CN215214096U - Forward blade for centrifugal fan impeller, centrifugal fan and range hood - Google Patents

Abstract

The utility model relates to a preceding to blade for centrifugal fan impeller, include: a blade body; supplementary blade of making an uproar falls, locate the second side of blade body, this supplementary blade of making an uproar falls extends to the direction of keeping away from first side from the second side, and to the pressure surface one side bending of blade body, thereby make this supplementary blade also be the arc on the whole, the width of the supplementary blade of making an uproar falls is less than the width of blade body, and the both sides border of the width direction of the supplementary blade of making an uproar falls has the interval with the both sides border of the width direction of blade body, the length of the supplementary blade of making an uproar falls is less than the length of blade body. The forward sweep design of the auxiliary noise reduction blade increases the integral axial chord length of the forward blade, better improves the separation flow in the middle of the air channel, inhibits the development of low-energy fluid mass on the pressure surface side, weakens the low-energy fluid mass on the suction surface side, greatly improves the integral through-flow condition of the air channel and reduces the aerodynamic noise. Still relate to a centrifugal fan and range hood.

Description

Forward blade for centrifugal fan impeller, centrifugal fan and range hood

Technical Field

The utility model relates to a range hood technical field especially relates to a preceding to blade, centrifugal fan and range hood for centrifugal fan impeller.

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. The centrifugal fan can divide the impeller of the fan into a forward type, a radial type and a backward type according to the angle of the blade at the air outlet end of the impeller. The blade of the centrifugal fan is provided with a pressure surface and a suction surface, wherein the pressure surface of the blade is a working surface, namely the windward surface of the blade; the suction surface of the blade is a non-working surface, namely the leeward surface of the blade.

The traditional range hood adopts a forward centrifugal fan, has a large number of blades, and has the characteristics of compact structure, high pressure coefficient, low flow coefficient and the like. When the range hood works, the motor is directly connected with the impeller to drive the impeller to rotate, and the axially sucked oil smoke is radially thrown out of the impeller from the center of the impeller under the action of centrifugal force. However, because the airflow has large impact on the front edge of the blade and the curvature of the blade is large, a counter pressure gradient is easily formed on the surface of the blade, flow separation at the tail edge of the suction surface is caused, the flow of the main flow area of the impeller is disturbed, the vortex shedding is generated at the tail edge, the flow loss is increased, meanwhile, the wall surface of the blade generates large pressure pulsation, large aerodynamic noise is generated, the large aerodynamic noise is a source for disturbing the quiet environment, and the kitchen environment is seriously influenced.

Therefore, for example, a chinese patent with the application number of cn20141032458. x (with the publication number of CN104100570B) discloses a bionic impeller for a range hood, which includes a plurality of groups of annular end surfaces and blades, wherein the blades are uniformly bridged between each two groups of annular end surfaces, the blades are bionic blades, the bionic blades face the suction side of the impeller range hood and are the leading edges of the waveform structure, and the tail edges of the sawtooth structure face the blowing side of the impeller range hood. The bionic blade is used for reducing the pressure impact of the front edge and the shedding frequency of the vortex of the tail edge, so that the pneumatic noise of the impeller during working is reduced.

For another example, chinese patent application No. CN201810157430.2 (publication No. CN108386383A) discloses a cross bionic blade combining a decapterus maruadsi body and a bird wing and a method for manufacturing the same, which includes a blade body, wherein a cross section of the blade body is in a profile imitating a cross section of a decapterus maruadsi, a mean camber line of the cross section of the blade body is in a single circular arc shape, a center position, a circular arc radius, and a circular arc center angle of the mean camber line of the cross section of the blade body are determined according to a design method of a front camber line of a multi-wing centrifugal fan, an end surface of the blade body facing a suction side of an impeller is in a wave-shaped structure, and an end surface of the blade body facing a blowing side of the impeller is in a zigzag structure.

Although the bionic impeller or the bionic blade structure in the patent plays a role in reducing the aerodynamic noise of the impeller during operation to a certain extent, the bionic impeller or the bionic blade structure is used for a forward fan of the range hood, and because the outlet angle of the blade of the bionic impeller is always over 160 degrees, a large amount of airflow is still easily accumulated at the outlet of the blade channel, the airflow resistance is large, the airflow of the blade channel is not smoothly discharged, and the aerodynamic performance is influenced. Therefore, how to improve the problem of airflow accumulation in the impeller flow channel of the centrifugal fan, improve the fluency of the airflow, and further reduce the aerodynamic noise becomes a technical problem to be solved urgently by the technical personnel.

SUMMERY OF THE UTILITY MODEL

The utility model discloses the first technical problem that will solve is to prior art's current situation, provides one kind and can effectively improve centrifugal fan impeller runner air current and pile up the problem, improves the smoothness degree of air current, and then reduces pneumatic noise's the preceding blade that is used for centrifugal fan.

The utility model discloses the second technical problem that will solve is to prior art's current situation, provides one kind and can effectively improve centrifugal fan impeller runner air current and pile up the problem, improves the smoothness degree of air current, and then reduces being used for centrifugal fan of pneumatic noise.

The utility model aims to solve the third technical problem to prior art's current situation, provide an above-mentioned centrifugal fan's range hood.

The utility model provides a technical scheme that first technical problem adopted does: a forward facing blade for a centrifugal fan impeller comprising:

the blade body is integrally arc-shaped and is provided with a first side edge and a second side edge which extend side by side in the length direction, the first side edge is an inlet edge corresponding to inflow of airflow, and the second side edge is an outlet edge corresponding to outflow of the airflow;

supplementary blade of making an uproar falls locates on the second side of blade body, this supplementary blade of making an uproar falls is from the second side of blade body to keeping away from the direction of first side extends, and to the pressure surface place lateral bending of blade body makes this supplementary blade also be the arc on the whole, the supplementary width of falling the blade of making an uproar is less than the width of blade body, and the supplementary width direction's of falling the blade both sides border of making an uproar with the width direction's of blade body both sides border has the interval, the supplementary length of falling the blade of making an uproar is less than the length of blade body.

As a refinement, the length of the blade body is L1, the length of the auxiliary noise reduction blade is L2, and the following conditions are satisfied: 2/7 is less than or equal to L2/L1 is less than or equal to 1/3. The auxiliary noise reduction blades are arranged to better improve the separation flow in the middle of the air duct, inhibit the development of low-energy fluid masses on the pressure surface side of the blade body, weaken the low-energy fluid masses on the suction surface side and improve the overall through-flow condition, but the auxiliary noise reduction blades are too small to play a role, and are too long in extension length, so that the separation flow in the middle of the air duct is greatly increased, and the low-energy fluid masses with the pressure surface are accumulated in the front of the auxiliary noise reduction blades to aggravate energy loss, although the low-energy fluid masses on the suction surface side are greatly improved, therefore, the length of the auxiliary noise reduction blades is preferably 2/7-2/L1-1/3, and the problem is solved.

As a refinement, the width of the blade body is D1, the width of the auxiliary noise reduction blade is D2, and the conditions between the two are satisfied: 1/2 is not less than D2/D1 is not less than 3/4. Because the flow loss of the blade body mainly comes from the mixing of separation flow and wake caused by the development of low-energy fluid masses on the surface of the blade, after the width of the auxiliary noise reduction blade is improved, the inhibiting effect of the auxiliary noise reduction blade on low-energy fluids in the middle of a blade channel of the blade body and on two sides of the blade channel can be effectively increased, the mixing of airflow separation flow and wake is reduced, and the noise reduction effect is improved.

As an improvement, the thickness of the blade body is H1, the thickness of the auxiliary noise reduction blade is H2, and the following conditions are met between the two: 1/5 is less than or equal to H2/H1 is less than or equal to 1/3. Because the supplementary blade of making an uproar of falling concentrates on the middle part of its blade body in the influence of blade body, supplementary the pressure differential that the blade of making an uproar of falling makes blade body middle part reduce, has weakened horizontal pressure gradient in the wind channel, helps preventing fluidic lateral flow, is difficult for causing the stall, when supplementary the blade thickness of making an uproar of falling, does not play a role, and when thickness was too big, then can lead to the pressure differential increase of the middle part both sides of blade body, makes the leakage loss increase, therefore, the utility model discloses it is most suitable between 1/5-1/3 for blade body width to fall the width design of the supplementary blade of making an uproar.

As an improvement, the auxiliary noise reduction blade further comprises a vibration reduction strip arranged on the tail end edge of the auxiliary noise reduction blade, wherein the vibration reduction strip extends from the tail end edge of the auxiliary noise reduction blade to the direction far away from the first side edge of the blade body and is bent towards one side of the suction surface of the blade body. The vibration reduction strip can swing back and forth under the action of air flow, and can swing back and forth when the acceleration rotation of the centrifugal fan starts, and act on the suction surface of the blade.

In order to reduce the dipole intensity distribution of the outlet of the forward blade, the two damping strips are respectively a first damping strip and a second damping strip which are sequentially arranged along the width direction of the auxiliary noise reduction blade, wherein the curvature of the first damping strip is larger than that of the second damping strip, and the first damping strip inclines towards one side of the suction surface of the blade body relative to the second damping strip.

As an improvement, the profile equation of the blade body is as follows:

r is 80 (tan α +0.5), and α has a value range of: alpha is more than or equal to 0 degree and less than or equal to 45 degrees;

the polar point of the polar coordinate is positioned at the central position of the centrifugal fan impeller, the polar axis direction is the direction extending from the central position of the centrifugal fan impeller to the position of the first side edge of the blade body, and the anticlockwise direction is the positive direction;

the profile equation of the auxiliary noise reduction blade is as follows:

r is 72 ═ c ((Cos θ) ^2+0.67), and the value range of θ is: theta is more than or equal to 0 degree and less than or equal to 27 degrees;

the pole of the polar coordinate is located at the central position of the centrifugal fan impeller, the polar axis direction is the direction extending from the central position of the centrifugal fan impeller to the position of the second side edge of the blade body, and the anticlockwise direction is the positive direction.

The utility model provides a technical scheme that second technical problem adopted does: the utility model provides an use above-mentioned centrifugal fan to blade, includes the spiral case, locates impeller and motor in the spiral case, the impeller includes back dish and front bezel, the back dish with the front bezel sets up relatively, preceding to the blade locate the back dish with between the front bezel, and follow the circumference interval distribution of front bezel, the power take off end of motor with the back dish drive of impeller is connected.

In order to ensure the air output of the centrifugal fan and match with the structure of the forward blades, the number of the forward blades is 18-37. The number of forward blades is preferably 20.

The utility model provides a technical scheme that third technical problem adopted does: a range hood is applied to the centrifugal fan.

Compared with the prior art, the utility model has the advantages that: the utility model discloses in to fall the structural design of the supplementary blade of making an uproar of blade for the middle part pressure differential of blade body reduces, has weakened horizontal pressure gradient in the wind channel, helps preventing fluidic lateral flow, is difficult for causing the stall. On the other hand, the forward-swept design of the auxiliary noise reduction blades increases the axial chord length of the whole forward-facing blades, better improves the separation flow in the middle of the air duct, inhibits the development of low-energy flow clusters on the pressure surface side, and simultaneously weakens the low-energy flow clusters on the suction surface side, so that the whole through-flow condition of the air duct formed between the adjacent blades is greatly improved.

Drawings

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

fig. 2 is a schematic view of a three-dimensional structure of the range hood according to the embodiment of the present invention after the front side plate of the housing is hidden;

fig. 3 is a schematic perspective view of a centrifugal fan of a range hood according to an embodiment of the present invention;

fig. 4 is a vertical cross-sectional view of the centrifugal fan of the range hood according to the embodiment of the present invention;

fig. 5 is a schematic perspective view of an impeller of a centrifugal fan according to an embodiment of the present invention;

fig. 6 is a vertical cross-sectional view of a centrifugal fan impeller according to an embodiment of the present invention;

fig. 7 is a schematic perspective view of a forward blade according to an embodiment of the present invention;

FIG. 8 is a side view of a forward facing blade of an embodiment of the present invention;

fig. 9 is a pressure distribution diagram of a blade path of an impeller of a centrifugal fan according to an embodiment of the present invention.

Detailed Description

The present invention will be described in further detail with reference to the following embodiments.

Directional terms such as "front", "rear", "upper", "lower", "left", "right", "side", "top", "bottom", and the like are used in the description and claims of the present invention to describe various example structural portions and elements of the present invention, but these terms are used herein for convenience of description only and are determined based on example orientations shown in the drawings. Because the disclosed embodiments may be arranged in different orientations, these directional terms are for illustrative purposes only and should not be construed as limiting, and for example, "upper" and "lower" are not necessarily limited to orientations opposite or consistent with the direction of gravity.

Referring to fig. 1 to 9, the range hood of the present embodiment includes a housing 50 and a centrifugal fan 40 disposed in the housing 50, wherein the centrifugal fan 40 includes a motor 43 and a centrifugal fan impeller 42 connected to an output shaft of the motor 43. The centrifugal fan impeller 42 includes a front disk 422, a rear disk 421 disposed opposite to the front disk 422, and forward blades 423. The forward blades 423 are disposed between the rear disk 421 and the front disk 422, and are spaced apart from each other in the circumferential direction of the front disk 422. The power output end of the motor 43 is in driving connection with the rear disc 421 of the impeller 42.

Referring to fig. 7 and 8, the forward blade of the present embodiment includes a blade body 10, an auxiliary noise reduction blade 20, and a vibration damping strip 30. Wherein, blade body 10 is the arc on the whole, and has first side 11 and the second side 12 that extend side by side in length direction, and first side 11 is the entry edge that corresponds the air current inflow, and second side 12 is the exit edge that corresponds the air current outflow. Both lateral sides of the blade body 10 in the lateral direction are fixed to the front disk 422 and the rear disk 421, respectively.

Referring to FIG. 7, the auxiliary noise reduction blade 20 of the present embodiment is provided on the second side edge 12 of the blade body 10. The auxiliary noise reduction blade 20 extends from the second side edge 12 to a direction away from the first side edge 11, and is bent to one side of the pressure surface of the blade body 10, so that the auxiliary blade is also arc-shaped as a whole. The bending direction of the auxiliary noise reduction blade 20 of the present embodiment coincides with the bending direction of the blade body 10.

Referring to fig. 7, the width of the auxiliary noise reduction blade 20 is smaller than the width of the blade body 10, and two widthwise edges of the auxiliary noise reduction blade 20 are spaced from the two widthwise edges of the blade body 10. That is, the auxiliary noise reduction blades 20 have gaps between the side edges thereof and the wall surfaces of the front disk 422 and the rear disk 421. Specifically, the width of the blade body 10 of the present embodiment is D1, the width of the auxiliary noise reduction blade 20 is D2, and the following conditions are satisfied: 1/2 is not less than D2/D1 is not less than 3/4. Because the flow loss of the blade body 10 mainly results from the mixing of the separated flow and the wake caused by the low-energy fluid mass on the surface of the blade, after the width of the auxiliary noise reduction blade 20 is improved, the inhibiting effect of the auxiliary noise reduction blade 20 on the low-energy fluid in the middle of the blade path of the blade body 10 and on the two sides of the blade path can be effectively increased.

Referring to FIG. 7, the auxiliary noise reduction blade 20 of the present embodiment has a length less than the length of the blade body 10. The auxiliary noise reduction blade 20 is arranged to better improve the separation flow in the middle of the air duct, inhibit the development of low-energy fluid masses on the pressure surface side of the blade body 10, weaken the low-energy fluid masses on the suction surface side, and improve the overall through-flow condition, but the extension length of the auxiliary noise reduction blade 20 is too small to be effective, and is too long, so that although the low-energy fluid masses on the suction surface side are greatly improved, the separation flow in the middle of the air duct is increased in a large range, and the low-energy fluid masses with the pressure surface are accumulated in the front of the auxiliary noise reduction blade 20, so that the energy loss is aggravated, therefore, the length L2 of the auxiliary noise reduction blade 20 and the length L1 of the blade body 10 in the embodiment meet the condition that: 2/7 is less than or equal to L2/L1 is less than or equal to 1/3.

Referring to fig. 8, the thickness of the auxiliary noise reduction blade 20 of the present embodiment is smaller than the thickness of the blade body 10, specifically, the thickness of the blade body 10 is defined as H1, the thickness of the auxiliary noise reduction blade 20 is defined as H2, and the following conditions are satisfied: 1/5 is less than or equal to H2/H1 is less than or equal to 1/3. Because the supplementary blade 20 of making an uproar that falls concentrates on the middle part of its blade body 10 to the influence of blade body 10, supplementary blade 20 of making an uproar that falls makes the pressure differential at blade body 10 middle part reduce, has weakened horizontal pressure gradient in the wind channel, helps preventing fluidic lateral flow, is difficult for causing the stall, when supplementary blade 20 thickness of making an uproar that falls is too little, does not play a role, and when thickness is too big, then can lead to the pressure differential increase of the middle part both sides of blade body 10, makes the leakage loss increase, therefore, the utility model discloses the width design of the supplementary blade 20 of making an uproar that falls is most suitable between 1/5-1/3 of blade body 10 width.

With reference to fig. 6, for optimizing the shape of the blade body 10 and the auxiliary noise reduction blade 20, the profile equation of the blade body 10 is: r is 80 (tan α +0.5), and α has a value range of: alpha is more than or equal to 0 degree and less than or equal to 45 degrees; the pole O of the polar coordinate is located at the center of the centrifugal fan impeller 42, the polar axis direction is the direction extending from the center of the centrifugal fan impeller 42 to the position of the first side 11 of the blade body 10, and the counterclockwise direction is the positive direction. The profile equation for the auxiliary noise reduction blade 20 is: r is 72 ═ c ((Cos θ) ^2+0.67), and the value range of θ is: theta is more than or equal to 0 degree and less than or equal to 27 degrees; the pole O of the polar coordinate is located at the center of the centrifugal fan impeller 42, the polar axis direction is the direction extending from the center of the centrifugal fan impeller 42 to the position of the second side 12 of the blade body 10, and the counterclockwise direction is the positive direction.

Referring to fig. 7 and 8, the vibration damping strip 30 is disposed on the end edge of the auxiliary noise reduction blade 20, wherein the vibration damping strip 30 extends from the end edge of the auxiliary noise reduction blade 20 to a direction away from the first side 11 of the blade body 10, and is bent toward a side where the suction surface of the blade body 10 is located. That is, the bending direction of the damper strip 30 is opposite to the bending direction of the blade body 10 (auxiliary noise reduction blade 20). The damping strips 30 of the present embodiment are two, namely, a first damping strip 31 and a second damping strip 32, and the first damping strip 31 and the second damping strip 32 are sequentially arranged along the width direction of the auxiliary noise reduction blade. The curvature of the first damping strip is greater than that of the second damping strip, and the first damping strip inclines towards one side of the suction surface of the blade body 10 relative to the second damping strip.

When the centrifugal fan 40 operates, the blade main body and the auxiliary noise reduction blade 20 interact with each other to form a pneumatic acoustic feedback cycle, so that the sound pressure of the sound source on the suction surface of the auxiliary noise reduction blade 20 is greater than that on the pressure surface, therefore, the pressure difference between the pressure surface and the suction surface exists, a tip vortex is generated, and when a vortex leaves the surface of the blade, the flow circulation around the blade changes, and shedding vortex noise is generated. The damping strip 30 of this embodiment can swing back and forth under the air current effect, when centrifugal fan 40's the rotatory initial stage that accelerates, damping strip 30 can swing backward to act on the suction surface of blade, when slowing down the stage, damping strip 30 can swing forward, act on the pressure surface of blade, damping strip 30 swing process can effectively reduce the vortex amplification effect that the breakage of dipole at the blade way export section leads to, especially carry out different curvature designs with above-mentioned two damping strips 30, the dipole intensity distribution of the export position department of blade has been reduced to the front.

The structural design of the auxiliary noise reduction blade 20 and the vibration reduction strip 30 of the forward blade of the embodiment is derived from the bionic design of the feet of the black shell worms. The black shell worms can fly in a short jump even after the wings fall off, and mainly depend on the special aerodynamic shape of the feet. When the foot meets natural enemies, the foot can deform, the small foot can cling to the abdominal wall, the joint can rotate, the small tarsal joint can be folded, the acting surface is changed from a wide surface to a narrow surface, and the air resistance is reduced. The utility model discloses a to the blade in the front is used to the research application of black shell worm drag reduction to restrain the separation that drops of swirl. Among them, the research on drag reduction of black beetle can be referred to as: (Zhongchanghai, Ningquan, Zhangrui, King Shujie, Zhao Weifu, etc.. relationship between the body surface structure of Huangyuan Zhenlong lice and its drag reduction function in water [ J ]. the university report of northeast China (Nature science edition), 2006, 38(2), 109-.

Referring to fig. 9, a simulation distribution diagram of the pressure in the blade path of the impeller 42 of the centrifugal fan 40 according to the embodiment of the present invention is shown, and it can be seen from the simulation diagram that the auxiliary noise reduction blade 20 is disposed at the outlet edge of the blade body 10, so that the pressure difference in the middle of the blade body 10 is reduced, the transverse pressure gradient in the air path is weakened, the transverse flow of the fluid is prevented, and stall is not easily caused. On the other hand, the forward-swept design of the auxiliary noise reduction blades 20 increases the axial chord length of the whole forward-facing blades, better improves the separation flow in the middle of the air duct, inhibits the development of low-energy flow masses on the pressure surface side, and simultaneously weakens the low-energy flow masses on the suction surface side, so that the whole through-flow condition of the air duct formed between the adjacent blades is greatly improved.

Claims (10)

1. A forward facing blade for a centrifugal fan impeller comprising:

the blade body (10) is arc-shaped as a whole and is provided with a first side edge (11) and a second side edge (12) which extend side by side in the length direction, the first side edge (11) is an inlet edge corresponding to inflow of airflow, and the second side edge (12) is an outlet edge corresponding to outflow of airflow;

it is characterized by also comprising:

supplementary blade (20) of making an uproar falls, locate on second side (12) of blade body (10), this supplementary blade (20) of making an uproar falls from second side (12) of blade body (10) to keeping away from the direction of first side (11) extends, and to the pressure surface place one side bending of blade body (10) to make this supplementary blade also be the arc on the whole, the width of supplementary blade (20) of making an uproar falls is less than the width of blade body (10), and the supplementary width direction's of making an uproar fall both sides border with the width direction's of blade body (10 both sides border has the interval, the supplementary length of falling the oar leaf (20) of making an uproar is less than the length of blade body (10).

2. A forward facing blade for a centrifugal fan impeller according to claim 1, wherein: the length of the blade body (10) is L1, the length of the auxiliary noise reduction blade (20) is L2, and the two satisfy the following conditions: 2/7 is less than or equal to L2/L1 is less than or equal to 1/3.

3. A forward facing blade for a centrifugal fan impeller according to claim 2, wherein: the width of the blade body (10) is D1, the width of the auxiliary noise reduction blade (20) is D2, and the two satisfy the following conditions: 1/2 is not less than D2/D1 is not less than 3/4.

4. A forward facing blade for a centrifugal fan impeller according to claim 3, wherein: the thickness of the blade body (10) is H1, the thickness of the auxiliary noise reduction blade (20) is H2, and the two satisfy the following conditions: 1/5 is less than or equal to H2/H1 is less than or equal to 1/3.

5. A forward facing blade for a centrifugal fan impeller according to any one of claims 1 to 4, wherein: the auxiliary noise reduction blade is characterized by further comprising a vibration reduction strip (30) arranged on the tail end edge of the auxiliary noise reduction blade (20), wherein the vibration reduction strip (30) extends from the tail end edge of the auxiliary noise reduction blade (20) to the direction far away from the first side edge (11) of the blade body (10), and is bent towards one side of the suction surface of the blade body (10).

6. The forward facing blade for a centrifugal fan impeller of claim 5, wherein: the damping strip (30) have two, are first damping strip (31) and second damping strip (32) respectively, and this first damping strip (31) and second damping strip (32) are followed the width direction of supplementary blade of making an uproar is fallen arranges in proper order, and wherein, the camber of first damping strip is greater than the camber of second damping strip, and relative second damping strip towards the suction surface place one side slope of blade body (10).

7. The forward facing blade for a centrifugal fan impeller of claim 5, wherein:

the profile equation of the blade body (10) is as follows:

r is 80 (tan α +0.5), and α has a value range of: alpha is more than or equal to 0 degree and less than or equal to 45 degrees;

the pole of the polar coordinate is positioned at the central position of the impeller (42) of the centrifugal fan (40), the polar axis direction is the direction extending from the central position of the impeller (42) of the centrifugal fan (40) to the position of the first side edge (11) of the blade body (10), and the anticlockwise direction is the positive direction;

the profile equation of the auxiliary noise reduction blade (20) is as follows:

r is 72 ═ c ((Cos θ) ^2+0.67), and the value range of θ is: theta is more than or equal to 0 degree and less than or equal to 27 degrees;

the pole of the polar coordinate is located at the center position of the impeller (42) of the centrifugal fan (40), the polar axis direction is the direction extending from the center position of the impeller (42) of the centrifugal fan (40) to the position of the second side edge (12) of the blade body (10), and the anticlockwise direction is the positive direction.

8. A centrifugal fan using the forward blade as claimed in any one of claims 1 to 7, wherein: including volute (41), locate impeller (42) and motor (43) in volute (41), impeller (42) are including back dish (421) and front disc (422), back dish (421) with front disc (422) set up relatively, preceding blade locate back dish (421) with between front disc (422), and follow the circumference interval distribution of front disc (422), the power take off of motor (43) with back dish (421) drive connection of impeller (42).

9. The centrifugal fan of claim 8, wherein: the number of the forward blades is 18-37.

10. A range hood, its characterized in that: use of a centrifugal fan according to claim 8 or 9.

Images