Patent ID: 8198747
Filing Date: 2012-06-12
Classification: F03D,F05B,Y02E

Abstract:
1. A blade for a windmill being disposed around a rotation center in a vertical direction so as to receive wind force, wherein the edge of the blade viewed from the vertical direction is formed by: a front surface curved convexly toward a front traveling direction of rotation about the rotation center, as viewed from the vertical direction; and a back surface, curved concavely toward a back traveling direction of rotation about the rotation center, being disposed on a back surface side of the blade and extending between a low speed back end portion and a high speed back end portion, the low speed back end portion being disposed closer to the rotation center than the high speed back end portion, and the front surface includes: a front nose surface being disposed at front of the blade with respect to the front traveling direction, also having a greatest average curvature, the front nose surface including a front portion disposed at a forward-most portion of the blade with respect to the front traveling direction and closer to the rotation center than the high speed back end portion, a low speed airflow passing surface disposed on a closer side to the rotation center, and formed continuously from the front nose surface, along the back traveling direction, to the low speed back end portion, and a high speed airflow passing surface disposed on a distant side from the rotation center, formed continuously from the front nose surface, along the back traveling direction to a high speed back end portion, with a curved surface swollen greater than the low speed airflow passing surface, and having length as viewed from the vertical direction greater than the low speed airflow passing surface, and wherein, when receiving wind only from the front, the blade produces lift force including a component in the reverse direction of the wind from the front.