Licentiatavhandling Stockholm : Kungliga tekniska högskolan. Institutionen för farkost och flyg, 2007

Shorter product development cycles, densely packed engine compartments and intensified noise legislation increase the need for accurate predictions of IC-engine air intake noise at early stages. The urgent focus on the increasing CO2 emissions and the efficiency of IC-engines, as well as new techniques such as homogeneous charge compression ignition (HCCI) might worsen the noise situation. Non-linear onedimensional (1D) computational fluid dynamic (CFD) time domain prediction codes are used within the automotive industry to predict intake and exhaust orifice noise. The inherent limitation of 1D plane wave propagation, however, limits this technique to sufficiently low frequencies where non-plane wave effects are small. Therefore this type of method will first fail in large components such as air cleaners. Further limitations, that might not be important for simulation of engine performance but indeed for acoustics, include difficulties to apply frequency dependent boundary conditions and losses as well as to include effects of vibrating walls. This thesis deals with the use of linear acoustics to improve the accuracy of intake orifice noise predictions.