Axial flow fan

Abstract

The utility model provides an axial flow fan which comprises a silencer shell, an impeller is arranged outside one side of an air outlet of the silencer shell, a flow guide cover is arranged on a hub on one side of an air inlet of the impeller, a machine shell barrel is arranged outside the impeller, a space guide vane is arranged on one side of the air outlet of the impeller and on the inner side of the barrel, a motor is arranged in the space guide vane, and a motor is arranged in the motor. And triangular rib plates are arranged on the inner sides of the flanges at the two ends of the shell cylinder. According to the utility model, the structural strength of the fan can be effectively enhanced, the vibration index of the shell barrel is improved, the total pressure efficiency of the fan is effectively improved, and the noise is reduced; the boundary dimension of the fan with the same purpose and the same performance is effectively reduced, and miniaturization is achieved; the rotor dynamic balance precision and the whole machine dynamic balance precision of the fan are effectively improved, the manufacturing process is simplified, and the whole machine stability is improved.

Description

Technical Field

[0001] The utility model relates to an axial flow fan. Background Art

[0002] The final design of a fan is mainly determined by the specific speed. Under the condition of large air volume and high total pressure requirements, traditional centrifugal fans are mainly selected. Because of their large air volume and high air pressure, for high-performance requirements of the fan, most traditional centrifugal fans are chosen. The fan not only has the disadvantages of large occupied space, but also has high vibration index, high noise, complex processing technology and high maintenance cost. Therefore, it is difficult to meet the requirements of higher performance in the design.

[0003] In the prior art, when a cooling fan needs to be applied in the GCU system (Gas Combustion Unit) of an LNG carrier (liquefied natural gas carrier), the working medium of the cooling fan is a mixed gas mainly composed of air. There are generally problems such as large vibration and noise and large occupied space. With the trend of compact hull structure, it is increasingly difficult for traditional centrifugal fans to meet the usage environment requirements of this facility. Summary of the Utility Model

[0004] The utility model provides an axial flow fan.

[0005] The axial flow fan provided by the utility model includes:

[0006] A casing cylinder;

[0007] A muffler housing which is arranged on one side of the air inlet of the casing cylinder and communicated with the casing cylinder;

[0008] An impeller, a motor, a space guide vane and a guide cover arranged in the casing cylinder. Among them, the impeller is arranged on one side of the air outlet of the muffler; the impeller includes: a hub and blade units uniformly connected to the outer side wall of the hub; a guide cover is connected to the hub on one side of the air inlet of the impeller; the space guide vane is arranged on one side of the air outlet of the impeller; the motor is connected inside the space guide vane, and the output shaft of the motor is connected to the hub of the impeller.

[0009] Both the muffler and the casing cylinder are cylindrical structures with openings at both ends, and the central axes of the guide cover, the impeller, the motor, the casing cylinder and the muffler housing are on the same straight line, which is collectively called the fan axis.

[0010] Furthermore, in the above axial flow fan, the root of each blade unit is connected to the outer sidewall of the hub, and the thickness of the side cross-section of each blade unit gradually increases from the tip of the blade unit to the root of the blade unit. The two sides of each blade unit are the leading edge and the trailing edge of the blade unit respectively, and the blade area between the leading edge and the trailing edge bulges. Among them, the leading edge of the blade unit is closer to the air inlet of the casing cylinder, and the trailing edge of the blade unit is slightly farther from the air inlet of the casing cylinder; the included angle between the line connecting the vertex of the tip of the leading edge of each blade unit or the vertex of the tip of the trailing edge of each blade unit and the axis of the fan is 40°, and there is a deviation margin of 3%.

[0011] Furthermore, in the above axial flow fan, a flow guide cover is provided on one side of the air inlet of the hub of the impeller. The flow guide cover includes: a hollow cylindrical surface and an arc surface connecting and closing one end opening of the hollow cylindrical surface. The outer edge of the arc surface is connected to the hollow cylindrical surface. The inner diameter of the hollow cylindrical surface of the flow guide cover matches the outer diameter of the air inlet side of the hub of the impeller, and the hollow cylindrical surface and the outer sidewall of the hub of the impeller are fastened by radial bolts.

[0012] Furthermore, in the above axial flow fan, the normal distance along the axis of the fan between the hollow cylindrical surface of the flow guide cover and the end face on the air inlet side of the hub is 30 mm, with a deviation float of 5%.

[0013] Furthermore, in the above axial flow fan, the trailing edge of the blade unit of the impeller and the leading edge of the space guide vane rotate around the axis of the fan and form an included angle of 70° - 90° with the meridian plane. The included angle between the projections of the trailing edge of the blade unit of the impeller and the leading edge of the space guide vane on the vertical plane is 70° - 135°; among them, the meridian plane refers to the swept surface formed by the rotation of the leading edge of the blade unit around the axis of the fan; the vertical plane is a plane perpendicular to the axis of the fan.

[0014] Furthermore, in the above axial flow fan, the number of blade units of the impeller and the number of blades of the space guide vane are relatively prime numbers, and the least common multiple of the number of blade units of the impeller and the number of blades of the space guide vane is divided by the number of blade units of the impeller 2 and the number of blades of the space guide vane respectively, and the smaller value of the two obtained quotients is not less than 3.

[0015] Furthermore, in the above axial flow fan, the thickness of each blade unit decreases uniformly from the root of the blade unit to the tip of the blade unit, and the fillet radius at the root of the blade unit is 23 mm.

[0016] Furthermore, in the above axial flow fan, the blade unit is a T-shaped blade, that is, the width of the blade changes spatially from the root of the blade unit to the tip of the blade unit, and gradually and uniformly widens or narrows along the radial direction of the impeller unit from the axis of the fan to the tip.

[0017] Further, in the above axial flow fan, the ratio of the width of the tip of the blade unit to the width of the root of the blade unit is 0.78. Herein, the width of the tip of the blade unit is the length of the line connecting the vertex of the tip of the leading edge of the blade unit and the vertex of the tip of the trailing edge of the blade unit; the width of the root of the blade unit is the length of the line connecting the bottom point of the root of the leading edge of the blade unit and the bottom point of the root of the trailing edge of the blade unit.

[0018] Further, in the above axial flow fan, a truss is also fixed inside the casing cylinder body, and the motor is supported by the truss. When viewed from the air inlet direction of the motor foot mounting truss, the position range of the left end of the truss is between the 5th and 6th space guide vanes counted counterclockwise from the uppermost vane of the space guide vanes, and the position range of the right end of the truss is between the 5th and 6th space guide vanes counted clockwise from the uppermost vane of the space guide vanes No. 5. The width range of the truss is the 6th to 9th space guide vanes counted clockwise from the uppermost vane of the space guide vanes.

[0019] The pneumatic efficiency of the present invention is high, the vibration and noise are low, and the structure is reliable and compact. Specifically, the beneficial effects of the present invention are as follows:

[0020] (1) Effectively strengthen the structural strength of the fan, improve the vibration index of the casing cylinder body, effectively improve the total pressure efficiency of the fan, and significantly reduce the vibration and noise level;

[0021] (2) Effectively reduce the external dimensions of fans with the same use and performance, and achieve a more miniaturized size;

[0022] (3) Effectively improve the rotor dynamic balance and the overall machine dynamic balance accuracy of the fan, simplify the manufacturing process, and improve the overall machine stability. Description of the Drawings

[0023] The present invention will be further described below with reference to the drawings and embodiments;

[0024] Figure 1 is a longitudinal sectional structure schematic diagram of an embodiment of the present invention;

[0025] Figure 2 is a transverse sectional structure schematic diagram of an embodiment of the present invention;

[0026] Figure 3 is a view of an embodiment of the present invention from the air inlet direction;

[0027] Figure 4 in Figure 1 is a partial enlarged structure schematic diagram at position A in;

[0028] Figure 5 is Figure 1 is a partial enlarged structure schematic diagram at position B in;

[0029] Figure 6 is Figure 3 a schematic diagram of a partially enlarged structure at position C in

[0030] Figure 7 is Figure 1 a schematic diagram of a partially enlarged structure at position D in

[0031] Figure 8 is Figure 7 a schematic diagram of a partially enlarged structure at position E in

[0032] Label description: 1. Silencer housing; 2. Impeller; 3. Guide cover; 4. Casing cylinder; 5. Spatial guide vane; 6. Motor; 7. Triangular rib plate; 8. Truss; 11. Silencing cavity; 12. Fan axis; 21. Hub; 22. Blade unit; 24. Through hole; 25. Leading edge of the blade unit; 26. Trailing edge of the blade unit; 27. Root of the blade unit; 28. Tip of the blade unit; 51. Blade of the spatial guide vane; 52. Leading edge of the spatial guide vane; 71. Bottom of the rib plate; 72. Top of the rib plate. Specific embodiments

[0033] The following further describes the present utility model in detail with reference to embodiments, but the protection scope of the present utility model is not limited thereto.

[0034] Embodiment 1

[0035] As Figures 1 to 6 shown, this embodiment provides an axial flow fan, including:

[0036] Casing cylinder 4;

[0037] A silencer housing 1 provided on the air inlet side of the casing cylinder 4 and communicating with the casing cylinder 4;

[0038] An impeller 2, a motor 6, a spatial guide vane 5 and a guide cover 3 provided in the casing cylinder 4. Among them, the impeller 2 is provided on the air outlet side of the silencer 1. The impeller 2 includes: a hub 21 and blade units 22 uniformly connected to the outer side wall of the hub 21. A guide cover 3 is connected to the hub 21 on the air inlet side of the impeller. The spatial guide vane 5 is provided on the air outlet side of the impeller 2. The motor 6 is connected inside the spatial guide vane 5, and the output shaft of the motor 6 is connected to the hub of the impeller 2.

[0039] Here, an impeller 2 is provided outside the air outlet side of the silencer housing 1, and a guide cover 3 is provided on the hub 21 on the air inlet side of the impeller 2, as Figure 1As shown, the flow guide cover 3 can be arc-shaped, and the raised part of the arc of the flow guide cover 3 is close to the air outlet side of the muffler housing 1. An outer casing cylinder 4 is provided outside the impeller 2. A space guide vane 5 is provided on the inner side of the air outlet side of the impeller 2 within the outer casing cylinder 4. A motor 6 is provided within the space guide vane 5. A truss 8 is also fixed within the outer casing cylinder 4, and the motor 6 is supported by the truss 8. As Figure 1 shown, flanges are respectively provided at both ends of the outer casing cylinder 4, and triangular gusset plates 7 are provided on the inner sides of the outer edges of each flange.

[0040] In this example, on the air outlet side outside the muffler housing 1 of the axial flow fan, an impeller 2 is provided. A flow guide cover 3 is installed on the hub 21 on the air inlet side of the impeller 2, and the outer casing cylinder 4 is fixed. Triangular gusset plates 7 are provided on the inner sides of the outer edges of each flange. A space guide vane 5 is provided on the inner side of the outer casing cylinder 4, and a motor 6 is installed within the space guide vane. The impeller 2 together with the flow guide cover 3 is installed at the output shaft end of the motor 6, and then the muffler is installed on the air inlet side of the fan.

[0041] In this example, both the muffler housing 1 and the outer casing cylinder 4 are cylindrical structures with openings at both ends. One end opening of the cylindrical structure of the muffler housing 1 can be communicated with one end opening of the outer casing cylinder 4 through the flange; the central axes of the muffler housing 1, the flow guide cover 3, the impeller 2, the motor 6, and the outer casing cylinder 4 are on the same straight line, which is collectively called the fan axis 12.

[0042] In this embodiment, when the motor 6 is energized and rotates, the output shaft of the motor 6 drives the impeller 2 to rotate and do work. The gas passes through the muffler housing 1 and is locally rectified by the flow guide cover 3 and then enters the channels between the blade units 22 of the impeller 2. Through the interaction between the impeller 2 and the gas, the gas obtains energy to form an air flow. The air flow is pressed into the front end of the space guide vane 5 and rectified by the space guide vane 5, and is output to the air outlet end of the space guide vane 5. The air flow field is improved and noise is treated through the flow guide cover 3 and the space guide vane, and finally the air flow flows out from the air outlet of the outer casing cylinder 4.

[0043] The axial flow fan can be a single-stage fan, and the whole only contains one impeller.

[0044] Embodiment 2

[0045] As Figure 2 and 3 shown, on the basis of Embodiment 1, the impeller 2 includes: a hub 21 and 9 blade units 22 evenly connected and distributed on the outside of the hub 21. Each blade unit 22 is arranged towards the air inlet side of the outer casing cylinder 4, and the included angles between each blade unit 22 and the air inlet plane of the outer casing cylinder 4 and the central fan axis 12 of the outer casing cylinder 4 are all acute angles. Each blade unit is spatially parallel to the adjacent two blade units.

[0046] In this embodiment, the hub 21 is fitted and installed with the output end of the motor 6, so that the impeller 2 as a whole rotates around the output shaft of the motor 6 by the rotational driving force of the motor 6; an air duct is formed between every two adjacent blade units 22 provided on the impeller 2, and air is discharged from the tips of two adjacent blade units 22. In the specific implementation process, the blade units 22 are evenly distributed. Specifically, as Figure 7 and 8 shown, the root 27 of each blade unit 22 is connected to the outer wall of the hub 21, and the thickness of the side cross-section of each blade unit 22 gradually increases from the tip 28 of the blade unit to the root 27 of the blade unit. The two sides of each blade unit 22 are respectively the leading edge 25 and the trailing edge 26 of the blade unit, and the blade area between the leading edge 25 and the trailing edge 26 bulges. Among them, the leading edge 25 of the blade unit is closer to the air inlet of the casing cylinder body 4, and the trailing edge 26 of the blade unit is slightly farther from the air inlet of the casing cylinder body 4; the included angle between the connection line of the vertex 251 of the tip 28 of the leading edge 25 of each blade unit or the vertex (not shown in the figure) of the tip 28 of the trailing edge 26 of each blade and the fan axis 12 is 40°, and a deviation margin of 3% is allowed.

[0047] In the actual processing and construction process, the impeller 2 can be integrally cast from high-strength aluminum alloy, and the details of its hub 21 are machined by a high-precision machining center. Therefore, the shape distribution of each blade unit 22 is uniform, and the thickness of each part is consistent. This process can effectively improve the dynamic balance and static balance accuracy of the impeller 2, and the dynamic balance accuracy can reach G1.0 level.

[0048] Embodiment 3

[0049] On the basis of Embodiment 2, a flow guide cover 3 is installed on the air inlet plane of the impeller 2, and the flow guide cover 3 is arranged outside the hub 21 of the impeller 2.

[0050] In the implementation process, a flow guide cover 3 is provided on one side of the air inlet of the hub of the impeller. The flow guide cover 3 includes: a hollow cylindrical surface and an arc surface connecting and closing one end opening of the hollow cylindrical surface. The outer edge of the arc surface is connected to the hollow cylindrical surface, and the opening at the other end of the hollow cylindrical surface is fitted and installed with the outer wall of the hub 21. Viewed from the radial direction of the flow guide cover and the impeller, the radian of the arc surface of the flow guide cover is 49.2°. The inner diameter of the hollow cylindrical surface of the flow guide cover 3 is matched with the outer diameter of the air inlet side of the hub 21 of the impeller 2. The hollow cylindrical surface of the flow guide cover 3 and the outer wall of the hub 21 of the impeller are fastened by radial bolts. The inner diameter of the hollow cylindrical surface of the flow guide cover 3 is 2 mm larger than the outer diameter of the hub 21,

[0051] Specifically, the inner diameter dimension of the hollow cylindrical surface is 400 mm, with a positive tolerance of 0.50 mm. As Figure 4As shown in the figure, through holes 24 with a diameter of 9 mm are machined on the outer cylindrical surface of the flow guide cover 3, and the flow guide cover 3 is connected to the hub 21 by bolts passing through the through holes 24. Specifically, four 9-mm through holes 24 are arranged on the hollow cylindrical surface at the outer edge of the flow guide cover 3, and the angle between the axes of every two adjacent through holes is 90°, with an allowable deviation of 3%.

[0052] In this example, the flow guide cover 3 is integrally machined by a machining center from high-strength aluminum alloy. The normal distance along the axis of the fan between the hollow cylindrical surface of the flow guide cover and the end face on the air inlet side of the hub 21 is 30 mm, with an allowable deviation of 5%. This can improve the rectifying effect of the flow guide cover 3 on the air flow at the air inlet and enhance the air flow work efficiency of the fan.

[0053] Embodiment 4

[0054] On the basis of Embodiment 2, the distribution of the blade units 22 of the impeller 2 and the design of the space guide vane 5 are based on the optimized matching of the angle difference compensation slip between the pressure surface and the suction surface and their dynamic and static interference characteristics; as Figure 7 shown in the figure, the trailing edge 26 of the blade unit of the impeller 2 and the leading edge 52 of the space guide vane rotate around the axis 12 of the fan and form an angle of 70° - 90° with the meridian plane. The projected angle of the trailing edge 26 of the blade unit of the impeller 2 and the leading edge of the space guide vane 5 in the vertical plane is 70° - 135°. Here, the meridian plane refers to the swept surface formed by the rotation of the leading edge of the blade unit around the axis 12 of the fan. Among them, the vertical plane is a plane perpendicular to the axis 12 of the fan.

[0055] The number of the blade units 22 of the impeller 2 and the number of the blades 51 of the space guide vane are relatively prime numbers, and when the least common multiple of the number of the blade units 22 of the impeller 2 and the number of the blades 51 of the space guide vane is divided by the number of the blade units of the impeller 2 and the number of the blades 51 of the space guide vane respectively, the smaller value of the two obtained quotients is not less than 3.

[0056] The thickness of each blade unit decreases uniformly from the root of the blade unit to the tip of the blade unit, and the fillet radius at the root of the blade unit is 23 mm.

[0057] In this embodiment, the outlets of the blade units 22 of the impeller 2 and the blades 51 of the space guide vane are subjected to a curved sweep treatment based on the optimized matching of the angle difference compensation slip between the pressure surface and the suction surface and their dynamic and static interference characteristics, which can solve the problem of the contradiction between the flow loss in the dynamic and static blade clearance and the pulsating pressure intensity of the dynamic and static interference, and achieve the effects of increasing efficiency, reducing vibration and noise.

[0058] In this embodiment, taking the cooperation design of the blade unit 22 and the blades 51 of the spacer guide vane 5 as an example, by using the spatial twist analysis technology and the improvement of the variable thickness of the blade unit 22 with space, through the spatial twist verification design, the primary and multiple flow losses in the transition channels of the blade unit 22 and the blades 51 of the spacer guide vane are reduced, the blade profile is optimized, and the coupled design of the two surfaces greatly improves the flow condition at the blade tip, realizing the compensation for the vector slip of the airflow direction at the outlet of the impeller 2; through the optimized design of the angle set for each blade unit 22 and the blades 51 of the spacer guide vane, the prominent problem of large flow losses at the inlet and outlet of the impeller 2 under off-design conditions of the fan is solved. Specifically: viewed from the meridional plane, the trailing edge of the outlet of the impeller 2 and the leading edge of the inlet of the spacer guide vane 5 rotate around the central axis and form an angle with the meridional plane, and the value is controlled between 70° and 90°; the meridional plane refers to the swept surface formed by the rotation of the leading edge of the blade unit around the axis, and this setting can effectively reduce the vibration and noise levels; project the trailing edge of the outlet of the impeller 2 and the leading edge of the inlet of the spacer guide vane 5 onto a plane perpendicular to the central axis, and the included angle formed by the two is controlled between 70° and 135°; the number of blades of the impeller 2 and the number of blades of the spacer guide vane 5 are preferably relatively prime numbers, and the least common multiple of the two is divided by the two respectively, and the smaller value of the two obtained quotients shall not be less than 3; through this measure, the intensity of the dynamic and static interference of the fan can be reduced, and the vibration and noise levels can be reduced.

[0059] Embodiment 5

[0060] On the basis of Embodiment 2, the blade unit 22 is a T-shaped blade, that is, the width of the blade changing with space from the blade root 27 to the blade tip 28 of the blade unit 22 gradually and uniformly widens or narrows along the radial direction of the impeller unit 22 from the fan axis 12 to the blade tip 28. In this example, it becomes narrower as it approaches the blade tip.

[0061] As Figure 8 shown, in this example, the blade unit is designed as a T-shaped blade. Specifically, the ratio of the width of the blade tip 28 of the blade unit 22 to the width of the blade root 27 of the blade unit 22 is 0.78. Among them, the width of the blade tip 28 of the blade unit 22 is: the length of the line connecting the vertex of the blade tip 28 of the leading edge 25 of the blade unit 22 and the vertex of the blade tip 28 of the trailing edge 26 of the blade unit; the width of the blade root 27 of the blade unit 22 is: the length of the line connecting the bottom point of the blade root 27 of the leading edge 25 of the blade unit 22 and the bottom point of the blade root 27 of the trailing edge 26 of the blade unit 22. The top of the blade unit 22 is the blade tip 28.

[0062] In this example, the blade unit 22 is designed by three-dimensional flow, which can improve the aerodynamic performance of the fan. Due to the spatial change of the blade profile of the blade unit 22, the structure of the impeller unit 2 can be simplified, which is beneficial to processing and assembly. At the same time, the load of the blade unit 22 under the action of centrifugal force can be reduced, the structural strength of the impeller 2 can be improved, and thus the vibration index can be reduced.

[0063] Example 6

[0064] In this example, a truss 8 is also fixed inside the casing cylinder body 4. The motor 6 is horizontally installed on the truss 8 through bolts. The truss 8 is firmly welded to the casing cylinder body 4, avoiding the spatial guide vane 5, so that the standard motor is arranged in the spatial guide vane 5 with limited dimensions.

[0065] In this example, as Figure 2 shown, the rotation axis of the output shaft of the motor 6 is consistent with the central axis of the casing cylinder body 4. Specifically: viewed from the air inlet direction of the truss 8 installed at the bottom feet of the motor 6, the position range of the left end of the truss 8 is between the 5th and 6th spatial guide vane blades 51 counted counterclockwise from the uppermost blade of the spatial guide vane 5, and the position range of the right end of the truss 8 is between the 5th and 6th spatial guide vane blades 51 counted clockwise from the uppermost blade of the spatial guide vane 5. The width range of the truss 8 is the 6th - 9th spatial guide vane blades 51 counted clockwise from the uppermost blade of the spatial guide vane 5.

[0066] Example 7

[0067] In this example, flanges are respectively arranged at both ends of the casing cylinder body 4, and triangular rib plates 7 are arranged inside the inner edges of the flanges at both ends of the casing cylinder body 4. Specifically, as Figure 5 shown, each triangular rib plate 7 is located exactly in the middle of two flange bolt holes. The acute angle 71 at the bottom of the rib plate of the triangular rib plate 7 is 38.7°, and the acute angle 72 at the top of the rib plate of the triangular rib plate 7 is 51°.

[0068] In this example, through the modal analysis of the fan, the shape and distribution of the triangular rib plates 7 can improve the overall stiffness of the fan, enhance the anti - impact effect, change the natural frequency of the fan, avoid the vibration frequency of the rotating components of the fan, prevent resonance, and reduce the vibration and noise level of the fan.

[0069] Example 8

[0070] Based on Example 1, a silencer housing 1 is arranged on the air inlet side of the fan. The silencer housing 1 includes: a silencer housing and a sound - absorbing cavity 11 arranged inside the silencer housing. The silencer housing is connected to the casing cylinder body 4 through a flange. The motor 6 is energized to drive the impeller 2 to rotate, and a negative pressure is formed on the air inlet side of the fan. Obviously, the air flow in the silencer housing 1 will enter from the side of the silencer away from the impeller 2 and flow out from the side of the silencer housing 1 close to the impeller 2, and then the impeller 2 does work on the air.

[0071] In this example, based on the verification of the air - dynamics and acoustics coupling simulation, a low - pressure noise area will be formed on the air inlet side. Therefore, the silencer housing 1 is set to reduce the air noise. Specifically, the silencer housing 1 is arranged on the air inlet side of the fan. The overall length of the silencer housing 1 is 1280 mm, allowing a 5% float. Among them, asFigure 1 As shown, a sound-absorbing cavity 11 is provided in the middle section of the muffler. The effective length of this section of the sound-absorbing cavity 11 is 1080 mm, allowing a floating range of +5%, and its axial position is located exactly in the middle of the entire muffler housing 1. That is, in the effective area, the distances from both the side of the sound-absorbing cavity 11 close to the fan and the side far from the fan to the respective end faces of the muffler housing 1 they are close to are 100 mm, allowing a floating amount of 3%.

[0072] In this embodiment, sound-absorbing materials are filled in the sound-absorbing cavity 11 of the effective section of the muffler housing 1, thereby significantly reducing the overall air noise level of the fan.

Claims

1. An axial flow fan, characterized in that: include: Casing cylinder; A muffler housing is arranged on one side of the air inlet of the casing cylinder and is connected to the casing cylinder; The impeller, motor, space guide vane and guide cover are arranged in the casing cylinder, wherein the impeller is arranged on the air outlet side of the muffler; the impeller comprises: a hub and blade units evenly connected to the outer wall of the hub; the hub on the air inlet side of the impeller is connected with a guide cover; the space guide vane is arranged on the air outlet side of the impeller; the motor is connected inside the space guide vane, and the output shaft of the motor is connected to the hub of the impeller; The silencer and the casing body are both cylindrical structures with openings at both ends. The central axes of the guide cover, impeller, motor, casing body and silencer shell are in a straight line, which is collectively referred to as the fan axis.

2. The axial flow fan according to claim 1, characterized in that: The root of each blade unit is connected to the outer side wall of the hub, and the side section thickness of each blade unit gradually becomes thicker from the tip of the blade unit to the root of the blade unit; the two sides of each blade unit are the leading edge and the trailing edge of the blade unit respectively, and the blade area between the leading edge and the trailing edge is arched, wherein the leading edge of the blade unit is closer to the air inlet of the casing cylinder, and the trailing edge of the blade unit is slightly farther from the air inlet of the casing cylinder; the angle between the apex of the tip of the leading edge of each blade unit or the apex of the tip of the trailing edge of each blade unit and the line connecting the fan axis is 40°, and there is a 3% deviation margin.

3. The axial flow fan according to claim 2, characterized in that: A guide cover is provided on one side of the air inlet of the impeller hub, and the guide cover includes: a hollow cylindrical surface and a curved surface connected to the closed hollow cylindrical surface with one end opening, the outer edge of the curved surface is connected to the hollow cylindrical surface, the inner diameter of the hollow cylindrical surface of the guide cover matches the outer diameter of the air inlet side of the impeller hub, and the hollow cylindrical surface and the outer side wall of the impeller hub are fastened by radial bolts.

4. The axial flow fan according to claim 3, characterized in that: The normal distance between the hollow cylindrical surface of the guide cover and the end surface of the hub on the air inlet side along the fan axis is 30 mm, with a deviation of 5%.

5. The axial flow fan according to claim 2, characterized in that: The trailing edge of the impeller blade unit and the leading edge of the space guide vane rotate around the fan axis and form an angle of 70° to 90° with the meridian plane, and the projection angle of the trailing edge of the impeller blade unit and the leading edge of the space guide vane on the vertical plane is 70° to 135°; wherein, the meridian plane refers to the swept surface formed by the leading edge of the blade unit rotating around the fan axis; the vertical plane is a plane perpendicular to the fan axis.

6. The axial flow fan according to claim 5, characterized in that: The number of blade units of the impeller and the number of blades of the spatial guide vanes are coprime numbers, and the smaller of the two quotients obtained by dividing the number of blade units of the impeller (2) and the number of blades of the spatial guide vanes (5) by the least common multiple of the number of blade units of the impeller and the number of blades of the spatial guide vanes is not less than 3.

7. The axial flow fan according to claim 1, characterized in that: The thickness of each blade unit decreases evenly from the root of the blade unit to the tip of the blade unit, and the fillet radius of the root of the blade unit is 23 mm.

8. The axial flow fan according to claim 2, characterized in that: The blade unit is a T-shaped blade, that is, the width of the blade space changes from the blade root of the blade unit to the blade tip of the blade unit, and gradually and evenly widens or narrows from the fan axis to the blade tip along the radius direction of the impeller unit.

9. The axial flow fan according to claim 8, characterized in that: The ratio of the width of the blade tip of the blade unit to the width of the root of the blade unit is 0.78, wherein the width of the blade tip of the blade unit is: the length of the line connecting the apex of the blade tip of the leading edge of the blade unit and the apex of the blade tip of the trailing edge of the blade unit; the root width of the blade unit is: the length of the line connecting the bottom point of the root of the leading edge of the blade unit and the bottom point of the root of the trailing edge of the blade unit.

10. The axial flow fan according to claim 1, characterized in that: A truss is also fixed in the casing cylinder, and the motor is supported by the truss. When the truss is installed at the bottom of the motor and viewed from the air inlet direction, the position range of the left end of the truss is between the 5th and 6th space guide vane blades counted counterclockwise from the top blade of the space guide vane, and the position range of the right end of the truss is between the 5th and 6th space guide vane blades counted clockwise from the top blade of the space guide vane (5). The width range of the truss is the 6th to 9th space guide vane blades counted clockwise from the top blade of the space guide vane.

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