Noise damper gate

Abstract

Silencer baffle with a housing which is filled with a sound-damping material and has a longitudinal side (10, 12), an end face (14, 16) running at right angles thereto and a curved transition section (26) which connects the longitudinal side to the end face, characterized in that the curvature of the transition section (26) is maximum in a central region and decreases continuously to zero towards at least one of the longitudinal and end sides.

Description

[0001] The invention relates to a silencer baffle with a housing which is filled with a sound-damping material and has a long side, a front side running at right angles thereto, and a curved transition section which connects the long side to the front side.

[0002] To dampen sound propagation in ventilation systems, so-called baffle silencers are used. These baffle silencers have a silencer housing that is installed in the ventilation duct so that it becomes part of the ventilation duct and through which air flows. Several silencer baffles are arranged parallel and spaced from one another in the silencer housing so that the long sides of the silencer baffle housings run parallel to the flow direction. The facing long sides of two adjacent silencer baffles then each form a flow gap through which air flows. On the upstream side, the air is deflected into the flow gaps by the end faces of the silencer baffles.Sound waves propagating parallel to the airflow in the ventilation duct are diffracted by the silencer baffles into the interior of the baffles, so that a large portion of the sound energy is absorbed by the sound-absorbing material. The wider the silencer baffles are in the direction perpendicular to the flow gaps, the greater the sound-dampening effect, but also the greater the pressure loss caused by the flow resistance of the silencer baffles.

[0003] The object of the invention is to create a silencer baffle which causes a lower pressure loss for a given sound dampening effect.

[0004] This object is achieved according to the invention in that the curvature of the transition section is maximum in a central region and decreases continuously to zero towards at least one of the longitudinal and end sides.

[0005] Measurements have shown that flow resistance is reduced when the edges of the silencer baffle housings are rounded so that the long sides and the front sides do not meet at right angles, but are connected by a curved transition section. A further reduction in pressure loss can be achieved by optimising the curvature profile of the transition section. A curvature profile has proven to be optimal in which the curvature is not constant, as in a circular arc with a given radius, but rather has a maximum in a central area of ​​the transition section, i.e. in an area where the tangent to the transition section forms an angle of 45° with the long side and the front side, and then steadily decreases to zero after at least one side, i.e. towards the long side and / or the front side.

[0006] If you define a coordinate system whose x-axis runs parallel to the front of the silencer baffle and whose y-axis runs parallel to the long side, the course of the transition section in the central area and the area adjacent to the front can be described by a function y = f(x). The curvature of the function graph, defined as the inverse of the radius of curvature, is greater the larger the second derivative of the function. If the curvature decreases continuously to zero towards the front of the housing, this means that the function y = f(x) at the point x 0 , which marks the boundary between the transition section and the front, is not only continuous, but also twice differentiable and has a second derivative of zero. This has been shown to have a positive effect on the flow behavior and thus on the flow resistance and pressure loss.

[0007] Accordingly, the course of the transition section in the zone between the central area and the long side can be described by a function x = g(y). If the curvature decreases continuously to zero towards the long side in this zone, this means that the function g(x) at the point y 0 , which marks the boundary between the transition section and the long side, is also continuous and twice differentiable and has a second derivative of zero. This also has a positive effect on the pressure loss, although it depends on the flow velocity prevailing in the ventilation duct whether the course of the curvature at the transition to the front side or the course of the curvature at the transition to the long side has the greater effect.

[0008] Advantageous embodiments of the invention are specified in the subclaims.

[0009] In one embodiment, the function that specifies the curvature of the transition section as a function of the arc length of this transition section can be continuous and differentiable over the entire length of this section, preferably infinitely differentiable. Optionally, the function can be axially symmetric with respect to the bisector of the angle between the long side and the end face.

[0010] In the following, an embodiment is explained in more detail using the drawings.

[0011] They show: Fig. 1 a view of a housing of a silencer baffle, Fig. 2 a section through a wall element of the housing of a silencer baffle according to the invention in the section plane II in Fig. 1 ; and Fig. 3 an enlarged section through a transition section of the wall element according to Fig. 2 and a curve indicating the curvature of this transition section.

[0012] In Fig. 1 A housing of a silencer baffle is shown, which has several wall elements made of sheet metal, which are detachably connected to each other, for example, by screws (not shown). The housing has the overall shape of an elongated cuboid with long sides 10, 12, end faces 14, 16, an upper wall 18 and a Fig. 1 invisible lower wall. In the example shown, the end walls 14, 16 as well as the upper wall 18 and the lower wall have longitudinal beads 20, 22. Two approximately square windows 24 are cut out in each of the long sides 10, 12, which can be closed with metal sheets or a glass fleece depending on the desired sound absorption properties. In a functional silencer baffle, the interior of the housing is filled with a sound-absorbing material that absorbs the energy of sound waves entering the housing through the windows 24. The edges formed between the long sides 10, 12 and the end faces 14, 16 of the housing are rounded, i.e. they are formed by curved transition sections 26.

[0013] The silencer baffle is installed with other silencer baffles arranged parallel to it in a silencer housing (not shown), which is part of a ventilation duct and through which air flows. The silencer baffles are oriented so that they are guided by the air in the direction of arrow A in Fig. 1 The incoming air thus impacts the end face 16 of the housing and is deflected so that it flows around the transition sections 26 and enters flow gaps formed between the facing longitudinal sides of the silencer baffles. Sound waves, which also propagate predominantly in direction A in the flow channel, are diffracted at the edges of the silencer baffles and enter the interior of the silencer baffles through the windows 24.

[0014] The edges of the housing formed by the transition sections 26 are rounded in such a way that the flow resistance and thus the pressure loss of the air flowing through the flow channel and the silencer is minimized.

[0015] Fig. 2 shows a section through a wall element 28 of the Fig. 1 shown housing in a sectional plane which is perpendicular to the long sides 10, 12 and the front side 14, the general course of which in Fig. 2 is indicated by straight lines. The wall element 28 forms the end face 14 of the housing, the two adjacent transition sections 26, as well as end sections of the adjacent long sides 10, 12. At the ends, which form the end sections of the long sides 10, 12, the sheet metal of the wall element is bent into pockets 30 into which a closure element, e.g. a sheet metal or a frame covered with glass fleece, for the adjacent window 24 can be inserted. In the area of ​​the pockets 30, the sheet metal is bent in such a way that, when the closure element is inserted, it rests largely stress-free against the closure element and holds it in position by clamping it.

[0016] In Fig. 3 In a coordinate system whose x-axis is parallel to the front side 14 and whose y-axis is parallel to the long side 10, a curve 26' is shown, which represents the cross-sectional shape of one of the transition sections 26 in Fig. 2 The point (x 0 , y 1 ) marks the boundary between the transition section 26 and the front side 14, and the point (x 1 , y 0 ) marks the boundary between the transition section 26 and the long side 10. A dash-dotted line shows an angle bisector 32 which runs at an angle of 45° to the front side 14 or the x-axis and to the long side 10 or the y-axis. The part of the curve 26' which is in Fig. 3 lies above and to the right of the angle bisector 32, can be understood as the graph of a function y = f(x). The second derivative of this function is a measure of the curvature of the curve and has a maximum at the point (xm , ym ), which lies on the angle bisector 32. Further to the right, i.e. with increasing x-values, the second derivative decreases continuously and reaches the value zero at the point (x 0 , y 1 ), i.e. at the boundary to the front side 14.

[0017] The part of curve 26' which is Fig. 3 lies below and to the left of the angle bisector 32, can be interpreted as the graph of a function x = g(y). The second derivative of this function also has a maximum at the point (xm , ym ), which lies on the angle bisector 32, and decreases continuously to zero up to the point (x 1 , y 0 ).

[0018] The functions f(x) and g(y) are preferably infinitely differentiable, so that a particularly smooth transition results between the transition section 26 and the front side 14 and the long side 10.

[0019] In the example shown, curve 26' is also axially symmetric to the angle bisector 32.

[0020] Typically, the curvature of a curve is defined as the inverse of the radius of curvature. Although the curvature defined in this way is not identical to the second derivative of the function f or g, it is a monotonically increasing function of this second derivative, meaning that the larger the second derivative, the larger the curvature. Fig. 3 Several curvature vectors k are drawn at regular intervals along the curve 26'. Each of these curvature vectors k is perpendicular to the curve 26', and its length is proportional to the curvature, i.e. to the inverse of the radius of curvature. A curve 34, which connects the ends of the curvature vectors k, indicates the course of the curvature as a function of the arc length λ along the curve 26'. This curve 34 also shows that the curvature is maximum at the point of the angle bisector 32 and decreases continuously to zero at the points (x 0 , y 1 ) and (x 1 , y 0 ). The function |k(λ)| is also infinitely differentiable.

[0021] The transition section 26 between the front side 14 and the long side 12 (right in Fig. 2 ) is a mirror image of the transition section between the front side 14 and the long side 10 described above and thus has the same curvature. The front side 16 in Fig. 1 is formed by a wall element which has the same shape as the wall element 28. Measurements have shown that at flow velocities such as those normally encountered in ventilation ducts, the curvature of the transition sections 26 described above leads to almost minimal flow resistance.

Claims

1. Silencer baffle with a housing filled with a sound-absorbing material and having a longitudinal side (10, 12), a front side (14, 16) running at right angles thereto and a curved transition section (26) connecting the longitudinal side to the front side, characterized in that the curvature of the transition section (26) is maximum in a central region and decreases continuously to zero towards at least one of the longitudinal and end sides.

2. Silencer baffle according to claim 1, wherein the curvature of the transition section (26) decreases continuously to zero both towards the longitudinal side (10) and towards the end face (14).

3. Silencer baffle according to claim 1 or 2, wherein in a coordinate system whose axes (x, y) are oriented parallel to the end face (14) and the longitudinal side (10), the cross-sectional shape of the transition section (26) can be described by a function of the form y = f(x) or x = g(y), whose second derivative is continuous.

4. Silencer baffle according to claim 3, wherein the function describing the cross-sectional shape of the transition section (26) is infinitely differentiable.

5. Silencer baffle according to one of the preceding claims, wherein the curvature of the transition section (26), defined as the inverse of the radius of curvature, is an infinitely differentiable function of the arc length along the transition section.

6. Silencer baffle according to one of the preceding claims, wherein the transition section (26) is symmetrical to the angle bisector (32) of the end face (14) and the longitudinal side (10).

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