Method of designing blade of axial flow fluid machine and blade

Abstract

To provide a method of designing a blade of an axial flow fluid machine that has a blade surface whose radius of curvature is continuous at a leading edge thereof and has a high aerodynamic performance. The method includes a step of determining a pressure surface curve and a suction surface curve as curves capable of first to third order differentiations at respective connection points to a leading edge curve, that is, a pressure surface connection point and a suction surface connection point, and a step of forming the leading edge curve as a fifth order Bezier curve that is defined by a first control point, a second control point, a third control point, a fourth control point, a fifth control point and a sixth control point. The first control point is the suction surface connection point. The sixth control point is the pressure surface connection point. Provided that an intersection of a tangent to the pressure surface curve at the pressure surface connection point and a tangent to the suction surface curve at the suction surface connection point is referred to as a point ahead of the blade, the second and fifth control points are points that internally divide line segments connecting the point ahead of the blade to the suction surface connection point and the pressure surface connection point, respectively. The third and fourth control points are points having coordinates that are determined as solutions of simultaneous equations obtained by applying continuity conditions for first to third differential coefficients at the first and sixth control points to a fifth order Bezier function.