Centrifugal fan and noise reduction control method thereof

Abstract

The invention provides a centrifugal fan and a noise reduction control method of the centrifugal fan, and relates to the technical field of centrifugal fans. The centrifugal fan comprises a centrifugal fan body. According to the centrifugal fan and the noise reduction control method of the centrifugal fan, the movable ring capable of independently translating in the axial direction of the air duct is arranged, and the angle of the silencing pipe arranged in the wall of the air duct is controlled in a linkage mode, so that dynamic adjustment of the silencing frequency band is achieved. The key problem that a traditional fixed silencer cannot adapt to variable-order noise frequency drift during variable-speed operation of a draught fan is effectively solved, the noise reduction module can actively track and aim at main noise components in changes, and the overall noise reduction effect and adaptability under the complex working condition are remarkably improved. A closed-loop control system composed of a front-end noise sensing device, a central control unit and a tail-end mechanical adjusting device is constructed, and a multi-stage series modular noise elimination structure is adopted, so that the self-adaptive noise reduction function is highly integrated in an air duct.

Description

Technical Field

[0001] This invention relates to the field of centrifugal fan technology, specifically to a centrifugal fan and a noise reduction control method for the centrifugal fan. Background Technology

[0002] In recent years, with the increasing demands for quieter operation in industrial production, building ventilation, and household appliances, noise control technology for centrifugal fans, a core power component, has made significant progress. Early noise reduction methods primarily relied on installing fixed resistive or reactive silencers at the fan inlet and outlet, and applying sound-insulating materials to the outside of the fan casing. These passive methods played a crucial role for a period. With the maturity of computational fluid dynamics (CFD) and computational acoustics (CAA) simulation technologies, optimizing the aerodynamic design of components such as the impeller and casing to reduce noise at its source has become the mainstream research direction in the industry. Furthermore, intelligent control systems combining sensors and variable frequency drives have enabled the proactive avoidance of high-noise operating conditions by adjusting the fan speed, marking a significant advancement in proactive noise reduction for centrifugal fans.

[0003] However, existing mainstream noise reduction solutions still have significant limitations when facing more complex and dynamic noise scenarios. The silencing frequency band and noise reduction amount of fixed silencers are determined during the design phase and cannot be adjusted once installed. They cannot effectively cope with "variable-order noise" caused by changes in fan speed and system load fluctuations—the core frequency components of this noise dynamically shift with operating conditions, causing the effectiveness of fixed silencers to decrease sharply at non-design frequencies. While active noise control technology that uses sound to reduce noise can respond dynamically, its systems are complex and costly, and its effectiveness in handling broadband noise and complex sound field environments is limited, restricting its widespread application in general industrial and civilian fields. More importantly, whether it is source aerodynamic optimization or terminal additional silencing, existing technologies mostly design the fan body and noise reduction device as relatively independent units, lacking a modular solution that can be tightly integrated into the duct system, has a relatively simple structure, and can adaptively track and suppress specific changes in noise in real time.

[0004] Therefore, it is necessary to improve and optimize its structure to solve the aforementioned existing problems. An ideal new noise reduction device should be directly embedded in the fan's airflow channel, operating as an intelligent module. It needs to have the ability to sense the noise spectrum in real time and dynamically change its acoustic characteristics through an adjustable physical structure (rather than a complex sound field interference system), thereby accurately matching and absorbing the changing primary order noise. This structural innovation aims to fill the gap between the poor adaptability of fixed silencers and the excessive cost of advanced active noise reduction systems, providing a highly reliable, responsive, and easily retrofittable or integrated noise reduction method for existing duct systems. This will enable stable and efficient noise suppression under a wider range of actual operating conditions, driving the development of centrifugal fan silencing technology towards greater intelligence and integration. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a centrifugal fan and a noise reduction control method for the centrifugal fan, thus solving the problems existing in the prior art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a centrifugal fan, comprising: The centrifugal fan body has a connecting pipe connected to its air outlet; A silencer is connected to the end of the connecting pipe away from the centrifugal fan body via a first mounting base, and a second mounting base is provided at the end of the silencer away from the first mounting base; the silencer includes an inner cylinder and an outer cylinder arranged coaxially, and an annular sandwich is formed between the inner cylinder and the outer cylinder; A noise detection device includes multiple sets of first microphones disposed on the inner sidewall of the first mounting base, and multiple sets of second microphones disposed on the inner sidewall of the second mounting base. A movable silencing device, which is disposed on the silencing cylinder; and, The central control unit is electrically connected to the multiple sets of first microphones, the multiple sets of second microphones, and the movable silencer.

[0007] Preferably, the movable silencing device includes a slide rail, a movable ring, and a pen-type electric telescopic rod; The slide rails are arranged in pairs on the upper and lower walls inside the outer cylinder; The upper and lower walls of the movable ring are provided with sliding grooves, and the movable ring is slidably connected between a pair of slide rails through the sliding grooves; The pen-shaped electric telescopic rod is located inside the outer cylinder, and the end of its protruding shaft is fixedly connected to one axial end of the movable ring.

[0008] Preferably, the inner cylinder has sound-absorbing holes along its axial direction on its cylinder wall; The movable silencing device also includes a movable silencing pipe, a silencing branch pipe, a sleeve, a first rotating seat, and a second rotating seat; The movable silencer pipe is rotatably connected to the outer wall of the inner cylinder via the first rotating seat and communicates with the silencer hole; Multiple silencer branches are distributed along the axial direction of the movable silencer and fixed to its outer wall, and there is an acute angle between the axis of the silencer branch and the axis of the movable silencer. One end of the sleeve is slidably connected to the end of the movable silencer tube away from the first rotating seat; The other end of the sleeve is rotatably connected to the inner wall of the movable ring via the second rotating seat.

[0009] Preferably, the inner walls of the movable silencer pipe and the silencer branch pipe are lined with sound-absorbing cotton.

[0010] Preferably, the sound-absorbing cotton is made of centrifugal glass wool or water-repellent rock wool.

[0011] Preferably, the first rotating seat and the second rotating seat are ball joint structures or spherical bearing structures.

[0012] Preferably, the angle between the centerline of the silencing branch pipe and the centerline of the movable silencing pipe is 45°.

[0013] Preferably, the inner cylinder has three sound-absorbing hole matrices arranged sequentially along its axial direction on its cylinder wall, corresponding to three movable rings and three pen-type electric telescopic rods.

[0014] Preferably, the connecting pipe is a square-to-round connector.

[0015] A noise reduction control method for a centrifugal fan, applied to the centrifugal fan described above, includes the following steps: S1. Acquire the noise signal collected by the first microphone and the noise signal collected by the second microphone, and perform spectrum analysis on the noise signal; S2. Based on the spectrum analysis results, determine the frequency of the target order noise, and based on this frequency, query the preset mapping relationship data to obtain the target displacement parameters of the corresponding active loop; S3. Based on the target displacement parameters, control the corresponding pen-type electric telescopic rod to drive the movable ring to move, so that the movable silencer tube deflects. S4. Adjust the displacement parameters of the movable ring according to the changes in the noise signal collected by the second microphone.

[0016] This invention provides a centrifugal fan and a noise reduction control method for the centrifugal fan. It has the following beneficial effects: 1. Compared with existing technologies, the centrifugal fan and its noise reduction control method achieve dynamic adjustment of the noise reduction frequency band by setting a movable ring that can move independently along the duct axis and controlling the angle of the silencer pipe built into the duct wall. This effectively solves the key problem that traditional fixed silencers cannot adapt to the frequency drift of "variable order noise" when the fan is running at variable speed. It enables the noise reduction module to actively track and target the changing main noise components, significantly improving the overall noise reduction effect and adaptability under complex operating conditions.

[0017] 2. Compared with existing technologies, this centrifugal fan and its noise reduction control method construct a closed-loop control system consisting of a front-end noise sensor, a central control unit, and a terminal mechanical adjustment device. It also employs a multi-stage, series-connected modular silencing structure, highly integrating adaptive noise reduction functionality within the air duct. This avoids the drawbacks of traditional sound silencing technologies, such as complexity and high cost, and provides a relatively simple, rapid-response, and easy-to-install active noise reduction solution, filling the technological gap between fixed silencing and advanced active noise reduction. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of the present invention; Figure 2 This is a schematic cross-sectional view of the connection structure between the outer cylinder and the inner cylinder of the present invention; Figure 3 For the present invention Figure 2 A magnified view of a section at point A in the middle; Figure 4 This is a partial top sectional view of the outer and inner cylinder connection structure of the present invention; Figure 5 For the present invention Figure 4 A magnified view of a section at point B in the middle; Figure 6 This is a schematic diagram of the active ring end face structure of the present invention.

[0019] The components include: 1. Centrifugal fan body; 2. Connecting pipe; 3. First mounting base; 4. Outer cylinder; 5. Second mounting base; 6. First microphone; 7. Second microphone; 8. Inner cylinder; 9. Silencing hole; 10. First rotating seat; 11. Movable silencing pipe; 12. Silencing branch pipe; 13. Sleeve; 14. Second rotating seat; 15. Slide rail; 16. Movable ring; 1601. Slide groove; 17. Pen-type electric telescopic rod. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example

[0021] like Figures 1 to 6 As shown in the figure, this embodiment of the invention provides a centrifugal fan and a noise reduction control method thereof.

[0022] To achieve real-time sensing and systematic intelligent control of centrifugal fan noise, this embodiment provides a complete system including detection, execution, and decision-making units. The system includes a centrifugal fan body 1, with a connecting pipe 2 connected to its outlet. One end of the connecting pipe 2, away from the centrifugal fan body 1, is connected to a silencer via a first mounting base 3. The other end of the silencer, away from the first mounting base 3, is provided with a second mounting base 5 for connecting to a downstream air duct. The silencer consists of an inner cylinder 8 and an outer cylinder 4 arranged coaxially, forming an annular sandwich. To acquire noise information in real time, this embodiment includes a noise detection device, comprising multiple sets of first microphones 6 disposed on the inner wall of the first mounting base 3, and multiple sets of second microphones 7 disposed on the inner wall of the second mounting base 5. Furthermore, the system includes a movable silencing device disposed on the silencer and a central control unit. The central control unit is electrically connected to the multiple sets of first microphones 6, the multiple sets of second microphones 7, and the movable silencing device. Through the above structure, the first microphone 6 can monitor the original noise spectrum from the wind turbine body, and the second microphone 7 can monitor the final noise after processing, providing feedforward and feedback signals to the central control unit, thereby forming a closed-loop intelligent control system that can evaluate the noise reduction requirements and effects in real time.

[0023] To achieve dynamic and precise adjustment of the silencing structure, this embodiment specifically designs the core driving component of the movable silencing device. The movable silencing device includes a slide rail 15, a movable ring 16, and a pen-type electric telescopic rod 18. Specifically, the slide rails 15 are arranged in pairs on the upper and lower walls inside the outer cylinder 4. The upper and lower walls of the movable ring 16 are each provided with a groove 1601, allowing the movable ring 16 to be precisely slidably connected between the pair of slide rails 15 via the groove 1601. The pen-type electric telescopic rod 18 is located inside the outer cylinder 4, and its protruding shaft end is fixedly connected to one axial end of the movable ring 16. With this structure, when the central control unit issues a command, the pen-type electric telescopic rod 18 can drive the movable ring 16 to perform a stable axial translation along the slide rail 15. This translational movement provides a precise and reliable mechanical driving basis for subsequent changes in the acoustic characteristics of the silencing assembly.

[0024] To convert the linear motion of the driving component into angular changes in the silencing unit, thereby dynamically adjusting its acoustic resonance frequency, this embodiment employs a clever linkage transmission mechanism. Multiple sets of silencing holes 9 are axially formed on the inner cylinder 8 wall. The movable silencing device also includes a movable silencing pipe 11, silencing branch pipes 12, a sleeve 13, a first rotating seat 10, and a second rotating seat 14. The movable silencing pipe 11 is rotatably connected to the outer wall of the inner cylinder 8 via the first rotating seat 10 and communicates with the silencing holes 9, allowing the airflow sound waves from the main duct to enter. Multiple silencing branch pipes 12 are distributed axially along the movable silencing pipe 11 and fixed to its outer wall; the axis of the silencing branch pipe 12 is designed to form a 45° acute angle with the axis of the movable silencing pipe 11. One end of the sleeve 13 is slidably connected to the end of the movable silencing pipe 11 away from the first rotating seat 10, while its other end is rotatably connected to the inner wall of the movable ring 16 via the second rotating seat 14. With the above structure, when the movable ring 16 is driven to translate by the pen-type electric telescopic rod 18, it pushes and pulls the free end of the movable silencer tube 11 through the second rotating seat 14 and the sleeve 13. Since the other end of the movable silencer tube 11 is defined as the rotation fulcrum by the first rotating seat 10, this push-pull action will force the entire movable silencer tube 11 to deflect around the first rotating seat 10, thereby changing the physical size and shape of the Helmholtz resonant cavity composed of the movable silencer tube 11, the silencer branch tube 12 and the inner cavity, so as to achieve continuous and precise adjustment of its silencing peak frequency.

[0025] To ensure effective absorption of broadband noise, especially regenerated noise that may be generated when airflow passes through the silencer pipe, while dynamically adjusting the silencing frequency, this embodiment optimizes the internal structure of the silencing unit. A layer of sound-absorbing cotton is attached to the inner wall of the movable silencer pipe 11 and all silencer branch pipes 12. The preferred material for this sound-absorbing cotton is centrifugal glass wool or hydrophobic rock wool. Through this structure, the inner lining sound-absorbing cotton can efficiently absorb mid-to-high frequency broadband noise transmitted through the silencer holes 9, and form a "resistance-impact composite" silencing mechanism with the adjustable resonant cavity structure. This not only broadens the overall silencing frequency band but also effectively suppresses eddy noise generated when airflow passes through the silencer branch pipes 12, avoiding the problem of the noise reduction device itself becoming a secondary noise source.

[0026] To ensure the flexibility and reliability of the transmission mechanism in multi-degree-of-freedom motion, this embodiment features a special design for key connecting components. Both the first rotating seat 10 and the second rotating seat 14 employ ball joint structures or spherical bearing structures. Through these structures, the ball joint connection allows the movable muffler tube 11 to possess a slight radial swing freedom during deflection, while simultaneously allowing the connection between the sleeve 13 and the movable ring 16 to automatically adapt to angle changes during the combined motion of the movable ring 16's translation and the movable muffler tube 11's deflection. This design effectively releases internal forces within the mechanism, ensuring smooth long-term operation of the entire linkage system and preventing jamming caused by assembly errors or thermal deformation.

[0027] To achieve graded and progressive deep noise reduction to cope with complex and variable noise spectra, this embodiment adopts a multi-stage adjustable silencing unit series layout. On the inner cylinder 8, three silencing hole matrices 9 are arranged sequentially along its axial direction. Each matrix corresponds to an independent actuator, namely a movable ring 16 and a pen-type electric telescopic rod 18 that drives it. Through this structure, the central control unit can coordinate the three movable rings 16 to different positions, thereby deflecting the three sets of movable silencing tubes 11 to different angles. This is equivalent to setting three independently adjustable silencing filters in series within the air duct. The first stage can be used to process the strongest fundamental frequency noise, while subsequent stages can perform refined secondary or tertiary attenuation on residual specific higher-order noise, thus achieving a better overall noise reduction and wider adaptability than a single-stage structure.

[0028] To accommodate the common rectangular air outlet and circular air duct connection of centrifugal fans and ensure a smooth airflow transition to reduce additional aerodynamic noise, this embodiment specifies the connecting components. Specifically, the connecting pipe 2 is a square-to-round connector. Through this structure, the connecting pipe 2 smoothly transitions the rectangular air outlet of the centrifugal fan body 1 to the circular cross-section of the silencer in this embodiment, avoiding severe eddies and impact noise caused by abrupt changes in the flow cross-section, and ensuring that the silencer can perform optimally in a stable airflow environment.

[0029] This embodiment also provides a noise reduction control method applied to the above-mentioned centrifugal fan, the method comprising the following steps: S1. Signal Acquisition and Feature Extraction: The central control unit acquires the original noise signal at the inlet end collected by the first microphone 6 and the processed noise signal at the outlet end collected by the second microphone 7 in real time, and performs Fast Fourier Transform (FFT) spectrum analysis on these noise signals.

[0030] S2. Target Parameter Mapping: Based on the spectrum analysis results, the central control unit identifies the frequency of the currently dominant target order noise that needs to be suppressed. Subsequently, the system queries the "noise frequency - optimal displacement of the active loop" mapping data pre-stored in the controller based on this frequency, thereby obtaining the target displacement parameters corresponding to the target silencing unit (a certain stage of active loop 16).

[0031] S3. Hierarchical Coordinated Adjustment: Based on the obtained target displacement parameters, the central control unit sends precise drive commands to the corresponding pen-type electric telescopic rod 18. The pen-type electric telescopic rod 18 retracts or extends according to the command, driving the target movable ring 16 to move along the slide rail 15 to the predetermined position. The movement of the movable ring 16 is transmitted through the second rotating seat 14 and the sleeve 13, pushing or pulling the corresponding movable silencer tube 11, causing it to deflect around the first rotating seat 10 to the target angle.

[0032] S4. Closed-loop feedback optimization: After the adjustment action is executed, the central control unit continuously monitors the output noise spectrum changes fed back by the second microphone 7. The system determines whether the sound pressure level of the target order noise has dropped below the expected threshold. If the optimal effect has not been achieved, the central control unit will fine-tune the displacement parameters of the active loop 16, performing small-range iterative optimization until the system reaches the optimal noise reduction state under the current operating conditions.

[0033] Working principle: The working principle of this invention is based on a closed-loop adaptive control logic of "perception-decision-execution-verification" and an adjustable acoustic structure. During system operation, the first microphone 6 acts as a "sentinel," monitoring the original sound field generated by the fan and containing variable-order noise in real time, and sending the signal to the central control unit. The central control unit, acting as the "brain," analyzes the noise spectrum in real time and identifies the dominant noise frequency components that need to be prioritized. Subsequently, based on a preset acoustic-mechanical mapping relationship, it calculates the mechanical adjustment amount (i.e., the target displacement of the movable ring 16) required to match the resonant frequency of the corresponding silencing unit to that noise frequency. Then, the command is issued to the pen-type electric telescopic rod 18, acting as the "actuator," driving the movable ring 16 to move. The linear motion of the movable ring 16 is converted into a precise angular deflection of the movable silencing tube 11 through a ball joint-linkage mechanism (second rotating seat 14, sleeve 13, first rotating seat 10). This deflection alters the equivalent volume and neck dimensions of the resonant cavity formed by the active silencer duct 11 and its upper silencer branch duct 12, thereby shifting the frequency of its Helmholtz resonance peak to precisely align with and absorb the target order noise. Simultaneously, the sound-absorbing cotton lining the duct wall continuously absorbs broadband noise. The second microphone 7, located at the final outlet, acts as an "effect evaluator," feeding back the noise-reduced sound field information to the central control unit, forming a closed loop. If the effect is not optimal, the system automatically fine-tunes, achieving adaptive iteration. Through the series connection of three such adjustable silencer units, the system can perform progressively refined, targeted processing of the noise spectrum, thereby achieving efficient and adaptive suppression of a wide range of varying order noise generated by the variable frequency fan.

[0034] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A centrifugal fan, characterized in that, include: Centrifugal fan body (1), its air outlet is connected to a connecting pipe (2); The silencer is connected to the end of the connecting pipe (2) away from the centrifugal fan body (1) via a first mounting base (3), and a second mounting base (5) is provided at the end of the silencer away from the first mounting base (3); the silencer includes an inner cylinder (8) and an outer cylinder (4) arranged coaxially, and an annular sandwich is formed between the inner cylinder (8) and the outer cylinder (4); The noise detection device includes multiple sets of first microphones (6) disposed on the inner wall of the first mounting base (3) and multiple sets of second microphones (7) disposed on the inner wall of the second mounting base (5). A movable silencing device, which is disposed on the silencing cylinder; and, The central control unit is electrically connected to the multiple sets of first microphones (6), the multiple sets of second microphones (7), and the movable silencer.

2. A centrifugal fan according to claim 1, characterized in that: The movable silencing device includes a slide rail (15), a movable ring (16), and a pen-type electric telescopic rod (18). The slide rails (15) are arranged in pairs on the upper and lower walls inside the outer cylinder (4); The upper and lower walls of the movable ring (16) are provided with sliding grooves (1601), and the movable ring (16) is slidably connected between a pair of slide rails (15) through the sliding grooves (1601); The pen-type electric telescopic rod (18) is located inside the outer cylinder (4), and the end of its protruding shaft is fixedly connected to one axial end of the movable ring (16).

3. A centrifugal fan according to claim 2, characterized in that: The inner cylinder (8) has a sound-absorbing hole (9) along its axial direction on its cylinder wall. The movable silencing device also includes a movable silencing pipe (11), a silencing branch pipe (12), a sleeve (13), a first rotating seat (10), and a second rotating seat (14). The movable silencer tube (11) is rotatably connected to the outer wall of the inner cylinder (8) through the first rotating seat (10) and communicates with the silencer hole (9); Multiple silencer branches (12) are distributed along the axial direction of the movable silencer (11) and fixed to its outer wall. The axis of the silencer branch (12) and the axis of the movable silencer (11) have an acute angle. One end of the sleeve (13) is slidably connected to the end of the movable silencer tube (11) away from the first rotating seat (10); The other end of the sleeve (13) is rotatably connected to the inner wall of the movable ring (16) via the second rotating seat (14).

4. A centrifugal fan according to claim 3, characterized in that: The inner walls of the movable silencer pipe (11) and the silencer branch pipe (12) are covered with sound-absorbing cotton.

5. A centrifugal fan according to claim 4, characterized in that: The sound-absorbing cotton is made of centrifugal glass wool or water-repellent rock wool.

6. A centrifugal fan according to claim 3, characterized in that: The first rotating seat (10) and the second rotating seat (14) are ball joint structures or spherical bearing structures.

7. A centrifugal fan according to claim 3, characterized in that: The angle between the centerline of the silencing branch pipe (12) and the centerline of the movable silencing pipe (11) is 45°.

8. A centrifugal fan according to claim 3, characterized in that: The inner cylinder (8) has three sound-absorbing holes (9) arranged in a matrix along its axial direction on its cylinder wall, and three movable rings (16) and three pen-type electric telescopic rods (18) are provided accordingly.

9. A centrifugal fan according to claim 1, characterized in that: The connecting pipe (2) is a square to round connector.

10. A noise reduction control method for a centrifugal fan, characterized in that, The method applied to the centrifugal fan as described in any one of claims 1 to 9 includes the following steps: S1. Obtain the noise signal collected by the first microphone (6) and the noise signal collected by the second microphone (7), and perform spectrum analysis on the noise signal; S2. Based on the spectrum analysis results, determine the frequency of the target order noise, and query the preset mapping relationship data based on the frequency to obtain the target displacement parameters of the corresponding active loop (16); S3. According to the target displacement parameters, control the corresponding pen-type electric telescopic rod (18) to drive the movable ring (16) to move, so that the movable silencer tube (11) deflects; S4. Adjust the displacement parameters of the active ring (16) according to the noise signal changes collected by the second microphone (7).

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