EP2904277A2

EP2904277A2 - Flow rectifier for an axial fan

Info

Publication number: EP2904277A2
Application number: EP13765661.7A
Authority: EP
Inventors: Thomas Heli
Original assignee: Ebm Papst Mulfingen GmbH and Co KG
Current assignee: Ebm Papst Mulfingen GmbH and Co KG
Priority date: 2012-10-08
Filing date: 2013-08-27
Publication date: 2015-08-12
Anticipated expiration: 2033-08-27
Also published as: WO2014056657A2; US20150330411A1; DE102012109542A1; CN104685220B; US10094394B2; WO2014056657A3; EP2904277B1; WO2014056657A4; CN104685220A

Abstract

The invention relates to a flow rectifier (1) for an axial fan (2), comprising a base body (3) which has a ring (4a, 4b, 4c, 4d, 4e) that is delimited radially inside and outside by in each case cylindrical surfaces (5, 6), said ring comprising a plurality of air guide vanes (7) which are distributed in the circumferential direction about a longitudinal axis (X-X) and are arranged in an essential radial manner and extend between the cylindrical surfaces (5, 6), wherein the air guide vanes (7), when seen in the circumferential direction, extend with a curvature (R1) relative to the axial direction (X-X) in each case between an inflow-side vane edge (7a) and an outflow-side vane edge (7b). In order to minimize the divergence of an airflow that exits such a flow rectifier (1) at a high volume stream and a high range of throw, it is proposed that two or more rings (4a, 4b, 4c, 4d, 4e) having air guide vanes (7) are provided in the base body (3).

Description

ebm-papst Mulfingen GmbH & Co. KG, Bachmühle 2, 74673 Mulfingen

"Flow straightener for an axial fan"

The present invention relates to a flow straightener for an axial fan, comprising a main body, which has a radially outwardly and externally delimited annular rim with a plurality of circumferentially distributed around a longitudinal axis and substantially radially arranged between the lateral surfaces extending air guide vanes, wherein the air guide vanes each extend in the circumferential direction between an inflow-side blade edge and a downstream-side blade edge with a curvature to the axial direction.

Such a flow straightener is an air guide element which is arranged with its air guide vanes immediately behind an axial fan in order to redirect the flow of air displaced by the axial fan impeller into as axial and uniform a flow as possible. Such an air guide is often referred to as "Nachleitrad".

Axial fans are used, among other things, in evaporators in cold rooms, where the cold air is distributed through the axial fan into the cold room via the heat exchanger. For large cold rooms, it is important that the cold air is transported as far as possible into the room, in order to cool the refrigerated goods in a more distant location. For this purpose, an axial fan is required, which provides the highest possible volume flow with a long throw. Under throw is doing a Distance understood, up to a limit speed of the air flow is maintained. Due to the swirling outflow of an axial fan this range is limited. With the help of a downstream flow straightener, which transforms the spin into a uniform axial flow, the throwing distance can be increased significantly. It is important that the flow straightener has the lowest possible flow resistance, so that it only an insignificant pressure drop occurs in the amount of air flowing through it.

A flow straightener of the type mentioned, which basically meets the above requirements, is known from DE 44 04 262 A1. A swirl reduction of the fluid is achieved in particular by the fact that seen in the circumferential direction, the air guide vanes extend in a curved manner in each case between an inflow-side blade edge and a downstream-side blade edge to the axial direction. In a special embodiment, it is also provided that one of the blade edges, namely the edge on the

Leitradschaufelvorderseite, a variable in the radial direction height. It is straight and runs inclined to the Laufradmittelachse. Any effect associated with this embodiment is not described.

A disadvantage of this known flow straightener that a

actually sets even axial flow only at a considerable distance from the fan or from the outlet of the stator. Thus, as illustrated in DE 44 04 262 A1 Fig. 1 illustrates an angle between the air flow and the fan axis in a peripheral optimum region of the radial length of the air guide vanes of the flow rectifier almost zero, but this angle grows radially outward and in particular radially inward relatively quickly. This leads to a divergent airflow. For given diameters of the cylindrical lateral surfaces of the walls, which bound radially inwardly and outwardly the rim of the air guide vanes, there is only one under the aspect of equalization of the flow of the fluid optimum blade length, which according to DE 44 04 262 A1 by consuming aerodynamic measurements one Conrad probe was determined. In addition, when using the known flow rectifier, a combination with a protective grid is required to ensure protection against contact.

The present invention is based on the object to provide a flow straightener of the type mentioned above, with the high volume flow and long throw the above-mentioned disadvantages can be overcome.

According to the invention this is achieved in that in the main body two or more wreaths with a plurality of circumferentially distributed around the longitudinal axis around and substantially radially arranged, extending between the lateral surfaces air guide vanes are present.

By virtue of this radial segmentation of the cross-section of the flow rectifier according to the invention, it is advantageously achieved that a swirl of the flowing gas in the outflow of an axial fan is effectively prevented at a constantly high volume flow. A uniform flow pattern is established at a closer distance from the flow straightener in comparison with the known prior art, and the throwing distance increases. A significant divergence of the air flow emerging from the flow straightener according to the invention can be effectively prevented by an increased number of blade rings. With changing dimensions, eg. As the inner and outer diameter of a Axialflugelrades the fan and thus the blade length, resulting in the consequence of corresponding changes in the dimensions of the flow rectifier, no complex measurements and / or optimization calculations must be carried out as blade rings, each with the same radial width and known Efficiency can be ranked side by side.

In the curvature to the axial direction, which the air guide vanes seen in the circumferential direction between each of their inflow side blade edge and their In this case, the inflow angle of the blades can be chosen such that it essentially corresponds to the outflow angle of the blade

Axial fan corresponds, and the outflow angle of the blades may be selected such that the blade is designed in this area parallel to an extending in the direction of the longitudinal axis of the air conveying direction. The respective inflow angles of the air vanes can all be the same size in the various rings, or alternatively vary from ring to ring, in particular depending on the outflow profile of the emerging from the fan fluid.

By selecting a corresponding number of rings with air guide vanes, the number of air vanes themselves and alternatively or additionally preferably by an effective height of the blading, so the arrangement of the air vanes, the rectifier according to the invention can be achieved that the rectifier according to the invention also has a function as contact protection. An additional guard can thus be dispensed with, because the existing between the Kranzwandungen and the air vanes openings so small or especially the axial length of the rectifier can be made so large that a reaching through the hand or with individual fingers to the rotating impeller not possible is. This ensures a safe distance to a rotating impeller of the axial fan.

The number of air vanes can thereby decrease from the outer rings to the inner rings in order to realize in this way in each wreath an approximately equal distance between the respective blades of a series and thus to achieve the lowest possible flow resistance.

The flow straightener according to the invention can be in one piece, preferably as an injection molded plastic, constructed in manufacturing technology little aufwand iger way. It can be designed with advantage such that it subsequently on a wall ring or on a protective or supporting grid of an existing Fan can be detachably mounted. In this case, the attachment can be designed such that the flow rectifier can be removed with only a few simple steps of the fan and easily - for example, in a dishwasher - can be cleaned.

By a suitable choice of material and a corresponding dimensioning of the axial length of the flow straightener according to the invention, it is also possible to ensure a high degree of robustness with respect to externally acting mechanical loads. Thus, when using the flow straightener according to the invention in combination with an evaporator fan a violent

Removal of ice formed from the surface, for example with a

Screwdriver, possible without damaging the rectifier structure. In particular, the relevant strength requirements according to the so-called ball impact test (eg according to UL 2218) of Underwriters Laboratories can be met. Specifically, in this test, a standardized steel ball with a diameter of about 50 mm from different heights (different degrees of sharpening eg 0.38 m, 1, 2 m ...) is dropped onto the flow straightener in free fall. It must survive the impact in such a way that the contact protection function against rotating and electrical parts is still fully in place.

One of the blade edges, in particular the edge on the air guide blade rear side, may preferably have a height that can be changed in the radial direction. In particular, the blade end directed in the outflow direction can have an edge which does not run straight, but which - in particular, for

Noise minimization - provided with a radius.

Between two blade rings, a third ring can be concentrically drawn in each case, which forms a transition between the two rings by being reduced in its axial length and thus adjoins the curved blade end. Each second blade ring ring can thus have a reduced axial length compared to the other, arranged next to it wreaths. Advantageous embodiments of the invention are contained in the subclaims and will be explained in more detail with reference to the embodiments illustrated in the accompanying drawings. Show it:

1 in a perspective exploded view, a preferred embodiment of a flow straightener according to the invention together with an axial fan,

FIG. 2 shows the flow rectifier according to the invention shown in FIG. 1 in the assembled state on the axial fan, FIG.

Fig. 3 is a comparison with Figs. 1 and 2 enlarged and partially cut

perspective view of the flow straightener according to the invention,

4 is a front view of the flow straightener according to the invention,

Fig. 5 shows the embodiment of the flow straightener according to the invention

4 in a partially sectioned longitudinal representation,

6 and 7 in Fig. 5 with VI and VII designated details of

inventive flow straightener in a greatly enlarged view.

In the figures of the drawing, like parts or functionally identical parts are also identified by the same reference numerals. If certain, described and / or removable from the drawings features of the flow straightener according to the invention or its components are mentioned only in connection with the embodiment, but these are also independent of this embodiment as a single feature or in accordance with the invention Combination with other features of the embodiment of meaning and can be claimed as belonging to the invention.

As initially apparent from FIGS. 1 and 2, a flow straightener 1 according to the invention is intended to be used in combination with an axial fan 2. This can be done in particular where, in complex cooling applications, an optimal air distribution in a cold room is crucial, with the entire refrigerated goods having to be circulated uniformly with circulated air. The advantage of using a flow rectifier 1 according to the invention in a cold room is, in particular, that a strong, bundled air flow with a long throw can be provided by it in cooperation with the axial fan 2.

The axial fan 2 can - as shown - in particular be designed as a so-called wall ring fan and comprise a wall ring 2a with a support grid 2b, in which a fan unit 2c is held. The fan unit 2c in this case has a motor, in particular an external rotor motor whose rotor is integrated in a preferred embodiment directly into an axial impeller. The supporting grid 3 of the axial ventilator 2 serving to hold the ventilator unit 2c can be designed in a wide-meshed manner, since it does not have to fulfill the function of a contact protection because it is taken over by the flow rectifier 1.

A flow rectifier 1 according to the invention has - in addition to FIGS. 1 and 2 and FIGS. 3 to 5 - a base body 3, the at least two, but preferably several - in the illustrated embodiment, there are five - wreaths 4a, 4b, 4c, 4d 4e. Each ring 4a, 4b, 4c, 4d, 4e is each bounded by a cylindrical surface radially inwardly and outwardly. Only in FIG. 3, by way of example, are an inner circumferential surface of the central rim 4d with the reference numeral 5 and the outer circumferential surface of the central rim 4d lying opposite it denoted by the reference numeral 6. In each ring 4a, 4b, 4c, 4d, 4e there is a plurality of circumferentially distributed around a longitudinal axis XX of the flow straightener 1 and arranged substantially radially, in each case between the lateral surfaces 5, 6 of the rings 4a, 4b, 4c 4d, 4e extending air guide vanes 7. The air guide vanes 7 run simultaneously - this is in particular exemplified on the illustrated ring 4c shown in Fig. 3 - each seen from an inflow-side blade edge 7a and ending in a downstream blade edge 7b in the circumferential direction curved to the axial direction XX. Due to the curvature R1 to the axial direction XX, which may be determined for example by a circular arc, in particular causes an inflow angle μ _{ζ of} the air to the air guide vane 7 on the upstream vane edge 7a is so large that it is substantially an outflow angle μ _Α the with swirling air from the axial fan 2 corresponds, while the discharge angle μ _{Α of} the air from the

Air guide vanes 7 is selected on the downstream side blade edge 7b such that the air guide blade 7 extends in this area parallel to an extending in the direction of the longitudinal axis X-X air conveying direction. This feature is also shown in Fig. 6 in a particularly clear manner.

The inflow angle μζ of the air to the air guide vane 7 is, as illustrated in FIG. 6, defined as the acute angle between a tangent T _z applied to the inflow side vane edge 7a and the longitudinal axis XX. It may preferably be in the range 20 ° <μζ -S 80 °. The outflow angle μ _Α is defined in the same way with a tangent T _A applied to the outflow-side blade edge 7 b and preferably has the value of 0 °. The inflow angle μ _ζ can be the same in all air vanes 7 located in a ring 4a, 4b, 4c, 4d, 4e, but of the respective inflow angle μ _{ζ of} the air to the air guide vanes 7 in another ring 4a, 4b, 4c , 4d, 4e differ. Here, the inflow angle μ _ζ depending on the outflow profile of the

Axial fan 2 exiting air from wreath 4a, 4b, 4c, 4d, 4e to wreath 4a, 4b, 4c, 4d, 4e be varied. In the illustrated embodiment of the flow straightener 1 according to the invention, the respective inflow angle μ _{ζ of} the air at all air guide vanes 7 is the same. By selecting the appropriate number of each having a same width B having wreaths 4a, 4b, 4c, 4d, 4e with air guide vanes 7 (see Fig. 4) and the number of air vanes 7, by wreath 4a, 4b, 4c, 4d, 4e to wreath 4a, 4b, 4c, 4d, 4e decreases from outside to inside, it is achieved that all the air guide vanes 7 and spaces in which the air guide vanes 7 are respectively or the mutual distances of the air vanes 7 from each other, almost uniform and with the same Size are formed, and therefore also contribute in terms of the desired effects of swirl reduction and increasing the throw in the same way to increase efficiency.

An inventive flow straightener 1 can be carried out in this way also with a very stable honeycomb structure whose strength is additionally increased if - as shown and in particular in Fig. 4 with reference numerals - the upstream blade edges 7a and the downstream blade edges 7b of the air vanes 7 are arranged in each adjacent wreaths 4a, 4b, 4c, 4d, 4e with circumferentially offset V to each other. In this case, the respective distances A, in which the air guide vanes 7 are arranged relative to one another, can preferably be the same in each case. In FIG. 4, in this regard, as an example, such a distance A is indicated between two adjacent upstream edges 7a.

By a selection of a corresponding number of rings 4a, 4b, 4c, 4d, 4e with air guide vanes 7, the number of the air guide vanes 7 itself and alternatively or additionally preferably also by the total height H of the blading (cf., FIGS. 6 and 7) that the axial length L of the flow straightener 1 according to the invention is significantly affected, it can be achieved that the flow straightener 1 according to the invention also assumes a function as contact protection. In order to improve the separation behavior of the air from the blades 7 - and thus for noise reduction - is shown in the preferred

Provision is made that the downstream blade edges 7b have a variable height in the radial direction, in particular a continuously changing height. It can be provided in particular that the outflow side blade edges 7b of the air guide vanes 7 for adjusting the variable height in the radial direction have a curvature R2, which also - as the blade curvature R1 in the circumferential direction - preferably by a circular arc can be described.

Another preferred feature of the flow straightener 1 according to the invention is that in the radial sequence of the rings 4a, 4b, 4c, 4d, 4e with the air guide vanes 7, the rings 4a, 4b, 4c, 4d, 4e respectively different, in particular two, each alternating heights H1, H2. Between every two

Blade rows (rings 4a, 4c, 4e) with peripherally greater height H1 of the blades, which decreases radially inwardly over the width of the rings 4a, 4c, 4e, each concentrically a ring (wreaths 4b, 4d) retracted, the peripheral in its height H2 is reduced, the blade height over the rim width B then increases radially inward again. As a result, the separation of the air guide vanes 7 is improved and the flow resistance at a constant overall, z. B. selected for reasons of protection against contact, axial total length L of the flow straightener 1 according to the invention is reduced in an optimum manner. The profile of the radial curvature R2 of the downstream blade edges 7b of the air guide vanes 7, through which the variable in the radial direction height is preferably adjusted to each blade, in each case adjacent wreaths 4a, 4b, 4c, 4d, 4e mirror images.

That is, if, for example - as illustrated in particular by FIG. 3 - in a ring 4c, the radially outward of a wall with a higher height H1 (outer surface 6) and radially inwardly from a wall with a lower height H2 (inner circumferential surface 5) is bounded, one caused by the curvature R2 Bumping the contour of the blade edge 7a is present radially outward follows in the adjacent wreath 4d, which is bounded radially outward by the wall with the lower height H2 and radially inward by a wall with a greater height H1, caused by the curvature R2 bulge the contour of the blade edge 7a - with respect to the wall between the rings 4c, 4d

mirrored to the curvature R2 in the adjacent wreath 4c - radially inward. With reduced use of material for the flow straightener 1 according to the invention due to the reduced height H2 can be counteracted by this structural design of a refluidization of the flowing air, as it is guided to the greater height H1 to form a laminar boundary layer on the air guide vanes 7.

The invention is not limited to the illustrated and described embodiment, but also includes all the same in the context of the invention embodiments. As shown as preferred, the main body 3 of a flow straightener 1 according to the invention may preferably be made in one piece and preferably as an injection molded plastic, but is also a multi-part design, possibly also of a metallic material, within the scope of the invention.

Furthermore, the person skilled in the art can provide appropriate supplementary technical measures without departing from the scope of the invention. Thus, on the main body 3 fastening means 8, 9 for releasable attachment to the

Axial fan 2, in particular z. B. locking means 8 for connection to the fan 2 associated with this wall ring 2a and / or mounting holes 9 for the passage of screwing to the fan 2 serving screws 10, be present. Also, an axial length co-determining, and therefore possible with a small length to be executed connecting or covering section 1 1 for the axial fan 2 may - as shown - be provided on a flow straightener 1 according to the invention. The total height H of the blading may optimally be in a range of 25 mm to 100 mm, which preferably corresponds to a size in the range 5 percent to 40 percent of the size of the outer diameter of the axial fan.

Furthermore, the invention is not yet limited to the feature combinations defined in claim 1, but may also be any other combination of certain features of all disclosed

Be defined individual characteristics. This means that in principle virtually every individual feature of the independent claim can be omitted or replaced by at least one individual feature disclosed elsewhere in the application. In this respect, the claims are to be understood merely as a first formulation attempt for an invention.

reference numeral

1 flow straightener

2 axial fans

2a wall ring of 2

2b supporting grid of 2

2c fan unit of 2

3 main body of 1

4a first wreath with 7 in 2

4b second wreath with 7 in 2

4c third wreath with 7 in 2

4d fourth wreath with 7 in 2

4th fifth wreath with 7 in 2

5 inner lateral surface of 4a, 4b, 4c, 4d, 4e

6 outer lateral surface of 4a, 4b, 4c, 4d, 4e

7 air guide vane

7a inflow-side blade edge of FIG. 7

7b outflow-side blade edge of FIG. 7

8 locking means on 1 for 2

9 passage opening from 1 to 10

10 screw to connect 1 and 2

A mutual distance of 7 or 7a (Fig. 4)

B width of 4a, 4b, 4c, 4d, 4e (Figure 4)

H total height of the blading with 7 (FIGS. 6, 7)

H1 greater height of 7 (Fig. 3) H2 smaller height of 7 (Fig. 3)

L axial length of 1 (Fig. 3, 5)

R1 circumferential curvature of 7 in the direction X-X (FIGS. 3, 6)

R2 radial curvature of 7b in the direction X-X (FIGS. 3, 7)

T _z tangent to 7a

T _A tangent to 7b

V circumferential displacement of 7 against each other (FIG. 4)

XX longitudinal axis of 1 μ _ζ inflow angle of the air at 7 (between T _z and XX) μ _Α outflow angle of the air of 7 (between T _A and XX)

Claims

claims

1 . Flow rectifier (1) for an axial fan (2), comprising a main body (3) having a respective of cylindrical lateral surfaces (5, 6) radially inwardly and outwardly bounded rim (4a, 4b, 4c, 4d, 4e) with a plurality of distributed in the circumferential direction about a longitudinal axis (XX) around and in

Essentially arranged radially, between the lateral surfaces (5, 6) extending air guide vanes (7), wherein the air guide vanes (7) seen in the circumferential direction in each case between an upstream side

Vane edge (7a) and a downstream vane edge (7b) with a curvature (R1) to the axial direction (X-X),

characterized in that in the base body (3) two or more rings (4a, 4b, 4c, 4d, 4e) distributed with a plurality of circumferentially about the longitudinal axis (XX) and arranged substantially radially, between the lateral surfaces (5 , 6) extending air guide vanes (7) are present.

2. Flow rectifier (1) according to claim 1,

characterized in that at least one of the blade edges (7a, 7b) of the air guide vanes (7), in particular the downstream blade edge (7b), a variable height in the radial direction, in particular a continuously changing height.

3. flow rectifier (1) according to claim 2,

characterized in that the blade edge (7b) of the air guide vane (7), which has the variable in the radial direction height, a

Curvature (R2), in particular a circular arc-shaped curvature has.

4. flow rectifier (1) according to one of claims 1 to 3, characterized in that at the curvature (R1) to the axial direction (XX). which have the air guide vanes (7) seen in the circumferential direction in each case between its inflow-side blade edge (7a) and its downstream blade edge (7b), the inflow angle (μ _ζ ) of the air to the

Air guide vane (7) is selected such that it substantially a

Outflow angle (μ _Α ) corresponds to the air from the axial fan (2), on which the base body (3) is mounted, and that the outflow angle (μ _Α ) of the air from the air guide vanes (7) is selected such that the air guide vane (7 ) is executed in this area parallel to an in the direction of the longitudinal axis (XX) extending air conveying direction.

5. flow rectifier (1) according to one of claims 1 to 4,

characterized in that one / the inflow angle of the air (μ _ζ ) on all air guide vanes (7) is equal.

6. flow rectifier (1) according to one of claims 1 to 4,

characterized in that one / the respective inflow angle (μ _ζ ) of the air at all in a ring (4a, 4b, 4c, 4d, 4e) lying air guide vanes (7) is the same size, however, from the respective inflow angle (μζ) of Air on the air guide vanes (7) in another ring (4a, 4b, 4c, 4d, 4e) differs.

7. flow rectifier (1) according to claim 6,

characterized in that the respective inflow (μ _ζ ) of the air at the air guide vanes (7) in dependence on the outflow profile of the air exiting from the axial fan (2) of wreath (4a, 4b, 4c, 4d, 4e) to wreath (4a, 4b, 4c, 4d, 4e) varies.

8. flow rectifier (1) according to one of claims 1 to 7, characterized in that the base body (3) in one piece and

is preferably designed as an injection molded part, in particular made of plastic.

9. flow rectifier (1) according to one of claims 1 to 8,

characterized in that in all wreaths (4a, 4b, 4c, 4d, 4e)

Openings between the air guide vanes (7) so small and / or

in particular, an axial height (H) of the arrangement of the air guide vanes (7) is designed so large that a reaching through the hand or with individual fingers to the rotating impeller is not possible.

10. Flow rectifier (1) according to one of claims 1 to 9,

characterized in that on the base body (3) fastening means (8, 9) for releasable attachment to the axial fan (2), in particular z. B. locking means (8) for connection to a axial fan (2) associated wall ring (2 a) and / or mounting holes (9) for the passage of the screw with the axial fan (2) serving screws (10) are present.

1 1. Flow rectifier (1) according to one of claims 1 to 10,

characterized in that a number of air vanes (7) of wreath (4a, 4b, 4c, 4d, 4e) arranged within a ring (4a, 4b, 4c, 4d, 4e) are turned into wreath (4a, 4b, 4c, 4d, 4e) decreases radially inwardly, so that in each ring (4a, 4b, 4c, 4d, 4e) there is an approximately equal distance (A) between the respective air guide vanes (7).

12. Flow rectifier (1) according to one of claims 1 to 1 1,

characterized in that in the radial sequence of the rings (4a, 4b, 4c, 4d, 4e) with the air guide vanes (7), these rings (4a, 4b, 4c, 4d, 4e) each have different heights (H1, H2), in particular two, each of wreath (4a, 4b, 4c, 4d, 4e) to garland (4a, 4b, 4c, 4d, 4e) alternating heights H1, H2 have.

13. Flow rectifier (1) according to claims 3 and 12,

characterized in that the respective course of the radial curvature (R2) of the blade edges (7b), through which in the radial direction

variable height is preferably set to each air guide vane (7), in each adjacent wreaths (4a, 4b, 4c, 4d, 4e)

Mirror image is executed to each other.

14. Flow rectifier (1) according to one of claims 1 to 3,

characterized in that in the radial sequence of the rings (4a, 4b, 4c, 4d, 4e) the upstream blade edges (7a) and the downstream blade edges (7b) of the air guide vanes (7) in each adjacent wreaths (4a, 4b, 4c , 4d, 4e) are arranged with circumferential offset (V) to each other.