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EP0316640A1 - Low-frequency silencer - Google Patents

Low-frequency silencer Download PDF

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Publication number
EP0316640A1
EP0316640A1 EP88117971A EP88117971A EP0316640A1 EP 0316640 A1 EP0316640 A1 EP 0316640A1 EP 88117971 A EP88117971 A EP 88117971A EP 88117971 A EP88117971 A EP 88117971A EP 0316640 A1 EP0316640 A1 EP 0316640A1
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EP
European Patent Office
Prior art keywords
feed pipe
damping
inlet tube
sectional area
medium
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Granted
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EP88117971A
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German (de)
French (fr)
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EP0316640B1 (en
Inventor
Jacob Dr. Keller
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BBC Brown Boveri AG Switzerland
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BBC Brown Boveri AG Switzerland
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N1/00—Silencing apparatus characterised by method of silencing

Definitions

  • the present invention relates to a silencer for damping low-frequency sound waves.
  • the impedance properties of flow feeders play an important role with regard to their acoustic stability properties, particularly with regard to low-frequency acoustic natural vibrations of such components.
  • Sound waves that are emitted into feed divisions should, if possible, not be reflected, or at most only to a small extent. Otherwise, the reflected waves can help to ignite strong resonant vibrations.
  • Effective damping of high-frequency sound waves can usually be achieved with simple technical precautions (e.g. use of a classic silencer: perforated plate over a small closed cavity). The attenuation of low-frequency sound waves, however, is much more difficult.
  • the invention seeks to remedy this.
  • the invention as characterized in the claims, is based on the object of achieving the attenuation of a wide frequency band in the smallest space in a silencer of the type mentioned.
  • the main advantage of the invention can be seen in the fact that waves of this type can also be strongly damped, the wavelength of which is substantially greater than four times the length of the feed pipe between the pipe inlet and the row of holes.
  • the absorption in the object according to the invention is proportional to the amplitude , in the vibration-free case, the damping holes are flowed through.
  • the subject matter according to the invention acts as an absorber for the frequency designed in each case, within an attenuation bandwidth of approximately 1 octave.
  • silencer can be integrated into all possible turbomachines at any time with only minor modifications due to its simple and space-saving shape, also as a retrofit measure.
  • the muffler consists of a supply pipe 1 through which a medium flows 3 and around which it flows 4. After a length L from the pipe inlet, this has a row of damper bores 2 distributed over the circumference, through which part 4 of the supplied pipe Medium flows into the interior of the feed pipe 1 and collides there with the medium 3 flowing through the feed pipe.
  • the medium 5 then leaves the feed pipe 1 and enters a turbomachine, not shown.
  • the medium in question is intended to be a gas, in many cases it will be air.
  • the wall 6 is intended to symbolize that the feed pipe 1 forming the muffler can communicate directly with the combustion chamber 7 of the turbomachine, not shown. Of course, the feed pipe 1 can be placed on a premixing element.
  • the type of combustion chamber determines whether a change in cross-section, for example due to a jump in the borehole, is required at the transition between feed pipe 1 and the premixing element (not shown) together.
  • the feed pipe 1 can be followed directly by a burner, which in turn is connected upstream of the combustion chamber. It is physically noticeable that the feed pipe 1 is only characterized by three geometrical sizes, namely by the cross-sectional area A of the feed pipe 1, by the effective length L of the feed pipe, which extends in the direction of flow from the pipe inlet to the center of the damper bores 2, and by the overall cross section B of all damping holes 2 on the bolt circle.
  • the total cross-sectional area B of all the damping bores 2 remains for the optimal design of the muffler.
  • the number of damping bores 2 distributed over the circumference and their diameter depend on the size of the feed pipe 1. The optimization must take into account that the flow velocity V in the damping bores 2 and the sound velocity c of the medium still play a role as further parameters.
  • the sound power of the sound wave of frequency f scattered back by the damper is expressed as a percentage of the radiated power:
  • FIG. 2 shows a further embodiment variant of the muffler, in which the guidance of the air portion 4 to the damping bores 2 is guided through an annular opening 9, which extends over the entire length of the feed pipe 1.
  • a second pipe 8 is provided concentrically with the feed pipe 1. The distance between the second tube 8 and the feed tube 1 depends on the determined amount of the air portion 4 and also on the desired speed of the flow V through the damping bores 2.
  • Fig. 3 shows a graphical representation, from the ⁇ OPTIMAL and the associated percentage performance of the silencer reflected wave are readable.
  • the abscissa 10 with the term represents the phase, ie the length of the muffler, which represents the ideal length for the value 1 on the abscissa 10.
  • one ordinate 11 plots the power of the wave reflected by the muffler in%, based on the incident wave, ie on the wave which is fanned in the combustion chamber and radiated into the muffler.
  • the other ordinate 12 represents ⁇ OPTIMAL . As already explained above, this value contains the total cross-sectional area B of the damping bores 2 as a weight.
  • Curve 13 describes the falling power in% of the wave reflected by the muffler as a function of an increasing phase ( ).
  • the other curve 14 describes the increasing value of ⁇ OPTIMAL with decreasing phase ( ).
  • the graph clearly shows how the ideal value 1 (ideal length) of the muffler means that the power in% of the wave reflected by the muffler is zero, ie complete absorption would have been achieved in such a case.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Exhaust Silencers (AREA)
  • Structures Of Non-Positive Displacement Pumps (AREA)

Abstract

In order to silence low-frequency sound waves, which can arise in components of turbo-engines, the silencer proposed here consists of an inlet tube (1) through (3) and around (4) which a medium flows. At the end of the inlet tube (1) in the outlet flow direction this tube has a row of silencing holes (2), distributed around the circumference, through which the medium (4) flowing around the inlet tube (1) flows into the interior of the inlet tube (1). The effective length L of the inlet tube (1), the cross-sectional area A of the inlet tube (1), and the overall cross-sectional area B of the silencing holes (2) form the geometrical parameters for calculating optimum silencing of the low-frequency sound waves. …<IMAGE>…

Description

Die vorliegende Erfindung betrifft einen Schalldämpfer zur Dämpfung tieffrequentiger Schallwellen.The present invention relates to a silencer for damping low-frequency sound waves.

STAND DER TECHNIKSTATE OF THE ART

Für zahlreiche Strömungsmaschinen, bzw. Komponenten von Strö­mungmaschinen (Brennkammern, Regulierventile etc.), spielen die Impedanzeigenschaften von Strömungszuführungen besonders im Hinblick auf tieffrequentige akustische Eigenschwingungen solcher Komponenten eine wichtige Rolle in bezug auf ihre akustischen Stabilitätseigenschaften. Schallwellen, die in Zufuhrteilungen hinein abgestrahlt werden, sollten möglichst nicht, oder höchstens zu einem geringen Teil, reflektiert werden. Andernfalls können die reflektierten Wellen zur Anfachung von starken resonanten Schwingungen beitragen. Eine wirksame Dämpfung hochfrequentiger Schallwellen kann in der Regel mit einfachen technischen Vorkehrungen (z.B. Verwendung eines klassischen Schalldämpfers: Lochblech über einem kleinen abge­schlossenen Hohlraum) erreicht werden. Die Dämpfung tieffre­quentiger Schallwellen ist dagegen ungleich schwieriger. Eine gängige Technik besteht darin, grosse Helmholzresonatoren an die Zufuhrleitungen anzukoppeln. Der Nachteil einer solchen Massnahme besteht allerdings darin, dass solche Dämpfungsreso­natoren viel Platz in Anspruch nehmen und entsprechend aufwendig und teuer sind. Ausserdem ist die Frequenzbandbreite der Dämp­fung recht klein, und der Dämpfungseffekt ist selbst im opti­malen Frequenzbereich schwach.For numerous turbomachines, or components of turbomachines (combustion chambers, regulating valves, etc.), the impedance properties of flow feeders play an important role with regard to their acoustic stability properties, particularly with regard to low-frequency acoustic natural vibrations of such components. Sound waves that are emitted into feed divisions should, if possible, not be reflected, or at most only to a small extent. Otherwise, the reflected waves can help to ignite strong resonant vibrations. Effective damping of high-frequency sound waves can usually be achieved with simple technical precautions (e.g. use of a classic silencer: perforated plate over a small closed cavity). The attenuation of low-frequency sound waves, however, is much more difficult. A common technique is to couple large Helmholz resonators to the supply lines. The disadvantage of such The measure, however, is that such damping resonators take up a lot of space and are correspondingly complex and expensive. In addition, the frequency bandwidth of the damping is quite small, and the damping effect is weak even in the optimal frequency range.

AUFGABE DER ERFINDUNGOBJECT OF THE INVENTION

Hier will die Erfindung Abhilfe schaffen. Der Erfindung, wie sie in den Ansprüchen gekennzeichnet ist, liegt die Aufgabe zugrunde, bei einem Schalldämpfer der eingangs genannten Art die Dämpfung eines breiten Frequenzbandes auf kleinstem Raum zu erzielen.The invention seeks to remedy this. The invention, as characterized in the claims, is based on the object of achieving the attenuation of a wide frequency band in the smallest space in a silencer of the type mentioned.

Der wesentliche Vorteil der Erfindung ist darin zu sehen, dass mit einem solchen Schalldämpfer auch Wellen stark gedämpft werden können, deren Wellenlänge wesentlich grösser ist als die vierfache Länge des Zufuhrrohres zwischen Rohreintritt und Lochreihe.The main advantage of the invention can be seen in the fact that waves of this type can also be strongly damped, the wavelength of which is substantially greater than four times the length of the feed pipe between the pipe inlet and the row of holes.

Des weiteren, während bei normalen Schalldämpfern, wie sie beispielsweise in der Abgasleitung von Verbrennungsmaschinen als Helmholzresonatoren anzutreffen sind, die Absorption qua­dratisch in der Schallwellenamplitude verläuft, wobei im schwin­gungsfreien Fall die dort vorgesehenen Bohrungen nicht durch­strömt werden, verläuft die Absorption beim erfindungsgemässen Gegenstand proportional zur Amplitude, im schwingungsfreien Fall sind die Dämpfungsbohrungen durchströmt.Furthermore, while in normal mufflers, such as those found in the exhaust pipe of internal combustion engines as Helmholz resonators, the absorption is quadratic in the sound wave amplitude, the holes provided there not being flowed through in the vibration-free case, the absorption in the object according to the invention is proportional to the amplitude , in the vibration-free case, the damping holes are flowed through.

Dies bedeutet, dass der vorliegende erfindungsgemässe Gegenstand für die jeweils ausgelegte Frequenz als Absorber wirkt, inner­halb einer Dämpfungsbandbreite von etwa 1 Oktav.This means that the subject matter according to the invention acts as an absorber for the frequency designed in each case, within an attenuation bandwidth of approximately 1 octave.

Ein weiterer Vorteil der Erfindung ist darin zu sehen, dass der Schalldämpfer durch seine einfache und platzsparende Form jederzeit mit nur geringfügigen Modifikationen in alle möglichen Strömungsmaschinen integriert werden kann, dies auch als Retro­fit-Massnahme.Another advantage of the invention is that the silencer can be integrated into all possible turbomachines at any time with only minor modifications due to its simple and space-saving shape, also as a retrofit measure.

Vorteilhafte und zweckmässige Weiterbildungen der erfindungsge­mässen Aufgabenlösung sind in den abhängigen Ansprüchen gekenn­zeichnet.Advantageous and expedient developments of the task solution according to the invention are characterized in the dependent claims.

Im folgenden werden anhand der Zeichnung Ausführungsbeispiele der Erfindung erläutert. Alle für das unmittelbare Verständnis der Erfindung nicht erforderlichen Elemente sind fortgelassen.Exemplary embodiments of the invention are explained below with reference to the drawing. All elements not necessary for the immediate understanding of the invention have been omitted.

KURZE BESCHREIBUNG DER ERFINDUNGBRIEF DESCRIPTION OF THE INVENTION

Es zeigt:

  • Fig. 1 einen Schalldämpfer,
  • Fig. 2 eine weitere Ausführung eines Schalldämpfers und
  • Fig. 3 die graphische Erfassung der optimalen Dämpfungseigen­schaften.
It shows:
  • 1 shows a silencer,
  • Fig. 2 shows another embodiment of a silencer and
  • Fig. 3 shows the graphic recording of the optimal damping properties.

BESCHREIBUNG DER AUSFÜHRUNGSBEISPIELEDESCRIPTION OF THE EMBODIMENTS

Wie aus Fig. 1 ersichtlich ist, besteht der Schalldämpfer aus einem von einem Medium durchströmten 3 und umströmten 4 Zufuhrrohr 1. Dieses weist nach einer Länge L ab Rohreintritt eine über den Umfang verteilte Reihe von Dämpferbohrungen 2 auf, durch welche ein Teil 4 des herangeführten Mediums ins Innere des Zufuhrrohres 1 strömt und stösst dort mit dem durch das Zufuhrrohr strömenden Mediums 3 zusammen. Anschliessend verlässt das Medium 5 das Zufuhrrohr 1 und tritt in eine nicht dargestellte Strömungsmaschine ein. Bestimmungsgemäss handelt es sich beim vorliegenden Medium um ein Gas, vielfach wird es sich um Luft handeln. Die Wand 6 will versinnbildlichen, dass das den Schalldämpfer bildende Zufuhrrohr 1 unmittelbar mit dem Brennraum 7 der nicht dargestellten Strömungsmaschine kommunizieren kann. Selbstverständlich kann das Zufuhrrohr 1 auf ein Vormischelement aufgesetzt werden. Ob am Uebergang zwischen Zufuhrrohr 1 und dem nicht dargestellten Vormisch­element eine Querschnittsänderung, beispielsweise durch einen Bordasprung, vonnöten ist, hängt mit der Art der Brennkammer zusammen. Aus Platzgründen kommt es des weiteren vor, dass dem Zufuhrrohr 1 unmittelbar ein Brenner folgen kann, der seinerseits dem Brennraum vorgeschaltet ist. Körperlich fällt auf, dass das Zufuhrrohr 1 lediglich durch drei geometrische Grössen charakterisiert ist, nämlich durch die Querschnitts­fläche A des Zufuhrrohres 1, durch die effektive Länge L des Zufuhrrohres, welche in Strömungsrichtung vom Rohreintritt bis zur Mitte der Dämpferbohrungen 2 reicht, und durch den Gesamtquerschnitt B aller Dämpfungsbohrungen 2 auf dem Loch­kreis. Weitere Parameter für die optimale Auslegung eines Schalldämpfers sind des weiteren die Geschwindigkeit der Strö­mung V durch die Dämpfungsbohrungen 2 und die Schallgeschwindig­keit c des Mediums selbst. Grundsätzlich hängt die Geschwindig­keit V auch von der Grösse der einzelnen Dämpfungsbohrungen 2 ab. Andererseits ist die Dimensionierung und Anzahl der Dämp­fungsbohrungen 2 von der Querschnittsfläche A des Zufuhrrohres 1 abhängig. Mathematisch wird der Gesamtquerschnitt B der Dämpfungsbohrungen 2 mit

Figure imgb0001
wobei n die Anzahl der Oeffnungen und dL deren Durchmesser bedeuten.As can be seen from FIG. 1, the muffler consists of a supply pipe 1 through which a medium flows 3 and around which it flows 4. After a length L from the pipe inlet, this has a row of damper bores 2 distributed over the circumference, through which part 4 of the supplied pipe Medium flows into the interior of the feed pipe 1 and collides there with the medium 3 flowing through the feed pipe. The medium 5 then leaves the feed pipe 1 and enters a turbomachine, not shown. The medium in question is intended to be a gas, in many cases it will be air. The wall 6 is intended to symbolize that the feed pipe 1 forming the muffler can communicate directly with the combustion chamber 7 of the turbomachine, not shown. Of course, the feed pipe 1 can be placed on a premixing element. The type of combustion chamber determines whether a change in cross-section, for example due to a jump in the borehole, is required at the transition between feed pipe 1 and the premixing element (not shown) together. For reasons of space, it also happens that the feed pipe 1 can be followed directly by a burner, which in turn is connected upstream of the combustion chamber. It is physically noticeable that the feed pipe 1 is only characterized by three geometrical sizes, namely by the cross-sectional area A of the feed pipe 1, by the effective length L of the feed pipe, which extends in the direction of flow from the pipe inlet to the center of the damper bores 2, and by the overall cross section B of all damping holes 2 on the bolt circle. Further parameters for the optimal design of a muffler are also the speed of the flow V through the damping bores 2 and the speed of sound c of the medium itself. In principle, the speed V also depends on the size of the individual damping bores 2. On the other hand, the dimensioning and number of damping bores 2 depend on the cross-sectional area A of the feed pipe 1. Mathematically, the total cross section B of the damping bores 2 with
Figure imgb0001
 where n is the number of openings and d L is the diameter.

Da in der Praxis die Querschnittsfläche A und die effektive Länge L des Zufuhrrohres 1 aus anlagetechnischen Dispositionen vorgegeben sind, verbleibt für die optimale Auslegung des Schalldämpfers vornehmlich die Geamtquerschnittsfläche B aller Dämpfungsbohrungen 2 übrig. Die Anzahl der auf den Umfang verteilten Dämpfungsbohrungen 2 und deren Durchmesser hängt dabei von der Grösse des Zufuhrrohres 1 ab. Die Optimierung muss dabei berücksichtigen, dass als weitere Parameter die Durchströmungsgeschwindigkeit V in den Dämpfungsbohrungen 2 und die Schallgeschwindigkeit c des Mediums noch eine Rolle spielen.Since, in practice, the cross-sectional area A and the effective length L of the feed pipe 1 are predefined from technical dispositions, the total cross-sectional area B of all the damping bores 2 remains for the optimal design of the muffler. The number of damping bores 2 distributed over the circumference and their diameter depend on the size of the feed pipe 1. The optimization must take into account that the flow velocity V in the damping bores 2 and the sound velocity c of the medium still play a role as further parameters.

Die Schall-Leistung der vom Dämpfer zurückgestreuten Schall­welle der Frequenz f beträgt in Prozenten der eingestrahlten Leistung ausgedrückt:

Figure imgb0002
The sound power of the sound wave of frequency f scattered back by the damper is expressed as a percentage of the radiated power:
Figure imgb0002

Dabei soll die Gesamtquerschnittsfläche B der Dämpfungsbohrungen so gewählt werden, dass der Parameter α seinen optimalen Wert αOPTIMAL erreicht:

αOPTIMAL= [ 1 +

Figure imgb0003
]1/2      (3)
The total cross-sectional area B of the damping holes should be selected so that the parameter α reaches its optimal value α OPTIMAL :

α OPTIMAL = [1 +
Figure imgb0003
] 1/2 (3)

Durch Einsetzung des so erhaltenen Wertes α OPTIMAL in Gleichung (2) errechnet sich dann die prozentuale Leistung der vom Schall­dämpfer reflektierten Welle für den jeweiligen zugrundegelegten Fall.By inserting the value α OPTIMAL thus obtained into equation (2), the percentage power of the wave reflected by the silencer is then calculated for the respective underlying case.

Fig. 2 zeigt eine weitere Ausführungsvariante des Schalldämpfers, bei welchem die Führung des Luftanteils 4 zu den Dämfpungs­bohrungen 2 durch eine Ringöffnung 9 geleitet wird, welche sich auf die ganze Länge des Zuführrohres 1 erstreckt. Zu diesem Zweck ist konzentrisch zum Zufuhrrohr 1 ein zweites Rohr 8 vorgesehen. Der Abstand des zweiten Rohres 8 zum Zuführ­rohr 1 hängt von der ermittelten Menge des Luftanteils 4 und auch von der angestrebten Geschwindigkeit der Strömung V durch die Dämpfungsbohrungen 2 ab.FIG. 2 shows a further embodiment variant of the muffler, in which the guidance of the air portion 4 to the damping bores 2 is guided through an annular opening 9, which extends over the entire length of the feed pipe 1. For this purpose, a second pipe 8 is provided concentrically with the feed pipe 1. The distance between the second tube 8 and the feed tube 1 depends on the determined amount of the air portion 4 and also on the desired speed of the flow V through the damping bores 2.

Fig. 3 zeigt eine graphische Darstellung, aus der αOPTIMAL und die dazugehörige prozentuale Leistung der vom Schalldämpfer reflektierten Welle herauslesbar sind. Die Abszisse 10 mit dem Term

Figure imgb0004
stellt die Phase dar, d.h. jene Länge des Schall­dämpfers, welche beim Wert 1 auf der Abszisse 10 die Ideallänge darstellt. die eine Ordinate 11 trägt die Leistung der vom Schalldämpfer reflektierten Welle in % auf, bezogen auf die einfallende Welle, d.h. auf die Welle, welche im Brennraum angefacht und in den Schalldämpfer eingestrahlt wird. Die andere Ordinate 12 stellt αOPTIMAL dar. In diesem Wert ist, wie oben bereits dargelegt wurde, gewichtig die Gesamtquer­schnittsfläche B der Dämpfungsbohrungen 2 enthalten. Die Kurve 13 beschreibt die abfallende Leistung in % der vom Schalldämpfer reflektierten Welle in Abhängigkeit zu einer zunehmenden Phase (
Figure imgb0005
). die andere Kurve 14 beschreibt den zunehmenden Wert von αOPTIMAL bei abnehmender Phase (
Figure imgb0006
). Gut ersichtlich ist in der Graphik, wie beim Idealwert 1 (Ideallänge) des Schalldämpfers die Leistung in % der vom Schalldämpfer reflek­tierten Welle Null beträgt, d.h. man hätte in einem solchen Fall eine vollständige Absorption erreicht.Fig. 3 shows a graphical representation, from the α OPTIMAL and the associated percentage performance of the silencer reflected wave are readable. The abscissa 10 with the term
Figure imgb0004
represents the phase, ie the length of the muffler, which represents the ideal length for the value 1 on the abscissa 10. one ordinate 11 plots the power of the wave reflected by the muffler in%, based on the incident wave, ie on the wave which is fanned in the combustion chamber and radiated into the muffler. The other ordinate 12 represents α OPTIMAL . As already explained above, this value contains the total cross-sectional area B of the damping bores 2 as a weight. Curve 13 describes the falling power in% of the wave reflected by the muffler as a function of an increasing phase (
Figure imgb0005
). the other curve 14 describes the increasing value of α OPTIMAL with decreasing phase (
Figure imgb0006
). The graph clearly shows how the ideal value 1 (ideal length) of the muffler means that the power in% of the wave reflected by the muffler is zero, ie complete absorption would have been achieved in such a case.

In der Praxis ist es indessen vielfach so, insbesondere bei einem Retrofit-Einbau des Schalldämpfers, dass eine verminderte Phase gewählt werden muss. Sind die einbauverhältnisse derge­stalt, dass beispielsweise nur 50 % der theoretischen Ideal­länge des Schalldämpfers gewählt werden kann, so entspricht dies einem αOPTIMAL von ca. 1,40 (senkrechte Schnittstelle mit Kurve 14). Setzt man diesen Werte in Formel (2a) ein, so lässt sich bei vorgegebener Querschnittsfläche A des Zufuhr­rohres 1 die Gesamtquerschnittsfläche B der Dämpfungsbohrungen 2 errechnen. Die andere Schnittstelle mit Kurve 14 ergibt die prozentuale Leistung der vom Schalldämpfer reflektierten Welle; in unserem Fall entspricht dies ca. 19 %, was immer noch eine nahezu vollständige Absorption darstellt. Als Einlei­tungshilfe zur Benutzung der Graphik gemäss Fig. 3 wird das angenommene Beispiel in form von gestrichelten Linien in die Graphik aufgenommen.In practice, however, it is often the case, particularly when the silencer is retrofitted, that a reduced phase must be selected. If the installation conditions are such that, for example, only 50% of the theoretical ideal length of the silencer can be selected, this corresponds to an α OPTIMAL of approx. 1.40 (vertical interface with curve 14). If these values are used in formula (2a), the total cross-sectional area B of the damping bores 2 can be calculated for a given cross-sectional area A of the feed pipe 1. The other interface with curve 14 gives the percentage power of the wave reflected by the silencer; in our case this corresponds to approx. 19%, which is still an almost complete absorption. As an introduction to the use of the graphic according to FIG. 3, the assumed example is included in the graphic in the form of dashed lines.

Claims (3)

1. Schalldämpfer zur Dämpfung tieffrequentiger Schallwellen, dadurch gekennzeichnet, dass der Schalldämpfer aus einem von einem Medium durchströmten (3) und umströmten (4) Zu­fuhrrohr (1) besteht, der ab Zufuhrrohreintritt nach einer Länge (L) in Abströmungsrichtung eine über den Umfang ver­teilte Reihe von Dämpfungsbohrungen (2) aufweist, über welche das das Zufuhrrohr (1) umströmende Medium (4) ins Innere des Zufuhrrohres (1) strömt.1. Muffler for damping low-frequency sound waves, characterized in that the muffler consists of a feed pipe (1) through which a medium flows (3) and around which (4), which from the inlet pipe inlet is distributed over the circumference after a length (L) in the outflow direction Row of damping bores (2), via which the medium (4) flowing around the feed pipe (1) flows into the inside of the feed pipe (1). 2. Schalldämpfer nach Anspruch 1, dadurch gekennzeichnet, dass die Leistung der vom Schalldämpfer reflektierten Welle, bezogen auf die einfallende Welle, in % ausgedrückt:
Figure imgb0007
 mit der Bedeutung, dass

A=Querschnittfläche des Zufuhrrohres (1)
B=Gesamtquerschnittsfläche der Dämpfungsbohrungen (2)
c=Schallgeschwindigkeit des Mediums (3)
f=Frequenz der Schallwelle
L=Effektive Länge des Zufuhrrohres (1) vom Rohreintritt bis zum Lochkreis
V=Geschwindigkeit der Strömung durch die Dämpfungsboh­rungen (2).
2. Silencer according to claim 1, characterized in that the power of the reflected wave from the silencer, based on the incident wave, expressed in%:
Figure imgb0007
 meaning that

A = cross-sectional area of the feed pipe (1)
B = total cross-sectional area of the damping holes (2)
c = speed of sound of the medium (3)
f = frequency of the sound wave
L = effective length of the feed pipe (1) from the pipe entry to the bolt circle
V = velocity of the flow through the damping holes (2).
3. Schalldämpfer nach Anspruch 1, dadurch gekennzeichnet, dass αOPTIMAL folgendermasse bestimmt wird:

αOPTIMAL = [ (1 +
Figure imgb0008
) ]1/2,
wobei
Figure imgb0009
 ist.3. Silencer according to claim 1, characterized in that α OPTIMAL is determined as follows:

α OPTIMAL = [(1 +
Figure imgb0008
)] 1/2 ,
in which
Figure imgb0009
 is.
EP88117971A 1987-11-18 1988-10-28 Low-frequency silencer Expired - Lifetime EP0316640B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CH449487 1987-11-18
CH4494/87 1987-11-18

Publications (2)

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EP0316640A1 true EP0316640A1 (en) 1989-05-24
EP0316640B1 EP0316640B1 (en) 1993-02-10

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Application Number Title Priority Date Filing Date
EP88117971A Expired - Lifetime EP0316640B1 (en) 1987-11-18 1988-10-28 Low-frequency silencer

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US (1) US4923035A (en)
EP (1) EP0316640B1 (en)
DE (1) DE3878408D1 (en)

Cited By (1)

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Publication number Priority date Publication date Assignee Title
DE10336738B4 (en) * 2002-08-28 2007-08-23 General Motors Corp., Detroit Silencer for opening a crankcase breather

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP3863588B2 (en) * 1995-04-29 2006-12-27 株式会社大宇エレクトロニクス Bubble generator for washing machine
US20040163886A1 (en) * 2002-02-15 2004-08-26 Sutera Anthony J. Air turbine for combustion engine
US7650965B2 (en) * 2006-06-09 2010-01-26 Emcon Technologies Llc Exhaust system
US9422843B2 (en) * 2013-09-08 2016-08-23 Michael Wayne Barrett Resonance generating muffler
DE102014226266A1 (en) 2014-12-17 2016-06-23 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Insulating and filtering material and its use as an inert sound-absorbing material

Citations (7)

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Publication number Priority date Publication date Assignee Title
US1338520A (en) * 1919-07-03 1920-04-27 George W Moores Muffler
US2838128A (en) * 1955-08-30 1958-06-10 Sr Edward A Kliewer Engine exhaust muffler
GB888853A (en) * 1958-12-30 1962-02-07 Edward Henry Phillips Exhaust silencer
US3361227A (en) * 1963-10-24 1968-01-02 Mekes Oy Mufflers and exhaust systems
DE1264864B (en) * 1960-06-27 1968-03-28 Leistritz Hans Karl Silencer for flowing gases
US3888331A (en) * 1974-05-03 1975-06-10 Gen Motors Corp Power tuned wave interference silencer
FR2363696A1 (en) * 1976-08-31 1978-03-31 Nihon Radiator Co Exhaust silencer for IC engine - has longitudinal division with inlet and discharge pipes opening in opposite compartments

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US944646A (en) * 1909-02-18 1909-12-28 Joseph A Xardell Exhaust-muffler.
US1966620A (en) * 1932-11-26 1934-07-17 Fluor Corp Muffler

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1338520A (en) * 1919-07-03 1920-04-27 George W Moores Muffler
US2838128A (en) * 1955-08-30 1958-06-10 Sr Edward A Kliewer Engine exhaust muffler
GB888853A (en) * 1958-12-30 1962-02-07 Edward Henry Phillips Exhaust silencer
DE1264864B (en) * 1960-06-27 1968-03-28 Leistritz Hans Karl Silencer for flowing gases
US3361227A (en) * 1963-10-24 1968-01-02 Mekes Oy Mufflers and exhaust systems
US3888331A (en) * 1974-05-03 1975-06-10 Gen Motors Corp Power tuned wave interference silencer
FR2363696A1 (en) * 1976-08-31 1978-03-31 Nihon Radiator Co Exhaust silencer for IC engine - has longitudinal division with inlet and discharge pipes opening in opposite compartments

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE10336738B4 (en) * 2002-08-28 2007-08-23 General Motors Corp., Detroit Silencer for opening a crankcase breather

Also Published As

Publication number Publication date
DE3878408D1 (en) 1993-03-25
US4923035A (en) 1990-05-08
EP0316640B1 (en) 1993-02-10

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