Design method of acoustic liner applied toaft-fan noise reduction and experimental validation

Liner design method applied to aft-fan noise reduction was implemented.The design phases were separated into two parts. In the first phase, an empirical impedance model was adopted to get the preliminary design. In the second phase, an optimization procedure was performed by numerical simulations based on high-order computational aeroacoustic method to achieve the optimal acoustic impedance and corresponding geometry parameters.In order to validate the method, an experimental investigation of aft-fan noise was carried out in the anechoic chamber of Beijing University of Aeronautics Astronautics.The fan noise source was modeled by a mode source generated by speakers.The circumferential mode was 1 and the radial mode was 0, the frequency was 3150Hz.The Mach numbers were 0.8 and 0.6 for the core and bypass ducts respectively. Experimental results showed that the preliminary design had 10dB insertion loss and the optimized liner achieved 3-4dB more attenuation.