Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
  • F04D29/00—Details, component parts, or accessories
  • F04D29/26—Rotors specially for elastic fluids
  • F04D29/32—Rotors specially for elastic fluids for axial flow pumps
  • F04D29/38—Blades
  • F04D29/384—Blades characterised by form
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
  • F04D29/00—Details, component parts, or accessories
  • F04D29/26—Rotors specially for elastic fluids
  • F04D29/28—Rotors specially for elastic fluids for centrifugal or helico-centrifugal pumps for radial-flow or helico-centrifugal pumps
  • F04D29/30—Vanes
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
  • F04D29/00—Details, component parts, or accessories
  • F04D29/26—Rotors specially for elastic fluids
  • F04D29/32—Rotors specially for elastic fluids for axial flow pumps
  • F04D29/321—Rotors specially for elastic fluids for axial flow pumps for axial flow compressors
  • F04D29/324—Blades
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
  • F04D29/00—Details, component parts, or accessories
  • F04D29/26—Rotors specially for elastic fluids
  • F04D29/32—Rotors specially for elastic fluids for axial flow pumps
  • F04D29/38—Blades
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
  • F04D29/00—Details, component parts, or accessories
  • F04D29/66—Combating cavitation, whirls, noise, vibration or the like; Balancing
  • F04D29/661—Combating cavitation, whirls, noise, vibration or the like; Balancing especially adapted for elastic fluid pumps
  • F04D29/663—Sound attenuation
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
  • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
  • F05D2240/00—Components
  • F05D2240/10—Stators
  • F05D2240/12—Fluid guiding means, e.g. vanes
  • F05D2240/121—Fluid guiding means, e.g. vanes related to the leading edge of a stator vane
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
  • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
  • F05D2240/00—Components
  • F05D2240/10—Stators
  • F05D2240/12—Fluid guiding means, e.g. vanes
  • F05D2240/122—Fluid guiding means, e.g. vanes related to the trailing edge of a stator vane
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
  • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
  • F05D2240/00—Components
  • F05D2240/20—Rotors
  • F05D2240/30—Characteristics of rotor blades, i.e. of any element transforming dynamic fluid energy to or from rotational energy and being attached to a rotor
  • F05D2240/303—Characteristics of rotor blades, i.e. of any element transforming dynamic fluid energy to or from rotational energy and being attached to a rotor related to the leading edge of a rotor blade
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
  • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
  • F05D2240/00—Components
  • F05D2240/20—Rotors
  • F05D2240/30—Characteristics of rotor blades, i.e. of any element transforming dynamic fluid energy to or from rotational energy and being attached to a rotor
  • F05D2240/304—Characteristics of rotor blades, i.e. of any element transforming dynamic fluid energy to or from rotational energy and being attached to a rotor related to the trailing edge of a rotor blade
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
  • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
  • F05D2250/00—Geometry
  • F05D2250/10—Two-dimensional
  • F05D2250/18—Two-dimensional patterned
  • F05D2250/184—Two-dimensional patterned sinusoidal
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
  • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
  • F05D2250/00—Geometry
  • F05D2250/60—Structure; Surface texture
  • F05D2250/61—Structure; Surface texture corrugated
  • F05D2250/611—Structure; Surface texture corrugated undulated

Definitions

• Fan wheels generally include radial fan wheels, diagonal fan wheels, axial fan wheels, but also guide wheels or post-guide wheels (stators) of fans.
• WO 2014/026246 A1 shows the design of a blade, for example for a fan.
• the fan does not have a cover ring.
• DE 31 37 544 A1 reveals a fan with an impeller in which the blades are serrated but not corrugated.
• DE 31 37 544 A1 reveals no waviness of the wing.
• EP 0 955 469 A2 and JP S56 143594 U show a fan without a cover ring.
• 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.
• EP 2 426 362 A2 shows a radial and a diagonal fan with comparable features to those in the previously mentioned publication.
• 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.
• 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 impeller diameter, with angular dimensions ranging from 0.3° to 3°.
• 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.
• the fan impeller can be a radial/diagonal/axial fan impeller or a guide vane or post-guide vane.
• a fan equipped accordingly 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.
• Iso-span surfaces are surfaces of rotation of certain curves, hereinafter referred to as iso-span curves, which lie in a meridional plane around the corresponding fan wheel axis. Sections of such iso-span surfaces with fan blades are then considered in particular.
• Figure 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.
• 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.
• 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.
• the edges 8 and 9 themselves are used as sections of the corresponding iso-span curves 10, 11.
• sufficiently long straight extensions are attached if necessary to the inflow and/or downstream endpoints of the two edges 8 and/or 9, which are then also part of the corresponding iso-span curves 10, 11.
• the straight section 12 is referred to as the upstream isomeridional position curve, at which the origin for the meridional longitude position m is defined.
• the straight section 13 is referred to as the downstream isomeridional position curve, at which the meridional longitude position m takes as its value the length of the corresponding iso-span curve from the straight section 12 to the straight section 13.
• the value of the meridional longitude position 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.
• 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. 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
• 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.
• Fig. 1c A schematic representation of an axial fan wheel 2 in a meridional plane.
• a cover ring is not present in this example; the fan blade 3 has an outer, free end.
• the iso-span curves equivalent to the statements on 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.
• 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.
• iso-span curves and iso-span areas can also be defined for stators (e.g., guide vanes or vanes).
• 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.
• a conformal (angle-conform) mapping is used, i.e., the angles shown in the Figures 2a and 2b have 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.
• FIG. 2a The section 16 of an unprofiled blade 3 with an iso-span area is shown schematically.
• the 2-dimensional coordinate system 15 with the coordinate axes ⁇ and m is drawn at the origin (zero point).
• ⁇ is a length coordinate in the circumferential direction of the fan wheel 2
• m is the already explained meridional coordinate.
• the origin (zero point) with respect to ⁇ 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.
• the wing section 16 is primarily characterized by its imaginary centerline 17. Superimposed on this centerline is a wing thickness d.
• the thickness d is essentially constant across the meridional extent of the blade.
• 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.
• the thickness d in the example deviates from the constant thickness because the sheet metal blade is rounded there, which can have acoustic advantages.
• 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.
• 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 extent of the wing section 16 in the circumferential direction depends largely on its extent I in the meridional direction and the stagger angle, i.e. approximately the mean value of ⁇ 1 and ⁇ 2.
• FIG. 2b The section 16 of a profiled wing 3 with an iso-span area is shown schematically.
• the thickness distribution is not constant. Rather, the thickness is a function of the meridional position m.
• a thickness distribution is present which is similar to that of an airfoil profile.
• Such thickness distributions are characteristic of profiled fan blades 3.
• Profiled fan blades 3 are advantageous for the efficiency and acoustics of a fan.
• the production of such fan blades 3 is more complex than with unprofiled blades, particularly when made from sheet metal.
• the thickness distribution and the maximum thickness d max can also depend on the span coordinate s.
• the wing cuts 16 in the Figures 2a and 2b encompass the entire area of the wing 3 from a wing leading edge 18 to a wing trailing edge 19 without interruption.
• 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.
• Figure 3 shows a function curve 21 of any desired value, which can be, for example, ⁇ 1, ⁇ 2, I, m c , ⁇ c , ⁇ 1- ⁇ 2, 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.
• the function curve of 21 is obviously 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 difference 23 between function curve 21 and the filtered function curve 22 is shown.
• suitable definitions of waviness can be specified.
• 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.
• the wavelength ⁇ and the amplitude A of a wave function are defined.
• the wavelength ⁇ 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.
• ⁇ 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/ ⁇ .
• a fan blade 3 is said to be wavy in the span direction if the course of at least one of the functions ⁇ 1, ⁇ 2, I, m c , ⁇ c , ⁇ 1- ⁇ 2, d max , ⁇ 1+ ⁇ 2 or d(m*) is wavy according to the definitions given.
• 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 ⁇ 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 ⁇ 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.
• the waviness of the blade leading edge 18 leads to a reduction in particular of the tonal noise which arises as a result of inflow disturbances to a fan wheel 2 during operation.
• the waviness of the sickle in the example of the Figures 4a and 4b From 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 ⁇ c in the circumferential direction, the acoustic behavior of a fan can be improved at several causal mechanisms.
• the outermost region 26 of the axial fan blade 3 is very specifically designed with the help of the corrugation.
• 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.
• the exemplary design also takes on the aeroacoustic function of a winglet.
• the winglet and corrugation have been perfectly and seamlessly integrated with one single design measure.
• 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 waviness of the quantities m c (position of the blade section in the direction of the meridional coordinate) and ⁇ 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.
• approximately 7.5 wavelengths are present across the entire span.
• the dimensioned wavelength ⁇ 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 trail
• Fig. 5b which is the subject of Fig. 5a in a radial section view
• 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.
• the waviness of m c and ⁇ c and other variables is selected in such a way that this surface, viewed in section, is not wavy.
• 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 .
• the non-wave-like reference blades have the same geometry.
• 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 ( ⁇ 1+ ⁇ 2)/2, i.e., in particular, a waveform of the stagger angle.
• the geometric deflection ( ⁇ 1- ⁇ 2), the coordinates ⁇ c and m c , and the meridional extension I of the fan blades 3 are non-waveform across the span direction.
• the amplitude A of the waveform of ( ⁇ 1+ ⁇ 2)/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.
• Fig. 6b shows the object in radial side view Figure 6a
• the waviness of the wing trailing edges 19 is noticeable to varying degrees depending on the viewing direction. Since m c 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.
• the waviness of ( ⁇ 1+ ⁇ 2)/2 leads to a waviness of the position in the circumferential direction of the wing 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.
• 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.
• Fig. 6c shows in a plane section the object from Figures 6a , 6b , viewed radially from the side. Waviness is also visible in the plane sections 24 of the blades.
• the surface of the fan blades 3 is also wavy. As already described, this leads to additional acoustic advantages. However, manufacturing them from 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 to create the wavy contour. Furthermore, it must be ensured that the sheets do not tear during such a deformation process. Special flowable metal or plastic sheets can be used.
• 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 m c nor ⁇ c are superimposed with a waviness.
• This design is particularly advantageous in the case of fan blades 3 made of sheet metal.
• the strong waviness is limited to the areas near the leading edge 18 and the trailing edge 19, which are most important in terms of noise generation.
• the less important area in the center of the fan blade viewed in the meridional direction, unnecessary deformation effort is largely avoided.
• 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.
• 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 fastening flange 28 for a motor is provided on the hub ring 4.
• a fastening area 29 is provided on the cover ring 5, with which the guide wheel 2 can be fastened, for example, to a housing.
• the waviness in this exemplary embodiment is due to a waviness of the local blade thickness d at a meridional position m* near the blade leading edge. 18. Both the leading edge 18 and the trailing edge 19 are not wavy.
• the waviness of the fan blades 3 can be recognized by the waviness of some view silhouettes 31.
• 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, an effect comparable to that achieved with a wavy design of a blade leading edge 18 is achieved.

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• Engineering & Computer Science (AREA)
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• General Engineering & Computer Science (AREA)
• Structures Of Non-Positive Displacement Pumps (AREA)
• Air-Conditioning Room Units, And Self-Contained Units In General (AREA)

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• 2015
  • 2015-08-31 DE DE102015216579.5A patent/DE102015216579A1/de active Pending
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  • 2016-08-04 EP EP16763436.9A patent/EP3289224B1/de active Active
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• 2021
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