Low-noise axial flow fan blade and impeller structure using same

Abstract

The application relates to the technical field of fan blades, in particular to a low-noise axial fan blade and an impeller structure applying the same, which comprises a blade main body; the blade main body is in a sheet structure, the blade main body has a pressure surface and a back pressure surface, and the peripheral contour of the blade main body is formed by a blade root edge, a blade leading edge, a blade outer edge and a blade tail edge; the blade tail edge is provided with a recessed part and a protruding part, the curvature of the recessed part and the curvature of the protruding part are discontinuously arranged; the blade outer edge is folded from the pressure surface to the back pressure surface to obtain a flow guide flange part, the axial width W of the flow guide flange part is greater than the axial width of the blade tail edge 翻边 and gradually decreases from one end of the blade tail edge to one end of the blade leading edge. The application solves the technical problems of noise and energy consumption existing in the prior art by improving the design of the blade structure.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fan blades, in particular to a low-noise axial fan blade and an impeller structure using the same. BACKGROUND

[0002] As a fluid machine widely used in industrial and civil fields, the noise problem of the axial fan has long been a key factor restricting the performance of the product and the user experience. During the operation of the traditional axial fan, due to the fluid dynamics phenomena such as airflow separation on the blade surface, trailing edge vortex shedding, and tip leakage vortex, significant aerodynamic noise will be generated, including discrete frequency noise (rotational noise) and broadband noise (turbulence noise). These noises not only affect the comfort of the working environment, but also may cause hearing damage to the operators, and in some precision instrument and equipment supporting scenarios, too high noise level may even interfere with the normal operation of the equipment.

[0003] In the prior art, the following methods are mainly used for noise control of the axial fan: 1. Optimizing the blade airfoil (such as using backward or forward sweep design) to improve airflow distribution and reduce tip vortex intensity; 2. Setting a muffler at the inlet and outlet of the fan, but this passive noise reduction method increases system resistance and energy consumption; 3. Improving the blade material (such as using composite material) to reduce vibration noise, but the cost is high and the effect of suppressing aerodynamic noise is limited. However, these methods still have certain limitations, for example, airfoil optimization may lead to a decrease in fan efficiency, and the use of a muffler increases the equipment size and maintenance cost.

[0004] Especially in the trailing edge region of the blade, the Karman vortex street generated by fluid separation is the main source of broadband noise, and the traditional continuous smooth trailing edge design cannot effectively suppress vortex shedding. At the same time, the leakage flow in the tip region forms a high-intensity rotating vortex, which not only produces noise but also reduces the efficiency of the fan. In addition, the planar structure of the existing blade outer edge cannot effectively guide and control the complex airflow flow in the tip region, resulting in difficulty in effectively improving the noise and energy consumption problems. Therefore, it is particularly necessary to design a low-noise axial fan blade that can optimize these key regions. SUMMARY

[0005] One purpose of the present application is to provide a low-noise axial fan blade, which improves the noise and energy consumption of the existing blade by improving the design of the blade structure.

[0006] Another purpose of the present application is to provide an impeller structure using the above low-noise axial fan blade, which can reduce noise and ensure the aerodynamic performance of the fan.

[0007] To achieve this purpose, the present application adopts the following technical solutions:

[0008] A low-noise axial fan blade, comprising a blade body;

[0009] The blade body is in a sheet structure, the blade body has a pressure surface and a back pressure surface, and the peripheral contour of the blade body is enclosed by a blade root edge, a blade leading edge, a blade outer edge and a blade trailing edge;

[0010] The blade trailing edge is provided with a recess and a protrusion, and the curvature of the recess and the curvature of the protrusion are discontinuous;

[0011] The blade outer edge is folded towards the back pressure surface from the pressure surface to obtain a flow guide flange, and the axial width W 翻边 The blade trailing edge gradually narrows from one end of the blade trailing edge to one end of the blade leading edge.

[0012] Preferably, the connection points between the blade root edge, the blade leading edge, the blade outer edge and the blade trailing edge are defined as design point A, design point B, design point C and design point D in sequence;

[0013] The blade root edge is controlled by a curve AB, and the blade outer edge is controlled by a curve CD, the curve AB and the curve CD are concentric arcs with the same center O, and the radius of the curve AB is smaller than the radius of the curve CD, and the arc length of the curve AB is smaller than the radius of the curve CD;

[0014] The angle ∠AOB formed by the design point A, the center O and the design point B is defined as α;

[0015] The angle ∠AOC formed by the design point A, the center O and the design point C is defined as α1;

[0016] The angle ∠AOD formed by the design point A, the center O and the design point D is defined as α2,

[0017] Wherein, 65°<α<75°;

[0018] 1.6<t1<1.63, t1 is a constant;

[0019] 0.52<t2<0.55, t2 is a constant.

[0020] Preferably, the straight line connecting the center O and the design point B is defined as straight line OB, a point on the extension line of the straight line OB is defined as design point I, the straight line connecting the design point B and the design point C is defined as straight line BC, a parallel line HI passing through the design point I and parallel to the straight line BC is drawn, and a point on the parallel line HI is defined as design point H;

[0021] Define the angle ∠HCB formed by the design points H, C and B as β1;

[0022] Define the included angle ∠IBC formed by the design points I, B, and C as β2;

[0023] Define the linear distance between the line BC and the parallel line HI as l1;

[0024] Among them, 40°<β1<45°, 50°<β2<55°, and 70mm<l1<74mm.

[0025] Preferably, the straight line connecting the center O and the design point A is defined as the straight line OA, a point on the extension of the straight line OA is defined as the design point K, the straight line connecting the design point A and the design point D is defined as the straight line AD, a parallel line JK passing through the design point K and parallel to the straight line AD is drawn, and a point on the parallel line JK is defined as the design point J.

[0026] Define the included angle ∠JDK formed by the design points J, D and A as β3;

[0027] Define the included angle ∠KAD formed by the design points K, A, and D as β4;

[0028] Define the linear distance between the line AD and the parallel line JK as l2;

[0029] Among them, 40°<β3<45°, 50°<β4<55°, and 32mm<l2<36mm.

[0030] Preferably, the five points on the trailing edge of the blade are defined as design point U, design point E, design point F, design point G and design point Q. The distribution order of design point U, design point E, design point F, design point G and design point Q is from design point A to design point D. The trailing edge of the blade is controlled and set by curve AUE, curve EFG, curve FGQ and straight line DQ.

[0031] Both curves AUE and FGQ are convex arcs, and design points U and G are the convex points of curves AUE and FGQ, respectively. Curve FGQ forms the convex portion.

[0032] The curve EFG is a concave arc, the design point F is the concave point of the curve EFG, and the curve EFG forms the concave part;

[0033] Define the included angle ∠AOB formed by the design point A, the center O, and the design point B as Φ1;

[0034] Define the included angle ∠AOU formed by the design point A, the center O, and the design point U as Φ2;

[0035] Define the angle ∠AOG formed by the design point A, the center O, and the design point G as Φ3;

[0036] Define the angle ∠AOF formed by the design point A, the center O, and the design point F as Φ4;

[0037] Where 65° < Φ1 < 75°, , 0.06 < m1 < 0.1, , 0.38 < m2 < 0.42, 0.43 < m3 < 0.46, where m1, m2, and m3 are all constants.

[0038] Preferably, a point on the leading edge of the blade is defined as the design point P, and the leading edge of the blade is controlled and set by the curve BP and the straight line PC;

[0039] The design point P and the design point Q are connected to form a curve PQ. The curve PQ and the curve CD enclose a region CPDQ. The region CPDQ is used to fold the outer edge of the blade from the pressure surface toward the back pressure surface to obtain the flow guide flange.

[0040] A polar coordinate system is established with the center O of the circle as the pole. The coordinates of the design point P in the polar coordinate system are defined as P(r1, θ1). The midpoint of the curve PQ is defined as the design point S. The coordinates of the design point S in the polar coordinate system are defined as S(r2, θ2). The coordinates of the design point Q in the polar coordinate system are defined as Q(r3, θ3).

[0041] The fitting curve function for curve PQ is defined as r(θ) = Xθ. 2 +Yθ+Z;

[0042] Where 0.002 < X < 0.0032, -0.95 < Y < -0.75, 317 < Z < 325, and X, Y, and Z are all constants.

[0043] Preferably, the angle at which the outer edge of the blade folds from the pressure surface toward the back pressure surface is defined as the folding angle θ4 of the guide flange.

[0044] Where 8°≤θ4≤15°.

[0045] An impeller structure includes a hub and a plurality of low-noise axial flow fan blades as described above, wherein the plurality of low-noise axial flow fan blades are uniformly distributed along the axial direction of the hub.

[0046] In several types of low-noise axial flow fan blades, the center O of the circle is arranged to coincide with the rotation axis O' of the hub.

[0047] Preferably, the radius of the wheel hub is defined as R1;

[0048] Define the straight-line distance between the design point A and the rotation axis O' as R. A The unit is mm;

[0049] Define the straight-line distance between the design point U and the rotation axis O' as R. U The unit is mm;

[0050] Define the straight-line distance between the design point F and the rotation axis O' as R. F The unit is mm;

[0051] Define the straight-line distance between the design point G and the rotation axis O' as R. G The unit is mm;

[0052] Among them, R A =R1, , 0.42 < n1 < 0.47, , 0.8 < n² < 0.84, , 0.87 < n3 < 0.89, n1, n2 and n3 are all constants.

[0053] Preferably, the straight-line distance from the rotation axis O' to the curve CD is defined as the radius R2 of the impeller structure, in mm;

[0054] Define the axial width W of the guide flange. 翻边 The unit is mm;

[0055] Among them, W 翻边 = (8% - 15%)R2.

[0056] One of the above technical solutions has the following beneficial effects:

[0057] 1. In terms of noise reduction, the discontinuous recesses and protrusions at the blade trailing edge disrupt the periodicity of the Karman vortex street, significantly reducing broadband noise and compensating for the shortcomings of traditional trailing edge designs in suppressing vortex shedding. The guide flange effectively reduces the rotating vortex noise generated by the tip leakage flow and works synergistically with the blade trailing edge structure to further enhance the noise reduction effect. Compared with existing passive noise reduction methods such as silencers, this method does not require increased system resistance or equipment size, resulting in more efficient noise reduction without affecting the smooth operation of the fan.

[0058] 2. In terms of improving efficiency, the guide flange suppresses tip leakage flow, reduces energy loss, and avoids the efficiency reduction problem caused by leakage flow in traditional blades. At the same time, its synergistic effect with the trailing edge structure suppresses local airflow separation, ensuring that the airflow can drive the blade to do work more efficiently, and solving the efficiency reduction problem that may accompany airfoil optimization.

[0059] 3. In terms of cost, there is no need to use high-cost composite materials. Noise reduction and efficiency improvement are achieved through structural optimization, thereby reducing production costs. The overall blade structure design is simple and can be directly adapted to the existing axial flow fan installation structure. There is no need to make major modifications to the fan casing and other components, which facilitates promotion and application. It can meet the needs of various scenarios such as industry and civil use for low-noise and high-efficiency fans, and is especially suitable for scenarios where precision instruments and equipment are sensitive to noise. Attached Figure Description

[0060] Figure 1 This is an axial projection view of a low-noise axial flow fan blade according to the present invention;

[0061] Figure 2 This is a design schematic diagram of design points A, B, C, and D in a low-noise axial flow fan blade according to the present invention.

[0062] Figure 3 This is a design schematic diagram of design points U, F, and G in a low-noise axial flow fan blade according to the present invention.

[0063] Figure 4 This is a design schematic diagram of design points P, S and Q in a low-noise axial flow fan blade according to the present invention;

[0064] Figure 5 This is a schematic diagram of the design of the flow guide folding part in the blade of a low-noise axial flow fan according to the present invention;

[0065] Figure 6 This is an axial projection view of an impeller structure using low-noise axial flow fan blades according to the present invention;

[0066] Figure 7 This is a power comparison chart between the present invention and the prior art under the same air volume;

[0067] Figure 8 This is a noise comparison chart between the present invention and the prior art under the same airflow.

[0068] In the attached diagram: 1. Blade root edge; 2. Blade leading edge; 3. Blade outer edge; 4. Blade trailing edge; 5. Recess; 6. Protrusion; 7. Guide flange; 10. Low-noise axial flow fan blade; 10. Pressure surface; 101. Back pressure surface; 102. Hub. Detailed Implementation

[0069] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0070] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to 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.

[0071] 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, unless otherwise stated, "a plurality of" means two or more.

[0072] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0073] A low-noise axial flow fan blade, comprising a blade body;

[0074] The blade body has a sheet-like structure, and the blade body has a pressure surface 101 and a back pressure surface 102. The peripheral contour of the blade body is formed by the leaf root edge 1, the leaf leading edge 2, the leaf outer edge 3 and the leaf trailing edge 4.

[0075] The leaf trailing edge 4 has a recessed portion 5 and a protruding portion 6, and the curvature of the recessed portion 5 and the curvature of the protruding portion 6 are not continuous.

[0076] The outer edge 3 of the blade folds from the pressure surface 101 toward the back pressure surface 102 to form a flow guide flange 7, the axial width of the flow guide flange 7 being W. 翻边 It gradually narrows from one end of the leaf trailing edge 4 to one end of the leaf leading edge 2.

[0077] The low-noise axial flow fan blades of this invention address the noise and efficiency problems of axial flow fans in the prior art by optimizing the structure of the blade trailing edge 4 and the outer edge 3, such as...Figure 1 and Figure 5 As shown.

[0078] In the blade trailing edge region, the traditional continuous and smooth trailing edge 4 is prone to forming a Karman vortex street, generating broadband noise. However, in this technical solution, the recessed portion 5 and the protruding portion 6 of the trailing edge 4 are designed with discontinuous curvature. When airflow passes over the trailing edge 4, the recessed portion 5 reduces the pressure gradient between the pressure surface 101 and the back pressure surface 102, suppressing fluid separation; the protruding portion 6 changes the airflow direction. Together, they break the periodicity of vortex shedding, dispersing the concentrated vortex shedding energy over a wider frequency range, avoiding excessively high broadband noise peaks, and reducing broadband noise generation at its source.

[0079] For the blade tip region, the existing planar structure of the blade's outer edge cannot effectively control leakage flow, leading to high-intensity rotating vortices generating noise and reducing efficiency. In this technical solution, the blade's outer edge 3 folds from the pressure surface 101 towards the back pressure surface 102 to form a guide flange 7, and its axial width W... 翻边 The blade gradually increases in width from one end of the leading edge 2 to the other end of the trailing edge 4. This design can adapt to the dynamic changes in airflow at the blade tip from inflow to outflow, acting like a "flow guide barrier" to guide the orderly flow of leakage flow at the blade tip and suppress the formation of high-intensity rotating vortices. At the same time, the gradually increasing width design makes the airflow in the blade tip region smoother, reducing the additional noise and energy loss caused by flow obstruction.

[0080] Furthermore, the guide flange 7, together with the recessed portion 5 and the protruding portion 6 of the blade trailing edge 4, forms a synergistic flow field. The guide flange 7 guides the airflow smoothly toward the blade trailing edge 4, while the protruding portion 6 accelerates the boundary layer flow, suppresses the local airflow separation that may be induced by the recessed portion 5, further reduces the intensity of vortex shedding, and enhances the noise reduction effect.

[0081] To further explain, the connection points between the leaf root edge 1, leaf leading edge 2, leaf outer edge 3, and leaf trailing edge 4 are defined as design point A, design point B, design point C, and design point D, respectively.

[0082] The leaf root edge 1 is controlled by curve AB, and the leaf outer edge 3 is controlled by curve CD. Curve AB and curve CD are concentric arcs with the same center O, and the radius of curve AB is smaller than the radius of curve CD, and the arc length of curve AB is smaller than the radius of curve CD.

[0083] Define the angle ∠AOB formed by the design point A, the center O, and the design point B as α;

[0084] Define the angle ∠AOC formed by the design point A, the center O, and the design point C as α1;

[0085] Define the angle ∠AOD formed by the design point A, the center O, and the design point D as α2.

[0086] Where 65° < α < 75°;

[0087] 1.6 < t1 < 1.63, where t1 is a constant;

[0088] , 0.52 < t2 < 0.55, where t2 is a constant.

[0089] like Figure 2 As shown, the leaf root edge 1 is controlled by curve AB, and the leaf outer edge 3 is controlled by curve CD. The two are concentric arcs. This concentric design ensures that the twist angle of the leaf body from the root to the outer edge presents a regular change.

[0090] ∠AOB, or α, is set between 65° and 75°. This angle range determines the curvature and length of the control curve AB of the blade root edge 1. A reasonable α value allows the blade root edge 1 to better fit the wind turbine hub, enabling the airflow to smoothly transition from the hub to the blade body, reducing impact noise and energy loss caused by sudden airflow changes, and laying the foundation for overall airflow guidance of the blade.

[0091] ∠AOC, or α1, is 1.6-1.63 times α. Since curves AB and CD are concentric arcs, α1 determines the position of the control curve CD of the outer edge 3 relative to the control curve AB of the root edge 1. This proportional relationship allows the outer edge 3 to extend appropriately in the radial direction. Combined with the radius difference between the root edge 1 and the outer edge 3, the blade's twist angle is further optimized, resulting in a more uniform airflow distribution on the blade surface, reducing airflow separation, and enhancing the blade's propulsion efficiency.

[0092] ∠AOD, where α2 is 0.52-0.55 times α, determines the position of the design point D relative to the design point A of the blade trailing edge 4. This setting places the recessed portion 5 and the raised portion 6 of the blade trailing edge 4 in a more reasonable circumferential position, matching the layout of the leading edge 2 and the outer edge 3, ensuring that the airflow can smoothly exit from the blade trailing edge 4 after passing through the blade. Combined with the effect of the recessed portion 5 and the raised portion 6, it more effectively breaks up the vortex in the wake region and reduces the intensity of vortex shedding.

[0093] To further explain, the straight line connecting the center O and the design point B is defined as line OB, a point on the extension of line OB is defined as design point I, the straight line connecting the design point B and the design point C is defined as line BC, a parallel line HI is drawn that passes through the design point I and is parallel to line BC, and a point on the parallel line HI is defined as design point H.

[0094] Define the angle ∠HCB formed by the design points H, C and B as β1;

[0095] Define the included angle ∠IBC formed by the design points I, B, and C as β2;

[0096] Define the linear distance between the line BC and the parallel line HI as l1;

[0097] Among them, 40°<β1<45°, 50°<β2<55°, and 70mm<l1<74mm.

[0098] like Figure 2 As shown, optimization is performed in the connection area between the leading edge 2 and the outer edge 33 of the blade: the straight line BC is an important design line for design point C, and the parallel line HI passing through design point I and parallel to the straight line BC, as well as the setting of design point H, provide a precise geometric reference for the design of design point C. ∠HCB, i.e., β1, is controlled at 40°-45°, and ∠IBC, i.e., β2, is controlled at 50°-55°. The combination of these two angles optimizes the profile curvature of the leading edge 2. When airflow flows in from the leading edge 2, this angle range allows the airflow to transition more smoothly from the leading edge 2 to the outer edge 3, reducing airflow separation and turbulence caused by excessively sharp corners, and lowering the resulting aerodynamic noise.

[0099] The design point I on the extension of straight line OB and the parallel line HI, as well as the 70mm-74mm distance l1 between straight line BC and parallel line HI, provide a reasonable spatial dimension for the design of the blade leading edge 2. This distance ensures that the blade leading edge 2 has sufficient width and curvature near the blade root edge 1, which can better capture and guide the airflow, allowing the airflow to form a stable flow state before entering the blade body. This lays the foundation for smooth flow on the blade pressure surface 101 and back pressure surface 102, and further reduces noise and energy loss caused by airflow turbulence.

[0100] To further explain, the straight line connecting the center O of the circle and the design point A is defined as the straight line OA, a point on the extension of the straight line OA is defined as the design point K, the straight line connecting the design point A and the design point D is defined as the straight line AD, a parallel line JK passing through the design point K and parallel to the straight line AD is drawn, and a point on the parallel line JK is defined as the design point J.

[0101] Define the included angle ∠JDK formed by the design points J, D and A as β3;

[0102] Define the included angle ∠KAD formed by the design points K, A, and D as β4;

[0103] Define the linear distance between the line AD and the parallel line JK as l2;

[0104] Among them, 40°<β3<45°, 50°<β4<55°, and 32mm<l2<36mm.

[0105] like Figure 2 As shown, further optimization is performed in the connection area between the blade root edge 1 and the blade trailing edge 4: ∠JDK, i.e., β3, is at 40°-45°, and ∠KAD, i.e., β4, is at 50°-55°. At the same time, the parallel line JK, which passes through the design point K and is parallel to the straight line AD, provides a reference for the two design points A and D at the two ends of the blade trailing edge 4, making the curvature change of the blade trailing edge 4 in this region more in line with the airflow characteristics, and further reducing the generation of turbulence.

[0106] The distance l2 between the straight line AD and the parallel line JK is set at 32mm-36mm. This distance parameter, in conjunction with the structural design of the leading edge 2, provides suitable space for airflow near the root edge 1. It ensures that the airflow has sufficient channel to flow through the area connecting the root edge 1 and the trailing edge 4, avoiding airflow congestion caused by limited space, allowing the airflow to pass through this area more smoothly and reducing energy loss.

[0107] To further explain, the five points on the blade trailing edge 4 are defined as design point U, design point E, design point F, design point G and design point Q. The distribution order of design point U, design point E, design point F, design point G and design point Q is from design point A to design point D. The blade trailing edge 4 is controlled and set by curve AUE, curve EFG, curve FGQ and straight line DQ.

[0108] Both curves AUE and FGQ are convex arcs, and design points U and G are the convex points of curves AUE and FGQ, respectively. Curve FGQ forms the protrusion 6.

[0109] The curve EFG is a concave arc, the design point F is the concave point of the curve EFG, and the curve EFG forms the concave portion 5;

[0110] Define the included angle ∠AOB formed by the design point A, the center O, and the design point B as Φ1;

[0111] Define the included angle ∠AOU formed by the design point A, the center O, and the design point U as Φ2;

[0112] Define the angle ∠AOG formed by the design point A, the center O, and the design point G as Φ3;

[0113] Define the angle ∠AOF formed by the design point A, the center O, and the design point F as Φ4;

[0114] Where 65° < Φ1 < 75°, , 0.06 < m1 < 0.1, , 0.38 < m2 < 0.42, 0.43 < m3 < 0.46, where m1, m2, and m3 are all constants.

[0115] like Figure 3 As shown, when m1 is in the range of 0.06-0.1, the geometry of the recess 5 can effectively reduce the pressure gradient at the recess, prevent airflow separation due to sudden pressure changes, and thus suppress turbulent noise. If it exceeds this range, it will lead to pressure distribution imbalance and decreased flow stability.

[0116] When ∠AOG (i.e., Φ3) is too small, the geometric features of the protrusion 6 are not obvious, and it cannot effectively guide the airflow, weakening the boundary layer control capability. This may lead to flow separation and increase turbulence noise. When m2 > 0.42, the height or angle of the protrusion is too large, which may locally accelerate the airflow and form a high-pressure zone, causing airflow stripping or high-frequency vortex shedding, which in turn aggravates the noise.

[0117] When m3 < 0.43, an excessively small angle will result in insufficient geometric spacing between the design point F on the recess 5 and the design point on the blade root edge 1. This prevents the large-scale vortices in the blade trailing edge region from being adequately broken up in a structured manner, reducing the noise reduction effect. Furthermore, an excessively small angle may weaken the guiding effect of the recess 5, causing local backflow or separation of the airflow near the blade trailing edge region, increasing turbulent noise. When m3 > 0.46, an excessively large angle may make the geometric configuration of the recess 5 too gentle, leading to an increased pressure gradient in the recess 5, which in turn exacerbates airflow separation and triggers high-frequency noise.

[0118] To further explain, a point on the leading edge 2 of the blade is defined as the design point P, and the leading edge 2 of the blade is controlled and set by the curve BP and the straight line PC;

[0119] The design point P and the design point Q are connected to form a curve PQ. The curve PQ and the curve CD enclose a region CPDQ. The region CPDQ is used to fold the outer edge 3 of the blade from the pressure surface 101 toward the back pressure surface 102 to obtain the flow guide flange 7.

[0120] A polar coordinate system is established with the center O of the circle as the pole. The coordinates of the design point P in the polar coordinate system are defined as P(r1, θ1). The midpoint of the curve PQ is defined as the design point S. The coordinates of the design point S in the polar coordinate system are defined as S(r2, θ2). The coordinates of the design point Q in the polar coordinate system are defined as Q(r3, θ3).

[0121] The fitting curve function for curve PQ is defined as r(θ) = Xθ. 2 +Yθ+Z;

[0122] Where 0.002 < X < 0.0032, -0.95 < Y < -0.75, 317 < Z < 325, and X, Y, and Z are all constants.

[0123] like Figure 4 As shown, 0.002 < X < 0.0032, X is too small, the curve PQ is close to flat, resulting in insufficient acceleration and difficulty in suppressing the wake vortex; X is too large, the flange changes too quickly, which can easily induce re-separation; -0.95 < Y < -0.75, Y is too small, the contraction is too fast, which can easily form a back pressure gradient; Y is too large, the guide flange 7 is too slow, which cannot form effective guidance; 317 < Z < 325, Z is too small, the curve PQ cannot effectively connect the blade trailing edge 4; Z is too large, the curve PQ will highlight the mainstream shape and disturb the airflow direction.

[0124] This curve function defines the contraction trajectory of the inner edge of the guide flange 7, which, together with curve CD, encloses a flange region with a continuous shape but a non-constant width. Viewed from the axial projection plane, the guide flange 7 exhibits a typical tapering profile: from the curve DQ region of the blade trailing edge 4 to the curve CP region of the blade leading edge 2, the axial width W of the guide flange 7... 翻边 The area gradually shrinks, with the narrowest region on curve CP and the widest region on curve DQ, thus forming an overall flange structure that gradually shrinks in width and has non-uniform spacing.

[0125] To further explain, the angle at which the outer edge 3 of the blade folds from the pressure surface 101 toward the back pressure surface 102 is defined as the folding angle θ4 of the guide flange portion 7;

[0126] Where 8°≤θ4≤15°.

[0127] like Figure 5 As shown, when the airflow passes through the outer edge 3 of the blade, the folding angle θ4 determines the blocking and guiding force of the guide flange 7 on the tip leakage flow. If the angle is too small, i.e., θ4 is less than 8°, the constraint ability of the guide flange 7 on the leakage flow is insufficient, making it difficult to effectively suppress the formation of tip vortices; if the angle is too large, i.e., θ4 is greater than 15°, it will increase the airflow resistance, leading to local airflow turbulence, which may generate new noise sources. A folding angle of 8°-15° can effectively block the tip leakage flow while guiding the airflow to flow smoothly along the guide flange 7, allowing it to move more smoothly toward the trailing edge 4, forming a better flow field synergy with the concave part 5 and the convex part 6 of the trailing edge 4, further enhancing the suppression effect on vortex shedding.

[0128] This angle design, combined with the previously mentioned width gradient characteristic, allows the guide flange to provide appropriate guiding force according to the dynamic changes of airflow throughout the entire extension process from the leading edge to the trailing edge 4 of the blade. This ensures that the airflow in the blade tip area always maintains a stable and orderly flow state, reducing noise and energy loss caused by airflow turbulence.

[0129] An impeller structure includes a hub 20 and a plurality of low-noise axial flow fan blades 10 as described above, wherein the plurality of low-noise axial flow fan blades 10 are uniformly distributed along the axial direction of the hub 20.

[0130] In a certain type of low-noise axial flow fan blade 10, the center O is arranged to coincide with the rotation axis O' of the hub 20.

[0131] like Figure 6 As shown, this impeller structure consists of a hub 20 and several low-noise axial flow fan blades 10. The blades 10 are evenly distributed along the hub axis, and the center O of the blades coincides with the rotation axis O' of the hub. This design allows the blades 10 to form a coordinated and orderly flow field when rotating.

[0132] When the hub 20 drives the blades 10 to rotate, since the center 0 of the blades coincides with the rotation axis 0' of the hub, the motion trajectory of each blade 10 unfolds around the same axis, ensuring the uniformity of the airflow channels between the blades 10. The blades 10 are evenly distributed along the axial direction, so that the airflow can be evenly distributed between each blade after entering the impeller, avoiding local airflow congestion or thinning caused by uneven blade distribution.

[0133] Meanwhile, the recessed portion 5, the protrusion 6, and the guide flange 7 of the blade itself, rotating around a unified axis, form a synergistic flow field. The gradually widening guide flange 7 effectively suppresses tip leakage vortices, while the discontinuous recessed portion 5 and the protrusion 6 break up vortices in the wake region. These effects of each blade superimpose to further enhance the guidance and noise reduction of the airflow, allowing the airflow to flow more smoothly over the impeller.

[0134] To further clarify, the radius of the wheel hub is defined as R1;

[0135] Define the straight-line distance between the design point A and the rotation axis O' as R. A The unit is mm;

[0136] Define the straight-line distance between the design point U and the rotation axis O' as R. U The unit is mm;

[0137] Define the straight-line distance between the design point F and the rotation axis O' as R. F The unit is mm;

[0138] Define the straight-line distance between the design point G and the rotation axis O' as R. G The unit is mm;

[0139] Among them, R A =R1, , 0.42 < n1 < 0.47, , 0.8 < n² < 0.84, , 0.87 < n3 < 0.89, n1, n2 and n3 are all constants.

[0140] like Figure 6 As shown, when n1 is in the range of 0.42-0.47, the concave part 5 and the convex part 6 work together to cause the vortex to break in a regular manner.

[0141] When n2 < 0.8, the design point F on the recess 5 is too close to the hub 20, resulting in insufficient vortex intervention capability in the blade trailing edge 4 region. When n2 > 0.84, the design point F on the recess 5 is too close to the blade trailing edge 4, which may destroy the streamline profile of the blade and increase the risk of local airflow separation.

[0142] When n3 is in the range of 0.87-0.89, the radial position of the design point G on the protrusion 6 can optimize the airflow distribution. The protrusion 6 near the blade trailing edge 4 accelerates the local airflow through streamlined design, suppresses boundary layer separation, reduces turbulence noise, and avoids the formation of high-pressure areas due to excessive distance, thus maintaining the uniformity of pressure distribution on the blade surface.

[0143] To further clarify, the straight-line distance from the rotation axis O' to the curve CD is defined as the radius R2 of the impeller structure, in mm;

[0144] Define the axial width W of the guide flange. 翻边 The unit is mm;

[0145] Among them, W 翻边 = (8% - 15%)R2.

[0146] like Figure 6 As shown, the axial width W of the guide flange 7 翻边 The ratio is set to 8%-15% of the impeller structure radius R2. This ratio works in conjunction with the folding angle θ4 to further optimize airflow control in the blade tip region.

[0147] From the overall impeller dimensions, W 翻边 The R2 ratio design ensures that the guide flange can effectively guide airflow in impellers of different sizes. For impellers with larger radii, W... 翻边Proportionally increasing the size provides sufficient blocking and guiding area for a stronger leakage flow at the blade tip, preventing leakage flow control failure due to insufficient flange width; for impellers with smaller radii, W 翻边 Reducing the size proportionally can prevent the airflow channel from becoming too narrow due to excessively wide flanges and reduce unnecessary flow resistance.

[0148] When airflow passes through the blade tip region, this width of the guide flange can create a more precise flow field match with the recessed portion 5 and the raised portion 6 of the blade trailing edge. The axial width W of the guide flange 7 翻边 This not only ensures effective interception of the leaking flow at the blade tip, but also provides sufficient space for the smooth transition of the airflow to the protrusion 6 on the trailing edge 4, so that the airflow remains stable during the flow from the blade tip to the trailing edge 4, further weakening the energy of vortex shedding.

[0149] It should be noted that the relationships between the above design points are all calculated under the axial projection of the impeller structure toward the pressure surface 101 of the blade body.

[0150] To further demonstrate the performance of the low-noise axial flow fan blades in this invention when applied to axial flow impellers, conventional blades were used as a comparative example to obtain performance test results of both under the same test conditions.

[0151] The wind turbine performance test results are shown in the table below, and the performance test comparison chart is shown below. Figures 7-8 As shown.

[0152]

[0153] The performance test results of the impeller show that as the rotational speed increases, both conventional and low-noise axial flow impellers generate increasing noise and airflow. However, under the same airflow output conditions, low-noise axial flow impellers exhibit superior overall performance compared to conventional blades. As measured data shows, at the same airflow, the noise level of low-noise axial flow impeller blades is approximately 1.5 dB lower than that of conventional blades. Figure 7 As shown. Meanwhile, the input power of the low-noise axial flow fan blades is reduced by approximately 6.8% compared to existing conventional blades, such as... Figure 8 As shown, a higher level of energy efficiency has been achieved.

[0154] In summary, the application of low-noise axial flow fan blades in this invention to axial flow impellers can improve the overall performance of the equipment.

[0155] The technical principles of the present invention have been described above with reference to specific embodiments. These descriptions are merely for explaining the principles of the invention and should not be construed as limiting the scope of protection of the invention in any way. Based on this explanation, those skilled in the art can readily conceive of other specific embodiments of the invention without inventive effort, and these equivalent variations or substitutions are all included within the scope defined by the claims of this application.

Claims

1. A low-noise axial flow fan blade (10), characterized in that, Including the blade body; The blade body has a sheet-like structure, and the blade body has a pressure surface (101) and a back pressure surface (102). The peripheral contour of the blade body is formed by the leaf root edge (1), the leaf leading edge (2), the leaf outer edge (3) and the leaf trailing edge (4). The leaf tip edge (4) is provided with a recess (5) and a protrusion (6), and the curvature of the recess (5) and the curvature of the protrusion (6) are not continuous. The outer edge (3) of the blade folds from the pressure surface (101) toward the back pressure surface (102) to form a flow guide flange (7), the axial width of the flow guide flange (7) being W 翻边 It gradually narrows from one end of the leaf's trailing edge (4) towards one end of the leaf's leading edge (2); The connection points between the leaf root margin (1), leaf leading margin (2), leaf outer margin (3) and leaf trailing margin (4) are defined as design point A, design point B, design point C and design point D, respectively; The leaf root edge (1) is controlled by curve AB, and the leaf outer edge (3) is controlled by curve CD. Curve AB and curve CD are concentric arcs with the same center O, and the radius of curve AB is smaller than the radius of curve CD, and the arc length of curve AB is smaller than the radius of curve CD. Define the included angle ∠AOB formed by the design point A, the center O, and the design point B as Φ1; Define the angle ∠AOC formed by the design point A, the center O, and the design point C as α1; Define the angle ∠AOD formed by the design point A, the center O, and the design point D as α2. Among them, 65° < Φ1 < 75°; α1 = t1 * Φ1, 1.6 < t1 < 1.63, t1 is a constant; α2 = t2*Φ1, 0.52 < t2 < 0.55, where t2 is a constant.

2. The low-noise axial flow fan blade according to claim 1, characterized in that, Define the straight line connecting the center O of the circle and the design point B as the straight line OB, define a point on the extension of the straight line OB as the design point I, define the straight line connecting the design point B and the design point C as the straight line BC, draw a parallel line HI that passes through the design point I and is parallel to the straight line BC, and define a point on the parallel line HI as the design point H. Define the angle ∠HCB formed by the design points H, C and B as β1; Define the included angle ∠IBC formed by the design points I, B, and C as β2; Define the linear distance between the line BC and the parallel line HI as l1; Among them, 40°<β1<45°, 50°<β2<55°, and 70mm<l1<74mm.

3. The low-noise axial flow fan blade according to claim 2, characterized in that, Define the straight line connecting the center O of the circle and the design point A as the straight line OA, define a point on the extension of the straight line OA as the design point K, define the straight line connecting the design point A and the design point D as the straight line AD, draw a line JK that passes through the design point K and is parallel to the straight line AD, and define a point on the parallel line JK as the design point J. Define the included angle ∠JDK formed by the design points J, D and A as β3; Define the included angle ∠KAD formed by the design points K, A, and D as β4; Define the linear distance between the line AD and the parallel line JK as l2; Among them, 40°<β3<45°, 50°<β4<55°, and 32mm<l2<36mm.

4. The low-noise axial flow fan blade according to claim 1, characterized in that, The five points on the trailing edge (4) of the blade are defined as design point U, design point E, design point F, design point G and design point Q. The distribution order of design point U, design point E, design point F, design point G and design point Q is distributed sequentially from design point A to design point D. The trailing edge (4) of the blade is controlled and set by curve AUE, curve EFG, curve FGQ and straight line DQ. Both curve AUE and curve FGQ are convex arcs. The design point U and design point G are the convex points of curve AUE and curve FGQ, respectively. Curve FGQ forms the convex part (6). The curve EFG is a concave arc, the design point F is the concave point of the curve EFG, and the curve EFG forms the concave part (5); the included angle ∠AOU formed by the design point A, the center O and the design point U is defined as Φ2; Define the angle ∠AOG formed by the design point A, the center O, and the design point G as Φ3; Define the angle ∠AOF formed by the design point A, the center O, and the design point F as Φ4; Where Φ2=m1*Φ1, 0.06<m1<0.1, Φ3=m2*Φ1, 0.38<m2<0.42, Φ4=m3*Φ1, 0.43<m3<0.46, and m1, m2 and m3 are all constants.

5. A low-noise axial flow fan blade according to claim 4, characterized in that, Define a point on the leading edge (2) of the blade as the design point P, and the leading edge (2) of the blade is controlled and set by the curve BP and the straight line PC; The design point P and the design point Q are connected to form a curve PQ. The curve PQ and the curve CD enclose a region CPDQ. The region CPDQ is used to fold the outer edge of the blade (3) from the pressure surface (101) toward the back pressure surface (102) to obtain the flow guide flange (7). A polar coordinate system is established with the center O of the circle as the pole. The coordinates of the design point P in the polar coordinate system are defined as P(r1, θ1). The midpoint of the curve PQ is defined as the design point S. The coordinates of the design point S in the polar coordinate system are defined as S(r2, θ2). The coordinates of the design point Q in the polar coordinate system are defined as Q(r3, θ3). The fitting curve function for curve PQ is defined as r(θ) = Xθ. 2 +Yθ+Z; Where 0.002 < X < 0.0032, -0.95 < Y < -0.75, 317 < Z < 325, and X, Y, and Z are all constants.

6. The low-noise axial flow fan blade according to claim 1, characterized in that, The angle at which the outer edge (3) of the blade folds from the pressure surface (101) toward the back pressure surface (102) is defined as the folding angle θ4 of the guide flange (7); Where 8°≤θ4≤15°.

7. An impeller structure, characterized in that, Includes a hub (20) and a plurality of low-noise axial flow fan blades (10) as described in any one of claims 1-6, wherein the plurality of low-noise axial flow fan blades (10) are uniformly distributed along the circumference of the hub (20); The center O of several of the low-noise axial flow fan blades (10) is set to coincide with the rotation axis O' of the hub (20).

8. The impeller structure according to claim 7, characterized in that, The radius of the hub is defined as R1; Define the straight-line distance between the design point A and the rotation axis O' as R. A The unit is mm; Define the straight-line distance between the design point U and the rotation axis O' as R. U The unit is mm; Define the straight-line distance between the design point F and the rotation axis O' as R. F The unit is mm; Define the straight-line distance between the design point G and the rotation axis O' as R. G The unit is mm; Among them, R A =R1,R U =n1*R1, 0.42<n1<0.47, R F =n2*R1, 0.8 < n2 < 0.84, R G =n3*R1, 0.87<n3<0.89, where n1, n2, and n3 are all constants.

9. The impeller structure according to claim 7, characterized in that, The straight-line distance from the rotation axis O' to the curve CD is defined as the radius R2 of the impeller structure, in mm; Define the axial width W of the guide flange (7). 翻边 The unit is mm; Among them, W 翻边 = (8% - 15%) * R2.

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