An axial flow fan rear guide vane and corresponding axial flow fan

Abstract

This invention belongs to the field of axial flow fans and discloses a rear guide vane of an axial flow fan and a corresponding axial flow fan. The central arc at the tip of the rear guide vane is smoothly connected by a straight line segment and a spline curve segment. Along the impeller radial direction, from the root to the tip of the guide vane, the projections of the leading edge points of the central arc at different radial positions of the impeller onto a plane parallel to both the impeller axial direction and radial direction are distributed along the spline curve. This invention uses the spline curve to control the relative position of the leading edge points at different blade heights of the rear guide vane, so that from the tip to the root of the guide vane, the projection of the leading edge points on the impeller meridional plane exhibits a changing trend of first moving towards the trailing edge, then moving away from the trailing edge, and finally moving towards the trailing edge again. By controlling the leading edge shape of the rear guide vane in this way, the leakage flow at the blade tip of the axial flow fan is affected, reducing losses caused by flow blockage and flow separation inside the blade passage, thereby improving the fan efficiency.

Description

Technical Field

[0001] This invention belongs to the field of axial flow fans, and more specifically, relates to a rear guide vane of an axial flow fan and a corresponding axial flow fan. The rear guide vane has a novel leading edge shape, and the leading edge of the rear guide vane blade is constructed from a spline curve. Background Technology

[0002] Axial flow fans with rear guide vanes are widely used in various ventilation, air exchange, and heat dissipation applications due to their large flow rate and high efficiency. Their working principle mainly involves: airflow entering the impeller, the impeller rotating and doing work on the gas, giving the gas kinetic and pressure energy. In the impeller passage, the gas gains axial velocity while simultaneously generating swirling velocity. During pipeline transport, this swirling velocity causes additional flow losses. Therefore, rear guide vanes are installed after the impeller to convert the swirling velocity of the airflow into axial velocity.

[0003] The flow conditions differ at different radial positions within the blade passages of a wind turbine impeller. At the blade tips, the larger impeller radius increases torque, resulting in greater pressure on the airflow in the tip region. Due to the tip clearance between the impeller and the casing, the pressure difference between the pressure and suction surfaces of the blades drives the airflow from the pressure surface along the clearance to the suction surface, creating tip leakage flow. This flow mixes with the mainstream high-energy fluid, forming tip leakage vortices and causing flow losses. Under low-flow conditions, tip leakage vortices can also block the flow channels, leading to pressure and efficiency losses in the wind turbine, and even causing stall, narrowing the normal operating range. Tip leakage flow is widespread in axial fans and is a significant factor contributing to performance degradation.

[0004] For traditional axial flow fan guide vanes, the blade design typically employs a straight blade shape (i.e., the blade overlap line is perpendicular to the hub surface), and the mid-curve of the blade is generally a single circular arc. Its main function is usually to reduce the airflow swirling speed, converting some kinetic energy into pressure energy. The guide vane profile is consistent at the top and root. After the tip gap vortex detaches from the blade's suction surface, it impacts the rear guide vane, causing flow separation on the pressure surface of the rear guide vane. Summary of the Invention

[0005] To address the aforementioned deficiencies or improvement needs of existing technologies, the present invention aims to provide a rear guide vane for an axial flow fan and a corresponding axial flow fan. By controlling the relative positions of the leading edge points at different blade heights of the rear guide vane, the projections of these leading edge points on a plane parallel to both the impeller axial and radial directions are distributed along a spline curve. This results in the projections of the leading edge points of the central arc at different radial positions of the impeller from the guide vane tip to the guide vane root exhibiting a changing trend: first moving towards the trailing edge, then moving away from the trailing edge, and finally moving towards the trailing edge again. This controls the shape of the rear guide vane's leading edge, influencing leakage flow at the blade tip of the axial flow fan, reducing losses caused by flow blockage and flow separation within the blade passage, and improving fan efficiency. In particular, the present invention can construct a radially distributed guide vane leading edge shape with a specific shape by controlling the control points of the spline curve (using parameters or vectors such as L1, L2, L3, L4, Z1, Z2, Z3, Z4, etc.), effectively reducing flow losses under low flow conditions and improving fan efficiency.

[0006] To achieve the above objectives, according to one aspect of the present invention, a rear guide vane for an axial flow fan is provided, characterized in that its profile is composed of a guide vane leading edge profile, a guide vane pressure surface profile, a guide vane suction surface profile, and a guide vane trailing edge profile, wherein the guide vane leading edge profile and the guide vane trailing edge profile are both arc-shaped, used to smoothly connect the guide vane pressure surface profile and the guide vane suction surface profile;

[0007] For the tip of the guide vane, the direction of the arc from the trailing edge to the leading edge is smoothly formed by a straight line segment and a spline curve segment;

[0008] Along the impeller radial direction, from the root of the guide vane to the tip of the guide vane, the projection of the central arc lines at different radial positions of the impeller onto the plane where the tip of the guide vane is located can be completely covered by the central arc line at the tip of the guide vane or can completely cover the central arc line at the tip of the guide vane; the guide vane pressure surface profile and the guide vane suction surface profile are obtained by stacking the corresponding central arc lines according to the pre-set thickness law of the rear guide vane blades.

[0009] Along the impeller radial direction, from the root of the guide vane to the tip of the guide vane, the projections of the leading edge points of the middle arc lines at different radial positions of the impeller onto a plane parallel to both the impeller axial direction and the impeller radial direction are distributed along a spline curve. This spline curve is denoted as the second spline curve. This spline curve makes the projections of the leading edge points of the middle arc lines at different radial positions of the impeller onto the impeller meridional plane exhibit a changing trend: first moving towards the trailing edge, then moving away from the trailing edge, and finally moving towards the trailing edge again.

[0010] As a further preferred embodiment of the present invention, for the second spline curve:

[0011] Let P1 be the projection point of the leading edge of the guide vane tip onto the plane that is simultaneously parallel to both the impeller axial direction and the impeller radial direction. Let P5 be the projection point of the leading edge of the guide vane root onto the plane that is simultaneously parallel to both the impeller axial direction and the impeller radial direction. In addition to the endpoint control points P1 and P5, the second spline curve also has three control points P2, P3, and P4 sequentially from P1 to P5. Furthermore, let H be the projection length of the line connecting P5 and P1 in the impeller radial direction, and H be the projection length of the line connecting P2 and P1 in the impeller radial direction. Let L1 be the projected length of the line connecting P3 and P2 in the radial direction of the impeller, L2 be the projected length of the line connecting P4 and P3 in the radial direction of the impeller, L3 be the projected length of the line connecting P5 and P4 in the radial direction of the impeller, and L4 be the projected length of the line connecting P5 and P4 in the radial direction of the impeller. Then: H is the distance between the root and tip of the guide vane in the radial direction of the impeller, 0.215≤L1 / H≤0.25, 0.25≤L2 / H≤0.285, 0.215≤L3 / H≤0.25, 0.25≤L4 / H≤0.285;

[0012] Furthermore, let Z1 be the component of the vector from P1 to P2 in the axial direction of the impeller, Z2 be the component of the vector from P2 to P3 in the axial direction of the impeller, Z3 be the component of the vector from P3 to P4 in the axial direction of the impeller, and Z4 be the component of the vector from P4 to P5 in the axial direction of the impeller. Then, the modulus of vectors Z1, Z2, Z3, and Z4 respectively satisfy: 0.02≤|Z1| / H≤0.1, 0.05≤|Z2| / H≤0.12, 0.05≤|Z3| / H≤0.12, and 0.02≤|Z4| / H≤0.1. Moreover, the vector direction of Z1 is from the leading edge to the trailing edge, the vector direction of Z2 is from the trailing edge to the leading edge, the vector direction of Z3 is from the trailing edge to the leading edge, and the vector direction of Z4 is from the leading edge to the trailing edge.

[0013] As a further preferred embodiment of the present invention, for the straight segment and the spline curve segment in the arc at the tip of the guide vane, the angle between the straight segment and the circumferential direction of the impeller is θ2, where θ2 is the outlet angle, and 60°≤θ2≤120°; the angle between the end tangent of the spline curve segment and the circumferential direction of the impeller is denoted as θ1, where θ1 is the inlet angle, and 0.40≤θ1 / θ2≤0.60.

[0014] As a further preferred embodiment of the present invention, for the arc at the tip of the guide vane, the spline curve segment therein is denoted as the first spline curve segment;

[0015] The projection length of the arc at the tip of the guide vane onto the impeller axial direction is S, where the projection length of the first spline curve segment onto the impeller axial direction is S1, and the projection length of the straight line segment onto the impeller axial direction is S2, and S = S1 + S2; then:

[0016] 0.65≤S / H≤0.815; 0.4≤S1 / S≤0.6, 0.4≤S2 / S≤0.6;

[0017] Where H is the distance between the root of the guide vane and the tip of the guide vane in the radial direction of the impeller.

[0018] As a further preferred embodiment of the present invention, for the arc at the tip of the guide vane, let C1 be the projection length of the first spline curve segment in the circumferential direction of the impeller; then:

[0019] 0.15≤C1 / H≤0.25;

[0020] Where H is the distance between the root of the guide vane and the tip of the guide vane in the radial direction of the impeller.

[0021] As a further preferred embodiment of the present invention, let the predetermined thickness of the rear guide vane be B, then 0.005≤B / H≤0.03;

[0022] Where H is the distance between the root of the guide vane and the tip of the guide vane in the radial direction of the impeller.

[0023] According to another aspect of the present invention, the present invention provides an application of the above-mentioned axial flow fan rear guide vane, characterized in that the axial flow fan rear guide vane is used to be mounted on an annular hub and placed behind the axial flow impeller.

[0024] According to another aspect of the present invention, the present invention provides a rear guide vane impeller having the above-mentioned axial flow fan rear guide vane, characterized in that it includes an annular hub and a plurality of axial flow fan rear guide vanes uniformly arranged on the annular hub, wherein any two axial flow fan rear guide vanes have the same outline shape.

[0025] According to another aspect of the invention, the invention provides an axial flow fan having the aforementioned rear guide vane impeller.

[0026] Compared with the prior art, the axial flow fan rear guide vane of the present invention is composed of the guide vane leading edge line (corresponding to the spline curve on which the projections of the leading edge points of the middle arc lines at different radial positions of the fan along the impeller radial direction, from the root of the guide vane to the tip of the guide vane, are distributed on a plane that is parallel to both the impeller axial direction and the impeller radial direction), the guide vane middle arc line, the guide vane profile (including the guide vane leading edge profile, the guide vane pressure surface profile, the guide vane suction surface profile, and the guide vane trailing edge profile), and the guide vane trailing edge line (as exemplified in the following embodiments, the straight line on which the trailing edge points of the middle arc lines at different radial positions of the fan are distributed along the impeller radial direction, from the root of the guide vane to the tip of the guide vane). Furthermore, the guide vane profile is obtained by stacking the guide vane middle arc line according to a pre-set blade thickness. The front and rear ends of the guide vane are smoothly connected by an arc, and the diameter of the arc is the guide vane thickness (the thickness is pre-set). The projection of the guide vane leading edge line onto a plane that is parallel to both the impeller axial direction and the impeller radial direction corresponds to a spline curve. In other words, the position of the leading edge point varies with the relative blade height (blade height is the radial distance from the root of the guide vane to the tip of the guide vane along the impeller radial direction).

[0027] This invention controls the leading edge profile of the guide vane using spline curves, thereby creating a structure with an upper concave side and a lower convex side at the leading edge of the guide vane. This influences the airflow exiting the impeller. The upper concave structure effectively disrupts the leakage vortex structure at the blade tip, reducing flow losses. A fan model using this design method was tested for aerodynamic performance according to GB / T1236-2000 "Industrial Ventilators—Standardized Duct Performance Tests," showing a certain degree of improvement in fan efficiency.

[0028] This invention designs the rear guide vane of an axial flow fan based on the specific leading edge and mid-arc shape of the guide vane. The axial flow rear guide vane blade in this invention has its leading edge shape fitted by spline curves to obtain the radial distribution of the leading edge of the rear guide vane. It is known in the prior art that the spline curve can be controlled by five control points. Taking a cubic spline curve as an example, for example, the complete spline curve expression can be obtained by using the B-spline basis function and the Hartley-Judd algorithm (related literature can be found in: [1] Kong Lingde. Computer Graphics Course Design Tutorial: Visual C++ Edition [M]. Peking University Press, 2010. [2] Faux ID, Pratt MJ. Computational geometry for design and (manufacture[J].1979.) This invention controls the top position of the leading edge of the rear guide vane via P1, the bottom position of the leading edge of the rear guide vane via P5, the middle position of the leading edge of the rear guide vane via P3, the degree of concavity of the upper half of the leading edge of the rear guide vane via P2, and the degree of convexity of the lower half of the trailing edge of the rear guide vane via P4. The radial distribution of the leading edge profile of the rear guide vane is fitted by spline curves. In this invention, the axial flow rear guide vane blade has an arc shape in the blade formed by spline curves and straight lines. The angle between the tangent of the leading edge of the arc of the guide vane and the circumferential direction of the impeller is θ1, and θ1 controls the airflow inlet angle of the rear guide vane. The tangents at the connection points of the spline curve and the straight line are in the same direction, and the two lines are smoothly connected. The angle between the tangent of the trailing edge of the arc of the guide vane and the circumferential direction of the impeller is θ2, and θ2 controls the airflow outlet angle of the rear guide vane. Preferably, 60°≤θ2≤120° and 0.40≤θ1 / θ2≤0.60 are used.

[0029] This invention utilizes spline curves to construct the leading edge profile of the rear guide vane, thereby controlling its shape. Specifically, by using five control points P1, P2, P3, P4, and Z1, Z2, Z3, and Z4 corresponding to specific values ​​or vector requirements, the upper half of the leading edge is designed to be concave, while the lower half is convex. This sharp-angled structure at the upper end breaks down the tip leakage vortex at the axial impeller outlet, thus suppressing flow losses caused by secondary flow. Furthermore, the use of a mid-arc line spliced ​​from spline curves and straight lines ensures a small angle of attack for the airflow at the blade inlet, reducing impact losses from the airflow entering the rear guide vane inlet. Simultaneously, it ensures that the airflow velocity is converted into axial velocity after exiting the rear guide vane, allowing the airflow to flow axially and reducing friction losses during duct transmission. The combined effect of these two factors suppresses flow separation on the blade surface and improves fan efficiency. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the leading edge profile and trailing edge profile of the rear guide vane of an axial flow fan (in the figure, the leading edge profile is an improvement based on this invention, while the trailing edge profile adopts a conventional straight line shape).

[0031] Figure 2 This is the top section of the guide vane blade of the axial flow fan of the present invention (corresponding to...). Figure 1 A schematic diagram of the arc and blade profile at point P1 in the diagram. Figure 2 Corresponding to the top-down view, Figure 2 Line A in the diagram represents the arc of the rear guide vane, and line B represents the blade profile of the rear guide vane (the leading edge of the rear guide vane of the axial flow fan is connected to the suction and pressure surfaces by a circular arc curve).

[0032] Figure 3 This is a schematic diagram of the existing technology's three-dimensional model of the rear guide vane blade and the corresponding rear guide vane impeller model.

[0033] in, Figure 3 (a) in the model corresponds to the three-dimensional model of the rear guide vane of an axial flow fan. Figure 3 (b) in the model corresponds to the impeller model of the rear guide vane of an axial flow fan.

[0034] Figure 4 This is a schematic diagram of the three-dimensional model of the rear guide vane blade and the corresponding rear guide vane impeller model of Embodiment 1 of the present invention. Figure 4 (a) in the model corresponds to the three-dimensional model of the rear guide vane of an axial flow fan. Figure 4 (b) in the model corresponds to the impeller model of the rear guide vane of an axial flow fan.

[0035] Figure 5 This is a schematic diagram of the three-dimensional model of the rear guide vane blade and the corresponding rear guide vane impeller model of Embodiment 2 of the present invention. Figure 5 (a) in the model corresponds to the three-dimensional model of the rear guide vane of an axial flow fan. Figure 5 (b) in the model corresponds to the impeller model of the rear guide vane of an axial flow fan.

[0036] Figure 6 This is a comparison chart of the total pressure-flow coefficient curves of axial flow fans with different designs.

[0037] Figure 7 This is a comparison chart of efficiency-flow coefficient curves for axial flow fans with different designs.

[0038] Figure 8 This is a schematic diagram of the simulated limit streamlines of the suction and pressure surfaces of the rear guide vane blades in an existing axial flow fan, as well as the simulated streamlines in the rear guide vane flow channel. Among them, Figure 8 (a) in the figure corresponds to the simulated limiting streamline near the suction surface of the rear guide vane of the axial flow fan. Figure 8 (b) in the figure corresponds to the simulated limiting streamline near the pressure surface of the rear guide vane of the axial flow fan. Figure 8 (c) in the figure corresponds to the simulated streamline in the guide vane channel of the axial flow fan.

[0039] Figure 9 This is a schematic diagram of the simulated limiting streamlines of the suction and pressure surfaces of the rear guide vane blades of the axial flow fan in Embodiment 1 of the present invention, and the simulated streamlines in the flow channel of the rear guide vane. Wherein, Figure 9 (a) in the figure corresponds to the simulated limiting streamline near the suction surface of the rear guide vane of the axial flow fan. Figure 9 (b) in the figure corresponds to the simulated limiting streamline near the pressure surface of the rear guide vane of the axial flow fan. Figure 9 (c) in the figure corresponds to the simulated streamline in the guide vane channel of the axial flow fan.

[0040] Figure 10 This is a schematic diagram of the simulated limiting streamlines of the suction and pressure surfaces of the rear guide vane blades of the axial flow fan in Embodiment 2 of the present invention, and the simulated streamlines in the flow channel of the rear guide vane. Wherein, Figure 10 (a) in the figure corresponds to the simulated limiting streamline near the suction surface of the rear guide vane of the axial flow fan. Figure 10 (b) in the figure corresponds to the simulated limiting streamline near the pressure surface of the rear guide vane of the axial flow fan. Figure 10 (c) in the figure corresponds to the simulated streamline in the guide vane channel of the axial flow fan.

[0041] Figure 11 This is a schematic diagram of the structure of the rear guide vane of the axial flow fan of the present invention. Wherein, Figure 11 (a) in the diagram corresponds to the left view. Figure 11 (b) in the diagram corresponds to the top view.

[0042] Figure 11 The meanings of the labels in the attached figures are as follows: 1 is the leading edge line of the guide vane, 2 is the middle arc line of the guide vane, 3 is the guide vane profile line, and 4 is the trailing edge line of the guide vane. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0044] In general, such as Figure 11 As shown, the novel leading-edge shaped axial flow fan guide vane of this invention is composed of a guide vane leading edge line 1, a guide vane mid-arc line 2, a guide vane profile line 3, and a guide vane trailing edge line 4. The guide vane mid-arc line 2 is a spline curve spliced ​​with a straight line (e.g., ...). Figure 2 As shown by line A in the diagram; for the spline curve portion (any spline curve will suffice), the guide vane profile 3 is obtained by stacking the guide vane's central arc line 2 according to a pre-set blade thickness. The blade thickness can be denoted as B.

[0045] Let the radial height of the guide vane be H, and the axial length S at the tip of the guide vane be determined by the ratio of the guide vane length to its height, S / H. Preferably, in this invention, 0.65 ≤ S / H ≤ 0.815. Specifically, the leading edge line 1 of the guide vane can be composed of a cubic spline curve, and its geometry is controlled by five control points, P1, P2, P3, P4, and P5 from the tip to the bottom of the guide vane; wherein:

[0046] Control point P1 is the leading edge of the guide vane tip;

[0047] The radial position of P2 is determined by the ratio L1 / H (radial distance between control points P1 and P2) to H (radial height of the guide vane), and the axial position of P2 is determined by the ratio |Z1| / H (modulus of the vector from control point P1 to P2 in the axial direction).

[0048] The radial position of P3 is determined by the ratio L2 (radial distance between control points P2 and P3) to H (radial height of guide vane) L2 / H, and the axial position of P3 is determined by the ratio |Z2| / H of the modulus of Z2 (the axial component of the vector between control points P2 and P3) to H (radial height of guide vane).

[0049] The radial position of P4 is determined by the ratio L3 / H (radial distance between control points P3 and P4) to H (radial height of the guide vane), and the axial position of P4 is determined by the ratio |Z3| / H (modulus of the vector component of control points P3 and P4 in the axial direction).

[0050] The radial position of P5 is determined by the ratio L4 (radial distance between control points P4 and P5) to H (radial height of the guide vane) L4 / H (of course, since L1+L2+L3+L4=H, L1 / H+L2 / H+L3 / H+L4 / H=1), and the axial position of P5 is determined by the ratio |Z4| / H ​​of the modulus of Z4 (the axial component of the vector between control points P4 and P5) to H (radial height of the guide vane).

[0051] Z1, Z2, Z3, and Z4 are all parallel to the axial direction. The positive direction is defined as the axial direction from the leading edge to the trailing edge, and the negative direction is the axial direction from the trailing edge to the leading edge. Therefore, for any vector Zn (n = 1, 2, 3, 4), the vector is positive if its direction is from the leading edge to the trailing edge, and negative if its direction is from the trailing edge to the leading edge. In the following text, scalars Zn (n = 1, 2, 3, 4) are used to represent the magnitude of Zn (n = 1, 2, 3, 4), and the sign of the scalar corresponds to the direction of Zn.

[0052] Control point P1 controls the position of the leading edge of the rear guide vane tip; control point P2 controls the shape of the upper leading edge of the rear guide vane; control point P3 controls the position of the leading edge of the middle of the rear guide vane; control point P4 controls the shape of the lower leading edge of the rear guide vane; and control point P5 controls the position of the leading edge of the bottom of the rear guide vane. The overall shape of the blade leading edge is as follows: Figure 1 As shown.

[0053] By rationally configuring the axial and radial positions of each control point, the shape of the guide vane leading edge is ensured to be concave on the upper side and convex on the lower side. For example, the radial positions of the control points can preferably satisfy 0.215≤L1 / H≤0.25, 0.25≤L2 / H≤0.285, 0.215≤L3 / H≤0.25, and 0.25≤L4 / H≤0.285; the axial positions of the control points can preferably satisfy 0.02≤Z1 / H≤0.1, -0.12≤Z2 / H≤-0.05, -0.12≤Z3 / H≤-0.05, and 0.02≤Z4 / H≤0.1. In this way, the upper concave structure breaks the tip leakage vortex at the axial flow impeller outlet, transforming the vortex structure that obstructs the airflow in the flow channel into smooth flow, thereby suppressing the flow loss caused by secondary flow. This invention provides Embodiment 1 and Embodiment 2 that conform to the aforementioned leading edge shape. In Embodiment 1, the radial positions of the control points satisfy L1 / H = 0.25, L2 / H = 0.25, L3 / H = 0.25, and L4 / H = 0.25; the axial positions of the control points satisfy Z1 / H = 0.1, Z2 / H = -0.05, Z3 / H = -0.05, and Z4 / H = 0.1. In Embodiment 2, the radial positions of the control points satisfy L1 / H = 0.215, L2 / H = 0.285, L3 / H = 0.215, and L4 / H = 0.285; the axial positions of the control points satisfy Z1 / H = 0.02, Z2 / H = -0.12, Z3 / H = -0.12, and Z4 / H = 0.02. The simulated limit streamlines of the blade surface and the simulated streamlines of the internal cross-section of the blade passage in Embodiments 1 and 2 are shown below. Figure 9 and Figure 10 As shown.

[0054] Meanwhile, the guide vane's arc is obtained by splicing a spline curve and a straight line. The leading edge of the arc 2 is a spline curve. The axial length S1 of the spline curve is configured reasonably, preferably 0.4≤S1 / S≤0.6, and the circumferential length C1 of the spline curve is configured reasonably, preferably 0.15≤C1 / H≤0.25. Correspondingly, the axial length S2 of the straight section is configured (in the prototype and embodiments 1 and 2, the outlet angle θ2 is defined as 90°. At this time, the straight section is parallel to the impeller axial direction, and S2 is the length of the straight section; of course, θ2 can also be other values ​​in the range of 60°≤θ2≤120°. In this case, S2 is the projected length of the straight section in the axial direction), that is, 0.4≤S2 / S≤0.6 (because S1+S2=S).

[0055] Specifically, the inlet angle of the rear guide vane is determined by the ratio of θ1 (the angle between the leading edge tangent of the mid-arc line of the top section and the circumferential direction of the impeller; the top section corresponds to the section parallel to both the axial and circumferential directions and passing through P1) to the outlet angle θ2 (the angle between the trailing edge tangent of the mid-arc line of the top section and the circumferential direction of the impeller; here, the outlet angle θ2 is defined as 90°; at this time, the outlet being parallel to the axial direction is beneficial to eliminating the swirling velocity of the airflow and increasing the static pressure of the fan). The inlet and outlet angles of the rear guide vane are reasonably configured so that 0.40≤θ1 / θ2≤0.60. Since the mid-arc line spliced ​​by spline curves and straight lines can ensure that the airflow angle of attack at the blade inlet is small, the impact loss caused by the airflow flowing into the rear guide vane inlet is reduced. At the same time, it can ensure that after the airflow flows out of the rear guide vane, the swirling velocity is converted into axial velocity, and the airflow flows out along the axis, reducing the friction loss during pipeline transmission.

[0056] Traditionally, axial flow fan guide vanes are designed with straight blades featuring a circular arc mid-curve. From the root to the tip, the vane profile remains constant regardless of radial position. However, at the impeller of an axial flow fan, as the impeller diameter increases, the blade load and work capacity increase, resulting in greater kinetic energy for the airflow in the flow channel. Gas flows into the guide vane from the impeller trailing edge, and the flow patterns differ at different radial positions. Guide vanes designed using traditional methods struggle to adapt to these varying radial flow conditions, especially at the impeller tip where tip leakage vortices can easily clog the guide vane flow channel, thus affecting fan performance. This invention preferably employs a parametric design process for the guide vanes, compiled using a Matlab platform. It fits the leading edge shape of the guide vane with spline curves and designs the mid-curve shape by splicing spline curves with straight lines. This allows for precise control of the vane profile at different radial positions and for varying axial flow patterns, achieving accurate control over the guide vane design.

[0057] The following detailed analysis is based on Example 1. The prototype fan is designed with straight blades based on the arc shape of the axial flow fan. The structural parameters of the prototype fan and the embodiment of the invention are shown in Table 1. Since the prototype fan does not use spline curves to design the blade leading edge, but uses straight blades, the arc is a circular arc shape. The parameters L1 / H, L2 / H, L3 / H, L4 / H, Z1 / H, Z2 / H, Z3 / H, Z4 / H, S1 / H, C1 / H, and S2 / H related to the spline curve are marked with "-". The blade shape comparison diagram is shown below. Figure 3 , Figure 4 As shown in the comparison. Furthermore, based on this invention, the specific values ​​of S, θ1, θ2, and B listed in Table 1 are merely examples and can be flexibly adjusted. The key focus of this invention lies in the shaping of the leading edge line and the mid-arc line of the guide vane.

[0058] Table 1

[0059]

[0060] The present invention embodiment 1 was applied to an axial flow fan. A prototype was made, and aerodynamic performance was tested according to GB / T1236-2000 "Industrial Fans - Standardized Duct Performance Test". The performance of the prior art prototype fan measured under the same experimental conditions was compared with that of the prototype fan. Their experimental test data are shown in Tables 2 and 3.

[0061] Table 2 Comparison of Total Pressure Coefficient of Axial Flow Fans with Different Schemes

[0062]

[0063] Table 3. Comparison of Efficiency of Axial Flow Fans with Different Schemes

[0064]

[0065]

[0066] Compared with prior art rear guide vanes, the axial flow fan using the rear guide vanes of this invention exhibits a slightly lower total pressure coefficient at flow rates greater than 0.4 when using the same flow rate coefficient. However, the total pressure coefficient is significantly improved at flow rates less than or equal to 0.4. The flow rate coefficient corresponding to the highest total pressure coefficient in Examples 1 and 2 is 0.37. Under this flow rate coefficient condition, compared with the prior art, the maximum total pressure coefficient of Example 1 is improved by 4.54%, and the maximum total pressure coefficient of Example 2 is improved by 6.28%. Furthermore, a comparison chart of the total pressure-flow rate coefficient curves of the fan under different operating conditions is provided below. Figure 6 Regarding fan efficiency, the efficiency trends of Examples 1 and 2 are the same as those of fans using existing rear guide vanes. Fan efficiency improves under different operating conditions, with a more significant improvement under conditions where the flow coefficient does not exceed 0.31. The highest efficiency condition corresponds to a flow coefficient of 0.4. Under this flow coefficient condition, the axial flow fan efficiency using rear guide vanes in Examples 1 and 2 is increased by 1.95% and 2.69% respectively compared to the axial flow fan using existing rear guide vanes. See the comparison chart of fan efficiency-flow coefficient curves under different operating conditions. Figure 7 .

[0067] like Figure 6 As shown, under the condition that the flow coefficient does not exceed 0.40, the total pressure coefficients of Examples 1 and 2 are superior to those of the prior art. Figure 7 As shown, when the flow coefficient is in the range of [0.24, 0.44], the efficiency of both Example 1 and Example 2 is better than that of the prior art.

[0068] In addition, this invention also simulated the suction and pressure surfaces of the rear guide vane blades and the flow channel of the rear guide vane obtained from the prototype fan and various embodiments, and the results are as follows. Figure 8 - Figure 10 As shown. Figure 8 As shown, severe secondary flow exists on the surface of the guide vane of the prototype fan, and severe separation vortices in different blade passages block the flow at the impeller outlet, resulting in severe flow loss in the fan. Figure 9 and Figure 10 The flow inside the guide vane passages in Examples 1 and 2 are shown respectively. In the example schemes, the spline curve leading edge structure reduces the guide vane angle of attack, which is effective in suppressing flow separation on the guide vane surface and reducing secondary flow blockage in the corner region.

[0069] The above embodiments are merely examples. For instance, the outlet angle θ2 can be set in the range of [60°, 120°] in addition to 90°. Furthermore, the above prototype fan and various embodiments all use a straight trailing edge line as an example (that is, along the impeller radial direction, from the root of the guide vane to the tip of the guide vane, the trailing edge points of the mid-arc lines at different radial positions of the impeller are distributed on the same straight line). Since this invention is a modification of the leading edge line, in addition to being used with a straight trailing edge line, it can also be used with other trailing edge shapes.

[0070] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A rear guide vane for an axial flow fan, characterized in that, Its profile consists of the guide vane leading edge profile, the guide vane pressure surface profile, the guide vane suction surface profile, and the guide vane trailing edge profile. The guide vane leading edge profile and the guide vane trailing edge profile are both arc-shaped to smoothly connect the guide vane pressure surface profile and the guide vane suction surface profile. For the tip of the guide vane, the direction of the arc line from the trailing edge to the leading edge is smoothly formed by a straight line segment and a spline curve segment; for the arc line at the tip of the guide vane, the spline curve segment is denoted as the first spline curve segment. The projection length of the arc at the tip of the guide vane onto the impeller axial direction is S, where the projection length of the first spline curve segment onto the impeller axial direction is S1, and the projection length of the straight line segment onto the impeller axial direction is S2, and S = S1 + S2; then: 0.65≤S / H≤0.815; 0.4≤S1 / S≤0.6, 0.4≤S2 / S≤0.6; Where H is the distance between the root of the guide vane and the tip of the guide vane in the radial direction of the impeller; For the arc at the tip of the guide vane, let C1 be the projection length of the first spline curve segment in the circumferential direction of the impeller; then: 0.15≤C1 / H≤0.25; Along the impeller radial direction, from the root of the guide vane to the tip of the guide vane, the projection of the central arc line at different radial positions of the impeller onto the plane where the tip of the guide vane is located can be completely covered by the central arc line at the tip of the guide vane or can completely cover the central arc line at the tip of the guide vane; The guide vane pressure surface profile and the guide vane suction surface profile are obtained by stacking the corresponding central arc line as a reference according to the preset rear guide vane blade thickness rule; Let the preset rear guide vane blade thickness be B, then 0.005≤B / H≤0.03; Along the impeller radial direction, from the root of the guide vane to the tip of the guide vane, the projections of the leading edge points of the middle arc lines at different radial positions of the impeller onto a plane parallel to both the impeller axial direction and the impeller radial direction are distributed along a spline curve. This spline curve is denoted as the second spline curve. This spline curve makes the projections of the leading edge points of the middle arc lines at different radial positions of the impeller onto the impeller meridional plane exhibit a changing trend: first moving towards the trailing edge, then moving away from the trailing edge, and finally moving towards the trailing edge again.

2. The rear guide vane of the axial flow fan as described in claim 1, characterized in that, For the second spline curve: Let P1 be the projection point of the leading edge point of the guide vane tip onto the plane that is simultaneously parallel to the impeller axial direction and the impeller radial direction. Let P5 be the projection point of the leading edge point of the guide vane root onto the plane that is simultaneously parallel to the impeller axial direction and the impeller radial direction. In addition to the endpoint control points P1 and P5, the second spline curve also has three control points P2, P3, and P4 sequentially from P1 to P5. Let H be the projection length of the line connecting P5 and P1 in the impeller radial direction. The projection length of the line connecting P1 and P2 in the radial direction of the impeller is L1, the projection length of the line connecting P3 and P2 in the radial direction of the impeller is L2, the projection length of the line connecting P4 and P3 in the radial direction of the impeller is L3, and the projection length of the line connecting P5 and P4 in the radial direction of the impeller is L4. Then: 0.215≤L1 / H≤0.25, 0.25≤L2 / H≤0.285, 0.215≤L3 / H≤0.25, 0.25≤L4 / H≤0.285; Furthermore, let Z1 be the component of the vector from P1 to P2 in the axial direction of the impeller, Z2 be the component of the vector from P2 to P3 in the axial direction of the impeller, Z3 be the component of the vector from P3 to P4 in the axial direction of the impeller, and Z4 be the component of the vector from P4 to P5 in the axial direction of the impeller. Then, the modulus of vectors Z1, Z2, Z3, and Z4 respectively satisfy: 0.02≤|Z1| / H≤0.1, 0.05≤|Z2| / H≤0.12, 0.05≤|Z3| / H≤0.12, and 0.02≤|Z4| / H≤0.

1. Moreover, the vector direction of Z1 is from the leading edge to the trailing edge, the vector direction of Z2 is from the trailing edge to the leading edge, the vector direction of Z3 is from the trailing edge to the leading edge, and the vector direction of Z4 is from the leading edge to the trailing edge.

3. The rear guide vane of the axial flow fan as described in claim 1, characterized in that, For the straight line segment and the spline curve segment in the arc at the tip of the guide vane, the angle between the straight line segment and the circumferential direction of the impeller is θ2, where θ2 is the exit angle, and 60°≤θ2≤120°; the angle between the end tangent of the spline curve segment and the circumferential direction of the impeller is θ1, where θ1 is the inlet angle, and 0.40≤θ1 / θ2≤0.

60.

4. A rear guide vane impeller having the rear guide vanes of an axial flow fan as described in any one of claims 1-3, characterized in that, The rear guide vane of the axial flow fan as described in any one of claims 1-3 is disposed on the annular hub and placed behind the axial flow impeller.

5. A rear guide vane impeller having the rear guide vanes of an axial flow fan as described in any one of claims 1-3, characterized in that, It includes an annular hub and multiple axial flow fan rear guide vanes evenly arranged on the annular hub, with any two axial flow fan rear guide vanes having the same outline shape.

6. An axial flow fan having a rear guide vane impeller as described in claim 5.

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