Blade of axial flow fan and axial flow fan applying same

Abstract

The application discloses a blade of an axial flow fan and an axial flow fan applying the blade. The overall forward sweep angle of the blade of the axial flow fan is θ. The forward sweep accumulation line is divided by span=0.5, and the forward sweep accumulation line comprises a first blade tip accumulation point, a first middle accumulation point and a first blade root accumulation point. The forward sweep angle of the blade below span=0.5 is θ1. A first straight line is obtained by connecting the first blade root accumulation point and the first middle accumulation point, and a second straight line is obtained by connecting the first middle accumulation point and the first blade tip accumulation point. The length of the first straight line is l1, and the length of the second straight line is l2. The forward sweep accumulation line passing through the three accumulation points is an arc-like line. The maximum distance between the first lower half accumulation line and the first straight line is t1, and the maximum distance between the first upper half accumulation line and the second straight line is t2. The accumulation line is determined by limiting the range of the parameters.

Description

Technical Field

[0001] The present invention relates to power devices, and more particularly to blades of an axial flow fan, and an axial flow fan using the blades of the axial flow fan. Background Technology

[0002] The working principle of an axial flow fan is that the fluid flows into the blade channel along the axis. When the impeller rotates under the drive of the motor, the rotating blades give the fluid around them an axial thrust (when the fluid flows around the blades, according to the principles of fluid mechanics, the fluid exerts a lift force on the blades. At the same time, according to the principle that action and reaction forces are equal, the blades also exert a force on the fluid that is equal in magnitude and opposite in direction to the lift force, i.e., a thrust). This thrust of the blades does work on the fluid, increasing the fluid's energy and causing it to be discharged along the axis.

[0003] Currently, the aerodynamic design of axial fan blades is mostly done at the element level, that is, designing the flow around the airfoil at different blade heights. Blades designed at the element level only consider the two-dimensional flow of the airfoil at different blade heights, while the flow inside the blade passage of an axial fan is actually a complex three-dimensional flow. This results in significant flow losses, often leading to axial fan efficiency lower than the theoretical design efficiency. For large fans and large-scale unit groups, this consumes a lot of energy and is not environmentally friendly.

[0004] To improve fan performance, some solutions involve sweeping the blades of axial flow fans. For example, Chinese Patent Application No. 202010699897.7 discloses a blade for an axial flow fan with uniform thickness and an axial flow fan itself. The blade includes a pressure surface, a suction surface, an upper surface, a lower surface, a leading edge surface, and a trailing edge surface. The upper and lower surfaces coincide with the sides of two coaxial cylinders. A series of cross-sections are formed by the intersection of the sides of a series of coaxial cylinders from radius RH to RS with the axial flow blade. The pressure and suction surface curves of each cross-section are generated by cubic spline curves that control the chord length, leading edge inlet angle, trailing edge outlet angle, blade mounting angle, and relative camber. An accumulation line is obtained by using the midpoint of the chord length of each cross-section as the accumulation point. This accumulation line sweeps forward axially and bends forward circumferentially.

[0005] This type of axial flow fan only specifies the sweep angle and parabolic shape of the blades, without considering other factors that have a significant impact on the fan's performance. The highest total pressure efficiency of the impeller in the optimal embodiment is about 72.5% under numerical simulation, which shows that the efficiency is not high. Moreover, the blade chord length varies in the blade height direction, which greatly increases the complexity and cost of manufacturing.

[0006] For example, Chinese Patent Application No. 202120313080.1 discloses an integrally formed swept combined blade and a mining axial flow fan. Multiple swept combined blades are evenly installed along the circumference of the hub to form an impeller. The swept combined blade adopts a quadratic Bezier curve as the centroid accumulation line that controls the shape of the blade body.

[0007] This type of axial flow fan requires a given control equation for the bending and sweeping of the blade stacking line, and overall control of the characteristics of the entire stacking line. Therefore, the blade shape control accuracy is very high, resulting in a high manufacturing cost. Summary of the Invention

[0008] The first technical problem to be solved by the present invention is to provide a blade for an axial flow fan that can improve the efficiency of the fan, in order to address the shortcomings of the prior art.

[0009] The second technical problem to be solved by the present invention is to provide an axial flow fan with the above-mentioned blades.

[0010] The technical solution adopted by the present invention to solve the first technical problem mentioned above is: a blade for an axial flow fan, wherein the overall forward sweep angle of the blade is θ, characterized in that:

[0011] The overlapping lines of the blade sweep forward are divided by span = 0.5, where span is the relative position in the radial direction of the blade. At the blade tip, span = 1, and at the blade root, span = 0. The overlapping lines of the blade sweep forward include a first blade tip overlapping point, a first intermediate overlapping point, and a first blade root overlapping point, wherein the first intermediate overlapping point is the overlapping point of the overlapping lines of the sweep forward at span = 0.5.

[0012] The position of the first leaf tip accumulation point is determined by θ and the first leaf root accumulation point. The forward sweep angle of the leaf below span = 0.5 is θ1. The position of the first intermediate accumulation point is determined by θ1 and the first leaf root accumulation point.

[0013] A first straight line is obtained by connecting the first leaf root accumulation point and the first intermediate accumulation point, and a second straight line is obtained by connecting the first intermediate accumulation point and the first leaf tip accumulation point. The length of the first straight line is l1, and the length of the second straight line is l2.

[0014] The accumulation line that sweeps forward through the above three accumulation points is an arc-like line, including the first lower half accumulation line formed between the first intermediate accumulation point and the first leaf root accumulation point, and the first upper half accumulation line formed between the first leaf tip accumulation point and the first intermediate accumulation point. The maximum distance between the first lower half accumulation line and the first straight line is t1, and the maximum distance between the first upper half accumulation line and the second straight line is t2.

[0015] The above parameters satisfy:

[0016]

[0017] By defining the blade segments (upper and lower), the forward sweep characteristics and structural parameter ranges of different parts of the blade, as well as key parts, can be accurately grasped. The influence of multiple parameters on the wind turbine performance can be fully considered, resulting in lower flow resistance and higher total pressure efficiency. Instead of controlling the shape of the entire stacking line, the focus is on the angle θ between the beginning and end of the stacking lines of the upper and lower halves of the blade (i.e., the blade tip and blade root), as well as the highest point of the "protrusion" in the middle (characterized by t1). Therefore, the feasibility of controlling the shape of the stacking line is stronger, and the blade forming cost is lower.

[0018] To further improve performance, the blades are swept blades.

[0019] Preferably, the overall forward bending angle of the blade is θ';

[0020] The overlapping line of the forward bend of the blade is divided by a span of 0.5. The overlapping line of the forward bend of the blade includes a second tip overlapping point, a second intermediate overlapping point, and a second root overlapping point, wherein the second intermediate overlapping point is the overlapping point of the forward bend at a span of 0.5.

[0021] The position of the second leaf tip accumulation point is determined by θ' and the second leaf root accumulation point. The forward bending angle of the leaf below span = 0.5 is θ1'. The position of the second intermediate accumulation point is determined by θ1' and the second leaf root accumulation point.

[0022] A third straight line is obtained by connecting the second leaf root accumulation point and the second intermediate accumulation point, and a fourth straight line is obtained by connecting the second intermediate accumulation point and the second leaf apex accumulation point. The length of the third straight line is l1', and the length of the fourth straight line is l2'.

[0023] The accumulation line that bends forward through the above three accumulation points is an arc-like line, including the second lower half accumulation line formed between the second intermediate accumulation point and the second leaf root accumulation point, and the second upper half accumulation line formed between the second leaf tip accumulation point and the second intermediate accumulation point. The maximum distance between the second lower half accumulation line and the third straight line is t1', and the maximum distance between the second upper half accumulation line and the fourth straight line is t2'.

[0024] The above parameters satisfy:

[0025]

[0026] The swept blades that meet the above parameters achieve a maximum total pressure efficiency of over 81% in numerical simulation (76% for a first-class efficiency line with an impeller diameter of 900mm), and have lower flow resistance, resulting in higher total pressure efficiency.

[0027] Preferably, the second leaf tip accumulation point is located on the circle containing the leaf tip in the circumferential direction, and the second intermediate accumulation point is located on the circle containing the leaf middle in the circumferential direction.

[0028] The blade has a uniform chord length along its radial direction, which makes it easy to manufacture and has a low cost.

[0029] Preferably, the technical solution adopted by the present invention to solve the second technical problem is: an axial flow fan, characterized in that: it uses the blades of the axial flow fan as described above.

[0030] Compared with the prior art, the advantages of the present invention are as follows: by using the segmented definition of the blade (upper and lower parts), the forward sweep characteristics and structural parameter range of different parts of the blade and key parts can be accurately grasped, and the influence of multiple parameters on the wind turbine performance can be fully considered, thereby resulting in lower flow resistance and higher total pressure efficiency; instead of controlling the shape of the entire stacking line, the focus is on the angle θ between the beginning and end of the stacking lines of the upper and lower halves of the blade (i.e., the two points of the blade tip and blade root), and the highest point of the middle "protrusion" (characterized by t1). Therefore, the feasibility of controlling the shape of the stacking line is stronger and the blade forming cost is lower. Attached Figure Description

[0031] Figure 1 This is a front view of an axial flow fan according to an embodiment of the present invention;

[0032] Figure 2 This is a side view of an axial flow fan according to an embodiment of the present invention;

[0033] Figure 3 This is a schematic diagram of the tip sweep and overlap lines of the blades of an axial flow fan according to an embodiment of the present invention;

[0034] Figure 4 This is a schematic diagram of the sharp bend and overlap lines of the blades of an axial flow fan according to an embodiment of the present invention;

[0035] Figure 5 Performance comparison curves of blades in the prior art (without sweep) and blades of the present invention;

[0036] Figure 6 The curves show a performance comparison between blades in the prior art (without sweep) and blades from the embodiments of the present invention. Detailed Implementation

[0037] The embodiments of the present invention are described in detail below. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions.

[0038] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Since the embodiments disclosed in this invention can be arranged in different directions, these terms indicating direction are only for illustration and should not be regarded as limitations. For example, "upper" and "lower" are not necessarily limited to directions opposite to or consistent with the direction of gravity. In addition, features defined with "first" and "second" may explicitly or implicitly include one or more of such features.

[0039] See Figure 1 and Figure 2 An axial flow fan includes at least two blades 1 and a hub 2, with each blade 1 arranged at intervals along the axial direction of the hub 2 on its outer periphery. This axial flow fan is primarily used for ventilation in tunnels, mines, subways, etc., and can also be applied to range hoods, integrated stoves, and auxiliary exhaust systems at the rear of public flues.

[0040] To facilitate the description and understanding of the present invention, the following definitions are provided (which are commonly used in the art):

[0041] Swing: In a meridional view, the axial displacement of a two-dimensional airfoil at different blade heights. The airfoil moving towards the direction of the incoming flow is called forward sweep, and the opposite is called backward sweep.

[0042] Bending: In the axial view, the two-dimensional airfoil at different blade heights rotates in the circumferential direction around the axial direction at the current blade root. The airfoil rotating towards the blade pressure surface is called forward bending, and the opposite is called backward bending.

[0043] Sweep angle: In the meridional view, the angle between the line connecting the points of overlap at the blade root and the blade tip and the radial direction is the sweep angle; in the axial view, the angle between the line connecting the points of overlap at the blade root and the blade tip and the radial direction is the bend angle.

[0044] Swept blades: The line connecting the accumulation points of the two-dimensional airfoil at different blade heights along the blade's spanwise (radial) direction forms the accumulation line. In axial flow fans, when the accumulation line of the impeller blades is a straight line and parallel to the radial direction, the blades are not swept, i.e., the blade sweep angle is 0°. When the line connecting the accumulation points at the blade root and blade tip is not parallel to the radial direction, or when the accumulation line is not a straight line, it is considered a swept blade.

[0045] Sharp sweep:

[0046] The blade 1 in this embodiment has a sweeping form that is a combination of pointed sweeping and pointed bending.

[0047] Tip sweep: A type of sweep that gradually increases in speed from the leaf root to the leaf tip; the same applies to the tip bend described below.

[0048] See Figure 3 The diagram illustrates the overlap line of the blade tip (the overlap line is divided into an upper and lower half, with span = 0.5 as the boundary). Here, span refers to the relative position in the radial direction of the blade; span = 1 at the blade tip and span = 0 at the blade root. Specifically, let the radius of the radial section of the blade be r. i The outer diameter of the axial flow fan is R2, and the radius of the blade root (hub diameter) is r. b , The parameters of the superposition line are as follows:

[0049] 1) The overall forward sweep angle of blade 1 is θ ( Figure 3 Taking an axial flow blade with a forward sweep of 16° as an example, the position of the first blade tip (airfoil) accumulation point C (i.e., the axial forward movement distance) can be determined by combining the first blade root accumulation point A (a determined point). The forward sweep angle of the lower half blade is θ1. Therefore, the position of the first intermediate accumulation point B (span = 0.5) can be determined by combining the first blade root accumulation point A.

[0050] 2) Connect the first leaf root accumulation point A and the first intermediate accumulation point B to obtain the first straight line AB, and connect the first intermediate accumulation point B and the first leaf tip accumulation point C to obtain the second straight line BC. The length of the first straight line AB is l1, and the length of the second straight line BC is l2.

[0051] 3) The accumulation line ABC passing through the above three accumulation points is an arc-like line. The maximum distance between the first lower half accumulation line AB (the accumulation line between the first leaf root accumulation point A and the first intermediate accumulation point B) and the first straight line AB is t1. The maximum distance between the first upper half accumulation line BC (the accumulation line between the first intermediate accumulation point B and the first leaf tip accumulation point) and the second straight line BC is t2.

[0052] 4) The preferred location for the airfoil overlap point at each blade section is the chord length l of each airfoil section. i At 40%-50%;

[0053] The above structural parameters fall within the following ranges:

[0054]

[0055] Preferred,

[0056]

[0057] More preferably, the swathe parameter is:

[0058] θ = 16°

[0059]

[0060]

[0061]

[0062] Sharp bend:

[0063] See Figure 4 The diagram shows the accumulation line of the blade tip (the blade accumulation line is divided into upper and lower half accumulation lines with span = 0.5 as the boundary). The shape of the accumulation line conforms to the following rules:

[0064] 1) The overall forward bending angle of blade 1 is θ'( Figure 3 Taking an axial flow blade with a forward bend of 16° as an example, the position of the second blade tip (airfoil) accumulation point C' can be determined by combining the second blade root accumulation point A' (a determined point) with the intersection of the blade tip circle and the straight line θ' = 16°. The forward bend angle of the lower half blade is θ1'. Based on the second blade root accumulation point A', the position of the second intermediate accumulation point B' (span = 0.5) can be determined, which is on the circle in the middle of the blade.

[0065] 2) Connect the second leaf root accumulation point A' and the second intermediate accumulation point B' to obtain the third straight line A'B', and connect the second intermediate accumulation point B' and the second leaf apex accumulation point C' to obtain the fourth straight line B'C'. The length of the third straight line A'B' is l1', and the length of the fourth straight line B'C' is l2'.

[0066] 3) The accumulation lines A'B'C' passing through the above three accumulation points are arc-like lines. The maximum distance between the second lower half accumulation line A'B' (the accumulation line between the second leaf root accumulation point A' and the second intermediate accumulation point B') and the third straight line A'B' is t1'. The maximum distance between the third upper half accumulation line B'C' (the accumulation line between the second intermediate accumulation point B' and the second leaf apex accumulation point C') and the fourth straight line B'C' is t2'.

[0067] 4) The preferred location for the airfoil overlap point at each blade section is the chord length l of each airfoil section. i At 40%-50% of;

[0068] The above structural parameters fall within the following ranges:

[0069]

[0070] Preferred,

[0071]

[0072] The morphological parameters of the stacking line of the blade bend are similar to those of the blade sweep. The difference is that the blade bend is obtained by rotating the stacking line rather than by displacement. Therefore, the second blade tip stacking point C' is located on the circle where the blade tip is located in the circumferential direction, and the second intermediate stacking point B' is located on the circle where the blade middle (the middle position along the radial direction of the blade) is located in the circumferential direction.

[0073] Preferably, the bending parameters are:

[0074] θ'=12°

[0075]

[0076]

[0077]

[0078] Other preferred parameters of the blade of the present invention include:

[0079] Blade chord length: Equal chord length along the blade height (radial), preferably 105–130 mm. Airfoil installation angle: 63°–67° at the blade root section, 33°–36° at the blade tip section; airfoil bending angle: 65°–75° at the blade root section, 36°–44° at the blade tip section. Here, "airfoil" refers to the two-dimensional airfoil presented by the blade cross-section along the radial direction (the airfoil shape varies depending on the radius of the blade), and "bending angle" refers to the angle formed by the tangents at the leading and trailing edges of the airfoil.

[0080] To verify performance under the above parameters, see [link / reference]. Figure 5 and Figure 6 The comparison of the simulated performance of the blades in this embodiment of the invention with the prototype blades without sweeping shows that the sweeping pattern and sweeping angle of the blades given in this invention can effectively improve the performance of axial flow fans compared with the blades without sweeping obtained from theoretical design.

[0081] Alternatively, a segmented definition method can be used, such as dividing the blade into upper and lower parts on both sides of span = 0.5, with the upper part using the sweep definition method of this invention and the lower part using other definition methods; or the lower part of the blade using a backward sweep (bend) and the upper part using a forward sweep (bend) or other combination methods; or, the line connecting the sweep coordinate points of other blade stacking lines conforms to the function definition of the sweep type of this invention.

Claims

1. A blade for an axial flow fan, wherein the blade has an overall forward sweep angle of θ, characterized in that: The overlapping lines of the blade sweep forward are divided by span = 0.5, where span is the relative position in the radial direction of the blade. At the blade tip, span = 1, and at the blade root, span = 0. The overlapping lines of the blade sweep forward include the first blade tip overlapping point (C), the first intermediate overlapping point (B), and the first blade root overlapping point (A), wherein the first intermediate overlapping point (B) is the overlapping point of the overlapping lines of the sweep forward at span = 0.

5. The position of the first leaf tip accumulation point (C) is determined by θ and the first leaf root accumulation point (A). The forward sweep angle of the leaf below span = 0.5 is θ1. The position of the first intermediate accumulation point (B) is determined by θ1 and the first leaf root accumulation point (A). A first straight line (AB) is formed by connecting the first leaf root accumulation point (A) and the first intermediate accumulation point (B). A second straight line (BC) is formed by connecting the first intermediate accumulation point (B) and the first leaf tip accumulation point (C). The length of the first straight line (AB) is l1, and the length of the second straight line (BC) is l2. The accumulation line that sweeps forward through the above three accumulation points is an arc-like line, including the first lower half accumulation line (AB) formed between the first intermediate accumulation point (B) and the first leaf root accumulation point (A) and the first upper half accumulation line (BC) formed between the first leaf tip accumulation point (C) and the first intermediate accumulation point (B). The maximum distance between the first lower half accumulation line (AB) and the first straight line (AB) is t1, and the maximum distance between the first upper half accumulation line (BC) and the second straight line (BC) is t2. The above parameters satisfy:

2. The blades of the axial flow fan according to claim 1, characterized in that: The blades are swept blades.

3. The blades of the axial flow fan according to claim 2, characterized in that: The overall forward bending angle of the blade is θ'; The overlapping lines of the forward-curving blade are divided by a span of 0.

5. The overlapping lines of the forward-curving blade include a second tip overlapping point (C'), a second intermediate overlapping point (B'), and a second root overlapping point (A'), wherein the second intermediate overlapping point (B') is the overlapping point of the forward-curving overlapping line at a span of 0.

5. The position of the second leaf tip accumulation point (C') is determined by θ' and the second leaf root accumulation point (A'). The forward bending angle of the leaf below span = 0.5 is θ1'. The position of the second intermediate accumulation point (B') is determined by θ1' and the second leaf root accumulation point (A'). A third straight line (A'B') is obtained by connecting the second leaf root accumulation point (A') and the second intermediate accumulation point (B'). A fourth straight line (B'C') is obtained by connecting the second intermediate accumulation point (B') and the second leaf apex accumulation point (C'). The length of the third straight line (A'B') is l1', and the length of the fourth straight line (B'C') is l2'. The accumulation line that curves forward through the above three accumulation points is an arc-like line, including the second lower half accumulation line (A'B') formed between the second intermediate accumulation point (B') and the second leaf root accumulation point (A'), and the second upper half accumulation line (B'C') formed between the second leaf tip accumulation point (C') and the second intermediate accumulation point (B'). The maximum distance between the second lower half accumulation line (A'B') and the third straight line (A'B') is t1', and the maximum distance between the second upper half accumulation line (B'C') and the fourth straight line (B'C') is t2'. The above parameters satisfy:

4. The blades of the axial flow fan according to claim 3, characterized in that: The second tip accumulation point (C') is located on the circle containing the tip of the leaf in the circumferential direction, and the second intermediate accumulation point (B') is located on the circle containing the middle of the leaf in the circumferential direction.

5. The blades of the axial flow fan according to any one of claims 1 to 4, characterized in that: The blade has a constant chord length along its radial direction.

6. An axial flow fan, characterized in that: The blades of the axial flow fan as described in any one of claims 1 to 5 are used.

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