The Case for Counter-Rotation of Installed Contra-Rotating Open Rotor Propulsion Systems

Abstract

Contra Rotating Open Rotor (CROR) propulsion systems have seen renewed interest as a possible economic and environmentally friendly powerplant for future transport aircraft. Installation effects, i.e. the mutual interactions between airframe components and the rotors, have a pronounced impact on the aerodynamic and aeroacoustic performance for this type of engine. In this paper, the impact on aerodynamic performance and noise emissions caused by the presence of a pylon as well as a variation in the sense of rotation of the rotors is numerically studied for a representative 10x8-bladed pusher-configuration CROR engine at typical take-off conditions. In particular, the sense of rotation influence on blade and rotor performance and loadings as well as on the handling quality relevant in-plane rotor forces is analyzed, as is the resulting impact on the noise emissions in the near- and farfield and the flyover noise results. Having been widely applied to the simulations of single as well as contra-rotation propellers, the DLR CFD code TAU and the aeroacoustic analysis tool APSIM allow for a detailed analysis and an improved understanding of the complex aerodynamics and aeroacoustics of this type of propulsion system.