Integrated dual-ducted fan and design method

Abstract

The application discloses an integrated double-duct fan and a design method, and relates to the field of fan structures.The integrated double-duct fan comprises an outer shell, a current collector coaxially arranged on one side of the outer shell, an inner shell coaxially arranged on the side of the outer shell away from the current collector, wherein the inner shell protrudes from the outer shell, the inner shell and the outer shell form an outer duct, a plurality of rear guide vanes are annularly arranged between the inner shell and the outer shell, a plurality of air inlets are annularly arranged on the outer wall of the inner shell close to the current collector, a driving motor is coaxially arranged in the inner shell, the driving motor blocks the side of the inner shell away from the current collector, a plurality of air outlets are annularly arranged on the outer wall of the inner shell and form an inner duct together with the plurality of air inlets and the inner shell, and an impeller is coaxially connected with an output shaft of the driving motor and rotatably arranged between the current collector and the inner shell.The integrated double-duct fan can solve the technical problems of poor heat dissipation of the driving motor and the electric control elements in the prior art, low reliability, poor blade root performance and low efficiency of a single flow channel under high pressure rise working conditions.

Description

Technical Field

[0001] This invention relates to the field of axial flow fan structure, specifically to an integrated dual-duct fan and its design method. Background Technology

[0002] In traditional fan designs, the drive motor is typically independent of the airflow channel or cooled solely by simple natural convection. For high-speed (e.g., above 40,000 rpm) micro fans, the motor windings generate significant heat. Ineffective heat dissipation leads to accelerated motor temperature rise, permanent magnet demagnetization, and faster winding insulation aging, ultimately limiting the fan's lifespan and operational reliability. While some existing technologies place the motor within the airflow channel, they often lack a dedicated design for the motor's heat dissipation path, resulting in persistently high motor temperatures. Furthermore, the control module is usually encapsulated in a separate housing, isolated from the main airflow, making it difficult to dissipate the heat generated by the control components.

[0003] Conventional axial flow fans employ a single-channel design, resulting in significant differences in flow parameters from the hub to the blade tip. Under high-pressure boosting requirements, the design specific speed typically falls within the low to medium specific speed range. At this point, the hub is relatively large, and the internal flow area is reduced. The relative velocity of the flow in the blade root region is low, the boundary layer is thick, and separation is prone to occur, leading to low blade root efficiency and even backflow. To improve blade root performance, traditional solutions often require increasing the blade chord length or employing complex blade twisting designs. However, this increases blade density, exacerbating flow blockage and friction losses. Summary of the Invention

[0004] The purpose of this invention is to provide an integrated dual-duct fan and its design method to solve the technical problems in the prior art, such as poor heat dissipation of the drive motor and electronic control components leading to decreased reliability, and poor blade root performance and low efficiency of a single flow channel under high pressure conditions.

[0005] The above-mentioned optimized structure of the present invention is achieved through the following technical solution: an integrated dual-duct fan, including a housing; A collector, which is coaxially disposed on one side of the housing; An inner shell is coaxially disposed on the side of the outer shell away from the collector, and the inner shell protrudes from the outer shell, forming an outer bypass duct with the outer shell; Multiple rear guide vanes are arranged in a ring between the inner shell and the outer shell; Multiple air inlets are arranged in a ring on the outer wall of the inner shell near the collector. A drive motor is coaxially disposed inside the inner housing, and the drive motor blocks the side of the inner housing away from the collector; Multiple air outlets are arranged in a ring on the outer wall of the inner shell, and together with multiple air inlets and the inner shell, they form an inner channel. An impeller is coaxially connected to the output shaft of the drive motor and is rotatably disposed between the collector and the inner shell.

[0006] A design method for an integrated dual-duct fan includes the following steps: S1. Determine the design target parameters: This includes design flow rate Q, design total pressure P, and operating speed n; S2, Core Aerodynamic Design: Based on the aforementioned design target parameters, the specific speed of the wind turbine is calculated. And according to the specific speed The value is used to determine and select a scheme that combines a single-stage impeller with a rear guide vane; S3, Impeller parameter design: Based on the selected scheme, calculate the outer diameter of the impeller. Hub diameter And determine the blade mounting hub ratio. ; S4. Definition of double-duct configuration: According to the outer diameter of the impeller Define an inner duct and an outer duct that are coaxially arranged, wherein the flow cross section of the inner duct is defined by the inner diameter of the inner shell, the flow cross section of the outer duct is defined by the inner diameter of the outer shell and the inner diameter of the inner shell, and the impeller is located at the boundary between the inner duct and the outer duct. S5, Three-dimensional blade design: The blade is divided into at least three calculation sections along the span. Based on the simplified radial equilibrium equation, the inlet and outlet velocity triangles of each section are calculated, and the installation angle, chord length and sweep profile of the blade are determined accordingly. The blade adopts a high lift coefficient airfoil in the section of the outer bypass duct region to match the lower relative velocity, and adopts a low density arrangement in the section of the inner bypass duct region to adapt to the flow under high hub ratio. S6. Rear guide vane matching design: Based on the airflow angle at the impeller outlet, the blade inlet angle of the rear guide vane is designed to eliminate the circumferential velocity component of the airflow and effectively convert kinetic energy into static pressure. S7, Air intake duct design: The design incorporates an integrated dual-duct collector, which is a contracting circular arc flow channel with its inner wall profile smoothly transitioning to the inlet sections of both the inner and outer ducts.

[0007] In some embodiments, in step S2, the specific rotational speed The calculation formula is:

[0008] when When the value is in the range of 25-50, the solution is determined to be a combination of a single-stage impeller and a rear guide vane.

[0009] In some embodiments, in step S3, the impeller outer diameter The estimation formula is as follows

[0010] Where Ka is a correction factor related to specific speed, based on specific speed Specific numerical adjustments are made to ensure that the impeller outer diameter is adapted to the design requirements of total pressure and operating speed. When =25-35, Ka takes values ​​of 1.7-1.9; when =35-50, Ka takes 1.9-2.1; The hub diameter = Among them, the ratio of installed wheel hubs The value range is 0.4-0.6.

[0011] In some embodiments, in step S4, the ratio of the flow area of ​​the outer duct to the flow area of ​​the inner duct is 5.0 to 7.0.

[0012] In some embodiments, in step S5, the number of blades is 8-14, and a variable relative thickness design is adopted along the span, with a relative thickness of 5%-8% for the blade tip section and a relative thickness of 10%-15% for the blade root section.

[0013] In some embodiments, in step S5, the lift coefficient of the high lift coefficient airfoil is not less than 1.2, and the consistency value of the low density arrangement is 0.6-0.9; the installation angle of each section along the blade span gradually decreases from the blade root to the blade tip along the blade height, with a decrease range of 8°-15°.

[0014] In some embodiments, in step S6, the number of blades of the rear guide vane and the number of blades of the impeller are coprime numbers.

[0015] In some embodiments, in step S7, the inner wall radius R of the collector satisfies: R ≥ 0.10 Its axial length L satisfies: L=(0.2~0.4) .

[0016] In some embodiments, step S8, aerodynamic performance verification and optimization, is also included: Based on the CFD numerical simulation method, the aerodynamic performance of the designed integrated dual-duct fan under all working conditions is simulated to obtain the total pressure, efficiency and flow field distribution under different flow rates. If the simulation results do not meet the design target parameters, the corresponding steps are returned to adjust the parameters until the design requirements are met. The CFD numerical simulation uses the RNG k-ε turbulence model, and the computational domain includes the collector, inner duct, outer bypass duct, impeller, and guide vane region.

[0017] The above-described technical solutions in the embodiments of the present invention have at least the following technical effects or advantages: (1) This invention integrates the drive motor and the electronic control module into the hollow cavity of the inner shell, achieving a unified design of the drive motor and the fan. A dedicated internal channel heat dissipation flow path is constructed using the air inlet, cavity, and air outlet, enabling forced convection heat dissipation. After the airflow is accelerated by the impeller, some of the gas enters the internal channel through the air inlet under pressure differential, axially and at high speed, scouring the surface of the motor housing and the electronic control module. After absorbing heat, it is discharged from the air outlet and merges into the main flow of the outer bypass channel, improving heat dissipation efficiency. Simultaneously, the heat dissipation airflow itself is part of the main airflow, eliminating the need for an additional cooling fan, thus avoiding additional power consumption and noise. Furthermore, after the heat generated by the motor and electronic control module is carried away by the airflow, the airflow temperature rises. With the internal channel cross-section remaining essentially unchanged, the temperature rise causes air volume expansion and increased flow velocity, leading to an increase in dynamic pressure at the air outlet. This pressure boosting effect can partially offset the flow loss of the internal channel and even generate additional thrust, allowing the overall pressure drop of the internal channel to approach zero or turn into positive pressure, converting the heat to be dissipated into wind pressure, achieving a beneficial effect of heat dissipation self-compensation.

[0018] (2) The present invention adopts a double-duct coaxial configuration, dividing a single flow channel into an inner duct and an outer duct, realizing differentiated design and management of airflow in the blade root and blade tip regions, which is conducive to improving blade root flow, reducing secondary flow loss, and improving overall efficiency. It can solve the defects of traditional single-duct design that is difficult to take into account the airflow characteristics of different regions, large flow loss at the blade root, and insufficient work done at the blade tip, and improve the overall aerodynamic performance of the fan.

[0019] (3) For medium specific speeds in the range of 25-50, the present invention optimizes the combination of a single-stage impeller and a rear guide vane. Compared with the multi-stage axial flow design, it shortens the axial length of the fan, simplifies the structure, reduces manufacturing costs and assembly difficulty, and achieves a balance between structural compactness and high pressure rise and high efficiency. It can be adapted to the installation requirements of miniaturized equipment.

[0020] (4) By designing that the number of the rear guide vanes and the number of impeller blades are prime numbers, the present invention can effectively suppress the airflow interference resonance noise between the impeller and the rear guide vanes; combined with the optimized air intake channel and blade shape, it reduces airflow separation and vortex generation, further reduces aerodynamic noise, and at the same time improves the stability of the fan operation and extends its service life. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the integrated dual-duct fan of the present invention; Figure 2 This is a structural schematic diagram of the integrated dual-duct fan of the present invention from another perspective; Figure 3 This is a cross-sectional view of the integrated dual-duct fan of the present invention; Figure 4 This is a simulation diagram of the overall flow field in Embodiment 1 of the present invention; Figure 5 This is a simulation diagram of the impeller flow field in Embodiment 1 of the present invention; Figure 6 This is a simulation diagram of the overall pressure distribution in Embodiment 1 of the present invention; Figure 7 This is a simulation diagram of the impeller pressure distribution in Embodiment 1 of the present invention; Figure 8 This is a flowchart of the design method of the present invention.

[0023] In the diagram: 1. Outer shell; 2. Collector; 3. Inner shell; 4. Outer duct; 5. Rear guide vane; 6. Air inlet; 7. Drive motor; 8. Air outlet; 9. Inner duct; 10. Impeller. Detailed Implementation

[0024] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0025] In the description of this invention, it should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0026] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0027] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0028] refer to Figure 1-7An integrated dual-duct fan includes a housing 1, a collector 2, an inner housing 3, an outer duct 4, multiple rear guide vanes 5, multiple air inlets 6, a drive motor 7, multiple air outlets 8, an inner duct 9, and an impeller 10. The housing 1 may have a cylindrical structure, and its inner wall further defines the flow path boundary of the outer duct 4. The collector 2 is coaxially disposed on one axial side of the housing 1, i.e., the air inlet end. The collector 2 has a converging arc flow channel structure, and its inner wall profile is a smooth arc curve, gradually converging inward from the air inlet to guide the airflow smoothly and rapidly into the fan interior. The inner housing 3 is coaxially disposed on the side of the housing 1 away from the collector 2, i.e., the air outlet end. The outer diameter of the inner housing 3 is smaller than the inner diameter of the housing 1, and the inner housing 3 protrudes axially from the end face of the housing 1. An annular gap is formed between the inner housing 3 and the housing 1, which constitutes the outer duct 4. Multiple rear guide vanes 5 are evenly distributed in an annular pattern between the inner housing 3 and the housing 1, i.e., within the outer duct 4. The root of the rear guide vane 5 is fixedly connected to the outer wall of the inner shell 3, and its top is fixedly connected to the inner wall of the outer shell 1. The rear guide vane 5 has a specific blade inlet angle and outlet angle, and its inlet angle matches the airflow angle at the outlet of the impeller 10. It is used to eliminate the circumferential velocity component generated after the airflow is accelerated by the impeller 10, converting the rotational kinetic energy of the airflow into static pressure energy. At the same time, it serves as a structural connector to fix the inner shell 3 and the outer shell 1 together, providing structural support. Multiple air inlets 6 are evenly arranged in a ring on the side of the inner shell 3 near the collector 2. The air inlets 6 penetrate the inner shell 3, connecting the outer bypass duct 4 outside the inner shell 3 with the hollow cavity inside the inner shell 3. The air inlets 6 constitute the air inlet of the inner bypass duct 9. The drive motor 7 is coaxially arranged and housed in the hollow cavity of the inner shell 3. The housing of the drive motor 7 is fixedly connected to the inner wall of the inner shell 3. The main body of the drive motor 7 axially blocks the side of the inner shell 3 away from the collector 2, which can be sealed with high-temperature potting compound. This forces the airflow passing through the inner duct 9 to bypass the motor surface before exiting from the outlet 8, achieving forced convection cooling. An electronic control module can be installed on the side of the drive motor 7 near the collector 2. The electronic control module is electrically connected to the drive motor 7 and is used to control the motor's speed, direction, and operating status. The electronic control module may further include a communication unit for data exchange with an external controller, enabling integrated intelligent control of the fan. Multiple outlets 8 are evenly arranged in a ring on the outer wall of the inner shell 3, located outside the outer shell 1. The outlets 8 penetrate the wall thickness of the inner shell 3, connecting the hollow cavity inside the inner shell 3 with the outer duct 4 inside the outer shell 1. The inlet 6, the hollow cavity of the inner shell 3, and the outlets 8 together constitute the inner duct 9. The airflow path of the inner duct 9 is as follows: external air enters the cavity of the inner shell 3 through the air inlet 6, flows axially over the surface of the drive motor 7 and the electronic control module, absorbs heat, and is then discharged through the air outlet 8 to the outer duct 4, where it merges with the mainstream gas. The impeller 10 is coaxially and fixedly connected to the output shaft of the drive motor 7, and is rotatably disposed in the axial gap between the collector 2 and the inner shell 3. The impeller 10 includes a hub and multiple blades, with the blades evenly distributed circumferentially around the outer periphery of the hub.The blade extends radially outward from the hub surface, with its root connected to the hub and its tip extending to a position close to the inner wall of the outer casing 1. The blade crosses the interface between the outer bypass duct 4 and the outer bypass duct 4, that is, the blade root region corresponds to the outlet section of the outer bypass duct 4, and the blade tip region corresponds to the section of the outer bypass duct 4.

[0029] Preferably, the air inlet 6 can be a curved waist-shaped hole structure, and six air inlets 6 can be evenly opened along the circumference. The ratio of the total opening area of ​​the air inlet 6 to the flow area of ​​the inner duct 9 can be 0.5-0.8. The inlet of the air inlet 6 faces the hub side of the impeller 10. The air outlet 8 is a waist-shaped hole structure, and the outlet of the air outlet 8 faces the airflow direction of the outer bypass duct 4. The ratio of the total area of ​​the air outlet 8 to the flow area of ​​the inner duct 9 is 0.7-0.9.

[0030] The fan also includes a front guide support component disposed between the collector 2 and the impeller 10. The front guide support component includes a central body, multiple support ribs, and guide vanes. The central body is coaxially arranged with the inner shell 3, and the support ribs radially connect the central body to the outer shell 1 or the collector 2. The guide vanes are disposed on the support ribs or independently, and are used to pre-rectify the airflow entering the impeller 10, reducing intake distortion and lowering intake noise. The front guide support component also provides support, forming a dual-point support for the fan rotor together with the rear guide vanes 5, improving the rotor's dynamic characteristics.

[0031] The specific working principle is as follows: When the fan is running, the drive motor 7 drives the impeller 10 to rotate at high speed. Outside air enters the fan through the collector 2 under the negative pressure of the impeller. After being rectified by the front guide assembly, it forms a uniform axial airflow that enters the impeller 10. The rotation of the impeller 10 does work on the airflow, simultaneously increasing its pressure and velocity. The airflow after this work is divided into two parts: the first part is the main flow of the outer bypass duct, which enters the outer bypass duct 4 and flows axially towards the rear guide vane assembly. The rear guide vane 5 eliminates the circumferential velocity component of the airflow, converting kinetic energy into static pressure, and finally discharges it from the outlet of the outer casing 1, thus achieving ventilation. The second part is the heat dissipation flow of the inner duct, which enters through the air inlet 6 on the outer wall of the inner casing 3. The airflow enters the inner duct 9 and first flows through the stator winding ends and rotor of the drive motor 7, where it undergoes forced convection heat exchange with the core heat-generating components, carrying away the heat generated by the motor's copper and iron losses. Subsequently, the airflow enters the mounting cavity of the electronic control integrated module, carrying away the heat generated by the operation of the electronic control module. After heat exchange, the air temperature rises. According to the ideal gas law PV=nRT, the increase in temperature causes the gas to expand when the volume remains constant. The airflow velocity and pressure increase simultaneously. The high-pressure hot airflow after thermal expansion is discharged into the outer bypass duct 4 through the air outlet 8 in the forward direction. After mixing with the mainstream of the outer bypass duct, it is rectified and discharged through the rear guide vanes, realizing the energy recovery of waste heat and the boosting of pressure and efficiency.

[0032] By embedding the drive motor 7 and the electronic control module within the hollow cavity of the inner shell 3, and constructing a dedicated internal cooling channel 9 using the air inlet 6, the cavity, and the air outlet 8, forced convection cooling is achieved. Specifically, after the airflow is accelerated by the impeller, some of the gas enters the internal cooling channel 9 through the air inlet 6 under pressure differential, axially and at high speed, washing over the motor housing and the surface of the electronic control module. After absorbing heat, it is discharged from the air outlet 8 and merges into the main flow of the outer bypass channel. The high-speed gas through the internal cooling channel 9 improves the heat dissipation efficiency of the drive motor 7 and the electronic control module. Simultaneously, the cooling airflow itself is part of the main airflow, eliminating the need for an additional cooling fan and avoiding additional power consumption and noise. Furthermore, after the heat generated by the motor and electronic control module is carried away by the airflow, the airflow temperature rises. With the cross-section of the internal cooling channel remaining essentially unchanged, the temperature rise causes the air volume to expand, increasing the flow velocity and thus raising the dynamic pressure at the air outlet. This pressure boosting effect can partially offset the flow loss of the internal cooling channel and even generate additional thrust, achieving a beneficial self-compensating effect in heat dissipation.

[0033] refer to Figure 8 A design method for an integrated dual-duct fan, used to design the aforementioned fan, includes the following steps: S1, determining the design target parameters: The core design target parameters of the integrated dual-duct fan are clearly defined, including the design flow rate Q (m³ / s), design total pressure P (Pa), and operating speed n (rpm). These parameters are determined based on the heat dissipation requirements of the target application scenario, the system flow resistance characteristics, and the characteristics of the drive motor. Specifically, the design flow rate Q is determined based on the ventilation requirements of the actual application scenario, the design total pressure P is calculated based on the resistance loss during airflow, and the operating speed n is determined in conjunction with the adaptability of the drive motor and the equipment installation space. These three parameters serve as the basic input parameters for subsequent aerodynamic design, ensuring that the design results closely match the actual application requirements.

[0034] S2, Core Aerodynamic Design: Based on the design target parameters determined in step S1, the specific speed of the wind turbine is calculated. Specific speed The calculation formula is:

[0035] By specific speed The value is used to determine the aerodynamic characteristics of the fan and the appropriate matching scheme. When the specific speed is in the range of 25-50, it is determined that a single-stage impeller combined with a rear guide vane is adopted. This solution can meet the medium pressure rise requirement, maintain structural compactness, avoid the increased complexity caused by multi-stage design, and adapt to the aerodynamic characteristics of the medium specific speed range.

[0036] S3, Impeller parameter design: Based on the single-stage impeller and follow-up guide vane combination scheme selected in step S2, the core parameters of the impeller are designed, specifically including: Estimate impeller outer diameter impeller outer diameter The estimation formula is:

[0037] Where Ka is a correction coefficient related to specific speed, based on specific speed. Specific numerical adjustments are made to ensure that the impeller outer diameter is adapted to the design requirements of total pressure and operating speed. When =25-35, Ka takes values ​​of 1.7-1.9; when =35-50, Ka takes 1.9-2.1; Determine the blade mounting hub ratio Installed wheel hub ratio The value range is 0.4-0.6, and should be selected reasonably based on the design flow rate and flow area requirements; Calculate the hub diameter Wheel hub diameter = By hub ratio With impeller outer diameter Correlation calculations were performed to determine the core dimensions of the impeller hub, providing a foundation for subsequent double-duct configuration design. The installation hub ratio ν ranged from 0.4 to 0.6. If ν was too small, the blade root strength would be insufficient and the flow area of ​​the inner duct 9 would be too large, resulting in a low axial velocity; if ν was too large, the inner duct 9 would be severely blocked, and the blade root flow would deteriorate.

[0038] S4. Definition of double-duct configuration: Based on the impeller outer diameter calculated in step S3 Define the coaxial inner and outer bypass ducts to construct a dual-bypass aerodynamic configuration, as detailed below: The inner diameter of the inner shell 3, calculated in step S3, is defined by its flow cross section. It is mainly used to guide the airflow in the blade root region and adapt to the flow characteristics under a high hub ratio. Inner shell 3 outer diameter = Ensure that the impeller hub is flush with the front end face of the inner shell 3; Inner shell 3 inner diameter = -2 ,in The thickness of the inner shell wall is 2. 4mm; its flow area .

[0039] Outer duct: Its flow cross section is defined by the inner diameter of the outer shell 1. The inner diameter of the inner shell 3 is defined by the inner diameter of the outer shell 1, which is determined by the outer diameter of the impeller. With proper design, it is mainly used to guide the airflow in the blade tip area and adapt to the flow characteristics of lower relative velocity. The inner diameter of the casing needs to be slightly larger than the outer diameter of the impeller to avoid airflow leakage. Inner diameter of outer shell 1 =(1.2-1.4) ; .

[0040] The ratio of the flow area of ​​the outer duct to the flow area of ​​the inner duct. / The preferred value is 5.0 to 7.0.

[0041] Impeller position: The impeller is located at the boundary between the inner duct and the outer duct. The blades of the impeller cover the transition area between the inner duct and the outer duct along the spanwise direction, so that the blades participate in the airflow work of the two ducts at the same time, and realize differentiated optimization of the airflow in different areas. Preferably, the ratio of the flow area of ​​the outer duct to the flow area of ​​the inner duct is 5.0 to 7.0. This ratio range can ensure that the airflow distribution of the two ducts is uniform, avoid airflow blockage or excessive flow loss in a single duct, and further improve the overall aerodynamic performance of the fan.

[0042] S5, Three-dimensional blade design: Based on the differences in airflow characteristics between the dual-duct configuration, a three-dimensional blade design was carried out to achieve precise aerodynamic matching between the blade and the dual-duct configuration. The specific steps are as follows: Section division: Divide the blade along the spanwise direction into at least three calculation sections, covering the blade root, blade middle and blade tip (the blade root corresponds to the inner bypass duct region), and the blade tip corresponds to the outer bypass duct region, to ensure the continuity and stability of the blade's spanwise aerodynamic characteristics; Velocity triangle calculation: Based on the simplified radial equilibrium equation, the inlet and outlet velocity triangles of each spanwise calculation section are calculated to clarify the magnitude, direction and relative velocity characteristics of the airflow velocity of each section, providing aerodynamic basis for blade design; Blade Parameter Determination: Based on the velocity triangle calculation results for each cross-section, the blade installation angle, chord length, and sweep profile are determined. Simultaneously, considering the differences in airflow characteristics between the two ducts, a differentiated design strategy is adopted. External bypass section: Due to the relatively low airflow velocity in this region, a high lift coefficient airfoil is adopted. The lift coefficient of the high lift coefficient airfoil is not less than 1.2, which improves the work capacity of the blade in this region and makes up for the deficiency of low relative velocity. Inner channel section: Due to the high hub ratio and narrow flow channel in this region, a low-consistency arrangement is adopted. The consistency value of the low-consistency arrangement is 0.6-0.9, which reduces the obstruction effect of the blades on the airflow and reduces flow friction loss. Blade thickness optimization: The blade adopts a variable relative thickness design along the span, with a relative thickness of 5%-8% at the blade tip and 10%-15% at the blade root. The greater thickness at the blade root can improve the structural strength of the blade, while the smaller thickness at the blade tip can reduce flow loss in the blade tip area. The number of blades is determined as follows: 8-14 blades, depending on the impeller outer diameter. The appropriate selection of the flow area ensures a balance between the blade's working efficiency and the airflow guidance effect; Preferably, the installation angle of each section along the blade span gradually decreases from the blade root to the blade tip along the blade height, with a reduction range of 8°-15°, so that the aerodynamic load distribution along the blade span is uniform, avoiding airflow separation caused by excessive local load, and further improving the aerodynamic efficiency of the blade.

[0043] S6, rear guide vane matching design To eliminate the circumferential velocity component of the airflow at the impeller outlet, effectively convert the kinetic energy of the airflow into static pressure, improve the total pressure efficiency of the fan, and reduce aerodynamic noise, a matching design for the rear guide vanes is implemented, with the following specific requirements: Inlet Angle Design: Based on the impeller outlet airflow angle calculated in step S5, design the blade inlet angle of the rear guide vane to match the impeller outlet airflow angle, ensuring that the airflow enters the rear guide vane smoothly and reducing airflow impact loss. Noise optimization: The number of blades in the rear guide vane is coprime to the number of blades in the impeller. This design avoids airflow interference between the impeller and the rear guide vane, which can generate resonance noise and effectively reduce the overall noise level of the fan. Kinetic energy recovery: The outlet angle of the rear guide vane is designed to be close to the axial direction, that is, about 90°, to eliminate the circumferential velocity of the airflow to the maximum extent, and to efficiently convert the kinetic energy of the airflow into static pressure, thereby improving the total pressure recovery coefficient of the fan.

[0044] S7, Air intake duct design: To ensure smooth and stable airflow into the dual-duct system and reduce flow separation and pressure loss during the intake process, an integrated dual-duct collector is designed. Specific design requirements are as follows: Flow channel type: The collector is a converging arc flow channel. The converging flow channel can achieve smooth acceleration of airflow and avoid the generation of vortices in the airflow during the intake process; Profile transition: The inner wall profile of the collector smoothly transitions to the inlet section of both the inner and outer ducts, ensuring that the airflow can be evenly distributed to the two ducts and avoiding flow losses caused by excessively high or low local airflow velocities. Dimensional requirements: The radius R of the inner wall arc of the collector must satisfy: R ≥ 0.1 Collector outer diameter = Its axial length L satisfies: L=(0.2~0.4) This size range ensures optimal aerodynamic performance of the collector, balancing intake efficiency with structural compactness.

[0045] In some embodiments, to ensure that the designed integrated dual-duct fan can achieve the design target parameters and improve design reliability, step S8, aerodynamic performance verification and optimization, is also included: Numerical simulation: Based on the CFD (Computational Fluid Dynamics) numerical simulation method, the aerodynamic performance of the designed integrated dual-duct fan under all operating conditions is simulated. The computational domain includes the collector, inner duct, outer duct, impeller and rear guide vane area, as well as the necessary inlet and outlet extensions to simulate the real installation environment. The CFD numerical simulation can use the RNG k-ε turbulence model to ensure the accuracy of the simulation results. Performance evaluation: Obtain the total pressure, efficiency and flow field distribution of the fan under different flow rates through numerical simulation, and determine whether the simulation results meet the design target parameters determined in step S1; Parameter optimization: If the simulation results do not meet the design target parameters, return to the corresponding step to adjust the relevant design parameters, such as impeller size, blade installation angle, duct area ratio, etc., and redesign and simulate until the design requirements are met.

[0046] Example 1: This embodiment details the specific process of designing a small, high-pressure axial flow fan for cooling precision electronic equipment according to the method described in this invention.

[0047] Step S1: Determine the design target parameters Based on the heat dissipation requirements of the target equipment and the system flow resistance characteristics, the core design target parameters of the fan are determined as follows: The design flow rate Q = 400 m³ / h, which is converted to instantaneous flow rate: Q = 400 / 3600 ≈ 0.111 m³ / s.

[0048] The design total pressure is P=3000Pa, which is determined by the aerodynamic resistance calculation of the equipment's cooling channels and is crucial for ensuring sufficient cooling airflow. The aerodynamic viscosity is μ=1.8×10⁻⁶. -5 Pa·s.

[0049] The operating speed n=43000rpm, which is determined based on the rated operating conditions of the selected high-efficiency micro drive motor to achieve power matching and operational stability.

[0050] The inlet pipe is approximately 300-400mm long, and the outlet pipe is 800mm long.

[0051] Step S2, Core Aerodynamic Design Calculate the specific speed of the fan based on the basic parameters determined in step S1. To guide the selection of core aerodynamic solutions:

[0052] Calculated specific speed The speed is within the medium specific speed range of 25-50 preset in this invention. Based on this, the aerodynamic solution using a single-stage impeller combined with a rear guide vane is deemed reasonable and efficient. This solution can achieve the target pressure rise within a single-stage structure while maintaining a compact structure, making it very suitable for installation in miniaturized equipment.

[0053] Step S3, Impeller Parameter Design Estimate impeller outer diameter Combined with specific speed Select a correction factor related to the specific speed. =1.9, and this coefficient typically ranges from 1.8 to 2.0 in the medium specific speed range. Substituting this into the impeller outer diameter estimation formula:

[0054] Determine the blade mounting hub ratio : Select the installation hub ratio based on the design flow rate and flow area requirements. =0.5, The value range is 0.4-0.6. Here, the middle value is selected to balance the flow of the inner and outer bypass channels. Calculate the hub diameter : .

[0055] Step S4: Definition and parameter determination of double-duct configuration Based on the impeller dimensions obtained in step S3, a coaxial double-duct structure is defined. Details are as follows: Inner shell 3 inner diameter = -2 =30-2*2=26 Its flow area .

[0056] .

[0057] The internal structure is defined by the inner diameter of the inner shell. =26mm limit. Its flow area

[0058] Outer bypass duct: The flow section is located between the inner shell and the outer wall of the third shell. With the inner wall of the outer shell 1 Between. The multiple here is 1.2. = =60 * ​​1.2 = 72 mm. Its flow area is...

[0059] Verification of culvert area ratio: Within the preferred range of 5.0 to 7.0 of this invention, the requirement for uniform airflow distribution is met, which is beneficial for achieving reasonable airflow distribution and load matching.

[0060] The impeller is located at the boundary between the two ducts, and its blades span the entire flow channel from the inner duct to the outer duct. It can do work on the airflow in both ducts at the same time, and optimize the aerodynamic performance at different radii through differentiated design.

[0061] Step S5: Three-dimensional modeling of impeller blades This step uses aerodynamic calculations to transform the impeller from basic geometric parameters into three-dimensional blades.

[0062] 1. Section Division: The blade is divided into 5 calculation sections along its span from the blade root (r=15mm) to the blade tip (r=30mm): r1=15mm, r2=18.75mm, r3=22.5mm, r4=26.25mm, r5=30mm. This ensures the continuity of the blade's spanwise aerodynamic characteristics to capture radial aerodynamic variations.

[0063] 2: Calculation of key aerodynamic parameters (based on average radius) (Taking a cross section as an example): Axial velocity calculation: Impeller annular flow area .

[0064] Axial velocity Assume a uniform axial velocity distribution.

[0065] Circumferential velocity at each cross section: .

[0066] Export torque Based on Euler's equations, it is assumed that there is no pre-spinning at the inlet. Then the theoretical total pressure Take the air density We can obtain:

[0067] This value reflects the circumferential momentum that the airflow gains from the impeller.

[0068] 3: Determining the velocity triangle and blade angle (same cross section): With median diameter For example, calculate:

[0069]

[0070]

[0071]

[0072]

[0073] Repeat steps 2-3 above for the five calculation sections to obtain the variation along the blade height. A series of values ​​were used to determine the blade bending and twisting behavior. Specific values ​​are shown in Table 1. Table 1

[0074] Blade geometry is determined as follows: Take the angle of attack i = 4° and the lag angle δ = 3°. Then: The blade root inlet angle is 52.2° + 4° = 56.2°, the outlet angle is 54.6° + 3° = 57.6°, and the installation angle is (56.2 + 57.6) / 2 = 56.9°.

[0075] The blade tip inlet angle is 68.8° + 4° = 72.8°, the outlet angle is 21.8° + 3° = 24.8°, and the installation angle is (72.8 + 24.8) / 2 = 48.8°.

[0076] The reduction in the installation angle is 56.9° - 48.8° = 8.1°, which falls within the range of 8° to 15°.

[0077] 4: Determination of overall span-direction styling parameters: At the same time, it was determined that: Number of leaves Z: Take Z=12 leaves.

[0078] Airfoil and consistency strategy: 0.9 for blade root and 0.7 for blade tip. A high-lift airfoil (Cl≥1.2) is used in the outer bypass duct region (near the blade tip) to cope with the lower relative speed; a lower consistency (0.6-0.9) is used in the inner bypass duct region (near the blade root) to reduce flow blockage at high hub ratios.

[0079] Variable thickness design: The relative thickness at the leaf root is 12% to ensure strength, and gradually decreases to 6% towards the leaf tip to reduce losses.

[0080] Step S6: Design of matching rear guide vanes The rear guide vanes are used to convert the rotational kinetic energy of the airflow at the impeller outlet into static pressure and rectify it into axial flow.

[0081] 1. Inlet Angle Design: Ensure that the inlet geometry of the guide vane blades is aligned with the absolute airflow angle at the impeller outlet calculated in step S5. Matching. For example, at the average radius, the guide vane inlet angle is designed to be... This is to achieve shock-free air intake.

[0082] 2. Exit Angle Design: Set the absolute airflow angle at the guide vane exit. The angle is close to but slightly less than 90°, which aims to essentially eliminate circumferential velocity while controlling flow channel expansion losses.

[0083] 3. Blade selection: The guide vane has 7 blades, which is a prime number relative to the impeller blades (12). This helps to break aerodynamic interference and reduce rotational noise.

[0084] Step S7, Intake Channel Design The design incorporates a contraction-type collector to guide airflow smoothly into the dual ducts.

[0085] Profile: The inlet end face of the collector is circular, and the inner wall adopts a circular arc contraction profile, which smoothly transitions to the inner duct. The inlet diameter is 30mm, and the inlet cross section of the outer duct has an inlet diameter of 62mm, ensuring stable airflow distribution.

[0086] Key dimensions: A 5mm axial clearance is maintained between the inner wall of the collector and the front end face of the inner shell 3, serving as the air collection chamber for the inner duct inlet, ensuring smooth airflow into the inlet 6. Arc radius. ; =(1.2-1.4) =72-84mm, collector axial length The dimensions are within the preferred range to ensure smooth flow.

[0087] Step S8: Aerodynamic performance verification and optimization Numerical simulation: The RNGk-ε turbulence model is used to construct a complete three-dimensional computational domain including collector 2, impeller 10, inner duct 9, outer bypass duct 4, rear guide vane 5, and outlet extension section to simulate the aerodynamic performance under all working conditions. Performance Evaluation: Simulation results show that under the conditions of design flow rate Q = 0.111 m³ / s and operating speed n = 43000 rpm, the total pressure of the fan is 3080 Pa and the efficiency is 82.3%, both meeting the design targets: total pressure ≥ 3000 Pa and efficiency ≥ 80%. The flow field distribution is uniform, with no obvious airflow separation or vortex phenomena. Flow field analysis shows that the airflow distribution within the dual ducts is reasonable, and no large-scale separation vortices appear, verifying the effectiveness of the design method of this invention. The final total axial length of the fan is approximately 80 mm, resulting in a compact structure. The mass flow rate at the pipe outlet is 0.164 kg / s, and the pipe outlet density is 1.172 kg / m³. 3 Outlet volumetric flow rate: 0.14 m³ 3 / s (converted to hours: 0.143600 = 504m) 3 / h), average impeller outlet pressure: -3554.53Pa.

[0088] Parameter optimization: Since the simulation results meet the design requirements, there is no need to adjust the design parameters, and the design is complete.

[0089] Through the above steps, the design of an integrated dual-duct fan for cooling precision electronic equipment was completed. The designed fan has an axial length of only 80mm, a compact integrated structure, and is suitable for installation in small equipment. It also boasts advantages such as high efficiency, high pressure rise, and low noise, fully meeting practical application requirements. The design was used in prototype manufacturing, and experimental verification showed that the actual performance of the prototype deviated from the numerical simulation results by less than 5%, proving that the design method of this invention is scientific, reliable, and highly practical in engineering.

[0090] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A design method for an integrated double-duct fan, used to design an integrated double-duct fan, characterized in that: The integrated dual-duct fan includes a housing (1); Collector (2), the collector (2) is coaxially disposed on one side of the outer casing (1); Inner shell (3), the inner shell (3) is coaxially disposed on the side of the outer shell (1) away from the collector (2), and the inner shell (3) protrudes from the outer shell (1), the inner shell (3) and the outer shell (1) form an outer bypass (4); Multiple rear guide vanes (5) are arranged in a ring between the inner shell (3) and the outer shell (1); Multiple air inlets (6) are arranged in a ring on the outer wall of the inner shell (3) near the collector (2); A drive motor (7) is coaxially disposed inside the inner shell (3), and the drive motor (7) blocks the side of the inner shell (3) away from the collector (2); Multiple air outlets (8) are arranged in a ring on the outer wall of the inner shell (3) and form an inner channel (9) with multiple air inlets (6) and the inner shell (3), so that the air entering through the air inlet (6) flows through the drive motor (7) and the inner channel (9) and is discharged from the air outlet (8). Impeller (10), the impeller (10) is coaxially connected to the output shaft of the drive motor (7), and is rotatably disposed between the collector (2) and the inner shell (3); The design method includes the following steps: S1. Determine the target design parameters: This includes design flow rate Q, design total pressure P, and operating speed n; S2, Core Aerodynamic Design: Based on the aforementioned design target parameters, the specific speed of the wind turbine is calculated. The specific speed The calculation formula is: when When the value is in the range of 25-50, the solution is determined to be a combination of a single-stage impeller and a rear guide vane. S3, Impeller parameter design: Based on the selected scheme, calculate the outer diameter of the impeller. Hub diameter And determine the blade mounting hub ratio. ; S4. Definition of double-duct configuration: According to the outer diameter of the impeller Define an inner duct and an outer duct that are coaxially arranged, wherein the flow cross section of the inner duct is defined by the inner diameter of the inner shell, and the flow cross section of the outer duct is defined by the inner diameter of the outer shell and the outer diameter of the inner shell, and the impeller is located at the boundary between the inner duct and the outer duct. S5, Three-dimensional blade design: The blade is divided into at least three calculation sections along its span. Based on the simplified radial equilibrium equation, the inlet and outlet velocity triangles of each section are calculated, and the blade's installation angle, chord length, and sweep profile are determined accordingly. The blade adopts a high lift coefficient airfoil in the section of the outer bypass duct region, with a lift coefficient of not less than 1.2, to match the lower relative velocity. The blade adopts a low-consistency arrangement in the section of the inner bypass duct region, with a consistency value of 0.6-0.9, to adapt to the flow under high hub ratio. S6. Rear guide vane matching design: Based on the airflow angle at the impeller outlet, the blade inlet angle of the rear guide vane is designed to eliminate the circumferential velocity component of the airflow and effectively convert kinetic energy into static pressure. S7, Air intake duct design: The design incorporates an integrated dual-duct collector, which is a contracting circular arc flow channel with its inner wall profile smoothly transitioning to the inlet sections of both the inner and outer ducts.

2. The design method of an integrated double-duct fan according to claim 1, characterized in that: In step S3, the impeller outer diameter The estimation formula is as follows Where Ka is a correction factor related to specific speed, based on specific speed Specific numerical adjustments are made to ensure that the impeller outer diameter is adapted to the design requirements of total pressure and operating speed. When =25-35, Ka takes values ​​of 1.7-1.9; when =35-50, Ka takes 1.9-2.1; The hub diameter = Among them, the ratio of installed wheel hubs The value range is 0.4-0.

6.

3. The design method of an integrated dual-duct fan according to claim 1, characterized in that: In step S4, the ratio of the flow area of ​​the outer duct to the flow area of ​​the inner duct is 5.0 to 7.

0.

4. The design method of an integrated double-duct fan according to claim 1, characterized in that: In step S5, the number of blades is 8-14, and a variable relative thickness design is adopted along the span, with a relative thickness of 5%-8% for the blade tip section and 10%-15% for the blade root section.

5. The design method of an integrated double-duct fan according to claim 1, characterized in that: In step S5, the installation angle of each section along the blade span gradually decreases from the blade root to the blade tip along the blade height, with a decrease range of 8°-15°.

6. The design method of an integrated double-duct fan according to claim 1, characterized in that: In step S6, the number of blades of the rear guide vane and the number of blades of the impeller are coprime numbers.

7. The design method of an integrated double-duct fan according to claim 1, characterized in that: In step S7, the inner wall radius R of the collector satisfies: R ≥ 0.1 Its axial length L satisfies: L=(0.2~0.4) .

8. The design method of an integrated double-duct fan according to claim 1, characterized in that: It also includes step S8, aerodynamic performance verification and optimization: Based on the CFD numerical simulation method, the aerodynamic performance of the designed integrated dual-duct fan under all working conditions is simulated to obtain the total pressure, efficiency and flow field distribution under different flow rates. If the simulation results do not meet the design target parameters, the corresponding steps are returned to adjust the parameters until the design requirements are met. The CFD numerical simulation uses the RNG k-ε turbulence model, and the computational domain includes the collector, inner duct, outer bypass duct, impeller, and guide vane region.

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