Contra-rotating open rotor testing An EU team studied the aerodynamics and sound performance of contra-rotating open rotors (CRORs) meant for the Airbus A320 aircraft. The data were used to optimise selection and placement of model components, for use with an unducted single fan (USF) propeller. Transport and Mobility © Alex Tanya, Shutterstock CRORs are aircraft propellers, whereby two rotors on the same axis rotate in opposite directions. The system offers efficiency advantages, although offset by mechanical complexity and a higher noise output that restricts commercial use. The EU-funded LAAME-CROW (Advanced measurement techniques in a low speed CROR wind tunnel test) project studied CROR aerodynamics, and specifically in the inflow region of the USF propeller. Researchers investigated the noise properties of the same propeller mounted on the Airbus A320 aircraft (Z08 model). The project also undertook a commissioning programme for new engine and propeller hardware. Flow field data were measured using a particle image velocimetry (PIV) system, while noise was measured and localised using a large-aperture phased microphone array. Researchers optimised the PIV and phased microphone array during the commissioning programme. The project was part of the EU’s Clean Sky programme. Researchers conducted low-speed aerodynamic and aeroacoustic tests in an 8x6 m wind tunnel. The Z08 was equipped with two compressed-air engine simulators, used to investigate the aerodynamic and aeroacoustic effects of a USF propulsion system. The team used the performance data to select the most interesting conditions for the propeller and wind tunnel settings, to achieve optimum application. The performance data were also used to optimise the selection of model components and their placement, to improve aerodynamic performance of the USF propulsion system. The consortium further measured near-field acoustic data using a traversable inflow wing. The wing was equipped with 48 inflow microphones. Project achievements included commissioning of modified air engines and successful optimisation for the USF rotor. As planned, the team ascertained the aerodynamic and aeroacoustic performance of the new USF engine, and determined the effects of installation in high-lift configurations. The consortium successfully combined the acoustic and propulsion simulations. LAAME-CROW results constitute an important step towards the development of a future European large passenger aircraft. The testing enabled development of a full-scale test aircraft. Keywords Contra-rotating open rotor, aerodynamics, CROR, unducted single fan, LAAME-CROW
