Low emissions design for reduced aircraft noise The contra-rotating open rotor (CROR) engine employs uncased blades (not enclosed within the engine nacelle) and promises enhanced efficiency. EU-funded scientists confronted the noise issue, made trickier by the open design, in order to speed up certification. Transport and Mobility Climate Change and Environment Industrial Technologies © Yannick Bury In line with Clean Sky objectives to reduce aircraft environmental impact, the CROR engine could cut fuel consumption and associated carbon dioxide emissions by 30 %. EU-funded scientists from the ISAE-SUPAERO and Aéroconseil consortium, in association with Airbus, have been working on the project ACcTIOM (Advanced pylon noise reduction design and characterization through flight worthy PIV). Addressing this challenge, they invented new active flow control strategies to minimise CROR-induced noise through a combination of aerodynamic optimisation of the propeller pylon shape and the development of an innovative active flow control system to erase the pylon wake before it interacts with the CROR blades. The active flow control system, a combination of scooping/blowing strategies, was designed and optimised by combining exhaustive Computational Fluid Dynamics (Reynolds-averaged Navier-Stokes) simulations and test bench experiments. The wind tunnel (WT) test model of the CROR pylon, including equipment, instrumentation and equipped with the so-developed embedded prototype of the active flow control system, was also finalised. Exhaustive series of WT tests were completed for the operating validation of the WT model of the CROR pylon equipped with its embedded flow control system, on-board instrumentation, and data acquisition and control systems. These tests confirmed the high efficiency of the developed embedded active flow control system in erasing the pylon wake. They also highlighted the robustness of the flow control system despite moderate variations of the flow conditions therefore acting as an aerodynamic stealth system. To develop advanced optical methodologies for in-flight operation dedicated to the validation of the efficiency of the CROR pylon design and associated active flow control system, the researchers developed numerical models of the expected vibratory environment inside the cabin of the FTB. These models have permitted to design experimental test benches, hereafter denoted Vibrational Environment Simulator or VES. Further, the team defined the hybrid, passive/active, vibration control strategy and required equipment for the design of a Vibration Correction Methodology (VCM) dedicated to the implementation and confident operation of in-flight 3C-PIV. The VCM will attenuate vibrations experienced by the 3C-PIV subsystems under VES influence during testing. ACcTIOM technologies will speed up certification and commercialisation of more energy-efficient aircraft. Advanced vibration-controlled 3C-PIV will enhance understanding of mechanisms in other airframe elements as well. Keywords Contra-rotating open rotor, ACcTIOM, pylon, noise reduction, vibration
