Axial flow fan and range hood comprising same

Abstract

The invention relates to the field of range hoods, and discloses an axial flow fan and a range hood comprising the axial flow fan, the axial flow fan comprises two rows of movable blades including front-row movable blades and rear-row movable blades, the front-row movable blades, the rear-row movable blades and the fixed blades are sequentially arranged in the fluid flowing direction, the number and chord length of the front-row movable blades are smaller than those of the rear-row movable blades, and the chord length of the rear-row movable blades is larger than that of the rear-row movable blades. And the rear row of movable blades share pressure rise, and meanwhile, fluid can flow out more uniformly, so that the noise of fluid flowing can be reduced. Compared with a single-stage axial flow fan, the axial flow fan is provided with the two rows of movable blades, the rotating speed can be smaller under the condition that the same pressure rise needs to be achieved, and therefore noise is smaller; and under the condition of the same noise, larger pressure rise can be realized. Compared with a multi-stage axial flow fan, the two rows of movable blades of the axial flow fan are arranged on the upstream of the fixed blades, and the movable blades and the fixed blades are not alternately arranged, so that the axial flow fan is simple in structure. Therefore, the axial flow fan can give consideration to both power and noise.

Description

Technical Field

[0001] The present invention relates to the field of range hoods, and particularly to an axial flow fan. Background Art

[0002] Forward-inlet multi-wing centrifugal fans (hereinafter referred to as "centrifugal fans") are commonly used in range hoods. The inlet and exhaust paths of the centrifugal fan are perpendicular, and the air flow is forced to turn at a right angle, resulting in an unsmooth air flow path, reducing the energy efficiency of the range hood and increasing the noise. By placing the centrifugal fan above and installing it on the ceiling, the characteristics of perpendicular inlet and exhaust paths can be utilized. However, due to the centrifugal fan having a volute, the structural size is large and the installation is restricted.

[0003] When an axial flow fan is used in a range hood, the axial flow fan does not have a volute, and the air flow enters and exits along the axis. Its volume is much smaller than that of a conventional centrifugal fan, and it has a high degree of freedom in the layout of the whole machine air duct. However, the axial flow fan itself has the characteristics of large flow rate and small pressure rise. Under the same conditions, its pressurization ability is not as good as that of a centrifugal fan. Using a multi-stage axial flow fan can increase the pressure rise of the axial flow fan. However, the multi-stage axial flow fan has a structure with alternating multi-stage moving blades and static blades, which makes the structural design more complex and increases the processing and assembly costs.

[0004] In summary, the existing range hoods have poor comprehensive performance and it is difficult to balance the requirements of a compact fan structure, good aerodynamic performance, low noise, and easy installation. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the defect of poor comprehensive performance of range hoods in the prior art, and provide an axial flow fan and a range hood including the same.

[0006] The present invention solves the above technical problem through the following technical solutions:

[0007] An axial flow fan includes two types of blades, moving blades and static blades. There are two rows of moving blades, namely the front-row moving blades and the rear-row moving blades. Along the fluid flow direction, the front-row moving blades, the rear-row moving blades, and the static blades are arranged in sequence. The number and chord length of the front-row moving blades are respectively less and longer than those of the rear-row moving blades.

[0008] In this solution, two rows of moving blades are provided, and the rear-row moving blades can share the pressure rise. On the one hand, the requirements for the manufacturing and load of a single row of moving blades can be reduced; on the other hand, compared with a single-stage axial flow fan, at the same pressure rise, the rotational speed can be smaller, so the noise is smaller, and at the same noise level, a larger pressure rise can be achieved; on the third hand, compared with a multi-stage axial flow fan with alternating moving blades and static blades, both rows of moving blades are arranged upstream of the static blades, and the moving blades and static blades are not arranged alternately, making the axial flow fan structure simple.

[0009] By setting the chord length of the front-row moving blades longer than that of the rear-row moving blades, there is sufficient chord length for the front-row moving blade profile to achieve a larger pressure rise; compared with the case where the chord lengths and numbers of the two rows of moving blades are the same or close, setting the rear-row moving blades shorter also facilitates reducing the axial length of the axial flow fan. Setting the number of rear-row moving blades more than that of the front-row moving blades, while the rear-row moving blades share the pressure rise, it can make the fluid outflow more uniform, thereby reducing the noise of fluid flow; at the same time, setting the chord length of the rear-row moving blades shorter than that of the front-row moving blades can also make the solidity at the front-row moving blades and the solidity at the rear-row moving blades close, improving the stability of the flow.

[0010] In addition, the axial flow fan itself has the advantages of a compact structure and convenient installation, so that the axial flow fan can meet the requirements of large power, low noise, compact structure, and convenient installation.

[0011] Preferably, the number of the stator blades is two rows, namely the front-row stator blades and the rear-row stator blades. Along the fluid flow direction, the front-row moving blades, the rear-row moving blades, the front-row stator blades, and the rear-row stator blades are arranged in sequence. The number and chord length of the front-row stator blades are respectively less and longer than those of the rear-row stator blades.

[0012] In this solution, by setting the chord length of the front-row stator blades longer than that of the rear-row stator blades, there is sufficient chord length for the front-row stator blade profile to achieve a good enough effect of guiding and deflecting the fluid. Setting the number of rear-row stator blades more than that of the front-row stator blades, while the rear-row stator blades continue to guide and deflect the fluid, it can make the fluid outflow more uniform, thereby reducing the noise of fluid flow; at the same time, setting the chord length of the rear-row stator blades shorter than that of the front-row stator blades can also make the solidity at the front-row stator blades and the solidity at the rear-row stator blades close, improving the stability of the flow.

[0013] Preferably, for the two rows of the same type of blades, the ratio of the number of the rear-row blades to the number of the front-row blades is between 2 and 4.

[0014] In this solution, such a setting makes the number of rear-row blades sufficient, so that the fluid outflow has good uniformity and generates little noise; and makes the number of rear-row blades small enough to reduce the difficulty and cost of manufacturing the axial flow fan.

[0015] Preferably, for the two rows of the same type of blades, the number of the rear-row blades is an integer multiple of the number of the front-row blades.

[0016] In this solution, such a setting makes the circumferential distance between the front-row blades and the rear-row blades constant among the same type of blades, improving the circumferential uniformity of the flow field.

[0017] Preferably, for the two rows of the same type of blades, the ratio of the average solidity of the front-row blades to the average solidity of the rear-row blades is between 0.9 and 1.3.

[0018] In this solution, such a setting can make the flow field between the same type of blades and between the front-row blades and the rear-row blades more uniform axially, thereby improving the stability of fluid flow, and further facilitating the improvement of pressure rise performance and the reduction of noise.

[0019] Preferably, in two rows of the same type of blades, the ratio of the average solidity of the front-row blades to that of the rear-row blades is between 1 and 1.2.

[0020] Preferably, in two rows of the same type of blades, the trailing end of the front-row blades is close to the leading end of the rear-row blades in the circumferential direction and / or the axial direction of the axial flow fan.

[0021] In this solution, such a setting facilitates the smooth transition of the fluid from the front-row blades to the rear-row blades and inhibits the separation of the fluid from the surface of the rear-row blades.

[0022] Preferably, the axial spacing between two rows of the same type of blades along the axial direction of the axial flow fan is between -10 mm and 10 mm.

[0023] In this solution, such a setting makes the axial spacing between the two rows of blades small enough to facilitate the smooth transition of the fluid from the front-row blades to the rear-row blades and inhibits the separation of the fluid from the surface of the rear-row blades; and makes the axial spacing between the two rows of blades large enough to facilitate manufacturing.

[0024] Preferably, the axial spacing between two rows of the same type of blades along the axial direction of the axial flow fan is between -5 mm and 5 mm.

[0025] Preferably, in two rows of the same type of blades, the circumferential spacing between the trailing end of the pressure surface of the front-row blades and the leading end of the suction surface of the rear-row blades is between 0 and 10 mm.

[0026] In this solution, the circumferential spacing between the two rows of blades is small enough to facilitate the smooth transition of the fluid from the front-row blades to the rear-row blades and inhibits the separation of the fluid from the surface of the rear-row blades.

[0027] Preferably, in two rows of the same type of blades, the circumferential spacing between the trailing end of the pressure surface of the front-row blades and the leading end of the suction surface of the rear-row blades is between 0 and 5 mm.

[0028] Preferably, the outlet angle of the root of the rear-row moving blade is smaller than the outlet angle of the root of the front-row moving blade.

[0029] In this solution, such a setting enables the rear-row moving blade to do further work on the fluid.

[0030] Preferably, in two rows of the same type of blades, the absolute value of the deflection angle of the front-row blades is greater than the absolute value of the deflection angle of the rear-row blades.

[0031] In this solution, such a setting is adopted that the pressure rise generated by the front-row blades or the guiding and deflecting effect on the fluid is greater than that of the rear-row blades, which can reduce the load on the rear-row blades and also facilitate reducing the complexity of the blade profile of the rear-row blades for easy machining and manufacturing.

[0032] Preferably, the number of the front-row stationary blades is less than or equal to 0.5 times the number of the rear-row moving blades.

[0033] In this solution, it is convenient to reduce the number of the front-row stationary blades to reduce the resistance of the front-row stationary blades to the fluid flow and lower the noise.

[0034] Preferably, the minimum distance between the rear-row moving blades and the stationary blades along the axial direction of the axial-flow fan is 0.5 to 1.5 times the distance between the front end of the front-row moving blades and the rear end of the rear-row moving blades along the axial direction of the axial-flow fan.

[0035] In this solution, such a setting is adopted that on the one hand, the axial distance between the rear end of the rear-row moving blades and the front end of the stationary blades is long enough, so that the fluid can flow out of the rear-row moving blades and be mixed evenly enough before flowing to the stationary blades, reducing the dynamic-static interference noise; on the other hand, the axial distance between the moving blades and the stationary blades is small enough, so that the axial dimension of the axial-flow fan is small enough and the structure is compact.

[0036] Preferably, the minimum distance between the rear-row moving blades and the stationary blades along the axial direction of the axial-flow fan is 0.75 times the distance between the front end of the front-row moving blades and the rear end of the rear-row moving blades along the axial direction of the axial-flow fan.

[0037] Preferably, the axial-flow fan further includes a rotating shaft, a support member, a motor, and a housing. A flow channel is formed between the inner surface of the housing and the outer surfaces of the rotating shaft and the support member. The blades are arranged in the flow channel. The moving blades are fixed on the rotating shaft and form a gap with the inner surface of the housing. The support member is fixed on the housing through the stationary blades. The motor is installed in the support member and is used to drive the rotating shaft to rotate.

[0038] In this solution, the rotating shaft and the motor are supported by the stationary blades, and the structure is simple. In addition, when two rows of stationary blades are provided, multi-point support can be formed, and the support length along the axial direction can be increased, thereby improving the stability of the support.

[0039] An oil fume extractor includes the axial-flow fan according to any one of the above technical solutions. The inlet of the axial-flow fan is the air inlet of the oil fume extractor or is communicated with the air inlet of the oil fume extractor, and the outlet of the axial-flow fan is the air outlet of the oil fume extractor or is communicated with the air outlet of the oil fume extractor.

[0040] In this solution, applying the axial-flow fan of the present invention to the oil fume extractor can meet the requirements of high power, low noise, compact structure, convenient installation, etc., and improve the comprehensive performance of the oil fume extractor.

[0041] The positive and progressive effects of the present invention are as follows:

[0042] By arranging two rows of moving blades, the rear row of moving blades can share the pressure rise. Firstly, the requirements for the manufacture, load, etc. of a single row of moving blades can be reduced; secondly, compared with a single-stage axial-flow fan, at the same pressure rise, the rotational speed can be smaller, resulting in less noise, and at the same noise level, a greater pressure rise can be achieved; thirdly, compared with a multi-stage axial-flow fan with alternating moving and stationary blades, both rows of moving blades are arranged upstream of the stationary blades, and the moving and stationary blades are not arranged alternately, making the structure of the axial-flow fan simple.

[0043] By setting the chord length of the front row of moving blades to be longer than that of the rear row of moving blades, there is sufficient chord length for the blade profile setting of the front row of moving blades to achieve a greater pressure rise; compared with the case where the chord lengths and numbers of the two rows of moving blades are the same or close, setting the rear row of moving blades shorter also facilitates reducing the axial length of the axial-flow fan. By setting the number of the rear row of moving blades to be more than that of the front row of moving blades, while the rear row of moving blades shares the pressure rise, the fluid outflow can be made more uniform, thereby reducing the noise of fluid flow; at the same time, setting the chord length of the rear row of moving blades to be shorter than that of the front row of moving blades can also make the solidity at the front row of moving blades and the solidity at the rear row of moving blades close, improving the stability of the flow.

[0044] In addition, the axial-flow fan itself has the advantages of a compact structure and convenient installation, so that the axial-flow fan can meet the requirements in terms of high power, low noise, compact structure, and convenient installation.

[0045] An axial-flow fan with good comprehensive performance used in a range hood can improve the comprehensive performance of the range hood. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is an overall schematic diagram of the axial-flow fan.

[0047] Figure 2 It is a schematic diagram of the blade;

[0048] Figure 3 It is a schematic diagram of the flow velocity comparison;

[0049] Figure 4 It is a schematic diagram of the distance marking;

[0050] Figure 5 It is a schematic diagram of the speed marking;

[0051] Figure 6 It is a schematic sectional view of the axial-flow fan.

[0052] Description of the reference numerals:

[0053] Axial-flow fan 1000;

[0054] Blade 1;

[0055] Moving blades 11, front-row moving blades 111, and rear-row moving blades 112;

[0056] Stationary blades 12, front-row stationary blades 121, and rear-row stationary blades 122;

[0057] Housing 2;

[0058] Rotating shaft 3;

[0059] Support member 4;

[0060] Flow channel 5. Specific embodiments

[0061] The present invention will be further described below by way of examples, but the present invention is not limited to the scope of the described examples.

[0062] This embodiment provides an oil fume extractor. The fan of the oil fume extractor uses an axial flow fan. The axial flow fan is arranged in the air duct of the oil fume extractor. The inlet of the axial flow fan is connected to the air inlet of the oil fume extractor, and the outlet of the axial flow fan is connected to the air outlet of the oil fume extractor. In other embodiments, the inlet of the axial flow fan can be used as the air inlet of the oil fume extractor, and / or the outlet of the axial flow fan can be used as the air outlet of the oil press. Figure 1 - Figure 2 , Figure 4 - Figure 6 is a schematic diagram of the axial flow fan in this embodiment.

[0063] As Figure 1 , Figure 2 , the axial flow fan 1000 includes moving blades 11 and stationary blades 12, and there are two rows of each of these two types of blades 1. Figure 1 In, the axis of the axial flow fan 1000 is indicated by L, and the arrow indicates the direction from the inlet to the outlet of the axial flow fan 1000. The fluid flows in the axial flow fan 1000 along the L direction. Along the L direction, the front-row moving blades 111, the rear-row moving blades 112, the front-row stationary blades 121, and the rear-row stationary blades 122 are arranged in sequence. Compared with the rear-row moving blades 112, the front-row moving blades 111 have fewer numbers and longer chord lengths. Compared with the rear-row stationary blades 122, the front-row stationary blades 121 also have fewer numbers and longer chord lengths. That is, among the same type of blades 1, the front-row blades 1 are long and few, and the rear-row blades 1 are short and many.

[0064] In the present invention, two rows of the same type of blades 1 are provided. The rear-row blades 1 can share the performance requirements of the front-row blades 1. The rear-row moving blades 112 can share the pressure rise, and the rear-row stationary blades 122 can further guide and deflect the air flow, which can reduce the requirements for the manufacture, load, etc. of a single row of blades 1. By providing two rows of moving blades 11, compared with a single-stage axial-flow fan, at the same pressure rise, the rotational speed can be smaller, resulting in less noise. In the case of the same noise, a greater pressure rise can be achieved. At the same time, by providing two rows of stationary blades 12, compared with a two-stage axial-flow fan in which the moving blades 11 and the stationary blades 12 are alternately arranged, both rows of moving blades 11 are arranged upstream of the stationary blades 12, and the moving blades 11 and the stationary blades 12 are not alternately arranged, making the structure of the axial-flow fan 1000 simple.

[0065] By setting the chord length of the front-row blades 1 in the same type of blades 1 to be longer than that of the rear-row blades 1, there is sufficient chord length for the blade profile setting of the front-row blades 1 to achieve a greater pressure rise or a sufficiently good air flow deflection and guiding effect. Compared with the case where the chord lengths and numbers of the two rows of blades 1 are the same or close, setting the rear-row blades 1 shorter also facilitates reducing the axial length of the axial-flow fan 1000.

[0066] By setting the number of the rear-row blades 1 in the same type of blades 1 to be more than that of the front-row blades 1, while the rear-row blades 1 share the pressure rise or air flow deflection requirements, the fluid outflow can be made more uniform, thereby reducing the noise of fluid flow. At the same time, by setting the chord length of the rear-row blades 1 in the same type of blades 1 to be shorter than that of the front-row blades 1, the solidity at the front-row blades 1 and the solidity at the rear-row blades 1 can also be made close, improving the stability of the flow.

[0067] In addition, the axial-flow fan 1000 itself has the advantages of being structurally compact and easy to install. Applying the axial-flow fan 1000 to a range hood enables the range hood to meet the requirements in terms of high power, low noise, structural compactness, and easy installation.

[0068] Such as Figure 1 , the axial-flow fan 1000 further includes a rotating shaft 3, a support member 4, a motor, and a housing 2. A flow passage 5 is formed between the inner surface of the housing 2 and the outer surfaces of the rotating shaft 3 and the support member 4. The blades 1 are arranged in the flow passage 5. The two rows of moving blades 11 are fixed on the rotating shaft 3 and form a gap with the inner surface of the housing 2. One end of the two rows of stationary blades 12 in the radial direction is fixed on the support member 4, and the other end is fixed on the housing 2. The motor is installed in the support member 4 and is power-connected to the rotating shaft 3 to drive the rotating shaft 3 to rotate. Support is achieved through the stationary blades 12, and the structure is simple. In addition, the two rows of stationary blades 12 can form multi-point support, and the axial support length of the two rows of stationary blades 12 is generally longer than that of a single row of stationary blades 12, thereby improving the stability of the support for the rotating shaft 3 and the motor.

[0069] In a preferred embodiment, the number ratio of the rear row moving blades 112 to the front row moving blades 111 can be set between 2 and 4, and / or the number ratio of the rear row stationary blades 122 to the front row stationary blades 121 can be set between 2 and 4, so that the number of the rear row blades 1 is large enough, resulting in good fluid outflow uniformity and low noise generation; and the number of the rear row blades 1 is small enough, thus reducing the manufacturing difficulty and cost of the axial flow fan 1000.

[0070] In a preferred embodiment, the number ratio of the rear row moving blades 112 to the front row moving blades 111 can be set as an integer, and / or the number ratio of the rear row stationary blades 122 to the front row stationary blades 121 can be set as an integer, so that the circumferential distance between the front row blades 1 and the rear row blades 1 among the same type of blades 1 is constant, improving the circumferential uniformity of the flow field. In this embodiment, the number of the rear row moving blades 112 is specifically set to be twice that of the front row moving blades 111, and the number of the rear row stationary blades 122 is also twice that of the front row stationary blades 121.

[0071] In a preferred embodiment, the average solidity ratio of the front row moving blades 111 to the rear row moving blades 112 can be set between 0.9 and 1.3, and / or the average solidity ratio of the front row stationary blades 121 to the rear row stationary blades 122 can be set between 0.9 and 1.3, which can make the flow field between the front row blades 1 and the rear row blades 1 among the same type of blades 1 more uniform axially, thus improving the stability of fluid flow, and further facilitating the improvement of the pressure rise performance and the reduction of noise. The effect is better when the average solidity ratio of the front row moving blades 111 to the rear row moving blades 112 is set between 1 and 1.2, and / or the average solidity ratio of the front row stationary blades 121 to the rear row stationary blades 122 is set between 1 and 1.2. In this embodiment, the chord length of the front row moving blades 111 is specifically set to be twice that of the rear row moving blades 112, and the chord length of the front row stationary blades 121 is twice that of the rear row stationary blades 122, so that the solidity ratio of the two rows of moving blades 11 is 1, and the solidity ratio of the two rows of stationary blades 12 is also 1. Among them, the chord length and the solidity are both well-known concepts. The chord length is the length from the front end to the rear end of the blade 1, and the solidity can be understood as the chord length of the blade 1 / the distance between two adjacent blades 1 in a single row of blades 1, and the average solidity is the average value of the solidity at different heights of the blade 1.

[0072] Figure 3 In the following, the front row moving blades 111 and the rear row moving blades 112 of this embodiment are used separately for comparative analysis, and the change of the static pressure profile of the air flow is compared after the air flow flows out the same distance D from the trailing end of the blade 1. It is concluded by comparison that under the condition of the same solidity, the static pressure profile of the air flow flowing out from the row of blades 1 with a large number and a short chord length becomes uniform rapidly along the flow direction; while the mixing of the gas flowing out from the row of blades 1 with a small number and a long chord length is slower along the flow direction. It is verified that in the present invention, the rear row blades 1 among the same type of blades 1 are shorter and more numerous than the front row blades 1 so that the air flow is more uniform, thereby achieving the effect of reducing noise.

[0073] In a preferred embodiment, the trailing end of the front row of moving blades 111 and the leading end of the rear row of moving blades 112 can be arranged to be close to each other axially and / or circumferentially of the axial flow fan 1000, and / or, the trailing end of the front row of stationary blades 121 and the leading end of the rear row of stationary blades 122 can be arranged to be close to each other axially and / or circumferentially of the axial flow fan 1000, so that when the fluid transitions between the two rows of the same type of blades 1, it can smoothly transition from the front row of blades 1 to the rear row of blades 1, and suppress the separation of the fluid from the surface of the rear row of blades 1.

[0074] Figure 4 In the figure, the axial and circumferential spacings between the trailing end of the front row of moving blades 111 and the leading end of the rear row of moving blades 112 of the axial flow fan 1000 are respectively marked with L1 and W1, and the axial and circumferential spacings between the trailing end of the front row of stationary blades 121 and the leading end of the rear row of stationary blades 122 of the axial flow fan 1000 are respectively marked with L2 and W2.

[0075] In a preferred embodiment, the range of L1 and / or L2 can be set between -10 mm and 10 mm, so that the axial spacing between the two rows of the same type of blades 1 is small enough for the fluid to smoothly transition from the front row of blades 1 to the rear row of blades 1, and suppress the separation of the fluid from the surface of the rear row of blades 1; and the axial spacing between the two rows of the same type of blades 1 is large enough for machining and manufacturing. Further, the effect is better when the range of L1 and / or L2 is set between -5 mm and 5 mm. Figure 4 In the figure, both L1 and L2 shown are positive. When there is an overlapping range of the two rows of moving blades 11 axially, L1 is negative, and when there is an overlapping range of the two rows of stationary blades 12 axially, L2 is negative.

[0076] In a preferred embodiment, the range of W1 and / or W2 can be set between 0 and 10 mm, so that the circumferential spacing between the two rows of blades 1 is small enough for the fluid to smoothly transition from the front row of blades 1 to the rear row of blades 1, and suppress the separation of the fluid from the surface of the rear row of blades 1. Further, the effect is better when the range of W1 and / or W2 is set between 0 and 5 mm.

[0077] As Figure 5 , the leading end and trailing end of the front row of moving blades 111 are respectively indicated by P1, P2, the leading end and trailing end of the rear row of moving blades 112 are respectively indicated by P3, P4, the inlet angle of the front row of moving blades 111, the outlet angle of the front row of moving blades 111, and the outlet angle of the rear row of moving blades 112 are respectively indicated by β1, β2, β4, and the rotation direction of the moving blades 1 is indicated by W. The inlet angle and outlet angle are negative in the same direction as W. As Figure 5 in the figure, β4 is negative, and is positive in the opposite direction to W. As Figure 5 in the figure, β2 is positive. The relationship between the inlet angle and outlet angle of the blade 1 satisfies the velocity triangle, that is:

[0078]

[0079] Wherein, $c_n$ is the velocity of point $P_n$ in the tangential direction along the surface of blade 1, $u$ is the rotational velocity of moving blade 11, parallel to the $W$ direction, and $c_n$ is the velocity of the fluid. Figure 5 In [reference], the letters representing velocities are simplified, and the vector symbols are omitted.

[0080] Such as Figure 5 , by setting the root outlet angle of the rear row of moving blades 112 to be smaller than the root outlet angle of the front row of stationary blades 121, the rear row of moving blades 112 can do further work on the fluid, increasing the fluid velocity from $c_2$ at the trailing end of the front row of moving blades 111 to $c_4$ at the trailing end of the rear row of moving blades 112. The deflection angle of blade 1 is the difference between the inlet angle and the outlet angle. In a preferred embodiment, by setting the absolute value of the deflection angle of the front row of moving blades 111 to be greater than the absolute value of the deflection angle of the rear row of moving blades 112, the pressure rise generated by the front row of moving blades 111 is greater than that generated by the rear row of moving blades 112, which can reduce the load of the rear row of moving blades 112 and also facilitate reducing the complexity of the blade profile of the rear row of moving blades 112 for machining and manufacturing. Similarly, the absolute value of the deflection angle of the front row of stationary blades 121 can be set to be greater than the absolute value of the deflection angle of the rear row of stationary blades 122, such that the guiding and deflecting effect of the front row of stationary blades 121 on the fluid is greater than that of the rear row of stationary blades 122.

[0081] In a preferred embodiment, the number of the front row of stationary blades 121 can be set to not exceed half of the number of the rear row of moving blades 112, that is, not more than 0.5 times, so that the number of the front row of stationary blades 121 is small enough to reduce the resistance of the front row of stationary blades 121 to the fluid flow and reduce noise.

[0082] Such as Figure 4 , the axial distance between the front end of the front row of moving blades 111 and the trailing end of the rear row of moving blades 112 is $L_3$, and the axial distance between the trailing end of the rear row of moving blades 112 and the front end of the front row of stationary blades 121 is $L_4$. In a preferred embodiment, $L_4$ can be set to be 0.5 - 1.5 times of $L_3$. On the one hand, the axial distance from the trailing end of the rear row of moving blades 112 to the front of the stationary blade 12 is long enough, so that the fluid flowing out of the rear row of moving blades 112 can be mixed evenly enough before flowing to the stationary blade 12, reducing the dynamic-static interference noise; on the other hand, the axial distance between the moving blade 11 and the stationary blade 12 is small enough, so that the axial dimension of the axial flow fan 1000 is small enough and the structure is compact. Preferably, $L_4$ is set to be 0.75 times of $L_3$.

[0083] In a preferred embodiment, the moving blade 11 can be set to be inclined forward to make the fluid inflow more stable; in this embodiment, both rows of moving blades 11 are inclined forward, that is, the inclination direction from the root to the tip is the same as the rotational direction $W$. Figure 6 The left side in [reference] shows the inclination condition of a row of moving blades 11.

[0084] In a preferred embodiment, the stator blades 12 can be set to be inclined backward to slow down the outward throw of the fluid, prevent the fluid from accumulating at the blade tip side, and avoid the trend of too slow flow velocity at the blade root side, making the fluid outflow smoother. In this embodiment, both rows of stator blades 12 are inclined backward, that is, the inclination direction from the blade root to the blade tip is opposite to the rotation direction W. Figure 6 The right side in the figure shows the inclination condition of a row of stator blades 12.

[0085] In other embodiments, the stator blades 12 and / or the rotor blades 11 can be set not to be inclined.

[0086] In a preferred embodiment, such as Figure 1 , the outlet inner diameter 2r2 of the axial flow fan 1000 can be set between 160 mm and 220 mm, so that the outlet inner diameter of the axial flow fan 1000 is close to the inner diameter of the commonly used general flue pipe, facilitating the connection between the outlet of the axial flow fan 1000 and the general flue pipe. Further, by setting the outlet inner diameter of the axial flow fan 1000 between 175 mm and 185 mm, the outlet inner diameter of the axial flow fan 1000 is closer to the inner diameter of most general flue pipes, further improving the convenience of connecting the axial flow fan 1000 and the flue pipe.

[0087] In a preferred embodiment, the materials of the rotor blades 11 and the stator blades 12 are soft plastics or aluminum alloys, which can reduce the wear on the mold when casting the blades 1; plastics or aluminum alloys are lighter in weight, and using them in the axial flow fan 1000 can reduce the weight of the axial flow fan 1000.

[0088] In a preferred embodiment, the maximum solidity of the single row of blades 1 can be set to be less than or equal to 2.2, so that the blades 1 in the single row of blades 1 are arranged sparsely enough, facilitating the demolding when the blades 1 are cast. The effect is better when the maximum solidity of the single row of blades 1 is less than or equal to 1.5.

[0089] Such as Figure 1 , in a preferred embodiment, the flow channel 5 is along the axial direction between the front end of the front row of rotor blades 111 and the tail end of the rear row of stator blades 122, and the inner diameter 2r1 and the outer diameter 2r2 are kept constant to improve the stability of the flow.

[0090] In a preferred embodiment, the hub ratio of the flow channel, r1 / r2, ranges between 0.4 and 0.8, so that the hub ratio is large enough, making the blade height small enough, facilitating the setting of smaller cambers at the blade tip and blade root of the blade 1, with smooth fluid flow and low noise; making the hub ratio small enough, so that the blade height is large enough, and the channel through which the fluid flows through the blade 1 is large enough and the flow rate is large enough. The effect is better when the r1 / r2 ranges between 0.6 and 0.7.

[0091] Generally speaking, the axial flow fan provided by the present invention has the following advantages:

[0092] 1. The advantages of the axial flow fan are retained. It is small in size and has a flexible layout in the flow channel, which provides convenience for noise reduction design. On the basis of a single-stage axial flow fan, a structure with two rows of moving blades and two rows of stationary blades connected in series is further adopted, which improves the disadvantage of small pressure rise of the axial flow fan, and the overall structure is still similar to that of the single-stage axial flow fan, with much lower structural complexity than that of the two-stage axial flow fan. The present invention applies this advantage to the oil fume machine occasion, and uses multiple blade rows to share the load and pressure rise, so as to achieve a large reduction in noise.

[0093] 2. The spacing between the moving and stationary blade rows, the number of blades, and the blade profile of the moving blades are reasonably designed, which respectively improve the optimization of the moving and stationary interference noise, the flow stability, and the work capacity of the moving blades.

[0094] 3. The processing cost of the multi-blade row axial flow fan is controlled by the following various methods:

[0095] Separate the rotating components from the stationary components, which has a smaller structural complexity compared to the multi-stage axial flow fan and reduces the processing cost;

[0096] Use softer materials such as plastics or aluminum alloys to form the blades, thereby reducing die wear;

[0097] Properly select parameters such as the blade consistency to ensure that the fan blades can be demolded by rotating in both directions;

[0098] All moving blades are designed with equal inner diameter and equal outer diameter, and all stationary blades are designed with equal inner diameter and equal outer diameter;

[0099] Since multiple blade rows are used to achieve the target pressure rise, the load of each row of blades is relatively light, and the degree of blade twist is relatively low, which also reduces the processing difficulty.

[0100] Although the specific implementation manners of the present invention are described above, those skilled in the art should understand that this is only an example, and the protection scope of the present invention is defined by the appended claims. Without departing from the principle and essence of the present invention, those skilled in the art can make various changes or modifications to these implementation manners, but these changes and modifications all fall within the protection scope of the present invention.

Claims

1. An axial flow fan, comprising two kinds of blades, moving blades and stationary blades, wherein the moving blades have two rows, namely, front row moving blades and rear row moving blades, and along the fluid flow direction, the front row moving blades, the rear row moving blades, and the stationary blades are arranged in sequence, characterized in that: The number and chord length of the front row of moving blades are respectively less and longer than those of the rear row of moving blades.

2. The axial flow fan according to claim 1, characterized in that: The number of the stationary blades is two rows, namely a front row of stationary blades and a rear row of stationary blades. Along the direction of fluid flow, the front row of moving blades, the rear row of moving blades, the front row of stationary blades, and the rear row of stationary blades are arranged in sequence. The number and chord length of the front row of stationary blades are respectively less and longer than those of the rear row of stationary blades.

3. The axial flow fan according to claim 1 or 2, characterized in that: In two rows of leaves of the same species, the ratio of the number of leaves in the back row to the number of leaves in the front row is between 2 and 4; And / or, in two rows of leaves of the same species, the ratio of the average density of the front row of leaves to that of the back row of leaves is between 0.9 and 1.

3.

4. The axial flow fan according to claim 1 or 2, characterized in that: In two rows of leaves of the same species, the number of leaves in the back row is an integer multiple of the number of leaves in the front row; And / or, in two rows of blades of the same type, the tail end of the front row of blades is close to the front end of the rear row of blades in the circumferential direction and / or axial direction of the axial flow fan.

5. The axial flow fan according to claim 1 or 2, characterized in that: The spacing between the two rows of blades of the same type along the axial direction of the axial flow fan is between -10mm and 10mm; And / or, in the two rows of blades of the same type, the circumferential spacing between the tail end of the pressure surface of the front row blades and the front end of the suction surface of the rear row blades is between 0 and 10 mm.

6. The axial flow fan according to claim 1 or 2, characterized in that: The outlet angle of the blade root of the rear row of moving blades is smaller than the outlet angle of the blade root of the front row of moving blades; And / or, in two rows of blades of the same type, the absolute value of the deflection angle of the blades in the front row is greater than the absolute value of the deflection angle of the blades in the rear row.

7. The axial flow fan according to claim 2, characterized in that: The number of the front row of stationary blades is less than or equal to 0.5 times the number of the rear row of moving blades.

8. The axial flow fan according to claim 1, characterized in that: The minimum spacing between the rear row moving blades and the stationary blades along the axial direction of the axial flow fan is 0.5 to 1.5 times the spacing between the front end of the front row moving blades and the tail end of the rear row moving blades along the axial direction of the axial flow fan.

9. The axial flow fan according to claim 1 or 2, characterized in that: The axial flow fan also includes a rotating shaft, a support, a motor, and a casing. A flow channel is formed between the inner surface of the casing and the outer surfaces of the rotating shaft and the support. The blades are arranged in the flow channel. The moving blades are fixed on the rotating shaft to form a gap with the inner surface of the casing. The support is fixed to the casing through the stationary blades. The motor is installed in the support to drive the rotating shaft to rotate.

10. A range hood, characterized in that: It includes an axial flow fan as described in any one of claims 1 to 9, the inlet of the axial flow fan is the air inlet of the range hood or is connected to the air inlet of the range hood, and the outlet of the axial flow fan is the air outlet of the range hood or is connected to the air outlet of the range hood.

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