Blade for centrifugal fan, double-suction centrifugal impeller using blade, and fan

Abstract

Provided in the present invention are a blade for a centrifugal fan, a double-suction centrifugal impeller using the blade, and a fan. The blade comprises a suction surface wall, a pressure surface wall, a leading edge, a trailing edge, a protruding air intake portion and a recessed air output portion, wherein the suction surface wall and the pressure surface wall are arranged opposite each other, and the suction surface wall and the pressure surface wall extend in the lengthwise direction of the blade first, and then extend between the leading edge and the trailing edge; the protruding air intake portion is formed by means of protruding from a leading-edge portion of the blade towards the suction surface wall, the recessed air output portion is formed by means of protruding from a trailing-edge portion of the blade towards the pressure surface wall, and in the direction from the leading edge to the trailing edge, the protruding air intake portion and the recessed air output portion are joined to each other; in the lengthwise direction of the blade, the protruding air intake portion is of a structure that is high in the middle and low on two sides, and the recessed air output portion is of a structure that is low in the middle and high on two sides; in the direction from the leading edge to the trailing edge, the height of the middle of the protruding air intake portion gradually decreases; and in the direction from the trailing edge to the leading edge, the depth of the middle of the recessed air output portion gradually decreases.

Description

Blade for centrifugal fan, double-suction centrifugal impeller and fan applying the same TECHNICAL FIELD

[0001] The present application relates to the technical field of centrifugal fan, in particular to a blade for centrifugal fan, double-suction centrifugal impeller and fan applying the same. BACKGROUND

[0002] The centrifugal fan is a machine that relies on input mechanical energy to increase the pressure of gas and discharge it. It is a driven fluid machine. The working principle is that the relative rotation of the impeller in the fan volute produces centrifugal force on the gas, which compresses and transports the gas, converting the mechanical energy of the fan into kinetic and potential energy of the gas.

[0003] The centrifugal fan can be divided into single-suction and double-suction types according to the number of suction inlets of the impeller. The double-suction centrifugal fan adopts a single-shaft double-support structure. Since it has two separate air inlet boxes and a double-sided suction impeller structure, it not only offsets the axial force of the impeller, but also evenly wears the bearings at both ends, making it stable and reliable in operation. The double-suction fan has a larger flow coefficient and can provide a larger gas flow than the single-suction fan, making it suitable for many industries that require large gas flow. By controlling the rotational speed of the impeller and designing the shape of the blades, the performance of the centrifugal fan and the pressure of the output airflow can be adjusted.

[0004] When the traditional centrifugal fan impeller rotates, the airflow between the blades is easily affected by fluid viscosity effects, adverse pressure gradients, and Coriolis forces, resulting in flow separation and the formation of secondary vortexes, which leads to low fan efficiency.

[0005] The information disclosed in this BACKGROUND section is only intended to increase an understanding of the general context in which the present application can be practiced. It should not be taken as an acknowledgement or any form of suggestion that this information forms a prior art that is already known to those skilled in the art.

[0006] SUMMARY

[0007] The present application aims to solve the technical problems of the prior art by providing a blade for centrifugal fan, double-suction centrifugal impeller and fan applying the same. The blade is applied to the double-suction centrifugal impeller, which can improve the operating efficiency of the fan.

[0008] To solve the above technical problems, the application discloses a blade for a centrifugal fan, which comprises a suction surface wall, a pressure surface wall, a leading edge, a trailing edge, a convex air inlet portion and a concave air outlet portion. The suction surface wall and the pressure surface wall are oppositely arranged, and both extend along the length direction of the blade firstly and then between the leading edge and the trailing edge. The convex air inlet portion is protrusively formed towards the suction surface wall side at the leading edge part of the blade, and the concave air outlet portion is protrusively formed towards the pressure surface wall side at the trailing edge part of the blade. In the direction from the leading edge to the trailing edge, the convex air inlet portion and the concave air outlet portion are connected.

[0009] In the length direction of the blade, the convex air inlet portion has a structure of high in the middle and low on both sides, and the concave air outlet portion has a structure of low in the middle and high on both sides. In the direction from the leading edge to the trailing edge, the middle height of the convex air inlet portion has a decreasing trend. In the direction from the trailing edge to the leading edge, the middle height of the concave air outlet portion has a decreasing trend.

[0010] Preferably, the shape of any cross-sectional profile of the blade perpendicular to the length direction of the blade is a circular arc shape, the inner arc surface of the blade is the pressure surface wall, the outer arc surface of the blade is the suction surface wall, and the leading edge and the trailing edge are oppositely arranged in the arc length direction of the blade.

[0011] Specifically, the blade is a double-section reverse torsion blade structure, comprising a first torsion blade section and a second torsion blade section connected in sequence along the length direction of the blade, and the torsion direction of the first torsion blade section is opposite to that of the second torsion blade section.

[0012] Specifically, the blade comprises a first end and a second end oppositely arranged along the length direction of the blade, and a junction end between the first end and the second end along the length direction of the blade, wherein the first end is used for connecting with the center disc of the impeller, and the second end is used for connecting with the disc of the impeller.

[0013] The first torsion blade section is formed by torsion of the first end relative to the junction end in a direction opposite to the rotation direction of the blade, and the second torsion blade section is formed by torsion of the second end relative to the junction end in the opposite direction, so that the leading edge part of the first torsion blade section and the leading edge part of the second torsion blade section are gradually protruded towards the outer arc surface of the blade from the first end and the second end respectively towards the junction end to form the convex air inlet portion, and the trailing edge part of the first torsion blade section and the trailing edge part of the second torsion blade section are gradually protruded towards the inner arc surface of the blade from the first end and the second end respectively towards the junction end to form the concave air outlet portion.

[0014] Specifically, the first twisted blade segment comprises a first inner-arc twisted surface and a first outer-arc twisted surface, the second twisted blade segment comprises a second inner-arc twisted surface and a second outer-arc twisted surface, the first inner-arc twisted surface of the first twisted blade segment and the second inner-arc twisted surface of the second twisted blade segment are connected to form a pressure surface wall of the blade, and the first outer-arc twisted surface of the first twisted blade segment and the second outer-arc twisted surface of the second twisted blade segment are connected to form a suction surface wall of the blade.

[0015] Preferably, the first twisted blade segment and the second twisted blade segment have a common twisted axis, and the common twisted axis is parallel to the length direction of the blade.

[0016] Preferably, the first twisted blade segment and the second twisted blade segment have the same size of cross-sectional profile perpendicular to the length direction of the blade.

[0017] Preferably, the cross-sectional profile of the blade perpendicular to the length direction of the blade has a midpoint, and the common twisted axis passes through the midpoint.

[0018] Preferably, the twisted angle of the first twisted blade segment and the second twisted blade segment ranges from 5° to 15°. More preferably, the twisted angle of the first twisted blade segment and the second twisted blade segment is 10°.

[0019] Preferably, the length ratio of the first twisted blade segment and the second twisted blade segment ranges from 0.25 to 1.5. More preferably, the length ratio of the first twisted blade segment and the second twisted blade segment is 1.

[0020] Further, the blade further comprises a notch, the notch is arranged at the trailing edge of the blade and is arranged at the connection between the first twisted blade segment and the second twisted blade segment, and the notch is arranged in the shape of a right-angled triangle.

[0021] The second aspect of the present application discloses a double-suction centrifugal impeller, which comprises a rotation axis, a hub and a blade for a centrifugal fan as described above, wherein a plurality of the blades are arranged, the plurality of the blades are divided into two groups, the two groups of the blades are symmetrically arranged on two sides of the hub and take the hub as a symmetric plane, and the plurality of the blades in each group are uniformly and circumferentially arranged along the rotation axis. The length direction of each blade is parallel to the rotation axis, and the leading edge of each blade is closer to the rotation axis of the double-suction centrifugal impeller than the trailing edge.

[0022] Specifically, the impeller comprises a wheel disc, and each group of the blades is respectively connected with a wheel disc on the side away from the hub along the rotation axis. Each wheel disc is provided with a wheel disc air inlet.

[0023] The third aspect of the present application discloses a fan, which comprises:

[0024] The double-suction centrifugal impeller as described above;

[0025] The support chassis;

[0026] The driving motor fixedly installed on the top surface of one end of the support chassis;

[0027] The volute fixedly installed on the top surface of the other end of the support chassis, wherein the double-suction centrifugal impeller is arranged in the volute; and the middle disc of the double-suction centrifugal impeller is connected with the impeller rotating shaft;

[0028] The transmission mechanism, wherein the power of the driving motor is transmitted to the impeller rotating shaft through the transmission mechanism, and the impeller rotating shaft rotates to drive the double-suction centrifugal impeller to rotate around the rotation axis of the double-suction centrifugal impeller.

[0029] Specifically, the volute comprises two oppositely arranged air inlet end plates, an annular plate connected between the two air inlet end plates, and a hollow cavity for accommodating the impeller formed by the two air inlet end plates and the annular plate; the annular plate is provided with a volute air outlet, and the two air inlet end plates are each provided with a volute air inlet, and the volute air outlet and each volute air inlet are in communication with the hollow cavity.

[0030] Further, the fan further comprises an outer shell, and the outer shell covers the volute.

[0031] Specifically, the fan comprises a rotating shaft through hole and a bearing base, the side wall of the outer shell is provided with a rotating shaft through hole, and one end of the impeller rotating shaft that extends out of the outer shell through the rotating shaft through hole is rotatably connected to the outer shell through the bearing base.

[0032] Specifically, the transmission mechanism adopts a transmission belt. Beneficial effects:

[0033] 1) The blade of the centrifugal fan of the present application, when applied to a double-suction centrifugal impeller, is provided with a protruding air inlet portion at the front edge, which can realize a larger air inlet at the same speed, reduce the separation and vortex of airflow at the front edge of the blade, reduce flow loss, and improve efficiency; on the other hand, the protruding air inlet portion can guide the airflow to make it flow more smoothly into the working area of the blade, thereby improving the working efficiency and working capacity of the fan; the blade is provided with a recessed air outlet portion at the rear edge, which can increase the air outlet, cooperate with the protruding air inlet portion, and further improve the efficiency; on the other hand, the recessed air outlet portion can move the separation point of the airflow backward, reduce the separation area, reduce the influence of vortex, and at the same time, can guide the airflow to pass through better, reduce turbulence and energy loss.

[0034] 2) One embodiment of the present application provides a notch structure at the middle tip of the recessed air outlet part, which can separate the accumulated vortex and reduce the flow resistance, thereby improving the efficiency and reducing the noise.

[0035] 3) Compared with the existing centrifugal fan, the fan provided by the present application has the driving motor outside the outer shell, and the inner machine including the impeller and the volute is stable in the outer shell, so that the stable and shock-absorbing effect is achieved. BRIEF DESCRIPTION OF DRAWINGS

[0036] The above and / or other aspects of the present application will become apparent and more readily appreciated from the following description, taken in conjunction with the accompanying drawings, in which:

[0037] Fig. 1 is a perspective view of an impeller provided by a first embodiment of the present application.

[0038] Fig. 2 is another perspective view of the impeller provided by the first embodiment of the present application.

[0039] Fig. 3 is a side view of the impeller shown in Fig. 1 along the rotation axis direction.

[0040] Fig. 4 is a partial enlarged view of the area A in Fig. 3.

[0041] Fig. 5 is a perspective view of a blade provided by the first embodiment of the present application.

[0042] Fig. 6 is another perspective view of the blade provided by the first embodiment of the present application.

[0043] Fig. 7 is a schematic view of an external structure of a fan provided by the first embodiment of the present application.

[0044] Fig. 8 is a schematic view of a structure in which the impeller provided by the first embodiment of the present application is arranged in a volute.

[0045] Fig. 9 is a schematic view of a volute profile of the present application, showing the impeller provided by the first embodiment.

[0046] Fig. 10 is a perspective view of an impeller provided by a second embodiment of the present application.

[0047] Fig. 11 is a perspective view of a blade provided by the second embodiment of the present application.

[0048] Fig. 12 is another perspective view of the blade provided by the second embodiment of the present application.

[0049] Fig. 13 is a perspective view of a conventional impeller in a first comparative example of the present application.

[0050] Figure 14 is a perspective view of a single-stage twisted blade impeller according to a second comparative example of the present application.

[0051] Figure 15(A) is a velocity vector contour plot of the numerical simulation of the impeller according to the first embodiment of the present application.

[0052] Figure 15(B) is a velocity vector contour plot of the numerical simulation of the impeller according to the second embodiment of the present application.

[0053] Figure 15(C) is a velocity vector contour plot of the numerical simulation of the impeller according to the first comparative example of the present application.

[0054] Figure 15(D) is a velocity vector contour plot of the numerical simulation of the impeller according to the second comparative example of the present application.

[0055] Figure 16(A) is a local vorticity contour plot of the impeller inlet end when the blade tip of the impeller inlet end is not chamfered.

[0056] Figure 16(B) is a local vorticity contour plot of the impeller inlet end when the blade tip of the impeller inlet end is chamfered.

[0057] Figure 17(A) is a surface vorticity distribution contour plot of the impeller according to the second embodiment of the present application.

[0058] Figure 17(B) is a surface vorticity distribution contour plot of the impeller according to the first comparative example of the present application.

[0059] Figure 18 is a photograph of the double-suction centrifugal impeller according to the first embodiment of the present application.

[0060] Figure 19 is a photograph of the double-suction centrifugal impeller according to the second embodiment of the present application.

[0061] Figure 20 is a partial photograph of the double-suction centrifugal impeller according to the second embodiment of the present application.

[0062] Figure 21 is another partial photograph of the double-suction centrifugal impeller according to the second embodiment of the present application.

[0063] Figure 22 is a comparison of the fan efficiency versus the volumetric flow rate of the centrifugal fan according to the first embodiment, the second embodiment, the first comparative example and the second comparative example of the present application.

[0064] Figure 23 is a comparison of the shaft power versus the volumetric flow rate of the centrifugal fan according to the first embodiment, the second embodiment, the first comparative example and the second comparative example of the present application.

[0065] Fig. 24 is a comparison of the pressure versus volume flow rate curves of the centrifugal fan provided by the first embodiment, the second embodiment, the first comparative example and the second comparative example of the present application.

[0066] Reference signs are as follows: 10, blade; 101, suction surface wall; 102, pressure surface wall; 103, leading edge; 104, trailing edge; 105, convex air inlet portion; 106, concave air outlet portion; 107, first twisted blade segment; 1071, first inner-arc twisted surface; 1072, first outer-arc twisted surface; 108, second twisted blade segment; 1081, second inner-arc twisted surface; 1082, second outer-arc twisted surface; 109, intersection end; 110, shared twisted axis; 20, flow passage; 30, double-suction centrifugal impeller; 112, first end; 113, second end; 40, rotation axis; 50, center disc; 60, wheel disc; 601, wheel disc air inlet; 70, fan; 71, support base; 72, driving motor; 73, volute; 731, air inlet end plate; 732, annular plate; 733, hollow chamber; 734, volute air outlet; 735, volute air inlet; 74, outer housing; 771, first pulley; 772, second pulley; 773, transmission belt; 111, notch; 11, circular-arc straight blade; 12, single-segment twisted blade. DETAILED DESCRIPTION

[0067] Impeller flow separation and air cross-concentration are two common phenomena in the internal flow process of an impeller. Among them, impeller flow separation refers to the separation of airflow from the surface of the blade in some areas inside the impeller due to changes in airflow velocity or the influence of blade shape, forming vortex or backflow phenomena. This separation can cause energy loss of the airflow, reducing the efficiency of the fan, while air cross-concentration refers to the meeting and concentration of airflow in different directions in a certain area inside the impeller due to the complex motion of the airflow. This phenomenon usually occurs at the outlet of the impeller or in some specific areas inside the impeller. Air cross-concentration can cause uneven airflow, affecting the normal operation of the impeller, and even causing airflow backflow, affecting the stability of the entire system. There is a close relationship between impeller flow separation and air cross-concentration. Flow separation can cause local airflow velocity to decrease, forming a low-pressure area, which in turn attracts the surrounding airflow to concentrate, forming a cross-concentration phenomenon. Conversely, air cross-concentration can also cause mutual interference of airflow, exacerbating the degree of flow separation.

[0068] At the same time, flow separation can cause non-uniform velocity and pressure distribution of fluid at the outlet of the impeller, affecting the uniform outflow of the airflow. For example, if the airflow separates severely at the outlet of the impeller, high-speed and low-speed regions can be formed at the outlet, causing the airflow to be unable to flow out uniformly, forming a so-called "jet-wake" flow structure, which reduces the effective flow area and increases the non-uniformity of the velocity distribution, affecting the flow state at the outlet of the impeller.

[0069] When the impeller of a conventional centrifugal fan is rotating, the airflow between the blades is easily separated due to the effects of fluid viscosity, adverse pressure gradient and Coriolis force, forming secondary vortex, which results in low efficiency of the double-suction centrifugal fan.

[0070] Embodiment 1

[0071] Therefore, referring to Figs. 1-6, the present embodiment discloses a blade for a centrifugal fan, which can be applied to a double-suction forward-inclined centrifugal impeller 30.

[0072] Referring to Figs. 4 and 5, the blade 10 comprises a suction surface wall 101, a pressure surface wall 102, a leading edge 103, a trailing edge 104, a convex air inlet portion 105 and a concave air outlet portion 106. The suction surface wall 101 and the pressure surface wall 102 are oppositely arranged, and extend firstly along the length direction of the blade 10 and secondly between the leading edge 103 and the trailing edge 104. The convex air inlet portion 105 is protrusively formed at the leading edge portion of the blade 10 towards the suction surface wall 101, and the concave air outlet portion 106 is protrusively formed at the trailing edge portion of the blade 10 towards the pressure surface wall 102, and in the direction from the leading edge to the trailing edge, the convex air inlet portion 105 is connected to the concave air outlet portion 106.

[0073] In the length direction of the blade 10, the convex air inlet portion 105 has a structure of high in the middle and low at both sides, and the concave air outlet portion 106 has a structure of low in the middle and high at both sides. In the direction from the leading edge to the trailing edge, the middle height of the convex air inlet portion 105 has a decreasing trend. In the direction from the trailing edge to the leading edge, the middle height of the concave air outlet portion 106 has a decreasing trend.

[0074] The blade 10 can reduce vortex and turbulence near both sides of the blade 10 close to the disc 60, so that the airflow uniformly flows into the convex air inlet portion 105, and then flows out from the concave air outlet portion 106 through the flow channel 20 between two adjacent blades 10. In this process, the convex air inlet portion 105 can increase the air inlet amount, reduce the separation and vortex of the airflow at the leading edge of the blade 10, reduce the flow loss and improve the efficiency, and at the same time, the convex air inlet portion 105 can also guide the airflow to enter the working area of the blade 10 more smoothly, thereby improving the working efficiency and working capacity of the fan. The concave air outlet portion 106 can move the separation point of the airflow backward, reduce the separation area, reduce the influence of vortex, and at the same time, can guide the airflow to pass through better, reduce the turbulence and energy loss. At the same time, the convex air inlet portion 105 can increase the air outlet amount, which cooperates with the convex air inlet portion 105 to greatly improve the efficiency of the fan.

[0075] In an embodiment, referring to FIG. 4, the shape of any cross-sectional profile of the blade 10 perpendicular to the length direction of the blade 10 is a circular arc shape, the inner arc surface of the blade 10 is the pressure surface wall 102, the outer arc surface of the blade 10 is the suction surface wall 101, and the leading edge 103 and the trailing edge 104 are oppositely arranged in the arc length direction of the blade 10.

[0076] In an embodiment, referring to FIG. 5 and FIG. 6, the blade 10 is a double-section reverse twist blade structure, including a first twist blade section 107 and a second twist blade section 108 connected in sequence along the length direction of the blade 10, and the twist direction of the first twist blade section 107 is opposite to the twist direction of the second twist blade section 108.

[0077] Specifically, referring to FIG. 5 and FIG. 6, the blade 10 has a first end 112 and a second end 113 oppositely arranged along the length direction of the blade 10, and a junction end 109 between the first end 112 and the second end 113 along the length direction of the blade 10. The first end 112 is used to connect with the hub 50 of the impeller, and the second end 113 is used to connect with the disc 60 of the impeller. The suction surface wall 101 and the pressure surface wall 102 of the blade 10 both extend between the first end 112 and the second end 113, so as to realize the extension of the suction surface wall 101 and the pressure surface wall 102 along the length direction of the blade 10.

[0078] Referring to FIG. 5 and FIG. 6, the first end 112 is twisted relative to the junction end 109 in a direction opposite to the rotation direction of the blade, so as to form the above-mentioned first twist blade section 107 between the first end 112 and the junction end 109. The second end 113 is twisted relative to the junction end 109 in the opposite direction, so as to form the above-mentioned second twist blade section 108 between the second end 113 and the junction end 109. And thereby realize the sequence connection of the first twist blade section 107 and the second twist blade section 108 along the length direction of the blade 10, and the twist direction of the first twist blade section 107 is opposite to the twist direction of the second twist blade section 108.

[0079] The leading edge part of the first twist blade section 107 and the leading edge part of the second twist blade section 108 respectively protrude from the first end 112 and the second end 113 to the outer arc surface of the blade 10 to form a convex air inlet part 105 towards the junction end 109. The trailing edge part of the first twist blade section 107 and the trailing edge part of the second twist blade section 108 respectively protrude from the first end 112 and the second end 113 to the inner arc surface of the blade 10 to form a concave air outlet part 106 towards the junction end 109.

[0080] More specifically, referring to Figs. 5 and 6, the first twisted blade segment 107 comprises a first inner-arc twisted surface 1071 and a first outer-arc twisted surface 1072, the second twisted blade segment 108 comprises a second inner-arc twisted surface 1081 and a second outer-arc twisted surface 1082, the first inner-arc twisted surface 1071 of the first twisted blade segment 107 and the second inner-arc twisted surface 1081 of the second twisted blade segment 108 are connected to form the pressure surface wall 102 of the blade 10, and the first outer-arc twisted surface 1072 of the first twisted blade segment 107 and the second outer-arc twisted surface 1082 of the second twisted blade segment 108 are connected to form the suction surface wall 101 of the blade 10.

[0081] In the present embodiment, referring to Figs. 4 and 5, the blade 10 comprises a common twisted axis 110, and the first twisted blade segment 107 and the second twisted blade segment 108 have the common twisted axis 110, i.e., are twisted around the common twisted axis 110. The common twisted axis 110 is parallel to the length direction of the blade 10.

[0082] It should be understood that, referring to Fig. 4, in the present embodiment, the cross-sectional shape of the first twisted blade segment 107 and the second twisted blade segment 108 perpendicular to the length direction of the blade 10 is circular arc-shaped, so as to realize that the shape of any cross-sectional profile of the blade 10 perpendicular to the length direction of the blade 10 is circular arc-shaped.

[0083] In the present embodiment, the cross-sectional size of the first twisted blade segment 107 and the second twisted blade segment 108 perpendicular to the length direction of the blade 10 is consistent. In other words, in the present embodiment, the blade 10 is a double-segment reverse-twisted blade structure with an invariable cross-section.

[0084] In the present embodiment, any cross-sectional profile of the blade 10 perpendicular to the length direction of the blade 10 has a midpoint M, and the common twisted axis 110 passes through the midpoint M.

[0085] Preferably, the twist angle of the first twisted blade segment 107 and the second twisted blade segment 108 is in the range of 5° to 15°. More preferably, referring to Fig. 6, the twist angle of the first twisted blade segment 107 and the second twisted blade segment 108 is 10°.

[0086] Preferably, in the length direction of the blade 10, the length ratio of the first twisted blade segment 107 and the second twisted blade segment 108 is in the range of 0.25 to 1.5. More preferably, referring to Fig. 6, the length ratio of the first twisted blade segment 107 and the second twisted blade segment 108 is 1.

[0087] Optionally, the blade 10 of the present embodiment can be formed by stamping and twisting a straight-plate single-circular-arc sheet metal structure.

[0088] Referring to FIG. 1 and FIG. 2, the embodiment further provides a double-suction centrifugal impeller 30, comprising the blade 10, the rotation axis 40 and the hub 50 for connecting with an external driving motor 72. The blade 10 is provided with a plurality of blades 10, which are divided into two groups and symmetrically arranged on both sides of the hub 50 with the hub 50 as a symmetric plane. The plurality of blades 10 in each group are uniformly and spacedly arranged along the circumferential direction of the rotation axis 40, and the length direction of each blade 10 is parallel to the rotation axis 40. The leading edge 103 of each blade 10 is closer to the rotation axis 40 of the double-suction centrifugal impeller than the trailing edge 104.

[0089] The embodiment connects the hub 50 with the output end of the external driving motor 72, so that the driving force applied by the driving motor 72 to the impeller is located at the middle part of the impeller in the axial direction, thereby making the rotation process of the impeller more balanced as a whole.

[0090] In the embodiment, referring to FIG. 1, the double-suction centrifugal impeller 30 comprises a wheel disc 60, and each group of blades 10 is connected with a wheel disc 60 on the side away from the hub 50 along the direction of the rotation axis 40. Each wheel disc 60 is provided with a wheel disc air inlet 601. The external airflow flows to the leading edge 103 of each blade 10 through the wheel disc air inlet 601. Each wheel disc air inlet 601 corresponds to the air inlet end of the double-suction centrifugal impeller.

[0091] In the embodiment, each group of blades 10 is stably supported by the corresponding wheel disc 60 and the hub 50, so that the impeller has high structural strength.

[0092] Referring to FIG. 7, the embodiment further provides a fan 70, which comprises the double-suction centrifugal impeller 30, a support base 71, the driving motor 72, a volute 73 and a transmission mechanism. The driving motor 72 is fixedly installed on the top surface of one end of the support base 71. The volute 73 is fixedly installed on the top surface of the other end of the support base 71, and the impeller is arranged in the volute 73. The hub 50 of the impeller is fixedly connected with an impeller rotating shaft 501. The power of the driving motor 72 is transmitted to the impeller rotating shaft 501 through the transmission mechanism, and the impeller rotating shaft 501 rotates to drive the impeller to rotate around the rotation axis 40 of the impeller.

[0093] Specifically, the support base 71 is positioned and connected by a shared connecting block.

[0094] Specifically, referring to FIG. 8, the volute 73 comprises two oppositely arranged air inlet end plates 731, an annular plate 732 connected between the two air inlet end plates 731, and a hollow cavity 733 formed by the two air inlet end plates 731 and the annular plate 732 for accommodating the impeller. The annular plate 732 is provided with a volute air outlet 734, and each of the two air inlet end plates 731 is provided with a volute air inlet 735, and the volute air outlet 734 and each volute air inlet 735 are in communication with the hollow cavity 733.

[0095] Specifically, referring to FIG. 7, the fan 70 further comprises an outer shell 74 covering the volute 73.

[0096] Specifically, the outer shell 74 is fixed on the support base 71 by screwing. The top surface of the support base 71 is provided with a 28 type steel motor foot, and the driving motor 72 is stably fixed on the 28 type steel motor foot by a hexagonal bolt and a hexagonal nut, and a 25GB / T95-2002 flat washer and a 25GB / T93-1987 standard elastic washer are arranged between the hexagonal bolt and the hexagonal nut.

[0097] Specifically, referring to FIG. 7, the fan 70 comprises a rotating shaft through hole and a bearing base, the side wall of the outer shell 74 is provided with the rotating shaft through hole, and one end of the impeller rotating shaft 501 extends out of the outer shell 74 through the rotating shaft through hole and is rotatably connected to the outer shell 74 through the bearing base.

[0098] Specifically, the transmission mechanism adopts belt transmission.

[0099] Specifically, referring to FIG. 7, the transmission mechanism comprises a first pulley 771, a second pulley 772 and a transmission belt 773, the first pulley 771 is connected to the output shaft of the driving motor 72, the second pulley 772 is connected to the impeller rotating shaft 501, and the first pulley 771 and the second pulley 772 are connected by the transmission belt 773. When the driving motor 72 is turned on, the driving motor 72 drives the first pulley 771, and then drives the transmission belt and the second pulley, and the second pulley 772 drives the impeller rotating shaft 501 to rotate, and finally drives the impeller to rotate, achieving the effect of air extraction.

[0100] Embodiment 2

[0101] Based on the embodiment 1, referring to FIG. 11 and FIG. 12, the blade 10 in the present embodiment further comprises a notch 111 arranged at the trailing edge 104 of the blade 10 and provided at the connection between the first twisted blade segment 107 and the second twisted blade segment 108.

[0102] The embodiment sets the notch 111 at the position where the trailing edge 104 of the blade 10 is located at the joint of the first twisted blade segment 107 and the second twisted blade segment 108, the notch 111 can reduce the accumulation of airflow at the middle tip of the concave air outlet part 106 of the blade 10, the notch 111 disperses the airflow, separates the accumulated vortex, is conducive to reducing the flow resistance, improving the efficiency of the ventilator, and reducing the noise.

[0103] In the embodiment, the notch 111 is in the shape of a right triangle. Specifically, the length of the sides of the right triangle is 2mm, 4mm and 4mm respectively. The top angle of the right triangle is located at the joint end 109.

[0104] Referring to FIG. 10, the embodiment also provides a double-suction centrifugal impeller 30 of a fan 70 using the blade 10 of the embodiment.

[0105] In the embodiment, referring to FIG. 10, the end of the leading edge side of the blade 10 corresponding to the air inlet end of the impeller adopts a rounded corner structure. Preferably, the radius of the rounded corner is 10mm, which can increase the inlet guide of the air inlet, eliminate the vortex generated by the blade tip, and reduce the inlet energy loss and noise. FIG. 16 shows the local vortex cloud diagram of the impeller after the end of the leading edge side of the blade 10 corresponding to the air inlet end of the impeller is not chamfered and chamfered, and it can be seen that continuous vortex appears near the disc when the disc is not chamfered, and the effect of vortex dispersion is not achieved, while after chamfering, continuous vortex does not appear, but in a dispersed state.

[0106] Comparative Example 1

[0107] Unlike the embodiment 1, the prototype fan 70 of the comparative example adopts a conventional impeller, the shape of which is shown in FIG. 13, and the blade in the conventional impeller is a non-twisted circular-arc straight blade 11. Except for the blade, the other structural parameters of the fan 70 of the embodiment are the same as the corresponding structural parameters of the fan of the embodiment 1.

[0108] Comparative Example 2

[0109] The fan 70 of the comparative example adopts a single-segment twisted blade impeller, the shape of which is shown in FIG. 14, and the single-segment twisted blade 12 is formed by twisting the end part for connecting the disc 50 relative to the other end part for connecting the wheel disc 60 in the circular-arc straight blade 11, and the twisting axis of the single-segment twisted blade 12 passes through the midpoint of the cross-sectional profile of the circular-arc straight blade 11 perpendicular to the length direction and parallel to the length direction of the circular-arc straight blade 11.

[0110] Referring to FIG. 14, the leading edge part of the single-segment twisted blade 12 gradually protrudes to the outer camber surface of the single-segment twisted blade 12 from the other end part for connecting the wheel disc 60 to the end part for connecting the disc 50.

[0111] ​The fan 70 of the present embodiment is identical to the fan of the first embodiment in terms of the structural parameters of the fan except for the blades. Fig. 9 shows a schematic view of the volute profile of the present application, showing the impeller of the first embodiment. The volute profile is known in the art and will not be described here. The main structural parameters of the volute profile are: R1 is 354.44 mm, R2 is 414.06 mm, R3 is 473.69 mm, R4 is 299.2 mm, H is 621.24 mm, and the axial length of the volute is 633 mm.

[0112] The main structural parameters of the fans provided by the first and second embodiments, the first and second comparative examples of the present application, except for the volute, are shown in Table 1.

[0113] Table 1 Main structural parameters of the fans provided by the first and second embodiments, the first and second comparative examples of the present application, except for the volute

[0114] The model was built and assembled by Solidworks software, and simulation was performed using Ansys Fluent software after the construction was completed. The rotational speed of the impeller was set to 935 r / min, the inlet volume flow rate was set to 21678.77 m 3 / h, and the airflow flowed into the inlet of the wheel disc 60 uniformly.

[0115] Figs. 15(A) to 15(D) respectively show the velocity vector cloud diagrams of the numerical simulation of the impeller provided by the first embodiment, the second embodiment, the first comparative example, and the second comparative example of the present application.

[0116] As can be seen by comparing Figs. 15(C) and 15(D), compared with the outlet of the first comparative example, the outlet of the second comparative example shows a clear airflow crossing and gathering phenomenon, and the flow rate near the middle disc 50 is significantly larger than that on both sides. The crossing and gathering of air in the volute 73 of the fan 70 leads to an increase in the air vorticity around the impeller. In addition, the crossing and gathering of air affects the normal operation of the impeller, and may even cause airflow backflow, affecting the stability of the entire system and being detrimental to improving the comprehensive performance of the fan 70.

[0117] The following compares the embodiment 1 of the present application with the comparative example 1. As can be seen from the comparison of FIG. 15(A) and FIG. 15(C), both the impeller airflow velocity vector cloud chart of the embodiment 1 of the present application and the impeller airflow velocity vector cloud chart of the conventional fan 70 in the comparative example 1 have more airflow aggregation near the middle disc 50, but the airflow velocity of the impeller in the embodiment 1 of the present application is greater than that in the comparative example 1 in the blade 10 area, which has a certain improvement effect on the instantaneous state pressure difference stability of the airflow, at the same time, can reduce the aerodynamic friction vibration of the impeller, reduce the power of the impeller, reduce the energy loss of the motor, relatively improve the efficiency of the fan, obtain the outlet dynamic pressure according to the momentum theorem, and further improve the efficiency of the fan according to the calculation formula that the fan total pressure is the pressure difference between the inlet and the outlet.

[0118] As can be seen from the comparison of FIG. 15(A), FIG. 15(B) and FIG. 15(C), compared with the embodiment 1, the embodiment 2 of the present application adds the notch 111, so that the impeller airflow velocity distribution is more uniform, and the airflow near the middle disc 50 does not appear aggregation phenomenon, and the airflow velocity is mainly concentrated near the blade 10 on both sides of the middle disc 50, which makes the running effect of the impeller of the embodiment 2 of the present application better than the previous several structures, and the system stability and the efficiency of the fan are better.

[0119] Specifically, the embodiment 1 has no notch structure, the intersection end 109 is protruding and sharp on one side close to the trailing edge, and the sharp point is the airflow aggregation point on both sides. From the theoretical stress analysis of the velocity vector and the wind resistance reaction force, it is not difficult to find that the aerodynamic intersection at this place pushes the blade in the opposite direction, increases the opposite moment, increases the power of the impeller, and thus increases the energy consumption of the motor. The embodiment 2 adds the notch 111 in the form of sharp angle segmentation on the basis of the embodiment 1, and the notch structure is easy to form a tip vortex in the flow guiding process according to the rotor vortex theory. The tip vortex at this place weakens the energy loss caused by the collision of the velocity vectors, and there is no stress transmission between solids at this place. At the same time, the side wall surface of the notch 111 is a flat surface, so that part of the airflow moves in a straight line, without the uniform flow guiding effect of the circular curved surface, and the energy loss caused by the mutual collision of the airflow is weakened. Therefore, compared with the embodiment 1 without notch structure, the power of the impeller of the embodiment 2 will be relatively reduced, and the efficiency of the fan will be relatively improved.

[0120] FIG. 16(A) and FIG. 16(B) respectively show the local vorticity cloud chart of the impeller air inlet end when the blade end corresponding to the air inlet end of the impeller has no chamfer and the local vorticity cloud chart of the impeller air inlet end when the blade end corresponding to the air inlet end of the impeller is provided with a chamfer structure. Comparing FIG. 16(A) and FIG. 16(B), for the unchamfered blade, there is continuous vorticity near the disc, and for the chamfered blade, there is no continuous vorticity near the disc, which shows that the chamfer structure plays a role in dispersing vorticity, which helps to reduce noise.

[0121] Fig. 17(A) and Fig. 17(B) respectively show the vortex distribution cloud diagrams of the impeller surface of the second embodiment and the first comparative example of the present application. As can be seen from Fig. 17(B), a large range of vortex aggregation occurs in the middle region of the impeller surface of the comparative example 1, which results in a larger fan noise of the comparative example 1. As can be seen from a comparison between Fig. 17(A) and Fig. 17(B), the vortex of the impeller surface of the embodiment 2 is more uniformly distributed than that of the comparative example 1, thereby playing a noise reduction effect.

[0122] Fig. 18 and Fig. 19 respectively show the actual photos of the double-suction centrifugal impeller provided by the first embodiment and the second embodiment of the present application. Fig. 20 and Fig. 21 are two partial actual photos of the centrifugal fan provided by the second embodiment of the present application.

[0123] The measured results of the main performance parameters of the four fans 70 respectively using the above four kinds of impellers are described below. The present application is tested under the environmental conditions of 1 standard atmosphere, 25℃ ambient temperature and 1.2kg / m3air density. 3 The test of the main performance parameters of the above four fan 70 structures is carried out under the environmental conditions of 1 standard atmosphere, 25℃ ambient temperature and 1.2kg / m3air density, according to GB / T1236-2017 “Standardized air duct performance test for industrial fans”.

[0124] Fig. 22 shows the comparison diagram of the relationship between the fan efficiency and the volume flow rate of the embodiment 1, the embodiment 2, the comparative example 1 and the comparative example 2 of the present application. Fig. 23 shows the comparison diagram of the relationship between the shaft power and the volume flow rate of the centrifugal fan 70 of the embodiment 1, the embodiment 2, the comparative example 1 and the comparative example 2 of the present application. Fig. 24 shows the comparison diagram of the relationship between the pressure and the volume flow rate of the centrifugal fan 70 of the embodiment 1, the embodiment 2, the comparative example 1 and the comparative example 2 of the present application.

[0125] In terms of fan efficiency, as can be seen from Fig. 22, the fan efficiency of the comparative example 2 is slightly improved compared with the comparative example 1, and the overall difference is not large, and the improvement effect is not obvious. The efficiency corresponding to the highest improvement point of the horizontal coordinate of the embodiment 1 is 34.28%, while the efficiency at this position of the comparative example 1 is 22.48%. According to these two values, the growth percentage is calculated to be 52.49%. Specifically, compared with the comparative example 1, the embodiment 1 sets the protruding air inlet part 105, which increases the air inlet amount, reduces the separation and vortex flow of the airflow in front of the blade 10, reduces the flow loss, improves the fan efficiency, and at the same time, the protruding air inlet part 105 plays a role in guiding the airflow, making the airflow more smoothly enter the working area of the blade 10, improving the working efficiency and working capacity of the fan.

[0126] In terms of fan efficiency, as shown in FIG. 22, the highest efficiency of the implementation example 2 is 29.9%, while the highest efficiency of the comparative example 1 is 10.62%. The growth percentage is 181.54% according to the two values. Specifically, the implementation example 2 adds the notch 111 based on the implementation example 1. The notch 111 reduces the airflow gathering at the tip of the concave air outlet part 106 of the blade 10, disperses the airflow, separates the gathered vortex, reduces the flow resistance, and improves the efficiency.

[0127] Therefore, the efficiency of the centrifugal fan 70 provided by the implementation example 2 is greatly improved, and is better than the other three structures.

[0128] In terms of shaft power, as shown in FIG. 23, the shaft power of the implementation example 1 and the implementation example 2 is basically the same. The highest shaft power of the implementation example 1 and the implementation example 2 is 13.135 kW, while the highest shaft power of the comparative example 1 is 16.23 kW. The reduction percentage is 23.56% according to the two values. Therefore, the shaft power of the centrifugal fan 70 provided by the implementation example 1 and the implementation example 2 is obviously reduced, and the effect is good.

[0129] In terms of fan pressure, as shown in FIG. 24, the highest fan pressure of the implementation example 1 is 550.6 Pa, while the highest fan pressure of the comparative example 1 is 450 Pa. The growth percentage is 22.35% according to the two values. Specifically, the airflow of the comparative example 1 is changed by a large angle from the entrance of the shell to the inside of the impeller. Because the blade of the comparative example 1 is a non-twisted circular arc straight blade 11, the circular arc straight blade 11 has no flow guide structure, so that the airflow of the blade is not uniform. The double-section twisted blade of the implementation example 1 increases the air inlet area, and the twist surface of the double-section twisted blade has a flow guide effect on the entering airflow. The flow guide effect reduces the kinetic energy loss of the airflow redirection, reduces the energy loss of the cross-flow collection of the middle disc, and improves the fan pressure of the implementation example 1.

[0130] As shown in FIG. 24, the highest fan pressure of the implementation example 2 is 520.1 Pa, while the highest fan pressure of the comparative example 1 is 229.6 Pa. The growth percentage is 126.52% according to the two values, which is much higher than the growth percentage of the highest fan pressure of the implementation example 1 compared with the comparative example 1.

[0131] Specifically, embodiment 2 increases the notch structure 111 on the basis of embodiment 1, the notch is divided in the form of sharp angle, the rotor vortex theory analysis shows that the structure is easy to form tip vortex in the flow guiding process, the tip vortex at the place weakens the energy loss of the velocity vector collision, and there is no force transmission between solids due to the notch structure at the place. At the same time, since the side wall surface of the notch is a flat surface, it makes part of the airflow move in a straight line, which does not have the uniform flow guiding effect of circular surface, thereby weakening the energy loss generated by the airflow impact. In addition, the leading edge side of the blade 10 corresponds to the end of the impeller air inlet end, which adopts a rounded corner structure, which can increase the inlet flow of the wheel disc air inlet, eliminate the vortex generated by the blade tip, and reduce the inlet energy loss and noise. For the above reasons, compared with embodiment 1, the highest lifting point of embodiment 2 corresponding to the fan pressure is further improved.

[0132] As can be seen from the above, in terms of fan efficiency, shaft power and fan pressure, embodiment 1 of the present application is better than comparative examples 1 and 2, and the overall centrifugal fan 70 provided by embodiment 2 is better than embodiment 1.

[0133] The present application provides a kind of blade for centrifugal fan, the thought and method of double suction centrifugal impeller and fan using the blade, there are many methods and ways to specifically realize the technical scheme, above is only preferred embodiment of the present application, it should be pointed out, for the ordinary skilled person in the art, without departing from the principles of the present application, can also make several improvements and refinements, these improvements and refinements should also be considered as the protection scope of the present application. The components not explicitly described in the embodiment can be realized by existing technology.

Claims

1. A blade for a centrifugal fan, characterized by, The blade (10) comprises a suction surface wall (101), a pressure surface wall (102), a leading edge (103), a trailing edge (104), a convex air inlet portion (105) and a concave air outlet portion (106); the suction surface wall (101) and the pressure surface wall (102) are oppositely arranged, and both extend along the length direction of the blade (10) and between the leading edge (103) and the trailing edge (104); the convex air inlet portion (105) is protrusively formed on the side of the leading edge portion of the blade (10) towards the suction surface wall (101), and the concave air outlet portion (106) is protrusively formed on the side of the trailing edge portion of the blade (10) towards the pressure surface wall (102), and the convex air inlet portion (105) and the concave air outlet portion (106) are connected in the direction from the leading edge to the trailing edge; In the length direction of the blade (10), the convex air inlet portion (105) has a structure of high in the middle and low on both sides, and the concave air outlet portion (106) has a structure of low in the middle and high on both sides; in the direction from the leading edge to the trailing edge, the middle height of the convex air inlet portion (105) has a decreasing trend; in the direction from the trailing edge to the leading edge, the middle height of the concave air outlet portion (106) has a decreasing trend.

2. The blade for a centrifugal fan according to claim 1, characterized by The shape of any cross-sectional profile of the blade (10) perpendicular to the length direction thereof is a circular arc shape, the inner arc surface of the blade (10) is the pressure surface wall (102), the outer arc surface of the blade (10) is the suction surface wall (101), and the leading edge (103) and the trailing edge (104) are oppositely arranged in the arc length direction of the blade (10).

3. The blade for a centrifugal fan according to claim 2, characterized by The blade (10) is a double-section reverse torsion blade structure, comprising a first torsion blade section (107) and a second torsion blade section (108) connected in sequence along the length direction of the blade (10), and the torsion direction of the first torsion blade section (107) is opposite to that of the second torsion blade section (108).

4. The blade for a centrifugal fan according to claim 3, characterized by The blade (10) comprises a first end (112) and a second end (113) oppositely arranged along the length direction of the blade (10), and a junction end (109) located between the first end (112) and the second end (113) along the length direction of the blade (10), wherein the first end (112) is used for connecting with the hub of an impeller, and the second end (113) is used for connecting with the disc of the impeller; The first twisted blade segment (107) is twisted by the first end (112) relative to the intersection end (109) in a direction opposite to the rotating direction of the blade, and the second twisted blade segment (108) is twisted by the second end (113) relative to the intersection end (109) in the opposite direction, so that the leading edge portions of the first twisted blade segment (107) and the second twisted blade segment (108) respectively protrude from the first end (112) and the second end (113) towards the intersection end (109) to form the convex air inlet portion (105) on the outer camber surface of the blade (10), and the trailing edge portions of the first twisted blade segment (107) and the second twisted blade segment (108) respectively protrude from the first end (112) and the second end (113) towards the intersection end (109) to form the concave air outlet portion (106) on the inner camber surface of the blade (10).

5. The blade for a centrifugal fan according to claim 4, characterized by The first twisted blade segment (107) comprises a first inner camber twisted surface (1071) and a first outer camber twisted surface (1072), and the second twisted blade segment (108) comprises a second inner camber twisted surface (1081) and a second outer camber twisted surface (1082), the first inner camber twisted surface (1071) of the first twisted blade segment (107) and the second inner camber twisted surface (1081) of the second twisted blade segment (108) are connected to form the pressure surface wall (102) of the blade (10), and the first outer camber twisted surface (1072) of the first twisted blade segment (107) and the second outer camber twisted surface (1082) of the second twisted blade segment (108) are connected to form the suction surface wall (101) of the blade (10).

6. The blade for a centrifugal fan according to claim 5, wherein The first twisted blade segment (107) and the second twisted blade segment (108) have a common twisted axis (110), and the common twisted axis (110) is parallel to the length direction of the blade (10).

7. The blade for a centrifugal fan according to claim 6, wherein The first twisted blade segment (107) and the second twisted blade segment (108) have the same size in the cross-sectional profile perpendicular to the length direction of the blade (10).

8. The blade for a centrifugal fan according to claim 7, characterized by The cross-sectional profile of the blade (10) perpendicular to the length direction thereof has a midpoint (M), and the common twisted axis (110) passes through the midpoint (M).

9. The blade for a centrifugal fan according to claim 3, characterized by The twisted angle of the first twisted blade segment (107) and the second twisted blade segment (108) ranges from 5° to 15°.

10. The blade for a centrifugal fan according to claim 9, characterized by The twisted angle of the first twisted blade segment (107) and the second twisted blade segment (108) is 10°.

11. The blade for a centrifugal fan according to claim 3, characterized by The length ratio of the first twisted blade segment (107) to the second twisted blade segment (108) ranges from 0.25 to 1.

5.

12. The blade for a centrifugal fan according to claim 11, wherein The length ratio of the first twisted blade segment (107) to the second twisted blade segment (108) is 1.

13. The blade for a centrifugal fan according to claim 3, characterized by Further comprising a notch (111) arranged at the trailing edge (104) of the blade (10) and opening at the joint of the first twisted blade segment (107) and the second twisted blade segment (108), the notch (111) is arranged in the shape of a right triangle.

14. A double suction centrifugal impeller characterized by The centrifugal fan blade according to any one of claims 1 to 13, comprising a rotation axis (40), a middle disc (50), and a plurality of the blades (10), the plurality of blades (10) are divided into two groups, the two groups of blades (10) are symmetrically arranged on both sides of the middle disc (50) with the middle disc (50) as a symmetric plane; the plurality of blades (10) in each group are uniformly spaced along the circumferential direction of the rotation axis (40); the length direction of each blade (10) is parallel to the rotation axis (40), and the leading edge (103) of each blade (10) is closer to the rotation axis (40) of the double-suction centrifugal impeller than the trailing edge (104).

15. The double suction centrifugal impeller of claim 14, wherein, The centrifugal fan blade according to any one of claims 1 to 13, comprising a wheel disc (60), each group of blades (10) is connected with a wheel disc (60) on the side away from the middle disc (50) along the direction of the rotation axis (40); each wheel disc (60) is provided with a wheel disc air inlet (601).

16. A fan, comprising: The centrifugal fan blade according to any one of claims 1 to 13, comprising: The double-suction centrifugal impeller (30) according to any one of claims 14 to 15; A support base (71); A driving motor (72) fixedly installed on the top surface of one end of the support base (71); A volute (73) fixedly installed on the top surface of the other end of the support base (71), the double-suction centrifugal impeller (30) is arranged in the volute (73); the middle disc (50) of the double-suction centrifugal impeller (30) is connected with an impeller rotating shaft (501); And a transmission mechanism, the power of the driving motor (72) is transmitted to the impeller rotating shaft (501) through the transmission mechanism, and the rotation of the impeller rotating shaft (501) drives the double-suction centrifugal impeller (30) to rotate around the rotation axis (40) of the double-suction centrifugal impeller (30).

17. The fan of claim 16, wherein, The volute (73) comprises: Two air inlet end plates (731) arranged oppositely; An annular plate (732) connected between the two air inlet end plates (731), And a hollow chamber (733) enclosed by the two air inlet end plates (731) and the annular plate (732) for accommodating the impeller; The annular plate (732) is provided with a volute air outlet (734), and the two air inlet end plates (731) are each provided with a volute air inlet (735), the volute air outlet (734) and each volute air inlet (735) are in communication with the hollow chamber (733).

18. The fan of claim 17, wherein, Further comprising an outer shell (74), the outer shell (74) covers the volute (73).

19. The fan of claim 18, wherein, The outer shell (74) is provided with a rotating shaft through hole, and one end of the impeller rotating shaft (501) that extends out of the outer shell (74) through the rotating shaft through hole is rotatably connected to the outer shell (74) through a bearing base.

20. The fan of claim 19, wherein, The transmission mechanism adopts a belt transmission. The transmission mechanism adopts a belt transmission.

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