FAN AND FAN BLADES

Abstract

A fan blade (1) has a front inflow edge (2) and a rear outflow edge (3). The fan blade (1) has an at least partially wavy inflow edge (4) that forms a wave (W) having a specific three-dimensional waveform.

Claims

1-13. (canceled)

14. A fan blade for a radial fan comprising an inflow edge and an outflow edge, the fan blade (1) has, at least in one section, a wavy inflow edge with a periodically repeating waveform of a period length λ, which is different from a sinusoidal or nearly sinusoidal waveform, in particular is different from a sinusoidal or nearly sinusoidal waveform having equal period length λ; the repeating waveform forms, per period, two adjacent wave troughs between two flanks extending toward one another obliquely to the flow direction and the obliquely extending wave flanks extend at a steep tangential angle in relation to the flow direction in or close to their flank center and form steeper flanks in relation to the flow direction in comparison to a sinusoidal waveform.

15. The fan blade as claimed in claim 14, wherein the wavy inflow edge has two or more periodically repeating waveforms.

16. The fan blade as claimed in claim 14, wherein the peak-trough value H of the wave, measured from the front edge in the region of the wavy inflow edge to the wave trough, has values viewed in the flow direction in relation to the period length λ, that are in the range 0.2≤λ/H≤2, wherein the values can vary along the inflow edge.

17. The fan blade as claimed in claim 16, wherein the fan blade, in particular in the region of the wavy inflow edge, has a chord length SL and the peak-trough value H in the region of the wave troughs is preferably approximately 10% of 30% of the chord length SL, more preferably 10% to 20% of the chord length SL.

18. The fan blade as claimed in claim 14, wherein the repeating waveform forms per period two adjacent wave troughs between two flanks extending toward one another obliquely to the flow direction with a wave peak located between the two wave troughs, that extends against the flow direction in the direction of the inflow-side front edge.

19. The fan blade as claimed in claim 14, wherein the obliquely extending wave flanks extend in or close to their flank middle in relation to the flow direction at a tangential angle β between 15° and 35°, preferably a tangential angle β of 25° to 30°.

20. The fan blade as claimed in claim 18, wherein the peak-trough value of the wave of a wave peak, which is located directly between two adjacent wave troughs, is approximately 10% to 80% in absolute value of the peak-trough value of the directly adjacent wave peak(s).

21. The fan blade as claimed in claim 18, wherein the wavy inflow edge, insofar as it has a non-wavy region, protrudes, at least in the region of existing wave peaks, against the flow direction in relation to the inflow edge in the non-wavy region.

22. The fan blade as claimed in claim 18, wherein the blade profile, at least viewed in a profile section in the region of a wave peak, respectively has a bump protruding out of the suction side and a dent extending on the pressure side, the surface profile of which is respectively defined so that the surface curvature changes twice viewed in the flow direction.

23. The fan blade as claimed in claim 14, wherein the blade profile, viewed frontally in the region of the inflow edge in a profile section, curves farther toward the pressure side in comparison to a or the region adjacent thereto curved less toward the pressure side, preferably with a spacing of one period, more preferably from period center to period center.

24. The fan blade as claimed in claim 14, wherein the fan blade is formed porous at least in sections in the region of the inflow edge, preferably having a connection from pressure side to suction side, having a plurality of channels extending through the fan blade.

25. An axial fan or diagonal fan having one or more fan blades as claimed in claim 14.

Description

DRAWINGS

[0034] In the figures:

[0035] FIG. 1 is a perspective view of a fan blade with a wavy inflow edge in sections;

[0036] FIG. 2 is an elevation cross-section a detail view of a profile section B through the fan blade in the peak of the inflow edge wave to explain the specific “S-waviness”;

[0037] FIG. 3 is a schematic view of a sine waveform of a wave at the inflow edge and a waveform modified in relation thereto, which extends through support points of the sine wave, variants with inflection points and deeper-cut wave trough;

[0038] FIG. 4 is a schematic view of a sine waveform of a wave at the inflow edge and a waveform modified in relation thereto, that extends through support points of the sine wave, variants with additional wave peak between two wave troughs;

[0039] FIG. 5 is a perspective view of a fan blade with an inflow edge wavy in sections with additional wave peak;

[0040] FIG. 6 is a detail cross-section view of a profile section through the fan blade to explain the adaptation of the flow angle at half wavelength;

[0041] FIG. 7 is a perspective view of an exemplary axial fan with five fan blades;

[0042] FIG. 8 is a perspective view of an exemplary diagonal fan with a circumferential ring having five fan blades.

DETAIL DESCRIPTION

[0043] The disclosure is explained in more detail hereinafter on the basis of an exemplary embodiment with reference to FIGS. 1 to 8. Identical reference signs in the figures indicate identical structural and/or functional features.

[0044] FIG. 1 shows a fan blade 1 with an inflow edge that is wavy in sections. The fan blade 1 has an inflow edge 2, 4 and an outflow edge 3. An at least partially wavy region on the inflow edge, that is identified by inflow edge 4, forms a wave of a specific waveform in this region of the inflow edge 4. The inflow edge of a reference blade without a wavy inflow edge is identified by 2*. The reference blade represents a non-optimized blade without the features of the present disclosure.

[0045] In addition, two circumferentially extending profile section lines A and B are shown. The position of the profile section A is selected so that the chord length of the fan blade 1 with the wavy inflow edge 4 approximately corresponds to the chord length of a reference blade with a non-wavy inflow edge 2*. The position of the profile section B is selected so that it extends through a wave peak of the fan blade 1 having the wavy inflow edge 4.

[0046] FIG. 2 is a detail view of the profile section B in the wavy region of the inflow edge 4 of the fan blade 1 to explain an S-shaped wave. The profile having the wavy inflow edge 4 leaves the reference profile having the non-wavy inflow edge 2* close to the inflow edge in the direction of pressure side DS and further downstream in the direction of suction side SS.

[0047] A measure is described hereinafter for how the waveform at the inflow edge can be derived or optimized starting from a sine wave. The waveform is defined over multiple support points S of the sine curve and the curve profile results by a spline interpolation. For this purpose, FIG. 3 shows a schematic view of an imaginary sine waveform 5 at the inflow edge and a modified waveform 6, that extends through six support points S on the sine wave 5 and an additional support point S1 in the middle of the wave. The peak-trough value H of the wave 6 is the distance from the highest point to the lowest point. The deviation from the sine wave is defined by a length h1 and the selection of the support points S. This waveform 6 causes a “deeper-cut” wave trough 7 of the waveform 6 with respect to the peak-trough value H.

[0048] In comparison to the sine waveform, the two flanks K1, K2 dropping toward the wave trough 7 are located closer together and their angle of attack is steeper in relation to the sine wave with respect to the direction of the inflow speed v. The effective inflow velocity, i.e., the component of the inflow speed v perpendicular to the inflow edge, with which the disturbance strikes on the inflow edge of the fan blade, is reduced with a steeper profile of the edge. This results in more effective reduction of the emitted sound. Preferred values for h1 are preferably in the range 0<h1<h with h=amplitude of the sine wave.

[0049] FIG. 4 shows a further alternative variation of the location of the support points. The support point in the middle of the wave is positioned upstream against the inflow direction, so that an additional wave peak 8 results in the middle of the wave. The deviation from the sine wave is defined by a length h2 and the selection of the support points S. Preferred values for h2 are in the range 0<h2<2h with h=amplitude of the sine wave.

[0050] FIG. 5 shows an embodied fan blade 1 having inflow edge 4 wavy in sections with additional wave peaks 8. The circumferentially extending profile section shown having the profile section line C is selected so that it extends through an additional wave peak 8 of the family 1 having the wavy input edge 4.

[0051] FIG. 6 is a detail view of the profile section C in the region of the wavy inflow edge of the fan blade 1 to explain a local adaptation of the blade profile in the region of the inflow edge to the inflow. The profile section is shifted in the region of the regional inflow edge 4 essentially perpendicularly to the center line between pressure side and suction side of the blade by the length h3 in the direction of the pressure side DS. The profile section thus adapted having modified inflow edge 9 prevents flow separations and noise emissions linked thereto. The described advantageous adaptation of the profile section is preferably in the middle of the wave, i.e., it can be located both in the region of the additional wave peak 8 and also in the region of the trough 7.

[0052] FIG. 7 shows an exemplary axial fan having five fan blades 1.

[0053] FIG. 8 shows an exemplary diagonal fan having circumferential ring 10 having five fan blades 1.

[0054] The disclosure is not restricted in its embodiment to the above-described preferred exemplary embodiments. Rather, a number of variants is conceivable, that makes use of the described solution even in fundamentally differently designed embodiments.