Sensitivity Investigation of Aircraft Engine Noise to Operational Parameters

Aircraft noise is associated to two main groups of acoustic sources: those which produce airframe noise and the other ones which produce engine noise. Airframe noise can be numerically simulated once defined aircraft geometry and its intensity depends on aerodynamic configuration of aircraft. Engine noise is due to contribution of several sources according to engine’s type: in several cases these sources are not all well theoretically defined for the difficulty of performing experimental campaigns, and this does not allow a general validation of numerical simulation tools. Sound pressure levels associated to fans, compressors, jets, propellers can be numerically evaluated through commercial codes that require a big amount of input parameters concerning the geometric description of the different engine parts and the engine operational conditions that are well known from a physical standpoint but can be difficult to manage in a preliminary assessment of the noise emission due to a typical civil aircraft engine. The numerical definition of all these parameters requires a deep knowledge of the mechanism of the engine part subject of investigation and, often, also having a clear view of how this part works, the values of operational parameters, during the aircraft engine working, can be not available. For this reason an investigation of the sensitivity of the overall sound pressure levels associated to the different noise sources to the engine operational parameters can be useful to understand how much the noise can change if the working conditions change and to rank the variables from an acoustic standpoint fixing the most influential parameters. The present paper focuses on some of the acoustic sources acting on a typical civil aircraft engine and is based on the use of commercial codes able to simulate numerically the sound pressure levels associated to these sources.