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A transient analysis simulation program is developed for studying the response of an indirect injection, naturally aspirated, diesel engine after a rapid increase in load when this is equipped with various types of indirect acting governors. Analytical expressions are presented for the better simulation of engine mechanical friction, inertia moments and heat loss to the walls under transient conditions, governor dynamics for both the sensing element and the servopiston, soot emissions and the fuel pump operation. Various types of governor sensing elements (i.e. mechanical, electrical, two-pulse) and feedbacks (i.e. unity and vanishing) for the servomechanism are studied. Explicit diagrams are given to show how each combination of governor type and technical parameters (i.e. mass and number of flyweights, geometrical dimensions, amplification factors) affects the speed response as well as the speed droop and the recovery period of the particular engine.

A comprehensive transient analysis simulation model is used for the calculation of diesel engine performance under variable speed and load conditions. The analysis includes a detailed description of engine subsystems under transient conditions, thus accounting for the continuously changing character of transient operation, simulating among others the fuel injection, transient mechanical friction, heat losses to the walls and governor operation. The results of engine performance, at every time step during the transient event, are used as inputs for the formulation of thermal boundary conditions, which are needed for the calculation in a parallel way of the thermal transients propagating inside the engine structure.

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.

A second-law analysis is performed in both chambers of an indirect injection turbocharged diesel engine and the simulation program developed is used to study the second-law performance of the engine at various operating conditions, steady state and transient. The simulation developed is based on the filling and emptying approach and provides detailed analysis of thermodynamic, dynamic and second-law differential equations on a degree crank angle basis. It incorporates a detailed mathematical simulation of the fuel pump and solves each equation separately for each one of the six cylinders of the engine in hand. The model is validated against experimental data at steady state and transient conditions, obtained at the authors' laboratory. The prechamber rate and cumulative availability terms and irreversibilities are computed and depicted against the main chamber ones during the 720 degrees crank angle of an engine cycle.

Thermodynamic, dynamic and design parameters have a significant and often conflicting impact on the transient response of a compression ignition engine. Knowing the contribution of each parameter on transient operation could direct the designer to the appropriate measures for better engine performance. To this aim an explicit simulation program developed is used to study the performance of a turbocharged diesel engine operating under transient load conditions. The simulation developed, based on the filling and emptying approach, provides various innovations as follows: Detailed analysis of thermodynamic and dynamic differential equations, on a degree crank angle basis, accounting for the continuously changing nature of transient operation, analysis of transient mechanical friction, and also a detailed mathematical simulation of the fuel pump. Each equation in the model is solved separately for every cylinder of the 6-cylinder diesel engine considered.