Investigation On Engine Intake/Exhaust Noise And Design Of Acoustic Simulation Platform

The noise of intake and exhaust system is the main noise source of an engine. In this thesis, an independently developed acoustic platform for intake and exhaust system is introduced, and acoustic optimization using the platform for a gasoline engine intake system is carried out, which reduces the intake noise by 15 dB in average.The acoustic platform for intake and exhaust system is developed based on the theory of linear acoustics. The platform can implement silencer modeling for intake or exhaust system, acoustic performance simulation and optimization, engine intake/exhaust sound source determination, snorkel noise/tail-pipe noise computation and results post-processing. In the thesis, the theories and functions of each module are introduced. Experiments and simulations are carried out to validate the platform.During the acoustic optimization for intake system, the acoustic effect of filter is analyzed based on experiments. The comparisons of two different simulation methods illustrate that the Finite-element method concerning the filter's effect produces better accuracy. Intake sound source characters are obtained using the Source module of the platform, combined with the measurement data for engine bench test. The actual intake noise is then predicted by employing the source to simulation model and the acoustic optimizations are developed based on the predicted noise. By the improved design, total intake noise is reduced by 15 dB in average.The thesis develops a new analysis tool and technical process in the acoustic analysis for intake or exhaust system from the view of engineering application and achieves practical valuable results, which can instruct engineering significantly.