| 摘要 |
PURPOSE:To maintain the efficiency of propulsion by raking either of adjacent propeller blades forward or backward, making a discrimination between mutual angles of rake, and increasing the pitch angle of the backward blade. CONSTITUTION:A propeller 3 is provided with even-number of blades. Out of adjacent individual blades 5 and 6, one blade 5 permits the reference line G1 to be raked forward just by the angle of rake thetaR1 and is provided with the angle of rake thetaP1 and the other blade 6 is spaced at an interval (d) at a contact on the external surface of a boss 4, raked backward just by the angle of rake thetaR2, and is provided with the larger pitch angle thetaP2 than thetaP1. As a result, since the blade 6 is placed in a stream of air accelerated by the blade 5, the propulsive efficiency of the blade 6 is hardly reduced, even if the operating conditions of the propeller and its diameter are varied slightly. Besides, since the axial length of the propeller is not elongated, neither the propeller shaft nor its bearing section needs reinforcement. |
