Axial fan comprising endplates at the tip of the blades

An axial fan comprising a rotor rotatable about an axis of rotation X and a cylindrical casing arranged about and coaxial with the rotor, wherein:

• the rotor comprises a hub and a plurality of blades;
• each blade comprises a radially inner root portion constrained to the hub, an aerodynamic portion that extends mainly in radial direction from the root portion outwardly, and an endplate at the radially outer end;
• the aerodynamic portion is obtained from an extruded/pultruded profile;
• the aerodynamic portion defines, in a cross section, an airfoil;
• the endplate extends mainly in the axial direction and in the circumferential direction;
• the endplate defines a radially inner surface and a radially outer surface which is shaped according to a cylindrical surface portion;
• when the endplate is correctly arranged adjacent to the casing, the radially outer surface defines with the casing a gap with uniform and constant thickness, and wherein the blade further comprises an interface positioned between the aerodynamic portion and the endplate;
• the interface is made structurally independent of the aerodynamic portion of the blade;
• the radially outer end of the aerodynamic portion is defined by a plane π;
• the radially outer end of the interface adheres continuously to the radially inner surface of the endplate;
• the radially inner end of the interface is defined by the plane π;
• the radially inner end of the interface is coupled and connected continuously to the aerodynamic portion;
• and
• the radially inner end of the interface comprises means for structural coupling with the radially outer end of the aerodynamic portion.

A method for modifying an existing axial fan comprising a hub rotatable about an axis of rotation X, a plurality of blades and a cylindrical casing arranged around the hub and coaxial therewith, wherein each blade comprises an aerodynamic portion obtained from an extruded/pultruded profile having its own longitudinal axis l and having a cross section, perpendicular to the longitudinal axis l, shaped according to an airfoil, and wherein the method comprises the steps of:

• based on the diameter of the casing, defining an endplate, wherein the endplate:
• extends in the axial direction and in the circumferential direction,
• defines a radially inner surface and a radially outer surface which is shaped according to a cylindrical surface portion,
• when the endplate is correctly arranged adjacent to the casing, the radially outer surface defines with the casing a gap with uniform and constant thickness;
• identifying the airfoil with which the aerodynamic portion of the blades is made;
• identifying the geometric design parameters of the blades of the rotor with an angle of attack α, precone angle β, and swing angle γ;
• defining a virtual blade having the airfoil and the geometric design parameters identified above and an indefinite radial extension;
• determining the spatial curve representing the intersection between the virtual blade and the radially inner surface of the endplate when the endplate is correctly arranged adjacent to the casing;
• providing an interface having a radially inner end that defines a rest plane π and shaped to couple and connect continuously to the radially outer end of the extruded/pultruded profile of the blade;
• cutting the radially outer end of the interface along the intersection spatial curve;
• constraining the radially outer end of the interface to the radially inner surface of the endplate;
• cutting the blade along the rest plane π;
• constraining the radially inner end of the interface to the radially outer end of the aerodynamic portion of the cut blade;
• and
• repeating the operations defined above for each blade.

A method for making an axial fan comprising a hub rotatable about an axis of rotation X, a plurality of blades and a cylindrical casing arranged around the hub and coaxial therewith, wherein the method comprises the steps of:

• defining the diameter of the casing;
• based on the diameter of the casing, defining an endplate, wherein the endplate:
• extends mainly in the axial direction and in the circumferential direction,
• defines a radially inner surface and a radially outer surface which is shaped according to a cylindrical surface portion,
• when the endplate is correctly arranged adjacent to the casing, the radially outer surface defines with the casing a gap with uniform and constant thickness;
• selecting the airfoil with which to make the aerodynamic portion of the blades;
• providing an extruded/pultruded profile having the airfoil selected above and an indefinite extension along its own longitudinal axis l perpendicular to the airfoil plane;
• providing a root portion at a radially inner end of the extruded or pultruded profile;
• defining the geometric design parameters of the blades of the rotor with an angle of attack α, precone angle β, and swing angle γ;
• defining a virtual blade having the airfoil selected above, the geometric design parameters defined above and an indefinite radial extension;
• determining the spatial curve representing the intersection between the virtual blade and the radially inner surface of the endplate when the endplate is correctly arranged adjacent to the casing;
• providing an interface having a radially inner end that defines a rest plane π and shaped to couple and connect continuously to the radially outer end of the extruded/pultruded profile of the blade;
• cutting the radially outer end of the interface along the intersection spatial curve;
• constraining the radially outer end of the interface to the radially inner surface of the endplate;
• cutting the extruded/pultruded profile of the blade along the rest plane π, so as to obtain the aerodynamic portion;
• constraining the radially inner end of the interface to the radially outer end of the aerodynamic portion;
• constraining the root portion of the blade to the hub according to the geometric design parameters;
• and
• repeating the operations defined above for each blade.