Optimization of Propeller Skew Distribution to Minimize the Vibratory Forces and Moments Acting at the Propeller Hub.

摘要

Propeller skew is now well recognized as a means of reducing the unsteady forces and moments produced by the propeller. The propeller skew design problem is formulated as an optimization problem to minimize a weighted,linear combination of the six vibratory forces and moments acting at the propeller hub. The skew distribution is taken as a cubic or quadratic function of radius subject to realistic geometric constraints. This allows the optimization to be economically solved using existing constrained,nonlinear mathematical programming or parameter optimization methods. The SKEWOPT propeller skew optimization program is described. This interactive program was developed to perform the propeller skew optimization in a routine design setting. The vibratory forces and moments are evaluated using either a two-dimensional,sinusoidal gust theory or a three-dimensional,unsteady,lifting-line theory. The optimization is performed by an external penalty function technique utilizing the Nelder and Mead simplex search. Design examples using the SKEWOPT program are presented to illustrate the use of the program and to validate the propeller skew design approach.