Centrifugal fan and range hood

Abstract

The invention relates to a centrifugal fan and a range hood. The centrifugal fan comprises a volute and an impeller. A current collector is arranged at the air inlet of the volute; the first disc and the second disc are oppositely arranged in the front-back direction; the blades are connected between the first disc and the second disc and distributed in the circumferential direction, the front edge of at least one blade is provided with a wave-shaped section, and the length H2 of the wave-shaped section in the axis direction of the impeller meets the conditions that 0.8 Dn < = D1 < = Dn, 0.5 < = Hz / Hq < = 2; wherein D1 is the maximum diameter of an inlet of the current collector, Dn is the minimum inner diameter of the impeller, Hz is the axial depth of the impeller, and Hq is the air inlet space depth of the front side or the rear side of the centrifugal fan in the machine shell. A plurality of parameters such as the axial length size of the wave-shaped section, the inlet size of the current collector, the inner diameter of the impeller, the depth direction size of the impeller on the single side and the depth of the air inlet space on the side are subjected to collaborative design synthesis and matching. The invention has the advantages that the pneumatic performance of the machine can be ensured while the airflow noise is obviously reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of range hood, in particular to a centrifugal fan and a range hood. BACKGROUND

[0002] The range hood is a kind of kitchen appliance for purifying kitchen environment. The centrifugal fan is a key component of the range hood. The centrifugal fan generally comprises a volute, an impeller rotating in the volute, and a motor for driving the impeller to rotate. The blades of the impeller of the existing centrifugal fan are mostly sheet metal structures with straight plates and single circular arcs, that is, the planar unfolded figure is basically rectangular. Due to the characteristics of the centrifugal fan, the airflow will exist multiple turning and changing directions in the flow process, and vortex phenomenon caused by flow separation will exist at the front and rear ends of the impeller, and there will also be dynamic and static interference with the volute. At present, some patents have disclosed that the wing type design of the blade can reduce flow separation, but such wing type blades are generally thick, which will reduce the working capacity of the impeller, such as the application number CN202220333700.2, a kind of impeller, centrifugal fan and range hood, which has made similar disclosure; some patents have also disclosed that the wave shape is independently arranged on the front or rear edge of the blade to break the vortex and reduce noise, such as the application number CN202010739577.X, a kind of blade for centrifugal fan, centrifugal fan and range hood, which has made similar disclosure.

[0003] However, the front edge of the blade of the impeller of the existing technology adopts the tooth-shaped or wave-shaped noise reduction design, which is mainly used for breaking the vortex at the front edge. When designing, the related tooth-shaped or wave-shaped structure is generally designed in the whole section of the impeller. However, the blade area far from the air inlet is the main airflow area, the airflow in this area is relatively stable, and there are relatively few large-scale vortexes. Therefore, the wave-shaped section structure is also arranged in this area, which can destroy the large-scale vortex structure existing in the local area, but at the same time, it will also interfere with the stable main airflow, and a large number of small-scale vortexes will be generated. The total vortex intensity of these small-scale vortexes may exceed that of the few large-scale vortexes. In addition, the wave shape of the blade will reduce the effective working area, thereby causing a significant decrease in the working capacity of the fan. Therefore, this is the main reason why the actual effect of the existing noise reduction structure of the front edge of the blade of the impeller is not ideal. Therefore, the existing centrifugal fan still needs to be further improved. SUMMARY

[0004] The first technical problem to be solved by the present application is to provide a centrifugal fan which can effectively reduce the influence on the stable airflow in the main airflow area of the front edge of the blade, weaken the influence of the size reduction of the blade on the working capacity of the impeller, and thereby improve the aerodynamic capacity and enhance the noise reduction effect, in view of the status quo of the prior art.

[0005] The second technical problem to be solved by the present application is to provide a range hood which adopts the above-mentioned centrifugal fan, in view of the status quo of the prior art.

[0006] The technical scheme adopted by the present application to solve the first technical problem is: a centrifugal fan, comprising: a volute and an impeller, the impeller comprising a first disc and a second disc oppositely arranged in the front-rear direction, the first disc being located at the air inlet of the fan; a flow collector is arranged at the air inlet of the volute; a plurality of blades are arranged between the first disc and the second disc and in the circumferential direction; each blade further has a leading edge corresponding to the air inlet side and a trailing edge corresponding to the air outlet side;

[0007] The length dimension H2 of the wave-shaped section of the leading edge of the at least one blade arranged close to the first disc in the direction of the impeller axis satisfies the condition:

[0008] And 0.8D n ≤D1≤D n , 0.5≤H z / H q ≤2; wherein D1 is the maximum diameter of the inlet of the flow collector, the maximum diameter of the inlet of the flow collector can be understood as follows: if the inlet of the flow collector is a non-circular shaped special-shaped inlet, the maximum diameter of the inlet of the flow collector should be the maximum distance between two points on the periphery contour of the flow collector passing through the center of the flow collector, if the inlet of the flow collector is a circular shape, it is the inlet diameter; D n is the minimum inner diameter of the impeller, that is, the minimum diameter formed by the leading edge of the blade in the radial direction of the impeller; H z is the axial depth of the impeller: for a single air inlet fan, the first disc is the front disc and the second disc is the rear disc, then H z is the distance from the front disc to the rear disc of the impeller, if it is a double air inlet centrifugal fan, the first disc is the front disc or the rear disc, and the second disc is the middle disc, then H z is the single-sided axial depth, that is, the distance from the front disc or the rear disc of the impeller to the middle disc; H q is the depth of the air inlet space in the front side or rear side of the range hood of the centrifugal fan, which is the distance from the side wall surface on the side of the corresponding air inlet of the volute to the front inner wall of the range hood, if there are other parts such as sound-absorbing boxes on the inner wall of the range hood, then it is the distance from the outer surface of the volute to the surface of other parts on the inner wall of the front range hood, when H q is not equal in thickness, then the arithmetic mean distance is used The area element A is generally the effective ventilation area surrounded by the inlet of the flow collector; the range hood is limited by installation conditions such as the depth of the cabinet, and therefore, H q is not easy to be too large, generally not more than twice H z , similarly, H qNot too small, too small will lead to the first disc into the wind side space is too small, not smooth. Because the collector and impeller inner diameter ratio and fan front air inlet space and corresponding side impeller depth ratio of two dimensions will affect the flow situation of the leading edge of the impeller, so the depth of the wave section needs to be considered according to the dimension which has higher influence.

[0009] The centrifugal fan is divided into single inlet fan and double inlet fan. For the single inlet fan, the axial length of the blade refers to the length of the blade arranged between the front disc and the rear disc; for the double inlet fan, the position of the middle disc is taken as the boundary to divide the blade into two segments, the leading edge of at least one of the two blade segments of the blade includes the wave section, and the axial length of the blade refers to the single side blade length, i.e. the length of the blade arranged between the front disc or the rear disc and the middle disc.

[0010] The centrifugal fan is limited by the size of the machine shell (i.e. the air box) and the inlet condition of the collector in actual application (such as the range hood). The flow separation and backflow phenomenon of the leading edge of the impeller blade are closely related to the flow guide design of the shell and the collector, so the length of the wave section in the axial direction of the impeller is neither the longer the better nor the shorter the better. The axial length dimension H2 of the wave section is designed in cooperation with the diameter D1 of the air inlet (i.e. the inlet of the collector), the inner diameter D n of the impeller, the depth dimension H Z of the impeller in the single side direction and the depth H q of the air inlet space on this side, so that the wave section of the blade can be matched under different air inlet conditions, so that the aerodynamic performance of the fan can be guaranteed without being greatly affected while effectively reducing the airflow noise.

[0011] As an improvement, the blade further includes a first non-wave section arranged closer to the first disc relative to the wave section; the length dimension H1 of the first non-wave section in the axial direction of the impeller satisfies the condition:

[0012] 0<H1<0.2(5H0+H z )*H z / H q ; wherein H0 is the distance from the first disc of the impeller to the front cover plate or the rear cover plate of the volute, H0∈(0,30]mm;

[0013] The area near the first disc corresponding to the impeller blades is a non-operating zone, primarily for recirculation. This is where the airflow direction is from the blade outlet to the inlet. Adding a wave-like structure would actually reduce the blade passage size. A longer blade passage helps suppress recirculation towards the inlet side; therefore, no wave-like structure is provided. The leading edge of the blades also includes a first non-wave-like section positioned closer to the first disc than the wave-like section. This is because the airflow from the (top-mounted fan) box (i.e., the fan frame) into the impeller needs to make a large-angle turn. z / H q The larger the value, the sharper the turn, and the more severe the backflow after entering the impeller. Of course, in some operating conditions, such as when the backflow zone on the front side of the impeller is not obvious, the first non-waveform segment may not be set. If experiments or simulations show that the backflow zone on the front side of the impeller is not obvious, H1 can be set to 0, that is, the first non-waveform segment is not set.

[0014] As an improvement, the blade further includes a second non-wave-shaped segment away from the first disc; the length of the second non-wave-shaped segment along the axial direction of the impeller is denoted as H3, where 0.5(H z -H1-H2)≤H3≤(H Z -H1-H2).

[0015] As mentioned earlier, the second non-wavelength section is the main inlet airflow area, where the airflow is relatively stable and there are relatively few large-scale vortices. Therefore, there is no need to set a waveform section. However, in order to balance the noise reduction effect and the fan performance, it is necessary to further design the lengths of the waveform section and the non-wavelength section.

[0016] The waveform segment at the leading edge of the blade has two dimensions: wavelength and wave height. The impact at the leading edge of the multi-blade centrifugal fan blade is related to the impeller inlet impact angle. Establishing a waveform dimension design relationship based on the impact angle can better match the characteristics of the multi-blade centrifugal fan. The established waveform dimension relationship is related to the waveform segment length, not directly related to the blade depth, thus ensuring the number of waveforms. Specifically, the wavelength of the waveform segment is denoted as S1, and S1 satisfies the following condition:

[0017] And α∈[30°, 90°];

[0018] Where α is the impeller inlet angle. The larger the inlet angle, the greater the impact, and the smaller the waveform segment is required to break the vortex.

[0019] As an improvement, the wave height of the waveform segment is denoted as N1, and satisfies the following condition:

[0020] 0.1sin(α)L≤N1≤0.4sin(α)L; L is the width dimension of the blade after it is flattened.

[0021] As an improvement, the wavelengths of any two adjacent bands in the waveform segment are respectively denoted as Sl.i and Sl i+1 The wave heights are denoted as Nl. i and Nl i+1 ;

[0022] The wavelength and wave height of any two adjacent wavebands in the waveform segment satisfy the following conditions:

[0023] Sl i <Sl i+1 ≤1.3Sl i ;

[0024] 0.8Nl i ≤Nl i+1 <Nl i .

[0025] Since the airflow in a multi-blade centrifugal fan is not uniformly distributed along the impeller axis, the wavelength and wave height are preferably gradually distributed. For cases with high turbulence intensity, it is generally required that the waveform segment has a short wavelength and a large wave height. As the axial direction extends closer to the mainstream region, the vortex situation will weaken, and the uniform design effect will be weakened. Therefore, as an improvement, the wavelength of the waveform segment gradually increases from the end closer to the first disc to the end farther away from the first disc, and the wave height of the waveform segment gradually decreases from the end closer to the first disc to the end farther away from the first disc.

[0026] Generally speaking, the first non-wave-shaped segment and the second non-wave-shaped segment mentioned above can be understood as the section at the leading edge of the blade. It should exclude the use of periodic undulating shapes such as sawtooth or wave. For example, a straight segment or a curve with a non-periodic undulating shape can be used. As an improvement, the first non-wave-shaped segment is a straight segment, and the extension direction of the first non-wave-shaped segment is parallel to or at an angle to the axis of the impeller; the second non-wave-shaped segment is a straight segment, and the extension direction of the second non-wave-shaped segment is parallel to or at an angle to the axis of the impeller.

[0027] The technical solution adopted by the present invention to solve the second technical problem is: a range hood, including a housing and a centrifugal fan disposed in the housing, wherein the centrifugal fan adopts the above-mentioned impeller assembly.

[0028] Compared with existing technologies, the advantages of this invention are as follows: This invention integrates and matches multiple parameters, such as the axial length of the waveform segment with the inlet size of the collector, the impeller inner diameter, the depth dimension of the impeller on one side, and the depth of the air inlet space on that side, thereby effectively reducing airflow noise while ensuring that the aerodynamic performance of the fan is not significantly affected. In a further improvement, the impeller blades of this invention enhance the control of the tip recirculation zone by setting a first non-waveform segment of a certain size, and reduce the impact on the stable airflow in the main airflow zone at the leading edge of the blade by setting a second non-waveform segment of a certain size, thus weakening the impact of the reduced blade area on the impeller's work capacity. The above-mentioned segmented design with different sizes achieves enhanced noise reduction while improving aerodynamic performance. Attached Figure Description

[0029] Figure 1 This is a three-dimensional structural diagram of a range hood according to an embodiment of the present invention;

[0030] Figure 2 This is a vertical sectional view of the range hood of the present invention, cut along the front-to-back direction. The centrifugal fan is a dual-inlet fan.

[0031] Figure 3 This is a three-dimensional structural diagram of a centrifugal fan according to an embodiment of the present invention. The centrifugal fan is a dual-inlet fan.

[0032] Figure 4 This is a vertical sectional view of a centrifugal fan cut along the axial direction according to an embodiment of the present invention. The centrifugal fan is a dual-inlet fan.

[0033] Figure 5 This is a three-dimensional structural diagram of the impeller of a centrifugal fan according to an embodiment of the present invention. The centrifugal fan is a double-inlet fan.

[0034] Figure 6 This is a front view of the impeller blades in an embodiment of the present invention; the centrifugal fan is a dual-inlet fan.

[0035] Figure 7 The image shows a vertical sectional view of the range hood in an embodiment of the present invention, with a sound-absorbing box provided on the side wall opposite to the main air inlet of the centrifugal fan.

[0036] Figure 8 This is a vertical sectional view of the range hood of the present invention, cut along the axial direction. The centrifugal fan is a single-inlet fan.

[0037] Figure 9 This is a vertical sectional view of a centrifugal fan according to an embodiment of the present invention, cut along the front-to-back direction. The centrifugal fan is a single-inlet fan.

[0038] Figure 10 This is a front view of the impeller blades in an embodiment of the present invention. The centrifugal fan is a single-inlet fan.

[0039] Figure 11 This is a vertical sectional view of a range hood according to an embodiment of the present invention, cut along the front-to-back direction. The range hood is a different model, and the front side of the range hood of this model has a non-smooth air intake.

[0040] Figure 12 This is a comparison diagram of the simulated velocity vectors of the centrifugal fan (dual-inlet fan) in this embodiment of the invention and the prototype (bladeless leading edge segmented waveform structure). Detailed Implementation

[0041] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0042] The specification and claims of this invention use terms indicating direction, such as "front," "rear," "upper," "lower," "left," "right," "side," "top," and "bottom," to describe various exemplary structural parts and elements of the invention. However, these terms are used herein merely for ease of explanation and are determined based on the exemplary orientations shown in the accompanying drawings. Since the embodiments disclosed in this invention can be arranged in different orientations, these terms indicating direction are for illustrative purposes only and should not be considered as limitations. For example, "upper" and "lower" are not necessarily limited to directions opposite to or consistent with the direction of gravity.

[0043] Figures 1-12 A preferred embodiment of the centrifugal fan and range hood of the present invention is shown. The range hood includes a housing 10 and a centrifugal fan 13 disposed within the housing 10. The housing 10 generally includes a fan frame 11 and a smoke collection hood 12 disposed at the bottom of the fan frame 11, with the inner cavity of the fan frame 11 communicating with the inner cavity of the smoke collection hood 12. An air inlet is provided on the front side wall of the smoke collection hood 12, through which external smoke can enter the smoke collection hood 12. The centrifugal fan 13 is disposed within the fan frame 11. When the centrifugal fan 13 operates, it generates negative pressure, allowing external oil fumes to be drawn into the smoke collection hood 12 through the air inlet. An oil screen is also provided at the air inlet of the smoke collection hood 12 for filtering oil fumes. An oil cup is provided at the bottom of the smoke collection hood 12, which is a long strip extending laterally to collect oil stains flowing down from the smoke collection hood 12. The front of the smoke hood 12 is also provided with a smoke baffle that can deflect back and forth relative to the smoke hood 12. The smoke baffle is connected to the main body of the smoke hood 12 via a hinge mechanism. Specifically, it can deflect forward to open the air inlet and deflect backward to block and close the air inlet. The hinge mechanism used to drive the deflection of the smoke baffle can be a conventional hinge mechanism in the prior art, which will not be described in detail here.

[0044] The centrifugal fan 13 is a key component of the range hood, comprising a volute 20, an impeller 30 rotating within the volute 20, and a motor 35 driving the impeller 30 to rotate. The volute 20 includes a front cover plate 21 and a rear cover plate 22 facing each other, and an annular wall between the front cover plate 21 and the rear cover plate 22. The front cover plate 21 generally has a main air inlet 210, and the rear cover plate 22 has a secondary air inlet 220. The motor 35 is fixed to the secondary air inlet of the volute 20 by a motor 35 bracket, so it will affect the air volume of the air inlet on that side to a certain extent. That is, under normal circumstances, the air volume of the main air inlet 210 is greater than that of the secondary air inlet 220.

[0045] The centrifugal fan of this invention can be either a single-inlet centrifugal fan or a double-inlet centrifugal fan. The difference is that the single-inlet centrifugal fan has no central plate, while the double-inlet centrifugal fan contains a central plate. For example... Figures 1-7 A dual-inlet centrifugal fan and a range hood using the dual-inlet centrifugal fan are shown. Figures 8-10 This invention illustrates a single-inlet centrifugal fan and a range hood using this single-inlet centrifugal fan. It should be further explained that the impeller of a dual-inlet fan is divided into two blade segments, with the central disc as the boundary. At least one blade segment in the two blade segments of this invention has a wavy leading edge. The second disc corresponds to the central disc, and the first disc corresponds to either the front or rear disc. The impeller design is applicable to either side of the blade segment. Since dual-inlet centrifugal fans currently have a wider range of applications, especially in the field of range hoods, this invention primarily uses a dual-inlet centrifugal fan as an example for explanation.

[0046] For a dual-inlet fan, the impeller 30 includes two opposing end rings, a central disc 33 located between the two end rings, and multiple blades 34. The two end rings are the front disc 31 and the rear disc 32, which are also known as the first disc, while the central disc is the second disc. Multiple blades 34 are connected between the front disc 31 and the rear disc 32 and are distributed circumferentially. Each blade 34 also has a leading edge 3401 corresponding to the air inlet side and a trailing edge 3402 corresponding to the air outlet side. Each blade 34 is divided into two segments, front and rear, with the central disc 33 as the boundary. The segment corresponding to the front disc 31 is the front blade segment, and the segment corresponding to the rear disc 32 is the rear blade segment. Generally, the central disc 33 is positioned relatively close to the rear disc 32, meaning the length of the front blade segment is usually greater than the length of the rear blade segment.

[0047] Most range hoods employ a top-mounted fan structure, with the centrifugal fan 13 housed within the fan frame 11. The air inlet of the centrifugal fan 13 is not open, and the airflow flows smoothly from bottom to top into the front of the fan inlet before turning at an angle to enter the centrifugal fan 13. In this case, it is necessary to consider the relationship between the segmented impeller noise reduction structure and the dimensions of the collector 211 and the fan inlet housing. In this embodiment, smooth airflow from bottom to top means that there are no structural protrusions obstructing airflow within a certain distance H below the centrifugal fan 13, where H ≥ 0.5H. q H q The depth of the air intake space on the front or rear side of the centrifugal fan 13 within the fan frame 11 of the casing 10, such as... Figure 7 As shown in the diagram; otherwise, it will cause the airflow to change direction multiple times, resulting in airflow turbulence. Figure 11 The range hood shown is a traditional range hood with an unconventional top-mounted fan.

[0048] In this embodiment, the leading edges 3401 of the two blade segments of the blade 34 both include a second non-wave-shaped segment 343 away from the front disc 31 and a wave-shaped segment 344 close to the front disc 31. The extension direction of the second non-wave-shaped segment 343 is parallel to or at an angle to the axis of the impeller 30.

[0049] The section of the blade 34 of the impeller 30 near the front disk 31 or the rear disk 32 is a non-working zone, mainly for backflow, i.e., the airflow direction is from the outlet of the blade 34 towards the inlet. Adding a wave structure would actually reduce the blade passage size. A longer blade passage size is beneficial for suppressing backflow towards the inlet side. Therefore, no wave structure is provided. As shown in 6, in some embodiments, the leading edge 3401 of the two blade segments of the blade 34 also includes a first non-wave section 345 arranged closer to the front disk 31 than the wave section 344. The first non-wave section 345 is preferably a straight section. The extension direction of the first non-wave section 345 is parallel to or at an angle to the axis of the impeller 30. In a preferred embodiment, the first non-wave section 345 gradually tilts towards the side where the axis of the impeller is located from the first disk to the second disk.

[0050] The length of the first non-waveform segment 345 along the axis of the impeller 30 is denoted as H1. The length H1 of the first non-waveform segment 345 along the axis of the impeller 30 satisfies the following condition:

[0051] And H0∈(0,30]mm;

[0052] Wherein, H0 is the distance from the front or rear disc of the impeller 30 to the front cover plate 21 or rear cover plate 22 of the volute 20;

[0053] H qThe depth of the air intake space on the front or rear side of the centrifugal fan 13 inside the housing 10;

[0054] H z The axial depth of impeller 30, such as Figure 2 and Figure 5 The impeller shown is a double-inlet impeller, and Hz represents the axial depth on one side, which is the distance from one end ring of the impeller 30 to the middle disc 33. It should be noted that for a single-inlet fan, the first disc is the front disc, and the second disc is the rear disc, then H... z This is the distance between the front and rear discs of the impeller; see details. Figures 8-10 .

[0055] The above H q The distance is taken from the side wall of the volute 20 where the air inlet is located to the inner wall of the front housing 10. If there are other components such as sound-absorbing boxes on the inner wall of the housing 10, then it is the distance from the outer surface of the volute 20 to the surface of the other components on the inner wall of the front housing 10. When H q When the thickness is not uniform, the arithmetic mean distance H is used. qc , Area element A is generally taken as the effective ventilation area enclosed by the inlet of collector 211, such as Figure 7 As shown.

[0056] Because the airflow from the (top-mounted fan) box (i.e., fan frame 11) into the impeller 30 needs to make a large-angle turn, H z / H q The larger the value, the sharper the turn, and the more severe the backflow after entering impeller 30. Of course, under some operating conditions, such as when experiments or simulations show that the backflow zone on the front side of impeller 30 is not obvious, H1 can be set to 0, that is, the first non-waveform segment 345 is not set.

[0057] The waveform segment 344 of the leading edge 3401 of the blade 34 can be understood as a curved segment with a periodic concave-convex structure. That is, the waveform segment 344 is constructed as a waveform curve with concave and convex parts arranged in sequence. The concave or convex parts of the waveform curve are set as tooth-shaped, arc-shaped or airfoil-shaped structures.

[0058] The length of the wave segment 344 of the leading edge 3401 of the blade 34 along the axial direction of the impeller 30 is denoted as H2. Considering the limitations of the centrifugal fan 13, especially the multi-blade centrifugal fan 13, such as the size of the range hood casing 10 (i.e., the air box) and the air intake conditions of the collector 211, the separation and recirculation state of the leading edge 3401 of the blade 34 of the impeller 30 is closely related to the flow guidance design of the casing 10 and the collector 211. Based on the flow characteristics inside the multi-blade centrifugal fan 13 and the air box, the length H2 of the wave segment 344 along the axial direction of the impeller 30 needs to be combined with the inlet size D1 of the air inlet, i.e., the collector 211, and the inner diameter D of the impeller 30. nImpeller 30, depth direction H on one side z The depth H of the air intake space on this side q The design is carried out by comprehensively considering parameters such as H2 = f0(D1, D...). n H q H Z Specifically, the centrifugal fan 13 is installed inside the casing 10 of the range hood. The centrifugal fan 13 includes a volute 20, and a collector 211 is provided at the air inlet of the volute 20. The length H2 of the wave segment 344 of the leading edge 3401 of the blade 34 in the axial direction of the impeller 30 satisfies the following condition:

[0059] And 0.8D n ≤D1≤D n 0.5≤H z / H q ≤2;

[0060] Where D1 is the inlet diameter of collector 211;

[0061] D n The inner diameter of the impeller 30 is the minimum diameter formed by the leading edge of each blade 34 in the radial direction.

[0062] If the diameter of collector 211 is less than 0.8D n If the inlet size of collector 211 is too small, it will affect the air intake volume; if it is greater than D... n If the airflow at the inlet edge directly enters the blade passage, it will also affect the aerodynamic performance.

[0063] As mentioned above, H z The axial depth of impeller 30, such as Figure 2 and Figure 5 The impeller shown is a double-inlet impeller, H z This is the axial depth on one side, which is the distance from one end ring (front or rear disc) of the impeller 30 to the middle disc 33.

[0064] H q The depth of the air intake space on the front or rear side of the centrifugal fan 13 inside the housing 10 is generally taken as the distance from the outer surface of one side perpendicular to the volute 20 to the inner wall of the front housing 10.

[0065] Range hoods are limited by installation conditions such as cabinet depth, H q It should not be too large, generally not exceeding H z Twice as much, H q It should not be too small, otherwise the space on the first air intake side will be too small, resulting in poor air intake.

[0066] The ratio of the inner diameter of the collector 211 to that of the impeller 30 and the ratio of the air intake space in front of the fan 13 to the depth of the corresponding side impeller 30 will affect the flow at the leading edge of the impeller 30 in two dimensions. The depth of the waveform segment 344 needs to be considered based on the dimension with a higher influence.

[0067] The waveform segment 344 of the leading edge 3401 of blade 34 has two dimensions: wavelength and wave height. The impact of the leading edge 3401 of blade 34 of multi-blade centrifugal fan 13 is related to the air volume and the inlet impact angle of impeller 30. Establishing a waveform dimension design relationship based on air volume, impact angle, etc., can better match the characteristics of multi-blade centrifugal fan 13. The established waveform dimension relationship is related to the length of waveform segment 344, but not directly related to the depth of blade 34, thereby ensuring the number of waveforms. Specifically, the wavelength of the waveform segment 344 is denoted as S1, and S1 satisfies the following condition:

[0068] And α∈[30°, 90°];

[0069] Where α is the inlet angle of impeller 30, the larger the inlet angle, the greater the impact, and the smaller the waveform segment 344 is required to break the vortex.

[0070] The wave height of the waveform segment 344 of the leading edge 3401 of blade 34 is denoted as N1, and the following condition is satisfied:

[0071] 0.1sin(α)L≤N1≤0.4sin(α)L; where L is the width dimension of the blade after it is flattened.

[0072] Since the airflow in the multi-blade centrifugal fan 13 is not uniformly distributed in the axial direction of the impeller 30, the wavelength and wave height are preferably gradually distributed. For cases with high turbulence intensity, it is generally required that the wavelength of the waveform segment 344 be short and the wave height be large. As the axial direction extends closer to the mainstream area, the vortex situation will weaken and the uniform design effect will be weakened. Therefore, the wavelength of the waveform segment 344 gradually increases from the end near the front plate 31 to the end away from the front plate 31, and the wave height of the waveform segment 344 gradually decreases from the end near the front plate 31 to the end away from the front plate 31.

[0073] More specifically, the wavelengths of any two adjacent bands in waveform segment 344 are denoted as Sl. i and Sl i+1 The wave heights are denoted as Nl. i and Nl i+1 In waveform segment 344, a waveform closer to the impeller 30 disk 33 is designated as "i+1", while a waveform farther from the impeller 30 disk 33 is designated as "i". The wavelength and wave height of any two adjacent bands in waveform segment 344 satisfy the following conditions:

[0074] Sl i<Sl i+1 ≤1.3Sl i ;

[0075] 0.8Nl i ≤Nl i+1 <Nl i .

[0076] The length of the second non-wavy segment 343 of the leading edge 3401 of blade 34 along the axial direction of impeller 30 is denoted as H3, 0.5(H z -H1-H2)≤H3≤(H Z -H1-H2), where H z This refers to the axial dimension of the impeller 30. Generally, the end of the second non-wave-shaped section 343 needs to extend to the position of the middle disk 33 because the second non-wave-shaped section 343 is the inlet mainstream area, where the airflow is relatively stable and there are relatively few large-scale vortices. If a wave-shaped section 344 is set (which can also be understood as the wave-shaped section 344 extending to this area), although it can destroy a small part of the large-scale vortices, the mainstream is destroyed, generating more small-scale vortices. The overall vortex intensity may actually be greater than the intensity of the original small part of the large-scale vortices. In addition, because of the partial loss of material in this area of ​​the blade 34, the work capacity will also be reduced.

[0077] Based on the above, the starting section of the leading and trailing edges of blade 34 (near the end) is generally rounded to avoid sharp corners, and the depth is included in the starting section.

[0078] For dual-inlet centrifugal fans, based on the flow rate, it is necessary to modify the leading edge characteristics of the front and rear blades to solve the problem of different flow states on both sides and achieve better noise reduction on both sides of the dual-inlet fan. Specifically, for impellers with dual inlets (that is, air is introduced from both the front and rear of the volute, with the side where the motor is located being the secondary air inlet and the other side being the main air inlet), the front and rear blade segments of the impeller adopt a similar design.

[0079] In this embodiment, the leading edge 3401 of the impeller 30 blade 34 adopts a segmented design, including a second non-wave-shaped segment 343 adjacent to the central disk 33 and a wave-shaped segment 344 away from the central disk 33. The second non-wave-shaped segment 343 is preferably a straight segment, and its extension direction is parallel to or at an angle to the axis of the impeller 30. In the preferred embodiment, the second non-wave-shaped segment 343 is a straight segment whose extension direction is parallel to the axis of the impeller 30. The region of the leading edge 3401 of the impeller 30 adjacent to the central disk 33 corresponds to the inlet mainstream region of the impeller 30, where the airflow is relatively stable and there are relatively few large-scale vortices. If a wave-shaped segment were set, although it could destroy a small number of large-scale vortices, the mainstream would be destroyed, generating more small-scale vortices. The overall vortex strength might actually be greater than the strength of the original few large-scale vortices. In addition, due to the partial loss of material in the blade 34, the work capacity would also be reduced. Therefore, the structural design of setting the second non-wave-shaped segment 343 is adopted. On the other hand, due to the influence of the casing 10 (i.e., the bellows) outside the centrifugal fan 13, the airflow near the front plate 31 or rear plate 32 of the centrifugal fan 13 impeller 30 has a large angle of bend, and the airflow has a large impact on the leading edge 3401 of the blade 34. The set waveform segment 344 can perform vortex breaking and noise reduction, breaking large-scale vortices into small-scale vortices, and reducing the intensity of vortices. The blade 34 of the impeller 30 of the present invention strengthens the control of the tip recirculation zone through segmented design, reduces the impact on the stable airflow in the main intake zone of the blade leading edge 3401, weakens the impact of the blade size reduction on the work capacity of the impeller 30, improves aerodynamic capability, and enhances the noise reduction effect.

[0080] Figure 12 The simulation compares the velocity vectors of the centrifugal fan 13 of this embodiment with a prototype (as a comparison model) featuring a bladeless leading-edge segmented waveform structure (i.e., a conventional rectangular blade mechanism). It can be seen that in this embodiment, the segmented waveform structure effectively breaks vortices near the impeller 30 inlet leading edge 3401. The vortex size above the impeller 30 leading edge 3401 is significantly smaller than that of the prototype, while the lower mainstream area remains unaffected. Due to the influence of the vortex above the impeller 30 leading edge 3401, the prototype exhibits weaker axial velocity uniformity at the impeller 30 outlet compared to this embodiment. Therefore, the aerodynamic efficiency of the centrifugal fan 13 in this embodiment can be improved by 2%.

Claims

1. A centrifugal fan, comprising: volute and impeller; A collector is provided at the air inlet of the volute. The impeller includes a first disk and a second disk arranged opposite to each other in the front-to-back direction, with the first disk located at the air inlet of the fan. Multiple blades are connected between the first and second discs and distributed circumferentially. Each blade also has a leading edge on the air inlet side and a trailing edge on the air outlet side. The feature is that: at least one of the blades has a wave-shaped segment on its leading edge, and the length H2 of the wave-shaped segment in the axial direction of the impeller satisfies the condition: And 0.8D n ≤D1≤D n 0.5≤H z / H q ≤2; where D1 is the maximum diameter of the collector inlet, D n H is the minimum inner diameter of the impeller. z H is the axial depth of the impeller. q The depth of the air intake space inside the range hood casing, located in front of or behind the centrifugal fan.

2. The centrifugal fan according to claim 1, characterized in that: The blade also includes a first non-waveform segment positioned closer to the first disk than the waveform segment; the length H1 of the first non-waveform segment along the axial direction of the impeller satisfies the following condition: And H0∈(0,30]mm; where H0 is the distance from the first disc of the impeller to the front or rear cover plate of the volute.

3. The centrifugal fan according to claim 1 or 2, characterized in that: When H q When the thickness is not uniform, the arithmetic mean distance H is used. qc , Area element A is generally taken as the effective ventilation area enclosed by the inlet of the collector.

4. The centrifugal fan according to claim 2, characterized in that: The blade also includes a second non-wave-shaped section located away from the air inlet; the length of the second non-wave-shaped section along the axis of the impeller is denoted as H3, where 0.5 (H z -H1-H2)≤H3≤(H Z -H1-H2).

5. The centrifugal fan according to claim 3, characterized in that: The wavelength of the waveform segment is denoted as S1, and S1 satisfies the following condition: And α∈[30°, 90°]; where α is the impeller inlet angle.

6. The centrifugal fan according to claim 5, characterized in that: The wavelength of the waveform segment gradually increases from the end closer to the first disk to the end farther away from the first disk.

7. The centrifugal fan according to claim 6, characterized in that: The wavelengths of any two adjacent bands in the waveform segment are denoted as Sl. i and Sl i+1 The wavelengths of any two adjacent bands in the waveform segment satisfy the condition: Sl i <Sl i+1 ≤1.3Sl i .

8. The centrifugal fan according to claim 3, characterized in that: The wave heights of any two adjacent wave bands in the waveform segment are denoted as N1, and the following condition must be met: 0.1sin(α)L≤N1≤0.4sin(α)L; where L is the width dimension of the blade after flattening, and α is the inlet angle of the impeller.

9. The centrifugal fan according to claim 8, characterized in that: The wave height of the waveform segment gradually decreases from the end closer to the first disk to the end farther away from the first disk.

10. The centrifugal fan according to claim 9, characterized in that: The wave heights of any two adjacent wave bands in the waveform segment satisfy the condition: 0.8Nl i ≤Nl i+1 <Nl i .

11. The centrifugal fan according to claim 4, characterized in that: The first non-waveform segment is a straight line segment, and the extension direction of the first non-waveform segment is parallel to or at an angle to the axis of the impeller. The second non-wavelength segment is a straight line segment, and the extension direction of the second non-wavelength segment is parallel to or at an angle to the axis of the impeller.

12. A range hood, comprising a housing and a centrifugal fan disposed within the housing, characterized in that: The centrifugal fan is the centrifugal fan according to any one of claims 1-11.

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