CN112377457A

CN112377457A - Impeller, centrifugal fan applying same and range hood

Info

Publication number: CN112377457A
Application number: CN202011090481.1A
Authority: CN
Inventors: 雷改
Original assignee: Ningbo Fotile Kitchen Ware Co Ltd
Current assignee: Ningbo Fotile Kitchen Ware Co Ltd
Priority date: 2020-10-13
Filing date: 2020-10-13
Publication date: 2021-02-19
Anticipated expiration: 2040-10-13
Also published as: CN112377457B; WO2022077585A1

Abstract

The invention discloses an impeller, which comprises a front disk, a rear disk and blades arranged between the front disk and the rear disk, and is characterized in that: the inlet mounting angle of the blades is gradually increased from the front disc to the rear disc along the axial direction of the impeller. Also discloses a centrifugal fan applying the impeller and a range hood applying the centrifugal fan. Compared with the prior art, the invention has the advantages that: by arranging the inlet installation angle gradually changed along the axial direction, the acting capacity is matched with the gas flow, so that the nonuniformity of the speed of the outlet of the impeller is improved, and the secondary vortex near the upper cover surface of the volute can be improved; through making the blade form the breach in the place of head disk, form and become internal diameter structure, can further improve the inhomogeneity of impeller exit velocity, can also widen the blade way, increase the air input.

Description

Impeller, centrifugal fan applying same and range hood

Technical Field

The invention relates to an oil fume purification device, in particular to a range hood.

Background

The range hood has become one of the indispensable kitchen household electrical appliances in modern families. The range hood works by utilizing the fluid dynamics principle, sucks and exhausts oil smoke through a centrifugal fan arranged in the range hood, and filters partial grease particles by using a filter screen. The centrifugal fan comprises a volute, an impeller arranged in the volute and a motor driving the impeller to rotate. When the impeller rotates, negative pressure suction is generated in the center of the fan, oil smoke below the range hood is sucked into the fan, accelerated by the fan and then collected and guided by the volute to be discharged out of a room.

For thin type machine of range hood, the fan system is generally placed horizontally, and the air outlet is mainly used for top air outlet. The ultra-thin top-suction type range hood disclosed in the chinese patent with the application number of 201720917014.9 at least comprises a shell and an air supply structural member, wherein the air supply structural member comprises a fan volute, a motor and a wind wheel which are matched with the fan volute for use, the fan volute comprises a front cover plate and a middle annular wall, the front cover plate is vertically connected with the front cover plate in a continuous smooth transition mode, and an inner flow channel with an upper opening and an air supply opening are formed in the middle annular wall.

Under the condition, the air inlet and the air outlet of the fan system are in the same direction, so that the fluid enters the volute in the fan system and turns 90 degrees, and after centrifugal throwing and sucking purification by the centrifugal impeller in the volute, the fluid can be discharged through the air outlet after turning 90 degrees. The fluid passes through two 90-degree turns at a high speed, the noise and energy loss of the fluid are large, and the noise is obviously high when the performance of the whole machine is under the same air volume.

Therefore, axial flow impellers and mixed flow impellers are adopted in the market, and the two impellers are relatively suitable for the range hood of the horizontal fan system. According to the range hood of the horizontal parallel double-fan system type, the axial flow impeller or the mixed flow impeller is adopted to better accord with the fluid motion rule, but the axial flow impeller, the mixed flow impeller, the centrifugal impeller and other impellers in the current market have the characteristic of high noise, so that the noise is still obviously higher in the performance test of the whole range hood in domestic use; a multi-blade centrifugal impeller (i.e., a sirocco-type impeller, which is a forward-facing impeller characterized by a large diameter ratio, a large relative width, and a large number of blades, but has low efficiency) is the only one with low noise. Therefore, although the axial flow impeller and the mixed flow impeller are relatively more suitable for the flow field motion law of the range hood, the noise of the impeller is high, and the multi-wing centrifugal impeller still has low noise under the same air volume through experimental comparison.

The most multi-wing centrifugal impeller of the range hood is composed of front and rear end disks of the impeller, blades, a wheel disk and the like. The blades of this type of impeller have equal chord lengths in the height direction. Because the impeller front disc is of a plane structure, a certain distance is reserved between the impeller front cover disc and the volute casing in consideration of the dynamic balance of the impeller, and the backflow phenomenon is easy to occur at the position. Furthermore, because the fluid enters the impeller from the flow collector along the axial direction and the relative width of the multi-wing centrifugal impeller is large, the air flow at the inlet of the fan impeller blade is wholly inclined towards the disk side in the axial direction of the impeller. The impeller outlet airflow is influenced by the air inlet condition and is unevenly distributed along the axial direction, so that secondary vortex in the volute of the forward fan is caused. Referring to fig. 18, the air flow enters the impeller through the flow collector to form a larger positive attack angle, and when the same impeller runs at a small flow rate, a larger positive attack angle is generated than that under a large-flow working condition.

Disclosure of Invention

The first technical problem to be solved by the present invention is to provide an impeller capable of reducing noise, aiming at the defects of the prior art.

The second technical problem to be solved by the invention is to provide a centrifugal fan using the impeller.

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

The technical scheme adopted by the invention for solving the first technical problem is as follows: the utility model provides an impeller, includes preceding dish, after-disc and sets up the blade between preceding dish and after-disc, its characterized in that: the inlet mounting angle of the blades is gradually increased from the front disc to the rear disc along the axial direction of the impeller.

Preferably, the inlet installation angle of each position of the vane along the axial direction is in a range of 65-87 degrees.

The chord length of the blade at the front disk is L1, the chord length of the blade at the rear disk is L2, the chord length of the blade gradually decreases from the front disk to the rear disk along the axial direction of the impeller, the outer diameter of the impeller is D2, the inner diameter of the impeller is D1, and the L1 is satisfied: l2 ∈ [15:14,5:2], D1: d2 ∈ [0.78,0.88 ].

According to one aspect of the invention, the impeller further comprises a middle disc positioned between the front disc and the rear disc, the blades penetrate through the middle disc, the chord length of the blades at the front disc is L1, the chord length of the blades at the rear disc is L2, the chord length of the blades at the middle disc is L3, the chord length of the blades gradually increases from the front disc to the middle disc and gradually decreases from the middle disc to the rear disc along the axial direction of the impeller, the outer diameter of the impeller is D2, the inner diameter of the impeller is D1, and L3: l1 ∈ [15:14,5:2], L3: l2 ∈ [15:14,5:2], D1: d2 ∈ [0.78,0.88 ].

According to another aspect of the invention, the vanes have outlet ends, the outlet ends of the vanes being straight between the front disk and the center disk, and between the center disk and the rear disk; or the outlet ends of the blades are curved between the front disc and the middle disc and between the middle disc and the rear disc, and the curves are Bezier curves or Archimedes spiral lines.

According to another aspect of the present invention, the chord length of the blade at the front disk is L1, the chord length of the blade at the rear disk is L2, the chord length of the blade gradually increases from the front disk to the rear disk in the impeller axial direction, the impeller outer diameter is D2, the impeller inner diameter is D1, and L1: l2 ∈ [2:5,14:15], D1: d2 ∈ [0.78,0.88 ].

In order to further improve the nonuniformity of the outlet speed of the blades, one end of each blade, which is connected with the front disc, is provided with a notch, the notch is formed by sinking from the inlet of each blade to the outlet direction, the overall height of each blade is B, the height of the notch is B1, and B1/B epsilon [1/16B, 3/16B ] is satisfied.

Preferably, the molded line of the notch comprises a linear section and a curved section which are sequentially connected, the starting point of the linear section is close to the front disc, the end point of the linear section is the same as the starting point of the curved section, the end point of the curved section is far away from the front disc, and the curved section is a smooth transition section.

In order to facilitate the impeller to be installed in the centrifugal fan, the airflow backflow phenomenon at the gap between the front disc and the volute is optimized, and the working efficiency of the centrifugal fan is improved.

Preferably, the molded line of the curved surface includes a first line segment, a second line segment and a third line segment which are smoothly connected in sequence from inside to outside in the radial direction, the first line segment is an arc-shaped transition segment, the second line segment is a variable helix angle logarithmic spiral line segment, and the third line segment is a bezier curve segment.

The technical scheme adopted by the invention for solving the second technical problem is as follows: a centrifugal fan, its characterized in that: an impeller as described above is applied.

The technical scheme adopted by the invention for solving the third technical problem is as follows: a range hood, its characterized in that: a centrifugal fan as described above is applied.

Compared with the prior art, the invention has the advantages that: by arranging the inlet installation angle gradually changed along the axial direction, the acting capacity is matched with the gas flow, so that the nonuniformity of the outlet speed of the impeller is improved, and when the impeller is applied to a fan, the secondary vortex near the upper cover surface of the volute can be improved; the blades form gaps at the front disc to form a variable inner diameter structure, so that the nonuniformity of the outlet speed of the impeller can be further improved, the blade channel can be widened, and the air inflow can be increased; the front end surface of the front disc adopts a curved surface design, so that when the front disc is applied to a fan, the airflow backflow phenomenon at the gap between the front disc and the volute can be optimized, and the working efficiency of a fan system is improved; the impeller is an inclined impeller, so that the flow separation area in the blade channel can be reduced, the flow separation degree is weakened, and the fluid noise is reduced.

Drawings

FIG. 1 is a schematic view of a range hood according to an embodiment of the present invention;

FIG. 2 is a cross-sectional view of a range hood in accordance with an embodiment of the present invention;

FIG. 3 is a schematic view of a first embodiment of the impeller of the present invention;

FIG. 4 is a side view of a first embodiment of the impeller of the present invention;

FIG. 5 is a front view (looking rearward from the front disk) of the vanes of the first embodiment of the impeller of the present invention;

FIG. 6 is a rear view (looking forward from the back disk) of the vanes of the first embodiment of the impeller of the present invention;

FIG. 7 is a schematic view of a blade of a first embodiment of an impeller of the present invention;

FIG. 8 is a schematic view of the front disk of the first embodiment of the impeller of the present invention;

FIG. 9 is an enlarged view of a portion I of FIG. 8;

fig. 10 is a schematic diagram illustrating a simulation of a flow field trajectory in an impeller vane according to a first embodiment of the present invention.

FIG. 11 is a side view of a second embodiment of the impeller of the present invention;

FIG. 12 is a schematic view of a vane of a second embodiment of an impeller of the present invention;

FIG. 13 is a side view of a third embodiment of the impeller of the present invention;

FIG. 14 is a schematic view of a third embodiment of a vane of an impeller of the present invention;

FIG. 15 is a side view of a fourth embodiment of the impeller of the present invention;

FIG. 16 is a schematic view of a vane of a fourth embodiment of an impeller of the present invention;

FIG. 17 is a side view of a fifth embodiment of the impeller of the present invention;

FIG. 18 is a schematic view of a blade of a fifth embodiment of an impeller of the present invention;

fig. 19 is a schematic diagram of a simulation of a flow field trajectory in a straight impeller blade path in the prior art.

Detailed Description

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like 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 is to be understood that the terms "central," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," "circumferential," and the like are used in the orientations and positional relationships indicated in the drawings for convenience in describing the present invention and to simplify the description, but are not intended to indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and that the directional terms are used for purposes of illustration and are not to be construed as limiting, for example, because the disclosed embodiments of the present invention may be oriented in different directions, "lower" is not necessarily limited to a direction opposite to or coincident with the direction of gravity. Furthermore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature.

Referring to fig. 1 and 2, a range hood, which is a thin range hood in the present embodiment, includes a smoke collecting hood 400 and a fan system disposed in the smoke collecting hood 400, where the fan system is two horizontal centrifugal fans 100 arranged in parallel. Alternatively, the centrifugal fan 100 may be used in other types of range hoods, such as a top suction type, a side suction type, etc., or the fan system may be a single fan system.

Centrifugal fan 100 includes a volute 300 and an impeller 200 disposed within volute 300.

Example one

Referring to fig. 3 and 4, the impeller 200 includes a front disk 1, a rear disk 2, and blades 3 disposed between the front disk 1 and the rear disk 2, the blades 3 having at least two, arranged at intervals along a circumferential direction of the front disk 1 (or the rear disk 2). The number of blades 3 is about 60. Centrifugal fan 100 is two air inlet fan, and impeller 200 still includes well dish 4, and well dish 4 is located between front bezel 1 and the back plate 2, and blade 3 passes well dish 4.

The "inlet mount angle" described below means: the included angle between the tangent of the leading edge point of the blade and the tangent of the circumference of the impeller at that point.

Referring to fig. 5 and 6, since the impeller 200 of the present invention has no prerotation effect in the centrifugal fan 100, the theoretical design is that the airflow enters the blades 3 vertically, i.e. the inlet installation angle is 90 °, but before the actual airflow enters the impeller 200, the impeller 200 rotates to drive the surrounding airflow to move, so that the nearby airflow has a prerotation-like inlet angle, the airflow enters the impeller along the axial direction, the airflow changes from the axial direction to the radial direction, and the inlet installation angle of the blades 3 along the axial direction is smaller than 90 °. The inlet setting angle of the blades 3 at the front disc 1, i.e. the first inlet setting angle, is beta₁The inlet setting angle of the blades 3 at the rear disc 2, i.e. the second inlet setting angle, is beta₂. Since the gas flow rate near the front disk 1 is smaller than the gas flow rate in the axially intermediate portion (the middle disk 4) and near the rear disk 2, the first inlet setting angle is β in the present embodiment₁Angle of beta less than the second inlet₂. Under the condition that the inlet mounting angles are different, the chord lengths of the blades 3 are also different, and the working capacities of the corresponding blades 3 are different, namely the first inlet mounting angle at the front disc 1 is beta₁The flow rate of the gas at the front disk 1 is small, the structure is matched with the flow rate, and the nonuniformity of the outlet speed is reduced. The vane 3 is gradually increased from the forward inlet mounting angle to the backward inlet mounting angle along the axial direction, and preferably, the inlet mounting angle of each position of the vane 3 along the axial direction ranges from 65 degrees to 87 degrees.

Referring to fig. 3 and 7, the impeller 200 has a small power capability near the front disk 1, and in order to widen the flow passage, a notch 31 is cut at one end of each blade 3 connected to the front disk 1 to increase the outlet diameter of the collector and thus increase the flow rate of the intake air, and the notch 31 is formed by being recessed from the inlet of each blade 3 toward the outlet. The molded line of the notch 31 includes a straight line segment a 'B' and a curved line segment B 'C' connected in sequence, a starting point a 'of the straight line segment a' B 'is close to the front disc 1, an end point B' of the straight line segment a 'B' is the same as a starting point B 'of the curved line segment B' C ', and an end point C' of the curved line segment B 'C' is far from the front disc 1. The curved line segment B 'C' is preferably a logarithmic spiral segment. The straight line section A 'B' is parallel to the velocity vector of the airflow inlet, the curved line section B 'C' is a smooth transition section, the logarithmic spiral adopts a variable spiral angle, the variable spiral angle is gradually increased or gradually reduced, the range of the variable spiral angle is-2 degrees to 2 degrees, and the initial radius of the logarithmic spiral is 5 mm. The height (dimension in the axial direction of the impeller 200) of the entire blade 3 is B, the height of the notch 31 is B1, B1/B is preferably [1/16B, 3/16B ], and more preferably 1/8.

Thereby, the impeller 200 forms a variable inner diameter structure. The main part of the impeller 200 that does work is near the rear disc 2 and the intermediate disc 4, while at the front disc 1 it does less work. The impeller 200 has an outer diameter of 250mm, an inner diameter of the impeller 200 is equal, preferably 198mm, at the portion of the blade 3 except the notch 31, and the inner diameter of the impeller 200 is 215mm at the maximum at the notch 31 of the blade 3.

The variable inlet mounting angle and the variable inner diameter structure of the vane 3 improve the nonuniformity of the outlet speed of the impeller 200, and contribute to improving the secondary vortex near the upper cover surface of the volute 300.

Referring to fig. 4, 8 and 9, in order to optimize the air flow confluence phenomenon at the gap between the front disk 1 and the scroll 300, the centrifugal fan operation efficiency is improved. The front end surface of the front disc 1 adopts a curved surface design, the radial inner side of the front disc 1 is towards the radial outer side, the front end surface of the front disc gradually inclines towards the rear disc 2, and the inclined surface is a curve which is sunken towards the impeller 200. The curved surface is flush with or slightly higher than the upper cover surface of the volute 300 at the upper vertex (the end part of the inner side of the front disc 1) in the assembly of the centrifugal fan, is matched with the current collector for use, is in accordance with the motion rule of the inlet fluid, and can effectively inhibit the airflow backflow phenomenon caused by the hesitation clearance between the impeller and the volute 300.

The molded line of the curved surface is mainly designed by a variable helix angle logarithmic spiral line and a Bezier curve, and comprises a first line segment AB, a second line segment BC and a third line segment CD which are smoothly connected from inside to outside in turn in the radial direction. Wherein the first line segment AB is a circular arc shaped transition segment. The second line segment BC is a logarithmic spiral line segment with a variable helix angle, the effective height of the impeller 200 is increased in the space with the limited volute 300 height, the work capacity is improved, the air quantity is increased, backflow is inhibited, the noise is reduced, and the gap between the front disc 1 and the volute 300 is optimizedThe air flow backflow phenomenon improves the working efficiency of the fan system. The second segment BC adopts a variable helical angle, the variable helical angle is gradually increased or gradually reduced, the range of the variable helical angle is preferably-5 degrees, and the initial radius of the logarithmic helical line is preferably 15 mm. The third line segment CD is a Bezier curve segment which comprises three sections of Ce, ed and dD and is smoothly connected, and preferably, the Bezier curve preferably satisfies the equation B (t) C (1-t)³+3·e·t·(1-t)²+3·d·(1-t)·t²+D·t³Where t is [0,1 ]]And C, e, D and D are four-point coordinates (the coordinate system takes the point D as an origin, the radial direction of the impeller 200 is an X axis, and the axial direction of the impeller 200 is a Y axis).

To reduce the flow separation area within the vane passage, the degree of flow separation is reduced, thereby reducing fluid noise. Referring to fig. 7, the blades 3 are of a pitched blade design, constituting a pitched impeller. The vane inlet setting angle and the impeller inner diameter are kept consistent (the inlet end of the vane 3 is parallel to the axis of the impeller 200), and the vane chord length and the outlet setting angle are changed (the outlet end of the vane 3 is inclined relative to the axis of the impeller 200). Fluid simulation is carried out on a flow field in a range hood fan system by adopting ANSYS18.0, and an airflow trace diagram in an impeller blade path is simulated by the fluent18.0 under the condition that other structures of a multi-wing centrifugal oblique impeller and a traditional straight impeller are kept unchanged respectively. As can be seen from fig. 10, the multi-wing centrifugal oblique impeller has a small positive attack angle of the airflow in the blade channel, and only a small number of flow separation areas are arranged inside the impeller; the positive attack angle of the air flow in the blade channel of the traditional straight impeller is obviously larger, and the flow separation area in the blade channel is more. Therefore, the flow separation phenomenon in the impeller blade channel is improved by improving the shape of the impeller blade, the working efficiency of the fan system is improved, and the noise of the fan system is reduced. In the test of the whole machine, a square-Tai-semi anechoic chamber is adopted to test the noise of the whole machine, and only the impeller is replaced, so that the noise of the multi-wing centrifugal oblique impeller is 1.5dB lower than that of the traditional multi-wing centrifugal straight impeller.

The outlet end 32 of the blade 3 forms a bevel edge which is an inclined straight line and is directly designed to delay the wake vortex from falling off along the axial direction according to linearity, so that the flow of fluid in the impeller is improved, and compared with the traditional impeller, the phenomenon of flow separation of air flow in the impeller is obviously reduced.

The chord length of the blade 3 at the front disk 1 is L1, the chord length of the blade 3 at the rear disk 2 is L2, the chord length of the blade 3 gradually decreases from the front disk 1 to the rear disk 2 in the impeller axial direction, and L1: L2E [15:14,5:2], the outer diameter of the impeller is D2, the inner diameter of the impeller is D1, D1: d2 ∈ [0.78,0.88 ]. Here D1 is taken to be where the blade 3 is unnotched 31. If the inclined angle of the inclined edge of the blade 3 is too large, the efficiency of the fan system is influenced, the overall efficiency of the fan system is reduced, the inclined angle is too small, the overall performance is changed slightly, and within the range, the performance of the fan system on the overall machine can be ensured, and the noise can be effectively reduced.

Example two

Referring to fig. 11 and 12, the present embodiment is different from the first embodiment in that the chord lengths of the blades 3 gradually increase from the front disk 1 to the middle disk 4 and gradually decrease from the middle disk 4 to the rear disk 2 in the axial direction of the impeller 200. The outlet ends of the vanes 3 are beveled between the front disk 1 and the central disk 4 and between the central disk 4 and the rear disk 2. The blade 3 still has the function of reducing the flow separation of the air flow in the blade channel of the impeller, thereby reducing the noise, and the structure of the blade 3 is simple to install.

The chord length of the blade 3 at the position corresponding to the central disc 4 is L3, and L3: l1 ∈ [15:14,5:2], L3: l2 ∈ [15:14,5:2], D1: d2 ∈ [0.78,0.88 ]. The height of the blades 3 between the front disk 1 and the middle disk 4 and the height of the blades 3 between the middle disk 4 and the rear disk 2 can be given according to the fluid motion law in the impeller 200 and the actual requirement.

EXAMPLE III

Referring to fig. 13 and 14, the difference from the second embodiment is that the outlet ends of the blades 3 are curved between the front disk 1 and the middle disk 4 and between the middle disk 4 and the rear disk 2, and the curves can adopt bezier curves or archimedes spiral lines according to the fluid motion law. According to the actual fluid flow requirement, two points of the front disc and the rear disc are determined, and a curve is fitted for the highest point of the blade at the place where the fluid is most unobstructed. Because the blade 3 of the type can better fit the law of fluid motion along the axial direction, the blade 3 has better effect of reducing the flow separation of air flow in the blade channel of the impeller 200, thereby reducing noise.

Example four

Referring to fig. 15 and 16, the present embodiment is different from the first embodiment in that the inclined direction of the outlet end of the blade 3 is opposite to that of the first embodiment, that is, the chord length of the blade 3 gradually increases from the front disk 1 to the rear disk 2, and L1: l2 ∈ [2:5,14:15], D1: d2 ∈ [0.78,0.88 ].

EXAMPLE five

Referring to fig. 17 and 18, in the present embodiment, the difference from the first embodiment is that the centrifugal fan 100 is a single-intake fan, that is, the impeller 200 is not provided with the central disk 4, and the form of the blades 3 remains unchanged, which still can reduce the flow separation of the airflow in the blade path of the impeller, thereby playing a role in reducing noise.

Claims

1. An impeller, includes preceding dish (1), after-disc (2) and sets up blade (3) between preceding dish (1) and after-disc (2), its characterized in that: and the inlet installation angle of the blade (3) is gradually increased from the front disc (1) to the rear disc (2) along the axial direction of the impeller.

2. The impeller of claim 1, wherein: the inlet mounting angles of the blades (3) at all positions along the axial direction are in the range of 65-87 degrees.

3. The impeller of claim 1, wherein: the chord length of the blade (3) at the front disc (1) is L1, the chord length of the blade (3) at the rear disc (2) is L2, the chord length of the blade (3) is gradually reduced from the front disc (1) to the rear disc (2) along the axial direction of the impeller, the outer diameter of the impeller is D2, the inner diameter of the impeller is D1, and L1 is satisfied: l2 ∈ [15:14,5:2], D1: d2 ∈ [0.78,0.88 ].

4. The impeller of claim 1, wherein: the impeller further comprises a middle disc (4) positioned between the front disc (1) and the rear disc (2), the blades (3) penetrate through the middle disc (4), the chord length of the blades (3) at the front disc (1) is L1, the chord length of the blades (3) at the rear disc (2) is L2, the chord length of the blades (3) at the middle disc (4) is L3, the chord length of the blades (3) gradually increases from the front disc (1) to the middle disc (4) and gradually decreases from the middle disc (4) to the rear disc (2) along the axial direction of the impeller, the outer diameter of the impeller is D2, the inner diameter of the impeller is D1, and L3 is satisfied: l1 ∈ [15:14,5:2], L3: l2 ∈ [15:14,5:2], D1: d2 ∈ [0.78,0.88 ].

5. The impeller of claim 4, wherein: the blades (3) are provided with outlet ends (32), and the outlet ends (32) of the blades (3) are straight lines between the front disc (1) and the middle disc (4) and between the middle disc (4) and the rear disc (2); or the outlet ends (32) of the blades (3) are curved between the front disc (1) and the middle disc (4) and between the middle disc (4) and the rear disc (2), and the curves are Bezier curves or Archimedes spiral lines.

6. The impeller of claim 1, wherein: the chord length of the blade (3) at the front disc (1) is L1, the chord length of the blade (3) at the rear disc (2) is L2, the chord length of the blade (3) gradually increases from the front disc (1) to the rear disc (2) along the axial direction of the impeller, the outer diameter of the impeller is D2, the inner diameter of the impeller is D1, and L1 is satisfied: l2 ∈ [2:5,14:15], D1: d2 ∈ [0.78,0.88 ].

7. The impeller according to any one of claims 1 to 6, wherein: one end of each blade (3) connected with the front disc (1) is provided with a notch (31), each notch (31) is formed by sinking from the inlet to the outlet of each blade (3), the overall height of each blade (3) is B, the height of each notch (31) is B1, and B1/B epsilon [1/16B, 3/16B ] is met.

8. The impeller of claim 7, wherein: the molded line of the notch (31) comprises a straight line segment (A 'B') and a curve segment (B 'C') which are connected in sequence, the starting point (A ') of the straight line segment (A' B ') is close to the front disc (1), the end point (B') of the straight line segment (A 'B') is the same as the starting point (B ') of the curve segment (B' C '), the end point (C') of the curve segment (B 'C') is far away from the front disc (1), and the curve segment (B 'C') is a smooth transition segment.

9. The impeller according to any one of claims 1 to 6, wherein: the front end face of the front disc (1) is designed to be a curved surface, the front end face of the front disc (1) gradually inclines towards the direction of the rear disc (2) from the radial inner side to the radial outer side, and the inclined front end face is a curve which is sunken towards the impeller.

10. The impeller of claim 9, wherein: the molded line of the curved surface comprises a first line segment (AB), a second line segment (BC) and a third line segment (CD) which are sequentially and smoothly connected from inside to outside in the radial direction, wherein the first line segment (AB) is an arc-shaped transition segment, the second line segment (BC) is a variable helix angle logarithmic spiral line segment, and the third line segment (CD) is a Bezier curve segment.

11. A centrifugal fan, its characterized in that: use of an impeller according to any one of claims 1 to 10.

12. A range hood, its characterized in that: use is made of a centrifugal fan according to claim 10.