FLOCON · Adaptive and Passive Flow Control for Fan Broadband Noise Reduction

Air traffic is predicted to grow by 5% per year in the short and medium term. Technology ad-vances are required to achieve this growth without unacceptable levels of noise. FLOCON addresses this issue by reducing fan noise at source through the development of innovative concepts based on flow control technologies. FLOCON is aimed primarily at reducing fan broadband noise. This is one of the most signifi-cant noise sources on modern aircraft and FLOCON provides one essential element of a wider effort by the industry to achieve established targets for noise reduction. Previous attempts at reducing broadband noise have been inhibited by a limited understand-ing of the dominant mechanisms and by a lack of high-fidelity numerical models. These is-sues are addressed in the ongoing PROBAND FP6 project. In FP7, FLOCON moves beyond the scope of PROBAND to the development of specific concepts for reducing noise in aero-engine fan stages. A wide range of concepts will be considered and brought up to Technology Readiness Level 4 (laboratory scale validation): • Rotor trailing edge blowing • Rotor tip vortex suction • Rotor overtip treatments • Rotor and Stator leading and trailing edge treatments • Partly lined stator vanes Experiments will be performed on two rotating rigs, supported where possible by more detailed measurements on a single airfoil and a cascade. Numerical methods will be used to optimize the concepts for experimental validation and to extrapolate the results from labora-tory scale to real engine application. The potential benefit of each concept will be assessed, including any associated penalties (weight, complexity, aerodynamic performance). Recommendations will be given as to which concepts could be integrated into new engine designs and which will require further valida-tion at industrial rig or full engine-scale. Required developments in enabling technologies will also be identified.