A computer analysis is developed for studying the energy and exergy performance of a turbocharged diesel engine, operating under transient load conditions. The model incorporates some novel features for the simulation of transient operation, such as detailed analysis of mechanical friction, separate consideration for the processes of each cylinder during a cycle (“multi-cylinder” model) and mathematical modelling of the fuel pump. The model is validated against experimental data taken from a turbocharged diesel engine, located at the authors' laboratory, operated under transient load conditions. The availability terms for the diesel engine and its subsystems are analyzed, i.e. cylinder for both the open and closed parts of the cycle, inlet and exhaust manifolds, turbocharger and aftercooler. The effect of various dynamic, thermodynamic and design parameters on the second-law transient performance of the engine, manifolds and turbocharger is investigated, i.e. magnitude of applied load, type of connected loading, turbocharger mass moment of inertia, exhaust manifold volume, cylinder wall temperature and aftercooler effectiveness.
Explicit diagrams are given to show how, after a ramp increase in load, each parameter examined affects the second-law properties of all subsystems such as cylinder, heat loss to the walls and exhaust gas availability as well as combustion, exhaust manifold and turbocharger irreversibilities.
It is revealed from the analysis that the in-cylinder (mainly combustion) irreversibilities outweigh all other similar terms for every transient event but with decreasing magnitude when load increases, with the exhaust manifold processes being the second biggest irreversibilities producer with increasing magnitude when load increases.
Design parameters such as cylinder wall insulation or aftercooler effectiveness can have a notable effect on the second-law properties of the engine, despite the fact that their effect on the (thermo)dynamic response is minimal.