Multi-point Adjoint-Based Design of Tilt-Rotors in a Noninertial Reference Frame

• Published in: NASA Center for AeroSpace Information (CASI). Conference Proceedings
• Main Authors: Jones, William T, Nielsen, Eric J, Lee-Rausch, Elizabeth M, Acree, Cecil W
• Format: Conference Proceeding
• Language: English
• Published: Hampton NASA/Langley Research Center 13.01.2014
• Subjects: Camber; Figure of merit; Optimization; Product design; Propulsive efficiency; Rotary wing aircraft; Rotor blades; Tilt rotor aircraft

Optimization of tilt-rotor systems requires the consideration of performance at multiple design points. In the current study, an adjoint-based optimization of a tilt-rotor blade is considered. The optimization seeks to simultaneously maximize the rotorcraft figure of merit in hover and the propulsive efficiency in airplane-mode for a tilt-rotor system. The design is subject to minimum thrust constraints imposed at each design point. The rotor flowfields at each design point are cast as steady-state problems in a noninertial reference frame. Geometric design variables used in the study to control blade shape include: thickness, camber, twist, and taper represented by as many as 123 separate design variables. Performance weighting of each operational mode is considered in the formulation of the composite objective function, and a build up of increasing geometric degrees of freedom is used to isolate the impact of selected design variables. In all cases considered, the resulting designs successfully increase both the hover figure of merit and the airplane-mode propulsive efficiency for a rotor designed with classical techniques.