An axial flow fan blade having wave crests and wave troughs disposed on the suction face

Abstract

The present application aims to provide a kind of axial flow fan blade in suction surface setting wave crest and wave trough, including blade body, leading edge, trailing edge, suction surface, pressure surface, suction surface from leading edge chord 1 / 5-1 / 4 It starts to trailing edge, setting wave crest and wave trough structure, the profile of wave crest and wave trough structure is with two different sizes as unit, from leading edge to the direction of continuously arranged structure of trailing edge, form corrugated structure.The present application can significantly reduce the vortex in the "wide" type blade suction surface area, fill the blank of noise reduction measures in this type fan field.Compared with the general way of noise reduction design in fan blade leading edge and trailing edge and suction surface, the present application will not have any influence on the doing function of fan, will not affect the airflow of fan blade pressure surface, so the present application can realize the purpose of reducing the noise of axial flow fan, and will not affect the overall performance of fan, so that fan runs more stably.

Description

Technical Field

[0001] The present invention relates to a blade, specifically an axial flow fan blade. Background Technology

[0002] Axial flow fans are a common type of fan, resembling a cylinder in shape, with the blades and motor housed within the cylinder. They are called axial flow fans because the airflow direction is the same as the axis. Axial flow fans are commonly used for ventilation in warehouses, offices, factories, and other similar locations. They can also be used as evaporators, coolers, and condensers. Considering the application scenarios of axial flow fans, noise control is essential. Generally, reducing fan noise is achieved through two main methods: first, addressing the noise propagation path, such as adding sound-absorbing structures or sound-absorbing cotton; second, modifying the fan itself by improving its structure. Currently, the first method is the most widely used, but its noise reduction capability is limited. Therefore, noise reduction design for the fan itself is urgent, and since the blades are the primary source of fan noise, noise reduction design for the blades is the main research direction.

[0003] The main reason for noise generation in axial flow fans is that the gas undergoes flow separation when flowing through the blades, generating a large number of vortices. The generation and collapse of these vortices lead to noise, so the fundamental goal of blade noise reduction design is to reduce the generation of vortices.

[0004] Currently, blade noise reduction design mainly focuses on the leading and trailing edges of the blade. This is generally achieved by arranging specific structures to reduce the generation of vortices at these edges, thus reducing noise. These structures are typically designed for general blades, but for "wide" blades (where the chord length is longer than the distance from the blade tip to the root, such as…),… Figure 1 For blades, the airflow separation that occurs as it flows over the suction surface of the blade is more intense, and the vortices generated by the flow separation are far more numerous than those of ordinary blades. Therefore, noise reduction design is essential for "wide" blades. Summary of the Invention

[0005] The purpose of this invention is to provide an axial flow fan blade with peaks and troughs on the suction surface to reduce the noise of the axial flow fan and improve the operating stability of the fan.

[0006] The objective of this invention is achieved as follows:

[0007] The present invention discloses an axial flow fan blade with crests and troughs on the suction surface, characterized in that: it includes a blade body, a leading edge, a trailing edge, a suction surface, and a pressure surface. The suction surface is provided with crests and troughs from 1 / 5 to 1 / 4 of the chord length of the leading edge to the trailing edge. The profile of the crests and troughs is a structure in which two arcs of different sizes are arranged continuously from the leading edge to the trailing edge to form a corrugated structure.

[0008] The present invention may also include:

[0009] 1. For a crest, the side near the leading edge is composed of small arcs, and the side near the trailing edge is composed of large arcs; for a trough, the small arcs are located near the leading edge, and the large arcs are located near the trailing edge.

[0010] 2. The diameter of the first small arc S1 near the leading edge is d1, and the diameter of the first large arc S2 near the leading edge is d2. Taking the center coordinates of the small arc S1 as the origin, the small arc S1 can be represented as:

[0011] x 2 +z 2 =d1 2

[0012] The value of d1 ranges from 1 / 30 to 1 / 40 of the chord length λ, where the tangent point between the small circular arc S1 and the suction surface is the starting position of the corrugated structure.

[0013] 3. Relative to the smaller arc S1, the larger arc S2 is represented as:

[0014] (x-a2) 2 +(z-c2) 2 =d2 2

[0015] a2 and c2 represent the difference between the X and Z coordinates of the two circular arcs, respectively. The diameter d2 of the larger circular arc S2 ranges from 1 / 3 to 1 / 4 of the chord length λ.

[0016] 4. The starting position of the second trough structure is tangent to the ending position of the first ripple structure. The size of the arc is exactly the same as that of the first trough structure. The difference is that the position of the center of the arc changes with the contour of the suction surface and extends to the tail edge. If the centers of the small arcs are connected to form a curve, the curve is the same as the contour curve of the suction surface. The same applies to the large arc.

[0017] 5. The distance between the first crest and trough structure and the leading edge of the blade is L3, which is 1 / 4 to 1 / 5 of the chord length λ. The distance between the structure and the tangent point of the suction surface and the circumferential surface S5 is L4, which is 1 / 10 of the chord length λ.

[0018] The advantages of this invention are:

[0019] (1) Generally, blade noise reduction design mainly focuses on the leading and trailing edges of the blade, with the main goal of reducing eddies generated by flow separation at the leading and trailing edges, thereby achieving the purpose of noise reduction. However, for "wide" blades, in addition to the eddies generated at the leading and trailing edges, the flow separation of gas as it flows through the suction surface of the blade will generate a large number of eddies in this area. This invention can significantly reduce the eddies in the suction surface area of ​​"wide" blades, filling the gap in noise reduction measures in this type of wind turbine.

[0020] (2) Compared with the general method of noise reduction design on the leading edge and trailing edge of the fan blades and the suction surface, the present invention will not affect the working capacity of the fan, nor will it affect the airflow on the pressure surface of the fan blades. Therefore, the present invention can reduce the noise of the axial fan without affecting the overall performance of the fan, making the fan operation more stable. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the transverse cross-section of the blade;

[0022] Figure 2 This is a schematic diagram of the suction surface of the blade;

[0023] Figure 3 A detailed schematic diagram of the corrugated structure;

[0024] Figure 4 Schematic diagram of the center of the arc of the corrugated structure on the suction surface of the blade;

[0025] Figure 5 This is a schematic diagram showing the distance between the starting position of the corrugated structure and the leading edge of the blade.

[0026] Figure 6 This is a schematic diagram showing the distance between the tangent point between the suction surface and the circumferential surface of the fan and the starting point of the corrugations;

[0027] Figure 7 This is a schematic diagram of the complete impeller. Detailed Implementation

[0028] The invention will now be described in more detail with reference to the accompanying drawings:

[0029] Combination Figure 1-7 The present invention is an axial flow fan blade with a corrugated structure for noise reduction on the suction surface of the blade, including a leading edge A, a trailing edge B, a suction surface C, a pressure surface D, a blade chord length λ, a blade width L1, a blade height L2, and a corrugated structure composed of arcs S1 and S2 with radii R1 and R2 respectively.

[0030] The suction surface of the blade, starting from 1 / 5 to 1 / 4 of the chord length at the leading edge (the flow separation point) and extending to the trailing edge, features a crest and trough structure running from the blade root to the blade tip. The crest and trough profiles from the leading edge to the trailing edge are two arcs of different sizes, which connect end to end to form the crest and trough. Furthermore, the crests and troughs extend from the blade tip all the way to the blade root.

[0031] The crest and trough structure is composed of two circular arcs of different diameters connected end to end. The crest and trough structures are arranged in sequence and extend all the way to the trailing edge of the blade, forming a special corrugated structure on the suction surface of the blade. It is this special corrugated structure that changes the flow characteristics of the flow field to achieve the purpose of noise reduction.

[0032] For the crests, the side closer to the leading edge of the blade is composed of small arcs, and the side closer to the trailing edge of the blade is composed of large arcs; for the troughs, the small arcs are located closer to the leading edge of the blade, and the large arcs are located closer to the trailing edge of the blade.

[0033] The initial position of the crest and trough structure is 1 / 4 to 1 / 5 of the chord length away from the leading edge of the blade, and 1 / 10 of the chord length away from the tangent point of the suction surface and the circumferential surface. The initial position of this structure is related to the flow separation generated on the suction surface of the blade. Placing this structure at the point where flow separation occurs can effectively disrupt the vortices generated by flow separation, preventing them from developing into large vortices, thereby reducing noise.

[0034] The crests and troughs connect end to end, following the contour of the blade's suction surface from the starting position to the trailing edge of the blade. That is, the contour of the blade's suction surface is tangent to each crest, and the point of tangency is located at the highest point of the crest.

[0035] For crests, the larger diameter arc is located near the leading edge of the blade, and the smaller diameter arc is located near the trailing edge of the blade; for troughs, the larger diameter arc is located near the trailing edge of the blade, and the smaller diameter arc is located near the leading edge of the blade.

[0036] The connection between two circular arcs with different radii at the crest is tangent. This allows for a smooth transition of the arc at the crest, preventing obstruction of airflow near the wall and reducing the impact on the aerodynamic performance of the fan.

[0037] The ripples begin at 1 / 5 to 1 / 4 of the chord length λ from the leading edge of the suction surface (the flow separation point). If we take the center coordinates of circle S1 as the origin, then arc S1 can be represented as:

[0038] x 2 +z 2 =d1 2

[0039] In the above formula, the value of d1 ranges from 1 / 30 to 1 / 40 of the chord length λ, where the tangent point between the circular arc S1 and the suction surface of the blade (near the leading edge A of the blade) is the starting position of the corrugated structure.

[0040] With respect to arc S1, the center coordinates of arc S2 are (23.04, 227.08, -87.58). Therefore, arc S2 can be represented as:

[0041] (x-a2) 2 +(z-c2) 2 =d2 2

[0042] In the above formula, a2 and c2 represent the difference between the X and Z coordinates of the two arcs, respectively. The arc diameter d2 of S2 ranges from 1 / 3 to 1 / 4 of the chord length λ. When the diameters of the two arcs are within the range of d1 and d2, the corrugated structure has the best effect on vortex destruction and the least impact on the overall performance of the fan. Therefore, when the arc diameter is within this range, the corrugated structure can effectively reduce fan noise.

[0043] like Figure 3 As shown, the intersection of arc S2 and arc S1 is the trough of the corrugated structure. The intersection of arc S2 and the blade suction surface is the end point of a trough structure, the highest point of a crest structure, and the starting point of the next trough structure. The starting position of the second trough structure is tangent to the end point of the first corrugated structure. The size of the arc is exactly the same as that of the first trough structure, except that the position of the center changes according to the contour of the suction surface. This continues until it reaches the trailing edge of the blade. Connecting the centers of the smaller arcs forms a curve that matches the contour curve of the suction surface, and the same applies to the larger arcs. Figure 4 As shown.

[0044] from Figure 3 As can be seen, for the troughs, the side near the leading edge of the blade is composed of arc S1, and the side near the trailing edge is composed of arc S2. For the crests, arc S2 is located near the leading edge of the blade, and arc S3 is located near the trailing edge. The reason for placing the smaller-diameter arc S1 near the leading edge is that after the airflow separates at the suction surface, the rotating vortex will collide with arc S1. Since arc S1 has a larger curvature, the vortex is immediately destroyed upon contact with arc S1 and will not develop further. Arc S2 has a larger curvature, and being placed after arc S1, it will not significantly impede the overall airflow.

[0045] The distance L3 between the crest and trough structure and the leading edge of the blade, such as Figure 5As shown, L3 is 1 / 4 to 1 / 5 of the chord length λ, and L4 is the distance from the tangent point of the suction surface and the circumferential surface S5, which is 1 / 10 of the chord length λ. The starting position of the corrugated structure is related to the blade installation angle and the blade shape of the suction surface. Both of these factors affect the flow generated at the suction surface, and together they determine the location where flow separation occurs at the suction surface. Setting the starting position of the corrugated structure at the point where flow separation occurs can effectively disrupt the vortices generated by flow separation and prevent small vortices from developing into large vortices, thereby achieving the purpose of reducing noise.

Claims

1. An axial flow fan blade with crests and troughs on its suction surface, characterized in that: Including blades The main body, leading edge, trailing edge, suction surface, and pressure surface are provided. The suction surface starts from 1 / 5 to 1 / 4 of the chord length of the leading edge and extends to the trailing edge. It is equipped with a wave crest and wave trough structure. The shape of the wave crest and wave trough structure is a structure that is continuously arranged from the leading edge to the trailing edge using two arcs of different sizes as units, forming a corrugated structure. For a crest, the side near the leading edge is composed of small arcs, and the side near the trailing edge is composed of large arcs; for a trough, the small arcs are located near the leading edge, and the large arcs are located near the trailing edge. The diameter of the first small arc S1 near the leading edge is d1, and the diameter of the first large arc S2 near the leading edge is d2. Taking the center coordinates of the small arc S1 as the origin, the small arc S1 can be represented as: The value of d1 ranges from 1 / 30 to 1 / 40 of the chord length λ, where the tangent point between the small circular arc S1 and the suction surface is the starting position of the corrugated structure. Relative to the smaller arc S1, the larger arc S2 is represented as: a2 and c2 represent the difference between the X and Z coordinates of the two circular arcs, respectively. The diameter d2 of the larger circular arc S2 ranges from 1 / 3 to 1 / 4 of the chord length λ.

2. The axial flow fan blade with crests and troughs on the suction surface according to claim 1, characterized in that: the second... The starting position of the trough structure is tangent to the ending position of the first corrugated structure. The size of the arc is exactly the same as that of the first trough structure. The difference is that the position of the center of the arc changes with the contour of the suction surface and extends to the tail edge. If the centers of the small arcs are connected to form a curve, the curve is the same as the contour curve of the suction surface. The same applies to the large arc.

3. The axial flow fan blade with crests and troughs on the suction surface according to claim 1, characterized in that: The distance between the first crest and trough structure and the leading edge of the blade is L3, which is 1 / 4 to 1 / 5 of the chord length λ. The distance between the structure and the tangent point of the suction surface and the circumferential surface S5 is L4, which is 1 / 10 of the chord length λ.

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