A uRANS-Based Hybrid CFD/CAA-Methodology for the Analysis of CROR Low-Speed Aerodynamic and Aeroacoustic Installation Effects

Abstract

Contra-Rotating Open Rotor (CROR) engines promise a significant efficiency improvement over turbofan engines, which they derive from their ultra-high bypass ratio, made possible through the omission of a nacelle around the contra rotating co-axial rotors. However, the absence of the nacelle as well as the complex aerodynamic interactions between the two rotors also make meeting requirements of further reductions in noise emissions a significant technical challenge. In this thesis a flexible and robust simulation approach is developed, which, through the coupling of modern numerical tools for the aerodynamic and aeroacoustic analysis, allows for a detailed and precise multi-disciplinary analysis of CROR powered aircraft configurations. In addition to establishing an accurate and efficient simulation approach, the validation of this methodology is a central aspect of this work. It is demonstrated that this coupled simulation method delivers high accuracy in the prediction of the aerodynamic performance of isolated and aircraft-installed CROR engines and yields an accurate representation of the impact of installation effects on the noise emissions. The application of this approach to the analysis of successively more complex CROR engine-airframe installation scenarios furthermore demonstrates the valuable insights gained on the complex aerodynamic phenomena as well as key tonal noise source mechanisms on the basis of the simulation data.