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

Abstract

The invention relates to the technical field of fan blades, in particular to a low-noise axial flow fan blade and an impeller structure applying the low-noise axial flow fan blade. The blade main body is of a sheet-shaped structure and is provided with a pressure surface and a back pressure surface, and the peripheral contour of the blade main body is defined by a blade root edge, a blade front edge, a blade outer edge and a blade tail edge; the blade tail edge is provided with a concave part and a convex part, and the radian of the concave part and the radian of the convex part are arranged in a non-continuous mode. The blade outer edge is turned over from the pressure surface to the back pressure surface to obtain a flow guide turnup part, and the axial width W turnup of the flow guide turnup part is gradually reduced from one end of the blade tail edge to one end of the blade front edge. The blade structure is improved and designed, so that the technical problems of noise, energy consumption and the like of an existing blade are solved.

Description

Technical Field

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

[0002] Axial flow fans, a fluid machinery widely used in industrial and civilian applications, have long faced noise challenges that have been a key factor limiting product performance and user experience. During operation, traditional axial flow fans generate significant aerodynamic noise, including discrete frequency noise (rotational noise) and broadband noise (turbulent noise), due to fluid dynamics phenomena such as airflow separation on the blade surface, trailing edge vortex shedding, and tip leakage vortices. This noise not only affects working comfort but can also cause hearing damage to operators. Furthermore, in certain precision instrumentation applications, excessive noise levels can even disrupt normal equipment operation.

[0003] Existing technologies primarily control axial fan noise using the following methods: First, optimizing the blade airfoil (e.g., adopting a swept or forward design) to improve airflow distribution and reduce tip vortex intensity; second, installing mufflers at the fan inlet and outlet, but this passive noise reduction method increases system resistance and energy consumption; and third, improving blade materials (e.g., using composite materials) to reduce vibration noise, but this is costly and has limited effectiveness in suppressing aerodynamic noise. However, these methods still have limitations. For example, airfoil optimization can lead to reduced fan efficiency, and the use of mufflers increases equipment size and maintenance costs.

[0004] Especially in the trailing edge area of ​​the blade, the Karman vortex street generated by fluid separation is the main source of broadband noise, and the traditional continuous and smooth trailing edge design is difficult to effectively suppress vortex shedding. At the same time, the leakage flow in the tip area will form a high-intensity rotating vortex, which not only generates 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 in the tip area, resulting in noise and energy consumption problems that are difficult to effectively improve. Therefore, it is particularly necessary to design a low-noise axial flow fan blade that can be optimized for these key areas. Summary of the Invention

[0005] One purpose of the present invention is to provide a low-noise axial flow fan blade, which solves the technical problems of noise and energy consumption of existing blades by improving the design of the blade structure.

[0006] Another object of the present invention is to provide an impeller structure that uses the above-mentioned low-noise axial flow fan blade to reduce noise while ensuring the aerodynamic performance of the fan.

[0007] To achieve this object, the present invention adopts the following technical solutions: A low-noise axial flow fan blade comprises a blade body; The blade body is a sheet-like structure, and the blade body has a pressure surface and a back pressure surface. The peripheral contour of the blade body is formed by a blade root edge, a blade leading edge, a blade outer edge and a blade trailing edge. The trailing edge of the blade is provided with a concave portion and a convex portion, and the curvature of the concave portion and the curvature of the convex portion are discontinuously arranged; The outer edge of the blade is folded from the pressure surface toward the back pressure surface to form a guide flange portion, and the axial width of the guide flange portion is W 翻边 The diameter of the blade gradually decreases from one end of the trailing edge of the blade to one end of the leading edge of the blade.

[0008] 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; The blade root edge is controlled and set by curve AB, and the blade outer edge is controlled and set 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. The angle ∠AOB formed by the design point A, the circle center O and the design point B is defined as α; The angle ∠AOC formed by the design point A, the center of the circle O and the design point C is defined as α1; Define the angle ∠AOD formed by the design point A, the center of the circle O and the design point D as α2, Among them, 65°<α<75°; , 1.6<t1<1.63, t1 is a constant; , 0.52<t2<0.55, t2 is a constant.

[0009] Preferably, a straight line connecting the center O and the design point B is defined as a straight line OB, a point on the extension line of the straight line OB is defined as a design point I, a straight line connecting the design point B and the design point C is defined as a straight line BC, a parallel line HI is drawn through the design point I and parallel to the straight line BC, and a point on the parallel line HI is defined as a design point H; The angle ∠HCB formed by the design point H, the design point C and the design point B is defined as β1; The angle ∠IBC formed by the design point I, the design point B and the design point C is defined as β2; Define the straight line distance between the straight line BC and the parallel line HI as l1; Among them, 40°<β1<45°, 50°<β2<55°, 70mm<l1<74mm.

[0010] Preferably, a straight line connecting the center O and the design point A is defined as a straight line OA, a point on the extension line of the straight line OA is defined as a design point K, a straight line connecting the design point A and the design point D is defined as a 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 a design point J; The angle ∠JDK formed by the design point J, the design point D and the design point A is defined as β3; The angle ∠KAD formed by the design point K, the design point A and the design point D is defined as β4; Define the straight line distance between the straight line AD and the parallel line JK as l2; Among them, 40°<β3<45°, 50°<β4<55°, 32mm<l2<36mm.

[0011] 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, and the distribution order of the design points U, design point E, design point F, design point G and design point Q is from design point A to design point D, and the trailing edge of the blade is controlled and set by curve AUE, curve EFG, curve FGQ and straight line DQ; The curve AUE and the curve FGQ are both convex arcs, the design point U and the design point G are convex points of the curve AUE and the curve FGQ respectively, and the curve FGQ forms the convex portion; The curve EFG is a concave arc, the design point F is a concave point of the curve EFG, and the curve EFG forms the concave portion; The angle ∠AOB formed by the design point A, the center of the circle O and the design point B is defined as Φ1; The angle ∠AOU formed by the design point A, the circle center O and the design point U is defined as Φ2; The angle ∠AOG formed by the design point A, the circle center O and the design point G is defined as Φ3; The angle ∠AOF formed by the design point A, the circle center O and the design point F is defined as Φ4; Among them, 65°<Φ1<75°, , 0.06<m1<0.1, , 0.38<m2<0.42, , 0.43<m3<0.46, m1, m2 and m3 are all constants.

[0012] Preferably, a point on the leading edge of the blade is defined as a design point P, and the leading edge of the blade is controlled and set by a curve BP and a straight line PC; Connecting the design point P and the design point Q to form a curve PQ, wherein the curve PQ and the curve CD enclose a region CPDQ, wherein the region CPDQ is used to form the guide flange portion by folding the outer edge of the blade from the pressure surface toward the back pressure surface; Establish a polar coordinate system with the center O as the pole, define the coordinates of the design point P in the polar coordinate system as P(r1, θ1), define the midpoint of the curve PQ as the design point S, define the coordinates of the design point S in the polar coordinate system as S(r2, θ2), and define the coordinates of the design point Q in the polar coordinate system as Q(r3, θ3); The fitting curve function of the curve PQ is expressed as r(θ)=Xθ 2 +Yθ+Z; Among them, 0.002<X<0.0032, -0.95<Y<-0.75, 317<Z<325, and X, Y and Z are all constants.

[0013] Preferably, the angle at which the outer edge of the blade is folded from the pressure surface toward the back pressure surface is defined as the folding angle θ4 of the guide flange portion; Among them, 8°≤θ4≤15°.

[0014] An impeller structure comprises 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 evenly distributed along the axial direction of the hub; In some of the low-noise axial flow fan blades, the circle center O is arranged to coincide with the rotation axis O' of the hub.

[0015] Preferably, 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 , unit is mm; Define the straight-line distance between the design point U and the rotation axis O' as R U , unit is mm; Define the straight-line distance between the design point F and the rotation axis O' as R F , unit is mm; Define the straight-line distance between the design point G and the rotation axis O' as R G , unit is mm; 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.

[0016] 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; Define the axial width W of the guide flange portion 翻边 , unit is mm; Among them, W 翻边 = (8%-15%) R2.

[0017] One of the above technical solutions has the following beneficial effects: 1. In terms of noise reduction, the discontinuous concave and convex portions of the trailing edge disrupt the periodicity of the Karman vortex street, significantly reducing broadband noise and compensating for the difficulty of suppressing vortex shedding in traditional trailing edge designs. The guide flange effectively reduces the swirling vortex noise generated by tip leakage flow and, in synergy with the trailing edge structure, further enhances the noise reduction effect. Compared to existing passive noise reduction methods such as mufflers, this design eliminates the need to increase system resistance or equipment size, resulting in more efficient noise reduction without affecting the smooth operation of the fan.

[0018] 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 of the blade suppresses local airflow separation, ensuring that the airflow can more efficiently drive the blade to work, solving the efficiency reduction problem that may be associated with airfoil optimization.

[0019] 3. In terms of cost, there is no need to use high-cost composite materials. Noise reduction and efficiency improvement can be achieved through structural optimization, thereby reducing production costs. The overall structural design of the blade is simple and can be directly adapted to the installation structure of existing axial fans. There is no need to make major modifications to components such as the fan casing, which is convenient for promotion and application. It can meet the needs of various scenarios such as industry and civil use for low-noise, high-efficiency fans, and is especially suitable for supporting scenarios of precision instruments and equipment that are sensitive to noise. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is an axial projection diagram of a low-noise axial flow fan blade according to the present invention; Figure 2 This is a schematic diagram of the design of design points A, B, C, and D in a low-noise axial flow fan blade according to the present invention; Figure 3 It is a schematic diagram of the design of the design point U, the design point F and the design point G in a low-noise axial flow fan blade of the present invention; Figure 4 Schematic diagram of the design of the design point P, design point S and design point Q in a low-noise axial flow fan blade according to the present invention; Figure 5 This is a schematic diagram of the design of a flow guide fold in a low-noise axial flow fan blade according to the present invention; Figure 6 This is an axial projection diagram of an impeller structure using low-noise axial flow fan blades according to the present invention; Figure 7 This is a power comparison chart between the present invention and the prior art at the same air volume; Figure 8 This is a noise comparison diagram between the present invention and the prior art at the same air volume; In the accompanying drawings: blade root edge 1, blade leading edge 2, blade outer edge 3, blade trailing edge 4, recessed portion 5, raised portion 6, guide flange portion 7, low-noise axial flow fan blade 10, pressure surface 101, back pressure surface 102, and hub 20. DETAILED DESCRIPTION

[0021] The technical solution of the present invention will be further described below with reference to the accompanying drawings and through specific implementation methods.

[0022] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "axial", "radial", "circumferential" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0023] 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 the technical features being referred to. Thus, a feature specified as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0024] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood broadly. For example, they may refer to fixed connections, detachable connections, or integral connections; they may refer to direct connections, indirect connections through an intermediary, or internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0025] A low-noise axial flow fan blade comprises a blade body; The blade body is a sheet-like structure, and has a pressure surface 101 and a back pressure surface 102. The peripheral contour of the blade body is formed by a blade root edge 1, a blade leading edge 2, a blade outer edge 3 and a blade trailing edge 4. The blade trailing edge 4 is provided with a concave portion 5 and a convex portion 6, and the curvature of the concave portion 5 and the curvature of the convex portion 6 are discontinuous. The outer edge 3 of the blade is folded from the pressure surface 101 toward the back pressure surface 102 to form a guide flange portion 7. The axial width W of the guide flange portion 7 is 翻边 It gradually narrows from one end of the blade trailing edge 4 to one end of the blade leading edge 2 .

[0026] The low-noise axial flow fan blade of the present invention aims at solving the noise and efficiency problems of the axial flow fan in the background art, and optimizes the structure of the blade trailing edge 4 and the blade outer edge 3. Figure 1 and Figure 5 shown.

[0027] In the blade tail region, the traditional continuous and smooth blade trailing edge 4 is prone to forming Karman vortex streets, generating broadband noise. However, in this technical solution, the recessed portion 5 and raised portion 6 provided on the blade trailing edge 4 adopt a discontinuous arc design. When air flows through the blade trailing edge 4, the recessed portion 5 can reduce the pressure gradient between the pressure surface 101 and the back pressure surface 102, inhibiting fluid separation; the raised portion 6 can change the outflow direction of the airflow. The two work together to 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 the generation of broadband noise at the source.

[0028] For the blade tip area, the existing planar structure of the blade outer edge cannot effectively control the leakage flow, resulting in high-intensity rotating vortexes that generate noise and reduce efficiency. In this technical solution, the blade outer edge 3 is folded from the pressure surface 101 to the back pressure surface 102 to form a guide flange 7, and its axial width W 翻边 The width gradually increases from the leading edge 2 to the trailing edge 4. This design adapts to the dynamic changes in the airflow from the blade tip as it flows in and out, acting as a "guiding barrier" to guide the tip leakage flow in an orderly manner and suppress the formation of high-intensity rotating vortices. At the same time, the gradual width design ensures smoother airflow in the blade tip area, reducing the additional noise and energy loss caused by flow obstruction.

[0029] Furthermore, the guide flange 7 forms a synergistic flow field with the recess 5 and raised portion 6 of the trailing edge 4. The guide flange 7 guides the airflow smoothly toward the trailing edge 4, while the raised portion 6 accelerates the boundary layer flow, suppressing the localized airflow separation that might be induced by the recess 5, further reducing the intensity of vortex shedding and enhancing the noise reduction effect.

[0030] To further illustrate, the connection points between the blade root edge 1, the blade leading edge 2, the blade outer edge 3 and the blade trailing edge 4 are defined as design point A, design point B, design point C and design point D in sequence; The blade root edge 1 is controlled and set by the curve AB, and the blade outer edge 3 is controlled and set by the 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. The arc length of the curve AB is smaller than the radius of the curve CD. The angle ∠AOB formed by the design point A, the circle center O and the design point B is defined as α; The angle ∠AOC formed by the design point A, the center of the circle O and the design point C is defined as α1; Define the angle ∠AOD formed by the design point A, the center of the circle O and the design point D as α2, Among them, 65°<α<75°; , 1.6<t1<1.63, t1 is a constant; , 0.52<t2<0.55, t2 is a constant.

[0031] like Figure 2 As shown, the blade root edge 1 is controlled by curve AB, and the blade outer edge 3 is controlled by curve CD, and the two are concentric arcs. This concentric design ensures that the torsion angle of the blade body from the root to the outer edge changes regularly.

[0032] ∠AOB, or α, is set between 65° and 75°. This angle determines the curvature and length of the control curve AB at the blade root edge 1. A reasonable α value allows the blade root edge 1 to better fit the turbine hub, ensuring a smooth transition of airflow from the hub to the blade body. This reduces impact noise and energy loss caused by sudden airflow changes, laying the foundation for overall airflow guidance on the blade. ∠AOC, or α1, is 1.6-1.63 times α. Since curves AB and CD are concentric arcs, α1 determines the position of control curve CD at blade outer edge 3 relative to control curve AB at blade root edge 1. This proportional relationship ensures an appropriate radial extension of blade outer edge 3. Combined with the radius difference between blade root edge 1 and blade outer edge 3, this further optimizes the blade's twist angle, achieving more uniform airflow distribution across the blade surface, reducing airflow separation, and enhancing the blade's efficiency in pushing air. ∠AOD, or α2, is 0.52-0.55 times α. This angle determines the position of design point D on the trailing edge 4 relative to design point A. This arrangement positions the concave portion 5 and convex portion 6 on the trailing edge 4 at a more optimal circumferential position, matching the layout of the leading edge 2 and outer edge 3. This ensures that airflow can be smoothly discharged from the trailing edge 4 after passing through the blade. The combined action of the concave portion 5 and convex portion 6 more effectively breaks up vortices in the wake zone and reduces vortex shedding intensity.

[0033] To further illustrate, define the straight line connecting the center O and the design point B as straight line OB, define a point on the extension line of straight line OB as design point I, define the straight line connecting the design point B and the design point C as straight line BC, draw a parallel line HI passing through the design point I and parallel to straight line BC, and define a point on the parallel line HI as design point H; The angle ∠HCB formed by the design point H, the design point C and the design point B is defined as β1; The angle ∠IBC formed by the design point I, the design point B and the design point C is defined as β2; Define the straight line distance between the straight line BC and the parallel line HI as l1; Among them, 40°<β1<45°, 50°<β2<55°, 70mm<l1<74mm.

[0034] like Figure 2 As shown, the connection area between the leading edge 2 and the outer edge 33 is optimized: Line BC is a key design line for design point C. Line HI, which passes through design point I and is parallel to Line BC, and the setting of design point H provide a precise geometric reference for the design of design point C. ∠HCB, or β1, is controlled within a range of 40°-45°, and ∠IBC, or β2, is controlled within a range of 50°-55°. The combination of these two angles optimizes the profile curvature of the leading edge 2. When air flows in from the leading edge 2, this angle range ensures a smoother transition from the leading edge 2 to the outer edge 3, reducing airflow separation and turbulence caused by sharp corners, and lowering the resulting aerodynamic noise.

[0035] The placement of design point I on the extension of line OB and parallel line HI, along with the 70mm-74mm distance l1 between line BC and parallel line HI, provides a reasonable spatial dimension for the design of the leading edge 2. This distance ensures sufficient width and curvature of the leading edge 2 near the root edge 1, effectively capturing and guiding the airflow. This creates a stable flow before it enters the main blade body, laying the foundation for subsequent smooth flow on the blade pressure surface 101 and back pressure surface 102, further reducing noise and energy loss caused by airflow turbulence.

[0036] To further illustrate, define the straight line connecting the center O and the design point A as straight line OA, define a point on the extension line of the straight line OA as design point K, define the straight line connecting the design point A and the design point D as straight line AD, draw a parallel line JK passing through the design point K and parallel to the straight line AD, and define a point on the parallel line JK as design point J; The angle ∠JDK formed by the design point J, the design point D and the design point A is defined as β3; The angle ∠KAD formed by the design point K, the design point A and the design point D is defined as β4; Define the straight line distance between the straight line AD and the parallel line JK as l2; Among them, 40°<β3<45°, 50°<β4<55°, 32mm<l2<36mm.

[0037] like Figure 2 As shown, the connection area between the blade root edge 1 and the blade trailing edge 4 is further optimized: ∠JDK, i.e., β3, is between 40° and 45°, and ∠KAD, i.e., β4, is between 50° and 55°. At the same time, a parallel line JK passing through the design point K and parallel to the straight line AD provides a reference for the design points A and D at both ends of the blade trailing edge 4, so that the curvature change of the blade trailing edge 4 in this area is more in line with the airflow characteristics, further reducing the generation of turbulence.

[0038] The distance l2 between line AD and parallel line JK is set at 32mm-36mm. This distance parameter, combined with the structural design of the blade leading edge 2, reserves appropriate space for airflow near the blade root edge 1. This ensures that airflow has sufficient flow through the area connecting the blade root edge 1 and the blade trailing edge 4, avoiding airflow congestion caused by cramped space. This allows airflow to flow more smoothly through this area, reducing energy loss.

[0039] To further illustrate, the five points on the 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 the design points U, E, F, G, and Q is from design point A to design point D. The trailing edge 4 is controlled and set by curves AUE, EFG, FGQ, and straight line DQ. The curve AUE and the curve FGQ are both convex arcs, the design point U and the design point G are convex points of the curve AUE and the curve FGQ respectively, and the curve FGQ forms the convex portion 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 portion 5; The angle ∠AOB formed by the design point A, the center of the circle O and the design point B is defined as Φ1; The angle ∠AOU formed by the design point A, the circle center O and the design point U is defined as Φ2; The angle ∠AOG formed by the design point A, the circle center O and the design point G is defined as Φ3; The angle ∠AOF formed by the design point A, the circle center O and the design point F is defined as Φ4; Among them, 65°<Φ1<75°, , 0.06<m1<0.1, , 0.38<m2<0.42, , 0.43<m3<0.46, m1, m2 and m3 are all constants.

[0040] like Figure 3 As shown, when m1 is within the range of 0.06-0.1, the geometric configuration of the recess 5 can effectively reduce the pressure gradient at the recess, preventing the airflow from separating due to sudden pressure changes, thereby suppressing turbulent noise. If it exceeds this range, it will lead to unbalanced pressure distribution and reduced flow stability.

[0041] When ∠AOG (Φ3) is too small, the geometric features of the protrusion 6 are unclear, making it unable to effectively guide the airflow. This weakens the boundary layer control capability and may lead to flow separation, increasing turbulent noise. When m2 > 0.42, the protrusion height or angle is too large, which may locally accelerate the airflow and form high-pressure areas, causing airflow separation or high-frequency vortex shedding, which in turn exacerbates noise.

[0042] When m3 is less than 0.43, a too small angle results 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 trailing edge from being fully structured and broken, reducing the noise reduction effect. Furthermore, a too small angle may weaken the flow-guiding effect of the recess 5, causing localized backflow or separation near the trailing edge, increasing turbulent noise. When m3 is greater than 0.46, an excessively large angle may make the geometric configuration of the recess 5 too flat, increasing the pressure gradient in the recess 5 and exacerbating airflow separation, which in turn causes high-frequency noise.

[0043] To further illustrate, a point on the blade leading edge 2 is defined as a design point P, and the blade leading edge 2 is controlled and set by a curve BP and a 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 form the guide flange portion 7 by folding the blade outer edge 3 from the pressure surface 101 toward the back pressure surface 102. Establish a polar coordinate system with the center O as the pole, define the coordinates of the design point P in the polar coordinate system as P(r1, θ1), define the midpoint of the curve PQ as the design point S, define the coordinates of the design point S in the polar coordinate system as S(r2, θ2), and define the coordinates of the design point Q in the polar coordinate system as Q(r3, θ3); The fitting curve function of the curve PQ is expressed as r(θ)=Xθ 2 +Yθ+Z; Among them, 0.002<X<0.0032, -0.95<Y<-0.75, 317<Z<325, and X, Y and Z are all constants.

[0044] 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 easily induces re-separation; -0.95<Y<-0.75, Y is too small, the contraction is too fast, and a back pressure gradient is easily formed. Y is too large, the guide flange part 7 is too slow, and effective guidance cannot be formed; 317<Z<325, Z is too small, the curve PQ cannot effectively connect to the blade trailing edge 4, and Z is too large, the curve PQ will highlight the mainstream shape and disrupt the airflow direction.

[0045] The curve function defines the contraction trajectory of the inner edge of the guide flange 7, and together with the curve CD, it encloses a flange area with a continuous shape but non-constant width. When observed from the axial projection surface, the guide flange 7 presents a typical tapered profile: from the curve DQ area of ​​the blade trailing edge 4 to the curve CP area of ​​the blade leading edge 2, the axial width W of the guide flange 7 is 翻边 The area located at the curve CP is the narrowest, and the area located at the curve DQ is the widest, thereby forming a flange structure with a gradually shrinking span and non-uniform width changes.

[0046] For further explanation, the angle at which the blade outer edge 3 is folded from the pressure surface 101 toward the back pressure surface 102 is defined as the folding angle θ4 of the guide flange portion 7; Among them, 8°≤θ4≤15°.

[0047] like Figure 5 As shown, when air flows through the outer edge 3 of the blade, the fold angle θ4 determines the ability of the guide flange 7 to block and guide the tip leakage flow. If the angle is too small, that is, θ4 is less than 8°, the guide flange 7 will not be able to effectively restrain the leakage flow, making it difficult to effectively suppress the formation of tip vortices. If the angle is too large, that is, θ4 is greater than 15°, it will increase the airflow resistance, causing local airflow turbulence, and may even generate new noise sources. A fold 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 better flow field coordination with the recessed portion 5 and raised portion 6 of the trailing edge 4, further enhancing the effect of suppressing vortex shedding.

[0048] This angle design, combined with the width gradient characteristics mentioned above, enables the guide flange to provide appropriate guiding force according to the dynamic changes of the airflow throughout the entire extension process from the leading edge of the blade to the trailing edge 4 of the blade, ensuring that the airflow in the tip area always maintains a stable and orderly flow state, reducing noise and energy loss caused by airflow turbulence.

[0049] 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 evenly distributed along the axial direction of the hub 20; In some of the low-noise axial flow fan blades 10 , the center O is arranged to coincide with the rotation axis O′ of the hub 20 .

[0050] like Figure 6 As shown, the impeller structure consists of a hub 20 and a plurality of the above-mentioned low-noise axial flow fan blades 10. The blades 10 are evenly distributed along the axial direction of the hub, and the center O of the blade 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. When the hub 20 rotates the blades 10, because the blade center O coincides with the hub's rotation axis O', the motion trajectory of each blade 10 revolves around the same axis, ensuring uniform airflow paths between blades 10. The blades 10 are evenly distributed along the axial direction, allowing the airflow to be evenly distributed among the blades after entering the impeller, avoiding localized airflow congestion or thinning caused by uneven blade distribution.

[0051] At the same time, the blade's internal structures, including the concave portion 5, convex portion 6, and guide flange 7, rotate about a unified axis to form a synergistic flow field. The gradually varying width of the guide flange 7 effectively suppresses tip leakage vortices, while the discontinuous concave portion 5 and convex portion 6 break up vortices in the wake zone. These combined effects of each blade further enhance airflow guidance and noise reduction, ensuring smoother airflow through the impeller.

[0052] To further illustrate, 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 , unit is mm; Define the straight-line distance between the design point U and the rotation axis O' as R U , unit is mm; Define the straight-line distance between the design point F and the rotation axis O' as R F , unit is mm; Define the straight-line distance between the design point G and the rotation axis O' as R G , unit is mm; 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] like Figure 6 As shown, when n1 is within the range of 0.42-0.47, the concave portion 5 and the convex portion 6 form a synergistic effect, causing the eddy current to be regularly broken.

[0054] When n2 is less than 0.8, the design point F on the recessed portion 5 is too close to the hub 20, resulting in insufficient ability to intervene in the vortex in the trailing edge 4 area. When n2 is greater than 0.84, the design point F on the recessed portion 5 is too close to the trailing edge 4, which may destroy the streamlined profile of the blade and increase the risk of local airflow separation.

[0055] When n3 is in the range of 0.87-0.89, the radial position of the design point G on the raised portion 6 can optimize the airflow distribution. The raised portion 6 close to the trailing edge 4 accelerates the local airflow through a streamlined design, suppresses boundary layer separation, reduces turbulent noise, and avoids the formation of a high-pressure area due to a position that is too far away, thereby maintaining the uniformity of the pressure distribution on the blade surface.

[0056] For further explanation, 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 portion 翻边 , unit is mm; Among them, W 翻边 = (8%-15%) R2.

[0057] like Figure 6 As shown, the axial width W of the guide flange portion 7 is 翻边 It is set to 8%-15% of the impeller structure radius R2. This proportional relationship works together with the folding angle θ4 to further optimize the airflow control in the tip area.

[0058] From the perspective of the overall impeller size, W 翻边 The proportional design with R2 ensures that the guide flange can play an adaptive guiding role in impellers of different sizes. 翻边 Proportionally increasing the width can provide sufficient blocking and guiding area for the stronger leakage flow at the blade tip, avoiding the failure of leakage flow control caused by insufficient flange width; for impellers with smaller radius, W 翻边 Proportional reduction can prevent the problem of narrow airflow channel caused by excessive flange width and reduce unnecessary flow resistance.

[0059] When the airflow passes through the blade tip area, the guide flange of this width can form a more precise flow field with the concave portion 5 and the convex portion 6 of the blade trailing edge. 翻边It not only ensures the effective interception of the tip leakage flow, but also provides sufficient space for the smooth transition of the airflow to the raised portion 6 of the trailing edge 4, so that the airflow remains stable during the flow from the tip to the trailing edge 4, further weakening the energy of vortex shedding.

[0060] It should be noted that the relationships between the above-mentioned design points are all calculated under the axial projection of the impeller structure toward the pressure surface 101 of the blade body.

[0061] In order to further demonstrate the performance of the low-noise axial flow fan blades in the present invention when applied to an axial flow impeller, existing conventional blades are used as a comparative example to obtain performance test results of the two under the same test conditions.

[0062] The wind turbine performance test results are shown in the following table, and the performance test comparison chart is as follows: Figure 7-8 shown.

[0063]

[0064] The test results of the wind wheel performance show that as the speed increases, the axial flow impeller, whether using existing conventional blades or low-noise axial flow fan blades, will generate increasingly louder noise and air volume. However, under the same air volume output conditions, the low-noise axial flow fan blades show better overall performance than the traditional conventional blades. For example, the measured data shows that: under the same air volume, the noise of the low-noise axial flow fan blades is about 1.5dB lower than that of the existing conventional blades. Figure 7 At the same time, the input power of the low-noise axial fan blade is about 6.8% lower than that of the existing conventional blades. Figure 8 As shown, a higher level of energy efficiency is achieved.

[0065] In summary, the low-noise axial flow fan blades of the present invention are applied to the axial flow impeller, which can improve the overall performance of the equipment.

[0066] The technical principles of the present invention have been described above with reference to specific embodiments. These descriptions are intended solely to illustrate the principles of the present invention and are not to be construed in any way as limiting the scope of protection of the present invention. Based on the explanations herein, those skilled in the art will be able to devise other specific embodiments of the present invention without inventive effort, and such equivalent variations or substitutions are intended to be encompassed within the scope of the claims of this application.

Claims

1. A low-noise axial flow fan blade, characterized in that: including a blade body; The blade body is 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 a blade root edge (1), a blade leading edge (2), a blade outer edge (3), and a blade trailing edge (4). The blade trailing edge (4) is provided with a recessed portion (5) and a raised portion (6), and the curvature of the recessed portion (5) and the curvature of the raised portion (6) are discontinuously arranged; The outer edge (3) of the blade is folded from the pressure surface (101) toward the back pressure surface (102) to obtain a flow guide flange portion (7), and the axial width W of the flow guide flange portion (7) is 翻边 The blade gradually narrows from one end of the trailing edge (4) to one end of the leading edge (2).

2. A low-noise axial flow fan blade according to claim 1, characterized in that: The connection points between the blade root edge (1), the blade leading edge (2), the blade outer edge (3) and the blade trailing edge (4) are defined as design point A, design point B, design point C and design point D in sequence; The blade root edge (1) is controlled and set by a curve AB, and the blade outer edge (3) is controlled and set by a curve CD, wherein the curve AB and the curve CD are concentric arcs having 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; The angle ∠AOB formed by the design point A, the circle center O and the design point B is defined as α; The angle ∠AOC formed by the design point A, the center of the circle O and the design point C is defined as α1; Define the angle ∠AOD formed by the design point A, the center of the circle O and the design point D as α2, Among them, 65°<α<75°; , 1.6<t1<1.63, t1 is a constant; , 0.52<t2<0.55, t2 is a constant.

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

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

5. The low-noise axial flow fan blade according to claim 2, characterized in that: The five points on the trailing edge (4) of the blade are defined as a design point U, a design point E, a design point F, a design point G and a design point Q. The order of distribution of the design points U, E, F, G and Q is from the design point A to the design point D. The trailing edge (4) of the blade is controlled and set by a curve AUE, a curve EFG, a curve FGQ and a straight line DQ. The curve AUE and the curve FGQ are both convex arcs, the design point U and the design point G are convex points of the curve AUE and the curve FGQ respectively, and the curve FGQ forms the convex portion (6); The curve EFG is a concave arc, the design point F is a concave point of the curve EFG, and the curve EFG forms the concave portion (5); The angle ∠AOB formed by the design point A, the center of the circle O and the design point B is defined as Φ1; The angle ∠AOU formed by the design point A, the circle center O and the design point U is defined as Φ2; The angle ∠AOG formed by the design point A, the circle center O and the design point G is defined as Φ3; The angle ∠AOF formed by the design point A, the circle center O and the design point F is defined as Φ4; Among them, 65°<Φ1<75°, , 0.06<m1<0.1, , 0.38<m2<0.42, , 0.43<m3<0.46, m1, m2 and m3 are all constants.

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

7. 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 is folded from the pressure surface (101) toward the back pressure surface (102) is defined as the folding angle θ4 of the guide flange portion (7); Among them, 8°≤θ4≤15°.

8. An impeller structure, characterized in that: It comprises a hub (20) and a plurality of low-noise axial flow fan blades (10) according to any one of claims 1 to 7, wherein the plurality of low-noise axial flow fan blades (10) are evenly distributed along the axial direction of the hub (20); In some of the low-noise axial flow fan blades (10), the center O is arranged to coincide with the rotation axis O' of the hub (20).

9. The impeller structure according to claim 8, characterized in that: Define the radius of the hub as R1; Define the straight-line distance between the design point A and the rotation axis O' as R A , unit is mm; Define the straight-line distance between the design point U and the rotation axis O' as R U , unit is mm; Define the straight-line distance between the design point F and the rotation axis O' as R F , unit is mm; Define the straight-line distance between the design point G and the rotation axis O' as R G , unit is mm; 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.

10. The impeller structure according to claim 8, 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 portion (7) 翻边 , unit is mm; Among them, W 翻边 = (8%-15%) R2.

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