Acoustic optimization design and experimental verification of marine diesel engine exhaust system

Finite element method (FEM) was used to calculate acoustic modes of a cylindrical duct. For the acoustic modal frequencies of a cylindrical duct, the FEM predictions agreed well with the experiments, it was shown that FEM can predict acoustic modes of a cylindrical duct accurately. For the problem of a platform supply vessel exhaust noise exceeded noise level limits, acoustic modal frequencies of the platform supply vessel exhaust system are investigated by using FEM. By comparing predictions with the frequencies of diesel engine exhaust noise, it can be seen that acoustic resonance occurred between exhaust system and diesel engine exhaust noise, leading to higher exhaust noise level which exceeded noise limits. Increasing length of the exhaust system based on finite element predictions shifts acoustic modal frequencies to avoid the engine fire frequencies of diesel engine exhaust noise. Then the noise problem was solved. The effect of diameter and lengths of the exhaust system and location of silencer as well as terminal silencer on the acoustic attenuation performance is discussed and some acoustic optimization design suggestions on diesel engine exhaust system are given.