Inlet nozzle for a radial, diagonal or axial-flow fan, and a radial, diagonal or axial-flow fan comprising an inlet nozzle

Abstract

The invention relates to an inlet nozzle (1) for a radial, diagonal or axial-flow fan, comprising an inlet section (3) that is circular in cross-section, has a radius of curvature, and tapers in diameter in the direction of flow (4), characterised by the presence of a measure or a flow element on or in the curved surface (5) of said inlet section for the purpose of forcing turbulent boundary layers in the flow, which can counteract a stall in this region. A radial, diagonal or axial-flow fan comprises a corresponding inlet nozzle (1).

Description

[0001] The invention relates to an inlet nozzle for a radial, diagonal, or axial fan, with an inlet section that is circular in cross-section, has a radius of curvature, and tapers in diameter in the direction of flow. Furthermore, the invention relates to a radial, diagonal, or axial fan with a corresponding inlet nozzle.

[0002] Axial fans and radial fans are well known in practice. For example, see JP H02 185700 A, US 2008 / 085186 A1, DE 200 01 746 U1, US 6,499,948 B1, and DE 10 2012 021 372 A1.

[0003] Such fans are regularly equipped with an inlet nozzle or inlet nozzle through which the fan sucks in air, which flows through an inlet opening first into the inlet area of ​​the inlet nozzle and from there to the outlet area of ​​the inlet nozzle.

[0004] In an axial-flow fan that draws air from the outside, the incoming air is guided through such an inlet nozzle. This nozzle can be designed with a fluidically optimized inlet radius. The inlet nozzle should direct the air flow to the rotating axial impeller with as little turbulence and loss as possible. Since there are no precise approaches to determining the geometry of an optimal inlet nozzle, the inlet radius is regularly determined experimentally, i.e., empirically, usually depending on the fan's design parameters.

[0005] It is known that insufficiently large radii can lead to flow separation in the inlet area or in the area of ​​the inlet radius. This flow separation interacts with the rotating impeller, leading to increased noise levels and power losses. A small inlet radius may be necessary due to installation conditions in the specific fan application. Furthermore, customer-specified flange dimensions for the nozzles are often specified, which must be observed when dimensioning the fan or inlet nozzle.

[0006] A reduction in the nozzle height and / or the flange dimensions without further loss of performance would offer enormous advantages, namely in terms of a reduction in the installation space or the height of the fan.

[0007] It is of fundamental importance that with a smaller inlet radius the overall size of the inlet nozzle, in particular the nozzle height and / or the flange dimensions, can be reduced, which in turn leads to material savings.

[0008] From the previously mentioned DE 10 2012 021 372 A1, measures are known in the outlet area of ​​the inlet nozzle, according to which the wall of the outlet area consists of consecutive wall sections, each of which is connected to each other via an edge running along the circumference of the wall sections. In practice, however, it has been shown that these measures are only partially suitable for eliminating the disruptive flow separation that leads to increased noise levels and power losses.

[0009] The present invention is therefore based on the object of specifying an inlet nozzle for a radial, diagonal or axial fan and a radial, diagonal or axial fan with a corresponding inlet nozzle, which is suitable for avoiding, or at least reducing, the disadvantages occurring in the prior art caused by unwanted flow separation, namely for reducing sound levels and power losses.

[0010] The above object is achieved with respect to the inlet nozzle by the features of claim 1. According to this, the generic inlet nozzle is characterized by a measure or a flow element on or in the curved surface of the inlet section, in particular for forcing turbulent boundary layers in the flow, which counteract / can counteract flow separation in this area.

[0011] A radial, diagonal, or axial fan equipped with such an inlet nozzle is characterized by the features of the independent claim 7, with the same features as the inlet nozzle according to the invention. The inlet nozzle according to the invention solves a problem that predominantly occurs with inlet nozzles with small radii in the inlet section, even with an optimized inlet radius. In the prior art, it is unavoidable that, particularly with small radii, flow separation occurs in the inlet radius, leading to turbulence in the flow. This turbulence is fed to the rotating fan wheel and causes significant losses there.

[0012] At this point, it should be noted that the inlet nozzle according to the invention has a radius of curvature, so that we are referring here to an inlet nozzle "with radius." The term "radius of curvature" is to be understood in the broadest sense. The "radius" can be composed of several subradii, each with a continuous or discontinuous transition between the subradii.

[0013] With a sufficiently large radius, it can be optimized in terms of noise generation and performance. As radii become smaller, this becomes problematic, so the inventive measure is particularly effective for small radii. The effects of geometric measures, which can be determined by sound power measurements on different geometries, indicate that it is possible to prevent flow separation even at small radii, namely when, for example, turbulent boundary layers are forced in the inflow area, i.e., in the radius of curvature (or in the respective partial radius), which can counteract flow separation.

[0014] In a particularly advantageous manner, the curved inflow section has an annular recess in the sense of a zonal extension of this region, namely a region running in a ring shape in the inner surface of the inflow section, which acts in the sense of a flow element that counteracts flow separation or at least delays it.

[0015] Instead of a single recess, two or more recesses spaced apart from each other can also be provided, as required, resulting from the radius to be realized according to the desired size.

[0016] According to the invention, the recess or extension is realized as a recessed edge, whereby the underlying idea is that a recessed edge initially separates the flow, whereby the main flow then reattaches to the separated geometry. This occurs through a vortex that literally sucks in the main flow in the separation area (source: Nitsche, W.: Strömungsmesstechnik, Springer-Verlag 1994 (geometrically induced separation)). The extension in the radius of the inflow section is designed as an outwardly recessed edge. Accordingly, the edge is formed by two bends or chamfer angles, namely the chamfer angles α and β with the rule 180° < α < 270° and 180° > β > 90°. Particularly favorable flow conditions arise in this area.

[0017] When providing a single setback, it is advantageous if it is located approximately in the middle or in the inner third of the inflow section in order to optimally promote the flow with regard to the forcing of turbulent boundary layers and thus to avoid flow separation.

[0018] The inlet nozzle can be made entirely of plastic. For a simple design, it is advisable to manufacture the inlet nozzle from metal, in particular from sheet metal, using conventional manufacturing processes for producing sheet metal parts. The extension or the annular recess can be greater than the wall thickness of the sheet metal to ensure sufficient stability. Furthermore, it is advantageous if the length of the recess is greater than the depth of the recess, namely to favor the flow conditions in such a way that the separation area for the flow defined immediately after the recess is in a suitable ratio to the length of the recess and the reattachment point of the flow. The recess can be generated, for example, by deep drawing or embossing the sheet metal.

[0019] There are now various possibilities for advantageously embodying and developing the teaching 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 a preferred embodiment of the invention with reference to the drawing. In conjunction with the explanation of the preferred embodiment of the invention with reference to the drawing, generally preferred embodiments and developments of the teaching are also explained. The drawing shows: Fig. 1 in a schematic view, sectioned, an embodiment of a conventional inlet nozzle with radius, Fig. 2 in a perspective view of a prior art inlet nozzle according to Fig. 1, Fig. 3in schematic views, partially, the profile of an inlet nozzle according to the invention (lower illustration) and in detail, enlarged, the inventive measure in the area of ​​the curved surface, ie the radius, Fig. 4in a schematic partial view the inlet section including the recess, Fig. 5in a detailed view (detail X) object from Fig. 4 and Fig. 6 in schematic views the inflow section of conventional inflow nozzles without measures influencing the flow (a) and b)) and in a schematic view the inflow nozzle according to the invention with recess or edge in the inflow section (c)).

[0020] Fig. 1 shows a schematic sectional view of an embodiment of a conventional inlet nozzle 1 with radius Ra. The inlet nozzle 1 comprises a mounting flange 2 and an inlet section 3 with a curved surface 5, wherein the radius Ra has a very special effect on the inflowing air 4.

[0021] Fig. 2 shows in perspective view an inlet nozzle 1 with radius Ra known from the prior art, wherein the inlet section 3 with curved surface 5 and the fastening flange 2 can be seen.

[0022] Fig. 3 shows in a lower illustration, partially, the profile of the inlet nozzle 1 according to the invention in the region of the radius Ra, ie the inlet section 3 with the curved surface 5 on the inside of the inlet nozzle 1. It can be seen that a measure influencing the flow is provided there, namely a recess 6, which is designed as a recessed, circumferential edge.

[0023] The detailed view above shows the inflow section 3 and the recess 6, the depth of which is smaller than the length or width in the flow direction 7 of the inflowing air.

[0024] The recess 6 can cause turbulent boundary layers in the flow with respect to the incoming air, which counteract the problematic flow separation and thus noise development and power loss.

[0025] Fig. 4 shows an enlarged view of the inlet section 3 of an inlet nozzle according to the invention with dimensions, with the following legend: R = nozzle inner radius r = start of the flow element R' = start of the inflow radius R" = distance at which the nozzle can be shortened without loss of performance t = wall thickness t' = depth of the flow element L = length of the flow element φ = angle of the draft angle A = axis of rotation in general R <r<R′<R" t>t′ L>t′ general "from / to" R*1.01≤r≤R*1.49 R*1.01≤R′≤R*1.50 R*1.02≤R"≤R*1.51 t*0.01≤t′≤t*0.95 t*0.50≤L≤t*25.00−90°≤∢φ≤+45° and preferably "from / to" R*1.02≤r≤R*1.10 R*1.07≤R′≤R*1.15 R∗1.10≤R"≤R∗1.18 t∗0,1≤t′≤t∗0,4 t∗1.00≤L≤t∗10.00 1° ≤ ∢ φ ≤ 10° with respect to the rotation axis A of the fan wheel.

[0026] The above dimensions / limits and ratios are to be understood as advantageous embodiments of the teaching according to the invention.

[0027] Fig. 5 shows that in Fig. 4 Detail X is marked with the corresponding label, from which the dimensions / limits are derived. The angles α and β are shown again enlarged, showing that the extension is designed as a recessed edge (6) with chamfer angles of 180° < α < 270° and 180° > β > 90°.

[0028] Fig. 6Finally, a comparison shows the profile of two conventional inlet nozzles 1 in the area of ​​the inlet section 3 with different radii Ra, with the inflow indicated by an arrow 7 symbolizing the flowing air. Variant b) is designed with a smaller radius, thus leading to power losses and increased noise levels. Variant c) shows the inventive inlet nozzle 1 with the previously discussed recess 6 in the area of ​​the curved surface 5, which produces the effect according to the invention, and this with the simplest design and manufacture.

[0029] With regard to further advantageous embodiments of the teaching according to the invention, reference is made to the general part of the description and to the appended claims in order to avoid repetition.

[0030] Finally, it should be expressly pointed out that the exemplary embodiment of the teaching according to the invention described above serves only to explain the claimed teaching, but does not limit it to the exemplary embodiment. List of reference symbols

[0031] 1Inlet nozzle 2Mounting flange 3Inlet section 4Arrow, air flow direction 5Curved surface 6Recess, edge 7Flow direction, inflow RRadius (inner nozzle radius) RaRadius

Claims

1. Inlet nozzle for a radial, diagonal or axial fan, having an inlet portion (3) which is circular in cross-section, which has a radius of curvature and which tapers in diameter in the flow direction (4), wherein a measure or a flow element is provided on or in the curved surface (5) of the inlet portion (3), in particular in order to force turbulent boundary layers in the flow, which counteracts / can counteract a flow separation in this region, characterised in that the measure or the flow element is an expansion or an annular recess in the form of a zonal expansion which is constructed as a recessed edge (6) with bending angles 180° < α < 270° and 180° > β > 90° , wherein the edge (6) is formed by the bending angles α and β, wherein α is a concave angle and wherein β is an obtuse angle downstream of the bending angle α in the flow direction (4).

2. Inlet nozzle according to claim 1, characterised in that two or more recesses (6) which are spaced apart from each other are provided.

3. Inlet nozzle according to claim 1 or 2, characterised in that the recess (6) is formed approximately centrally or in the inner third of the inlet portion (3).

4. Inlet nozzle according to any one of claims 1 to 3, characterised in that the inlet nozzle (1) is produced from metal, in particular from sheet metal, or from plastics material.

5. Inlet nozzle according to any one of claims 1 to 4, wherein the inlet nozzle (1) is produced from sheet metal, characterised in that the recess (6) is greater than the wall thickness of the sheet metal and / or in that the length of the recess (6) is greater than the depth of the recess (6).

6. Radial, diagonal or axial fan, having a rotationally driven impeller for producing an air flow and an inlet-side inlet nozzle (1) according to any one of claims 1 to 5.

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