GB2117046A - Silencing in fluid flow impelling systems - Google Patents

Silencing in fluid flow impelling systems Download PDF

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Publication number
GB2117046A
GB2117046A GB08306542A GB8306542A GB2117046A GB 2117046 A GB2117046 A GB 2117046A GB 08306542 A GB08306542 A GB 08306542A GB 8306542 A GB8306542 A GB 8306542A GB 2117046 A GB2117046 A GB 2117046A
Authority
GB
United Kingdom
Prior art keywords
sound
fluid moving
moving system
counter
casing
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
GB08306542A
Other versions
GB8306542D0 (en
GB2117046B (en
Inventor
Wolfgang Neise
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Deutsches Zentrum fuer Luft und Raumfahrt eV
Original Assignee
Deutsche Forschungs und Versuchsanstalt fuer Luft und Raumfahrt eV DFVLR
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Deutsche Forschungs und Versuchsanstalt fuer Luft und Raumfahrt eV DFVLR filed Critical Deutsche Forschungs und Versuchsanstalt fuer Luft und Raumfahrt eV DFVLR
Publication of GB8306542D0 publication Critical patent/GB8306542D0/en
Publication of GB2117046A publication Critical patent/GB2117046A/en
Application granted granted Critical
Publication of GB2117046B publication Critical patent/GB2117046B/en
Expired legal-status Critical Current

Links

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D29/00—Details, component parts, or accessories
    • F04D29/66—Combating cavitation, whirls, noise, vibration or the like; Balancing
    • F04D29/661—Combating cavitation, whirls, noise, vibration or the like; Balancing especially adapted for elastic fluid pumps
    • F04D29/663—Sound attenuation
    • F04D29/665—Sound attenuation by means of resonance chambers or interference
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/16—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/175—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound
    • G10K11/178—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound by electro-acoustically regenerating the original acoustic waves in anti-phase
    • G10K11/1785—Methods, e.g. algorithms; Devices
    • G10K11/17857—Geometric disposition, e.g. placement of microphones
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/16—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/175—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound
    • G10K11/178—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound by electro-acoustically regenerating the original acoustic waves in anti-phase
    • G10K11/1787—General system configurations
    • G10K11/17873—General system configurations using a reference signal without an error signal, e.g. pure feedforward
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/16—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/175—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound
    • G10K11/178—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound by electro-acoustically regenerating the original acoustic waves in anti-phase
    • G10K11/1787—General system configurations
    • G10K11/17875—General system configurations using an error signal without a reference signal, e.g. pure feedback
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K2210/00—Details of active noise control [ANC] covered by G10K11/178 but not provided for in any of its subgroups
    • G10K2210/10—Applications
    • G10K2210/109—Compressors, e.g. fans
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K2210/00—Details of active noise control [ANC] covered by G10K11/178 but not provided for in any of its subgroups
    • G10K2210/10—Applications
    • G10K2210/121—Rotating machines, e.g. engines, turbines, motors; Periodic or quasi-periodic signals in general
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K2210/00—Details of active noise control [ANC] covered by G10K11/178 but not provided for in any of its subgroups
    • G10K2210/30—Means
    • G10K2210/321—Physical
    • G10K2210/3212—Actuator details, e.g. composition or microstructure
    • G10K2210/32121—Fluid amplifiers, e.g. modulated gas flow speaker using electrovalves
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K2210/00—Details of active noise control [ANC] covered by G10K11/178 but not provided for in any of its subgroups
    • G10K2210/30—Means
    • G10K2210/321—Physical
    • G10K2210/3216—Cancellation means disposed in the vicinity of the source

Abstract

A chamber 17 housing one or more loudspeakers 18 extends to the smallest radius of the impeller casing 10 and the loudspeaker is energised at a frequency determined by a pulse producing circuit (20... 23, Fig. 2) associated with the impeller drive shaft (19) or a microphone (24, Fig. 3) in the casing or an associated flow duct. The loudspeaker output at the least partially, extinguishes the impeller produced sound. <IMAGE>

Description

SPECIFICATION Low noise fluid moving system The invention relates to a low noise fluid moving system comprising a casing having a rotating impeller housed therein, and a sound chamber connected to the inner chamber of the casing by at least one sound passage opening.
The substantial source region for the rotary sound in case of a radial fluid moving system without a guide wheel resides in the casing tongue at which the peripheral wall of the casing changes over into a duct via a bending area. At this point, the helically shaped casing has the smallest diameter. In case of axial fluid moving systems, the radial guide blades carrying the bearing for the axle of the impeller and being arranged transversely in the flow channel form the substantial zones of sound sources.
It has been known to provide in case of fluid moving systems a perforated wall in the bending zone of the casing tongue, or of the guide blades respectively, to arrange therebehind a resonator (EP Patent Application 0 039 459). The resonator is a A/4-type resonator for the substantial interfering sound frequency. A stationary wave is formed in it which is phased oppositely to the oscillation of the rotary sound thus extinguishing part of said rotary sound. The interfering rotary sound of the fluid moving system is substantially reduced accordingly. It is a disadvantage of the known sound compensation that the ;1/4-resonator must be tuned to the respective parasitic frequency, which, however, is substantially dictated by the speed of the fluid moving system.If its speed is changeable, a constant tuning of the length of the ;1/4-resonator is necessary subject to the respective speed.
It is the object of the invention to provide a lownoise fluid moving system of the above mentioned type in which the sound compensation is automatically adapted to different speeds of the device.
To solve this problem, the invention provides in the sound chamber a counter-sound source which is excited by a frequency changing subject to the speed of the impeller.
The counter-sound source is an active sound source, e.g. a loudspeaker. Said sound source is excited by a frequency changing responsive to the speed of the impeller. Thus, the frequency of the counter-sound source is automatically adapted to the respective speed of the impeller. The countersound source produces a sound which, if possible, is oppositely phased to the interfering amount of frequency of the rotary sound, to ensure that said amount of the rotary sound and the counter-sound are mutually extinguished at least partly. As a result thereof, the noise level will be iower.
In contradistinction to prior art, the fluid moving device of the invention comprises an "active" counter-sound source. In other words, it is not provided with a resonator having a fixed or variable resonance frequency, but with a compensating counter-sound source effective in the substantial source region of the rotary sound.
Preferably, the counter-sound source is excited via an adjustable phase shifter circuit by which the phase position of the counter-sound can be so adjusted that it is phase-shifted by 1 800 relative to the phase position of the rotary sound. Such phase shifting can be easily performed and controlled manually, because the phase of the exciter signal of the counter-sound source must be shifted as long as to reach the lowest rotary sound level for the human sense of hearing. It is also possible to automatically adjust the phase shifter circuit so that it is setting the corresponding phase position which is most effective. To this effect, a sound transducer taking up the rotary sound and a corresponding controller are required.
The frequency by which the counter-sound source is excited, can be obtained by a sensor which is responsive to the elements rotating with the drive shaft of the impeller. It is possible, in this regard, to secure to the shaft of the impeller a coding disk whose marks pass by a contactless sensor which generates corresponding pulses. By a respective distribution of the marks at the coding disk, the produced frequency may correspond to a specific harmonic of the rotary sound dictated by the speed. As a rule, the principal interfering frequency in the noise of fluid moving systems can be considered the blade frequency (speed x number of blades of the impeller) and multiple thereof.By deviating the exciter frequency for the counter-sound source from the impeller speed via a speed pick-up, it is ensured that the frequencies of the counter-sound source are always exactly equal to those of the primary aerodynamic pressure fluctuations.
According to another variant of the invention, the counter-sound source is excited by at least one pressure sensor converting the noises into electric oscillations. Said pressure sensor may be a microphone that is provided in the source region of the interfering noise. Via a control circuit, the counter-sound source is so controlled that the pressure fluctuations formed at the point of the pressure sensor have oniy a minimum amplitude.
According to an advantageous embodiment of the invention, there are provided several counter sound sources which are excited by different frequencies. Said counter-sound sources may be controlled either in common by one sensor or they may be controlled by different sensors. Said sensors which may be situated at various points of the casing, may be of different frequency sensitivities.
In the fluid moving machine of the invention, the shape and geometric dimensions of the inner chamber of the housing need not be changed to mount the counter-sound sources. Therefore, the characteristics and efficiency of the fluid moving machine remain unchanged.
For a better understanding of the present invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 is a schematic perspective view of a radial fluid moving system; Figure 2 is a schematic view showing the excitation of the counter-sound source; and Figure 3 is a second embodiment showing the excitation of the counter-sound source.
Figure 1 shows a radial fluid moving device comprising a casing 10 having a helically shaped peripheral wall 11 continued by the external wall of a tangential duct 12.
In the casing 10, the impeller 13 with blades 14 is pivotally attached. The driven shaft to which the impeller 13 is secured is not illustrated in Figure 1 so as to have a better survey. The point at which the peripheral wall 11 of the casing with respect to the axle of the impeller 13 - has the shortest radius is occupied by the casing tongue 1 5 which consists of a bending region in which the casing wall 11 changes over into the upper wall 1 6 of the duct 12. As a matter of fact, the casing tongue 15 is the substantial source of the inconvenient rotary sound.
The casing tongue 1 5 is a perforated wall containing a great number of holes extending into the closed sound chamber 1 7 arranged behind the casing tongue 1 5. All of the walls of the sound chamber 1 7 are closed, except for the openings in the casing tongue 1 5 and for one opening at which a loudspeaker 1 8 is mounted. The excitation of the latter will be still explained hereinafter, and it forms the counter-sound source which produces in the sound chamber 17 acoustic oscillations which are transmitted to the holes of the casing tongue 15, and which, in said holes, are oppositely phased to the rotary sound component to be suppressed.
According to Figure 2, a coding disk 20 mounted at the drive shaft 1 9 of the impeller 13 is provided with peripheral marks for instance, slots, colour marks, metal elements or the like. A sensor 21 mounted beside the coding disk 20 rotating with the drive shaft 1 9 produces an electric pulse with each passing mark. The pulses are supplied to a phase shifter circuit 22 in which the phase position of the pulses can be changed, for instance manually. In a very simple design, the phase shifter circuit 22 consists of a delay circuit, e.g. an RC-member.
The output of the phase shifter circuit 22 is connected via an amplifier to a loudspeaker 1 8.
The frequency by which the latter is excited is equal to the r.p.s. of the drive shaft 10 multiplied by the number of marks on the coding disk 20. If the loudspeaker is to be excited at a lower frequency, a frequency divider circuit can be connected behind the sensor 21 producing the pulses to correspondingly reduce the frequency.
According to the principle of the invention, the counter-sound source consisting of the loudspeaker 1 8 produces a sound having a frequency equal to that of an interfering component of the rotary sound. By suitably setting the phase shifter circuit 22 and the amplifier, the corresponding rotary sound component and the counter-sound produced by the loudspeaker 1 8 at least partly extinguish themselves mutually within the range of the casing tongue 1 5.
In the embodiment of Figure 3, the casing tongue 10 houses a microphone 24 to receive the rotary sound produced at the casing tongue 1 5 and to supply corresponding electric signals to an amplifier 25. Via a phase shifter circuit 22, the output signal of the amplifier gets to the loudspeaker 18 mounted in the sound chamber 1 7 just as shown in the first embodiment. The phase shifter circuit 22 is so adjusted that the amplitude of the audible rotary sound is of a minimum value. In addition, the level of the counter-sound source can be changed at the amplifier 25.
According to another alternative, the microphone for the control of the counter-sound source is mounted at an optional point within or outside the fluid moving device, where the reduction of the noise level is particularly desirable, e.g. in a channel connected to the fluid moving device.
The shape of the holes at the casing tongue 1 5 is optional. it is also possible to provide in place of a perforated wall an opening closed by a diaphragm.
The counter-sound source may be also a diaphragm disposed in the casing tongue and excited directly by an oscillation exciter (structureborne noise exciter).
The invention can be used with all fluid moving devices, e.g. fans, blowers, ventilators, one- or multiple-stage blowers, compressors and pumps.

Claims (8)

1. A low noise fluid moving system comprising a casing having a rotating impeller housed therein and a sound chamber connected to the inner chamber of the casing by at least one sound passage opening, wherein, in the sound chamber, a counter-sound source is effective which is excited by a frequency changing responsive to the speed of the impeller.
2. A fluid moving system according to claim 1, wherein the counter-sound source is excited via an adjustable phase shifting circuit.
3. A fluid moving system according to claim 1 or 2, wherein a sensor, reacting on elements rotating with the drive shaft of the impeller, produces signals for the periodic excitation of the counter-sound source.
4. A fluid moving system according to claim 1, wherein at least one pressure sensor is provided that converts noises into electric oscillations and whose output signal, optionally upon amplification and phase shifting, excites the counter-sound source.
5. A fluid moving system according to any preceding claim, wherein a plurality of countersound sources is provided which are excited by different frequencies.
6. A fluid moving system according to any preceding claim, wherein the sound chamber is closed against the casing inside by a perforated wall.
7. A fluid moving system according to any of claims 1 to 5, wherein the sound chamber is closed against the casing inside by a diaphragm.
8. A low noise fluid moving system substantially as hereinbefore described with reference to, and as shown in, the accompanying drawing.
GB08306542A 1982-03-17 1983-03-09 Silencing in fluid flour impelling systems Expired GB2117046B (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE3209617A DE3209617C2 (en) 1982-03-17 1982-03-17 Low noise turbo working machine

Publications (3)

Publication Number Publication Date
GB8306542D0 GB8306542D0 (en) 1983-04-13
GB2117046A true GB2117046A (en) 1983-10-05
GB2117046B GB2117046B (en) 1985-07-10

Family

ID=6158445

Family Applications (1)

Application Number Title Priority Date Filing Date
GB08306542A Expired GB2117046B (en) 1982-03-17 1983-03-09 Silencing in fluid flour impelling systems

Country Status (4)

Country Link
JP (1) JPS59600A (en)
DE (1) DE3209617C2 (en)
FR (1) FR2523658B1 (en)
GB (1) GB2117046B (en)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2554170A1 (en) * 1983-11-02 1985-05-03 Ffowcs Williams John E COMBUSTION SYSTEM FOR A GAS TURBINE ENGINE
GB2177238A (en) * 1985-06-29 1987-01-14 Voith Gmbh J M Control apparatus for damping vibrations
WO1993025998A1 (en) * 1992-06-08 1993-12-23 Ford Motor Company Limited An active noise cancellation muffler for a motor vehicle
EP0594626A1 (en) * 1991-07-16 1994-05-04 Noise Cancellation Technologies, Inc. High efficiency fan with adaptive noise cancellation
WO1994011244A1 (en) * 1992-11-06 1994-05-26 ABB Fläkt AB Air distributor for ventilation in ships

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4408278A1 (en) * 1994-03-11 1995-09-14 Gaggenau Werke Extractor hood with at least partial cancellation of the fan noise

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1456018A (en) * 1972-11-24 1976-11-17 Nat Res Dev Active control of sound waves
WO1981003201A1 (en) * 1980-04-28 1981-11-12 G Koopmann Noise reduction system

Family Cites Families (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2225398A (en) * 1939-09-13 1940-12-17 Clyde M Hamblin Construction of ventilating fans
US3826870A (en) * 1970-03-20 1974-07-30 Quest Electronics Corp Noise cancellation
US4174020A (en) * 1975-07-01 1979-11-13 Challis Louis A Acoustic treatment for fans
GB1577322A (en) * 1976-05-13 1980-10-22 Bearcroft R Active attenuation of recurring vibrations
FR2370170A1 (en) * 1976-11-05 1978-06-02 Snecma METHOD AND DEVICE FOR REDUCING TURBOMACHINE NOISE
JPS545402A (en) * 1977-06-14 1979-01-16 Jinichi Nishiwaki Low frequency silencer
WO1982004479A1 (en) * 1981-06-12 1982-12-23 Chaplin George Brian Barrie Method and apparatus for reducing repetitive noise entering the ear

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1456018A (en) * 1972-11-24 1976-11-17 Nat Res Dev Active control of sound waves
WO1981003201A1 (en) * 1980-04-28 1981-11-12 G Koopmann Noise reduction system

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2554170A1 (en) * 1983-11-02 1985-05-03 Ffowcs Williams John E COMBUSTION SYSTEM FOR A GAS TURBINE ENGINE
GB2177238A (en) * 1985-06-29 1987-01-14 Voith Gmbh J M Control apparatus for damping vibrations
GB2177238B (en) * 1985-06-29 1989-07-19 Voith Gmbh J M A preparation system for fibrous stock suspensions having control apparatus for damping vibrations
EP0594626A1 (en) * 1991-07-16 1994-05-04 Noise Cancellation Technologies, Inc. High efficiency fan with adaptive noise cancellation
EP0594626A4 (en) * 1991-07-16 1995-08-23 Noise Cancellation Tech High efficiency fan with adaptive noise cancellation
WO1993025998A1 (en) * 1992-06-08 1993-12-23 Ford Motor Company Limited An active noise cancellation muffler for a motor vehicle
WO1994011244A1 (en) * 1992-11-06 1994-05-26 ABB Fläkt AB Air distributor for ventilation in ships

Also Published As

Publication number Publication date
FR2523658A1 (en) 1983-09-23
DE3209617C2 (en) 1985-10-10
FR2523658B1 (en) 1988-06-03
JPS59600A (en) 1984-01-05
DE3209617A1 (en) 1983-10-06
GB8306542D0 (en) 1983-04-13
GB2117046B (en) 1985-07-10

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PCNP Patent ceased through non-payment of renewal fee