WO1996007050A1 - Attenuateur de sons emis dans l'air - Google Patents
Attenuateur de sons emis dans l'air Download PDFInfo
- Publication number
- WO1996007050A1 WO1996007050A1 PCT/FR1995/000919 FR9500919W WO9607050A1 WO 1996007050 A1 WO1996007050 A1 WO 1996007050A1 FR 9500919 W FR9500919 W FR 9500919W WO 9607050 A1 WO9607050 A1 WO 9607050A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- flow
- attenuator
- section
- air
- sounds
- Prior art date
Links
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16L—PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
- F16L55/00—Devices or appurtenances for use in, or in connection with, pipes or pipe systems
- F16L55/02—Energy absorbers; Noise absorbers
- F16L55/033—Noise absorbers
Definitions
- the invention relates to an attenuator of sounds emitted into the air, consisting of a flow pipe surrounded by a tight wall, which is traversed by a gaseous medium at subsonic speed, as well as a device for suppressing emissions. sounds in the air, connected to the flow line.
- Such attenuators of sounds emitted into the air are generally known and form, for example, a constituent element of a motor vehicle exhaust designed as an air exhaust channel. Sound attenuators emitted into the air of this type are arranged in the direction of flow behind the noise source, which in this case is constituted by the engine of the motor vehicle.
- the sound attenuators emitted into the air known up to now are not suitable for parts with gas circulation, such as for example fans or gas control parts, such as for example valves, in which the propagation of the its takes place in the direction opposite to the direction of flow.
- the object of the invention is to improve a sound attenuator emitted into the air of the prior art, so that it causes absorption of the sounds emitted into the air in the case of machines and parts to gas circulation and gas control, in the direction opposite to the direction of flow, and so as to avoid practically all emission of sounds into the air.
- the flow pipe as an air intake channel, to arrange the device in the direction of flow of the medium before a source of noise emitting sounds, to eliminate the emission of sounds into the air in the direction opposite to the direction of flow, and to cause the device to include at least one means of modifying the flow, which causes at least in one place an increase in the speed of the gaseous medium almost up to the speed of sound.
- Gas circulating and gas controlled machines and parts often produce high noise levels when used as directed. The causes are mostly due to high flow velocities and unfavorable geometries from the point of view of fluid technology.
- the noises propagate in the gas column of the medium both in the direction of its flow and in the opposite direction.
- the advantage of the sound attenuator emitted into the air according to the invention lies in the fact that it is arranged in an air intake channel in which the means for modifying the flow is arranged in the direction of flow of the medium before the source of noise emitting sounds.
- the sounds emitted by the noise source which propagate in the direction of the flow modification means, cannot, when they reach it, propagate further in the direction opposite to the flow direction, because the speed of sound is reached when the medium passes through the means for modifying the flow.
- the arrival of the gaseous medium passing at the speed of sound in the direction of the noise source means that the undesirable noises cannot propagate in the region which is before the means of modification of the flow.
- the gases passing at the speed of sound through the device act, with respect to the sounds emitted by the noise source, as a sound-absorbing barrier.
- the means for modifying the flow can be formed by at least one nozzle which has a substantially circular passage cross section to minimize flow loss.
- the volume flow rate of the gaseous medium is only very slightly reduced.
- the nozzle can be designed as a Laval nozzle.
- Means for modifying the flow, of a shape different from that, such as for example diaphragms, can also be used, when it is guaranteed that the gaseous medium will be accelerated to almost the speed of sound in at least one place.
- the flow noise produced by the nozzle in the case of high flow velocities is only very low due to the favorable geometry of the nozzles in the case of Laval nozzles.
- the nozzle has, in the region of its axial ends, first and third opening cross sections, the first etan opening cross section disposed on the side opposite to the noise source, and narrowing in the direction of the flows, at the side facing the noise source, at a second opening cross section and the second opening cross section being widened at the side facing the noise source in the direction of flow, up to the third opening cross section, which is at least as large as the first opening cross section.
- the second opening cross section preferably widens conically in the direction of the third opening cross section.
- the area of the first opening cross section is 1.01 to 2.5 times larger than the area of the second opening cross section
- the area of the third opening cross section is 1.05 to 4 times larger than the area of the second opening cross section
- the length of the nozzle in the direction of flow is 4 to 12 times larger than the diameter of the second opening cross section.
- the wall d limiting the opening cross section of the nozzle between the second and third opening cross sections forms, with the axis of symmetry of the nozzle, preferably an angle of 2 to 8 °.
- Such an embodiment is advantageous if a laminar flow and a flow rate which is essentially free of flow losses are desired.
- the second and third opening cross sections are therefore designed, according to an advantageous embodiment, without discontinuous changes in cross section, in gradual transition from one to the other.
- flow modification means having small dimensions and good efficiency.
- it can be provided to have, inside the flow pipe, in the direction of flow before the noise source, at least two nozzles uniformly spaced in the peripheral direction in functional parallel mounting.
- Such a means of modifying the flow allows high volume flow rates through the sound attenuator, is of small size and can be produced economically.
- the flow modification means protect the environment reliably from the sounds emitted into the air produced by the noise source.
- the nozzles have, for stationary states of flow of the medium, a coincident design with the same cross section of flow passage. If the flow conditions of the air intake are largely constant inside the flow pipe, and the medium is accelerated inside the nozzles up to the speed of sound, it follows an excellent sound insulation of the sounds emitted by the noise source in the direction opposite to the direction of the flow.
- the nozzles may be advisable for the nozzles to have a flow passage cross section which is distinguished from one another in the case of non-stationary flow states, so that even under different flow conditions, the medium can be accelerated at the speed of sound at least in one of the nozzles, and therefore that it occurs at least reduced noise emissions to the air.
- the sound attenuator emitted in the air it can be provided, according to an advantageous embodiment of the sound attenuator emitted in the air, that at least one of the nozzles used as a means for modifying the flow is provided with an auxiliary element for modifying and / or closing at least one cross section of the nozzle.
- the auxiliary element can for example be formed by a stop valve, which regulates the cross section of the nozzles according to the existing flow conditions so that the medium reaches the speed of sound at the place of cross section the narrower of the nozzles.
- the nozzles can be designed as a pre-assembled unit and can be inserted together in the flow pipe. In this case, it is advantageous that the manufacture of the unit and that the assembly can be carried out without problem.
- the individual nozzles are always optimally positioned with respect to each other during installation of the unit in the flow line. Handling - unlike mounting individual nozzles - is considerably simplified.
- the unit can be designed as an injection molded plastic part. In this case, it is advantageous that the manufacturing of the unit can be carried out in a simple and economical manner. In addition, the unit has a low weight.
- the air sound attenuator is used for example in a brake booster of a motor vehicle. There is a valve in the distributor piston of the brake booster, in which there is, on one side of the gas control valve, a strong negative pressure, so that upon activation of this valve, a strong current of air immediately passes through the valve.
- a strong negative pressure so that upon activation of this valve, a strong current of air immediately passes through the valve.
- Laval nozzle which plays the role of a sound attenuator emitted in the air.
- the flow noises in the passenger compartment of the motor vehicle are therefore not perceived. Despite the considerable reduction in noise, the maximum air flow rate determining for the efficiency of a brake booster is not reduced.
- the sound attenuator emitted into the air according to the invention will be explained in more detail below with the aid of the drawing.
- the drawing illustrates a flow pipe 1, which is surrounded by a gas-tight wall.
- the flow line 1 is designed as an air intake channel and surrounds a noise source 5 which is not described further.
- the noise source 5 can for example be constituted by a fan or a valve, a differential pressure acting at the noise source 5 in the direction of the flow 4.
- a device 3 having a flow modification means, the flow modification means being formed in this example by two nozzles 6, which are designed as Laval nozzles.
- the two nozzles 6 are arranged in a functional parallel arrangement and each have three opening cross sections 7, 8, 9.
- the first opening cross section 7 is disposed on the side of nozzles 6 opposite the noise source 5.
- the third opening cross section 9 are arranged on the largest side and facing the noise source 5.
- the medium 2 is accelerated in the region of the first opening cross sections 7, and presents, in l region of the second opening cross sections 8, which form the narrowest cross section locations of the nozzles 6, its highest speed. In this region, the speed of sound is reached. Because the medium 2 flows through the nozzles 6 at the speed of sound, the sound emitted by the noise source 5 remains on the negative pressure side 10 of the nozzles and therefore does not reach the overpressure side 1 1.
Landscapes
- Engineering & Computer Science (AREA)
- General Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Exhaust Silencers (AREA)
- Details Of Valves (AREA)
Abstract
Description
Claims
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP95925030A EP0778930A1 (fr) | 1994-08-30 | 1995-07-10 | Attenuateur de sons emis dans l'air |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DEP4430698.9 | 1994-08-30 | ||
DE19944430698 DE4430698C1 (de) | 1994-08-30 | 1994-08-30 | Luftschalldämpfer |
Publications (1)
Publication Number | Publication Date |
---|---|
WO1996007050A1 true WO1996007050A1 (fr) | 1996-03-07 |
Family
ID=6526871
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/FR1995/000919 WO1996007050A1 (fr) | 1994-08-30 | 1995-07-10 | Attenuateur de sons emis dans l'air |
Country Status (3)
Country | Link |
---|---|
EP (1) | EP0778930A1 (fr) |
DE (1) | DE4430698C1 (fr) |
WO (1) | WO1996007050A1 (fr) |
Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO1990009243A1 (fr) * | 1989-02-08 | 1990-08-23 | Cold Jet, Inc. | Tuyere supersonique attenuant le bruit |
US5088575A (en) * | 1990-09-13 | 1992-02-18 | Nelson Industries, Inc. | Acoustic system with transducer and venturi |
Family Cites Families (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE1929307C3 (de) * | 1969-06-10 | 1975-09-04 | Meto-Gesellschaft Oscar Kind Mbh, 6932 Hirschhorn | Druck- oder Stempelvorrichtung mit Typenbändern |
DE3625566A1 (de) * | 1986-07-29 | 1987-01-02 | Escher Wyss Gmbh | Daempfungsvorrichtung fuer eine fluessigkeitsstroemung |
-
1994
- 1994-08-30 DE DE19944430698 patent/DE4430698C1/de not_active Expired - Fee Related
-
1995
- 1995-07-10 WO PCT/FR1995/000919 patent/WO1996007050A1/fr not_active Application Discontinuation
- 1995-07-10 EP EP95925030A patent/EP0778930A1/fr not_active Ceased
Patent Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO1990009243A1 (fr) * | 1989-02-08 | 1990-08-23 | Cold Jet, Inc. | Tuyere supersonique attenuant le bruit |
US5088575A (en) * | 1990-09-13 | 1992-02-18 | Nelson Industries, Inc. | Acoustic system with transducer and venturi |
Non-Patent Citations (2)
Title |
---|
ATZ AUTOMOBILTECHNISCHE ZEITSCHRIFT, vol. 92, STUTTGART, DE, pages 565, XP000174822 * |
VLASOV ET AL: "Reduction of supersonic turbulent jet noise", ACOUSTIC PHYSICS, vol. 39, WOODBURY, NY, US, pages 425 - 427, XP000434033 * |
Also Published As
Publication number | Publication date |
---|---|
DE4430698C1 (de) | 1996-02-08 |
EP0778930A1 (fr) | 1997-06-18 |
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