Optimization Procedure for Design of High‐Speed Prop‐Rotors

Abstract

An optimization procedure has been developed to address the complex and conflicting requirements associated with the design of high‐speed proprotor aircraft. Since the key technical issues are maintenance of propulsive efficiency and aeroelastic stability in high‐speed cruise without deteriorating figure of merit in hover, rotor aerodynamic performance and aeroelastic analysis are coupled, inside a closed loop, to the optimizer. The discipline couplings provide actual blade air‐loads, during hover and cruise, and also provide realistic blade designs. The propulsive efficiency in high‐speed cruise is used as the objective function. Constraints are also imposed on the aeroelastic stability in axial flight and the rotor figure of merit in hover. Both structural and planform design variables are used. The optimization procedure yields significant improvements in the aerodynamic characteristics of the rotor. Off‐design performance studies, conducted with the optimum blade, show overall design improvements.