阅读说明：本技术 具有降噪功能的离心风机、吸油烟机以及降噪方法 (Centrifugal fan with noise reduction function, range hood and noise reduction method ) 是由 刘畅 俞辉 郑军妹 于 2021-01-08 设计创作，主要内容包括：本发明涉及一种具有降噪功能的离心风机,包括：蜗壳,包括环壁；叶轮；噪音检测机构,用于对蜗壳的环壁内侧的噪音进行检测,并获取噪音信息；降噪装置,设于蜗壳的环壁上,与噪音检测机构电信号连接,降噪装置包括减振腔室及脉动激发装置,该减振腔室具有布置在蜗壳的环壁上的减振部,脉动激发装置能根据噪音检测机构获取到的噪音信息作用于减振腔室,而使减振部产生周期性的频率振动,以消除蜗壳的环壁上的压力脉动。能有针对性的削减叶片表面的压力脉动引起的偶极子噪声声源,并且,赫姆霍兹共鸣腔的设置与上述主动降噪方式相结合,在更广范围内削减因叶片表面的压力脉动引起的偶极子噪声声源,达到降噪目的。还涉及一种吸油烟机及降噪方法。(The invention relates to a centrifugal fan with noise reduction function, comprising: a volute comprising an annular wall; an impeller; the noise detection mechanism is used for detecting the noise on the inner side of the annular wall of the volute and acquiring noise information; the noise reduction device is arranged on the annular wall of the volute and is in electrical signal connection with the noise detection mechanism, the noise reduction device comprises a vibration reduction cavity and a pulsation excitation device, the vibration reduction cavity is provided with a vibration reduction part arranged on the annular wall of the volute, and the pulsation excitation device can act on the vibration reduction cavity according to noise information acquired by the noise detection mechanism to enable the vibration reduction part to generate periodic frequency vibration so as to eliminate pressure pulsation on the annular wall of the volute. The dipole noise sound source caused by the pressure pulsation on the surface of the blade can be reduced in a targeted manner, and the arrangement of the Helmholtz resonance cavity is combined with the active noise reduction mode, so that the dipole noise sound source caused by the pressure pulsation on the surface of the blade is reduced in a wider range, and the purpose of reducing noise is achieved. Also relates to a range hood and a noise reduction method.)

1. A centrifugal fan with a noise reduction function, comprising:

a volute (10) comprising an annular wall (13);

an impeller (20) disposed within the volute (10);

it is characterized by also comprising:

the noise detection mechanism is in electrical signal connection with the control system and is used for detecting the noise on the inner side of the annular wall (13) of the volute (10) and acquiring the noise information on the inner side of the annular wall (13);

the noise reduction device (400) is arranged on the annular wall (13) of the volute (10), the noise reduction device (400) comprises a vibration reduction chamber (40) and a pulsation excitation device, the vibration reduction chamber (40) is provided with a vibration reduction part which is arranged on the annular wall (13) of the volute (10) and is used as a part of the annular wall, the pulsation excitation device can act on the vibration reduction chamber (40) according to the noise information acquired by the noise detection mechanism, and the vibration reduction part generates periodic frequency vibration so as to eliminate pressure pulsation caused by the action of airflow in the volute (10) on the annular wall (13) of the volute (10).

2. The centrifugal fan with the noise reduction function according to claim 1, characterized in that: the vibration damping device is characterized in that a first flexible diaphragm (45) is arranged in the vibration damping cavity (40), the vibration damping cavity (40) is divided into a first cavity (41) and a second cavity (42) by the first flexible diaphragm (45), the vibration damping portion corresponds to the first cavity (41) and forms a part of the first cavity (41), the second cavity (42) is a sealed cavity for filling non-compressed fluid medium, and the pulsation excitation device can act on the second cavity (42) and enables the volume of the second cavity (42) to change periodically.

3. The centrifugal fan with noise reduction function according to claim 2, wherein: the second chamber (42) is provided with a piston channel (47) communicated with the interior of the second chamber, the pulsation excitation device comprises a first driving mechanism connected with a control system and a piston piece (51) arranged in the piston channel (47), and the power output end of the first driving mechanism is connected with the piston piece (51).

4. The centrifugal fan with the noise reduction function according to claim 3, characterized in that: the damping chamber (40) is a stepped cylinder body with a large hole section (43) and a small hole section (44), the damping part is a second flexible membrane (46) arranged on the port of the large hole section (43) of the stepped cylinder body, and the small hole section (44) forms the piston channel (47).

5. The centrifugal fan with the noise reduction function according to claim 1, characterized in that: the noise detection mechanism comprises a sound pressure sensor (30) arranged at the tail edge position of the blade (21) of the impeller (20), and the sound pressure sensor (30) is in electric signal connection with a control system.

6. The centrifugal fan with the noise reduction function according to any one of claims 2 to 5, wherein: the vibration damping part is provided with a communication hole (60) for communicating an inner cavity of the volute (10) with a first chamber (41), so that the first chamber (41) forms a Helmholtz resonance cavity for eliminating pressure pulsation on a ring wall (13) of the volute (10).

7. The centrifugal fan with the noise reduction function according to claim 6, wherein: the vibration damping device is characterized by further comprising a second driving mechanism and a communicating pipe (61) which is movably arranged on the vibration damping portion in a penetrating mode and communicated with the inner cavity of the volute (10) and the first chamber (41), wherein the power output end of the second driving mechanism is connected with the communicating pipe (61), so that the communicating pipe (61) is driven to move.

8. A range hood, its characterized in that: comprising a centrifugal fan according to any of claims 1-7.

9. A noise reduction method using a centrifugal fan with a noise reduction function according to any one of claims 1 to 7, characterized by comprising the steps of:

s1, starting a centrifugal fan;

s2, detecting the noise inside the annular wall (13) of the volute (10) through a noise detection mechanism, and acquiring the noise information inside the annular wall (13);

and S3, analyzing and processing the noise information collected by the noise detection mechanism, determining the frequency and the phase of the noise sound wave, starting the pulsation excitation device, and acting on the vibration damping chamber (40) through the pulsation excitation device, so that the vibration damping part of the vibration damping chamber (40) generates periodic pulse vibration with the same frequency and the opposite phase of the noise sound wave, and pressure pulsation caused by the action of the airflow in the volute (10) on the annular wall (13) of the volute (10) is eliminated.

10. The noise reduction method according to claim 9, characterized in that: a first flexible diaphragm (45) is arranged in the vibration reduction cavity (40), the first flexible diaphragm (45) divides the vibration reduction cavity (40) into a first cavity (41) and a second cavity (42), the vibration reduction part corresponds to the first cavity (41) and forms a part of the first cavity (41), and the second cavity (42) is filled with a non-compressible fluid medium;

in the above step S3: the pulsation excitation device acts on the second chamber (42) to periodically change the volume of the second chamber (42), so that the first flexible diaphragm (45) is periodically deformed, and the vibration damping part of the first chamber (41) is periodically subjected to pulse vibration.

11. The noise reduction method according to claim 10, characterized in that: the damping chamber (40) is a stepped cylinder body with a large hole section (43) and a small hole section (44), the damping part is a second flexible membrane (46) arranged on the port of the large hole section (43) of the stepped cylinder body, the small hole section (44) forms a piston channel (47), the pulsation excitation device comprises a first driving mechanism connected with a control system and a piston piece (51) arranged in the piston channel (47), and the power output end of the first driving mechanism and the piston piece (51) can drive the piston piece to do periodic reciprocating motion along the piston channel (47) at a fixed frequency.

12. The noise reduction method according to claim 11, characterized in that: the step of S3 includes the steps of:

collecting a pulse signal at the tail edge of a blade (21) of an impeller (20) by taking a sound pressure sensor (30) arranged at the tail edge of the blade (21) as a noise detection mechanism, analyzing and processing the pulse signal by a data analysis module of a control system according to the distance between the tail edge of the blade (21) and a piston piece, determining the frequency and the phase of the noise sound, driving the piston piece to move at a fixed frequency by the control system, acquiring the vibration frequency and the phase of a vibration damping part of a vibration damping chamber, judging whether the pulse frequency of the vibration damping part of the vibration damping chamber is consistent with the frequency of the noise sound, keeping the motion frequency of the piston piece to move continuously if the pulse frequency is consistent with the frequency of the noise sound, changing the motion frequency of the piston piece according to a set value if the pulse frequency is not consistent with the frequency of the noise sound; and

and judging whether the pulsation phase of the vibration damping part of the vibration damping chamber is opposite to the phase of the noise sound wave, if so, keeping the motion frequency and the phase of the piston piece to continuously move, if not, stopping the motion of the piston piece, after a set time T, re-driving the piston piece to move at the original frequency, and repeating the step.

13. The noise reduction method according to any one of claims 10 to 12, characterized by: the vibration damper further comprises a second driving mechanism and a communicating pipe (61) movably arranged on the vibration damping portion in a penetrating mode, the communicating pipe (61) is communicated with an inner cavity of the volute (10) and the first chamber (41), so that the first chamber (41) forms a Helmholtz resonance cavity used for eliminating pressure pulsation on the annular wall (13) of the volute (10), and a power output end of the second driving mechanism is connected with the communicating pipe (61) so as to drive the communicating pipe (61) to move;

the noise reduction method further comprises the following steps:

s4, using a sound pressure sensor (30) arranged at the tail edge of a blade (21) of an impeller (20) as the noise detection mechanism, collecting a pulse signal at the tail edge of the blade (21), analyzing the pulse signal through a data analysis module of a control system to obtain frequency domain information of the noise sound wave, identifying a corresponding frequency value f0 when the sound pressure level is maximum, calculating the depth of the communication pipe (61) required to be inserted into the annular wall (13) of the volute (10) under the frequency value f0, controlling a second driving mechanism to operate to drive the communication pipe (61) to move according to a set value, judging whether the resonance frequency of a Helmholtz resonance cavity of the communication pipe (61) at the insertion depth is consistent with the frequency f0 of the noise sound wave, if so, keeping the insertion depth of the communication pipe (61) unchanged, and if not, continuing to move the communication pipe (61) according to the set value, and the procedure is repeated.

Technical Field

The invention relates to the technical field of range hoods, in particular to a centrifugal fan with a noise reduction function, a range hood and a noise reduction method.

Background

The range hood has become one of the essential kitchen equipments of ordinary family, and the range hood that wherein adopts centrifugal fan is welcomed with its relative suction great, noise is lower and is welcomed, however, the noise still exists anyhow, and the main noise of centrifugal fan is pneumatic noise, mechanical noise, motor noise. Wherein, pneumatic noise is the main noise component of centrifugal fan, and intensity is also the biggest. The pneumatic noise sources of the impeller machine are mainly divided into a monopole sound source, a dipole sound source and a quadrupole sound source. Wherein the monopole sound source is present in an unstable state with low air flow velocity, which is generally not considered; dipole sound sources are sound sources caused by pressure pulsation, and generally occur when an airflow meets foreign matters; the quadrupole acoustic source derives from the shear stress of the turbulence. For the rotating wall surface of the impeller, a rotating dipole sound source and a spatial quadrupole sound source of the rotating wall surface are mainly considered, wherein the rotating dipole sound source is a main noise component. The prior pneumatic noise control method of the centrifugal fan mainly comprises the following steps: optimizing blade profile and layout, optimizing volute profile, adopting porous noise reduction materials and the like.

For example, in the blade for centrifugal fan impeller, the centrifugal fan impeller and the range hood disclosed in the chinese invention patent application with application number CN201910872060.5 (publication number CN110657127A), aerodynamic noise of the impeller is reduced by optimizing blade profile and layout. For example, the centrifugal fan volute structure disclosed in the invention patent with the application number of CN201721352626.4 (with the publication number of CN207261316U) achieves the purpose of noise reduction by optimizing the volute profile. However, analysis has found that optimization of the vane profile and the volute profile involves numerous angular and dimensional parameters, and finding the best combination of these parameters is difficult.

For another example, the invention of chinese patent No. ZL00216346.2, microporous chamber muffling volute (publication No. CN2406094Y), discloses a technical solution, which is formed by assembling a scroll plate, a rear plate and a front plate, wherein the scroll plate, the rear plate and the front plate are all provided with a plurality of micropores, the microporous scroll plate, the microporous rear plate and the microporous front plate are assembled into an inner volute, an outer volute is installed in the periphery of the outer side of the inner volute at a certain distance, and the inner volute and the outer volute are assembled and fixed together. On the other hand, the noise reduction volute structure has the advantages that the noise reduction and noise elimination effect is not obvious and an ideal result cannot be achieved because only one layer of cavity is used for noise elimination, and the space for consuming sound energy is limited due to the back-and-forth friction of air in small holes.

In the prior art, there are few technical means for reducing the aerodynamic noise of the centrifugal fan by using active noise suppression means, and therefore, how to provide a noise reduction volute of the centrifugal fan of the range hood, which can actively reduce the pressure pulsation generated by the airflow transmitted to the surface of the volute, so as to effectively improve the noise reduction effect, is a technical problem to be solved by those skilled in the art.

Disclosure of Invention

The first technical problem to be solved by the present invention is to provide a centrifugal fan capable of actively reducing pressure pulsation generated by airflow transmitted to a volute surface, thereby effectively improving noise reduction effect.

The second technical problem to be solved by the present invention is to provide a range hood using the centrifugal fan in view of the current situation of the prior art.

The third technical problem to be solved by the present invention is to provide a noise reduction method using the above centrifugal fan, aiming at the current situation of the prior art.

The technical scheme adopted by the invention for solving the first technical problem is as follows:

a centrifugal fan with a noise reduction function, comprising:

a volute comprising an annular wall;

the impeller is arranged in the volute;

the noise detection mechanism is in electrical signal connection with the control system and is used for detecting the noise on the inner side of the annular wall of the volute and acquiring the noise information on the inner side of the annular wall;

the noise reduction device is arranged on the annular wall of the volute and is in electrical signal connection with the noise detection mechanism, the noise reduction device comprises a vibration reduction chamber and a pulsation excitation device, the vibration reduction chamber is provided with a vibration reduction part which is arranged on the annular wall of the volute and is used as a part of the annular wall, and the pulsation excitation device can act on the vibration reduction chamber according to the noise information acquired by the noise detection mechanism and enables the vibration reduction part to generate periodic frequency vibration so as to eliminate pressure pulsation caused by the action of air flow in the volute on the annular wall of the volute.

In order to drive a vibration damping part of a vibration damping cavity to generate periodic vibration, a first flexible diaphragm is arranged in the vibration damping cavity, the first flexible diaphragm divides the vibration damping cavity into a first cavity and a second cavity, the vibration damping part corresponds to the first cavity and forms a part of the first cavity, the second cavity is a sealed cavity for filling a non-compressed fluid medium, and the pulsation excitation device can act on the second cavity and enables the volume of the second cavity to generate periodic change.

In order to enable the volume of the second chamber to change periodically, a piston channel communicated with the interior of the second chamber is arranged on the second chamber, the pulsation excitation device comprises a first driving mechanism connected with a control system and a piston piece arranged in the piston channel, and the power output end of the first driving mechanism is connected with the piston piece.

As an improvement, the damping chamber is a stepped cylinder body with a large hole section and a small hole section, the damping part is a second flexible diaphragm arranged on a port of the large hole section of the stepped cylinder body, and the small hole section forms the piston channel. The small hole section with the relatively small inner diameter is used as a piston channel, so that the volume change of the second chamber can be accurately controlled.

In order to monitor and collect the dipole pulsation value at the tail edge of the blade and acquire the noise information of the inner side of the ring wall, the noise detection mechanism comprises a sound pressure sensor arranged at the tail edge of the blade of the impeller, and the sound pressure sensor is in electrical signal connection with a control system. Preferably, the sound pressure sensor is wireless type, that is to say transmits signals in a wireless communication mode, and the sound pressure sensor is arranged at the tail edge of the blade in an attaching mode so as to ensure that the sound pressure sensor does not fall off in the working process of the fan.

In order to further improve the noise reduction effect, the vibration reduction part is provided with a communication hole for communicating an inner cavity of the volute with the first chamber, so that the first chamber forms a Helmholtz resonance cavity for eliminating pressure pulsation on the annular wall of the volute. The Helmholtz resonance cavity structure can also play a role in weakening pressure pulsation generated by airflow on the surface of the volute, and is combined with an active noise reduction mode of generating equal-strength pressure pulsation in a phase opposite to the dipole pressure pulsation on the surface of the blade by excitation of the pulsation excitation device, so that a dipole noise sound source caused by the pressure pulsation on the surface of the blade can be reduced in a wider range, and the purpose of reducing noise is achieved. That is, the dipole pulsation is basically periodic rotational noise generated on the blade, which may be only some fundamental frequency and harmonic on the pulsation spectrogram, but also some non-blade rotational noise exists, which is some sharp peaks on the spectrogram, and the helmholtz resonance cavity can cut the non-blade rotational noise, thereby achieving the purpose of effective noise reduction on the whole.

As an improvement, the device further comprises a second driving mechanism and a communicating pipe which is movably arranged on the vibration reduction part in a penetrating mode and is communicated with the inner cavity of the volute and the first chamber, and a power output end of the second driving mechanism is connected with the communicating pipe so as to drive the communicating pipe to move. Because the effect of fixed point reduction can be realized to the dipole sound source of the different intensity of the different positions of blade to helmholtz resonance chamber of not unidimensional, the inserted position of adjustment communicating pipe, can realize the pertinence noise reduction effect, especially, can carry out fast Fourier transform to the time domain data of the noise of gathering through noise detection mechanism and obtain the frequency domain signal, the frequency that corresponds when the sound pressure level is the biggest in the discernment frequency domain signal, and regard this frequency as resonant frequency, calculate the depth of insertion of communicating pipe in the helmholtz resonance chamber, thereby reach the purpose of pertinence noise reduction.

The technical scheme adopted by the invention for solving the second technical problem is as follows:

a range hood comprises the centrifugal fan.

The technical scheme adopted by the invention for solving the third technical problem is as follows:

a noise reduction method using the centrifugal fan with the noise reduction function comprises the following steps:

s1, starting a centrifugal fan;

s2, detecting the noise on the inner side of the annular wall of the volute through a noise detection mechanism, and acquiring the noise information on the inner side of the annular wall;

and S3, analyzing and processing the noise information collected by the noise detection mechanism, determining the frequency and the phase of the noise sound wave, starting the pulsation excitation device, and acting on the vibration damping chamber through the pulsation excitation device, so that the vibration damping part of the vibration damping chamber generates periodic pulse vibration with the same frequency and the opposite phase as the noise sound wave, and the pressure pulsation caused by the action of the airflow in the volute on the annular wall of the volute is eliminated.

In order to drive a vibration damping part of a vibration damping cavity to generate periodic vibration, a first flexible diaphragm is arranged in the vibration damping cavity and divides the vibration damping cavity into a first cavity and a second cavity, the vibration damping part corresponds to the first cavity and forms a part of the first cavity, and a non-compressive fluid medium is filled in the second cavity;

in the above step S3: the pulsation excitation device acts on the second chamber to enable the volume of the second chamber to change periodically, so that the first flexible diaphragm deforms periodically, and the vibration reduction part of the first chamber vibrates periodically in a pulse mode.

In order to enable the volume of the second chamber to generate periodic change, the vibration damping chamber is a stepped cylinder body with a large hole section and a small hole section, the vibration damping part is a second flexible membrane arranged on a port of the large hole section of the stepped cylinder body, the small hole section forms a piston channel, the pulsation excitation device comprises a first driving mechanism connected with a control system and a piston piece arranged in the piston channel, and a power output end of the first driving mechanism and the piston piece can drive the piston piece to do periodic reciprocating motion along the piston channel at a fixed frequency.

In order to accurately achieve the purpose of actively reducing the pressure pulsation generated by the airflow transmitted to the surface of the volute, the step of S3 includes the following steps:

collecting a pulse signal at the tail edge of a blade of an impeller by taking a sound pressure sensor arranged at the tail edge of the blade as a noise detection mechanism, analyzing and processing the pulse signal by a data analysis module of a control system by combining the distance from the tail edge of the blade to a piston piece, determining the frequency and the phase of the noise sound wave, driving the piston piece to move at a fixed frequency by the control system, acquiring the vibration frequency and the phase of a vibration damping part of a vibration damping chamber, judging whether the pulse frequency of the vibration damping part of the vibration damping chamber is consistent with the frequency of the noise sound wave, keeping the motion frequency of the piston piece to move continuously if the pulse frequency of the vibration damping part of the vibration damping chamber is consistent with the frequency of the noise sound wave, changing the motion frequency of the piston piece according to a set value if the; and

and judging whether the pulsation phase of the vibration damping part of the vibration damping chamber is opposite to the phase of the noise sound wave, if so, keeping the motion frequency and the phase of the piston piece to continuously move, if not, stopping the motion of the piston piece, after a set time T, re-driving the piston piece to move at the original frequency, and repeating the step.

In order to further improve the noise reduction effect, the noise reduction device further comprises a second driving mechanism and a communicating pipe which is movably arranged on the vibration reduction part in a penetrating mode, the communicating pipe is communicated with an inner cavity of the volute and a first chamber, so that the first chamber forms a Helmholtz resonance cavity used for eliminating pressure pulsation on the annular wall of the volute, and a power output end of the second driving mechanism is connected with the communicating pipe so as to drive the communicating pipe to move;

the noise reduction method further comprises the following steps:

s4, collecting a pulse signal at the tail edge of the blade by taking a sound pressure sensor arranged at the tail edge of the blade of the impeller as the noise detection mechanism, analyzing and processing the pulse signal through a data analysis module of a control system to obtain frequency domain information of the noise sound wave, identifying a corresponding frequency value f0 when the sound pressure level is maximum, calculating the depth of the communicating pipe which needs to be inserted into the annular wall of the volute under the frequency value f0, controlling a second driving mechanism to act, driving the communicating pipe to move according to a set value, judging whether the resonance frequency of the Helmholtz resonance cavity of the communicating pipe under the insertion depth of the communicating pipe is consistent with the frequency f0 of the noise sound wave, if so, keeping the insertion depth of the communicating pipe unchanged, if not, continuing to move the communicating pipe according to the set value, and repeating the step. The structural design of the movable communicating pipe can adapt to the change of the rotating speed of the blades, and the adaptability adjustment is made according to different pressures in the volute.

Compared with the prior art, the invention has the advantages that: the pulsation excitation device of the noise reduction device can act on the vibration reduction chamber according to the noise information acquired by the noise detection mechanism, so that the vibration reduction part of the vibration reduction chamber generates periodic frequency vibration (pressure pulsation with opposite phase and equal frequency to the pressure pulsation of the dipole on the surface of the blade), and the pressure pulsation caused by the action of the air flow in the volute on the annular wall of the volute is eliminated. On the other hand, the Helmholtz resonance cavity can also play a role in weakening pressure pulsation generated on the surface of the volute by airflow, and is combined with an active noise reduction mode of generating equal-strength pressure pulsation in a phase opposite to the dipole pressure pulsation on the surface of the blade by excitation of the pulsation excitation device, so that a dipole noise sound source caused by the pressure pulsation on the surface of the blade can be reduced in a wider range, and the purpose of reducing noise is achieved. In the preferred scheme, the size of helmholtz resonance chamber can be adjusted (adjust the inserted position of communicating pipe), and the helmholtz resonance chamber of different sizes can realize the fixed point to the dipole sound source of the different intensity that the different positions of blade correspond the production and reduce, has strengthened noise reduction effect.

Drawings

Fig. 1 is a schematic perspective view of a centrifugal fan according to an embodiment of the present invention;

FIG. 2 is a transverse cross-sectional view of a centrifugal fan according to an embodiment of the present invention;

FIG. 3 is a partial schematic structural view of a centrifugal fan according to an embodiment of the present invention;

fig. 4 is a flowchart of a noise reduction method according to an embodiment of the present invention.

Detailed Description

The invention is described in further detail below with reference to the accompanying examples.

Referring to fig. 1 to 4, a centrifugal fan with a noise reduction function includes a scroll casing 10, an impeller 20, a noise detection device, and a noise reduction device 400. The volute 10 comprises a front cover 11, a rear cover 12 and an annular wall 13 connecting the two. An impeller 20 is provided within the volute 10, including vanes 21. The noise detecting means may be provided on the surface of the vane 21, and the noise detecting means may be provided on the circumferential wall 13 of the scroll casing 10.

Referring to fig. 2, the dipole sound source in the centrifugal fan system is mainly generated due to the change of the interaction force (aerodynamic force on the surface of the rotating blade 21) between the blades 21, and is essentially pressure pulsation on the surface of the blade 21, and the intensity distribution of the dipole sound source of the blades 21 of the fan system can be obtained through CFX simulation software, wherein the dipole sound source is mainly distributed at the trailing edge of the blade 21 and shows a decreasing trend from the trailing edge of the blade 21 to the leading edge. Thus, in order to ensure the noise reduction effect, the noise detection device of the present embodiment may be provided at the trailing edge position of the vane 21 to detect the noise inside the annular wall 13 of the volute 10 and acquire the noise information inside the annular wall 13.

Referring to fig. 2, the noise detection device of the present embodiment is a sound pressure sensor 30 disposed at the trailing edge position of the blade 21 of the impeller 20, and the sound pressure sensor 30 is electrically connected to the control system. Specifically, the sound pressure sensor 30 is wireless and is disposed at the trailing edge of the blade 21 in an attached manner, so as to ensure that the sound pressure sensor 30 does not fall off during the operation of the fan.

Referring to fig. 2 and 3, the noise reducer 400 is electrically connected to the noise detecting mechanism. The noise reduction device 400 includes the damping chamber 40 and a pulsation excitation device. The vibration damping chamber 40 is provided with a vibration damping part which is arranged on the annular wall 13 of the volute 10 and is a part of the annular wall, and the pulsation excitation device can act on the vibration damping chamber 40 according to the noise information acquired by the noise detection mechanism to enable the vibration damping part to generate periodic frequency vibration so as to eliminate pressure pulsation caused by the action of airflow in the volute 10 on the annular wall 13 of the volute 10.

Referring to fig. 2 and 3, a first flexible diaphragm 45 is disposed in the damping chamber 40, and the first flexible diaphragm 45 divides the damping chamber 40 into a first chamber 41 and a second chamber 42. The vibration damping portion of the present embodiment is a second flexible diaphragm 46, and the second flexible diaphragm 46 corresponds to the first chamber 41 and constitutes a part of the first chamber 41. The second chamber 42 is a sealed chamber for filling with a non-compressible fluid medium, such as water or oil or other liquid.

Referring to fig. 2 and 3, the second chamber 42 of the present embodiment is provided with a piston channel 47 communicating with the inside thereof, and correspondingly, the pulsation excitation device includes a first driving mechanism (not shown) connected to the control system and a piston member 51 disposed in the piston channel 47, and a power output end of the first driving mechanism is connected to the piston member 51. Under the action of the first drive mechanism, the piston member 51 reciprocates cyclically in the piston passage 47, thereby causing the volume of the second chamber 42 to change cyclically. Specifically, the damping chamber 40 of the present embodiment is a stepped cylinder having a large hole section 43 and a small hole section 44, the damping portion is a second flexible diaphragm 46 disposed at a port of the large hole section 43 of the stepped cylinder, the small hole section 44 forms a piston channel 47, and the small hole section 44 having a relatively small inner diameter is used as the piston channel 47 in the present embodiment, so that the volume change of the second chamber 42 can be accurately controlled. The first driving mechanism of this embodiment may be implemented by using a driving motor and a connecting rod transmission mechanism, and may also be implemented by using other driving mechanisms capable of driving the piston member to reciprocate in the prior art.

The dipole pulsation on the blade 21 is basically periodic rotational noise generated on the blade 21, which may be only some fundamental frequencies and harmonics on a pulsation spectrogram, but also some non-blade 21 rotational noise which is some sharp peaks on the spectrogram exists, and the embodiment is to reduce the non-blade 21 rotational noise by arranging a helmholtz resonance cavity, thereby achieving the purpose of effective noise reduction on the whole.

In the present embodiment, the damper portion has a communication hole 60 for communicating the inner chamber of the scroll casing 10 with the first chamber 41, so that the first chamber 41 constitutes a helmholtz resonance chamber for canceling pressure pulsation on the annular wall 13 of the scroll casing 10. The helmholtz resonance cavity structure can also play a role in weakening pressure pulsation generated by airflow on the surface of the volute 10, and is combined with an active noise reduction mode of generating equal-strength pressure pulsation in a phase opposite to the dipole pressure pulsation on the surface of the blade 21 through excitation of the pulsation excitation device, so that a dipole noise sound source caused by the pressure pulsation on the surface of the blade 21 can be reduced in a wider range, and the purpose of reducing noise is achieved.

Referring to fig. 2 and 3, the noise reducer 400 further includes a second driving mechanism (not shown) and a communicating pipe 61 movably inserted through the vibration damping portion. The power output end of the second driving mechanism is connected with the communicating pipe 61, so that the communicating pipe 61 is driven to move. The communication pipe 61 communicates the inner chamber of the scroll case 10 with the communication pipe 61 of the first chamber 41. Because the effect of fixed point reduction can be realized to the dipole sound source of the different intensity of the different positions of blade 21 to the helmholtz resonance chamber of different sizes, the inserted position of communicating pipe 61 is adjusted, the pertinence noise reduction effect can be realized, especially, can carry out fast Fourier transform to the time domain data of the noise of gathering through noise detection mechanism and obtain the frequency domain signal, the frequency that corresponds when the sound pressure level is the biggest in the discernment frequency domain signal, and regard this frequency as resonant frequency, calculate the depth of insertion of communicating pipe 61 in the helmholtz resonance chamber, thereby reach the purpose of pertinence noise reduction. The second driving mechanism of this embodiment can be realized by matching a driving motor and a screw rod slider mechanism, and can also be realized by adopting other various driving mechanisms capable of driving the communicating pipe to reciprocate in the prior art.

The embodiment also relates to a range hood, and the range hood adopts the centrifugal fan with the noise reduction function.

With reference to fig. 4, a noise reduction method using the centrifugal fan with noise reduction function includes the following steps:

and S1, starting the centrifugal fan.

S2, the noise detection means detects the noise inside the annular wall 13 of the scroll casing 10, and acquires the noise information inside the annular wall 13.

S3, analyzing and processing the noise information collected by the noise detection mechanism, determining the frequency and phase of the noise sound, then starting the pulsation excitation device, and acting on the vibration damping chamber 40 through the pulsation excitation device, so that the vibration damping portion of the vibration damping chamber 40 generates periodic pulse vibration with the same frequency and opposite phase as the noise sound, so as to eliminate the pressure pulsation caused by the airflow in the volute 10 acting on the annular wall 13 of the volute 10.

Specifically, in step S3, the sound pressure sensor 30 provided at the trailing edge of the blade 21 of the impeller 20 is used as the noise detection means to collect the pulsation signal at the trailing edge of the blade 21, and then the pulsation signal is analyzed by the data analysis module of the control system in accordance with the distance from the trailing edge of the blade 21 to the piston member to determine the frequency and phase of the noise sound wave; then the control system drives the piston piece to move at a fixed frequency, obtains the vibration frequency and the phase of the vibration damping part of the vibration damping chamber, and then judges whether the pulsation frequency of the vibration damping part of the vibration damping chamber is consistent with the frequency of the noise sound wave; if so, keeping the piston part moving continuously at the movement frequency; if not, changing the movement frequency of the piston piece according to a set value, and repeating the step; and

judging whether the pulsation phase of the vibration damping part of the vibration damping cavity is opposite to the phase of the noise sound wave; if so, keeping the motion frequency and the phase of the piston piece to move continuously; if not, the piston member is stopped and, after a set time T, the piston member is re-driven to move at the original frequency and the procedure is repeated.

S4, the sound pressure sensor 30 provided at the trailing edge of the blade 21 of the impeller 20 is also used as a noise detection means, the pulsation signal at the trailing edge of the blade 21 is collected, the pulsation signal is analyzed and processed by a data analysis module of the control system, frequency domain information of the noise sound wave is obtained, a frequency value f0 corresponding to the maximum sound pressure level is identified, the depth of the communication pipe 61 required to be inserted into the annular wall 13 of the volute 10 at the frequency value f0 is calculated, the second driving means is controlled to operate, the communication pipe 61 is driven to move according to a set value, whether the resonance frequency of the helmholtz resonance chamber at the insertion depth of the communication pipe 61 is consistent with the frequency f0 of the noise sound wave is determined, if yes, the insertion depth of the communication pipe 61 is kept unchanged, if no, the communication pipe 61 is continuously moved according to the set value, and the step is repeated.

The resonant frequency of the helmholtz resonator is calculated as:

wherein: f0 is the resonance frequency of the vibration damping chamber, c is the sound velocity, S is the cross-sectional area of the communicating pipe, d is the diameter of the communicating pipe, V is the volume of the vibration damping chamber, and l is the depth of the communicating pipe inserted into the volute chamber.

It can be seen from the above resonant frequency calculation formula that the frequency f corresponding to the maximum sound pressure level identified by the data analysis module of the control system₀As the resonant frequency, the depth of the communicating tube 61 inserted into the volute cavity can be solved in reverse:

therefore, the insertion position of the communicating pipe is adjusted, the rotating speed change of the blades can be adapted, the adaptability adjustment is carried out aiming at different pressures in the volute 10, and the targeted noise reduction effect is achieved.