High-efficiency two-stage axial impeller and axial flow fan

Abstract

The present application relates to the technical field of axial flow fan, in particular to a high-efficiency two-stage axial flow impeller and axial flow fan, which comprises a flow collector, a hub, a first-stage blade group and a second-stage blade group. The hub is installed at the center of the flow collector, and the first-stage blade group and the second-stage blade group are both fixed on the hub and rotate synchronously with the hub. The blades of the second-stage blade group are embedded in the flow channel formed by two adjacent blades of the first-stage blade group. By arranging the second-stage blade group in the flow channel between the two adjacent blades of the first-stage blade group, the flow channel area between the trailing edges of the two adjacent blades of the first-stage blade group is reduced, so that the airflow can continue to be accelerated by the blades of the second-stage blade group, thereby inhibiting the airflow separation phenomenon and improving the aerodynamic efficiency of the impeller. Compared with the single-stage impeller, the chord length of the two-stage impeller is greatly reduced, which reduces the probability of vortex generated when the fluid passes through the blades, reduces the flow resistance of the airflow on the blade surface, and further improves the aerodynamic efficiency of the impeller.

Description

Technical Field

[0001] This invention relates to the field of axial flow fan technology, specifically to a high-efficiency two-stage axial flow impeller and axial flow fan. Background Technology

[0002] As the core working component of axial flow fans in the field of fluid machinery, axial flow impellers are widely used in various scenarios such as industrial ventilation, equipment heat dissipation, and HVAC. Their performance directly determines the air volume, air pressure, efficiency, and operational stability of axial flow fans. Currently, the most commonly used axial flow fan structure is the single-stage axial flow impeller. This type of impeller typically consists of a collector, a hub, and single-stage blades evenly arranged circumferentially on the hub. The collector guides the airflow smoothly into the blade channel, and the hub drives the blades to rotate to do work on the fluid, achieving axial transport of the airflow.

[0003] For example, Chinese patent application CN116181672A discloses an axial flow impeller and fan, including a hub and first blades. Multiple first blades are circumferentially fixed to the outer circumferential surface of the hub, and a reinforcement mechanism is fitted between the hub and the first blades to strengthen the connection between them. A heat dissipation mechanism is also provided inside the hub to actively dissipate heat from the stator, allowing the heat generated during operation to dissipate quickly and preventing overheating within the stator.

[0004] In practical applications, the aforementioned axial flow impellers exhibit significant performance defects under high-speed, low-flow conditions, or when designed for axial flow fans with small inlet angles, making it difficult to meet the requirements for high-efficiency operation. When the impeller operates at high speed and low flow, the installation angles of each blade section need to be designed to be small to adapt to the airflow parameters. This causes the flow channel area formed between adjacent blades to increase significantly at the blade outlet, resulting in a sharp drop in fluid velocity as it flows through the outlet; simultaneously, the pressure in the outlet region is relatively high. Under the combined effect of these two factors, boundary layer separation easily occurs at the blade trailing edge, which can even lead to flow channel blockage in severe cases. This not only limits the maximum airflow output of the impeller but also significantly reduces its aerodynamic efficiency.

[0005] Meanwhile, due to the small blade inlet angle, in order to ensure the blade's work capacity and structural strength, the blade chord length of a conventional single-stage impeller needs to be designed to be a large size. However, the large chord length makes it easy for the fluid to form strong flow vortices on the blade suction surface. These vortices will significantly increase the flow resistance of the blade to the fluid, causing energy loss and further aggravating the problem of low impeller efficiency. The above problems are difficult to solve by simply adjusting the blade installation angle and optimizing the airfoil surface. Summary of the Invention

[0006] This invention provides a high-efficiency two-stage axial flow impeller and an axial flow fan to solve the technical problem of low aerodynamic efficiency in the use of existing axial flow impellers.

[0007] To solve the above problems, the present invention provides a high-efficiency two-stage axial flow impeller with the following technical solution: A high-efficiency two-stage axial flow impeller includes a collector, a hub, a first-stage blade group, and a second-stage blade group. The hub is installed at the center of the collector. Both the first-stage blade group and the second-stage blade group are fixed on the hub and rotate synchronously with the hub. The blades of the second-stage blade group are embedded inside the flow channel formed by two adjacent blades of the first-stage blade group. The first-stage blade group and the second-stage blade group have the same number of blades, and the number of blades is at least two.

[0008] This invention discloses a high-efficiency two-stage axial flow impeller. By setting up a synchronously rotating first-stage blade group and a second-stage blade group, and placing the second-stage blade group within the flow channel between adjacent blades of the first-stage blade group, the flow channel area between the trailing edges of two adjacent blades of the first-stage blade group is significantly reduced. This allows the airflow to continue to be accelerated, thereby suppressing airflow separation at the trailing edges of the first-stage blade group and preventing airflow blockage due to a sudden decrease in velocity, thus improving the aerodynamic efficiency of the impeller. Furthermore, compared to a single-stage impeller, the blade chord length of the two-stage impeller is significantly reduced, thereby decreasing the probability of vortex generation when the fluid flows over the blades and reducing the flow resistance on the blade surface, further improving the aerodynamic efficiency of the impeller.

[0009] Furthermore, the blades of the second-stage blade group are arranged in the middle of the flow channel streamline of two adjacent blades of the first-stage blade group, and the blades of the second-stage blade group are located downstream of the first-stage blade group.

[0010] Furthermore, the blades of the first-stage blade group and the blades of the second-stage blade group are both inclined from the blade root to the blade tip toward the rotation direction of the impeller and toward the inlet side of the impeller. The blades are also inclined from the leading edge to the trailing edge toward the pressure surface in the axial direction of the hub. The suction surface of the blade is a convex curved surface, and the pressure surface of the blade is a concave curved surface, in order to improve the aerodynamic efficiency of the blade rotation.

[0011] Furthermore, the root thickness of the blades in the first-stage blade group and the second-stage blade group is greater than the tip thickness of the blades to improve the connection strength between the blades and the hub.

[0012] Furthermore, the blade is characterized by having a blunt edge structure with a rounded transition at the leading edge to reduce airflow separation at the leading edge; and a rounded trailing edge to reduce the intensity of trailing edge vortices.

[0013] Furthermore, the hub and each blade are integrally formed using injection molding or compression molding processes.

[0014] Furthermore, the blades of the first-stage blade group and the blades of the second-stage blade group are staggered in the axial direction of the hub to reduce the difficulty of demolding the impeller.

[0015] Furthermore, the chord length at the tip of the blade is greater than the chord length at the root of the blade to increase the impeller's work capacity and improve fluid pressure.

[0016] Furthermore, the blades of both the first-stage blade group and the second-stage blade group are detachably connected to the hub.

[0017] The beneficial effects of the high-efficiency two-stage axial flow impeller provided by this invention are: 1. The present invention provides a high-efficiency two-stage axial flow impeller by setting a first-stage blade group and a second-stage blade group that rotate synchronously, and placing the second-stage blade group within the flow channel between adjacent blades of the first-stage blade group. This significantly reduces the flow channel area between the trailing edges of two adjacent blades of the first-stage blade group, allowing the airflow to continue to be accelerated. This suppresses airflow separation at the trailing edges of the first-stage blade group, preventing airflow blockage due to a sudden decrease in velocity and improving the aerodynamic efficiency of the impeller. Furthermore, compared to a single-stage impeller, the blade chord length of the two-stage impeller is greatly reduced, thereby decreasing the probability of vortex generation when the fluid flows over the blades and reducing the flow resistance on the blade surface, further improving the aerodynamic efficiency of the impeller.

[0018] 2. By arranging the second-stage blades within the flow channel of the first-stage blades, the impeller achieves higher aerodynamic efficiency compared to other positions in the flow channel. Furthermore, by arranging the second-stage blade group downstream of the first-stage blade group, secondary pressurization and guidance of the airflow can be achieved, further enhancing the impeller's work capacity and air pressure output, resulting in a more significant efficiency improvement under small installation angle conditions.

[0019] 3. By designing the blades to be inclined from the blade root to the blade tip towards the impeller's rotation direction and towards the impeller's inlet side, and by having the blades inclined from the leading edge to the trailing edge towards the pressure surface in the axial direction of the hub, the angles of each position of the blade can be more closely aligned with the airflow direction, reducing airflow separation on the blade surface. This also guides the airflow to accelerate smoothly in axial flow, avoiding the formation of impacts and vortex accumulation on the blade surface. Furthermore, the convex curved surface of the blade's suction surface helps the airflow adhere to the blade surface when entering the flow channel, further reducing the risk of airflow separation at the leading edge; the concave curved surface of the blade's pressure surface increases the effective contact area of ​​the blade with the airflow, enhancing the blade's work capacity during rotation, thereby improving the blade's aerodynamic efficiency.

[0020] 4. As the connection between the blade and the hub, the blade root bears the maximum torque and centrifugal force brought about by high-speed rotation. The thickened design can improve the connection strength and deformation resistance of the blade, avoiding the risk of blade root breakage and deformation under high-speed conditions. The design with a smaller blade tip thickness can reduce the blade's resistance to airflow and improve the aerodynamic efficiency of the impeller.

[0021] 5. The blunt edge structure with a rounded transition at the leading edge of the blade can enhance its adaptability to incoming flow from different directions and avoid airflow separation. The rounded structure at the trailing edge allows the airflow to smoothly detach at the trailing edge, reducing the intensity of trailing edge vortices and flow resistance, ultimately reducing energy loss and further improving the aerodynamic efficiency of the impeller.

[0022] 6. The staggered projection design can avoid interference between the two stages of the impeller during demolding, and can achieve one-piece molding without the need for complex core-pulling molds, which reduces the difficulty of mold design and manufacturing and reduces production costs.

[0023] 7. The blade tip region is where the airflow velocity and pressure change most significantly. Increasing the chord length of the blade tip section can increase the area of ​​the blade's interaction with the airflow in this region, enhance the pressurization effect of the blade tip on the airflow, and thus increase the overall delivery pressure of the impeller.

[0024] 8. The detachable blades significantly improve the impeller's maintenance convenience and adaptability to operating conditions. When the blades are worn or damaged, the damaged blades can be replaced individually without replacing the entire impeller, reducing maintenance costs. At the same time, users can replace blades with different airfoils and chord lengths according to different operating conditions, making the impeller adaptable to a wider range of flow and pressure, thus improving the impeller's flexibility and service life.

[0025] To solve the above problems, the present invention provides a high-efficiency axial flow fan using the following technical solution: A high-efficiency axial flow fan, comprising a high-efficiency two-stage axial flow impeller.

[0026] The beneficial effects of the high-efficiency axial flow fan provided by this invention are: By applying the aforementioned high-efficiency two-stage axial flow impeller to an axial flow fan, the blades of the second-stage blade group can reduce the flow channel area between the trailing edges of two adjacent blades in the first-stage blade group. This allows the airflow to continue to be accelerated, thereby suppressing airflow separation at the trailing edges of the first-stage blade group and preventing airflow blockage due to a sudden decrease in velocity, thus effectively improving the aerodynamic efficiency of the fan. Furthermore, compared to a single-stage impeller, the blade chord length of the two-stage impeller is significantly reduced, thereby decreasing the probability of vortex generation when the fluid flows over the blades and reducing the flow resistance on the blade surface, further improving the aerodynamic efficiency of the fan. Attached Figure Description

[0027] Figure 1 A schematic diagram of a high-efficiency two-stage axial flow impeller provided by the present invention; Figure 2 for Figure 1 Schematic diagram of the current collector structure; Figure 3 The front view of the first-stage blade group and the second-stage blade group; Figure 4 Side view of the first-stage blade group and the second-stage blade group; Figure 5 This is a rear view of the first-stage blade group and the second-stage blade group.

[0028] Explanation of reference numerals in the attached figures: 1. Collector; 11. Mounting plate; 12. Flow guide tube; 2. First stage blade group; 21. First stage blade; 3. Second stage blade group; 31. Second stage blade; 4. Hub; 5. Blade tip; 51. Blade root; 52. Leading edge; 53. Trailing edge. Detailed Implementation

[0029] The main concept of this invention lies in employing a coaxially integrated two-stage blade group design. The blades of the second-stage blade group 3 are precisely embedded within the flow channel formed by the blades of two adjacent first-stage blade groups 2, ensuring that the number of blades in both stages is equal. This achieves step-by-step guidance and pressurization of the airflow. By filling the excess space at the trailing edge of the flow channel of the first-stage blade group 2 with the blades of the second-stage blade group 3, airflow separation and blockage can be suppressed. Simultaneously, the blade morphology is further optimized, so that the blades are inclined from the blade root 51 to the blade tip 5 towards the impeller's rotation direction and towards the impeller's inlet side. Furthermore, the blades from the leading edge 52 to the trailing edge 53 are inclined towards the pressure surface in the axial direction of the hub 4, guiding the airflow smoothly axially. Combined with the curved surface structure with an outwardly convex suction surface and an inwardly concave pressure surface, the fluid is less prone to separation when flowing through the blades. In addition, the design of the blade root 51 being thicker than the blade tip 5, the rounded blunt edge of the leading edge 52, and the rounded trailing edge 53 can further reduce flow resistance and eddy current loss; the design of staggered axial projection of the blades can reduce the manufacturing difficulty and production cost of the impeller, ensuring operational stability while taking into account the production process, and ultimately improving the aerodynamic efficiency of the impeller.

[0030] The principles and spirit of the present invention will be explained in detail below with reference to several representative embodiments.

[0031] Embodiment 1 of a high-efficiency two-stage axial flow impeller provided by the present invention: like Figures 1 to 5As shown, the present invention provides a high-efficiency two-stage axial flow impeller comprising a collector 1, a hub 4, a first-stage blade group 2, and a second-stage blade group 3. The hub 4 is a cylindrical rotating body, rotatably mounted at the center of the collector 1 and coaxially arranged with the collector 1. The first-stage blade group 2 and the second-stage blade group 3 are both fixed on the hub 4 and rotate synchronously with the hub 4. In this embodiment, the first-stage blade group 2 and the second-stage blade group 3 each include five blades. The blades of the first-stage blade group 2 are defined as first-stage blades 21, and the blades of the second-stage blade group 3 are defined as second-stage blades 31. Each first-stage blade 21 of the first-stage blade group 2 is circumferentially distributed on the outer surface of the hub 4, and each second-stage blade 31 of the second-stage blade group 3 is also circumferentially distributed on the outer surface of the hub 4. In the airflow direction, the second-stage blade group 3 is located downstream of the first-stage blade group 2.

[0032] Furthermore, such as Figure 1 , Figure 2 As shown, the collector 1 includes a mounting plate 11 and a guide tube 12. The guide tube 12 has an annular structure. The mounting plate 11 is fixed on the outer circumferential surface of the guide tube 12 to fix and support the guide tube 12. The guide tube 12 is sleeved on the outside of the first-stage blade group 2 and the second-stage blade group 3 to guide the airflow from the free flow state to the impeller inlet and form a uniform radial gap between the blade tips 5 of the first-stage blade 21 and the second-stage blade 31. The width of the gap is less than 1% of the diameter of the blade tip 5 to form an approximately closed flow channel inlet, thereby reducing the amount of airflow leakage from the gap.

[0033] In this embodiment, as Figure 1 , Figure 3 , Figure 4 , Figure 5 As shown, the hub 4 is an axially extending cylindrical structure. The end near the airflow inlet is the first-stage blade mounting area, where each first-stage blade 21 is circumferentially evenly distributed, forming a flow channel between adjacent first-stage blades 21. The end of the hub 4 near the airflow outlet is the second-stage blade mounting area, axially separated from the first-stage blade mounting area. Each second-stage blade 31 is circumferentially evenly distributed within this area. The hub 4, the first-stage blades 21, and the second-stage blades 31 are integrally formed using injection molding / compression molding to improve the impeller's strength.

[0034] Furthermore, each second-stage blade 31 is staggered from the two adjacent first-stage blades 21 in the circumferential direction to ensure that the second-stage blade 31 can be embedded inside the flow channel formed by the two adjacent first-stage blades 21. At this time, the second-stage blade 31 fills part of the flow channel outlet area, reducing the passage area of ​​the flow channel trailing edge between the two adjacent first-stage blades 21. This avoids fluid separation caused by sudden expansion of the channel, prevents blockage due to a sudden decrease in flow velocity, and improves the aerodynamic efficiency of the impeller.

[0035] Furthermore, the blade widths of each first-stage blade 21 and each second-stage blade 31 are staggered in the axial direction. This restricts the chord length of each section of the first-stage blade 21 and the second-stage blade 31, reducing the probability of vortices forming on their surfaces during rotation. This, in turn, reduces the drag on the airflow, contributing to improved aerodynamic efficiency of the impeller. In addition, the axial staggering of the first-stage blade 21 and the second-stage blade 31 prevents interference during demolding, eliminating the need for complex core-pulling molds for integral molding. This simplifies mold design and manufacturing, and reduces production costs.

[0036] It should be noted that when the impeller's ejection form is not limited, the second-stage blade 31 is located in the middle of the flow channel formed by two adjacent first-stage blades 21. At this position, the second-stage blade 31 can minimize the airflow's passage area at the trailing edge of the flow channel, thus giving the impeller good aerodynamic efficiency.

[0037] like Figure 4 As shown, in this embodiment, both the first-stage blade 21 and the second-stage blade 31 are torsional blades. The first-stage blade 21 and the second-stage blade 31 are inclined from the blade root 51 to the blade tip 5 towards the impeller's rotation direction and towards the impeller's inlet side. Furthermore, the blades are inclined from the leading edge 52 to the trailing edge 53 towards the pressure surface in the axial direction of the hub 4. This inclined blade design allows the blades to better conform to the airflow direction, reducing airflow separation on the blade surface during rotation and preventing the formation of vortices and impacts on the blade surface. The suction surface of the blade is a convex curved surface, and the pressure surface is a concave curved surface. The convex curved surface allows the airflow to adhere to the blade surface when entering the flow channel, reducing the risk of airflow separation at the blade's leading edge 52; the concave curved surface increases the effective contact area of ​​the blade with the airflow, thereby enhancing the blade's work capacity during rotation.

[0038] Furthermore, the thickness of the first-stage blade 21 and the second-stage blade 31 gradually decreases from the blade root 51 to the blade tip 5 to ensure the connection strength between the blade and the hub 4 and to improve the blade's resistance to deformation.

[0039] Furthermore, the leading edge 52 of the blade has a blunt edge structure with a rounded transition, which improves the blade's adaptability to different incoming flow directions and reduces airflow separation at the leading edge 52. The trailing edge 53 of the blade has a rounded structure to improve the flow separation effect at the trailing edge 53 and reduce the intensity of the vortex at the trailing edge 53. In addition, the chord length of the tip of the first-stage blade 21 and the second-stage blade 31 is greater than the chord length at the root. This design increases the area of ​​the blade tip 5 that acts on the airflow, improves the pressurization effect of the blade tip 5 on the airflow, and thus helps to increase the overall delivery pressure of the impeller.

[0040] Furthermore, in the circumferential direction, each secondary blade 31 corresponds to the flow channel center of two adjacent primary blades 21, and its leading edge 52 is offset from the trailing edge 53 of the primary blade 21. The trailing edge 53 of the secondary blade 31 is offset from the leading edge 52 of the next primary blade 21. In the axial direction, the leading edge 52 of the secondary blade 31 is located downstream of the trailing edge 53 of the primary blade 21, but is still within the flow channel of two adjacent primary blades 21.

[0041] When the motor drives the hub 4 to rotate, the first-stage blade group 2 and the second-stage blade group 3 rotate synchronously with the hub 4. The airflow is guided into the flow channel of the first-stage blade group 2 through the collector 1. The first-stage blades 21 do work on the airflow, giving it kinetic energy. Since the blades of the second-stage blade group 3 are all embedded in the corresponding flow channels of the first-stage blade group 2, the outlet area of ​​each flow channel of the first-stage blade group 2 is partially filled, avoiding the problems of velocity reduction and airflow separation caused by the sudden increase in the outlet area of ​​the single-stage impeller flow channel. This effectively improves the impeller's anti-clogging ability and maximum air volume under high speed and low flow conditions. Then the airflow enters the flow channel of the second-stage blade group 3, where the second-stage blades 31 further do work on the airflow. At the same time, since the chord lengths of the first-stage blades 21 and the second-stage blades 31 are relatively small, vortices and flow resistance are significantly reduced. Compared with single-stage impellers and tandem blade axial flow fans, the axial flow fan using this impeller has higher aerodynamic efficiency, which is even more obvious in axial flow fans with small installation angles.

[0042] In different application scenarios, the structure of the two-stage axial flow impeller of the present invention can be adaptively adjusted: in high-flow ventilation scenarios, the number of blades in the first-stage blade group 2 and the second-stage blade group 3 can be increased, and the circumferential spacing between adjacent blades can be reduced; for low-noise scenarios, the airfoil of the two-stage blades can be replaced with a low-noise airfoil, and the radius of the arc of the blade leading edge 52 can be increased to reduce the impact noise of the airflow; in high-pressure scenarios, the diameter of the hub 4 can be increased, and the installation angle of the blades can be increased to enhance the impeller's work capacity; for lightweight scenarios, one-piece injection molded blades can be used to reduce the weight of the impeller while ensuring structural strength. In addition, to simplify manufacturing, the blades of the first-stage blade group 2 and the blades of the second-stage blade group 3 can be selected with the same area and shape according to the operating conditions to reduce production costs.

[0043] The working principle of a high-efficiency two-stage axial flow impeller is summarized as follows: During operation, each first-stage blade 21 and each second-stage blade 31 rotates synchronously with the hub 4. The airflow is first guided into the flow channel of the first-stage blade group 2 through the collector 1. Since the blades adopt airfoil structures at different cross-sections from the blade root 51 to the blade tip 5, with concave pressure surfaces and convex suction surfaces, the fluid is first effectively captured and initially pressurized and guided by the blades of the first-stage blade group 2. Secondly, since the second-stage blades 31 are precisely embedded in the middle of the flow channel of two adjacent first-stage blades 21 and are located downstream of the airflow, they can fill the excess space at the end of the first-stage flow channel, avoiding airflow separation and blockage caused by a sudden drop in airflow velocity, thus improving the aerodynamic efficiency of the impeller. At the same time, the staggered layout of the projections of the first-stage blades 21 and the second-stage blades 31 in the axial direction can also reduce the difficulty of manufacturing the mold and reduce production costs.

[0044] Embodiment 2 of a high-efficiency two-stage axial flow impeller provided by the present invention: Its main difference from Example 1 is: In Example 1, the hub, the first-stage blade assembly, and the second-stage blade assembly are integrally formed using injection molding or compression molding processes.

[0045] In this embodiment, the first-stage blade assembly and the second-stage blade assembly are detachably connected to the hub via clips / bolts.

[0046] Embodiment 3 of a high-efficiency two-stage axial flow impeller provided by the present invention: Its main difference from Example 1 is: In Example 1, both the first-stage blade group and the second-stage blade group have 5 blades.

[0047] In this embodiment, the number of blades in the first-stage blade group and the second-stage blade group is at least 2, and the specific number can be adjusted according to the operating conditions.

[0048] An embodiment of a high-efficiency axial flow fan provided by the present invention: A high-efficiency axial flow fan includes a drive motor and a two-stage axial flow impeller as described in Embodiment 1 above. The drive motor is fixedly connected to the collector 1, and its output end is fixedly connected to the hub 4. The drive motor drives the impeller to rotate through the hub 4 to improve the aerodynamic efficiency of the fan.

[0049] Based on the description in this specification, those skilled in the art will also understand that the following terms, such as "upper," "lower," "front," "rear," "left," "right," "horizontal," "top," "bottom," "inner," and "outer," which indicate positional relationships, are based on the positional relationships shown in the accompanying drawings of this specification. They are only for the purpose of facilitating the explanation of the present invention and simplifying the description. Therefore, the above terms should not be construed as limiting the present invention.

[0050] In addition, "multiple" means at least two, such as two, three or more, unless otherwise explicitly specified.

Claims

1. A high-efficiency two-stage axial flow impeller, characterized in that, It includes a collector, a hub, a first-stage blade group, and a second-stage blade group. The hub is installed at the center of the collector. The first-stage blade group and the second-stage blade group are both fixed on the hub and rotate synchronously with the hub. The blades of the second-stage blade group are embedded in the flow channel formed by two adjacent blades of the first-stage blade group. The first-stage blade group and the second-stage blade group have the same number of blades, and the number of blades is at least two.

2. The high-efficiency two-stage axial flow impeller according to claim 1, characterized in that, The blades of the second-stage blade group are arranged in the middle of the flow channel streamline of two adjacent blades of the first-stage blade group, and the blades of the second-stage blade group are located downstream of the first-stage blade group.

3. The high-efficiency two-stage axial flow impeller according to claim 2, characterized in that, Both the blades of the first-stage blade group and the blades of the second-stage blade group are inclined from the blade root to the blade tip toward the rotation direction of the impeller and toward the inlet side of the impeller. The blades are also inclined from the leading edge to the trailing edge toward the pressure surface in the axial direction of the hub. The suction surface of the blade is an outwardly convex curved surface, and the pressure surface of the blade is an inwardly concave curved surface, in order to improve the aerodynamic efficiency of the blade rotation.

4. A high-efficiency two-stage axial flow impeller according to any one of claims 1-3, characterized in that, The root thickness of the blades in the first-stage blade group and the second-stage blade group is greater than the tip thickness of the blades to improve the connection strength between the blades and the hub.

5. A high-efficiency two-stage axial flow impeller according to any one of claims 1-3, characterized in that, The leading edge of the blade has a blunt edge structure with a rounded transition to reduce airflow separation at the leading edge; the trailing edge of the blade has a rounded structure to reduce the intensity of trailing edge vortices.

6. The high-efficiency two-stage axial flow impeller according to claim 1, characterized in that, The hub and each blade are integrally formed using injection molding or compression molding processes.

7. A high-efficiency two-stage axial flow impeller according to claim 6, characterized in that, The blades of the first-stage blade group and the blades of the second-stage blade group are staggered in the axial direction of the hub to reduce the difficulty of demolding the impeller.

8. A high-efficiency two-stage axial flow impeller according to claim 3, characterized in that, The chord length at the tip of the blade is greater than the chord length at the root of the blade to increase the impeller's work capacity and improve fluid pressure.

9. A high-efficiency two-stage axial flow impeller according to any one of claims 1, characterized in that, Both the blades of the first-stage blade group and the blades of the second-stage blade group are detachably connected to the hub.

10. A high-efficiency axial flow fan, characterized in that, Includes the two-stage axial flow impeller as described in any one of claims 1-9.

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