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The modeling of transient turbocharged diesel engine operation appeared in the early seventies and continues to be in the focal point of research, due to the importance of transient response in the everyday operating conditions of engines. The majority of research has focused so far on issues concerning thermodynamic modeling, as these directly affect heat release predictions and consequently performance and pollutants emissions. On the other hand, issues concerning the dynamics of transient operation are often disregarded or over-simplified, possibly for the sake of speeding up program execution time. In the present work, an experimentally validated transient diesel engine simulation code is used to study and evaluate the importance of such dynamic issues. First of all, the development of various forces (piston, connecting rod, crank and main crankshaft bearings) is computed and illustrated in order to evaluate the importance of abrupt load increases on the bearings durability.

The transient operation of turbocharged diesel engines during turbocharger compressor surging is investigated through simulation. This form of compressor dynamic instability can generate large amplitude compressor mass flow and pressure rise oscillations, sometimes leading even to flow reversals, and may also induce severe torsional loading to the turbocharger shaft. A model predicting the dynamic behavior of the engine air-charging system when compressor surging occurs was developed in conjunction with a linearized quasi-steady diesel engine simulation code. This analysis possesses the advantage over the more detailed engine codes of basic simplicity, speed of calculation and no need of many engine and turbocharger components parameters given as input data. Emphasis is given to the correct modeling of the physics of the phenomena concerned. Transient operation runs, including critical cases for surging initiation, were applied for two similar six-cylinder diesel engines.