Fan And Fan Blade

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). The wavy inflow edge (4) forms a wave (W) with a specific three-dimensional waveform.

Claims

1. A fan blade for a radial fan comprising: an inflow edge and an outflow edge, and at least in one section, a wavy inflow edge with a periodically repeating waveform of the period length λ, that is different from a sinusoidal or nearly sinusoidal waveform, in particular is different from a sinusoidal or nearly sinusoidal waveform having an 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; a wave peak is located between the two wave troughs, the peak extends against the flow direction in the direction of the inflow-side front edge and a peak-trough value of the wave of the wave peak, which is directly between two adjacent wave troughs, is in absolute value approximately 10% to 80% of the peak-trough value of the directly adjacent wave peak(s).

2. The fan blade as claimed in claim 1, wherein the wavy inflow edge has two or more periodically repeating waveforms.

3. The fan blade as claimed in claim 1, wherein the peak-trough value of the wave, measured from a front edge in a 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.

4. The fan blade as claimed in claim 1, wherein the fan blade, in particular in the region of the wavy inflow edge, has a chord length and the peak-trough value in the region of the wave troughs is preferably approximately 10% of 30% of the chord length, more preferably 10% to 20% of the chord length.

5. The fan blade as claimed in claim 1, wherein the repeating waveform has, per period, at least one wave trough with two wave flanks extending toward one another and in each case obliquely to the flow direction.

6. The fan blade as claimed in claim 1, 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°.

7. The fan blade as claimed in claim 1, wherein the wavy inflow edge, insofar as it has a non-wavy region, at least in the region of provided wave peaks, protrudes against the flow direction in relation to the inflow edge in the non-wavy region.

8. The fan blade as claimed in claim 1, 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 pressure side and a dent at the corresponding opposite position of the suction side, the surface profile is respectively defined so that the surface curvature changes twice viewed in the flow direction.

9. The fan blade as claimed in claim 1, wherein the blade profile, viewed frontally in the region of the inflow edge in a profile section, curves farther toward the suction side in comparison to a or the region adjacent thereto curved less toward the suction side, preferably with a spacing of one period, more preferably from period center to period center.

10. The fan blade as claimed in claim 1, 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, for example, having a plurality of channels extending through the fan blade.

11. A radial fan having one or more fan blades as claimed in claim 1.

Description

DRAWINGS

[0036] FIG. 1 is a perspective view of a fan blade having wavy inflow edge in sections;

[0037] FIG. 2 is a cross-section detail view of a profile section B through the fan blade in the peak of the inflow edge wave to explain the S-shaping;

[0038] 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 having inflection points and deeper-cut wave trough;

[0039] FIG. 4 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 having additional wave peak in the center of the wave;

[0040] FIG. 5 is a cross-section detail view of profile section C through the fan blade according to FIG. 1;

[0041] FIG. 6 is a perspective view of an exemplary radial fan having seven fan blades.

DETAILED DESCRIPTION

[0042] The disclosure is explained in more detail hereinafter on the basis of an exemplary embodiment with reference to FIGS. 1 to 6. Identical reference signs in the figures indicate identical structural and/or functional features.

[0043] 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, identified by inflow edge 4 in this region of the inflow edge 4, forms a wave of a specific waveform. A theoretically non-wavy inflow edge of a reference blade is identified by 2*. It is a profile of the shape of the inflow edge that would result without the presence of the wave. In addition, three meridionally extending profile section lines A, B, and C are shown.

[0044] The position of the profile section A is selected so that the chord length of the fan blade 1 having the wavy inflow edge 4 approximately corresponds to the chord length of a reference blade having 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 with the wavy inflow edge 4. The position of the profile section C is selected so that it extends through a wave trough of the wavy region (4) of the inflow edge of the fan blade 1.

[0045] 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 with the non-wavy inflow edge 2* close to the inflow edge in the direction of suction side SS and further downstream in the direction of pressure side DS. For this purpose, the blade profile has a bump protruding out of the pressure side DS and a dent extending into the suction side SS (in relation to the dashed reference profile).

[0046] 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.

[0047] In comparison to the sine waveform, the two flanks K1, K2, dropping toward the wave trough 7, are located closer together. 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 v, i.e., the component of the inflow speed v perpendicular to the inflow edge, where the disturbance strikes on the inflow edge of the fan blade, is reduced with a steeper profile of the flanks K1, K2. This results in an 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.

[0048] 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. Thus 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.

[0049] FIG. 5 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, 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. It can be located both in the region of the additional wave peak 8 and also in the region of the trough 7.

[0050] FIG. 6 shows an exemplary axial fan having five fan blades 1.

[0051] The disclosure is not restricted in its embodiment to the above-described preferred exemplary embodiments. Rather, a number of variants is conceivable, which makes use of the described solution even in fundamentally differently designed embodiments.