EP2904277B1 - Flow rectifier for an axial fan - Google Patents

Description

The present invention relates to a flow straightener for an axial fan according to claim 1.

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

Axial fans are used, for example, in evaporators in cold rooms, where the cold air is distributed through the axial fan into the cold room via the heat exchanger. In the case of large cold rooms, it is important that the cold air is transported as far into the room as possible in order to also cool the chilled goods at a location further away. This requires an axial fan that provides the highest possible volume flow with a large throw. Throw distance is understood to mean a distance up to which a limit speed of the air flow is maintained. Due to the swirling outflow of an axial fan, this throw distance is limited. With the help of a downstream flow straightener, which converts the twist back into a uniform axial flow, the throw distance can be significantly increased. It is important that the flow straightener has a has the lowest possible flow resistance, so that there is only an insignificant drop in pressure in the amount of air flowing through it.

A flow straightener of the type mentioned, which basically meets the above requirements, is from DE 44 04 262 A1 known. A reduction in swirl of the flow medium is achieved in particular in that the air guide vanes, viewed in the circumferential direction, each run curved to the axial direction between an inflow-side vane edge and an outflow-side vane edge. In a special embodiment, it is also provided that one of the blade edges, specifically the edge on the front side of the stator blade, has a variable height in the radial direction. It is straight and runs inclined to the center axis of the impeller. Any effect associated with this embodiment is not described.

The disadvantage of this known flow straightener is that an actually uniform axial flow only sets in at a considerable distance from the fan or from the exit from the guide wheel. So is like the in the DE 44 04 262 A1 included 1 As illustrated, an angle between the air flow and the fan axis is almost zero in a peripheral optimum range of the radial length of the air guide vanes of the flow straightener, but this angle increases relatively rapidly radially outwards and in particular radially inwards. This results in a divergent airflow. With given diameters of the cylindrical lateral surfaces of the walls, which delimit the ring of the air guide vanes radially inside and outside, there is only one vane length that is optimal from the point of view of equalizing the flow of the fluid, which according to the DE 44 04 262 A1 was determined by complex aerodynamic measurements with a Conrad probe. In addition, when using the known flow straightener, a combination with a protective grid is required in order to ensure protection against accidental contact.

Furthermore disclosed U.S. 2005/0186070 A1 discloses a fan assembly having an impeller mounted on the rotor of a motor. The impeller is of a casing surrounded, wherein the housing comprises a arranged downstream of the impeller flow straightener. The blades of the flow straightener have a constant height in the radial direction.

The present invention is based on the object of creating a flow straightener of the type mentioned at the outset, with which the disadvantages mentioned above can be overcome with a high volume flow and large throw distance.

The blade edge of the air guide blade, which has the height changing in the radial direction, has a curvature.

Due to the existing radial segmentation of the cross section of the flow straightener, it is advantageously achieved that a swirl of the flowing gas in the outflow of an axial fan is prevented more effectively with a consistently high volume flow. In comparison with the known state of the art, a uniform flow pattern occurs at a smaller distance from the flow straightener, and the throw 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. If the dimensions change, e.g. B. the inner and outer diameter of an axial impeller of the fan and thus the blade length, which subsequently result in corresponding changes in the dimensions of the flow straightener, no complex measurements and / or optimization calculations have to be carried out, since blade rings with the same radial width and known efficiency can be lined up next to each other.

With the curvature to the axial direction, which the air guide vanes each have between their inflow-side vane edge and their outflow-side vane edge, viewed in the circumferential direction, the inflow angle of the vanes can be selected in such a way that it essentially corresponds to the outflow angle of the axial fan, and the outflow angle of the vanes can be such be chosen that the blade in this area is designed parallel to an air conveying direction running in the direction of the longitudinal axis. The respective inflow angles of the air guide vanes can all be the same size in the different rings, or alternatively vary from ring to ring, in particular depending on the outflow profile of the flow medium emerging from the fan.

By choosing a corresponding number of rings with air guide vanes, the number of air guide vanes themselves and, alternatively or additionally, also preferably by an effective height of the blading, i.e. the arrangement of the air guide vanes, of the rectifier according to the invention, it can be achieved that the rectifier according to the invention also has a function as protection against accidental contact. An additional protective grille can therefore be dispensed with because the openings between the rim walls and the air guide vanes can be designed so small or, in particular, the axial length of the rectifier can be designed so large that it is not possible to reach through with the hand or individual fingers to the rotating impeller is. This ensures a safe distance from a rotating impeller of the axial fan.

According to the invention, the number of air guide vanes decreases from the outer rims to the inner rims in order in this way to be able to realize an approximately equal distance between the respective vanes of a row in each rim and thus to achieve the lowest possible flow resistance.

The flow straightener according to the invention can be constructed in one piece, preferably as an injection-molded part made of plastic, in a manner that is not very complex in terms of production technology. It can advantageously be designed in such a way that it can subsequently be releasably mounted on a wall ring or on a protective or support grid of an already existing fan. The fastening can be designed in such a way that the flow straightener can be removed from the fan in just a few movements and easily cleaned, for example in a dishwasher.

Through 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 regard to mechanical loads acting from the outside. Thus, when using the flow straightener according to the invention in combination with an evaporator fan, ice that has formed can be forcibly removed from the surface, for example with a screwdriver, without damaging the straightener structure. In particular, the relevant strength requirements according to the so-called ball impact test (e.g. according to UL 2218) of the Underwriters Laboratories can also be met. Specifically, in this test, a standardized steel ball with a diameter of approx. 50 mm is dropped from different heights (different degrees of sharpness, e.g. 0.38m, 1.2m ...) in free fall onto the flow straightener. It must survive the impact in such a way that the contact protection function against rotating and electrical parts is still fully available.

One of the blade edges, in particular the edge on the rear side of the air guide blade, has a variable height in the radial direction.

In this case, the blade end directed in the outflow direction has an edge which does not run straight but which—particularly to minimize noise—is provided with a radius.

A third ring can be drawn in concentrically between two blade rings, which forms a transition between the two rings by being reduced in its axial length and thus adjoining the curved blade end. Each second bladed ring can thus have a reduced axial length compared to the other rings arranged next to it.

Fig. 1

in perspektivischer Explosionsdarstellung, eine bevorzugte Ausführung eines erfindungsgemäßen Strömungsgleichrichters zusammen mit einem Axiallüfter,

Fig. 2

den in Fig. 1 dargestellten erfindungsgemäßen Strömungsgleichrichter im Montagezustand an dem Axiallüfter,

Fig. 3

eine gegenüber Fig. 1 und 2 vergrößerte und teilgeschnittene perspektivische Ansicht des erfindungsgemäßen Strömungsgleichrichters,

Fig. 4

eine Frontansicht des erfindungsgemäßen Strömungsgleichrichters,

Fig. 5

die Ausführung des erfindungsgemäßen Strömungsgleichrichters gemäß Fig. 4 in einer teilgeschnittenen Längsdarstellung,

Fig. 6 und 7

die in Fig. 5 mit VI und VII bezeichneten Einzelheiten des erfindungsgemäßen Strömungsgleichrichters in einer stark vergrößerten Darstellung.

Advantageous embodiments of the invention are contained in the subclaims and are explained in more detail with reference to the exemplary 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,

2

the in 1 illustrated flow rectifier according to the invention in the assembled state on the axial fan,

3

one opposite Figures 1 and 2 enlarged and partially sectioned perspective view of the flow straightener according to the invention,

4

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

figure 5

the design of the flow straightener according to the invention 4 in a partially sectioned longitudinal view,

Figures 6 and 7

in the figure 5 with VI and VII designated details of the flow straightener according to the invention in a greatly enlarged view.

In the figures of the drawing, the same parts or parts with the same function are also identified by the same reference symbols. If certain features of the flow straightener according to the invention or its components that are described and/or can be taken from the drawings are only mentioned in connection with the exemplary embodiment, these are also independent of this exemplary embodiment according to the invention as an individual feature or in combination with other features of the exemplary embodiment of importance and can be claimed as pertaining to the invention.

How first off Figures 1 and 2 shows, 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 optimal air distribution in a cold room is crucial in complex cooling applications, where the entire refrigerated goods must be evenly circulated with circulated air. The advantage of using a flow straightener 1 according to the invention in a cooling room consists in particular in the fact that it can provide a strong, bundled air flow with a large throw distance in cooperation with the axial fan 2 .

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

A flow straightener 1 according to the invention has - this show next Figures 1 and 2 also Figures 3 to 5 - A base body 3, which comprises 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 delimited radially on the inside and outside by a cylindrical outer surface. Only in 3 In this regard, an inner lateral surface of the middle ring 4d is given the reference number 5 and the outer lateral surface of the middle ring 4d lying opposite it is given the reference number 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 essentially radially, each between the lateral surfaces 5, 6 of the rings 4a, 4b, 4c, 4d , 4e running air guide vanes 7. The air guide vanes 7 run at the same time - for this purpose, the rim 4c shown in section in 3 referred - each starting from an inflow-side blade edge 7a and ending in an outflow-side blade edge 7b, viewed in the circumferential direction, curved relative to the axis direction XX. through the Curvature R1 to the axis direction XX, which can be determined, for example, by an arc of a circle, has the effect, in particular, that an inflow angle µ _Z of the air to the air guide vane 7 at the inflow-side vane edge 7a is so large that it essentially corresponds to an outflow angle µ _A of the twist tainted air from the axial fan 2, while the deflection angle µ _A of the air from the air guide vanes 7 at the outflow-side blade edge 7b is selected in such a way that the air guide vane 7 in this area runs parallel to an air conveying direction running in the direction of the longitudinal axis XX. This feature is also 6 in a particularly clear way.

The inflow angle μ _Z of the air to the air guide vane 7 is how 6 1, defined as the acute angle between a tangent T _Z applied to the leading blade edge 7a and the longitudinal axis XX. It can preferably be in the range of 20°≦ _μZ ≦80°. The outflow angle μ _A is defined in the same way with a tangent T _A applied to the outflow-side blade edge 7b and preferably has the value of 0°. The inflow angle μ _Z can be the same on all air guide vanes 7 in a ring 4a, 4b, 4c, 4d, 4e, but differ from the respective inflow angle μ _Z of the air on the air guide vanes 7 in another ring 4a, 4b, 4c , 4d, 4e differ. Here, the inflow angle μ _Z can be varied depending on the outflow profile of the air emerging from the axial fan 2 from ring 4a, 4b, 4c, 4d, 4e to ring 4a, 4b, 4c, 4d, 4e.

In the illustrated embodiment of the flow straightener 1 according to the invention, the respective inflow angle μ _Z of the air is the same on all air guide vanes 7 . By choosing the appropriate number of rings 4a, 4b, 4c, 4d, 4e, each having the same width B, with air guide vanes 7 (see 4 ) and the number of air guide vanes 7, which decreases from ring 4a, 4b, 4c, 4d, 4e to ring 4a, 4b, 4c, 4d, 4e from the outside inwards, it is achieved that all air guide vanes 7 and spaces in which the Air guide vanes 7 are each located or the mutual distances of the air guide vanes 7 from each other, are formed almost uniformly and with the same size, and therefore also with regard to the desired Effects of reducing the twist and increasing the throwing distance contribute in the same way to increasing efficiency.

In this way, a flow straightener 1 according to the invention can also be designed with a very stable honeycomb structure, the strength of which is additionally increased if--as shown and in particular in FIG 4 denoted by reference symbols - the inflow-side blade edges 7a and the outflow-side blade edges 7b of the air guide vanes 7 are arranged in adjacent rings 4a, 4b, 4c, 4d, 4e with a circumferential offset V relative to one another. The respective distances A, in which the air guide vanes 7 are arranged in relation to one another, can preferably each be of the same size. In 4 in this regard, the distance A between two adjacent edges 7a on the inflow side is specified as such an example.

By choosing a corresponding number of rings 4a, 4b, 4c, 4d, 4e with air guide vanes 7, the number of air guide vanes 7 themselves and alternatively or additionally also preferably by the total height H of the blading (cf. Figures 6 and 7 ), by which the axial length L of the flow straightener 1 according to the invention is significantly influenced, it can be achieved that the flow straightener 1 according to the invention also assumes a function as protection against accidental contact.

In order to improve the detachment behavior of the air from the blades 7—and associated noise reduction—the illustrated embodiment provides that the outflow-side blade edges 7b have a variable height in the radial direction, in particular a constantly changing height. It is provided that the outflow-side blade edges 7b of the air guide vanes 7 have a curvature R2 for setting the variable height in the radial direction, which likewise—like the blade curvature R1 in the circumferential direction—can preferably be described by an arc of a circle.

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 each have different, in particular two, alternating heights have H1, H2. Between two rows of blades (rings 4a, 4c, 4e) with a peripherally greater height H1 of the blades, which decreases radially inward over the width of the rings 4a, 4c, 4e, a ring (rings 4b, 4d) is drawn in concentrically, the peripheral is reduced in its height H2, whereby the blade height over the rim width B then increases again radially inwards. This improves the detachment from the air guide vanes 7 and the flow resistance with an overall constant z. B. for reasons of protection against accidental contact, the total axial length L of the flow straightener 1 according to the invention is reduced in an optimal manner. The course of the radial curvature R2 of the outflow-side blade edges 7b of the air guide vanes 7, through which the variable height in the radial direction is preferably set on each blade, can run in mirror image in adjacent rings 4a, 4b, 4c, 4d, 4e.

That is, if, for example - as in particular by 3 is illustrated - in a ring 4c, which is delimited radially on the outside by a wall with a greater height H1 (outer lateral surface 6) and radially on the inside by a wall with a lower height H2 (inner lateral surface 5), a bulging of the contour caused by the curvature R2 of the blade edge 7a is present radially outwards, follows in the adjacent ring 4d, which is delimited radially on the outside by the wall with the smaller height H2 and radially on the inside by a wall with a greater height H1, a bulging caused by the curvature R2 of the contour of the Blade edge 7a - in relation to the wall between the rims 4c, 4d mirror-inverted to the curvature R2 in the adjacent rim 4c - radially inwards. With reduced use of material for the flow straightener 1 according to the invention due to the reduced height H2, this structural design can counteract back-turbulence of the flowing air, since this is guided up to the greater height H1, forming a laminar boundary layer on the air guide vanes 7.

The invention is not limited to the exemplary embodiment shown and described, but also includes all embodiments that have the same effect within the meaning of the invention. As shown as preferred, the base body 3 of a flow straightener 1 according to the invention can preferably be designed in one piece and preferably as an injection molded part made of plastic, but a multi-part design, optionally also made of a metallic material, is also 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. So the base body 3 fasteners 8, 9 for releasable attachment to the axial fan 2, in particular z. B. latching means 8 for connection to the wall ring 2a associated with this fan 2 and/or fastening openings 9 for the passage of screws 10 serving for screwing to the fan 2. A connecting or covering section 11 for the axial fan 2 can also be provided on a flow straightener 1 according to the invention, as illustrated, which also determines the axial length in an increasing manner and is therefore to be designed with as short a length as possible.

The total height H of the blading can optimally be in a range from 25 mm to 100 mm, which preferably corresponds to a size in the range from 5 percent to 40 percent of the size of the outside diameter of the axial fan wheel.

Reference sign

1

flow straightener

2

axial fan

2a

wall ring of 2

2 B

Support grid from 2

2c

Fan unit from 2

3

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

4e

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

upstream blade edge of 7

7b

downstream blade edge of 7

8th

Latch means on 1 for 2

9

Passage opening of 1 for 10

10

Screw connecting 1 and 2

A

mutual distance of 7 or 7a ( 4 )

B

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

H

Overall height of blading with 7 ( Figures 6, 7 )

H1

greater height of 7 ( 3 )

H2

smaller height of 7 ( 3 )

L

axial length of 1 ( 3 , 5 )

R1

circumferential curvature of 7 in direction XX ( 3 , 6 )

R2

radial curvature of 7b towards XX ( 3 , 7 )

TZ

Tangent to 7a

TA

Tangent to 7b

V

circumferential offset of 7 to each other ( 4 )

X-X

longitudinal axis of 1

µZ

Airflow angle at 7 (between T _Z and XX)

µA

Air flow angle of 7 (between T _A and XX)

Claims (13)

1. Flow rectifier (1) for an axial fan (2), having a base body (3), which comprises a ring that is delimited radially inside and outside, in each case, by cylindrical curved surface areas (5, 6), said ring (4a, 4b, 4c, 4d, 4e) having a plurality of air guide blades (7), which are distributed in a circumferential direction about a longitudinal axis (X-X), and which are disposed in an essentially radial manner such that they extend between the curved surface areas (5, 6), wherein, when viewed in a circumferential direction, the air guide blades (7) extend with a curvature (R1) relative to the axial direction (X-X), in each case extending between an inflow-side blade edge (7a) and an outflow-side blade edge (7b), characterized in that two or more rings (4a, 4b, 4c, 4d, 4e) are provided in the base body (3), said rings having a plurality of air guide blades (7), which are distributed in a circumferential direction about the longitudinal axis (X-X), and which are disposed in an essentially radial manner such that they extend between the curved surface areas (5, 6), wherein two or more rings (4a, 4b, 4c, 4d, 4e) are provided in the base body (3), said rings having a plurality of in air guide blades (7), which are distributed in a circumferential direction about the longitudinal axis (X-X), and which are disposed in an essentially radial manner such that they extend between the curved surface areas (5, 6), wherein at least the outflow-side blade edge (7b) of the air guide blades (7) has a height that can be changed in a radial direction, wherein the outflow-side blade edge (7b) of the air guide blade (7), which has an adjustable height in the radial direction, has a curvature (R2), characterized in that the number of air guide blades (7) disposed within a ring (4a, 4b, 4c, 4d, 4e) decrease from ring (4a, 4b, 4c, 4d, 4e) to ring (4a, 4b, 4c, 4d, 4e) moving radially inward, so that almost the same spacing (A) between the respective air guide blades (7) exists in each ring (4a, 4b, 4c, 4d, 4e).
2. Flow rectifier (1) according to Claim 1, characterized in that the blade edge (7a, 7b) has an adjustable height in the radial direction.
3. Flow rectifier (1) according to one of the preceding claims, characterized in that the blade edge (7b) of the air guide blade (7), which has an adjustable height in the radial direction, has a circular arc-shaped curvature.
4. Flow rectifier (1) according to one of the preceding claims, characterized in that, in the case of the curvature (R1) relative to the axial direction (XX), which each of the air guide blades (7) has, viewed in a circumferential direction, between the inflow-side blade edge (7a) thereof and the outflow-side blade edge (7b), the inflow angle (µZ) of the air to the air guide blade (7) is selected in such a way that said angle essentially corresponds to an outflow angle (µA) of the air out of the axial fan (2), on which the base body (3) is mounted, and in that the outflow angle (µA) of the air from the air guide blades (7) is selected in such a way that, in this region, the air guide blade (7) is designed such that it extends parallel to an air flow direction, which extends in the direction of the longitudinal axis (X-X).
5. Flow rectifier (1) according to one of the preceding claims, characterized in that the respective inflow angle (µ_z) of the air is identical at all air guide blades (7).
6. Flow rectifier (1) according to one of Claims 1 through 4, characterized in that the respective inflow angle (µ_z) of the air is identical at all of the air guide blades (7) that are located in a ring (4a, 4b, 4c, 4d, 4e), however said angle may differ from the respective inflow angle (µ_z) of the air at the air guide blades (7) in another ring (4a, 4b, 4c, 4d, 4e).
7. Flow rectifier (1) according to Claim 6, characterized in that the respective inflow angle (µZ) of the air at the air guide blades (7) varies from ring (4a, 4b, 4c, 4d, 4e) to ring (4a, 4b, 4c, 4d, 4e) as a function of the outflow profile of the air leaving the axial fan (2).
8. Flow rectifier (1) according to one of the preceding claims, characterized in that the base body (3) is designed one-part, and in particular designed as an injection-molded component, in particular made from plastic.
9. Flow rectifier (1) according to one of the preceding claims, characterized in that in all of the rings (4a, 4b, 4c, 4d, 4e), openings between the air guide blades (7) are designed such that they are small enough and/or in particular, an axial height (H) of the assembly of the air guide blades (7) is designed such that it is large enough that it is not possible to reach a hand or an individual finger through to the rotating impeller.
10. Flow rectifier (1) according to one of the preceding claims, characterized in that fasteners (8, 9) are provided on the base body (3) for releasable attachment to the axial fan (2), in particular a catch means (8) for connection to a wall ring (2a) associated with the axial fan (2) and/or mounting openings (9), through which screws (10) serving as the screw connection to the fan (2) may pass.
11. Flow rectifier (1) according to one of the preceding claims, characterized in that in the radial sequence of the rings (4a, 4b, 4c, 4d, 4e) with the air guide blades (7), these rings (4a, 4b, 4c, 4d, 4e) each have different heights (H1, H2), in particular two heights (H1, H2), which each alternate from ring (4a, 4b, 4c, 4d, 4e) to ring (4a, 4b, 4c, 4d, 4e).
12. Flow rectifier (1) according to Claim 11, characterized in that the respective course of the radial curvature (R2) of the blade edges (7b), using the height, which is adjustable height in the radial direction, may be adjusted, in particular on each blade (7), is designed such that the radial curvatures in adjacently located rings (4a, 4b, 4c, 4d, 4e) are a mirror image of one another.
13. Flow rectifier (1) according to one of the preceding claims, characterized in that, in the radial sequence of the rings (4a, 4b, 4c, 4d, 4e), the inflowside blade edges (7a) and the outflow-side blade edges (7b) of the air guide blades (7) in the respective, adjacently located rings (4a, 4b, 4c, 4d, 4e) are disposed having a circumferential offset (V) relative to one another.

Images