SK50102008U1 - Resonator for reducing noise and particular tones in pipelines - Google Patents

Abstract

A sound baffle system for a duct, e.g. air ducts, exhaust gas ducts, has a widened duct section (3) with an inner sleeve (4) of similar diameter as the duct. The ends of the sleeve have connections to the main part of the duct and link resonance damping chambers (10, 20) to the duct flow. The inner sleeve is made of the same material as the duct and is secured to the inner wall of the widened section by securing brackets.

Description

NOISE AND SINGLE TONE RESONATOR IN PIPES

WIW-ar

Technical field

The technical solution concerns a resonator for sound attenuation and individual tones in pipes.

BACKGROUND OF THE INVENTION

Several different types of resonators are known for attenuating noise in pipes and channels e.g. from Schmidt, Helmut: Sound Technical Handbook: 4th Edition, Dusseldorf, 1989. For practical use, two principal embodiments are possible, which are based either on branching of the pipe or on changing the pipe diameter. One of the types of resonator used is e.g. A Helmholtz resonator, which in principle consists of a hollow space, which is generally connected to a damped pipe by means of one or more circular openings. The openings are distributed regularly or symmetrically over the entire surface between the chamber and the pipe. A disadvantage is that the damping effect of the Helmholtz resonator is limited to a single frequency region, namely the resonant frequency of the system. In the remaining frequency bands, this is essentially the slightest reduction in noise levels.

A variant of this type of resonator is a so-called hole resonator. It consists essentially of a hollow space which is separated from the damped space by means of a perforated plate with a certain proportion of holes.

A less known resonator is the so-called whistle resonator. The action of the whistle resonator is based on the interference between the incoming sound wave in the pipe and the reflected sound wave. Reflection arises eg. in piping parts attached to the pipeline itself, or in areas with large variations in cross-section compared to that of the pipeline itself, into which the pipeline still extends. The damping effect of the interference phenomena is in this case dependent on the length of the pipe part to be fastened or the length by which the pipe extends into the area of enlarged cross-section. The maximum damping of such a whistle resonator lies at a wavelength corresponding to four times the length of the fixed pipe section or into the area of the extending pipe section (lambda / 4-pipe). Other areas in which the damping occurs are an odd multiple of the lambda / 4 thus given. The lambda represents the wavelength of the sound wave in the medium which is propagated through the conduit. In order to accurately determine the length of the lambda, it must be taken into account that the physical length of the air vibration duct will be extended by a certain distance. Therefore, the physical pipe length of such a whistle resonator will be shortened by end correction.

A disadvantage of the described resonators is that they achieve effective noise attenuation only at certain possibly discrete (resonant) frequencies. In addition, resonators, based on the principle of a sudden change in pipe cross-section, cause a high pressure drop inside the pipe system.

A typical resonator is known from DE-A1-198 55 708 for engine exhaust gas pipes, especially those intended for exhaust turbochargers. A problem with known resonators is that they cannot be used in bent pipes, they are only intended for straight pipes, because the boundary - usually a straight inner pipe - is not otherwise possible to install.

The essence of the technical solution

The object of the present invention is to provide such a noise damping resonator that is easy to install even in bent pipes of any length.

The resonator consists predominantly of two different chambers, which border on the pipeline or. through which the pipe is routed. The section through which the boundary (part of the conduit) enters the enlarged part of the conduit that surrounds it or delimits the chambers is determined in particular after determining the dimensions (dimensions) of the whistle resonator, as is usual in the art. The resonators act as Helmholtz resonators, which makes it possible to determine the resonance frequencies at which the damping is effective, when appropriately sized. Appropriate sizing will be readily appreciated by one skilled in the art. If the gas mixture in the damped piping contains no or only a very small proportion of contaminants or corrosive substances, the volume of the chamber may be filled in whole or in part with a suitable material, such as e.g. mineral wool.

This task is addressed by a damping resonator having at least two chambers located in the expanded section of the pipe and each having one orifice required to communicate with the inner section of the pipe and a boundary separating the chambers from the pipe and having a length L1 + L2; measured in the direction of the pipe, the pipe having an enlarged portion and divided therein and the boundary being arranged such that chambers are formed between the boundary and the widened portion of the pipeline. The essence is explained in the examples. The resonator consists predominantly of two different chambers, which border on the pipeline or. through which the pipe is routed. The section through which the boundary (part of the conduit) enters the enlarged part of the conduit that surrounds it or delimits the chambers is determined in particular after determining the dimensions (dimensions) of the whistle resonator, as is usual in the art. The resonators act as Helmholtz resonators, which makes it possible to determine the resonance frequencies at which the damping is effective, when appropriately sized. Appropriate sizing will be readily appreciated by one skilled in the art. If the gas mixture in the damped piping contains no or only a very small proportion of contaminants or corrosive substances, the volume of the chamber may be filled in whole or in part with a suitable material, such as e.g. mineral wool.

Since the boundary itself - usually a piece of pipe - is inserted into an expanded piece of pipe and fixed there after splitting the pipe at the resonator installation site, such resonators can also be used in bent pipes of any length without so that they need to be welded on both sides into a bent pipe. The advantages of the present solution are:

Since the boundary itself is inserted into and fixed in the extended piece of pipe, such resonators can also be used in the case of bent pipes of any length of pipe.

It is preferred that the boundary is of the same material as the pipe itself, since this can eliminate recycling problems as well as problems that could be caused by different coefficients of expansion.

It is advantageous if the boundary is fixed to the expanded part of the pipe by means of clips which can also serve as a chamber wall.

In one embodiment, the brackets connect the two expanded portions of the pipeline while retaining the boundary.

It is also possible to form the clips by at least one bent end of the expanded part of the pipe. However, the chambers and their boundaries can also be formed by the bent, extended ends of the two piping parts.

Overview of the figures in the drawing

The submitted images represent

Fig. 1 shows a schematic construction of a resonator

Fig. 2 shows a further type of preferred embodiment of a resonator corresponding to the present invention

Fig. 3 another type of resonator corresponding to the present technical solution

Fig. 4 shows another type of embodiment of the resonator

Fig. 5 shows a type of resonator in a perspective view

Fig. 6 longitudinal section, one type of resonator,

Fig. 7,7a, 7b, 7c another type of resonator with a slit in the inner boundary

Fig. 8 shows another type of resonator with a rounded inner pipe with a slit

Fig. 9 shows a different type of resonator with a slit in the inner pipe

Examples of technical solution

Example 1

In FIG. 1 is a schematic representation of an embodiment of a resonator corresponding to a technical solution. The Helmholtz resonator in FIG. 1 consists of one chamber 10 of length L1 with one aperture 11 and another chamber 20 of length L2 with aperture 21, which is defined by an enlarged part of the pipe 6 by a grip 6 and an inner boundary 4.

The resonator consists predominantly of two different chambers bordering the conduit or through which the conduit is routed. The section through which the boundary (part of the conduit) enters the enlarged part of the conduit that surrounds it or delimits the chambers is determined primarily after determining the dimensions (dimensions) of the whistle resonator as is customary in the art. The resonators act as Helmholtz resonators, which makes it possible to determine the resonance frequencies at which the damping is effective, when appropriately sized. Appropriate sizing will be readily appreciated by one skilled in the art. If the gas mixture in the damped piping contains no or only a very small proportion of contaminants or corrosive substances, the volume of the chamber may be filled in whole or in part with a suitable material, such as e.g. mineral wool. A typical embodiment of such a resonator is made of a metal such as aluminum sheet, steel sheet, etc. However, for special designs, it is also possible to use plastic, or combinations of plastic and metal, or fasteners, depending on the installation location. Thus, the silencers can be made of materials available to the skilled person in such a way that they have a long service life even in the ducts through which the gases pass through the polluted gases, e.g. corrosive substances.

The pipe 2 will be divided in the expanded single pipe J. An inner boundary 4, here in the form of a portion of the pipe, will be inserted at the splitting point so that the inlet opening defined by size 21 remains, and an inner boundary 4 is fixed in the expanded portion J of the pipe 5 by the U-shaped fastening tab 6. whose opening 21 permits connection to the interior of the duct. The next step will be to slide the second expanded portion 3 onto the attachment tab 6 and attach it thereto so as to form a one-sided open resonant chamber 10 of the Lis length 10 through the opening 11 to enable it to connect with the interior of the duct. Thus, FIG. 5 shows a pipe with a silencer shown in perspective.

Since there are now two chambers 10, 20 of different volume in communication with the interior of the pipe (see Fig. 6), in each of the chambers when the liquid column is activated in pipe 2, a standing wave can be qualified with a frequency previously determined and which Interference deletes certain vibrations inside the pipe. The determination of the volume of the chambers 10, 20 is easy for the person skilled in the art and depends on the diameter of the pipe, the medium transported therein and the size of the openings 11, 21.

Example 2

Fig. 2, another type of resonator is shown in which the chambers 10, 20 are formed by welded bent portions of the conduit (corresponding to two interconnected clamps 6j each having a longitudinally extending wall). This type of design can be formed by placing welded clamps 6 in the widened portion of the pipe, and attaching them so as to form the widened portion of the pipe 10 with the opening 11 and then inserting another expanded pipe end over the hooks. 6 and secured to form another chamber 20 with an opening 21 communicating with the interior of the pipe.

Example 3

Fig. 3 illustrates another type in which the expanded portions of the duct 3 will be bent and then bluntly connected to each other, forming two chambers 10, 20 with openings 11, 21 facing the interior of the duct.

Example 4

Fig. 4 proposes a combination of one bent extension part 3 with one pipe part attached thereto, wherein another extension part of the duct 3 is connected to the bend of the second extension part 3.

Example 5

Fig. 7 shows a combination of a split outer pipe 2 with an inner boundary 4 with a slot 5 - this construction allows the endings of the inner boundary to be fixed on both sides of the outer pipe 2 so that the inner boundaries 4 with the slot S are fixed on the clamp 6 and both ends on the inner side The communication of the liquid columns in the two chambers 10, 20 with the liquid column within the boundary 4 is possible due to the slots 5.

In FIG. 7a is the inner boundary of FIG. 7 are shown separately - slots are clearly visible which allow communication with the resonant chambers 10, 20. FIG. 7b and 7c are longitudinal sections of the pipe of FIG. 7a - offset at an angle to each other.

Example 6

Fig. 8 shows another type of embodiment of the resonator, in which the rounded inner boundary 4 with the slot 5 forms a ring generally rounded at right angles to allow the inner boundary 4 to be attached to the expanded four-pipe 4 of the pipe 2 thereby saving another separate fastening element. The ends of the inner boundary 4 are again fixed to the inner side of the pipe 2. This type of embodiment can only be realized with very ductile materials of the inner pipe.

Example 7

In FIG. 9 shows another type of resonator corresponding to the present solution, but the inner boundary 4 with the slot 5 is similar to that of FIG. 7 - fixed by another type of embodiment of the holder 6. The holder may be a ring, a part of the pipe, or is of solid material and connects a separate expanded part of the pipe and thereby forms a sealed fluid flow conduit 2.

The choice of type of design and connection technology depends mainly on the material used, the damped medium and the dimensions of the silencer. When using less ductile material, bending the expanded pipe ends may be disadvantageous, and conversely, using a very ductile material, making bent portions of the expanded pipe ends can be very simple. Any common technique is suitable as a connection technique for individual components of silencers - welding of all kinds, soldering or gluing is possible with steel pipes.

Although the technical solution has been explained in more detail on the basis of the above examples, it is by no means limited to these. It is clear to any expert that various embodiments are possible within the scope of the protection claimed.

Claims (8)

PROTECTION REQUIREMENTS Resonator for attenuation of noise and individual tones in pipes, characterized in that it is formed by at least two chambers (10, 20) located in an enlarged part of the pipe (3), the chamber (10) has an opening (11), the chamber (20) has an opening (21), the openings (11, 21) are connected to the duct (2), separated from the duct (2) of the chamber (10, 20) by an inner boundary (4) of length l1 + L2) measured in the duct direction; it has an expanded part 15 of the pipe (i) within which it is divided and an inner boundary (4) is fixed therein. Resonator according to claim 1, characterized in that the inner boundary (4) is made of the same material as the pipe (2). Resonator according to one of Claims 1 to 2, characterized in that the inner boundary (4) inserted into the notrubium (2) is fixed to the expanded part of the pipe φ by means of at least one clamp (6). Resonator according to one of Claims 1 to 3, characterized in that the clamps (6) connect the two parts of the pipe (2) while holding the inner boundary (4) at the same time. Resonator according to one of Claims 1 to 4, characterized in that the clips (6) are formed by at least one bent end of the expanded pipe section ®. Resonator according to one of Claims 1 to 5, characterized in that the chambers (10, 20) and the inner boundary (4) are formed by the bent ends of two expanded duct parts (3). Resonator according to one of Claims 1 to 6, characterized in that the inner boundary (4) is an inner pipe with a slot (5), the end parts of which are fixed on the inner side of the pipe (2). Resonator according to one of the claims 1 to 8, characterized in that at least one part thereof is made of a material such as aluminum sheet and / or steel sheet. coarsely