Axial flow fan structure

[0001] 1. Field of the Invention

[0002] The present invention relates to an axial flow fan structure, and more particularly to an axial flow fan structure which has the optimal airflow rate and pressure head.

[0003] 2. Description of the Related Prior Art

[0004] A conventional axial flow fan 10 in accordance with the prior art shown in FIG. 1 comprises a plurality of blades 11 that are separate from each other, and are not overlapped with each other. However, the conventional axial flow fan 10 has the following disadvantages.

[0005] 1. The blades 11 are separate from each other with a large space 12 defined therebetween, so that the number of the blades 11 that may be mounted on the conventional axial flow fan 10 is greatly limited. Therefore, the action surfaces of the smaller number of blades 11 cannot provide a sufficient pressurization to the space 12 between two adjacent blades 11, so that the conventional axial flow fan 10 does not efficiently provide the airflow rate in the spaces 12.

[0006] 2. After the blade 11 of the conventional axial flow fan 10 has exerted pressure on the space 12, the space 12 is pressed by the action surface of the blade 11, so that the airflow rate in the space 12 will produce an airflow rate with the flow movement in the tangent direction and the normal direction. The space 12 is larger, but the action curve of the blade 11 is not sufficient, so that the conventional axial flow fan 10 cannot increase the pressurization of the airflow rate.

[0007] The primary objective of the present invention is to provide an axial flow fan structure having an optimal airflow rate and pressure head. The axial flow fan structure includes a rotor provided with a plurality of fan blades which are overlapped with each other so as to increase the total action area of the overlapping blade action surface, thereby producing the optimal airflow rate with the greatest total pressure head.

[0008] Another objective of the present invention is to provide an axial flow fan structure having a smaller loss of pressure head. The fan blades of the rotor may co-operate with a set of stator guide vanes, thereby further increasing the pressurization of the airflow rate, while the fan having a high flow rate and high pressurization is guided to a predetermined direction more efficiently, thereby decreasing the loss of pressure head.

[0009] In accordance a first embodiment of with the present invention, there is provided an axial flow fan structure comprising: a rotor provided with a plurality of fan blades, each of the fan blades including a chord angle, an air inlet angle, and an air outlet angle, variations of the chord angle, the air inlet angle, and the air outlet angle of the fan blade co-operate with rotation of the fan blade to produce a pressurized airflow rate; wherein, the fan blades are arranged in a head-tail overlap arrangement manner with each other, so that more fan blades may be arranged in the axial flow fan structure in a head-tail overlap arrangement manner of the fan blades, an overlap distance of the fan blades is greater than zero and smaller than one third of a blade average distance, the chord angle of each of the fan blades is ranged between twenty degrees and sixty degrees, and the overlapped fan blades have an action surface whose total action area is increased to co-operate with the chord angle of each of the fan blades, for generating an airflow rate with the greatest efficiency.

[0010] In accordance a second embodiment of with the present invention, there is provided an axial flow fan structure comprising: a rotor provided with a plurality of fan blades, each of the fan blades including a chord angle, an air inlet angle, and an air outlet angle, variations of the chord angle, the air inlet angle, and the air outlet angle of the fan blade co-operate with rotation of the fan blade to produce a pressurized airflow rate; wherein, the fan blades are arranged in a head-tail overlap arrangement manner with each other, a set of stator guide vanes, are sealingly mounted on a predetermined flow direction side of the fan blades, each of the stator guide vanes includes a chord angle, an air inlet angle, and an air outlet angle, and variations of the chord angle, the air inlet angle, and the air outlet angle of the stator guide vane further increase a pressurization of the pressurized airflow rate, while the airflow rate having a high flow rate can be guided more efficiently to a predetermined direction with the best recovery of pressure head.

[0011] Further benefits and advantages of the present invention will become apparent after a careful reading of the detailed description with appropriate reference to the accompanying drawings.

[0012] FIG. 1 is a front plan view of a conventional axial flow fan in accordance with the prior art;

[0013] FIG. 2 is a perspective view of an axial flow fan structure in accordance with a first embodiment of the present invention;

[0014] FIG. 3 is a front plan view of the axial flow fan structure as shown in FIG. 2;

[0015] FIG. 4 is a partially cut-away perspective cross-sectional view of an axial flow fan structure in accordance with a second embodiment of the present invention;

[0016] FIG. 5 is a front plan cross-sectional view of the axial flow fan structure as shown in FIG. 4;

[0017] FIG. 6 is a schematic view of fan blades and stator guide vanes of the axial flow fan structure as shown in FIG. 4; and

[0018] FIG. 7 is a graph of experimental results of the axial flow fan structure in accordance with the present invention.

[0019] Referring to the drawings and initially to FIGS. 2 and 3, an axial flow fan structure in accordance with a first embodiment of the present invention comprises a rotor 20 that is driven by an electrical motor and/or driving devices to rotate axially, and is provided with a plurality of fan blades 21. The fan blades 21 are arranged in a head-tail overlap arrangement manner with each other, that is, the head of one fan blade 21 overlaps with the tail of the adjacent fan blade 21. By means of the head-tail overlap arrangement manner of the fan blades 21, the periphery of the rotor 20 of the axial flow fan structure may be provided with more fan blades 21, more front spaces 23, and more action surfaces 22 of the fan blades 21.

[0020] Each of the fan blades 21 includes a chord angle A, an air inlet angle B, and an air outlet angle C, wherein variations of the chord angle A, the air inlet angle B, and the air outlet angle C of the fan blade 21 together with the overlap distance D of the fan blades 21 may co-operate with rotation of the fan blades 21 to produce a predetermined pressurized airflow rate. The overlap distance D of the fan blades 21 is limited to be greater than zero and smaller than one third of a blade average distance E (0<D<E), while the chord angle A of each of the fan blades 21 is ranged between twenty degrees and sixty degrees (20<A<60).

[0021] In such a manner, the overlapped fan blades 21 have an action surface whose total action area is increased to co-operate with the chord angle A of each of the fan blades 21, for generating an airflow rate with the greatest efficiency.

[0022] Referring to FIGS. 4-6, an axial flow fan structure in accordance with a second embodiment of the present invention comprises a stator 30 sealingly mounted on a predetermined airflow direction side of the rotor 20. The stator 30 includes a plurality of stator guide vanes 31 which are sealingly arranged on a predetermined airflow direction side of the fan blades 21.

[0023] Each of the stator guide vanes 31 includes an action surface 32 having a chord angle a, an air inlet angle b, and an air outlet angle c, wherein variations of the chord angle a, the air inlet angle b, and the air outlet angle c of the action surface 32 of the stator guide vane 31 further increase the pressurization of the pressurized airflow rate, thereby guiding the airflow rate with a high flow rate sent from the rotor 20. In such a manner, the airflow rate having a high flow rate and high pressurization can be guided more efficiently to a predetermined direction. In addition, the stator guide vane 31 has a configuration that can be adjusted according to the requirements of the generated airflow rate of the rotor 20.

[0024] In practice, referring to FIGS. 2-6, the rotor 20 is provided with a plurality of fan blades 21 that are arranged in a head-tail overlap arrangement manner with each other. By means of the head-tail overlap arrangement of the fan blades 21, the periphery of the rotor 20 may be provided with more fan blades 21, and more action surfaces 22 of the fan blades 21. Therefore, the action surface 22 of the fan blade 21 has a larger total action area, so that the action surface 22 of the fan blade 21 can provide the front space 23 with a sufficient pressurization, while variations of the chord angle A, the air inlet angle B, and the air outlet angle C of the fan blade 21 together with the overlap distance D of the fan blades 21 will reduce pressure loss of the airflow of the front space 23. Accordingly, the airflow rate sent by the rotor 20 of the present invention is greater than that sent by the conventional fan. Therefore, the axial flow fan structure in accordance with the present invention has the optimal airflow rate with an increase of pressure head.

[0025] Subsequently, in accordance with the present invention, a stator 30 is sealingly mounted on a predetermined airflow direction side of the rotor 20, and the stator 30 includes a plurality of stator guide vanes 31 which are sealingly arranged on a predetermined airflow direction side of the fan blades 21.

[0026] Although the airflow sent by the rotor 20 of the present invention still produces a non-directional flow momentum, all of the flow momentum still has to be drained outward through the stator guide vanes 31 of the stator 30, so that the non-directional airflow with flow momentum of the tangent direction and the normal direction will enter the spans of the stator guide vanes 31 of the stator 30. By means of pressure of the pressurization of the action surface 32 of the stator guide vane 31, the airflow sent by the rotor 20 will be pressurized again through the pressure recovery from tangential flow momentum, and the action surface 32 of the stator guide vane 31 will have the airflow having a high flow rate and high pressurization be guided to a predetermined direction more efficiently, thereby preventing generating excessive non-directional flow momentum, and thereby further reducing loss of the pressure head.

[0027] Referring to FIG. 7, in general, a high flow rate region 33 produced by a common axial flow fan is not directly suitable in a flow conduit of a more closed cooling system, and will be affected by the non-directional airflow (loss of airflow pressure), while a common working range is usually located in the low and middle flow rate region 34. Therefore, the present invention is especially used to inspect and test the increase of airflow pressure of the low and middle flow rate region 34. FIG. 7 is a graph showing the experimental results of the rotor 20 and stator 30 of the present invention in conjunction with the conventional axial flow fan 10. Type I is a performance curve tested from the conventional axial flow fan structure 10. Type II is a performance curve tested from the conventional axial flow fan structure 10 in conjunction with the stator 30 of the present invention. Type III is an airflow rate performance curve tested from the axial flow fan structure of the present invention, wherein the rotor 20 co-operates with the stator 30 to achieve the function of the present invention. It can be seen from Type III that, the rotor 20 co-operating with the stator 30 of the present invention has the optimal airflow rate and pressure head.

[0028] It should be clear to those skilled in the art that further embodiments may be made without departing from the scope of the present invention.