The blade is of the type in which, between the entry side (13) and the exit side (14), the curvature varies. On the convex or pressure side the blade angle increases gradually up to point (B). Point (B) is the intersection with the convex side of a logarithmic spiral (16) through the exit point (14') of the adjacent blade. The blade angle in this point is 10 deg. to 60 deg. greater than at the entry (13). The inclination of the spiral relative to the circles concentric with the rotational axis is between 10 deg. and 40 deg. The blade angle from point (B) to the exit (14) reduces gradually and at the exit is 5 deg. to 50 deg. smaller than at (B). On the concave or suction side the blade angle decreases gradually up to point (A), which is the intersection with the concave side of a logarithmic spiral (17) through the entry point of the adjacent blade. The blade angle at this point is 1 deg. to 20 deg. smaller than at the entry (13). The inclination of the spiral (17) is from 10 deg. to 40 deg. The blade angle from point (A) to the exit (14) increases gradually and at the exit is 10 deg. to 60 deg. greater than at (A).
展开▼
