Paper presented at the 9th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Malta, 16-18 July, 2012.
This paper characterizes the exergy (availability) analysis in the bi-fuel (CNG and gasoline) spark ignition engines. The engine is modeled using a quasi-dimensional (QD) two-zone thermodynamic analysis. The differential equations relating to the compression, combustion and the expansion are solved by an approximation method. The model includes the intake, exhaust processes and a turbulent combustion model. The engine model is capable of simulating the burn rate, and compared to the computational fluid dynamic (CFD) models is it considerably faster. The developed model is based upon the second law of thermodynamics, and exergy analysis terms. These terms includes thermo-mechanical availability, chemical availability, heat transfer availability, work availability, and the irreversible processes that are the source of destroyed availability. Finally, the effect of the availability, the first law of thermodynamics (FLT) and the second law of thermodynamics (SLT) efficiency of equivalence ratio, ignition time and engine speed are presented and discussed.