CN117345689A - Tandem type current collector and centrifugal fan with same - Google Patents

Abstract

The invention provides a serial current collector and a centrifugal fan with the serial current collector. The tandem current collector includes: the collector body is provided with an airflow channel, the airflow channel is provided with an airflow inlet end and an airflow outlet end, the airflow outlet end is used for extending into the air inlet end of the upper disc of the centrifugal fan impeller so that airflow enters the upper disc of the centrifugal fan impeller along the airflow channel, and the air outlet direction of the airflow is the direction from the airflow inlet end to the airflow outlet end; the air flow channel sequentially comprises a first flow channel and a second flow channel along the air outlet direction, the flow channel area of the first flow channel is gradually reduced along the air outlet direction, and the second flow channel is internally provided with a throat part in a protruding mode, so that the flow channel area of the second flow channel is gradually reduced and then gradually increased along the air outlet direction. By applying the technical scheme of the invention, when the airflow flows through the throat, a diffusion effect is generated, the fluid is diffused for the first time, stored kinetic energy is converted into static pressure, the pressure head of the fan is increased, and the aerodynamic performance of the fan is improved.

Description

Tandem type current collector and centrifugal fan with same

Technical Field

The invention relates to the technical field of centrifugal fans, in particular to a serial current collector and a centrifugal fan with the serial current collector.

Background

The collector has a diversion effect on the air flow, and the special morphological structure can improve the uniformity of the air flow at the inlet of the impeller, thereby reducing the resistance and loss of the air flow when entering the impeller. The radial and axial clearances (or axial distances) at the collector and impeller inlet may cause leakage of the airflow or generate vortex and spin back flow, affecting the overall aerodynamic performance of the fan.

The conventional common current collector is generally manufactured by metal stretching, and as shown in fig. 1, the cross section of the common current collector is usually formed by arc sections and straight sections due to the limitation of manufacturing process. The air flow inlet end face of the current collector is required to be made into a flat surface due to the assembly with a plane, and the outlet end of the current collector is expected to be in an expanded state, but the metal is easy to split due to stretching, and is difficult to be pulled into an expanded state at the end, and is often in a flat state, so that the static pressure is only converted into kinetic energy when the air flow flows through the inner wall of the current collector, and the kinetic energy is not converted into the static pressure again, thereby reducing the pressure head of the whole fan and affecting the aerodynamic performance of the fan. The gap formed after the common current collector and the centrifugal ventilator are assembled easily causes more leakage loss, the assembly schematic diagram is shown in fig. 2, the air flow outlet end of the common current collector is inserted into the air flow inlet end of the centrifugal impeller, a radial gap A is formed at the end face, as shown in fig. 3, part of air flowing out from the impeller flows back to the vicinity of the gap A due to the pressure difference effect, flows into the impeller through the gap A again, and forms an air flow circulation, and the part of air flow circulation is not expected, otherwise, the energy loss of the whole system is caused, and the whole pressure head of the fan is lowered.

Aiming at the technical problems that the outlet end of the current collector is difficult to form an expansion shape in the prior art, so that the pressure head of a fan is low, no effective solution is proposed at present.

Disclosure of Invention

The invention mainly aims to provide a serial current collector and a centrifugal fan with the serial current collector, so as to solve the technical problem that an outlet end of the current collector is difficult to form an expanded shape in the prior art, so that a pressure head of the fan is low.

In order to achieve the above object, according to one aspect of the present invention, there is provided a tandem current collector including: the collector body is provided with an airflow channel, the airflow channel is provided with an airflow inlet end and an airflow outlet end, the airflow outlet end is used for extending into the air inlet end of the upper disc of the centrifugal fan impeller so that airflow enters the upper disc of the centrifugal fan impeller along the airflow channel, and the air outlet direction of the airflow is the direction from the airflow inlet end to the airflow outlet end; the air flow channel sequentially comprises a first flow channel and a second flow channel along the air outlet direction, the flow channel area of the first flow channel is gradually reduced along the air outlet direction, and the second flow channel is internally provided with a throat part in a protruding mode, so that the flow channel area of the second flow channel is gradually reduced and then gradually increased along the air outlet direction.

Further, the inner wall of the collector body is surrounded to form an airflow channel, the outer wall of the collector body is provided with an annular bulge protruding along the circumferential direction of the collector body, the annular bulge is positioned outside the upper disc of the centrifugal fan impeller, and the annular bulge is arranged at a distance from the upper disc of the centrifugal fan impeller.

Further, an annular protrusion is arranged at the joint of the first flow channel and the second flow channel.

Further, the current collector body includes: the first end of the body section forms an airflow inlet end, the body section is provided with a first inner wall and a first outer wall, and the first inner wall is enclosed to form a first flow channel; the first end of the series section is connected with the second end of the body section, the second end of the series section forms an airflow outlet end, the series section is provided with a second inner wall and a second outer wall, the second inner wall encloses a second flow channel, an annular bulge is arranged at the joint of the second outer wall and the first outer wall, and a throat part is convexly arranged on the second inner wall; wherein, first inner wall, first outer wall, second inner wall, second outer wall are the arc section.

Further, the curvature of the second inner wall is greater than the curvature setting of the first inner wall.

Further, the curvature of the second outer wall is set the same as the curvature of the second inner wall.

Further, the curvature of the first outer wall is set the same as the curvature of the first inner wall.

Further, when the collector body is assembled with the upper disc of the centrifugal fan impeller, at least a portion of the series section extends into the air inlet end of the upper disc of the centrifugal fan impeller, and the body section is arranged at a distance from the air inlet end of the upper disc of the centrifugal fan impeller.

Further, the serial current collector is made of plastic.

According to another aspect of the present invention, there is provided a centrifugal fan having a series collector, which is the above-described series collector.

By applying the technical scheme of the invention, when the air flows along the first flow channel, the flow channel area is continuously reduced, the fluid kinetic energy is continuously increased, the static pressure is reduced, after the air flows enter the second flow channel, the flow channel area of the second flow channel is firstly reduced, the air flow rate is increased, the static pressure is more converted and stored into kinetic energy, when the air flows through the throat, the flow channel area of the second flow channel is initially increased, a diffusion effect is generated, the fluid is subjected to first diffusion, the stored kinetic energy is converted into the static pressure, the pressure head of the fan is increased, the pneumatic performance of the fan is improved, and the required static pressure and flow can be achieved by using lower rotating speed when the fan operates due to higher pressure head of the fan.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention. In the drawings:

fig. 1 shows a schematic structure of a prior art tandem current collector;

FIG. 2 shows a schematic diagram of a prior art assembly of a tandem collector with a centrifugal fan impeller;

FIG. 3 shows an enlarged schematic view of portion A of FIG. 2;

fig. 4 shows a schematic structural view of a first embodiment of a tandem current collector according to the present invention;

fig. 5 shows a schematic structural view of a second embodiment of a tandem current collector according to the present invention;

fig. 6 shows a schematic structural view of a third embodiment of a tandem current collector according to the present invention;

FIG. 7 shows an enlarged schematic view of portion P of FIG. 6;

fig. 8 shows a schematic structural view of a fourth embodiment of a tandem current collector according to the present invention;

fig. 9 shows a schematic structural view of an embodiment of a tandem collector and centrifugal fan impeller assembly according to the present invention.

Wherein the above figures include the following reference numerals:

1. a current collector body;

101. a body straight section; 102. A body circular arc section;

103. an annular protrusion; 104. A throat; 105. A series section;

201. a centrifugal fan impeller upper disc; 202. centrifugal fan impeller blades; 203. the lower disc of the centrifugal fan impeller.

Detailed Description

It should be noted that, in the case of no conflict, the embodiments and features in the embodiments may be combined with each other. The invention will be described in detail below with reference to the drawings in connection with embodiments.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments in accordance with the present application. As used herein, the singular is also intended to include the plural unless the context clearly indicates otherwise, and furthermore, it is to be understood that the terms "comprises" and/or "comprising" when used in this specification are taken to specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof.

It should be noted that the terms "first," "second," and the like in the description and claims of the present application and the above figures are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments of the application described herein are, for example, capable of operation in sequences other than those illustrated or otherwise described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.

Exemplary embodiments according to the present application will now be described in more detail with reference to the accompanying drawings. These exemplary embodiments may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. It should be understood that these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of these exemplary embodiments to those skilled in the art, that in the drawings, it is possible to enlarge the thicknesses of layers and regions for clarity, and that identical reference numerals are used to designate identical devices, and thus descriptions thereof will be omitted.

For convenience of description, the structure of the serial current collector in the prior art is described as follows:

the conventional common current collector is generally manufactured by metal stretching, and as shown in fig. 1, the cross section of the common current collector is usually formed by arc sections and straight sections due to the limitation of manufacturing process. The air flow inlet end face of the current collector is required to be made into a flat surface due to the assembly with a plane, and the outlet end of the current collector is expected to be in an expanded state, but the metal is easy to split due to stretching, and is difficult to be pulled into an expanded state at the end, and is often in a flat state, so that the static pressure is only converted into kinetic energy when the air flow flows through the inner wall of the current collector, and the kinetic energy is not converted into the static pressure again, thereby reducing the pressure head of the whole fan and affecting the aerodynamic performance of the fan. The gap formed after the common current collector and the centrifugal ventilator are assembled easily causes more leakage loss, the assembly schematic diagram is shown in fig. 2, the air flow outlet end of the common current collector is inserted into the air flow inlet end of the centrifugal impeller to form a radial gap A at the end surface, as shown in fig. 3, part of air flowing out from the impeller flows back to the vicinity of the gap A under the action of pressure difference and flows into the impeller through the gap A again to form an air flow circulation, and the part of air flow circulation is not expected, otherwise, the energy loss of the whole system is caused, so that the whole pressure head of the fan is lowered; in addition to the above drawbacks, the material costs of a metal-fabricated current collector are generally high.

Aiming at the problems of poor manufacturability, higher cost, more energy loss generated during working, poor aerodynamic performance and the like of a common current collector in the prior art, according to theoretical analysis and finite element simulation analysis, the application provides the serial current collector for the centrifugal fan, which is used for reducing leakage loss, improving the pressure head and efficiency of the fan, and has high strength, better manufacturability and lower cost.

As shown in connection with fig. 4-9, a tandem current collector is provided according to an embodiment of the present application.

The serial collector comprises a collector body 1, wherein the collector body 1 is provided with an air flow channel, the air flow channel is provided with an air flow inlet end and an air flow outlet end, the air flow outlet end is used for extending into the air inlet end of the upper disc 201 of the centrifugal fan impeller, so that air flow enters the upper disc 201 of the centrifugal fan impeller along the air flow channel, and the air outlet direction of the air flow is the direction from the air flow inlet end to the air flow outlet end; the airflow channel sequentially comprises a first flow channel and a second flow channel along the air outlet direction, the flow channel area of the first flow channel is gradually reduced along the air outlet direction, and the second flow channel is internally provided with a throat 104 in a protruding manner, so that the flow channel area of the second flow channel is gradually reduced and then gradually increased along the air outlet direction.

By applying the technical scheme of the embodiment, when the airflow flows in the first flow channel, the flow channel area is continuously reduced, the fluid kinetic energy is continuously increased, the static pressure is reduced, after the airflow enters the second flow channel, the flow channel area of the second flow channel is firstly reduced, the airflow rate is increased, the static pressure is more converted and stored into kinetic energy, when the airflow flows through the throat 104, the flow channel area of the second flow channel is initially increased, a diffusion effect is generated, the fluid is subjected to first diffusion, the stored kinetic energy is converted into the static pressure, the pressure head of the fan is increased, the pneumatic performance of the fan is improved, and the required static pressure and flow can be achieved by using a lower rotating speed when the fan runs due to the higher pressure head of the fan.

Further, the inner wall of the collector body 1 encloses an air flow channel, the outer wall of the collector body 1 is provided with an annular protrusion 103 protruding along the circumferential direction of the collector body 1, the annular protrusion 103 is located outside the upper disc 201 of the centrifugal fan impeller, and the annular protrusion 103 is located at a distance from the upper disc 201 of the centrifugal fan impeller.

In this embodiment, the annular protrusion 103 breaks up the flow direction of the fluid therein, part of the air flow continues to flow into the impeller for recirculation, and the other part of the air flow is blocked by the flow passage to convert kinetic energy into static pressure. Meanwhile, the radius of vortex formed at the outer wall of the current collector and the inner wall of the upper disc of the impeller is also reduced, namely, the vortex with larger radius and speed is blocked originally, so that fluid is difficult to enter a gap again to form invalid internal circulation, the energy loss of the system is further reduced, and the pressure head of the fan is improved.

Specifically, an annular protrusion 103 is provided at the junction of the first flow channel and the second flow channel. The arrangement can enable the position of the annular bulge 103 to be closer to the throat 104, the scattering vortex effect of the annular bulge 103 is more remarkable, and the annular bulge is matched with the diffusion effect of the throat 104, so that the pressure head of the fan is effectively improved.

Specifically, the collector body 1 includes a body section and a series section 105, a first end of the body section forming an air flow inlet end, the body section having a first inner wall and a first outer wall, the first inner wall surrounding a first flow passage; the first end of the series section 105 is connected with the second end of the body section, the second end of the series section 105 forms an air flow outlet end, the series section 105 is provided with a second inner wall and a second outer wall, the second inner wall encloses a second flow channel, an annular bulge 103 is arranged at the joint of the second outer wall and the first outer wall, and a throat 104 is convexly arranged on the second inner wall; wherein, first inner wall, first outer wall, second inner wall, second outer wall are the arc section. By arranging the body section and the series section 105 into an arc structure, the change rate of the sectional area of the airflow channel can be adjusted by adjusting the curvatures of the body section and the series section 105, and then the change rate of the flow rate of the airflow can be adjusted.

Specifically, the curvature of the second inner wall is greater than the curvature setting of the first inner wall. By the arrangement, the flow passage area of the second flow passage can be switched from reduced to increased in a shorter flow distance, the throat 104 is steeper, the airflow flow rate is changed faster, and the fluid diffusion effect is better.

Preferably, the curvature of the second outer wall is set the same as the curvature of the second inner wall. The arrangement can make the manufacturing process of the current collector simpler and more convenient, and the processing efficiency is improved.

Alternatively, the curvature of the second outer wall may be greater than or less than the curvature of the second inner wall, and may be adjusted as desired.

Preferably, the curvature of the first outer wall is set the same as the curvature of the first inner wall. The arrangement can make the manufacturing process of the current collector simpler and more convenient, and the processing efficiency is improved.

Preferably, the first inner wall and the first outer wall have a curvature of less than 50 m-1 and the second inner wall and the second outer wall have a curvature of greater than 50 m-1.

Alternatively, the curvature of the first outer wall may be greater than or less than the curvature of the first inner wall, and may be adjusted according to actual needs.

Further, when the collector body 1 is assembled with the upper disc 201 of the centrifugal fan wheel, at least part of the series section 105 extends into the air inlet end of the upper disc 201 of the centrifugal fan wheel, the body section being arranged at a distance from the air inlet end of the upper disc 201 of the centrifugal fan wheel. Through the arrangement, the air flow can enter the centrifugal fan after being diffused through the throat 104, the annular protrusion 103 is arranged outside the centrifugal fan, the annular protrusion 103 is ensured to scatter the return air flow, and the pressure head of the fan is increased.

Preferably, the projection of the outer edge of the air inlet end of the upper disc 201 of the centrifugal fan impeller in the radial direction of the air flow channel is arranged coincident with the projection of the throat 104 in the radial direction of the air flow channel, and the throat 104 may also be arranged outside the centrifugal fan.

Preferably, the tandem current collector is made of plastic. The plastic material can save material cost and has better manufacturing manufacturability.

According to another embodiment of the present application, there is provided a centrifugal fan having a series collector, which is the series collector in the above embodiment.

The present application also provides a preferred embodiment of a tandem current collector.

As shown in fig. 4 to 9, the series current collector is composed of a body section and a series section 105, the body section includes a body straight section 101 and a body arc section 102 connected, wherein the body arc section 102 is connected with the series section 105. The series section 105 is a circular arc section. The inner wall surface and the outer wall surface of the current collector are in different line shapes in a serial connection mode.

When the serial current collector is in rotation operation of the centrifugal fan, gas is collected from the straight section 101 of the body and flows into the current collector through the connection part of the serial section 105 and the circular section 102 of the body due to the action of pressure difference between the inside and the outside of the impeller, in the process, the flow passage area is continuously reduced, the fluid kinetic energy is continuously increased, the static pressure is reduced, the flow passage area is continuously reduced to the throat 104 because the curvature of the serial section 105 is larger than the curvature of the circular section 102 of the body, the speed is increased in the process, the static pressure is more converted and stored into kinetic energy, the cross section area is suddenly increased after the flow passage area of the serial section 105 is at the minimum, the fluid is subjected to first diffusion, the stored kinetic energy is converted into the static pressure, and the pressure head of the fan is increased. Part of the air flowing out from the blades 202 of the centrifugal fan impeller flows back to the outer wall of the body section due to the pressure difference effect and is turned around at the annular protrusion 103, so that the large vortex at the position is broken up, the air flow is prevented from entering the gap P between the serial section 105 and the upper disc 201 of the centrifugal fan impeller again, and the pressure head of the fan is increased.

As shown in fig. 8, according to the serial positions, three sections B-B, C-C, D-D are respectively taken in the current collector, and the sections are divided into an inner wall and an outer wall, wherein the section B-B is an air flow inlet position, the inner wall is located at the position with the largest flow passage area, and after passing through the inner wall flow passage, the section B-B reaches the position with the smallest flow passage area of the inner wall of the section C-C.

According to the flow characteristic equation in the pipe:

a is the sectional area of the pipeline, M is Mach number, and c is the flow velocity of the gas.

It is known that in the section from the B-B section to the C-C section, the flow area is reduced, namely dA/A is smaller than 0, and M is smaller than 1 under the working condition, in the equation, dc/C is larger than 0, and the fluid velocity from the B-B section to the C-C section tends to increase.

Again according to bernoulli's equation:

p-a certain point pressure in the fluid, ρ -the point density, V-the flow velocity, ρgh-the gravitational potential energy, and C-the constant.

It can be seen that the pressure P decreases from the B-B section to the C-C section of the series collector as the fluid velocity V increases and the gravitational potential energy is unchanged, i.e. the original static pressure is converted into more kinetic energy.

In order to convert more kinetic energy of the gas in the flow channel into static pressure, the flow channel needs to be expanded, i.e. the section increases along with the flow direction, and the serial section from the C-C section to the D-D section is added on the current collector body in the embodiment. The flow area from the C-C section to the D-D section is reduced and then increased as shown in FIG. 8, thereby forming a throat 104 where the section is smallest, and a diffusion effect is generated after the throat 104, so that more stored kinetic energy is converted into static pressure, and the pressure head of the fan is improved.

As shown in fig. 2 and 6, compared with the fluid flowing condition at the outer walls of the common current collector and the serial current collector, the common current collector is smooth and unobstructed at the gap a, part of the fluid flowing out from the impeller flows back to the position a to continue to flow into the impeller due to the pressure difference, and the fluid forms a large circulation at the position as a whole, which can be assumed to be a large vortex motion.

According to the vorticity calculation formula: m=ρvωr.

Wherein: ρ -fluid density, V-fluid velocity, ω -fluid angular velocity, r-fluid radius.

The amount of vorticity measures the kinetic energy of the fluid and reflects the fluid flow state. The common collector forms a larger vortex at the outer wall of the common collector and the inner wall of the impeller upper disc, and the fluid speed, the angular velocity and the radius of the vortex at the common collector can be reduced in order to break up the vortex at the common collector.

In this embodiment, the serial current collector forms an annular protrusion 103 at the serial position, so that the fluid flow direction at the serial position is broken up, part of the fluid continuously flows into the impeller to circulate again, and the other part of the fluid is blocked by the flow passage to convert kinetic energy into static pressure. At the same time, the radius of the vortex is also reduced, namely, the vortex with larger radius and speed is blocked, so that the fluid is difficult to enter the gap again to form ineffective internal circulation.

In summary, in this embodiment, the pressure head of the serial current collector is larger, so that the required static pressure and flow rate can be achieved with a lower rotation speed when the fan is running, and compared with the similar rotation speed, the noise is relatively reduced. In addition, the serial current collector in the embodiment is formed by plastic, and the special inner and outer wall structures of the serial current collector enable the serial current collector to respectively form a reinforcing rib on the circumference of the inner wall and the circumference of the outer wall, so that the strength of the serial current collector is improved.

The serial current collector in the embodiment has the following technical effects:

1) The characteristics formed at the serial connection position of the serial current collectors enable the leakage loss of the fan to be small, the pressure head of the fan is high, and the efficiency of the whole machine is high;

2) The serial current collector can reach the static pressure requirement with lower rotating speed compared with other competing products because of higher pressure head, and the wind noise of the whole machine is improved after the rotating speed is reduced;

3) The serial current collector is formed by plastic, and structurally analyzed, the characteristics of the serial connection position of the serial current collector are equivalent to that of the current collector which is formed by adding a circle of ribs in the circumferential direction of the inner wall and the outer wall, so that the structural strength of the current collector is enhanced;

4) The serial current collector is formed by plastic, so that the manufacturing manufacturability is better;

5) In terms of cost, the plastic material is adopted, so that the material cost consumption in the case of large quantity is saved.

Spatially relative terms, such as "above … …," "above … …," "upper surface at … …," "above," and the like, may be used herein for ease of description to describe one device or feature's spatial location relative to another device or feature as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as "above" or "over" other devices or structures would then be oriented "below" or "beneath" the other devices or structures. Thus, the exemplary term "above … …" may include both orientations of "above … …" and "below … …". The device may also be positioned in other different ways (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

In addition to the foregoing, references in the specification to "one embodiment," "another embodiment," "an embodiment," etc., mean that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment described in general terms in the application. The appearances of the phrase in various places in the specification are not necessarily all referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with any embodiment, it is intended that such feature, structure, or characteristic be implemented within the scope of the invention.

In the foregoing embodiments, the descriptions of the embodiments are emphasized, and for parts of one embodiment that are not described in detail, reference may be made to related descriptions of other embodiments.

The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (10)

1. A tandem current collector, comprising:

a collector body (1), the collector body (1) having an airflow channel with an airflow inlet end and an airflow outlet end, the airflow outlet end being configured to extend into an air inlet end of a centrifugal fan impeller upper plate (201) so that an airflow enters the centrifugal fan impeller upper plate (201) along the airflow channel, and an air outlet direction of the airflow being a direction along the airflow inlet end to the airflow outlet end;

the air flow channel sequentially comprises a first flow channel and a second flow channel along the air outlet direction, the flow channel area of the first flow channel is gradually reduced along the air outlet direction, and a throat (104) is convexly arranged in the second flow channel, so that the flow channel area of the second flow channel is gradually reduced and then gradually increased along the air outlet direction.

2. The tandem collector according to claim 1, characterized in that the inner wall of the collector body (1) encloses the air flow channel, that an annular protrusion (103) protruding in the circumferential direction of the collector body (1) is provided on the outer wall of the collector body (1), that the annular protrusion (103) is located outside the centrifugal fan impeller upper disc (201), and that the annular protrusion (103) is provided at a distance from the centrifugal fan impeller upper disc (201).

3. The tandem current collector according to claim 2, wherein the connection of the first flow channel and the second flow channel is provided with the annular protrusion (103).

4. The tandem current collector according to claim 2, wherein the current collector body (1) comprises:

a body section, a first end of the body section forming the airflow inlet end, the body section having a first inner wall and a first outer wall, the first inner wall surrounding the first flow passage;

a series section (105), wherein a first end of the series section (105) is connected with a second end of the body section, the second end of the series section (105) forms the airflow outlet end, the series section (105) is provided with a second inner wall and a second outer wall, the second inner wall surrounds the second flow passage, the connection part of the second outer wall and the first outer wall is provided with the annular bulge (103), and the second inner wall is convexly provided with the throat (104);

the first inner wall, the first outer wall, the second inner wall and the second outer wall are arc-shaped sections.

5. The tandem current collector according to claim 4, wherein the curvature of said second inner wall is greater than the curvature setting of said first inner wall.

6. The tandem current collector according to claim 4 or 5, wherein the curvature of said second outer wall is set the same as the curvature of said second inner wall.

7. The tandem current collector according to claim 4 or 5, wherein the curvature of said first outer wall is set identically to the curvature of said first inner wall.

8. The tandem collector according to claim 4, characterized in that, when the collector body (1) is assembled with the centrifugal fan impeller upper disc (201), at least part of the tandem section (105) extends into the air inlet end of the centrifugal fan impeller upper disc (201), the body section being arranged at a distance from the air inlet end of the centrifugal fan impeller upper disc (201).

9. The tandem current collector according to claim 1, wherein said tandem current collector is made of plastic.

10. A centrifugal fan having a series collector as defined in any one of claims 1 to 9.