Noise prediction of a multi-cylinder engine prototype using multi-body dynamic simulation

In the paper a coupled Multi-Body and FEM-BEM methodology used to predict the noise radiated by a turbocharged 4-cylinder diesel engine prototype is described. A Multi-Body Dynamic Simulation (MBDS) of the engine has been carried out, simulating an engine speed sweep from 1500 to 4000 rpm, in order to determine the excitation force of the powertrain, and in particular to estimate the forces acting on the cylinder block. Thanks to the Multi-Body approach, the dynamics of the engine powertrain have been described taking into account both the effects of the burnt gas pressure during the combustion process and the inertia forces of the moving parts. Moreover to assess the real engine operating behaviour, both the crank and the block have been considered as flexible bodies. Afterwards, the cylinder block excitations, in terms of Modal Participation Factors, have been used to evaluate the engine radiated noise with the wellknow MATV methodology, at a distance of one meter from the engine according to the ISO 3744 directives. The dynamics of the engine powertrain and its vibro-acoustic behaviour have been described using LMS Virtual.Lab tools.