Based on the vortex lattice method and nonlinear programming, the problem for predicting optimum propeller blade twist has been formulated and solved to maximize the propulsive efficiency under the constraint of constant power consumption. The propeller is represented by a curved lifting line and a number of control points. The optimum twist distribution can be determined for a specified geometry of the lifting line. The method can be applied to complex blade shapes (swept, bent, propletted, and biblades). To demonstrate the method, the geometry of the lifting line of a straight blade and a propletted blade has been employed. The twist distribution and the ideal efficiency for the optimized and unoptimized blades are compared. The predicted improvement in ideal efficiency is about 1-6% for the optimized blade with proplet over that of the original propeller.
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