A heat dissipation fan based on mixed flow noise reduction design

Abstract

The utility model discloses a kind of heat dissipation fans based on mixed flow noise reduction design, it is related to heat dissipation technical field.The fan includes fan frame, motor and impeller, its core is in the blade of the impeller mixed flow design is used, make airflow outlet direction and axis present a acute angle.This design changes core aerodynamic structure, and the sharp discrete noise energy that traditional axial flow fan generates is concentrated in blade pass frequency (BPF) is dispersed to wider frequency band, to fundamentally eliminate the sharp sound that makes people unpleasant, so that noise quality becomes more soft.The utility model can provide higher wind pressure while effectively reducing noise, and be applicable to the application scene that both noise and heat dissipation performance have high requirement.

Description

Technical Field

[0001] This utility model relates to the field of heat dissipation technology for electronic devices, and specifically to a cooling fan that reduces operating noise by improving the aerodynamic design of the fan. Background Technology

[0002] As the performance of electronic devices continues to improve, their power consumption and heat generation are also increasing dramatically, placing higher demands on heat dissipation systems. Axial fans, due to their advantages such as simple structure, large air volume, and low cost, are widely used in the heat dissipation systems of various devices.

[0003] However, traditional axial fans suffer from significant noise problems. Their noise spectrum typically includes a very prominent, discrete, sharp noise associated with the blade pass frequency (BPF) and its higher harmonics. This frequency is calculated as: BPF = (RPM × N) / 60, where RPM is the fan speed and N is the number of blades. This high-frequency, sharp noise is extremely jarring and severely impacts user experience and the operating environment of the equipment.

[0004] Currently, most common noise reduction methods take a passive approach, such as optimizing blade airfoils, adding airflow deflectors, and using vibration-damping materials. While these methods have some effect, they often only address the symptoms and not the root cause, failing to fundamentally eliminate the acoustic characteristics of the blade rotation frequency. Sometimes, they may even sacrifice performance such as airflow or air pressure.

[0005] Therefore, there is an urgent need in this field for a new fan design that can effectively suppress the sharp noise of BPF from the perspective of aeroacoustics, without sacrificing heat dissipation performance. Utility Model Content

[0006] Purpose of the utility model: The purpose of this utility model is to overcome the significant sharp noise defect of existing axial fans and provide a cooling fan based on a mixed-flow design. This design disperses concentrated acoustic energy across a wider frequency band by changing the airflow path and outlet direction within the fan, thereby significantly reducing perceptible BPF sharp noise while maintaining excellent heat dissipation performance.

[0007] The technical solution of this utility model is: a cooling fan based on mixed-flow noise reduction design, including: a fan frame, a motor and an impeller.

[0008] The impeller consists of a hub and multiple blades, and the motor is fixed to the fan frame, with its output shaft connected to the impeller hub.

[0009] The impeller blades are mixed-flow blades, and their configuration causes the airflow direction after passing through the impeller to form an acute angle θ with the fan axis.

[0010] In a further embodiment, the acute angle θ ranges from 30° to 75°, meaning that the airflow in the impeller undergoes both axial and radial flow, and the direction of the combined airflow forms an angle θ with the axial direction. This is fundamentally different from traditional axial fans (where the airflow direction is basically parallel to the axis) and centrifugal fans (where the airflow direction is basically perpendicular to the axis).

[0011] In a further embodiment, the acute angle θ is 45°.

[0012] In a further embodiment, the fan frame is provided with a guide shroud at the outlet that matches the air outlet direction. The guide shroud is a tapered structure with an inlet cross-sectional area smaller than its outlet cross-sectional area. The guide shroud is used to receive the inclined airflow discharged from the impeller. The profile of the guide shroud matches the air outlet angle of the mixing blades to smoothly guide the airflow and reduce eddies and secondary noise.

[0013] In a further embodiment, the tapering angle of the fairing is between 5° and 15°.

[0014] In a further embodiment, the blade root installation angle is 15°~45°, the blade tip installation angle is 5°~30°, and the range of the blade root to blade tip installation angle is between 5°~15°. The installation angle of the mixed-flow blade changes continuously from the blade root to the blade tip, and its variation law is aerodynamically optimized based on a specific algorithm to ensure a uniform load distribution along the blade span and avoid excessive local loads that generate additional noise.

[0015] In a further embodiment, the installation angle from the leaf root to the leaf tip varies by 10°.

[0016] In a further embodiment, the number of the mixed-flow blades is prime to reduce potential resonance with structural components.

[0017] In a further embodiment, the number of mixed-flow blades is 7 or 11.

[0018] The design methods used for cooling fans include: the three-dimensional modeling of mixed-flow blades is aerodynamically optimized using Computational Fluid Dynamics and Computational AeroAcoustics software.

[0019] In a further embodiment, the continuous variation of the installation angle of the mixed-flow blade from the blade root to the blade tip is aerodynamically optimized based on a specific algorithm to ensure a uniform load distribution along the blade span and avoid excessive local loads that could generate additional noise.

[0020] In a further embodiment, the specific algorithm includes a genetic algorithm or a simulated annealing algorithm.

[0021] The beneficial effects of this invention are: 1. Significant noise reduction, especially reduction of sharp sounds: The core effect of this invention lies in the fact that the mixed-flow design breaks away from the strong periodic vortex shedding and pressure pulse of traditional axial fans, dispersing sound energy from the narrow BPF discrete frequency point to a wider continuous frequency band. Subjectively, it completely eliminates the unpleasant "humming" or "whistling" sound, making the noise quality softer, similar to "white noise." Although the total sound pressure level may not decrease much, the perceived noise level is significantly reduced.

[0022] 2. Balancing Airflow and Static Pressure: The mixed-flow design combines the advantages of the large airflow of an axial fan and the high static pressure of a centrifugal fan. At the same size and speed, the fan provided by this invention can generate higher static pressure than a traditional axial fan while providing sufficient cooling airflow, making it particularly suitable for scenarios with dense heatsink fins and high system resistance.

[0023] 3. Compact structure and wide applicability: The overall structure of the fan of this utility model is still compact, and the installation size is compatible with traditional axial fans. It can directly replace the fans in existing equipment and is widely used in noise-sensitive fields such as servers, graphics cards, workstations, and high-end home appliances. Attached Figure Description

[0024] Figure 1 This is a side cross-sectional view of the cooling fan in an embodiment of the present invention, showing the airflow direction.

[0025] Figure 2 This is a three-dimensional structural diagram of the cooling fan in an embodiment.

[0026] Figure 3 This is a schematic diagram of the three-dimensional structure of the cooling fan in the embodiment from another angle.

[0027] Figure 4 This is a schematic diagram comparing the typical noise spectrum of a traditional axial fan and the mixed-flow fan of this invention.

[0028] The attached diagram is labeled as follows: fan frame 1, motor 2, hub 3, shroud 4, blades 5, air intake direction A, air exhaust direction B, fan axis C. Detailed Implementation

[0029] In the following description, numerous specific details are set forth in order to provide a more thorough understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention can be practiced without one or more of these details. In other instances, certain technical features well-known in the art have not been described in order to avoid confusion with the present invention.

[0030] See Figure 1 , 2In embodiment 3, the cooling fan of this utility model mainly includes a fan frame, a motor, and an impeller. The impeller consists of a hub and multiple mixed-flow blades, preferably 7 or 11 blades. The motor is fixed to the center of the fan frame, and its output shaft is connected to the hub of the impeller.

[0031] Mixed-flow blades are fixed to the hub, such as Figure 1 The hub shown has a conical inlet and a cylindrical outlet. Its key features include: a blade root installation angle of 15°~45°, a blade tip installation angle of 5°~30°, and a variation range of the blade root to tip installation angle between 5°~15°. In a preferred embodiment, the variation is approximately 10°. The installation angle of the mixed-flow blades changes continuously from the blade root to the blade tip, ensuring that the air intake direction is axial, while the air outlet direction is at an angle θ with the fan axis. When the impeller rotates, the intake airflow, under the action of the blades, moves axially and is then guided to exit obliquely at an acute angle θ with the axis. The acute angle θ ranges from 30° to 75°; in a preferred embodiment, the acute angle θ is 45°.

[0032] See Figure 1 The arrows indicate the airflow path. The airflow enters axially from above, and as it passes through the mixed-flow impeller, it is subjected to both axial thrust and radial centrifugal force. The combined effect causes the airflow to exit in a direction inclined to the axis.

[0033] See Figure 4 In the noise spectrum of the cooling fan of this invention, the peak sound pressure level at the blade passing frequency (BPF) is significantly lower than that of a traditional axial fan of the same size and speed, and the spectrum curve is smoother. Preferably, the fan frame outlet is provided with a guide shroud matching the exhaust direction. The guide shroud is a tapered structure with an inlet cross-sectional area smaller than its outlet cross-sectional area. The guide shroud is used to receive the inclined airflow discharged from the impeller, wherein the tapering angle of the guide shroud is between 5° and 15°. See also Figure 1 The fairing is fitted onto the hub. Its upper part is a tapered structure and its lower part is a cylindrical structure. It is used to receive the inclined airflow discharged from the impeller and guide it to the outlet more smoothly, reducing airflow separation and vortex generation, and further optimizing aerodynamic and acoustic performance.

[0034] The three-dimensional shape of the mixed-flow blades is optimized using Computational Fluid Dynamics (CFD) and Computational AeroAcoustics (CAA) software, so that the airflow direction after passing through the impeller forms an acute angle θ with the fan axis, ensuring high efficiency and low noise.

[0035] Preferably, the continuous variation of the installation angle of the mixed-flow blade from the blade root to the blade tip is aerodynamically optimized based on specific algorithms such as genetic algorithms or simulated annealing algorithms to ensure a uniform load distribution along the blade span.

[0036] As described above, although the present invention has been shown and described with reference to specific preferred embodiments, it should not be construed as limiting the present invention itself. Various changes in form and detail may be made to the present invention without departing from the spirit and scope of the appended claims.

Claims

1. A cooling fan based on a mixed-flow noise reduction design, comprising: Fan frame, motor, and impeller; The impeller consists of a hub and multiple blades, and the motor is fixed to the fan frame, with its output shaft connected to the hub of the impeller. The impeller is characterized by having mixed-flow blades, the configuration of which causes the airflow direction after passing through the impeller to form an acute angle θ with the fan axis.

2. A cooling fan based on mixed-flow noise reduction design according to claim 1, characterized in that, The acute angle θ ranges from 30° to 75°.

3. A cooling fan based on mixed-flow noise reduction design according to claim 1, characterized in that, The acute angle θ is 45°.

4. A cooling fan based on mixed-flow noise reduction design according to claim 1, characterized in that, The fan frame is provided with a shroud at the outlet that matches the air outlet direction; The flow guide is a tapered structure with an inlet cross-sectional area smaller than its outlet cross-sectional area, and the flow guide is used to receive the inclined airflow discharged from the impeller.

5. A cooling fan based on mixed-flow noise reduction design according to claim 4, characterized in that, The convergence angle of the fairing is between 5° and 15°.

6. A cooling fan based on mixed-flow noise reduction design according to claim 1, characterized in that, The blade root installation angle is 15°~45°, and the blade tip installation angle is 5°~30°, with the range of the blade root to blade tip installation angle being between 5° and 15°. The installation angle of the mixed-flow blade changes continuously from the blade root to the blade tip.

7. A cooling fan based on mixed-flow noise reduction design according to claim 6, characterized in that, The installation angle from the leaf root to the leaf tip changes by 10°.

8. A cooling fan based on mixed-flow noise reduction design according to claim 1, characterized in that, The number of the mixed-flow blades is a prime number.

9. A cooling fan based on mixed-flow noise reduction design according to claim 8, characterized in that, The number of mixed-flow blades is 7 or 11.

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