CN116398469A - Centrifugal fan and range hood with same - Google Patents

Abstract

The invention discloses a centrifugal fan and a range hood with the same, wherein the centrifugal fan comprises an impeller, the impeller comprises a disc far away from an air inlet side and at least two blades, and the blades are fixed with the disc far away from the air inlet side; the centrifugal fan also comprises annular guide vanes which encircle the outlets of the blades and extend outwards along the radial direction of the centrifugal fan from the fixing positions of the guide vanes and the blades; the deflector comprises a deflector segment which deflects towards the disk remote from the air inlet side. Compared with the prior art, the invention has the advantages that: through setting up the guide vane at the blade export, the guide vane has the guide section of deflecting to the dish that keeps away from the air inlet side, can induce the air current to flow towards the export from this, reduces transverse flow, reduces the risk of developing into secondary flow, even backward flow, promotes impeller holistic acting capacity, can promote amount of wind and efficiency under the unchangeable circumstances of size or rotational speed, noise reduction.

Description

Centrifugal fan and range hood with same

Technical Field

The invention relates to a power device, in particular to a centrifugal fan and a range hood using the centrifugal fan.

Background

The multi-wing centrifugal fan has the characteristics of high pressure, low noise and the like, so that a multi-wing centrifugal fan system is commonly used as a power source in the society at present, and the two functions of acting and filtering are completed in a volute by utilizing an impeller rotating at high speed. The multi-wing centrifugal fan comprises a volute, an impeller arranged in the volute and a motor for driving the impeller to rotate, when the impeller rotates, negative pressure suction is generated at the center of the fan, oil smoke below the range hood is sucked into the fan, and is collected and guided by the volute to be discharged outdoors after being accelerated by the fan.

The area close to the middle disc (for single suction of short axial size close to the rear disc) of the conventional multi-wing centrifugal fan for the range hood is a main working area, which is shown in fig. 9 and 10, wherein the arrow in fig. 9 shows a gas flow path. Because the air inlet along the axial direction is uneven, the pressure difference is easy to cause the air flow to flow out of the impeller channel along the axial direction, and the effect of the pressure difference easily causes the air flow to form a large secondary flow vortex 100 in the volute, even the air flow is developed to flow back to the inlet area from the front disc area to the rear disc area, the overall aerodynamic efficiency is reduced, the noise is increased, and the effective acting blade segment is low in duty ratio.

The conventional solution for improving the air quantity often depends on the increase of the rotating speed or the increase of the size, the noise is further increased due to the increase of the rotating speed, and the space of the cabinet is further occupied by the increase of the size.

Disclosure of Invention

The first technical problem to be solved by the invention is to provide a centrifugal fan aiming at the defects existing in the prior art, so that secondary flow vortex at an impeller outlet is reduced, the whole working capacity of the impeller is improved, and noise is reduced.

The second technical problem to be solved by the invention is to provide the range hood with the centrifugal fan.

The technical scheme adopted by the invention for solving the first technical problem is as follows: a centrifugal fan comprising an impeller, wherein the impeller comprises a disc far away from an air inlet side and at least two blades, and the blades are fixed with the disc far away from the air inlet side; the method is characterized in that:

the centrifugal fan also comprises annular guide vanes which encircle the outlets of the blades and extend outwards along the radial direction of the centrifugal fan from the fixing positions of the guide vanes and the blades; the deflector comprises a deflector segment which deflects towards the disk remote from the air inlet side.

Through setting up the guide vane at the blade export, the guide vane has the guide section of deflecting to the dish that keeps away from the air inlet side, can induce the air current to flow towards the export from this, reduces transverse flow, reduces the risk of developing into secondary flow, even backward flow, promotes impeller holistic acting capacity, can promote amount of wind and efficiency under the unchangeable circumstances of size or rotational speed, noise reduction.

Because the impeller does work differently along the axis direction, so that there is a pressure difference along the axis direction, the airflow flowing out of different positions deflects the airflow main flow area forward to the weaker area under the action of the axial pressure difference, and the more serious the airflow main flow area deflects, so that the deflection compensation angle formed by deflection of the flow guide section gradually increases along with the increase of the distance between the impeller and the disk far away from the air inlet side along the axial direction of the centrifugal fan and on the same side of the disk far away from the air inlet side.

This may have the following advantages: (1) the small compensating angle is arranged near the main flow because the differential pressure is small and the deflection is not serious, so that the direction of the air flow can be corrected, the transverse flow is blocked, meanwhile, the air flow speed is high for the area, the small compensating angle is also beneficial to the air flow passing, and the flow resistance is reduced; (2) the deflection of the airflow flowing out is more serious along with the deviation from the main flow area, at the moment, the angle is increased in the design of the compensation angle, the deviation rectifying guiding capability is improved, although the resistance coefficient is increased due to the increase of the angle, the airflow speed in the area is smaller than that in the main flow area, the contribution to the whole resistance is less obvious, the secondary flow vortex caused by the cross flow can be obviously reduced after the deviation rectifying, and the flow loss is further reduced.

Preferably, the deflection of the flow guiding section forms a flow guiding deflection compensation angle, the cross section of the flow guiding sheet is provided with an edge line segment at one side of the axial direction of the centrifugal fan, in the edge line segment, the starting point of the part corresponding to the flow guiding section is a first starting point, the end point of the part corresponding to the flow guiding section is a first end point, the flow guiding deflection compensation angle is the residual angle of an included angle between a straight line connecting the first starting point and the first end point and the axial direction of the centrifugal fan, and the value range of the flow guiding deflection compensation angle is [0 degree, 60 degrees ].

In order to reduce the friction resistance between the guide vane and the air flow, according to one aspect of the invention, the connecting line between the first starting point and the first ending point is a straight line segment, and the guide vane in the form is simple to process.

In order to reduce the friction resistance between the guide vane and the air flow, according to another aspect of the invention, the connecting line between the first starting point and the first ending point is a folded line segment. The diversion section generates separation vortex gas at the fold line concave part, the vortex can enable the airflow behind to slide like a wheel to reduce friction resistance, and also can avoid the small vortex from developing into a large vortex.

In order to reduce the friction resistance between the guide vane and the air flow, according to another aspect of the invention, the part corresponding to the guide section in the edge line section is also provided with a middle point, the connecting line between the first starting point and the middle point is an arc line section, and the middle point is connected with the first end point. The middle circular arc section can induce the transition of the airflow deflection to be less separated than the smooth guide surface, and the back surface is separated, but large vortex can be avoided.

In order to reduce the friction resistance between the guide vane and the air flow, according to another aspect of the invention, the part corresponding to the guide section in the edge line section is also provided with a middle point, the connecting line between the first starting point and the middle point is a spiral line section, and the middle point is connected with the first ending point. The spiral line segment can be changed along with the airflow, the size is long, the effect is more obvious than that of the circular arc segment, the transition for inducing the airflow deflection is smooth, the guide surface is seldom separated, and the back surface is separated, but large vortex can be avoided.

For ease of manufacture and installation, the guide vane further comprises a fixing section for fixing with the blade, the guide section extending outwardly from the fixing section.

Preferably, the outer diameter of the impeller is D2, on 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 part corresponding to the guide section is a first starting point, the ending point of the part corresponding to the guide section is a first ending point, the starting point of the part corresponding to the fixed section is a second starting point, the first starting point is the ending point of the edge line segment corresponding to the fixed section, the connecting line between the second starting point and the first starting point forms a straight line perpendicular to the axial direction of the centrifugal fan, and the value range of the ratio of the connecting line length between the second starting point and the first starting point to D2 is [0.004,0.08]. If the fixed section is too short to install, too long frictional resistance is too great and is liable to interfere with the volute tongue on the volute.

Preferably, the ratio of the total length of the edge line segment to the length of the straight line segment corresponding to the fixed segment is in the range of [1,8]. Too short guide section induces weak steering effect, too long guide section causes too large friction resistance and is easy to interfere with the volute tongue.

Preferably, the impeller has an outer diameter D2, and the ratio of the distance between any two adjacent guide vanes to D2 is within a range of [0.03,0.15] on the same side of the disk far from the air inlet side along the axial direction of the centrifugal fan. If the ratio is too low, the flow guide plate is too dense, the friction resistance is too high, the weight is increased, and the impeller efficiency is reduced; too high results in too sparse, and the flow guiding effect is weakened or not obvious.

Preferably, the centrifugal fan further comprises a volute, an air inlet is formed in the volute, and the impeller is a single-suction impeller or a double-suction impeller;

when the impeller is a single suction impeller, the number of the air inlets is one, the impeller comprises a front disc and a rear disc, the blades are respectively fixed with the front disc and the rear disc, the front disc is close to the air inlets, and the disc far away from the air inlets is the rear disc;

when the impeller is a double-suction impeller, the number of the air inlets is two, the impeller comprises a front disc, a middle disc and a rear disc, the blades are respectively fixed with the front disc, the middle disc and the rear disc, the front disc and the rear disc are respectively close to one of the air inlets, and the disc far away from the air inlet side is the middle disc.

Preferably, the flow deflector is mainly used for air flow outside the main acting area, the flow deflector is arranged outside a main flow area at the outlet of the blade, the main flow area is positioned adjacent to the disc far away from the air inlet side, and the value range of the ratio of the axial height of the main flow area to the axial height of the impeller is [0.1,0.5] along the axial direction of the centrifugal fan.

The invention solves the second technical problem by adopting the technical proposal that: a range hood, characterized in that: the centrifugal fan as described above is applied.

Compared with the prior art, the invention has the advantages that: by arranging the guide vane at the outlet of the vane, the guide vane is provided with a guide section deflected towards a disk far away from the air inlet side, so that the air flow can be induced to flow towards the outlet, the transverse flow is reduced, the risk of developing into secondary flow and even back flow is reduced, the integral acting capacity of the impeller is improved, the air quantity and efficiency can be improved under the condition of unchanged size or rotating speed, and the noise is reduced; the small compensation angle is arranged on the guide vane close to the main flow area, so that the air flow can pass through the guide vane, the flow resistance is reduced, the compensation angle is larger as the guide vane is farther from the main flow area, and the deviation rectifying guide capability is improved.

Drawings

FIG. 1 is a cross-sectional view of a centrifugal fan according to an embodiment of the invention;

FIG. 2 is an enlarged schematic view of part I of FIG. 1;

fig. 3 is a schematic view of a hidden volute (double suction impeller) of a centrifugal fan according to an embodiment of the present invention;

FIG. 4-1 is a simplified schematic cross-sectional view of a first embodiment of a baffle of a centrifugal fan of the present invention;

FIG. 4-2 is a flow field simulation schematic of FIG. 4-1;

FIG. 5-1 is a simplified schematic cross-sectional view of a second embodiment of a deflector of a centrifugal fan of the present invention;

FIG. 5-2 is a flow field simulation schematic of FIG. 5-1;

FIG. 6-1 is a simplified schematic cross-sectional view of a third embodiment of a deflector of a centrifugal fan of the present invention;

FIG. 6-2 is a flow field simulation schematic of FIG. 6-1;

FIG. 7-1 is a simplified schematic cross-sectional view of a first embodiment of a baffle of a centrifugal fan of the present invention;

FIG. 7-2 is a flow field simulation schematic of FIG. 7-1;

FIG. 8 is a schematic diagram of a centrifugal fan hiding volute and motor (single suction impeller) of an embodiment of the present invention;

FIG. 9 is a cross-sectional view of a centrifugal fan of the prior art;

fig. 10 is a flow field simulation velocity diagram of a centrifugal fan of the prior art.

Detailed Description

Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals refer to the same or similar elements or elements having the same or similar functions.

In the description of the present 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", "circumferential", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings are merely for purposes of describing the present invention and simplifying the description, and do not indicate or imply that the device or element being referred to must have a specific orientation, be configured and operated in a specific orientation, and because the disclosed embodiments of the present invention may be arranged in different orientations, these directional terms are merely for illustration and should not be construed as limitations, such as "upper", "lower" are not necessarily limited to orientations opposite or coincident with the direction of gravity. Furthermore, features defining "first", "second" may include one or more such features, either explicitly or implicitly.

Referring to fig. 1 to 3, a centrifugal fan includes a scroll 1, an impeller 2 disposed in the scroll 1, and a motor 3 for driving the impeller 2 to rotate. The volute 1 comprises two cover plates 11 which are arranged at intervals, an annular wall 12 which is formed between the cover plates 11, and an air inlet 13 is formed in the cover plates 11.

The impeller 2 comprises a front disc 21, a rear disc 22, a middle disc 23 and blades 24, wherein the middle disc 23 and the blades 24 are arranged between the front disc 21 and the rear disc 22, the two cover plates 11 are provided with air inlets 13, and the front disc 21 and the rear disc 22 are close to the corresponding air inlets 13. The blades 24 extend in the axial direction of the centrifugal fan, pass through the front plate 21, the middle plate 23, and the rear plate 22 described above, and are fixed to the front plate 21, the middle plate 23, and the rear plate 22, respectively. The number of the blades 24 is not less than 2, preferably about 60, to form a double suction impeller, and the centrifugal fan is a double air inlet fan. The impeller 2 alternatively does not comprise a middle disc 23 and forms a single suction impeller, see fig. 5, wherein only one cover plate 11 is provided with an air inlet 13, the front disc 21 is close to the air inlet 13, and the rear disc 22 is far away from the air inlet 13. The above structure is the same as that of the centrifugal fan in the prior art, and will not be described here again.

The centrifugal fan further comprises a guide vane 4, wherein the guide vane 4 is annular and is arranged at the outlet of each blade 24 (the outlet is the outer edge of the blade 24). The guide vanes 4 may have one or at least two, and when there are at least two, the guide vanes 4 are arranged at intervals along the axial direction of the centrifugal fan. Since the axial non-uniformity of the air flow in the main flow area is not obvious, the flow deflector 4 is preferably arranged outside the main flow area of the outlet of the blades 24 of the impeller 2, so that the cost can be reduced, and the main flow area is defined by the following modes: the main flow area is positioned at the position adjacent to the disc far away from the air inlet side, and the axial height of the main flow area is relative to the axial height of the impeller 2 along the axial direction of the centrifugal fan, and the ratio of the main flow area to the impeller 2 is [0.1,0.5]. When the impeller 2 is a single suction impeller, the disk far from the air intake side is the rear disk 22, and the main flow area is located between the rear disk 22 and the front disk 21 and extends from the rear disk 22 to the front disk 21, and the baffle 4 is disposed between the front disk 21 and the rear disk 22; when the impeller 2 is a double suction impeller, the disk far from the air intake side is a middle disk 23, and the main flow area is located at two axial sides of the middle disk 23, so that the overall axial height is kept as described above, and the ratio of two sides of the middle disk 23 is not strictly limited, and the flow guide 4 is arranged between the front disk 21 and the middle disk 23 and between the rear disk 22 and the middle disk 23. Of course, the guide vane 4 may be provided in the main flow region.

In the following, a double air intake fan is taken as an example, and a single air intake fan is similar to the double air intake fan, and the middle plate 23 is replaced by the rear plate 22. For easy processing and installation, the guide vane 4 includes a fixing section 41 and a guide section 42, where the fixing section 41 and the vane 24 can be fixed by clamping, welding, bonding, etc., and the fixing section extends radially outwards from the fixing position with the vane 24. The deflector segment 42 is located at the end of the stationary segment 41 remote from the blades 24 and is deflected towards the intermediate disk 23. The outer diameter of the impeller 2 is recorded as D2, the distance between the guide vanes on the same side of the disk far away from the air inlet side is L, the value range of L to D2 is [0.03,0.15], the friction resistance of the guide vane 4 is too large and the weight is increased when the density is too low, so that the efficiency of the impeller 2 is reduced; if the flow guiding sheet 4 is too high, the flow guiding effect is weakened or not obvious.

Referring to fig. 4-1 and 4-2, there is shown a simplified schematic illustration of a cross-section of a baffle according to one embodiment of the present invention, the cross-section being a cross-section through the axis of the centrifugal fan and perpendicular to the radial plane of the centrifugal fan, as shown in fig. 1 as the plane of the paper, and for clarity in illustrating the shape of the baffle 4, the cross-section is simplified as an edge line segment (inner or outer edge) of the baffle 4, with "inner" referring to the side facing the central disk 23 and "outer" referring to the side facing away from the central disk 23, the baffle 4 being in the form of an equal thickness sheet, whereby the inner and outer edges conform to the shape of the central disk 23. The meanings of fig. 5-1 to 7-2 are the same as those described above, and will not be repeated.

The start point of the edge line segment corresponding to the guide section 42 is a first start point B (also the end point corresponding to the fixed section 41), the end point is a first end point D, the start point of the edge line segment corresponding to the fixed section 41 is a second start point a, the second start point a is an end point fixed to the blade 24, the edge line segment corresponding to the fixed section 41 is a straight line segment perpendicular to the centrifugal fan, and the edge line segment of the guide section 42 is also a straight line segment. The outer diameter of the impeller 2 is denoted as D2, wherein the range of the size of the straight line section corresponding to the fixed section 41 and the value of D2 is [0.004,0.08], and if AB is too short to be installed, the friction resistance is too large and is easy to interfere with the volute tongue on the volute 1. AD (here, the total length of the edge line corresponding to the guide flow sheet 4) is AB (here, the length between two points) with the value range of [1,8], and too short the induced steering effect is weak, too long the friction resistance is too large and the volute tongue is easy to interfere. The two straight segments BD and AB are arranged obliquely with respect to each other.

The arrows in fig. 4-2 show the flow path of the air flow, whereby it is known that after the original deflected air flow passes the fixed section 41, deflection adjustment is performed on the guiding surface (the surface facing the middle disc 23) of the guiding section 42, and that the flow separation on the rear surface (the surface facing away from the middle disc 23) of the guiding vane 4 is also within an acceptable range. The guide vane 4 with the structure has the advantages of simple die and convenient processing, and can be obtained by bending or adding plastic edges through sheet metal.

Referring to fig. 5-1 and 5-2, there is shown a simplified schematic of a cross-section of a baffle according to one embodiment of the present invention, the edge line segment of the baffle segment 42 further having a midpoint C, which in the present invention is referred to as being located between the first point B and the first end point D, and is not defined as being the midpoint between the first point B and the first end point D. The BC connection line may be a folded line segment or a straight line segment, and the CD connection line type is not limited, but is preferably a straight line segment. Therefore, the edge line of the whole diversion section 42 forms a folding line section, separation vortex gas is generated at the concave position of the folding line, the vortex can enable the rear airflow to slide like a wheel to reduce friction resistance, small vortex can be prevented from being developed into large vortex, and because the large vortex is larger in damage noise, more energy is dissipated, the efficiency can be further improved, and the noise is reduced. AD (here, the total length of the edge line corresponding to the guide flow sheet 4) is AB (here, the length between two points) with the value range of [1,8], and too short the induced steering effect is weak, too long the friction resistance is too large and the volute tongue is easy to interfere.

Referring to fig. 6-1 and 6-2, there are shown simplified schematic diagrams of cross-sections of a baffle according to one embodiment of the present invention, differing from the embodiment shown in fig. 5-1 in that the midpoint is C ', the BC' line is a circular arc segment, the middle circular arc segment can be separated less from the smooth guide surface by the transition of arc-induced flow deflection, and the back side, although separated, can avoid large vortices.

Referring to fig. 7-1 and 7-2, there is shown a simplified schematic of a cross-section of a baffle according to one embodiment of the present invention, compared to the embodiment shown in fig. 6-1, with the difference that the midpoint is C ", the BC" line is a circular arc segment, the curvature can vary with helix angle, can vary with airflow, is of a longer dimension, has a more pronounced effect than the circular arc segment, induces a smooth transition of airflow deflection, has little separation of the guide surfaces, and, although the back surfaces are separated, can avoid large eddies. The spiral line can be an equiangular logarithmic spiral line or an angle-variable logarithmic spiral line so as to better adapt to deceleration flow after airflow flows out.

In the above embodiment, the diversion deflection compensation angle α is defined, which is the angle of deflection of the diversion section 42 toward the disk far from the air intake side, that is, the complementary angle of the included angle between the first end point D of the edge line section of the diversion section 42 and the axial direction of the centrifugal fan, and α gradually increases with the increase of the distance from the disk far from the air intake side, and the value range of α is [0 °,60 ° ], more preferably (0 °,60 ° ].

Claims (14)

1. A centrifugal fan comprising an impeller (2), the impeller (2) comprising a disc remote from an air intake side and at least two blades (24), the blades (24) being fixed to the disc remote from the air intake side; the method is characterized in that:

the centrifugal fan further comprises annular guide vanes (4), wherein the guide vanes (4) encircle the outlet of each blade (24) and extend outwards along the radial direction of the centrifugal fan from the fixing position of the guide vanes with the blades (24); the deflector (4) comprises a deflector segment (42), the deflector segment (42) being deflected towards the disk remote from the air intake side.

2. The centrifugal fan according to claim 1, wherein: along the axial direction of the centrifugal fan, on the same side of the disc far away from the air inlet side, the diversion deflection compensation angle (alpha) formed by deflection of the diversion section (42) gradually increases along with the increase of the distance from the disc far away from the air inlet side.

3. The centrifugal fan according to claim 1, wherein: the deflection of the flow guiding section (42) forms a flow guiding deflection compensation angle (alpha), the flow guiding sheet (4) is provided with an edge line segment at one side of the axial direction of the centrifugal fan, the starting point of the part corresponding to the flow guiding section (42) in the edge line segment is a first starting point (B), the ending point of the part corresponding to the flow guiding section (42) is a first ending point (D), the flow guiding deflection compensation angle (alpha) is the complementary angle of an included angle between a straight line connecting line between the first starting point (B) and the first ending point (D) and the axial direction of the centrifugal fan, and the value range of the flow guiding deflection compensation angle (alpha) is [0 DEG, 60 DEG ].

4. A centrifugal fan according to claim 3, wherein: the connecting line between the first starting point (B) and the first ending point (D) is a straight line segment.

5. A centrifugal fan according to claim 3, wherein: the connecting line between the first starting point (B) and the first ending point (D) is a folded line segment.

6. A centrifugal fan according to claim 3, wherein: the part corresponding to the diversion section (42) in the edge line segment is also provided with a middle point (C '), the connecting line between the first starting point (B) and the middle point (C ') is an arc line segment, and the middle point (C ') is connected with the first end point (D).

7. A centrifugal fan according to claim 3, wherein: the part corresponding to the diversion section (42) in the edge line segment is also provided with a middle point (C '), the connecting line between the first starting point (B) and the middle point (C ') is a spiral line segment, and the middle point (C ') is connected with the first ending point (D).

8. The centrifugal fan according to claim 1, wherein: the guide vane (4) further comprises a fixing section (41) for fixing with the blade (24), and the guide section (42) extends outwards from the fixing section (41).

9. The centrifugal fan according to claim 8, wherein: the outer diameter of the impeller (2) is D2, the cross section of the guide vane (4) is provided with an edge line segment at one side in the axial direction of the centrifugal fan, in the edge line segment, the starting point of the part corresponding to the guide section (42) is a first starting point (B), the ending point of the part corresponding to the guide section (42) is a first ending point (D), the starting point of the part corresponding to the fixed section (41) is a second starting point (A), the first starting point (B) is the ending point of the edge line segment corresponding to the fixed section (41), a connecting line between the second starting point (A) and the first starting point (B) forms a straight line perpendicular to the axial direction of the centrifugal fan, and the value range of the ratio of the connecting line length between the second starting point (A) and the first starting point (B) to the D2 is [0.004,0.08].

10. The centrifugal fan according to claim 9, wherein: 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) is in the range of [1,8].

11. The centrifugal fan according to claim 1 or 2, wherein: the outer diameter of the impeller (2) is D2, and the value range of the ratio of the interval between any two adjacent guide vanes (4) and D2 is [0.03,0.15] on the same side of the disc far away from the air inlet side along the axial direction of the centrifugal fan.

12. The centrifugal fan according to claim 1 or 2, wherein: the centrifugal fan further comprises a volute (1), an air inlet (13) is formed in the volute (1), 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 the air inlets (13) is one, the impeller (2) comprises a front disc (21) and a rear disc (22), the blades (24) are respectively fixed with the front disc (21) and the rear disc (22), the front disc (21) is close to the air inlets (13), and the disc far away from the air inlets is the rear disc (22);

when impeller (2) are double suction impeller, the quantity of air intake (13) is two, impeller (2) are including front disc (21), middle dish (23) and back dish (22), blade (24) are fixed with front disc (21), middle dish (23) and back dish (22) respectively, front disc (21) and back dish (22) are close to one of them air intake (13) respectively, keep away from the dish of air inlet side and be middle dish (23).

13. The centrifugal fan according to claim 12, wherein: the guide vane (4) is arranged outside a main flow area at the outlet of the vane (24), the main flow area is positioned adjacent to the disc far away from the air inlet side, and the value range of the ratio of the axial height of the main flow area to the axial height of the impeller (2) along the axial direction of the centrifugal fan is 0.1 and 0.5.

14. A range hood, characterized in that: use of a centrifugal fan according to any one of claims 1-13.

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