Exergy as a second law analysis parameter in thermodynamic diesel engine cycle simulation.

摘要

In the thermodynamic analysis of diesel engines; second law availability has only of late emerged as being an important parameter. However, "exergy" (the maximum work that can be extracted from a given system by bringing it into thermal, physical, and chemical equilibrium with its environment) provides more insight into the effectiveness of a thermodynamic system than availability alone. It is shown in this study how a simple diagnostic evaluation of a given engine can prove fruitful in identifying where improvement is necessary in the engine.; A thermodynamic simulation of a single cylinder diesel engine is performed, with an arbitrary heat release rate. The model configuration is such that parametric studies of existing engines can be performed with varying degrees of experimental input for different operating conditions and design configurations. Detailed formulations for heat transfer estimation and simulations of the intake and exhaust manifold gas flow processes are also included so that subsystem analysis can be performed.; The results obtained from this study help identify the processes where irreversibilities occur, and the magnitudes of these losses relative to the work output. For example, at 2000 rpm and 0.7 fuel/air equivalence ratio, the net indicated work for the single cylinder diesel engine simulated here is 49% of the fuel exergy. The loss due to irreversibilities is 27.6%, of which 14.8% is due to throttling loss in the exhaust valve and 9.3% is due to irreversibility in the combustion process.