Low-wind-noise high-efficiency direct-current brushless fan and control method thereof

Abstract

The application relates to the technical field of low-noise fans, and particularly discloses a low-wind-noise high-efficiency direct-current brushless fan and a control method thereof. The fan comprises a shell, a cover plate, an air inlet pipe, an air outlet pipe, a rotating component and a connecting component. The rotating component comprises a rotating disc and a slidable polygonal piece, and the connecting component comprises a fan blade in rotating connection with the rotating disc. The air pressure of the air inlet pipe is monitored through an air pressure sensor, a control module calculates an optimal fan blade inclination angle according to an angle of attack-air pressure relationship model, and a motor-driven telescopic rod is driven to adjust the position of the polygonal piece, so that the angle of attack of the fan blade is changed. The method realizes airflow adhesion flow state, effectively reduces wind noise and improves efficiency. The application solves the airflow separation problem caused by the fixed fan blade angle of a traditional fan and is suitable for ventilation scenes requiring high efficiency and low noise.

Description

Technical Field

[0001] This invention relates to the field of low-noise fan technology, and more specifically, to a low-noise, high-efficiency DC brushless fan and its control method. Background Technology

[0002] In existing technologies, brushless DC fans are widely used in ventilation, refrigeration, and vacuuming, but their performance is often limited by the fixed blade design. The blade tilt angle of traditional fans is set during manufacturing and cannot be dynamically adjusted according to changes in air pressure inside the casing during operation. When the fan operates under different load conditions, the fixed-angle blades easily cause airflow to separate from the blade surface, forming boundary layer separation and vortices, generating significant wind noise and reducing efficiency. Specifically, when airflow passes through the blades, if the angle of attack (the angle between the airflow direction and the blade chord line) exceeds a critical point, it will trigger an adverse pressure gradient, causing the boundary layer airflow kinetic energy to be depleted, resulting in separation and generating chaotic vortices and noise.

[0003] This problem is particularly prominent in high wind pressure or variable load scenarios, which limits the application range and energy efficiency of wind turbines.

[0004] Therefore, there is an urgent need for a low-noise, high-efficiency fan solution that can adjust the blade angle in real time to adapt to changes in wind pressure. Summary of the Invention

[0005] The purpose of this invention is to provide a low-noise, high-efficiency brushless DC fan and its control method to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides a low-noise, high-efficiency DC brushless fan and its control method. A cover plate is sealed and connected to the housing and the opening at the top of the housing. The housing and the cover plate are fastened together by bolts. An air inlet pipe is connected to the top center of the cover plate, and an air outlet pipe is tangentially and fixedly connected to the outer arc surface of the housing. A rotating component is rotatably arranged inside the housing, and a connecting component is connected to the rotating component. The rotating component includes a turntable and a multi-faceted component that slides along the rotation axis of the turntable. The connecting component includes fan blades rotatably connected to the top of the turntable. The multi-faceted component is used to adjust the tilt angle of the fan blades relative to the turntable, thereby changing the angle of attack of the fan blades when the airflow enters.

[0007] As a further improvement to this technical solution, the rotating component includes a rotating motor, a driving gear, a driven gear, an electric telescopic rod, a turntable, a polygonal component, and a wind pressure sensor; the rotating motor drives the driving gear to mesh with the driven gear, thereby driving the turntable to rotate.

[0008] As a further improvement to this technical solution, the diameter of the driving gear is larger than that of the driven gear, and the rotational speed of the turntable is increased by the gear ratio to enhance the wind pressure output; the telescopic end of the electric telescopic rod is connected to the polygonal piece for linear sliding.

[0009] As a further improvement to this technical solution, the connecting components include a telescopic connecting rod, a rotating bracket, a rotating connector, a connecting column, a fan blade, and a rotating bracket; the telescopic connecting rod is connected to the polygonal component, and the linear motion of the electric telescopic rod is converted into the tilting rotation of the fan blade through the vertical rotation combination of the rotating bracket and the rotating connector, thus avoiding jamming during the adjustment process.

[0010] As a further improvement to this technical solution, the fan blades are circumferentially distributed on the top of the turntable and fixed by a rotating bracket; the tilt angle of the fan blades is adjustable to adapt to different wind pressure conditions and ensure that the airflow is close to the airfoil surface.

[0011] As a further improvement to this technical solution, a wind pressure sensor is set at the center of the top of the polygonal part to monitor the airflow pressure at the air inlet duct in real time; a mounting cavity is fixedly set on the outer surface of the housing, and a control module is fixedly set in the mounting cavity to receive the wind pressure sensor signal and control the movement of the electric telescopic rod.

[0012] A low-noise, high-efficiency DC brushless fan control method includes the following steps: S1 starts the fan, performs system self-check and initialization through the control module, and sets the initial speed of the turntable and the initial tilt angle of the fan blades; The S2 wind pressure sensor monitors the wind pressure value at the air inlet duct in real time and transmits the signal to the control module; The S3 control module calculates the optimal blade tilt angle based on the wind pressure value, using a preset angle of attack-wind pressure relationship model. The S4 control module drives the electric telescopic rod to move, causing the polygonal component to slide, and adjusting the fan blade angle of attack through the connecting parts. S5 forms a closed-loop control, continuously monitoring and optimizing parameters to adapt to load changes.

[0013] As a further improvement to this technical solution, in step S3, the angle of attack-wind pressure relationship model is established based on Bernoulli's principle and boundary layer theory. When the wind pressure increases, the angle of attack is increased to overcome the adverse pressure gradient, and when the wind pressure decreases, the angle of attack is decreased to optimize energy consumption.

[0014] As a further improvement to this technical solution, in step S4, the displacement of the electric telescopic rod is converted into the tilting rotation of the fan blades through the connecting component, wherein the combination of the rotating connecting component and the vertical rotation of the rotating bracket ensures smooth adjustment; the control module monitors the displacement feedback in real time to ensure accuracy.

[0015] As a further improvement to this technical solution, in step S5, the control module integrates a fault self-diagnosis function, dynamically adjusts the angle of attack-wind pressure model parameters to cope with wear or environmental changes, and uses PID control or machine learning methods to minimize wind noise and energy loss.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. In this low-noise, high-efficiency DC brushless fan and its control method, the wind pressure at the air inlet duct is monitored in real time by a wind pressure sensor. The control module drives an electric telescopic rod to adjust the angle of attack of the fan blades, ensuring that the airflow always adheres closely to the blade surface and avoiding boundary layer separation. The overall structure is compact and the airflow path is optimized, reducing eddies and noise generation at the source. Based on Bernoulli's principle and boundary layer theory, the angle of attack-wind pressure relationship model dynamically matches the fan blade tilt angle with the wind pressure conditions, enabling kinetic energy to be efficiently converted into static pressure energy and reducing energy loss. The fan blade circumferential distribution and rotation mechanism optimize airflow management and improve suction and exhaust efficiency.

[0017] 2. This low-noise, high-efficiency brushless DC fan and its control method utilize a closed-loop control approach to continuously monitor air pressure and adjust parameters to adapt to load changes. For example, when the outlet duct resistance fluctuates, the system automatically increases or decreases the angle of attack to maintain stable operation. The precise design of rotating and connecting components ensures the reliability and smoothness of the adjustment. The connecting components employ a vertical rotation combination of a rotating bracket and a rotating connector, converting the linear motion of the electric telescopic rod into the tilting rotation of the fan blades, avoiding jamming and extending service life. The control module integrates a fault self-diagnosis function, further enhancing the system's safety and durability. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the overall structure assembly of the present invention; Figure 2 This is a schematic diagram of the structure of the mounting cavity in this invention; Figure 3 This is a schematic diagram of the air outlet duct in this invention; Figure 4 for Figure 3 Enlarged view of the structure at point A in the middle; Figure 5 This is a schematic diagram of the rotating motor in this invention; Figure 6 This is a schematic diagram of the suction direction of the fan blade 805 in this invention.

[0019] The labels in the diagram represent the following: 1. Shell; 2. Cover plate; 3. Air inlet duct; 4. Air outlet duct; 5. Mounting cavity; 6. Control module; 7. Rotating component; 701. Rotating motor; 702. Driving gear; 703. Driven gear; 704. Electric telescopic rod; 705. Turntable; 706. Polygonal component; 707. Wind pressure sensor; 708. Guide groove; 8. Connecting component; 801. Telescopic connecting rod; 802. Rotating bracket; 803. Rotating connecting component; 804. Connecting column; 805. Fan blade; 806. Rotating bracket. Detailed Implementation

[0020] The technical solutions in 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.

[0021] Example 1 Please see Figures 1-6 As shown, this embodiment provides a low-noise, high-efficiency DC brushless fan, including a housing 1 and a cover plate 2 sealed at the top opening of the housing 1. The housing 1 and the cover plate 2 are fastened together by bolts. An air inlet pipe 3 is connected to the top center of the cover plate 2. An air outlet pipe 4 is tangentially connected to the outer arc surface of the housing 1. By setting a rotating blade structure inside the housing 1, a unidirectional pressurization and conduction effect of airflow can be achieved. The airtightness of the connection point of the device can be improved by setting a connecting ring between the air inlet pipe 3 and the air outlet pipe 4. However, in actual use, since the rotating blades are at a fixed tilt angle at different speeds, the blade tilt angle cannot be adjusted according to the changes in air pressure inside the housing 1, which leads to the airflow separating from the blade surface and generating significant wind noise. Specifically, the principle of airflow detaching from the blade surface is disclosed: Ideally, when airflow approaches the blades, it smoothly splits into two streams, flowing over the upper and lower surfaces of the blades. Due to the unique airfoil structure of the blades, the airflow path over the upper surface (suction surface) is longer and faster, resulting in lower static pressure according to Bernoulli's principle. Conversely, the airflow over the lower surface (pressure surface) has a slower velocity and higher static pressure. This pressure difference is the source of lift (manifested as wind pressure in a wind turbine). Crucially, the airflow remains "attached" to the blade profile, flowing smoothly to the trailing edge. This flow state, called "attached flow," minimizes energy loss and maximizes efficiency. The extremely thin layer of airflow adhering closely to the blade surface is called the boundary layer. Due to friction with the surface, the airflow velocity within this layer gradually increases from zero velocity at the surface to the mainstream velocity outside. Therefore, the airflow within the boundary layer itself has relatively weak kinetic energy. When this already "weak" boundary layer airflow enters the adverse pressure gradient region, it needs to overcome the ever-increasing pressure to continue moving forward, which consumes its own kinetic energy. As a result, the airflow velocity within the boundary layer further decreases, causing the boundary layer airflow to continuously move forward in the adverse pressure gradient, and its kinetic energy continues to decay. Eventually, at a certain point on the blade surface, the airflow kinetic energy is completely exhausted, and the velocity drops to zero. This point is called the separation point or stagnation point. After the separation point, the adverse pressure gradient becomes so strong that it begins to cause the airflow to reverse—that is, the airflow near the surface no longer flows towards the trailing edge of the blade, but is pushed back by the high pressure, forming a countercurrent. The mainstream airflow from the front and the reverse countercurrent from the rear meet, collide, and swirl together near the separation point. This prevents the boundary layer from adhering to the blade surface, instead "lifting" it away to form a large-scale, chaotic vortex region, known as a separation bubble. The chaotic vortex compresses the air, resulting in significant wind noise.

[0022] Based on the above principles, it can be concluded that the airfoil structure and tilt angle of the blades play a crucial role in whether the airflow adheres closely to the blade surface. Therefore, by adjusting the tilt angle of the blades according to the wind pressure, the effect of the airflow always adhering closely to the blade surface can be achieved. The specific principle is as follows: One of the key parameters for airflow separation is the "angle of attack"—the angle between the airflow direction and the blade chord (the straight line connecting the leading and trailing edges of the blade). Within a certain range, increasing the angle of attack will increase lift (which manifests as wind pressure in a wind turbine), but beyond a certain critical point, the airflow will separate from the suction side of the blade. When the outlet air pressure of the fan increases (i.e., the system resistance increases), the airflow has more difficulty "pushing away" the obstruction in front and is more likely to stall on the blade surface. At this time, if the tilt angle of the blades can be increased in real time and precisely (increasing the angle of attack), more energy can be applied to the airflow, allowing it to better adhere to the blade surface, overcome the higher reverse pressure gradient, and thus delay or avoid separation.

[0023] To enable the blade tilt angle to be adaptively adjusted according to the changes in wind pressure inside the housing 1, thereby ensuring that the airflow is always in close contact with the blade surface, a rotating component 7 is provided inside the housing 1. The rotating component 7 includes an electric telescopic rod 704 and a turntable 705. The electric telescopic rod 704 is fixedly connected to the side of the housing 1 away from the cover plate 2 through the mounting cavity 5. The central control module 6 is provided inside the mounting cavity 5. The telescopic end of the electric telescopic rod 704 faces the inside of the housing 1 and is rotatably provided with a polygonal component 706. A connecting component 8 is provided on the outer edge of the polygonal component 706. The connecting component 8 includes a fan blade 805 that is rotatably connected to the turntable 705. By driving the polygonal component 706 to slide linearly along the rotation axis of the turntable 705 through the electric telescopic rod 704, multiple sets of fan blades 805 can be tilted and rotated through the connecting component 8, thereby changing the angle of attack between the fan blades 805 and the airflow. When the device is stationary, the fan blade 805 is in a vertical position. As the turntable 705 rotates, it generates a unidirectional airflow into the housing 1. By adjusting the rotation speed of the turntable 705, different wind pressure airflow effects can be achieved. Furthermore, the tilt angle of the fan blade 805 can be adjusted according to different wind pressure environments, thereby changing the angle of attack of the fan blade 805 on the airflow. This ensures that the airflow is closely attached to the airfoil structure surface of the fan blade 805, thereby reducing the overall wind noise of the device.

[0024] In order to enable the fan blade 805 to adaptively adjust its tilt angle according to changes in wind pressure, other structures of the rotating component 7 also need to be disclosed: The rotating component 7 includes a rotating motor 701 fixedly installed inside the mounting cavity 5. The output end of the rotating motor 701 is fixedly provided with a drive gear 702. The drive gear 702 is rotatably connected to the outer side of the housing 1. The drive gear 702 is meshed with a driven gear 703. The driven gear 703 is rotatably connected to the outer side of the housing 1. The diameter of the drive gear 702 is larger than the diameter of the driven gear 703. Stable rotational transmission can be achieved through gear transmission, and the rotating motor 701 is located in a non-axial position, thereby providing control space for the electric telescopic rod 704. Furthermore, the gear ratio in the gear combination can increase the rotational speed of the turntable 705, thereby increasing the maximum wind pressure of the device. Driven gear 703 is provided with a conventional sleeve that penetrates the bottom of housing 1. The telescopic end of electric telescopic rod 704 slides from the inside of the sleeve. The end of the transmission sleeve away from driven gear 703 is fixedly connected to the bottom of turntable 705. A wind pressure sensor 707 is fixedly installed at the center of the top of polygonal part 706. The structure of the wind pressure sensor 707 enables the detection of the air pressure of the airflow entering from the air inlet duct 3, thus achieving the effect of detecting the current air pressure. Since the fan blade 805 is not actually oriented towards the center of the turntable 705 during installation, the connecting component 8 needs to avoid jamming when the fan blade 805 is tilted and rotated during the adjustment of the tilt angle of the fan blade 805. Therefore, the specific structure of the connecting component 8 also needs to be disclosed. The connecting component 8 includes a telescopic connecting rod 801 that is fixedly connected to the side edge of the polygonal component 706. A rotating bracket 802 is rotatably provided at the telescopic end of the telescopic connecting rod 801, and a rotating connecting piece 803 is rotatably provided at the other end of the rotating bracket 802. The rotation directions of the rotating connecting piece 803 and the rotating bracket 802 are perpendicular to each other. The vertical rotation combination of the rotating connector 803 and the rotating bracket 802 can effectively avoid problems such as jamming during the tilting rotation transmission of the fan blade 805. The telescopic connecting rod 801 can ensure that the fan blade 805 maintains a continuous connection during the tilting rotation. A connecting post 804 is fixedly provided at one end of the rotating connector 803 away from the rotating bracket 802. The other end of the connecting post 804 is fixedly connected to the side of the fan blade 805. A rotating bracket 806 is rotatably provided at the bottom of the fan blade 805. The bottom of the rotating bracket 806 is fixedly connected to the top of the turntable 705. Several rotating brackets 806 and the fan blade 805 are circumferentially distributed on the top of the turntable 705. The fan blades 805, which are distributed at equal intervals around the circumference, can generate suction towards the inside and outside of the housing 1 when the turntable 705 rotates, thereby drawing air from the air inlet pipe 3 at the center. Specifically, the principle by which the rotation of the fan blade 805 generates suction force into the housing 1 is disclosed: When fan blade 805 is driven to rotate at high speed by rotor 705, the blades do work on the air, giving it velocity. In common centrifugal fans, gas typically enters the flow channel between the blades axially and rotates with the impeller under its drive; simultaneously, the gas gains energy due to inertia and leaves the impeller radially, relying on the generated centrifugal force to do work. The airflow direction of axial fans is different, but the fundamental reason for their suction is also the impeller rotation causing air movement; the suction directly stems from the formation of a pressure difference. When the fan blades rotate, especially when the impeller of a centrifugal fan rotates at high speed, the blades do work on the air, giving it extremely high tangential velocity. Under the action of centrifugal force, the air is violently thrown radially from the center to the outer edge along the blade channel. This causes the air in the central region of the impeller to be continuously "thrown away," resulting in a sharp decrease in air density in that region, forming a local vacuum, i.e., a negative pressure zone. A pressure difference is generated between this negative pressure zone and the external environment (usually standard atmospheric pressure). Under atmospheric pressure, outside air naturally flows towards this low-pressure area and is "drawn" into the fan through the air inlet of the casing. This is what we call "suction." In the volute fan of the sweeper, this negative pressure area is transmitted through the air duct system (filter, dust box, suction channel) all the way to the floor brush suction port, thereby generating suction and sucking in dust and air from the ground.

[0025] The air drawn in does not remain at the center of the impeller. In a centrifugal fan, the high-speed air thrown to the outer edge of the impeller has high kinetic energy but low static pressure. After leaving the impeller, this high-speed airflow enters the volute surrounding the impeller. The volute is a gradually expanding spiral channel with a gradually increasing cross-section. According to Bernoulli's principle, the high-speed airflow gradually slows down within the expanding volute, converting most of its kinetic energy into static pressure energy, resulting in a significant increase in pressure. This high-pressure airflow is eventually discharged from the outlet at the end of the volute. Therefore, the fan achieves a continuous operating process of "drawing in" at the inlet and "discharging" at the outlet. As long as the impeller continues to rotate, air in the central area is constantly being thrown away, creating a continuous negative pressure to draw in fresh air, while the high-speed air thrown out continuously enters the volute for energy conversion and is then continuously discharged as high-pressure gas.

[0026] A sealed space is formed by bolt fastening. The core innovation lies in adjusting the tilt angle of the 805 fan blades in real time to adapt to different wind pressure conditions, ensuring that the airflow is close to the blade surface, reducing wind noise and improving efficiency; The principle of airflow separation is based on the influence of the angle of attack (the angle between the airflow direction and the blade chord line): when the angle of attack exceeds the critical point, the airflow will detach from the suction surface of the blade, forming boundary layer separation and vortices, generating wind noise. This invention uses a wind pressure sensor 707 to detect the wind pressure at the air inlet duct 3 and feeds it back to the control module 6, driving the electric telescopic rod 704 to move. The extension and retraction of the electric telescopic rod 704 causes the polygonal component 706 to slide along the axis of the turntable 705, thereby changing the tilt angle of the fan blade 805 through the connecting components 8 (including the telescopic connecting rod 801, the rotating bracket 802, the rotating connecting component 803, etc.), adjusting the angle of attack, and keeping the airflow in an attached flow state on the blade surface, reducing energy loss. This adjustment mechanism ensures that under high wind pressure conditions, the angle of attack is increased to give the airflow more energy, overcome the adverse pressure gradient, and avoid separation. The rotating component 7 is specifically implemented by a transmission system consisting of a rotating motor 701, a driving gear 702, and a driven gear 703. This gear combination increases the rotational speed of the turntable 705, thereby enhancing wind pressure output. An electric telescopic rod 704 is embedded in the transmission sleeve and works in conjunction with the wind pressure sensor 707 to achieve precise control. The design of the connecting component 8 avoids the problem of jamming during fan blade 805 adjustment: the telescopic connecting rod 801 connects to the polygonal piece 706, and the vertical rotation combination of the rotating bracket 802 and the rotating connecting component 803 converts linear motion into tilting rotation of the fan blades, ensuring smooth and reliable adjustment. The fan blades 805 are circumferentially distributed on the turntable 705, and their bottoms are fixed by the rotating bracket 806 to achieve stable rotation. The suction principle of the fan is based on centrifugal operation: the rotary disc 705 drives the fan blades 805 to rotate at high speed. Under the action of centrifugal force, air is thrown radially from the center to the outer edge, forming a negative pressure zone at the center of the impeller. External air is then drawn in through the inlet pipe 3. The high-speed airflow enters the volute-shaped casing 1, decelerates in the gradually expanding channel, converting kinetic energy into static pressure, and is finally discharged under high pressure from the outlet pipe 4. The control method monitors the air pressure in real time and dynamically adjusts the fan blade angle to ensure that the fan maintains high-efficiency and low-noise operation under different loads. The overall workflow, from air intake and energy conversion to exhaust, achieves continuous optimized management of airflow.

[0027] Example 2 Please see Figures 1-6 As shown, this embodiment provides a low-noise, high-efficiency DC brushless fan control method, including the following steps: S1 starts the low-noise, high-efficiency brushless DC fan. The system performs self-checks and initialization via the control module (central control module 6). Initialization includes setting the fan's default operating parameters, such as the initial speed of the turntable 705, the initial tilt angle of the blades 805 (usually set to vertical for minimum angle of attack startup), and the calibration value of the wind pressure sensor 707. Control module 6 loads a preset angle of attack-wind pressure relationship curve, based on fluid mechanics principles and experimental data, to define the optimal blade tilt angle under different wind pressure conditions, ensuring the airflow adherence state. During initialization, the rotating motor 701 drives the drive gear 702 and driven gear 703, causing the turntable 705 to rotate at a low speed, generating basic airflow. Simultaneously, the electric telescopic rod 704 is in its initial position, ensuring that the polygonal component 706 does not interfere with the rotation of the blades 805. This step aims to lay the foundation for stable fan operation and avoid noise or efficiency reduction due to parameter mismatch during startup. The S2 wind pressure sensor 707 monitors the airflow pressure at the inlet duct 3 in real time. Mounted at the center of the top of the polygonal component 706, the sensor accurately detects changes in airflow pressure entering the housing. The monitoring signal is transmitted to the control module 6 via wired or wireless means. The sampling frequency is dynamically adjusted according to the fan speed to ensure real-time data accuracy. The control module 6 filters and preprocesses the collected wind pressure signal to eliminate noise interference and calculates the average wind pressure value as a basis for adjustment. The key to this step is continuously tracking wind pressure fluctuations. For example, when the fan load increases (e.g., when the outlet duct 4 is obstructed), the wind pressure rises, and the airflow easily separates from the fan blade surface; conversely, when the wind pressure decreases, the angle of attack needs to be reduced to maintain efficiency. Through real-time monitoring, the system can respond promptly to changes in the external environment, providing reliable data support for subsequent adjustments. Based on the wind pressure value collected in step two, and combined with a preset angle-of-attack-wind pressure relationship model, the S3 control module 6 calculates the optimal blade tilt angle required at the current time. The calculation principle is based on Bernoulli's equation and boundary layer theory: when the wind pressure increases, the system needs to increase the angle of attack to give the airflow more energy, overcome the adverse pressure gradient, and avoid boundary layer separation; when the wind pressure decreases, the angle of attack is reduced to optimize energy consumption. The control module 6 outputs a control signal, specifying the extension displacement of the electric telescopic rod 704. This displacement is proportional to the linear sliding distance of the polygonal part 706, and is then converted into a change in the tilt angle of the blade 805 through the connecting component 8. The decision-making process also includes safety checks, such as limiting the angle of attack adjustment range to prevent excessive tilting from causing mechanical jamming or efficiency loss. This step embodies the core of intelligent control, achieving dynamic matching of wind pressure and angle of attack through algorithms to ensure that the fan maintains low wind noise and high efficiency under various operating conditions. The S4 control signal drives the electric telescopic rod 704 to move. The telescopic end of the electric telescopic rod 704 drives the polygonal component 706 to slide linearly along the axis of the turntable 705. The movement of the polygonal component 706 is transmitted to the fan blade 805 through the connecting component 8: the telescopic connecting rod 801 moves with the polygonal component 706, pushing the rotating bracket 802 and the rotating connecting component 803 to rotate. Since the rotation directions of the rotating connecting component 803 and the rotating bracket 802 are perpendicular to each other, this design avoids the problem of jamming during the adjustment process. Finally, the connecting column 804 converts the motion into the tilting rotation of the fan blade 805 around the rotating bracket 806, changing the angle of attack of the fan blade and the airflow. During the adjustment process, the control module 6 monitors the displacement feedback of the electric telescopic rod 704 in real time to ensure accuracy; at the same time, the turntable 705 maintains high-speed rotation, using centrifugal force to draw airflow from the inlet pipe 3 and discharge it from the outlet pipe 4. This step achieves precise adjustment through mechanical transmission, making the fan blade angle of attack adapt to changes in wind pressure and maintaining the airflow attachment state. After the S5 wind turbine enters stable operation, the system continuously executes steps S2 to S4, forming a closed-loop control. Control module 6 periodically evaluates the adjustment effect, such as by detecting wind noise indicators (e.g., pressure fluctuation frequency) through wind pressure sensor 707, and dynamically adjusts the angle-of-attack-wind pressure relationship model parameters to adapt to wear or environmental changes during long-term use. Optimization algorithms may include PID control or machine learning methods to minimize energy loss and wind noise. Simultaneously, the system has a fault self-diagnosis function; for example, if the electric telescopic mast 704 or sensor malfunctions, it automatically switches to a safety mode to prevent equipment damage. This step ensures that the wind turbine maintains optimal performance during long-term operation, extends its service life, and adapts to diverse application scenarios.

[0028] In traditional fans, the fan blades have a fixed tilt angle at different speeds, which easily leads to airflow detaching from the blade surface, generating boundary layer separation and vortices, thus causing significant wind noise. This invention adjusts the tilt angle (angle of attack) of the fan blades 805 in real time to adapt to changes in internal wind pressure within the housing 1, ensuring that the airflow always adheres closely to the blade surface and maintains an attached flow state. Specifically, when the wind pressure sensor 707 detects an increase in wind pressure at the air inlet duct 3, the control module 6 drives the electric telescopic rod 704 to move, causing the polygonal component 706 to slide linearly, thereby changing the fan blade angle of attack through connecting components 8 (such as the telescopic connecting rod 801, rotating bracket 802, etc.). This dynamic adjustment avoids the formation of airflow separation points, reducing wind noise at its source. Figure 1 As shown in the diagram, the overall structural assembly diagram illustrates the layout of the shell 1, cover plate 2, and internal components, providing intuitive support for the aforementioned adjustment mechanism; By optimizing airflow management, this invention reduces energy loss and achieves higher energy efficiency. Based on Bernoulli's principle, when the airflow is close to the airfoil surface of the fan blade 805, kinetic energy can be efficiently converted into static pressure energy, avoiding energy dissipation caused by flow separation. The control method monitors wind pressure in real time and adjusts the angle of attack to ensure that the fan maintains optimal operating conditions under different loads (such as when the resistance of the outlet duct 4 changes). For example, under high wind pressure conditions, increasing the angle of attack gives the airflow more energy to overcome the adverse pressure gradient; while under low wind pressure conditions, decreasing the angle of attack reduces energy consumption. Figure 3 and Figure 4 The distribution and rotation mechanism of the fan blades 805 are demonstrated. The circumferentially arranged blades generate centrifugal force under the drive of the turntable 705, creating a continuous negative pressure zone to optimize suction and exhaust efficiency. Mechanical design features, such as the rotating connector 803 in the connecting component 8, which rotates vertically with the rotating support 802, prevent jamming during blade adjustment and ensure long-term stable operation. Simultaneously, the control module 6 integrates a self-diagnostic function, enabling real-time parameter adjustments to cope with wear or environmental changes. Figure 5 and Figure 6 The details of the rotating component 7 are highlighted, such as the linkage between the electric telescopic rod 704 and the polygonal part 706, as well as the installation position of the wind pressure sensor 707, which demonstrate the precision and controllability of the structure.

[0029] Comparative Example 1 This comparative example uses the exact same fan hardware structure, test environment, and measurement standards as Example 1. The only difference is that the tilt angle of the fan blade 805 is locked in a fixed and non-adjustable state. By testing the wind noise characteristics of different fixed tilt angles at all typical operating speeds, the optimal static tilt angle corresponding to different speeds is determined and compared with the noise reduction effect of the dynamic adjustment scheme of this invention.

[0030] The test was conducted in a semi-anechoic chamber that conforms to GB / T2888-2008 "Method for Noise Measurement of Fans and Roots Blowers". The background noise was ≤20dBA. The test point was located 1m in front of the fan outlet duct 4 and at the same height as the center of the outlet. The steady-state wind noise value was measured using A-weighted sound pressure level. At the same time, the fan input power was recorded to evaluate the energy efficiency matching.

[0031] Speed ​​gradient: Covering the typical operating range of DC brushless centrifugal fans, it is set to 5 operating points: 10000rpm, 15000rpm, 20000rpm, 25000rpm, and 30000rpm. Fixed tilt angle: covering the dynamic adjustment range of the fan blades of this invention (0°~25°), set to 6 gradients: 0° (perpendicular to the turntable plane), 5°, 10°, 15°, 20°, and 25°; Data processing: Each working condition was tested three times, and the arithmetic mean was taken as the final result. The test error was controlled within ±0.3 dBA. Optimal static tilt angle at different speeds The test data clearly shows the fixed tilt angle of the fan blades that corresponds to the minimum wind noise at each speed: 10000rpm low speed condition: The optimal tilt angle is 0°. At this time, the airflow velocity is low, and a small angle of attack can maintain the complete attached flow state, with the lowest wind noise. At low to medium speeds of 15,000 rpm: the optimal tilt angle is 5°, and wind noise is reduced by 3.7 dBA compared to 0° and by 1.4 dBA compared to 10°. At 20,000 rpm, the optimal tilt angle is 10°, which reduces wind noise by 1.5 dBA compared to 5° and by 2.4 dBA compared to 15°. Under medium-high speed conditions of 25,000 rpm: the optimal tilt angle is 15°, and the wind noise is reduced by 2.1 dBA compared to 10° and by 4.5 dBA compared to 20°; High-speed operation at 30,000 rpm: The optimal tilt angle is 20°, and the wind noise is reduced by 2.8 dBA compared to 15° and by 5.9 dBA compared to 25°.

[0032] Experimental results show that the optimal blade tilt angle of the fan increases approximately linearly with increasing rotational speed, which is consistent with boundary layer theory: the higher the rotational speed, the faster the airflow velocity, the greater the adverse pressure gradient, and the greater the angle of attack required to replenish the airflow with energy to avoid boundary layer separation.

[0033] Traditional fixed-angle fan blades cannot adapt to the optimal angle of attack requirements across the entire speed range. They can only achieve low wind noise at a specific speed, and the wind noise deteriorates sharply beyond that speed. For example: If a fixed 10° angle is used (suitable for 20,000 rpm), the wind noise reaches 51.9 dBA at a high speed of 30,000 rpm, which is 0.6 dBA higher than the optimal 20° angle, and the input power increases by 9.2%. If a fixed 15° angle is used (suitable for 25,000 rpm), the wind noise reaches 38.9 dBA at a low speed of 10,000 rpm, which is 6.8 dBA higher than the optimal 0° angle, and the energy efficiency loss reaches 14.7%.

[0034] Embodiment 1 of this invention monitors the air pressure in the inlet duct in real time using a wind pressure sensor (positively correlated with the fan speed). Based on the angle of attack-wind pressure relationship model, it dynamically adjusts the fan blade tilt angle to the optimal value for the corresponding operating condition, maintaining the lowest wind noise operation across the entire speed range of 10,000 rpm to 30,000 rpm. Comparative tests show that the average wind noise of the dynamic adjustment scheme of this invention is reduced by 8.2 dBA compared to traditional fixed-angle fans, and the average input power is reduced by 12.5%, completely solving the technical pain point of fixed-angle fans where the performance is optimal under single operating conditions but deteriorates under all operating conditions.

[0035] Comparative Example 2 This comparative example uses the exact same fan hardware structure, test environment, and measurement standards as Example 1. The only difference is that the tilt angle of the fan blade 805 is locked in a fixed and non-adjustable state. By testing the wind noise and energy efficiency characteristics of different fixed tilt angles under constant speed and different system loads (inlet duct air pressure), the optimal static tilt angle corresponding to different loads is determined, verifying the core advantage of the dynamic angle of attack adjustment of this invention under variable load conditions, and forming a complementary verification with Comparative Example 1.

[0036] The test was conducted in a semi-anechoic chamber conforming to GB / T2888-2008 "Method for Noise Measurement of Fans and Roots Blowers". The background noise was ≤20dBA. The test point was located 1m directly in front of the fan outlet duct 4 and at the same height as the center of the outlet. The steady-state wind noise value was measured using A-weighted sound pressure level. The fan input power was recorded simultaneously using a power analyzer. The static pressure value at the inlet duct 3 was measured using a high-precision differential pressure sensor to characterize the system load.

[0037] Fixed speed: Select 20,000 rpm, the most commonly used medium speed condition for DC brushless centrifugal fans (covering mainstream application scenarios such as household ventilation, refrigeration, and vacuuming). System load gradient: Different system resistances are simulated by adjusting the opening of the adjustable damper at the end of the air outlet duct 4. The corresponding static pressure of the air inlet duct is set to 5 operating points: 50Pa (low load, damper fully open), 150Pa (medium-low load), 250Pa (medium load), 350Pa (medium-high load), and 450Pa (high load, damper half open). Fixed tilt angle: consistent with Comparative Example 1, covering the dynamic adjustment range of this invention, set to 6 gradients: 0°, 5°, 10°, 15°, 20°, and 25°; Data processing: The test begins after each operating condition has been running stably for 30 seconds. The test is repeated 3 times, and the arithmetic mean is taken as the final result. The wind noise test error is ≤ ±0.3 dBA, and the power test error is ≤ ±0.5 W. The test data clearly shows the minimum fan blade tilt angle for different system loads (inlet duct air pressure) at a speed of 20,000 rpm: 50Pa low load condition: The optimal tilt angle is 10°. At this time, the system resistance is small, the airflow velocity is low, and a medium to small angle of attack can maintain the attached flow, resulting in the lowest wind noise and the best energy efficiency. Under medium and low load conditions of 150Pa: the optimal tilt angle remains at 10°, and the wind noise is reduced by 3.8 dBA compared to 5° and by 2.4 dBA compared to 15°; Under medium load conditions of 250Pa: the optimal tilt angle is 10°, which matches the initial operating conditions preset by this invention, and both wind noise and power consumption are at the lowest level. Under medium to high load conditions of 350Pa: the optimal tilt angle is 15°, and the wind noise is reduced by 1.4 dBA compared to 10° and by 3.4 dBA compared to 20°; Under 450Pa high load conditions: the optimal tilt angle is 15°, the wind noise is reduced by 4.8dBA compared to 10° and by 1.5dBA compared to 20°, and the input power is reduced by 11.9% compared to 10°.

[0038] Experimental results show that the optimal blade tilt angle of the fan increases stepwise with the increase of system load (inlet duct pressure), which is in complete agreement with the angle of attack-pressure relationship model established by this invention based on Bernoulli's principle and boundary layer theory: the higher the system load, the greater the inlet duct pressure, the stronger the reverse pressure gradient faced by the airflow, and the greater the angle of attack is needed to replenish the airflow with energy and delay the occurrence of boundary layer separation.

[0039] Traditional fixed-angle fan blades cannot adapt to the optimal angle of attack requirements under varying load conditions. In practical applications (such as scenarios with load fluctuations caused by blocked ventilation ducts, dust accumulation on filters, and switching between multiple air outlets), wind noise and energy efficiency will significantly deteriorate. For example: If a fixed 10° angle is used (suitable for medium load conditions of 250Pa), the wind noise reaches 52.4dBA under high load of 450Pa, which is 4.8dBA higher than the optimal 15° angle. The input power increases by 13.5%, and long-term high load operation will accelerate the wear of fan blades and motor. If a fixed 15° angle is used (suitable for high load conditions above 350Pa), the wind noise reaches 45.3dBA under a low load of 50Pa, which is 3.5dBA higher than the optimal 10° angle, and the input power increases by 13.1%, resulting in unnecessary energy waste.

[0040] Embodiment 1 of this invention uses a wind pressure sensor 707 to monitor changes in air pressure in the inlet duct in real time. Based on the angle-of-attack-wind pressure relationship model, it automatically adjusts the fan blade tilt angle to the optimal value for the corresponding load, maintaining the lowest wind noise and highest energy efficiency across the entire load range of 50Pa to 450Pa. Comparative tests show that at a constant speed of 20,000rpm, the average wind noise of this invention's dynamic adjustment scheme is reduced by 6.7dBA compared to traditional fixed-angle fans, and the average input power is reduced by 10.8%, completely solving the industry pain point of sudden increase in wind noise and sudden decrease in energy efficiency of fixed-angle fans under variable load conditions.

[0041] Combining the experimental results of Comparative Example 1 and Comparative Example 2, we can draw the final conclusion that: traditional fixed-angle fan blades can only achieve better performance under a single working condition of "specific speed and specific load", while the dynamic angle of attack adjustment technology of the present invention can simultaneously adapt to the optimal operating requirements of the full speed range and the full load range, achieving a qualitative improvement in both low wind noise and high efficiency.

[0042] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A low-noise, high-efficiency DC brushless fan, comprising a housing (1) and a cover plate (2) sealed at the top opening of the housing (1), the housing (1) and the cover plate (2) being fastened together by bolts, an air inlet pipe (3) being conductively connected to the top of the center of the cover plate (2), and an air outlet pipe (4) being tangentially and fixedly connected to the outer arc surface of the housing (1), characterized in that: The housing (1) is equipped with a rotating component (7) for rotation, and the rotating component (7) is connected to a connecting component (8) for transmission, wherein: The rotating component (7) includes a turntable (705) and a multi-faceted component (706) that slides along the rotation axis of the turntable (705). The connecting component (8) includes a fan blade (805) that is rotatably connected to the top of the turntable (705). The multi-faceted component (706) is used to adjust the tilt angle of the fan blade (805) relative to the turntable (705), thereby changing the angle of attack of the fan blade (805) when the airflow enters.

2. The low-noise, high-efficiency brushless DC fan according to claim 1, characterized in that: The rotating component (7) includes a rotating motor (701), a driving gear (702), a driven gear (703), an electric telescopic rod (704), a turntable (705), a polygonal component (706), and a wind pressure sensor (707); the rotating motor (701) drives the driving gear (702) to mesh with the driven gear (703), thereby driving the turntable (705) to rotate.

3. The low-noise, high-efficiency brushless DC fan according to claim 2, characterized in that: The diameter of the driving gear (702) is larger than that of the driven gear (703), and the rotational speed of the turntable (705) is increased by the gear ratio to enhance the wind pressure output; the telescopic end of the electric telescopic rod (704) is connected to the polygonal piece (706) for linear sliding.

4. The low-noise, high-efficiency brushless DC fan according to claim 3, characterized in that: The connecting component (8) includes a telescopic connecting rod (801), a rotating bracket (802), a rotating connector (803), a connecting column (804), a fan blade (805), and a rotating bracket (806); the telescopic connecting rod (801) is connected to the polygonal component (706), and the linear motion of the electric telescopic rod (704) is converted into the tilting rotation of the fan blade (805) by the vertical rotation combination of the rotating bracket (802) and the rotating connector (803), thus avoiding jamming during the adjustment process.

5. The low-noise, high-efficiency brushless DC fan according to claim 4, characterized in that: Multiple fan blades (805) are circumferentially distributed on the top of the turntable (705) and fixed by a rotating bracket (806); the tilt angle of the fan blades (805) is adjustable to adapt to different wind pressure conditions and ensure that the airflow is close to the airfoil surface.

6. The low-noise, high-efficiency brushless DC fan according to claim 5, characterized in that: The wind pressure sensor (707) is located at the top center of the polygonal part (706) and is used to monitor the airflow pressure at the air inlet pipe (3) in real time. An installation cavity (5) is fixedly provided on the outer surface of the housing (1), and a control module (6) is fixedly provided inside the installation cavity (5) to receive the signal from the wind pressure sensor (707) and control the action of the electric telescopic rod (704).

7. A control method for a low-noise, high-efficiency brushless DC fan, characterized in that: Includes the following steps: S1 starts the fan, performs system self-test and initialization through the control module (6), and sets the initial speed of the turntable (705) and the initial tilt angle of the fan blades (805); The S2 wind pressure sensor (707) monitors the wind pressure value at the air inlet pipe (3) in real time and transmits the signal to the control module (6). The S3 control module (6) calculates the optimal blade tilt angle based on the wind pressure value, based on the preset angle of attack-wind pressure relationship model; The S4 control module (6) drives the electric telescopic rod (704) to move, causing the polygonal part (706) to slide, and adjusts the angle of attack of the fan blade (805) through the connecting component (8); S5 forms a closed-loop control, continuously monitoring and optimizing parameters to adapt to load changes.

8. The low-noise, high-efficiency brushless DC fan according to claim 7, characterized in that: In step S3, the angle of attack-wind pressure relationship model is established based on Bernoulli's principle and boundary layer theory. When the wind pressure increases, the angle of attack is increased to overcome the adverse pressure gradient, and when the wind pressure decreases, the angle of attack is decreased to optimize energy consumption.

9. The low-noise, high-efficiency brushless DC fan according to claim 8, characterized in that: In step S4, the displacement of the electric telescopic rod (704) is converted into the tilting rotation of the fan blade (805) through the connecting component (8), wherein the vertical rotation combination of the rotating connector (803) and the rotating bracket (802) ensures smooth adjustment; the control module (6) monitors the displacement feedback in real time to ensure accuracy.

10. The low-noise, high-efficiency brushless DC fan according to claim 9, characterized in that: In step S5, the control module (6) integrates a fault self-diagnosis function, dynamically adjusts the angle of attack-wind pressure model parameters to cope with wear or environmental changes, and uses PID control or machine learning methods to minimize wind noise and energy loss.

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