Axial flow fan and design method thereof

Abstract

The invention provides an axial flow fan and a design method thereof, the axial flow fan comprises a rotating shaft and a plurality of blades arranged on the rotating shaft at equal intervals, and the part, from 20%-80% of the spanwise position to 100% of the spanwise position, of each blade is divided into at least two sub-blades. The axial flow fan design method comprises the steps that the shapes and the number of blades of an axial flow fan are designed; selecting a starting point spanwise position for blade segmentation, and segmenting the part of the blade from the starting point spanwise position to 100% spanwise position into at least two sub-blades; and the aerodynamic performance and the noise value of the axial flow fan are verified through analogue simulation or tests, and the starting point spanwise position and / or the design parameters of the sub-blades are / is adjusted till the design requirements are met. The part with the longer chord length of the blade is divided into at least two parts, so that the flow separation phenomenon can be reduced, the flow loss is reduced, the fan efficiency is improved, and the noise is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of axial flow fans, and in particular to an axial flow fan and a design method thereof. Background Art

[0002] Axial flow fans are fans whose airflow direction is in the same direction as the blade axis, such as electric fans and air conditioner outdoor fans. Axial flow fans are usually used in situations where the flow rate requirements are high and the pressure requirements are low.

[0003] At present, the structure of conventional axial flow fans at home and abroad is as follows Figure 1 As shown, it includes a rotating shaft 10 and a plurality of blades 20 arranged on the rotating shaft at equal intervals. When designing and optimizing the performance of an axial flow fan, the prior art usually optimizes the appearance of the blade 20 by changing the blade shape parameters such as the mid-arc line, chord length, maximum curvature, geometric inlet angle and geometric outlet angle of each plane cascade blade shape of the blade 20. However, no matter how the plane cascade blade shape parameters of the blade 20 are adjusted, the conventional axial flow fan will have obvious flow separation at the position of 60% to 80% of the blade chord length due to the large adverse pressure gradient, resulting in large flow loss and noise of the axial flow fan. Summary of the invention

[0004] The purpose of the present invention is to overcome the defects of the prior art and to provide an axial flow fan and a design method thereof, which can solve the problems of prominent flow separation phenomenon, large flow loss and high noise of the axial flow fan in the prior art.

[0005] In order to achieve the above purpose and other purposes, the present invention is implemented by including the following technical solutions: As a first aspect, the present invention proposes an axial flow fan, including a rotating shaft and a plurality of blades arranged on the rotating shaft at equal intervals, and the portion of the blade from the spanwise position of 20% to 80% to the spanwise position of 100% is divided into at least 2 sub-blades.

[0006] As a second aspect, the present invention provides a method for designing an axial flow fan, comprising the steps of: S1. Design the blade shape and number of the axial flow fan; S2, selecting a starting spanwise position for blade segmentation, and segmenting the portion of the blade from the starting spanwise position to 100% spanwise position into at least two sub-blades; S3. Verify the aerodynamic performance and noise value of the axial flow fan through simulation or experiment, and adjust the spanwise position of the starting point and / or the design parameters of the sub-blades until they meet the design requirements.

[0007] In one embodiment, the step S2 specifically includes the steps of: S21, selecting a spanwise position to obtain a planar unfolded view of the blade at the spanwise position; S22, selecting the segmentation points of the sub-blades on the planar unfolded view, and determining the chord length, the mid-camber line and the planar blade shape of the sub-blades; S23, repeating the above steps S21-S22, obtaining the chord length, the mid-camber line and the plane blade shape of the sub-blade at any spanwise position within the interval from the starting spanwise position to the 100% spanwise position, and obtaining all the sub-blades by sequentially lofting.

[0008] In one embodiment, in step S22, the chord length of the sub-blade is determined by relative length and relative height; the median camber line is determined by the chord length and geometric angle; and the planar cascade blade shape is determined by the chord length and median camber line.

[0009] In one embodiment, the number of the sub-blades is 2, including a first sub-blade and a second sub-blade.

[0010] Furthermore, the spanwise position of the starting point is between 20% and 80% of the spanwise position.

[0011] Further, at any spanwise position, the relative length of the first / second sub-blade is 0.2-0.8, and the sum of the relative lengths of the first sub-blade and the second sub-blade is less than 1.

[0012] Further, at any spanwise position, the relative height of the first / second sub-blade is 0.02-1.

[0013] Further, at any spanwise position, the geometric angle of the first / second sub-blade has a value range of 10° to 60°.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention divides the portion with a longer blade chord length into at least two portions. Compared with traditional axial flow fans, the flow separation phenomenon caused by the longer blade chord length can be reduced, thereby reducing flow losses, improving fan efficiency and reducing noise. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It shows a schematic diagram of the structure of an axial flow fan (Comparative Example 1) in the prior art.

[0016] Figure 2 Shown is a flow chart of the steps of an axial flow fan design method of the present invention.

[0017] Figure 3 Shown is a schematic diagram of the spanwise relative positions of blades in an axial flow fan of the present invention.

[0018] Figure 4It shows a planar expansion diagram of a blade in an axial flow fan in the prior art at a certain spanwise position.

[0019] Figure 5 Shown is a schematic diagram of the arc designed according to the chord length.

[0020] Figure 6 Shown is a schematic diagram of blade profile design based on chord length and camber line.

[0021] Figure 7 Shown is a schematic structural diagram of blades in an axial flow fan of the present invention.

[0022] Figure 8 It is a schematic diagram of the structure of Example 1 of the present invention.

[0023] Fig. 9 Shown is a flow rate and static pressure value curve diagram of Example 1 and Comparative Example 1.

[0024] Fig.10 Shown is a flow rate and efficiency value curve diagram of Example 1 and Comparative Example 1. DETAILED DESCRIPTION

[0025] See also Figure 1-Figure 10 The following describes the embodiments of the present invention through specific examples. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification.

[0026] It should be noted that the structures, proportions, sizes, etc. illustrated in the drawings in this specification are only used to match the contents disclosed in the specification for the technical personnel in this field to understand and read, and are not used to limit the conditions under which the present invention can be implemented. Therefore, they have no substantive technical significance. Any modification of the structure, change in the proportion relationship or adjustment of the size should still fall within the scope of the technical contents disclosed in the present invention without affecting the effects and purposes that can be achieved by the present invention.

[0027] Unless otherwise defined, the technical or scientific terms used herein shall have the usual meaning as understood by a person having ordinary skills in the field to which the invention belongs. The words "one", "an" or "the" and the like used in the present invention do not indicate a quantitative limitation, but are only used to indicate the existence of at least one. The words "include" or "comprise" and the like mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. The serial numbers for the components in this specification, such as "first", "second", etc., are only used to distinguish the objects described and do not have any order or technical meaning. The "connection" mentioned in the present invention, unless otherwise specified, includes direct and indirect connections.

[0028] In order to avoid confusion with the present invention, some technical features known in the art are not described.

[0029] like Figure 2~Figure 8 As shown, the present invention proposes a design method for an axial flow fan, comprising the steps of: S1. Design the shape and number of blades 20 of the axial flow fan, for example Figure 1 The conventional axial flow fan shown; S2, such as Figure 3 As shown, the starting spanwise position 20b for segmenting the blade 20 is selected, and the starting spanwise position 20b may be a 20% to 80% spanwise position; the portion of the blade 20 in the interval from the starting spanwise position 20b to the 100% spanwise position 20c is segmented into at least two sub-blades, such as the first sub-blade 21 and the second sub-blade 22 shown in the figure; the portion in the interval from the 0% spanwise position 20a to the starting spanwise position 20b maintains the original shape of the blade 20; Specifically, the design process of the first sub-blade 21 and the second sub-blade 22 is as follows: S21, unfold the blade 20 at any spanwise position within the range from the starting spanwise position 20b to the 100% spanwise position 20c, and obtain the following: Figure 4 In the planar development diagram shown, the chord length C1 of the blade 20; S22, selecting the division point of the first sub-blade 21 and the second sub-blade 22 on the plane development diagram, determining the chord length C2, the mid-arc line A and the plane cascade blade shape of the first sub-blade 21, and the chord length C3, the mid-arc line B and the plane cascade blade shape of the second sub-blade 22; Specifically, Figure 4 As shown in the figure, L1 represents the chord length parameter of the first sub-blade 21, which extends parallel to the chord length C1 direction with the leading edge point of the blade 20 as a fixed point; L2 represents the chord length parameter of the second sub-blade 22, which extends parallel to the chord length C1 direction with the trailing edge point of the blade 20 as a fixed point; h1 represents the height parameter of the first sub-blade 21, and h2 represents the height parameter of the second sub-blade 22. The ratio of the chord length parameter L1 to the chord length C1 is called the relative length γ1 of the first sub-blade 21, and the ratio of the height parameter h1 to the chord length C1 is called the relative height η1 of the first sub-blade 21. The chord length C2 of the first sub-blade 21 can be determined by γ1 and η1. The ratio of the chord length parameter L2 to the chord length C1 is called the relative length γ2 of the second sub-blade 22, and the ratio of the height parameter h2 to the chord length C1 is called the relative height η2 of the second sub-blade 22. The chord length C3 of the second sub-blade 22 can be determined by γ2 and η2.

[0030] Further, at any spanwise position, the value range of γ1 or γ2 may be 0.2-0.8, and the sum of γ1 and γ2 is less than 1. The value range of η1 and η2 may be 0.02-1.

[0031] like Figure 5 As shown, after determining the chord length C2 of the first sub-blade 21 and the chord length C3 of the second sub-blade 22, the center arc line A of the first sub-blade 21 and the center arc line B of the second sub-blade 22 can be designed by a single circular arc line, that is, the unique center arc line A of the first sub-blade 21 and the center arc line B of the second sub-blade 22 are determined by giving the geometric angle α1 of the first sub-blade 21 and the geometric angle β1 of the second sub-blade 22.

[0032] Furthermore, at any spanwise position, the geometric angle α1 of the first sub-blade 21 and the geometric angle β1 of the second sub-blade 22 may be in the range of 10° to 60°.

[0033] like Figure 6 As shown, multiple equally divided vertical lines are made through the chord length C2 of the first sub-blade 21 and the chord length C3 of the second sub-blade 22, which intersect with the median arc line A and the median arc line B respectively, and then equally divided lines perpendicular to the median arc line A and the median arc line B are made through the intersection points of the multiple equally divided vertical lines with the median arc line A and the median arc line B respectively; by giving the equally divided line lengths and connecting them in sequence through spline curves, the suction surface profile line 21a of the first sub-blade 21, the pressure surface profile line 21b of the first sub-blade 21, the suction surface profile line 22a of the second sub-blade 22, and the pressure surface profile line 22b of the second sub-blade 22 can be obtained respectively.

[0034] S23, repeat the above steps S21-S22 to obtain the chord length, the mid-camber line and the plane cascade blade shape of the first sub-blade 21 and the second sub-blade 22 at any spanwise position within the interval from the starting spanwise position 20b to the 100% spanwise position 20c, and obtain the following by sequentially lofting: Figure 7 A first sub-blade 21 and a second sub-blade 22 are shown.

[0035] S3. Verify the aerodynamic performance and noise value of the axial flow fan through simulation or experiment, and adjust the starting span position 20b and / or the blade shape parameters of the sub-blades until they meet the design requirements.

[0036] (Example 1) Taking the design of an axial flow fan with a diameter of 500 mm as an example, it specifically includes: Step 1: Design Figure 1 The conventional axial flow fan with three blades shown, wherein the rotating shaft 10 has a diameter of 120 mm; Step 2: With the 53% spanwise position, i.e., the circumference with a diameter of 325 mm, as the starting spanwise position 20b of the blade segmentation, the chord length, the mid-camber line and the plane cascade blade shape of the first sub-blade 21 and the second sub-blade 22 are designed at the 53% spanwise position, the 80% spanwise position and the 100% spanwise position of the blade respectively; Specifically, the design of the chord length and the mid-arc is completed first, where γ1, η1, γ2, η2, α1, and β1 at the 53% spanwise position are 0.6, 0.066, 0.38, 0.09, 15.6°, and 16.5°, respectively; γ1, η1, γ2, η2, α1, and β1 at the 80% spanwise position are 0.6, 0.055, 0.38, 0.07, 11.3°, and 12.5°, respectively; γ1, η1, γ2, η2, α1, and β1 at the 100% spanwise position are 0.6, 0.09, 0.39, 0.012, 9°, and 10.2°, respectively. Then, the chord length of the first sub-blade 21 and the second sub-blade 22 is divided into 6 equal parts, and a vertical line perpendicular to the chord length is drawn at the dividing point. The vertical line intersects with the mid-arc line, and a dividing line perpendicular to the mid-arc line is drawn through the intersection. The length of the dividing line is obtained by multiplying the chord length C2 or C3 by the relative thickness of the blade shape, wherein the relative thickness of the blade shape from the leading edge point to the trailing edge point is 0.043, 0.048, 0.047, 0.036, and 0.023, respectively. In this embodiment, the relative thickness of the blade shape at the 53% spanwise position, the 80% spanwise position, and the 100% spanwise position is kept consistent. Finally, the blade shapes at the 53% spanwise position, the 80% spanwise position, and the 100% spanwise position are respectively lofted to obtain an axial flow fan in which the blade 20 is divided into the first sub-blade 21 and the second sub-blade 22 at the longer chord length (see Figure 8 ).

[0037] Step 3: Verify the axial fan starting performance.

[0038] (Comparative Example 1) The conventional axial flow fan obtained in the first step of Example 1 is taken as Comparative Example 1.

[0039] (Performance test) The performance of Example 1 and Comparative Example 1 were tested under the same motor and the same test conditions to obtain a flow rate and static pressure value curve (see Fig. 9 ) and flow rate and efficiency value curve (see Fig.10 ), it can be seen from the test results that: Example 1 has obvious advantages over Comparative Example 1 in the small flow area, its high-efficiency area is wider and has a wide range of applications; at the same time, the maximum efficiency of Example 1 is increased by about 1% compared with Comparative Example 1; the noise value of Example 1 in the high-efficiency area is reduced by about 1.5dB(A) compared with Comparative Example 1.

[0040] In summary, the axial flow fan and its design method provided by the present invention can realize the division of the longer chord length of the blade into at least two parts, so that its flow separation phenomenon and flow loss are reduced compared with the traditional fan, thereby having higher efficiency and lower noise. The present invention can solve the flow separation phenomenon and flow loss caused by the longer chord length of the traditional axial flow fan, especially the flow separation phenomenon existing at the spanwise position of 60% to 80% of the chord length due to the large adverse pressure gradient.

[0041] Therefore, the present invention effectively overcomes various shortcomings in the prior art and has a high industrial utilization value. The above embodiments are only illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the technology can modify or change the above embodiments without violating the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical ideas disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. An axial flow fan, comprising a rotating shaft and a plurality of blades arranged on the rotating shaft at equal intervals, characterized in that: The portion of the blade from the 20% to 80% spanwise position to the 100% spanwise position is divided into at least two sub-blades.

2. A method for designing an axial flow fan, characterized in that: Includes steps: S1. Design the blade shape and number of the axial flow fan; S2, selecting a starting spanwise position for blade segmentation, and segmenting the portion of the blade from the starting spanwise position to 100% spanwise position into at least two sub-blades; S3. Verify the aerodynamic performance and noise value of the axial flow fan through simulation or experiment, and adjust the spanwise position of the starting point and / or the design parameters of the sub-blades until they meet the design requirements.

3. The axial flow fan design method according to claim 2, characterized in that: The step S2 specifically includes the following steps: S21, selecting a spanwise position to obtain a planar unfolded view of the blade at the spanwise position; S22, selecting the segmentation points of the sub-blades on the planar unfolded view, and determining the chord length, the mid-camber line and the planar blade shape of the sub-blades; S23, repeating the above steps S21-S22, obtaining the chord length, the mid-camber line and the plane blade shape of the sub-blade at any spanwise position within the interval from the starting spanwise position to the 100% spanwise position, and obtaining all the sub-blades by sequentially lofting.

4. The axial flow fan design method according to claim 3, characterized in that: In step S22, the chord length of the sub-blade is determined by the relative length and the relative height; the median camber line is determined by the chord length and the geometric angle; and the planar cascade blade shape is determined by the chord length and the median camber line.

5. The axial flow fan design method according to claim 4, characterized in that: The number of the sub-blades is 2, including a first sub-blade and a second sub-blade.

6. The axial flow fan design method according to claim 5, characterized in that: The spanwise position of the starting point is 20% to 80% of the spanwise position.

7. The axial flow fan design method according to claim 6, characterized in that: At any spanwise position, the relative length of the first sub-blade / the second sub-blade is 0.2-0.8, and the sum of the relative lengths of the first sub-blade and the second sub-blade is less than 1.

8. The axial flow fan design method according to claim 7, characterized in that: At any spanwise position, the relative height of the first sub-blade / the second sub-blade is 0.02-1.

9. The axial flow fan design method according to claim 8, characterized in that: At any spanwise position, the geometric angle of the first sub-blade / the second sub-blade has a value range of 10° to 60°.

Images