EP3308030B1 - Flow-conducting grille for arranging on a fan - Google Patents

Description

The invention relates to a flow guide grille for arrangement on the suction side of a fan, with a grating web structure which comprises radial webs spaced in the circumferential direction and coaxial circumferential webs spaced in the radial direction.

From a standing start, for example, the sponsorship application EP 2 778 432 A1 , generic flow guide grids are known.

Due to constant further development, fans are becoming ever quieter during operation. The noise level is now so low that rotating tones become clearer emerge. Rotation tones are narrow-band, tonal sound components, which are also referred to as propeller noise. The rotary tones occur in particular in an asymmetrical suction situation, which is present, for example, on the suction side when the device walls are close to one another. Then strong air vortices can form, which connect to the so-called vortex braids at the narrowest points and directly hit the rotating impeller blades.

The known flow baffles have a lattice structure with straight radial webs running radially outward and constant inclined peripheral webs. This structure is not optimal in certain installation situations with regard to the resulting rotary tones.

Against this background, the invention is based on the object of providing a flow guide grille which reduces rotary tones in fans, the air flow of which takes place in particular from the radial direction.

This object is achieved by the combination of features according to claim 1.

According to the invention, a flow guide grille is proposed for arrangement on the suction side of a fan with a grating web structure which comprises radial webs spaced in the circumferential direction and coaxial circumferential webs spaced in the radial direction. The radial webs of at least one quadrant of the flow guide grid are each curved over their radial extent in the circumferential direction towards a predetermined radial plane extending from a central axis of the flow guide grid.

The radial plane to which the radial webs bend in the circumferential direction is aligned or mounted in such a way that it points in a main inflow direction of the sucked-in air. It is therefore defined according to the invention as a zero degree radial plane delimiting a first quadrant.

The curvature of the radial webs and in particular their respective curved radial end offer a flow situation which changes the flow and reduces the rotary tones of the fan connected downstream. Due to the special geometry, the inflow is not constant over the circumference and is not directed towards the center of the axis of the flow guide grille.

In an advantageous embodiment variant, it is provided that the radial webs of two adjacent quadrants of the flow guide grille are each curved over their radial extent in the circumferential direction toward the predetermined radial plane. In particular, these are the two adjacent quadrants of the flow guide grille, which point in the main inflow direction of the intake air.

In a further advantageous embodiment variant, the radial webs of all four quadrants of the flow guide grille are curved in the circumferential direction towards the predetermined radial plane, viewed over their radial extent. This is particularly advantageous if there is only one radial main inflow direction due to the installation, which is then determined such that it runs along the extent of the zero degree radial plane.

The radial webs bend in the shape of an arc in the circumferential direction, the angle of curvature being variable over their radial extent. The curvature of the radial webs is preferably less in a region close to the central axis of the flow guide grille than in their respective radial ends.

At their respective radial ends, the radial webs determine an angle a, which is formed from a straight line each extending from a central axis of the flow guide grille to the respective radial end of the respective radial web and an imaginary curvature-free extension of the respective radial web beyond its respective radial end. According to the invention it is provided that the angle α varies with different radial webs. This means that the radial webs have a different curvature at their respective radial ends and their shape is dependent on each are adjusted by the inflow direction.

• α(ρ) = r1^∗ρ für 0°≤ρ≤45°,
• α(ρ) = 90^∗r1-r1^∗ρ für 45°<ρ≤90°,
• α(ρ) = -90^∗r1 +r1^∗ρ für 90°<ρ≤135°,
• α(ρ) = 180^∗r1-r1^∗ρ für 135°<ρ≤180°,
• wobei r1 in einem Bereich von 0,6 bis 1,2, weiter bevorzugt in einem Bereich von 0,8 bis 1,0 liegt.

The curvature of the individual radial webs is adjusted in the circumferential direction, an angle ρ being determined in the circumferential direction starting from the zero degree radial plane. The zero degree radial plane preferably runs in the main inflow direction. The radial webs, which are spaced apart at a predetermined angle ρ in the circumferential direction, determine the angle α at their radial ends, which according to the invention varies with the function depending on the angle ρ:

• α (ρ) = r1 ^∗ ρ for 0 ° ≤ρ≤45 °,
• α (ρ) = 90 ^∗ r1-r1 ^∗ ρ for 45 ° <ρ≤90 °,
• α (ρ) = -90 ^∗ r1 + r1 ^∗ ρ for 90 ° <ρ≤135 °,
• α (ρ) = 180 ^∗ r1-r1 ^∗ ρ for 135 ° <ρ≤180 °,
• wherein r1 is in a range from 0.6 to 1.2, more preferably in a range from 0.8 to 1.0.

Seen in the circumferential direction across two quadrants (ρ = 0 - 180 °), this leads to a different curvature of the individual radial webs towards the zero degree radial plane pointing in the main inflow direction, with the curvature in the first quadrant initially becoming stronger and then becoming weaker again (ρ = 0 - 90 °) and second quadrant (ρ = 90 - 180 °). In a further development of the invention, the circumferential webs also have a defined shape. In an advantageous embodiment, the circumferential webs are convex along their axial extent and at least partially pointing in the direction of the central axis of the flow guide grille. The axial extent is defined as the extent along the central axis of the flow guide grille.

In the case of the flow guide grille according to the invention, a further development provides that at least one of the circumferential webs has an average axial extent that is opposite the central axis of the flow guide grille runs inclined by an angle β. The average axial extent is formed from an axial start point and an axial end point of the respective circumferential web and thus takes into account a possible convex shape of the circumferential webs.

In an embodiment variant which has an advantageous effect on the reduction of rotary tones, the inclination angle β changes over at least one, preferably all, circumferential webs over its course in the circumferential direction. This leads to a further adaptation of the geometry of the flow guide grille as a function of the inflow direction, as is already done by the radial webs.

The changing angle of inclination β of the circumferential webs is determined according to the formula β = a + b ^∗ cos (ρ), where a is an average value of the angle β over the circumference of the respective circumferential web, b is a defined fluctuation value and ρ is the angle in the circumferential direction based on the Corresponds to the zero degree radial plane. Here b is in a range from b _min = 2 * e ^{-0.022 ∗ a} to b _max = 16 * e ^{- 0.02.2 ∗ a} , preferably b _min = 7 * e ^{-0.022 ∗ a} to b _max = 12 ^∗ e ^{-0.022 ∗ a} determined.

Depending on the number of main radial inflow directions, the flow guide grille is adapted with regard to its radial and circumferential webs in order to produce a partially symmetrical or asymmetrical geometry. In the case of only one main inflow direction, the two adjacent quadrants of the flow guide grille are mirror-symmetrical with respect to the zero degree radial plane. In other words, the two quadrants that the main flow meets have the same mirrored shape.

Fig. 1

eine Draufsicht auf ein Strömungsleitgitter;

Fig. 2a

ein seitliche Schnittansicht A-A des Strömungsleitgitters aus Fig. 1;

Fig. 2b

ein seitliche Schnittansicht B-B des Strömungsleitgitters aus Fig. 1;

Fig. 3

ein Diagramm mit Darstellung der Entwicklung des Winkels α der einzelnen Radialstege in Umfangsrichtung;

Fig. 4

ein Diagramm mit Darstellung der Entwicklung des Neigungswinkels β der einzelnen Umfangsstege in Umfangsrichtung;

Fig. 5

ein Diagramm mit bevorzugtem Korridor der Werte des Mittelwerts des Winkels β über dem Umfang und dem Schwankungswert b.

Other advantageous developments of the invention are characterized exclusively in the subclaims. A preferred embodiment is shown below together with the description based on the figures. Show it:

Fig. 1

a plan view of a flow guide grid;

Fig. 2a

a side sectional view AA of the flow guide from Fig. 1 ;

Fig. 2b

a side sectional view BB of the flow guide from Fig. 1 ;

Fig. 3

a diagram showing the development of the angle α of the individual radial webs in the circumferential direction;

Fig. 4

a diagram showing the development of the angle of inclination β of the individual circumferential webs in the circumferential direction;

Fig. 5

a diagram with a preferred corridor of the values of the mean value of the angle β over the circumference and the fluctuation value b.

In the Figures 1-2 An embodiment of a flow guide grille 1 according to the invention with a main inflow direction is shown in different views. The same reference symbols designate the same parts in all views.

Figure 1 shows a plan view of the flow guide grille 1 with a grid web structure, which is designed for arrangement on the suction side of a fan. On the radial Three tabs 5 are provided on the outer edge for attachment to the fan. The grid web structure is formed by radial webs 2 spaced in the circumferential direction and coaxial circumferential webs 3 spaced in the radial direction. The radial webs 2 have different lengths and extend from their radial edge 4 to a circumferential web 3 in the direction of the central axis of the flow guide grid 1 leads to the fact that the mesh size in the radial outer area is smaller than in the central area around the central axis.

The main inflow direction is represented by the arrow P and runs along the zero degree radial plane NR, which extends radially outward from the central axis. The flow guide grille 1 has a geometry optimized for this main inflow direction, the radial webs 2 and circumferential webs 3 in the four quadrants 1Q-4Q being adapted for this in terms of their shape and extent. In the first and fourth quadrants 1Q, 4Q and in the second and third quadrants 2Q, 3Q, the flow guide grating is mirror-symmetrical to one another. The radial webs 2 of the flow guide grid 1 are curved in all four quadrants 1Q-4Q, viewed over their radial extent in the circumferential direction towards the zero degree radial plane NR. The arcuate curvature of the individual radial webs 2 varies depending on their position in the circumferential direction (angle p) within the individual quadrants. The curvature becomes stronger within a quadrant in the circumferential direction and then decreases again. At their radial ends 4, the individual radial webs 2 each determine a varying angle a, α being formed on each radial web 2 from the straight line G extending from the central axis of the flow guide grille 1 to the respective radial end 4 of the respective radial web 2 and the imaginary curvature-free one Extension V of the respective radial web 2 beyond its respective radial end 4.

• α(ρ) = 0,89*ρ für 0°≤ρ45°, α(ρ) = 90*0,89-0,89*ρ für 45°<ρ≤90°,
• α(ρ) = -90*0,89+0,89*ρ für 90°<ρ≤135°
• α(ρ) = 180*0,89-0,89*ρ

für 135°<ρ≤180° bestimmt. Die entsprechende Kurve ist in der Diagrammdarstellung in Figur 3 als gestrichelte Linie gezeigt. Figur 3 zeigt zudem einen Korridor mit oberen und unteren Grenzkurven für die oben genannten Werte von r1=0,6 und r1=1,2. Durch die symmetrische Ausbildung des Strömungsleitgitters 1 gelten die Kurven entsprechend für die Quadranten 3Q und 4Q.According to the invention, the curvature, ie the angle α at the respective radial end 4 of the radial webs 2, is a function of the position in the circumferential direction (angle p) in the quadrants 1Q and 2Q

• α (ρ) = 0.89 * ρ for 0 ° ≤ρ45 °, α (ρ) = 90 * 0.89-0.89 * ρ for 45 ° <ρ≤90 °,
• α (ρ) = -90 * 0.89 + 0.89 * ρ for 90 ° <ρ≤135 °
• α (ρ) = 180 * 0.89-0.89 * ρ

determined for 135 ° <ρ≤180 °. The corresponding curve is shown in the diagram in Figure 3 shown as a dashed line. Figure 3 also shows a corridor with upper and lower limit curves for the above values of r1 = 0.6 and r1 = 1.2. Due to the symmetrical design of the flow guide grid 1, the curves apply accordingly to the quadrants 3Q and 4Q.

The coaxial circumferential webs 3 are convex along their axial extent and point in the direction of the central axis of the flow guide grille 1, as is well shown in the lateral sectional views AA and BB Figure 2a and 2b can be seen. In addition, the inclination of the circumferential webs 3 changes with respect to the central axis of the flow guide grille 1 over its course in the circumferential direction. The inclination is according to a circumferential web 3 at the intersection Figure 2b sketched as angle β. The circumferential webs 3 lying radially further outward are more inclined than those running near the central axis. Since the inclination is variable in the circumferential direction by the angle β, it is determined according to the formula β = a + b ^∗ cos (ρ), where a is the respective mean value of the angle β over the circumference of the circumferential web 3, b in question, the specified fluctuation value and ρ corresponds to the angle in the circumferential direction starting from the zero degree radial plane (NR).

Figure 4 shows an example of the course of the inclination of a circumferential web 3 and the change in the angle β in the circumferential direction from 0-180 °, ie within the quadrants 1Q and 2Q. In the view shown, the circumferential web 3 is viewed with a mean value a of the inclination of 12 °, which lies at 18 ° along the zero degree radial plane NR and then decreases to 6 °. The value b is around 6.

A preferred range for fluctuation values b of the individual circumferential webs 3, which are characterized by their mean values a, is shown in Fig. 5 reproduced. The higher the mean value a, the further the respective circumferential web 3 is located radially outward from the central axis. The fluctuation values b are in the range of approx. 6 - 9 for small mean values a, in the range of 1.8 - 3 for large mean values a. The dashed lines indicate the total range, the solid lines the preferred range of the fluctuation value b as a function of the Average of the angle β over the circumference again. The dotted line connects the values marked by crosses of the circumferential webs 3 of the flow guide grille 1 Figure 1 .

The embodiment of the invention is not limited to the preferred exemplary embodiments specified above. Rather, a number of variants are conceivable which make use of the solution shown, even in the case of fundamentally different types. For example, the flow guide grille can be used with axial fans, radial fans and diagonal fans. However, the scope of the invention is determined solely by the claims that follow.

Claims (11)

1. Flow conducting grille for arrangement on the suction side of a fan, with a grille bar structure comprising radial bars (2) spaced apart in the circumferential direction and coaxial circumferential bars (3) spaced apart in the radial direction, wherein the radial bars (2) of at least one quadrant of the flow conducting grille (1) are each curved in the circumferential direction, viewed over their radial extension, towards a predetermined radial plane extending from a central axis of the flow conducting grille (1).
   wherein the predetermined radial plane is a zero-degree radial plane (NR) restricting a first quadrant (1Q),
   wherein the radial bars (2) each have radial ends (4) and define an angle (a) formed by a straight line (G) extending from a central axis of the flow conducting grille to the respective radial end of the respective radial bar and an imaginary curve-free extension (V) of the respective radial bar (2) beyond its respective radial end (4),
   wherein the angle (a) varies with different radial bars (2), and
   wherein, starting from the zero-degree radial plane (NR), an angle ρ is determined in the circumferential direction and the radial bars (2) arranged spaced apart in the circumferential direction respectively at a predetermined angle ρ determine the angle α at their radial ends (4), said angle α varying according to the angle ρ with the function:

   α(ρ) = r1^∗ρ for 0°≤ρ≤45°,

   α(ρ) = 90^∗r1-r1^∗ρ for 45°<ρ≤90°,

   α(ρ) = -90^∗r1 +r1^∗ρ for 90°<ρ≤135°,

   α(ρ) = 180^∗r1-r1^∗ρ for 135°<ρ≤180°,

   where r1 is in a range from 0.6 to 1.2.
2. Flow conducting grille according to claim 1, characterized in that viewed over their radial extension, the radial bars (2) of two adjacent quadrants of the flow conducting grille (1) are each curved in the circumferential direction towards the predetermined radial plane.
3. Flow conducting grille according to claim 1 or 2, characterized in that viewed over their radial extension, the radial bars (2) of all four quadrants of the flow conducting grille (1) are each curved in the circumferential direction towards the predetermined radial plane.
4. Flow conducting grille according to at least one of claims 1 to 3, characterized in that the circumferential bars (3) are convex along their axial extension and are formed at least partially pointing in the direction of the central axis of the flow conducting grille (1).
5. Flow conducting grille according to claim 1, characterized in that r1 is in a range from 0.8 to 1.0.
6. Flow conducting grille according to one of the preceding claims 1 to 5, characterized in that at least one of the circumferential bars (3) has an averaged axial extension which is inclined at an angle β with respect to the central axis of the flow conducting grille.
7. Flow conducting grille according to the preceding claim, characterized in that with the at least one circumferential bar (3) the angle of inclination β changes over its course in the circumferential direction.
8. Flow conducting grille according to the preceding claim, characterized in that with the at least one circumferential bar (3), the angle of inclination β is determined according to the formula β = a+b^∗cos(ρ), wherein a corresponds to an average value of the angle β over the circumference of the respective circumferential bar (3), b to a fluctuation value and ρ to the angle in the circumferential direction starting from the zero-degree radial plane (NR), and wherein b is determined within a range of $$b_{\min }=2\ast e^{-\mathrm{0,022}\ast a}$$

   

   to $$b_{\max }=16\ast e^{-\mathrm{0,022}\ast a}.$$

   
9. Flow conducting grille according to the previous claim, characterized in that b is determined within a range of $$b_{\min }=7\ast e^{-\mathrm{0,022}\ast a}$$

   

   to $$b_{\max }=12\ast e^{-\mathrm{0,022}\ast a}.$$

   
10. Flow conducting grille according to one of the preceding claims 6 to 9, characterized in that all circumferential bars (3) have an inclination of the angle β.
11. Flow conducting grille according to at least one of claims 1 to 10, characterized in that respectively two adjacent quadrants (1Q; 4Q) of the flow conducting grille are formed mirror-symmetrically with respect to the zero-degree radial plane (NR).

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