Aerodynamic design optimization of helicopter rotor blades including airfoil shape for hover performance

TLDR

The study develops an optimization process to design helicopter rotor blades that minimize required hover power. Using a class‑function/shape‑function (CST) representation, the authors formulate an integrated optimization with design variables such as twist, taper ratio, taper initiation point, root chord, and airfoil distribution coefficients, subject to hover‑power and trim constraints. The optimized blade reduces hover power by 7.4 % and improves the figure of merit by 6.5 %, with sensitivity analysis indicating that airfoil shape is a key performance driver.

Abstract

This study proposes a process to obtain an optimal helicopter rotor blade shape for aerodynamic performance in hover flight. A new geometry representation algorithm which uses the class function/shape function transformation (CST) is employed to generate airfoil coordinates. With this approach, airfoil shape is considered in terms of design variables. The optimization process is constructed by integrating several programs developed by author. The design variables include twist, taper ratio, point of taper initiation, blade root chord, and coefficients of the airfoil distribution function. Aerodynamic constraints consist of limits on power available in hover and forward flight. The trim condition must be attainable. This paper considers rotor blade configuration for the hover flight condition only, so that the required power in hover is chosen as the objective function of the optimization problem. Sensitivity analysis of each design variable shows that airfoil shape has an important role in rotor performance. The optimum rotor blade reduces the required hover power by 7.4% and increases the figure of merit by 6.5%, which is a good improvement for rotor blade design.