Noise suppression refracting inlet for jet engines

摘要

A noise-reducing jet engine air inlet duct contoured to control air flow such that sound waves (noise) propagating upstream from the engine toward the entryway of the air inlet duct are refracted to the duct wall and/or engine inlet centerbody is disclosed. The inlet duct wall and/or engine inlet centerbody are contoured to establish a cross-sectional duct region having substantial airflow velocity gradients in a direction transverse to the direction of the airflow. Starting at the inlet duct entryway, the contoured duct region includes a parallel or diverging section followed by a rapidly contracting section before a final diffusion section extending to the engine. The velocity gradients created in the region of the contracting section refract the sound waves toward the wall and/or engine centerbody of the air inlet duct. Embodiments in which the noise energy of the refracted sound waves is absorbed by suitable acoustic linings and embodiments in which noise reduction is achieved without the inclusion of acoustic linings are disclosed.