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EP-4737739-A1 - FAN AND AIR CONDITIONER

EP4737739A1EP 4737739 A1EP4737739 A1EP 4737739A1EP-4737739-A1

Abstract

An axial fan (30) includes a plurality of blades (33) configured to rotate about a predetermined axis (A1). Each blade has a leading edge portion (38) including a leading edge (36) and a porous portion (46) that is located behind the leading edge portion in a rotation direction (D1) and forms a positive pressure surface (40). In a blade cross section taken along a chord line (CLa) of the blade, the positive pressure surface of the leading edge portion has a raised portion (49) in which an absolute value of an angle formed by a tangent (TLa) to the positive pressure surface and the chord line decreases to zero with increasing distance from the leading edge toward a rear side in the rotation direction, and then increases to reach a change point (Pc) at which a rate of change of the absolute value starts to decrease.

Inventors

  • KIMURA KOTA
  • CHEN ZUOZHOU
  • TERAKAWA AZUMI
  • HIGASHIDA MASAHITO

Assignees

  • Daikin Industries, Ltd.

Dates

Publication Date
20260506
Application Date
20250418

Claims (12)

  1. A fan comprising: a blade (33, 56) configured to rotate about a predetermined axis (A1, A2), wherein the blade (33, 56) has: a leading edge portion (38, 68) including a leading edge (36, 57) which is a front edge in a rotation direction; and a porous portion (46, 66) which is located behind the leading edge portion (38, 68) in the rotation direction and forms a positive pressure surface (40, 60) of the blade (33, 56), and in a blade cross section taken along a chord line (CLa, CLb) of the blade (33, 56), the positive pressure surface (40, 60) of the leading edge portion (38, 68) has a curved portion (49, 69) in which an absolute value of an angle formed by a tangent (TLa, TLb) to the positive pressure surface (40, 60) and the chord line (CLa, CLb) decreases to zero with increasing distance from the leading edge (36, 57) toward a rear side in the rotation direction (D1, D2), and then increases to reach a change point (Pc) at which a rate of change of the absolute value starts to decrease.
  2. The fan of claim 1, wherein the leading edge portion (38, 68) has a first portion (38a, 68a) provided with the curved portion, and in the blade cross section including the first portion (38a, 68a), a relationship of H1 > H2 is satisfied, where H1 represents a first distance H1 which is a maximum distance from a camber line (SLa, SLb) in the leading edge portion (38, 68) to the positive pressure surface (40, 60), and H2 represents a second distance H2 which is a maximum distance from the camber line (SLa, SLb) in a portion behind the leading edge portion (38, 68) in the rotation direction (D1, D2) to the positive pressure surface (40, 60).
  3. The fan of claim 1 or 2, wherein the leading edge portion (38, 68) has a first portion (38a, 68a) provided with the curved portion, and in the blade cross section including the first portion (38a 68a), the positive pressure surface (40, 60) of the blade (33, 56) is shaped such that the tangent (TLa, TLb) to the positive pressure surface (40, 60) is continuous from the leading edge portion (38, 68) to the portion behind the leading edge portion (38, 68) in the rotation direction (D1, D2).
  4. The fan of any one of claims 1 to 3, wherein the leading edge portion (38, 68) has a first portion (38a, 68a) provided with the curved portion, and in the blade cross section including the first portion (38a, 68a), a relationship of H3 < L1 is satisfied, where H3 represents a third distance H3 which is a maximum distance from the chord line (CLa, CLb) of the leading edge portion (38, 68) to the positive pressure surface (40, 60), and L1 represents a length L1 between a first point (P1) on the chord line (CLa, CLb) at which a distance to the positive pressure surface (40, 60) is the third distance H3, and a second point (P2) corresponding to the change point (Pc).
  5. The fan of any one of claims 1 to 4, wherein the leading edge portion (38, 68) has a first portion (38a, 68a) provided with the curved portion, and in the blade cross section including the first portion (38a, 68a), a relationship of L2 < L1 is satisfied, where L1 represents a length L1 between a first point (P1) on the chord line (CLa, CLb) at which a distance to the positive pressure surface (40, 60) is a third distance H3, and a second point (P2) corresponding to the change point (Pc), the third distance H3 being a maximum distance from the chord line (CLa, CLb) of the leading edge portion (38, 68) to the positive pressure surface (40, 60), and L2 represents a length L2 between the leading edge (36, 57) and the first point (P1) on the chord line (CLa, CLb).
  6. The fan of any one of claims 1 to 5, wherein the leading edge portion (38, 68) has a first portion (38a, 68a) provided with the curved portion, and in the blade cross section including the first portion (38a, 68a), a relationship of H1 ≤ H2 × 3 is satisfied, where H1 represents a first distance H1 which is a maximum distance from a camber line (SLa, SLb) in the leading edge portion (38, 68) to the positive pressure surface (40, 60), and H2 represents a second distance H2 which is a maximum distance from the camber line (SLa, SLb) in a portion behind the leading edge portion (38, 68) in the rotation direction (D1, D2) to the positive pressure surface (40, 60).
  7. The fan of any one of claims 1 to 6, further comprising: a hub (31) rotatable about the axis (A1), wherein multiple blades (33), each being identical to the blade (33), are arranged at intervals from each other in a circumferential direction of the hub (31), each of the multiple blades (33) extending radially outward from the hub (31).
  8. The fan of claim 7, wherein the leading edge portion (38) has a first portion (38a) provided with the curved portion, and in the blade cross section including the first portion (38a), a relationship of H4 < H3 is satisfied, where H3 represents a third distance H3 which is a maximum distance from the chord line (CLa) in the leading edge portion (38) to the positive pressure surface (40) of the blade (33), and H4 represents a fourth distance H4 which is a maximum distance from the chord line (CLa) in the leading edge portion (38) to a negative pressure surface (41) of the blade (33).
  9. The fan of claim 8, wherein the third distance H3 in the first portion (38a) decreases from an inner periphery to an outer periphery of the blade (33) in the leading edge portion (38).
  10. The fan of any one of claims 7 to 9, wherein the leading edge portion (38) has a first portion (38a) provided with the curved portion, and the first portion (38a) is provided on an inner peripheral side of the leading edge portion (38), and the porous portion (46) is provided outside of the first portion (38a) in a direction of radius of rotation of the blade (33).
  11. The fan of any one of claims 1 to 6, further comprising: a plate-shaped member (51) rotatable about the axis (A2); and a shroud (53) spaced from the plate-shaped member (51) in an axial direction of the axis (A2), wherein multiple blades (56), each being identical to the blade (56), are arranged at intervals from each other in the rotation direction (D2) between the plate-shaped member (51) and the shroud (53), with the leading edge (57) positioned inward and a trailing edge (58) positioned outward, the trailing edge (58) being a rear edge in the rotation direction (D2).
  12. An air conditioning apparatus comprising the fan (30, 50) of any one of claims 1 to 11.

Description

TECHNICAL FIELD The present disclosure relates to a fan and an air conditioning apparatus. BACKGROUND ART Patent Document 1 discloses an axial fan. This axial fan includes a plurality of blades each having a porous portion. The porous portion is provided to reduce noise generated by the rotation of the axial fan. CITATION LIST PATENT DOCUMENT Patent Document 1: Japanese Unexamined Patent Publication No. 2023-151184 SUMMARY OF THE INVENTION TECHNICAL PROBLEM The faster the blades rotate, the greater the volume of air the axial fan generates. The flow velocity of the air passing over a positive pressure surface of each blade increases, and a turbulent flow of the air remarkably develops on the positive pressure surface. The inventors of the present application have found that an axial fan having blades each having a porous portion as disclosed by Patent Document 1 impairs the effect of noise reduction by the porous portion when the turbulent flow develops and becomes larger on the positive pressure surface of the blades. An object of the present disclosure is to obtain a suitable noise reduction effect for a fan having blades each provided with a porous portion by means of the porous portion. SOLUTION TO THE PROBLEM A first aspect of the present disclosure is directed to a fan (30, 50). The fan (30, 50) of the first aspect includes a blade (33, 56) configured to rotate about a predetermined axis (A1, A2). The blade (33, 56) has: a leading edge portion (38, 68) including a leading edge (36, 57) which is a front edge in a rotation direction (D1, D2); and a porous portion (46, 66) which is located behind the leading edge portion (38, 68) in the rotation direction (D1, D2) and forms a positive pressure surface (40, 60) of the blade (33, 56). In a blade cross section taken along a chord line (CLa, CLb) of the blade (33, 56), the positive pressure surface (40, 60) of the leading edge portion (38, 68) has a curved portion (49, 69) in which an absolute value of an angle formed by a tangent (TLa, TLb) to the positive pressure surface (40, 60) and the chord line (CLa, CLb) decreases to zero with increasing distance from the leading edge (36, 57) toward a rear side in the rotation direction (D1, D2), and then increases to reach a change point (Pc) at which a rate of change of the absolute value starts to decrease. According to the first aspect, in the blade cross section taken along the chord line (CLa, CLb) of the blade (33, 56), the positive pressure surface (40, 60) of the leading edge portion (38, 68) of the blade (33, 56) has a curved portion (49, 69) in which an absolute value of an angle formed by a tangent (TLa, TLb) to the positive pressure surface (40, 60) and the chord line (CLa, CLb) gradually changes in a mountain-shaped curve. Such a curved portion (49, 69) forms a raised portion (49, 69) raised on the positive pressure surface of the blade (33, 56). The raised portion (49, 69) provided on the positive pressure surface (40, 60) of the leading edge portion (38, 68) increases the area of the leading edge portion (38, 68) with which the airflow collides during the rotation of the blade (33, 56). Thus, when the airflow collides with the leading edge portion (38, 68) of the blade (33, 56), an airflow (F1) including minute vortices (Vt) is generated on the positive pressure surface (40, 60) of the blade (33, 56). The airflow (F1) including the minute vortices (Vt) is less likely to be separated from the curved raised portion (49, 69) and flows along the positive pressure surface (40, 60) with reduced generation of the turbulent flow. This can reduce the development of the turbulent flow on the positive pressure surface (40, 60) formed by the porous portion (46, 66). As a result, a suitable noise reduction effect can be achieved by the porous portion (46, 66). A second aspect of the present disclosure is the fan (30, 50) of the first aspect, in which the leading edge portion (38, 68) has a first portion (38a, 68a) provided with the curved portion (49, 69). In the blade cross section including the first portion (38a, 68a), a relationship of H1 > H2 is satisfied, where H1 represents a first distance H1 which is a maximum distance from a camber line (SLa, SLb) in the leading edge portion (38, 68) to the positive pressure surface (40, 60), and H2 represents a second distance H2 which is a maximum distance from the camber line (SLa, SLb) in a portion behind the leading edge portion (38, 68) in the rotation direction (D1, D2) to the positive pressure surface (40, 60). According to the second aspect, in the blade cross section taken along the chord line (CLa, CLb) of the blade (33, 56) including the first portion (38a, 68a), the first distance H1 which is the maximum distance from the camber line (SLa, SLb) in the leading edge portion (38, 68) to the positive pressure surface (40, 60) is greater than the second distance H2 which is the maximum distance from the camber line (SLa, SLb) in the portion behind the leading ed