Aerofoil tip structure, particularly for a HAWT rotor blade

A tip structure for use in a use position at a free end region of an aerofoil of a rotor blade of a wind turbine,

• the aerofoil extending along a length axis from the free end region to an opposite, supported end region,
• the aerofoil being mounted in use at the supported end region for motion in a direction of motion in an airflow relative to the aerofoil, the airflow at the free end region being opposed to the direction of motion,
• wherein the airflow is generated by rotation of the aerofoil about an axis of rotation, and the direction of motion is defined as a tangent of a swept circle at the tip structure, the swept circle defined by rotation of the tip structure about the axis of rotation;
• wherein, when considered in section in a section plane normal to the length axis, the aerofoil defines a profile having a maximum length dimension defined by a chord, the chord being a straight line having a length between a leading edge point on the profile and a trailing edge point on the profile;
• the profile extending between the leading edge point and the trailing edge point on a first, pressure side of the aerofoil and a second, suction side of the aerofoil, the profile being configured to generate a reduced pressure on the suction side relative to the pressure side when the aerofoil is arranged in use in the airflow with the leading edge point upstream of the trailing edge point;
• the length axis being defined as a line extending through an axis point on the chord in every position of the section plane from the free end region to the supported end region of the aerofoil, the axis point being located at 25% of the length of the chord from the leading edge point;
• wherein a respective said section plane at the free end region of the aerofoil is defined as a first reference plane, and the chord of the aerofoil lying in the first reference plane is defined as a reference chord;
• a first pressure side plane containing the reference chord is defined at an angle from 75° to 90° relative to the first reference plane;
• and
• a first suction side plane containing the reference chord is defined at an angle from 75° to 90° relative to the first reference plane;
• the tip structure comprising a pressure side structure extending from the pressure side of the aerofoil, and a suction side structure extending from the suction side of the aerofoil;
• wherein, when considered in the use position:
• the pressure side structure, when considered in section in a second pressure side plane parallel with the first pressure side plane, defines a profile having a maximum length dimension defined by a chord, the chord being a straight line between a leading edge point on the profile and a trailing edge point on the profile, the leading edge point being upstream of the trailing edge point with respect to the airflow, and
• the suction side structure, when considered in section in a second suction side plane parallel with the first suction side plane, defines a profile having a maximum length dimension defined by a chord, the chord being a straight line between a leading edge point on the profile and a trailing edge point on the profile, the leading edge point being upstream of the trailing edge point with respect to the airflow;
• and
• wherein, when the direction of motion is represented by a straight line respectively in the second pressure side plane and in the second suction side plane:
• when considered in the second pressure side plane, the chord of the pressure side structure extends at an angle αP relative to the direction of motion;
• when considered in the second suction side plane, the chord of the suction side structure extends at an angle αS relative to the direction of motion;
• and
• the angle αP is less positive or more negative than the angle αS,
• wherein the angle αP or αS is defined as positive where the respective chord extends forwardly and towards the supported end region with respect to the direction of motion, and as negative where the respective chord extends forwardly and away from the supported end region with respect to the direction of motion;
• wherein
• at least one aperture is formed in the tip structure between respective suction and pressure surfaces of the tip structure.

A tip structure for use in a use position at a free end region of an aerofoil of a rotor blade of a wind turbine,

• the aerofoil extending along a length axis from the free end region to an opposite, supported end region,
• the aerofoil being mounted in use at the supported end region for motion in a direction of motion in an airflow relative to the aerofoil, the airflow at the free end region being opposed to the direction of motion,
• wherein the airflow is generated by rotation of the aerofoil about an axis of rotation, and the direction of motion is defined as a tangent of a swept circle at the tip structure, the swept circle defined by rotation of the tip structure about the axis of rotation;
• wherein, when considered in section in a section plane normal to the length axis, the aerofoil defines a profile having a maximum length dimension defined by a chord, the chord being a straight line having a length between a leading edge point on the profile and a trailing edge point on the profile;
• the profile extending between the leading edge point and the trailing edge point on a first, pressure side of the aerofoil and a second, suction side of the aerofoil, the profile being configured to generate a reduced pressure on the suction side relative to the pressure side when the aerofoil is arranged in use in the airflow with the leading edge point upstream of the trailing edge point;
• the length axis being defined as a line extending through an axis point on the chord in every position of the section plane from the free end region to the supported end region of the aerofoil, the axis point being located at 25% of the length of the chord from the leading edge point;
• wherein a respective said section plane at the free end region of the aerofoil is defined as a first reference plane, and the chord of the aerofoil lying in the first reference plane is defined as a reference chord;
• a first pressure side plane containing the reference chord is defined at an angle from 75° to 90° relative to the first reference plane;
• and
• a first suction side plane containing the reference chord is defined at an angle from 75° to 90° relative to the first reference plane;
• the tip structure comprising a pressure side structure extending from the pressure side of the aerofoil, and a suction side structure extending from the suction side of the aerofoil;
• wherein, when considered in the use position:
• the pressure side structure, when considered in section in a second pressure side plane parallel with the first pressure side plane, defines a profile having a maximum length dimension defined by a chord, the chord being a straight line between a leading edge point on the profile and a trailing edge point on the profile, the leading edge point being upstream of the trailing edge point with respect to the airflow, and
• the suction side structure, when considered in section in a second suction side plane parallel with the first suction side plane, defines a profile having a maximum length dimension defined by a chord, the chord being a straight line between a leading edge point on the profile and a trailing edge point on the profile, the leading edge point being upstream of the trailing edge point with respect to the airflow;
• and
• wherein, when the direction of motion is represented by a straight line respectively in the second pressure side plane and in the second suction side plane:
• when considered in the second pressure side plane, the chord of the pressure side structure extends at an angle αP relative to the direction of motion;
• when considered in the second suction side plane, the chord of the suction side structure extends at an angle αS relative to the direction of motion;
• and
• the angle αP is less positive or more negative than the angle αS,
• wherein the angle αP or αS is defined as positive where the respective chord extends forwardly and towards the supported end region with respect to the direction of motion, and as negative where the respective chord extends forwardly and away from the supported end region with respect to the direction of motion;
• wherein
• the tip structure includes a serrated or furrowed trailing edge or a trailing edge with rivulets.