy. The fan wheel 2 in this example is similar to the one in the example according to Fig. 5a , 5b . In particular, the non-wave-like reference blades have the same geometry. However, the waveform of these fan blades 3 in this exemplary embodiment differs from the previous one. It is expressed in particular by a waveform of magnitude (β1+β2) / 2, i.e., in particular, a waveform of the stagger angle. The geometric deflection (β1-β2), the coordinates Θ c and mc, and the meridional extension I of the fan blades 3 are non-waveform across the span direction. The amplitude A of the waveform of (β1+β2) / 2 is approximately 1°. The amplitudes of waveforms of angle sizes are 0.5°-3°. Fig. 6a It can be seen that, caused by the described waviness, in particular the profiles of the leading edges 18 and trailing edges 19 of the fan blades 3 have a pronounced waviness, which leads to the acoustic advantages already described.

[0053] Fig. 6b shows the object in radial side view Figur 6a The waviness of the wing trailing edges 19 is noticeable to varying degrees depending on the viewing direction. Since mc and I are not wavy, the position of the wing trailing edges 19 in the meridional direction is also not wavy. This can be seen, for example, in the Fig. 6b the trailing edge 19 located below. However, the waviness of (β1+β2) / 2 leads to a waviness of the position in the circumferential direction of the trailing edges 19. In Fig. 6b This is particularly evident at the trailing edge 19 of the blade, located approximately in the center of the image. The amplitude A of this trailing edge waviness is preferably 3 mm to 20 mm, or 0.5% to 5% of the maximum fan diameter. What has been described for the profile of the trailing edges 19 also applies to the profile of the leading edges 18 of the blades in the illustrated embodiment.

[0054] In Fig. 6b The particularly advantageous design of the inner and outer regions 25 and 26 of the fan blades 3 of the sheet metal fan wheel 2 can also be seen. The special design of the waviness in the inner region 25 and the outer region 26 of the fan blades 3 has resulted in the dihedral angle formed by the hub ring 4 and the cover ring 5 with the fan blades 3 at the connection area being close to 90° over a wide area. This is very advantageous for production, particularly when welding sheet metal wheels and when injection molding complete fan wheels. In the case of radial fan wheels, this property is particularly advantageous for acoustics in the intersection area between the cover ring 5 and the blade leading edges 18. This perpendicularity has been achieved even though the aerodynamic and efficiency-optimized preliminary design, which is characterized by the non-wavily corrugated reference fan blade, requires angles that are significantly more acute or obtuse.A particularly advantageous design of the waviness is achieved when the largest and / or average deviation of 90° between fan blades 3 and hub ring 4 or cover ring 5 has been reduced by at least 10° due to the waviness.

[0055] Fig. 6c shows in a plane section the object from Figuren 6a , 6b, seen radially from the side. Waviness is also visible in the plane sections 24 of the blades. In this exemplary embodiment according to the invention, the surface of the fan blades 3 is also wavy. As already described, this leads to additional acoustic advantages. However, manufacturing them using sheet metal is more difficult. The application of a relatively high deformation energy for embossing or deep-drawing the fan blades 3 is necessary, in particular in order to create the wavy contour. Furthermore, it must be ensured that the sheets do not crack during such a deformation process. Special flowable metal or plastic sheets can be used. A decisive measure of the deformation energy to be applied is the local wave amplitude A of the displacement of the blade surface due to the waviness relative to its non-wavy reference position based on the dimensioned wavelength Λ.In order to achieve good acoustic effects and still obtain manufacturable sheet metal blades, a ratio A / Λ in the range between 0.03 and 0.3 has proven to be particularly advantageous.

[0056] The waviness of the fan blades 3 in the example according to Fig. 6a-6c has the special feature that in the area of ​​the center of the blade sections, seen in the meridional direction, i.e. approximately in the middle of the fan blades, no or only a slight waviness appears (there, the amplitude of the waviness appears zero or close to zero in the section). At the lower blade section 24 in Fig. 6c such a central region is roughly cut, which is why the extent of the waviness appears relatively small there. This is due in particular to the fact that neither mc nor Θ c are superimposed with a waviness. This design is particularly advantageous for fan blades 3 made of sheet metal. Firstly, the strong waviness is limited to the areas most important in terms of noise generation, near the blade leading edge 18 and the blade trailing edge 19. In the less important area in the center of the fan blade, viewed in the meridional direction, unnecessary deformation effort is largely avoided. Furthermore, the central area, which is largely unwrapped or only relatively slightly waviness, has considerable advantages with regard to the deformation of the fan blades 3 during operation. The presence of this area makes it possible to significantly reduce deformations in the span direction and approximately perpendicular to the surface of the fan blades.

[0057] Fig. 7a shows a perspective view of a fan wheel 2 not according to the invention, which is a guide wheel (stator) that does not rotate during operation, seen obliquely from the front. The fan wheel 2 has a hub ring 4 and a cover ring 5, which are connected to one another by undulating fan blades 3. A mounting flange 28 for a motor is provided on the hub ring 4. A mounting area 29 is provided on the cover ring 5, with which the guide wheel 2 can be attached, for example, to a housing. The waviness in this exemplary embodiment has been constructed by a waviness of the local blade thickness d at a meridional position m* near the blade leading edge 18. Both the blade leading edge 18 and the blade trailing edge 19 are not wavy. Fig. 7a the waviness of the fan blades 3 can be recognized by the waviness of some view silhouettes 31.

[0058] Fig. 7b shows, seen from the front, the object Fig. 7a in a section along a plane perpendicular to the axis of rotation, with the axial position of the section plane near the blade leading edges 18. In the sections 24 through blade 3, the waviness of the thickness is very clearly visible. There are approximately 9 wavelengths of waviness of the local thickness d across the span. The maximum amplitude of this waviness is approximately 4 mm. Such an embodiment is advantageously manufactured by casting due to the non-constant thickness of the fan blades 3. The fan blades 3 are then advantageously profiled, as in the exemplary embodiment. The waviness of the thickness of the fan blades 3 near the leading edge 18 leads to a reduction in the tonal noise due to inflow disturbances (leading edge noise). In this respect, a comparable effect is achieved to that achieved with a wavy design of a blade leading edge 18.

[0059] With regard to further advantageous embodiments of the fan wheel according to the invention, reference is made to the general part of the description and to the appended claims in order to avoid repetition.

[0060] Finally, it should be expressly noted that the exemplary embodiments described above serve merely to illustrate the claimed teaching and do not limit it. The scope of protection is determined by the following claims. Bezugszeichenliste

[0061] 1 Fan wheel axis 2 Fan wheel 3 Fan blade 3 Ameridional fan blade surface 4 Hub ring 5 Cover ring 6 Upstream boundary 7 Downstream boundary 8 Inner boundary 9 Outer boundary 10 Innermost iso-span curve 11 Outermost iso-span curve 12 Upstream isomeridional position curve 13 Downstream isomeridional position curve 14 Example of an iso-span curve at s=0.7 15 Two-dimensional coordinate system (Θ, m) 16 Section of a blade with an iso-span curve 17 Centerline 18 Blade leading edge 19 Blade trailing edge 20 Centerline center 21 Wavy function 22 Filtered function 23 Difference function 24 Plane section of a blade 25Inner area of ​​a blade 26Outer area of ​​a blade 27Direction of rotation 28Motor mounting flange 29Housing mounting area 30Inlet nozzle of a stator 31Silhouette line of a fan blade

Claims

1. Fan wheel (2) for a fan, with at least two fan blades (3) with wavy design, with a hub ring (4) and with a cover ring (5), the fan blades extending between the hub ring (4) and the cover ring (5) from a fan blade leading edge (18) to a fan blade trailing edge (19), the fan blades (3) being secured both at the hub ring (4) and at the cover ring (5), the waviness of the fan blades (3) extending over the entire fan blade (3) in such a form that the fan blades (3) are positioned at an angle of 75° to 105°, preferably of approximately 90°, to the hub ring (4) and to the cover ring (5), characterized in that the waviness runs in an approximately sinus shape with amplitudes in the region of 3 mm to 50 mm and / or between 0.5 and 5% of the maximum fan wheel diameter and with instances of waviness with angles with amplitudes in the region of 0.3° to 3°.

2. Fan wheel according to claim 1, characterized in that the fan blade (3) is produced from sheet material.

3. Fan wheel according to claim 1, characterized in that the entire fan wheel (2) is manufactured employing casting technology.

4. Fan wheel according to one of the claims 1 to 3, characterized in that it is designed as a radial / diagonal / axial fan wheel or as an inlet or outlet guide vane.

5. Fan with at least one fan wheel (2) according to one of the claims 1 to 4.

6. Fan according to Claim 5, with at least one further known fan wheel (2) per se according to the prior art.

7. System with at least one fan according to claim 5 or 6, whereby the system is a compact / climate box device, an electronic cooling module, a generator ventilation system, a cooling device for industrial or residential premises, a heating pump etc.