Centrifugal fan, design method thereof and cleaning and sweeping vehicle

Abstract

The invention discloses a centrifugal fan, a design method of the centrifugal fan and a cleaning and sweeping vehicle, and belongs to the technical field of centrifugal fans. The centrifugal fan specifically comprises a machine shell assembly, an impeller, a current collector assembly, an air inlet box and a driving device. According to the centrifugal fan, the design method of the centrifugal fan and the cleaning and sweeping vehicle, the centrifugal fan reduces the size of the fan without reducing the performance of the fan by increasing the rotating speed of the fan, and the centrifugal fan is designed according to the characteristics of a pneumatic system of the sweeping equipment, so that the fan can be installed on the sweeping equipment with different tonnages and keeps high-efficiency operation.

Description

Technical Field

[0001] This invention relates to the field of centrifugal fan technology, specifically to a centrifugal fan and its design method, and a sweeper truck. Background Technology

[0002] As a core component of the pneumatic system of cleaning equipment, the performance of the centrifugal fan and its compatibility with the pneumatic system are crucial to the operational performance and energy consumption of the cleaning equipment. Currently, cleaning equipment has evolved into various categories such as vacuum cleaners, road sweepers, and other cleaning equipment. Different types of cleaning equipment have different pneumatic system characteristics, and therefore different requirements for the performance and characteristics of the fan. Only when the characteristics of the fan and the pneumatic system are properly matched can the entire system operate efficiently.

[0003] The blowers used in existing cleaning equipment are mostly modified from the 9-19 and 9-26 series industrial blowers. Due to the limitations of engine speed in the fuel-powered era, the blower speed is relatively fixed, generally between 1800 and 2600 rpm. Because the blower speed is relatively low, forward-curved blades are often used to improve blower performance, and the blower size is also relatively large, resulting in low blower efficiency. Different tonnage vehicles also require different models and sizes of blowers.

[0004] Therefore, it is necessary to design special fans according to the pneumatic system characteristics of different types of cleaning equipment, and reduce the size of the fans so that they can be installed on cleaning equipment of different tonnage sizes and maintain high-efficiency operation. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a centrifugal fan and its design method, as well as a sweeper truck. By increasing the fan speed, the fan volume can be reduced without reducing the fan performance. The design is tailored to the pneumatic system characteristics of sweeping equipment, allowing the fan to be installed on sweeping equipment of different tonnages. The three-dimensional backward centrifugal blade design makes the blade shape more in line with the fluid flow law, reducing flow losses inside the impeller, improving fan efficiency, and reducing flow noise.

[0006] To achieve the above objectives, the present invention is implemented using the following technical solution:

[0007] In a first aspect, the present invention provides a centrifugal fan, comprising:

[0008] A housing assembly, including a bracket and a volute, wherein the volute is mounted on one side of the bracket;

[0009] An impeller, installed inside a volute, includes a front disc, a rear disc, and multiple blades. The blades are installed between the front and rear discs and are evenly arranged circumferentially along the axes of the front and rear discs. An impeller inlet is provided at the center of the front disc, and a shaft hole is provided at the center of the rear disc. The blades are three-dimensional backward centrifugal blades.

[0010] The collector assembly is installed on the side of the volute away from the support, and includes a collector and a fixing plate. The fixing plate is installed on the outside of the collector for fixing the collector. The collector includes a collector inlet and a collector outlet, wherein the collector outlet cooperates with the impeller inlet.

[0011] The air intake box has an inlet and an outlet. The inlet has a rectangular cross-section and is connected to the pneumatic system of the cleaning equipment. The air intake direction is perpendicular to the axis of the impeller. The outlet has a circular cross-section and matches the air inlet of the collector.

[0012] The drive unit is fixed on the mounting bracket and located on the side of the volute opposite to the collector assembly. The drive end of the drive unit extends into the volute and engages with the shaft hole at the center of the impeller's rear disc. The drive unit is used to drive the impeller to rotate.

[0013] Furthermore, the inlet placement angle of the blade near the front disc is smaller than the inlet placement angle of the blade near the rear disc.

[0014] The exit angle of the blade is 18°~35°;

[0015] The blade has a leading edge close to the axis of the front disc and a trailing edge away from the axis of the front disc;

[0016] The cross-section of the leading edge along the airflow direction is semi-elliptical;

[0017] The trailing edge gradually thins along the airflow direction, and its cross-section is a rectangle with one corner obliquely cut, with the oblique cut located on the pressure surface of the blade.

[0018] And / or, the fixing plate includes

[0019] The front flange of the collector is installed on the side of the collector inlet and connected to the air inlet box;

[0020] The rear flange of the collector is installed on the collector outlet side of the collector and is connected to the volute.

[0021] Side cover, installed between the rear flange and the front flange of the collector;

[0022] And / or, the intake box has an axisymmetric structure;

[0023] The rear end of the air intake box is an arc surface, and the radius of the circle containing the arc surface profile is larger than the radius of the circle containing the air intake box outlet profile.

[0024] The center E' of the circle containing the arc surface profile and the center E of the circle containing the air intake box outlet profile are both located on the axis of symmetry of the air intake box. The center E' is far away from the tail end of the air intake box relative to the center E. The distance between the center E' and the center E is 10~60mm.

[0025] Furthermore, the volute includes a front volute plate, a surrounding plate, and a rear volute plate;

[0026] The front and rear side plates of the volute are correspondingly arranged, and the surrounding plate surrounds the outer edges of the front and rear side plates of the volute. The profile of the surrounding plate consists of an Archimedean spiral and a straight line, wherein the straight line is close to the airflow outlet of the volute.

[0027] The profile of the enclosure panel includes, in sequence:

[0028] Starting point A is located at the beginning of the Archimedes spiral segment;

[0029] The first dividing point B is located on the Archimedes spiral segment;

[0030] The second dividing point C is located at the intersection of the Archimedes spiral segment and the straight line segment;

[0031] End point D is located at the end point of the straight line segment;

[0032] The origin of the Archimedes spiral is O, and the included angle AOB ranges from 30° to 150°.

[0033] The front side plate of the volute has a through hole corresponding to the mounting center of the impeller, for mounting the air outlet of the collector.

[0034] Furthermore, the connecting edges between the enclosure plate and the front side plate of the volute and the connecting edges between the enclosure plate and the rear side plate of the volute are both rounded. The rounding radius remains constant from the starting point A to the second dividing point C, and gradually decreases from the second dividing point C to the ending point D, until the airflow outlet of the volute. The airflow outlet cross-section of the volute is rectangular.

[0035] Furthermore, the connecting edges between the enclosure plate and the front side plate of the volute and the connecting edges between the enclosure plate and the rear side plate of the volute are both rounded. The rounding radius gradually increases from the starting point A to the first dividing point B, remains unchanged from the first dividing point B to the second dividing point C, and gradually decreases from the second dividing point C to the ending point D, until the airflow outlet of the volute. The airflow outlet cross-section of the volute is rectangular.

[0036] Furthermore, the collector, from the collector inlet to the collector outlet, sequentially includes a converging section whose diameter gradually decreases along the airflow direction and a expanding section whose diameter gradually increases along the airflow direction. The profile of one side of the collector's axial cross-section is a smooth curve, including a first arc and a second arc. The first arc is the profile of one side of the converging section along the axial cross-section, and the second arc is the profile of one side of the expanding section along the axial cross-section. The radius of the circle containing the first arc is greater than the radius of the circle containing the second arc.

[0037] Furthermore, the tapering section includes a first tapering section and a second tapering section, the first tapering section being connected to the side of the second tapering section near the airflow source, and the diameter of the first tapering section decreasing linearly.

[0038] Furthermore, it also includes a straight section with a constant diameter, connecting the tapering and expanding sections.

[0039] Secondly, the present invention provides a design method for a centrifugal fan, comprising:

[0040] Determine the size of the inlet placement angle; the inlet placement angle of the blade near the front plate is smaller than the inlet placement angle of the blade near the rear plate;

[0041] Determine the size of the outlet placement angle; the outlet placement angle is 18°~35°;

[0042] The shape of the leading edge is determined; the cross-section of the leading edge along the airflow direction is semi-elliptical.

[0043] The trailing edge shape is determined; the trailing edge gradually thins along the airflow direction, and the cross-section is a rectangle with one corner obliquely cut, and the oblique cut position is located on the pressure surface of the blade.

[0044] Thirdly, the present invention provides a sweeper truck that employs the aforementioned centrifugal fan.

[0045] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0046] The centrifugal fan provided by this invention includes a casing assembly, an impeller, a collector assembly, an air inlet box, and a drive device. The installation and connection relationships of each component are designed according to the characteristics of the pneumatic system of the cleaning equipment, so that it has a high degree of matching with cleaning equipment of various tonnages. By increasing the fan speed, the fan size is reduced without reducing the fan performance, so that the fan can be installed on cleaning equipment of different tonnages.

[0047] The centrifugal fan provided by this invention adopts a three-dimensional backward centrifugal blade design, which makes the blade shape more in line with the fluid flow law, reduces the flow loss inside the impeller, improves the fan efficiency, and reduces the occurrence of flow noise. Attached Figure Description

[0048] Figure 1 This is a schematic diagram of the structure of the centrifugal fan provided in an embodiment of the present invention;

[0049] Figure 2 This is a side sectional view of the centrifugal fan provided in an embodiment of the present invention;

[0050] Figure 3 This is a schematic diagram of the structure of the support and volute provided in an embodiment of the present invention;

[0051] Figure 4 This is a schematic diagram of the volute structure provided in an embodiment of the present invention;

[0052] Figure 5 This is a schematic diagram of the impeller structure provided in an embodiment of the present invention;

[0053] Figure 6 This is a cross-sectional schematic diagram of the impeller provided in an embodiment of the present invention;

[0054] Figure 7 This is a cross-sectional schematic diagram of the blade provided in an embodiment of the present invention;

[0055] Figure 8 This is a cross-sectional view of the current collector assembly provided in an embodiment of the present invention;

[0056] Figure 9 This is a cross-sectional view of the current collector provided in an embodiment of the present invention;

[0057] Figure 10 This is a cross-sectional view of the current collector provided in an embodiment of the present invention;

[0058] Figure 11 This is a schematic diagram of the air intake box provided in an embodiment of the present invention;

[0059] Figure 12 This is a cross-sectional schematic diagram of the air intake box provided in an embodiment of the present invention;

[0060] Figure 13 This is a schematic diagram of the structure of the air inlet box outlet surface provided in an embodiment of the present invention.

[0061] In the diagram: 1. Casing assembly; 11. Bracket; 12. Volute; 121. Front side plate of volute; 122. Enclosure plate; 123. Rear side plate of volute; 2. Impeller; 21. Front plate; 22. Blade; 221. Leading edge; 222. Trailing edge; 23. Rear plate; 3. Collector assembly; 31. Collector; 311. Converging section; 312. Diverging section; 313. Straight section; 32. Rear flange of collector; 33. Side cover; 34. Front flange of collector; 4. Inlet box; 41. Inlet; 42. Outlet; 5. Drive unit. Detailed Implementation

[0062] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0063] The following detailed description of some embodiments of the present invention is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0064] In one embodiment of the present invention, such as Figure 1 and Figure 2 As shown, the centrifugal fan includes a casing assembly 1, an impeller 2, a collector assembly 3, an air inlet box 4, and a drive unit 5, wherein:

[0065] Housing assembly 1, such as Figure 3 As shown, the system includes a support 11 and a volute 12, with the volute 12 mounted on one side of the support 11; an impeller 2, installed inside the volute 12, including a front disc 21, a rear disc 23, and multiple blades 22, the blades 22 being installed between the front disc 21 and the rear disc 23 and evenly arranged circumferentially along the axes of the front disc 21 and the rear disc 23, the front disc 21 having an impeller inlet at its center, and the rear disc 23 having a shaft hole at its center, the blades 22 being three-dimensional backward centrifugal blades; a collector assembly 3, installed on the side of the volute 12 away from the support 11, including a collector 31 and a fixing plate, the fixing plate being installed on the outside of the collector for fixing the collector, the collector 31 including a collector inlet and a collector outlet, wherein the collector outlet cooperates with the impeller inlet; and an air inlet box 4, as shown. Figure 11 and Figure 12 As shown, the housing has an inlet 41 and an outlet 42. The inlet 41 has a rectangular cross-section and is connected to the pneumatic system of the cleaning equipment. The air intake direction is perpendicular to the axis of the impeller 2. The outlet 42 has a circular cross-section and is matched with the air inlet of the collector. The drive device 5 is fixed on the mounting bracket 11 and is located on the side of the volute 12 opposite to the collector assembly 3. The drive end of the drive device 5 extends into the volute 12 and is matched with the shaft hole at the center of the rear plate 23 of the impeller 2. The drive device 5 is used to drive the impeller 2 to rotate.

[0066] In one embodiment of the present invention, an electric motor is used as the driving device 5, and the rated speed of the electric motor is between 4000 and 8000 rpm.

[0067] The mounting bracket 11 serves to connect and fix the fan, cleaning equipment, and motor to the volute 12, and is not limited to such a purpose. Figure 1 The aforementioned form.

[0068] The number of blades 22 is 6 to 12. In one embodiment of the present invention, such as... Figure 5As shown, it includes seven blades 22, the inlet placement angle of the blades 22 near the front plate 21 is smaller than the inlet placement angle of the blades 22 near the rear plate 23; the outlet placement angle of the blades 22 is 18°~35°.

[0069] The blade 22 has a leading edge 221 close to the axis of the front disk 21 and a trailing edge 222 away from the axis of the front disk; such as Figure 6 As shown, the angle between the tangent of the leading edge 221 at the front plate 21 and the tangent of the circumference at that point (in the opposite direction of rotation) is α, and the angle between the tangent of the leading edge 221 at the rear plate 23 and the tangent of the circumference at that point is β, then α < β. The angle between the tangent of the leading edge 222 at any point and the tangent of the circumference at that point is γ, then γ = 18°~35°.

[0070] like Figure 7 As shown, the leading edge 221 has a semi-elliptical cross-section along the airflow direction, where M is the center of the ellipse containing the semi-elliptical cross-section of the leading edge 221, MX is the major semi-axis, and MY is the minor semi-axis, so MX / MY = 2~6. The trailing edge 222 gradually thins along the airflow direction, and its cross-section is a rectangle with one corner obliquely cut, and the oblique cut position is located on the pressure surface of the blade 22. The right triangle under the oblique cut has a leg perpendicular to the trailing edge 222, and the other leg is b, so a / b = 2~10. The blade passage profiles where the blade 22 connects to the front disk 21 and the rear disk 23 are all smooth curves along the airflow direction.

[0071] like Figure 8 As shown, the fixing plate includes a front flange 34 of the collector, which is installed on the side of the collector inlet of the collector 31; a rear flange 32 of the collector, which is installed on the side of the collector outlet of the collector 31, connected to the volute 12 and connected to the air inlet box 4; and a side cover 33, which is installed between the rear flange 32 and the front flange 34 of the collector.

[0072] In one embodiment of the present invention, the volute 12 includes a front side plate 121, a surrounding plate 122, and a rear side plate 123; the front side plate 121 and the rear side plate 123 are correspondingly arranged, and the surrounding plate 122 surrounds the outer edges of the front side plate 121 and the rear side plate 123; the profile of the surrounding plate 122 is composed of a section of Archimedean spiral and a section of straight line, wherein the straight line is close to the airflow outlet of the volute 12. For ease of processing and manufacturing, the profile of the surrounding plate 122 can be approximately replaced by multiple segments of circular arcs.

[0073] like Figure 4As shown, in one embodiment of the present invention, the profile of the enclosure 122 sequentially includes a starting point A, located at the beginning of the Archimedean spiral segment; a first dividing point B, located on the Archimedean spiral segment; a second dividing point C, located at the intersection of the Archimedean spiral segment and the straight line segment; and an ending point D, located at the end of the straight line segment. The origin of the coordinate system of the Archimedean spiral is O, and the included angle AOB ranges from 30° to 150°.

[0074] In one embodiment of the present invention, the connecting edge between the enclosure 122 and the front side plate 121 of the volute and the connecting edge between the enclosure 122 and the rear side plate 123 of the volute are both rounded. The rounding radius remains unchanged from the starting point A to the second dividing point C, and gradually decreases from the second dividing point C to the ending point D until the airflow outlet of the volute 12. The airflow outlet cross section of the volute 12 is rectangular.

[0075] In one embodiment of the present invention, the connecting edge between the enclosure plate 122 and the front side plate 121 of the volute and the connecting edge between the enclosure plate 122 and the rear side plate 123 of the volute are both rounded. The rounding radius gradually increases from the starting point A to the first dividing point B, remains unchanged from the first dividing point B to the second dividing point C, and gradually decreases from the second dividing point C to the ending point D, until the airflow outlet of the volute 12. The airflow outlet cross section of the volute 12 is rectangular.

[0076] The front side plate 121 of the volute has a through hole at the installation center position of the impeller 2 for installing the air outlet of the collector.

[0077] In one embodiment of the present invention, the rounding radius of point A is 10~40mm, and the rounding radius of point B is 50~100mm.

[0078] In one embodiment of the present invention, such as Figure 9 As shown, the collector 31 includes a tapered section 311 with a gradually decreasing diameter along the airflow direction and a expanding section 312 with a gradually increasing diameter along the airflow direction, from the collector inlet to the collector outlet. The profile of one side of the collector 31 along the axial section is a smooth curve, including a first arc and a second arc. The first arc is the profile of one side of the tapered section 311 along the axial section, and the second arc is the profile of one side of the expanding section 312 along the axial section. The radius of the circle containing the first arc is greater than the radius of the circle containing the second arc.

[0079] In one embodiment of the present invention, the tapering section 311 includes a first tapering section and a second tapering section, the first tapering section being connected to the side of the second tapering section near the airflow source, and the diameter of the first tapering section decreasing linearly.

[0080] like Figure 10As shown, in one embodiment of the present invention, a straight section 313 with a constant diameter is also included, which is connected between the tapered section 311 and the expanding section 312.

[0081] like Figure 13 As shown, in one embodiment of the present invention, the air intake box 4 has an axisymmetric structure; the tail end of the air intake box 4 is an arc surface, and the radius of the circle containing the arc surface profile is greater than the radius of the circle 42 containing the air intake box outlet profile; the center E' of the circle containing the arc surface profile and the center E of the circle 42 containing the air intake box outlet profile are both located on the axis of symmetry of the air intake box 4, and the center E' is farther away from the tail end of the air intake box 4 relative to the center E, and the distance between the center E' and the center E is 10~60mm.

[0082] An embodiment of the present invention also provides a design method for the centrifugal fan, comprising:

[0083] Determine the size of the inlet placement angle; the inlet placement angle of the blade 22 on the side near the front plate 21 is smaller than the inlet placement angle of the blade 22 on the side near the rear plate 23;

[0084] Determine the size of the outlet placement angle; the outlet placement angle is 18°~35°;

[0085] The shape of the leading edge 221 is determined; the cross-section of the leading edge 221 along the airflow direction is semi-elliptical.

[0086] The shape of the trailing edge 222 is determined; the trailing edge 222 gradually thins along the airflow direction, and the cross-section is a rectangle with one corner obliquely cut, and the oblique cut position is located on the pressure surface of the blade 22.

[0087] An embodiment of the present invention also provides a sweeper truck that employs the aforementioned centrifugal fan.

[0088] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only used to explain the relative positional relationship and movement between components in a specific posture. If the specific posture changes, the directional indication will also change accordingly. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0089] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0090] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A centrifugal fan, characterized in that, include: The housing assembly (1) includes a bracket (11) and a volute (12), the volute (12) being mounted on one side of the bracket (11); The impeller (2) is installed inside the volute (12) and includes a front disc (21), a rear disc (23) and multiple blades (22). The blades (22) are installed between the front disc (21) and the rear disc (23) and are evenly arranged circumferentially along the axis of the front disc (21) and the rear disc (23). The center of the front disc (21) is provided with an impeller inlet and the center of the rear disc (23) is provided with a shaft hole. The blades (22) are three-dimensional backward centrifugal blades. The collector assembly (3) is installed on the side of the volute (12) away from the bracket (11), and includes a collector (31) and a fixing plate. The fixing plate is installed on the outside of the collector for fixing the collector. The collector (31) includes a collector inlet and a collector outlet, wherein the collector outlet is matched with the impeller inlet. The air intake box (4) has an inlet (41) and an outlet (42) on its body. The inlet (41) has a rectangular cross-section and is connected to the pneumatic system of the cleaning equipment. The air intake direction is perpendicular to the axis of the impeller (2). The outlet (42) has a circular cross-section and is matched with the air inlet of the collector. The drive device (5) is fixed on the mounting bracket (11) and located on the side of the volute (12) opposite to the collector assembly (3). The drive end of the drive device (5) extends into the volute (12) and engages with the shaft hole at the center of the rear plate (23) of the impeller (2). The drive device (5) is used to drive the impeller (2) to rotate.

2. The centrifugal fan according to claim 1, characterized in that: The inlet placement angle of the blade (22) on the side near the front plate (21) is smaller than the inlet placement angle of the blade (22) on the side near the rear plate (23); The outlet angle of the blade (22) is 18°~35°; The blade (22) has a leading edge (221) close to the axis of the front disc (21) and a trailing edge (222) away from the axis of the front disc. The cross-section of the leading edge (221) along the airflow direction is semi-elliptical; The trailing edge (222) gradually thins along the airflow direction, and the cross-section is a rectangle with one corner obliquely cut, and the oblique cut position is located on the pressure surface of the blade (22); And / or, the fixing plate includes The front flange (34) of the collector is installed on the side of the collector inlet of the collector (31) and connected to the air inlet box (4); The rear flange (32) of the collector is installed on the side of the collector outlet of the collector (31) and connected to the volute (12); Side cover (33) is installed between the rear flange (32) and the front flange (34) of the collector; And / or, the intake box (4) is an axisymmetric structure; The tail end of the air intake box (4) is an arc surface, and the radius of the circle containing the arc surface profile is greater than the radius of the circle (42) containing the air intake box outlet profile. The center E' of the circle containing the arc surface profile and the center E of the circle (42) containing the air intake box outlet profile are both located on the axis of symmetry of the air intake box (4). The center E' is far away from the tail end of the air intake box (4) relative to the center E. The distance between the center E' and the center E is 10~60mm.

3. The centrifugal fan according to claim 1, characterized in that: The volute (12) includes a front volute plate (121), a surrounding plate (122), and a rear volute plate (123). The front side plate (121) and the rear side plate (123) of the volute are respectively arranged. The surrounding plate (122) surrounds the outer edge of the front side plate (121) and the rear side plate (123) of the volute. The profile of the surrounding plate (122) is composed of a section of Archimedean spiral and a section of straight line, wherein the straight line is close to the airflow outlet of the volute (12). The profile of the enclosure (122) includes, in sequence, the following lines: Starting point A is located at the beginning of the Archimedes spiral segment; The first dividing point B is located on the Archimedes spiral segment; The second dividing point C is located at the intersection of the Archimedes spiral segment and the straight line segment; End point D is located at the end point of the straight line segment; The origin of the Archimedes spiral is O, and the included angle AOB ranges from 30° to 150°. The front side plate (121) of the volute has a through hole at the installation center position of the impeller (2) for installing the air outlet of the collector.

4. The centrifugal fan according to claim 3, characterized in that: The connecting edge between the enclosure plate (122) and the front side plate (121) of the volute and the connecting edge between the enclosure plate (122) and the rear side plate (123) of the volute are both rounded. The rounding radius remains unchanged from the starting point A to the second dividing point C, and gradually decreases from the second dividing point C to the ending point D, until the airflow outlet of the volute (12). The airflow outlet cross section of the volute (12) is rectangular.

5. The centrifugal fan according to claim 3, characterized in that: The connecting edges of the enclosure (122) and the front side plate (121) of the volute and the connecting edges of the enclosure (122) and the rear side plate (123) of the volute are all rounded. The rounding radius gradually increases from the starting point A to the first dividing point B, remains unchanged from the first dividing point B to the second dividing point C, and gradually decreases from the second dividing point C to the ending point D, until the airflow outlet of the volute (12). The airflow outlet cross section of the volute (12) is rectangular.

6. The centrifugal fan according to claim 1, characterized in that: The collector (31) consists of a converging section (311) whose diameter gradually decreases along the airflow direction and a expanding section (312) whose diameter gradually increases along the airflow direction, from the collector inlet to the collector outlet. The profile of one side of the collector (31) along the axial section is a smooth curve, including a first arc and a second arc. The first arc is the profile of one side of the converging section (311) along the axial section, and the second arc is the profile of one side of the expanding section (312) along the axial section. The radius of the circle containing the first arc is greater than the radius of the circle containing the second arc.

7. The centrifugal fan according to claim 6, characterized in that: The tapering section (311) includes a first tapering section and a second tapering section. The first tapering section is connected to the side of the second tapering section near the airflow source, and the diameter of the first tapering section decreases linearly.

8. The centrifugal fan according to claim 7, characterized in that: It also includes a straight section (313) with a constant diameter, which is connected between the tapering section (311) and the expanding section (312).

9. A design method for a centrifugal fan, characterized in that, include: Determine the size of the entrance placement angle; The inlet placement angle of the blade (22) on the side near the front plate (21) is smaller than the inlet placement angle of the blade (22) on the side near the rear plate (23); Determine the size of the outlet placement angle; the outlet placement angle is 18°~35°; The shape of the leading edge (221) is determined; the cross section of the leading edge (221) along the airflow direction is semi-elliptical; Determine the shape of the trailing edge (222); the trailing edge (222) gradually thins along the airflow direction, the cross section is a rectangle with one corner obliquely cut, and the oblique cut position is located on the pressure surface of the blade (22).

10. A sweeper truck, characterized in that, The centrifugal fan described in any one of claims 1-8 is used.

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