Innovative trials for high-speed aircraft propellers with better aeroacoustics An EU initiative performed a series of aeroacoustic and aerodynamic tests on a commercial passenger aircraft. The work lays the foundation for quieter planes. Transport and Mobility Climate Change and Environment Industrial Technologies Fundamental Research © Nyvlt-art, Shutterstock With EU funding, the LAC-LORR OTS (Low speed aeroacoustic test of an open rotor powered complete model) project carried out low-speed aerodynamic and aeroacoustic tests on a single-aisle large passenger aircraft model with installed counter-rotating open rotor (CROR) engines. Testing took place in a low-speed wind tunnel in the Netherlands. The aircraft model was equipped with powered (compressed air) engine simulators to simulate the aerodynamic and aeroacoustic effects of an installed unducted single fan (USF) propulsion system. It was mounted on a dorsal sting located at the tunnel’s centre line. The LAC-LORR OTS team investigated the aerodynamic behaviour and performance of the new USF propulsion system when installed on the model with realistic high-lift wing configurations. To execute the tests with the current wind tunnel model, project partners built two high-performance air-powered engines to drive the newly developed USF propellers. These propellers provided detailed performance data. The team effectively applied a new system of four acoustic observer lines. Data was generated on the aerodynamic and aeroacoustic characteristics of the USF rotor and stator blade design and on the installation effects on a full aircraft model that includes high-lift wing configurations. Acoustic measurements and propulsion simulations were successfully combined. Scientists measured the model’s aerodynamic performance data and the USF propeller’s performance. Dynamic and steady data from the highly instrumented USF rotor blades were continuously observed, measured and processed by data acquisition systems. They also measured near-field, semi-near-field and out-of-flow far-field acoustic data, and investigated the far-field noise caused by the model airframe. This will help assess the feasibility of USF propeller technology for an energy-efficient engine system with tolerable environmental noise impact. The LAC-LORR OTS tests pave the way for development of tomorrow’s large passenger aeroplanes and the design rules of USF engines installed as puller configurations in fuselages behind wings. The maiden flight of a test aircraft is not far behind. Keywords Aircraft, aeroacoustics, LAC-LORR OTS, counter-rotating open rotor, unducted single fan
