Axial flow fans and range hoods and air supply equipment including them

Abstract

This invention relates to the field of range hoods, and provides an axial flow fan and a range hood and air supply device including the same. The axial flow fan includes a K-stage blade assembly, which includes moving blades and stationary blades. Along the axial direction of the axial flow fan and from the inlet to the outlet of the axial flow fan, the first stage blade assembly, the second stage blade assembly, ..., the K-stage blade assembly are arranged sequentially. In the same stage of the blade assembly, the moving blade is located upstream of the stationary blade. As the number of stages increases, the axial spacing between the moving blade and the stationary blade of the same stage, and the axial spacing between the stationary blade of the previous stage and the moving blade of the next stage are monotonically changing and not exactly the same, thereby reducing the noise at the inlet or outlet of the axial flow fan.

Description

Technical Field

[0001] This invention relates to the field of range hoods, and particularly to axial flow fans. Background Technology

[0002] Range hoods commonly use forward-intake multi-blade centrifugal fans (referred to as "centrifugal fans"). Centrifugal fans mainly consist of an impeller and a volute. To reduce noise, the impeller diameter needs to be increased. Adding the volute to the impeller further increases the fan's size, thus increasing manufacturing and installation costs. The limited space in household kitchens restricts the increase in centrifugal fan size, resulting in limited noise reduction potential.

[0003] like Figure 1 As shown, the intake and exhaust paths of the centrifugal fan 5000' are vertical; the range hood 10000' draws air upwards from the smoke collection hood 2000', while the centrifugal fan draws air horizontally, forcing the airflow to make a right-angle bend. This obstructs the airflow path, reduces the range hood's energy efficiency, and increases noise. Figure 1 The arrows in the middle indicate the direction of the airflow.

[0004] To improve the overall performance of the range hood, the following solutions are available:

[0005] (1) Use axial flow fans in range hoods. For example Figure 2 The axial flow fan 1000' has an internal intermediate shaft 3' within its housing 1'. A stationary blade 22' is fixed to the housing, and a moving blade 21' is fixed to the rotating part 32' of the intermediate shaft. The rotating part is rotatably positioned relative to the stationary part 31' of the intermediate shaft. The stationary part is fixed to the housing via the stationary blades, driving the rotating part to rotate, which in turn drives the stationary blades to rotate, performing work on the airflow. The axial flow fan does not have a volute, and the airflow enters and exits along the Z-axis. Its volume is much smaller than that of a conventional centrifugal fan, and it offers high flexibility in its layout within the overall ductwork, saving space for installing thicker sound-absorbing and sound-insulating structures. It is also easy to place in the ceiling, keeping noise sources away from users, and is convenient for use with low-resistance sound-absorbing ducts. However, axial flow fans inherently have a large flow rate but low pressure rise; under the same conditions, their pressurization capacity is not as good as that of centrifugal fans. If an axial flow fan is to be used in a range hood, a higher speed is required, which makes it difficult to reduce noise. Unlike centrifugal fans, axial flow fans cannot increase their pressurization capacity by increasing their outer diameter. This is because, under the same rotational speed, similar geometry, and similar velocity triangle shapes, the flow rate and pressure rise of an axial flow fan are approximately quadratic in relation to its outer diameter; while the flow rate and pressure rise of a centrifugal fan are approximately linear and quadratic in relation to their outer diameter, respectively. Furthermore, to achieve better aerodynamic performance, axial flow fans often require the use of three-dimensional twisted blades. However, due to manufacturing cost limitations, the design freedom for the blade shape is relatively low, thus typically preventing the achievement of high efficiency.

[0006] (2) such as Figure 3Placing the centrifugal fan on the ceiling cleverly utilizes its vertical airflow direction, reducing the number of bends in the exhaust duct and thus lowering resistance and improving efficiency. To ensure optimal overall performance, the centrifugal fan must be installed inside the ceiling, at the original bend in the exhaust duct. However, the size of the centrifugal fan in a range hood typically far exceeds the size of a ceiling panel, necessitating the removal of multiple ceiling panels and the supporting frame during installation, increasing installation difficulty and cost. Figure 4 If the centrifugal fan in the ceiling is too large, the air intake duct 4000' will inevitably shift forward relative to the wall 20000', making the range hood's shape complex. For example... Figure 5 Placing the air intake duct close to the wall to simplify the range hood's appearance can lead to uneven airflow. Reducing the size of the centrifugal fan in the ceiling will decrease its aerodynamic and noise reduction performance.

[0007] In summary, existing range hoods have poor overall performance and cannot meet the requirements of compact fan structure, good aerodynamic performance, low noise, and easy installation. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to overcome the defect of poor overall performance of the fan in the existing range hood, and to provide an axial flow fan and a range hood and air supply equipment including the fan.

[0009] The present invention solves the above-mentioned technical problems through the following technical solution:

[0010] An axial flow fan includes a K-stage blade assembly, the blade assembly including two types of blades, moving blades and stationary blades, where K is an integer and K≥2;

[0011] Along the axial direction of the axial flow fan and from the inlet of the axial flow fan to the outlet of the axial flow fan: the first stage blade assembly, the second stage blade assembly, ..., the Kth stage blade assembly are arranged sequentially, and in the same stage blade assembly, the moving blade is arranged upstream of the stationary blade;

[0012] The average axial distance between the trailing edge of the i-th stage moving blade and the leading edge of the i-th stage stationary blade is drs_i, i=1, 2, ..., K; the average axial distance between the trailing edge of the j-th stage stationary blade and the leading edge of the (j+1)-th stage moving blade is dsr_j, j=1, 2, ..., K-1.

[0013] As i increases, as j increases, drs_i and dsr_j change monotonically in the same direction;

[0014] When K = 2, drs_1 ≠ drs_K;

[0015] When K > 2, drs_1 ≠ drs_K and / or dsr_1 ≠ dsr_K-1.

[0016] In this design, a larger drs_i in the axial flow fan results in more uniform mixing of the fluid as it flows from the trailing edge of the moving blade to the trailing edge of the stationary blade, thus improving blade frequency noise and reducing fluid flow noise. Similarly, a larger dsr_j results in more uniform mixing of the fluid as it flows from the trailing edge of the preceding stationary blade to the leading edge of the following moving blade, also improving blade frequency noise and reducing fluid flow noise.

[0017] As i and j increase, drs_i and dsr_j change monotonically in the same direction. Furthermore, when K = 2, drs_1 ≠ drs_K, and when K > 2, drs_1 ≠ drs_K and / or dsr_1 ≠ dsr_K-1. This ensures that drs_i and dsr_j are larger the closer they are to the inlet or outlet of the axial flow fan.

[0018] Firstly, when the values ​​of drs_i and dsr_j are larger closer to the inlet of the axial flow fan, the fluid is mixed more evenly at the blades closer to the inlet, and the noise generated by the fluid flow itself is smaller. Moreover, the noise generated by the fluid flow at the downstream blades, which is relatively greater than that at the upstream blades, is gradually weakened by the shielding of multiple rows of blades, thereby reducing the noise transmitted upstream. Therefore, the noise in the upstream part of the axial flow fan, especially at the inlet, can be reduced.

[0019] Secondly, similar to the first point, when the values ​​of drs_i and dsr_j are larger closer to the outlet of the axial flow fan, the fluid is mixed more evenly at the blades closer to the outlet, and the noise generated by the fluid flow itself is smaller. Moreover, the noise generated by the fluid flow at the upstream blades, which is relatively greater than that at the downstream blades, is gradually weakened by the shielding of multiple rows of blades, thereby reducing the noise transmitted downstream. Therefore, the noise in the downstream part of the axial flow fan, especially at the outlet, can be reduced.

[0020] Thirdly, it is possible to reduce the noise at the inlet or outlet of the axial flow fan while avoiding an increase in the axial dimension of the axial flow fan; or, while avoiding an increase in the noise at the inlet or outlet of the axial flow fan, it is possible to reduce the axial dimension of the axial flow fan.

[0021] Ideally, as i increases, drs_i and dsr_j increase or decrease monotonically in the same direction as j increases.

[0022] In this scheme, the following settings can further reduce the noise at the inlet or outlet of the axial flow fan while avoiding an increase in the axial dimension of the axial flow fan; or, while avoiding an increase in the noise at the inlet or outlet of the axial flow fan, further reduce the axial dimension of the axial flow fan.

[0023] Ideally, dsr_j > drs_i, j = i;

[0024] And / or, dsr_j > drs_(i+1), j = i.

[0025] Setting dsr_j > drs_i and / or dsr_j > drs_(i+1) increases the axial spacing between the j-stage stationary blades and the j+1-stage moving blades, making the fluid more evenly mixed as it flows from the front stationary blades to the leading edge of the rear moving blades, thus reducing the overall noise of the axial flow fan.

[0026] Ideally, the moving blades at each level have the same shape and size, and the stationary blades at each level have the same shape and size.

[0027] In this scheme, regardless of the number of blade assembly stages, only two sets of blade molds are needed: moving blade and stationary blade. The aerodynamic performance of the axial flow fan can be changed by increasing or decreasing the number of blade assembly stages. It has good versatility and low processing cost.

[0028] Preferably, in a single-stage blade assembly, the number of blades of the same type is greater than or equal to 19.

[0029] In this design, the outflow from each stage of the blades is made more uniform, reducing noise.

[0030] Preferably, in a single-stage blade assembly, the number of blades of the same type is greater than or equal to 39.

[0031] Preferably, in a single-stage blade assembly, the maximum consistency of the same type of blade is less than or equal to 1.8.

[0032] In this design, the blades are set up in a way that facilitates demolding during casting.

[0033] Preferably, in a single-stage blade assembly, the maximum consistency of the same type of blade is less than or equal to 1.4.

[0034] Preferably, the blade is made of plastic or aluminum alloy.

[0035] In this design, the relatively soft plastic or aluminum alloy materials can reduce wear on the mold when casting the blades; the relatively light plastic or aluminum alloy materials can reduce the weight of the axial flow fan when used in the axial flow fan.

[0036] Preferably, the axial flow fan further includes a housing and an intermediate shaft disposed within the housing, a flow channel is formed between the inner surface of the housing and the outer surface of the intermediate shaft, the blade assembly is disposed within the flow channel, and the portion of the flow channel along the axial direction from the leading edge of the first stage moving blade to the trailing edge of the last stage stationary blade is the blade flow channel;

[0037] The inner and outer diameters of the blade flow channel are constant along the axial direction.

[0038] In this design, the inner and outer diameters of the blade flow channel remain constant along the axial direction. This simplifies the blade flow channel structure and makes it easier to manufacture. Furthermore, it stabilizes the blade flow channel and reduces noise.

[0039] Preferably, the axial flow fan further includes a housing and an intermediate shaft disposed within the housing, a flow channel is formed between the inner surface of the housing and the outer surface of the intermediate shaft, the blade assembly is disposed within the flow channel, and the portion of the flow channel along the axial direction from the leading edge of the first stage moving blade to the trailing edge of the last stage stationary blade is the blade flow channel;

[0040] The inner diameter of the blade flow channel at the same position along the axial direction is d1, and the outer diameter is d2, with the ratio of d1 / d2 ranging from 0.4 to 0.8.

[0041] In this design, the blades are set in the blade flow channel. By setting the hub ratio d1 / d2 of the blade flow channel, the hub ratio is made large enough, which makes the blade height small enough. This allows for a smaller blade tip and root curvature, resulting in smooth fluid flow and low noise. The hub ratio is also made small enough, which makes the blade height large enough, thus making the channel for fluid to flow through the blade large enough and the flow rate large enough.

[0042] Ideally, the range of d1 / d2 is between 0.6 and 0.7.

[0043] Preferably, the axial flow fan further includes a housing, two types of suspension brackets, and an intermediate shaft disposed within the housing. The intermediate shaft includes two stationary parts located at both ends along the axial direction and a rotating part located between the two stationary parts and rotating about the axial direction. The two stationary parts are respectively fixed to the housing by one of the suspension brackets. The blade assembly is located between the two types of suspension brackets along the axial direction. The moving blade is fixed to the rotating part, and the stationary blade is fixed to the housing.

[0044] In this design, front and rear suspension brackets are installed to fix both ends of the intermediate shaft to the housing, which can improve the reliability and stability of the installation of the rotating part and moving blades of the intermediate shaft.

[0045] Preferably, the leaf height of a single type of leaf is H, the average chord length is L, and H / L ≥ 2.1;

[0046] And / or, the axial dimension of the axial flow fan is less than or equal to 300 mm.

[0047] In this solution, by setting it like this, the axial dimension of the blade can be made small enough, so that the axial dimension of the axial-flow fan is small enough for easy installation. If the axial-flow fan is applied to a range hood and the axis of the axial-flow fan is set vertically, the space occupied by the axial-flow fan in the vertical direction can be reduced; if the axial-flow fan is installed on the ceiling, enough space can be available for installing the axial-flow fan without removing the ceiling keel, thus saving the installation cost.

[0048] Preferably, for a single type of the blade, the blade height is H and the average chord length is L, and H / L≥3.4.

[0049] Preferably, the tip chord length and the root chord length of the moving blade are L1 and L2 respectively, and L1 / L2≥1.1.

[0050] In this solution, by setting L1 / L2 large enough, the bending degree of the tip of the moving blade is reduced, the fluid flows more smoothly here, and thus the noise is reduced.

[0051] Preferably, L1 / L2≥1.4.

[0052] Preferably, the axial coordinates of the tip trailing edge and the root trailing edge of the moving blade are Z1 and Z2 respectively, Z1<Z2, and the axial coordinate increases in the direction from the inlet to the outlet of the axial-flow fan.

[0053] In this solution, in the same blade assembly, the tip trailing edge of the moving blade is inclined axially away from the stationary blade relative to the root trailing edge, so as to increase the axial distance between the tip trailing edge of the moving blade and the leading edge of the stationary blade, and thus reduce the noise generated when the fluid flows from the tip trailing edge of the moving blade to the leading edge of the stationary blade.

[0054] Preferably, the root chord length of the moving blade is L2, and |Z1-Z2|≤5%L2.

[0055] Preferably, for the same type of blade in a single-stage blade assembly, the average relative flow velocity at the outlet and the average relative flow velocity at the inlet are V1 and V2 respectively, and V1 / V2≥0.75.

[0056] In this solution, by setting it like this, the pressure difference and the amplitude of pressure pulsation on the blade surface can be reduced, and the load on the blade can be reduced.

[0057] Preferably, V1 / V2≥0.82.

[0058] Preferably, in at least one type of blade, the phases of the same type of blades at different stages around the axis are different.

[0059] In this solution, by setting the phases of the stationary blades at different stages to be the same and the phases of the moving blades at different stages to be different, during the process that the fluid flows from the upstream blades to the downstream blades and pats the downstream blades, the dynamic-static interference abnormal noise generated between the moving blades and the stationary blades in each blade assembly can be scattered, and obvious blade-frequency abnormal noise no longer appears.

[0060] Preferably, in the same type of blades at each level, the number of blades in a single row is ZR, and the phase difference between adjacent blades of the same type around the axial direction is 360° / (ZR*K).

[0061] In this solution, the configuration is convenient for processing and better avoids or reduces blade frequency noise.

[0062] A range hood includes an axial flow fan as described in any of the above technical solutions, wherein the inlet of the axial flow fan is the inlet of the range hood or is connected to the inlet of the range hood, and the outlet of the axial flow fan is the outlet of the range hood or is connected to the outlet of the range hood, drs_1≥drs_2≥……≥drs_K, dsr_1≥dsr_2≥……≥dsr_(K-1).

[0063] In this solution, an axial flow fan is used in the range hood. The inlet of the axial flow fan is closer to the user than the outlet. By setting drs_1≥drs_2≥……≥drs_K and dsr_1≥dsr_2≥……≥dsr_(K-1), the noise at the inlet of the axial flow fan can be reduced, thereby reducing the noise transmitted to the user.

[0064] Preferably, the inner diameter of the outlet of the axial flow fan is between 160mm and 220mm.

[0065] In this design, the inner diameter of the axial flow fan outlet is made close to the inner diameter of the general-purpose flue pipe, which facilitates the connection between the outlet of the axial flow fan and the general-purpose flue pipe.

[0066] Preferably, the inner diameter of the outlet of the axial flow fan is between 175mm and 185mm.

[0067] An air supply device includes an axial flow fan as described in any of the above technical solutions, wherein the inlet of the axial flow fan is the inlet of the air supply device or is connected to the inlet of the air supply device, and the outlet of the axial flow fan is the outlet of the air supply device or is connected to the outlet of the air supply device, drs_1≤drs_2≤……≤drs_K, dsr_1≤dsr_2≤……≤dsr_(K-1).

[0068] In this scheme, the air supply equipment is used for air supply. The outlet of the axial flow fan is closer to the user than the inlet. The settings drs_1≤drs_2≤……≤drs_K and dsr_1≤dsr_2≤……≤dsr_(K-1) are used to reduce the noise at the outlet of the axial flow fan, thereby reducing the noise transmitted to the user.

[0069] The positive and progressive effects of this invention are as follows:

[0070] Using K-class axial flow fans to achieve the pressure rise and flow rate required by axial flow fans ensures sufficient aerodynamic performance while maintaining a low noise level. Furthermore, designing K-class blade assemblies allows each row of blades to reflect and absorb noise, further reducing noise levels. Applying K-class axial flow fans to range hoods results in good aerodynamic performance and low noise.

[0071] As i and j increase, drs_i and dsr_j are set to monotonically change in the same direction. Furthermore, when K = 2, drs_1 ≠ drs_K; when K > 2, drs_1 ≠ drs_K and / or dsr_1 ≠ dsr_K-1. This ensures that drs_i and dsr_j are larger closer to the inlet or outlet of the axial flow fan, resulting in lower noise at the inlet or outlet. Additionally, this configuration can reduce noise at the inlet or outlet of the axial flow fan while avoiding an increase in the axial dimension of the fan; or, it can reduce the axial dimension of the axial flow fan while avoiding an increase in noise at the inlet or outlet.

[0072] In range hoods, the inlet of the axial flow fan is closer to the user than the outlet. By setting the inlet closer to the inlet of the axial flow fan, the values ​​of drs_i and dsr_j are larger, resulting in lower noise at the inlet of the axial flow fan and reducing the noise transmitted to the user.

[0073] In air supply equipment, the outlet of the axial flow fan is closer to the user than the inlet. By setting the outlet closer to the axial flow fan, the larger drs_i and dsr_j are, the lower the noise at the outlet of the axial flow fan, thus reducing the noise transmitted to the user. Attached Figure Description

[0074] Figure 1 This is a schematic diagram of an existing range hood;

[0075] Figure 2 A schematic diagram of an existing axial flow fan.

[0076] Figure 3 This is a schematic diagram of an existing range hood;

[0077] Figure 4 This is a schematic diagram of an existing range hood;

[0078] Figure 5 This is a schematic diagram of an existing range hood;

[0079] Figure 6 This is a schematic diagram of the range hood in Example 1;

[0080] Figure 7 This is a schematic diagram of the axial flow fan in Example 1;

[0081] Figure 8 This is a meridional view of the axial flow fan in Example 1;

[0082] Figure 9 This is a schematic diagram of the blades, intermediate shaft, and rear suspension bracket in Example 1;

[0083] Figure 10 This is a schematic diagram of the blades, intermediate shaft, and rear suspension bracket in Example 1;

[0084] Figure 11 This is a schematic diagram of the intermediate shaft and rear suspension bracket in Example 1;

[0085] Figure 12 This is a cross-sectional view of the intermediate shaft and rear suspension bracket in Example 1;

[0086] Figure 13 This is a schematic diagram of the moving blade on the intermediate shaft in Example 1;

[0087] Figure 14 This is a schematic diagram of the moving blade in Example 1;

[0088] Figure 15 This is a schematic diagram of the moving blade in Example 1;

[0089] Figure 16 This is a schematic diagram of the blade phase in Example 1;

[0090] Figure 17 This is a schematic diagram of the blade phase in Example 2.

[0091] Explanation of reference numerals in the attached figures:

[0092] Figures 1-5 The marker in:

[0093] Axial flow fan 1000', casing 1', moving blade 21', stationary blade 22', intermediate shaft 3', stationary part 31', rotating part 32', rear suspension bracket 42';

[0094] 2000' smoke hood, 4000' air intake duct, 5000' centrifugal fan, 10000' range hood;

[0095] Wall 20000';

[0096] Figures 6-17 The marker in:

[0097] 1000 axial flow fan;

[0098] Housing 1, front housing 11, rear housing 12;

[0099] Blade assembly 2;

[0100] 21 moving leaves, 211 primary moving leaves, 212 secondary moving leaves, 213 tertiary moving leaves;

[0101] Static Leaf 22, Level 1 Static Leaf 221, Level 2 Static Leaf 222, Level 3 Static Leaf 223;

[0102] Leading edge 231, trailing edge 232, leaf tip 241, leaf base 242;

[0103] Intermediate shaft 3;

[0104] Stationary section 31, fairing 311, exhaust tail cone 312;

[0105] Rotating part 32, first-stage rotating part 321, second-stage rotating part 322, third-stage rotating part 323, rotating shaft 34;

[0106] Suspension bracket 4, front suspension bracket 41, rear suspension bracket 42;

[0107] Blade channel 5;

[0108] Smoke hood 2000, outer casing 3000;

[0109] Range hood 10000. Detailed Implementation

[0110] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments that do not specify specific conditions were performed according to conventional methods and conditions, or as selected according to the product instructions.

[0111] Example 1

[0112] This embodiment provides a range hood 10000. Figures 6-16 This is a schematic diagram of this embodiment.

[0113] like Figure 6 The range hood 10000 includes an axial flow fan 1000, a smoke collection hood 2000, and a housing 3000. The structure of the axial flow fan 1000 is as follows: Figures 7-16 The bottom of the smoke hood 2000 has an opening to serve as the inlet of the range hood 10000. The outer casing 3000 and the smoke hood 2000 are fixed together. The axial flow fan 1000 is installed inside the outer casing 3000. The inlet of the axial flow fan 1000 is connected to the inlet of the range hood 10000. The outlet of the axial flow fan 1000 forms the outlet of the range hood 10000.

[0114] In this embodiment, the length, width, and height directions of the range hood 10000 are X, Y, and Z, respectively. These three directions are perpendicular to each other, with the Z direction parallel to the vertical direction. In the accompanying drawings of this invention, the Z direction is parallel to the axial direction of the axial flow fan 1000. For ease of description below, the Z direction is defined as unidirectional. The arrow direction of the Z direction corresponds to the direction from the inlet to the outlet of the axial flow fan 1000, and also corresponds to the direction in which the fluid flows from upstream to downstream in the axial flow fan 1000.

[0115] In a preferred embodiment, the outlet inner diameter of the axial flow fan 1000 is between 160mm and 220mm, making it close to the inner diameter of commonly used general-purpose flue pipes, thus facilitating the connection between the outlet of the axial flow fan 1000 and the general-purpose flue pipe. Furthermore, setting the outlet inner diameter of the axial flow fan 1000 to between 175mm and 185mm makes it close to the inner diameter of most general-purpose flue pipes, further improving the convenience of connecting the axial flow fan 1000 and the flue pipe.

[0116] In other embodiments, the shape and installation direction of the range hood 10000 can be adjusted according to usage requirements. The inlet of the axial fan 1000 can be used as the inlet of the range hood 10000, for example, when the smoke collection hood 2000 is not installed; or, the inlet of the axial fan 1000 and the inlet of the range hood 10000 can be connected. The outlet of the axial fan 1000 can be used as the outlet of the range hood 10000; or, the outlet of the axial fan 1000 and the outlet of the range hood 10000 can be connected by a pipe.

[0117] like Figures 7-10 The axial flow fan 1000 includes a K-stage blade assembly 2, where K=3. The single-stage blade assembly 2 includes a row of moving blades 21 and a row of stationary blades 22. Along the Z-direction, the first-stage moving blade 211, the first-stage stationary blade 221, the second-stage moving blade 212, the second-stage stationary blade 222, the third-stage moving blade 213, and the third-stage stationary blade 223 are arranged at intervals.

[0118] In this embodiment, by using a K-class axial flow fan 1000 to achieve the pressure rise and flow rate, the sound power can be reduced to 1 / K of the original. This allows the axial flow fan 1000 to maintain a low noise level while ensuring sufficient aerodynamic performance. Furthermore, the K-class blade assembly 2 is designed so that each row of blades blocks noise transmission, providing reflection and absorption, further reducing noise. Applying the K-class axial flow fan 10000 to the range hood 10000 results in good aerodynamic performance and low noise.

[0119] In other embodiments, the axial fan 1000 may be provided with two, three or more stages of blade assembly 2. By increasing the number of stages of blade assembly 2, the aerodynamic performance of the range hood 10000 can be improved, and the radial dimension of the axial fan 1000 can be made smaller, so as to reduce the space occupied by the axial fan 1000 in the X and Y directions in the kitchen.

[0120] The leading edge 231, trailing edge 232, leaf tip 241, and leaf base 242 are well-known concepts; please refer to [reference needed]. Figures 14-15 The annotations in the text.

[0121] like Figure 8 The average distance between the trailing edge of the i-th stage moving blade 21 and the leading edge of the i-th stage stationary blade 22 is drs_i, where i = 1, 2, ..., K. As i increases, drs_i decreases, meaning that the closer to the inlet of the axial flow fan 1000, the larger drs_i becomes. K = 3, and the corresponding drs_i are drs_1, drs_2, and drs_3, respectively. In this embodiment, drs_1 > drs_2 > drs_3. The average distance can be understood as the average distance at different blade heights. Figure 8 The spacing at a certain blade height is simplified and labeled as the average spacing.

[0122] like Figure 8 The average distance along the Z-direction between the trailing edge of the j-th stage stationary blade 22 and the leading edge of the (j+1)-th stage moving blade 21 is dsr_j, where j = 1, 2, ..., K-1. As j increases, dsr_j decreases, meaning that the closer to the inlet of the axial flow fan 1000, the larger dsr_j becomes. With K = 3, dsr_j are dsr_1 and dsr_2, respectively, and in this embodiment, dsr_1 > dsr_2. In other embodiments, if two-stage blade assemblies 2 are provided, corresponding to one dsr_j, i.e., dsr_1, it can be considered that dsr_j decreases or increases with the number of stages.

[0123] In a range hood 10000, the inlet is generally closer to the user than the outlet. The closer the axial flow fan 1000 is to the inlet, the greater the noise impact on the user. A larger drs_i indicates more uniform mixing of the fluid as it flows from the trailing edge of the moving blade 21 to the trailing edge of the stationary blade 22, thus improving blade frequency noise and reducing fluid flow noise. In a range hood 10000, the closer the drs_i and dsr_j are to the inlet, the larger they are. On one hand, the more uniform the airflow is mixed at the blades closer to the inlet, the lower the noise generated by the airflow itself, and the less noise is transmitted to the user. On the other hand, although a smaller drs_i and dsr_j are closer to the outlet, resulting in greater noise at the downstream blades than at the upstream blades, the closer to the outlet, the greater the impact on the user. The farther away the source of noise is, the less impact it has on the user. Furthermore, the closer the source is to the outlet of the axial flow fan 1000, the greater the noise generated by the airflow. When the noise reaches the inlet of the axial flow fan 1000, it needs to pass through more rows of blades for shielding. This causes the noise generated at the downstream blades to gradually weaken as it travels upstream, thereby reducing the noise transmitted to the user. Combining these two aspects, the upstream part of the axial flow fan 1000, especially at the inlet, has less noise, thus reducing the noise transmitted from the range hood 10000 to the user.

[0124] If the noise level at the inlet of the axial flow fan 1000 is kept consistent, compared to a scheme where all drs_i and dsr_j are the same, this embodiment, by setting drs_i and dsr_j to be larger the closer they are to the inlet of the axial flow fan 1000, facilitates a reduction in the axial dimension of the axial flow fan 1000, resulting in a more compact structure. If the axial dimension of the axial flow fan 1000 is kept constant, compared to a scheme where all drs_i and dsr_j are the same, this embodiment, by setting drs_i and dsr_j to be larger the closer they are to the inlet of the axial flow fan 1000, can significantly reduce the noise at the inlet of the axial flow fan 1000. In the range hood 10000, the inlet of the range hood 10000 is generally closer to the user than the outlet. This makes the upstream blade assembly 2 of the axial flow fan 1000 closer to the user. By setting drs_i and dsr_j to decrease, the noise transmitted from the axial flow fan 1000 to the user can be reduced. At the same time, the compact structure of the axial flow fan 10000 can also be maintained. Thus, the range hood 10000 can achieve both compact structure and low noise.

[0125] In other embodiments, it can be set that as i increases, drs_i and dsr_j change monotonically in the same direction; when K = 2, drs_1 ≠ drs_K; when K > 2, drs_1 ≠ drs_K and / or dsr_1 ≠ dsr_K-1. This can reduce the noise at the inlet or outlet of the axial flow fan 1000, or it can balance the axial dimensions and noise reduction performance of the axial flow fan 1000. For example, drs_1 ≥ drs_2 …… ≥ drs_K, and dsr_1 ≥ dsr_2 …… ≥ drs_K-1; or drs_1 ≤ drs_2 …… ≤ drs_K, and dsr_1 ≤ dsr_2 …… ≤ drs_K-1, can all be considered as drs_i and dsr_j changing monotonically in the same direction.

[0126] In other embodiments, the axial flow fan 1000 of this embodiment or other embodiments can be applied to other scenarios besides the range hood 10000.

[0127] In other embodiments, when the inlet of the axial flow fan 1000 is closer to the user than the outlet, drs_1≥drs_2≥……≥drs_K, dsr_1≥dsr_2≥……≥dsr_(K-1) can be set. When K>2, drs_1≠drs_K and / or dsr_1≠dsr_K-1, which can reduce the noise at the inlet of the axial flow fan 1000, thereby reducing the noise transmitted to the user, or can take into account both the axial dimension and noise reduction performance of the axial flow fan 1000. Furthermore, setting drs_1>drs_2>……>drs_K, dsr_1>dsr_2>……>dsr_(K-1) is even more effective.

[0128] In other embodiments, when the outlet of the axial flow fan 1000 is closer to the user than the inlet, such as in air supply equipment like air conditioners or blowing devices, drs_1≤drs_2≤……≤drs_K, dsr_1≤dsr_2≤……≤dsr_(K-1) can be set. When K=2, drs_1≠drs_K; when K>2, drs_1≠drs_K and / or dsr_1≠dsr_K-1, making the noise at the outlet of the axial flow fan 1000 smaller, thereby reducing the noise transmitted to the user. Furthermore, setting drs_1<drs_2<……<drs_K, dsr_1<dsr_2<……<dsr_(K-1) is even better.

[0129] In other embodiments, the primary stationary or moving blade may have only one row of blades; or, multiple rows of leaflets connected in series may form a single-stage moving or stationary blade. In this case, for a primary blade, the leading edge of the first row of leaflets is considered the leading edge of the blade at that stage, and the trailing edge of the last row of leaflets is considered the trailing edge of the blade at that stage. Leaflets can be understood as blades.

[0130] In a preferred embodiment, by setting dsr_j > drs_i, j = i, that is, the axial spacing between the j-stage stationary blade 22 and the j+1-stage moving blade 21 is greater than the axial spacing between the j-stage moving blade 21 and the j-stage stationary blade 22; and / or, by setting dsr_j > drs_(i+1), j = i, that is, the axial spacing between the j-stage stationary blade 22 and the j+1-stage moving blade 21 is greater than the axial spacing between the j+1-stage moving blade 21 and the j+1-stage stationary blade 22; the axial spacing between the j-stage stationary blade and the j+1-stage moving blade can be increased, so that the fluid is mixed more evenly when flowing from the front stage stationary blade to the leading edge of the rear stage moving blade, thereby reducing the overall noise of the axial flow fan.

[0131] In a preferred embodiment, the moving blades 21 at each stage have the same shape and size, and the stationary blades 22 at each stage have the same shape and size. With this configuration, regardless of the number of stages in the blade assembly 2, only two sets of molds are needed for the moving blades 21 and the stationary blades 22. The aerodynamic performance of the axial flow fan 1000 can be changed by increasing or decreasing the number of stages in the blade assembly 2, resulting in good versatility and low processing costs.

[0132] In a preferred embodiment, the number of blades in a single row can be greater than or equal to 19 to make the outflow more uniform across each row and further reduce noise. Setting the number of blades in a single row to greater than or equal to 39 yields even better results.

[0133] The density of blades is a well-known concept, which can be understood as the chord length of the blade divided by the distance between two adjacent blades in a single row. In a preferred embodiment, the maximum density of a single row of blades can be set to be less than or equal to 1.8, so that the blades in the single row are arranged sparsely enough to facilitate demolding when the blades are cast. Setting the maximum density of a single row of blades to be less than or equal to 1.4 yields even better results.

[0134] In a preferred embodiment, the blades are made of a softer material, such as plastic or aluminum alloy, which reduces wear on the mold during the casting process. The lighter weight of the plastic or aluminum alloy material reduces the weight of the axial flow fan 1000.

[0135] like Figure 7 The housing of the axial flow fan 1000 includes a front housing 11 and a rear housing 12, and the flanges of the front housing 11 and the rear housing 12 are fixedly connected.

[0136] like Figure 8 The intermediate shaft 3 of the axial flow fan 1000 is installed inside the housing 1. A flow channel is formed between the inner surface of the housing 1 and the outer surface of the intermediate shaft 3. The blades are installed in this flow channel. The part of the flow channel along the Z direction from the leading edge of the first-stage moving blade 211 to the trailing edge of the third-stage stationary blade 223 is the blade flow channel 5. Figure 8 The Z_YPLD diagram illustrates the range of the blade flow channel 5 along the Z direction. In a preferred embodiment, the inner diameter and outer diameter are the same throughout the blade flow channel 5, resulting in a simple structure and convenient manufacturing; it also ensures the stability of the blade flow channel 5 and reduces noise. The inner diameter is d1, and the outer diameter is d2; see [reference needed]. Figure 8 The annotation.

[0137] In a preferred embodiment, the hub ratio of the blade flow channel 5 is d1 / d2, ranging from 0.4 to 0.8, which makes the hub ratio large enough, thereby making the blade height small enough, so that the blade tip and root curvature can be set to be small, the fluid flow is smooth, and the noise is low; making the hub ratio small enough makes the blade height large enough, thereby making the channel for the fluid to flow through the blade large enough, and the flow rate large enough.

[0138] In a preferred embodiment, such as Figure 8The intermediate shaft 3 includes a stationary part 31, a rotating part 32, and another stationary part 31 arranged sequentially along the Z-direction. The axial flow fan 1000 also includes two types of suspension brackets 4: a front suspension bracket 41 upstream and a rear suspension bracket 42 downstream. Each of the two stationary parts 31 is fixed to the housing 1 by a suspension bracket 4, so that they are stationary relative to the housing 1. The stationary blade 22 is fixed to the housing 1 with a gap between it and the intermediate shaft 3. The moving blade 21 is fixed to the rotating part 32 with a gap between it and the housing 1. The rotating part 32 is rotatably arranged relative to the two stationary parts 31 to drive the moving blade 21 to rotate and do work on the fluid. The front suspension bracket 41 and the rear suspension bracket 42 are provided to fix both ends of the intermediate shaft 3 to the housing 1, which can improve the reliability and stress stability of the installation of the rotating part 32 and the moving blade 21 of the intermediate shaft 3. It can be understood that the axis of the axial flow fan 1000 is the axis of the rotating part 32, and the axial direction is the extension direction of the axis of the rotating part 32.

[0139] In this embodiment, a suspension bracket 4, also known as a set, is formed by multiple support plates evenly spaced around the Z direction; the two stationary parts 31 are as follows: the upstream one is a fairing 311 with a hemispherical outer surface to reduce fluid flow resistance, and the downstream one is an exhaust tail cone 312 with a conical tail to reduce fluid wake and noise.

[0140] like Figures 11-12 The rotating part 32 includes a rotating shaft 34 and three rotating parts arranged sequentially along the Z-direction: a first-stage rotating part 321, a second-stage rotating part 322, and a third-stage rotating part 323. An N-stage moving blade 21 is mounted on the N-stage rotating part 32. The rotating shaft 34 is located within the three rotating parts 32, with its two ends rotatably mounted relative to the two stationary parts 31. For example, rotation can be achieved through bearing connections. The rotating shaft 34 and the three rotating parts 32 are all fixedly connected. Driving the rotating shaft 34 to rotate will drive the three rotating parts 32 and the moving blade 21 to rotate. Figure 12 The adjacent suspension brackets 4 and the rotating part 32, or the two adjacent rotating parts 32, have a small gap along the Z direction. Within the design allowable range, the inner diameter of the blade flow channel 5 can be considered constant.

[0141] The blade height H, chord length, tip chord length L1, root chord length L2, and average chord length L are well-known concepts. Blade height H can be understood as the dimension of the blade along a 1000° radial direction of the axial flow fan. Chord length can be understood as the length of the tangent from the leading edge to the trailing edge of the blade. Tip chord length L1 can be understood as the chord length at the blade tip. Root chord length L2 can be understood as the chord length at the blade root. Average chord length L can be understood as the average chord length of the blade at different blade heights. For L1 and L2, please refer to [reference needed]. Figure 14 The annotation.

[0142] In a preferred embodiment, H / L ≥ 2.1, which can make the axial dimension of the blade small enough, so that the axial dimension of the axial flow fan 1000 is small enough for easy installation. Applying the axial flow fan 1000 to the range hood 10000 can reduce the space occupied by the axial flow fan 1000 in the Z direction; if the axial flow fan 1000 is installed on the ceiling, there is enough space to install the axial flow fan 1000 without removing the ceiling keel, so as to save the installation cost. When H / L ≥ 3.4 is set, the axial dimension of the axial flow fan 1000 can be further reduced.

[0143] In a preferred embodiment, the axial dimension of the axial flow fan 1000 can be set to be less than or equal to 300 mm, so that the axial dimension is small enough for easy installation.

[0144] In a preferred embodiment, for the moving blade 21, L1 / L2 ≥ 1.1. Setting L1 / L2 large enough makes the tip of the moving blade 21 less curved and the fluid flow more smoothly here, thus reducing noise. The effect is better when L1 / L2 ≥ 1.4.

[0145] Such as Figure 14 、 Figure 15 , along the Z direction, that is, from the inlet to the outlet direction of the axial flow fan 1000, the axial coordinate increases. The axial coordinate of the tip trailing edge of the moving blade 21 is Z1, and the axial coordinate of the root trailing edge is Z2. In a preferred embodiment, for the moving blade 21, Z1 < Z2 is set, so that in the same-stage blade assembly 2, the tip trailing edge of the moving blade 21 is inclined axially away from the stator blade 22 relative to the root trailing edge, so as to increase the axial distance between the tip trailing edge of the moving blade 21 and the leading edge of the stator blade 22, thus reducing the noise generated when the fluid flows from the tip trailing edge of the moving blade 21 to the leading edge of the stator blade 22. Further, for the moving blade 21, |Z1 - Z2| ≤ 5%L2 is set to avoid the value of |Z1 - Z2| in the moving blade 21 being too large, resulting in a complex blade shape.

[0146] In a preferred embodiment, the ratio V1 / V2 of the average relative flow velocity V1 at the outlet of the blade to the average relative flow velocity V2 at the inlet is V1 / V2 ≥ 0.75, so that the flow velocity difference between the suction surface and the pressure surface of the blade is small, so as to reduce the pressure difference and the pressure pulsation amplitude on the blade surface and reduce the load of the blade. The effect is better when V1 / V2 ≥ 0.82. V1 / V2 can also be called the Dehaller number and can be obtained through simulation or experiment.

[0147] The phase of the blade around the axis can be understood as the position of the blade in the circumferential direction of the axial flow fan 1000 and can be represented by the corresponding circumferential angle. Such as Figure 16The phases of the moving blades 21 at each stage are different around the Z-axis. Specifically, the distance difference between the first-stage moving blade 211 and the second-stage moving blade 212 in the circumferential direction is A1, and the corresponding phase difference is ∠1. The distance difference between the second-stage moving blade 212 and the third-stage moving blade 213 in the circumferential direction is A2, and the corresponding phase difference is ∠2. As the fluid flows from the upstream blades to the downstream blades, it will slap against the downstream blades. By setting different phase differences for each stage of the moving blades 21, the dynamic-static interference noise emitted between the moving blades 21 and the stationary blades 22 in each stage of the blade assembly 2 can be dispersed, and no obvious blade frequency noise will appear.

[0148] Example 2

[0149] This embodiment provides an axial flow fan 1000. Figure 17 This is a schematic diagram of this embodiment. The main difference between this embodiment and Embodiment 1 is the phase setting of the blades. Other structures in this embodiment can be referred to in Embodiment 1.

[0150] like Figure 17 The phases of the stationary blades 22 at each stage are the same, while the phases of the moving blades 21 at each stage are different.

[0151] In a single row of moving blades 21, the circumferential distance between two adjacent moving blades 21 is A0, and the corresponding phase difference is ∠0, where ∠0 = 360° / ZR, and ZR is the number of moving blades 21 in a single row.

[0152] In a preferred embodiment, ∠1=∠2=∠0 / K=360° / (ZR*K).

[0153] In other embodiments, the phases of the stationary blades 22 at each stage and / or the phases of the moving blades 21 at each stage can be set to be different, so that the abnormal noise caused by the interference between the moving blades 21 and the stationary blades 22 in each stage blade assembly 2 can be dispersed, and there will be no obvious blade frequency noise, thereby reducing the noise of the axial flow fan 1000. When the phases of the stationary blades 22 at each stage are set to be different, the number of stationary blades 22 in a single row can be set to ZR, and the phase difference between two adjacent stages of stationary blades 22 around the axial direction can be 360° / (ZR*K).

[0154] Overall, the axial flow fan 1000 provided by this invention has the following advantages:

[0155] 1. The axial flow fan 1000 is small in size and occupies little space when used in the range hood 10000. Its layout in the air duct is flexible and free, which facilitates noise reduction design. Because the axial flow fan 1000 has the characteristic of straight airflow, it is very easy to stack multiple stages without bringing high complexity to the structure. When applied to the range hood 10000, multi-stage blade assembly 2 is set to distribute the pressure rise, thereby achieving a significant reduction in noise.

[0156] 2. The blades of the axial flow fan 1000 are usually twisted, which causes inconvenience in processing. This invention improves the problem of high processing cost of the axial flow fan 1000 through the following aspects:

[0157] 2-1. The moving blades 21 and stationary blades 22 are the same for each stage. The blade mold of the whole product only needs two sets of moving blades 21 and stationary blades 22. The aerodynamic performance of the axial flow fan 1000 can be changed by increasing or decreasing the number of stages of the blade assembly 2, so that the axial flow fan 1000 can be applied to products with different performance specifications and reduce processing costs.

[0158] 2-2. Use softer materials such as plastic or aluminum alloy to make the blades, thereby reducing mold wear;

[0159] 2-3. By setting the blade consistency, it is easy for the blade to rotate bidirectionally for demolding;

[0160] 2-4. The moving blades 21 of each stage have the same shape and size, and the stationary blades 22 of each stage have the same shape and size, so as to reduce the manufacturing cost of the axial flow fan 1000 and make it easy to increase or decrease the number of blade assembly stages to adjust the performance of the axial flow fan 1000.

[0161] 2-5. The multi-stage blade assembly 2 is set up to achieve the target pressure rise, so the load on each stage blade assembly 2 is relatively light and the degree of blade twist is relatively low, which also reduces the processing difficulty.

[0162] 3. In the axial flow fan 1000 with multi-stage blade assemblies 2 in the range hood 10000, the aerodynamic noise of the first stage blade assembly 2 is directly transmitted to the inlet of the range hood 10000. However, the aerodynamic noise of subsequent stages of blade assemblies 2 is blocked by several rows of blades before reaching the inlet of the range hood 10000, and the noise transmitted from the later stages is blocked by more blades. Therefore, the earlier stages contribute more to the noise perceived by the user. Therefore, in this invention, both drs_i and dsr_j decrease as the number of stages increases, thereby weakening the pulsating noise generated at the upstream blade assembly 2 and reducing the overall noise perceived by the user.

[0163] While specific embodiments of the present invention have been described above, those skilled in the art should understand that these are merely illustrative examples, and the scope of protection of the present invention is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of the present invention, but all such changes and modifications fall within the scope of protection of the present invention.

Claims

1. An axial flow fan, characterized in that, It includes a K-level blade assembly, which includes two types of blades: moving blades and stationary blades, where K is an integer and K≥2; Along the axial direction of the axial flow fan and from the inlet of the axial flow fan to the outlet of the axial flow fan: the first stage blade assembly, the second stage blade assembly, ..., the Kth stage blade assembly are arranged sequentially, and in the same stage blade assembly, the moving blade is arranged upstream of the stationary blade; The average axial distance between the trailing edge of the i-th stage moving blade and the leading edge of the i-th stage stationary blade is drs_i, i=1, 2, ..., K; the average axial distance between the trailing edge of the j-th stage stationary blade and the leading edge of the (j+1)-th stage moving blade is dsr_j, j=1, 2, ..., K-1. As i increases, and as j increases, drs_i and dsr_j change monotonically in the same direction to reduce the noise at the inlet or outlet of the axial flow fan. When K = 2, drs_1 ≠ drs_K; When K > 2, drs_1 ≠ drs_K and / or dsr_1 ≠ dsr_K-1.

2. The axial flow fan as described in claim 1, characterized in that, As i increases, as j increases, drs_i and dsr_j increase or decrease monotonically in the same direction. And / or, dsr_j > drs_i, j = i; And / or, dsr_j > drs_(i+1), j = i.

3. The axial flow fan as described in claim 1, characterized in that, All moving blades at each level have the same shape and size, and all stationary blades at each level have the same shape and size.

4. The axial flow fan as described in claim 1, characterized in that, In a single-stage blade assembly, the number of blades of the same type is greater than or equal to 19; And / or, in a single-stage blade assembly, the maximum consistency of the same type of blade is less than or equal to 1.8; And / or, the blade is made of plastic or aluminum alloy.

5. The axial flow fan as described in claim 1, characterized in that, In a single-stage blade assembly, the number of blades of the same type is greater than or equal to 39; And / or, in a single-stage blade assembly, the maximum consistency of the same type of blade is less than or equal to 1.

4.

6. The axial flow fan as described in claim 1, characterized in that, The axial flow fan also includes a housing and an intermediate shaft disposed within the housing. A flow channel is formed between the inner surface of the housing and the outer surface of the intermediate shaft. The blade assembly is disposed within the flow channel. The portion of the flow channel along the axial direction from the leading edge of the first-stage moving blade to the trailing edge of the last-stage stationary blade is the blade flow channel. The inner and outer diameters of the blade flow channel are constant along the axial direction; and / or, the inner diameter of the blade flow channel at the same position along the axial direction is d1, the outer diameter is d2, and the range of d1 / d2 is between 0.4 and 0.

8.

7. The axial flow fan as described in claim 6, characterized in that, The range of d1 / d2 is between 0.6 and 0.

7.

8. The axial flow fan as described in claim 1, characterized in that, The axial flow fan also includes a housing, two types of suspension brackets, and an intermediate shaft disposed within the housing. The intermediate shaft includes two stationary parts located at both ends along the axial direction and a rotating part located between the two stationary parts and rotating about the axial direction. The two stationary parts are respectively fixed to the housing by one of the suspension brackets. The blade assembly is located between the two types of suspension brackets along the axial direction. The moving blade is fixed to the rotating part, and the stationary blade is fixed to the housing.

9. The axial flow fan as described in claim 1, characterized in that, The leaf height of a single type of leaf is H, the average chord length is L, and H / L ≥ 2.1; And / or, the axial dimension of the axial flow fan is less than or equal to 300 mm.

10. The axial flow fan as described in claim 1, characterized in that, The leaf height of the single-species leaf is H, the average chord length is L, and H / L ≥ 3.

4.

11. The axial flow fan as described in claim 1, characterized in that, The tip chord length and root chord length of the moving blade are L1 and L2 respectively, and L1 / L2 ≥ 1.

1.

12. The axial flow fan as described in claim 11, characterized in that, L1 / L2 ≥ 1.

4.

13. The axial flow fan as described in claim 1, characterized in that, The axial coordinates of the tip trailing edge and root trailing edge of the moving blade are Z1 and Z2 respectively, Z1 < Z2, and the axial coordinate increases in the direction from the inlet to the outlet of the axial flow fan.

14. The axial flow fan as described in claim 13, characterized in that, The root chord length of the moving blade is L2, and |Z1 - Z2| ≤ 5%L2.

15. The axial flow fan as described in claim 1, characterized in that, For the same type of blade in the single-stage blade assembly, the average relative flow velocity at the outlet and the average relative flow velocity at the inlet are V1 and V2 respectively, and V1 / V2 ≥ 0.

75.

16. The axial flow fan as described in claim 15, characterized in that, V1 / V2 ≥ 0.

82.

17. The axial flow fan as described in claim 1, characterized in that, In at least one type of blade, the phases of the same type of blades at each stage around the axis are different.

18. The axial flow fan as described in claim 17, characterized in that, Among the same type of blades at each stage, the number of blades in a single row is ZR, and the phase difference of the same type of blades in adjacent two stages around the axis is 360° / (ZR*K).

19. A range hood, characterized in that, It includes the axial flow fan according to any one of claims 1-18. The inlet of the axial flow fan is the inlet of the range hood or is connected to the inlet of the range hood, and the outlet of the axial flow fan is the outlet of the range hood or is connected to the outlet of the range hood, drs_1 ≥ drs_2 ≥ …… ≥ drs_K, dsr_1 ≥ dsr_2 ≥ …… ≥ dsr_(K - 1), so as to reduce the noise at the inlet of the axial flow fan.

20. The range hood as described in claim 19, characterized in that, The inner diameter of the outlet of the axial flow fan is between 160 mm and 220 mm.

21. The range hood as described in claim 19, characterized in that, The inner diameter of the outlet of the axial flow fan is between 175 mm and 185 mm.

22. An air supply device, characterized in that, It includes the axial flow fan according to any one of claims 1-18. The inlet of the axial flow fan is the inlet of the air supply device or is connected to the inlet of the air supply device, and the outlet of the axial flow fan is the outlet of the air supply device or is connected to the outlet of the air supply device, drs_1 ≤ drs_2 ≤ …… ≤ drs_K, dsr_1 ≤ dsr_2 ≤ …… ≤ dsr_(K - 1), so as to reduce the noise at the outlet of the axial flow fan.

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