Compact, efficient and low-noise closed axial flow fan and impeller thereof

Abstract

The invention belongs to the technical field of axial flow fans, and mainly relates to a compact, efficient and low-noise closed axial flow fan and an impeller of the compact, efficient and low-noise closed axial flow fan. The chord length of the blades, the projection of the blade stacking line on the meridian plane and the projection of the blade stacking line on the plane perpendicular to the rotating shaft of the impeller are restrained. The axial flow fan comprises a plurality of guide vanes and the impeller, the guide vanes are distributed in a circumferential array mode, a motor is fixed to the guide vanes, and the motor is in transmission connection with the hub to drive the impeller to rotate. Through the constraint of a chord length equation of the blade, the maximum chord length of the blade is located in the middle, acting is prevented from being concentrated on the blade top, turbulent kinetic energy of air is reduced, noise can be reduced, meanwhile, the surface, the front edge and the tail edge of the blade are optimized, and the blade is more suitable for air flowing.

Description

Technical Field

[0001] The invention belongs to the technical field of axial flow fans, and mainly relates to a compact, high-efficiency and low-noise closed axial flow fan and an impeller thereof. Background Art

[0002] Noise is the main source of pollution in today's world. In order to control the environmental pollution caused by noise and improve people's living and working environment, countries around the world have invested a lot of manpower and material resources to carry out research on vibration and noise reduction, and have formulated a series of standards and regulations.

[0003] Axial flow fans are widely used mechanical equipment in industrial and agricultural production and people's daily life. They cover multiple engineering fields such as power, electricity, chemical industry, metallurgy and machinery. For example, in the industrial field, they are used for ventilation of factory workshops, ventilation and dehumidification of warehouses, and ventilation of tunnels; in the construction field, they are used for building ventilation systems and fire smoke exhaust of buildings; in the agricultural field, they are used for greenhouse ventilation and ventilation of animal husbandry.

[0004] In recent years, the number of various axial flow fans has increased year by year, the speed has become higher and higher, and the impact of axial flow fan operation noise on people's lives has become more and more serious.

[0005] For axial flow fans, aerodynamic noise is the main noise source, and mechanical noise is much smaller than aerodynamic noise. The aerodynamic noise of axial flow fans is composed of broadband noise distributed in the frequency spectrum and discrete noise of each order of harmonics. The former is turbulent noise, which is caused by pressure and speed fluctuations; the latter is rotational noise, which is caused by the mutual interference between the moving blades and the stationary blades of the axial flow fan. At present, the working position of the axial flow fan blades is concentrated at the blade top. The blade top has a large amount of work, and the energy is mainly concentrated at the blade top. The turbulent kinetic energy of the flow will become larger, causing relatively large noise. Summary of the invention

[0006] The invention provides a compact, high-efficiency, low-noise closed axial flow fan and an impeller thereof, so as to solve the problem of high aerodynamic noise of the axial flow fan in the prior art.

[0007] To solve the above problems, the present invention adopts the following technical solutions: An impeller, comprising a hub, wherein a plurality of blades are fixedly mounted on the hub in the circumferential direction, and the chord length equation of the blades is: ; The projection equation of the blade stacking line on the meridian plane is: ; The projection equation of the blade stacking line on the plane perpendicular to the impeller rotation axis is:

[0008] in, is the percentage of leaf height, The range is 0%-100%, The range is 13mm-30mm, The range is 4mm-50mm, and The actual size of the blade stacking line; , , The unit is mm. is the chord length of the blade at each height, and The actual size of the blade stacking line.

[0009] It has the following beneficial effects: through the constraint of the chord length equation of the blade, the maximum chord length of the blade is located in the middle position, avoiding the concentration of work on the blade tip and reducing the turbulent kinetic energy of the air, which can reduce noise. At the same time, the surface, leading edge and trailing edge of the blade are optimized to make it more suitable for air flow.

[0010] Furthermore, the chord length of the blade increases from small to small and then decreases, and the maximum chord length is located at 50%±10% of the blade height.

[0011] The invention has the following beneficial effects: through the constraint of the chord length equation of the blade, the maximum chord length of the blade is located at 50%±10% of the blade height, thus avoiding the work being concentrated on the blade tip and reducing the turbulent kinetic energy of the air, thereby reducing the noise.

[0012] Furthermore, outer edges of the plurality of blades are fixedly mounted with wheel covers.

[0013] Furthermore, the impeller is integrally injection molded.

[0014] The invention has the following beneficial effects: the blades are connected with the wheel cover and the wheel hub to form a closed structure, and are processed by integral injection molding, so that the impeller has higher reliability.

[0015] Furthermore, the wheel cover has a flange facing outwards.

[0016] A compact, high-efficiency, low-noise closed axial flow fan comprises a guide vane and any of the impellers described above, wherein the guide vanes are multiple and distributed in a circular array, a motor is fixed on the guide vanes, and the motor is connected to the hub to drive the impeller to rotate.

[0017] The invention has the following beneficial effects: the guide vanes are reasonably distributed, which is beneficial to the flow of air and reduces the generation of noise.

[0018] Furthermore, the projection equation of the guide vane stacking line on the plane perpendicular to the rotation axis is: ; in, The range is 0mm-38mm, The unit is mm.

[0019] Furthermore, the projection of the guide vane stacking line on the meridian plane is a straight line.

[0020] Furthermore, the guide vane adopts a forward curved structure.

[0021] Furthermore, an air guide ring is fixedly mounted on the outer edges of the plurality of guide vanes, and a plurality of connecting seats are fixedly mounted on the outer circumference of the air guide ring.

[0022] The invention has the following beneficial effects: the air guide ring is used to fix a plurality of guide vanes; when the axial flow fan is used, the axial flow fan needs to be fixed to relevant equipment through a plurality of connecting seats 8. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] By reading the following detailed description with reference to the accompanying drawings, the above and other objects, features and advantages of the exemplary embodiments of the present invention will become readily understood. In the accompanying drawings, several embodiments of the present invention are shown in an exemplary and non-limiting manner, and the same or corresponding reference numerals represent the same or corresponding parts, wherein: Figure 1 It is an exploded view of the axial flow fan; Figure 2 is a cross-sectional view of an axial flow fan; Figure 3 It is a structural schematic diagram of an axial flow fan; Figure 4 is a top view of the impeller; Figure 5 It is a top view of the guide vane; Figure 6 is the blade chord length variation diagram; Figure 7 It is the projection diagram of the blade stacking line on the meridian plane; Figure 8 It is the projection diagram of the blade stacking line on the plane perpendicular to the impeller rotation axis; Fig. 9 It is the projection diagram of the guide vane stacking line on the plane perpendicular to the rotation axis.

[0024] Description of reference numerals: 1. Blades; 2. Hub; 3. Wheel cover; 4. Motor; 5. Mounting seat; 6. Guide vanes; 7. Air guide ring; 8. Connecting seat. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Those skilled in the art should know that the embodiments described below are part of the embodiments of the present disclosure, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0026] Various non-limiting embodiments of the present invention are described in detail below. Any number of elements in the accompanying drawings is for illustration and not for limitation, and any naming is only for distinction and does not have any limiting meaning. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

[0027] The aerodynamic noise of the axial flow fan is mainly caused by the following parts of the blade 1: When the airflow flows through the leading edge of blade 1, the airflow will separate at this position. This is because the combined influence of the shape of the leading edge of blade 1 and the incoming flow conditions makes it impossible for the airflow to flow smoothly along the surface of blade 1. For example, under some working conditions, the unevenness of the incoming flow or the slight geometric defects of the leading edge of blade 1 may cause the airflow to generate local vortices at this location. The formation and shedding of these vortices will produce pressure pulsations, which in turn radiate noise outward. This noise is more obvious in the high-frequency range, and its frequency is related to the frequency of vortex shedding, which in turn depends on factors such as the incoming flow velocity and the geometric characteristics of the leading edge of blade 1. Among them, "incoming flow" is a mechanical term, which refers to the flow state of a fluid or gas before it enters a system or device. This term is often used to describe the flow conditions of a fluid before it enters a pipeline, equipment or system for the purpose of analysis and design.

[0028] The trailing edge of blade 1 is an important source of aerodynamic noise. At the trailing edge of blade 1, due to the pressure difference between the upper and lower surfaces of blade 1, the airflow will produce a strong shear layer. This shear layer is very unstable and will form a Karman vortex street. The Karman vortex street is a series of alternating vortices that produce periodic pressure changes. Just like placing an obstacle in a river, the water will form regular vortices downstream after bypassing the obstacle. The Karman vortex street at the trailing edge of blade 1 of the axial flow fan will produce discrete frequency noise. Its frequency is related to factors such as the chord length of blade 1 and the airflow velocity. The frequency component of this noise is relatively simple, but the intensity may be large and it persists during the operation of the axial flow fan.

[0029] The roughness and unevenness of the surface of blade 1 can also cause aerodynamic noise. Even if the surface processing accuracy of blade 1 is high during the manufacturing process, in the actual operating environment, the surface of blade 1 may become rough due to corrosion, wear, or adsorption of impurities such as dust. When the airflow flows through these rough surfaces, friction and local airflow disturbances will occur. This disturbance will produce small-scale vortices, which in turn generate noise. This noise is usually broadband noise with a relatively wide frequency range, and it increases with the increase of surface roughness and the increase of airflow speed. In addition, if there are local protrusions or depressions on the surface of blade 1, it will also cause local acceleration or separation of the airflow at these locations, thereby increasing the generation of noise.

[0030] The airflow situation at the blade tip is relatively complex. Due to the gap between the blade tip and the air guide ring 7, part of the airflow will leak from the gap. This part of the leakage airflow will interact with the mainstream to produce strong shear and vortex. For example, the speed and direction of the leakage airflow are different from the mainstream, and the mixing process between them will produce large pressure fluctuations. Moreover, the vortex intensity at the blade tip is relatively large, and the noise it generates will radiate to the surrounding space. The noise caused by this blade tip leakage vortex is more obvious in the area close to the blade tip, and will change with the size of the blade tip gap and the operating conditions of the axial flow fan. Its frequency components are also relatively complex, with both low-frequency components and high-frequency components.

[0031] like Figure 1-Figure 3 As shown, this embodiment provides a compact, high-efficiency, low-noise closed axial flow fan, including a mounting base 5, a motor 4, an impeller, a guide vane 6, and an air guide ring 7. Figure 5 As shown, there are multiple guide vanes 6, and the multiple guide vanes 6 are assembled on the circumference of the mounting seat 5, and the multiple guide vanes 6 are distributed in a circumferential array on the mounting seat 5. The guide vanes 6 are reasonably distributed, which is conducive to the flow of air and reduces the generation of noise. A motor 4 is fixed on the mounting seat 5, and the motor 4 is connected to the impeller to drive the impeller to rotate. The guide vanes 6 in this embodiment adopt a forward curved structure.

[0032] like Figure 3 , Figure 5 As shown, the air guide ring 7 is fixedly assembled on the outer edge of the plurality of guide vanes 6, and four connecting seats 8 are fixedly assembled on the outer circumference of the air guide ring 7. The air guide ring 7 is used to fix the plurality of guide vanes 6; when the axial flow fan is used, the axial flow fan also needs to be fixed to the relevant equipment through the four connecting seats 8.

[0033] In other embodiments, the number of the connection sockets 8 can be determined according to actual needs, such as three connection sockets 8 , or five connection sockets 8 , or six connection sockets 8 .

[0034] like Figure 4As shown, the impeller includes a hub 2, a plurality of blades 1 and a wheel cover 3. The plurality of blades 1 are fixedly mounted on the circumference of the hub 2 and arranged in a circumferential array. The wheel cover 3 is fixedly mounted on the outer edges of the plurality of blades 1. The wheel cover 3 is located on the inner side of the air guide ring 7. In this embodiment, the blade 1 has a blade height of 300 mm.

[0035] The motor 4 is connected to the hub 2 of the impeller, and the motor 4 drives the hub 2 to rotate, thereby driving the blades 1 to rotate. The hub 2 covers the motor 4 on the guide vanes 6.

[0036] The wheel cover 3 in this embodiment has a flange facing outwards so as to half-wrap the air guide ring 7 .

[0037] The impeller in this embodiment is integrally injection molded, wherein the blade 1 is connected with the wheel cover 3 and the wheel hub 2 to form a closed structure, and is processed by integral injection molding, so that the impeller has higher reliability.

[0038] like Figure 6 As shown, the chord length equation of the blade 1 in this embodiment is: ; The chord length equation shows the chord length at various height positions of the blade 1. The chord length of the blade 1 increases from small to small and then decreases, and the maximum chord length position is at 50%±10% of the blade 1 height position.

[0039] By constraining the chord length equation of blade 1, the maximum chord length of blade 1 is located at 50%±10% of the height of blade 1, avoiding the concentration of work on the blade tip, reducing the turbulent kinetic energy of the air, and thus reducing noise.

[0040] like Figure 7 As shown, in this embodiment, the projection equation of the stacking line of blade 1 on the meridian plane is: .

[0041] like Figure 8 As shown, the projection equation of the stacking line of blade 1 on the plane perpendicular to the impeller rotation axis is: .

[0042] in, is the percentage of the height of blade 1, The range is 0%-100%, The range is 13mm-30mm, The range is 4mm-50mm, and It is the actual size of the stacked line of blade 1.

[0043] , , The unit is mm. is the chord length of blade 1 at various heights, and It is the actual size of the stacked line of blade 1.

[0044] The equation is the chord length of blade 1 at various heights; equation The axis of the rotation axis is the x-axis, and the y-axis passes through the initial endpoint of the stacking line projection of blade 1, so the origin of the coordinate system corresponds to the initial endpoint of the stacking line projection of blade 1; equation The origin is the axis of the impeller's rotation shaft.

[0045] By constraining the chord length equation of blade 1, the maximum chord length of blade 1 is located in the middle position, avoiding the concentration of work on the blade tip, reducing the turbulent kinetic energy of the air, which can reduce noise, and at the same time optimize the surface, leading edge and trailing edge of blade 1 to make it more suitable for air flow. Since the total work of the entire blade 1 remains unchanged, the work near the blade tip is relatively reduced, which reduces the flow separation near the blade tip, thereby reducing noise.

[0046] The stacking line of blade 1 is an important concept in the design of axial fan blade 1. It refers to the line connecting the centroids of each cross section of blade 1. This line determines the overall shape and spatial geometric characteristics of blade 1 to a large extent.

[0047] The shape of the stacking line has a key influence on the flow path of the airflow in the axial flow fan. For example, a reasonable stacking line can guide the airflow to enter and leave the blade 1 channel at a desired angle, thereby improving the efficiency of the axial flow fan. If the stacking line design is unreasonable, it may cause the airflow to separate, swirl and other undesirable flow phenomena in the blade 1 channel, increasing energy loss.

[0048] The stacking line is closely related to the performance parameters of the axial flow fan, such as flow rate, head (pressure rise), efficiency, etc. By optimizing the shape of the stacking line, the performance of the axial flow fan can be improved to a certain extent. For example, when designing a high-flow axial flow fan, the shape of the stacking line may be designed to be more stretched to accommodate a larger airflow.

[0049] From the perspective of mechanical structure, the design of the stacking line also needs to consider the strength and vibration of the blade 1. A reasonable stacking line shape can enable the blade 1 to better withstand loads such as centrifugal force and aerodynamic force during rotation, reducing the possibility of vibration and fatigue damage of the blade 1. For example, when designing a large axial fan blade 1, in order to avoid resonance when the blade 1 rotates at high speed, factors such as the shape of the stacking line and the thickness distribution of the blade 1 will be comprehensively considered to ensure that the blade 1 has a suitable natural frequency.

[0050] When designing an axial flow fan with a large flow rate, the stacking line may extend radially outward to increase the effective flow area of ​​the blade 1 channel to ensure that sufficient airflow can pass smoothly through the blade 1. For example, in an axial flow fan in a large ventilation system, the stacking line of blade 1 is relatively closer to the top of blade 1, so that blade 1 can handle more air flow.

[0051] If there is a higher requirement for the pressure increase of the axial flow fan, the shape of the stacking line may be more complex, and may take the form of a twisted blade 1. The stacking line of the twisted blade 1 can better control the velocity and pressure distribution of the airflow in the blade 1 channel, thereby achieving a higher pressure increase. For example, in the axial flow fan of an industrial boiler, in order to overcome the larger system resistance, the blade 1 stacking line will be designed to produce a higher pressure increase.

[0052] In order to improve the efficiency of axial flow fans, the design of the stacking line needs to consider minimizing the loss of airflow in the blade 1 channel. This usually involves fine control of factors such as the incident angle of the airflow and the velocity distribution. Through numerical simulation and experimental research, engineers will adjust the shape of the stacking line so that the airflow can pass through blade 1 more smoothly, reducing friction loss and flow separation loss. For example, in the axial compressor part of an aircraft engine, in order to achieve high efficiency, the blade 1 stacking line is precisely designed and optimized to ensure good performance under high speed and complex working conditions.

[0053] In an axial flow fan, the meridian plane refers to the plane passing through the axis of rotation of the axial flow fan. The axial flow fan can be imagined as a cylinder, and the meridian plane is like the plane obtained by cutting it along the axis of the cylinder.

[0054] The meridian plane is critical for analyzing the flow characteristics of the fluid (usually air) inside the axial fan. On the meridian plane, the flow of the fluid in the axial and radial directions can be observed and studied. For example, by setting measurement points on the meridian plane, the distribution of parameters such as the velocity and pressure of the fluid in the axial and radial directions can be obtained.

[0055] Different from the plane perpendicular to the impeller's rotating axis (circumferential surface), the circumferential surface is mainly used to analyze the rotation of the fluid in the circumferential direction, while the meridian surface focuses on the axial and radial flow analysis. For example, when studying the vortex loss of an axial flow fan, the circumferential surface can observe the vortex in the circumferential direction, while the meridian surface can observe the axial and radial fluid reflow, etc. They help engineers understand the complex flow phenomena inside the axial flow fan from different angles.

[0056] like Fig. 9 As shown, the projection equation of the stacking line of the guide vane 6 on the plane perpendicular to the rotation axis is: .

[0057] in, The range is 0mm-38mm, The unit is mm. and It is the actual size of the guide vane stacking line.

[0058] The projection of the stacking line of the guide vane 6 on the meridian plane is a straight line.

[0059] In this embodiment, the wind wheel noise is reduced according to the characteristics of the stacking law.

[0060] At the same time, the above design makes the work of the axial fan mainly concentrated in the range of 50-75% of the height of the blade 1, avoiding the problem of high noise caused by large work on the blade tip. At the same time, due to the design structure, the installation angle of the impeller blade 1 is relatively small, thereby reducing the overall height of the impeller.

Claims

1. An impeller, characterized in that: The impeller comprises a hub, and a plurality of blades are fixedly mounted on the hub in the circumferential direction. The chord length equation of the blades is: ； The projection equation of the blade stacking line on the meridian plane is: ； The projection equation of the blade stacking line on the plane perpendicular to the impeller rotation axis is: in, is the percentage of leaf height, The range is 0%-100%, The range is 13mm-30mm, The range is 4mm-50mm, and The actual size of the blade stacking line; , , The unit is mm. is the chord length at each height of the blade, and The actual size of the blade stacking line.

2. An impeller according to claim 1, characterized in that: The chord length of the blade increases from small to small and then decreases, and the maximum chord length is located at 50%±10% of the blade height.

3. An impeller according to claim 2, characterized in that: The outer edges of the plurality of blades are fixedly equipped with wheel covers.

4. An impeller according to claim 3, characterized in that: The impeller is integrally injection molded.

5. An impeller according to claim 7, characterized in that: The wheel cover has a flange facing outward.

6. A compact, high-efficiency, low-noise closed axial flow fan, characterized in that: It comprises a guide vane and an impeller as claimed in any one of claims 1 to 4, wherein there are a plurality of guide vanes, the plurality of guide vanes are distributed in a circular array, a motor is fixed on the plurality of guide vanes, and the motor is connected to a hub to drive the impeller to rotate.

7. A compact, high-efficiency, low-noise closed axial flow fan according to claim 6, characterized in that: The projection equation of the guide vane stacking line on the plane perpendicular to the rotation axis is: ； in, The range is 0mm-38mm, The unit is mm. and It is the actual size of the guide vane stacking line.

8. A compact, high-efficiency, low-noise closed axial flow fan according to claim 7, characterized in that: The projection of the guide vane stacking line on the meridian plane is a straight line.

9. A compact, high-efficiency, low-noise closed axial flow fan according to claim 8, characterized in that: The guide vane adopts a forward curved structure.

10. A compact, high-efficiency, low-noise closed axial flow fan according to claim 9, characterized in that: An air guide ring is fixedly mounted on the outer edges of the plurality of guide vanes, and a plurality of connecting seats are fixedly mounted on the outer circumference of the air guide ring.

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