Wind turbine blade, wind power generation system including the same, and method for designing wind turbine blade

A wind turbine blade comprising:

• a blade body whose chord length increases from a blade tip toward a blade root,
• wherein the blade body is represented by a thickness ratio and Y125 which correlates with a design lift coefficient,
• the thickness ratio being a percentage obtained by dividing a maximum thickness by the chord length,
• Y125 being a percentage obtained by dividing a distance from a chord on a suction side, at a 1.25% position, by the chord length, wherein the position of a leading edge along the chord length is defined as 0% and the position of a trailing edge along the chord length is defined as 100%,
• then the blade body has
• a Y125 of 2.575±0.13% at a position having a thickness ratio of 21%,
• a Y125 of 2.6±0.15% at a position having a thickness ratio of 24%, and
• a Y125 of 2.75±0.25% or 2.75±0.20%, or 2.75±0.15%, at a position having a thickness ratio of 30%.

A wind turbine blade comprising:

• a blade body whose chord length increases from a blade tip toward a blade root,
• wherein the blade body is represented by a thickness ratio and a suction-side convexity YS which correlates with a design lift coefficient,
• the thickness ratio being a percentage obtained by dividing a maximum thickness by the chord length,
• the suction-side convexity YS being a percentage obtained by dividing a distance from a chord on a suction side, at a maximum-thickness position, by the chord length,
• then the blade body has
• a suction-side convexity YS of 12.0±0.6% at a position having a thickness ratio of 21%,
• a suction-side convexity YS of 12.3±0.7% at a position having a thickness ratio of 24%, and
• a suction-side convexity YS of 13.3±1.2% or 13.3±1.0% or 13.3±0.8%, at a position having a thickness ratio of 30%.

A wind turbine blade comprising:

• a blade body whose chord length increases from a blade tip toward a blade root,
• wherein the blade body is represented by a thickness ratio and a pressure-side convexity YP which correlates with a design lift coefficient,
• the thickness ratio being a percentage obtained by dividing a maximum thickness by the chord length,
• the pressure-side convexity YP being a percentage obtained by dividing a distance from a chord on a pressure side, at a maximum-thickness position, by the chord length,
• then the blade body has
• a pressure-side convexity YP of 9.0±0.6% at a position having a thickness ratio of 21%,
• a pressure-side convexity YP of 11.7±0.7% at a position having a thickness ratio of 24%, and
• a pressure-side convexity YP of 16.7±1.2% or 16.7±1.0% or 16.7±0.8%, at a position having a thickness ratio of 30%.

A wind turbine blade comprising:

• a blade body whose chord length decreases from a blade root toward a blade tip in a radial direction,
• wherein
• the blade body has a plurality of airfoil profiles at a plurality of radial positions, and
• when a suction-side profile of one of the plurality of airfoil profiles is defined as a reference suction-side profile, each of the suction-side profiles of the rest of the plurality of the airfoil profiles is a profile of extending or contracting the reference suction-side profile in a Y direction perpendicular to a chordwise direction.

A method for designing a wind turbine blade including a blade body whose chord length increases from a blade tip toward a blade root, the method comprising:

• assigning a first design lift coefficient to the entirety of a blade tip region located near the blade tip of the blade body and whose chord length increases gradually toward the blade root;
• assigning a second design lift coefficient higher than the first design lift coefficient to a maximum-chord-length position located near the blade root of the blade body and having a maximum chord length;
• and
• assigning a design lift coefficient, which increases gradually between the blade tip region and the maximum-chord-length position in a direction from the blade tip toward the blade root, to a transition region extending from the blade tip region to the maximum-chord-length position,
• wherein:
• the blade tip region is provided in a range of dimensionless radial positions of 0.5 to 0.95, the dimensionless radial position being a radial position of a blade section divided by a blade radius-that is a distance from the center of rotation of the blade to the blade tip, or is provided in a range of thickness ratios of 12% to 30%, the thickness ratio being a percentage obtained by dividing a maximum thickness by the chord length,
• X is a median of the first design lift coefficient,
• the first design lift coefficient is X±0.10 or X±0.05, and,
• the second design lift coefficient of the maximum-chord-length position is X+0.3±0.2 or X+0.3±0.1, and
• the design lift coefficient of the transition region at a central position between an end of the blade tip region facing the blade root and the maximum-chord-length position is X+0.15±0.15 or X+0.15±0.075.

A method for designing a wind turbine blade including a blade body whose chord length increases from a blade tip toward a blade root, the method comprising:

• a design-lift-coefficient determining step of determining a design lift coefficient at each of a plurality of blade sections of the blade body;
• and
• a Y125-determining step of determining Y125 which correlates with the design-lift-coefficient such that the design lift coefficient determined in the design-lift-coefficient determining step is satisfied, Y125 being a percentage obtained by dividing a distance from a chord on a suction side, at a 1.25% position, by the chord length,
• wherein the position of a leading edge along the chord length is defined as 0% and the position of a trailing edge along the chord length is defined as 100%,
• then the blade body has
• a Y125 of 2.575±0.13% at a position having a thickness ratio of 21%,
• a Y125 of 2.6±0.15% at a position having a thickness ratio of 24%, and
• a Y125 of 2.75±0.25% or 2.75±0.20% or 2.75±0.15%, at a position having a thickness ratio of 30%.

A method for designing a wind turbine blade including a blade body whose chord length increases from a blade tip toward a blade root, the method comprising:

• a design-lift-coefficient determining step of determining a design lift coefficient at each of a plurality of blade sections of the blade body;
• and
• a YS-determining step of determining a suction-side convexity YS which correlates with the design-lift-coefficient such that the design lift coefficient determined in the design-lift-coefficient determining step is satisfied, the suction-side convexity YS being a percentage obtained by dividing a distance from a chord on a suction side, at a maximum-thickness position, by the chord length,
• then the blade body has
• a suction-side convexity YS of 12.0±0.6% at a position having a thickness ratio of 21%,
• a suction-side convexity YS of 12.3±0.7% at a position having a thickness ratio of 24%, and
• a suction-side convexity YS of 13.3±1.2% or 13.3±1.0% or 13.3±0.8%, at a position having a thickness ratio of 30%.

A method for designing a wind turbine blade including a blade body whose chord length increases from a blade tip toward a blade root, the method comprising:

• a design-lift-coefficient determining step of determining a design lift coefficient at each of a plurality of blade sections of the blade body;
• and
• a YP-determining step of determining a pressure-side convexity YP which correlates with the design-lift-coefficient such that the design lift coefficient determined in the design-lift-coefficient determining step is satisfied, the pressure-side convexity YP being a percentage obtained by dividing a distance from a chord on a pressure side, at a maximum-thickness position, by the chord length,
• then the blade body has
• a pressure-side convexity YP of 9.0±0.6% at a position having a thickness ratio of 21%,
• a pressure-side convexity YP of 11.7±0.7% at a position having a thickness ratio of 24%, and
• a pressure-side convexity YP of 16.7±1.2% or 16.7±1.0% or 16.7±0.8%, at a position having a thickness ratio of 30%.