Blade of an air-conveying wheel with an S-shaped blade edge geometry

Abstract

The disclosure relates to a blade edge of at least one blade of an air-conveying wheel with an axial-side blade edge contour which extends from a blade leading edge to a blade trailing edge along a curve, wherein the blade edge contour has at least one front section which adjoins the blade leading edge in the radial direction, a rear section which adjoins the blade trailing edge in the radial direction, and a central section which lies between the front section and the rear section. The blade edge contour has an S-shaped curve progression in the central section in a lateral cross-sectional view, thus increasing an axial height of the blade in the direction of the blade trailing edge.

Claims

1. A blade edge of at least one blade of an air-conveying wheel with an axial-side blade edge contour that extends from a blade leading edge to a blade trailing edge along a curve, the blade edge contour has at least one front section (I) that adjoins the blade leading edge in the radial direction, a rear section (III) that adjoins the blade trailing edge in the radial direction, and a central section (II) that lies between the front section (I) and the rear section (III), the blade edge contour has an S-shaped curve progression in the central section (II) in a lateral cross-sectional view, this increasing an axial height h of the blade in the direction of the blade trailing edge, the central section (II) has a curve progression along a chord length s of the blade from a beginning of the central section s.sub.central section.sup.min to an end of the central section s.sub.central section.sup.max, that is determined normalized by the formula $h\left(s\right)=\tanh \left(\frac{s-\left(\frac{s_{\mathrm{central}\mathrm{section}}^{\min }+s_{\mathrm{central}\mathrm{section}}^{\max }}{2}\right)}{t}\right)*\frac{h\left(s_{\mathrm{central}\mathrm{section}}^{\min }\right)+h\left(s_{\mathrm{central}\mathrm{section}}^{\max }\right)}{2}+h\left(s_{\mathrm{central}\mathrm{section}}^{\min }\right)+\frac{h\left(s_{\mathrm{central}\mathrm{section}}^{\min }\right)+h\left(s_{\mathrm{central}\mathrm{section}}^{\max }\right)}{2}$ wherein h corresponds to an axial height of the blade and s to a chord length of the blade, that extends from the blade leading edge to the blade trailing edge, wherein h and s in each case have values of 0 to 1, and t[0, 1],
0.1s.sub.central section.sup.mins.sub.central section.sup.max,
s.sub.central section.sup.mins.sub.central section.sup.max0.8.

2. The blade edge according to claim 1, wherein the S-shaped curve progression corresponds to a curve of a hyperbolic tangent.

3. The blade edge according to claim 1, wherein the blade edge contour has a continuous curve progression in the front section (I) and in the rear section (III) at least in sections.

4. The blade edge according to claim 3, wherein the blade edge contour has a continuous curve progression in the front section (I) and in the rear section (III) over 50-100% of the radial length thereof.

5. The blade edge according to claim 1, wherein the front section (I) and the rear section (III) directly adjoin the central section (II).

6. The blade edge according to claim 5, wherein the curve of the blade edge contour is, in each case, continuously differentiable on both sides at the respective adjoining points of the front section (I) and the central section (II) as well as of the rear section (III) and the central section (II).

7. The blade edge according to claim 1, wherein the front section (I) has a curve progression along a chord length s of the blade that is determined normalized by the formula
h(s)=as+d where h corresponds to an axial height of the blade and s corresponds to a chord length of the blade, which extends from the blade leading edge (3) to the blade trailing edge (4) from the value 0 to 1, and:
s[0,s.sub.central section.sup.min] and
0.5a1,
0<d1,
a+d1.

8. The blade edge according to claim 1, wherein the rear section (III) has a curve progression along a chord length s of the blade, which is determined normalized by the formula
h(s)=a(ss.sub.central section.sup.max)+d where h corresponds to an axial height of the blade and s corresponds to a chord length of the blade, which extends from the blade leading edge to the blade trailing edge from the value 0 to 1, and:
s[0,s.sub.central section.sup.max,1] and
0.5a1,
0<d1,
a+d1,

9. The blade edge according to claim 1, wherein the front section (I) has a curve progression in a transition from an axial extent to a radial extent having a rounding r, that is determined by 0rH, where H corresponds to the axial maximum height of the blade.

10. The blade edge according to claim 1, wherein in an axial top view onto the blade, the blade trailing edge has a bevel with respect to a radial extent of the blade at an angle , where 5<<70.

11. An air-conveying wheel with at least one blade with a blade edge according to claim 1, wherein the blade edge is open to inflow, i.e., uncovered.

12. A use of an air-conveying wheel according to claim 11, wherein the installation position in an electric motor occurs in such a manner that a thin head gap (K) adjoining the blade edge in an axial direction relative to an axially adjoining component of the electric motor is in a range from 0.02 H<K<0.4 H, wherein H corresponds to the maximum height of the blade.

Description

DRAWINGS

(1) The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure.

(2) FIG. 1 is a lateral cross-sectional view of a blade of an air-conveying wheel.

(3) FIG. 2 is a top plan view onto the blade according to FIG. 1.

(4) FIG. 3 is a side view onto an external rotor motor with integrated air-conveying wheel with a blade geometry according to FIG. 1.

DETAILED DESCRIPTION

(5) Identical reference numerals designate identical parts in all the views.

(6) FIG. 1 represents an embodiment example of a blade 1 of an air-conveying wheel 2 with a blade edge 10. The blade edge 10 includes an axial-side blade edge contour extending from the blade leading edge 3 to the blade trailing edge 4 along a curve subdivided into three sections. In the radial direction, when viewed along the chord length s, the front section I adjoins the blade leading edge 3 and transitions directly into the central section II. The rear section III directly adjoins the central section II, wherein the rear section III ends with the blade trailing edge 4.

(7) The front section I has a curve progression with a rounding r at the transition from the axial extent into the radial extent of the blade edge contour. In the represented design, the rounding r corresponds to a value of r=5, H=16.5. H is the axial maximum height of the blade 1. The blade edge contour in the front section I corresponds to a horizontal parabola. The axial height h of the blade 1 increases in the direction of the adjoining central section. Over a section of more than 50% of the radial extent, the blade edge contour has a continuous curve progression in the front section I.

(8) In the central section II, radially adjoining along the chord length, the blade edge contour has an elongated or flattened S-shaped curve progression. Thus, the axial height h of the blade 1 at first increases slightly in the direction of the blade trailing edge 4. At the start of the S shape, the axial height h increases considerably and then levels off flat in a direction of the rear section III. The curve progression in the central section II corresponds to a hyperbolic tangent, as described in greater detail below.

(9) In the rear section, the curve of the blade edge contour extends continuously over the entire radial chord length and substantially without slope to the blade trailing edge 4. The curve of the blade edge contour of the blade edge 10 is in each case continuously differentiable at the respective adjoining points of the front section I and central section II and of the rear section III and the central section II, and consequently without jumps. Both the blade leading edge 3 and also the blade trailing edge 4 extend axially in a straight line.

(10) The curve progression of the blade edge contour is defined in the non-rounded area in the front section I by the equation
h(s)=(as)+d
wherein, in the represented design: front section: a=0 and d=6/16.5

(11) The curve progression of the blade edge contour is defined in the rear section III by the equation
h(s)=a(ss.sub.central section.sup.max)+d
wherein, in the represented design: rear section: a=0 and d=1 Thus,

(12) $S=\frac{x}{L}$
where x[0, L] and

(13) $h=\frac{y}{H}$
where y[0, H], where L=24 and H=16.5.

(14) The curve progression of the blade edge contour is defined in the central section II by the equation

(15) $h\left(s\right)=\tanh \left(\frac{s-\left(\frac{s_{\mathrm{central}\mathrm{section}}^{\min }+s_{\mathrm{central}\mathrm{section}}^{\max }}{2}\right)}{t}\right)*\frac{h\left(s_{\mathrm{central}\mathrm{section}}^{\min }\right)+h\left(s_{\mathrm{central}\mathrm{section}}^{\max }\right)}{2}+h\left(s_{\mathrm{central}\mathrm{section}}^{\min }\right)+\frac{h\left(s_{\mathrm{central}\mathrm{section}}^{\min }\right)+h\left(s_{\mathrm{central}\mathrm{section}}^{\max }\right)}{2}$
wherein, in the design represented:

(16) $s_{\mathrm{central}\mathrm{section}}^{\min }=0.3$$s_{\mathrm{central}\mathrm{section}}^{\max }=0.7$$h\left(s_{\mathrm{cental}\mathrm{section}}^{\min }\right)=\frac{6}{16.5}$$h\left(s_{\mathrm{central}\mathrm{section}}^{\max }\right)=1$$t=\frac{\mathrm{tdesign}}{L}$
with tdesign[0, L]

(17) FIG. 2 shows a cross-sectional view of the blade 1 from FIG. 1 in a top view. The blade 1 extends in the shape of an arc from the blade leading edge 3 to the blade trailing edge 4. The blade leading edge 3 is rounded. The blade trailing edge 4 has the inclination 5 with respect to the radial extent of the blade 1 at an angle =60. In the design shown, the width n of the blade 1 along the inclination 5 in projection corresponds to approximately 5% of the chord length s. In conventional external rotor motors for fans, the value for n is preferably between 2 and 15 mm.

(18) In FIG. 3, an installation position of an air-conveying wheel 2 with a blade geometry of a blade 1 according to FIG. 1 in an external rotor motor 20 is shown. The air-conveying wheel 2 has a bottom plate 12, but, along the blade edges 10, it is open to inflow in the axial direction. It is without a cover plate and completely uncovered. The external rotor motor 20 comprises a stator bushing 25, a plurality of stator bushing cooling ribs 23 as well as a rotor 22. The bushing cooling ribs 23 are arranged in each case spaced apart from one another in a peripheral direction and extend in the axial direction. Additional components of the external rotor motor 20 correspond, for example, to the components of the prior art cited at the beginning. In the stator bushing 25, a suctioning opening 24 is provided, via which the air-conveying wheel 2, in operation, suctions and radially blows out the cooling air stream. The suctioned air flows along the heated components such as the electronics housing and the stator bushing and dissipates the heat. The axially free blade edges 10 directly face the stator bushing cooling ribs 23 which are also axially free. They are spaced via the head gap K whose size in the design shown is determined by K=0.15 H. The blade edges 10, with regard to the axial extent, have a complementary shape relative to the stator bushing cooling ribs 23, so that the head gap K is constant over the chord length s.

(19) The disclosure, in terms of its design, is not limited to the above-indicated preferred embodiment examples. Instead, a number of variants are conceivable, which make use of the represented solution even in designs of fundamentally different type. For example, the blade leading edge as well as the blade trailing edge can also extend at an inclination in the axial direction.

(20) The present disclosure has been described with reference to the preferred embodiment. Obviously, modifications and alternations will occur to those of ordinary skill in the art upon reading and understanding the preceding detailed description. It is intended that the present disclosure be construed to include all such alternations and modifications insofar as they come within the scope of the appended claims or their equivalents.