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A predictive technique aimed at investigating the behaviour of intake and exhaust systems of internal combustion engine and at evaluating their influence on engine breathing and radiated noise is herewith presented. Such a technique is based on coupling a time domain gas dynamic model (composed of zero-dimensional, one-dimensional and three-dimensional methods) with a frequency domain linear acoustic analysis (transfer matrix method); thus a realistic prediction of complete engine systems is realised by adopting in each region the most appropriate method, according to the main features of the phenomena involved. The whole procedure has been applied to the intake system of an automotive engine and the results regarding different operative conditions are presented.

In the last years, the increasing concern for the environmental issues of IC engines has promoted the development of new strategies capable of reducing both pollutant emissions in atmosphere and noise radiation. Engines can produce different types of noise: 1) aerodynamic noise due to intake and exhaust systems and 2) surface radiated noise. Identification and analysis of noise sources are essential to evaluate the individual contribution (injection, combustion, piston slap, turbocharger, oil pump, valves) to the overall noise with the aim of selecting appropriate control strategies. Previous paper focused on the combustion related noise emission. The research activity aimed at diagnosing and controlling the combustion process via acoustic measurements. The optimal placement of the microphone was selected, where the signal was strongly correlated to the in-cylinder pressure development during the combustion process.