Green aircraft for cleaner skies
Clean Sky, the most ambitious aeronautical research programme ever initiated in Europe, is developing the Smart Fixed Wing Aircraft Integrated Technology Demonstrator (SFWA ITD). The innovative aircraft concept will significantly reduce noise and fuel consumption for eco-friendly air transport and the CROR is an important part of it. The EU-funded project 'Design of innovative CROR blade and pylon' (DINNO-CROR) contributed significantly to the development effort. Scientists evaluated two different low-technology–readiness level (TRL) noise-control methods, one based on porous treatment of rotor blades and one employing active blade-surface modulation. They also improved the predictive capability of innovative computational fluid dynamics (CFD) / computational aero-acoustic software systems to determine noise sources and describe noise propagation. Wall pressure spectra enabled evaluation of the noise-reduction effects of porous blade liners. Corroborating model data with experimental measurements demonstrated that the porosity required (around 25 %) to reduce noise resulted in an unacceptable loss in model performance. Researchers also evaluated the effect of dielectric barrier discharge actuators placed at the trailing (blunt) edge of the front blade of the CROR. CFD computations showed that plasma actuation did not significantly affect the wake behind the airfoil, demonstrating minimal potential for noise reduction in the CROR configuration. Extensive simulation work was devoted to the CROR configuration with the inclusion of an upstream pylon (a suspension device used for attachments). The pylon only marginally affected aerodynamic blade performance. However, the sound pressure level of the emitted noise from the front rotor was significantly increased in the upstream direction when the pylon was present. By eliminating two low-TRL noise-reduction concepts from further investigation, researchers are honing in on the truly promising technologies. Enhanced understanding of CROR aerodynamics and aero-acoustics has led to clear guidelines regarding simulation development for accurate results. DINNO-CROR has helped streamline the Clean Sky research programme, bringing the EU even closer to realisation of major fuel and emissions reductions.
