Acoustically optimized screen for use in air-guiding tubes in an aircraft

Abstract

A screen (14) of an air duct (8) of an air-conditioning system (6) of an aircraft (2) contains a main part (16) and at least one duct (18a-e) in the main part (16), wherein the screen (14) is designed to be acoustically optimized with regard to flow noises during operation (B) by virtue of the following variants: a channel (18a-e) has a tapering funnel shape (24a,b), and / or a channel (18a-e) has a lateral opening (32) with an adjoining cavity (34), which form a Helmholtz resonator, and / or the outlet end (28) of a channel (18a-e) is a free end (46) with a sawtooth structure (30) surrounding the channel (18a-e), and / or a channel (18a-e) in the form of a slot (38) has a constant cross-section throughout, and / or a channel (18a-e) has a circular, elliptical, or slot-shaped cross-section, and / or the upstream end face (42) of the main part (16) supports pointed shapes (44) which taper opposite the flow direction (10). A duct assembly (50) contains the air duct (8) with screens (14) in the assembled state (M).

Description

[0001] RT / ND / dk

[0002] Acoustically optimized baffle for use in air ducts in an aircraft

[0003] The invention relates to a baffle in an air duct (also called air guide tube) of an aircraft air conditioning system, which, during operation of the air duct, slows down the air flowing in it, i.e., the airflow, and thereby makes it adjustable.

[0004] From DE 102007 001 052 A1, an orifice system is known for use in an air conditioning system, in particular an aircraft air conditioning system; this system comprises an orifice frame that can be attached to an open end of a pipe of the air conditioning system and an orifice that defines a flow cross-section of the pipe. A receiving groove is formed on the orifice frame and / or the orifice, which extends only over a portion of the circumference of the orifice frame and / or the orifice. The orifice can be inserted into the receiving groove formed on the orifice frame and / or a first guide web formed on the orifice frame can be inserted into the receiving groove formed on the orifice.

[0005] The object of the present invention is to propose improvements relating to such apertures.

[0006] The problem is solved by an aperture according to claim 1. Preferred or advantageous embodiments of the invention and of other invention categories will become apparent from the further claims, the following description and the accompanying figures.

[0007] The baffle is designed and intended to be installed in an air duct (also called an "air distribution duct" or "ventilation pipe"). Once installed, the baffle is in its intended position within the air duct. The air duct is a designated air duct for the baffle. It is part of an aircraft's air conditioning system, specifically the passenger cabin of a passenger aircraft. When the air duct (and the baffle installed within it) is in operation, air flows through it. The baffle, by virtue of its presence in the air duct, slows down the airflow; in other words, it acts as a flow restrictor. In other words, the airflow is slowed compared to what it would be if the baffle were not installed in the air duct.

[0008] Designed for use means that the baffle is tailored to a specific type of air duct. This tailoring also relates to the operation and the prevailing flow, pressure, and dynamic conditions. In other words, the air ducts in question are assumed to be known with regard to their geometry, operating conditions, etc. During operation, the airflow direction at the baffle location is also known. Therefore, the flow direction can be assigned to the baffle as a fixed direction. Its relative position to the baffle is thus defined. This also applies to the air duct.

[0009] The air duct contains a base body. This base body extends along a longitudinal axis. In the assembled state, the orientation / direction of the longitudinal axis corresponds to the airflow direction of the air duct. In other words, during operation, air flows in the air duct in the direction of airflow, and the longitudinal axis runs parallel to or in the direction of this airflow. The baffle is specifically designed for the intended air duct in such a way that, in the assembled state, it would essentially completely close off the air duct if it were not itself permeable to air. "Essentially" means that air can only pass through the baffle via the channels described below, which penetrate the base body. Thus, the airflow in the air duct is slowed by the baffle. Specifically, in the assembled state, the base body rests completely against the inner wall of the air duct (e.g., by means of seals, etc.).However, other designs are also possible.

[0010] The baffle contains at least one channel. Each channel passes through the base body along its longitudinal axis, allowing air to flow through the channel and thus through the baffle. The term "base body" is to be understood broadly here and can also refer to a wall of the channel(s). In other words, the baffle can, for example, consist of a single channel; the base body is then the wall surrounding the channel—which may be thin-walled. The baffle is acoustically optimized with regard to flow noise. Flow noise refers to that caused by the baffle or the air flowing through the air channel at the baffle during operation. The baffle is acoustically optimized by incorporating at least one of the following features. At least one of these features is implemented in the baffle; however, several features can also be combined (provided they do not contradict each other):

[0011] • In a first variant, at least one of the channels has a funnel shape along its longitudinal axis. "At least one" is to be understood as "at least one, in particular several or all of the channels." This also applies to further such formulations throughout the following description. At least one of the funnel shapes is tapered in the direction of flow. During operation and when the baffle is installed in the air duct, air thus flows through a funnel-shaped channel, whereby—at least in the section of one funnel shape—the cross-section of the funnel shape decreases downstream to form the tapered funnel shape.

[0012] • In a second variant, at least one of the channels has at least one lateral opening. In other words, there is a hole in the otherwise closed channel wall. The opening leads to a cavity. The cavity is located within the base body, but can also be formed by an element separate from the base body. The opening and cavity are configured together with respect to the channel in the manner of a Helmholtz resonator. During operation, air flows through the channel past the opening and causes a Helmholtz resonance in the cavity, which in turn affects the channel and thus the acoustic properties of the aperture.

[0013] • In a third variant, at least one of the ducts has a downstream outlet designed as follows: The duct has a wall extending along its longitudinal axis, thus being bounded or formed by this wall. In the installed state, the wall projects into the downstream air duct as the free end of the duct in this area, meaning it has a radial distance from the inner wall of the air duct. At this free end, the wall is designed as a sawtooth structure surrounding the duct. In other words, a downstream outlet edge or end face of the duct or wall is designed as a sawtooth pattern. • In a fourth variant, at least one of the ducts has a slotted cross-section and a constant cross-section along its longitudinal axis.In particular, the entire channel is designed in a slit-like, i.e. cuboid shape, with its cross-section having a slit shape, i.e. forming a rectangle with significantly different width and height (e.g. ratio greater than 2:1 or 3:1 or 4:1 or 5:1).

[0014] • In a fifth variant, at least one of the channels has a cross-section that is circular or elliptical or in the manner of an elongated hole (parallel sides that each end in a semicircle).

[0015] • In a sixth variant, at least one pointed shape is formed on one of the upstream end faces of the base body during operation. This pointed shape tapers towards the direction of airflow, in other words forming a point / thorn / spine / pyramid / etc. that opposes the airflow during operation.

[0016] Depending on the actual conditions in the intended air duct or the entire air conditioning system (geometry, dimensions, possible flow velocities, mutual influence of all components, etc.), at least one or more of the variants can be selected in combination to acoustically optimize the airflow noise in the air duct or the entire air conditioning system. Optimization includes, for example, minimizing / reducing the sound levels (e.g., compared to differently designed baffles previously used in the same air duct), influencing the frequencies towards those typically perceived as "more pleasant" by passengers or away from resonant frequencies, etc.

[0017] Acoustic optimization, particularly the reduction of airflow noise, eliminates the need for additional silencers in the air duct / air conditioning system. This improves passenger comfort in the vicinity of the air conditioning system during operation. In a preferred embodiment, at least one of the ducts comprises exactly one of the aforementioned variants on its own, or exactly two, or exactly three of the aforementioned variants in combination. The remaining variants are therefore not implemented in this duct. This allows for the creation of particularly cost-effective yet versatile ducts or baffles.

[0018] In a preferred embodiment, which relates to the variant with funnel shapes, the following applies: At least one of the channels has at least two funnel shapes. The channel thus has a design in which a funnel shape is present at two different locations / sections in the longitudinal direction. At least two of the funnel shapes are, in a first alternative, symmetrically arranged relative to each other, or asymmetrically arranged relative to each other in a second alternative. Each of the alternatives has certain advantages and disadvantages with regard to acoustic optimization, so that the more favorable alternative can be selected if necessary.

[0019] In a preferred embodiment, which also relates to the variant with funnel shapes, the following applies: At least one of the funnel shapes—viewed in a central longitudinal section along the longitudinal axis—is, in a first alternative, continuously curved (i.e., without kinks), or, in a second alternative, sectionally straight (i.e., formed by straight segments joined together at kinks). The continuous shape thus results in a type of horn funnel. The sectionally straight shape, for example, results in a funnel similar to a typical household funnel, formed from a conically tapered conical section followed by a circular cylinder (here, however, oriented either upstream or downstream). Again, each alternative has certain advantages and disadvantages that can be implemented in the baffle as needed to optimize the overall acoustic properties during operation.

[0020] The next two embodiments also refer to the aforementioned variant with funnel shapes and represent alternatives to each other:

[0021] In a first alternative, at least one of the funnel-shaped channels exhibits only the funnel shape that tapers in the direction of flow. No other funnel shapes are present in this channel. This does not preclude the channel from being combined with other variations. In a second alternative, at least one of the funnel-shaped channels exhibits exactly one further funnel shape downstream of the tapering funnel shape, which widens again downstream. In other words, the channel initially tapers into a funnel shape and then subsequently widens again in a funnel shape. Again, no other funnel shapes are present in the channel. However, this channel may also exhibit other variations mentioned above.

[0022] Here too, the different variants and combinations of funnels exhibit different properties in order to optimize the acoustic properties if necessary, so that a suitable variant can be chosen for each specific application.

[0023] The next two embodiments also represent alternatives to each other. However, these do not refer to the funnel-shaped variant. In both of these alternatives, the orifice acts as a rectifier. This means that the laminar flow component of the airflow in the air duct is never smaller downstream of the orifice than upstream of it.

[0024] In one alternative, the aperture contains only a single channel. This channel has the aforementioned slot-shaped design. Specifically, the channel exclusively features this design. However, it can also be combined with other designs.

[0025] In a second alternative, the aperture is also designed as a rectifier and features multiple channels. Each channel has a slotted shape. Here too, the channels primarily have this slotted shape, but can also be combined with other shapes. The slotted shapes in the aperture are aligned parallel to each other in cross-section. In other words, the aperture has several slots on its end faces as inlets and outlets for the channels, with the orientation of the slots running parallel to each other. In other words, the rectangular slots are aligned with their longer sides parallel to each other. Again, each of the two rectifiers has different properties to optimize the acoustic performance of the aperture. The alternatives can be selected and used as needed.

[0026] Another preferred embodiment relates to the variant with pointed shapes. At least one of the pointed shapes is then a wedge shape, a pyramid shape, or a cone shape. In other words, wedges, points, spikes, pyramids, etc., project from the upstream end face of the baffle into the oncoming airflow, against the direction of airflow. Such shapes have proven to be particularly effective in optimizing the acoustic properties of the baffle.

[0027] The problem is also solved by a duct arrangement according to claim 10. The duct arrangement is one for the aircraft's air conditioning system, as already described above in connection with the baffle. The duct arrangement includes at least one of the baffles according to the invention. The duct arrangement also includes the aforementioned air duct. The baffles are installed in the air duct in the assembled state, so that during operation they act as a flow-reducing element in the air duct, i.e., they slow down the air flowing through the air duct, as already described above.

[0028] The channel arrangement and at least some of its possible embodiments, as well as their respective advantages, have already been explained in substance in connection with the aperture according to the invention. In particular, the preferred embodiments mentioned above in connection with the aperture also constitute preferred embodiments of the channel arrangement.

[0029] The invention is based on the following findings, observations, and considerations and further comprises the following preferred embodiments. These embodiments are sometimes referred to simply as "the invention." The embodiments may also include parts or combinations of the embodiments mentioned above, correspond to them, and / or may include previously unmentioned embodiments.

[0030] According to the invention, an acoustically optimized louvre is provided, particularly for use in aviation. Specifically, an acoustically optimized louvre is provided for the air conditioning system of an aircraft.

[0031] Thanks to the baffle(s), the acoustics of the overall system are improved. The different variants are presented, which can be used depending on the requirements.

[0032] In air conditioning systems, pipe baffles are used at various positions to ensure even air distribution. When air flows through these baffles, they generate noise that is then transmitted into the aircraft cabin via the air outlet. The silencer's function is to reduce the noise generated by the upstream baffle. To regulate the pressure or volume flow in the air conditioning system, plug-in baffles (single-hole or multi-hole baffles) are currently placed in front of the air outlet using frames or riveted, plugged, or glued baffles. The hole pattern of each baffle is tuned to a specific frequency range. The resulting noise is then dampened by the downstream silencer.

[0033] In other concepts, the panels could be riveted, glued or plugged in.

[0034] The present invention does not concern the installation or assembly principle of apertures, but rather their properties.

[0035] A fundamental idea of ​​the invention, besides regulating the volume flow and pressure, is to pursue the reduction of flow noise generated in the system as a primary objective.

[0036] The orifices known from previous practical applications were tuned to a higher frequency range so that these noise components could be absorbed by the downstream silencer. The orifices according to the invention can be designed, by selecting / combining variants, in such a way that the flow noise is reduced to a minimum from the outset. Depending on the integrated concept (selection of variants), the entire frequency spectrum or only specific frequencies can be considered / optimized. To achieve this goal, the orifice geometries and / or the material are optimized until the disturbing noise components are no longer perceptible.

[0037] According to the invention, the following advantages result: • Improvement of acoustic properties / Flow noise is reduced to a minimum

[0038] • Replacement of costly insulation measures

[0039] • Reduction of the overall system weight (sustainability)

[0040] • Reduction of costs for the overall system

[0041] • Reduction of installation space

[0042] The acoustically optimized aperture according to the invention can be, or is, optimized in the audible frequency range to such an extent that a downstream silencer can be dispensed with. Passenger comfort is maintained. The reduced weight, the smaller installation space, and the compact design are also positive advantages. The various geometric approaches, for example, in the form of a funnel (funnel shape variant) in combination with a Helmholtz resonator (opening and cavity variant) or the sawtooth profile (sawtooth structure variant), but also the flow around pyramidal or wedge-shaped components (pointed shape variant) as well as the use of a rectifier (slot shape variant as rectifier), are aperture designs that differ significantly from the principle previously known in practice.

[0043] The baffle according to the invention can be used in a single-aisle passenger aircraft, for example, in front of or within a so-called "riser duct". In principle, the baffle according to the invention can be used wherever a baffle (with or without a silencer) is installed in previously known practice.

[0044] Particularly preferred individual variants or combinations of variants include:

[0045] Funnel apertures:

[0046] • A funnel-shaped orifice plate comprises a tapered inlet, a constriction, and a fanning outlet geometry. This is created by an orifice plate with a single channel. The only variations of this channel are a funnel shape that initially tapers in the direction of flow, combined with a widening funnel shape. The tapering or fanning of the funnel-shaped orifices can, in one variation, have sharp edges for both funnels, or in another variation, a smooth and gentle transition for both funnels, and / or be symmetrical or asymmetrical (symmetry of the funnel shapes with respect to a plane of symmetry running transversely between them along the longitudinal axis).

[0047] • One possible variation of the funnel-shaped orifice involves exclusively using a downstream tapered funnel shape, with the funnel's exit edges designed as a sawtooth pattern. This sawtooth pattern can be varied in size and number of "sawtooths" and alters the flow field of the exiting air jet in such a way as to reduce the resulting flow noise.

[0048] • Another possibility is to implement the aforementioned funnel aperture as, or with, a so-called Helmholtz resonator. In this design, an opening is provided in the funnel (its chronically widening portion), which leads into a cavity. The Helmholtz resonator operates on the principle of absorption. An aperture constructed in this way can be tuned to any required frequency.

[0049] • The different concepts can be combined with each other to achieve an optimal result.

[0050] • The different design approaches can also be combined with different materials.

[0051] Rectifier:

[0052] • A rectifier has exclusively one or more (especially three) channels, each designed as slots.

[0053] • By using different geometric approaches such as the number, position or shape of the individual slots, these baffles can be adjusted so that sound reduction can occur at different frequencies.

[0054] It is also possible to combine the rectifier apertures with the so-called Helmholtz resonators as described above. Furthermore, the different design approaches can be combined with different materials.

[0055] Inlet geometry:

[0056] • Acoustic baffles can have different inlet geometries (design of the surface shape of the upstream facing end face of the baffle).

[0057] • This constructive measure can achieve noise reduction in certain frequency ranges.

[0058] • The inlet can be designed as or with wedges, pyramids, or cones. These different inlets are combined with various through-holes. The through-holes can be round, elliptical, or oblong.

[0059] • Combination with so-called Helmholtz resonators is also possible.

[0060] Further features, effects, and advantages of the invention will become apparent from the following description of a preferred embodiment of the invention and the accompanying figures. These figures are shown in a schematic diagram:

[0061] Figure 1 shows a cross-section along the longitudinal axis or flow direction of an air duct with a baffle having two opposite funnel shapes in an angular shape.

[0062] Figure 2a and rounder, each more symmetrical,

[0063] Figure 2b and round asymmetrical design,

[0064] Figure 3a with exclusively tapered funnel shape and sawtooth structure in a first doubly curved

[0065] Figure 3b and second simply curved embodiment,

[0066] Figure 4 shows an alternative funnel aperture, Figure 1 with an additional Helmholtz resonator.

[0067] Figure 5a shows an aperture as a rectifier with three slot channels in a top view of the upstream end face, Figure 5b shows a side view according to Figures 1 to 4,

[0068] Figure 6a shows the rectifier from Figure 5 with only one slot channel and Helmholtz resonator in a view according to Figure 5a,

[0069] Figure 6b and Figure 5b,

[0070] Figure 7a shows an aperture with inlet geometry featuring pointed shapes and circular channels in a view according to Figure 5a.

[0071] Figure 7b and a symbolically corresponding view according to Figure 5b,

[0072] Figure 8a shows an alternative aperture according to Figure 7 with a single elliptical channel in a view according to Figure 7a,

[0073] Figure 8b and Figure 7b,

[0074] Figure 9a shows a further alternative aperture according to Figure 7 with a multitude of channels and alternative tip shapes in a view according to Figure 7a,

[0075] Figure 9b and Figure 7b,

[0076] Figure 9c and in a perspective oblique view.

[0077] Figure 1 shows a section of an aircraft 2, here a passenger aircraft or its passenger cabin 4, namely a section of its air conditioning system 6 in the form of part of an air duct 8 of the air conditioning system 6. The air conditioning system 6 is operating in mode B, with air 12 flowing through the air duct 8 in a flow direction 10.

[0078] An aperture 14 is located in the air duct 8 in its intended installation state M. It completely fills the air duct 8, or rather its interior / cross-section (perpendicular to the flow direction 10), so that all the air 12 in the air duct 8 must flow through the aperture 14. The aperture 14 acts as a flow restrictor on the air 12, thus slowing down the flow of air 12 compared to a state in which no aperture 14 were arranged in the air duct 8.

[0079] Air duct 8 and aperture 14 together form a duct arrangement 50, in which aperture 14 is inserted into the air duct in assembly state M.

[0080] The aperture 14 comprises a base body 16 and a single channel 18a. The base body 16 is configured here as the wall 20 of the channel 18a. The base body 16 extends along a longitudinal axis 22, which in the assembly state M corresponds to the flow direction 10 of the air channel 8 or runs parallel to it and coincides with it.

[0081] Channel 18a has two funnel shapes 24a and 24b. The first funnel shape 24a tapers in the flow direction 10, meaning its internal cross-section decreases in the flow direction 10. Downstream of the first funnel shape 24a is the second funnel shape 24b, which, however, widens in the flow direction 10, i.e., its cross-section increases in the flow direction 10. Both funnel shapes 24a and 24b are partially straight and longitudinally symmetrical to each other along the longitudinal axis 22. A corresponding plane of symmetry 26 is symbolically indicated in Figure 1.

[0082] Figure 1 shows a funnel-shaped orifice with a tapered inlet, a constriction, and a fanning / widening outlet geometry. The tapering or securing of the funnel-shaped orifice has a sharp edge and is symmetrically constructed.

[0083] Figure 2a shows a variant of the funnel aperture from Figure 1, which also has two symmetrical (plane of symmetry 26) funnel shapes 24a, b. However, these have a smooth and gentle curve, i.e., they are continuously curved.

[0084] Figure 2b shows a variant of the funnel aperture from Figure 2a, which also has the smooth and gentle / continuously curved profile, but in which the funnel shapes 24a, b are asymmetrically constructed.

[0085] Figure 3a shows an alternative funnel-shaped orifice in the form of orifice 14. This contains only a single funnel shape 24a, which tapers in the flow direction 10. Here, however, the downstream outlet 28 of the channel 18a is designed as a wall 20 of the channel extending in the direction of the longitudinal axis 22, forming a free end 46 of the channel 18a. At the free end 46, the wall 20 is radially spaced (radial direction relative to the longitudinal axis 22 / flow direction 10) from an inner wall 48 of the air duct 8. The wall 20 is formed at the free end 46 with a sawtooth structure 30 surrounding the channel 18a. Figure 3a thus shows a variant of the funnel orifice in which the exit edge (downstream end of the channel 8a or of the base body 16 in the form of the wall 20) for the air 12 is designed as or with a sawtooth pattern.

[0086] This sawtooth pattern can be varied in size and number (of the "sawtooths") and changes the flow field of the exiting air jet (air 12) in the air duct 8 so that the resulting flow noises are reduced.

[0087] Figure 3b therefore shows a variant of the embodiment according to Figure 3a with a larger number of sawtooth structures and a modified geometry of the funnel shape 24a. Here, the funnel shape 24a (viewed from the channel 18a) is always designed to taper convexly. In contrast, the funnel shape 24a in Figure 3a, viewed in the flow direction 10, is initially concave and only subsequently convexly tapered. Thus, in a mathematical sense, the profile of the wall 20 has an inflection point in Figure 3a, but not in Figure 3b.

[0088] Figure 4 shows a funnel-shaped orifice, which, according to its characteristics, is designed according to Figure 1, only with different dimensional ratios. Here, however, the channel 18a has a lateral opening 32 in the funnel section of the funnel shape 24b, which opens in the flow direction 10 and leads to a cavity 34.

[0089] The cavity 34 is an integral part of the base body 16. To illustrate this, the base body 16 is shown set back from the inner wall 48 of the air duct 8 in Figure 4, although in practice these are in direct contact. The opening 32 and cavity 34 are designed and configured as a Helmholtz resonator with respect to the duct 18a. In other words, the diaphragm aperture is also designed as a Helmholtz resonator. This operates on the principle of absorption. An aperture 14 designed in this way can be tuned to any required frequency.

[0090] Figures 5 and 6 show embodiments of the orifices 14 as rectifiers 36. Figures 5a and 6a each show a top view of the orifice 14 in the flow direction 10 or in the direction of arrows Va and Via, respectively, in other words, of its upstream end faces 42. Figures 5b and 6b show—like Figures 1 to 4—a side view of a cross-section through the orifices 14 along lines Vb and Vlb. The embodiments according to Figures 5 and 6 exclusively feature channels 16a-c with a respective slot-shaped cross-section 38. For channel 18a in Figure 5a, the cross-section or slot shape is shown hatched.

[0091] As shown in Figure 5, the aperture 14 has three channels 18a-c. Each of the channels 18a-c is designed in the slot shape 38. Furthermore, the cross-section of the channels 18a-c is constant along its longitudinal extent along the longitudinal axis 10. The slot shape 38 is therefore a cuboid shape with significantly different side lengths. The slot shapes 38 are aligned parallel to each other in the cross-section of the aperture 14, which is symbolically illustrated in Figure 5a by the parallelism of their respective directions of extension 40.

[0092] Figure 6 shows a variant of Figure 5, in which the aperture 14 has only a single channel 18a, but again in the form of a slot 38 as in Figure 5. Here, a Helmholtz resonator, consisting of an opening 32 and a cavity 34 in the base body 16, is provided at the channel 18a, as in Figure 4, or combined with the slot shape.

[0093] Figures 5 and 6 thus show rectifiers with one or more slots.

[0094] Figures 7 to 9 show different inlet geometries at apertures 14.

[0095] Figures 7a, 8a, and 9a again show views of the end faces 42 of the apertures 14 according to Figures 5a and 6a. Figures 7b, 8b, and 9b show lateral cross-sections of the apertures 14 according to Figures 1 to 4, 5b, and 6b.

[0096] The aperture 14 from Figure 7 has a total of five channels 18a-e, each with a circular cross-section. Several pointed shapes 44 are attached to the upstream end face 42 of the aperture 14. The pointed shapes 44 taper in the opposite direction of flow 10 and each have a pyramidal shape.

[0097] Therefore, the embodiments shown in Figures 7 to 9 describe acoustic apertures 14 with different inlet geometries. Figures 7 to 9, like Figures 5 and 6, show channels 18a-e with a cross-section that is constant along the longitudinal axis 22 and runs parallel to each other.

[0098] In contrast to Figure 7, Figure 8 again shows an embodiment with a single channel 18a with Helmholtz resonator, i.e. with opening 32 and cavity 34. The channel 18a also has an elliptical cross-section.

[0099] The number and arrangement of the pointed forms 44 are to be understood only symbolically in relation to Figures 7 and 8; the side and top views do not actually correspond in this respect. The channels 18a-e are also not depicted consistently in this regard.

[0100] Figure 9, on the other hand, shows in actually corresponding representations the front view Fig. 9a (according to Fig. 8a etc.), the side view Figure 9b (according to Fig. 8b etc.) and a perspective top view Figure 9c of the front face 42 of another alternative aperture 14 with a plurality of channels 18, which are completely surrounded by pointed forms 44.

[0101] In Figures 9a and 9b, as in Figure 4, the air duct 8 is again shown at a distance from the aperture 14, although in reality they are in contact with each other, in order to clearly illustrate the shape of the aperture 14. In Figure 9c, the air duct 8 is omitted.

[0102] Reference symbol list

[0103] 2 airplanes

[0104] 4 passenger cabin

[0105] 6 Air conditioning

[0106] 8 air duct

[0107] 10 Flow direction

[0108] 12 Air

[0109] 14 aperture

[0110] 16 basic shapes

[0111] 18a-e Channel

[0112] 20 Wall (Channel)

[0113] 22 Longitudinal axis

[0114] 24a, b T funnel shape

[0115] 26 Plane of symmetry

[0116] 28 Omissions

[0117] 30 sawtooth structure

[0118] 32 Opening

[0119] 34 Cavity

[0120] 36 rectifiers

[0121] 38 slotted shape

[0122] 40 Direction of extension (slot)

[0123] 42 Front

[0124] 44 Pointed shape

[0125] 46 Free Ends

[0126] 48 Interior wall (air duct)

[0127] 50 channel arrangement

[0128] B Operation

[0129] M Assembly state

Claims

PATENT CLAIMS 1. Aperture (14) which is designed to be used in a flow-reducing manner in a designated assembly state (M) in a designated air duct (8) of an air conditioning system (6) of an aircraft (2) in a designated operation (B), - with a base body (16) extending along a longitudinal axis (22) which, in the assembly state (M) and operation (B), corresponds to a flow direction (10) of the air duct (8), - with at least one channel (18a-e) passing through the base body (16) along the longitudinal axis (22), - wherein the aperture (14) is acoustically optimized with regard to the flow noise caused during operation (B) by having at least one of the following variants: - at least one of the channels (18a-e) has at least one funnel shape (24a, b) along the longitudinal axis (22), wherein at least one of the funnel shapes (24a, b) is tapered in the direction of flow (10), and / or - at least one of the channels (18a-e) has at least one lateral opening (32) leading into a cavity (34), and the opening (32) and cavity (34) are configured in relation to the channel (18a-e) in the manner of a Helmholtz resonator, and / or in at least one of the channels (18a-e) a downstream outlet end (28) of the channel (18a-e) is formed as a wall (20) of the channel (18a-e) extending in the direction of the longitudinal axis (22), which in the assembly state (M) projects as a free end (46) into the downstream air channel (8), wherein the wall (20) at the free end (46) is formed as a sawtooth structure (30) surrounding the channel (18a-e), and / or - at least one of the channels (18a-e) has a slotted cross-section (38) and is designed with a constant cross-section along the longitudinal axis (22), and / or - at least one of the channels (18a-e) has a cross-section that is circular or elliptical or in the form of an elongated hole, and / or at least a pointed shape (44) tapering in the opposite direction of the flow (10) is formed on an upstream end face (42) of the base body (16).

2. Aperture (14) according to claim 1, characterized in that at least one of the channels (18a-e) has exclusively one or two or three of the variants.

3. Aperture (14) according to one of the preceding claims, characterized in that at least one of the channels (18a-e) with respect to the variant with funnel shapes (24a, b) has at least two funnel shapes (24a, b) and at least two of the funnel shapes (24a, b) are formed symmetrically or asymmetrically to each other along the longitudinal axis (22).

4. Aperture (14) according to one of the preceding claims, characterized in that, with regard to the variant with funnel shapes (24a, b), at least one of the funnel shapes (24a, b) is continuously curved along the longitudinal axis (22) or is sectionally straight.

5. Aperture (14) according to one of claims 1 to 4, characterized in that at least one of the channels (18a-e) with respect to the variant with funnel shapes (24a, b) has exclusively the funnel shape (24a, b) which tapers in the direction of flow (10), 6. Aperture (14) according to one of claims 1 to 4, characterized in that at least one of the channels (18a-e) with respect to the variant with funnel shapes (24a, b) has a further widening funnel shape (24b) downstream of the tapered funnel shape (24a).

7. Aperture (14) according to one of claims 1 to 6, characterized in that the aperture (14) is designed as a rectifier (36) and contains only a single channel (18a) which has the variant with slot shape (38).

8. Aperture (14) according to one of claims 1 to 6, characterized in that the aperture (14) is designed as a rectifier (36) and has several channels (18a-e), each of which channels (18a-e) has a variant of the slot shape (38), wherein the slot shapes (38) are aligned parallel to each other in the cross-section of the aperture (14).

9. Aperture (14) according to one of the preceding claims, characterized in that, with regard to the variant with pointed shapes (44), at least one of the pointed shapes (44) is a wedge shape or a pyramid shape or a cone shape.

10. Channel arrangement (50) of an air conditioning system (6) of an aircraft (2), - with at least one aperture (14) according to one of the preceding claims, and - with the air duct (8), wherein the baffles (14) are used in the air duct (8) in the assembly state (M) in a flow-reducing manner during operation (B).

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