Composite curved swept axial flow fan structure and its design method

Abstract

The present invention discloses a composite curved swept axial flow fan structure and a design method thereof, comprising a hub and blades; the stacking mode of the blades is stacking at the midpoint of the chord length of the blade section, and the curved stacking line is a parabola, the swept stacking line is a cubic B-spline curve, and the outer edge of the blade is set as a flange structure; the blade height direction is defined as the positive direction of the Y axis, the hub axis direction is the X axis direction, and the radius at the hub section is recorded as R H , the radius of the blade tip section is R T , the radius at any cross section between the hub and the blade tip is; by separating the design of the blade outer edge flange structure into a parametric design, it is beneficial to improve the design efficiency of the axial flow fan blade, while ensuring that the design of the blade outer edge flange structure is more reasonable, which is beneficial to reducing flow losses, and can effectively improve the efficiency of the axial flow fan and reduce noise.

Description

Technical Field

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

[0002] Axial flow fans are an important and large-volume type of fan, which are widely used in coal mines, mines, tunnels, chemicals, energy, textiles and other industries to play a ventilation and dust removal role. Due to the particularity of the air duct structure in the outdoor unit of the air conditioner, the chord length of this type of axial flow fan is small near the hub and the chord length of the blade tip is long. The efficiency of the axial flow fan is greatly affected by the blade sweep effect.

[0003] At present, this type of axial flow fan adopts projection method to complete the sweep design in 3D modeling software. This method has low design efficiency, and the sweep angle and stacking line are difficult to control, which affects the air output efficiency and quiet effect of the axial flow fan. Summary of the invention

[0004] In order to overcome the deficiencies of the prior art, the present invention provides a composite swept-curve axial flow fan structure and a design method thereof.

[0005] The technical solution adopted by the present invention to solve the technical problem is: to provide a design method for a composite curved swept axial flow fan, including a hub and blades; the stacking mode of the blades is the midpoint stacking of the chord length of the blade section, and the curved stacking line is a parabola, the swept stacking line is a cubic B-spline curve, and the outer edge of the blade is set as a flange structure; the blade height direction is defined as the positive direction of the Y axis, the axis direction of the hub is the X axis direction, and the radius at the hub section is recorded as R H , the radius of the blade tip section is R T The radius of any section between the hub and the blade tip is r. Select several sections along the positive direction of the Y axis, and the corresponding value K = (rR H ) / (R T -R H ), when K is 90% to 100%, it corresponds to the flange structure, and when K is 0% to 90%, it corresponds to other positions of the blade; the midpoint of the chord length of each section is taken as the stacking point, and a spatial stacking line is formed by the stacking point, and the spatial stacking line is projected to the XOY plane and the YOZ plane respectively to obtain a bent stacking line and a swept stacking line; on the XOY plane, from the origin O of the spatial rectangular coordinate system to the blade top section, when K=100%, the angle between the line connecting the stacking points and the positive direction of the Y axis is recorded as the bending angle δ; on the YOZ plane, from the origin O of the spatial rectangular coordinate system to the blade top section, when K=100%, the angle between the line connecting the stacking points and the positive direction of the Y axis is called the swept angle θ.

[0006] According to the axial fan design method provided by the present invention, by separating the design of the blade outer edge flange structure into a parameterized design, it is beneficial to improve the design efficiency of the axial fan blade, while ensuring that the design of the blade outer edge flange structure is more reasonable, which is beneficial to reducing flow losses and can effectively improve the efficiency of the axial fan and reduce noise.

[0007] As some preferred embodiments of the present invention, the values ​​of K are 0%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 92.5%, 95%, 97.5%, and 100%, respectively.

[0008] A composite curved swept axial flow fan structure, using the composite curved swept axial flow fan design method;

[0009] The curved stack is a parabola, and the control equation of the parabola is defined as:

[0010] y=A[xa(R T -R H )-R H ] 2 +B

[0011]

[0012] Wherein A and B are coefficients of a quadratic function,

[0013] H S =R T tanδ

[0014]

[0015] Wherein H S is the distance from the tip of the blade to the radial line, H is the distance from the maximum radial curvature of the curved stack line to the radial line; the value of the curvature angle is 20.0°~25.0°, and the value of the curvature factor is 0.1~0.2; the swept stack line is a cubic B-spline curve, which is generated by four control points P0~P3, where the straight line P0P3 and the straight line P1P2 are parallel to each other; the angle between the tangent of the swept stack line at the blade root control point P0 and the radial line Y axis is called the blade root sweep control angle θ H The angle between the tangent line at the blade tip control point P3 and the radial line Y axis is called the blade tip sweep control angle θ T The ratio of the maximum curvature F of the swept stack line to the length of the straight line P0P3 is called the relative curvature f of the swept stack line; the sweep angle is 4.0° to 8.0°, and the blade root sweep control angle θ H The value of is 10.0°~20.0°, and the blade tip sweep control angle θ TThe value of is 75.0°~85.0°, and the value of the relative curvature f of the swept stack line is 0.1~0.2.

[0016] The axial flow fan provided by the present invention can effectively improve the efficiency of the axial flow fan and reduce the noise by improving the structure of the blades and reducing the flow loss.

[0017] The beneficial effects of the present invention are:

[0018] 1. The blade shape is adjusted by controlling the bend angle, bend factor, sweep angle, blade root sweep control angle, blade tip sweep control angle and relative curvature of the sweep stack line, so that the outer edge of the blade presents a flange structure toward the suction surface, reducing flow losses, and effectively improving the efficiency of the axial flow fan and reducing noise;

[0019] 2. By designing an axial flow fan through the technical solution of the present invention, the design of the flange structure of the outer edge of the blade can be parameterized, which is beneficial to improving the design efficiency of the axial flow fan blades and also facilitates the subsequent optimization design of the axial flow fan. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0021] Figure 1 is a stereogram of the present invention;

[0022] Figure 2 is a top view of the present invention;

[0023] Figure 3 yes Figure 1 Schematic diagram of the three-dimensional surface structure of the central axial flow fan blade shape;

[0024] Figure 4 is a schematic diagram of the circumferential bend of a blade of the present invention;

[0025] Figure 5 It is a schematic diagram of the axial sweep of the blade of the present invention.

[0026] Reference numerals: hub 100 , blade 200 . DETAILED DESCRIPTION

[0027] In order to make the purpose, technical scheme and advantages of the present application clearer, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. In order to thoroughly understand the invention, some specific details will be involved in the following description. In the absence of these specific details, the invention can still be implemented, that is, the technical personnel in the relevant field can use these descriptions and statements here to more effectively introduce the essence of their work to other technical personnel in the relevant field. In addition, it should be noted that the words "inside" and "outside" refer to the direction toward or away from the geometric center of a specific component, respectively, and the relevant technical personnel should not be understood as a technology outside the scope of protection of this application when making simple, non-creative adjustments to the above directions. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the actual scope of protection. In order to avoid confusing the purpose of the invention, the well-known manufacturing methods, control procedures, component sizes, material compositions, pipeline layouts, etc. are already easy to understand, so they are not described in detail.

[0028] Figure 1 is a perspective view of an embodiment of the present invention, referring to Figure 1 An embodiment of the present invention provides a design method for a composite curved swept axial flow fan, including a hub 100 and blades 200, wherein the blades 200 are stacked in a manner of stacking at the midpoints of the chord length of the blade cross section, and the curved stacking line is a parabola, the swept stacking line is a cubic B-spline curve, and the outer edge of the blade is set as a flange structure.

[0029] Reference Figure 2 , Figure 3 , define the blade height direction as the positive direction of the Y axis, the hub axis direction as the X axis direction, and the radius of the hub cross section as R H , the radius of the blade tip section is R T The radius of any section between the hub and the blade tip is r. Select several sections along the positive direction of the Y axis, and the corresponding value K = (rR H ) / (R T -R H ), when K is 90% to 100%, it corresponds to the flange structure, and when K is 0% to 90%, it corresponds to other positions of the blade. That is, the main part of the blade and the flange structure are distinguished, and the cross-section corresponding to K is selected respectively.

[0030] The midpoint of the chord length of each section is taken as the stacking point, and a spatial stacking line is formed by the stacking points. The spatial stacking line is projected to the XOY plane and the YOZ plane respectively to obtain the curved stacking line and the swept stacking line.

[0031] On the XOY plane, from the origin O of the spatial rectangular coordinate system to the blade tip section (when (rR H ) / (R T -R H)=100%) The angle between the line connecting the overlapping points and the positive direction of the Y axis is recorded as the bending angle δ.

[0032] On the YOZ plane, from the origin O of the spatial rectangular coordinate system to the blade tip section (when (rR H ) / (R T -R H )=100%) The angle between the line connecting the overlapping points and the positive direction of the Y-axis is called the sweep angle θ.

[0033] This design can be targeted at different positions of the blade, especially the position of the flange structure. By controlling the parameters of the corresponding bend stacking line and swept stacking line, a suitable shape can be designed.

[0034] Reference Figure 2 , Figure 3 One embodiment of the present invention provides a composite curved swept axial flow fan, which adopts the above-mentioned composite curved swept axial flow fan design method.

[0035] Reference Figure 4 , the curved line is a parabola, and the governing equation of the parabola is defined as,

[0036] y=A[xa(R T -R H )-R H ] 2 +B

[0037]

[0038] Where A and B are the coefficients of the quadratic function,

[0039] H S =R T tanδ

[0040]

[0041] Among them, H S is the distance from the blade tip overlap point to the radial line, and H is the distance from the radial maximum curvature of the curved overlap line to the radial line.

[0042] The value of the bend angle is 20.0°~25.0°, and the value of the bend factor is 0.1~0.2. When the bend angle δ is constant and the bend factor a increases, the position of the maximum bend of the bend stack line shifts toward the tip of the blade, and the distance H from the maximum bend to the radial line increases. When the bend factor a is 0, the blade is in a forward bend form on the entire radial line. When the bend factor a is a value between (0, 0.5), the blade is in a backward bend form at the root and still in a forward bend form at the tip. Axial flow fans with backward-bent blades at the root and forward-bent blades at the tip help reduce the aggregation of low-energy fluids in the boundary layer at the root and tip of the blade, thin the boundary layer, and reduce flow losses. However, excessive backward bend at the root and forward bend at the tip of the blade cause a large amount of low-energy fluid to gather in the middle of the blade, which increases the loss.

[0043] Reference Figure 5 , the swept accumulation line is a cubic B-spline curve, which is generated by four control points P0~P3, where the straight line P0P3 and the straight line P1P2 are parallel to each other;

[0044] The angle between the tangent line of the swept stack line at the blade root control point P0 and the radial line Y axis is called the blade root swept control angle θ H The angle between the tangent line at the blade tip control point P3 and the radial line Y axis is called the blade tip sweep control angle θ T The ratio of the maximum curvature F of the swept-over line to the length of the straight line P0P3 is called the relative curvature f of the swept-over line.

[0045] The sweep angle is 4.0°~8.0°, and the blade root sweep control angle θ H The value of is 10.0°~20.0°, and the blade tip sweep control angle θ T The value of is 75.0°~85.0°, and the value of the relative curvature f of the stacking line is 0.1~0.2.

[0046] The shape of the swept stack line is determined by the sweep angle θ, the blade root sweep control angle θH, the blade tip sweep control angle θT, and the relative curvature f of the swept stack line. When the blade root sweep control angle is 0°, the blade is in a forward swept form on the entire radial line. When the blade root control angle is a certain angle, the blade is in a backward swept form at the blade root and is still forward swept at the blade tip. For axial flow fans with better aerodynamic performance, the forward sweep angle is smaller than the forward bend angle. Appropriate root sweep and blade tip forward sweep can adjust the shape of the blade and solve the problem of excessive blade warping caused by a large forward bend angle.

[0047] According to the design method of the present invention, a larger relative curvature f of the swept stack line causes the outer edge of the blade to present a flange structure toward the suction surface, and the larger f is, the greater the degree of outer edge flange. When f is greater than 0.1, a flange structure appears on the outer edge of the blade. Blades with an outer edge flange structure can reduce the generation and development of tip vortices and reduce aerodynamic noise.

[0048] In addition to improving the aerodynamic performance of the axial flow fan, the appropriate blade sweep degree can also reduce the equivalent stress of the blades, reduce deformation, improve the fatigue strength of the axial flow fan, and extend its service life.

[0049] The following is a description with reference to embodiments.

[0050] In Example 1, the values ​​of K are 0%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 92.5%, 95%, 97.5%, and 100%, respectively, i.e., 14 sections are selected along the blade height direction (positive direction of the Y axis), of which 0%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, and 100% correspond to the main part of the blade, and 92.5%, 95%, and 97.5% are for the larger surface deformation at the flange structure of the outer edge of the blade, and 3 sections are evenly selected between 90% and 100% of the blade height. In this way, it is more targeted at the flange structure of the outer edge of the blade.

[0051] In Example 2, the impeller diameter is 420 mm, the number of blades is 3, the bend angle is 20.0°, and the bend factor is 0.15. The sweep angle is 7.5°, the blade root sweep control angle is 10.0°, the blade tip sweep control angle is 75.0°, and the relative camber of the swept stack line is 0.15. The numerical simulation results of the prototype and the example are compared under the rotation speed of 870 rpm, and the results are as follows.

[0052]

[0053] The table shows the numerical simulation results of the prototype and the embodiment at a speed of 870 rpm. Under a given large static pressure condition, the flow rate of the embodiment is slightly reduced, which will relatively reduce noise, reduce power, and improve efficiency, especially under low flow conditions. The efficiency improvement is most obvious. It shows that by adopting the axial flow fan design method of the present invention, its aerodynamic performance and acoustic performance can be effectively improved.

[0054] According to the above principle, the present invention can also make appropriate changes and modifications to the above implementation. Therefore, the present invention is not limited to the specific implementation disclosed and described above, and some modifications and changes to the present invention should also fall within the protection scope of the claims of the present invention.

Claims

1. A composite curved swept axial flow fan structure, comprising a hub (100) and blades (200), characterized in that: The stacking method of the blades (200) is stacking at the midpoint of the chord length of the blade cross section, the curved stacking line is a parabola, the swept stacking line is a cubic B-spline curve, and the outer edge of the blade is set as a flange structure; Define the blade height direction as the positive direction of the Y axis, the hub axis direction as the X axis direction, and the radius of the hub cross section as R H , the radius of the blade tip section is R T The radius of any section between the hub and the blade tip is r. Select several sections along the positive direction of the Y axis, and the corresponding value K = (rR H ) / (R T -R H ), when K is When K is , corresponding to other positions of the blade; The midpoint of the chord length of each section is used as an accumulation point, a spatial accumulation line is formed by the accumulation point, and the spatial accumulation line is projected onto the XOY plane and the YOZ plane respectively to obtain a curved accumulation line and a swept accumulation line; On the XOY plane, from the origin O of the spatial rectangular coordinate system to the blade tip section, when K = 100%, the angle between the line connecting the overlapping points and the positive direction of the Y axis is recorded as the bending angle δ; On the YOZ plane, from the origin O of the spatial rectangular coordinate system to the blade tip section, when K = 100%, the angle between the line connecting the overlapping points and the positive direction of the Y axis is called the sweep angle θ; The curved stack is a parabola, and the control equation of the parabola is defined as: y=A[x-a(R T -R H )-R H ] 2 +B Wherein A and B are coefficients of a quadratic function, H S =R T tanδ Wherein H S is the distance from the blade tip overlap point to the radial line, and H is the distance from the radial maximum curvature of the curved overlap line to the radial line; The value of the bending angle is The bending factor is taken as The swept curve is a cubic B-spline curve, which consists of four control points Control generation, where the straight line P0P3 and the straight line P1P2 are parallel to each other; The angle between the tangent line of the swept stack line at the blade root control point P0 and the radial line Y axis is called the blade root swept control angle θ H The angle between the tangent line at the blade tip control point P3 and the radial line Y axis is called the blade tip sweep control angle θ T The ratio of the maximum curvature F of the swept-over line to the length of the straight line P0P3 is called the relative curvature f of the swept-over line; The sweep angle is taken as The blade root sweep control angle θ H The value of The blade tip sweep control angle θ T The value of The relative curvature f of the swept stack line is 2. The composite curved axial flow fan structure according to claim 1, characterized in that: The values ​​of K are 0%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 92.5%, 95%, 97.5%, and 100%, respectively.

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