Asymmetric impeller and multi-blade centrifugal fan

Abstract

An asymmetric impeller, comprising a hub (4), a front disc (6) and blades (5), wherein a plurality of blades (5) are circumferentially distributed between the hub (4) and the front disc (6); and the plurality of blades (5) are divided into a plurality of blade periods in the circumferential direction, wherein blade outlet angles of the blades (5) located in the same blade period are the same, and the blade outlet angles of the blades (5) in adjacent blade periods are different. By means of changing the symmetry of distribution of the outlet angles of the blades in the circumferential direction of the impeller, the aim of changing the periodic impact of an airflow on a volute tongue at an outlet of an impeller passage is achieved, and rotation noise of a multi-blade centrifugal fan is reduced. In addition, further provided is a multi-blade centrifugal fan having the asymmetric impeller.

Description

FIELD OF THE INVENTION

[0001] The disclosure relates to the technical field of centrifugal fans, and in particular to an asymmetric impeller and a multi-blade centrifugal fan.BACKGROUND OF THE INVENTION

[0002] With the improvement of industrialization, noise pollution has become an important environmental problem faced by mankind. Noise not only affects normal rest, study and work of people, but also can seriously endanger human health and induce a variety of diseases. Multi-blade centrifugal fan is a kind of centrifugal fan, and belongs to a blade fan. The impeller of such fan is mainly characterized in that forward blades with a large diameter ratio and a large relative width are adopted, and the number of blades is large. As a general machine, the fan is mainly used in ventilation of mines and underground engineering, ventilation and induced draft of boilers, delivery of high-temperature corrosive gases in chemical plants, ventilation of air conditioning and protective equipment, and the like. The area where the multi-blade centrifugal fan is used most widely is the air conditioning industry. With the rapid development of domestic air conditioning industry, increasingly higher requirements are proposed for miniaturization, low noise and high efficiency of fans. With the improvement of people's living standards, the requirements for the quality of air conditioner, including two indexes of refrigeration (heat) and noise, are also getting higher and higher. Multi-blade centrifugal fan is a key factor affecting the quality of air conditioner, and the performance of the multi-blade centrifugal fan inevitably has a significant impact on the overall quality of the air conditioner.

[0003] The main noise of the fan is aerodynamic noise, which is mainly composed of two parts: rotational noise and turbulent noise. The rotational noise is a discrete noise whose frequency is the blade passing frequency and its harmonics, while the turbulent noise is a broadband noise whose spectrum is a broadband continuous spectrum. In general, the discrete noise exceeds the continuous portion by 5 to 10 dB, especially for the case of small volute tongue gaps and high rotational speeds. Therefore, the rotational noise is the main component of fan noise. The source generating the rotational noise mainly lies in that the outlet of the impeller has a wake, the velocity and pressure distribution of the airflow are not uniform, and the non-uniform airflow acts on the volute tongue to form pulse power that changes along with time, resulting in generation of the rotational noise.

[0004] Most of the previous low-noise designs of multi-blade centrifugal fans will cause a large loss in the performance of the fan, and also bring difficulties to the processing of the impeller structure.SUMMARY OF THE INVENTION

[0005] A first objective of the present disclosure is to provide an asymmetric impeller, which can solve the problem of fan performance loss caused by noise reduction in the prior art.

[0006] According to the present disclosure, there is provided an asymmetric impeller including a hub, a front disk and a plurality of blades distributed circumferentially between the hub and the front disk,

[0007] in which the plurality of blades are divided into a plurality of blade cycles in the circumferential direction, blade outlet angles of the blades in the same blade cycle are the same, and the blade outlet angle of the blade in one blade cycle is different from that in a blade cycle adjacent to the one blade cycle.

[0008] Preferably, according to the blade outlet angle, the impeller is divided into a plurality of impeller cycles, and each impeller cycle occupies the same angle in the circumferential direction.

[0009] Preferably, according to the blade outlet angle, the number of cycles in which the impeller is divided is not less than 3.

[0010] Preferably, the number of cycles in which the impeller is divided is 3 to 9.

[0011] Preferably, the numbers of blades in adjacent blade cycles are not equal.

[0012] Preferably, the blade outlet angle of the blade in one blade cycle is different from that in another blade cycle by not less than 2°.

[0013] Preferably, the difference from the blade outlet angle of the blade in one blade cycle to that in another blade cycle is ranged from 2° to 10°.

[0014] Preferably, the difference from the blade outlet angle of the blade in a certain blade cycle to that in one blade cycle adjacent to the certain blade cycle is different from the difference from the blade outlet angle of the blade in the certain blade cycle to that in another blade cycle adjacent to the certain blade cycle.

[0015] According to the present disclosure, there is further provided a multi-blade centrifugal fan including the impeller as described above, a volute, a collector and a volute tongue.

[0016] Preferably, the volute tongue is a straight volute tongue or an inclined volute tongue.

[0017] According to the present disclosure, there are provided the beneficial effects as follows.

[0018] By changing the symmetry of the outlet angle of the blades in the circumferential distribution of the impeller, the purpose of changing the periodicity of the impact of the airflow on the volute tongue at the outlet of the impeller flow channel is achieved, and the rotation noise of the multi-blade centrifugal fan is reduced.BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the specific implementation of the present disclosure or the technical solution in the prior art, the following will briefly introduce the drawings required for use in the specific implementation or prior art description. Obviously, the drawings in the following description are some implementations of the present disclosure. For ordinary technicians in this field, other drawings can also be obtained based on these drawings without creative work.

[0020] FIG. 1 is a schematic diagram of a multi-blade centrifugal fan according to an embodiment of the present disclosure;

[0021] FIG. 2a is a side view of a multi-blade centrifugal fan according to an embodiment of the present disclosure;

[0022] FIG. 2b is a sectional view taken along line A-A of FIG. 2a;

[0023] FIG. 3 is a schematic diagram of an asymmetric impeller according to the present disclosure; and

[0024] FIG. 4 is a schematic diagram of the blade outlet angle distribution of an asymmetric impeller according to the present disclosure.

[0025] Reference signs are denoted as follows:

[0026] 1: volute; 2: impeller; 3: collector; 4: hub; 5: blade; 6: front disk; 7: volute tongue.DETAILED DESCRIPTION OF THE INVENTION

[0027] The technical solution of the present disclosure will be described clearly and completely in conjunction with the embodiments below. Obviously, the described embodiments are part of the embodiments of the present disclosure, rather than all of the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present disclosure.

[0028] In the description of the present disclosure, it should be noted that the orientation or position relationship indicated by the terms “center”, “longitudinal”, “lateral”, “length”, “width”, “thickness”, “up”, “down”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inside”, “outside”, “clockwise”, “counterclockwise”, and the like is based on the orientation or position relationship shown in the accompanying drawings, which is only for the convenience of describing the present disclosure and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present disclosure.

[0029] In addition, the terms “first” and “second” are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as “first” and “second” may explicitly or implicitly include one or more of the features. In the description of the present disclosure, “a plurality of” means two or more, unless otherwise clearly and specifically defined. In addition, the terms “installed”, “connected” and “connecting” should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present disclosure can be understood according to specific circumstances.

[0030] The following is a further detailed description of the present application with reference to the accompanying drawings.

[0031] As shown in FIGS. 1 to 4, according to the present embodiment, there is provided an asymmetric impeller, in which the impeller 2 includes a hub 4, a front disk 6 and blades 5, and a plurality of blades 5 are distributed circumferentially between the hub 4 and the front disk 6.

[0032] The plurality of blades 5 are divided into a plurality of blade cycles in the circumferential direction, the blade outlet angles of the blades in the same blade cycle are the same, and the blade outlet angle of the blade in one blade cycle is different from that in a blade cycle adjacent to the one blade cycle.

[0033] The asymmetric impeller means that the blades 5 in the circumference of the impeller 2 are designed with circumferential asymmetric outlet angles, The asymmetric outlet angles refers to that, according to the outlet angle, the blades are divided into a plurality of cycles in the circumferential direction, the outlet angles of the blades in each cycle are the same, but the blade outlet angle of the blade in one blade cycle is different from that in a blade cycle adjacent to the one blade cycle.

[0034] The blade cycle is divided as follows. The circumferentially distributed blades are divided into different cycles (intervals) in turn, and each cycle includes a number of blades.

[0035] In the present embodiment, by changing the symmetry of the outlet angle of the blades 5 in the circumferential distribution of the impeller 2, the purpose of changing the periodicity of the impact of the airflow on the volute tongue 7 at the outlet of the impeller flow channel is achieved, and the rotation noise of the multi-blade centrifugal fan is reduced.

[0036] The rotation noise of the multi-blade centrifugal fan is the noise generated by the air thrown out of the blade outlet flow channel hitting the volute tongue 7. The rotation noise is the maximum when the airflow at the outlet of the blade 5 collides with the volute tongue 7.

[0037] Specifically, for a fan impeller with the same outlet angle, the intensity and phase of the noise generated by each airflow at the outlet of the flow channel in the impeller colliding with the volute tongue 7 are the same, so the noise generated by the airflows at the outlet of the flow channel of two adjacent blades 5 colliding with the volute tongue 7 has the same phase difference, resulting in the noise generated when the airflow at each flow channel outlet hits the volute tongue 7 will be superimposed with the previous one, so that the pulsation intensity at the rotation frequency is continuously superimposed and enhanced, resulting in an increase in the rotation noise.

[0038] The frequency of the rotation noise is the product of the number of blades 2 and the rotation speed in the unit of second of the impeller.

[0039] In the present application, due to the different impact strengths on the volute tongue caused by two blades 5 with different outlet mounting angles in adjacent blade cycles, the frequency of noise generated by the airflow at the outlet of the blade 5 impacting the volute tongue 7 in one cycle is different from that in a cycle adjacent to the one cycle. Therefore, in adjacent cycles, the noise generated by the airflow at the outlet of the blade 5 impacting the volute tongue 7 cannot be superimposed, thereby reducing the rotation noise of the multi-blade centrifugal fan.

[0040] In the asymmetric impeller 2 described in the present disclosure, in a single cycle, the outlet mounting angles of the blades 5 are equal, but the number of blades 5 is small. Thus, compared with the frequency of the rotation noise of a conventional multi-blade centrifugal fan, the frequency of the noise generated will be lower, thereby resulting in a shift in the fan noise band. At the same time, the outlet angles of the blades in the alternate cycles are the same, so the amplitude of the noise sound pressure level generated will be the same. However, there will be a phase difference from the noise in other cycles with the same number of blades, and no obvious sound wave superposition phenomenon will occur.

[0041] Furthermore, during the rotation of the multi-blade centrifugal fan, if the phase difference of the impact noise of the volute tongue 7 generated at the outlet of the blades 5 in the alternate cycles is opposite, the sound waves may be weakened to each other during the superposition process, thereby reducing the noise intensity of the fan.

[0042] The blade outlet angle of the impeller 2 refers to the airflow outlet mounting angle of the blade, that is, the outlet angle of the blade at the outer diameter of the impeller, such as the angle θ shown in FIGS. 2 and 4. The periodic impact of different blade outlets on the fan volute tongue 7 is reduced by different blade mounting angles.

[0043] According to the outlet angle of the blade, the impeller is divided into a plurality of impeller cycles, and each impeller cycle occupies the same angle in the circumferential direction. According to the outlet angle of the blade, the number of the divided impeller cycles is not less than 3, and the value is ranged from 3 to 9. As shown in FIG. 4, the impeller is divided into 4 impeller cycles, and the 4 cycles are A1, A2, A3, and A4, respectively. In four impeller cycles A1, A2, A3, and A4, each impeller cycle is correspondingly provided with a plurality of blades, and the plurality of blades in each impeller cycle constitute a blade cycle. In FIG. 4, the corresponding blade outlet angles in the four blade cycles A1, A2, A3, and A4 are θ2, θ1, θ4, and θ3, respectively.

[0044] Both the blade cycle and the impeller cycle are artificially defined cycles, and there is a one-to-one correspondence between the blade cycle and the impeller cycle.

[0045] The outlet angles of the blades in each blade cycle are equal, which has no effect on the dynamic balance of the fan impeller. The blades are rotated to do work with the dynamic balance of the impeller being kept, and at the same time the operability of the impeller design is increased.

[0046] The outlet angles of the blades in adjacent blade cycles are not equal, and the numbers of blades in adjacent blade cycles are not equal. This method realizes circumferential asymmetry, which is beneficial to the design of the fan impeller and the control of the difference in the blade outlet flow field in adjacent cycles.

[0047] For processing of the blade 5, there are no special requirements for the material and processing of the blade, and it has the universal characteristics of material and processing.

[0048] The difference in blade outlet angles in adjacent cycles is not less than 2°, and the asymmetric distribution of blades in the circumferential direction of the impeller is achieved by adjusting the difference in blade outlet angles in adjacent cycles. In addition, the difference in blade outlet angles in different cycles is generally ranged from 2° to 10°, and the difference in outlet angles in one set of adjacent cycles is different from that in another set of adjacent cycles. The difference in blade outlet angles between adjacent cycles is controlled to be ranged from 2° to 10°, which avoids excessive difference in blade outlet angles during cycle transition, resulting in excessive difference in the reaction aerodynamic force on the impeller and causing periodic vibration of the impeller.

[0049] In this embodiment, a multi-blade centrifugal fan is further provided, which includes the impeller 2 as described above, a volute 1, a collector 3 and a volute tongue 7.

[0050] In this embodiment, there is no requirement for the structure of the volute tongue 7, which can be a straight volute tongue or an inclined volute tongue with a certain angle.

[0051] In summary, a multi-blade centrifugal fan based on an asymmetric impeller is provided. In order to reduce the aerodynamic noise of the centrifugal fan, the impeller in the centrifugal fan is designed in a manner of a circumferential asymmetric blade outlet mounting angle to reduce the periodic scouring of the volute tongue by the airflow at the outlet of the blade flow channel. The number of cycles into which the impeller is divided is 3 to 9. The blade spacing outlet angles in each cycle are equal, and the blades in the diagonally distributed cycles have the same distribution. The fan impeller has the characteristics of good dynamic balance. It overcomes the characteristics of large aerodynamic noise of existing multi-blade centrifugal fans, and the existing noise reduction methods have the characteristics of low aerodynamic noise reduction, large aerodynamic performance loss and difficult processing.

[0052] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Examples

Embodiment Construction

[0027]The technical solution of the present disclosure will be described clearly and completely in conjunction with the embodiments below. Obviously, the described embodiments are part of the embodiments of the present disclosure, rather than all of the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present disclosure.

[0028]In the description of the present disclosure, it should be noted that the orientation or position relationship indicated by the terms “center”, “longitudinal”, “lateral”, “length”, “width”, “thickness”, “up”, “down”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inside”, “outside”, “clockwise”, “counterclockwise”, and the like is based on the orientation or position relationship shown in the accompanying drawings, which is only for the convenience of describing the present disclosure ...

FIELD OF THE INVENTION

[0001] The disclosure relates to the technical field of centrifugal fans, and in particular to an asymmetric impeller and a multi-blade centrifugal fan.BACKGROUND OF THE INVENTION

[0002] With the improvement of industrialization, noise pollution has become an important environmental problem faced by mankind. Noise not only affects normal rest, study and work of people, but also can seriously endanger human health and induce a variety of diseases. Multi-blade centrifugal fan is a kind of centrifugal fan, and belongs to a blade fan. The impeller of such fan is mainly characterized in that forward blades with a large diameter ratio and a large relative width are adopted, and the number of blades is large. As a general machine, the fan is mainly used in ventilation of mines and underground engineering, ventilation and induced draft of boilers, delivery of high-temperature corrosive gases in chemical plants, ventilation of air conditioning and protective equipment, and the like. The area where the multi-blade centrifugal fan is used most widely is the air conditioning industry. With the rapid development of domestic air conditioning industry, increasingly higher requirements are proposed for miniaturization, low noise and high efficiency of fans. With the improvement of people's living standards, the requirements for the quality of air conditioner, including two indexes of refrigeration (heat) and noise, are also getting higher and higher. Multi-blade centrifugal fan is a key factor affecting the quality of air conditioner, and the performance of the multi-blade centrifugal fan inevitably has a significant impact on the overall quality of the air conditioner.

[0003] The main noise of the fan is aerodynamic noise, which is mainly composed of two parts: rotational noise and turbulent noise. The rotational noise is a discrete noise whose frequency is the blade passing frequency and its harmonics, while the turbulent noise is a broadband noise whose spectrum is a broadband continuous spectrum. In general, the discrete noise exceeds the continuous portion by 5 to 10 dB, especially for the case of small volute tongue gaps and high rotational speeds. Therefore, the rotational noise is the main component of fan noise. The source generating the rotational noise mainly lies in that the outlet of the impeller has a wake, the velocity and pressure distribution of the airflow are not uniform, and the non-uniform airflow acts on the volute tongue to form pulse power that changes along with time, resulting in generation of the rotational noise.

[0004] Most of the previous low-noise designs of multi-blade centrifugal fans will cause a large loss in the performance of the fan, and also bring difficulties to the processing of the impeller structure.SUMMARY OF THE INVENTION

[0005] A first objective of the present disclosure is to provide an asymmetric impeller, which can solve the problem of fan performance loss caused by noise reduction in the prior art.

[0006] According to the present disclosure, there is provided an asymmetric impeller including a hub, a front disk and a plurality of blades distributed circumferentially between the hub and the front disk,

[0007] in which the plurality of blades are divided into a plurality of blade cycles in the circumferential direction, blade outlet angles of the blades in the same blade cycle are the same, and the blade outlet angle of the blade in one blade cycle is different from that in a blade cycle adjacent to the one blade cycle.

[0008] Preferably, according to the blade outlet angle, the impeller is divided into a plurality of impeller cycles, and each impeller cycle occupies the same angle in the circumferential direction.

[0009] Preferably, according to the blade outlet angle, the number of cycles in which the impeller is divided is not less than 3.

[0010] Preferably, the number of cycles in which the impeller is divided is 3 to 9.

[0011] Preferably, the numbers of blades in adjacent blade cycles are not equal.

[0012] Preferably, the blade outlet angle of the blade in one blade cycle is different from that in another blade cycle by not less than 2°.

[0013] Preferably, the difference from the blade outlet angle of the blade in one blade cycle to that in another blade cycle is ranged from 2° to 10°.

[0014] Preferably, the difference from the blade outlet angle of the blade in a certain blade cycle to that in one blade cycle adjacent to the certain blade cycle is different from the difference from the blade outlet angle of the blade in the certain blade cycle to that in another blade cycle adjacent to the certain blade cycle.

[0015] According to the present disclosure, there is further provided a multi-blade centrifugal fan including the impeller as described above, a volute, a collector and a volute tongue.

[0016] Preferably, the volute tongue is a straight volute tongue or an inclined volute tongue.

[0017] According to the present disclosure, there are provided the beneficial effects as follows.

[0018] By changing the symmetry of the outlet angle of the blades in the circumferential distribution of the impeller, the purpose of changing the periodicity of the impact of the airflow on the volute tongue at the outlet of the impeller flow channel is achieved, and the rotation noise of the multi-blade centrifugal fan is reduced.BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the specific implementation of the present disclosure or the technical solution in the prior art, the following will briefly introduce the drawings required for use in the specific implementation or prior art description. Obviously, the drawings in the following description are some implementations of the present disclosure. For ordinary technicians in this field, other drawings can also be obtained based on these drawings without creative work.

[0020] FIG. 1 is a schematic diagram of a multi-blade centrifugal fan according to an embodiment of the present disclosure;

[0021] FIG. 2a is a side view of a multi-blade centrifugal fan according to an embodiment of the present disclosure;

[0022] FIG. 2b is a sectional view taken along line A-A of FIG. 2a;

[0023] FIG. 3 is a schematic diagram of an asymmetric impeller according to the present disclosure; and

[0024] FIG. 4 is a schematic diagram of the blade outlet angle distribution of an asymmetric impeller according to the present disclosure.

[0025] Reference signs are denoted as follows:

[0026] 1: volute; 2: impeller; 3: collector; 4: hub; 5: blade; 6: front disk; 7: volute tongue.DETAILED DESCRIPTION OF THE INVENTION

[0027] The technical solution of the present disclosure will be described clearly and completely in conjunction with the embodiments below. Obviously, the described embodiments are part of the embodiments of the present disclosure, rather than all of the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present disclosure.

[0028] In the description of the present disclosure, it should be noted that the orientation or position relationship indicated by the terms “center”, “longitudinal”, “lateral”, “length”, “width”, “thickness”, “up”, “down”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inside”, “outside”, “clockwise”, “counterclockwise”, and the like is based on the orientation or position relationship shown in the accompanying drawings, which is only for the convenience of describing the present disclosure and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present disclosure.

[0029] In addition, the terms “first” and “second” are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as “first” and “second” may explicitly or implicitly include one or more of the features. In the description of the present disclosure, “a plurality of” means two or more, unless otherwise clearly and specifically defined. In addition, the terms “installed”, “connected” and “connecting” should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present disclosure can be understood according to specific circumstances.

[0030] The following is a further detailed description of the present application with reference to the accompanying drawings.

[0031] As shown in FIGS. 1 to 4, according to the present embodiment, there is provided an asymmetric impeller, in which the impeller 2 includes a hub 4, a front disk 6 and blades 5, and a plurality of blades 5 are distributed circumferentially between the hub 4 and the front disk 6.

[0032] The plurality of blades 5 are divided into a plurality of blade cycles in the circumferential direction, the blade outlet angles of the blades in the same blade cycle are the same, and the blade outlet angle of the blade in one blade cycle is different from that in a blade cycle adjacent to the one blade cycle.

[0033] The asymmetric impeller means that the blades 5 in the circumference of the impeller 2 are designed with circumferential asymmetric outlet angles, The asymmetric outlet angles refers to that, according to the outlet angle, the blades are divided into a plurality of cycles in the circumferential direction, the outlet angles of the blades in each cycle are the same, but the blade outlet angle of the blade in one blade cycle is different from that in a blade cycle adjacent to the one blade cycle.

[0034] The blade cycle is divided as follows. The circumferentially distributed blades are divided into different cycles (intervals) in turn, and each cycle includes a number of blades.

[0035] In the present embodiment, by changing the symmetry of the outlet angle of the blades 5 in the circumferential distribution of the impeller 2, the purpose of changing the periodicity of the impact of the airflow on the volute tongue 7 at the outlet of the impeller flow channel is achieved, and the rotation noise of the multi-blade centrifugal fan is reduced.

[0036] The rotation noise of the multi-blade centrifugal fan is the noise generated by the air thrown out of the blade outlet flow channel hitting the volute tongue 7. The rotation noise is the maximum when the airflow at the outlet of the blade 5 collides with the volute tongue 7.

[0037] Specifically, for a fan impeller with the same outlet angle, the intensity and phase of the noise generated by each airflow at the outlet of the flow channel in the impeller colliding with the volute tongue 7 are the same, so the noise generated by the airflows at the outlet of the flow channel of two adjacent blades 5 colliding with the volute tongue 7 has the same phase difference, resulting in the noise generated when the airflow at each flow channel outlet hits the volute tongue 7 will be superimposed with the previous one, so that the pulsation intensity at the rotation frequency is continuously superimposed and enhanced, resulting in an increase in the rotation noise.

[0038] The frequency of the rotation noise is the product of the number of blades 2 and the rotation speed in the unit of second of the impeller.

[0039] In the present application, due to the different impact strengths on the volute tongue caused by two blades 5 with different outlet mounting angles in adjacent blade cycles, the frequency of noise generated by the airflow at the outlet of the blade 5 impacting the volute tongue 7 in one cycle is different from that in a cycle adjacent to the one cycle. Therefore, in adjacent cycles, the noise generated by the airflow at the outlet of the blade 5 impacting the volute tongue 7 cannot be superimposed, thereby reducing the rotation noise of the multi-blade centrifugal fan.

[0040] In the asymmetric impeller 2 described in the present disclosure, in a single cycle, the outlet mounting angles of the blades 5 are equal, but the number of blades 5 is small. Thus, compared with the frequency of the rotation noise of a conventional multi-blade centrifugal fan, the frequency of the noise generated will be lower, thereby resulting in a shift in the fan noise band. At the same time, the outlet angles of the blades in the alternate cycles are the same, so the amplitude of the noise sound pressure level generated will be the same. However, there will be a phase difference from the noise in other cycles with the same number of blades, and no obvious sound wave superposition phenomenon will occur.

[0041] Furthermore, during the rotation of the multi-blade centrifugal fan, if the phase difference of the impact noise of the volute tongue 7 generated at the outlet of the blades 5 in the alternate cycles is opposite, the sound waves may be weakened to each other during the superposition process, thereby reducing the noise intensity of the fan.

[0042] The blade outlet angle of the impeller 2 refers to the airflow outlet mounting angle of the blade, that is, the outlet angle of the blade at the outer diameter of the impeller, such as the angle θ shown in FIGS. 2 and 4. The periodic impact of different blade outlets on the fan volute tongue 7 is reduced by different blade mounting angles.

[0043] According to the outlet angle of the blade, the impeller is divided into a plurality of impeller cycles, and each impeller cycle occupies the same angle in the circumferential direction. According to the outlet angle of the blade, the number of the divided impeller cycles is not less than 3, and the value is ranged from 3 to 9. As shown in FIG. 4, the impeller is divided into 4 impeller cycles, and the 4 cycles are A1, A2, A3, and A4, respectively. In four impeller cycles A1, A2, A3, and A4, each impeller cycle is correspondingly provided with a plurality of blades, and the plurality of blades in each impeller cycle constitute a blade cycle. In FIG. 4, the corresponding blade outlet angles in the four blade cycles A1, A2, A3, and A4 are θ2, θ1, θ4, and θ3, respectively.

[0044] Both the blade cycle and the impeller cycle are artificially defined cycles, and there is a one-to-one correspondence between the blade cycle and the impeller cycle.

[0045] The outlet angles of the blades in each blade cycle are equal, which has no effect on the dynamic balance of the fan impeller. The blades are rotated to do work with the dynamic balance of the impeller being kept, and at the same time the operability of the impeller design is increased.

[0046] The outlet angles of the blades in adjacent blade cycles are not equal, and the numbers of blades in adjacent blade cycles are not equal. This method realizes circumferential asymmetry, which is beneficial to the design of the fan impeller and the control of the difference in the blade outlet flow field in adjacent cycles.

[0047] For processing of the blade 5, there are no special requirements for the material and processing of the blade, and it has the universal characteristics of material and processing.

[0048] The difference in blade outlet angles in adjacent cycles is not less than 2°, and the asymmetric distribution of blades in the circumferential direction of the impeller is achieved by adjusting the difference in blade outlet angles in adjacent cycles. In addition, the difference in blade outlet angles in different cycles is generally ranged from 2° to 10°, and the difference in outlet angles in one set of adjacent cycles is different from that in another set of adjacent cycles. The difference in blade outlet angles between adjacent cycles is controlled to be ranged from 2° to 10°, which avoids excessive difference in blade outlet angles during cycle transition, resulting in excessive difference in the reaction aerodynamic force on the impeller and causing periodic vibration of the impeller.

[0049] In this embodiment, a multi-blade centrifugal fan is further provided, which includes the impeller 2 as described above, a volute 1, a collector 3 and a volute tongue 7.

[0050] In this embodiment, there is no requirement for the structure of the volute tongue 7, which can be a straight volute tongue or an inclined volute tongue with a certain angle.

[0051] In summary, a multi-blade centrifugal fan based on an asymmetric impeller is provided. In order to reduce the aerodynamic noise of the centrifugal fan, the impeller in the centrifugal fan is designed in a manner of a circumferential asymmetric blade outlet mounting angle to reduce the periodic scouring of the volute tongue by the airflow at the outlet of the blade flow channel. The number of cycles into which the impeller is divided is 3 to 9. The blade spacing outlet angles in each cycle are equal, and the blades in the diagonally distributed cycles have the same distribution. The fan impeller has the characteristics of good dynamic balance. It overcomes the characteristics of large aerodynamic noise of existing multi-blade centrifugal fans, and the existing noise reduction methods have the characteristics of low aerodynamic noise reduction, large aerodynamic performance loss and difficult processing.

[0052] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Examples

Embodiment Construction

[0027]The technical solution of the present disclosure will be described clearly and completely in conjunction with the embodiments below. Obviously, the described embodiments are part of the embodiments of the present disclosure, rather than all of the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present disclosure.

[0028]In the description of the present disclosure, it should be noted that the orientation or position relationship indicated by the terms “center”, “longitudinal”, “lateral”, “length”, “width”, “thickness”, “up”, “down”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inside”, “outside”, “clockwise”, “counterclockwise”, and the like is based on the orientation or position relationship shown in the accompanying drawings, which is only for the convenience of describing the present disclosure ...

Claims

1. An asymmetric impeller comprising a hub, a front disk and a plurality of blades distributed circumferentially between the hub and the front disk,wherein the plurality of blades are divided into a plurality of blade cycles in the circumferential direction, blade outlet angles of the blades in the same blade cycle are the same, and the blade outlet angle of the blade in one blade cycle is different from that in a blade cycle adjacent to the one blade cycle.

2. The asymmetric impeller according to claim 1, wherein the impeller is divided into a plurality of impeller cycles according to the blade outlet angle, and each impeller cycle occupies the same angle in the circumferential direction.

3. The asymmetric impeller according to claim 2, wherein the number of cycles in which the impeller is divided is not less than 3 according to the blade outlet angle.

4. The asymmetric impeller according to claim 3, wherein the number of cycles in which the impeller is divided is 3 to 9.

5. The asymmetric impeller according to claim 1, wherein the numbers of blades in adjacent blade cycles are not equal.

6. The asymmetric impeller according to claim 1, wherein the blade outlet angle of the blade in one blade cycle is different from that in another blade cycle by not less than 2°.

7. The asymmetric impeller according to claim 6, wherein the difference from the blade outlet angle of the blade in one blade cycle to that in another blade cycle is ranged from 2° to 10°.

8. The asymmetric impeller according to claim 6, wherein the difference from the blade outlet angle of the blade in a certain blade cycle to that in one blade cycle adjacent to the certain blade cycle is different from the difference from the blade outlet angle of the blade in the certain blade cycle to that in another blade cycle adjacent to the certain blade cycle.

9. A multi-blade centrifugal fan comprising the impeller according to claim 1, a volute, a collector and a volute tongue.

10. The multi-blade centrifugal fan according to claim 9, wherein the volute tongue is a straight volute tongue or an inclined volute tongue.

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