Axial flow fan impeller with swept angle blades

Abstract

The present invention discloses an axial flow fan impeller with swept-angle blades, comprising a hub and unit blades, wherein the unit blades are arranged at equal intervals along the outer circumference of the hub with the hub axis as the center, and the unit blades are composed of a straight blade section and a swept-angle blade tip section, the swept-angle blade tip section is cross-fixed with the straight blade section, the inner edge of the straight blade section is fixedly connected to the hub, the outer edge of the swept-angle blade tip section is a free end, and the outer edge shape is an arc. The present invention has the advantages of novel structure, high aerodynamic efficiency, low operating noise, low air resistance, simple processing and manufacturing, and high production efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of axial flow fans, in particular to an axial flow fan impeller with swept-angle blades. Background Art

[0002] The impellers used in conventional large-scale industrial cooling towers generally adopt equal-width hollow airfoil pultruded blade impeller structures, such as Figure 1 As shown, the advantage of this impeller structure is that it can obtain relatively high aerodynamic efficiency, while having low production cost and high production efficiency; its disadvantage is that it is difficult to meet the increasingly stringent ultra-low noise technical requirements, and the products tend to be mature, so there is limited room for further improvement in aerodynamic efficiency.

[0003] In recent years, the demand for ultra-low noise impellers has increased. Therefore, it is urgent to develop an impeller with a new structural form that can not only meet the requirements of improving efficiency and reducing noise, but also ensure that the cost will not be significantly increased compared to the conventional equal-width hollow aerofoil blade impeller, and the delivery cycle can meet customer requirements. Summary of the Invention

[0004] The purpose of the present invention is to solve the above-mentioned deficiencies in the prior art and to provide an axial flow fan impeller with swept blades that has a novel structure, high aerodynamic efficiency, low operating noise, low air resistance, simple processing and high production efficiency.

[0005] The technical solution adopted by the present invention to solve its technical problem is:

[0006] An axial fan impeller with swept-angle blades includes a hub and unit blades, wherein the unit blades are arranged at equal intervals along the outer circumference of the hub with the hub axis as the center, and is characterized in that: the unit blades are composed of a straight blade portion and a swept-angle blade tip portion, the swept-angle blade tip portion is cross-fixed with the straight blade portion, the inner edge of the straight blade portion is fixedly connected to the hub, the outer edge of the swept-angle blade tip portion is a free end, and the outer edge shape is an arc, so as to reduce the impact of the impeller on the airflow when it rotates, improve the aerodynamic efficiency and reduce the aerodynamic noise, and at the same time, the processing and manufacturing cost is low, thereby improving production efficiency.

[0007] The sweep angle of the tip of the swept section relative to the straight section of the blade is 30 degrees to 90 degrees. The sweep angle within this range is adapted to the airflow inlet angle when the impeller rotates, so as to further reduce the impact of the impeller on the airflow during rotation, improve aerodynamic efficiency and reduce aerodynamic noise.

[0008] The preferred angle at which the tip of the swept-angle blade section is swept forward or backward relative to the straight blade section of the present invention is 60 degrees. When the swept-forward or backward angle is 60 degrees, the effect of improving aerodynamic efficiency and reducing noise is best.

[0009] The centerline length of the straight blade portion of the present invention is L2, the radial length of the unit blade is L, and the L2:L size range is between (0.3:1) and (0.85:1). The setting of this size ratio matches the impeller rotation speed and aerodynamic performance requirements, maximizes the aerodynamic efficiency and reduces the aerodynamic noise generated when the blade rotates.

[0010] The straight blade section and the swept blade tip section of the present invention are made of hollow airfoil-shaped pultruded profiles.

[0011] The outer edge of the tip of the swept angle section of the present invention is fixedly connected with an arc-shaped tip winglet, and the outer periphery of the tip winglet extends outward along the outer edge of the tip of the swept angle section. By providing the tip winglet to prevent the formation of tip tail vortex, the fan efficiency is improved and the noise is further reduced.

[0012] The width of the straight blade section of the present invention gradually decreases from the middle to the tip of the swept angle section, thereby improving the aerodynamic performance.

[0013] The beneficial effects of the present invention are as follows: the tip of the swept section is swept forward or backward relative to the straight section, and the sweep angle type, sweep angle, and size ratio are matched with the impeller rotation speed and aerodynamic performance requirements, so as to reduce the impact of the impeller on the airflow during rotation, improve aerodynamic efficiency and aerodynamic performance, and reduce aerodynamic noise; the setting of the sweep angle further optimizes the radial structure of the blade tip that has the greatest impact on the airflow, reduces the adverse effects such as the large resistance and noise caused by the frontal impact of the airflow on the leading edge of the blade, reduces the air resistance, thereby further improving the aerodynamic performance of the blade, and reducing eddy noise. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of an impeller structure with equal-width hollow airfoil-shaped blades in the prior art.

[0015] Figure 2 Schematic diagram of the swept-angle blade of the present invention (towards the air inlet).

[0016] Figure 3 This is a schematic diagram of the structure of the axial flow fan impeller with forward swept angle blades (towards the air outlet) of the present invention.

[0017] Figure 4 This is a schematic diagram of the structure of an axial flow fan impeller with swept-angle blades (towards the air outlet) according to the present invention.

[0018] Figure 5 The swept angle blade of the present invention and Figure 1 Schematic diagram of blade comparison.

[0019] Figure 6 These are the comparative test data of total pressure efficiency and A-grade ratio between the prior art pultruded impeller and the forward-swept impeller of the present invention.

[0020] Figure 7 It is a comparison curve of the static pressure efficiency and total pressure efficiency of the prior art pultruded impeller and the forward-swept impeller of the present invention.

[0021] Figure 8 This is a comparison curve of the A-level of the pultruded impeller in the prior art and the forward-swept impeller of the present invention.

[0022] Figure 9 These are the test data comparing the total pressure efficiency and A-grade ratio of the prior art pultruded impeller and the swept impeller of the present invention.

[0023] Figure 10 It is a comparison curve of the static pressure efficiency and total pressure efficiency of the prior art pultruded impeller and the swept impeller of the present invention.

[0024] Figure 11 It is a comparison curve of the A-level of the pultruded impeller in the prior art and the swept impeller of the present invention.

[0025] Figure markings: hub-1, unit blade-2, straight section blade portion-201, blade inner edge-2011, blade outer edge-2012, blade leading edge-2013, blade trailing edge-2014, swept angle section blade tip portion-202, blade tip outer edge-2021, blade tip leading edge-2022, blade tip trailing edge-2023, blade tip winglet-2024. DETAILED DESCRIPTION

[0026] The present invention will be described below with reference to the accompanying drawings and embodiments.

[0027] like Figure 2-5 As shown, an axial fan impeller with swept-angle blades includes a hub 1 and unit blades 2. The unit blades 2 are arranged at equal intervals along the outer circumference of the hub with the hub axis as the center. The unit blades 2 are composed of a straight blade portion 201 and a swept-angle blade tip portion 202. The swept-angle blade tip portion 202 is cross-fixed to the straight blade portion 201. The inner edge of the straight blade portion 201 is fixedly connected to the hub 1. The outer edge of the swept-angle blade tip portion 202 is a free end, and the outer edge shape is arc-shaped, so as to reduce the impact of the impeller on the airflow when it rotates, improve the aerodynamic efficiency and reduce the aerodynamic noise. At the same time, the processing and manufacturing cost is low, and the production efficiency is improved. In this embodiment, the straight section of the blade is surrounded by the blade inner edge 2011, the blade leading edge 2013, the blade outer edge 2012, and the blade trailing edge 2014. The swept angle section of the blade tip is surrounded by the blade tip inner edge, the blade tip leading edge 2022, the blade tip outer edge 2021, and the blade tip trailing edge 2023. The arc-shaped blade tip outer edge of the unit blade forms the outer circle of the impeller and cooperates with the inner wall of the wind tube.

[0028] The swept angle of the tip portion 202 of the swept section relative to the straight section blade portion 201 is 30 degrees to 90 degrees. The swept angle within this range is adapted to the airflow inlet angle when the impeller rotates, so as to further reduce the impact of the impeller on the airflow when the impeller rotates, improve aerodynamic efficiency and reduce aerodynamic noise. Figure 2 The angle θ in the sweep angle section is the angle at which the blade tip is swept forward or backward.

[0029] like Figure 2 As shown, the midline length of the straight blade portion 201 is L2, the radial length of the unit blade is L, and the L2:L size range is between (0.3:1) and (0.85:1). The setting of this size ratio matches the impeller rotation speed and aerodynamic performance requirements, maximizes the aerodynamic performance and reduces the aerodynamic noise generated when the blade rotates.

[0030] In this embodiment, the trailing edge of the straight blade portion is composed of a trailing edge straight section and a trailing edge oblique section. Figure 2 Where R is the outer diameter of the impeller, L4 is the radial length of the trailing edge of the straight blade portion, L3 is the radial length of the straight section of the trailing edge of the straight blade portion, L4 minus L3 is the radial length of the oblique section of the trailing edge, and the range of L3:L4 is (0~1):1, thereby improving the aerodynamic performance. In this embodiment, L3:L4 is 0.5:1, and the width of the straight blade portion gradually decreases from the middle to the tip of the swept angle section, thereby improving the aerodynamic performance.

[0031] like Figure 5 As shown, a represents the area of the straight blade, b represents the area of the swept angle blade tip, c represents the width of the swept angle blade tip, and d represents the width of the straight blade. As can be seen from the figure, since the width of the straight blade decreases from the middle to the swept angle blade tip, the size of d is slightly larger than the size of c. After the blade tip is swept, the total area of a plus b is greater than Figure 1 The area of the blades increases the solidity of the impeller and improves the aerodynamic performance of the impeller.

[0032] In this embodiment, a straight blade section 201 and a swept angle blade tip section 202 are joined together to form a unit blade. In this embodiment, the straight blade section and the swept angle blade tip section are connected by welding, or by bolts. A straight petiole is inserted into the straight blade section, and a swept angle blade tip section is inserted into the swept angle blade tip section. The straight petiole and the swept angle blade tip section are fixedly connected. Bolt holes are provided near the outer edge of the straight blade section and near the inner edge of the swept angle blade tip section. Bolts are used to securely connect the straight blade section and the straight petiole, and the swept angle blade tip section and the swept angle blade tip section to the petiole. The straight blade section and the swept angle blade tip section are then welded together at their junction. Alternatively, a connecting plate and bolts may be used. Bolt holes are provided on the connecting plate, which is located on the surface of the connecting portion between the straight blade section and the swept angle blade tip section. Bolts are used to connect the connecting plate to the straight blade section and the swept angle blade tip section. The straight blade section and the swept angle blade tip section are then welded together at their junction. In this embodiment, the straight blade section and the swept angle blade tip section are spliced and connected, and can also be made into one piece, which also has a low production cost.

[0033] The straight blade section and the swept blade tip section are made of hollow airfoil-shaped pultruded profiles.

[0034] The outer edge of the swept-angle section blade tip is fixedly connected to an arcuate tip winglet 2024. The outer periphery of the tip winglet 2024 extends outward along the outer edge of the swept-angle section blade tip. The tip winglet is provided to prevent the formation of tip vortices, thereby improving fan efficiency and further reducing noise. In this embodiment, the shape of the tip winglet matches the shape of the outer edge of the swept-angle section blade tip and extends outward. The length of the tip winglet extending toward the trailing edge of the unit blade is greater than the length extending toward the leading edge, which helps to eliminate vortices at the trailing edge. The method of fixing the tip winglet to the blade tip is conventional and will not be described in detail here.

[0035] During the manufacturing process of the present invention, the straight blade section and the swept angle blade tip section are first processed separately. After the processing is completed, the straight blade section and the swept angle blade tip section are welded to form a unit blade, and then the unit blade is installed on the hub.

[0036] The present invention applies the principle of bionics, and the blade structure is based on the shape of an eagle's wings when it is flying. In actual tests and applications, it has excellent aerodynamic performance and can significantly reduce aerodynamic noise.

[0037] Figure 6-Figure 8 The existing pultruded impeller prototype ( Figure 1 Comparative test data of the impeller in the present invention and the forward swept impeller prototype, Figures 9-11 The existing pultruded impeller prototype ( Figure 1 Comparative test data of the swept impeller prototype of the present invention) and the impeller in the embodiment of the present invention.

[0038] The impeller diameter of the prototype used in the comparative test is 2100mm, the motor power is 7.5kW, the impeller speed is 328r / min, the actual test air volume range is 90000m^3 / h~125000m^3 / h, the pressure is 80Pa~150Pa, the forward sweep angle and the backward sweep angle are 60 degrees, and the ratio of the straight section blade centerline length L2: the unit blade radial length L is 0.59:1. As shown in the data and curves in the accompanying drawings, the aerodynamic efficiency of the forward swept structure of this invention is increased by 2%~8%, and the noise is reduced by 8dB~12dB. The aerodynamic efficiency of the backward swept structure of this invention is increased by 2%~10%, and the noise is reduced by 7dB~11dB. In actual testing and application, it meets the Level I noise requirements specified in the GB / T 7190.1-2018 standard, and has excellent aerodynamic performance and low aerodynamic noise.

Claims

1. An axial flow fan impeller with swept blades, comprising a hub and unit blades, wherein the unit blades are arranged at equal intervals along the outer circumference of the hub with the hub axis as the center, and characterized in that: The unit blade is composed of a straight blade section and a swept angle blade tip section, the swept angle blade tip section is cross-fixed with the straight blade section, the inner edge of the straight blade section is fixedly connected to the hub, and the outer edge of the swept angle blade tip section is a free end, and the outer edge shape is an arc; An arc-shaped tip winglet is fixedly connected to the outer edge of the swept angle segment blade tip, the outer periphery of the tip winglet extends outward along the outer edge of the swept angle segment blade tip, the shape of the tip winglet matches the shape of the outer edge of the swept angle segment blade tip, and the length of the tip winglet extending toward the trailing edge of the unit blade is greater than the length extending toward the leading edge; The straight blade section and the swept blade tip section are made of hollow airfoil-shaped pultruded profiles; The trailing edge of the straight blade portion is composed of a straight trailing edge section and an oblique trailing edge section, L4 is the radial length of the trailing edge of the straight blade portion, L3 is the radial length of the straight trailing edge section, and the range of L3:L4 is (0-1):

1. The width of the oblique trailing edge section of the trailing edge of the straight blade portion gradually decreases toward the tip of the swept angle section. A straight segment petiole is inserted inside the straight blade portion, and a swept angle segment petiole is inserted inside the swept angle segment tip portion. Bolt holes are provided at the position of the straight blade portion close to the outer edge of the blade and at the position of the swept angle segment tip close to the inner edge of the tip. The straight blade portion and the straight segment petiole are connected via bolts, and the swept angle segment tip and the swept angle segment petiole are connected via bolts. The straight segment petiole and the swept angle segment petiole are fixedly connected, and the connection between the straight blade portion and the swept angle segment tip portion is welded; or bolt holes are provided at the position of the straight blade portion close to the outer edge of the blade and at the position of the swept angle segment tip portion close to the inner edge of the tip, and a connecting plate is provided on the surface of the connection between the straight blade portion and the swept angle segment tip portion, and bolt holes are provided on the connecting plate. The straight blade portion, the swept angle segment tip and the connecting plate are connected via bolts, and the connection between the straight blade portion and the swept angle segment tip portion is welded.

2. The axial flow fan impeller with swept blades according to claim 1, characterized in that: The swept angle of the blade tip portion of the swept angle section relative to the straight blade section is 30 degrees to 90 degrees.

3. The axial flow fan impeller with swept blades according to claim 2, characterized in that: The swept angle of the blade tip portion of the swept angle section relative to the straight blade section is 60 degrees.

4. An axial flow fan impeller with swept-angle blades according to claim 1, 2 or 3, characterized in that: The midline length of the straight blade portion is L2, the radial length of the unit blade is L, and the L2:L size range is between (0.3:1) and (0.85:1).

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