Multi-objective optimization design method for propeller structure of a high-altitude airship

To avoid the resonance of blade caused by rotating exciting force, it is necessary to increase the bending frequency of blade, but this will inevitably increase mass. In order to solve contradiction between low mass and high frequency, a two-objective optimization method of propeller was proposed. The minimum mass and maximum bending frequency were taken as two optimization objectives. The laying angle, thickness and region of the composite were taken as design variables. The maximum strain, maximum tip displacement and torsion angle at the 50%, 75% and 85% section of the blade were taken as constraints. The non-dominated sorting genetic algorthm Ⅱ (NSGA-Ⅱ) algorithm was used to optimize the propeller, and the Pareto solution of mass and frequency was obtained. The rotation frequency of the two blades at 520 r/min was 8.76 Hz and the crossing frequency was 17.33 Hz. The scheme far away from these two points was selected on the Pareto solution set according to the frequency. Through manufacturing and testing, the frequency of the real blade was 12.29 Hz, which was far away from the two resonance points, but can effectively avoid the blade resonance.