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

Abstract

The utility model provides a blade for a centrifugal fan, a double-suction centrifugal impeller applying the blade and the fan. The blade comprises a suction surface wall, a pressure surface wall, a front edge, a rear edge, a convex air inlet part and a concave air outlet part, the suction surface wall and the pressure surface wall are arranged back to back and extend in the length direction of the blade firstly and then extend between the front edge and the rear edge; the protruding air inlet part is formed in the mode that the front edge part of the blade protrudes towards one side of the suction surface wall, the concave air outlet part is formed in the mode that the rear edge part of the blade protrudes towards one side of the pressure surface wall, and the protruding air inlet part and the concave air outlet part are connected in the direction from the front edge to the rear edge. In the length direction of the blade, the convex air inlet part is of a structure with high middle and two low sides, and the concave air outlet part is of a structure with low middle and two high sides; in the direction from the front edge to the rear edge, the middle height of the convex air inlet part is in a decreasing trend; and in the direction from the rear edge to the front edge, the middle height of the sunken air outlet part is in a decreasing trend.

Description

Technical Field

[0001] The utility model relates to the technical field of centrifugal fans, in particular to a blade for a centrifugal fan, a double-suction centrifugal impeller using the blade and a fan. Background Art

[0002] A centrifugal fan is a machine that relies on input mechanical energy to increase gas pressure and discharge gas. It is a driven fluid machine. The working principle is that the impeller makes relative rotational motion in the fan volute, and the centrifugal force generated compresses and transmits the gas, converting the mechanical energy of the fan into kinetic energy and potential energy of the gas.

[0003] Centrifugal fans can be divided into single-suction and double-suction types according to the number of suction ports on the impeller. Among them, the double-suction centrifugal fan adopts a single-axis double-support structure. Since it has two separate air inlet boxes and a double-sided suction impeller structure, it can not only offset the axial force of the impeller, but also the bearings at both ends wear evenly, and the operation is stable and reliable. The double-suction fan has a larger flow coefficient and can provide a larger gas flow than the single-suction fan. It is suitable for many industries with large gas flow requirements. By controlling the rotation speed of the impeller and designing the shape of the blades, the performance of the centrifugal fan and the pressure of the output air flow can be adjusted.

[0004] When the impeller of a traditional centrifugal fan is rotating, the airflow between the blades is easily affected by the fluid viscosity effect, adverse pressure gradient and rotating Coriolis force, which can easily cause flow separation and form secondary vortex, resulting in low fan efficiency.

[0005] The information disclosed in this background technology section is only intended to increase the understanding of the overall background of the utility model, and should not be regarded as acknowledging or suggesting in any form that the information constitutes the prior art already known to ordinary technicians in this field. Utility Model Content

[0006] Purpose of the utility model: The technical problem to be solved by the utility model is to address the deficiencies in the prior art and to provide a blade for a centrifugal fan, a double-suction centrifugal impeller and a fan using the blade. The blade is applied to a double-suction centrifugal impeller to improve the operating efficiency of the fan.

[0007] In order to solve the above technical problems, the utility model discloses a blade for a centrifugal fan, which includes a suction surface wall, a pressure surface wall, a leading edge, a trailing edge, a raised air inlet portion and a recessed air outlet portion. The suction surface wall and the pressure surface wall are arranged back to back, and the two extend firstly along the length direction of the blade, and secondly between the leading edge and the trailing edge. The raised air inlet portion is protrudingly formed on the side of the leading edge portion of the blade toward the suction surface wall, and the recessed air outlet portion is protrudingly formed on the side of the trailing edge portion of the blade toward the pressure surface wall, and in the direction from the leading edge to the trailing edge, the raised air inlet portion and the recessed air outlet portion are connected.

[0008] Along the length direction of the blade, the raised air inlet presents a structure with high center and low sides, and the recessed air outlet presents a structure with low center and high sides. In the direction from the leading edge to the trailing edge, the middle height of the raised air inlet presents a decreasing trend. In the direction from the trailing edge to the leading edge, the middle height of the recessed air outlet presents a decreasing trend.

[0009] Preferably, any cross-sectional profile of the blade perpendicular to its own length direction is in the shape of an arc, 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 relatively arranged in the arc length direction of the blade.

[0010] Specifically, the blade is a double-section reverse twisted blade structure, including a first twisted blade segment and a second twisted blade segment connected in sequence along the length direction of the blade, and the twisting direction of the first twisted blade segment is opposite to the twisting direction of the second twisted blade segment.

[0011] Specifically, the blade includes a first end and a second end arranged opposite to each other along the length direction of the blade, and an intersection end located between the first end and the second end along the length direction of the blade, wherein the first end is used to connect to the center disk of the impeller, and the second end is used to connect to the wheel disk of the impeller.

[0012] The first twisted blade segment is formed by twisting the first end relative to the intersection end in a direction opposite to the rotational speed direction of the blade, and the second twisted blade segment is formed by twisting the second end relative to the intersection end in the opposite direction, so that the leading edge portion of the first twisted blade segment and the leading edge portion of the second twisted blade segment gradually protrude from the first end and the second end toward the intersection end toward the outer arc surface of the blade to form the raised air inlet portion, and the trailing edge portion of the first twisted blade segment and the trailing edge portion of the second twisted blade segment gradually protrude from the first end and the second end toward the intersection end toward the inner arc surface of the blade to form the recessed air outlet portion.

[0013] Specifically, the first twisted blade segment includes a first inner arc twisted surface and a first outer arc twisted surface, the second twisted blade segment includes 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 is connected to the second inner arc twisted surface of the second twisted blade segment to form the pressure surface wall of the blade, and the first outer arc twisted surface of the first twisted blade segment is connected to the second outer arc twisted surface of the second twisted blade segment to form the suction surface wall of the blade.

[0014] Preferably, the first twisted blade segment and the second twisted blade segment have a common twist axis, and the common twist axis is parallel to the blade length direction.

[0015] Preferably, the cross-sectional profiles of the first twisted blade segment and the second twisted blade segment perpendicular to the length direction of the blade are consistent in size.

[0016] Preferably, the cross-sectional profile of the blade perpendicular to its own length direction has a midpoint, and the common twist axis passes through the midpoint.

[0017] Preferably, the torsion angles of the first twisted blade segment and the second twisted blade segment are in a range of 5° to 15°. More preferably, the torsion angles of the first twisted blade segment and the second twisted blade segment are both 10°.

[0018] Preferably, the length ratio of the first twisted blade segment to the second twisted blade segment is in a range of 0.25 to 1.5. More preferably, the length ratio of the first twisted blade segment to the second twisted blade segment is 1.

[0019] Furthermore, the blade also includes a notch, which is arranged at the trailing edge of the blade and opened at the connection between the first twisted blade segment and the second twisted blade segment, and the notch is arranged in a right-angled triangle.

[0020] The second aspect of the utility model discloses a double-suction centrifugal impeller, which includes a rotation axis, a middle disk, and the centrifugal fan blades as described above, wherein the blades are provided in plurality, and the plurality of blades are divided into two groups, and the two groups of blades are distributed on both sides of the middle disk and are arranged symmetrically with the middle disk as a symmetry plane. The plurality of blades in each group are evenly spaced along the circumference of 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 its trailing edge.

[0021] Specifically, the impeller includes a wheel disc, and each group of blades is connected to a wheel disc on one side away from the middle disc along the direction of the rotation axis. Each wheel disc is provided with a wheel disc air inlet.

[0022] A third aspect of the utility model discloses a fan, comprising:

[0023] A double suction centrifugal impeller as described above;

[0024] Support chassis;

[0025] A driving motor fixedly mounted on the top surface of one end of the supporting chassis;

[0026] A volute fixedly mounted on the top surface of the other end of the supporting chassis, wherein the double-suction centrifugal impeller is arranged in the volute; an impeller shaft is connected to the middle disk of the double-suction centrifugal impeller;

[0027] And a transmission mechanism, the power of the driving motor is transmitted to the impeller shaft through the transmission mechanism, and the rotation of the impeller shaft drives the double-suction centrifugal impeller to rotate around the rotation axis of the double-suction centrifugal impeller.

[0028] Specifically, the volute includes two air inlet end plates arranged opposite to each other, an annular plate connected between the two air inlet end plates, and a hollow chamber for accommodating an 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 both provided with a volute air inlet, and the volute air outlet and each of the volute air inlets are connected to the hollow chamber.

[0029] Furthermore, the fan also includes an outer shell, and the outer shell is covered on the volute.

[0030] Specifically, the fan comprises a shaft through hole and a bearing base. The side wall of the outer shell is provided with a shaft through hole. One end of the impeller shaft extending through the shaft through hole and extending out of the outer shell is rotatably connected to the outer shell through the bearing base.

[0031] Specifically, the transmission mechanism adopts a conveyor belt transmission.

[0032] Beneficial effects:

[0033] 1) When the centrifugal fan blade of the utility model is used in a double-suction centrifugal impeller, a raised air inlet portion is provided at the leading edge portion thereof. On the one hand, the raised air inlet portion can achieve a larger air intake volume at the same rotation speed, reduce the separation of the airflow at the leading edge of the blade and the generation of vortices, reduce flow losses, and improve efficiency; on the other hand, the raised air inlet portion can guide the airflow, so that the airflow enters the working area of ​​the blade more smoothly, and improves the work efficiency and work capacity of the fan; a recessed air outlet portion is provided at the trailing edge portion of the blade. On the one hand, the recessed air outlet portion can increase the air outlet volume, and cooperate with the raised air inlet portion to further improve efficiency; on the other hand, the recessed air outlet portion can move the airflow separation point backward, reduce the separation area, and reduce the influence of vortices. At the same time, it can guide the airflow to pass better, reduce turbulence and energy loss.

[0034] 2) An embodiment of the utility model provides a notch structure at the middle tip of the recessed air outlet portion, and the notch can achieve separation of the gathered vortex, which is beneficial to reducing flow resistance, thereby improving efficiency and reducing noise.

[0035] 3) Compared with the existing centrifugal fans, the fan provided by the utility model achieves a stable and shock-absorbing effect by placing the driving motor outside the outer shell and stabilizing the inner machine including the impeller and the volute inside the outer shell. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific implementation methods, and the above and / or other advantages of the present invention will become more clear.

[0037] Figure 1 The three-dimensional structure diagram of the impeller provided in the first embodiment of the utility model Figure 1 .

[0038] Figure 2 The three-dimensional structure diagram of the impeller provided in the first embodiment of the utility model Figure 2 .

[0039] Figure 3 for Figure 1 The impeller shown is a side view along the axial direction of rotation after the wheel disk is removed.

[0040] Figure 4 for Figure 3 A partial enlarged view of area A.

[0041] Figure 5 The three-dimensional structure of the blade provided in the first embodiment of the utility model is shown in FIG. Figure 1 .

[0042] Figure 6 The three-dimensional structure of the blade provided in the first embodiment of the utility model is shown in FIG. Figure 2 .

[0043] Figure 7 A schematic diagram of the external structure of a fan using the impeller of the first embodiment of the utility model is provided.

[0044] Figure 8 This is a schematic structural diagram of an impeller provided in a volute in the first embodiment of the utility model.

[0045] Fig. 9 It is a schematic diagram of the volute profile of the utility model, showing the impeller provided by the first embodiment.

[0046] Fig.10 A schematic diagram of the three-dimensional structure of an impeller provided in the second embodiment of the utility model.

[0047] Fig.11 A schematic diagram of the three-dimensional structure of a blade provided in the second embodiment of the utility model Figure 1 .

[0048] Fig.12 A schematic diagram of the three-dimensional structure of a blade provided in the second embodiment of the utility model Figure 2 .

[0049] Fig.13 It is a schematic diagram of the three-dimensional structure of a conventional impeller in the first comparative example of the utility model.

[0050] Fig.14 A schematic diagram of the three-dimensional structure of a single-stage twisted blade impeller provided for the second comparative example of the utility model.

[0051] Fig.15 (A) is a velocity vector cloud diagram of the numerical simulation of the impeller provided in the first embodiment of the utility model.

[0052] Fig.15 (B) is a velocity vector cloud diagram of the numerical simulation of the impeller provided in the second embodiment of the present invention.

[0053] Fig.15 (C) is a velocity vector cloud diagram of the numerical simulation of the impeller provided in the first comparative example of the present invention.

[0054] Fig.15 (D) is a velocity vector cloud diagram of the numerical simulation of the impeller provided in the second comparative example of the present invention.

[0055] Fig.16 (A) is the local vorticity cloud diagram at the impeller inlet end when there is no chamfer at the blade end corresponding to the impeller inlet end.

[0056] Fig.16 (B) is a local vortex cloud diagram when a chamfer is provided at the blade end corresponding to the impeller inlet end.

[0057] Fig.17 (A) is a vortex distribution cloud diagram of the impeller surface provided by the second embodiment of the utility model.

[0058] Fig.17 (B) is a cloud diagram of the vortex distribution on the impeller surface provided by the first comparative example of the present utility model.

[0059] Fig.18 This is a comparison diagram of the relationship between the fan efficiency and volume flow of the centrifugal fans provided in the first embodiment, the second embodiment, the first comparative example and the second comparative example of the utility model.

[0060] Fig.19 This is a comparison diagram of the relationship curves between the shaft power and the volume flow rate of the centrifugal fans provided in the first embodiment, the second embodiment, the first comparative example and the second comparative example of the utility model.

[0061] Fig. 20 This is a comparison diagram of the relationship curves between pressure and volume flow of the centrifugal fans provided in the first embodiment, the second embodiment, the first comparative example and the second comparative example of the present invention.

[0062] The description of the accompanying drawings is:

[0063] 10. Blade; 101. Suction surface wall; 102. Pressure surface wall; 103. Leading edge; 104. Trailing edge; 105. Raised air inlet; 106. Concave air outlet; 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. Junction end; 110. Common twisted axis; 20. Flow channel; 30. Double-suction centrifugal impeller; 112. One end; 113, second end; 40, rotation axis; 50, center disk; 60, wheel disk; 601, wheel disk air inlet; 70, fan; 71, support frame; 72, drive motor; 73, volute; 731, air inlet end plate; 732, annular plate; 733, hollow chamber; 734, volute air outlet; 735, volute air inlet; 74, outer shell; 771, first pulley; 772, second pulley; 773, conveyor belt; 111, notch; 11, arc-shaped straight blades; 12, single-stage twisted blades. DETAILED DESCRIPTION

[0064] Impeller airflow separation and air cross-gathering are two common phenomena in the flow process inside the impeller. Among them, impeller airflow separation refers to the separation of airflow from the blade surface in certain areas inside the impeller due to changes in airflow velocity or the influence of blade shape, forming vortex or backflow phenomenon. This separation will cause energy loss of airflow and reduce the efficiency of the fan, while air cross-gathering refers to the meeting and gathering of airflows in different directions in a certain area inside the impeller due to the complex movement of airflow. This phenomenon usually occurs at the impeller outlet or in certain specific areas inside the impeller. Air cross-gathering may cause uneven airflow, affect the normal operation of the impeller, and may even cause airflow backflow, affecting the stability of the entire system. There is a close connection between impeller airflow separation and air cross-gathering. Airflow separation may cause a decrease in local airflow velocity, forming a low-pressure area, which in turn attracts the surrounding airflow to gather and form a cross-gathering phenomenon. Conversely, air cross-gathering may also cause mutual interference of airflows, exacerbating the degree of airflow separation.

[0065] At the same time, airflow separation will cause the fluid to form non-uniform velocity and pressure distribution at the impeller outlet, which will affect the uniform outflow of the airflow. For example, if the airflow is severely separated at the impeller outlet, high-speed areas and low-speed areas may be formed at the outlet, resulting in uneven outflow of the airflow, forming the so-called "jet-wake" flow structure, which will reduce the effective flow area, increase the unevenness of the velocity distribution, and affect the flow state of the impeller outlet.

[0066] When the impeller of a traditional centrifugal fan is rotating, the airflow between the blades is easily affected by the viscosity effect of the fluid, the adverse pressure gradient and the rotating Coriolis force, which can easily cause flow separation and form secondary vortices, leading to low working efficiency of the double-suction centrifugal fan.

[0067] Example 1

[0068] Based on this, see Figures 1 to 6 This embodiment discloses a centrifugal fan blade of the utility model. The blade 10 can be applied to a forward-inclined double-suction centrifugal impeller 30 .

[0069] See also Figure 4 and Figure 5The blade 10 includes a suction surface wall 101, a pressure surface wall 102, a leading edge 103, a trailing edge 104, a raised air inlet portion 105, and a recessed air outlet portion 106. The suction surface wall 101 and the pressure surface wall 102 are arranged back to back, and the two extend firstly in the length direction of the blade 10, and secondly between the leading edge 103 and the trailing edge 104. The raised air inlet portion 105 is protrudingly formed at the leading edge of the blade 10 toward the suction surface wall 101, and the recessed air outlet portion 106 is protrudingly formed at the trailing edge of the blade 10 toward the pressure surface wall 102, and in the direction from the leading edge to the trailing edge, the raised air inlet portion 105 is connected with the recessed air outlet portion 106.

[0070] Along the length direction of the blade 10, the raised air inlet 105 presents a structure with a high middle and low sides, and the recessed air outlet 106 presents a structure with a low middle and high sides. In the direction from the leading edge to the trailing edge, the middle height of the raised air inlet 105 tends to decrease. In the direction from the trailing edge to the leading edge, the middle height of the recessed air outlet 106 tends to decrease.

[0071] The blade 10 can reduce the eddy current and turbulence on both sides of the blade 10 close to the wheel 60, and allow the airflow to flow in evenly from the raised air inlet 105. Through the flow channel 20 between two adjacent blades 10, it flows out from the recessed air outlet 106. In this process, the raised air inlet 105 can increase the air intake, reduce the separation of the airflow at the leading edge of the blade 10 and the generation of eddy currents, reduce flow losses, and improve efficiency. At the same time, the raised air inlet 105 can also guide the airflow, allowing the airflow to enter the working area of ​​the blade 10 more smoothly, and improve the work efficiency and work capacity of the fan; the recessed air outlet 106 can move the airflow separation point backward, reduce the separation area, and reduce the influence of the eddy current. At the same time, it can guide the airflow to pass better, reduce turbulence and energy loss, and at the same time, the raised air inlet 105 can increase the air outlet, and work together with the raised air inlet 105 to greatly improve the efficiency of the fan.

[0072] In one embodiment, see Figure 4 The shape of any cross-sectional profile of the blade 10 perpendicular to its own length direction is an 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 relatively arranged in the arc length direction of the blade 10.

[0073] In one embodiment, see Figure 5 and Figure 6 The blade 10 is a double-section reverse twisted blade structure, including a first twisted blade segment 107 and a second twisted blade segment 108 connected in sequence along the length direction of the blade 10 , and the twisting direction of the first twisted blade segment 107 is opposite to the twisting direction of the second twisted blade segment 108 .

[0074] Specifically, see Figure 5 and Figure 6 The blade 10 has a first end 112 and a second end 113 that are oppositely arranged along the length direction of the blade 10, and a junction end 109 that is located 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 center disk 50 of the impeller, and the second end 113 is used to connect with the wheel disk 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 that the suction surface wall 101 and the pressure surface wall 102 extend along the length direction of the blade 10.

[0075] See also Figure 5 and Figure 6 The first end 112 is twisted in a direction opposite to the rotational speed direction of the blade relative to the intersection end 109, so as to form the above-mentioned first twisted blade segment 107 between the first end 112 and the intersection end 109. The second end 113 is twisted in an opposite direction relative to the intersection end 109, so as to form the above-mentioned second twisted blade segment 108 between the second end 113 and the intersection end 109. Thus, the first twisted blade segment 107 and the second twisted blade segment 108 are sequentially connected along the length direction of the blade 10, and the twisting direction of the first twisted blade segment 107 is opposite to the twisting direction of the second twisted blade segment 108.

[0076] The leading edge of the first twisted blade segment 107 and the leading edge of the second twisted blade segment 108 respectively protrude gradually from the first end 112 and the second end 113 toward the intersection end 109 toward the outer arc surface of the blade 10 to form a raised air inlet portion 105. The trailing edge of the first twisted blade segment 107 and the trailing edge of the second twisted blade segment 108 respectively protrude gradually from the first end 112 and the second end 113 toward the intersection end 109 toward the inner arc surface of the blade 10 to form a recessed air outlet portion 106.

[0077] More specifically, see Figure 5 and Figure 6 The first twisted blade segment 107 includes a first inner arc twisted surface 1071 and a first outer arc twisted surface 1072, and the second twisted blade segment 108 includes 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 is connected to the second inner arc twisted surface 1081 of the second twisted blade segment 108 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 is connected to the second outer arc twisted surface 1082 of the second twisted blade segment 108 to form the suction surface wall 101 of the blade 10.

[0078] In this embodiment, see Figure 4 and Figure 5The blade 10 includes a common twist axis 110. The first twist blade segment 107 and the second twist blade segment 108 have the common twist axis 110, that is, both are twisted around the common twist axis 110. The common twist axis 110 is parallel to the length direction of the blade 10.

[0079] It should be understood that see Figure 4 In this embodiment, the cross-sectional shapes of the first twisted blade segment 107 and the second twisted blade segment 108 perpendicular to the length direction of the blade 10 are both arc-shaped, so that the shape of any cross-sectional profile of the blade 10 perpendicular to its own length direction is an arc-shaped.

[0080] In this embodiment, the cross-sectional dimensions of the first twisted blade segment 107 and the second twisted blade segment 108 perpendicular to the length direction of the blade 10 are consistent. In other words, in this embodiment, the blade 10 is a double-section reverse twisted blade structure with a constant cross-section.

[0081] In the present embodiment, any cross-sectional profile of the blade 10 perpendicular to its own length direction has a midpoint M, and the common torsion axis 110 passes through the midpoint M.

[0082] Preferably, the torsion angles of the first torsion blade segment 107 and the second torsion blade segment 108 are both in the range of 5° to 15°. More preferably, see Figure 6 The twist angles of the first twisted blade segment 107 and the second twisted blade segment 108 are both 10°.

[0083] Preferably, in the length direction of the blade 10, the length ratio of the first twisted blade segment 107 to the second twisted blade segment 108 is in the range of 0.25 to 1.5. More preferably, see Figure 6 , the length ratio of the first twisted blade segment 107 and the second twisted blade segment 108 is 1.

[0084] Optionally, the blade 10 of the present embodiment may be formed by stamping and twisting a straight single arc sheet metal structure.

[0085] See also Figure 1 and Figure 2 The present embodiment also provides a double suction centrifugal impeller 30, comprising the above-mentioned blades 10, a rotation axis 40 and a middle disk 50, wherein the middle disk 50 is used to connect to an external drive motor 72. A plurality of blades 10 are provided, and the plurality of blades 10 are divided into two groups, and the two groups of blades 10 are distributed on both sides of the middle disk 50 and are arranged symmetrically with the middle disk 50 as a symmetry plane. The plurality of blades 10 in each group are evenly spaced along the circumference 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 its trailing edge 104.

[0086] In this embodiment, the middle disk 50 is connected to the output end of the external drive motor 72 so that the driving force applied by the drive motor 72 to the impeller is located in the middle of the impeller along the axial direction, thereby making the overall balance of the impeller's rotation process better.

[0087] In this embodiment, see Figure 1 The double suction centrifugal impeller 30 includes a wheel disc 60, and each set of blades 10 is connected to a wheel disc 60 on a 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. 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.

[0088] In this embodiment, each group of blades 10 is stably supported by the wheel disc 60 and the middle disc 50 on the corresponding side, so that the impeller has a higher structural strength.

[0089] See also Figure 7 The present embodiment further provides a fan 70, which includes the above-mentioned double-suction centrifugal impeller 30, a support frame 71, a drive motor 72, a volute 73 and a transmission mechanism. The drive motor 72 is fixedly mounted on the top surface of one end of the support frame 71. The volute 73 is fixedly mounted on the top surface of the other end of the support frame 71, and the impeller is arranged in the volute 73. An impeller shaft 501 is fixedly connected to the middle plate 50 of the impeller. The power of the drive motor 72 is transmitted to the impeller shaft 501 through the transmission mechanism, and the rotation of the impeller shaft 501 drives the impeller to rotate around the rotation axis 40 of the impeller.

[0090] Specifically, the supporting frame 71 is formed by positioning and connecting with a common connecting block.

[0091] Specifically, see Figure 8 The volute 73 includes two air inlet end plates 731 arranged opposite to each other, an annular plate 732 connected between the two air inlet end plates 731, and a hollow chamber 733 for accommodating an impeller formed by the two air inlet end plates 731 and the annular plate 732. The annular plate 732 is provided with a volute air outlet 734, and the two air inlet end plates 731 are both provided with a volute air inlet 735. The volute air outlet 734 and each volute air inlet 735 are connected to the hollow chamber 733.

[0092] Specifically, see Figure 7 The fan 70 further includes an outer shell 74 , which is covered on the volute 73 .

[0093] Specifically, the outer shell 74 is fixed to the support frame 71 by screwing. A 28-type steel motor foot is installed on the top surface of the support frame 71, and the drive motor 72 is fixed to 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.

[0094] Specifically, see Figure 7 The fan 70 includes a shaft through hole and a bearing base. The side wall of the outer shell 74 is provided with a shaft through hole. One end of the impeller shaft 501 extends out of the outer shell 74 through the shaft through hole and is rotatably connected to the outer shell 74 through the bearing base.

[0095] Specifically, the transmission mechanism adopts a conveyor belt transmission.

[0096] Specifically, see Figure 7 The transmission mechanism includes a first pulley 771, a second pulley 772 and a conveyor belt 773. The first pulley 771 is connected to the output shaft of the driving motor 72, and the second pulley 772 is connected to the impeller shaft 501. The first pulley 771 and the second pulley 772 form a belt transmission connection through the conveyor belt 773. When the driving motor 72 is turned on, the driving motor 72 drives the first pulley 771, and then drives the conveyor belt and the second pulley. The second pulley 772 rotates to drive the impeller shaft 501 to rotate, and finally drives the impeller to rotate, achieving the effect of exhausting air.

[0097] Example 2

[0098] Based on Example 1, see Fig.11 and Fig.12 The blade 10 in this embodiment further includes a notch 111 , which is disposed at the trailing edge 104 of the blade 10 and opened at the connection between the first twisted blade segment 107 and the second twisted blade segment 108 .

[0099] In this embodiment, a notch 111 is provided at the position where the trailing edge 104 of the blade 10 is located at the connection between the first twisted blade segment 107 and the second twisted blade segment 108. The notch 111 can reduce the gathering of airflow at the middle tip of the recessed air outlet portion 106 of the blade 10. The notch 111 disperses the airflow to achieve separation of the gathered vortex, which is beneficial to reducing flow resistance, improving fan efficiency, and reducing noise.

[0100] In this embodiment, the notch 111 is arranged in a right triangle. Specifically, the side lengths of the right triangle are The vertex of the right triangle is located at the intersection 109.

[0101] See also Fig.10The present embodiment further provides a fan 70 that uses a double-suction centrifugal impeller 30 using the blades 10 of the present embodiment.

[0102] In this embodiment, see Fig.10 The end of the leading edge side of the blade 10 corresponding to the impeller inlet end adopts a rounded structure. Preferably, the fillet radius is 10 mm. This structure can increase the inlet flow guidance of the air inlet, eliminate the vortex generated by the blade tip, and reduce the inlet energy loss and noise. Fig.16 The impeller local vorticity cloud diagram of the leading edge side of the blade 10 corresponding to the impeller air inlet end without chamfering and after chamfering is shown. It can be seen that continuous vorticity appears near the unchamfered wheel disk, and the vorticity dispersion effect is not achieved. After chamfering, no continuous vorticity appears, but a dispersed state.

[0103] Comparative Example 1

[0104] Different from Example 1, the prototype fan 70 of this comparative example adopts a conventional impeller, the shape of which is shown in FIG. Fig.13 The blades in the conventional impeller are straight arc-shaped blades 11 without twisting. Except for the blades, other structural parameters of the fan 70 of this embodiment are the same as the corresponding structural parameters of the fan in the first embodiment.

[0105] Comparative Example 2

[0106] The fan 70 of this comparative example adopts a single-stage twisted blade impeller, the shape of which is shown in FIG. Fig.14 The single-stage twisted blade 12 is formed by twisting the end of the arc-shaped straight blade 11 for connecting to the middle disk 50 relative to the other end of the single-stage twisted blade 12 for connecting to the wheel disk 60. The twisting axis of the single-stage twisted blade 12 passes through the midpoint of the cross-sectional profile of the arc-shaped straight blade 11 perpendicular to the length direction and is parallel to the length direction of the arc-shaped straight blade 11.

[0107] See also Fig.14 The leading edge of the single-stage twisted blade 12 gradually protrudes toward the outer arc surface of the single-stage twisted blade 12 from the other end for connecting to the wheel disc 60 to the end for connecting to the middle disc 50 .

[0108] Except for the blades, other structural parameters of the fan 70 of this embodiment are the same as the corresponding structural parameters of the fan in Example 1. Fig. 9 The schematic diagram of the volute profile used in the utility model is shown, showing the impeller provided by the first embodiment. The volute profile is a prior art, so it is not described here. The main structural parameters of the volute profile are: R1 is 354.44mm, R2 is 414.06mm, R3 is 473.69mm, R4 is 299.2mm, H is 621.24mm, and the axial length of the volute is 633mm.

[0109] The other main structural parameters of the fans provided in Example 1, Example 2, Comparative Example 1 and Comparative Example 2 of the present invention except for the volute are shown in Table 1.

[0110] Table 1 Main structural parameters of the fans except the volute provided in Example 1, Example 2, Comparative Example 1 and Comparative Example 2 of the utility model

[0111]

[0112]

[0113] The utility model uses Solidworks software to construct and assemble the model, and after completion of the construction, Ansys Fluent software is used for simulation. The impeller rotation speed is set to 935r / min, and the inlet volume flow rate is 21678.77m 3 / h, the air flows in evenly from the air inlet of the wheel 60.

[0114] Fig.15 (A) to Fig.15 (D) respectively shows the velocity vector cloud diagram 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 invention.

[0115] contrast Fig.15 (C) and Fig.15 (D) It can be seen that compared with the air outlet of comparative example 1, the air outlet of comparative example 2 shows obvious air flow cross-gathering phenomenon, and the flow velocity near the middle disk 50 is obviously larger than that on both sides. The air cross-gathering in the volute 73 of the fan 70 causes the air vortex around the impeller to increase. In addition, the air cross-gathering affects the normal operation of the impeller and may even cause air flow backflow, affecting the stability of the entire system, which is not conducive to improving the comprehensive performance of the fan 70.

[0116] The following is a comparison between Example 1 of the present utility model and Comparative Example 1. Fig.15 (A) and Fig.15 (C) It can be seen that the impeller airflow velocity vector cloud diagram of Example 1 of the utility model and the impeller airflow velocity vector cloud diagram of the conventional fan 70 in Comparative Example 1 both have more airflow gathered near the middle disk 50. The difference is that the airflow velocity of the impeller in Example 1 of the utility model in the blade 10 area is greater than the impeller airflow velocity in Comparative Example 1, which has a certain improvement effect on the transient pressure difference stability of the airflow. At the same time, it can reduce the aerodynamic friction vibration of the impeller, reduce the impeller power, reduce the energy loss of the motor, and relatively improve the efficiency of the fan. According to the momentum theorem, the outlet dynamic pressure increase is obtained. Combined with the calculation formula of the fan total pressure as the inlet and outlet pressure difference, the fan efficiency is further improved.

[0117] contrast Fig.15 (A) Fig.15 (B) and Fig.15 (C) It can be seen that compared with Example 1, Example 2 of the utility model makes the impeller airflow velocity distribution more uniform by adding the notch 111, and the airflow near the middle disk 50 does not gather, and the airflow velocity is mainly concentrated near the blades 10 located on both sides of the middle disk 50. This makes the impeller operation effect of Example 2 of the utility model better than the previous structures, and the system stability and fan efficiency are better.

[0118] Specifically, in the embodiment 1, there is no notch structure, and the side of the intersection end 109 near the trailing edge is in the shape of a protruding spike, and the spike point is the wind gathering point on both sides. From the theoretical force analysis of the velocity vector and the wind resistance reaction force, it is not difficult to find that the aerodynamic cross here pushes the blades in the opposite direction, increases the reverse torque, increases the impeller power, and thus increases the motor energy consumption. In the embodiment 2, a notch 111 is added on the basis of the embodiment 1, which is in the shape of a sharp angle segmentation. The rotor vortex theory analysis shows that the structure is easy to form a blade tip vortex during the flow diversion process. The blade tip vortex at this location weakens the energy loss of the collision of the velocity vector, and there is no force transmission between solids in the notch structure at this location. 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 direction, and there is no uniform flow diversion effect of the circular curved surface, which weakens the energy loss caused by the collision of the airflows. Therefore, compared with the embodiment 1 without a notch structure, the impeller power of the embodiment 2 will be relatively reduced, and the fan efficiency will be relatively improved.

[0119] Fig.16 (A) and Fig.16 (B) shows the local vorticity cloud diagram when the blade end at the corresponding impeller inlet end has no chamfer and the local vorticity cloud diagram when the blade end at the corresponding impeller inlet end has a chamfer structure. Fig.16 (A) and Fig.16 (B) For the blades without chamfers, continuous vorticity appears near the disk, while for the blades with rounded corners, no continuous vorticity appears near the disk, indicating that the rounded corner structure plays a role in dispersing the vorticity, which helps to reduce noise.

[0120] Fig.17 (A) and Fig.17 (B) shows the vortex distribution cloud diagram of the impeller surface of the second embodiment and the first comparative example of the utility model. Fig.17 (B) It can be seen that a large range of vortex accumulation occurs in the middle area of ​​the impeller surface of Comparative Example 1, and this large range of vortex accumulation causes the fan noise of Comparative Example 1 to be relatively large. Fig.17 (A) and Fig.17 (B) It can be seen that the vortex on the impeller surface of Example 2 is more evenly distributed than that of Comparative Example 1, thereby achieving a noise reduction effect.

[0121] The following is a description of the actual test results of the main performance parameters of the four types of fans 70 using the above four types of impellers. 3 The main performance parameters of the above four fan 70 structures are tested under the environmental conditions of air density, based on GB / T 1236-2017 "Standardized Air Duct Performance Test for Industrial Ventilators".

[0122] Fig.18 A comparison diagram of the relationship between the efficiency and volume flow of the fans of Example 1, Example 2, Comparative Example 1 and Comparative Example 2 of the utility model is shown. Fig.19 A comparative graph of the relationship between the shaft power and the volume flow rate of the centrifugal fan 70 of Example 1, Example 2, Comparative Example 1 and Comparative Example 2 of the utility model is shown. Fig. 20 A comparison diagram of the relationship curves between the pressure and the volume flow of the centrifugal fan 70 of Example 1, Example 2, Comparative Example 1 and Comparative Example 2 of the utility model is shown.

[0123] For fan efficiency, see Fig.18 It can be seen that the efficiency of the fan in Example 2 is improved less than that in Example 1, and the overall difference is not large, and the improvement effect is not obvious. The efficiency corresponding to the horizontal coordinate of the highest improvement point in Example 1 is 34.28% compared with Example 1, while the efficiency of this position in Example 1 is 22.48%. The growth percentage calculated based on these two values ​​is 52.49%. Specifically, compared with Example 1, Example 1 is provided with a raised air inlet 105, which increases the air intake volume, reduces the separation and vortex generation of the airflow at the leading edge of the blade 10, reduces flow losses, and improves the efficiency of the fan. At the same time, the raised air inlet 105 plays a role in guiding the airflow, allowing the airflow to enter the working area of ​​the blade 10 more smoothly, thereby improving the work efficiency and work capacity of the fan.

[0124] For fan efficiency, see Fig.18 It can be seen that the efficiency corresponding to the horizontal coordinate of the highest improvement point of Example 2 compared with Comparative Example 1 is 29.9%, while the efficiency of this position of Comparative Example 1 is 10.62%. The increase percentage calculated based on these two values ​​is 181.54%. Specifically, on the basis of Example 1, Example 2 adds a notch 111, and the notch 111 reduces the gathering of the airflow at the tip of the middle of the concave air outlet 106 of the blade 10, so that the airflow here is dispersed, and the separation of the gathered vortex is achieved, thereby reducing the flow resistance and improving the efficiency.

[0125] It can be seen from this that the efficiency of the centrifugal fan 70 provided in Example 2 is greatly improved, and is overall better than the other three structures.

[0126] In terms of shaft power, see Fig.19 It can be seen that the shaft power of Example 1 and Example 2 is basically the same. The shaft power corresponding to the horizontal coordinate of the highest reduction point of Example 1 and Example 2 compared with Comparative Example 1 is 13.135kW, while the shaft power at this position of Comparative Example 1 is 16.23kW. The reduction percentage calculated based on these two values ​​is 23.56%. It can be seen that the shaft power of the centrifugal fan 70 provided in Example 1 and Example 2 of the utility model is significantly reduced, and the effect is good.

[0127] For fan pressure, see Fig. 20 It can be seen that the fan pressure corresponding to the horizontal coordinate of the highest lifting point of Example 1 is 550.6Pa compared with Comparative Example 1, while the fan pressure at this position of Comparative Example 1 is 450Pa. The growth percentage calculated based on these two values ​​is 22.35%. Specifically, the airflow of Comparative Example 1 has a large angle change from the inlet of the shell to the inside of the impeller. Because the blades of Comparative Example 1 are arc-shaped straight blades 11 without twisting, the arc-shaped straight blades 11 have no guide structure, which makes the air volume of each blade uneven. The double-stage twisted blades of Example 1 increase the air inlet area. At the same time, the twisted surface in the double-stage twisted blades has a guide effect on the incoming wind. The guide effect reduces the kinetic energy loss of the airflow redirection outflow. On this basis, the energy loss of the cross-wind collection in the middle disk is reduced, so the fan pressure of Example 1 is increased.

[0128] See also Fig. 20 It can be seen that the fan pressure corresponding to the horizontal coordinate of the highest lifting point of Example 2 compared with Comparative Example 1 is 520.1Pa, while the fan pressure at this position of Comparative Example 1 is 229.6Pa. The growth percentage calculated based on these two values ​​is 126.52%, which is much higher than the growth percentage of 22.35% of the fan pressure corresponding to the horizontal coordinate of the highest lifting point of Comparative Example 1 compared with Example 1.

[0129] Specifically, embodiment 2 adds a notch structure 111 on the basis of embodiment 1, and the notch is in a sharp-angle segmented shape. The rotor vortex theory is used to analyze that the structure is easy to form a tip vortex during the diversion process. The tip vortex at this location weakens the energy loss of the collision of the velocity vectors, and because of the notch structure at this location, there is no force transfer between solids. At the same time, since the side wall surface of the notch is a flat surface, this makes part of the airflow move in a straight direction, and does not have the uniform diversion effect of a circular surface, thereby weakening the energy loss caused by the collision of the airflow. In addition, the end of the leading edge side of the blade 10 corresponding to the impeller air inlet end adopts a chamfered structure, which can increase the inlet diversion of the wheel 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 fan pressure corresponding to the highest lifting point of embodiment 2 is further improved.

[0130] In summary, in terms of fan efficiency, shaft power and fan pressure, Example 1 of the utility model is superior to Comparative Examples 1 and 2, and the centrifugal fan 70 provided by Example 2 is superior to Example 1 as a whole.

[0131] The utility model provides a centrifugal fan blade, a double suction centrifugal impeller using the blade, and a fan idea and method. There are many methods and ways to implement the technical solution. The above is only the preferred implementation of the utility model. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the utility model. These improvements and modifications should also be regarded as the protection scope of the utility model. All components not specified in this embodiment can be implemented by existing technologies.

Claims

1. A centrifugal fan blade, characterized in that: The blade (100) comprises a suction surface wall (101), a pressure surface wall (102), a leading edge (103), a trailing edge (104), a raised air inlet portion (105) and a recessed air outlet portion (106); the suction surface wall (101) and the pressure surface wall (102) are arranged back to back, and the two extend firstly in the length direction of the blade (10), and secondly between the leading edge (103) and the trailing edge (104); the raised air inlet portion (105) is formed protrudingly on the leading edge of the blade (10) toward the suction surface wall (101), and the recessed air outlet portion (106) is formed protrudingly on the trailing edge of the blade (10) toward the pressure surface wall (102), and in the direction from the leading edge to the trailing edge, the raised air inlet portion (105) and the recessed air outlet portion (106) are connected; Along the length direction of the blade (10), the raised air inlet portion (105) presents a structure that is high in the middle and low on both sides, and the recessed air outlet portion (106) presents a structure that is 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 raised air inlet portion (105) tends to decrease; and in the direction from the trailing edge to the leading edge, the middle height of the recessed air outlet portion (106) tends to decrease.

2. The centrifugal fan blade according to claim 1, characterized in that: Any cross-sectional profile of the blade (10) perpendicular to its own length direction is in the shape of a circular arc, 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 arranged opposite to each other in the arc length direction of the blade (10).

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

4. The centrifugal fan blade according to claim 3, characterized in that: The blade (10) comprises a first end (112) and a second end (113) which are arranged opposite to each other along the length direction of the blade (10), and a junction end (109) which is 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 to connect to a center disk of an impeller, and the second end (113) is used to connect to a wheel disk of an impeller; The first twisted blade segment (107) is formed by twisting the first end (112) relative to the intersection end (109) in a direction opposite to the rotational speed direction of the blade, and the second twisted blade segment (108) is formed by twisting the second end (113) relative to the intersection end (109) in the opposite direction, so that the leading edge portion of the first twisted blade segment (107) and the leading edge portion of the second twisted blade segment (108) respectively protrude gradually from the first end (112) and the second end (113) toward the intersection end (109) toward the outer arc surface of the blade (10) to form the convex air inlet portion (105), and the trailing edge portion of the first twisted blade segment (107) and the trailing edge portion of the second twisted blade segment (108) respectively protrude gradually from the first end (112) and the second end (113) toward the intersection end (109) toward the inner arc surface of the blade (10) to form the recessed air outlet portion (106).

5. The centrifugal fan blade according to claim 4, characterized in that: 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 a pressure surface wall (102) of the blade (10); 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 a suction surface wall (101) of the blade (10).

6. The centrifugal fan blade according to claim 5, characterized in that: 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 centrifugal fan blade according to claim 6, characterized in that: The first twisted blade segment (107) and the second twisted blade segment (108) have the same size of cross-sectional profile perpendicular to the length direction of the blade (10).

8. The centrifugal fan blade according to claim 7, characterized in that: The cross-sectional profile of the blade (10) perpendicular to its own length direction has a midpoint (M), and the common twist axis (110) passes through the midpoint (M).

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

10. The centrifugal fan blade according to claim 9, characterized in that: The twist angles of the first twisted blade segment (107) and the second twisted blade segment (108) are both 10°.

11. The centrifugal fan blade according to claim 3, characterized in that: 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 centrifugal fan blade according to claim 11, characterized in that: The length ratio of the first twisted blade segment (107) to the second twisted blade segment (108) is 1.

13. The centrifugal fan blade according to claim 3, characterized in that: It also comprises a notch (111), wherein the notch (111) is arranged at the trailing edge (104) of the blade (10) and is opened at the connection between the first twisted blade segment (107) and the second twisted blade segment (108), and the notch (111) is arranged in the shape of a right triangle.

14. A double suction centrifugal impeller, characterized in that: A centrifugal fan blade comprising a rotation axis (40), a middle disk (50) and a blade for a centrifugal fan as claimed in any one of claims 1 to 13, wherein a plurality of blades (10) are provided, and the plurality of blades (10) are divided into two groups, and the two groups of blades (10) are distributed on both sides of the middle disk (50) and are symmetrically arranged with the middle disk (50) as a symmetry plane; the plurality of blades (10) in each group are evenly spaced along the circumference 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) thereof.

15. The double-suction centrifugal impeller according to claim 14, characterized in that: It comprises a wheel disc (60), and each group of blades (10) is respectively connected to a wheel disc (60) on one 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, characterized in that: include: A double-suction centrifugal impeller (30) as claimed in any one of claims 14 to 15; Supporting chassis (71); A driving motor (72) fixedly mounted on the top surface of one end of the supporting base frame (71); A volute (73) fixedly mounted on the top surface of the other end of the supporting base frame (71), wherein the double-suction centrifugal impeller (30) is arranged in the volute (73); an impeller shaft (501) is connected to the center plate (50) of the double-suction centrifugal impeller (30); and a transmission mechanism, wherein the power of the drive motor (72) is transmitted to the impeller shaft (501) through the transmission mechanism, and the impeller shaft (501) rotates to drive the double-suction centrifugal impeller (30) to rotate around the rotation axis (40) of the double-suction centrifugal impeller (30).

17. The fan according to claim 16, characterized in that: The volute (73) comprises: Two air inlet end plates (731) arranged opposite to each other; an annular plate (732) connected between the two air inlet end plates (731), and a hollow chamber (733) for accommodating an impeller, formed by the two air inlet end plates (731) and the annular plate (732); The annular plate (732) is provided with a volute air outlet (734), and the two air inlet end plates (731) are both provided with a volute air inlet (735), and the volute air outlet (734) and each of the volute air inlets (735) are connected to the hollow chamber (733).

18. The fan according to claim 17, characterized in that: It also includes an outer shell (74), wherein the outer shell (74) is covered on the volute (73).

19. The fan according to claim 18, characterized in that: It comprises a shaft through hole and a bearing base, wherein the side wall of the outer shell (74) is provided with a shaft through hole, and one end of the impeller shaft (501) that passes through the shaft through hole and extends out of the outer shell (74) is rotatably connected to the outer shell (74) via the bearing base.

20. The fan according to claim 19, characterized in that The transmission mechanism adopts conveyor belt transmission.

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