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The present work aims at developing and setting up a methodology in which non-intrusive measurements (engine block vibration) are used for monitoring combustion characteristics (combustion diagnosis, combustion development). The engine block vibration appears as a very complex signal in which different sources can be identified, since every moving component or physical process involved in the operation of the engine produces a vibration signal (exhaust valve open/close, inlet valve open/close, fuel injection, combustion, piston slap). Aimed at monitoring the engine running condition, the information carried by the vibration signal has to be broken down into its various contributions and then they have to be related to their respective excitation sources. Concerning combustion-induced vibration, experimental measures has been at first devoted to the selection of the best location where to place the piezoelectric accelerometer.

The present work investigates a multi-cylinder Diesel engine with integrated automatic transmission and gearbox, equipped with a common rail injection system for mini-car sector application. Previous research work has been devoted to examine the engine NVH characteristics; the attention has been addressed to the analysis of the direct relationship existing between in-cylinder pressure and engine block vibration signals with the final purpose of developing and setting up a methodology able to monitor and optimize the combustion process by means of non-intrusive measurements. The aim of this paper is to improve the performance of the engine in different operating conditions by means of both experimental and numerical approaches. Experimental tests have been conducted on the engine in a dynamic test bed in order to account for the actual loading conditions.

The paper concerns with gas exchange and combustion process in a 2T high speed gasoline engine and presents the results of a numerical-experimental investigation, in which zero-dimensional, one dimensional and three dimensional calculation schemes are used and the tuning between numerical and experimental results is performed. The different flow patterns from which the efficiency of the scavenging strongly depends are analysed, the variation with time of the spatial distribution of the fresh charge and combustion product in the cylinder is evaluated. The combustion process is simulated and the influence of geometric parameters of the ports on the scavenging efficiency, on the emission of hydrocarbons in the exhaust system and on the performance of the combustion process is investigated.