A centrifugal fan and a range hood using the same

Abstract

The application discloses a centrifugal fan and an extractor hood using the same. The centrifugal fan comprises an impeller, the impeller comprises a disc far from an air inlet side and at least two blades, the blades are fixed with the disc far from the air inlet side; the centrifugal fan further comprises a ring-shaped guide vane, the guide vane surrounds the outlet of each blade and extends outward along the radial direction of the centrifugal fan from the fixed position of the blade; the guide vane comprises a guide section, the guide section is deflected towards the disc far from the air inlet side. Compared with the prior art, the centrifugal fan has the advantages that by arranging the guide vane at the outlet of the blade, the guide vane has the guide section deflected towards the disc far from the air inlet side, thereby the air flow can be induced to flow to the outlet, the transverse flow is reduced, the risk of developing into secondary flow or even backflow is reduced, the overall performance of the impeller is improved, the air volume and the efficiency can be improved under the condition that the size or the rotating speed is unchanged, and the noise is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to a power device, in particular to a centrifugal fan and a range hood using the same. BACKGROUND

[0002] Multi-wing centrifugal fan has the characteristics of high pressure and low noise, so it is widely used as a power source in the society at present. The multi-wing centrifugal fan uses a high-speed rotating impeller to complete the functions of work and filtration in a volute. For example, it is commonly used in range hoods to suck and exhaust oil fume. The multi-wing centrifugal fan includes a volute, an impeller installed in the volute, and a motor driving the impeller to rotate. When the impeller rotates, a negative pressure suction is generated at the center of the fan, which sucks the oil fume below the range hood into the fan. After being accelerated by the fan, the oil fume is collected and guided by the volute to be discharged outside.

[0003] The main working area of the multi-wing centrifugal fan of the conventional range hood is close to the middle disc area (close to the rear disc for a single suction with a short axial dimension), as shown in Figure 9 and Figure 10 , wherein Figure 9 the arrow in the middle disc area indicates the gas flow path. Because the air inlet is not uniform along the axial direction, it is easy to cause a pressure difference along the axial direction after the gas flow flows out of the impeller passage. The action of this pressure difference easily causes the gas flow to form a large secondary flow vortex 100 in the volute, and even develops to flow back to the inlet area from the front and rear disc areas, which reduces the overall aerodynamic efficiency, increases the noise, and makes the effective working blade segment ratio low.

[0004] The common solution to increase the air volume often relies on speed increase or size increase. Speed increase leads to further increase in noise, and size increase further occupies the cabinet space. SUMMARY

[0005] The first technical problem to be solved by the present application is to provide a centrifugal fan to reduce the secondary flow vortex at the outlet of the impeller, improve the overall working capacity of the impeller, and reduce the noise in view of the deficiencies of the prior art.

[0006] The second technical problem to be solved by the present application is to provide a range hood using the above-mentioned centrifugal fan.

[0007] The technical solution adopted by the present application to solve the first technical problem is a centrifugal fan, which includes an impeller, the impeller includes a disc away from an air inlet side and at least two blades, the blades are fixed with the disc away from the air inlet side, and the centrifugal fan is characterized by:

[0008] The centrifugal fan further comprises a ring-shaped guide vane, which surrounds the outlet of each blade and extends radially outward from the fixing position of the blade along the centrifugal fan; the guide vane comprises a guide deflection section, which deflects towards the disc away from the air inlet side.

[0009] By arranging the guide vane at the outlet of the blade, the guide vane has the guide deflection section deflecting towards the disc away from the air inlet side, so that the airflow can be induced to flow to the outlet, the transverse flow is reduced, the risk of developing into secondary flow or even backflow is reduced, the overall working capacity of the impeller is improved, the air volume and efficiency can be improved under the condition of unchanged size or rotating speed, and the noise is reduced.

[0010] Due to the difference in working capacity of the impeller along the axial direction, there is a pressure difference along the axial direction, and the airflow flowing out at different positions deflects the main airflow region to the forward weak region under the action of the axial pressure difference, and the deflection becomes more serious away from the main airflow region. Therefore, along the axial direction of the centrifugal fan, on the same side of the disc away from the air inlet side, the guide deflection compensation angle formed by the deflection of the guide deflection section gradually increases with the increase of the distance from the disc away from the air inlet side.

[0011] Therefore, the following advantages can be obtained: ①near the main flow, the deflection is not serious because the pressure difference is small, a small compensation angle can correct the airflow direction and block the transverse flow, and at the same time, the small compensation angle is also helpful for the airflow to pass through and reduce the flow resistance because the airflow speed in this region is high; ②as the distance from the main flow region increases, the deflection of the airflow flowing out becomes more serious, at this time, the angle of the compensation angle is increased to improve the deflection guiding ability, although the resistance coefficient will increase due to the increase of the angle, the airflow speed in this region is smaller than that in the main flow region, and the contribution to the overall resistance is not too obvious, and the secondary flow vortex caused by the transverse flow can be obviously reduced after the deflection of the guide vane, thereby reducing the flow loss.

[0012] Preferably, the guide deflection section has a guide deflection compensation angle, in the cross section of the guide vane, the guide vane has an edge line segment on one side in the axial direction of the centrifugal fan, in the edge line segment, the starting point of the corresponding part of the guide deflection section is a first starting point, and the ending point of the corresponding part of the guide deflection section is a first ending point, the guide deflection compensation angle is the complementary angle of the included angle between the straight line connecting the first starting point and the first ending point and the axial direction of the centrifugal fan, and the value range of the guide deflection compensation angle is [0°, 60°].

[0013] In order to reduce the frictional resistance between the guide vane and the airflow, according to one aspect of the present application, the connecting line between the first starting point and the first ending point is a straight line segment, and the guide vane of this form is simple to process.

[0014] To reduce the frictional resistance between the guide vane and the airflow, according to another aspect of the invention, the line connecting the first starting point and the first ending point is a broken line segment. The guide vane generates separated vortices at the concave part of the broken line. These vortices allow the subsequent airflow to slide like a wheel, reducing frictional resistance. They also prevent small vortices from developing into large vortices, as large vortices generate more noise and dissipate more energy, thus further improving efficiency and reducing noise.

[0015] To reduce the frictional resistance between the guide vane and the airflow, according to another aspect of the invention, the edge segment corresponding to the guide segment also has a midpoint, and the line connecting the first starting point and the midpoint is an arc segment, with the midpoint connected to the first ending point. The arc segment in the middle can induce less separation in the transition of airflow deflection compared to a smooth guide surface. Although there is separation on the back side, large vortices can be avoided.

[0016] To reduce the frictional resistance between the guide vane and the airflow, according to another aspect of the invention, the edge segment corresponding to the guide segment also has a midpoint, and the line connecting the first starting point and the midpoint is a spiral segment, with the midpoint connected to the first ending point. The spiral segment can change with the airflow, is longer, and has a more pronounced effect than a circular arc segment. It induces a smooth transition in airflow deflection, with minimal separation on the guide surface, while although there is separation on the back side, large vortices are avoided.

[0017] To facilitate manufacturing and installation, the guide vane also includes a fixing section for fixing to the blade, the guide section extending outward from the fixing section.

[0018] Preferably, the outer diameter of the impeller is D2. On the cross-section of the guide vane, the guide vane has an edge segment on one side along the axial direction of the centrifugal fan. The starting point of the edge segment corresponding to the guide segment is a first starting point, the ending point of the guide segment is a first ending point, and the starting point of the segment corresponding to the fixed segment is a second starting point. The first starting point is the ending point of the edge segment corresponding to the fixed segment. The line connecting the second starting point and the first starting point forms a straight line perpendicular to the axial direction of the centrifugal fan. The ratio of the length of the line connecting the second starting point and the first starting point to D2 ranges from [0.004, 0.08]. If the fixed segment is too short, it is difficult to install; if it is too long, the frictional resistance is too high, and it is prone to interference with the volute tongue on the volute casing.

[0019] Preferably, the ratio of the total length of the edge segment to the length of the corresponding straight line segment of the fixed segment is in the range of [1, 8]. If the guide segment is too short, the induced steering effect will be weak; if it is too long, the frictional resistance will be too large and it will easily interfere with the volute tongue.

[0020] Preferably, the outer diameter of the impeller is D2. Along the axial direction of the centrifugal fan, on the same side of the disc furthest from the air inlet side, the ratio of the spacing between any two adjacent guide vanes to D2 ranges from [0.03, 0.15]. If this ratio is too low, the vanes will be too dense, resulting in excessive frictional resistance and increased weight, thus reducing impeller efficiency; if it is too high, the vanes will be too sparse, weakening or diminishing the guiding effect.

[0021] Preferably, the centrifugal fan further includes a volute, on which an air inlet is formed, and the impeller is a single-suction impeller or a double-suction impeller;

[0022] When the impeller is a single-suction impeller, the number of air inlets is one. The impeller includes a front plate and a rear plate. The blades are fixed to the front plate and the rear plate respectively. The front plate is close to the air inlet, and the plate away from the air inlet side is the rear plate.

[0023] When the impeller is a double-suction impeller, there are two air inlets. The impeller includes a front plate, a middle plate, and a rear plate. The blades are fixed to the front plate, the middle plate, and the rear plate respectively. The front plate and the rear plate are close to one of the air inlets. The plate away from the air inlet side is the middle plate.

[0024] Preferably, the guide vane is mainly used for airflow outside the main working area. The guide vane is arranged outside the mainstream area at the outlet of the blade. The mainstream area is located adjacent to the disk away from the air inlet side. Along the axial direction of the centrifugal fan, the ratio of the axial height of the mainstream area to the axial height of the impeller ranges from [0.1, 0.5].

[0025] The technical solution adopted by the present invention to solve the second technical problem mentioned above is: a range hood, characterized in that: it uses a centrifugal fan as described above.

[0026] Compared with the prior art, the advantages of the present invention are as follows: by setting guide vanes at the blade outlet, the guide vanes have a guide section that deflects away from the air inlet side, thereby inducing airflow to flow towards the outlet, reducing lateral flow, reducing the risk of developing into secondary flow or even backflow, improving the overall work capacity of the impeller, and increasing air volume and efficiency while keeping the size or speed unchanged, and reducing noise; setting a small compensation angle for the guide vanes close to the mainstream area helps the airflow pass through and reduces flow resistance, and the compensation angle increases as it moves further away from the mainstream area, improving the guiding ability to correct deviation. Attached Figure Description

[0027] Figure 1 This is a cross-sectional view of a centrifugal fan according to an embodiment of the present invention;

[0028] Figure 2 for Figure 1 A magnified schematic diagram of part I;

[0029] Figure 3 This is a schematic diagram of a centrifugal fan with a hidden volute (double-suction impeller) according to an embodiment of the present invention;

[0030] Figure 4-1 This is a simplified cross-sectional schematic diagram of the guide vanes of the centrifugal fan of the present invention in a first embodiment;

[0031] Figure 4-2 for Figure 4-1 A schematic diagram of the flow field simulation;

[0032] Figure 5-1 This is a simplified cross-sectional schematic diagram of a second embodiment of the guide vane of the centrifugal fan of the present invention;

[0033] Figure 5-2 for Figure 5-1 A schematic diagram of the flow field simulation;

[0034] Figure 6-1 This is a simplified cross-sectional schematic diagram of the guide vane of the centrifugal fan of the present invention in a third embodiment;

[0035] Figure 6-2 for Figure 6-1 A schematic diagram of the flow field simulation;

[0036] Figure 7-1 This is a simplified cross-sectional schematic diagram of the guide vanes of the centrifugal fan of the present invention in a first embodiment;

[0037] Figure 7-2 for Figure 7-1 A schematic diagram of the flow field simulation;

[0038] Figure 8 This is a schematic diagram of a centrifugal fan with a concealed volute and motor (single-suction impeller) according to an embodiment of the present invention.

[0039] Figure 9 A cross-sectional view of a centrifugal fan in the prior art;

[0040] Figure 10 The flow field simulation velocity diagram is for existing centrifugal fans. Detailed Implementation

[0041] The embodiments of the present invention are described in detail below. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions.

[0042] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Since the embodiments disclosed in this invention can be arranged in different directions, these terms indicating direction are only for illustration and should not be regarded as limitations. For example, "upper" and "lower" are not necessarily limited to directions opposite to or consistent with the direction of gravity. In addition, features defined with "first" and "second" may explicitly or implicitly include one or more of such features.

[0043] See Figures 1-3 A centrifugal fan includes a volute 1, an impeller 2 disposed within the volute 1, and a motor 3 for driving the impeller 2 to rotate. The volute 1 includes two spaced-apart cover plates 11 and an annular wall 12 formed between the cover plates 11, with an air inlet 13 provided on the cover plates 11.

[0044] The impeller 2 includes a front disc 21, a rear disc 22, a middle disc 23 positioned between the front disc 21 and the rear disc 22, and blades 24. Both cover plates 11 have air inlets 13, with the front disc 21 and rear disc 22 close to their respective air inlets 13. The blades 24 extend axially along the centrifugal fan, passing through the front disc 21, middle disc 23, and rear disc 22, and are fixed to each of them. The number of blades 24 is not less than two, preferably around 60, forming a double-suction impeller, making the centrifugal fan a double-inlet fan. Alternatively, the impeller 2 can be modified to exclude the middle disc 23, forming a single-suction impeller (see Figure 5). In this case, only one cover plate 11 has an air inlet 13, with the front disc 21 close to the air inlet 13 and the rear disc 22 away from it. This structure is the same as that of existing centrifugal fans and will not be described further here.

[0045] The centrifugal fan also includes guide vanes 4, which are annular and arranged around the outlet of each blade 24 (the outlet being the outer edge of the blade 24). There may be one or at least two guide vanes 4; when there are at least two, the guide vanes 4 are spaced apart along the axial direction of the centrifugal fan. Since the axial airflow in the main flow region is not significantly uneven, the guide vanes 4 are preferably located outside the main flow region at the outlet of the blade 24 of the impeller 2, which also reduces costs. Here, the "main flow region" refers to the main working area, defined as follows: the main flow region is located adjacent to the disc away from the air inlet side, along the axial direction of the centrifugal fan, and the ratio of the axial height of the main flow region to the axial height of the impeller 2 is [0.1, 0.5]. When impeller 2 is a single-suction impeller, the disc furthest from the inlet side is the rear disc 22. In this case, the mainstream area is located between the rear disc 22 and the front disc 21, extending from the rear disc 22 to the front disc 21. The guide vane 4 is positioned between the front disc 21 and the rear disc 22. When impeller 2 is a double-suction impeller, the disc furthest from the inlet side is the middle disc 23. In this case, the mainstream area is located on both axial sides of the middle disc 23, maintaining the overall axial height as described above, without strictly limiting the ratio between the two sides of the middle disc 23. The guide vane 4 is positioned between the front disc 21 and the middle disc 23, and between the rear disc 22 and the middle disc 23. Of course, guide vanes 4 can also be positioned within the mainstream area.

[0046] The following explanation uses a dual-inlet fan as an example; the single-inlet fan is similar, except that the middle plate 23 is replaced by the rear plate 22. For ease of processing and installation, the guide vane 4 includes a fixed section 41 and a guide section 42. The fixed section 41 is fixed to the blade 24 by snap-fit, welding, or bonding, extending radially outward from its fixing point with the blade 24. The guide section 42 is located at the end of the fixed section 41 away from the blade 24, deflected towards the middle plate 23. Let the outer diameter of the impeller 2 be D2, and the spacing between the guide vanes on the same side of the plate away from the air inlet side be L. The value range of L:D2 is [0.03, 0.15]. If it is too low and too dense, the frictional resistance of the guide vane 4 will be too high, increasing the weight and reducing the efficiency of the impeller 2; if it is too high, the guide vane 4 will be too sparse, weakening or diminishing the guiding effect.

[0047] See Figure 4-1 and Figure 4-2 The diagram shows a simplified schematic of the cross-section of a guide vane according to an embodiment of the present invention. This cross-section is located through the axis of the centrifugal fan and perpendicular to the radial plane of the centrifugal fan. Figure 1 The plane shown is the plane on which the paper is located. To clearly show the shape of the guide plate 4, the cross section is simplified to the edge line segment (inner edge or outer edge) of the guide plate 4. "Inner" refers to the side facing the middle plate 23, and "outer" refers to the side away from the middle plate 23. The guide plate 4 is a sheet of equal thickness, so the inner edge and the outer edge have the same shape. Figures 5-1-7-2 The meaning is the same as above, and will not be repeated below.

[0048] The starting point of the edge segment corresponding to the guide section 42 is the first starting point B (which is also the ending point corresponding to the fixed section 41), and the ending point is the first ending point D. The starting point of the edge segment corresponding to the fixed section 41 is the second starting point A, which is the endpoint fixed to the blade 24. The edge segment corresponding to the fixed section 41 forms a straight line segment perpendicular to the centrifugal fan, and the edge segment of the guide section 42 also forms a straight line segment. Let the outer diameter of the impeller 2 be D2. The dimension of the straight line segment corresponding to the fixed section 41 and the value range of D2 are [0.004, 0.08]. If AB is too short, it will be difficult to install; if it is too long, the frictional resistance will be too large and it will easily interfere with the volute tongue on the volute 1. AD (here refers to the total length of the edge line corresponding to the guide vane 4): AB (here refers to the length between the two points) has a value range of [1, 8]. If it is too short, the induced steering effect will be weak; if it is too long, the frictional resistance will be too large and it will easily interfere with the volute tongue. The two straight lines BD and AB are set at a relative angle.

[0049] Figure 4-2 The middle arrow indicates the airflow path. It shows that the originally deflected airflow, after passing through the fixed section 41, completes its deflection adjustment at the guide surface of the guide section 42 (the side facing the central plate 23), while the flow separation on the back of the guide vane 4 (the side away from the central plate 23) is also within an acceptable range. This type of guide vane 4 has a simple mold and is easy to process; it can be obtained by sheet metal bending or by adding a plastic edge.

[0050] See Figure 5-1 and Figure 5-2 The diagram shows a simplified cross-sectional view of a guide vane according to an embodiment of the present invention. The edge segment of the guide section 42 also has a midpoint C. In the present invention, the "midpoint" refers to the position located between the first starting point B and the first ending point D, and is not limited to the midpoint between the first starting point B and the first ending point D. The BC line can be a broken line segment or a straight line segment, and the CD line type is not limited, but a straight line segment is preferred. Thus, the edge line of the guide section 42 as a whole constitutes a broken line segment, and separation vortices are generated at the concave part of the broken line. This type of vortex can make the airflow behind it slide like a wheel, reducing frictional resistance, and can also prevent small vortices from developing into large vortices, because large vortices cause greater noise and dissipate more energy, so efficiency can be further improved and noise reduced. AD (here refers to the total length of the edge line corresponding to the guide vane 4): AB (here refers to the length between the two points) takes values ​​in the range of [1, 8]. If it is too short, the induced steering effect is weak; if it is too long, the frictional resistance is too large and it is easy to interfere with the volute tongue.

[0051] See Figure 6-1 and Figure 6-2 A simplified schematic diagram of the cross-section of a guide vane according to an embodiment of the present invention is shown. Figure 5-1The difference in the embodiment shown is that the midpoint is C', and the line connecting BC' is an arc segment. The arc segment in the middle can induce a smoother transition of airflow deflection with less separation than the guide surface. Although there is separation on the back side, it can avoid large vortices.

[0052] See Figure 7-1 and Figure 7-2 This shows a simplified schematic diagram of the cross-section of a guide vane according to an embodiment of the present invention, compared to... Figure 6-1 The embodiment shown differs in that its midpoint is "C", and the line connecting "BC" is an arc segment. The curvature can vary with the helix angle and can change with the airflow. Its longer length makes the effect more pronounced than a circular arc segment, resulting in a smoother transition inducing airflow deflection and minimal separation on the guide surface. While there is separation on the back side, large vortices are avoided. The helix can be either an equal-angle logarithmic helix or a variable-angle logarithmic helix to better adapt to the decelerating flow after the airflow exits.

[0053] In the above embodiment, the guide deflection compensation angle α is defined as the angle at which the guide section 42 deflects towards the disk away from the air inlet side. That is, it is the complementary angle between the line connecting the first endpoint D and the first starting point B of the edge segment of the guide section 42 and the axial direction of the centrifugal fan. α gradually increases with the increase of the distance from the disk away from the air inlet side, and the value range of α is [0°, 60°], more preferably (0°, 60°). Because of the difference in work done by the impeller 2 along the axial direction, there is a pressure difference along the axial direction. Under the action of the axial pressure difference, the mainstream airflow region deflects towards the weaker region, and the deflection is more severe the further away from the mainstream region. The above-mentioned angle changes are as follows: ① Near the mainstream, the deflection is not severe due to the small pressure difference. Setting a small compensation angle can correct the airflow direction and block the lateral flow. At the same time, because the airflow velocity in this area is high, setting a small compensation angle also helps the airflow pass through and reduces flow resistance. ② As the distance from the mainstream area increases, the deflection of the outflow becomes more severe. At this time, the angle in the compensation angle design is increased to improve the guiding ability of the deflection correction. Although the drag coefficient will increase due to the increase in angle, the airflow velocity in this area is lower than that in the mainstream area, so the contribution to the overall drag will not be too significant. After the flow is guided and corrected, the secondary flow vortex caused by the lateral flow can be significantly reduced, thereby reducing flow loss.

Claims

1. A centrifugal fan, comprising an impeller (2), said impeller (2) including a disk away from the air inlet side and at least two blades (24), said blades (24) being fixed to the disk away from the air inlet side; characterized in that: The centrifugal fan also includes an annular guide vane (4), which surrounds the outlet of each blade (24) and extends radially outward from the fixing point with the blade (24); the guide vane (4) includes a guide section (42) which deflects toward the disk away from the air inlet side; along the axial direction of the centrifugal fan, on the same side of the disk away from the air inlet side, as the distance from the disk away from the air inlet side increases, the guide deflection compensation angle (α) formed by the deflection of the guide section (42) gradually increases.

2. The centrifugal fan according to claim 1, characterized in that: On the cross-section of the guide vane (4), the guide vane (4) has an edge segment on one side of the centrifugal fan axis. In the edge segment, the starting point of the part corresponding to the guide section (42) is the first starting point (B), and the ending point of the part corresponding to the guide section (42) is the first ending point (D). The guide deflection compensation angle (α) is the complementary angle between the straight line connecting the first starting point (B) and the first ending point (D) and the centrifugal fan axis. The value range of the guide deflection compensation angle (α) is [0°, 60°].

3. The centrifugal fan according to claim 2, characterized in that: The line connecting the first starting point (B) and the first ending point (D) is a straight line segment.

4. The centrifugal fan according to claim 2, characterized in that: The line connecting the first starting point (B) and the first ending point (D) is a broken line segment.

5. The centrifugal fan according to claim 2, characterized in that: The edge segment has a midpoint (C') corresponding to the guide segment (42), and the line connecting the first starting point (B) and the midpoint (C') is an arc segment, and the midpoint (C') is connected to the first ending point (D).

6. The centrifugal fan according to claim 2, characterized in that: The edge segment has a midpoint (C'') corresponding to the guide segment (42), and the line connecting the first starting point (B) and the midpoint (C'') is a spiral segment, and the midpoint (C'') is connected to the first ending point (D).

7. The centrifugal fan according to claim 1, characterized in that: The guide vane (4) also includes a fixing section (41) for fixing to the blade (24), the guide section (42) extending outward from the fixing section (41).

8. The centrifugal fan according to claim 7, characterized in that: The outer diameter of the impeller (2) is D2. On the cross-section of the guide vane (4), the guide vane (4) has an edge segment on one side of the centrifugal fan axis. Among the edge segments, the starting point of the part corresponding to the guide section (42) is the first starting point (B), the ending point of the part corresponding to the guide section (42) is the first ending point (D), and the starting point of the part corresponding to the fixed section (41) is the second starting point (A). The first starting point (B) is the ending point of the edge segment corresponding to the fixed section (41). The line connecting the second starting point (A) and the first starting point (B) forms a straight line perpendicular to the centrifugal fan axis. The ratio of the length of the line connecting the second starting point (A) and the first starting point (B) to D2 is in the range of [0.004, 0.08].

9. The centrifugal fan according to claim 8, characterized in that: The ratio of the total length of the edge line segment to the length of the straight line segment corresponding to the fixed segment (41) ranges from [1, 8].

10. The centrifugal fan according to claim 1, characterized in that: The outer diameter of the impeller (2) is D2. Along the axial direction of the centrifugal fan, on the same side of the disc away from the air inlet side, the ratio of the distance between any two adjacent guide vanes (4) to D2 ranges from [0.03, 0.15].

11. The centrifugal fan according to claim 1, characterized in that: The centrifugal fan also includes a volute (1), on which an air inlet (13) is formed, and the impeller (2) is a single-suction impeller or a double-suction impeller; When the impeller (2) is a single-suction impeller, the number of air inlets (13) is one. The impeller (2) includes a front plate (21) and a rear plate (22). The blades (24) are fixed to the front plate (21) and the rear plate (22) respectively. The front plate (21) is close to the air inlet (13), and the plate away from the air inlet side is the rear plate (22). When the impeller (2) is a double-suction impeller, there are two air inlets (13). The impeller (2) includes a front plate (21), a middle plate (23) and a rear plate (22). The blades (24) are fixed to the front plate (21), the middle plate (23) and the rear plate (22) respectively. The front plate (21) and the rear plate (22) are close to one of the air inlets (13) respectively. The plate away from the air inlet side is the middle plate (23).

12. The centrifugal fan according to claim 11, characterized in that: The guide vane (4) is arranged outside the mainstream area at the outlet of the blade (24). The mainstream area is located adjacent to the disk away from the air inlet side. Along the axial direction of the centrifugal fan, the ratio of the axial height of the mainstream area to the axial height of the impeller (2) ranges from [0.1, 0.5].

13. A range hood, characterized in that: The application uses a centrifugal fan as described in any one of claims 1 to 12.

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