System Noise Assessment of Hybrid Wing-Body Aircraft with Open-Rotor Propulsion

An aircraft system noise study is presented for the hybrid wing-body aircraft concept with open-rotor engines mounted on the upper surface of the airframe. The aircraft chosen for the study is of a size comparable to the Boeing 787 aircraft. It is shown that, for such a hybrid wing-body aircraft, the cumulative effective perceived noise level is about 24 dB below the current aircraft noise regulations of stage 4. Although this makes the design acoustically viable in meeting the regulatory requirements, even with the consideration of more stringent noise regulations in the next decade or so, the design will likely meet stiff competition from aircraft with turbofan engines. The noise levels of the hybrid wing-body design are held up by the inherently high noise levels of the open-rotor engines and the limitation on the shielding benefit due to the practical design constraint on the engine location. Furthermore, it is shown that the hybrid wing-body design has high levels of noise from the main landing gear, due to their exposure to high-speed flow at the junction between the centerbody and outer wing. To identify approaches that may further reduce noise, parametric studies are also presented, including variations in engine location, vertical tail and elevon variations, and airframe surface acoustic liner treatment effect. These have the potential to further reduce noise, but some of these technologies are only at the proof-of-concept stage.