Design Optimization of HALE Propeller by using SLSQP Method

The existing propeller of a HALE UAV (High Altitude Long Endurance Unmanned Aerial Vehicle) needs an improvement in its performance operating at higher altitude, a special design which is different from a UAV that operates at a lower altitude. For achieving this purpose an optimization technique called the SLSQP (Sequential Least Squares Programming) method is used. This method uses least–square problem formulation that replaces the standard quadratic problem to help in finding a optimum point. This gradient-based optimization method requires a large number of solver evaluations. The performance of the propeller is evaluated using the solution of Blade-Element Momentum Theory (BEMT). The existing propeller for a HALE UAV has, with a current efficiency of the propeller being of 57% at 60,000 ft during cruise condition. The design variables are the chord and twist distribution. Running the optimization scheme yields a propeller design that has an efficiency of 60.4%, which is an increase of 3.4% from the baseline geometry. The result is verified by high-fidelity method by employing CFD (Computational Fluid Dynamics). Good agreement is found between the BEMT and CFD predictions, both for cruise and off-design conditions.