Helicopter Rotor Shape Optimization for the Improvement of Aeroacoustic Performance in Hover

摘要

A helicopter rotor is optimally designed for aeroacoustic performance improvement. As shown in previousnreports, the blade shapes can be designed to minimize high-speed impulsive noise but tend to have excessively highntapers and be swept back. Since an overly short chord length around the blade-tip region may cause structuralnproblems and safety issues in autorotation, an autorotation index has been introduced to keep the tip region fromnhaving excessive taper ratios. In addition, the changes in thickness and camber of the airfoils can also be taken intonaccount to better represent realistic rotor shapes. Aeroacoustic analysis is performed using Kirchhoff’s methodncoupled with computational fluid dynamics analysis, and the optimization is performed using the kriging-model-nbased genetic algorithm method. Optimization results are presented that show that the designed blades havenimproved aerodynamic performance and reduced high-speed impulsive noise characteristics. It is found that amorenpractical blade shape can be obtained by using airfoil transitions and an autorotation index. The results of thenanalysis of variance and self-organization map indicate that the taper ratios, the swept back, the tip chord length,nthe protrusion shape, the camber, and the thickness of the root airfoil are the prominent features affecting thenaeroacoustic performance of the rotor.