BEMT-based blade twist optimisation of a tiltrotor in hover using artificial bee colony algorithm

In this study, the aerodynamic effects of rotor blade twist geometry on the hover performance of the XV-15 tiltrotor were investigated. For this purpose, the twist distribution of the XV-15 tiltrotor was optimised under hover conditions using the artificial bee colony (ABC) algorithm coupled with a Blade Element Momentum Theory (BEMT)-based numerical model validated against the NASA Ames experimental data. The blade twist was parameterised using a fifth-order continuous polynomial, whose coefficients were optimised to minimise the power coefficient while maintaining a constant thrust. The developed model was subsequently employed to evaluate the aerodynamic performance of candidate twist distributions under the prescribed hover thrust condition. In addition to the single-objective optimisation, the trade-off between aerodynamic performance and total blade twist was evaluated within a Pareto-based multi-objective optimisation framework, with total blade twist treated as a geometric design metric associated with practical blade manufacturing considerations. The best-found solution reduced the power coefficient by approximately 8.63% and increased the figure of merit (FOM) by approximately 9.45% relative to the reference geometry within the present BEMT framework. This study presents a practical optimisation approach for the aerodynamic assessment of rotor blade twist distributions under hover conditions with relatively low computational cost.