Noise reduction type sweepback blade fan structure

Abstract

The utility model relates to a noise reduction type sweepback blade fan structure which comprises a hub, and a plurality of blades spaced in the circumferential direction are connected to the outer circumferential side face of the hub. The blades extend outwards in the radial direction of the hub, and the front edges and the tail edges of the blades are in an arc shape protruding in the same direction in the circumferential direction of the hub. The blade middle-sized line has the radian protruding towards the suction face of the blade, the chord length of the blade middle-sized line of the blade root is larger than that of the blade tip middle-sized line, and the chord length of the blade middle-sized line is gradually reduced from the blade root to the blade tip. The curvature radius of the blade middle-sized line of the blade root is smaller than that of the blade tip, and the curvature radius of the blade middle-sized line is gradually increased from the blade root to the blade tip. The structure is a non-equidistant blade, the sweepback type bent blade design is adopted, the chord length and curvature of the blade are gradually changed to reduce the vortex effect, the bending-torsion coupling deformation of the blade tip is reduced through the integrated flow collecting cover, and meanwhile, the auxiliary blade is additionally arranged on the flow collecting cover to improve the high air volume; therefore, the noise and vibration of the fan are reduced while the air volume is ensured.

Description

Technical Field

[0001] The utility model belongs to the technical field of fan blade design, and in particular relates to a noise reduction type swept-back blade fan structure. Background Art

[0002] In order to obtain a large air flow, automotive cooling fans generally use axial cooling fans. The electrification of new energy vehicles eliminates the masking effect of traditional engine noise, and fan noise will become more prominent. Excessive noise will affect riding comfort, which makes the working noise control of new energy vehicle cooling fans particularly important.

[0003] The blades are installed on the impeller, which is the main working part of the fan. The good design of the blades will directly affect the performance and noise of the fan. When the fan is operating normally, the aerodynamic noise generated by the blades is much greater than the mechanical noise and electromagnetic noise of the fan. From the root of the aerodynamic noise of the fan, it is mainly due to the vortex and vortex separation on the blades. Even under the best working conditions, the vortex in the impeller and the vortex separation at the trailing edge of the blade are inevitable. However, as long as the blade design is reasonable and the blade parameters are properly selected, the vortex and vortex separation can be minimized, thereby reducing noise.

[0004] In the prior art, there are fan blade optimization solutions such as those disclosed in CN 106704261 A and CN 117366017 A, which can reduce noise and improve efficiency, but the morphological structure of the blades is greatly changed, which is relatively complex and costly; in the form of equidistantly arranged blades, the sound pressure pulsation formed by the blade wake airflow periodically impacting the downstream object is superimposed on the blade pulsation fundamental frequency and its harmonic frequency, which will make the sound pressure level of discrete noise high. The fan blade of the automotive cooling fan disclosed in CN 207178299 U has light noise reduction, but adopts a backward-bending and then forward-bending blade form, and the blade root chord length is small, which becomes larger later, and the vortex shedding edge on the blade is large, which is not conducive to noise reduction. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, the technical problem to be solved by the utility model is to provide a noise-reducing swept-blade fan structure, which intends to optimize the changes in the blade chord length, curvature, pitch-to-chord ratio, and tangential curvature, so as to avoid the problem of excessive noise when the fan is in use and achieve an effective noise reduction effect.

[0006] In order to solve the above technical problems, the utility model adopts the following technical solutions:

[0007] A noise reduction swept-back blade fan structure comprises a hub, and a plurality of circumferentially spaced blades are connected to the outer circumferential side of the hub; the blades extend outwardly along the radial direction of the hub, and the leading edge and the trailing edge of the blades are both bent and extended backward along the circumference of the hub; the blades are provided with a blade median line, the blade median line has an arc that is convex toward the suction surface of the blade, the chord length of the blade median line at the blade root of the blade is greater than the chord length of the blade median line at the blade tip, and the chord length of the blade median line gradually decreases from the blade root to the blade tip.

[0008] To further improve the above technical solution, the ratio of the radius of the rotating surface where the blade root is located to the chord length of the blade mid-line of the blade root is the root chord ratio, and the root chord ratio is 1.37 to 1.46;

[0009] The ratio of the radius of the rotating surface where the blade tip is located to the chord length of the blade midline at the blade tip is the tip chord ratio, and the tip chord ratio is 4.23 to 4.57.

[0010] Further, the radius of curvature of the blade median line at the blade root of the blade is smaller than the radius of curvature of the blade median line at the blade tip, and the radius of curvature of the blade median line gradually increases from the blade root to the blade tip.

[0011] Furthermore, the ratio of the radius of curvature of the blade midline to the radius of the rotating surface is the tangential curvature, and the tangential curvature gradually decreases from 2.28 to 1.32 from the blade root to the blade tip.

[0012] Furthermore, the angle between the chord line of the blade midline and the plane perpendicular to the axis is the installation angle of the blade, the installation angles of the blade from the blade root to the blade tip are equal, and the installation angle is 15-22°.

[0013] Furthermore, a sawtooth groove is provided on one end of the trailing edge of the blade close to the blade tip, and the sawtooth groove penetrates along the thickness direction of the blade.

[0014] Furthermore, the blade tips of all blades are connected to the inner ring of the collecting cover which is coaxial with the hub.

[0015] Furthermore, between two adjacent blades, an auxiliary blade is provided on the inner circle of the collecting cover protruding inwardly, and the inclination direction of the auxiliary blade is the same as the inclination direction of the blade installation angle.

[0016] Further, all blades are arranged at irregular intervals with non-equidistant distances in the circumferential direction; and all auxiliary blades are arranged at irregular intervals with non-equidistant distances in the circumferential direction.

[0017] Furthermore, the included angle between the auxiliary blade installation angle and the blade installation angle is less than 5°; in the axial direction, the auxiliary blade is smaller than the blade; in the radial direction, the length of the auxiliary blade protruding inward from the inner circle of the collector is not more than 15 mm.

[0018] Compared with the prior art, the utility model has the following beneficial effects:

[0019] The noise-reducing swept-blade fan structure of the utility model is a non-equidistant blade structure, adopts a swept-back curved blade design, and the blade chord length and curvature are gradually designed to reduce the vortex effect. The bending-torsion coupling deformation of the blade tip is reduced by an integrated collector, and auxiliary blades are added to the collector to increase the high air volume, thereby ensuring the air volume while reducing the fan noise and vibration. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a structural schematic diagram of a noise reduction swept blade fan structure of a specific embodiment (rotates clockwise when in use);

[0021] Figure 2 for Figure 1 The right side view of the figure, with the lower part partially cut away to illustrate the blades;

[0022] Figure 3 for Figure 1 The B-direction view in the figure mainly shows the blade root cross section (three-dimensional local, enlarged);

[0023] Figure 4 for Figure 1 The C-direction view in the figure mainly shows the blade tip cross section (three-dimensional local, enlarged);

[0024] Figure 5 for Figure 1 D-view (local, rotated) in;

[0025] Among them, there are a collecting cover 1, a blade 2, a leading edge 21, a trailing edge 22, a suction surface 23, a blade mid-line 24, a serrated groove 25, a hub 3, and an auxiliary blade 4. DETAILED DESCRIPTION

[0026] The specific implementation of the utility model is further described in detail below in conjunction with the accompanying drawings.

[0027] See also Figure 1-Figure 5, a noise reduction swept-back blade fan structure of a specific embodiment includes a hub 3, and a plurality of circumferentially spaced blades 2 are connected to the outer circumferential side of the hub 3; the blades 2 extend outwardly along the radial direction of the hub 3, and the leading edge 21 and the trailing edge 22 of the blades 2 are arc-shaped and convex in the same direction along the circumference of the hub 3; a cross section is formed with the blade 2 by a truncated circle coaxial with the hub 3, and a blade median line 24 is provided on the blade 2 in the cross section, and the blade median line 24 is designed so that the pressure surface profile line of the pressure surface of the blade 2 and the suction surface profile line of the suction surface 23 of the blade 2 are arranged at equal thickness on both sides of the blade median line 24, thereby dividing the blade thickness of the blade 2 into equal parts, which is an existing term; the blade median line 24 has an arc convex toward the suction surface 23 of the blade 2, the chord length of the blade median line 24 at the blade root of the blade 2 is greater than the chord length of the blade median line 24 at the blade tip, and the chord length of the blade median line 24 decreases linearly from the blade root to the blade tip.

[0028] Specifically, the ratio of the radius of the rotating surface where the blade root is located (i.e., the outer circle of the hub) to the chord length of the blade median line 24 of the blade root is the root chord ratio, and the root chord ratio is 1.37-1.46; the ratio of the radius of the rotating surface where the blade tip is located (i.e., the inner circle of the collector 1) to the chord length of the blade median line 24 of the blade tip is the tip chord ratio, and the tip chord ratio is 4.23-4.57. During implementation, the chord length of the blade median line 24 of the blade root can be selected to be 57-61 mm, and the chord length of the blade median line 24 of the blade tip can be selected to be 52-56 mm.

[0029] On the radial normal surface, the curvature radius of the blade median line 24 at the blade root of the blade 2 is smaller than the curvature radius of the blade median line 24 at the blade tip, and the curvature radius of the blade median line 24 gradually increases from the blade root to the blade tip.

[0030] Specifically, the ratio of the radius of curvature of the blade median line 24 to the radius of the rotating surface is the tangential curvature, and the tangential curvature gradually decreases from 2.28 to 1.32 from the blade root to the blade tip.

[0031] The main source of noise generated by the fan is the airflow pulsation force acting on the blade 2. When the turbulent boundary on the surface of the blade 2 passes through the trailing edge, local pulsation force will be generated. In addition, the Karman vortex at the trailing edge 22 of the blade also generates local pulsation force with a narrower frequency characteristic. Due to the existence of these airflow pulsation forces, vortex shedding is generated on the blade 2, thereby generating vortex shedding noise. The unsteady aerodynamic parts acting on blade 2 are accompanied by an equal reverse force acting on the fluid. Such a force, whether it is a discrete or continuous frequency characteristic, causes direct radiation of dipole or sound power. For a dipole noise source, the radiated sound power generally varies with the sixth power of the velocity, and the magnitude of the exponent is related to the length of the vortex shedding edge (blade trailing edge). The longer the vortex shedding edge is, the larger the exponent is, and the length of the vortex shedding edge is inversely proportional to the cosine of the blade trailing edge sweep angle. Therefore, in order to reduce the noise radiated sound power of blade 2, the embodiment adopts a blade structure with a gradually decreasing chord length in the direction of the blade tip at the outer end of the blade with a swept angle. The smaller curvature will not aggravate the airflow separation on the surface of blade 2 much. On the contrary, adopting an appropriate curvature of blade 2 will also reduce the airflow separation on the surface of blade 2. However, if the blade curvature is too large, the airflow separation on the surface of blade 2 will be aggravated, and the width of the wake of blade 2 will rapidly increase, thereby increasing the arc speed of the noise generated by the fan. Therefore, in the process of transforming from the low-speed airflow at the hub 3 to the high-speed airflow at the blade tip, a transition design from large to small curvature is adopted (the radius of curvature gradually increases).

[0032] Please continue to see Figure 1-Figure 3 , wherein the tips of all blades 2 are connected to the inner ring of the hood 1 coaxial with the hub 3. A serrated groove 25 is provided on one end of the trailing edge 22 of the blade 2 close to the tip, and the serrated groove 25 penetrates along the thickness direction of the blade 2. Due to the reaction of the force, the chord length in the direction of the tip of the outer end of the blade 2 is designed to gradually decrease, and it is necessary to increase the hood 1 to change the strength of the impeller and reduce the bending and torsional coupling deformation of the blade tip caused by the centrifugal force and the rotary force; by adding a serrated structure to the tail wing, the mixing of the airflow between the pressure surface and the suction surface 23 is promoted, the boundary layer separation is delayed, the strength of the tail vortex is weakened, and the noise is further reduced.

[0033] Please continue to see Figure 5 , wherein the angle between the chord line of the blade midline 24 and the plane perpendicular to the axis is the installation angle of the blade 2, and the installation angles of the blade 2 from the root to the tip are equal, and the installation angle is 15-22°. Between two adjacent blades 2, an auxiliary blade 4 is provided on the inner ring of the collector 1, and the inclination direction of the auxiliary blade 4 is the same as the inclination direction of the installation angle of the blade 2. Adding the auxiliary blade 4 to the collector 1 can effectively compensate for the air volume loss caused by the shortening of the outer chord length of the blade 2.

[0034] All blades 2 are arranged at irregular intervals with non-equidistant distances in the circumferential direction; all auxiliary blades 4 are arranged at irregular intervals with non-equidistant distances in the circumferential direction. The included angle between the installation angle of the auxiliary blade 4 and the installation angle of the blade 2 is less than 5°; in the axial direction, the height of the auxiliary blade 4 is less than that of the blade 2, and the height difference is not greater than 3mm; in the radial direction, the length of the auxiliary blade 4 protruding inward from the inner ring of the collector 1 is not greater than 15mm.

[0035] When the fan blades are distributed at equal intervals, the sound pressure pulsation formed by the blade wake airflow periodically impacting the downstream object is superimposed on the blade pulsation fundamental frequency and its harmonics, making the sound pressure level of discrete noise much higher than the sound pressure level of broadband noise; for any harmonic, the unequally spaced blade distribution does not correspond to an obvious peak like the equal spacing, but is composed of many frequency bands corresponding to the amplitude, that is, the unequally spaced blade distribution causes the frequency to be modulated. The amplitude corresponding to the center frequency of any harmonic of the unequally spaced blades after modulation is smaller than the amplitude corresponding to the equally spaced blades. Therefore, this embodiment adopts a non-equidistant arrangement of seven blades 2 and auxiliary blades 4, and the impeller balance can be corrected according to the sinusoidal modulation formula of the unequally spaced blades.

[0036] In this embodiment, please refer to Figure 1-Figure 5 , outer diameter of collecting cover 1 Ф D = 500,

[0037] The radius of curvature of the blade median line at the root is r2 = 190, the radius of curvature of the blade median line at the tip is r1 = 315, the tangential curvature gradually decreases from 2.28 to 1.32, and the tangential curvature = the radius of curvature r / the radius of the rotating circle R, then,

[0038] The diameter of the rotating surface where the blade root is located (i.e. the outer circle of the hub) is Ф b≈167, and the diameter of the rotating surface where the blade tip is located (i.e. the inner circle of the collector) is Ф a≈477.

[0039] The chord length of the blade midline at the root is L2=61, and the root chord ratio is 1.37.

[0040] The chord length of the blade midline at the tip is L1=53, and the tip chord ratio is 4.5.

[0041] Blade height H=20, auxiliary blade height H2=18,

[0042] The blade installation angle β1 = 18°, the auxiliary blade installation angle β2 = 23°, the auxiliary blade protrudes inward from the inner circle of the collecting cover by 13, and the length unit is mm.

[0043] Comparison and verification, test conditions: the fan is installed on the front end heat dissipation module, powered on with 13.5V, and the test distance is one meter behind the fan motor. The fan of this embodiment has an increased air volume of 450m on the basis of the fan before optimization compared with the fan without chord length, curvature gradient blade design and auxiliary blade structure.3 / H (test conditions are back pressure 0Pa, impeller speed 2450r), the noise is reduced from 83.5db to 80.5db. The utility model adopts a non-equidistant blade structure, a swept curved blade design, a gradual change in the chord length and curvature of the blade section to reduce the vortex effect, an integrated collector is used to reduce the bending and torsional coupling deformation of the blade tip, and auxiliary blades are added to the collector to increase the high air volume, thereby ensuring the air volume while reducing the fan noise and vibration.

[0044] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the utility model rather than to limit it. Although the utility model has been described in detail with reference to the preferred embodiments, ordinary technicians in the field should understand that the technical solution of the utility model can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the utility model, which should be included in the scope of the claims of the utility model.

Claims

1. A noise reduction swept blade fan structure, comprising a hub, a plurality of circumferentially spaced blades connected to the outer circumferential side of the hub; the blades extend outwardly in the radial direction of the hub and the leading edge and the trailing edge of the blades are bent and extended backward in the circumferential direction of the hub; characterized in that: The blade is provided with a blade median line having an arc convex toward the suction surface of the blade, the chord length of the blade median line at the blade root of the blade is greater than the chord length of the blade median line at the blade tip, and the chord length of the blade median line gradually decreases from the blade root to the blade tip.

2. The noise reduction swept blade fan structure according to claim 1, characterized in that: The ratio of the radius of the rotating surface where the blade root is located to the chord length of the blade median line of the blade root is the root chord ratio, and the root chord ratio is 1.37 to 1.46; The ratio of the radius of the rotating surface where the blade tip is located to the chord length of the blade midline at the blade tip is the tip chord ratio, and the tip chord ratio is 4.23 to 4.

57.

3. The noise reduction swept blade fan structure according to claim 1, characterized in that: The curvature radius of the blade median line at the blade root of the blade is smaller than the curvature radius of the blade median line at the blade tip, and the curvature radius of the blade median line gradually increases from the blade root to the blade tip.

4. The noise reduction swept blade fan structure according to claim 3, characterized in that: The ratio of the radius of curvature of the blade midline to the radius of the rotating surface is the tangential curvature. From the blade root to the blade tip, the tangential curvature gradually decreases from 2.28 to 1.

32.

5. The noise reduction swept blade fan structure according to claim 1, characterized in that: The angle between the chord line of the blade midline and the plane perpendicular to the axis is the installation angle of the blade. The installation angles of the blade from the root to the tip are equal, and the installation angle is 15-22°.

6. The noise reduction swept blade fan structure according to claim 1, characterized in that: A sawtooth groove is provided on one end of the trailing edge of the blade close to the blade tip, and the sawtooth groove penetrates along the thickness direction of the blade.

7. The noise reduction swept blade fan structure according to claim 1 or 2, characterized in that: The blade tips of all blades are connected to the inner ring of the collecting cover which is coaxial with the hub.

8. The noise reduction swept blade fan structure according to claim 7, characterized in that: Between two adjacent blades, an auxiliary blade is provided on the inner circle of the collecting cover protruding inwardly, and the inclination direction of the auxiliary blade is the same as the inclination direction of the blade installation angle.

9. The noise reduction swept blade fan structure according to claim 8, characterized in that: All blades are arranged at irregular intervals with non-equidistant distances in the circumferential direction; all auxiliary blades are arranged at irregular intervals with non-equidistant distances in the circumferential direction.

10. The noise reduction swept blade fan structure according to claim 8, characterized in that: The included angle between the auxiliary blade installation angle and the blade installation angle is less than 5°; in the axial direction, the auxiliary blade is smaller than the blade; in the radial direction, the length of the auxiliary blade protruding inward from the inner circle of the collector is not more than 15mm.

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