Fans and air conditioning systems

Abstract

In a fan having a porous section on its blades, the noise reduction effect provided by the porous section is preferably obtained. [Solution] The axial flow fan (30) comprises a plurality of blades (33) that rotate around a predetermined rotation axis (A1). The blade has a leading edge portion (38) including a leading edge (36) and a porous portion (46) located behind the leading edge portion in the rotation direction (D1) and forming a positive pressure surface (40). In the blade cross section in the direction along the chord line (CLa) of the blade, a curved raised portion (49) is formed on the positive pressure surface of the leading edge portion. The absolute value of the angle between the tangent to the positive pressure surface (TLa) and the chord line decreases from the leading edge toward the rear in the rotation direction, passes through 0, then increases, and reaches a point of change (Pc) where the rate of change of the absolute value begins to decrease.

Description

Technical Field

[0001] The present disclosure relates to a fan and an air conditioner.

Background Art

[0002] Patent Document 1 discloses an axial fan. In this axial fan, a plurality of blades are each configured to include a porous portion. The porous portion is provided to suppress noise generated as the axial fan rotates.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In an axial fan, as the blades rotate at high speed, the air volume generated by the fan increases. Then, the flow velocity of the air passing through the positive pressure surface of the blade increases, and the development of air turbulence generated on the positive pressure surface becomes remarkable. The inventors of the present application have found that in an axial fan having a porous portion on the blade as in Patent Document 1, when the air turbulence on the positive pressure surface of the blade develops and becomes large, the noise reduction effect by the porous portion is impaired.

[0005] An object of the present disclosure is to suitably obtain the noise reduction effect by the porous portion in a fan having a porous portion on the blade.

Means for Solving the Problems

[0006] A first aspect of this disclosure relates to a fan (30, 50). The fan (30, 50) of the first aspect comprises blades (33, 56) that rotate around a predetermined axis of rotation (A1, A2). The blades (33, 56) have a leading edge portion (38, 68) including a leading edge (36, 57) which is the front edge in the direction of rotation (D1, D2), and a porous portion (46, 66) located behind the leading edge portion (38, 68) in the direction of rotation (D1, D2) and forming a positive pressure surface (40, 60) of the blade (33, 56). In the airfoil cross-section of the airfoil (33, 56) in the direction along the chord line (CLa, CLb), a curved portion (49, 69) is formed on the positive pressure surface (40, 60) of the leading edge (38, 68). The absolute value of the angle between the tangent line (TLa, TLb) of the positive pressure surface (40, 60) and the chord line (CLa, CLb) decreases from the leading edge (36, 57) toward the rear in the rotational direction (D1, D2), passes through 0, and then increases until it reaches a point of change (Pc) where the rate of change of the absolute value begins to decrease.

[0007] In the first embodiment, in the airfoil cross-section along the chord line (CLa,CLb) of the wing (33,56), a curved portion (49,69) is formed on the positive pressure surface (40,60) of the leading edge (38,68) of the wing (33,56), such that the absolute value of the angle between the tangent to the positive pressure surface (40,60) (TLa,TLb) and the chord line (CLa,CLb) gradually changes in a mountain-like shape. Such a curved portion (49,69) constitutes a raised portion (49,69) that rises on the positive pressure side of the wing (33,56). When this raised portion (49,69) is provided on the positive pressure surface (40,60) of the leading edge (38,68), the area of ​​the leading edge (38,68) that the airflow collides with during rotation of the wing (33,56) increases. Therefore, when airflow collides with the leading edge (38,68) of the wing (33,56), an airflow (F1) containing minute vortices (Vt) is generated on the positive pressure surface (40,60) side of the wing (33,56). This airflow (F1) containing minute vortices (Vt) is less likely to separate from the curved raised portion (49,69) and flows along the positive pressure surface (40,60) while suppressing turbulence. As a result, the development of turbulence flowing over the positive pressure surface (40,60) formed by the porous portion (46,66) can be suppressed. Consequently, the noise reduction effect of the porous portion (46,66) can be suitably obtained.

[0008] A second aspect of the present disclosure is a fan (30,50) of the first aspect, wherein the leading edge (38,68) has a first portion (38a,68a) on which the curved portion (49,69) is formed. In the airfoil section including the first portion (38a,68a), the first distance H1 is the maximum distance from the camber line (SLa,SLb) of the leading edge (38,68) to the positive pressure surface (40,60), and the second distance H2 is the maximum distance from the camber line (SLa,SLb) of the portion behind the leading edge (38,68) in the rotational direction (D1,D2) to the positive pressure surface (40,60), such that H1 > H2.

[0009] In the second embodiment, in the airfoil cross-section of the airfoil (33,56) along the chord line (CLa,CLb), including the first portion (38a,68a), the first distance H1, which is the maximum distance from the camber line (SLa,SLb) of the leading edge (38,68) to the positive pressure surface (40,60), is longer than the second distance H2 from the camber line (SLa,SLb) of the portion behind the leading edge (38,68) in the rotational direction (D1,D2) to the negative pressure surface (41,61) (H1 > H2). According to the shape of the airfoil (33,56) that satisfies this relationship, the airfoil thickness does not become excessive in the portion behind the leading edge (38,68), and the weight of the airfoil (33,56) can be reduced. This is advantageous for improving the energy efficiency of the fan (30,50).

[0010] A third aspect of the present disclosure is a fan (30,50) of the first or second aspect, wherein the leading edge (38,68) has a first portion (38a,68a) on which the curved portion (49,69) is formed. In the airfoil section including the first portion (38a,68a), the positive pressure surface (40,60) of the airfoil (33,56) is connected such that the tangents (TLa,TLb) of the positive pressure surface (40,60) are continuous from the leading edge (38,68) to the portion behind the leading edge (38,68) in the rotational direction.

[0011] In the third aspect, in the airfoil cross-section along the chord line (CLa, CLb) of the airfoil (33, 56) including the first portion (38a, 68a), the pressure surface (40, 60) of the airfoil (33, 56) is connected such that the tangent lines (TLa, TLb) are continuous from the leading edge (38, 68) to the rear portion thereof. When the pressure surface (40, 60) of the airfoil (33, 56) is smoothly connected from the leading edge (38, 68) including the raised portion (49, 69) to the rear side thereof in this way, the airflow (F1) including the minute vortex (Vt) generated by the collision of the airflow with the leading edge (38, 68) can be caused to flow along the pressure surface (40, 60) from the leading edge (38, 68) to the rear side. This is advantageous for suppressing the development of turbulent flow flowing on the pressure surface (40, 60).

[0012] A fourth aspect of the present disclosure is a fan (30, 50) according to any one of the first to third aspects, wherein the leading edge (38, 68) has a first portion (38a, 68a) in which the curved portion (49, 69) is formed. In the airfoil cross-section including the first portion (38a, 68a), when the maximum value of the distance from the chord line (CLa, CLb) of the leading edge (38, 68) to the pressure surface (40, 60) is defined as a third distance H3, the length L1 between a first position (P1) where the distance to the pressure surface (40, 60) on the chord line (CLa, CLb) is the third distance H3 and a second position (P2) corresponding to the change point (Pc), the third distance H3 satisfies the relationship H3 < L1.

[0013] In the fourth aspect, in the airfoil cross-section along the chord line (CLa, CLb) of the blade (33, 56) including the first portion (38a, 68a), the length L1 between the first position (P1) and the second position (P2) on the chord line (CLa, CLb) is longer than the third distance H3 (H3 < L1). The first position (P1) is the position where the distance from the chord line (CLa, CLb) to the pressure surface (40, 60) is maximum at the raised portion (49, 69) of the leading edge (38, 68), and the second position (P2) is the position corresponding to the change point (Pc) of the curved shape of the raised portion (49, 69). When the shape of the raised portion (49, 69) takes the third distance H3, that is, when the distance from the chord line (CLa, CLb) to the pressure surface (40, 60) is relatively long towards the rear side from the position where it is maximum, the shape of the pressure surface (40, 60) of the leading edge (38, 68) becomes smooth. Thereby, it is possible to suppress the separation of the airflow (F1) including the minute vortex (Vt) generated by the collision of the airflow against the leading edge (38, 68) from the pressure surface (40, 60) in the process of flowing from the leading edge (38, 68) to the rear side.

[0014] In the fifth aspect of the present disclosure, in the fan (30, 50) according to any one of the first to fifth aspects, the leading edge (38, 68) has the first portion (38a, 68a) in which the curved portion (49, 69) is formed. In the airfoil cross-section including the first portion (38a, 68a), when the maximum value of the distance from the chord line (CLa, CLb) of the leading edge (38, 68) to the pressure surface (40, 60) is defined as the third distance H3, the length L1 between the first position (P1) where the distance to the pressure surface (40, 60) on the chord line (CLa, CLb) is the third distance H3 and the second position (P2) corresponding to the change point (Pc), and the length L2 between the leading edge (38, 68) and the first position (P1) on the chord line (CLa, CLb) satisfy the relationship L2 < L1.

[0015] In the fifth aspect, in the airfoil section of the blade (33, 56) along the chord line (CLa, CLb) of the blade including the first part (38a, 68a), the length L1 between the first position (P1) and the second position (P2) on the chord line (CLa, CLb) is longer than the length L2 between the leading edge (36, 57) and the first position (P1) on the chord line (CLa, CLb) of the blade (33, 56) (L2 < L1). The first position (P1) is the position where the distance from the chord line (CLa, CLb) to the pressure surface (40, 60) is maximum at the raised part (49, 69) of the leading edge part (38, 68), and the second position (P2) is the position corresponding to the change point (Pc) of the curved shape of the raised part (49, 69). When the shape of the raised part (49, 69) takes the third distance H3, that is, when the distance from the chord line (CLa, CLb) to the pressure surface (40, 60) is relatively long toward the rear side from the position where it is maximum, the shape of the pressure surface (40, 60) of the leading edge part (38, 68) becomes gentle. Thereby, it is possible to suppress the separation of the airflow (F1) including the minute vortex (Vt) generated by the collision of the airflow to the leading edge part (38, 68) from the pressure surface (40, 60) in the process of flowing from the leading edge part (38, 68) to the rear side.

[0016] In the sixth aspect of the present disclosure, in the fan (30, 50) according to any one of the first to fifth aspects, the leading edge part (38, 68) has a first part (38a, 68a) in which the curved part (49, 69) is formed. In the airfoil section including the first part (38a, 68a), a first distance H1 which is the maximum value of the distance from the camber line (SLa, SLb) of the leading edge part (38, 68) to the pressure surface (40, 60), and a second distance H2 which is the maximum value of the distance from the camber line (SLa, SLb) of the part on the rear side in the rotational direction (D1, D2) than the leading edge part (38, 68) to the pressure surface (40, 60) satisfy the relationship of H1 ≦ H2 × 3.

[0017] In the sixth aspect, in the airfoil cross-section along the chord line (CLa, CLb) of the blade (33, 56) including the first portion (38a, 68a), the first distance H1 at the leading edge (38, 68) is less than three times the second distance H2 at the portion behind the leading edge (38, 68) (H1≦H2×3). According to this, while increasing the area of the leading edge (38, 68) where the airflow collides during the rotation of the blade (33, 56), it is possible to suppress the excessive increase in the blade thickness of the leading edge (38, 68).

[0018] The seventh aspect of the present disclosure is a fan (30) including any one of the first to sixth aspects, the fan (30) including a hub (31) rotatable about the rotation axis (A1). The blades (33) are provided a plurality of them at intervals in the circumferential direction of the hub (31), and each extends radially outward from the hub (31).

[0019] In the seventh aspect, a plurality of blades (33) are provided at intervals in the circumferential direction of the hub (31). Each blade (33) extends radially outward from the hub (31). In such an axial fan (30), since it is possible to suitably obtain the noise reduction effect by the porous portion (46), the technology of the present disclosure is effective.

[0020] The eighth aspect of the present disclosure is a fan (30) according to the seventh aspect, wherein the leading edge (38) has a first portion (38a) in which the curved portion (49) is formed. In the airfoil cross-section including the first portion (38a), a third distance H3 which is the maximum value of the distance from the chord line (CLa) of the leading edge (38) to the positive pressure surface (40) of the blade (33), and a fourth distance H4 from the chord line (CLa) of the leading edge (38) to the negative pressure surface (41) of the blade (33) satisfy the relationship H4<H3.

[0021] In the eighth aspect, in the airfoil section of the blade (33) along the chord line (CLa) of the blade, the third distance H3 from the chord line (CLa) of the leading edge portion (38) to the pressure surface (40) is greater than the fourth distance H4 from the chord line (CLa) to the suction surface (41) (H4 < H3). According to this, in the axial flow fan (30), while effectively increasing the area of the leading edge portion (38) where the airflow collides during the rotation of the blade (33), the airflow (F1) including the minute vortex (Vt) generated by the collision of the airflow against the leading edge portion (38) can be made to flow along the pressure surface (40) of the blade (33). As a result, the noise reduction effect by the porous portion (46) can be suitably obtained.

[0022] The ninth aspect of the present disclosure is a fan (30) according to the eighth aspect, in which the third distance H3 of the first portion (38a) becomes smaller as it goes from the inner circumferential side to the outer circumferential side of the blade (33) at the leading edge portion (38).

[0023] In the ninth aspect, the third distance H3 of the first portion (38a) becomes smaller as it goes from the inner circumferential side to the outer circumferential side of the blade (33) at the leading edge portion (38). If the first portion (38a) is provided only in a part of the leading edge portion (38) located on the upstream side of the airflow (F1) flowing on the pressure surface (40) formed by the porous portion (46), the shape change of the blade (33) can be minimized to suitably obtain the noise reduction effect by the porous portion (46). In addition, the decrease in the static pressure characteristics of the fan (30) due to the provision of the first portion (38a) at the leading edge portion (38) of the blade (33) can be suppressed.

[0024] The tenth aspect of the present disclosure is a fan (30) according to any one of the seventh to ninth aspects, in which the first portion (38a) is provided on the inner circumferential side of the leading edge portion (38). The porous portion (46) is provided outside the first portion (38a) in the radial direction of the rotation radius of the blade (33).

[0025] In the tenth aspect, the first part (38a) is provided on the inner peripheral side of the leading edge (38) of the blade (33), and the porous part (46) is provided on the outer side in the radial direction of the blade (33) than the first part (38a). In the axial flow fan (30), as the air volume increases, the airflow (F1) on the positive pressure surface (40) of the blade (33) tends to flow toward the outer peripheral side due to centrifugal force. Therefore, the airflow (F1) including the minute vortex (Vt) generated by the collision of the airflow against the leading edge (38) including the first part (38a) can be made to flow on the positive pressure surface (40) formed by the porous part (46). Thereby, the noise reduction effect by the porous part (46) can be suitably obtained.

[0026] In the eleventh aspect of the present disclosure, in any one of the fans (50) of the first to sixth aspects, there is provided a plate-like member (51) rotatable about the rotation axis (A2), and a shroud (53) arranged at an interval in the axial direction of the rotation axis (A2) from the plate-like member (51). The blades (56) are provided in plurality between the plate-like member (51) and the shroud (53) at intervals in the rotation direction (D2) such that the leading edge (57) is located on the inner peripheral side and the trailing edge (58) which is the edge on the rear side in the rotation direction (D2) is located on the outer peripheral side.

[0027] In the eleventh aspect, a plurality of blades (56) are provided between the plate-like member (51) and the shroud (53) at intervals in the rotation direction (D2). Each blade (56) takes a posture in which the leading edge (57) is located on the inner peripheral side and the trailing edge (58) is located on the outer peripheral side. In such a turbofan (50), since it is possible to suitably obtain the noise reduction effect by the porous part (66), the technique of the present disclosure is effective.

[0028] The twelfth aspect of the present disclosure is directed to an air conditioner (1). The air conditioner (1) of the twelfth aspect includes any one of the fans (30, 50) of the first to eleventh aspects.

[0029] In the twelfth embodiment, the air conditioning unit (1) is equipped with fans (30, 50). The fans (30, 50) can suitably obtain the noise reduction effect of porous parts (46, 66). Therefore, in the air conditioning unit (1), noise caused by the rotational operation of the fans (30, 50) can be reduced, and quietness can be improved. [Brief explanation of the drawing]

[0030] [Figure 1] Figure 1 is a schematic diagram of the air conditioning system of Embodiment 1. [Figure 2] Figure 2 is a plan view illustrating an axial flow fan according to Embodiment 1. [Figure 3] Figure 3 is an enlarged plan view of the blades of an axial flow fan. [Figure 4] Figure 4 is a cross-sectional perspective view illustrating the main part of the blades of an axial flow fan. [Figure 5] Figure 5 is a cross-sectional view of the blades of an axial flow fan along the VV line in Figure 2. [Figure 6] Figure 6 is a graph showing the relationship between the distance from the leading edge of the airfoil section along the chord line of the airfoil, and the absolute value of the angle between the tangent to the positive pressure surface and the chord line. [Figure 7] Figure 7 is a conceptual diagram illustrating the airflow on the positive pressure surface of the blades during the operation of the propeller fan of Embodiment 1. [Figure 8] Figure 8 is a conceptual diagram illustrating the airflow on the positive pressure surface of the blades during the operation of an axial flow fan in a comparative example. [Figure 9] Figure 9 is a graph showing the relationship between airflow rate and static pressure in the axial flow fan of the embodiment and the axial flow fans of Comparative Examples 1 and 2. [Figure 10] Figure 10 is a graph showing the relationship between airflow rate and specific noise for the axial flow fan in the embodiment and the axial flow fans in Comparative Examples 1 and 2. [Figure 11] Figure 11 is a perspective view illustrating a turbofan according to Embodiment 2. [Figure 12] Figure 12 is a plan view of the turbofan. [Figure 13]Figure 13 is a cross-sectional view of a turbofan blade. [Modes for carrying out the invention]

[0031] The following exemplary embodiments will be described in detail with reference to the drawings. The following embodiments will be examples of the application of the fan according to this disclosure to an axial fan and a turbo fan. The drawings are intended to conceptually illustrate the technology of this disclosure. Therefore, in order to facilitate understanding of the technology of this disclosure, dimensions, ratios, or numbers may be exaggerated or simplified in the drawings.

[0032] Embodiment 1 In this Embodiment 1, an axial flow fan (30) is described as the fan according to the present disclosure. The axial flow fan (30) is used in an air conditioning system (1). In other words, the air conditioning system (1) includes an axial flow fan (30).

[0033] -Air conditioning system- The air conditioning system (1) is a device that adjusts the temperature of the air in a target space. In this example, the target space is an indoor space. As shown in Figure 1, the air conditioning system (1) is a paired air conditioning system and consists of one indoor unit (3) and one outdoor unit (5). The indoor unit (3) is installed indoors. The outdoor unit (5) is installed outdoors. The indoor unit (3) and the outdoor unit (5) are connected to each other via a liquid connection pipe (7) and a gas connection pipe (9).

[0034] The indoor unit (3), outdoor unit (5), liquid connection pipe (7), and gas connection pipe (9) constitute a refrigerant circuit (11). The refrigerant circuit (11) is filled with refrigerant. The refrigerant circuit (11) mainly includes a compressor (13), an outdoor heat exchanger (15), an expansion valve (17), a switching mechanism (19), and an indoor heat exchanger (21). The compressor (13), outdoor heat exchanger (15), expansion valve (17), and indoor heat exchanger (21) are connected by piping.

[0035] The compressor (13), outdoor heat exchanger (15), expansion valve (17), and switching mechanism (19) are included in the outdoor unit (5). That is, the outdoor unit (5) has a compressor (13), an outdoor heat exchanger (15), an expansion valve (17), and a switching mechanism (19). The outdoor unit (5) further has an outdoor fan (23). A first fan motor (25) is connected to the outdoor fan (23). The outdoor fan (23) rotates when driven by the first fan motor (25). The axial flow fan (30) of this embodiment is used as the outdoor fan (23).

[0036] The compressor (13) draws in low-pressure gaseous refrigerant, compresses it, and discharges the compressed refrigerant. The outdoor fan (23) transports outdoor air so that it passes through the outdoor heat exchanger (15). The outdoor heat exchanger (15) exchanges heat between the outdoor air transported by the outdoor fan (23) and the refrigerant flowing inside. The outdoor heat exchanger (15) is configured, for example, as a fin-and-tube type. The expansion valve (17) reduces the pressure of the refrigerant.

[0037] The switching mechanism (19) switches the circulation direction of the refrigerant in the refrigerant circuit (11). The switching mechanism (19) is, for example, a four-way switching valve. The switching mechanism (19) has a first port (19a), a second port (19b), a third port (19c), and a fourth port (19d). The first port (19a) is connected to the discharge side of the compressor (13). The second port (19b) is connected to the suction side of the compressor (13). The third port (19c) is connected to the outdoor heat exchanger (15). The fourth port (19d) is connected to the gas connection pipe (9).

[0038] The switching mechanism (19) switches between a first state (shown by the solid line in Figure 1) and a second state (shown by the dashed line in Figure 1). In the first state, the switching mechanism (19) connects the first port (19a) and the third port (19c), and also connects the second port (19b) and the fourth port (19d). In the second state, the switching mechanism (19) connects the first port (19a) and the fourth port (19d), and also connects the second port (19b) and the third port (19c).

[0039] The indoor heat exchanger (21) is included in the indoor unit (3). That is, the indoor unit (3) has the indoor heat exchanger (21). The indoor unit (3) further has an indoor fan (27). For example, a cross-flow fan or a turbo fan can be used as the indoor fan (27). The indoor fan (27) may also be a fan of another type, such as a centrifugal fan.

[0040] A second fan motor (29) is connected to the indoor fan (27). The indoor fan (27) rotates under the drive of the second fan motor (29) and transports indoor air so that it passes through the indoor heat exchanger (21). The indoor heat exchanger (21) exchanges heat between the indoor air transported by the indoor fan (27) and the refrigerant flowing inside. The indoor heat exchanger (21) is configured, for example, as a fin and tube type.

[0041] The air conditioning system (1) performs both cooling and heating operations.

[0042] Cooling operation is the operation of cooling the air in the indoor space. In cooling operation, the switching mechanism (19) is set to the first state, and the compressor (13), outdoor fan (23), and indoor fan (27) are operated. As a result, the refrigerant in the refrigerant circuit (11) flows in the direction of the arrow shown by the solid line in Figure 1, the outdoor heat exchanger (15) functions as a heat radiator, and the indoor heat exchanger (21) functions as an evaporator. During cooling operation, the air transported by the indoor fan (27) is cooled by the indoor heat exchanger (21) and supplied to the indoor space.

[0043] Heating operation is the operation of heating the air in the indoor space. In heating operation, the switching mechanism (19) is set to the second state, and the compressor (13), outdoor fan (23), and indoor fan (27) are operated. As a result, the refrigerant in the refrigerant circuit (11) flows in the direction of the arrow shown by the dashed line in Figure 1, the outdoor heat exchanger (15) functions as an evaporator, and the indoor heat exchanger (21) functions as a radiator. During heating operation, the air transported by the indoor fan (27) is heated in the indoor heat exchanger (21) and supplied to the indoor space.

[0044] -Axial flow fan- The axial flow fan (30) is a propeller-type fan. As shown in Figure 2, the axial flow fan (30) comprises one hub (31) and multiple blades (33). The hub (31) and the multiple blades (33) are integrally formed. In this example, the axial flow fan (30) has three blades (33). The number of blades (33) may be two, or four or more.

[0045] The hub (31) is formed in a cylindrical shape. The hub (31) is the rotating shaft portion of the axial flow fan (30) and is located at the center of the axial flow fan (30). An axle hole (32) is formed in the central part of the hub (31). The drive shaft of the first fan motor (25) is attached to the hub (31) through the axle hole (32). When the first fan motor (25) is driven, the hub (31) rotates around a predetermined rotation axis (A1). The central axis of the hub (31) coincides with the rotation axis (A1) of the axial flow fan (30).

[0046] Multiple blades (33) are arranged around the hub (31) at intervals from one another. Each blade (33) extends radially outward from the outer surface of the hub (31). Multiple blades (33) radiate outward from the hub (31) in the radial direction of rotation of the axial fan (30). Adjacent blades (33) do not overlap in a front view or a rear view. The shapes of the multiple blades (33) are identical to each other.

[0047] Each wing (33) adopts a so-called forward-swept wing shape. Each of these wings (33) is formed in a smoothly curved plate shape with a slight convexity on one wing surface side (negative pressure surface (41) side) along the radial direction of rotation and the direction of rotation (D1). Each wing (33) has a base (34), a tip (35), a leading edge (36), and a trailing edge (37). The base (34), tip (35), leading edge (36), and trailing edge (37) constitute the outer edge of the wing (33) in a plan view.

[0048] The blade root (34) is the end of the blade (33) on the central side in the radial direction of the axial fan (30), that is, the inner end in the radial direction of rotation of the blade (33). The blade tip (35) is the end of the blade (33) on the outer side in the radial direction of the axial fan (30), that is, the outer end in the radial direction of rotation of the blade (33). The blade root (34) and blade tip (35) of each blade (33) extend along the rotational direction (D1) of the axial fan (30).

[0049] The base (34) of each blade (33) is connected to the hub (31). The distance from the rotation axis (A1) of the axial fan (30) to the base (34) is substantially constant along the entire length of the base (34). In addition, the tip (35) of each blade (33) is curved to form a convex shape on the outer circumference of the axial fan (30). The distance from the rotation axis (A1) of the axial fan (30) to the tip (35) is substantially constant along the entire length of the tip (35). The length of the tip (35) is longer than the length of the base (34).

[0050] The leading edge (36) is the front edge of the blade (33) in the direction of rotation (D1). The trailing edge (37) is the rear edge of the blade (33) in the direction of rotation (D1). The leading edge (36) and trailing edge (37) of each blade (33) extend from the hub (31) side to the outer circumference of the axial flow fan (30). These leading edges (36) and trailing edges (37) each have an arc-shaped portion and extend apart from each other from the blade base (34) towards the blade tip (35).

[0051] The leading edge (36) of each wing (33) extends forward in the direction of rotation (D1) from the wing root (34) towards the wingtip (35). The leading edge (36) curves inward towards the rear in the direction of rotation (D1) of the wing (33). The trailing edge (37) extends slightly backward in the direction of rotation (D1) from the wing root (34) towards the wingtip (35). The leading edge (36) curves inward towards the front in the direction of rotation (D1) of the wing (33).

[0052] In the airfoil cross-section of the airfoil (33) in the direction of rotation (D1), the line segment connecting the leading edge (36) and the trailing edge (37) of the airfoil (33) is the chord line (CLa). An example of the chord line (CLa) is shown in Figure 2. In the axial flow fan (30), the airfoil cross-section in the direction along the chord line (CLa) of the airfoil (33) corresponds to the airfoil cross-section in the direction of rotation (D1) of the airfoil (33), and in this embodiment, it is referred to as the "symmetric airfoil cross-section". The length of the chord line (CLa) is the chord length L1. The chord length L1 increases as you move away from the base (34) in the direction of the rotational radius of the airfoil (33), and is maximum at the tip (35).

[0053] Each blade (33) is inclined to intersect a plane perpendicular to the rotation axis (A1) of the axial fan (30). The leading edge (36) of each blade (33) is located on the rear side (negative pressure side) of the axial fan (30) and extends upstream of the air being transported from a position near one end of the hub (31) (the air inlet side). The trailing edge (37) of each blade (33) is located on the front side (positive pressure side) of the axial fan (30) and is located near the other end of the hub (31) (the air outlet side).

[0054] As shown in Figures 4 and 5, each blade (33) further has a positive pressure surface (40) and a negative pressure surface (41). The positive pressure surface (40) is the blade surface that becomes the positive pressure side due to the airflow being transported when the axial flow fan (30) rotates, and constitutes the surface facing the front side of the axial flow fan (30) from which the air flows out. The negative pressure surface (41) is the blade surface that becomes the negative pressure side due to the airflow being transported when the axial flow fan (30) rotates, and constitutes the surface facing the rear side of the axial flow fan (30) from which the air flows in.

[0055] As shown in Figure 2, the outer edge portion along the wingtip (35) of each wing (33) constitutes a winglet (42). The winglet (42) is slightly curved toward the negative pressure surface (41) relative to the rest of the wing (33). The winglet (42) is provided so as to gradually widen from the leading edge (36) toward the trailing edge (37). The winglet (42) plays a role in straightening the airflow near the wingtip (35). Providing a winglet (42) is advantageous in suppressing the generation of wingtip vortices.

[0056] Multiple blades (33) rotate together with the hub (31) around the rotation axis (A1). As the axial fan (30) rotates around the rotation axis (A1), the positive pressure surfaces (40) of each blade (33) push out air. As a result, air flows from the inlet side at the back of the axial fan (30) to the outlet side at the front as the multiple blades (33) rotate. At this time, the pressure increases on the positive pressure surface (40) side of each blade (33) to push out the air. On the other hand, the pressure decreases relatively on the negative pressure surface (41) side of the blade (33).

[0057] When the axial fan (30) rotates, the air flowing over the positive pressure surface (40) of the blade (33) reaches the blade tip (35) and separates from the positive pressure surface (40), forming a vortex as it is drawn from the positive pressure surface (40) to the negative pressure surface (41). The vortex that forms on the blade tip (35) side is called a blade tip vortex. The blade tip vortex develops backward as the blade (33) rotates, becoming a wake vortex that flows backward in the direction of rotation (D1) from the trailing edge (37) of the blade (33). The higher the energy of the blade tip vortex and wake vortex, the greater the noise generated when the axial fan (30) is operating.

[0058] Noise during the operation of the axial flow fan (30) is also generated by pressure fluctuations on the blade surface of the blade (33). To counteract noise caused by pressure fluctuations on the blade surface of the blade (33), a portion of each blade (33) of the axial flow fan (30) is formed of a porous material. The non-porous material is a material that is not porous, for example, a non-foamed synthetic resin. Each blade (33) has a blade body (44) and a porous portion (46).

[0059] As shown in Figure 3, the wing body (44) forms the wing root (34), wingtip (35), leading edge (36), and trailing edge (37). The wing body (44) is made of a non-porous material. The wing body (44) is made of the same synthetic resin as the hub (31). The wing body (44) is integrally molded with the hub (31), for example, by injection molding. The wing body (44) constitutes the majority of the wing (33). That is, the majority of the wing (33) is made of a non-porous material. The porous portion (46) is fixed to the wing body (44) by fitting, bonding, welding, etc.

[0060] The porous portion (46) is provided in the region enclosed by the blade base (34), blade tip (35), leading edge (36), and trailing edge (37). In this example, the porous portion (46) is located midway along the rotational direction (D1) of the blade (33) and closer to the blade tip (35), and is surrounded by the portion that makes up the blade body (44). The porous portion (46) has the function of suppressing pressure fluctuations on the blade surface of the blade (33) and reducing noise generated as the axial flow fan (30) rotates. The noise reduction effect of the porous portion (46) varies depending on the position and area of ​​the porous portion (46) on the blade (33).

[0061] The porous portion (46) is provided in a rectangular shape, for example (more specifically, a rectangular shape with curved corners). The porous portion (46) may also be provided in other shapes, such as triangular or oval. The porous portion (46) constitutes the entirety of the wing (33) in the thickness direction. The porous portion (46) is exposed to the positive pressure surface (40) and the negative pressure surface (41) of the wing (33), respectively, and forms a part of the positive pressure surface (40) and a part of the negative pressure surface (41).

[0062] The porous section (46) is composed of a porous material having multiple fine pores in a continuous pattern. The multiple fine pores in the porous material communicate with the positive pressure surface (40) and the negative pressure surface (41) of the blade (33). The average diameter of the pores (voids) in the porous section (46) is, for example, in the range of 15 μm to 300 μm. The porosity (= volume of voids / total volume of the porous section) of the porous section (46) is, for example, in the range of 35% to 90%.

[0063] Porous materials include synthetic resins, ceramics, and metals. For example, synthetic resins, ceramics, and metals are used as porous sintered bodies. Porous sintered bodies are formed by partially welding powder materials together by heating them in an aggregated state. The synthetic resin may be a foamed resin containing open cells. The strength of the porous portion (46) made of such a porous material is lower than the strength of the wing body (44).

[0064] The position of the porous portion (46) on the wing (33) is expressed by the chord ratio (Lb / La) and radius ratio (Rb / Ra) of the center (C1) of the porous portion (46). The center (C1) of the porous portion (46) refers to the central position of the wing (33) in the radial and rotational directions (D1). The chord ratio (Lb / La) is the ratio of the distance Lb from the leading edge (36) to the chord length La in the symmetric airfoil cross-section of the wing (33). The radius ratio (Rb / Ra) is the ratio of the distance Rb from the base (34) to the distance Ra from the base (34) to the tip (35) in the radial direction of the wing (33).

[0065] The center (C1) of the porous section (46) is located in the range of 0.4 to 0.8 for the chord ratio (Lb / La) and 0.6 to 0.8 for the radius ratio (Rb / Ra). The porous section (46) is located radially outward from the raised portion (49) of the leading edge (38), which will be described later. The area of ​​the porous section (46) is set to a range that can exert a noise reduction effect (noise reduction effect). In this example, the area of ​​the porous section (46) is 30% or less of the total area of ​​the positive pressure surface (40).

[0066] When the axial fan (30) rotates, air forms airflows (F1, F2) that flow from the leading edge (36) of the blade (33) to the positive pressure side (40) and the negative pressure side (41). As the axial fan (30) rotates, these airflows (F1, F2) flow along the blade surface (positive pressure side (40), negative pressure side (41)) and exit from the trailing edge (37). At this time, pressure fluctuations occur on the blade surface due to various factors, such as pressure fluctuations at the interface of the airflows (F1, F2) and pressure fluctuations when transitioning from laminar flow to turbulent flow. Such pressure fluctuations on the blade surface are a factor that increases the noise (fan noise) when the axial fan (30) rotates.

[0067] In the porous section (46), air enters and exits between the positive pressure surface (40) and the negative pressure surface (41) through multiple microscopic pores in response to pressure fluctuations on the blade surface. When the air pressure on the positive pressure surface (40) side increases, a small amount of that air leaks through the porous section (46) to the negative pressure surface (41) side. Conversely, when the pressure on the negative pressure surface (41) side increases, a small amount of that air leaks through the porous section (46) to the positive pressure surface (40) side. As a result, pressure fluctuations on the blade surface are suppressed in the porous section (46). This is advantageous for reducing noise during rotation of the axial flow fan (30).

[0068] In a conventional axial fan having a blade (33) as shown in Figure 8, as the speed at which the blade (33) rotates increases, the airflow volume increases, and the velocity of the air passing over the positive pressure surface (40) of the blade (33) also increases, leading to a significant development of turbulent airflow on the positive pressure surface (40). When the turbulent airflow on the positive pressure surface (40) of the blade develops and becomes large, the noise reduction effect of the porous portion (46) is impaired. Therefore, in the axial fan (30) of this embodiment, the shape of the leading edge portion (38) of the blade (33) is designed to suitably obtain the noise reduction effect of the porous portion (46) at high airflow volumes.

[0069] Specifically, as shown in Figures 4 and 5, a raised portion (49) is provided on the positive pressure surface (40) of the leading edge (38) of the wing (33). Here, the leading edge (38) is the portion including the leading edge (36) of the wing (33), and represents the portion 10% from the leading edge (36) with respect to the chord length L1. The raised portion (49) is a curved portion that rises on the positive pressure side of the wing (33). The raised portion (49) is provided on the inner circumference side of the leading edge (38) of the wing (33). In this example, the raised portion (49) extends from the wing root (34) to a position where the radius ratio (R2 / R1) is 0.4 to 0.7.

[0070] Figure 4 shows the surface shape of the raised portion (49) for convenience, indicated by a dashed line. In the symmetric airfoil cross-section of the wing (33), the surface of the raised portion (49) is formed in a curved shape. The curved shape of the raised portion (49) is represented by the angle between the tangent (TLa) of the positive pressure surface (40) and the chord line (CLa), the distance from the camber line (SLa) to the positive pressure surface (40) (first distance H1, second distance H2), and the distance from the chord line (CLa) to the positive pressure surface (40) and the negative pressure surface (41) (third distance H3, fourth distance H3).

[0071] As shown in Figure 6, the curved shape of the raised portion (49) is such that, in the symmetric airfoil cross-section of the wing (33), the absolute value of the angle between the tangent (TLa) of the positive pressure surface (40) and the chord line (CLa) decreases from the leading edge (36) toward the rear in the rotational direction (D1) of the wing (33), passes through 0, then increases, and reaches a point of change (Pc) where the rate of change of the absolute value begins to decrease. A portion of the tangent (TLa) of the positive pressure surface (40) formed by the raised portion (49) is shown in Figure 5. In the symmetric airfoil cross-section of the wing (33) including the first portion (38a), the positive pressure surface (40) of the wing (33) is connected such that the tangent (TLa) of the positive pressure surface (40) is continuous from the leading edge (38) to the portion behind the leading edge (38) in the rotational direction (D1).

[0072] Thus, the positive pressure surface (40) of the leading edge (38) changes smoothly, including the raised portion (49). The leading edge (38) of the wing (33) has a first portion (38a) and a second portion (38b). The first portion (38a) is the portion where the raised portion (49) is formed. The second portion (38b) is the portion without the raised portion (49). In the symmetrical airfoil cross-section of the wing (33), the line connecting the midpoints of the positive pressure surface (40) and the negative pressure surface (41) is the camber line (SLa). In the first portion (38a), the camber line (SLa) has a shape that protrudes convexly toward the positive pressure surface (40) side, following the surface shape of the raised portion (49), and smoothly connects to the rear side of the first portion (38a).

[0073] In the symmetric airfoil section of the wing (33), the maximum distance from the camber line (SLa) at the leading edge (38) to the positive pressure surface (40) is defined as the first distance H1. Furthermore, in the symmetric airfoil section of the wing (33), the maximum distance from the camber line (SLa) behind the leading edge (38) in the rotational direction (D1) to the positive pressure surface (40) is defined as the second distance H2.

[0074] In the symmetric airfoil section of the wing (33) including the first part (38a), the first distance H1 and the second distance H2 satisfy the relationship H1 > H2. This relationship means that in the symmetric airfoil section of the wing (33), the raised portion (49) protrudes most towards the positive pressure side at the leading edge (38). Furthermore, in the symmetric airfoil section of the wing (33), the first distance H1 and the second distance H2 satisfy the relationship H1 ≤ H2 × 3. On the other hand, in the symmetric airfoil section of the wing (33) including the second part (38b), the first distance H1 and the second distance H2 satisfy the relationship H1 ≤ H2.

[0075] In the symmetric airfoil section of the wing (33), the maximum distance from the chord line (CLa) at the leading edge (38) to the positive pressure surface (40) of the wing (33) is defined as the third distance H3. Furthermore, in the symmetric airfoil section of the wing (33), the maximum distance from the chord line (CLa) at the leading edge (38) to the negative pressure surface (41) of the wing (33) is defined as the fourth distance H4. For convenience, in Figure 5, the positions of the third distance H3 and the fourth distance H4 are shown shifted from the first position (P1).

[0076] In the target wing cross-section of the wing (33) including the first part (38a), the third distance H3 and the fourth distance H4 satisfy the relationship H4 < H3. This relationship means that while the wing (33) adopts a curved shape convex toward the suction surface (41) side in the rotational direction (D1), the raised portion (49) is provided at the leading edge (38). On the other hand, in the target wing cross-section of the wing (33) including the second part (38b), the third distance H3 and the fourth distance H4 satisfy the relationship H4 ≥ H3.

[0077] The third distance H3 of the first part (38a) decreases as it goes from the inner peripheral side to the outer peripheral side of the wing (33) at the leading edge (38) (see FIG. 4). In other words, the third distance H3 of the first part (38a) becomes longer as it approaches the wing root (34) from the end on the wing tip (35) side of the first part (38a), and is maximum at the wing root (34). The height H4 of the raised portion (49) changes corresponding to the third distance H3 of the first part (38a).

[0078] The height of the raised portion (49) is the distance from the change point (Pc) of the raised portion (49) in the direction orthogonal to the chord line (CLa) of the wing (33) to the raised end (Pe) which is the end on the pressure surface (40) side. The farther away from the wing root (34) of the leading edge (38), the lower the height H4 of the raised portion (49). The raised end (Pe) is located closer to the leading edge (36) with respect to the leading edge (36) side of the raised portion (49), that is, with respect to the entire length of the raised portion (49) in the target wing cross-section of the wing (33).

[0079] In the target wing cross-section of the wing (33) including the first part (38a), the position where the distance to the pressure surface (40) on the chord line (CLa) is the third distance H3 is defined as the first position (P1). Also, in the target wing cross-section of the wing (33) including the first part (38a), the position corresponding to the change point (Pc) of the raised portion (49) on the chord line (CLa) is defined as the second position (P2).

[0080] The length L1 between the first position (P1) and the second position (P2), and the third distance H3 satisfy the relationship H3 < L1. Further, the length L1 between the first position (P1) and the second position (P2), and the length L2 between the leading edge (36) and the first position (P1) on the chord line (CLa) satisfy the relationship L2 < L1. These relationships mean that the raised portion (49) has a shape that extends relatively long to the rear side in the rotational direction (D1) of the blade (33) from the raised end (Pe).

[0081] -Silencing performance of axial flow fan- The air volume-static pressure characteristics (P-Q curve) and the air volume-specific noise characteristics of the axial flow fan (30) of the embodiment will be described in comparison with the axial flow fans of Comparative Examples 1 and 2. The configuration of the axial flow fan (30) of the embodiment is the same as that of the above-described Embodiment 1. The axial flow fan of Comparative Example 1 is the same fan as the axial flow fan (30) of the embodiment, except that it does not have the porous portion (46) and the raised portion (49) on the blade (33). The axial flow fan of Comparative Example 2 is the same fan as the axial flow fan (30) of the embodiment, except that it does not have the raised portion (49) on the blade (33).

[0082] FIG. 9 shows the air volume-static pressure characteristics (P-Q curve) of the axial flow fan (30) of the embodiment and the axial flow fans of Comparative Examples 1 and 2. In FIG. 9, the air volume-static pressure characteristics (P-Q curve) of the axial flow fan (30) of the embodiment are shown by a solid line, the air volume-static pressure characteristics (P-Q curve) of the axial flow fan of Comparative Example 1 are shown by a broken line, and the air volume-static pressure characteristics (P-Q characteristics) of the axial flow fan of Comparative Example 2 are shown by a one-dot chain line. As shown in FIG. 9, the line showing the air volume-static pressure characteristics (P-Q curve) of the axial flow fan (30) of the embodiment and the lines showing the air volume-static pressure characteristics (P-Q curve) of the axial flow fans of Comparative Examples 1 and 2 overlap so as to almost coincide. Thus, the axial flow fan (30) of the embodiment has substantially the same air volume-static pressure characteristics as the axial flow fans of Comparative Examples 1 and 2.

[0083] Figure 10 shows the airflow-specific noise characteristics of the axial fan (30) of the embodiment and the axial fans of Comparative Examples 1 and 2. In Figure 10, the airflow-specific noise characteristics of the axial fan (30) of the embodiment are shown by a solid line, the airflow-specific noise characteristics of the axial fan of Comparative Example 1 are shown by a dashed line, and the airflow-specific noise characteristics of the axial fan of Comparative Example 2 are shown by a dashed line. As shown in Figure 10, the axial fan (30) of the embodiment exhibits reduced specific noise at the same airflow compared to the axial fans of Comparative Examples 1 and 2 at high airflow levels. As can be seen from the above, the axial fan (30) of the embodiment can reduce noise during operation at high airflow levels while maintaining the airflow-static pressure characteristics compared to the axial fans of Comparative Examples 1 and 2.

[0084] -Features of Embodiment 1- In this embodiment 1 of the axial flow fan (30), a curved raised portion (49) is formed on the positive pressure surface (40) of the leading edge (38) of the blade (33) in the symmetrical airfoil cross-section, such that the absolute value of the angle between the tangent to the positive pressure surface (40) and the chord line (CLa) gradually changes in a V-shape. When such a curved raised portion (49) is provided on the positive pressure surface (40) of the leading edge (38), the area of ​​the leading edge (38) that the airflow collides with when the blade (33) rotates increases in the first portion (38a) that includes the raised portion (49). Therefore, as shown in Figure 7, when the airflow collides with the leading edge (38) of the blade (33), an airflow (F1) containing a minute vortex (Vt) is generated on the positive pressure surface (40) side of the blade (33). The airflow (F1) containing the minute vortex (Vt) is less likely to separate from the curved portion and flows along the positive pressure surface (40) while suppressing turbulence. This suppresses the development of turbulence flowing on the positive pressure surface (40) formed by the porous portion (46). As a result, the noise reduction effect of the porous portion (46) can be suitably obtained.

[0085] In the axial fan (30) of this embodiment 1, in the symmetric airfoil cross-section of the blade (33) including the first portion (38a), the first distance H1, which is the maximum distance from the camber line (SLa) of the leading edge (38) to the positive pressure surface (40), is longer than the second distance H2, which is the maximum distance from the camber line (SLa) of the portion behind the leading edge (38) in the rotational direction (D1) to the negative pressure surface (41) (H1 > H2). With a blade (33) shape that satisfies this relationship, the blade thickness does not become excessive in the portion behind the leading edge (38), and the weight of the blade (33) can be reduced. This is advantageous for improving the energy efficiency of the axial fan (30).

[0086] In the axial flow fan (30) of this embodiment 1, in the symmetric airfoil cross-section of the blade (33) including the first portion (38a), the positive pressure surface (40) of the blade (33) is connected such that the tangent line (TLa) is continuous from the leading edge (38) to the rear portion. When the positive pressure surface (40) of the blade (33) is smoothly connected from the leading edge (38) including the raised portion (49) to the rear, the airflow containing minute vortices (Vt) generated by the collision of airflow with the leading edge (38) can be directed along the positive pressure surface (40) from the leading edge (38) to the rear. This is advantageous in suppressing the development of turbulence flowing over the positive pressure surface (40).

[0087] In the axial flow fan (30) of this Embodiment 1, in the target blade cross-section of the blade (33) including the first portion (38a), the length L1 between the first position (P1) and the second position (P2) on the chord line (CLa) of the blade is longer than the third distance H3 (H3 < L1). The first position (P1) is the position where the distance from the chord line (CLa) to the pressure surface (40) is maximum at the raised portion (49) of the leading edge (38), and the second position (P2) is the position corresponding to the change point (Pc) of the curved shape of the raised portion (49). When the shape of the raised portion (49) takes the third distance H3, that is, when the distance from the chord line (CLa) to the pressure surface (40) is relatively long towards the rear side from the position where it is maximum, the shape of the pressure surface (40) of the leading edge (38) becomes smooth. Thereby, it is possible to suppress the separation of the airflow including the minute vortex (Vt) generated by the collision of the airflow against the leading edge (38) from the pressure surface (40) in the process of flowing from the leading edge (38) to the rear side.

[0088] In the axial flow fan (30) of this Embodiment 1, in the target blade cross-section of the blade (33) including the first portion (38a), the length L1 between the first position (P1) and the second position (P2) on the chord line (CLa) of the blade is longer than the length L2 between the leading edge (36) and the first position (P1) on the chord line (CLa) of the blade (L2 < L1). The first position (P1) is the position where the distance from the chord line (CLa) to the pressure surface (40) is maximum at the raised portion (49) of the leading edge (38), and the second position (P2) is the position corresponding to the change point (Pc) of the curved shape of the raised portion (49). When the shape of the raised portion (49) takes the third distance H3, that is, when the distance from the chord line (CLa) to the pressure surface (40) is relatively long towards the rear side from the position where it is maximum, the shape of the pressure surface (40) of the leading edge (38) becomes smooth. Thereby, it is possible to suppress the separation of the airflow including the minute vortex (Vt) generated by the collision of the airflow against the leading edge (38) from the pressure surface (40) in the process of flowing from the leading edge (38) to the rear side.

[0089] In the axial flow fan (30) of the first embodiment, in the target blade cross section of the blade (33) including the first portion (38a), the first distance H1 at the leading edge (38) is less than three times the second distance H2 at a portion behind the leading edge (38) (H1≦H2×3). According to this, while increasing the area of the leading edge (38) where the airflow collides during the rotation of the blade (33), it is possible to suppress the excessive increase in the blade thickness of the leading edge (38).

[0090] In the axial flow fan (30) of the first embodiment, a plurality of blades (33) are provided at intervals in the circumferential direction of the hub (31). Each blade (33) extends radially outward from the hub (31). In such an axial flow fan (30), since it is possible to suitably obtain the noise reduction effect by the porous portion (46), the technology of the present disclosure is effective.

[0091] In the axial flow fan (30) of the first embodiment, in the target blade cross section of the blade (33) including the first portion (38a), the third distance H3 from the chord line (CLa) of the leading edge (38) to the positive pressure surface (40) is greater than the fourth distance H4 from the chord line (CLa) of the leading edge (38) to the negative pressure surface (41) (H4<H3). According to this, in the axial flow fan (30), while effectively increasing the area of the leading edge (38) where the airflow collides during the rotation of the blade (33), the airflow (F1) including the minute vortex (Vt) generated by the collision of the airflow with the leading edge (38) can be made to flow along the positive pressure surface (40) of the blade (33). As a result, the noise reduction effect by the porous portion (46) can be suitably obtained.

[0092] In this embodiment 1 of the axial fan (30), the first portion (38a) is provided on the inner circumference side of the leading edge (38) of the blade (33), and the porous portion (46) is provided further outward than the first portion (38a) in the direction of the rotational radius of the blade (33). In the axial fan (30), as the airflow increases, the airflow on the positive pressure surface (40) of the blade (33) tends to flow outward due to centrifugal force. Therefore, the airflow (F1) containing minute vortices (Vt) generated by the collision of the airflow with the leading edge (38), including the first portion (38a), can be flowed over the positive pressure surface (40) formed by the porous portion (46). This allows for a favorable noise reduction effect from the porous portion (46).

[0093] In the axial fan (30) of this embodiment 1, the third distance H3 of the first portion (38a) decreases as it moves from the inner circumference to the outer circumference of the blade (33) at the leading edge (38). By providing the first portion (38a) only on a part of the leading edge (38) located upstream of the airflow (F1) flowing over the positive pressure surface (40) formed by the porous portion (46), the noise reduction effect of the porous portion (46) can be suitably obtained with minimal modification of the blade (33) shape. Furthermore, the reduction in the static pressure characteristics of the axial fan (30) caused by providing the first portion (38a) at the leading edge (38) of the blade (33) can be suppressed.

[0094] The air conditioning system (1) of this embodiment 1 is equipped with an axial flow fan (30). The axial flow fan (30) can suitably obtain the noise reduction effect of the porous part (46). Therefore, in the air conditioning system (1), the noise caused by the rotational operation of the axial flow fan (30) can be reduced and the quietness can be improved.

[0095] Embodiment 2 In this second embodiment, a turbo fan (50) is described as the fan according to the present disclosure. The turbo fan (50) is used in the air conditioning system (1) described in the first embodiment above. In other words, the air conditioning system (1) includes a turbo fan (50). The turbo fan (50) is used as an indoor fan (27) in the indoor unit (3) of the air conditioning system (1). The indoor unit (3) is configured as a so-called ceiling-mounted type.

[0096] As shown in Figures 11 and 12, the turbofan (50) comprises one plate-shaped member (51), one shroud (53), and multiple blades (56). In this example, the turbofan (50) has seven blades (56). The number of blades (56) may be six or fewer, or eight or more.

[0097] The plate-shaped member (51) is a disc-shaped member with a recess in the center. The plate-shaped member (51) is the hub of the turbofan (50) and is positioned substantially coaxially with the drive shaft of the second fan motor (29). An axle hole (52) is formed in the central part of the plate-shaped member (51). The drive shaft of the second fan motor (29) is attached to the plate-shaped member (51) through the axle hole (52). When the second fan motor (29) is driven, the plate-shaped member (51) rotates around a predetermined axis of rotation (A2). The central axis of the plate-shaped member (51) coincides with the axis of rotation (A2) of the turbofan (50).

[0098] The shroud (53) is an annular member. The shroud (53) is positioned opposite the plate-shaped member (51) at a distance from the plate-shaped member (51) in the axial direction of the rotation axis (A2). The shroud (53) is also positioned substantially coaxially with the plate-shaped member (51). The outer diameter of the shroud (53) is approximately equal to the outer diameter of the plate-shaped member (51). The inner peripheral edge of the shroud (53) protrudes away from the plate-shaped member (51). In the turbofan (50), the inner peripheral edge of the shroud (53) forms an intake port (54), and the outer peripheral edge of the plate-shaped member (51) and the outer peripheral edge of the shroud (53) form an outlet port (55).

[0099] Multiple blades (56) are provided between the plate-like member (51) and the shroud (53). The multiple blades (56) are spaced apart from each other in the circumferential direction of the plate-like member (51) and the shroud (53), that is, in the rotation direction (D2) of the turbofan (50). Each blade (56) is located in the region near the outer edge of the plate-like member (51). Each blade (56) is provided upright in a direction facing the plate-like member (51) and the shroud (53), such that the leading edge (57) is located on the inner side and the trailing edge (58) is located on the outer side. One edge of each blade (56) is fixed to the plate-like member (51), and the other edge of each blade (56) is fixed to the shroud (53).

[0100] Each blade (56) has a leading edge (57), a trailing edge (58), a positive pressure surface (60), and a negative pressure surface (61). The leading edge (57) is the front edge in the direction of rotation (D2) of the blade (56). The trailing edge (58) is the rear edge in the direction of rotation (D2) of the blade (56). The positive pressure surface (60) is the blade surface that becomes the positive pressure side due to the airflow when the turbofan (50) rotates, and constitutes the surface facing the outer circumference of the turbofan (50) from which the air flows out. The negative pressure surface (61) is the blade surface that becomes the negative pressure side due to the airflow when the turbofan (50) rotates, and constitutes the surface facing the inner circumference of the turbofan (50) from which the air flows in.

[0101] In the turbofan (50), the portion of the space between the plate-shaped member (51) and the shroud (53) where the blades (56) are located constitutes an air passage (62). The air passage (62) is an annular passage continuous with the outlet (55). Air passing through the turbofan (50) flows from the radially inside to the outside of the air passage (62). Each blade (56) increases the air pressure due to the change in velocity in the rotational direction (D2) of the airflow between the leading edge (57) and the trailing edge (58), and the difference in peripheral velocity between the leading edge (57) and the trailing edge (58). The turbofan (50) takes in air from the intake (54), pressurizes it, and then blows it out from the outlet (55).

[0102] Each blade (56) is curved to form a convex shape on the outer circumference of the turbofan (50). As shown in Figure 13, in the airfoil cross-section of the blade (56) in the direction of rotational radius (airfoil cross-section in a plane perpendicular to the rotation axis (A2)), the line segment connecting the leading edge (57) and the trailing edge (58) of the blade (56) is the chord line (CLb). In the turbofan (50), the airfoil cross-section of the blade (56) in the direction along the chord line (CLb) corresponds to the airfoil cross-section of the blade (56) in the direction of rotational radius, and in this embodiment, it is referred to as the "symmetrical airfoil cross-section". In the symmetrical airfoil cross-section of the blade (56), the line connecting the midpoints of the positive pressure surface (60) and the negative pressure surface (61) is the camber line (SLb).

[0103] Each wing (56) has a wing body (64) and a porous section (66). The wing body (64) is made of a non-porous material such as a non-foaming synthetic resin. The wing body (64) constitutes the majority of the wing (56). That is, the majority of the wing (56) is made of a non-porous material. The porous section (66) is fixed to the wing body (64) by fitting, bonding, welding, etc. The shape, material, average diameter of the pores, and porosity of the porous section (66) in this example are the same as those of the porous section (46) in Embodiment 1 described above.

[0104] The porous portion (66) is located in the middle of the width direction of the blade (56) and closer to the trailing edge (58), and is surrounded by the portion that makes up the blade body (64). The porous portion (66) has the function of suppressing pressure fluctuations on the blade surface of the blade (56) and reducing noise generated as the turbofan (50) rotates. The porous portion (66) constitutes the entirety of the blade (56) in the thickness direction. The porous portion (66) is exposed to the positive pressure surface (60) and the negative pressure surface (61) of the blade (56), respectively, and forms a part of the positive pressure surface (60) and a part of the negative pressure surface (61).

[0105] Furthermore, in the turbo fan (50) of this embodiment, the shape of the leading edge (68) of the blade (56) is designed in order to suitably obtain the noise reduction effect of the porous portion (66) at the high airflow side. Specifically, a raised portion (69) is provided on the positive pressure surface (60) of the leading edge (68) of the blade (56). Here, the leading edge (68) is the portion including the leading edge (57) of the blade (56), and means the portion 10% from the leading edge (57) with respect to the chord length L1. The raised portion (69) is a curved portion that rises on the positive pressure surface (60) side of the blade (56). In this example, the raised portion (69) is provided along the entire length of the leading edge (68).

[0106] In the symmetric airfoil cross-section of the blade (56), the surface of the raised portion (69) is formed in a curved shape. The curved shape of the raised portion (69) is similar to that of the raised portion (69) of the blade (33) in the axial flow fan (30) of Embodiment 1 above, in which the absolute value of the angle between the tangent (TLb) of the positive pressure surface (60) and the chord line (CLb) decreases from the leading edge (57) toward the rear in the rotational direction (D2) of the blade (56), passes through 0, then increases, and reaches a point of change (Pc) where the rate of change of the absolute value begins to decrease (see Figure 6). A portion of the tangent (TLb) of the positive pressure surface (60) formed by the raised portion (69) is shown in Figure 13.

[0107] In the symmetric airfoil cross-section of the wing (56), the positive pressure surface (60) of the wing (56) is connected such that the tangent line (TLb) of the positive pressure surface (60) is continuous from the leading edge (68) to the portion behind the leading edge (68) in the rotational direction (D2). The positive pressure surface (60) of the leading edge (68) changes smoothly, including the raised portion (69). The leading edge (68) of the wing (56) constitutes a first portion (68a). The first portion (68a) is the portion where the raised portion (69) is formed. In the first portion (68a), the camber line (SLb) exhibits a shape that protrudes convexly toward the positive pressure surface (60) side, following the surface shape of the raised portion (69), and connects smoothly to the rear side of the first portion (68a).

[0108] In the target wing section of the wing (56), the maximum value of the distance from the camber line (SLb) of the leading edge (68) to the pressure surface (60) is defined as the first distance H1. Also, in the target wing section of the wing (56), the maximum value of the distance from the camber line (SLb) behind the leading edge (68) in the rotational direction (D2) to the pressure surface (60) is defined as the second distance H2. Similar to the first embodiment, in the target wing section of the wing (56), the first distance H1 and the second distance H2 satisfy the relationship H1 > H2 and also satisfy the relationship H1 ≤ H2 × 3.

[0109] In the target wing section of the wing (56), the maximum value of the distance from the chord line (CLb) of the leading edge (68) to the pressure surface (60) of the wing (56) is defined as the third distance H3. Also, in the target wing section of the wing (56), the maximum value of the distance from the chord line (CLb) of the leading edge (68) to the suction surface (61) of the wing (56) is defined as the fourth distance H4. In FIG. 13, for the sake of convenience, the positions of the third distance H3 and the fourth distance H4 are shown shifted from the first position (P1). In the target wing section of the wing (56), the third distance H3 and the fourth distance H4 satisfy the relationship H4 < H3.

[0110] In the target wing section of the wing (56), the position on the chord line (CLb) where the distance to the pressure surface (60) is the third distance H3 is defined as the first position (P1). Also, in the target wing section of the wing (56), the position corresponding to the change point (Pc) of the raised portion (69) on the chord line (CLb) is defined as the second position (P2). Similar to the first embodiment, the length L1 between the first position (P1) and the second position (P2), and the third distance H3 satisfy the relationship H3 < L1. Further, the length L1 between the first position (P1) and the second position (P2), and the length L2 between the leading edge (57) and the first position (P1) on the chord line (CLb) satisfy the relationship L2 < L1.

[0111] -Features of the Second Embodiment- In this embodiment 2 of the turbofan (50), a curved raised portion (69) is formed on the positive pressure surface (60) of the leading edge (68) of the blade (56) in the symmetrical blade cross-section. As a result, the area of ​​the leading edge (68) that the airflow collides with when the blade (56) rotates increases, and when the airflow collides with the leading edge (68) of the blade (56), an airflow containing minute vortices is generated on the positive pressure surface (60) side of the blade (56). This suppresses the development of turbulence flowing over the positive pressure surface (60) formed by the porous portion (66), and as a result, the noise reduction effect of the porous portion (66) can be suitably obtained.

[0112] In this embodiment 2 of the turbofan (50), a plurality of blades (56) are provided between a plate-shaped member (51) and a shroud (53) at intervals from each other in the direction of rotation. Each blade (56) is positioned with its leading edge (57) on the inner circumference side and its trailing edge (58) on the outer circumference side. In such a turbofan (50), the noise reduction effect due to the porous portion (66) can be suitably obtained, and therefore the technology of this disclosure is effective. In addition, effects related to the surface shape of the raised portion (69), which are represented by the first to fourth distances H1, H2, H3, and H4, similar to those of embodiment 1, can be obtained.

[0113] Other embodiments In the axial fan (30) of Embodiment 1 described above, the raised portion (49) of the blade (33) may be provided along the entire length of the leading edge (38). That is, the entire length of the leading edge (38) may constitute the first portion (38a). Alternatively, the raised portion (49) of the blade (33) may be provided only on the outer circumference of the leading edge (38). In the turbofan (50) of Embodiment 2 described above, the raised portion (69) of the blade (56) may be provided only on a part of the leading edge (68). In short, it is sufficient that curved raised portions (49, 69) are formed on the positive pressure surfaces (40, 60) of the leading edges (38, 68) of the blades (33, 56).

[0114] In the axial fan (30) of Embodiment 1 described above, the leading edge (38) of the blade (33) may be less than 10% of the leading edge (36) relative to the chord length L1. For example, the leading edge (38) may be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, or 9% of the leading edge (36) relative to the chord length L1. The same applies to the leading edge (68) of the blade (56) in the turbofan (50) of Embodiment 2 described above.

[0115] In the axial flow fan (30) of Embodiment 1 described above, the center (C1) of the porous portion (46) may be located outside the range of 0.4 to 0.8 for chord ratio (Lb / La) and outside the range of 0.6 to 0.8 for radius ratio (Rb / Ra). The area of ​​the porous portion (46) may be greater than 30% of the total area of ​​the positive pressure surface (40), provided that the strength of the blade (33) is ensured. In the turbo fan (50) of Embodiment 2 described above, the porous portion (66) may be provided so as to extend towards the leading edge (57) of the blade (56), or may be provided in multiple sections. In short, the porous portions (46, 66) should be located behind the leading edge portions (38, 68) in the rotational direction to constitute the positive pressure surface (40, 60) of the blade (33, 56).

[0116] The fan described herein can also be applied to other types of fans, such as mixed-flow fans. Furthermore, the fan described herein can be used in various other devices that require airflow, in addition to air conditioning devices (1) that regulate the temperature of the air in a target space. Examples of other devices include humidity control devices that regulate the humidity of the air in a target space, ventilation devices that ventilate a target space, and air purifiers that purify the air in a target space.

[0117] While embodiments and variations have been described above, it will be understood that a variety of modifications to the form and details are possible without departing from the spirit and scope of the claims. Furthermore, these embodiments and variations may be combined or substituted as appropriate, as long as they do not impair the functions covered by this disclosure.

[0118] Furthermore, the notations "1st," "2nd," etc., mentioned above are merely used to distinguish the phrases to which these notations are attached, and do not limit the number or order of such phrases. Also, the notation "~" in numerical ranges means a range that includes the numbers before and after it. In other words, if X and Y are used as substitutes for numbers, then "X~Y" indicates a range of "greater than or equal to X and less than or equal to Y." [Industrial applicability]

[0119] As described above, this disclosure is useful for fans and air conditioning systems. [Explanation of Symbols]

[0120] A1, A2 rotation axis CLa,CLb chord line D1, D2 Rotation direction Pc change point P1 1st position P2 2nd position TLa,TLb tangent 1. Air conditioning system 30 Axial flow fan (fan) 31 Hubs 33 Wings 36 Leading edge 38 Front edge 38a Part 1 40 Positive pressure surface 41 Suction surface 49. Raised portion (curved portion) 50 Turbo Fan (Fan) 51 Plate-shaped member 53 Shroud 56 Wings 57 Leading edge 58 Trailing edge 60 Positive pressure surface 68 Front edge 68a Part 1 69. Raised portion (curved portion)

Claims

1. It is equipped with blades (33, 56) that rotate around predetermined axes of rotation (A1, A2), The blade (33, 56) has a leading edge portion (38, 68) including a leading edge (36, 57) which is the front edge in the direction of rotation, and a porous portion (46, 66) located behind the leading edge portion (38, 68) in the direction of rotation and forming the positive pressure surface (40, 60) of the blade (33, 56). A fan in which, in the airfoil cross-section along the chord line (CLa,CLb) of the airfoil (33,56), a curved portion (49,69) is formed on the positive pressure surface (40,60) of the leading edge (38,68), where the absolute value of the angle between the tangent line (TLa,TLb) of the positive pressure surface (40,60) and the chord line (CLa,CLb) decreases from the leading edge (36,57) toward the rear in the rotational direction (D1,D2), passes through 0, then increases, and reaches a point of change (Pc) where the rate of change of the absolute value begins to decrease.

2. In the fan described in claim 1, The aforementioned front edge portion (38, 68) has a first portion (38a, 68a) on which the curved portion is formed, In the airfoil cross-section including the first portion (38a, 68a), the first distance H1 is the maximum distance from the camber line (SLa, SLb) of the leading edge portion (38, 68) to the positive pressure surface (40, 60), and the second distance H2 is the maximum distance from the camber line (SLa, SLb) of the portion behind the leading edge portion (38, 68) in the rotational direction (D1, D2) to the positive pressure surface (40, 60), such that H1 > H2, the relationship is satisfied.

3. In the fan described in claim 1, The aforementioned front edge portion (38, 68) has a first portion (38a, 68a) on which the curved portion is formed, In the airfoil cross-section including the first portion (38a, 68a), the positive pressure surface (40, 60) of the airfoil (33, 56) is connected such that the tangents (TLa, TLb) of the positive pressure surface (40, 60) are continuous from the leading edge (38, 68) to the portion behind the leading edge (38, 68) in the rotational direction (D1, D2) relative to the leading edge (38, 68) of the fan.

4. In the fan described in claim 1, The aforementioned front edge portion (38, 68) has a first portion (38a, 68a) on which the curved portion is formed, In the airfoil cross section including the first portion (38a, 68a), if the maximum distance from the chord line (CLa, CLb) of the leading edge portion (38, 68) to the positive pressure surface (40, 60) is defined as the third distance H3, then the length L1 between the first position (P1) where the distance from the chord line (CLa, CLb) to the positive pressure surface (40, 60) is the third distance H3 and the second position (P2) corresponding to the change point (Pc), and the third distance H3 satisfy the relationship H3 < L1.

5. In the fan described in claim 1, The aforementioned front edge portion (38, 68) has a first portion (38a, 68a) on which the curved portion is formed, In the airfoil cross section including the first portion (38a, 68a), if the maximum distance from the chord line (CLa, CLb) of the leading edge (38, 68) to the positive pressure surface (40, 60) is defined as the third distance H3, then the length L1 between the first position (P1) where the distance from the chord line (CLa, CLb) to the positive pressure surface (40, 60) is the third distance H3 and the second position (P2) corresponding to the change point (Pc), and the length L2 between the leading edge (36, 57) on the chord line (CLa, CLb) and the first position (P1), satisfy the relationship L2 < L1, for a fan.

6. In the fan described in claim 1, The aforementioned front edge portion (38, 68) has a first portion (38a, 68a) on which the curved portion is formed, In the airfoil cross-section including the first portion (38a, 68a), the first distance H1 is the maximum distance from the camber line (SLa, SLb) of the leading edge portion (38, 68) to the positive pressure surface (40, 60), and the second distance H2 is the maximum distance from the camber line (SLa, SLb) of the portion behind the leading edge portion (38, 68) in the rotational direction (D1, D2) to the positive pressure surface (40, 60), such that the relationship H1 ≤ H2 × 3 is satisfied.

7. In the fan described in claim 1, The hub (31) is rotatable around the aforementioned rotation axis (A1), The fan comprises a plurality of blades (33) provided at intervals from each other in the circumferential direction of the hub (31), each extending radially outward from the hub (31).

8. In the fan described in claim 7, The leading edge portion (38) has a first portion (38a) on which the curved portion is formed, In the airfoil cross section including the first portion (38a), the third distance H3, which is the maximum distance from the chord line (CLa) of the leading edge (38) to the positive pressure surface (40) of the airfoil (33), and the fourth distance H4, which is the maximum distance from the chord line (CLa) of the leading edge (38) to the negative pressure surface (41) of the airfoil (33), satisfy the relationship H4 < H3, respectively.

9. In the fan described in claim 8, The third distance H3 of the first portion (38a) decreases as you move from the inner circumference to the outer circumference of the wing (33) at the leading edge portion (38), in a fan.

10. In the fan described in claim 7, The leading edge portion (38) has a first portion (38a) on which the curved portion is formed, The first portion (38a) is provided on the inner circumference side of the leading edge portion (38), The porous portion (46) is provided on the outside of the first portion (38a) in the direction of the rotational radius of the blade (33) of the fan.

11. In the fan described in claim 1, A plate-shaped member (51) that can rotate around the aforementioned rotation axis (A2), The device comprises a shroud (53) positioned at a distance from the plate-shaped member (51) in the axial direction of the rotating shaft (A2), A fan comprising multiple blades (56) provided between the plate-shaped member (51) and the shroud (53) at intervals from each other in the rotational direction (D2), such that the leading edge (57) is located on the inner circumference side and the trailing edge (58), which is the rear edge in the rotational direction (D2), is located on the outer circumference side.

12. An air conditioning device comprising fans (30, 50) according to any one of claims 1 to 11.

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