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Acoustic Liners for air conditioning system (ALIAS)
Start date: Jan 1, 2013, End date: May 31, 2015 PROJECT  FINISHED 

"The ALIAS project consists in designing optimized locally reacting treatments for mid-frequency acoustic attenuation in air conditioning system. The French Aerospace Lab (ONERA) and the SME ATECA, specialized in Aeronautics, Advanced Materials & Manufacturing, will combine their research and technological capabilities to propose a solution of TRL5 that meets the industrial requirements.First, technical specifications will be defined with the CFP partner. Then, a fast modal analysis code as well as a more complex solver of the linearized Euler equations will be used to assess the impedance that maximizes the acoustic damping of the set of cut-on modes in the target range of frequency. A sheared flow profile in a cylindrical duct will be considered. Next, an optimisation procedure will be carried out to find the locally reacting liners whose impedance law fits at best the target impedance in the whole range of frequency. An attenuation of at least 10dB will be aimed at. For this, appropriate semi-empiricals models from the literature linking the geometrical features of the liners to their impedance will be used. This will allow the selection of five concepts of acoustic treatments, which will then be manufactured and tested in laboratory, with a grazing flow up to M=0.3. The impedance will be obtained by direct in-situ methods or by applying an eduction procedure from pressure measurements. This experimental impedance will then be used as an input for the numerical propagation code, to predict the expected attenuation in the industrial configuration. This will allow the selection of the best two concepts.Finally, large-scale prototypes of the two chosen liners will be manufactured and provided to the CFP partner for tests in the industrial configuration. An analysis for integration of proposals solutions in an industrial context will also be performed. Especially, issues about costs and weight and operating constraints will be dealt with."
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