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In this paper the turbocharged diesel engine operation is analyzed by means of a second law based method. The instantaneous release and storage of availability inside the several components (cylinders, manifolds, compressor and turbine) are evaluated by following a theoretical-experimental methodology that has been recently proposed by the authors. Examples of availability balances are compared for different values of some parameters which influence the combustion and the exhaust process, or for several arrangements of the engine and turbomachine system. The availability analysis of the engine transient development will show the amounts of mechanical energy employed for both in-cylinder storage and turbocharger acceleration and of those available for conversion into external output. These amounts will be compared with the fuel availability and with those destroyed during the several processes (i.e. combustion, gas exchange, turbocharger operation).

The authors present a method for turbocharged I.C.E. analysis, based upon an unsteady non-dimensional flow-model, whose accuracy level has been improved by means of experimental investigations. Experimental activities allowed a higher prediction level to be reached for both engine cycles and turbocharger operation. The results are also compared with those of an experimental methodology recently proposed by the authors, based upon one-dimensional unsteady flow models and fast pressure data acquisition. The method is mainly utilized, in this paper, as to compare the effects of two different turbochargers on engine performance and turbomachinery operating conditions. The engine and turbocharger matching is considered under both steady and transient conditions.